Melatonin Renoprotection against Vancomycin Toxicity: Dual Activation of Melatonin Receptors and NRF2 Signaling

Abstract ID 100225 Poster Board 015 Background and Purpose Vancomycin-associated acute kidney injury (VA-AKI) is a critical concern in hospitalized patients with sepsis. Frequent use of vancomycin, a broad-spectrum antibiotic, to empirically treat septic patients and insufficient mitigation strategies necessitate a novel renoprotective intervention. In a recent retrospective analysis, we observed a significantly lower incidence of VA-AKI in patients receiving melatonin, a preferred sleep medication in hospitals. Beyond its role as a free radical scavenger, melatonin has been speculated to exert its indirect antioxidant activity potentially through G-protein coupled receptors, melatonin receptor type 1 (MT1) and type 2 (MT2) and the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant transcription factor. In this study, we sought to identify the signaling mechanisms by which melatonin protects against vancomycin toxicity in human kidney cells. Methods Human kidney proximal tubule HK-2 cells and shRNA-generated NRF2 knockdown HK-2 cells were treated with increasing concentrations of vancomycin (0-40 mM) for up to 30 h. Cells were pretreated with melatonin at clinically-relevant concentrations (16-32 μM) for 24 h followed by co-incubation with vancomycin (4 or 6 mM). To investigate the specific role of MT receptors in renoprotection, FDA-approved MT1/MT2 agonists (ramelteon, 1-1,000 nM; tasimelteon, 0.1-50 nM), the nonselective MT1/2 antagonist luzindole (1-5 uM), and the MT2 antagonist 4-P-PDOT (10-20 nM) were used. Cytotoxicity was assessed every 4 hours by propidium iodide (PI) staining using a Cytation 5 imager with a Biospa incubator. Results Melatonin significantly reduced the cytotoxicity of vancomycin (4 and 6 mM) by up to 26% in HK-2 cells pretreated with melatonin. Similarly, vancomycin cytotoxicity was decreased by both MT receptor agonists. By comparison, co-treatment with MT receptor antagonists, particularly MT2, blunted the anti-apoptotic effects of melatonin. In addition, the ability of melatonin to prevent vancomycin-induced kidney toxicity was not observed in NRF2 knockdown HK-2 cells. Conclusions Melatonin prevented the apoptosis of kidney cells exposed to vancomycin by activating the signaling of MT receptors and the NRF2 antioxidant pathway. Additional in vitro studies are investigating the intertwined molecular signaling between NRF2 and MT receptors. We are also conducting a randomized controlled trial to evaluate the clinical utility of melatonin for preventing drug-induced kidney injury in hospitalized patients. Supported by R01DK131214, T32ES007148, UL1TR003017, and P30ES005022.