BLT2 expression improves skin integrity and protects from alterations caused by hyperglycemia in type 2 diabetes

Abstract

Type 2 diabetes (T2D) can go undiagnosed for years, leading to a stage where chronic high blood sugar produces complications such as delayed wound healing. Reports have shown that BLT2 activation improves keratinocyte migration and wound healing, as well as protecting the epidermal barrier through the promotion of actin polymerization.The goal of this study was to elucidate the role of BLT2 expression in skin epithelial integrity in T2D.For this purpose, we used both wild type (WT) and BLT2 knockout mice in a model, in which a T2D-like phenotype was induced by keeping the animals on a high fat (HF) diet over 5 weeks. In a parallel in vitro approach, we cultured BLT2-transfected HaCaT cells at both low and high glucose concentrations for 48 h. Structure, transepithelial resistance (TEER), IL-1ß, IL-8 or CXCL2, MMP9, Filaggrin, Loricrin and Keratin 10 (K10) were evaluated ex vivo and in vitro. Additionally, wound healing (WH) was studied in vitro.The skin from T2D and BLT2 knockout mice showed a reduction in TEER and the expression of IL-1ß, and in increase in CXCL2, MMP9, Filaggrin, Loricrin and K10 expression. The structure suggested an atrophic epidermis; however, the skin was dramatically affected in the BLT2 knockout mice kept on a HF diet.HaCaT-BLT2 cells presented as an organized monolayer and showed higher TEER and wound healing compared with vector only-transfected HaCaT-Mock cells. Likewise, alterations in the expression of skin inflammatory, matrix degradation and differentiation markers under low and high glucose conditions were less severe than in HaCaT-Mock cells.Our results suggest that BLT2 improves epithelial integrity and function by regulating differentiation markers, cytokines and MMP9. Furthermore, BLT2 attenuates the damaging effects of high glucose levels, thereby accelerating wound healing.

The streptozotocin-high fat diet induced diabetic mouse model exhibits severe skin damage and alterations in local lipid mediators

“…Based on the findings presented in this study and our previous report [7] we suggest that the severe hyperglycemia and no the insulin, in the STZ-high fat diet model, leads to an outburst of pro-inflammatory cytokines and oxidative stress on the keratinocyte, that activates LOX/COX dependent pathways causing changes on local lipid mediators associated with loose on the epidermal integrity that might cause the spontaneous skin injuries observed [20] .…”

“…Previous results using the HF diet model have described mild skin alterations associated with reduction on TEER, epidermis thickness and increased inflammatory markers [7] . Using a STZ type 1 diabetic rat model it was described in skin an increase on inflammatory cells infiltration and oxidative stress [8] .…”

The 12-HHT/BLT2/NO Axis Is Associated to the Wound Healing and Skin Condition in Different Glycaemic States

“…As we previously described, high glucose reduced the wound healing capacity, an effect prevented by the BLT2 expression in a HaCaT [9]. The NOS unspecific inhibition by L-NAME at 5 mM glucose altered differentially the HaCaT-BLT2, reducing the wound closure.…”

“…Various reports have validated the use of a HF diet over several weeks to provide a model of T2D [14,15,16]. As we previously demonstrated, the diabetic mice exhibited important skin alterations and BLT2 expression in keratinocytes protected from the damage caused by hyperglycaemia [9].…”

“…BLT2 is a G-Protein Coupled Receptor (GPCR) that binds to Leukotriene B4 (LTB4) and 12-HHT, and is mainly expressed in epithelial cells, such as epidermal keratinocytes and intestinal epithelial cells [6,7,8]. We previously reported that BLT2 activation improves epithelial integrity and function by regulating differentiation markers, cytokines and matrix metallopeptidase (MMP9), attenuating the damaging effects of high glucose levels, thereby accelerating wound healing [9]. Furthermore, the skin from diabetic mice presents higher levels of oxidative stress, lower levels of adhesion proteins and alterations in lipid mediators, particularly a reduction on 12-HHT [10].…”