Fact-checked by Grok 2 weeks ago

Ischemic cascade

The ischemic cascade refers to a progressive series of neurobiological and biochemical events triggered by cerebral ischemia, such as in acute ischemic stroke, where reduced blood flow deprives brain tissue of oxygen and glucose, ultimately leading to neuronal injury, cell death, and potential irreversible brain damage.^[1]^[2] The cascade begins within minutes of ischemia onset with rapid depletion of adenosine triphosphate (ATP), impairing the sodium-potassium ATPase pump and causing cellular membrane depolarization, ionic imbalances (including sodium and potassium shifts), and cytotoxic edema.^[3]^[1] This initial energy failure prompts excessive release of the excitatory neurotransmitter glutamate, which overactivates N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, resulting in calcium influx, excitotoxicity, and activation of destructive enzymes like proteases, lipases, and endonucleases.^[2]^[3] Subsequent stages involve oxidative stress from reactive oxygen species (ROS) production, mitochondrial dysfunction, and neuroinflammation, where activated microglia release pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), further exacerbating tissue damage through blood-brain barrier disruption and white matter injury.^[2]^[3] These processes can propagate from the ischemic core to the surrounding penumbra—a potentially salvageable region—over hours to days if blood flow is not restored, contributing to infarct expansion and long-term neurological deficits.^[1]

Overview and Definition

Definition

The ischemic cascade refers to a progressive series of biochemical and physiological events triggered by cerebral hypoperfusion, characterized by reduced blood flow to brain tissue, which initiates energy failure, ionic imbalances, and subsequent neuronal dysfunction leading to potential infarction if not reversed.^[4] This process begins with the deprivation of oxygen and glucose supply to affected neurons, rapidly escalating into a cascade of interconnected pathological changes that can culminate in irreversible cell death.^[3] The concept of the ischemic cascade was first described in the early 1980s by Astrup and colleagues, who emphasized the existence of a therapeutic window during which interventions could salvage reversibly damaged tissue, particularly within the penumbral region surrounding the ischemic core.^[5] Their work highlighted the time-sensitive nature of stroke pathophysiology, underscoring that delays in restoring perfusion narrow the opportunity for neuroprotection and recovery.^[4] Key characteristics of the ischemic cascade include its sequential and interdependent mechanisms, such as initial energy depletion followed by excitotoxicity, which differentiate it from discrete or isolated ischemic insults by promoting widespread tissue injury through amplifying feedback loops.^[3] These interconnected events, including neurotransmitter dysregulation and membrane potential collapse, occur within minutes to hours, emphasizing the urgency of timely therapeutic interventions to interrupt progression.^[4]

Physiological and Clinical Context

The brain, comprising only 2% of body weight, demands a continuous and substantial supply of oxygen and glucose to sustain its high metabolic activity, consuming approximately 20% of the body's total oxygen and glucose utilization at rest. This requirement is met by cerebral blood flow (CBF), which accounts for about 15-20% of cardiac output, delivering roughly 750 mL/min of blood to the brain under normal conditions.^[6]^[7] To maintain stable perfusion and prevent fluctuations in neuronal function, cerebral autoregulation adjusts vascular resistance, keeping CBF constant across a mean arterial pressure (MAP) range of 60-160 mmHg in healthy adults.^[8] Outside this range, autoregulatory mechanisms fail, potentially leading to ischemia if blood pressure drops sufficiently. The ischemic cascade is triggered when CBF falls below critical thresholds, disrupting the brain's oxygen and nutrient delivery. Reversible neuronal dysfunction begins at CBF levels around 20 mL/100 g/min, where electrical activity slows but structural integrity remains intact, forming the ischemic penumbra. Further reduction to below 10 mL/100 g/min initiates irreversible cellular damage, as energy failure escalates and infarction develops in the core region.^[9]^[10] Clinically, the cascade most commonly manifests in cerebral ischemic stroke, which constitutes approximately 65% of all strokes globally (or up to 87% in high-income countries) as of 2025 and results from focal arterial occlusion.^[11]^[12]^[13] It also occurs in transient ischemic attacks (TIAs), where brief interruptions in blood flow cause temporary symptoms without permanent infarction.^[14] Beyond focal events, global ischemia from cardiac arrest activates the cascade across the entire brain due to systemic hypoperfusion, often leading to widespread neuronal injury.^[15] While the term is primarily used in the cerebral context, analogous processes unfold in other organs, such as during myocardial infarction in cardiac tissue following coronary occlusion, progressing from metabolic derangements to necrosis if reperfusion is delayed.^[16]

Pathophysiological Stages

Initiation and Early Events

The ischemic cascade is initiated by a sudden reduction in cerebral blood flow, typically caused by occlusion of cerebral arteries due to thrombus formation, embolus, or systemic hypoperfusion, which severely limits oxygen and glucose delivery to brain tissue, resulting in hypoxia.^[17] This interruption halts oxidative phosphorylation in mitochondria almost immediately, marking the onset of energy failure. Within seconds of ischemia onset, particularly in complete ischemia, adenosine triphosphate (ATP) levels begin to deplete rapidly due to the reliance on aerobic metabolism, with significant reduction occurring within 1-2 minutes of oxygen deprivation.^[18] The decline in ATP impairs ATP-dependent ionic pumps, such as the sodium-potassium ATPase, leading to failure of membrane potential maintenance and subsequent neuronal depolarization. This depolarization is associated with cerebral blood flow thresholds around 15-18 mL/100 g/min for initial electrical failure, where synaptic transmission and electroencephalographic activity cease within 1-5 minutes. Immediately upon ischemia onset, cells shift to anaerobic glycolysis to compensate for energy needs, accelerating glucose breakdown to pyruvate and its conversion to lactate, which accumulates and causes intracellular acidosis with pH dropping below 6.8 within minutes to tens of minutes depending on severity.^[19] During this early phase, the changes remain potentially reversible; restoration of perfusion within approximately 15 minutes can allow neuronal recovery and prevent progression to irreversible damage, in contrast to prolonged ischemia exceeding this window.^[20]

