调控含ITAM的免疫球蛋白G Fc受体（FcγRs）信号通路在老年糖尿病合并痴呆中的作用

Cognitive impairment is a common and important complication in geriatric diabetic patients and will progress to overt dementia. Inflammatory cytokines, such as C-reactive protein (CRP), play an important role in the pathogenesis of cognitive impairment and dementia among elderly diabetics. The activation of Immunoglobulin G Fc receptors (FcγRs) with an immunoreceptor tyrosine-based activation motif (ITAM) might participate in the development and progression of cognitive decline. We previously found that anti-ITAM- FcγRs antibody inhibit the effect of CRP on IL-1β、TNF-αand TGFβ1 and decrease their expression in HK-2 cell ambient high glucose. Based on our previous findings, we plan to construct the PC12 cells and SD rats models of ITAM- FcγRs gene inhibition by transfection in vivo and vitro in the current study. Then, the cells will be stimulated by high glucose and the rats treated with high-carbonhydrate and fat diet. The expression and activity of ITAM- FcγRs gene and influences on downstream signaling pathways will be tested at different time points. The cognitive function, apoptosis of neurons and brain pathology will also be evaluated at different time points. We aim to investigate the role of ITAM- FcγRs activation and their mechanisms in the dementia among elderly diabetics and to identify new target for treatment and prevention of the disease.

以CRP为代表的炎症因子在老年糖尿病合并痴呆的发病机制中起重要作用。含免疫受体酪氨酸激活基序的免疫球蛋白G Fc受体(ITAM- FcγRs)激活可能参与病变。我们前期研究发现，高糖培养的HK-2细胞中加入抗ITAM-FcγRs的抗体抑制CRP对IL-1β、TNF-α和TGFβ1产生的刺激作用，下调其表达。由此我们假设：ITAM-FcγRs激活及其下游信号通路改变可能是老年糖尿病合并痴呆发病机制的核心。因此，本课题拟采用体内外转染方法, 构建ITAM-FcγRs基因抑制的细胞和SD大鼠，高糖刺激细胞和高糖高脂饮食诱导动物模型，在不同时间点检测ITAM-FcγRs表达、活性及对下游信号通路的影响；检测认知功能、脑组织病理、细胞凋亡，从分子-细胞-个体水平探讨ITAM-FcγRs激活在老年糖尿病合并痴呆发生的作用机制。研究将为调控ITAM-FcγRs，防治老年糖尿病合并痴呆提供新的治疗靶点。

老年糖尿病是老年人最常见的疾病之一，认知障碍是老年糖尿病的重要慢性并发症，病情加重可进展为痴呆，降低患者的生活质量，增加患者死亡率，给家庭和社会带来沉重负担。探讨老年糖尿病合并认知障碍的发病机制，具有重大的社会意义和经济价值。既往研究发现炎症因子在老年糖尿病合并认知障碍的发病机制中起重要作用。本课题在前期研究基础上采用基因重组技术，构建FcγRIV的shRNA的质粒，分别进行体外转染大鼠PC12细胞株和体内转染老年糖尿病大鼠模型，在不同时间点，检测ITAM-FcγRs(FcγRI、FcγRIII和FcγRIV)表达及对下游信号通路关键炎症因子白介素-6(IL-6)、肿瘤坏死因子α（TNF-α）表达的影响。我们的研究发现以FcγRIV为代表的ITAM-FcγRs在糖尿病状态下表达增加，激活NF-κB炎症信号通路，上调炎症因子IL-6、TNF-α的表达，导致大脑海马CA1区域神经细胞变性、丢失和超微结构改变，影响大鼠认知功能。选择性抑制ITAM-FcγRs可抑制激活的NF-κB信号通路，下调炎症因子IL-6、TNF-α表达，改善脑组织病理变化和认知功能，证实ITAM-FcγRs信号通路激活参与老年糖尿病认知障碍的作用机制，为靶向调控ITAM-FcγRs信号通路减轻老年糖尿病的认知障碍并预防其进展为痴呆奠定理论基础。