The suppression of immunity by ultraviolet radiation: UVA, nitric oxide and DNA damage

Abstract

We have examined the mechanism by which solar-simulated ultraviolet radiation (ssUV) suppresses memory immunity to nickel in allergic humans. In initial studies, we used inbred mice to determine the contribution of different wavebands to sunlight-induced immunosuppression. We found that low dose UVA can enhance memory, medium dose UVA (half the amount in one minimum erythemal dose of ssUV) is immunosuppressive, but higher doses protect from UVB. This is genetically dependent, as it is not observed in all mouse strains. UVA caused a similar dose-related change in recall immunity in humans. ssUV dose responses determined the limits of protection provided by sunscreens from immunosuppression in humans. Immune protection factors calculated from these data correlated with UVA protection, but not with sun protection factor, showing that in commercial sunscreens that provide good UVB protection, UVA protection limits prevention of immunosuppression. N(G)-monomethyl-l-arginine acetate (l-NMMA) was used to inhibit nitric oxide (NO) production and T4N5 liposomes containing T4 endonuclease V to enhance DNA repair. Sub-erythemal ssUV caused a dose-related local suppression of recall immunity to nickel in humans. l-NMMA and the liposomes protected the nickel reaction, suggesting that NO and DNA damage are mediators of UV-induced immunosuppression in humans.

Photoprotection by 1α,25-dihydroxyvitamin D and analogs: Further studies on mechanisms and implications for UV-damage

“…Our studies in hairless mice showed that topical application of 1,25D reduced systemic immune suppression measured 2 weeks after the UV exposure [25], though 1,25D can be immunosuppressive under other conditions [30]. Since increased CPD and reactive nitrogen species both contribute to UV-induced immunosuppression [11,31], it is likely that both the reduced CPD and reduced reactive nitrogen species measured post-UV in the presence of 1,25D contribute to the reduced immunosuppression. An altered cytokine profile is probably a downstream effect [32].…”

In vitro photoprotection and antioxidant capacity of Sphagnum meridense extracts, a novel source of natural sunscreen from the mountains of Colombia

“…On the other hand, uncontrolled exposure to UV radiation can cause multiple dermal disorders such as skin cancer, erythema, melanoma, photoaging, etc. All of them may stimulate numerous processes associated to premature aging such as depigmentation, folds and distortions [5,6].…”

Ultraviolet Light Induced Alteration to the Skin

“…According to studies, the UVA effect is very intricate and shows a strong genetic dependence. Medium doses modulate immunity; higher doses can protect the immune system from the suppressive effect of UVB, while lower doses (below 840 mJ/cm 2 ) of UVA can enhance the memory of cell development 29 . Photoaging includes a complex of biologic processes affecting various layers of the skin with the major damage seen in the cognitive tissue of the dermis 30 .…”