Progression to Cellular Dysfunction

Following the initial hypoperfusion in cerebral ischemia, the ischemic cascade progresses to form the penumbra within the first 1-6 hours, a region of tissue surrounding the ischemic core that exhibits electrical dysfunction and metabolic compromise but remains structurally viable due to residual blood flow from collateral circulation.^[21] This penumbral zone, defined by cerebral blood flow thresholds between approximately 20-45% of baseline (10-22.5 ml/100 g/min in gray matter), experiences increased oxygen extraction and anaerobic metabolism, leading to lactate accumulation and pH decline, yet it can recover with timely reperfusion.^[22] Over days 1-7, cytotoxic and vasogenic edema peak, causing brain swelling and elevated intracranial pressure that further impairs perfusion and expands the infarct.^[23] Key transitions during this period include the propagation of spreading depression—a wave of neuronal depolarization traveling at 3-5 mm/min through the penumbra—which exacerbates energy demands and ionic imbalances, converting viable tissue to infarction if unchecked.^[24] Premature reperfusion can induce secondary injury through oxidative stress and inflammation, worsening edema and hemorrhage in the penumbra.^[25] The progression unfolds in distinct phases: the acute phase (0-24 hours) features rapid metabolic collapse with ATP depletion and cytotoxic edema in the core; the subacute phase (1-7 days) involves inflammatory expansion with neutrophil infiltration and vasogenic edema; and the chronic phase (>7 days) entails gliosis and tissue remodeling, forming glial scars that limit recovery.^[26] Factors such as robust collateral circulation can prolong penumbral viability by sustaining partial blood flow, thereby slowing progression, while comorbidities like diabetes accelerate the cascade by impairing microvascular integrity and reperfusion efficacy.^[27]

Molecular and Cellular Mechanisms

Energy Metabolism Failure

During cerebral ischemia, the lack of oxygen supply rapidly halts the mitochondrial electron transport chain, particularly at complex IV, preventing oxidative phosphorylation and leading to a profound reduction in adenosine triphosphate (ATP) production.^[28] Normal ATP concentrations in brain cells, typically ranging from 3 to 5 mM, drop to less than 1 mM within minutes of ischemia onset.^[29]^[30] As aerobic metabolism fails, cells shift to anaerobic glycolysis to generate ATP, producing only 2 molecules of ATP per glucose molecule compared to approximately 36 under aerobic conditions. This process is represented by the equation:

\text{C}_6\text{H}_{12}\text{O}_6 + 2 \text{ADP} + 2 \text{P}_i \rightarrow 2 \text{lactate} + 2 \text{ATP} + 2 \text{H}_2\text{O}

The accumulation of lactate as a byproduct causes cytosolic acidosis, further impairing cellular function.^[31]^[32] The depletion of ATP compromises the Na⁺/K⁺-ATPase pump, which normally maintains ionic gradients by extruding sodium ions; its failure results in sodium influx, osmotic water entry, and cytotoxic cell swelling.^[33]^[34] Neurons, which rely heavily on glucose for energy due to their high metabolic demands and limited energy reserves, experience the fastest depletion of substrates during ischemia, exacerbating vulnerability in affected brain regions.^[35]^[36]

Excitotoxicity and Calcium Dysregulation

During cerebral ischemia, energy depletion leads to neuronal depolarization, which triggers the excessive release of glutamate, the primary excitatory neurotransmitter, into the extracellular space. This glutamate overload overactivates ionotropic receptors, particularly N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, on neuronal membranes. The sustained activation of these receptors results in a massive influx of sodium (Na⁺) and calcium (Ca²⁺) ions, depolarizing the cell further and initiating a vicious cycle of excitotoxicity that amplifies ischemic damage.^[37]^[38]^[39] Calcium dysregulation is a central consequence of this receptor overactivation, with intracellular Ca²⁺ levels rising more than 10-fold above baseline due to the high permeability of NMDA channels to Ca²⁺. This excessive Ca²⁺ entry activates destructive enzymes, including proteases (e.g., calpains), lipases (e.g., phospholipase A2), and endonucleases, which degrade cellular proteins, membranes, and DNA, respectively, leading to irreversible neuronal injury. The NMDA receptor activation process is voltage-dependent and requires both glutamate and glycine as co-agonists, facilitating Ca²⁺ influx as follows:

\text{Glutamate + Glycine (co-agonist)} \rightarrow \text{NMDA receptor opening} \rightarrow \text{Ca}^{2+} \text{ influx}

This ionic imbalance peaks within the first 1-2 hours of ischemia, contributing significantly to acute neuronal death in the ischemic core.^[40]^[41]^[42] Mild ischemic preconditioning, involving brief sublethal episodes of ischemia, can confer tolerance by upregulating glutamate transporters such as GLT-1 (also known as EAAT2), which enhance extracellular glutamate clearance and mitigate subsequent excitotoxic overload. This adaptive response reduces receptor overactivation and Ca²⁺ dysregulation during a major ischemic event, highlighting a potential neuroprotective mechanism.^[43]^[44]^[45]

Oxidative Stress and Inflammation

During reperfusion following cerebral ischemia, oxidative stress arises primarily from the excessive production of reactive oxygen species (ROS), such as superoxide and hydroxyl radicals, generated through enzymatic pathways like xanthine oxidase activation and mitochondrial electron transport chain dysfunction.^[46] In damaged mitochondria, electron leakage from the respiratory chain reduces molecular oxygen to superoxide anion, as depicted in the reaction:

