Abstract 043: The Role Of Nicotine-induced Nitrosative And Oxidative Stress In The Development Of Podocyte Damage In The Dahl Ss Rat

Abstract

Introduction: Patients with hypertension or renal disease are more likely to exhibit glomerular pathology associated with smoking. Smoking has been linked to lower nitric oxide (NO) bioavailability, oxidative and nitrosative stress. Nicotine triggers the formation of peroxynitrite (ONOO - ), a highly damaging redox molecule, and was also recently implicated as a contributor to hypertensive renal disease. Here we hypothesize that nicotine induces podocyte damage through peroxynitrite formation, thus causing glomerular function decline and aggravation of kidney damage in the Dahl SS rat. Methods: We performed live confocal imaging on human podocytes to detect the production of ONOO - (HPF), Ca 2+ (Fluo-8), and nitric oxide NO (DAF-FM) in response to nicotine. Seahorse assay was used to detect changes in mitochondrial health. Then, nicotine was chronically infused in the Dahl SS rats using Alzet pumps (0.2 mg/kg/day s.c., 0.4% NaCl, 21 days). Electron microscopy (EM) and Masson's trichrome staining were used to blindly evaluate glomerular and mitochondrial damage. ANOVA with post-hoc comparisons was used for statistical analysis. Results: IHC indicated that human and rat glomerular podocytes express nAChRs. Acute application of nicotine promoted intracellular Ca 2+ and ONOO - transients. The ONOO - response was blocked in the presence of SOD, indicating that ONOO - production requires superoxide. The application of specific nAChR agonists elicited Ca 2+ transients but did not produce ONOO - , suggesting that nitrosative processes may occur independently from Ca 2+ influx or nAChR activation. Incubation with nicotine (12-hrs) resulted in a significant decrease in podocytes’ NO bioavailability (p<0.05) and mitochondrial respiration (p<0.05). In vivo, in the Dahl SS rat nicotine infusion promoted mitochondrial damage in podocytes, which exhibited swelling, loss of cristae, and signs of mitophagy. Masson's trichrome staining and the assessment of glomerular damage showed deterioration of glomerular health. Conclusion: The pathological shift in redox balance in the podocyte is directly associated with nicotine. It may be the primary mechanism responsible for podocyte damage, renal function decline, and blood pressure development in smokers.