NLRP3炎症小体在血管稳态失衡和重构中的作用机制

Chronic activation of NLRP3 inflammasomes causes atherosclerosis or hypertension. The imbalance of vascular homeostasis and vascular remodeling is the common pathophysiological conditions for both atherosclerosis and hypertension, but the underlying mechanism for inflammasome-mediated vascular remodeling is not well known. Recent evidence shows that vascular endothelial cells and smooth muscle cells in atherosclerosis and hypertensive subjects have increased mitochondrial oxidative phosphorylation for cellular energy sources compared to normal condition, indicating the abnormal energic metabolism might be the underlying mechanisms for imbalance of vascular homeostasis and vascular remodeling in atherosclerosis and hypertension. Our preliminary data show that the activity of pyruvate dehydrogenase complex and oxygen consumption rate have increased in vascular endothelial cells and smooth muscle cells co-cultured respectively with lipopolysaccharide-treated monocytes and CD4+ T lymphocytes, therefore we hypothesize that activation of NLRP3 inflammasomes causes imbalance of vascular homeostasis and vascular remodeling is through increased activity of pyruvate dehydrogenase complex and abnormal energy metabolism, which eventually resulting in atherosclerosis or hypertension. To test the hypothesis, we propose to study the mechanisms of activation of NLRP3 inflammasomes on PDC activities and the energy metabolism, vascular homeostasis and remodeling, and development of atherosclerosis and hypertension in monocytes, ApoE-/- mice with conditional deficiency of Akt, SGK3, or PDC components, and atherosclerosis and hypertensive subjects. Fluorescence probes and nanoparticles targeting to pyruvate dehydrogenase complex for early diagnosis and therapy of atherosclerosis and hypertension have also been proposed in this study. Overall, this study will help us further understand the role and mechanisms of NLRP3 inflammasomes in the vascular homeostasis and remodeling and pathogenesis of atherosclerosis and hypertension, which will have theoretical and applied significance in the prevention and therapy of atherosclerosis and hypertension.

NLRP3炎症小体的活化可导致动脉粥样硬化或高血压。血管稳态失衡和血管重构是动脉粥样硬化和高血压的共同病理生理基础，但其机制并不完全清楚。近期报道动脉粥样硬化和高血压时，血管内皮细胞(EC)和平滑肌细胞(VSMC)由氧化磷酸化供能较正常时显著增加，提示能量代谢异常可能导致血管稳态失衡和血管重构。我们的前期研究发现，脂多糖处理的单核巨噬细胞和CD4+ T淋巴细胞，与EC和VSMC分别共培养后，EC和VSMC丙酮酸脱氢酶复合体（PDC）活性增高，氧耗量增加，因而推测炎症小体活化是通过PDC活性增高所致的代谢异常而致血管稳态失衡和血管重构。为证实这一假说，本项目拟在细胞、PDC各亚基条件性（EC或VSMC）基因敲除小鼠、动脉粥样硬化和高血压病人的多层面上，深入探讨炎症小体活化所致的能量代谢异常，对血管稳态失衡和血管重构的调控，并探索针对PDC的荧光探针和纳米粒子对动脉粥样硬化和高血压的早期预警。

血管稳态失衡和血管重构是动脉粥样硬化（AS）和高血压的共同病理生理基础，研究发现NLRP3炎症小体的活化可导致AS或高血压，但其参与血管稳态失衡和重构的机制仍不完全清楚。本项研究发现NLRP3在非AKT依赖途径调控AS的发生发展中起关键作用，SGK家族是重要节点。通过抑制THP-1巨噬细胞中PI3K或AKT可抑制ox-LDL诱导的NF-kB信号通路的激活，抑制NLRP3炎症小体的活化，减少IL-1β和 IL-18的表达，而PI3K的抑制作用更强。抑制PI3K或 AKT能够减轻ApoE-/-小鼠AS的形成，减少NLRP3和IL-1β的表达水平，且PI3K的抑制作用更强，提示存在非AKT依赖的途径参与NLRP3调控AS形成。明确SGK3作为PI3K信号通路非AKT依赖途径的新靶点，在AS发生、发展中发挥着重要的调控作用。敲除SGK3有效抑制小鼠AS形成，改善主动脉血管内膜斑块形成、脂质沉积及纤维增生，减少病变中脂蛋白受体LOX-1、血管粘附因子VACM-1、CD68、P-P65的表达，缓解小鼠全身炎症疾病状态。将过表达SGK3-K191M突变至THP-1细胞中，P65磷酸化水平及P65的核定位不受影响，提示PI3K/SGK3途径通过NF-kB活化和入核减轻AS形成。临床水平上，冠心病患者外周血单核细胞中SGK家族、NLRP3、下游因子以及丙酮酸脱氢酶（PDH）及丙酮酸脱氢酶激酶（PDK）的表达水平明显增加。同时我们发现NLRP3调控盐敏感高血压大鼠心肌重构。NLRP3抑制剂MCC950可减轻SS大鼠的心肌肥大、纤维化，并发现可能通过TGF-β-Smad2/3通路减轻心肌纤维化，同时SS大鼠心肌炎症水平明显增加，MCC950能够减轻下游IL-1、IL-18炎症表达。另外，Rac3通过下调自噬调节NLRP3，促进ox-LDL诱导的内皮功能障碍，影响AS的形成。综上，应用骨髓移植技术、基因敲除等技术，研究发现PI3K/SGK家族能够通过影响NLRP3及下游炎症因子对AS或高血压心肌肥厚起到调控作用，提示NLRP3在血管稳态失衡和重构中起到至关重要的作用，可能成为治疗动脉粥样硬化和高血压的新靶点。