Salt-induced vascular damage in hypertension involves redox activation of PARP/TRPM2 signalling and inflammasome assembly.

Abstract

Objectives: Excess sodium intake induces vascular dysfunction. Molecular mechanisms underlying this are unclear. Here we investigated the role of reactive oxygen species (ROS), Ca2+ signalling and inflammation in salt-induced vascular injury, focusing on the interplay between redox-sensitive Poly(ADP-ribose) polymerase (PARP), which activates transient receptor potential melastatin 2 (TRPM2) Ca2+ channel, and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome. Specifically, we sought to determine if salt excess induces a pro-oxidant environment, leading to PARP-induced TRPM2 activation and increased Ca2+ influx, inflammasome assembly, and consequent vascular damage.

Methods and results: Vascular smooth muscle cells (VSMCs) from rats and humans were exposed to normal NaCl (140 mM) and high salt conditions (180 mM). High salt increased ROS generation, PARP activation, and TRPM2-mediated Ca2+ transients. Osmotic controls had no effect on these processes. High-salt medium promoted release of pro-inflammatory cytokines IL-18 and IL-1β and increased phosphorylation of myosin light chain (MLC) in VSMCs. These effects were attenuated by inhibitors of PARP (Olaparib), TRPM2 (8-Br-cADPR) and NLRP3 inflammasome (MCC950). To validate these findings in in vivo, mice were subjected to a high-salt diet (4% NaCl, 5 weeks), resulting in elevated blood pressure and vascular remodelling and dysfunction. Exposure of vessels to olaparib and MCC950 attenuated the hypercontractility associated with high-salt diet.

Conclusion: salt-induced vascular injury in hypertension involves ROS generation in VSMCs leading to activation of the PARP/TRPM2 axis, increased Ca2+ influx, NLRP3 activation and vascular injury. Our study provides new insights into molecular pathways involved in high-salt diet-induced vascular dysfunction, important in hypertension.