Table_2_Pharmacological Inhibition of Fatty Acid-Binding Protein 4 (FABP4) Protects Against Rhabdomyolysis-Induced Acute Kidney Injury.DOC

<p>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.</p

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<p>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.</p