Abdallah, M. F. | bioRxiv Science

bioRxiv2023

Elucidating the combined toxicity of aflatoxin B1 and fumonisin B1 on HepG2 cells based on respirometry and transcriptome analyses

Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are two toxic mycotoxins widely found in food contaminants, and known for their hepatotoxicity in human. However, their combined toxicity still needs to be deeply investigated especially for their harmful effect. Therefore, the current work aimed at investigating the (combined) effect of AFB1 and FB1 on mitochondrial and glycolytic activity of HepG2 cell line, a well-recognized in vitro model system to study liver cell function. In our previous work, we studied the impact of a short term exposure to different doses of AFB1, FB1, and their binary mixture (MIX) on the bioenergetic status of HepG2 cells. Seahorse respirometry analysis revealed that the co-exposure, especially at high doses (8 {micro}g/mL for AFB1 and 160 {micro}g/mL for FB1), is more toxic as a result of more inhibition of all parameters of mitochondrial respiration. RNA transcriptome sequencing showed that the p53 signaling pathway, which is a major orchestrator of mitochondrial apoptosis, was differentially expressed. Moreover, the co-exposure has significantly downregulated Cx I, Cx II, Cx III, and Cx IV genes, which represent the onset of the suppressed mitochondrial respiration in HepG2 cells. It was found that FB1 is contributed more to the MIX effects than AFB1. Environmental ImplicationAflatoxin B1 (AFB1) and fumonisin B1 (FB1) are two main mycotoxins that frequently (co-)contaminate maize and maize-based ingredients in several parts of the world. Both toxins are well-known for their hepatotoxicity in humans as the liver is their main target organ. However, the combined toxicity of AFB1 and FB1 still needs to be deeply investigated especially for their effect on cellular respiration. In this study, we proved that a binary mixture of AFB1 and FB1 is more toxic on mitochondrial respiration, and disrupted the p53 signaling pathway to induce apoptosis, which promised a novel insight of hazardous materials-induced hepatic damage.

pharmacology and toxicology↗

bioRxiv2020

A novel, ataxic mouse model of Ataxia Telangiectasia caused by a clinically relevant nonsense mutation

Ataxia Telangiectasia (A-T) and Ataxia with Ocular Apraxia Type 1 (AOA1) are devastating neurological disorders caused by null mutations in the genome stability genes, A-T mutated (ATM) and Aprataxin (APTX), respectively. Our mechanistic understanding and therapeutic repertoire for treating these disorders is severely lacking, in large part due to the failure of prior animal models with similar null mutations to recapitulate the characteristic loss of motor coordination (i.e., ataxia) and associated cerebellar defects. By increasing genotoxic stress through the insertion of null mutations in both the Atm (nonsense) and Aptx (knockout) genes in the same animal, we have generated a novel mouse model that for the first time develops a progressively severe ataxic phenotype associated with atrophy of the cerebellar molecular layer. We find biophysical properties of cerebellar Purkinje neurons are significantly perturbed (e.g., reduced membrane capacitance, lower action potential thresholds, etc.), while properties of synaptic inputs remain largely unchanged. These perturbations significantly alter Purkinje neuron neural activity, including a progressive reduction in spontaneous action potential firing frequency that correlates with both cerebellar atrophy and ataxia over the animals first year of life. Double mutant mice also exhibit a high predisposition to developing cancer (thymomas) and immune abnormalities (impaired early thymocyte development and T-cell maturation), symptoms characteristic of A-T. Lastly, by inserting a clinically relevant nonsense-type null mutation in Atm, we demonstrate that Small Molecule Read-Through (SMRT) compounds can restore ATM production, indicating their potential as a future A-T therapeutic.

neuroscience↗