An Agonist of Zinc-Sensing G-Protein Coupled Receptor 39 Accelerates Skin Wound Healing and Protects Against UVB-Induced Keratinocyte Damage.

INTRODUCTION: Keratinocytes establishes skin barrier integrity. Wound and ultraviolet B (UVB)-induced keratinocyte damage mainly contributes to the disruption of skin barrier properties. Recently, we found that pharmacological activation of zinc-sensing G-protein coupled receptor 39 (GPR39) promotes keratinocyte proliferation. Here, we further investigated the effects of TC-G 1008, a synthetic GPR39 agonist, on skin wound healing and UVB-induced keratinocyte damage. METHODS: Scratch assay was used as a cell-based wound healing model. UVB exposure was performed to induce oxidative stress and cell death. BrdU incorporative assay was used to assess the rate of keratinocyte proliferation. MTT assay and Hoechst33342/ethidium homodimer-1 co-staining assay were used to evaluate cell viability and apoptosis, respectively. Western blot analysis was performed to investigate protein expression of AMP-activated protein kinase (AMPK) and extracellular signal-regulated kinase (ERK) phosphorylation. Sirtuin-1 (SIRT-1) activity assay and DCFDA assay were used to investigate SIRT-1 activity and to measure levels of intracellular reactive oxygen species (ROS). RESULTS: We found that TC-G 1008 (up to 10 µM) dose-dependently enhanced the wound healing rate in a keratinocyte-like HaCaT cell line in a cell proliferation-independent manner. TC-G1008 reduced apoptosis and ROS production following UVB exposure. Notably, GPR39 agonism-induced wound healing and its protective effects against UVB-induced keratinocyte damage were abrogated by co-treatment with inhibitors of intracellular signaling, including protein kinase A (PKA), AMPK, sirtuin-1 (SIRT-1), and ERK. TC-G 1008 treatment induced AMPK phosphorylation via a PKA-dependent mechanism and promoted ERK phosphorylation by stimulating the AMPK/SIRT-1 pathway. In addition, TC-G 1008 treatment enzymatically activated SIRT-1 and this effect was suppressed by pretreatment with an AMPK inhibitor. DISCUSSION AND CONCLUSION: Collectively, activation of GPR39 promoted wound healing and protected keratinocytes from UVB exposure via PKA/AMPK/SIRT-1/ERK-dependent mechanisms.