\mathrm{O_2 + e^- \rightarrow O_2^{\bullet-}}

^[47] This process is exacerbated by reperfusion, where restored oxygen supply overwhelms endogenous antioxidant defenses, leading to lipid peroxidation, protein oxidation, and DNA damage in neuronal and vascular cells.^[48] The inflammatory response in the ischemic cascade is triggered by resident glial cells, including microglia and astrocytes, which become activated shortly after the onset of ischemia. These cells release pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), along with chemokines that facilitate the recruitment of peripheral immune cells, notably neutrophils, which infiltrate the brain parenchyma within the first 24 hours post-ischemia.^[49] This cascade amplifies tissue injury by promoting further ROS production and enzymatic degradation of cellular components, creating a vicious cycle of inflammation and oxidative damage.^[50] Blood-brain barrier (BBB) integrity is compromised during the ischemic cascade due to oxidative and inflammatory insults, resulting in increased permeability and vasogenic edema. Endothelial tight junctions are disrupted by ROS-mediated signaling and cytokine-induced matrix metalloproteinase activation, allowing plasma proteins and fluid to leak into the brain tissue, with edema peaking between 24 and 72 hours after ischemia.^[51] This secondary injury contributes to intracranial pressure elevation and neuronal compression, worsening outcomes in ischemic conditions.^[52] Recent research from 2024 highlights the role of ferroptosis, an iron-dependent form of cell death driven by lipid peroxidation, in amplifying the inflammatory response during ischemia-reperfusion injury. Ferroptosis exacerbates neuroinflammation by releasing damage-associated molecular patterns that further activate microglia and promote cytokine storms, linking oxidative stress directly to prolonged immune-mediated damage.^[53] Studies indicate that inhibiting ferroptotic pathways, such as through glutathione peroxidase 4 modulation, may mitigate this amplification, offering potential therapeutic avenues.^[54] Calcium dysregulation from prior excitotoxic events can indirectly trigger ROS production, intensifying this oxidative-inflammatory interplay.^[47]

Cell Death Pathways

In the ischemic core, where severe energy depletion occurs, necrosis predominates as an uncontrolled form of cell death characterized by rapid cellular swelling, membrane rupture, and release of intracellular contents, primarily driven by ATP exhaustion.^[55] This process leads to secondary damage through inflammation and edema in surrounding tissues.^[56] In the penumbra region, where partial perfusion allows for delayed injury, apoptosis emerges as a programmed cell death pathway, involving the release of cytochrome c from mitochondria, which activates the caspase cascade leading to caspase-3 executioner function.^[57] This intrinsic mitochondrial pathway is influenced by calcium dysregulation, with the activation of procaspase-9 to active caspase-9 via the apoptosome as part of the broader apoptotic signaling.^[58]

\text{Procaspase-9} \rightarrow \text{[Active caspase-9](/page/caspase-9)}

Other cell death modalities contribute to the ischemic cascade, including autophagy, which can either promote survival by clearing damaged organelles or exacerbate injury when dysregulated; necroptosis, a regulated necrotic pathway involving RIPK3 and MLKL that amplifies inflammation; and ferroptosis, an iron-dependent form of lipid peroxidation driven by glutathione peroxidase 4 (GPX4) inhibition, which has gained significant attention in 2025 research for its role in neuronal damage post-ischemia.^[59]^[60]^[54] Necrosis manifests immediately in the core upon ischemia onset, whereas apoptosis unfolds over 24-72 hours in the penumbra, allowing a therapeutic window for intervention.^[61] Inflammation serves as an amplifier of these pathways, further propagating tissue damage.^[62]

Clinical Manifestations and Implications

Role in Ischemic Stroke

The ischemic cascade in stroke manifests as a rapid sequence of events triggered by occlusion of a cerebral artery, leading to focal neurological deficits that correspond to the affected vascular territory. For instance, middle cerebral artery occlusion often results in hemiparesis, aphasia, or hemianopia due to energy failure and excitotoxic neuronal damage in the supplied brain region.^[63] The severity of these deficits, as measured by the National Institutes of Health Stroke Scale (NIHSS), directly correlates with the extent of the ischemic core and penumbral involvement, with higher initial NIHSS scores indicating more advanced cascade progression and poorer early clinical outcomes.^[64] This progression underscores the focal nature of ischemic stroke, where the cascade's initiation causes immediate ionic imbalances and ATP depletion, evolving into widespread cellular dysfunction within minutes to hours if untreated.^[3] Imaging modalities provide critical correlates to the cascade's spatiotemporal dynamics in ischemic stroke. Diffusion-weighted magnetic resonance imaging (DWI-MRI) detects cytotoxic edema in the infarct core as restricted diffusion, becoming apparent within minutes of ischemia onset when cerebral blood flow falls below 30 mL/100 g/min.^[65] Perfusion computed tomography (CT), meanwhile, identifies the ischemic penumbra as hypoperfused but viable tissue through metrics like delayed time-to-maximum (>5-6 seconds) or preserved cerebral blood volume, highlighting regions at risk of recruitment into the infarct without prompt intervention.^[66] These findings allow clinicians to delineate the core from the salvageable penumbra, guiding therapeutic decisions based on the cascade's ongoing expansion. The ultimate outcomes of the ischemic cascade in stroke are profoundly influenced by its duration, with prolonged ischemia resulting in larger infarct volumes due to irreversible progression from penumbra to core infarction.^[67] Recent analyses indicate that approximately 25-36% of acute ischemic strokes exhibit a salvageable penumbra detectable on advanced imaging, particularly when reperfusion is achieved within the 4.5-hour window for intravenous thrombolysis, thereby limiting infarct growth and improving functional recovery.^[68]^[69] However, reperfusion itself can precipitate complications such as secondary intracranial hemorrhage, occurring in 6-7% of treated cases through mechanisms including blood-brain barrier breakdown from oxidative stress and matrix metalloproteinase activation—exacerbations of the cascade's inflammatory phase.^[70]

Involvement in Other Conditions

The ischemic cascade plays a critical role in global cerebral ischemia following cardiac arrest, where systemic hypoperfusion leads to widespread brain hypoxia and initiates energy failure, excitotoxicity, and inflammation across multiple regions.^[71] In this context, the hippocampus is particularly vulnerable, exhibiting selective neuronal damage that manifests as delayed neuronal death, typically 2–4 days post-event, due to progressive calcium dysregulation and apoptotic pathways.^[72] This delayed hippocampal injury contributes to cognitive deficits and higher mortality in survivors, distinguishing global ischemia from focal events by its uniform onset but regionally variable progression.^[73] Beyond the brain, the ischemic cascade manifests in peripheral organs, adapting to tissue-specific physiologies while retaining core elements of metabolic collapse and reperfusion injury. In myocardial ischemia, energy depletion from ATP hydrolysis triggers ion imbalances and acidosis, often culminating in arrhythmias such as ventricular tachycardia or fibrillation, which exacerbate contractile dysfunction and risk sudden cardiac death.^[74] Similarly, in renal ischemia associated with acute kidney injury, the cascade drives tubular epithelial cell necrosis and apoptosis through oxidative stress and inflammatory signaling, impairing filtration and promoting systemic complications like uremia.^[75] Notably, peripheral tissues demonstrate greater tolerance to ischemia compared to cerebral tissue, reflecting differences in metabolic reserves and oxygen demand. The heart, for instance, can withstand 20–40 minutes of global ischemia before irreversible damage, versus the brain's critical threshold of approximately 5 minutes, largely attributable to the myocardium's higher glycogen stores that support anaerobic glycolysis and delay acidosis.^[76]^[77] These glycogen reserves enable sustained substrate-level phosphorylation, preserving cellular homeostasis longer than in neurons, which rely heavily on continuous oxidative metabolism.^[78] Emerging research highlights overlaps between the ischemic cascade and traumatic brain injury (TBI), where mechanical disruption induces secondary hypoxic-ischemic insults that activate similar pathways of inflammation and cell death. Studies from 2024–2025 indicate that TBI elevates long-term ischemic stroke risk through vascular compromise and neuroinflammatory cascades, with hypoxic lesions frequently observed in the hippocampus and cortex, underscoring shared mechanisms amenable to targeted interventions.^[79]^[80]

