Possible therapeutic role of short-chain fatty acids from skin commensal bacteria in UVB-induced skin carcinogenesis

Abstract

Solar ultraviolet B (UVB) radiation is a major skin cancer-causing agent. Initiation, promotion, and progression are the diverse phases of UVB-induced carcinogenesis. Exposure to UVB causes abnormalities in a series of biochemical and molecular pathways: thymine dimer formation, DNA damage, oxidative stress, inflammatory responses, and altered cell signaling, eventually resulting in tumor formation. The increased skin cancer rates urge researchers to develop more efficient drugs, but synthetic chemotherapeutic drugs have more contrary effects and drug resistance issues, which have been reported recently. The current review focuses on the relationship between microbes and cancer. Human skin acts as a barrier against the external environment and serves as a protective shield for its inhabitant microbiota, collectively called skin microbes. The gut microbiome plays a vital role in cancer therapy. Production of short-chain fatty acids (SCFAs) such as butyrate, acetate, and propionate by intestinal microbes has anti-cancer properties against various cancer cell lines. Yet, the knowledge of SCFAs produced by skin microbes remains yet to be elucidated exhaustively. In this review, we strive to summarize the findings of studies performed to date regarding the anti-cancer properties of SCFA against various cancer cell lines and provide insight into future directions in the skin microbiome field.Radiation, 2011). Both UVA and UVB are carcinogens. Especially, UVB directly causes DNA damage, prompting the development of massive damage between adjacent pyrimidine sites and the generation of reactive oxygen species (ROS) (Levav-Cohen et al., 2014). Preventive measures should be taken to overcome the global increase in skin cancer rates (Domingues et al., 2018). This review addresses the harmful side of UVB in skin cancer and the necessity of short-chain fatty acids (SCFAs) in managing them. Harmful effects of ultraviolet B on the skinThe sun produces electromagnetic radiation that encompasses a broad range of wavelengths. Among them, only a few wavelengths are able to pass through the ozone layer and reach the earth surface; these include ultraviolet (UV) radiation, infrared (IR), and visible light (VL). Solar UV radiations occur in the wavelength range of around 200-400 nm; however, only UVA (400-315 nm) and UVB (315-280 nm) can reach the earthbound surface, while UVC (280-100 nm) is completely absorbed by the ozone layer (Svobodová et al., 2003). Fig. 1 demonstrates how extreme exposure to UVB harms the capacity of basal keratinocytes for maintaining skin homeostasis and will prompt different skin diseases, which incorporate erythema, edema, sunburn,