Abstract TAC276: Nicotine Causes Nitrosative Stress and Elevated Intracellular Ca ²⁺ in Renal Proximal Tubule Cells

Introduction: Chronic nicotine exposure (via vaping, smoking or nicotine replacement therapy) poses substantial risks to CV health, particularly in individuals with pre-existing renal disease and hypertension (HTN). It has been reported that nicotine exacerbates endothelial injury, however, the mechanisms of nicotine-induced renal epithelial damage are unknown. Proximal tubule (PT) epithelial cells play a critical role in renal disease progression, and due to their high metabolic demands, are especially vulnerable to stress. We hypothesize that nicotine disrupts calcium homeostasis and promotes nitrosative stress in PT cells, contributing to cellular injury and HTN development. Methods: 0.4% NaCl (normal salt) diet fed male Dahl SS rats were implanted with telemeters and infused with nicotine (4.8 mg/kg/day) via s.c. osmotic pumps for 21 days. Mitochondrial morphology in the PTs was evaluated by electron microscopy. Live confocal imaging was performed on cultured opossum kidney (OK) PT cells using HPF, Fluo-8, and TMRM to detect peroxynitrite (ONOO - ), calcium transients, and mitochondrial ΔΨm following nicotine exposure (100 nM–5 mM). MTT assays evaluated cell proliferation in response to nicotine. Data were analyzed using OriginPro (1-way ANOVA). Results: Nicotine-infused rats showed elevated MAP throughout the recording period (average increase in MAP compared to control was 11 mmHg, p<0.05 on days 10 to 14); no differences in heart rate were observed. In the PTs, EM revealed increased mitochondrial swelling, cristae loss and increased damage in nicotine-exposed rat PT (p < 0.05). In cultured PT cells, nicotine reduced ΔΨm, induced acute production of peroxynitrite, and dose-dependent Ca 2+ transients with an EC 50 of 178 ± 15 μM (quantified based on peak Ca 2+ signal). MTT assays revealed a concentration-dependent decline in PT cell viability, with up to 20% cell death from 100 nM–300 μM and up to 45% at 5 mM after a 5 min acute exposure to nicotine (p<0.05). Conclusion: Chronic nicotine exposure results in increased BP and mitochondrial damage in the PT. Acute application of nicotine impairs PT cell viability, disrupts calcium signaling, induces transient peroxynitrite generation, and reduces ΔΨm. These findings highlight the continuing need to elucidate nicotine’s mechanistic effects on renal epithelial cells to better inform therapies for nicotine-related kidney disease.