RESUMO
AIM:Early calcification of atherosclerotic plaques are colocalized with macrophage and high mobility group box 1 (HMGB1), a cytokine associated with biomineralizing process under physiological and pathological conditions .Our study aims to evaluate whether HMGB1 induces ectopic mineralization via promoting the secretion of matrix vesicles ( MVs) from macrophages .METHODS:HMGB1 was added to the medium of macrophages , the secretion of MVs in the supernatant was tested by flow cytometry analysis .The mineral deposition in calcifying medium was detected by Alizarin Red staining and von Kossa staining .Transmission electron microscopy showed the formation of hydroxyapatite crystals in MVs .Then we subcutaneous injection into mice with MVs to induce regional minera-lization.RESULTS:HMGB1 significantly promoted secretion of MVs from macrophages as raveled by flow cytometry analysis .TNAP activity, considered as a marker of MVs maturation , was higher in HMGB1-induced MVs compared to the control-MVs.HMGB1-MVs also led to mineral deposition in an in vitro MVs-collagen mineralization model .Subcutaneous injection into mice with MVs derived from HMGB1-treated cells showed a greater potential to initiate regional mineralization .Mechanistic experiments revealed that HMGB 1 activated neutral sphingomyelinase 2 ( nSMase2 ) that involved the receptor for advanced glycation end products ( RAGE ) and p38 MAPK (upstream of nSMase2).Inhibition of nSMase2 with GW4869 or p38 MAPK with SB-239063 prevented MVs secretion and min-eral deposition .CONCLUSIONS: HMGB1 induces MVs secretion from macrophages at least in part , via the RAGE/p38 MAPK/nSMase2 signaling pathway .Our findings thus reveal a novel mechanism by which HMGB 1 may participated in the early calcification of atherosclerotic plaques .