ABSTRACT
Delayed wound healing in diabetes is characterized by sustained activation of inflammasome and increased expression of IL-1ß in macrophages. Identification and validation of novel pathways to regulate IL-1ß expression will provide therapeutic targets for diabetic wounds. Here we report sustained over-expression of histone deacetylase 6 (HDAC6) in wounds of diabetic mice and its role in delayed wound healing. Topical application of HDAC6 inhibitor; Tubastatin A (TSA) gel promoted the wound healing in diabetic mice. TSA hydrogel reduced the infiltration of neutrophils, T-cells and macrophages in the early phase of wound healing. TSA treatment promoted the wound healing by inducing collagen deposition, angiogenesis (CD31) and fibrotic factors (TGF-ß1) in the late phase of healing. Protein analysis of the diabetic wounds treated with TSA showed increased acetylated α-tubulin and decreased levels of mature IL-1ß with no significant effect on the expression of pro-IL-1ß, pro-caspase-1 and active caspase-1. In in vitro assays, macrophages exhibited upregulation of HDAC6, IL-1ß and downregulation of IL-10 upon stimulation with high glucose and LPS. TSA inhibited the IL-1ß secretion and promoted IL-10 in stimulated macrophages with high glucose and LPS. Further investigations showed that TSA inhibits IL-1ß release by inhibiting tubulin dependent lysosomal exocytosis without affecting its transcription and maturation. Nocodazole (known acetylation inhibitor) pre-treatment inhibited TSA effect on IL-1ß secretion in high glucose stimulated macrophages. Overall, our findings indicate that sustained HDAC6 expression in diabetic wounds contributes to impaired healing responses and HDAC6 may represent a new therapeutic target for diabetic wounds.
