Effects of Aflatoxin B1 on CSN3 Gene Expression under in Vitro Cultured Iranian Holstein Cow Mammary Epithelial Cells

Aflatoxins are toxic compounds which are produced by Aspergillus Flavus and A. parasiticus. These toxins can be transmitted into the animal body via contaminated feed. When these toxins enter the animal body, they can penetrate into different tissues. One of the most important tissues which can be influenced by aflatoxin is the mammary gland. Milk protein is one the most important factors in determining the milk quality. This protein is controlled by different genes; still, the most important gene that affects milk protein is CSN3. When aflatoxin B1, as the most toxic aflatoxin, penetrates into the mammary gland, it can affect the expression of CSN3 gene and consequently milk protein. To study this subject, a 2×2 cm specimen of the epithelial tissue of the bovine mammary gland in sterile condition was cut and transferred to the laboratory where enzyme digestion with collagenase was carried out. After enzyme digestion, in order to achieve a suitable cell count, primary cell culture was done. After 10 days, the cells were passaged to 24 flasks (6 repeats for each treatment) in order to exert the treatments. One week after passaging the cells, three concentrations (15, 25 and 35 µL) of aflatoxin B1 were exerted. Twenty-four hours later, the cells were separated for RNA extraction, cDNA synthesis, and real-time PCR. MTT assay was performed to measure cell viability. The results showed that the 25 and 35 µL concentrations of aflatoxin B1 decreased the expression of CSN3 gene (P<0.0001). In addition, the results of MTT assay showed that cell viability was reduced after increasing the concentrations of toxin and duration of exposure. According to the results, it seems that aflatoxin B1, by reducing the expression of CSN3 gene, can decrease the milk protein.