A comprehensive role of Toll-like receptors (TLRs) in diabetic wound healing
Diabetes is marked by delayed wound healing response and prolonged phase of inflammation. Toll-like receptors (TLRs) are the key pathogen recognition receptors known to regulate inflammation in wound healing. Therefore, we aim to investigate the role of TLRs in delayed healing of diabetic wounds. TLR (1-9) expression studies were conducted using J774 macrophage cell line. Further, primary macrophages were isolated from wound tissues of db/db mice, subjected to RT-PCR and western blot analysis. The RT-PCR expression of TLRs revealed that expression of TLR2, TLR4, TLR5, TLR6, TLR7 and TLR8 were significantly upregulated in macrophage cells, cultured in high glucose medium. Expression of TLR 1-9 were significantly upregulated in wound tissues of db/db mice. However, TLR1, TLR2 and TLR4, TLR6, TLR7 were only found upregulated in the primary macrophages. Only TLR2 and TLR4 exhibited significantly increased protein expression. Further, TLR2 and TLR4 inhibition by OxPAPC (1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine) impregnated hydrogels, resulted in a significantly increased rate of wound healing in db/db mice via decreasing the significant levels of TNF- and IL-1{beta}. These results show that increased TLR 2 and TLR 4 expression underlies delayed wound healing in diabetes and a hydrogel impregnated with OxPAPC may be a promising therapeutic strategy for the management of diabetic wounds. Our study goes closer in understanding the molecular mechanism and provides a novel treatment method in diabetic wounds.