12-Hydroxyheptadecatrienoic acid promotes epidermal wound healing by accelerating keratinocyte migration via the BLT2 receptor.
Bottom Line: Leukotriene B4 (LTB4) receptor type 2 (BLT2) is a G protein-coupled receptor (GPCR) for 12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) and LTB4.Despite the well-defined proinflammatory roles of BLT1, the in vivo functions of BLT2 remain elusive.These results identify a novel mechanism underlying the action of the 12-HHT/BLT2 axis in epidermal keratinocytes and accordingly suggest the use of BLT2 agonists as therapeutic agents to accelerate wound healing, particularly for intractable wounds, such as diabetic ulcers.
Affiliation: Department of Biochemistry, Juntendo University School of Medicine, Tokyo 113-8421, Japan Department of Medical Biochemistry, Kyushu University, Fukuoka 812-8582, Japan.Show MeSH
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Mentions: Detailed morphometric analyses of punched skin tissues were next performed on HE-stained sections. No apparent structural differences were found in the HE-stained intact skin of BLT2 WT versus BLT2 KO mice at the light microscopy level (unpublished data). After injury, re-epithelialization and wound contraction are important processes that control the overall rate of repair. We observed that re-epithelialization (determined by measuring the lengths of the wounds within the neoepithelium) was impaired in BLT2 KO mice (Fig. 2, D and F) and aspirin-treated WT (Fig. 2, E and G), whereas wound length (determined by measuring the lengths between the wound margins) was unaffected (Fig. 2, D and E, middle). In addition, keratinocyte proliferation (evaluated by counting Ki67-positive cells) were also unaffected by BLT2 deficiency (Fig. 2 D, right) or aspirin administration (Fig. 2 E, right). Because fibroblasts are also a crucial component of wound healing by enhancing wound contraction, collagen deposition in wound tissue was evaluated by Masson’s trichrome staining. The results showed that neither BLT2 deficiency nor aspirin treatment affected collagen deposition during wound healing (Fig. 2, H and I). The delayed skin wound healing brought about by BLT2 deficiency and aspirin treatment was not due to a modified immune response because skin inflammation (evaluated by measuring myeloperoxidase [MPO] activity in the skin [Fig. 3 A], as well as by flow cytometry analysis of the immune cells [Fig. 3, B and C]) was unaltered. Given that BLT2 is expressed in keratinocytes but not in dermal fibroblasts (Fig. 1, A–D), we hypothesized that the 12-HHT/BLT2 axis enhances re-epithelialization by accelerating keratinocyte migration during wound healing.
Affiliation: Department of Biochemistry, Juntendo University School of Medicine, Tokyo 113-8421, Japan Department of Medical Biochemistry, Kyushu University, Fukuoka 812-8582, Japan.