title: P2X7 receptors mediate deleterious renal epithelial-fibroblast cross talk.
abstract: 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.
authors.affiliation: Department of Medicine, Rhode Island Hospital and Warren Alpert Medical School of Brown University, Middle House 301, 593 Eddy St., Providence, RI 02903, USA.
authors.forename: Murugavel
authors.initials: M
authors.lastname: Ponnusamy
authors.forename: Li
authors.initials: L
authors.lastname: Ma
authors.forename: Rujun
authors.initials: R
authors.lastname: Gong
authors.forename: Maoyin
authors.initials: M
authors.lastname: Pang
authors.forename: Y Eugene
authors.initials: YE
authors.lastname: Chin
authors.forename: Shougang
authors.initials: S
authors.lastname: Zhuang
mesh_terms: D058186:Acute Kidney Injury; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D018920:Coculture Techniques; D005347:Fibroblasts; D007668:Kidney; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000473:pathology; D009336:Necrosis; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D058486:Receptors, Purinergic P2X7 / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013777:Tetrazoles / Q000494:pharmacology; D013778:Tetrazolium Salts; D013844:Thiazoles
chemical_list: C523668:3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methylpyridine; D058920:Purinergic P2X Receptor Antagonists; D011725:Pyridines; D058486:Receptors, Purinergic P2X7; D013777:Tetrazoles; D013778:Tetrazolium Salts; D013844:Thiazoles; D000255:Adenosine Triphosphate; C022616:thiazolyl blue