Melatonin Inhibits in Vitro Smooth Muscle Cell Inflammation and Proliferation and Atherosclerosis in Apolipoprotein E-Deficient Mice

Chronic inflammation and proliferation play important roles in atherosclerosis progression. This study aimed to identify the mechanisms responsible for the anti-inflammatory and antiproliferative effects of melatonin on tumor necrosis factor-α (TNF-α)- and platelet-derived growth factor-BB (PDGF-BB)-treated rat aortic smooth muscle cells (RASMCs). Melatonin reduced TNF-α-induced RASMC inflammation by decreasing vascular cell adhesion molecule-1 (VCAM-1) expression and nuclear factor-kappa B (NF-κB) P65 activity by inhibiting P38 mitogen-activated protein kinase phosphorylation ( P < 0.05). Additionally, melatonin inhibited PDGF-BB-induced RASMC proliferation by reducing mammalian target of rapamycin (mTOR) phosphorylation ( P < 0.05) but not migration in vitro. Melatonin also reduced TNF-α- and PDGF-BB-induced reactive oxygen species (ROS) production ( P < 0.05). Furthermore, melatonin treatment (prevention and treatment groups) significantly repressed high cholesterol diet-stimulated atherosclerotic lesions in vivo (19.59 ± 4.11%, 20.28 ± 5.63%, 32.26 ± 12.06%, respectively, P < 0.05). Taken together, the present study demonstrated that melatonin attenuated TNF-α-induced RASMC inflammation and PDGF-BB-induced RASMC proliferation in cells and reduced atherosclerotic lesions in mice. These results showed that melatonin has anti-inflammatory and antiproliferative properties and may be a novel therapeutic target in atherosclerosis.