Rho-Kinase Inhibition Improves Ischemic Perfusion Deficit in Hyperlipidemic Mice

Abstract

Hyperlipidemia is a major cardiovascular risk factor associated with progressive cerebrovascular dysfunction and diminished collateral perfusion in stroke. Rho-associated kinase (ROCK) may be an important mediator of hyperlipidemic vascular dysfunction. We tested the efficacy of acute or chronic ROCK inhibition on the size of dynamic perfusion defect using laser speckle flowmetry in hyperlipidemic apolipoprotein E knockout mice fed on a high-fat diet for 8 weeks. Mice were studied at an age before the development of flow-limiting atherosclerotic stenoses in aorta and major cervical arteries. Focal ischemia was induced by distal middle cerebral artery occlusion (dMCAO) during optical imaging. The ROCK inhibitor fasudil (10 mg/kg) was administered either as a single dose 1 hour before ischemia onset, or daily for 4 weeks. Fasudil decreased both baseline arterial blood pressure and cerebrovascular resistance (CVR) by B15%, and significantly improved tissue perfusion during dMCAO. Interestingly, peri-infarct depolarizations were also reduced. Chronic treatment did not further enhance these benefits compared with acute treatment with a single dose. These data show that ROCK inhibition improves CVR and ischemic tissue perfusion in hyperlipidemic mice. Keywords: ApoE knockout; distal middle cerebral artery occlusion; fasudil; hydroxyfasudil; hyperlipidemia; laser speckle flowmetry INTRODUCTION Hyperlipidemia is among the most prevalent vascular risk factors associated with stroke. Vascular endothelial and smooth muscle dysfunction has been shown in hyperlipidemic animal models as well as in patients. 1,2 In cerebral vasculature, hyperlipidemia impairs endothelium-dependent relaxations, 3 diminishes resting perfusion, and blunts major vasodilator reflexes, such as neurovascular coupling, hypercapnic hyperemia, and autoregulation. 4 We have recently shown that hyperlipidemic vascular dysfunction is associated with markedly larger perfusion defects on focal cerebral arterial occlusion. 4 A large body of evidence suggests that upregulation of Rho-associated kinase (ROCK) activity is one mechanism by which hyperlipidemia leads to vascular dysfunction. [5][6][7][8] Numerous studies have also shown that ROCK inhibition improves stroke outcome in otherwise normal animals, 9 and that the mechanism involves endothelium-dependent improvement in ischemic tissue perfusion presumably by augmenting the collateral blood supply. 10 Because hyperlipidemia is associated with upregulation of ROCK activity, we tested the efficacy of ROCK inhibitors in improving cortical perfusion on focal arterial occlusion in hyperlipidemic apolipoprotein E knockout (ApoE KO) mice. Journal of Cerebral

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“…13 Fasudil, the clinically prescribed analog of Y27632, is used to prevent vasospasms after subarachnoid hemorrhage, 28 to improve tissue perfusion during cerebral ischemia, 29 to prevent the progression of cerebral aneurisms. 30 Our work suggests that Fasudil might be used to improve the delivery of Pgp substrates through the BBB.…”

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“…Sixty minutes after collagenase injection, mice were treated with isoform non‐selective ROCK inhibitor fasudil (IC50 2–10 μ mol/L; 10 mg/kg in saline, intraperitoneal; Tocris, Bristol, UK) or ROCK2‐selective inhibitor KD025 (IC50 of 60 nmol/L; 200 mg/kg in 0.4% cyclodextrin suspension, oral gavage; kindly provided by Kadmon, New York, NY), and compared to their respective vehicles. These doses were selected as the most efficacious in previous studies . Although the half‐life of fasudil is under 30 min after intraperitoneal administration, its active metabolite hydroxyfasudil has a longer half‐life (~1 h) .…”

“…For almost two decades ROCK has been explored as a therapeutic target in cerebrovascular diseases. In experimental focal cerebral ischemia, ROCK inhibition has been uniformly efficacious …”

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“…Abnormal activation of ROCK is thought to have a key role in numerous pathologies, including hypertension, diabetes and atherosclerosis, conditions known to have poor outcome from stroke [30-33]. Stroke injury is also linked to ROCK activation through hemodynamic and microvascular dysfunction as well inflammation and oxidative stress [34-38]. Numerous animal studies have shown that inhibition of ROCK improves stroke outcome in normal as well as diseased animals, likely through several mechanisms including augmenting collateral flow [35-40].…”