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Updated: Sep 29, 2026
Studying Chronic Exposure of Mice to Ultraviolet B Radiation
Published on: August 19, 2025
Measurement of UVB-Induced DNA damage and its consequences in models of immunosuppression
Daniel B Yarosh1, Stavroula Boumakis, Anne B Brown
1AGI Dermatics, Freeport, NY 11520, USA. danyarosh@agiderm.com
Abstract:
Exposure to UVB results in formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts in DNA. These can be quantified by a variety of techniques including alkaline gel electrophoresis, ELISAs, Southwestern blotting, and immunohistochemistry. Damage to DNA results in activation of damage response pathways, as indicated by Western blotting using antibodies specific for p53 and breast cancer-associated gene 1 (BRCA1) phosphorylation. The signal from DNA damage to activation of these response pathways appears to be mediated by FKBP12-rapamycin-associated protein (FRAP), since these phosphorylation events are blocked by rapamycin. UVB-induced DNA damage also leads to induction of immunosuppressive cytokines including tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-10 in skin. Induction of TNF-alpha by UVB is readily detectable in cultured normal human epidermal keratinocytes (NHEKs) using ELISA, while induction of IL-10 is readily detectable in cultured mouse keratinocytes but not in NHEKs. Induction of DNA damage by liposome-encapsulated HindIII results in induction of immunosuppressive responses similar to UVB. Clinical testing shows that liposome-encapsulated T4 endonuclease V or photolyase stimulates repair of CPDs in the skin of human subjects, and prevents UVB-induced immunosuppression. Stimulation of repair and prevention of immunosuppression have been linked to prevention of skin cancer by liposome-encapsulated T4 endonuclease V in repair-deficient xeroderma pigmentosum patients.
Insights
UVB exposure damages DNA, activating repair pathways mediated by FRAP. Liposomal T4 endonuclease V repairs DNA damage, preventing UVB-induced immunosuppression and skin cancer in xeroderma pigmentosum patients.
Area of Science:
- Molecular biology
- Dermatology
- Immunology
Background:
- UVB radiation causes DNA damage, forming cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts.
- DNA damage triggers cellular responses, including phosphorylation of p53 and BRCA1, mediated by FRAP.
- UVB exposure induces immunosuppressive cytokines like TNF-alpha and IL-10 in the skin.
Purpose of the Study:
- To investigate the molecular mechanisms of UVB-induced DNA damage and immunosuppression.
- To evaluate the efficacy of liposomal T4 endonuclease V and photolyase in DNA repair and immunosuppression prevention.
- To assess the potential of these therapies in preventing skin cancer, particularly in xeroderma pigmentosum patients.
Main Methods:
- Quantification of DNA damage using techniques like alkaline gel electrophoresis and ELISAs.
- Western blotting to detect phosphorylation of p53 and BRCA1.
- ELISA to measure cytokine induction in cultured keratinocytes.
- Clinical studies using liposomal T4 endonuclease V and photolyase.
Main Results:
- UVB-induced DNA damage activates p53 and BRCA1 phosphorylation, a process blocked by rapamycin, suggesting FRAP mediation.
- UVB induces TNF-alpha in human keratinocytes and IL-10 in mouse keratinocytes.
- Liposomal T4 endonuclease V and photolyase effectively repair CPDs in human skin and prevent UVB-induced immunosuppression.
- Liposomal T4 endonuclease V prevents skin cancer in xeroderma pigmentosum patients.
Conclusions:
- FRAP is a key mediator in the signaling pathway from UVB-induced DNA damage to cellular response.
- Liposomal delivery of DNA repair enzymes offers a promising strategy for mitigating UV-induced skin damage and immunosuppression.
- Targeted DNA repair can prevent skin cancer development, especially in individuals with DNA repair deficiencies like xeroderma pigmentosum.
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