Angiotensin II type 1 receptor-associated protein prevents vascular smooth muscle cell senescence via inactivation of calcineurin/nuclear factor of activated T cells pathway

Abstract 

Emerging new research suggests that the functions of the angiotensin (Ang) II type 1 (AT₁) receptor are regulated in a complex manner. AT₁ receptor-associated protein (ATRAP) has been reported to reduce AT₁ receptor signaling with enhancement of AT₁ receptor internalization and to regulate the calcineurin/nuclear factor of activated T cells (NFAT) pathway. We examined the possibility that ATRAP could attenuate AT₁ receptor-mediated vascular senescence via inactivation with the calcineurin/NFAT pathway. Ang II stimulation significantly increased senescence-associated β-galactosidase (SA-β-gal)-stained cells, oxidative stress, and expression of p53 and p21 in wild-type (WT) vascular smooth muscle cells (VSMC). Moreover, in WT VSMC, Ang II stimulation enhanced NFAT transcriptional activity, which was prevented by CAML-siRNA treatment. NFAT-siRNA treatment attenuated Ang-II-increased SA-β-gal activity and p53 and p21 expression. Treatment with a calcineurin activity inhibitor, cyclosporin A, reduced Ang-II-induced NFAT transcriptional activity and senescent VSMC. In contrast, VSMC prepared from ATRAP transgenic (ATRAP-Tg) mice exhibited attenuation of Ang-II-induced SA-β-gal activity, oxidative stress, NFAT transcriptional activity, and expression of p53 and p21. Moreover, ATRAP-Tg VSMC showed a more reduction of Ang-II-induced NFAT transcriptional activity by CAML-siRNA treatment than WT VSMC. Furthermore, we demonstrated that in ATRAP-Tg VSMC, NFAT activity and senescent cells induced by ultraviolet irradiation were decreased compared with those in WT VSMC. Treatment with an AT₁ receptor blocker, valsartan, blocked these senescent cells but did not change NFAT activity in both cells. These results suggest that ATRAP negatively regulates VSMC senescence by reducing AT₁ receptor signaling, and that ATRAP-mediated inactivation of the calcineurin/NFAT pathway could be at least partly involved in prevention of VSMC senescence, irrespective of AT₁ receptor blockade in some conditions.

Keywords: Angiotensin II type 1 receptor-associated protein, Vascular smooth muscle cell, Senescence, Vascular disease, Calcineurin/nuclear factor of activated T cells