Hepatic Transcriptome Responses of Domesticated and Wild Turkey Embryos to Aflatoxin B₁

Differential Hepatic Expression of miRNA in Response to Aflatoxin B1 Challenge in Domestic and Wild Turkeys

Aflatoxin B1 (AFB1) is a major foodborne mycotoxin that poses a significant economic risk to poultry due to a greater degree of susceptibility compared to other agricultural species. Domesticated turkeys (Meleagris gallopavo) are especially sensitive to AFB1; however, wild turkeys (M. g. silvestris) are more resistant. A lack of functional isoforms of hepatic glutathione S-transferases (GSTs), an enzyme that plays a role in the detoxification of aflatoxin, is suspected as the reason for the increased sensitivity. Previous studies comparing the gene expression of domesticated and wild turkeys exposed to AFB1 identified hepatic genes responding differentially to AFB1, but could not fully explain the difference in response. The current study examined differences in the expression of microRNAs (miRNAs) in the livers of wild and domesticated turkeys fed dietary AFB1 (320 μg/kg in feed). Short-read RNA sequencing and expression analysis examined both domesticated and wild turkeys exposed to AFB1 compared to controls. A total of 25 miRNAs was identified as being significantly differentially expressed (DEM) in pairwise comparisons. The majority of these have mammalian orthologs with known dysregulation in liver disease. The largest number of DEMs occurred between controls, suggesting an underlying difference in liver potential. Sequences of the DEMs were used to identify potential miRNA binding sites in target genes, resulting in an average of 4302 predicted target sites per DEM. These DEMs and gene targets provide hypotheses for future investigations into the role of miRNAs in AFB1 resistance.

Embryo injected with Ochratoxin A induced jejunum injury in ducklings by activating the TLR4 signaling pathway: Involvement of intestinal microbiota

Ochratoxin A (OTA) is a common mycotoxin that causes intestinal injury in humans and various animal species. OTA may lead to intestinal injury in offspring due to the maternal effect. The aim of this study was to investigate the mechanism of embryo injected with OTA induced jejunum injury in ducklings. The results showed that OTA disrupted the jejunum tight junctions in hatching ducklings, and promoted the secretion of inflammatory cytokines. And this inflammatory response was caused by the activation of the TLR4 signaling pathway. Moreover, embryo injected with OTA could cause damage to the intestinal barrier in 21-day-old ducks, characterized by shortened villi, crypt hyperplasia, disrupted intestinal tight junctions, increased level of LPS in the jejunum, activation of the TLR4 signaling pathway, and increased levels of pro-inflammatory cytokines. Meanwhile, OTA induced oxidative stress in the jejunum. And dysbiosis of gut microbiota was mainly characterized by an increased the relative abundance of Bacteroides, Megamonas, Fournierella, and decreased the relative abundance of Alistipes and Weissella. Interestingly, embryo injected with OTA did not induce these changes in the jejunum of antibiotics-treated 21-day-old ducks. In conclusion, embryo injected with OTA induced jejunum injury in ducklings by activating the TLR4 signaling pathway, which involvement of intestinal microbiota.

AFB1 and OTA Promote Immune Toxicity in Human LymphoBlastic T Cells at Transcriptomic Level

Aflatoxin B1 (AFB1) and ochratoxin A (OTA) are typical contaminants of food and feed, which have serious implications for human and animal health, even at low concentrations. Therefore, a transcriptomic study was carried out to analyze gene expression changes triggered by low doses of AFB1 and OTA (100 nM; 7 days), individually and combined, in human lymphoblastic T cells. RNA-sequencing analysis showed that AFB1-exposure resulted in 99 differential gene expressions (DEGs), while 77 DEGs were obtained in OTA-exposure and 3236 DEGs in the combined one. Overall, 16% of human genome expression was altered. Gene ontology analysis revealed, for all studied conditions, biological processes and molecular functions typically associated with the immune system. PathVisio analysis pointed to ataxia telangiectasia mutated signaling as the most significantly altered pathway in AFB1-exposure, glycolysis in OTA-exposure, and ferroptosis in the mixed condition (Z-score > 1.96; adjusted p-value ≤ 0.05). Thus, the results demonstrated the potential DNA damage caused by AFB1, the possible metabolic reprogramming promoted by OTA, and the plausible cell death with oxidative stress prompted by the mixed exposure. They may be considered viable mechanisms of action to promote immune toxicity in vitro.

