Interleukin-8 stimulating activity of low molecular weight β-glucan depolymerized by γ-irradiation

Since many studies reveal that the biological properties of various biopolymers depend on their molecular weight. Therefore, it was considered of importance to investigate how molecular weight affected on the interleukin-8 (IL-8) stimulating activity of the β-glucan from Ophiocordyceps dipterigena BCC2073. γ-Irradiation of the glucan with various doses (0-100 kGy) was chosen as a clean method to produce different low molecular weight samples. The result showed that average molecular weight (MW) of irradiated samples significantly decreased as the irradiation dose increased whereas the functional groups of before and after irradiated glucans detected by FTIR and 13C-NMR were identical. However, difference in intensity of an absorption peak at 270 nm was found in the UV/vis spectra. The biological properties such as cytotoxicity, proliferation and IL-8 secretion of normal human dermal fibroblast contacted with various MW glucans were also tested. It was found that the glucan with MW of approximately 5 kDa exhibited the highest ability to induce IL-8 production. Apart from the MW effect, chain conformation seems to be involved. Thus, differences in solution conformation of various MW glucans via Congo red analysis were evaluated.