Preventative effects of the flowers of Inula britannica on autoimmune diabetes in C57BL/KsJ mice induced by multiple low doses of streptozotocin.

We have reported that an aqueous extract from the flowers of Inula britannica L. subsp. japonica Kitam. (IB) prevented immunologically induced experimental hepatitis in mice and suggested that the antihepatitic effect of IB is due to inhibition of IFN-gamma production. We then investigated the effects of IB on diabetes in mice induced by multiple low doses of streptozotocin (MLDSTZ), which is a mouse model for IFN-gamma-dependent autoimmune diabetes. C57BL/KsJ mice (male, 7 weeks) were provided with IB extract (500 mg/ kg/ day) in drinking water ad libitum, starting 7 days before the first STZ injection. Autoimmune diabetes was induced by MLDSTZ (40 mg/kg/day for 5 daily doses, i.p.). The IB treatment significantly suppressed the increase of blood glucose levels. Histological analysis of the pancreas showed that the degree of insulitis and destruction of beta-cells were reduced by IB treatment. The IFN-gamma production from stimulated splenic T lymphocytes was inhibited by the IB treatment. Moreover, the proportion of IFN-gamma-producing cells in the CD4(+) population, which was increased by MLDSTZ, was significantly decreased by the IB treatment. These results suggest that IB has a preventative effect on autoimmune diabetes by regulating cytokine production.