Rhabdomyolysis-Induced AKI Was Ameliorated in NLRP3 KO Mice via Alleviation of Mitochondrial Lipid Peroxidation in Renal Tubular Cells.

Seok Jong Song,Yang Gyun Kim,Kyung Hwan Jeong,Su-Mi Kim,Jin Sug Kim,Ju-Young Moon,Hyeon Seok Hwang,Seon-Hwa Park,Sang-Ho Lee

doi:10.3390/ijms21228564

Abstract

Introduction: A recent study showed that early renal tubular injury is ameliorated in Nod-like receptor pyrin domain-containing protein 3 (NLRP3) KO mice with rhabdomyolysis-induced acute kidney injury (RIAKI). However, the precise mechanism has not been determined. Therefore, we investigated the role of NLRP3 in renal tubular cells in RIAKI. Methods: Glycerol-mediated RIAKI was induced in NLRP3 KO and wild-type (WT) mice. The mice were euthanized 24 h after glycerol injection, and both kidneys and plasma were collected. HKC-8 cells were treated with ferrous myoglobin to mimic a rhabdomyolytic environment. Results: Glycerol injection led to increase serum creatinine, aspartate aminotransferase (AST), and renal kidney injury molecule-1 (KIM-1) level; renal tubular necrosis; and apoptosis. Renal injury was attenuated in NLRP3 KO mice, while muscle damage and renal neutrophil recruitment did not differ between NLRP3 KO mice and WT mice. Following glycerin injection, increases in cleaved caspase-3, poly (ADP-ribose) polymerase (PARP), and a decrease in the glutathione peroxidase 4 (GPX-4) level were observed in the kidneys of mice with RIAKI, and these changes were alleviated in the kidneys of NLRP3 KO mice. NLRP3 was upregulated, and cell viability was suppressed in HKC-8 cells treated with ferrous myoglobin. Myoglobin-induced apoptosis and lipid peroxidation were significantly decreased in siNLRP3-treated HKC-8 cells compared to ferrous myoglobin-treated HKC-8 cells. Myoglobin reduced the mitochondrial membrane potential and increased mitochondrial fission and reactive oxygen species (ROS) and lipid peroxidation levels, which were restored to normal levels in NLRP3-depleted HKC-8 cells. Conclusions: NLRP3 depletion ameliorated renal tubular injury in a murine glycerol-induced acute kidney injury (AKI) model. A lack of NLRP3 improved tubular cell viability via attenuation of myoglobin-induced mitochondrial injury and lipid peroxidation, which might be the critical factor in protecting the kidney.

Highlights

A recent study showed that early renal tubular injury is ameliorated in Nod-like receptor pyrin domain-containing protein 3 (NLRP3) KO mice with rhabdomyolysis-induced acute kidney injury (RIAKI)
We demonstrated the following: (1) renal damage caused by rhabdomyolysis is mitigated in NLRP3-depleted mice compared to WT mice via alleviation of renal inflammation, apoptosis, and ferroptosis despite no difference in muscle damage; (2) myoglobin-induced apoptosis and lipid peroxidation are attenuated in NLRP3-depleted tubular cells; (3) depletion of NLRP3 in renal tubular cells improves mitochondrial damage and alters mitochondrial biogenesis induced by myoglobin; and (4) the preservation of mitochondria following myoglobin simulation might contribute to alleviating lipid peroxidation
Our study suggested that reduction in mitochondrial damage and lipid peroxidation in renal tubules is the main contributor to the protection of the kidneys in NLRP3 KO mice with RIAKI

Summary

Introduction

A recent study showed that early renal tubular injury is ameliorated in Nod-like receptor pyrin domain-containing protein 3 (NLRP3) KO mice with rhabdomyolysis-induced acute kidney injury (RIAKI). One study demonstrated that glycerol-mediated rhabdomyolysis-induced acute kidney injury (RIAKI) is ameliorated in NLRP3 knockout (KO) mice compared to control mice [13]. We reported that NLRP3 depletion decreases mitochondrial damage and apoptosis in hypoxia; in contrast, overexpression of NLRP3 is sufficient to elevate mitochondrial reactive oxygen species (ROS) levels even under normoxic condition [14] When it forms a complex with ASC and caspase-8 in mitochondria, NLRP3 regulates apoptotic cell death in the renal and gut epithelium [15]. We hypothesized that inflammasome-independent NLRP3, especially in renal tubular cells, is involved in mediating renal injury in RIAKI and we attempted to clarify the precise mechanism underlying myoglobin-induced apoptosis and ferroptosis

Methods

Results

Conclusion