Glomerulonephritis and autoimmune vasculitis are independent of P2RX7 but may depend on alternative inflammasome pathways

Abstract

P2RX7, an ionotropic receptor for extracellular adenosine triphosphate (ATP), is expressed on immune cells, including macrophages, monocytes, and dendritic cells and is upregulated on nonimmune cells following injury. P2RX7 plays a role in many biological processes, including production of proinflammatory cytokines such as interleukin (IL)‐1β via the canonical inflammasome pathway. P2RX7 has been shown to be important in inflammation and fibrosis and may also play a role in autoimmunity. We have developed and phenotyped a novel P2RX7 knockout (KO) inbred rat strain and, taking advantage of the human‐resembling unique histopathological features of rat models of glomerulonephritis, we induced three models of disease: nephrotoxic nephritis, experimental autoimmune glomerulonephritis, and experimental autoimmune vasculitis. We found that deletion of P2RX7 does not protect rats from models of experimental glomerulonephritis or the development of autoimmunity. Notably, treatment with A‐438079, a P2RX7 antagonist, was equally protective in WKY WT and P2RX7 KO rats, revealing its ‘off‐target’ properties. We identified a novel ATP/P2RX7/K+ efflux‐independent and caspase‐1/8‐dependent pathway for the production of IL‐1β in rat dendritic cells, which was absent in macrophages. Taken together, these results comprehensively establish that inflammation and autoimmunity in glomerulonephritis is independent of P2RX7 and reveals the off‐target properties of drugs previously known as selective P2RX7 antagonists. Rat mononuclear phagocytes may be able to utilise an ‘alternative inflammasome’ pathway to produce IL‐1β independently of P2RX7, which may account for the susceptibility of P2RX7 KO rats to inflammation and autoimmunity in glomerulonephritis. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

P2X7 accelerate tissue fibrosis via metalloproteinase 8‐dependent macrophage infiltration in a murine model of unilateral ureteral obstruction

“…In a model of renal fibrosis secondary to E. coli ‐induced pyelonephritis, we were able to show that P2X 7 R‐deficient mice were protected against renal fibrosis without interfering with the earlier stage of renal damage, inflammation and activation of tissue fibroblasts (Therkildsen et al., 2019). In support of the notion that P2X 7 Rs are not involved in early renal damage, it has been demonstrated that the lack of P2X 7 Rs did not influence the renal damage seen in models of glomerulonephritis and autoimmune vasculitis, including the activation of fibroblasts measured as increased α‐SMA expression (Prendecki et al., 2022). Moreover, various reports about the P2X 7 R in renal damage and fibrosis have been inconsistent (Goncalves et al., 2006; Luz et al., 2019; Xu et al., 2022), questioning the P2X 7 as a relevant target for interference against fibrosis.…”

“…This study was carried out in female mice because urinary tract infections are primarily a female‐associated condition. There have been deviating findings regarding the P2X 7 receptor in experimental models for more severe renal fibrosis (Goncalves et al., 2006; Prendecki et al., 2022; Therkildsen et al., 2019). Here, we use unilateral ureteral obstruction (UUO) to evaluate the effect of lacking the P2X 7 receptor and review the potential effect of gender on the overall response.…”

“…In addition to the mice models, a P2X 7 receptor‐deficient rat is also available. However, the P2X 7 R‐deficient rat has a limited phenotype and has residual effects of P2X 7 specific antagonists (Prendecki et al., 2022). It must be noted that the GSK P2X 7 −/− mouse on BALB/cJ background used here has a distinct phenotype in terms of renal fibrosis, which has previously been found to be comparable to P2X 7 receptor inhibition (Therkildsen et al., 2019).…”

Animal Models for the Investigation of P2X7 Receptors

“…Rats with this deletion, compared to wild-type PCK rats, had impaired renal cyst development and ATP urinary release, with the latter corresponding to decreased amounts of renal pannexin-1 protein. Zinc finger nuclease technology has been used to globally delete the P2rx7 gene in Wistar Kyota rats, although the presence of escape variants in the brain could not be excluded [164]. This deletion did not protect rats from nephrotoxic nephritis, glomerulonephritis, or autoimmune nephritis, indicating P2X7 is not essential for the development of these disorders.…”