Leukotriene B₄receptor type 2 (BLT2) enhances skin barrier function by regulating tight junction proteins

Abstract

GPCRs are involved in numerous physiologic functions and are important drug targets. Although the epithelial barrier is important for protection from invading pathogens, the correlation between GPCRs and epithelial barrier function remains unknown. Leukotriene B 4 (LTB 4 ) receptor type 2 (BLT2), mainly expressed in epithelial cells, is a GPCR for 12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) and LTB 4 . In our study, BLT2 localized at the lateral membrane in BLT2-overexpressing Madin-Darby canine kidney (MDCK) II cells and in the small intestine of BLT2-transgenic mice. BLT2-deficient mice exhibited higher transepidermal water loss and were more sensitive to epicutaneous sensitization. MDCK-BLT2 cells recovered transepithelial electrical resistance (TER) after a calcium switch faster than did MDCK-Mock cells, and 12-HHT stimulation accelerated TER recovery only in MDCK-BLT2 cells. Quantitative PCR and immunoblot analyses revealed that the 12-HHT/ BLT2 axis up-regulated claudin-4 (CLDN4) expression in MDCK-BLT2 cells and human primary keratinocytes, and CLDN4 knockdown abolished 12-HHT-dependent TER recovery. Acceleration of TER recovery and induction of CLDN4 expression by 12-HHT stimulation were abolished by inhibition of Ga i protein or p38 MAPK. These results show that 12-HHT/BLT2 enhances epithelial barrier function by increasing CLDN4 expression via the Ga i protein-p38 MAPK pathway.-Ishii, Y

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

“…In vitro TEER measurement was performed following the protocol described in reference 15 . Briefly, 40000 cells were seeded onto a 0.4 μm pore, 12 mm polycarbonate filter suspended inside a cell culture well.…”

“…BLT2 has been implicated in the regulation of tight junction proteins, 15 as well as in actin polymerization 16 ; both of these processes are central to enhancing skin barrier function 15 . In addition, pharmacological activation of the BLT2 receptor has been found to promote keratinocyte migration, thereby enhancing fibroblast proliferation and improving wound healing in a model of type 1 diabetes 17 …”

The leukotriene B4 receptor BLT2 protects barrier function via actin polymerization with phosphorylation of myosin phosphatase target subunit 1 in human keratinocytes

“…Recently, we reported on impaired skin barrier function in BLT2‐deficient mice, which was attributable to increased permeability of tight junctions, because the ligation of BLT2 by 12‐HHT intensified the expression of claudin 4, a major tight junction protein, in cultured mouse and human keratinocytes directed to terminally differentiate by high‐calcium conditions . As BLT2 was shown to be readily expressed in human keratinocytes with low‐calcium conditions, mimicking the basal layer , the purpose of this study was to investigate the role of BLT2 in human keratinocytes under low‐calcium conditions.…”

Epidermal barrier disruption by 9‐hydroxy‐10E,12Z‐octadecadienoic acid in human keratinocytes

“…The tight junction binding between keratinocytes also plays a major role as a physical barrier to protect against various external pathogens and substances. Thus, dysfunction of tight junctions can induce infection or inflammation . As a method of evaluating this barrier function, transepithelial electrical resistance (TER) assay has been demonstrated to be a suitable in vitro model to determine the permeability of water‐soluble ions and is considered to represent an appropriate index of skin barrier functions .…”

“…Therefore, the dysfunction of tight junctions including redundant actin rearrangement induces the loss of water from the body and excessive percutaneous sensitization. This tight junction instability is known to cause allergic skin or inflammatory bowel diseases . We identified a potential barrier‐disrupting function of 9‐HODE, which is abundantly generated in various pro‐inflammatory conditions.…”