Department of Medicine, Rhode Island Hospital and Warren Alpert Medical School of Brown University, Middle House 301, 593 Eddy St., Providence, RI 02903, USA.
Am J Physiol Renal Physiol. 2011 Jan;300(1):F62-70. doi: 10.1152/ajprenal.00473.2010. Epub 2010 Sep 22.
Peritubular fibroblasts in the kidney are the major erythropoietin-producing cells and also contribute to renal repair following acute kidney injury (AKI). Although few fibroblasts were observed in the interstitium adjacent to damaged tubular epithelium in the early phase of AKI, the underlying mechanism by which their numbers were reduced remains unknown. In this study, we tested the hypothesis that damaged renal epithelial cells directly induce renal interstitial fibroblast death by releasing intracellular ATP and activating purinergic signaling. Exposure of a cultured rat renal interstitial fibroblast cell line (NRK-49F) to necrotic renal proximal tubular cells (RPTC) lysate or supernatant induced NRK-49F cell death by apoptosis and necrosis. Depletion of ATP with apyrase or inhibition of the P2X purinergic receptor with pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid blocked the deleterious effect of necrotic RPTC supernatant. The P2X7 receptor, an ATP-sensitive purinergic receptor, was not detected in cultured NRK-49F cells but was inducible by necrotic RPTC supernatant. Treatment with A438079, a highly selective P2X7 receptor inhibitor, or knockdown of the P2X7 receptor with small interference RNA diminished renal fibroblast death induced by necrotic RPTC supernatant. Conversely, overexpression of the P2X7 receptor potentiated this response. Collectively, these findings provide strong evidence that damaged renal epithelial cells can directly induce the death of renal interstitial fibroblasts by ATP activation of the P2X7 receptor.
肾脏中的肾小管周细胞是主要的促红细胞生成素产生细胞，在急性肾损伤 (AKI) 后也有助于肾脏修复。尽管在 AKI 的早期阶段，损伤的肾小管上皮细胞附近的间质中观察到的成纤维细胞很少，但它们数量减少的潜在机制尚不清楚。在这项研究中，我们检验了这样一个假设，即受损的肾上皮细胞通过释放细胞内 ATP 并激活嘌呤能信号直接诱导肾间质成纤维细胞死亡。将培养的大鼠肾间质成纤维细胞系 (NRK-49F) 暴露于坏死的肾近端肾小管细胞 (RPTC) 裂解物或上清液中，通过凋亡和坏死诱导 NRK-49F 细胞死亡。用 apyrase 耗尽 ATP 或用吡哆醛-6-偶氮苯-2',4'-二磺酸抑制 P2X 嘌呤能受体阻断了坏死 RPTC 上清液的有害作用。P2X7 受体是一种对 ATP 敏感的嘌呤能受体，在培养的 NRK-49F 细胞中未检测到，但可被坏死的 RPTC 上清液诱导。用 A438079（一种高度选择性的 P2X7 受体抑制剂）治疗，或用小干扰 RNA 敲低 P2X7 受体，可减少坏死的 RPTC 上清液诱导的肾成纤维细胞死亡。相反，过表达 P2X7 受体增强了这种反应。总的来说，这些发现提供了有力的证据，表明受损的肾上皮细胞可以通过 ATP 激活 P2X7 受体直接诱导肾间质成纤维细胞死亡。