Mitigation Strategies

Acute Reperfusion Therapies

Acute reperfusion therapies aim to restore cerebral blood flow promptly to halt the progression of the ischemic cascade in acute ischemic stroke. Intravenous thrombolysis with tissue plasminogen activator (tPA), specifically alteplase, is the primary pharmacological approach, administered as a bolus followed by infusion within a 4.5-hour window from symptom onset. Alteplase works by binding to fibrin in thrombi and converting plasminogen to plasmin, which degrades the clot and promotes recanalization.^[81] However, this therapy carries a risk of reperfusion injury upon blood flow restoration, potentially exacerbating cellular damage through oxidative stress and inflammation.^[82] For patients with large vessel occlusions, mechanical thrombectomy provides an endovascular alternative or adjunct, involving catheter-based retrieval of the clot to achieve rapid recanalization. This procedure is particularly effective in proximal occlusions, such as those in the internal carotid or middle cerebral artery, and has been shown to improve outcomes in select cases up to 24 hours from last known well, based on perfusion imaging criteria demonstrating a mismatch between infarct core and penumbra.^[83] The DAWN trial (2018) demonstrated that thrombectomy in this extended window resulted in better functional independence at 90 days compared to medical management alone.^[83] When administered within the therapeutic window, these therapies reduce the progression of the ischemic cascade and disability rates by 30-50% relative to standard care, as evidenced by increased odds of favorable outcomes in meta-analyses of randomized trials.^[84] Combined intravenous tPA followed by mechanical thrombectomy achieves recanalization rates of approximately 70% in eligible patients with large vessel occlusions.^[85] Despite these benefits, limitations include a risk of hemorrhagic transformation, occurring in 6-7% of cases treated with intravenous tPA, often manifesting as symptomatic intracranial hemorrhage.^[86] Patient selection based on imaging and time metrics remains crucial to maximize efficacy while minimizing complications.

Neuroprotective Interventions

Neuroprotective interventions aim to interrupt the downstream cellular processes of the ischemic cascade, such as excitotoxicity, inflammation, and cell death, particularly after reperfusion has been achieved to restore blood flow. These strategies focus on pharmacological agents and non-pharmacological approaches to preserve viable tissue in the ischemic penumbra, where cells are at risk but not yet irreversibly damaged. By targeting specific mechanisms like glutamate-mediated excitotoxicity and microglial activation—detailed in the molecular and cellular mechanisms section— these interventions seek to extend the therapeutic window beyond initial vascular recanalization. Agents targeting excitotoxicity, a key early event in the cascade involving excessive glutamate release and NMDA receptor overactivation, include NMDA receptor antagonists such as memantine. Memantine, an uncompetitive low-affinity antagonist, has shown neuroprotective effects in preclinical models of ischemic stroke by reducing neuronal apoptosis and calpain-caspase activation, with one rat study demonstrating approximately 50% reduction in infarct size when administered up to 2 hours post-ischemia. However, clinical trials in stroke patients have revealed limited efficacy, with high-dose memantine failing to significantly improve neurological outcomes in randomized studies, likely due to the drug's modest potency and challenges in achieving therapeutic brain concentrations without side effects. Therapeutic hypothermia represents a prominent non-pharmacological intervention that reduces cerebral metabolic demand and mitigates multiple cascade elements, including excitotoxicity and oxidative stress. Cooling to 33-35°C decreases the cerebral metabolic rate by approximately 6% for every 1°C reduction in brain temperature, thereby limiting energy failure and secondary injury. In clinical practice, induced hypothermia post-cardiac arrest—often targeting 32-34°C for 24 hours—has improved neurological outcomes, as evidenced by earlier trials showing higher rates of favorable recovery compared to normothermia; the 2013 Targeted Temperature Management (TTM) trial, while finding no difference between 33°C and 36°C, supported overall benefits of controlled cooling in comatose patients. Anti-inflammatory drugs, such as minocycline, target microglial activation and subsequent inflammatory cascades that exacerbate ischemic damage. Minocycline, a tetracycline derivative, inhibits microglia-mediated release of pro-inflammatory cytokines like IL-1β and reduces matrix metalloproteinase activity in animal models of focal cerebral ischemia, leading to smaller infarct volumes and improved behavioral outcomes when administered post-reperfusion. Preclinical studies in rats have consistently shown these effects, with neuroprotection persisting even with delayed dosing up to 24 hours, highlighting its potential to modulate the inflammatory phase of the cascade. Stem cell therapy is under investigation in clinical trials to salvage the penumbra by promoting tissue repair and anti-apoptotic effects. Mesenchymal stem cells, administered intravenously, have demonstrated safety and modest functional improvements in phase I/II trials for acute ischemic stroke, with mechanisms including secretion of neurotrophic factors that rescue apoptotic neurons in the peri-infarct region. A systematic review of multiple trials reported better clinical scores in treated patients, though larger phase III studies are needed to confirm efficacy for penumbra preservation. Despite these advances, neuroprotective interventions face significant challenges, including a narrow therapeutic window often limited to hours post-ischemia and high failure rates in phase III trials due to patient heterogeneity, such as variations in stroke severity and comorbidities. Over two decades of trials have seen most agents, including NMDA antagonists and free radical scavengers, succeed preclinically but fail clinically, underscoring the need for better translational models and combination therapies.

