Introduction: The chronic inflammatory skin disease psoriasis
vulgaris is characterized by itchy plaques, often accompanied by
life-threatening comorbidities severely impairing the quality of life
and cause high socioeconomic costs. Despite the known cancer risk, radon
inhalation is used as a treatment for various chronic inflammatory
diseases, including psoriasis. Knowledge about the underlying mechanism
is scarce, largely due to the lack of suitable mouse models. Methods:
Here, we used transgenic mice that spontaneously develop chronic
psoriatic skin lesions inflicted by constitutive low-level
IL-17A-production by CD11c+ cells (CD11c-IL-17Aind/ind
mice). Mice underwent single or multiple radon exposures under therapy
relevant conditions and observed until plaque formation or predefined
time points. Blood and tissue were collected for immunohistological
analysis and immune phenotyping. Comprehensive transcriptome profiling
of non-lesional skin was performed 3 days and 2 weeks after multiple
radon exposures. Results and discussion: Following multiple radon exposures, plaque formation was significantly delayed in CD11c-IL-17Aind/ind
mice, although IL-17A concentrations were not reduced. Cellular and
molecular analyses indicated transient immunosuppressive effects after
radon exposure and, on the cellular level, pDCs were significantly
reduced in lymph nodes. Comprehensive transcriptome profiling of
non-lesional skin showed a different gene expression profile after radon
exposure. Notably, at an early time point after exposure, the Tbx21
gene, associated with psoriasis initiation, and at a late time point
Tgfbr1were significantly downregulated, Furthermore, genes related to
the suppression of inflammation and immune activation (Ccr6), for
example Gata3 and others were upregulated. This points to immune
modulation after radon exposure. In line with this, pathway enrichment
analysis revealed immunosuppressive effects related to T cell
regulation, similar to UV radiation-induced response. Conclusion:
This study provides the first evidence of the efficacy of radon
treatment, including the underlying mechanisms in a preclinical mouse
model.