Rhabdomyolysis induced AKI via the regulation of endoplasmic reticulum stress and oxidative stress in PTECs

Therapeutic propensity of ginsenosides Rg1 and Rg3 in rhabdomyolysis-induced acute kidney injury and renohepatic crosstalk in rats

BACKGROUND

Ginseng is a traditional herbal medicine used for thousands of years in Southeast Asian countries because of its medicinal properties. Ginsenosides Rg1 and Rg3 have demonstrated therapeutic properties against a broad spectrum of diseases.

PURPOSE

Here in this study, we investigated the therapeutic efficacy of Rg1 and Rg3 in alleviating glycerol-induced acute kidney injury, also known as rhabdomyolysis-induced acute kidney injury (RAKI).

METHODS

AKI was induced in male Wistar rats through intramuscular injection of 10 mL/kg glycerol and simultaneous oral treatment of ginsenosides Rg1 and Rg3 for 3 days. We also evaluated the therapeutic potential of Rg1 and Rg3 on human embryonic kidney epithelial (HEK-293). Cell viability and LDH assay were performed on HEK-293 cells to evaluate the toxicity of Rg1 and Rg3. Evaluation of important kidney damage markers such as creatinine and blood urea nitrogen (BUN) was carried out at different time points from the rat serum. Histopathological analysis was performed on kidney tissues. We also performed experiments such as ELISA assay, immunohistochemistry, immunofluorescence staining, COMET assay, western blotting, TUNEL assay, and flow cytometry to obtain results.

RESULTS

Rg1 and Rg3 significantly downregulated the expression of kidney damage markers such as creatinine and BUN in a dose-dependent manner. Histopathological analysis revealed damage across the glomerulus, tubules, and collecting duct rendering the kidney dysfunctional in glycerol treatment groups. However, Rg1 and Rg3 treated groups showed a significant reduction in tubular necrosis at both 10 and 20 mg/kg. There was also a sharp downregulation of oxidative and ER stress markers. Additionally, we observed nuclear translocation of Nrf2 which were more prominent in kidney tissues. Rg1 and Rg3 were also able to mitigate apoptotic cell death in vitro and in vivo evaluated through immunofluorescence staining for p53, TUNEL assay, flow cytometry, and immunoblotting for intrinsic apoptosis markers.

CONCLUSION

In summary, we conclude that Rg1 and Rg3 exhibited natural therapeutic remedy against AKI.

Rhabdomyolysis-induced acute kidney injury and concomitant apoptosis induction via ROS-mediated ER stress is efficaciously counteracted by epigallocatechin gallate

Rhabdomyolysis induced acute kidney injury (RIAKI) is a life-threatening condition responsible for approximately 19-58% of AKI cases worldwide. We performed an intramuscular injection of glycerol (10 mL/kg) in male wistar rats to induce AKI. Epigallocatechin gallate (EGCG) was administered for 3 consecutive days to evaluate its protective effects. We observed significant downregulation in serum creatinine, blood urea nitrogen (BUN) and LDH at different time points on EGCG treatment groups in a dose-dependent manner. Similarly, H&E staining also revealed that EGCG was able to reduce the formation of damaged tubules and tubular necrosis which was prominently spread throughout the kidney tissue of glycerol treatment group. Concomitantly, we observed upregulated inflammation, ER stress and elevated oxidative stress in the glycerol treated group only, which was significantly normalized upon EGCG treatment in both in vitro and in vivo studies. The occurrence of apoptosis in kidney tubules was found to be relatively higher in glycerol treated group and H₂O₂ treated HEK-293 cells. The results obtained after EGCG treatment revealed a significant decrease in apoptotic cell population, which was further validated by immunofluorescence staining against p53 and comet assay in HEK-293 cells and p53 IHC in kidney tissues. Western blotting also revealed a systemic downregulation of intrinsic mitochondrial apoptotic pathway markers such as bax, bcl-2, pro and cleaved caspase 3, caspase 9 and PARP1. Additionally, the results for flow cytometry analysis and TUNEL assay corroborated apoptotic equilibrium. Conclusively, we reckon EGCG as a multi-therapeutic natural product that can be used the for treatment of AKI.

Mitochondrial targeted ROS Scavenger based on nitroxide for Treatment and MRI imaging of Acute Kidney Injury

INTRODUCTION

Overproduction of reactive oxygen species (ROS) during oxidative stress is a hallmark of acute kidney injure (AKI), which induced the damage to the renal cells and mitochondrial injury.

PURPOSE

In this contribution, we prepared mitochondrial targeted nitroxide, which linked 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl (carboxy-PROXYL) with (2-aminoethyl)triphenylphosphonium bromide (TPP), named TPP-PROXYL to eliminate the ROS in situ and image the oxidative stress reaction by MRI.

METHODS

2,7-Dichlorodihydrofluorescein diacetate (DCFH-DA) staining, mitochondrial membrane potential assay (JC-1) staining and transmission electron microscope (TEM) experiments were processed to verify that TPP-PROXYL could target mitochondria, scavenge the ROS, and prevent damage to mitochondria in live cells. Contrast enhanced MRI also been used to monitor these redox reaction in AKI model.