New evidence for deleterious effects of environmental contaminants on the male gamete

The decreasing trend in human and domestic animal fertility in recent decades has resulted in the question of whether reduced sperm quality is associated with changes in global climate and the environment. Proposed causes for reduced sperm quality include environmental contaminants, which enter into the body of animals through the food chain and are transported to the reproductive tract, where contaminating agents can have effects on fertilization capacities of gametes. In this review, there is a focus on various environmental contaminants and potential effects on male fertility. Human-derived contaminants, particularly endocrine-disrupting phthalates and the pesticide atrazine, are discussed. Naturally occurring toxins are also addressed, in particular mycotoxins such as aflatoxin which can be components in food consumed by humans and animals. Mechanisms by which environmental contaminants reduce male fertility are not clearly defined; however, are apparently multifactorial (i.e., direct and indirect effects) with there being diverse modes of action. Results from studies with humans, rodents and domestic animals indicate there are deleterious effects of contaminants on male gametes at various stages of spermatogenesis (i.e., in the testis) during passage through the epididymis, and in mature spermatozoa, after ejaculation and during capacitation. Considering there is never detection of a single contaminant, this review addresses synergistic or additive effects of combinations of contaminants. There is new evidence highlighted for the long-lasting effects of environmental contaminants on spermatozoa and developing embryos. Understanding the risk associated with environmental contaminants for animal reproduction may lead to new management strategies, thereby improving reproductive processes.

Protective effect of glutathione S-transferase enzyme activity against aflatoxin B1 in poultry species: relationship between glutathione S-transferase enzyme kinetic parameters, and resistance to aflatoxin B1

Comparative studies designed to investigate the role of glutathione S-transferase (GST) activity on the enzyme catalyzed trapping of aflatoxin B1-8,9-epoxide (AFBO) with glutathione, and the relationship with aflatoxin B1 (AFB1) resistance have not been conducted in poultry. Hepatic cytosolic fractions of chickens, quail, turkeys and ducks were used to measure in vitro the enzymatic parameters maximal velocity (Vmax), Michaelis-Menten constant (Km) and intrinsic clearance (CLint) for GST activity. AFB1 used ranged from 2.0 to 157.5 µM and the AFB1-GSH produced was identified and quantitated by HPLC. Significant differences were found in GST Vmax values, being the highest in chickens, followed by quail, ducks and turkeys. The Km values were also significantly different, with chickens < ducks < turkeys < quail. Chickens had the higher CLint value in contrast to ducks. Differences by sex showed that duck females had a higher CLint value than the turkey and quail, whereas duck males had a CLint close to that of turkey. The ratio "AFBO production /AFB1-GSH production" follows the order duck>turkey>quail>chicken, in agreement with the known poultry sensitivity. The extremely high "AFB1 epoxidation activity/ GST activity" ratio observed in ducks might be the explanation for the development of hepatocellular carcinoma in this species.

Biocontrol of Aflatoxins Using Non-Aflatoxigenic Aspergillus flavus: A Literature Review

Aflatoxins (AFs) are mycotoxins, predominantly produced by Aspergillus flavus, A. parasiticus, A. nomius, and A. pseudotamarii. AFs are carcinogenic compounds causing liver cancer in humans and animals. Physical and biological factors significantly affect AF production during the pre-and post-harvest time. Several methodologies have been developed to control AF contamination, yet; they are usually expensive and unfriendly to the environment. Consequently, interest in using biocontrol agents has increased, as they are convenient, advanced, and friendly to the environment. Using non-aflatoxigenic strains of A. flavus (AF⁻) as biocontrol agents is the most promising method to control AFs’ contamination in cereal crops. AF⁻ strains cannot produce AFs due to the absence of polyketide synthase genes or genetic mutation. AF⁻ strains competitively exclude the AF⁺ strains in the field, giving an extra advantage to the stored grains. Several microbiological, molecular, and field-based approaches have been used to select a suitable biocontrol agent. The effectiveness of biocontrol agents in controlling AF contamination could reach up to 99.3%. Optimal inoculum rate and a perfect time of application are critical factors influencing the efficacy of biocontrol agents.

