Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Biochim Biophys Acta Mol Basis Dis. 2021 Jul 1;1867(7):166146. doi: 10.1016/j.bbadis.2021.166146. Epub 2021 Apr 14.
The nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been implicated in podocyte injury and glomerular sclerosis in response to hyperhomocysteinemia (hHcy). However, it remains unknown how the products of NLRP3 inflammasome in cytoplasm are secreted out of podocytes. In the present study, we tested whether exosome release serves as a critical mechanism to mediate the action of NLRP3 inflammasome activation in hHcy-induced glomerular injury. By various approaches, we found that hHcy induced NLRP3 inflammasome activation and neutrophil infiltration in glomeruli of WT/WT mice. Lysosome-MVB interaction in glomeruli remarkably decreased in WT/WT mice fed with FF diet, leading to elevation of urinary exosome excretion of these mice. Podocyte-derived exosomes containing pro-inflammatory cytokines increased in urine of WT/WT mice in response to hHcy. The release of inflammatory exosomes from podocytes was prevented by Smpd1 gene deletion but enhanced by podocyte-specific Smpd1 gene overexpression (Smpd1 encodes Asm in mice). Pathologically, hHcy-induced podocyte injury and glomerular sclerosis were blocked by Smpd1 gene knockout but amplified by podocyte-specific Smpd1 gene overexpression. Taken together, our results suggest that Asm-ceramide signaling pathway contributes to NLRP3 inflammasome activation and robust release of inflammatory exosomes in podocytes during hHcy, which together trigger local glomerular inflammation and sclerosis.
核苷酸结合寡聚化结构域样受体包含 pyrin 结构域 3 (NLRP3) 炎性小体已被牵连到足细胞损伤和高同型半胱氨酸血症（hHcy）引起的肾小球硬化。然而，尚不清楚细胞质中 NLRP3 炎性小体的产物如何从足细胞中分泌出来。在本研究中，我们测试了外泌体释放是否作为一种关键机制来介导 NLRP3 炎性小体激活在 hHcy 诱导的肾小球损伤中的作用。通过各种方法，我们发现 hHcy 诱导 NLRP3 炎性小体激活和中性粒细胞浸润在 WT/WT 小鼠的肾小球中。FF 饮食喂养的 WT/WT 小鼠肾小球中溶酶体-MVB 相互作用显著减少，导致这些小鼠尿液中外泌体的排泄增加。响应 hHcy，WT/WT 小鼠尿液中足细胞来源的含有促炎细胞因子的外泌体增加。Smpd1 基因缺失可防止炎性外泌体从足细胞中释放，但足细胞特异性 Smpd1 基因过表达（Smpd1 在小鼠中编码 Asm）增强其释放。病理性地，Smpd1 基因敲除可阻断 hHcy 诱导的足细胞损伤和肾小球硬化，但足细胞特异性 Smpd1 基因过表达则增强其损伤。总之，我们的结果表明，Asm-神经酰胺信号通路有助于 hHcy 期间 NLRP3 炎性小体的激活和炎性外泌体的大量释放，这共同触发局部肾小球炎症和硬化。
