i style=""Lentinula edodes/i (Shiitake) mushroom extract protects against hydrogen peroxide induced cytotoxicty in peripheral blood mononuclear cells

摘要

i style=""Lentinula edodes/i (Berk) Pegler, commonly known as Shiitake mushroom has been used as medicinal food in Asian countries, especially in China and Japan and is believed to possess strong immunomodulatory property. In the present study, the methanolic extract of the fruit bodies of i style=""L. edodes/i was investigated for cytoprotective effect against Hsub2/subOsub2/sub-induced cytotoxicity in human peripheral blood mononuclear cells (PBMCs) by measuring the activities of xanthine oxidase (XO) and glutathione peroxidase (GPx) . Hsub2/subOsub2 /subat a concentration of 5 μM caused 50% inhibition of PBMCs viability. The extract improved the PBMC viability and exerted a dose-dependent protection against Hsub2/subOsub2/sub-induced cytotoxicity. At 100 μg/ml of extract concentration, the cell viability increased by 60% compared with the PBMCs incubated with Hsub2/subOsub2 /subalone. The extract alsoi style="" /iinhibited XO activity in PBMC, while showing moderate stimulatory effect on GPx. However, in the presence of Hsub2/subOsub2/sub alone, both the enzyme activities were increased significantly. The GPx activity increased, possibly in response to the increased availability of Hsub2/subOsub2 /subin the cell. When the cells were pretreated with the extract and washed (to remove the extract) prior to the addition of Hsub2/subOsub2/sub, the GPx and XO activities as well as the cell viability were comparable to those when incubated with the extract alone. Thus, it is suggested that one of the possible mechanisms i style=""via/i which i style=""L. edodes/i methanolic extract confers protection against Hsub2/subOsub2/sub-induced oxidative stress in PBMC is by inhibiting the superoxide-producing XO and increasing GPx activity which could rapidly inactivate Hsub2/subOsub2/sub.