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Published on: September 7, 2013
Enhanced inflammation and immunosuppression by ultraviolet radiation in xeroderma pigmentosum group A (XPA) model
H Miyauchi-Hashimoto1, K Tanaka, T Horio
1Department of Dermatology, Kansai Medical University, Osaka, Japan.
Abstract:
Xeroderma pigmentosum group A (XPA) gene-deficient mice were developed by gene targeting in mouse embryonic stem cells. To examine whether these XPA-model mice display photodermatologic abnormalities similar to those in human xeroderma pigmentosum, we investigated the effects of acute ultraviolet radiation on the homozygous (-/-) mice compared to the wild type (+/+) and heterozygous (+/-) mice. A single irradiation with ultraviolet B or topical psoralen plus ultraviolet A treatment induced stronger and longer lasting ear swelling in the (-/-) mice than in the (+/+) and (+/-) mice. Histologic changes including epidermal necrosis, cell infiltration, and sunburn cell formation after ultraviolet B radiation were more prominent in the (-/-) model mice than in the control mice. The (-/-) model mice showed damage of ADPase(+)Langerhans cells at a lower ultraviolet B dose than did the control mice. Moreover, the reappearance of ADPase(+)Langerhans cells after ultraviolet B radiation was delayed in the (-/-) mice compared to the control mice. Although contact hypersensitivity was induced equally in all mice, ultraviolet B-induced local and systemic immunosuppression were greatly enhanced in the (-/-) model mice. The data suggest that the XPA gene-deficient mice may be a useful model of human XPA, because the responses to UV radiation in the mice were very similar to those in the patients with XPA. Moreover, it is possible that enhanced ultraviolet immunosuppression is involved in the development of skin cancers in xeroderma pigmentosum.
Insights
New Xeroderma pigmentosum group A (XPA) gene-deficient mice exhibit photodermatologic abnormalities mirroring human XPA. These XPA model mice show heightened sensitivity to ultraviolet radiation, indicating their utility in studying this condition.
Area of Science:
- Genetics and Molecular Biology
- Dermatology
- Immunology
Background:
- Xeroderma pigmentosum (XP) is a rare genetic disorder characterized by extreme sensitivity to ultraviolet (UV) radiation.
- Individuals with XP have a significantly increased risk of developing skin cancers.
- The Xeroderma pigmentosum group A (XPA) gene plays a crucial role in DNA repair pathways, particularly nucleotide excision repair.
Purpose of the Study:
- To develop and validate a mouse model for Xeroderma pigmentosum group A (XPA).
- To investigate the phenotypic responses of XPA gene-deficient mice to ultraviolet radiation exposure.
- To compare the UV radiation sensitivity and immune responses of XPA-deficient mice with wild-type and heterozygous controls.
Main Methods:
- Gene targeting in mouse embryonic stem cells was used to create XPA gene-deficient mice (homozygous -/-).
- Acute UV radiation (UVB) and topical psoralen plus UVA (PUVA) treatments were administered to homozygous (-/-), heterozygous (+/-), and wild-type (+/+) mice.
- Photodermatologic responses, including ear swelling, histological changes (epidermal necrosis, sunburn cells), Langerhans cell dynamics, and contact hypersensitivity, were assessed.
- UVB-induced local and systemic immunosuppression was evaluated.
Main Results:
- XPA gene-deficient mice (-/-) exhibited significantly stronger and more prolonged ear swelling following UV irradiation compared to control mice (+/+ and +/-).
- Histological examination revealed more prominent epidermal necrosis, cell infiltration, and sunburn cell formation in (-/-) mice after UVB exposure.
- Damage to ADPase(+)Langerhans cells occurred at lower UVB doses in (-/-) mice, with delayed reappearance post-irradiation.
- While contact hypersensitivity induction was similar across groups, UVB-induced immunosuppression was markedly enhanced in XPA-deficient mice.
Conclusions:
- The developed XPA gene-deficient mouse model effectively recapitulates key photodermatologic abnormalities observed in human XPA patients.
- These mice serve as a valuable preclinical tool for studying the pathogenesis of XPA and evaluating potential therapeutic strategies.
- Enhanced UV-induced immunosuppression in XPA deficiency may contribute to the high incidence of skin cancers in individuals with Xeroderma pigmentosum.
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