RESULTS

TPP-PROXYL demonstrated excellent ROS T₁-weighted magnetic resonance imaging (MRI) enhancement in vitro and in vivo, with r₁ value about 0.190 mM^-1·s^-1. In vivo AKI treatment experiments proved that TPP-PROXYL could improve the survival rate of mice and inhibit kidney damage. Moreover, the great ROS scavenging capability and the renal damage reduction during AKI treatment of TPP-PROXYL was verified via MR imaging technology.

CONCLUSION

Collectively, this research provides TPP-PROXYL would serve as a powerful platform to realize ROS scavenging, treatment and MR imaging of AKI.

2-Methylquinazoline derivative 23BB as a highly selective histone deacetylase 6 inhibitor alleviated cisplatin-induced acute kidney injury

Histone deacetylases 6 (HDAC6) has been reported to be involved in the pathogenesis of cisplatin-induced acute kidney injury (AKI). Selective inhibition of HDAC6 might be a potential treatment for AKI. In our previous study, a highly selective HDAC6 inhibitor (HDAC6i) 23BB effectively protected against rhabdomyolysis-induced AKI with good safety. However, whether 23BB possessed favorable renoprotection against cisplatin-induced AKI and the involved mechanisms remained unknown. In the study, cisplatin-injected mice developed severe AKI symptom as indicated by acute kidney dysfunction and pathological changes, companied by the overexpression of HDAC6 in tubular epithelial cells. Pharmacological inhibition of HDAC6 by the treatment of 23BB significantly attenuated sCr, BUN and renal tubular damage. Mechanistically, 23BB enhanced the acetylation of histone H3 to reduce the HDAC6 activity. Cisplatin-induced AKI triggered multiple signal mediators of endoplasmic reticulum (ER) stress including PERK, ATF6 and IRE1 pathway, as well as CHOP, GRP78, p-JNK and caspase 12 proteins. Oral administration of our HDAC6i 23BB at a dose of 40 mg/kg/d for 3 days notably improved above-mentioned responses in the injured kidney tissues. HDAC6 inhibition also reduced the number of TUNEL-positive tubular cells and regulated apoptosis-related protein expression. Overall, these data highlighted that HDAC6 inhibitor 23BB modulated apoptosis via the inhibition of ER stress in the tubular epithelial cells of cisplatin-induced AKI.

Pharmacological Inhibition of Fatty Acid-Binding Protein 4 (FABP4) Protects Against Rhabdomyolysis-Induced Acute Kidney Injury

Acute kidney injury (AKI) is a common and potentially life-threatening complication. Studies confirmed that circulating FABP4 depended on renal function of AKI patients. In our previous study, FABP4 was involved in the pathogenesis of I/R-induced AKI. However, the function of FABP4 in rhabdomyolysis-induced AKI remained poorly understood. In the study, we further investigated the effect of FABP4 in a murine model of glycerol injection-induced rhabdomyolysis. Following glycerol injection, the mice developed severe AKI as indicated by acute renal dysfunction and histologic changes, companied by the increased FABP4 expression in the cytoplasm of tubular epithelial cells. Pharmacological inhibition of FABP4 by a highly selective inhibitor BMS309403 significantly reduced serum creatinine level, proinflammatory cytokine mRNA expression of tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein 1 as well as attenuated renal tubular damage in glycerol-injured kidneys. Oral administration of FABP4 inhibitor also resulted in a significant attenuation of ER stress indicated by transmission electron microscope analysis and its maker proteins expression of GRP78, CHOP, p-perk, and ATF4 in kidneys of AKI. Furthermore, BMS309403 could attenuate myoglobin-induced ER stress and inflammation in renal proximal tubular epithelial cell line (HK-2). Overall, these data highlighted that renal protection of selective FABP4 inhibitor was substantiated by the reduction of ER stress and inflammation in tubular epithelial cells of rhabdomyolysis-induced injured kidneys and suggested that the inhibition of FABP4 might be a promising therapeutic strategy for AKI treatment.

Pharmacological Inhibition of Macrophage Toll-like Receptor 4/Nuclear Factor-kappa B Alleviates Rhabdomyolysis-induced Acute Kidney Injury

Background:

Acute kidney injury (AKI) is the most common and life-threatening systemic complication of rhabdomyolysis. Inflammation plays an important role in the development of rhabdomyolysis-induced AKI. This study aimed to investigate the kidney model of AKI caused by rhabdomyolysis to verify the role of macrophage Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) signaling pathway.

Methods:

C57BL/6 mice were injected with a 50% glycerin solution at bilateral back limbs to induce rhabdomyolysis, and CLI-095 or pyrrolidine dithiocarbamate (PDTC) was intraperitoneally injected at 0.5 h before molding. Serum creatinine levels, creatine kinase, the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, and hematoxylin and eosin stainings of kidney tissues were tested. The infiltration of macrophage, mRNA levels, and protein expression of TLR4 and NF-κB were investigated by immunofluorescence double-staining techniques, reverse transcriptase-quantitative polymerase chain reaction, and Western blotting, respectively. In vitro, macrophage RAW264.7 was stimulated by ferrous myoglobin; the cytokines, TLR4 and NF-κB expressions were also detected.

