The transient receptor potential melastatin 2 cation channel (TRPM2) is redox-sensitive and promotes Ca
2+
influx after H
2
O
2
activation through oxidative modification and PARP-ADPR-dependent mechanisms. TRPM2 also regulates Na
+
influx, and by increasing [Na
+
]i interferes with the Na
+
-Ca
2+
exchanger (NCX) inducing reverse mode action, promoting Ca
2+
influx. These processes may be driven by Nox4-derived H
2
O
2.
We tested the hypothesis that vascular dysfunction in hypertension involves oxidative stress-induced TRPM2 activation through H
2
O
2
production, which in turn promotes Ca
2+
influx. Mesenteric arteries isolated from wildtype (WT), LinA3 (mice expressing human renin with Ang II-dependent hypertension), Nox4
-/-
and LinA3/Nox4
-/-
mice and vascular smooth muscle cells (VSMCs) from hypertensive and normotensive patients were used. Arteries from hypertensive LinA3 mice, exhibit increased U46619-induced vasoconstriction versus WT mice (Emax - LinA3
vs
WT: 9.37 ± 0.51
vs
6.79 ± 0.29), an effect attenuated by olaparib (PARP-ADPR inhibitor) and 2-APB (TRPM2 blocker) and also increased mRNA expression (Fold change - related to control) of NOX4 (3.05 ± 0.30), TRPM2 (1.38 ± 0.24), NCX (1.973 ± 0.34) and salt inducible kinase 1 (1.833 ± 0.12) and sodium-potassium pump (1.43 ± 0.16), which are activated when intracellular levels of Na
+
rise beyond a critical point. These events seem to be regulated by NOX4, since they were not observed in mesenteric arteries from LinA3/Nox4
-/-
mice. Ang II-induced Ca
2+
influx is potentiated in VSMCs from hypertensive patients (AUC-Ex490/Em535: normotensive: 15400±917.5
vs
hypertensive - 22460±2388), a response followed by increased generation of O
2
-
and H
2
O
2
in cells from hypertensive patients. These ROS effects were attenuated by catalase, and 2-APB, 8-br and olaparib (TRPM2 inhibitors) and benzamil, KB-R7943 and YM244769 (NCX inhibitors). Our data indicate that TRPM2 ion channel activation contributes to redox-sensitive vascular dysfunction in hypertension. These findings suggest that dysregulation of TRPM2-NOX4-derived ROS and NCX may contribute to redox- and Ca
2+
signalling important in vascular function in hypertension. TRPM2 may be a point of cross-talk between ROS and Ca
2+
signalling.
Critical Intracellular Ca2+Dependence of Transient Receptor Potential Melastatin 2 (TRPM2) Cation Channel Activation
