Cardioprotection against endotoxins

描述（由申请方提供）：许多研究表明，啮齿动物接受轻度全身热休克后，对随后致死剂量的脂多糖（LPS）产生抗性。 目前还不清楚预热处理是如何防止内毒素的，但热休克的主要结果之一是增加了一组被称为热休克蛋白（hsp）的蛋白质的合成。 热休克蛋白70是这些热休克蛋白中最丰富的，并已被假定为所观察到的对LPS的保护的主要介质。 由于内毒素血症的主要后果之一是诱导心肌收缩功能障碍，而hsp 70先前已被证明可防止由于梗死引起的心肌功能障碍。 因此，我们建议调查的机制，热休克蛋白70保护心肌在内毒素血症。 我们的初步结果表明，热休克分离的大鼠新生心肌细胞耐受随后暴露于LPS。 此外，用含有hsp 70基因的腺病毒载体感染的心肌细胞也耐受体外内毒素暴露。 我们还发现，过表达hsp 70基因的转基因小鼠品系比不表达hsp 70转基因的同窝小鼠更耐受内毒素血症。 根据我们的初步结果，热休克蛋白70使心肌细胞在体外和体内耐受内毒素损伤的机制似乎涉及诱导型一氧化氮合酶表达的减少。 因此，我们建议研究在两个分离的心肌细胞和转基因小鼠的心脏组织，内毒素诱导的细胞损伤的介质的水平：TNF-α，IL-1，一氧化氮（NO），诱导型NO合酶和转录因子NFkB，以及它们是如何受到热休克蛋白70的存在增加。 拟议的研究项目应清楚地表明，如果单独存在的增加水平的热休克蛋白70是保护对内毒素血症。 这项研究可能为利用心肌细胞的内源性保护机制以及针对内毒素引起的心肌抑制的新的创新和有效的治疗开辟了道路。

DESCRIPTION (provided by applicant): A number of studies have shown that rodents submitted to a mild whole body heat shock become resistant to a subsequent lethal dose of lipopolysaccharides (LPS). It is still unclear how a pre-heat treatment protects against endotoxins but one of the main results of a heat shock is the increased synthesis of a group of proteins known as the heat shock proteins (hsp). The hsp70 is the most abundant of these hsps and has been postulated to be the principal mediator of the observed protection against LPS. Since one of the majors consequences of endotoxemia is the induction of myocardial contractile dysfunction and hsp70 has been previously shown to protect against myocardial dysfunction due to infarction. We therefore propose to investigate the mechanism by which the hsp70 protects the myocardium during endotoxemia. Our preliminary results show that heat shocked isolated rat neonatal cardiomyocytes are tolerant to a subsequent exposure to LPS. In addition, cardiomyocytes infected with adenoviral vectors containing the hsp70 gene are also tolerant to endotoxin exposure in vitro. We also find that a transgenic mouse line overexpressing a hsp70 gene is more tolerant to endotoxemia than littermates that do not express the hsp70 transgene. The mechanism in which hsp70 renders the cardiomyocyte both in vitro and in vivo tolerant to endotoxemic injury would seem to involve a reduction in inducible nitric oxide synthase expression according to our preliminary results. We therefore propose to study in both isolated cardiomyocytes and the heart tissue of transgenic mice, the level of the mediators of endotoxin-induced cell injury: TNF-alpha, IL-1, nitric oxide (NO), inducible NO synthase and the transcription factor NFkB and how they are affected by the increased presence of hsp70. The proposed research project should clearly demonstrate if the sole presence of increased levels of hsp70 is protective against endotoxemia. This proposed study may open the way to harness the endogenous protective mechanisms in cardiomyocytes and to new innovative and effective therapies against the myocardial depression caused by endotoxins.