Transcriptome Analyses Throughout Chili Pepper Fruit Development Reveal Novel Insights into the Domestication Process

Chili pepper (Capsicum spp.) is an important crop, as well as a model for fruit development studies and domestication. Here, we performed a time-course experiment to estimate standardized gene expression profiles with respect to fruit development for six domesticated and four wild chili pepper ancestors. We sampled the transcriptomes every 10 days from flowering to fruit maturity, and found that the mean standardized expression profiles for domesticated and wild accessions significantly differed. The mean standardized expression was higher and peaked earlier for domesticated vs. wild genotypes, particularly for genes involved in the cell cycle that ultimately control fruit size. We postulate that these gene expression changes are driven by selection pressures during domestication and show a robust network of cell cycle genes with a time shift in expression, which explains some of the differences between domesticated and wild phenotypes.

Effect of environmental contamination on female and male gametes - A lesson from bovines

Endocrine-disrupting compounds (EDCs) and foodborne contaminants are environmental pollutants that are considered reproductive toxicants due to their deleterious effects on female and male gametes. Among the EDCs, the phthalate plasticizers are of growing concern. In-vivo and in-vitro models indicate that the oocyte is highly sensitive to phthalates. This review summarizes the effects of di(2-ethylhexyl) phthalate and its major metabolite mono(2-ethyhexyl) phthalate (MEHP) on the oocyte. MEHP reduces the proportion of oocytes that fertilize, cleave and develop to the blastocyst stage. This is associated with negative effects on meiotic progression, and disruption of cortical granules, endoplasmic reticulum and mitochondrial reorganization. MEHP alters mitochondrial membrane polarity, increases reactive oxygen species levels and induces alterations in genes associated with oxidative phosphorylation. A carryover effect from the oocyte to the blastocyst is manifested by alterations in the transcriptomic profile of blastocysts developed from MEHP-treated oocytes. Among foodborne contaminants, the pesticide atrazine (ATZ) and the mycotoxin aflatoxin B1 (AFB1) are of high concern. The potential hazards associated with exposure of spermatozoa to these contaminants and their carryover effect to the blastocyst are described. AFB1 and ATZ reduce spermatozoa's viability, as reflected by a high proportion of cells with damaged plasma membrane; induce acrosome reaction, expressed as damage to the acrosomal membrane; and interfere with mitochondrial function, characterized by hyperpolarization of the membrane. ATZ and AFB1-treated spermatozoa show a high proportion of cells with fragmented DNA. Exposure of spermatozoa to AFB1 and ATZ reduces fertilization and cleavage rates, but not that of blastocyst formation. However, fertilization with AFB1- or ATZ-treated spermatozoa impairs transcript expression in the formed blastocysts, implying a carryover effect. Taken together, the review indicates the risk of exposing farm animals to environmental contaminants, and their deleterious effects on female and male gametes and the developing embryo.

Transcriptome profiling of the liver among the prenatal and postnatal stages in chickens

The liver is an important organ that has pivotal functions in the synthesis of several vital proteins, the metabolism of various biologically useful materials, the detoxification of toxic substances, and immune defense. Most liver functions are not mature at a young age and many changes happen during postnatal liver development, which lead to differential functions of the liver at different developmental stages. However, the transcriptome details of what changes occur in the liver after birth and the molecular mechanisms for the regulation of the developmental process are not clearly known in chickens. Here, we used RNA-sequencing to analyze the transcriptome of chicken liver from the prenatal (at an embryonic day of 13) to the postnatal stages (at 5 wk and 42 wk of age). A total of approximately 161.17 Gb of raw data were obtained, with 4,127 putative and 539 differentially expressed lncRNAs, and with 13,949 putative and 6,370 differentially expressed mRNAs. Coexpression of lncRNAs-mRNAs in hepatic transcriptome analysis showed that the liver plays important roles in providing energy for organisms through the mitochondrial respiratory chain in chickens, meanwhile, acting as a crucial part of antioxidant stress. The developmental transcriptome date revealed that antioxidant defenses are likely to act on chicken embryo development and that significant functional changes during postnatal liver development are associated with the liver maturation of chickens. These results provide a timeline for the functional transcriptome transition from the prenatal to adult stages in chickens and will be helpful to reveal the underlying molecular mechanisms of liver development.

