PDF(Pubmed)
Abstract：
(+)-JQ1, a specific chemical inhibitor of bromodomain and extraterminal (BET) family protein 4 (BRD4), has been reported to inhibit smooth muscle cell (SMC) proliferation and mouse neointima formation via BRD4 regulation and modulate endothelial nitric oxide synthase (eNOS) activity. This study aimed to investigate the effects of (+)-JQ1 on smooth muscle contractility and the underlying mechanisms. Using wire myography, we discovered that (+)-JQ1 inhibited contractile responses in mouse aortas with or without functional endothelium, reducing myosin light chain 20 (LC20) phosphorylation and relying on extracellular Ca2+. In mouse aortas lacking functional endothelium, BRD4 knockout did not alter the inhibition of contractile responses by (+)-JQ1. In primary cultured SMCs, (+)-JQ1 inhibited Ca2+ influx. In aortas with intact endothelium, (+)-JQ1 inhibition of contractile responses was reversed by NOS inhibition (L-NAME) or guanylyl cyclase inhibition (ODQ) and by blocking the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway. In cultured human umbilical vein endothelial cells (HUVECs), (+)-JQ1 rapidly activated AKT and eNOS, which was reversed by PI3K or ATK inhibition. Intraperitoneal injection of (+)-JQ1 reduced mouse systolic blood pressure, an effect blocked by co-treatment with L-NAME. Interestingly, (+)-JQ1 inhibition of aortic contractility and its activation of eNOS and AKT were mimicked by the (-)-JQ1 enantiomer, which is structurally incapable of inhibiting BET bromodomains. In summary, our data suggest that (+)-JQ1 directly inhibits smooth muscle contractility and indirectly activates the PI3K/AKT/eNOS cascade in endothelial cells; however, these effects appear unrelated to BET inhibition. We conclude that (+)-JQ1 exhibits an off-target effect on vascular contractility.
摘要：
（+）-JQ1，溴结构域和外端（BET）家族蛋白4（BRD4）的特异性化学抑制剂，据报道，通过BRD4调节抑制平滑肌细胞（SMC）增殖和小鼠新内膜形成，并调节内皮型一氧化氮合酶（eNOS）活性。本研究旨在探讨(+)-JQ1对平滑肌收缩性的影响及其机制。使用导线肌电图,我们发现（+）-JQ1抑制有或没有功能性内皮的小鼠主动脉的收缩反应，减少肌球蛋白轻链20（LC20）磷酸化并依赖细胞外Ca2。在缺乏功能性内皮的小鼠主动脉中，BRD4敲除不改变(+)-JQ1对收缩反应的抑制。在原代培养的SMC中，(+)-JQ1抑制Ca2+内流。在完整内皮的主动脉中，通过NOS抑制（L-NAME）或鸟苷酸环化酶抑制（ODQ）并通过阻断磷脂酰肌醇3-激酶（PI3K）/蛋白激酶B（AKT）途径来逆转（）-JQ1对收缩反应的抑制。在培养的人脐静脉内皮细胞（HUVECs）中，(+)-JQ1快速激活AKT和eNOS,被PI3K或ATK抑制逆转。腹腔注射(+)-JQ1可降低小鼠收缩压,与L-NAME共同治疗阻断的效果。有趣的是,（-）-JQ1对映体模拟（-）-JQ1对主动脉收缩的抑制作用及其对eNOS和AKT的激活，在结构上不能抑制BET溴结构域。总之,我们的数据表明，(+)-JQ1直接抑制平滑肌收缩，间接激活内皮细胞中的PI3K/AKT/eNOS级联反应；然而，这些作用似乎与BET抑制无关。我们得出的结论是，（）-JQ1对血管收缩性具有脱靶作用。
