SCF/KIT信号通路抑制感光细胞变性的神经保护功能及其分子机制研究

Photoreceptor cell degeneration, commonly exsited in retinal degenerative diseases, is a major cause of blindness and results in a considerable health burden. Nevertheless, effective therapeutic or preventive strategies have not so far become available for retinal diseases associated with progressive photoreceptor cell degeneration. We found that upon light damage (LD), photoreceptor cells upregulated stem cell factor (SCF) and then activated KIT signaling, while Kit-Wps mutation abrogated activation of Kit, accelerted light-induced photoreceptor cell degeneration and downregulated Heme oxygenase 1 (Hmox1) expression, suggesting that receptor KIT protects photoreceptor cell from light damage. However, the function of its ligand SCF and the underlying molecular mechanisms are still unknown. Here, we propose a hypothesis that SCF/KIT signaling upregulates HMOX1 to prevent photoreceptor cell degeneration in retina. In this project, we will use LD treated Kit-Wps homozygous mice and retinitis pigmentosa animal model of rd1 mice combined with adeno-associated virus type 8 (AAV8) to overexpress SCF in retina to further analyze the neuroprotective role of SCF/KIT against photoreceptor cell degeneration. In order to investigate the functional molecular mechanism of SCF/KIT signaling, we plan to use multipe methods such as immunofluoresence (IF) and western blot (WB) to further analyze the regulatory relationship between SCF/KIT and Hmox1 in vivo and in vitro. Further more, we will also use AAV8-Hmox1 combined with light damage model to analyze whether overexpression of Hmox1 could rescue the light-induced photoreceptor cell degeneration of Kit-Wps homozygous retinas. Through this original research project, we expect that this proposal will dissect how SCF/KIT signaling pathway plays a neuroprotective role for preventing the photoreceptor cell degeneration. We hope that the outcomes from this project will provide a new potential treatment of photoreceptor cell degeneration that may serve as a potential therapeutic target for retinal diseases associated with progressive photoreceptor cell degeneration.

感光细胞变性是视网膜变性疾病致盲的主要病因之一，严重危害视觉健康，目前尚难治愈。本研究前期采用光损伤模型结合Kit基因突变小鼠，发现该突变阻断了受体KIT的活性，促进感光细胞变性，且下调Hmox1的表达，说明KIT对感光细胞具有保护作用，但其配体SCF的功能及分子机制尚不清楚。我们假设SCF/KIT在视网膜中通过上调Hmox1来抑制感光细胞变性。本研究拟采用AAV8过表达SCF，结合光诱导视网膜损伤的Kit突变小鼠和遗传性视网膜变性rd1小鼠，分析SCF在视网膜中抑制感光细胞变性的保护功能；为解析其分子机制，利用多种研究手段体内、体外分析SCF/KIT对Hmox1的表达调控，并通过AAV8过表达Hmox1去挽救光损伤诱导的Kit突变小鼠感光细胞变性。本项目旨在阐明该信号通路抑制感光细胞变性的神经保护功能及其分子机制，有望为攻克感光细胞变性致盲的视网膜疾病提供前瞻性思路和转化医学的潜在靶点。

感光细胞变性是视网膜色素变性（RP）和年龄相关性黄斑变性（AMD）等致盲眼病的主要病因之一，如何有效抑制感光细胞变性成为亟待解决的关键科学问题。在本项目的资助下，我们通过光损伤模型、生物信息学分析、AAV基因过表达技术和基因缺陷小鼠模型等，首次发现SCF/KIT信号通路可以应答光损伤而被激活，随后通过调控NRF2的核转位进而调控抗氧化基因HMOX1的表达，阐明了SCF/KIT-NRF2/HMOX1的调控网络。随后，采用RP疾病模型和AAV基因递送技术，原创性地发现SCF可以抑制光损伤和遗传性因素引起的感光细胞变性，为治疗RP和AMD等疾病提供新的作用靶点和干预途径。研究结果发表于国际著名杂志eLife和Redox Biology等，并获得国家发明专利一项，国际发明专利一项。. 下游分子HMOX1是一个典型的氧化损伤应答分子，在神经变性类疾病中被报道发挥保护与毒害的双重作用，但其机制不明，阻碍了其在临床上的应用。我们假设HMOX1的双重作用可能与其诱导表达水平有关，故采用AAV过表达系统，通过不同的病毒剂量来控制HMOX1在视网膜中的表达水平，进而分析视网膜变性情况。我们发现低水平HMOX1能抑制感光细胞变性，而高水平HMOX1会直接引起感光细胞变性。通过生物信息学分析和体内外的基因功能分析系统，我们发现高水平HMOX1会引起铁离子产生过度，进而激发内质网应激，通过DDIT3诱导细胞死亡。该研究为预防HMOX1发挥毒害作用提供重要的干预途径，加深了对视网膜变性病理机制的理解。研究结果发表于神经领域顶级期刊Molecular Neurodegeneration杂志。. 基于本项目的研究，我们原创性地提出细胞因子SCF可作为抑制感光细胞变性的潜在治疗靶点、揭示了HMOX1在视网膜中发挥双重作用的分子机制，从而丰富了现有的视网膜神经保护理论，为干预RP和AMD等致盲疾病提供潜在的作用靶点。