Induction of antioxidant genes by sulforaphane and klotho in human aortic smooth muscle cells

Vascular smooth muscle cell (SMC) dysfunction due to enhanced oxidative stress contributes to age-related cardiovascular diseases such as atherosclerosis and calcification. Klotho, a protein with multiple pleiotropic effects associated with anti-ageing, can extend lifespan when overexpressed while its deficiencies result in rapid aging. It exists in membrane and secreted forms with distinct pleiotropic functions, with the secreted form regulating ion channels, suppressing growth factor signaling and oxidative stress while the transmembrane protein forms a co-receptor for FGF23, although the mechanisms involved in its actions remain to be fully elucidated. Sulforaphane (SFN) is an isothiocyanate present in cruciferous vegetables that can induce antioxidant defence enzymes such as heme oxygenase-1 (HO-1) and peroxiredoxin-1 (Prx-1). The present study investigates whether SFN or klotho increases antioxidant defences in cultured human aortic SMC. Cells were treated (0-24h) with either SFN (0-5µM) or klotho (0-1nM) and HO-1, Prx-1 expression determined by western blot analyses and glutathione (GSH) levels measured using the o-phthalaldehyde fluorescence assay. SFN significantly (p<0.05, n=3) enhanced both HO-1 and Prx-1 protein expression and GSH levels in SMC at 12 and 24h while klotho treatments significantly (p<0.05, n=3) augmented HO-1 and Prx-1 expression only at 24h but significantly increased GSH levels after both 8h and 24h. Interestingly preliminary data suggest that treatment of SMC with SFN for 12 or 24h enhances the expression of klotho. Taken together, these findings demonstrate that both SFN and klotho can enhance antioxidant defences which may protect against vascular SMC dysfunction in age-related cardiovascular diseases