The macrophage phenotype and inflammasome component NLRP3 contributes to nephrocalcinosis-related chronic kidney disease independent from IL-1–mediated tissue injury

Abstract

Primary/secondary hyperoxalurias involve nephrocalcinosis-related chronic kidney disease (CKD) leading to end-stage kidney disease. Mechanistically, intrarenal calcium oxalate crystal deposition is thought to elicit inflammation, tubular injury and atrophy, involving the NLRP3 inflammasome. Here, we found that mice deficient in NLRP3 and ASC adaptor protein failed to develop nephrocalcinosis, compromising conclusions on nephrocalcinosis-related CKD. In contrast, hyperoxaluric wild-type mice developed profound nephrocalcinosis. NLRP3 inhibition using the β-hydroxybutyrate precursor 1,3-butanediol protected such mice from nephrocalcinosis-related CKD. Interestingly, the IL-1 inhibitor anakinra had no such effect, suggesting IL-1-independent functions of NLRP3. NLRP3 inhibition using 1,3-butanediol treatment induced a shift of infiltrating renal macrophages from pro-inflammatory (CD45F4/80CD11bCX3CR1CD206) and pro-fibrotic (CD45F4/80CD11bCX3CR1CD206TGFβ) to an anti-inflammatory (CD45F4/80CD11bCD206TGFβ) phenotype, and prevented renal fibrosis. Finally, in vitro studies with primary murine fibroblasts confirmed the non-redundant role of NLRP3 in the TGF-β signaling pathway for fibroblast activation and proliferation independent of the NLRP3 inflammasome complex formation. Thus, nephrocalcinosis-related CKD involves NLRP3 but not necessarily via intrarenal IL-1 release but rather via other biological functions including TGFR signaling and macrophage polarization. Hence, NLRP3 may be a promising therapeutic target in hyperoxaluria and nephrocalcinosis.

Novel Insights into Crystal-Induced Kidney Injury

“…Deficiency of inflammasome components, NLRP3, and ASC in mice reduced renal inflammation during progressive renal failure in nephrocal­cinosis-related CKD [39, 40]. Furthermore, chemical inhibition of NLRP3 using a specific inhibitor – CP-456773 or β-hydroxybutyrate – reduced renal inflammation and progressive decline in renal function in murine nephrocalcinosis-related CKD [40, 41]. Inflammasome activation leads to secretion of mature IL-1β and IL-18 that contribute to renal inflammation.…”

“…Inflammasome activation leads to secretion of mature IL-1β and IL-18 that contribute to renal inflammation. Surprisingly, IL-1 receptor inhibition using anakinra has no effect on progressive decline in renal function in murine nephrocalcinosis-related CKD [40, 41], suggesting a contribution of inflammasome-independent functions of NLRP3, which involve transforming growth factor beta receptor signaling-mediated renal fibrosis [42]. Indeed, chemical inhibition of NLRP3 by CP-456773 during oxalate and adenine nephropathy or by β-hydroxybutyrate during oxalate nephropathy reduced intrarenal fibrosis in murine crystalline CKD models [40, 41].…”

“…Surprisingly, IL-1 receptor inhibition using anakinra has no effect on progressive decline in renal function in murine nephrocalcinosis-related CKD [40, 41], suggesting a contribution of inflammasome-independent functions of NLRP3, which involve transforming growth factor beta receptor signaling-mediated renal fibrosis [42]. Indeed, chemical inhibition of NLRP3 by CP-456773 during oxalate and adenine nephropathy or by β-hydroxybutyrate during oxalate nephropathy reduced intrarenal fibrosis in murine crystalline CKD models [40, 41]. In addition, our own data demonstrated that β-hydroxybutyrate induced M2 macrophage phenotype shift and also contributed to a decline in renal inflammation and preserved renal function during chronic oxalate nephropathy without affecting intrarenal crystal deposition [40].…”

“…Indeed, chemical inhibition of NLRP3 by CP-456773 during oxalate and adenine nephropathy or by β-hydroxybutyrate during oxalate nephropathy reduced intrarenal fibrosis in murine crystalline CKD models [40, 41]. In addition, our own data demonstrated that β-hydroxybutyrate induced M2 macrophage phenotype shift and also contributed to a decline in renal inflammation and preserved renal function during chronic oxalate nephropathy without affecting intrarenal crystal deposition [40]. …”

Aminooxyacetic acid attenuates post‐infarct cardiac dysfunction by balancing macrophage polarization through modulating macrophage metabolism in mice

“…Further, studies proved that NLRP3 inflammasome is predominantly activated in macrophages and up‐regulated in M1 macrophages but down‐regulated in M2 . What is more, the inhibition of NLRP3 impeded glycolysis and induced a macrophage phenotype transformation from pro‐inflammatory to anti‐inflammatory . Therefore, we investigated the effect of AOAA on NLRP3‐Caspase1/IL‐1β signalling pathway by Western blotting and qPCR analysis.…”