Novel 14,21-dihydroxy-docosahexaenoic acids: structures, formation pathways, and enhancement of wound healing

Ultraviolet-radiation induced skin inflammation: dissecting the role of bioactive lipids

Acute exposure of human skin to the ultraviolet radiation (UVR) in sunlight results in the sunburn response. This is mediated in part by pro-inflammatory eicosanoids and other bioactive lipids, which are in turn produced via mechanisms including UVR-induction of oxidative stress, cell signalling and gene expression. Sunburn is a self-limiting inflammation offering a convenient and accessible system for the study of human cutaneous lipid metabolism. Recent lipidomic applications have revealed that a wider diversity of eicosanoids may be involved in the sunburn response than previously appreciated. This article reviews the effects of UVR on cutaneous lipids and examines the contribution of bioactive lipid mediators in the development of sunburn. Since human skin is an active site of polyunsaturated fatty acid (PUFA) metabolism, and these macronutrients can influence the production of eicosanoids/bioactive lipids, as well as modulate cell signalling, gene expression and oxidative stress, the application of PUFA as potential photoprotective agents is also considered.

Novel 14S,21-dihydroxy-docosahexaenoic acid rescues wound healing and associated angiogenesis impaired by acute ethanol intoxication/exposure

Acute ethanol intoxication and exposure (AE) has been known to impair wound healing and associated angiogenesis. Here, we found that AE diminished the formation of novel reparative lipid mediator 14S,21-dihydroxy-docosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid (14S,21-diHDHA) and its biosynthetic intermediate 14S-hydroxy-DHA (14S-HDHA) from docosahexaenoic acid (DHA) in murine wounds. However, AE did not reduce the formation of DHA and the intermediate 21-HDHA. These results indicate that in the biosynthetic pathways of 14S,21-diHDHA in wounds, AE suppresses the 14S-hydroxy-generating activity of 12-lipoxygenase-like (LOX-like), but does not suppress the 21-hydroxy-generating activity of cytochrome P450 and DHA-generating activities. The AE-suppression of 12-LOX-like activity was further confirmed by the diminished formation of 12-hydroxy-eicosatetraenoic acid in wounds under AE. Supplementing 14S,21-diHDHA to wounds rescued the AE-impaired healing and vascularization. 14S,21-diHDHA restored AE-impaired processes of angiogenesis in vitro: endothelial cell migration, tubulogenesis, and phosphorylation of p38 mitogen-activated protein kinase (MAPK). Taken together, the suppression of 14S,21-diHDHA formation is responsible, at least partially, for the AE-impairment of cutaneous wound healing and angiogenesis. Supplementing 14S,21-diHDHA to compensate its deficit in AE-impaired wounds rescues the healing and angiogenesis. These results provide a novel mechanistic insight for AE-impaired wound healing that involves the necessary roles of 14S,21-diHDHA. They also offer leads for developing 14S,21-diHDHA-related therapeutics to ameliorate AE-impairment of wound healing.

14S,21R-dihydroxydocosahexaenoic acid remedies impaired healing and mesenchymal stem cell functions in diabetic wounds

Treatment of diabetes-impaired wound healing remains a major unresolved medical challenge. Here, we identified suppressed formation of a novel reparative lipid mediator 14S,21R-dihydroxydocosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid (14S,21R-diHDHA) in cutaneous wounds of diabetic db/db mice. These results indicate that diabetes impedes the biosynthetic pathways of 14S,21R-diHDHA in skin wounds. Administration of exogenous 14S,21R-diHDHA to wounds in diabetic animals rescued healing and angiogenesis. When db/db mesenchymal stem cells (MSCs) were administered together with 14S,21R-diHDHA to wounds in diabetic animals, they coacted to accelerate wound re-epithelialization, granulation tissue formation, and synergistically improved vascularization. In the pivotal cellular processes of angiogenesis, 14S,21R-diHDHA enhanced VEGF release, vasculature formation, and migration of db/db dermal microvascular endothelial cells (DMVECs), as well as remedied paracrine angiogenic functions of db/db MSCs, including VEGF secretion and the promotion of DMVEC migration and vasculature formation. Our results show that 14S,21R-diHDHA activates the p38 MAPK pathway in wounds, db/db MSCs, and DMVECs. Overall, the impeded formation of 14S,21R-diHDHA described in this study suggests that diabetes could affect the generation of pro-healing lipid mediators in wound healing. By restoring wound healing and MSC functions, 14S,21R-diHDHA is a new lead for the development of better therapeutics used in treating wounds of diabetics.