ABSTRACT
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 .
ABSTRACT
AIM: To study the effect of tick anticoagulant peptide-staphylococcal superantigen like protein 5 (TAP-SSL5), an anti-inflammatory and anticoagulant fusion protein , on the binding of activated platelets to human lym-phocytes.METHODS:Human periphery lymphocytes were isolated by magnetic activated cell sorting (MACS).The toxic-ity of TAP-SSL5 on the viability of Jurkat cell was assessed by CCK-8 assay.Flow cytometry was applied to detect the ex-pression of CD162 (PSGL-1) on the Jurkat cells (human peripheral blood leukemia T lymphocyte cell line ) and the inhibi-tory effect of TAP-SSL5 on the binding of mouse anti-human CD162 monoclonal antibody (KPL-1) to Jurkat cells.Platelets were activated by ADP at concentration of 20μmol/L, the binding rates of activated platelets to Jurkat cells or human lym-phocytes were assayed by flow cytometry .RESULTS:The concentration of TAP-SSL5 below 30 mg/L didn’ t affect the vi-ability of Jurkat cells .TAP-SSL5 at 10 mg/L competitively inhibited KPL-1 binding to Jurkat cells .The binding rates of activated platelets to Jurkat cells or lymphocytes were (11.86 ±4.49)% and (8.32 ±1.00)%, respectively, which de-creased to (6.73 ±2.71)%and (5.51 ±0.70)%after the Jurkat cells and lymphocytes were pre-incubated with 10 mg/L TAP-SSL5 (P <0.05).CONCLUSION:TAP-SSL5 binds to PSGL-1 expressed on lymphocyte surface and directly in-hibits the binding of activated platelets to human lymphocytes , which may be one of the anti-inflammatory mechanisms of TAP-SSL5.