白蛋白抑制细胞外组蛋白诱导的血管内皮细胞损伤及其在脓毒症中潜在的应用价值

Sepsis remains a major cause of death and complications in intensive care units, especially for those with primary diseases. Circulating histones were demonstrated as major mediators of death in septic mice models, but their roles in septic patients and the benefits of pertinent treatment are not clarified. Circulating histone levels in 130 septic children of our hospital and their correlation with disease progression was analyzed and found that histone levels in the plasma of septic children were significantly higher than healthy controls, and are positively correlated with disease severity. Circulating histones might serve as key factors in the pathogenesis of sepsis and their levels in plasma might be a marker for disease progression and prognosis. We found that FBS (Fetal Bovine Serum) even normal human plasma could inhibit histones induced HUVEC (Human Umbilical Vein Endothelial Cells) death in vitro, so we prepare to searching for which matter has protective effects against histones in plasma and found albumin (the most abundant protein in plasma) could inhibit histones induced HUVEC death. Since treating severe septic children with albumin could hamper disease progression and significantly reduce the 28-day mortality in a meta-analysis and vascular endothelium injury, the key factor in sepsis which could gradually lead to MODS, was a potential target in treating sepsis, we suspect maybe albumin's protection in sepsis is to protect endothelial cells against histone-induced injury. Our object is to investigate the underlying mechanisms of the protective effects of exogenous albumin against histone-induced toxicity in cultured human endothelial cells and in various septic mice models.

在脓毒症的病理过程中，内皮细胞是病原体及毒素的一个主要靶器官，由此造成的内皮损伤是导致全身炎症反应综合征和多脏器功能障碍的重要机制。有研究在动物模型中证实细胞外组蛋白是脓毒症的关键致死因素，我们前期的工作发现脓毒症患儿血清中组蛋白浓度显著增高，且与疾病的严重程度呈正相关，因此本课题组拟寻找对抗细胞外组蛋白的物质以减轻其损伤，进而改善脓毒症病情进展、提高生存率。我们发现在体外胎牛血清可以有效抑制细胞外组蛋白诱导的血管内皮细胞死亡，正常人血浆也有类似的作用，因此本课题组拟寻找血浆中存在的对抗细胞外组蛋白的物质。我们发现在体外血浆中含量最多的蛋白——白蛋白可以显著抑制细胞外组蛋白诱导的血管内皮细胞死亡，结合meta分析得出的临床上白蛋白对于脓毒症的治疗作用，本研究拟探索白蛋白得以在脓毒症中发挥保护作用的机制，为采用白蛋白治疗脓毒症或研发新型药物以改善脓毒症病情进展、进一步提高生存率提供理论依据。

在脓毒症的病理过程中，内皮细胞是病原体及毒素的一个主要靶器官，由此造成的内皮损伤是导致全身炎症反应综合征和多脏器功能障碍的重要机制。本课题组发现脓毒症患儿血清中组蛋白浓度显著增高，且与疾病的严重程度呈正相关，因此本课题组拟寻找对抗细胞外组蛋白的物质以减轻其损伤，进而改善脓毒症病情进展、提高生存率。我们发现在体外胎牛血清、正常人血浆可以有效抑制细胞外组蛋白诱导的血管内皮细胞死亡，因此本课题组拟寻找血浆中存在的对抗细胞外组蛋白的物质，发现血浆中含量最多的蛋白——白蛋白可以显著抑制细胞外组蛋白诱导的血管内皮细胞死亡，结合meta分析得出的临床上白蛋白对于脓毒症的治疗作用，本研究拟探索白蛋白得以在脓毒症中发挥保护作用的机制，为采用白蛋白治疗脓毒症或研发新型药物以改善脓毒症病情进展、进一步提高生存率提供理论依据。关于白蛋白抑制细胞外组蛋白的诱导血管内皮损伤的机制，本课题组研究发现：白蛋白并非降解细胞外组蛋白，从源头抑制细胞外组蛋白对血管内皮细胞的损伤。在体外，外源性白蛋白抑制细胞外组蛋白介导的血管内皮细胞死亡主要由于白蛋白可对抗胞外组蛋白诱导的TLR下游：NFκB、MAPK及ERK等通路的激活并明确一段多肽可显著抑制组蛋白的毒性，以便于将来开展多肽药物的研发；通过尾静脉注射小鼠源性的白蛋白到重组组蛋白模型中，发现外源性白蛋白可以降低组蛋白（脓毒症）的致死率，抑制组蛋白对其他器官的损伤。脓毒症患者血浆中白蛋白水平显著下降，脓毒症患者常并发低白蛋白血症，导致病情的进一步加重，增加病死率。血清白蛋白浓度下降是脓毒症及感染性休克患者预后的独立预测因素，因此脓毒症患者白蛋白水平下降，细胞外组蛋白浓度上升很可能是导致脓毒症生存率低下的关键因素。本项目一方面明确了白蛋白抑制细胞外组蛋白的机制，另一方面鉴定出白蛋白中一段多肽可发挥抗组蛋白的作用以便将来研发多肽类药物，改善脓毒症病情进展、提高生存率。