PDK4/SMAD3/HIF-1α Circle Enhances AKI Susceptibility in DKD through Fibrosis

Abstract

<p>Background</p><p>Patient with diabetic kidney disease (DKD) is more susceptible to acute kidney injury (AKI). Our RNAseq data suggested that the reactive oxygen species (ROS) may contribute to AKI sensitivity. Pyruvate dehydrogenase kinase 4 (PDK4) is the key regulator of mitochondria-derived metabolites in cells. Previous studies have revealed that TGF-β/SMAD3 signaling activation promotes fibrosis in DKD. The study aimed to investigate whether the interplay among PDK4, SMAD3 and HIF-1α enhances AKI sensitivity in patients with DKD.<br></p><p>Methods</p><p>The ischemia/reperfusion (I/R) induced AKI models were conducted in db/m and db/db mice. Kidney epithelial cells were treated high glucose with/without the hypoxia and reoxygenation (HG + H/R) conditions. Chromatin immunoprecipitation (ChIP)-qPCR were utilized to identify the promoter binding site at gene transcriptional level. Gain to loss-function of inter-players were used to further confirm the results.<br></p><p>Results</p><p>The injuries (KIM-1, fibronectin) in the I/R-treated db/db mice and the HG + H/R treated kidney epithelial cells were significant increased, associated with the elevated levels of PDK4, p-SMAD3 and HIF-1α. Suppression of PDK4 by PDK4-IN-1 hydrochloride attenuated AKI (KIM-1, fibronectin) and downregulated p-SMAD3 and HIF-1α. In addition, inhibition of p-SMAD3 by SIS3 downregulated HIF-1α. The ChIP-qPCR data showed that p-SMAD3 bound to HIF-1α promoter region and enhanced HIF-1α transcription. Interestingly, overexpressed HIF-1α increased PDK4 while inhibition of HIF-1α by YC-1 down-regulated PDK4, suggesting PKD4/SMAD3/HIF-1α play the circular regulation in AKI in diabetic kidney. <br></p><p>Conclusion</p><p>The PDK4/SMAD3/HIF-1α circular regulatory loop enhances AKI in DKD. Targeting on the regulatory loop may suppress the AKI in patients with DKD.</p>