Differential effect of Coriolus versicolor (Yunzhi) extract on cytokine production by murine lymphocytes in vitro

Abstract

Being one of the commonly used Chinese medicinal herbs, Coriolus versicolor (CV), also named as Yunzhi, was known to possess both anti-tumor and immunopotentiating activities. The present study aimed to investigate the in vitro immunomodulatory effect of a standardized ethanol–water extract prepared from CV on the proliferation of murine splenic lymphocytes using the MTT assay, and the production of six T helper (Th)-related cytokines using the enzyme-linked immunosorbent assay (ELISA) technique. The results showed that the CV extract significantly augmented the proliferation of murine splenic lymphocytes in a time- and dose-dependent manner, maximally by 2.4-fold. Moreover, the production of two Th1-related cytokines, including interleukin (IL)-2 and IL-12, in culture supernatants from the CV extract-activated lymphocytes was prominently upregulated at 48 and 72 h. Positive correlations were found between the levels of these two cytokines and the MTT-based proliferative response. In contrast, the production of two other Th1-related cytokines, including interferon (IFN)-γ and IL-18, was significantly augmented only at 24 h, but not at 48 and 72 h. On the other hand, the levels of two Th2-related cytokines such as IL-4 and IL-6 were undetectable in the culture supernatants of lymphocytes treated with the CV extract. The CV extract was suggested to be a lymphocyte mitogen by differentially enhancing the production of Th1-related cytokines.

Introduction

Plant-derived extracts have been historically considered as an important remedy for maintaining health, enhancing overall immune status, and prevention and treatment of chronic diseases [1]. Recent studies have demonstrated that mushroom extracts possess a wide range of biological activities including antiviral, anti-tumor and immunopotentiating activities [2], [3], [4], [5], [6]. Coriolus versicolor (CV), known as Yunzhi in China, is a mushroom species belonging to the Basidiomycetes class of fungi. The medicinal value of Yunzhi was recorded in the Compendium of Chinese Materia Medica and Shen Non Compendium Medica thousands of years ago in China. Nowadays, its therapeutic potentials have been gaining acceptance among patients worldwide [3], [6].

Among various bioactive components derived from CV, polysaccharopeptide (PSP) was found to be the most prominent in anti-tumor and immunomodulatory efficacy. PSP is a protein-bound polysaccharide isolated from the deep-layer cultivated mycelia of C. versicolor COV-1 strain [7]. The polysaccharide moiety of PSP is a β (1→3)-glucan branching at 4′ and 6′ positions, and consists of five different sugars including arabinose, glucose, galactose, mannose and xylose. Its polysaccharide moiety is rich in aspartic and glutamic acids. The substance has a molecular weight of about 100,000 and is highly water-soluble [4], [8]. Previous in vitro studies have reported that ethanol–water extract of CV [9], PSP and PSK (protein-bound polysaccharide Krestin) [10] can directly inhibit the proliferation of leukemia, lymphoma, hepatoma, breast and lung tumor cell lines in a dose-dependent manner [3], [11], [12], [13], [14], [15], [16]. PSP was also found to stimulate both humoral and cell-mediated immune responses. It can induce the production of interferon (IFN)-γ and interleukin (IL)-2, increase the T-cell proliferation and counteract the immunosuppression induced by cytotoxic drugs such as cyclophosphamide [8], [16], [17], [18]. Another research group reported that the water extract of CV (I'm-Yunity™) significantly increased IL-1β and IL-6 secretion while substantially lowering IL-8 production of HL-60 leukemic cells in vitro, suggesting the extract may play key roles in the mediation of inflammatory and immune responses [14]. In clinical trials, PSP administration to patients with esophageal cancer, gastric cancer and lung cancer, who are undergoing radiotherapy or chemotherapy, can help to alleviate symptoms and prevent the decline in immune status [3], [4], [19]. A recent study has demonstrated that regular consumption of capsules containing both Yunzhi and Danshen (Salvia miltiorrhiza) extract could improve cellular immunity in normal healthy subjects by elevating the gene expression of IL-2 receptor in peripheral blood mononuclear cells, and increasing the percentage and absolute counts of T helper (Th) cells [20]. It has been demonstrated that Th1/Th2 balance plays important roles in anti-tumor immunity in which Th1 cells producing IFN-γ and IL-2 are essential for inducing cellular and tumor immunity, whereas Th2 cells producing IL-4 and IL-6 are associated with suppression of cytolytic activity [21], [22].

The objective of the present study was to examine the in vitro immunomodulatory effects of a wildly grown C. versicolor ethanol–water standardized extract, supplied by Vita Green Health Products, on murine splenic lymphocytes. The test parameters included the proliferation response of murine lymphocytes using MTT proliferation assay, and the production of six Th1- and Th2-related cytokines using ELISA technique.