In vitro studies (human cell lines)
Aqueous extracts of the sporophores of eight mushroom species have been assessed for their ability to prevent H2O2-induced oxidative damage to cellular DNA using the single-cell gel electrophoresis ("Comet") assay. The highest genoprotective effects were obtained with cold (20ºC) and hot (100ºC) water extracts of Agaricus bisporus and Ganoderma lucidum fruit bodies, respectively. No protective effects were observed with mushroom derived preparations from Flammulina velutipes, Auricularia auricula, Hypsizygus marmoreus, Lentinula edodes, Pleurotus sajor-caju, or Volvariella volvacea. Some edible mushrooms therefore represent a valuable source of biologically active compounds with potential for protecting cellular DNA from oxidative damage (Rocha et al., 2002).
A heat-labile protein has also been identified in fruit bodies of Agaricus bisporus which protects Raji cells (a human lymphoma cell line) against H2O2-induced oxidative damage to cellular DNA (Shi et al., 2002). Similar reductions in DNA fragmentation (Comet assay), compared with H2O2 as a positive control, have been reported from Chaga mushroom (Inonotus obliquus)(Park et al., 2004), while an aqueous extract from Agrocybe cylindracea strain B has also been shown to protect against DNA damage in HepG2 cells (Wang et al., 2004).
Protein extracts from selenium-enriched Ganoderma lucidum (Se-GLPr) have been reported to possess strong DNA protective effects from oxidative damage, which increased with the increase of Se content, indicating indirectly that Se plays an important role in increasing the antioxidant activities of protein extracts (Zhao et al., 2004). Polysaccharide extracts from Se-enriched G. lucidum have also been shown to protect DNA from hydroxyl radical oxidative damage in a dose dependent manner (Zhao et al., 2008).
Protective effects of beta-glucan (BG) extracted from Agaricus brasiliensis against chemically induced DNA damage in human lymphocytes have been reported. The genotoxic and antigenotoxic effects of beta-glucans extracted from Agaricus brasiliensis (=Agaricus blazei Murrill ss. Heinemann) have been studied. Beta-glucan was devoid of mutagenic activity and a significant dose-dependent protective effect against DNA damage occurred in the dose range 20-80 µg/ml (Angeli et al., 2006). Furthermore, a possible chemoprotective effect of beta-glucan extracted from Agaricus blazei against DNA damage induced by benzo[a]pyrene (B[a]P), using the comet assay (genotoxicity) and micronucleus assay with cytokinesis block (mutagenicity) in a human hepatoma cell line (HepG2) has recently been studied (Angeli et al., 2009b). The results showed that beta-glucan did not exert a genotoxic or mutagenic effect, but that it did protect against DNA damage caused by B[a]P.
The potential of an Ganoderma lucidum extract as a radioprotector and antioxidant defense against oxygen radical-mediated damage has been studied and it was demonstrated that a hot-water extract of Ganoderma lucidum had good radioprotective ability, as well as protection against DNA damage induced by metal-catalyzed Fenton reactions and UV irradiation, although the evidence was based on in vitro tests using isolated DNA. It was also found that the water-soluble polysaccharide isolated from the fruit body of Ganoderma lucidum was as effective as a hot-water extract in protecting against hydroxyl radical-induced DNA strand breaks, indicating that the polysaccharide compound is associated with the protective properties (Kim and Kim, 1999).
Subsequent studies of others on the radioprotective properties of an aqueous extract of Ganoderma lucidum have confirmed the effects on protection of radiation-induced plasmid pBR322 DNA strand breaks and inhibition of lipid peroxidation. These data indicate that an aqueous extract of G. lucidum possesses significant protective activity against radiation-induced cellular damage (Pillai et al., 2006).
The combination of nutritional supplements (cat's claw water extract (C-Med-100, carboxy alkyl esters as the active ingredients) and mushroom extracts (Cordyceps sinensis, Grifola blazei, Grifola frondosa, Trametes versicolor and Ganoderma lucidum polysaccharides as the active ingredients) with nicotinamide and zinc into a formulation designed to optimize different modes of immuno-stimulatory action, have been shown to be synergistic, and not metabolically competitive, on growth inhibition of HL-60 human leukemic cells in vitro. Furthermore, an in vivo study showed significant health benefitsfor 14 subjects treated for 4 weeks with the C-Med100/mushroom extract formulation, in that they had reduced pain, reduced fatigue and weight loss and a reduced presence of DNA damage in peripheral blood as assessed by (8-OH) guanine DNA adducts and elevation in serum protein thiols (Pero et al., 2005).
Beta-glucans from Agaricus blazei has been reported to not exert a genotoxic or mutagenic effect, but that it does protect against DNA damage caused by benzo[a]pyrene in the human hepatoma cell line HepG2. The data suggest that beta-glucan acts through binding to benzo[a]pyrene orthe capture of free radicals produced during its activation (Angeli et al., 2009a).
Animal model (mouse) studies
Agaritine measured in mouse plasma and urine has been shown to peak 20min after oral administration to mice (4.0 and 40mg/kg). The concentration gradually decreased and returned to the basal level in 100min. One agaritine metabolite was found in the plasma and the urine from agaritine-administered mice. HMPH (4-(hydroxymethyl) phenylhydrazine) was generated from agaritine. The oxidative stress marker 8-OHdG was detected in agaritine-administered mouse urine. After administration, the 8-OHdG level immediately tripled, and then decreased to the control level over 48h. Its level then elevated again and remained high for 11 days. The authors suggested that agaritine quickly metabolizes and disappears in the plasma, whereas DNA damage lasts for a longer time after a single administration of agaritine to mice (Kondo et al., 2008). The inference for DNA damage was from a result of a separate in vitro test. While the data with a particular marker of oxidative stress showed this effect, a similar experiment with a different marker of oxidative stress did not show this effect. The authors have made the comment based on their results with one particular marker only. The data is therefore not strong and further research needs to be done. Furthermore, this study was using synthetic agaritine of high purity, and not mushrooms or mushroom extracts.
DNA strand breaking by the carbon-centered radical generated from 4-(hydroxymethyl) benzenediazonium salt from Agaricus bisporus has been reported in the mouse (Hiramoto et al., 1995).
Animal model (rat) studies
The effects of crude extracts of the mushroom Agaricus blazei Murrill (Agaricaceae) on both DNA damage and placental form glutathione S-transferase (GST-P)-positive liver foci induced by diethylnitrosamine (DEN) have been investigated in adult male Wistar rats. The data indicated that previous treatment with the highest concentration of Agaricus blazei (11.5mg/ml) significantly reduced DNA damage, indicating a protective effect against DEN-induced liver cytotoxicity/genotoxicity (Barbisan et al., 2003a) while in a subsequent study, the same group reported that treatment with aqueous extracts of Agaricus blazei does not exert a protective effect against the development of GST-P-positive foci induced by DEN (Barbisan et al., 2003b).