P物质调控巨噬细胞M2极化促进脓毒症右心室纤维化的作用和机制

High incidence of right ventricular insufficiency in sepsis is associated with poor long-term prognosis and is an important clinical problem. Recent studies have shown that myocardial fibrosis induced by M2 polarization of mononuclear macrophages may be the pathologic basis of cardiac insufficiency. However, the process behind this pathology remains unknown. In our previous study, we successfully constructed a model of sepsis mice with right ventricular fibrosis by bacterial lipopolysaccharide (LPS). The mouse right ventricle enriched M2-polarized mononuclear macrophages and showed significant fibrosis at 4 weeks. Interestingly, a small neuropeptide called substance P (SP) was also increased in the early as well as in the later stage of sepsis. Furthermore, our in vitro studies showed that SP was able to activate peroxisome proliferators-activated receptors gamma (PPARγ), which was crucial in regulating M2 polarization. Hence, we estimated that SP might promote M2 macrophages polarization by regulating PPARγ levels, which in turn might play an important role in inducing right ventricular fibrosis in sepsis. In this program, we will explore the key role of SP in the development of right ventricular fibrosis in sepsis. Besides, by PPARγ gene knockout mice, we will further explore the exact regulation mechanism of SP-induced M2 polarization, which promotes right ventricular fibrosis in sepsis. This study will reveal the pathological mechanism of right ventricular dysfunction in sepsis, and provide a new idea to improve the long-term survival rate of patients with sepsis.

脓毒症时右心功能不全发生率高，长期预后差，是临床面临的重要难题。最新研究表明单核巨噬细胞M2极化诱导的心肌纤维化可能是心功能不全的病理基础，但诱因不明。我们前期研究以细菌脂多糖(LPS)成功构建了右心室纤维化的脓毒症小鼠模型。该小鼠右心室富集M2极化的单核巨噬细胞并在4周时出现明显纤维化样病变。进一步检测发现小分子神经肽P物质(SP)在脓毒症早期于右心室中上调并持续增高。体外细胞实验显示SP能够激活巨噬细胞M2极化调控蛋白过氧化物酶体增生激活受体γ(PPARγ)，因此我们推测SP激活PAPRγ促进单核巨噬细胞M2极化可能是脓毒症右心室纤维化的重要诱因。本课题拟探索SP在脓毒症右心纤维化发生发展中的关键作用，并使用PPARγ基因敲除小鼠进一步探究SP诱导巨噬细胞M2极化促进脓毒症右心纤维化的确切调控环节，为揭示脓毒症右心功能不全的病理机制、最终提高脓毒症患者远期生存率提供新的思路。

脓毒症时右心功能不全发生率高，长期预后差，是临床面临的重要难题。研究表明单核巨噬细胞M2极化诱导的心肌纤维化可能是心功能不全的病理基础，但诱因不明。本项目的研究内容包括：1.以细菌脂多糖(LPS)成功构建了右心室纤维化的脓毒症小鼠模型，明确小鼠心脏组织P物质水平升高、巨噬细胞发生极性转化，心脏出现明显的纤维化病变。2.体外实验使用P物质(SP)与巨噬细胞共孵育，SP能够正反馈调节巨噬细胞进一步分泌SP，并呈现浓度依赖性；以SP与巨噬细胞共孵育，M1极化亚型表面分子iNOS及CD86蛋白表达减少，而M2极化亚型表面分子arg-1、CD206表达增加，且该作用随SP的浓度增加、时间延长而增强；NK-1受体拮抗剂能够减少SP的上述作用。说明SP与NK-1受体结合诱导巨噬细胞向M2亚型极化。3.体外实验发现SP诱导巨噬细胞活化，PPARγ表达明显增加。4.在脓毒症心脏纤维化小鼠模型给予NK-1受体拮抗剂，马松染色提示心脏纤维化减轻，心脏炎性细胞浸润减少，证明SP可能在脓毒症心肌纤维化中发挥关键作用。本研究有助于进一步明确SP在脓毒症远期心肌纤维化中的作用，对于改善脓毒症患者的心功能、提高远期生存率具有重要意义。