Emerging Therapies and Research

Recent advancements in targeting the ischemic cascade have focused on novel molecular pathways to mitigate mitochondrial dysfunction and iron-dependent cell death. Activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) has emerged as a promising strategy for mitochondrial protection, particularly through preconditioned olfactory mucosa-derived mesenchymal stem cells (OM-MSCs). A 2025 study demonstrated that hypoxia-preconditioned OM-MSCs enhance PGC-1α expression, thereby improving neuroinflammatory responses and reducing ischemic brain injury in preclinical models by promoting mitochondrial biogenesis and autophagic clearance.^[87] Similarly, overexpression of PGC-1α in microglia has been shown to alleviate inflammation and oxidative stress following cerebral ischemia by enhancing mitochondrial quality control mechanisms.^[88] In parallel, inhibitors of ferroptosis, an iron-mediated form of regulated cell death implicated in the later stages of the ischemic cascade, are advancing in preclinical evaluations. Ferrostatin-1, a potent ferroptosis inhibitor, has been tested in animal models of ischemic stroke, where it attenuates lipid peroxidation and neuronal damage, leading to reduced infarct size and improved neurological outcomes.^[54] Analogs like Srs11-92, derived from ferrostatin-1, further demonstrate efficacy in countering oxidative stress and ferroptosis during reperfusion, highlighting their potential to interrupt the cascade's propagation without exacerbating reperfusion injury.^[89] Gene editing technologies, such as CRISPR-Cas9, are being explored to modulate excitotoxicity-related genes, offering precise interventions against glutamate-mediated calcium overload. Preclinical research in 2024 utilized CRISPR-CasRx to downregulate Ripk1 and Nsf genes, which are linked to necroptosis and excitotoxic signaling, resulting in decreased stroke volume and enhanced neuronal recovery in ischemic models.^[90] Complementing these efforts, nanotechnology enables targeted delivery of therapeutics across the blood-brain barrier (BBB). Nanoparticle formulations of antioxidants, including polyphenol-based systems, have shown success in 2025 studies by facilitating BBB penetration and neutralizing reactive oxygen species in ischemic regions, thereby preserving endothelial integrity and reducing secondary injury.^[91] Thrombin-responsive nanoplatforms further enhance this approach by sequentially targeting thrombi and the BBB for sustained antioxidant release.^[92] Ongoing clinical trials from 2024 to 2025 are evaluating dynamic interventions for ischemia-reperfusion injury, emphasizing phased targeting of the pathological cascade. These trials incorporate neuroprotective agents and exosomes to modulate energy failure and inflammation in real-time, with promising results in reducing infarct expansion during reperfusion.^[93] For instance, strategies focusing on timely restoration of perfusion while inhibiting downstream cascade events, such as oxidative bursts, have demonstrated improved functional recovery in phase II studies.^[94] Looking ahead, future directions emphasize personalized medicine leveraging biomarkers of the ischemic cascade for tailored therapies. Emerging biomarkers, including inflammatory cytokines and cell-free DNA, enable stratification of patients based on cascade progression, facilitating individualized neuroprotective regimens.^[95] Artificial intelligence models are also advancing to predict cascade dynamics, with 2025 algorithms using MRI data to forecast post-intervention outcomes and guide dynamic treatment adjustments.^[96] These AI-driven predictions integrate multimodal data to anticipate ferroptosis or excitotoxicity risks, paving the way for precision interventions.^[97]

