Activation of nicotinamide phosphoribosyltransferase protects against unilateral renal ischemia-reperfusion injury via the NAD+/SIRT1/PGC-1α signaling pathway and modulation of NFκB/TNF-α/IL-6

Abstract

• In AKI, NAD + is depleted leading to mitochondrial dysfunction and poor outcomes • NAMPT/NAD + protects against IRI while NAMPT inhibition exacerbates renal injury • Via NAD + /SIRT1/PGC-1α, NAMPT activation improves renal function parameters • NAMPT activation inhibits ischemia-driven inflammatory responses through modulation of NFκB/TNF-α/IL-6 reducing immune-mediated damage • NAMPT activation upregulates key mitochondrial biogenesis markers in IRI Renal ischemia is a common cause of acute kidney injury (AKI), particularly in critical care settings, and remains a major challenge in nephrology due to the lack of effective therapeutic options. In AKI, there is an overstimulation of NAD + -consuming enzymes leading to NAD + depletion. To help replenish cellular NAD + stores, this study explores for the first time the therapeutic potential of activating nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme in the NAD + salvage pathway, in a rat model of unilateral renal ischemia-reperfusion injury (IRI). Our findings demonstrate that SBI797812 (SBI)-induced NAMPT activation significantly improves renal function post-IRI, primarily through the NAD + /SIRT1/PGC-1α signaling pathway. NAMPT activation resulted in significant improvement in kidney function, including restored urine flow rate, reduced creatinine and blood urea nitrogen (BUN) levels, and decreased kidney injury biomarkers such as KIM-1 and NGAL. Additionally, SBI led to a reduction in inflammatory markers (NFκB, TNF-α and IL-6), oxidative stress markers, and caspase-3, indicating enhanced renal protection. Western blot analysis further revealed upregulation of key mitochondrial biogenesis markers, including SIRT1, PGC-1α, and TFAM, highlighting the link between NAD + restoration and improved mitochondrial function. In contrast, the inhibition of NAMPT with FK866 exacerbates injury, as indicated by worsened histological features, increased inflammation, and tubular necrosis, confirming the crucial role of NAMPT in mitigating ischemic damage. Considering the importance of NAD metabolism in mitochondrial function and cellular resiliency to tissue injury, these results underscore NAMPT activation as a promising therapeutic strategy for renal IRI, offering new insights for the management of ischemic AKI.