Radiation Sources Providing Increased UVNUVB Ratios Induce Photoprotection Dependent on the UVA Dose in Hairless Mice

Abstract

In studies involving mice in which doses of UVA (320-400 nm) and UVB (290-320 nm) radiation were administered alone or combined sequentially, we observed a protective effect of UVA against UVB-induced erythema/edema and systemic suppression of contact hypersensitivity. The UVA immunoprotection was mediated by the induction of the stress enzyme heme oxygenase-1 (HO-1) in the skin, protection of the cutaneous Th1 cytokines interferon-gamma (IFN-gamma) and IL-12 and inhibition of the UVB-induced expression of the Th2 cytokine IL-10. In this study, we seek evidence for an immunological waveband interaction when UVA and UVB are administered concurrently to hairless mice as occurs during sunlight exposure in humans. A series of spectra providing varying ratios of UVA/UVB were developed, with the UVA ratio increased to approximately 3.5 times the UVA component in solar simulated UV (SSUV). We report that progressively increasing the UVA component of the radiation while maintaining a constant UVB dose resulted in a reduction of both the erythema/edema reaction and the degree of systemic immunosuppression, as measured as contact hypersensitivity. The UVA-enhanced immunoprotection was abrogated in mice treated with a specific HO enzyme inhibitor. UVA-enhanced radiation also upregulated the expression of cutaneous IFN-gamma and IL-12 and inhibited expression of both IL-6 and IL-10, compared with the activity of SSUV. The results were consistent with the previously characterized mechanisms of photoprotection by the UVA waveband alone and suggest that the UVA component of solar UV may have beneficial properties for humans.

Topical ‘Sydney’ Propolis Protects against UV-Radiation-Induced Inflammation, Lipid Peroxidation and Immune Suppression in Mouse Skin

“…Treatment with 100 mg/kg propolis solution alone resulted in a modest increase in MDA (p < 0.05) to 1.67 p M /mg protein, which might indicate the peroxidative potential of some minor flavonoid constituents [30]. However, exposure to UVA radiation resulted in a marked 3-fold increase (p < 0.001) in MDA concentration to 3.72 p M /mg protein, indicating the induction of strong lipid peroxidation in the skin.…”

“…The samples were fixed for 6 h in Histochoice (Amresco, Solon, Ohio, USA), processed by an automated formalin/ethanol-based system overnight, and wax-embedded. Sections of 5 um were cut and were stained for the cytokines IL-12, IL-6 and IL-10, using goat anti-mouse IL-12, IL-6 and IL-10 primary antibodies (R&D Systems, Minneapolis, Minn., USA) followed by the secondary antibody (horse HRP-conjugated anti-goat IgG(H+L), Vector Laboratories, Burlingame, Calif., USA), stained with the chromogen 3,3′-diaminobenzidine (DAB; Kirkegaard and Perry Laboratories, Gaithersburg, Md., USA), then counter-stained briefly with hematoxylin, as previously described in detail [29,30]. The sections were examined for positive brown staining under light microscopy, and images were captured digitally using a Sony HyperHAD color video camera (Sony, Melbourne, Australia) connected to a Leica Q500MC computer (Leica Microsystems, Sydney, Australia).…”

CYP11A1 in skin: An alternative route to photoprotection by vitamin D compounds

“…Irradiance was measured with an International Light IL1500 radiometer (Newburyport, MA), using UVA and UVB detectors calibrated to the spectral output of the sources. The output spectrum with cellulose acetate filter and the minimal erythemal dose (MED) of solarsimulated UVR for female Skh:hr1 mice has been previously established as containing 1.33 kJ m À2 UVB and 23.7 kJ m À2 of UVA [36]. Groups of mice were exposed on the dorsum, unrestrained in their boxes with the wire tops removed, to a single dose of 2.5 MED of solar simulated UV.…”

Sun exposure and malignant lymphoma: A population‐based case–control study in Germany

“…On the other hand, UV-A itself seems to suppress expression of IL-10 and also IL-6 in the skin. 46 However, UV-A and UV-B-induced immunosuppression remains controversial. There seems to be some kind of dose relationship with different effects on different dose levels 47,48 and chronology of effects.…”