Gum Arabic-induced oral photoprotection: Shifting the balance against circulating immune suppressive cytokines

Abstract

Oral dietary botanicals are gaining considerable attention as complementary measures for photoprotection. Gum Arabic (GA) is a natural dietary fibre known for its potent antioxidant and immunomodulatory effects. We sought to evaluate the efficacy of GA as an oral photo- protective agent by assessing the effect of regular GA consumption on ultraviolet radiation (UVR)-induced systemic imbalance in circulating cytokines and T lymphocyte populations. The study included six groups of mice (n=10/group): Control group; GA group =Mice on GA supplementation (20 g/kg/day for 28 days); group 3 and 4=Mice exposed to sunlight, mice in group 4 were on GA supplementation (sunUVR+ GA); group 5 and 6=Mice exposed to ultraviolet B, mice in group 6 were on GA supplementation (UVB+GA). UVR exposure was conducted during the last four days of a 28 days follow-up period as follows: 30 minutes/day for sunlight exposure and 20 minutes/day for UVB. Plasma cytokines were measured using ELISA, and blood CD4+ and CD8+ T lymphocytes and the CD4/CD8 ratio were evaluated using flow cytometry. Mice exposed to sunlight and UVB following a period of GA supplementation had lower levels of anti-inflammatory cytokines (IL-10 and TGF-β) and higher levels of proinflammatory cytokines (IL-12, IFN-γ, and TNF-α) than mice exposed to radiation without prior GA intake. GA supplementation significantly increased the proportion of CD8 in sun exposure group, and the proportion of CD4 in UVB exposure group. In conclusion, GA intake tipped the balance of circulating cytokines in favour of proinflammatory cytokines; therefore, it attenuated UVR-induced immunosuppression. The photo protective effects of GA detected might be attributed to increased circulating short chain fatty acids (SCFA) from GA colonic fermentation. GA is a potential candidate for oral photoprotection.