Inhibition of UV-induced immune suppression and interleukin-10 production by plant oligosaccharides and polysaccharides

Application of Aloe barbadensis poly/oligosaccharides to UV-irradiated skin prevents photosuppression of delayed-type hypersensitivity (DTH) responses in mice. We tested the hypothesis that these carbohydrates belong to a fam ily of biologically active, plant-derived polysaccharides that can regulate responses to injury in animal tissues, C3H mice were exposed to 5 kJ/m(2) UVB from unfiltered FS40 sunlamps and treated with between 1 pg and 10 mu g tamarind xyloglucans or control polysaccharides methylcellulose or dextran in saline. The mice were sensitized 3 days later with Candida albicans, Ta marind xyloglucans and purified Aloe poly/oligosaccharides prevented suppre ssion of DTH responses in vivo and reduced the amount of interleukin (IL)-1 0 observed in UV-irradiated murine epidermis, Tamarind xyloglucans were imm unoprotective at low picogram doses. In contrast, the control polysaccharid es methylcellulose and dextran had no effect on immune suppression or cutan eous IL-10 at any dose. Tamarind xyloglucans and Alae poly/oligosaccharides also prevented suppression of immune responses to alloantigen in mice expo sed to 30 kJ/m(2) UVB radiation. To assess the effect of the carbohydrates on keratinocytes, murine Pam212 cells were exposed to 300 J/m(2) UVB radiat ion and treated for 1 h with tamarind xyloglucans or Aloe poly/oligosacchar ides . Treatment of keratinocytes with immunoprotective carbohydrates reduc ed IL-10 production by approximately 50% compared with the cells treated wi th UV radiation alone and completely blocked suppressive activity of the cu lture supernatants in vivo. The tamarind xyloglucans also blocked UV-activa ted phosphorylation of SAPK/JNK protein but had no effect on p38 phosphoryl ation. These results indicate that animals, like plants, may use carbohydra tes to regulate responses to environmental stimuli.