Involvement of transient receptor potential canonical 1 (TRPC1) in angiotensin II-induced vascular smooth muscle cell hypertrophy

Angiotensin II (Ang II) induces vascular smooth muscle cell (VSMC) hypertrophy as one of the major events leading to atherosclerosis. Increased Ca2+ entry is an important stimulus for VSMC hypertrophy, but the association with Ang II remains to be determined. Transient receptor potential canonical 1 (TRPC1) forms store-operated Ca2+ (SOC) channels that are involved in Ca2+ homeostasis. Our aim was to ascertain the potential involvement of TRPC1 in Ang II-induced VSMC hypertrophy. For this purpose, we used cultured human coronary artery smooth muscle cells (hCASMCs). Store-operated Ca2+ entry (SOCE) increased in the Ang II-induced hypertrophied cells, and SOC channel blocker inhibited the Ang II-induced hypertrophic response. Although hCASMCs constitutively expressed TRPC1, C3, C4, C5, and C6, only TRPC1 increased in response to Ang II stimulation. TRPC1 siRNA decreased SOCE and prevented Ang II-induced hypertrophy. We found NF-κB binding sites in the 5′-regulatory region of the human TRPC1 gene. An electrophoretic mobility shift assay showed that Ang II increased the TRPC1 promoter's NF-κB binding activity. Co-treatment with NF-κB decoy oligonucleotides not only reduced TRPC1 expression, but also inhibited the hypertrophic responses. In conclusion, our data suggest that Ang II and subsequent NF-κB activation induces hCASMC hypertrophy through an enhancement of TRPC1 expression.