Cathepsin S inhibition in dendritic cells prevents Th17 cell differentiation in perivascular adipose tissues following vascular injury in diabetic rats

Abstract In the context of diabetes mellitus (DM), the circulating cathepsin S (CTSS) level is significantly higher in the cardiovascular disease group. Therefore, this study was designed to investigate the role of CTSS in restenosis following carotid injury in diabetic rats. To induce DM, 60 mg/kg of streptozotocin (STZ) in citrate buffer was injected intraperitoneally into Sprague‐Dawley rats. After successful modeling of DM, wire injury of the rat carotid artery was performed, followed by adenovirus transduction. Levels of blood glucose and Th17 cell surface antigens including ROR‐γt, IL‐17A, IL‐17F, IL‐22, and IL‐23 in perivascular adipose tissues (PVAT) were evaluated. For in vitro analysis, human dendritic cells (DCs) were treated with 5.6−25 mM glucose for 24 h. The morphology of DCs was observed using an optical microscope. CD4 + T cells derived from human peripheral blood mononuclear cells were cocultured with DCs for 5 days. Levels of IL‐6, CTSS, ROR‐γt, IL‐17A, IL‐17F, IL‐22 and IL‐23 were measured. Flow cytometry was conducted to detect DC surface biomarkers (CD1a, CD83, and CD86) and Th17 cell differentiation. The collected DCs presented a treelike shape and were positive for CD1a, CD83, and CD86. Glucose impaired DC viability at the dose of 35 mM. Glucose treatment led to an increase in CTSS and IL‐6 expression in DCs. Glucose‐treated DCs promoted the differentiation of Th17 cells. CTSS depletion downregulated IL‐6 expression and inhibited Th17 cell differentiation in vitro and in vivo. CTSS inhibition in DCs inhibits Th17 cell differentiation in PVAT tissues from diabetic rats following vascular injury.