Chemopreventive effect of Red yeast (Sporidiobolus pararoseus) on Aflatoxin B1 induced carcinogenesis

Abstract

The contamination of mycotoxins, particularly aflatoxins, in various agricultural products have resulted in significant economic losses and have been determined to be the cause of a range of human health problems. Aflatoxin B1 (AFB1) is a highly potent genotoxic carcinogen that is known to cause liver cancer. One approach to resolving AFB1 contamination in agricultural products involves the utilization of sorbent additives. Recently, several studies have supported the contention that red yeast (Sporidiobolus pararoseus) is a key component in an alternative method of reducing mycotoxin contamination. Red yeast is a single-cell microorganism belonging to the class Basidiomycota that can be grown on crude glycerol and fermented in an air-lift bioreactor. Red yeast contains numerous active compounds including particular polysaccharides and various carotenoids that exert a variety of biological activities. These activities include a range of antioxidant, anti-inflammatory, anti-apoptosis, and anti-cancer properties. However, there have been a limited number of studies that initiate the biomedical research of red yeast. Therefore, the present study has aimed to investigate the safety and efficacy of a cancer prevention approach involving red yeast by testing its genotoxicity and antigenotoxicity against AFB1 induced mutagenesis using Salmonella mutation assay and the rat liver micronucleus test. The inhibitory mechanisms of the effective extract(s) derived from red yeast powder via xenobiotic metabolizing enzymes and DNA repairing enzymes were examined. In this study, red yeast powder was composed of 82.42% carbohydrates, 4.43% protein, and 0.44% lipids. Red yeast was further extracted by hexane, acetone and then steamed by being autoclaved to obtain the hexane extract, acetone extract, autoclaved extract, and a residual part. The results indicate that the hexane extract contained high - carotene and lycopene contents. Furthermore, phenolic compounds, including - hydroxybenzoic acid, were found to be present in the acetone extract. The autoclaved extract primarily contained carbohydrates including -glucan, while the proteins were largely presented in the residual part. The mutagenicity and antimutagenicity of red yeast and its extracts were evaluated using Ames test. Red yeast and its extracts were not found to be mutagenic in Salmonella Typhimurium strains TA 98 and TA 100 in the presence and absence of metabolic activation indicating the non-mutagenicity of red yeast. Interestingly, the hexane extract exhibited the strongest degree of antimutagenicity against AFB1 induced mutagenesis in TA98 and TA100 strains. The acetone extract and residual part presented moderate and mild levels of antimutagenicity, respectively, whereas the autoclaved extract did not inhibit AFB1-induced mutagenesis. Furthermore, -carotene exhibited greater antimutagenicity than lycopene and -glucan. The resulting data indicate that - carotene could be a major active ingredient in red yeast. The clastogenic and anticlastogenic effects of red yeast were further investigated using rat micronucleus assay. Male wistar rats were divided into 14 groups. Groups 1 to 7 were designated for the study of clastogenicity. On days 21 and 25, they were intraperitoneally injected with 0.9% normal saline. Subsequently, Groups 8 to 14 received 200 µg/kg of AFB1 in order to investigate anticlastogenicity. Groups 1 and 8 were fed with 5% Tween 20 for 28 days. Groups 2 and 9 were then fed with red yeast powder at 33 mg/kg bw, while Groups 3 and 10 were fed with red yeast powder at 100 mg/kg bw. Furthermore, Groups 4 and 11 were treated with hexane extract at 1 mg/kg bw, while Groups 5 and 12 were treated with hexane extract at 3 mg/kg bw. Groups 6 and 13 received the autoclaved extract at 66 mg/kg bw, while Groups 7 and 14 received the autoclaved extract at 100 mg/kg bw. All rats were partially hepatectomized to amplify the initiated hepatocytes on day 29. Liver tissues were collected in order to assess their xenobiotic metabolism. On day 33, single hepatocytes were isolated to investigate micronucleus formations and hepatocyte morphology. The results indicated that red yeast, the hexane extract, and the autoclaved extract did not induce micronucleus formation in the livers of rats. Notably, they did not alter various cytochrome P450 activities including Cytochrome P450 1A1, 1A2, and CYP3A2 and NADPH-cytochrome P450 reductase, but they did enhance the activity of some phase II metabolizing enzymes including glutathione-S-transferase (GST), heme oxygenase, and NADPH quinone oxidoreductase1. Remarkably, red yeast, the hexane extract, and the autoclaved extract significantly decreased the amount of micronucleus formations in the livers of AFB1-treated rats. It has been suggested that red yeast could prevent the initiation stage of carcinogenesis. Furthermore, red yeast and the hexane extract modulated GST activity, but not its protein expression in the livers of AFB1-initiated rats. Importantly, the hexane extract and the autoclaved extract significantly increased XPA protein expression, a nucleotide excision repairing enzyme. In conclusion, red yeast was not found to be mutagenic in bacterial models and was determined not to be clastogenic in rats. Moreover, red yeast exhibited antimutagenicity and anticlastogenicity against AFB1 mutagenesis via the modulation of AFB1 detoxifying enzymes and the DNA repairing system. Notably, β-Carotene may be an important cancer chemopreventive ingredient in red yeast that displays protective properties at the initiation stage of hepatocarcinogenesis in rats.