Antioxidant Defence Systems and Oxidative Stress in Poultry Biology: An Update

Poultry in commercial settings are exposed to a range of stressors. A growing body of information clearly indicates that excess ROS/RNS production and oxidative stress are major detrimental consequences of the most common commercial stressors in poultry production. During evolution, antioxidant defence systems were developed in poultry to survive in an oxygenated atmosphere. They include a complex network of internally synthesised (e.g., antioxidant enzymes, (glutathione) GSH, (coenzyme Q) CoQ) and externally supplied (vitamin E, carotenoids, etc.) antioxidants. In fact, all antioxidants in the body work cooperatively as a team to maintain optimal redox balance in the cell/body. This balance is a key element in providing the necessary conditions for cell signalling, a vital process for regulation of the expression of various genes, stress adaptation and homeostasis maintenance in the body. Since ROS/RNS are considered to be important signalling molecules, their concentration is strictly regulated by the antioxidant defence network in conjunction with various transcription factors and vitagenes. In fact, activation of vitagenes via such transcription factors as Nrf2 leads to an additional synthesis of an array of protective molecules which can deal with increased ROS/RNS production. Therefore, it is a challenging task to develop a system of optimal antioxidant supplementation to help growing/productive birds maintain effective antioxidant defences and redox balance in the body. On the one hand, antioxidants, such as vitamin E, or minerals (e.g., Se, Mn, Cu and Zn) are a compulsory part of the commercial pre-mixes for poultry, and, in most cases, are adequate to meet the physiological requirements in these elements. On the other hand, due to the aforementioned commercially relevant stressors, there is a need for additional support for the antioxidant system in poultry. This new direction in improving antioxidant defences for poultry in stress conditions is related to an opportunity to activate a range of vitagenes (via Nrf2-related mechanisms: superoxide dismutase, SOD; heme oxygenase-1, HO-1; GSH and thioredoxin, or other mechanisms: Heat shock protein (HSP)/heat shock factor (HSP), sirtuins, etc.) to maximise internal AO protection and redox balance maintenance. Therefore, the development of vitagene-regulating nutritional supplements is on the agenda of many commercial companies worldwide.

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

Susceptibility and/or resistance to aflatoxin B₁ (AFB₁) is a threshold trait governed principally by glutathione S transferase (GST)-mediated detoxification. In poultry, domesticated turkeys are highly sensitive to AFB₁, most likely due to dysfunction in hepatic GSTs. In contrast, wild turkeys are comparatively resistant to aflatoxicosis due to the presence of functional hepatic GSTAs and other possible physiological and immunological interactions. The underlying genetic basis for the disparate GST function in turkeys is unknown as are the broader molecular interactions that control the systemic response. This study quantifies the effects of dietary AFB₁ on gene expression in the turkey spleen, specifically contrasting genetically distinct domesticated (DT, susceptible) and Eastern wild (EW, resistant) birds. Male turkey poults were subjected to a short-term AFB₁ treatment protocol with feed supplemented with 320 ppb AFB₁ beginning on day 15 of age and continuing for 14 days. Spleen tissues were harvested and subjected to deep RNA sequencing and transcriptome analysis. Analysis of differential gene expression found the effects of AFB₁ treatment on the spleen transcriptomes considerably more prominent in the DT birds compared to EW. However, expression of the differentially expressed genes (DEGs) was directionally biased, with the majority showing higher expression in EW (i.e., down-regulation in DT). Significantly altered pathways included FXR/RXR and LXR/RXR activation, coagulation system, prothrombin activation, acute phase response, and atherosclerosis signaling. Differential extra-hepatic expression of acute phase protein genes was confirmed by quantitative real time PCR (qRT-PCR) in the original experiment and additional turkey lines. Results demonstrate that wild turkeys possess a capacity to more effectively respond to AFB₁ exposure.

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

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.

Transcriptional profiling of liver tissues in chicken embryo at day 16 and 20 using RNA sequencing reveals differential antioxidant enzyme activity

Considering the high proportion of polyunsaturated fatty acids, the antioxidant defense of chick embryo tissues is vital during the oxidative stress experienced at hatching. In order to better understand the mechanisms of the defense system during chicken embryo development, we detected the activity of antioxidant enzymes during the incubation of chicken embryo. Results showed that the activity of superoxide dismutase (SOD) and (GSH-PX) in livers were higher than those in hearts. Based on these results, liver tissues were used as the follow-up study materials, which were obtained from chicken embryo at day 16 and day 20. Thus, we used RNA sequencing (RNA-Seq) analysis to identify the transcriptome from 6 liver tissues. In total, we obtained 45,552,777-45,462,856 uniquely mapped reads and 18,837 mRNA transcripts, across the 6 liver samples. Among these, 1,154 differentially expressed genes (p<0.05, foldchange≥1) were identified between the high and low groups, and 1,069 GO terms were significantly enriched (p<0.05). Of these, 10 GO terms were related to active oxygen defense and antioxidant enzyme activity. GO enrichment and KEGG pathway analysis indicated that GSTA2, GSTA4, MGST1, GPX3, and HAO2 participated in glutathione metabolism, and were considered as the most promising candidate genes affecting the antioxidant enzyme activity of chicken embryo at day 16 and day 20. Using RNA-Seq and differential gene expression, our study here investigated the complexity of the liver transcriptome in chick embryos and analyzed the key genes associated with the antioxidant enzyme.

