In Vitro Effects of Curcumin on Transforming Growth Factor-β-mediated Non-Smad Signaling Pathway, Oxidative Stress, and Pro‐inflammatory Cytokines Production with Human Vascular Smooth Muscle Cells

Transforming growth factor-β (TGF-β) induces pro-inflammatory cytokines expression including interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) and these cytokines are associated with the development of atherosclerosis. Curcumin has anti-atherogenic effects and anti-inflammatory properties in the vascular wall, but the relative mechanisms are almost unknown. In the present study, we investigate the effect of curcumin on modulating the proinflammatory action of TGF-β in human vascular smooth muscle cells (VSMCs) and its molecular mechanisms. Cultured VSMCs were seeded into several groups: a control group (untreated group), a group treated with TGF-β, and several groups treated with TGF-β plus inhibitors. The cells were pretreated with diphenyleneiodonium chloride, DPI, (20 μM), curcumin (5, 10 and 20 μM) and NAcetyl- L-Cysteine, NAC, (10 mM) and then TGF-β (5 ng/mL) was added to the culture medium. The mRNA levels of IL-6 and TNF-α were detected by quantitative Real-Time Polymerase Chain Reaction. For monitoring the Smad2 linker region phosphorylation (pSmad2L), the westernblotting technique was applied and reactive oxygen species (ROS) generation was measured by utilizing 2′,7′-dichlorofluorescein diacetate-based assay.