Key Laboratory of Microecology-Immune Regulatory Network and Related Diseases, School of Basic Medicine, Jiamusi University, Jiamusi, Heilongjiang Province, 154000, People's Republic of China.
Mol Med. 2024 May 21;30(1):67. doi: 10.1186/s10020-024-00831-w.
Gouty arthritis (GA) is characterized by monosodium urate (MSU) crystal accumulation that instigates NLRP3-mediated pyroptosis; however, the underlying regulatory mechanisms have yet to be fully elucidated. The present research endeavors to elucidate the regulatory mechanisms underpinning this MSU-induced pyroptotic cascade in GA.
J774 cells were exposed to lipopolysaccharide and MSU crystals to establish in vitro GA models, whereas C57BL/6 J male mice received MSU crystal injections to mimic in vivo GA conditions. Gene and protein expression levels were evaluated using real-time quantitative PCR, Western blotting, and immunohistochemical assays. Inflammatory markers were quantified via enzyme-linked immunosorbent assays. Pyroptosis was evaluated using immunofluorescence staining for caspase-1 and flow cytometry with caspase-1/propidium iodide staining. The interaction between MDM2 and PPARγ was analyzed through co-immunoprecipitation assays, whereas the interaction between BRD4 and the MDM2 promoter was examined using chromatin immunoprecipitation and dual-luciferase reporter assays. Mouse joint tissues were histopathologically evaluated using hematoxylin and eosin staining.
In GA, PPARγ was downregulated, whereas its overexpression mitigated NLRP3 inflammasome activation and pyroptosis. MDM2, which was upregulated in GA, destabilized PPARγ through the ubiquitin-proteasome degradation pathway, whereas its silencing attenuated NLRP3 activation by elevating PPARγ levels. Concurrently, BRD4 was elevated in GA and exacerbated NLRP3 activation and pyroptosis by transcriptionally upregulating MDM2, thereby promoting PPARγ degradation. In vivo experiments showed that BRD4 silencing ameliorated GA through this MDM2-PPARγ-pyroptosis axis.
BRD4 promotes inflammation and pyroptosis in GA through MDM2-mediated PPARγ degradation, underscoring the therapeutic potential of targeting this pathway in GA management.
痛风性关节炎（GA）的特征是单钠尿酸盐（MSU）晶体积累，引发 NLRP3 介导的细胞焦亡；然而，其潜在的调控机制尚未完全阐明。本研究旨在阐明 MSU 诱导 GA 中细胞焦亡级联反应的调控机制。
将 J774 细胞暴露于脂多糖和 MSU 晶体中，建立体外 GA 模型，而 C57BL/6J 雄性小鼠接受 MSU 晶体注射，模拟体内 GA 条件。通过实时定量 PCR、Western blot 和免疫组织化学检测评估基因和蛋白表达水平。通过酶联免疫吸附试验定量测定炎症标志物。通过 caspase-1 免疫荧光染色和 caspase-1/碘化丙啶染色的流式细胞术评估细胞焦亡。通过免疫共沉淀分析检测 MDM2 和 PPARγ 之间的相互作用，通过染色质免疫沉淀和双荧光素酶报告基因检测分析 BRD4 与 MDM2 启动子之间的相互作用。通过苏木精和伊红染色对小鼠关节组织进行组织病理学评估。
在 GA 中，PPARγ 下调，而过表达可减轻 NLRP3 炎性小体激活和细胞焦亡。GA 中上调的 MDM2 通过泛素-蛋白酶体降解途径使 PPARγ 不稳定，而沉默 MDM2 则通过提高 PPARγ 水平来减轻 NLRP3 的激活。同时，BRD4 在 GA 中上调，并通过转录上调 MDM2 加剧 NLRP3 激活和细胞焦亡，从而促进 PPARγ 降解。体内实验表明，BRD4 通过 MDM2-PPARγ-细胞焦亡轴沉默减轻 GA。
BRD4 通过 MDM2 介导的 PPARγ 降解促进 GA 中的炎症和细胞焦亡，凸显了靶向该途径治疗 GA 的潜力。
