Malabaricone C inhibits PDGF-induced proliferation and migration of aortic smooth muscle cells through induction of heme oxygenase-1

Malabaricone C (Mal-C), isolated from nutmeg, is known to exert a variety of pharmacological activities. However, the effect of Mal-C on vascular smooth muscle cells (VSMCs) is unknown. This study examined the effect of Mal-C on proliferation and migration of primary rat aortic smooth muscle cells (RASMCs) as well as its underlying mechanisms. Treatment of RASMCs with Mal-C induced both protein and mRNA expression of heme oxygenase-1 (HO-1) in a dose- and time-dependent manner. Mal-C-mediated HO-1 induction was inhibited by treatment with actinomycin D or by cycloheximide. SB203580 (a p38 inhibitor), SP600125 (a JNK inhibitor), U0126 (a MEK inhibitor), and N-acetylcysteine (NAC, an antioxidant) did not suppress Mal-C-induced HO-1 expression. In contrast, LY294002 (a PI3K inhibitor) blocked Mal-C-induced HO-1 expression. Moreover, RASMCs treated with Mal-C exhibited activation of AKT in a dose- and time-dependent manner. Treatment of RASMCs with Mal-C increased nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2), which is a key regulator of HO-1 expression, and this translocation was also inhibited by LY294002. Consistent with the notion that HO-1 has protective effects against VSMCs, Mal-C remarkably inhibited platelet-derived growth factor (PDGF)-induced proliferation and migration of RASMCs. However, inhibition of HO-1 significantly attenuated the inhibitory effects of Mal-C on PDGF-induced proliferation and migration of RASMCs. Taken together, these findings suggest that Mal-C could suppress PDGF-induced proliferation and migration of RASMCs through Nrf2 activation and subsequent HO-1 induction via the PI3K/AKT pathway, and may be a potential HO-1 inducer for preventing or treating vascular diseases.