VX‐745 Inhibits Smooth Muscle Cell p38 Mitogen‐Activated Protein Kinase Alpha (MAPKα) and Heat‐Shock Protein 27 (Hsp27) Phosphorylation to Induce Vasodilation in Resistance Mesenteric Arteries

Abstract

VX‐745, a selective inhibitor of the alpha isoform of the mitogen‐activated serine/threonine protein kinase p38 MAPK, is under clinical investigation for its efficacy in Alzheimer’s disease (AD) and dementia with Lewy Bodies (DLB). Although enhanced vascular tone and hypertension contribute to cognitive impairment in AD and DLB, no studies have examined if acute VX‐745 application could relax resistance arteries that control vascular resistance and blood pressure. Here, we investigated if VX‐745 could induce vasodilation in resistance‐size rat mesenteric arteries and the underlying mechanisms. Freshly isolated fourth order rat mesenteric arteries were cannulated and maintained in a temperature‐controlled perfusion chamber. Arterial segments were subjected to a stepwise increase in intraluminal pressure to 80 mmHg. Development of sustained myogenic tone at 80 mmHg generated a baseline diameter after which a cumulative concentration‐responses (100 pM to 10 μM) to VX‐745 were performed and diameter changes recorded. Our pressure myography data showed that VX‐745 produced a dose‐dependent vasodilation in mesenteric arteries. On application of 10 μM VX‐745 the mesenteric arteries dilated by ~μm after 2 to 3 minutes of drug application. Vasodilation induced by VX‐745 remained unchanged upon endothelium denudation (intact ~41 μm vs denuded ~38 μm), suggesting an endothelium‐independent mechanism. Endothelium denudation or pharmacological inhibition of endothelium‐derived vasodilators such as nitric oxide (NO) and prostacyclin (PGI2) had no effect on such vasodilation. Our Western blotting data revealed that acute VX‐745 treatment significantly reduced the phosphorylation of p38 MAPKα by 33.74±0.3.7% compared to that in control arteries and its downstream target heat‐shock protein 27 (Hsp27) involved in cytoskeletal reorganization and smooth muscle contraction by 37.75±1.19% compared to control arteries. Likewise, non‐selective inhibition of p38 MAPK by SB203580 attenuated p38 MAPKα and Hsp27 phosphorylation by 32.25±0.1.8% and 31.57±3.47% respectively compared to control arteries and induced vasodilation in mesenteric arteries. VX‐745‐evoked vasorelaxation remained unaltered by the inhibition of smooth muscle cell large‐conductance Ca2+‐activated K+ channels (BKCa), ATP‐sensitive K+ channels (KATP), and voltage‐gated K+ channels (KV). Altogether, our data for the first time demonstrates that, in resistance mesenteric arteries, VX‐745‐mediated selective inhibition of p38 MAPKα reduces the phosphorylation of the actin‐associated protein Hsp27, leading to vasodilation. This novel finding may be clinically significant and is likely to improve systemic blood pressure and cognitive deficits in AD and DLB patients for which VX‐745 is being investigated.