References

[1]
Ischemic Cascade - an overview | ScienceDirect Topics
The ischemic cascade is defined as a complex series of neurobiological events triggered by a loss of blood flow to the brain, leading to neuronal injury and ...
[2]
Signaling pathways involved in ischemic stroke - Nature
Jul 6, 2022 · Ischemic stroke is caused primarily by an interruption in cerebral blood flow, which induces severe neural injuries, and is one of the ...
[3]
Pathophysiologic cascades in ischemic stroke - PMC
In this minireview, we summarize the basics of ischemic cascades after stroke, covering neuronal death mechanisms, white matter pathophysiology, and ...
[4]
The role of neurophysiological tools in the evaluation of ischemic ...
Apr 27, 2023 · The ischemic cascade [modified from Endres et al. (7)]. This figure ... first described by Astrup and colleagues in the early '80s (14).
[5]
https://doi.org/10.1161/01.STR.12.6.723
[6]
Regulation of cerebral blood flow and metabolism during exercise
Aug 8, 2017 · The human brain, despite being only 2–3% of the total body mass while requiring ∼15% of the total cardiac output, consumes ∼20% of the total ...
[7]
Regulation of Cerebral Metabolic Rate - Basic Neurochemistry - NCBI
For a whole brain this amounts to almost 800 ml/min, or approximately 15% of the total basal cardiac output. This must be maintained within relatively narrow ...
[8]
Cerebral Blood Flow Autoregulation and Dysautoregulation - PMC
In healthy adults, the limits are between 50 and 150 mm Hg cerebral perfusion pressure (CPP) or 60 and 160 mm Hg mean arterial pressure (MAP), where CPP = MAP ...
[9]
Acute Stroke Imaging Part II: The Ischemic Penumbra
Jun 22, 2009 · Areas where CBF decreases below 10 ml/100g/min are irreversibly injured (infarct core). Tissue with. CBF between 10 and approximately 20 ml/100 ...
[10]
Regulation of cerebral blood flow | STROKE MANUAL
May 16, 2023 · 25% of basal glucose demand (~ 75-100 mg/min; ~5.6 mg glucose/100 g brain tissue/min) (Mergenthaler, 2013); 14-20% of cardiac output (CBF is ...
[11]
Cerebrovascular Disease - StatPearls - NCBI Bookshelf - NIH
Approximately 85% of strokes are ischemic and rest are hemorrhagic.[1] In this discussion, we mainly confine to ischemic strokes. Over the past several ...Cerebrovascular Disease · History And Physical · Treatment / Management
[12]
Transient Ischemic Attack (TIA) | American Stroke Association
A transient ischemic attack, or TIA, is a temporary blockage of blood flow to the brain. The clot usually dissolves on its own or gets dislodged.
[13]
Resuscitating the Globally Ischemic Brain: TTM and Beyond - PMC
Hemodynamic Changes. CA leads to reduced cerebral blood flow (CBF), initiating a cascade of primary metabolic dysfunction in the neurons and secondary ...
[14]
The ischemic cascade: Temporal sequence of hemodynamic ...
Each ischemic episode is initiated by an imbalance between myocardial oxygen supply and demand that may ultimately be manifested as angina pectoris.
[15]
[PDF] Ischaemic stroke - Burke Neurological Institute
This Primer describes the epidemiology, patho- physiology and diagnosis of ischaemic stroke and TIA. The acute reperfusion therapies are discussed in detail.
[16]
[PDF] 2 Biology of Cell Survival in the Cold - andrew.cmu.ed
2.3.1 The Ischemic Cascade ... The pivotal event is ATP depletion, which occurs within 1–2 minutes of oxygen deprivation.
[17]
Brain Lactic Acidosis and Ischemic Cell Damage: 1. Biochemistry ...
This study explores the influence of severe lactic acidosis in the ischemic rat brain on postischemic recovery of the tissue energy state and ...Missing: timeline | Show results with:timeline
[18]
The Critical Role of Spreading Depolarizations in Early Brain Injury
Mar 7, 2022 · However, if the ischemic core is reperfused within ~ 15 min, all neurons of the ischemic core will survive, even though the neurons have been ...
[19]
Thresholds in cerebral ischemia - the ischemic penumbra. | Stroke
Thresholds in cerebral ischemia - the ischemic penumbra. J Astrup, B K Siesjö, and L SymonAuthor Info & Affiliations ... /doi/10.1161/STROKEAHA.125.051270.Missing: et | Show results with:et
[20]
Viability thresholds and the penumbra of focal ischemia - Hossmann
The classic concept of the viability thresholds of ischemia differentiates between two critical flow rates, the threshold of electrical failure and the ...
[21]
https://www.ahajournals.org/doi/10.1161/01.str.12.6.723
[22]
Physiopathology of ischemic stroke and its modulation using ...
Energy Failure and Ionic Imbalance. Severe decrease of blood perfusion produces a depletion of oxygen and glucose and a consequent decline of ATP levels in ...Excitotoxicity And Calcium... · Peri-Infarct Depolarizations · Stages Of Ischemic Stroke
[23]
Pathobiology of ischaemic stroke: an integrated view - ScienceDirect
In this article, evidence will be presented that ischaemic brain injury results from a complex sequence of pathophysiological events that evolve over time and ...
[24]
The complexity of neurobiological processes in acute ischemic stroke
In this review, we describe how tissue damage following acute focal cerebral ischemia results from multiple complex pathophysiological processes.
[25]
The complexity of neurobiological processes in acute ischemic stroke
In this review, we summarize the actual knowledge on the pathophysiology of acute ischemic stroke. We focus on the ischemic cascade, which is a complex series ...
[26]
[PDF] Rescuing Ischemic Brain Injury by Rewiring Mitochondrial Electron ...
However, during ischemia, oxygen deprivation halts electron flow at complex IV, leading to respiratory chain reduction, ATP depletion, and metabolic ...
[27]
Spreading depolarizations exhaust neuronal ATP in a model ... - PNAS
Here, we show that SDs lead to a transient decrease in intracellular neuronal ATP even in presence of glucose and oxygen.Missing: timeline | Show results with:timeline
[28]
The neurobiological mechanisms and therapeutic prospect of ...
Feb 20, 2024 · Intracellularly, ATP concentration ranges around 5 mM ... It is possible that within the normal range of ATP concentration, insufficient ATP ...
[29]
Anaerobic Glycolysis and Ischemic Stroke: From Mechanisms and ...
Aug 14, 2024 · Energy supply by anaerobic glycolysis and acidosis caused by lactic acid accumulation are important pathological processes after ischemic stroke ...
[30]
2 Understanding cerebral energy metabolism: a key to successful ...
One of the damaging events has been postulated to be lactic acidosis; the accumulation of lactic acid due to increased glucose utilization via anaerobic ...
[31]
Molecular Mechanisms of Ischemic Cerebral Edema
The Na+-K+-ATPase pre- vents the intracellular accumulation of sodium ions, thus preventing an influx of solute and water that would result in cell swelling, ...
[32]
Ionic Regulation of Cell Volume Changes and Cell Death after ...
