Article Impact Level: HIGH Data Quality: STRONG Summary of Journal of Investigative Dermatology, S0022202X25004051. https://doi.org/10.1016/j.jid.2025.03.035 Dr. VijayKumar Patra et al.
Points
- Researchers found that skin bacteria such as Staphylococcus epidermidis can metabolize cis-urocanic acid, a UVB photoproduct, reducing its immunosuppressive effects on the skin.
- Acute UVB exposure significantly altered the skin microbiome, favoring bacteria capable of breaking down cis-UCA and thereby modulating immune responses.
- Blocking the bacterial enzyme urocanase restored UV-induced immunosuppression, demonstrating a direct link between microbial metabolism and skin immune regulation.
- These findings suggest that skin-resident microbes help fine-tune immune responses to UV radiation, with implications for therapies that modify the microbiome.
- The study highlights new opportunities for microbiome-based sun protection and phototherapy approaches that leverage bacterial metabolism to influence immune tolerance.
Summary
This study investigates the role of the skin microbiome in modulating immune responses to ultraviolet (UV) radiation, specifically through the metabolism of cis-urocanic acid (cis-UCA), a key photoproduct formed by UVB radiation. Using a combination of 16S microbiome sequencing, in vitro cultures, and gnotobiotic mouse models, researchers found that bacteria like Staphylococcus epidermidis metabolize cis-UCA using the enzyme urocanase (HutU), which limits its immunosuppressive properties. By reducing cis-UCA’s ability to suppress immune responses, this microbial metabolism plays a critical role in fine-tuning how the skin reacts to UV exposure.
The study revealed that acute UVB radiation induces significant restructuring of bacterial communities on the skin, with specific bacteria such as S. epidermidis proliferating through their ability to metabolize cis-UCA. Adding a topical urocanase inhibitor, which blocks the metabolism of cis-UCA by HutU+ bacteria, restored UV-induced immunosuppression, suggesting a potential therapeutic avenue for enhancing UV tolerance in clinical settings. This indicates that skin-resident bacteria can directly influence the skin’s immune responses to environmental stressors like UV radiation.
These findings suggest a novel interplay between the skin microbiome and immune function, where microbial metabolism of UV-induced products modulates immune tolerance. This discovery opens the possibility for microbiome-aware sun protection strategies, where treatments could target microbial metabolism to minimize or enhance UV-induced immunosuppression, particularly in phototherapy applications. This work represents a significant step toward understanding how microbial communities contribute to skin health, sun protection, and potentially skin cancer prevention.
Link to the article: https://www.jidonline.org/article/S0022-202X(25)00405-1/fulltext
References Patra, V., Trajanoski, S., Joshi, A., Lenief, V., Goyet, C., Cornu, A., Golob-Schwarzl, N., Somlapura, M., Mosnier, A., Zarfl, M., Eichmann, T., Köefeler, H., Norval, M., Nicolas, J.-F., Wolf, P., & Vocanson, M. (2025). Urocanase-positive skin resident bacteria metabolize cis-urocanic acid and in turn reduce the immunosuppressive properties of UV radiation. Journal of Investigative Dermatology, S0022202X25004051. https://doi.org/10.1016/j.jid.2025.03.035
