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Nitric Oxide Contributes
to Solar-Simulated Ultraviolet Radiation-Induced Immunosuppression in
Humans
Kuchel, Johanna 1,2,
Barnetson, Ross1,2 and Halliday, Gary1,2
Melanoma and Skin Cancer Research Institute, Royal Prince Alfred Hospital,
Sydney, Australia1
The University of Sydney, Australia2
Abstract-
The aim of this study was to determine the role of nitric oxide (NO)
and hydroxyl radicals in solar simulated ultraviolet radiation (ssUVR)
induced local immunosuppression in humans. Two sets of fifteen healthy,
nickel-allergic volunteers of Fitzpatrick skin type I-III were recruited
from the general population. NG-methyl-L-arginine (L-NMMA)
was used to inhibit NO production and 2,2,-dipyridyl was
used to reduce hydroxyl radical formation. Each antioxidant was applied
to a separate group of volunteers. Skin was irradiated with a 1000W
Oriel xenon-arc lamp. Two, six cm squares on the lower back of each
volunteer was randomized to receive either an antioxidant or base lotion
15 minutes prior to UV irradiation. Both UV and antioxidant were administered
daily for four consecutive days. After the final irradiation, nickel
patches were applied to each test site for 48 hours. Contact hypersensitivity
(CHS)-induced erythema was measured with a reflectance spectrometer
24 hours after patch removal. On a further 20 volunteers, a sun protection
factor for L-NMMA and 2,2,-dipyridyl was determined. Both
antioxidants provided only marginal, significant protection from sunburn.
Low, sub-erythemal doses of ssUVR caused local immunosuppression in
a dose-dependent manner. L-NMMA but not 2,2,-dipyridyl protected
the immune system from suppression, suggesting that NO, but not iron-catalyzed
production of hydroxyl radicals, are involved in UV-induced immunosuppression
in humans.
Keywords: Nitric
oxide, Immunosuppression
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