The protective effects of TGR5 against ultraviolet B irradiation in epidermal stem cells

Role of mitochondria on UV-induced skin damage and molecular mechanisms of active chemical compounds targeting mitochondria

Mitochondria are the principal place of energy metabolism and ROS production, leading to mtDNA being especially sensitive to the impacts of oxidative stress. Our review aims to elucidate and update the mechanisms of mitochondria in UV-induced skin damage. The mitochondrial deteriorative response to UV manifests morphological and functional alterations, including mitochondrial fusion and fission, mitochondrial biogenesis, mitochondrial energy metabolism and mitophagy. Additionally, we conclude the effect and molecular mechanisms of active chemical components to protect skin from UV-induced damage via mitochondrial protection which have been described in the last five years, showing prospective prospects in cosmetics as new therapeutic targets.

Reversal of alopecia areata, osteoporosis follow treatment with activation of Tgr5 in mice

BACKGROUND

Alopecia areata is an autoimmune hair loss disease with infiltration of pro-inflammatory cells into hair follicles. The role of Tgr5 in dermatitis has attracted considerable attention. The present study aimed to investigate the effect of Tgr5 in the development of Alopecia areata.

METHODS

The study utilized a comparison control group design with four groups of wild-type group, wild-type+INT777 group, Tgr5-/- group, and Tgr5-/-+INT777 group. The mice were treated with INT777 (30 mg/kg/day) or the carrier solution (DMSO) intraperitoneally for 7 weeks, and the back skin was collected and analyzed by histology and immunohistochemistry staining. The lumbar vertebrae 4 has also been analyzed by DXA and Micro-CT.

RESULTS

Tgr5-/- mice displayed the decreasingly significant in hair area and length, skin thickness, and the ratio of anagen and telogen, collagen, and mast cell number and loss the bone mass than WT group. After treating with INT777, the appearance of alopecia areata and bone microstructure has improved. Immunohistochemistry and qPCR analysis showed that activation of Tgr5 can down-regulate the express of JAK1, STAT3, IL-6, TNF-α, and VEGF.

CONCLUSION

These findings indicate that activation of Tgr5 mediated amelioration of alopecia areata and osteoporosis by down-regulated JAK1-STAT3 signaling pathway.

Agonism of Gpr40 Protects the Capacities of Epidermal Stem Cells (ESCs) Against Ultraviolet-B (UV-B)

Introduction

Skin damage due to overexposure to ultraviolet B (UV-B) radiation can lead to the development of cancers and reduce the skin's functionality as a vital protective barrier. Epidermal stem cells (ESCs) are pluripotent cells responsible for skin regeneration and healing. Upon exposure to UV-B radiation, ESCs produce excess amounts of reactive oxygen species (ROS) and inflammatory cytokines. However, the functional protection of ESCs is not fully explored. G-protein coupled G protein-coupled receptor 40 (Gpr40) is a free fatty acid receptor that is emerging as a potential treatment target for various diseases. Gpr40 has been found to be expressed in various cell types.

Methods

ESCs were exposed to UV-B at the intensities of 25, 50, and 100 mJ/cm² for 24 h using TL 20 W/12 RS UV lamps. ESCs were treated with UV-B at 50 mJ/cm² in the presence or absence of 25 or 50 µM of the Gpr40 agonist GW9508 for 24 h. The gene expression of the Wnt1 pathway and proinflammatory cytokines were evaluated. To antagonize Gpr40 expression, ESCs were treated with 10 µM GW1100.

Results

Our findings demonstrate that Gpr40 agonism can reduce the production of ROS as well as the expression of interleukins 1β and 8, two key proinflammatory cytokines. We demonstrate that agonism of Gpr40 can rescue the reduction in integrin β1 and Krt19 induced by UV-B exposure, thereby improving the capacities of ESCs to resist UV-B damage. Moreover, we show that the effects of Gpr40 agonism observed in our experiments are mediated through the Wnt/β-catenin canonical signaling pathway, as evidenced by the expression of Wnt1 and cyclin D1.

Conclusion

Our findings present evidence of the role of Gpr40 agonism in mediating the protective capacities of ESCs against insult from UV-B radiation.