Macrophage accumulation in the arterial wall and smooth muscle cell (SMC) proliferation are features of type 2 diabetes mellitus (DM) and its vascular complications. However, the effects of diabetic monocyte-derived macrophages on vascular SMC proliferation are not clearly understood. In the present study, we investigated the pro-proliferative effect of macrophages isolated from DM patients on vascular SMCs. Macrophage-conditioned media (MCM) were prepared from macrophages isolated from DM patients. DM-MCM treatment induced HASMC proliferation, decreased p21Cip1 and p27Kip1 expressions, and increased microRNA (miR)-17-5p and miR-221 expressions. Inhibition of either miR-17-5p or miR-221 inhibited DM-MCM-induced cell proliferation. Inhibition of miR-17-5p abolished DM-MCM-induced p21Cip1 down-regulation; and inhibition of miR-221 attenuated the DM-MCM-induced p27Kip1 down-regulation. Furthermore, blocking assays demonstrated that PDGF-CC in DM-MCM is the major mediators of cell proliferation in SMCs. In conclusion, our present data support the hypothesis that SMC proliferation stimulated by macrophages may play critical roles in vascular complications in DM patients and suggest a new mechanism by which arterial disease is accelerated in diabetes.

Resistin may be an important link between obesity and diabetes. Recent studies have suggested an association between resistin and atherogenic processes. In addition, CCL19 is highly expressed in human atherosclerotic lesions. The interplays among resistin, CCL19, and shear stress in regulating vascular endothelial function are not clearly understood. In the present study, resistin stimulation induced dose- and time-dependent CCL19 expression in human aortic endothelial cells (HAECs). By using neutralizing antibody and small interfering (si)RNA, we demonstrated that toll-like receptor 4 (TLR4) is critical for resistin-induced CCL19 expression. Transcription factor ELISA and chromatin immunoprecipitation assays showed that resistin increased NF-κB-DNA binding activities in ECs. Inhibition of NF-κB activation by specific siRNA blocked the resistin-induced CCL19 promoter activity and expression. Preshearing of ECs for 12 h at 20 dyn/cm(2) inhibited the resistin-induced NF-κB activation and CCL19 expression. Our findings serve to elucidate the molecular mechanisms underlying the resistin induction of CCL19 expression in ECs and the shear-stress protection against this induction.