Sequential dietary exposure to aflatoxin B1 and fumonisin B1 in F344 rats increases liver preneoplastic changes indicative of a synergistic interaction

Dietary co-exposure to aflatoxin B1 (AFB1) and fumonisin B1 (FB1) and their interaction on hepatocellular carcinogenesis is of particular concern in toxicology and public health. In this study we evaluated the liver preneoplastic effects of single and sequential dietary exposure to AFB1 and FB1 in the F344 rat carcinogenesis model. Serum biochemical alterations, liver histopathological changes, and the formation of liver glutathione S transferase positive (GST-P+) foci were the major outcome parameters examined. Compared to the AFB1-only treatment, the FB1-only treatment induced less dysplasia, and more apoptosis and mitoses. Sequential AFB1 and FB1 treatment lead to increased numbers of dysplasia, apoptosis and foci of altered hepatocytes, as compared to either mycotoxin treatment alone. More importantly, sequential exposure to AFB1 and FB1 synergistically increased the numbers of liver GTP-P+ foci by approximately 7.3-and 12.9-fold and increased the mean sizes of GST-P+ foci by 6- and 7.5-fold, respectively, as compared to AFB1- or FB1-only treatment groups. In addition, liver ALT and AST levels were significantly increased after sequential treatment as compared to single treatment groups. The results demonstrate the interactive effect of dietary AFB1 and FB1 in inducing liver GST-P+ foci formation and provide information to model future intervention studies

Experimental chronic hepatitis B infection of neonatal tree shrews (<it>Tupaia belangeri chinensis</it>): A model to study molecular causes for susceptibility and disease progression to chronic hepatitis in humans

<p>Abstract</p> <p>Background</p> <p>Hepatitis B virus (HBV) infection continues to be an escalating global health problem. Feasible and effective animal models for HBV infection are the prerequisite for developing novel therapies for this disease. The tree shrew (<it>Tupaia</it>) is a small animal species evolutionary closely related to humans, and thus is permissive to certain human viral pathogens. Whether tree shrews could be chronically infected with HBV in vivo has been controversial for decades. Most published research has been reported on adult tree shrews, and only small numbers of HBV infected newborn tree shrews had been observed over short time periods. We investigated susceptibility of newborn tree shrews to experimental HBV infection as well as viral clearance over a protracted time period.</p> <p>Results</p> <p>Forty-six newborn tree shrews were inoculated with the sera from HBV-infected patients or tree shrews. Serum and liver samples of the inoculated animals were periodically collected and analyzed using fluorescence quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, Southern blot, and immunohistochemistry. Six tree shrews were confirmed and four were suspected as chronically HBV-infected for more than 48 (up to 228) weeks after inoculation, including three that had been inoculated with serum from a confirmed HBV-infected tree shrew.</p> <p>Conclusions</p> <p>Outbred neonatal tree shrews can be long-term chronically infected with HBV at a frequency comparable to humans. The model resembles human disease where also a smaller proportion of infected individuals develop chronic HBV related disease. This model might enable genetic and immunologic investigations which would allow determination of underlying molecular causes favoring susceptibility for chronic HBV infection and disease establishment vs. viral clearance.</p