HMGB1 enhances AGE-mediated VSMC proliferation via an increase in 5-LO-linked RAGE expression

Receptors for advanced glycation end-product (RAGE) play a pivotal role in the progression of proliferative vascular diseases. However, the precise mechanisms regulating RAGE expression in vascular smooth muscle cells (VSMCs) of the injured vasculatures is unclear. Given the potential importance of 5-lipoxygenase (5-LO) derived mediators in cellular responses mediated by RAGE, this study aimed to evaluate in VSMCs treated with high mobility group box 1 (HMGB1): 1) the RAGE expression; 2) the AGE-induced VSMC proliferation; 3) the role of 5-LO signaling in HMGB1-induced RAGE expression. In cultured human VSMCs stimulated with HMGB1 (100 ng/ml), RAGE mRNA and protein expression were markedly increased along with an increase in AGE-mediated VSMC proliferation. Both of these effects were markedly attenuated in cells pretreated with zileuton (1-10 μM), a 5-LO inhibitor, as well as in cells transfected with 5-LO siRNA, suggesting a potential involvement of 5-LO signaling in HMGB1-mediated RAGE expression in VSMCs. Moreover, 5-LO expression, accompanied by production of leukotrienes was markedly increased in HMGB1-stimulated VSMCs, which was attenuated in cells deficient of TLR2 or RAGE. Taken together, our results suggest that HMGB1-induced increase in 5-LO expression enhances RAGE expression in VSMCs, which stimulates AGE-mediated VSMC proliferation. Thus, the 5-LO-RAGE signaling axis in VSMCs might serve as a potential therapeutic target for vascular remodeling in the injured vasculature.