A few minutes after occlusion of cerebral blood flow, ischemic brain tissues become deprived of oxygen and glucose, resulting in mitochondrial dysfunction and ...
[33]
Deciphering the brain glucose metabolism: A gateway to innovative ...
May 29, 2025 · Among brain cells, neurons are the most susceptible to ischemia because of their high metabolic demand and low reservoir of energy substrates.
[34]
Sugar for the brain: the role of glucose in physiological and ...
Within minutes, glucose depletion and associated compromised bioenergetic pathways cause extensive neuronal death in the core of the infarction, and over time ...
[35]
Ischemia-Triggered Glutamate Excitotoxicity From the Perspective of ...
Mar 19, 2020 · Neuronal cells, astrocytes, microglia, NG2 glia, and oligodendrocytes all have their roles in what is known as glutamate excitotoxicity.
[36]
Excitotoxic injury in Hypoxia-Ischemia - Basic Neurochemistry - NCBI
NMDA and AMPA/kainate receptors contribute to excitotoxic neuronal degeneration. Excitotoxicity (toxic glutamate receptor activation) is a key mediator of ...
[37]
Excitotoxicity: Still Hammering the Ischemic Brain in 2020 - PMC
Glutamate receptors were classified into N-methyl-D-aspartate (NMDA) and non-NMDA types, the latter subsequently further divided into kainite and quisqualate ...Nmda Antagonists, Stroke... · Nmdars And Ca Source... · Excitotoxic Glial Cell Death
[38]
Ionized Intracellular Calcium Concentration Predicts Excitotoxic ...
After NMDA exposure, BTC reported a rapid increase in [Ca2+]i to 5–10 μm ... Intracellular calcium levels during the period of delayed excitotoxicity.
[39]
Molecular mechanisms of NMDA receptor-mediated excitotoxicity
... intracellular calcium, which activates cell death signaling to produce ... In ischemic regions, extracellular glutamate levels acutely rise several fold ...
[40]
Extrasynaptic NMDA receptors in acute and chronic excitotoxicity
Jul 3, 2023 · An ischemic insult, however, can cause rapid increases in glutamate concentration and excessive activation of NMDARs, leading to swift Ca2+ ...
[41]
In Vitro Ischemic Tolerance Involves Upregulation of Glutamate ...
A short ischemic event [ischemic preconditioning (IPC)] can result in a subsequent resistance to severe ischemic injury (ischemic tolerance).
[42]
Preconditioning and tolerance against cerebral ischaemia
Glutamate uptake by specific transporters is the most effective mechanism to maintain glutamate concentrations below excitotoxic concentrations. The glial ...
[43]
In vitro ischemic tolerance involves upregulation of glutamate ...
A short ischemic event [ischemic preconditioning (IPC)] can result in a subsequent resistance to severe ischemic injury (ischemic tolerance).
[44]
Targeting Oxidative Stress and Inflammation to Prevent Ischemia ...
Oxidative stress and inflammation are interactive and play critical roles in ischemia/reperfusion injury in the brain.
[45]
Oxidative Stress in Ischemic Brain Damage: Mechanisms of Cell ...
During brain ischemia/reperfusion, multiple detrimental processes take place, including overproduction of oxidants, inactivation of detoxification systems, and ...
[46]
Ischemia-reperfusion injury: molecular mechanisms and therapeutic ...
Jan 8, 2024 · Selenium alleviates cerebral ischemia/reperfusion injury by regulating oxidative stress, mitochondrial fusion and ferroptosis. Neurochem ...
[47]
Microglia in Ischemic Stroke: Pathogenesis Insights and Therapeutic ...
May 22, 2024 · This is caused by the excessive production of various cytotoxic factors including ROS, IL-1β, TNF-α, and nitric oxide (NO)., Microglial ...
[48]
Neuroinflammation: friend and foe for ischemic stroke
Jul 10, 2019 · However, during ischemic stroke, activated microglia have been shown to play a dual role, and they secrete pro-inflammatory cytokines resulting ...
[49]
Blood-brain barrier breakdown in brain ischemia: Insights from MRI ...
Dec 21, 2024 · Moreover, BBB breakdown can lead to vasogenic edema, characterized by the accumulation of fluid in the extracellular space due to increased ...
[50]
The blood brain barrier in cerebral ischemic injury – Disruption and ...
BBB dysfunction can be accompanied by a series of deleterious complications, including, cerebral edema, hemorrhage transformation, seizure and epilepsy, ...
[51]
The interplay between ferroptosis and inflammation - PubMed Central
Nov 8, 2024 · The relationship between inflammation and ferroptosis is increasingly recognized as vital in the process of cerebral ischemia-reperfusion (I/R).2. Ferroptosis And Cerebral... · 4.2. Ferroptosis Exacerbates... · 5. Therapeutic Mechanisms
[52]
https://www.sciencedirect.com/science/article/pii/S2589238X20300048
[53]
Apoptotic and Necrotic Death Mechanisms Are Concomitantly ...
Background and Purpose— Both necrotic and apoptotic cell death mechanisms are activated after cerebral ischemia. However, whether they are concomitantly ...
[54]
Necrosis predominates in the ischemic core, whereas apoptosis and...
Necrosis primarily occurs in the ischemic core, characterized by rapid and uncontrolled cell death ... Apoptosis is a highly conserved cell death pathway ...<|control11|><|separator|>
[55]
Apoptotic Mechanisms After Cerebral Ischemia | Stroke
Jan 29, 2009 · Recent research has revealed that many neurons in the ischemic penumbra or periinfarct zone may undergo apoptosis after several hours or days, ...Intrinsic Mechanisms Of... · Channels Mediating... · Extrinsic Mechanisms Of...
[56]
Calcium and apoptosis: ER-mitochondria Ca2+ transfer in the ... - PMC
Calcium (Ca2+) is a second messenger that shapes the signal for apoptosis. ER and mitochondria exchange Ca2+ and ER is a principal store of calcium.
[57]
Death and survival of neuronal and astrocytic cells in ischemic brain ...
Aug 1, 2011 · This article highlights the activation of autophagy during cerebral ischemia and/or reperfusion, especially in neurons and astrocytes.
[58]
Necroptosis: a regulated inflammatory mode of cell death
Jul 6, 2018 · Necroptosis is an alternative mode of regulated cell death mimicking features of apoptosis and necrosis.
[59]
Review Emerging immune and cell death mechanisms in stroke
Beside apoptosis, which occurs mainly in the penumbra within few hours to days after brain injury, necrosis starts in the first hours in the ischemic core.
[60]
Regulated necrosis pathways: a potential target for ischemic stroke
Nov 18, 2023 · In the infarct region, cell injuries follow either the regulated pathway involving precise signaling cascades, such as apoptosis and autophagy, ...
[61]
Ischemic Stroke - StatPearls - NCBI Bookshelf
Feb 21, 2025 · Ischemic stroke, the most common type of stroke, is caused by thrombotic or embolic occlusion that reduces blood flow to the brain. The ...Missing: cascade | Show results with:cascade
[62]
Progression in Acute Stroke | Stroke
This study suggests that the early clinical course of the neurological deficit after acute stroke is dependent on the initial stroke severity.
[63]
Challenging the Ischemic Core Concept in Acute Ischemic Stroke ...