HAfTs are novel lncRNA transcripts from aflatoxin exposure

The transcriptome can reveal insights into precancer biology. We recently conducted RNA-Seq analysis on liver RNA from male rats exposed to the carcinogen, aflatoxin B1 (AFB1), for 90 days prior to liver tumor onset. Among >1,000 differentially expressed transcripts, several novel, unannotated Cufflinks-assembled transcripts, or HAfTs (Hepatic Aflatoxin Transcripts) were found. We hypothesized PCR-cloning and RACE (rapid amplification of cDNA ends) could further HAfT identification. Sanger data was obtained for 6 transcripts by PCR and 16 transcripts by 5’- and 3’-RACE. BLAST alignments showed, with two exceptions, HAfT transcripts were lncRNAs, >200nt without apparent long open reading frames. Six rat HAfT transcripts were classified as ‘novel’ without RefSeq annotation. Sequence alignment and genomic synteny showed each rat lncRNA had a homologous locus in the mouse genome and over half had homologous loci in the human genome, including at least two loci (and possibly three others) that were previously unannotated. While HAfT functions are not yet clear, coregulatory roles may be possible from their adjacent orientation to known coding genes with altered expression that include 8 HAfT-gene pairs. For example, a unique rat HAfT, homologous to Pvt1, was adjacent to known genes controlling cell proliferation. Additionally, PCR and RACE Sanger sequencing showed many alternative splice variants and refinements of exon sequences compared to Cufflinks assembled transcripts and gene prediction algorithms. Presence of multiple splice variants and short tandem repeats found in some HAfTs may be consequential for secondary structure, transcriptional regulation, and function. In summary, we report novel, differentially expressed lncRNAs after exposure to the genotoxicant, AFB1, prior to neoplastic lesions. Complete cloning and sequencing of such transcripts could pave the way for a new set of sensitive and early prediction markers for chemical hepatocarcinogens.

Comparative Response of the Hepatic Transcriptomes of Domesticated and Wild Turkey to Aflatoxin B₁

The food-borne mycotoxin aflatoxin B₁ (AFB₁) poses a significant risk to poultry, which are highly susceptible to its hepatotoxic effects. Domesticated turkeys (Meleagris gallopavo) are especially sensitive, whereas wild turkeys (M. g. silvestris) are more resistant. AFB₁ toxicity entails bioactivation by hepatic cytochrome P450s to the electrophilic exo-AFB₁-8,9-epoxide (AFBO). Domesticated turkeys lack functional hepatic GST-mediated detoxification of AFBO, and this is largely responsible for the differences in resistance between turkey types. This study was designed to characterize transcriptional changes induced in turkey livers by AFB₁, and to contrast the response of domesticated (susceptible) and wild (more resistant) birds. Gene expression responses to AFB₁ were examined using RNA-sequencing. Statistically significant differences in gene expression were observed among treatment groups and between turkey types. Expression analysis identified 4621 genes with significant differential expression (DE) in AFB₁-treated birds compared to controls. Characterization of DE transcripts revealed genes dis-regulated in response to toxic insult with significant association of Phase I and Phase II genes and others important in cellular regulation, modulation of apoptosis, and inflammatory responses. Constitutive expression of GSTA3 was significantly higher in wild birds and was significantly higher in AFB₁-treated birds when compared to controls for both genetic groups. This pattern was also observed by qRT-PCR in other wild and domesticated turkey strains. Results of this study emphasize the differential response of these genetically distinct birds, and identify genes and pathways that are differentially altered in aflatoxicosis.

