Differential Transcriptome Responses to Aflatoxin B1 in the Cecal Tonsil of Susceptible and Resistant Turkeys

Abstract

The nearly-ubiquitous food and feed-borne mycotoxin aflatoxin B1 (AFB1) is carcinogenic and mutagenic, posing a food safety threat to humans and animals. One of the most susceptible animal species known and thus a good model for characterizing toxicological pathways, is the domesticated turkey (DT), a condition likely due, at least in part, to deficient hepatic AFB1-detoxifying alpha-class glutathione S-transferases (GSTAs). Conversely, wild turkeys (Eastern wild, EW) are relatively resistant to the hepatotoxic, hepatocarcinogenic and immunosuppressive effects of AFB1 owing to functional gene expression and presence of functional hepatic GSTAs. This study was designed to compare the responses in gene expression in the gastrointestinal tract between DT (susceptible phenotype) and EW (resistant phenotype) following dietary AFB1 challenge (320 ppb for 14 days); specifically in cecal tonsil which functions in both nutrient absorption and gut immunity. RNAseq and gene expression analysis revealed significant differential gene expression in AFB1-treated animals compared to control-fed domestic and wild birds and in within-treatment comparisons between bird types. Significantly upregulated expression of the primary hepatic AFB1-activating P450 (CYP1A5) as well as transcriptional changes in tight junction proteins were observed in AFB1-treated birds. Numerous pro-inflammatory cytokines, TGF-β and EGF were significantly down regulated by AFB1 treatment in DT birds and pathway analysis suggested suppression of enteroendocrine cells. Conversely, AFB1 treatment modified significantly fewer unique genes in EW birds; among these were genes involved in lipid synthesis and metabolism and immune response. This is the first investigation of the effects of AFB1 on the turkey gastro-intestinal tract. Results suggest that in addition to the hepatic transcriptome, animal resistance to this mycotoxin occurs in organ systems outside the liver, specifically as a refractory gastrointestinal tract.

Insights into Aflatoxin B1 Toxicity in Cattle: An In Vitro Whole-Transcriptomic Approach

“…For instance, the extreme sensitiveness of poultry species to AFB1 appears to be a consequence of the high activity of phase I drug metabolizing enzymes (involved in AFB1 bioactivation) and a deficiency of key conjugative enzymes [17]. Interestingly, whole-transcriptome studies in turkeys proved these mechanisms are also responsible for the different susceptibility to AFB1 between wild and domesticated animals (e.g., [18,19]).…”

AFB1 Induced Transcriptional Regulation Related to Apoptosis and Lipid Metabolism in Liver of Chicken

“…The liver also has well-defined roles in the maintenance of nutrient homeostasis, the metabolism of xenobiotics and endogenous hormones, and the detoxification of exogenous compounds [34]. Although some of the effects of AFB1 on poultry have been reported by transcription data [11,35] which were mainly focused on mRNA, the regulatory mechanism of lncRNAs, miRNAs and their co-expression with mRNA in response to AFB1 in chicken liver remains unexplored.…”

Altered Gene Response to Aflatoxin B1 in the Spleens of Susceptible and Resistant Turkeys

“…Expression was also significantly higher in AFB 1 -treated birds compared to controls. In the intestine, AFB 1 significantly up-regulated expression of the primary AFB 1 -activating P450 ( CYP1A5 ) and produced transcriptional changes in several tight junction proteins [26]. Significant down-regulation was seen in domesticated birds for numerous pro-inflammatory cytokines, TGF-β and EGF and gene pathway analysis suggested AFB 1 suppression of enteroendocrine cells.…”