Sep 16, 2020 · DWI-MRI measures cytotoxic edema, which occurs in ischemic brain cells at a CBF between 0 to 30/100 g/min and is manifested as a high DWI-signal ...
[64]
Review of Perfusion Imaging in Acute Ischemic Stroke
Feb 3, 2020 · In this review, we give an overview of computed tomography perfusion (CTP) and perfusion magnetic resonance imaging (MRP) in acute ischemic stroke.
[65]
Fast Versus Slow Progressors of Infarct Growth in Large Vessel ...
Aug 9, 2017 · We refer to patients with LVO who experience rapid infarct growth as fast progressors. These patients have failing collaterals and a large ischemic core.
[66]
Molecular Mechanisms of Ischemic Stroke: A Review Integrating ...
Apr 7, 2024 · Ischemic stroke (IS) immediately triggers a complex molecular and cellular process known as the ischemic cascade. The process sequentially ...
[67]
Stroke Reperfusion Injury - StatPearls - NCBI Bookshelf - NIH
May 16, 2024 · Stroke reperfusion injury refers to the exacerbation of cellular dysfunction and death upon restoration of blood flow to previously ischemic brain tissues.
[68]
Brain injury after cardiac arrest: pathophysiology, treatment, and ...
Oct 27, 2021 · Post-cardiac arrest brain injury (PCABI) is caused by initial ischaemia and subsequent reperfusion of the brain following resuscitation.
[69]
Selective Dysfunction of Hippocampal CA1 Astrocytes Contributes to ...
Apr 18, 2007 · Transient global ischemia, as with cardiac arrest, causes loss of CA1 hippocampal neurons 2–4 d later, whereas nearby dentate gyrus (DG) neurons are relatively ...
[70]
Delayed neuronal death and delayed neuronal recovery in the ...
The data obtained demonstrate the occurrence of delayed neuronal death in human hippocampus and, in a minor form, in cerebellar Purkinje cells. This is in ...
[71]
Cardiac ischemia on-a-chip to investigate cellular and molecular ...
These complex cellular cascades and pathophysiologies that occur in response to myocardial ischemia can result in arrhythmias and potentially heart failure.
[72]
Mechanisms and therapeutic targets of ischemic acute kidney injury
Dec 31, 2019 · Renal ischemia and subsequent reperfusion injury initiates signaling cascades mediating renal cell necrosis, apoptosis, and inflammation, leading to AKI.
[73]
Guidelines for experimental models of myocardial ischemia and ...
Apr 9, 2018 · Ischemic cardiomyopathy is the most common cause of heart failure and can arise from remodeling after an acute ST segment elevation myocardial ...In Vitro And Ex Vivo Models · Chronic Coronary Artery... · Coronary Stenosis And...
[74]
Brain tissue responses to ischemia - PMC - NIH
The brain is particularly vulnerable to ischemia. Complete interruption of blood flow to the brain for only 5 minutes triggers the death of vulnerable neurons.
[75]
Ischemic injury of the developing heart - PMC - NIH
The high stores of glycogen that characterize the fetal and newborn myocardium are essential for enhancing tolerance to oxygen deprivation, but these decrease ...
[76]
Risk of Long-Term Ischemic Stroke in Patients With Traumatic Brain ...
Apr 22, 2024 · Emerging data suggest that TBI is associated with increased risk of ischemic stroke, as is hypertension. Previously, the factors that mediate ...
[77]
Cerebral Vascular Disturbances Following Traumatic Brain Injury
Sep 18, 2025 · Similarly, Laaksonen et al. (2024), in a forensic autopsy study, found frequent hypoxic–ischemic lesions in the hippocampus and cerebral cortex ...
[78]
Tissue Plasminogen Activator Therapy - StatPearls - NCBI Bookshelf
Aug 9, 2025 · Administration of alteplase is highly time-sensitive, particularly in ischemic stroke, and requires accurate weight-based dosing, careful ...
[79]
Neurovascular Inflammation and Complications of Thrombolysis ...
Sep 7, 2023 · However, tPA administration is accompanied by reperfusion injury, including increased risk of hemorrhagic transformation (HT). In addition, ...
[80]
Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between ...
Nov 11, 2017 · The DAWN trial was a multicenter, prospective, randomized, open-label trial with a Bayesian adaptive–enrichment design and with blinded ...
[81]
A cost-utility analysis of mechanical thrombectomy as an adjunct to ...
Results: For the baseline scenario, the recanalization rate was 72.9% for the interventional strategy and 46.2% for the medical strategy. For the interventional ...
[82]
Tissue Plasminogen Activator for Acute Ischemic Stroke
Dec 14, 1995 · Symptomatic intracerebral hemorrhage within 36 hours after the onset of stroke occurred in 6.4 percent of patients given t-PA but only 0.6 ...
[83]
https://www.nejm.org/doi/full/10.1056/NEJMoa1706442
[84]
Mitochondrial Quality Control: Insights into Intracerebral Hemorrhage
Aug 14, 2025 · Overexpression of microglial PGC-1α enhances mitochondrial autophagic clearance, reduces NLRP3 activation, and alleviates inflammation (Han et ...
[85]
Srs11‐92, a ferrostatin‐1 analog, improves oxidative stress and ...
Feb 27, 2023 · Preclinical studies have shown that early intervention of ferroptosis inhibitor ferrostatin‐1 (Fer‐1) or liproxstatin‐1 effectively improves ...
[86]
Downregulation of Ripk1 and Nsf mediated by CRISPR-CasRx ...
Jun 10, 2024 · And the results in this study demonstrated reduced stroke volume and improved neuronal deficits after stroke intervened by CasRx-Ripk1-Nsf, ...
[87]
A Universal Strategy for BBB Transport Mediated by an Inflammatory ...
Sep 8, 2025 · Schematic illustration of the design and mechanism of receptor antagonist-guided polyphenol nanoparticles for ischemic stroke treatment.
[88]
Developing targeted antioxidant nanomedicines for ischemic ...
May 7, 2024 · The thrombin-responsive "nanoplatelet" platform has sequential targeting abilities for both thrombi and the BBB, improving drug efficacy, ...
[89]
Cerebral ischemia-reperfusion injury: mechanisms and promising ...
This review summarizes current treatment approaches for Cerebral I/R injury, which include traditional drugs, antioxidants, neuroprotective agents, exosomes, ...
[90]
Dynamic mechanisms and targeted interventions in cerebral ...
For ischemic stroke, timely restoration of blood flow for reperfusion is the key to treatment. To date, methods such as intravenous thrombolysis and mechanical ...
[91]
Emerging biomarkers in ischemic stroke - PMC - PubMed Central
Aug 14, 2025 · These newly developed biomarkers would allow personalized treatment and prognostic approaches for the patients. Although numerous ...
[92]
AI post-intervention operational and functional outcomes prediction ...
Aug 14, 2025 · AI post-intervention operational and functional outcomes prediction in ischemic stroke patients using MRIs. Emily Wittrup,; John Reavey ...
[93]
Predicting Stroke Treatment Outcomes with Deep Learning - ScaDS.AI
Aug 26, 2025 · AI predicts who benefits most from thrombectomy, helping doctors make faster, precise decisions to improve stroke outcomes.