Inflammasome-Independent Role of NLRP3 Mediates Mitochondrial Regulation in Renal Injury

Abstract

The NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome has been implicated in renal inflammation and fibrosis. However, the biological function of inflammasome-independent NLRP3 in non-immune cells is still unclear. We evaluated the role of inflammasome-independent NLRP3 in renal tubular cells and assessed the value of NLRP3 as a therapeutic target for acute kidney injury (AKI). Various renal tubular cell lines and primary cultured tubular cells from NLRP3 knockout (KO) mice were used for in vitro studies. We also tested the role of tubular NLRP3 in AKI with a unilateral ureter obstruction model (UUO). Hypoxia induced significant increase of NLRP3 independent of ASC, caspase-1, and IL-1β. NLRP3 in renal tubular cells relocalized from the cytosol to the mitochondria during hypoxia and bound to mitochondrial antiviral signal protein (MAVS). The deletion of NLRP3 or MAVS in renal tubular cells attenuated mitochondrial reactive oxygen species (ROS) production and depolarization of the mitochondrial membrane potentials under hypoxia. In response to UUO, NLRP3 KO mice showed less fibrosis, apoptosis, and ROS injury than wild type (WT) mice. Compared with WT kidney, mitophagy was up-regulated in NLRP3 KO kidney relative to the baseline and it was protective against AKI. Our results indicate that inflammasome-independent NLRP3 in renal tubular cells plays important role in mitochondrial ROS production and injury by binding to MAVS after hypoxic injury. This mitochondrial regulation in the absence of NLRP3 increases autophagy and attenuates apoptosis after UUO. We suggest that inflammasome-independent NLRP3 could be a therapeutic target of AKI to prevent the progression of chronic kidney disease.

Enhancer of zeste homolog 2 modulates oxidative stress‐mediated pyroptosis in vitro and in a mouse kidney ischemia‐reperfusion injury model

“…B, Representative bands of western blot analysis for the expression of EZH2 and bar graph showed the quantification, n = 3; Two-tailed t test was used for the statistical analysis; Values are expressed as the mean ± SEM. 23,25,31,32 At the cellular level, our further study revealed that the ablation of ROS with NAC abolished H/Rmediated elevation of pyroptosis-related protein expression and caspase-1 activity, and the induction in pyroptotic cells and LDH release strongly confirmed that pyroptosis was inhibited by decreased ROS generation. C-J, HK-2 cells were transfected with an siRNA against EZH2 or a negative control siRNA (si-NC) for 48 h and were pretreated with or without DZNeP at dose of 2.5 μM for 1 h before being exposed to H/R.…”

“…15,16 Structural damage of renal tubules is induced by I/R injury via triggering renal inflammatory responses. 23 However, whether EZH2 is linked to Nox4-mediated ROS generation and activation of pyroptosis still remains to be unknown in renal I/R injury. [17][18][19] Oxidative stress, a pathological phenomenon in which the generation of reactive oxygen species (ROS) surpasses the capacity of endogenous antioxidant systems, always causes renal tissue injury.…”

Sweroside Prevents Non-Alcoholic Steatohepatitis by Suppressing Activation of the NLRP3 Inflammasome

“…For detecting tissue protein expression, immunohistochemistry was performed [40]. To demonstrate fibrosis, liver sections were stained 2 h with Masson's trichrome reagent [41].…”

The rOX‐stars of inflammation: links between the inflammasome and mitochondrial meltdown

“…69 In keeping with the assertion that loss of membrane potential is a consequence rather than cause of NLRP3 activation, another study reported that NLRP3 deficiency in renal tubular cells protected mitochondria against depolarisation during hypoxia. 79 The above models may not be mutually exclusive; it is possible that an early loss of mitochondrial membrane integrity results in just enough externalised mtDNA to participate in NLRP3 signalling, which then drives further mitochondrial damage. In line with this, one study examining temporal changes in mitochondrial stability during NLRP3 activation reported that LPS-primed BMDMs treated with ATP or nigericin exhibited some inflammasome-independent mitochondrial hyperpolarisation at early time points (up to 15 min post treatment).…”