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Cutaneous UVB Irradiation Alters Gut Microbiota Independently of Skin Inflammation in SKH-1 Hairless Mice

Year: 2025

Type: article

Abstract: IntroductionUltraviolet B (UVB) radiation, with wavelengths ranging from 280 to 315 nm, primarily affects the epidermal layer of the skin, in contrast to UVA radiation, which penetrates more deeply [1].Within the epidermis, the stratum corneum, basal keratinocytes, and melanocytes are the main targets of UVB exposure.UVB induces various cellular and molecular responses, including DNA damage, the generation of reactive oxygen species (ROS), and the production of pro-inflammatory cytokines [2,3].Although cells possess repair mechanisms to counteract UVB-induced damage, repeated or excessive exposure may overwhelm these systems.As a result, cells may undergo cycle arrest, activate aging-or apoptosis-related signaling pathways, and recruit immune cells [4].This cascade can lead to the release of inflammatory mediators, immune cell infiltration, and tissue injury.Prolonged UVB exposure, particularly in the absence of sufficient repair, has been implicated in the development of photoaging and skin cancers [5,6].Advancements in metagenomic sequencing have expanded our understanding of the human microbiota, which consists of trillions of microorganisms residing across different body sites [7].Among these, the gut microbiota plays a central role in regulating immune function, metabolism, and nutrient absorption [8].Emerging evidence has highlighted a functional connection between the gut and skin, commonly referred to as the gut-skin axis [9,10].Alterations in gut microbial communities, known as dysbiosis, have been associated with a range of skin disorders, including acne vulgaris, atopic dermatitis, psoriasis, and rosacea [11][12][13].The beneficial effects of certain probiotics, such as Lactobacillus paracasei, Bifidobacterium longum, and Weissella viridescens, further underscore the significance of the gut microbiota in supporting skin health [11,14,15].Recent findings suggest that UVB exposure may influence gut microbial composition, even without direct light exposure to the gastrointestinal tract.Short-term exposure to narrow-band UVB (311 nm) has been shown to modulate the gut microbiota in both human and mouse models, alongside increases in circulating vitamin D levels [16][17][18].However, the long-term impact of chronic UVB exposure on gut microbial composition and diversity remains unclear.In particular, the effects of repeated, low-level UVB exposure that does not visibly damage the skin have not been extensively studied.The biological effects of UVB are known to extend beyond the skin and may affect distant organs, including the gut, through systemic signaling.Understanding these skin-togut interactions is essential to assess the broader physiological consequences of UVB radiation.In this context, the present study aimed to investigate whether chronic exposure to low-dose UVB could alter gut microbial homeostasis.To eliminate confounding variables such as diet and fluctuations in vitamin D levels, we employed a mouse model under controlled environmental conditions.This study investigates the impact of chronic ultraviolet B (UVB) exposure on gut microbiota composition and skin inflammation.Mice were subjected to a 12-week regimen of low-dose UVB irradiation designed to mimic mild photoaging.Although no significant changes were observed at the phylum level, UVB exposure resulted in a significant decrease in the genus Lactobacillus (P=0.0302) and an increase in Duncaniella (P = 0.046), accompanied by a reduction in α-diversity.At the species level, Lactobacillus johnsonii, a known probiotic, was significantly decreased, while Duncaniella freteri was increased in the UVB-exposed group.Despite these microbial alterations, no significant skin inflammation was detected, as mRNA levels of interleukin (IL)-1β and TNF-α and protein levels of IL-1β and IL-2 remained unchanged.These findings suggest that chronic low-dose UVB exposure can alter gut microbial homeostasis independently of local inflammatory responses, highlighting a potential role for the skin-gut axis in mediating systemic effects of environmental UVB exposure.

Source: Journal of Microbiology and Biotechnology

DOI: 10.4014/jmb.2507.07020

Authors: Eunjung Lee, Woo-Jin Sim, Tae-Gyu Lim

Institutions: Korea Food Research Institute, Korea University of Science and Technology, Sejong University

Language: English

Topic: Gut microbiota and health

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: bronze

Funders: National Research Foundation, National Research Foundation of Korea, Ministry of Science and ICT, South Korea, Korea Food Research Institute