Results:

In an in vivo study, using CLI-095 or PDTC to block TLR4/NF-κB, functional and histologic results showed that the inhibition of TLR4 or NF-κB alleviated glycerol-induced renal damages (P < 0.01). CLI-095 or PDTC administration suppressed proinflammatory cytokine (TNF-α, IL-6, and IL-1β) production and macrophage infiltration into the kidney (P < 0.01). Moreover, in an in vitro study, CLI-095 or PDTC suppressed myoglobin-induced expression of TLR4, NF-κB, and proinflammatory cytokine levels in macrophage RAW264.7 cells (P < 0.01).

Conclusion:

The pharmacological inhibition of TLR4/NF-κB exhibited protective effects on rhabdomyolysis-induced AKI by the regulation of proinflammatory cytokine production and macrophage infiltration.

Selective Histone Deacetylase 6 Inhibitor 23BB Alleviated Rhabdomyolysis-Induced Acute Kidney Injury by Regulating Endoplasmic Reticulum Stress and Apoptosis

Histone deacetylase 6 (HDAC6) contributed to the pathogenesis of rhabdomyolysis-induced acute kidney injury (AKI) and selective inhibition of HDAC6 activity may be a promising strategy for the treatment of AKI. Compound 23BB as a highly selective HDAC6 inhibitor was designed, synthesized by our lab and exhibited therapeutic potential in various cancer models with good safety. However, it remained unknown whether 23BB as a drug candidate could offer renal protective effect against rhabdomyolysis-induced AKI. In the present study, we investigated the effect of 23BB in a murine model of glycerol (GL) injection-induced rhabdomyolysis. Following GL injection, the mice developed severe AKI as indicated by acute renal dysfunction and histologic changes, accompanied by increased HDAC6 expression in the cytoplasm of tubular epithelial cells. Pharmacological inhibition of HDAC6 by 23BB pretreatment significantly reduced serum creatinine and serum blood urea nitrogen (BUN) levels as well as attenuated renal tubular damage in GL-injured kidneys. HDAC6 inhibition also resulted in reduced TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells, suppressed BAX, BAK, cleaved caspase-3 levels, and preserved Bcl-2 expression, indicating that 23BB exerted potent renoprotective effects by the regulation of tubular cell apoptosis. Moreover, GL-induced kidney injury triggered multiple signal mediators of endoplasmic reticulum (ER) stress including GRP78, CHOP, IRE1α, p-eIF2α, ATF4, XBP1, p-JNK, and caspase-12. Oral administration of 23BB improved above-mentioned responses in injured kidney tissues and suggested that 23BB modulated tubular cell apoptosis via the inactivation of ER stress. Overall, these data highlighted that renal protection of novel HDAC6 inhibitor 23BB is substantiated by the reduction of ER stress-mediated apoptosis in tubular epithelial cells of rhabdomyolysis-induced AKI.

Pharmacological inhibition of fatty acid-binding protein 4 (FABP4) protects against renal ischemia-reperfusion injury

Fatty acid-binding protein 4 (FABP4) is a key mediator of endoplasmic reticulum (ER) stress and apoptosis in diabetes and atherosclerosis. Studies also confirmed that circulating FABP4 depended on renal function in chronic kidney disease (CKD) and acute kidney injury (AKI) patients. However, the function of FABP4 in AKI remains poorly understood and the aim of this study was to investigate the role of FABP4 in ischemia-reperfusion (I/R)-induced AKI. In the present study, renal I/R injury triggered the high expression of the FABP4 gene and protein in the nucleus and cytoplasm of tubular cells of mouse kidney tissue compared to that of Sham. Pretreatment with BMS309403, a highly selective inhibitor of FABP4 at a dose of 20 mg kg⁻¹ d⁻¹ for 4 d, significantly reduced serum creatinine levels to improve acute renal dysfunction and attenuated renal tubular damage in injured kidneys. Pharmacological inhibition of FABP4 also decreased the number of TdT-mediated dUTP nick-end labeling (TUNEL) positive apoptotic tubular cells, accompanied by the down-regulation of cleaved-caspase-3 expression. Furthermore, oral administration of FABP4 inhibitor resulted in a significant attenuation of ER stress indicated by its maker proteins expression of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and caspase-12 in I/R injured kidneys. In vitro, the increased expression of FABP4 in the human renal proximal tubule cell line (HK-2 cell) was induced by hypoxia followed by reoxygenation (HR) and the FABP4 inhibitor resulted in a significant attenuation of cell apoptosis and ER stress in HR-induced HK-2 cells. In summary, these findings indicated that FABP4 contributed to the pathogenesis of I/R-induced AKI and suggested that the inhibition of FABP4 might be a promising therapeutic strategy for AKI treatment.

FABP4 inhibition might attenuate I/R-induced AKI through reducing ER stress and apoptosis.