Aflatoxin B1 impairs sperm quality and fertilization competence

Aflatoxins are poisonous byproducts of the soilborne fungus Aspergillus, involved in the decomposition of plant materials. Aflatoxins can be found in various food products, such as maize, sorghum, millet, rice and wheat. AFB1 is the most toxic of these, classified as a carcinogen and mutagen for both humans and animals. AFB1 has been detected in human cord blood and placenta; however, its toxic effect on sperm is less known. The current study examines sperm responses associated with AFB1 exposure. These included acrosome integrity and function, mitochondrial polarity, DNA fragmentation, fertilization competence and early embryonic development. Spermatozoa were obtained from bull ejaculate and epididymis and capacitated in vitro for 4h with 0, 0.1, 1, 10 and 100μM AFB1. Following capacitation, acrosome reaction (AR) was induced by Ca²⁺ ionophore. The integrity and functionality of sperm were examined simultaneously by florescent staining. A Halosperm DNA fragmentation kit was used to evaluate DNA integrity. An in-vitro culture system was used to evaluate fertilization competence and blastocyst formation rate, using bovine oocytes. Findings indicate dose-responsive variation among compartments to AFB1 exposure. Sperm viability, expressed by integrity of the plasma membrane, was lower in sperm isolated from ejaculate or epididymis after culturing with AFB1. Exposure to AFB1 reduced the proportion of sperm from the epididymis tail undergoing acrosome reaction induced by Ca²⁺ ionophore. AFB1 impaired mitochondrial membrane potential (ΔYm) in sperm isolated from ejaculate and the epididymis tail. Exposing ejaculated sperm to AFB1 increased the proportion of sperm with fragmented DNA and reduced the proportion of embryos that cleaved to the 2- to 4-cell stage, 42h postfertilization, however, the proportion of embryos that developed to blastocysts, 7days postfertilization, did not differ among groups. The findings explore the harmful effects of AFB1 on sperm viability, ΔΨm and DNA integrity associated with fertility competence. We postulate that AFB1-induced fragmentation in paternal DNA might have a carryover effect on the quality of developing embryos. Further evaluation for the quality of blastocysts derived from sperm exposed to AFB1 is warranted.

Curcumin Successfully Inhibited the Computationally Identified CYP2A6 Enzyme-Mediated Bioactivation of Aflatoxin B1 in Arbor Acres broiler

Cytochrome P450 enzymes are often responsible for the toxic and carcinogenic effects of toxicants, such as aflatoxin B1 (AFB1). The human hepatic CYP2A6 enzyme mediates the oxidative metabolism of several procarcinogens. In this study, we characterized a partial sequence of CYP2A6 gene from Arbor Acres (AA) broiler and studied its role in AFB1 bioactivation. Moreover, the effect of curcumin on CYP2A6 is illustrated. Six groups of AA broiler were treated for 28 days including the control group (fed only basal diet), curcumin alone-treated group (450 mg/kg feed), the group fed AFB1-contaminated feed (5 mg/kg feed) plus the low (150 mg), medium (300 mg) or high (450 mg) of curcumin, and the group fed AFB1-contaminated diet alone (5 mg/kg feed). After the end of treatment period, liver samples were collected for different analyses. The results revealed that the histopathological examination showed clear signs of liver toxicity in AA broliers in AFB1-fed group, but curcumin-supplementation in feed prevented partially AFB1-induced liver toxicity. Liver and body weights were recorded to study the AFB1 harmful effects. We noted an obvious increase in liver weight and decrease in body weight in AFB1-fed group. But, the administration of curcumin partially ameliorated the increase in liver weight and decrease in body weight in a dose-dependent manner. The results (RT-PCR and Elisa) revealed that mRNA and protein expression level enhanced in AFB1-fed group. Consistently, CYP2A6 enzyme activity also increased in AFB1-fed group, suggesting that AA broiler CYP2A6 actively involved in bioactivation of AFB1. However, curcumin treatment inhibited CYP2A6 at mRNA and protein levels in AFB1 treated AA broiler in a dose-dependent manner. Maximum inhibition of liver CYP2A6 enzyme activity in AA broiler has been achieved at a dose of 450 mg/kg curcumin. This is the first study identifying and confirming the role of CYP2A6 enzyme in AFB1 bioactivation in AA broiler liver (in vivo), and the hepatoprotective role of curcumin via inhibiting CYP2A6 expression and enzyme activity. The study contributed to identify an important CYP enzyme involved in AFB1 bioactivation in broilers and thus could pave the way for the prevention of the harmful effects of AFB1 in broilers.