Optimization of Se- and Zn-Enriched Mycelium of Lentinula edodes (Berk.) Pegler as a Dietary Supplement with Immunostimulatory Activity.

Mycelial cultures of Lentinula edodes, an edible and medicinal mushroom, have been used in our previous research to obtain selenium-containing immunomodulatory preparations. Our current attempts to obtain a new preparation containing both selenium and zinc, two micronutrients necessary for the functioning of the immune system, extended our interest in the simultaneous accumulation of these elements by mycelia growing in media enriched with selenite and zinc(II) ions. Subsequently, we have studied the effects of new L. edodes mycelium water extracts with different concentrations of selenium and zinc on the activation of T cell fraction in human peripheral blood mononuclear cells (PBMCs). Flow cytometry analysis was used to measure the expression of activation markers on human CD4+ and CD8+ T cells stimulated by anti-CD3 and anti-CD3/CD28 antibodies (Abs). It was demonstrated that statistically significant changes were observed for PD-1 and CD25 antigens on CD8+ T cells. The selenium and zinc content in the examined preparations modified the immunomodulatory activity of mycelial polysaccharides; however, the mechanisms of action of various active ingredients in the mycelial extracts seem to be different.

Selective Biological Effects of Selenium-Enriched Polysaccharide (Se-Le-30) Isolated from Lentinula edodes Mycelium on Human Immune Cells.

A common edible mushroom Lentinula edodes, is an important source of numerous biologically active substances, including polysaccharides, with immunomodulatory and antitumor properties. In the present work, the biological activity of the crude, homogenous (Se)-enriched fraction (named Se-Le-30), which has been isolated from L. edodes mycelium by a modified Chihara method towards human peripheral blood mononuclear cells (PBMCs) and peripheral granulocytes, was investigated. The Se-Le-30 fraction, an analog of lentinan, significantly inhibited the proliferation of human PBMCs stimulated with anti-CD3 antibodies or allostimulated, and down-regulated the production of tumor necrosis factor (TNF)-α by CD3+ T cells. Moreover, it was found that Se-Le-30 significantly reduced the cytotoxic activity of human natural killer (NK) cells. The results suggested the selective immunosuppressive activity of this fraction, which is non-typical for mushroom derived polysaccharides.

Selenium-Containing Exopolysaccharides Isolated from the Culture Medium of Lentinula edodes: Structure and Biological Activity.

In continuation of our research on the influence of selenium incorporation on the biosynthesis, structure, and immunomodulatory and antioxidant activities of polysaccharides of fungal origin, we have isolated from a post-culture medium of Lentinula edodes a selenium (Se)-containing exopolysaccharide fraction composed mainly of a highly branched 1-6-α-mannoprotein of molecular weight 4.5 × 106 Da, with 15% protein component. The structure of this fraction resembled mannoproteins isolated from yeast and other mushroom cultures, but it was characterized by a significantly higher molecular weight. X-ray absorption fine structure spectral analysis in the near edge region (XANES) suggested that selenium in the Se-exopolysaccharide structure was present mainly at the IV oxidation state. The simulation analysis in the EXAFS region suggested the presence of two oxygen atoms in the region surrounding the selenium. On the grounds of our previous studies, we hypothesized that selenium-enriched exopolysaccharides would possess higher biological activity than the non-Se-enriched reference fraction. To perform structure-activity studies, we conducted the same tests of biological activity as for previously obtained mycelial Se-polyglucans. The Se-enriched exopolysaccharide fraction significantly enhanced cell viability when incubated with normal (human umbilical vein endothelial cells (HUVEC)) cells (but this effect was absent for malignant human cervical HeLa cells) and this fraction also protected the cells from oxidative stress conditions. The results of tests on the proliferation of human peripheral blood mononuclear cells suggested a selective immunosuppressive activity, like previously tested Se-polyglucans isolated from L. edodes mycelium. The Se-exopolysaccharide fraction, in concentrations of 10-100 µg/mL, inhibited human T lymphocyte proliferation induced by mitogens, without significant effects on B lymphocytes. As with previously obtained Se-polyglucans, in the currently tested Se-polymannans, the selenium content increased the biological activity. However, the activity of selenium exopolysaccharides in all tests was significantly lower than that of previously tested mycelial isolates, most likely due to a different mode of selenium binding and its higher degree of oxidation.

Identification of the Primary Structure of Selenium-Containing Polysaccharides Selectively Inhibiting T-Cell Proliferation.

We previously described the biosynthesis, isolation, and immunosuppressive activity of the selenium-containing polysaccharide fraction isolated from the mycelial culture of Lentinula edodes. Structural studies have shown that the fraction was a protein-containing mixture of high molar mass polysaccharides α- and ß-glucans. However, which of the components of the complex fraction is responsible for the immunosuppressive activity non-typical for polysaccharides of fungal origin has not been explained. In the current study, we defined four-polysaccharide components of the Se-containing polysaccharide fraction determined their primary structure and examined the effect on T- and B-cell proliferation. The isolated Se-polysaccharides, α-1,4-glucan (Mw 2.25 × 106 g/mol), unbranched ß-1,6-d-glucan, unbranched ß-1,3-d-glucan and ß-1,3-branched ß-1,6-d-glucan (Mw 1.10 × 105 g/mol), are not typical as components of the cell wall of L. edodes. All are biologically active, but the inhibitory effect of the isolated polysaccharides on lymphocyte proliferation was weaker, though more selective than that of the crude fraction.

Selenium-containing polysaccharides from Lentinula edodes-Biological activity.

We hypothesized that selenium(Se)-enriched polysaccharides would possess superior biological activity when compared to those non-enriched. To verify this hypothesis, we obtained by biotechnological methods a Se-enriched analog of Japanese anticancer drug lentinan and, as a reference, the non-Se-enriched fraction. We tested the effects of the obtained fractions on the proliferation of human peripheral blood mononuclear cells. The results suggested a selective immunosuppressive activity, non-typical for mushroom derived polysaccharides. Both fractions caused significant inhibition of human T lymphocyte proliferation induced by mitogens, without significant effects on B lymphocytes. The inhibitory effect was not due to the toxicity of the examined polysaccharides. In normal (HUVEC) or malignant (HeLa) cells tested fractions significantly enhanced cell viability and protected the cells from oxidative stress conditions. However, we observed no effect of the polysaccharide fractions on the production of reactive oxygen species by granulocytes in vitro. The selenium content increased the biological activity of the tested polysaccharide fractions.