Abstract 36: High Salt Induces Vascular Damage Through Redox-sensitive Parp/trpm2-induced Calcium Influx And Inflammasome Modulation Without Influencing Blood Pressure

Abstract

High salt diet (HSD) has deleterious effects on the vasculature by mechanisms not fully elucidated. We demonstrated tight coupling between Na + and Ca 2+ levels in VSMCs, where PARP-regulated TRPM2, a redox-sensitive Ca 2+ channel, plays an important role. Increased [Ca 2+ ]i also contributes to inflammasome assembly, which dysregulates vascular function. We hypothesized that HSD induces a pro-oxidant environment that contributes to PARP-induced TRPM2-activation, Ca 2+ influx and inflammasome assembly, leading to vascular damage. WKY rats were treated with 1% HSD (3 weeks). Blood pressure was assessed by tail-cuff methodology, vascular reactivity was assessed in mesenteric arteries and calcium influx, ROS generation, inflammasome and pro-contractile marker in vascular smooth muscle cells (VSMCs) in presence and absence of HS medium (HSM-140mM). HSD did not increase blood pressure (BP), but vascular contractility was exaggerated (Emax(mN): WT 10.20 ± 0.70 vs 15.17 ± 1.74), effect reversed by PARP (Emax: 11.14 ± 1.24) and TRPM2 (8-br) (Emax: 11.45 ± 1.11) inhibitors. In VSMCs, HSM behaves as a pro-oxidant agent (ROS-AU: Control 77.51 ± 2.80 vs 130.04 ± 13.89 HSM), leading to increased [Ca 2+ ]i (AUC: Control 25562.45 ± 880.48 vs 30924.8 ± 1263.85 HSM) and activation of myosin light chain (pMLC-AU: Control 99.27 ± 1.01 vs 626.87 ±71.28 HSM), by mechanisms dependent on ROS and PARP/TRPM2 activation. HSM also increased expression of inflammasome components NLRP3 (2 ΔΔCt : Control 1.20 ± 0.01 vs 1.85 ± 0.19 HSM), ASC (2 ΔΔCt : Control 1.02 ± 0.01 vs 1.49 ± 0.17 HSM) and Caspase 1 (2 ΔΔCt : Control 1.06 ± 0.03 vs 2.35 ± 0.46 HSM), which was prevented by ROS scavenger Tiron and PARP inhibitor. In conclusion, HSD-induced vascular hypercontractility involves ROS activation of PARP/TRPM2 signalling. Activation of PARP/TRPM2 was associated with increased [Ca 2+ ]i and activation of pro-contractile signaling and inflammasome assembly. Normal BP in HSD-fed rats in the presence of vascular damage suggests that ROS/PARP/TRPM2 signaling induced by salt influences vascular function independently of BP elevation. We identify a novel pathway that underlies salt-induced vascular damage and suggest a potential therapeutic role for PARP/TRPM2 inhibitors in vascular dysfunction.