Abstract
Aflatoxins are carcinogenic secondary metabolites of fungi that contaminate many staple crops and foods. Aflatoxin contamination is a worldwide problem, especially in developing countries, posing health hazards, e.g., causing aflatoxicosis and hepatocellular carcinoma, and even death. Biological solutions for aflatoxin detoxification are environmentally friendly and a cheaper alternative than chemical methods. The aims of the current study were to investigate: (1) the ability of MSMEG_5998, an aflatoxin-degrading F420H2-dependent reductase from Mycobacterium smegmatis, to degrade aflatoxin B1 (AFB1) and reduce AFB1-caused damage in HepG2 cell culture model; and (2) whether a thioredoxin (Trx) linkage of MSMEG_5998 enhanced the enzyme activity. We show that Trx-linked MSMEG_5998 degraded 63% AFB1 and native MSMEG_5998 degraded 31% after 4 h at 22 °C, indicating that the Trx-linked enzyme had a better AFB1-degrading ability. In a HepG2 cell culture model, Trx-linked MSMEG_5998 reduced DNA damage and p53-mediated apoptosis caused by AFB1 to a greater extent than the native enzyme. These findings suggest that Trx-linked MSMEG_5998 could potentially be developed to protect the liver from AFB1 damage, or as a candidate protein to reduce AFB1-related toxicity in animals.
Highlights
Aflatoxin, a group of mycotoxins produced by Aspergillus species, is a human liver carcinogen whose contamination of food is a significant risk factor for hepatocellular carcinoma [1].Aflatoxins commonly contaminate staple commodities, such as cereals, nuts, rice, corn, peanuts, and many others, during poor storage and processing conditions [2]
To test whether aflatoxin B1 (AFB1)-induced apoptosis in HepG2 cells was associated with p53 pathway, To test whether AFB1-induced apoptosis in HepG2 cells was associated with p53 pathway, we we evaluated p53 levels in cells treated for 48 h (Figure 4B)
In a HepG2 cell culture model, Trx-linked MSMEG_5998 reduced DNA damage and p53-mediated apoptosis caused by AFB1 to a greater extent than the native enzyme
Summary
A group of mycotoxins produced by Aspergillus species, is a human liver carcinogen whose contamination of food is a significant risk factor for hepatocellular carcinoma [1]. Aflatoxins commonly contaminate staple commodities, such as cereals, nuts, rice, corn, peanuts, and many others, during poor storage and processing conditions [2]. Aflatoxin M1 is a toxic metabolite of aflatoxins, which is found in milk in animals administered with feed containing aflatoxins [4]. It is very likely that we are exposed to this toxin metabolite. Early symptoms of liver hepatotoxicity caused by aflatoxins comprise abdominal pain, vomiting, and hepatitis [5]. Chronic toxicity caused by aflatoxins involves immunosuppressive and carcinogenic effects. Aflatoxins can cause liver damage, decreased milk production, and death
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