Cytoprotective Role of Heat Shock Proteins in IBD

描述(申请人提供)：肠道内稳态是维持正常粘膜功能、完整性、自我更新和宿主防御的要素的基本和动态平衡。在急性疾病中，致病的损害是自我限制的，肠道内平衡得到恢复。在炎症性肠病(IBD)中，由于慢性、破坏性的粘膜炎症持续存在，肠道内稳态无法恢复。然而，较少考虑的是这样一种可能性，即恢复肠道内稳态所需的对抗机制在令人不快的侮辱期间甚至在解决之后受到损害。因此，这项建议将检验一种假设，即可诱导的热休克蛋白Hsp70对于维持肠道内环境稳定是必不可少的，并且其在炎症期间的缺陷表达有助于慢性结肠炎和结肠炎相关结肠癌的发展。对这一观点的支持来自以下观察：(1)Hsp70具有强大的细胞保护和抗炎特性，(2)在实验性和人类结肠炎中观察到Hsp70的表达下调，使粘膜更容易受到损伤，并加剧炎症反应，(3)基因靶向缺失Hsp70将原本自限性的DSS诱导的结肠炎转变为慢性IBD样结肠炎，以及(4)在AOM/DSS攻击后，平坦的异型增生到癌症序列结肠癌发生在Hsp70缺失的小鼠身上，而不是它们的野生型小鼠，后者发展为散发性息肉到癌症序列结肠癌，5)Hsp70的强劲表达与散发性人类结肠癌有关，但与IBD癌症无关。研究Hsp70(上皮细胞和免疫来源细胞)在肠道内稳态中的作用，以及炎症引起的表达受损是否导致慢性结肠炎和IBD样结肠癌的发生。首先，我们将确定Hsp70是否是维持肠道内环境稳定所必需的，以及它在急性炎症和基于免疫的结肠炎模型中的表达下调是否会导致慢性或更严重的IBD样结肠炎。其次，将定义导致观察到的与肠道炎症和促炎细胞因子相关的HSP70选择性翻译下调的机制(S)。最后，我们将研究Hsp70表达/功能的丧失是否对于慢性结肠炎小鼠的自发性和致癌物诱导的结肠癌的发生是必要的和充分的。将采用体外和体内相结合的方法，后者包括基因靶向Hsp70缺失和上皮或髓系细胞特异性Hsp70转基因表达的新模型。通过这些研究获得的洞察力将提供破坏肠道内稳态的过程可能导致IBD和炎症相关结肠癌的发展的原则证据。因此，恢复肠道内环境平衡的策略对于预防、治疗和改变炎症性肠病的自然病史具有重要意义。 公共卫生相关性这项建议将检验一种假说，即可诱导的热休克蛋白Hsp70对维持肠道内环境稳定是必不可少的，并且其在发炎的粘膜中的表达不足会导致慢性结肠炎和结肠炎相关结肠癌的发生。恢复炎症性肠黏膜HSP70表达的策略对于预防、治疗和改变炎症性肠病的自然病程具有重要意义。

DESCRIPTION (provided by applicant): Intestinal homeostasis is the essential and dynamic equilibrium of factors that maintain normal mucosal function, integrity, self-renewal, and host defense. In acute diseases, the pathogenic insult is self- limited and intestinal homeostasis is restored. In inflammatory bowel diseases (IBD), intestinal homeostasis cannot be restored because of the persistence of chronic, destructive mucosal inflammation. However, less well considered is the possibility that countering mechanisms necessary for restoring intestinal homeostasis are impaired during and even after resolution of the offending insult. This proposal will therefore examine the hypothesis that the inducible heat shock protein, Hsp70, is essential for maintaining intestinal homeostasis and that its deficient expression during inflammation contributes to the development of chronic colitis and colitis-associated colon cancer. Support for this notion comes from the following observations: (1) Hsp70 has both potent cytoprotective and anti-inflammatory properties, (2) down-regulated expression of Hsp70 is observed in experimental and human colitis, rendering the mucosa more susceptible to injury and intensifying the inflammatory response, (3) gene-targeted deletion of Hsp70 transforms the otherwise, self-limited, DSS-induced colitis to a chronic, IBD -like colitis, and (4) after AOM/DSS challenge, multi-focal, flat dysplasia-to-cancer sequence colon cancer develops in Hsp70- deficient mice as opposed to their wild-type counterparts that develop sporadic polyp-to-cancer sequence colon cancer, and 5) robust Hsp70 expression is associated with sporadic human colon cancer, but not IBD cancer. Three specific aims are proposed to investigate the role of Hsp70 (in epithelial versus immune-derived cells) in intestinal homeostasis and whether impaired expression caused by inflammation contributes to the development of chronic colitis and IBD-like colon cancer. First, we will determine if Hsp70 is essential for maintenance of intestinal homeostasis and whether it down-regulated expression in acute inflammatory and in immune-based models of colitis leads to chronic or more severe IBD-like colitis. Second, the mechanism(s) causing the observed selective translational down-regulation of Hsp70 associated with intestinal inflammation and pro-inflammatory cytokines will be defined. Finally, we will investigate whether the loss of Hsp70 expression/function is necessary and sufficient for development of spontaneous and carcinogen-induced colon cancer in mice with chronic colitis. A combination of in vitro and in vivo approaches will be employed, the latter including novel models of gene-targeted-Hsp70 deletion and epithelial- or myeloid cell-specific Hsp70 transgene expression. The insights gained through these studies will provide proof of principle that processes that impair intestinal homeostasis can contribute to the development of IBD and inflammation-associated colon cancer. Strategies to restore intestinal homeostasis would therefore be important for preventing, treating, and changing the natural history of inflammatory bowel diseases. PUBLIC HEALTH RELEVANCE This proposal will examine the hypothesis that the inducible heat shock protein, Hsp70, is essential for maintaining intestinal homeostasis and that its deficient expression in inflamed mucosa contributes to the development of chronic colitis and colitis-associated colon cancer. Strategies to restore Hsp70 expression in inflamed mucosa would be important for preventing, treating, and changing the natural history of inflammatory bowel diseases.