Ghrelin attenuates ultraviolet B radiation-induced impairment in capacities of epidermal stem cells

Persistent exposure to solar ultraviolet radiation (UVR) causes continuous damages to skin, including progressive impairment of epidermal stem cells (ESCs) capacities. Ghrelin is the only known endogenous orexigenic hormone, which has displayed its various pharmacological functions. In the current study, we found that the specific receptor of ghrelin, growth hormone secretagogue receptor (GHS-R), is expressed in ESCs. Interestingly, GHS-R expression is significantly upregulated in response to ultraviolet B (UVB) radiation. We also found that ghrelin treatment prevented UVB radiation-induced reduction in cell viability and the release of lactate dehydrogenase (LDH). Additionally, ghrelin reduced UVB radiation-induced generation of reactive oxygen species (ROS) and restored the intracellular level of reduced glutathione (GSH). UVB radiation significantly suppressed the expressions of integrin β1 and Krt19, the two major ESC markers, which were restored by ghrelin. Notably, knockdown of GHS-R abolished the effects of ghrelin on the expressions of integrin β1 and Krt19, suggesting the involvement of GHS-R. Also, we found that ghrelin treatment inhibited UVB radiation- induced reduction of Wnt1, Wnt3a, Myc, and cyclin D1 at both the mRNA levels and the protein levels. Taken together, our findings identify a novel function of ghrelin on maintaining the capacities of ESCs against UVB radiation.