An oxidant‐sensitive TRPM2 channel expressed in the afferent arteriole regulates Ang II‐induced vessel constriction

TRPM2 is oxidant‐activated and non selective cation channel expressed in mammalian tissues. We hypothesized that TRPM2 is expressed in renal afferent arterioles (Af‐Art) and regulates AngII‐induced vasoconstriction. A superficial Af‐Art with its attached glomerulus was microdissected from a mouse kidney and perfused with an array of pipettes at 60 mm Hg. Ang II (10 −9 M) induced constriction of the Af‐Art from 11.2 ± 0.5 to 8.7 ± 0.8 μm. This constriction was blocked by treating the Af‐Arts with either 3,4‐dihydro‐5‐[4‐(1‐piperidinyl)butoxyl]‐1(2H)‐isoquinolinone (DPQ, 10 −5 M) or 3‐aminobenzamide (3‐AB, 10 −3 M), non‐specific inhibitors of TRPM2. We then confirmed that these perfused Af‐Arts expressed TRPM2 using RT‐PCR and immunoblotting. Finally, we silenced the TRPM2 in the Af‐Arts by treating them with a siRNA against TRPM2 for 24 hours. Expression of TRPM2 was decreased by 75% as measured by RT‐PCR and 70% as measured by immunoblotting. Silencing TRPM2 with the anti‐TRPM2 siRNA also blocked AngII‐induced vasoconstriction of the perfused Af‐Art, whereas Af‐Arts treated with scrambled siRNA showed the same responsiveness to AngII as freshly dissected and perfused Af‐Arts. Thus our results suggest that TRPM2 channels in mice Af‐Art are necessary for AngII‐induced vasoconstriction, and thus may play an important role in the regulation of the renal microcirculation.