Stroke neuroprotection revisited: Intra-arterial verapamil is profoundly neuroprotective in experimental acute ischemic stroke

Abstract

While clinical trials have now solidified the role of thrombectomy in emergent large vessel occlusive stroke, additional therapies are needed to optimize patient outcome. Using our previously described experimental ischemic stroke model for evaluating adjunctive intra-arterial drug therapy after vessel recanalization, we studied the potential neuroprotective effects of verapamil. A calcium channel blocker, verapamil is often infused intra-arterially by neurointerventionalists to treat cerebral vasospasm. Such a direct route of administration allows for both focused targeting of stroke-impacted brain tissue and minimizes potential systemic side effects. Intra-arterial administration of verapamil at a flow rate of 2.5 µl/min and injection volume of 10 µl immediately after middle cerebral artery recanalization in C57/Bl6 mice was shown to be profoundly neuroprotective as compared to intra-arterial vehicle-treated stroke controls. Specifically, we noted a significant (P ≤ 0.05) decrease in infarct volume, astrogliosis, and cellular apoptosis as well as a significant increase in neuronal survival and functional outcome over seven days. Furthermore, intra-arterial administration of verapamil was well tolerated with no hemorrhage, systemic side effects, or increased mortality. Thus, verapamil administered intra-arterially immediately following recanalization in experimental ischemic stroke is both safe and neuroprotective and merits further study as a potential therapeutic adjunct to thrombectomy.

Prevention of Severe Hypoglycemia-Induced Brain Damage and Cognitive Impairment With Verapamil

“…Excess calcium influx from the endoplasm reticulum and extracellular space initiates a positive feedback loop that leads to brain cell necrosis (9,11). Consistent with a major role of calcium influx in mediating other types of brain damage, treatment with the calcium-channel blocker, verapamil, has been shown to reduce neural damage by up to 96% in other models of brain injury (12,13).To test the hypothesis that verapamil administration (during the recovery period immediately after an episode of severe hypoglycemia) may prevent brain damage, experimental rats were subjected to an episode of insulininduced severe hypoglycemic (10-15 mg/dL), followed by treatment with or without verapamil. Results demonstrate that a one-time treatment with verapamil prevented ;90% of the hypoglycemia-induced neural damage and completely prevented the hypoglycemia-induced cognitive impairment.…”

“…These experiments did not directly examine the precise mechanism by which verapamil was able to prevent neural damage. Because verapamil crosses the blood-brain barrier and can reduce ischemic brain damage (12,13) and synaptic activation in neurons (13,22), verapamil's neuroprotective effect could be mediated via direct blockade of neuron calcium influx or indirectly through an unknown mechanism. Regardless of the mechanism, verapamil's effect was profound in completely preventing neural damage and cognitive dysfunction mediated by severe hypoglycemia.…”

“…Excess calcium influx from the endoplasm reticulum and extracellular space initiates a positive feedback loop that leads to brain cell necrosis (9,11). Consistent with a major role of calcium influx in mediating other types of brain damage, treatment with the calcium-channel blocker, verapamil, has been shown to reduce neural damage by up to 96% in other models of brain injury (12,13).…”

Intra-arterial verapamil post-thrombectomy is feasible, safe, and neuroprotective in stroke

“…18 We demonstrated that, when administered IA following recanalization, verapamil was physiologically safe (heart rate and blood pressure), and it significantly reduced infarct volume and significantly improved functional outcome. 19 Furthermore, IA verapamil did not significantly alter post-reperfusion flow or cerebral perfusion, suggesting a therapeutic mechanism separate from its vasodilatory effects, possibly related to reduction of excitotoxic damage through its calcium channel activity. 19 We hypothesize that verapamil is a safe, feasible, and efficacious neuroprotectant for direct administration after thrombectomy.…”

“…For surviving animals, euthanasia occurred via cervical dislocation at seven days, whereupon the whole brain was removed, and either cut and stained with TTC, or flash frozen, sectioned on the cryostat (20 mm), and stained with Cresyl Violet for infarct volume using methods previously detailed. 18,19 NeuN immunohistochemistry was performed to evaluate mature neuron survival (1:1000 antibody dilution, Abcam) in the peri-infarct region. This corresponds to the cortical region that was the epicenter of the stroke morphologically identified based on cryostat sectioning to include the greatest affected area.…”