Epigenetic Regulation of the COX-2/PGE2 Pathway in Macrophages Results in Impaired Wound Healing in Diabetes

Abstract

Abstract Macrophage (Mϕ) plasticity, allowing for transition of Mϕs from an inflammatory to a reparative phenotype, is critical for normal wound healing. In pathologic conditions, such as type 2 diabetes (T2D), wounds fail to heal due to impaired resolution of inflammation. There is increasing evidence that epigenetic-based mechanisms, including DNA hypomethylation, control Mϕ function. The cyclooxygenase (COX)-2/Prostaglandin E2 (PGE2) axis as well as upstream pathways including cytosolic phospholipase (c(PL)A2), involved in the release arachidonic acid, have been associated with chronic inflammation, however they have not been examined in diabetic wounds. The purpose of this study was to investigate if epigenetic modifications alter gene expression of the COX-2/PGE2 and c(PL)A2 pathway leading to derangements in macrophage inflammation in diabetes. Using the murine diet induce obesity (DIO) model, we evaluated diabetic wound healing compared with control mice. We demonstrate that TGFβ is elevated in DIO wound Mϕs in comparison to control wound Mϕs. Further, the increase in TGFβ stimulates miR-29B production in wound Mϕs resulting in hypomethylation and overexpression of the COX-2 gene. This results in diabetic wound Mϕs displaying increased levels of COX-2 which shunts amino acid metabolism towards the COX-2 pathway increasing PGE2 while limiting leukotriene synthesis via 5-lipoxygenase (5-LO) pathways. Lastly, c(PL)A2 appears to be upregulated in diabetic wound Mϕs and human diabetic monocytes. In summary, these results demonstrate that the COX-2/PGE2 pathway is increased in diabetic wound Mϕs by elevated TGFβ/miR-29b and results in elevated PGE2 that drives Mϕ-mediated inflammation preventing wound repair.