Effect of Arginine on Nlrp3 and Nrf2 Signaling Pathways in the Kidney: Models of Septic Acute Kidney Injury and Chronic Diabetic Nephropathy

Kidney disease is the 9th leading cause of death in Taiwan. Sepsis-induced acute kidney injury and chronic nephropathy are complications commonly seen in critically ill and diabetic patients. Inflammasome is a nucleotide-binding domain leucine-rich repeat containing protein (NLRP) family. Among them, NLRP3 is most closely related to inflammation. Activation of NLRP3 promote the production of interleukin (IL)-1 and IL-18 which may result in oxidative stress and pyroptosis of the kidney. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor. Under catabolic and oxidative stress, Nrf2 moves from cytosol to the nucleus and binds antioxidant response element (ARE), which may consequently enhance the anti-oxidative gene expression. The expression of Nrf2 signaling pathway was thought to alleviate the inflammation associated with NLRP3 activation. Arginine (Arg) can be synthesized via citrulline-Arg pathway in the kidney. Therefore, kidney dysfunction may reduce the levels of Arg in the body. Arg is the precursor of nitric oxide which have regulatory role in maintaining normal kidney physiological function. At present, no study investigated the impact of Arg on NLRP3/Nrf2 signaling pathway in kidney disease. We plan to carry out 4 experiments in this study to clarify the possible role of Arg-NO on the regulation of NLRP3/Nrf2-associated signal expression under acute and chronic kidney diseases. Exp. 1 is an animal study. Acute kidney injury will be induced by cecal ligation and puncture. Arg or iNOS inhibitor will be administered by tail vein injection in order to know whether NO is responsible for the alteration of NLRP3/Nrf2 pathway under acute kidney injury. Exp. 2 is an in vitro study to mimic an inflammatory condition of kidney immune cells and tubular cells. LPS will be treated as a stimulator and dendritic cell derived from mouse bone marrow, macrophage and mouse primary tubular cells will be used to investigate the influence of different Arg concentrations and iNOS inhibitor on NLRP3/Nrf2 pathway. Exp. 3 is a chronic diabetic nephropathy model. Mice will be fed a high fat diet either with or without 2% Arg for 32 weeks. This study design intends to understand whether Arg administration alleviate hyperglycemic-induced inflammation and regulate the balance of NLRP3/Nrf2 pathway. Exp. 4 propose to use the same cell models as Exp. 2. The cells will be cultured in high glucose medium to mimic a hyperglycemic environment and different Arg levels and iNOS inhibitor will be administered to investigate the effect of Arg/NO on regulating the homeostasis of NLRP3/Nrf2 pathway. This study will provide useful information for clinical application in subjects with acute kidney injury and diabetic nephropathy.