Background: Aflatoxin B1 (AFB1) is a toxic metabolite generated by Aspergillus species and is commonly detected during the processing and storage of food; it is considered a group I carcinogen. The hepatotoxic effects, diseases, and mechanisms induced by AFB1 owing to chronic or acute exposure are well documented; however, there is a lack of research on its effects on the intestine, which is a crucial organ in the digestive process. Dogs are often susceptible to chronic AFB1 exposure owing to lack of variation in their diet, unlike humans, thereby rendering them prone to its effects. Therefore, we investigated the effects of AFB1 on canine small intestinal epithelial primary cells (CSIc). Methods: We treated CSIc with various concentrations of AFB1 (0, 1.25, 2.5, 5, 10, 20, 40, and 80 μM) for 24 h and analyzed cell viability and transepithelial-transendothelial electrical resistance (TEER) value. Additionally, we analyzed the mRNA expression of tight junction-related genes (OCLN, CLDN3, TJP1, and MUC2), antioxidant-related genes (CAT and GPX1), and apoptosis-related genes (BCL2, Bax, and TP53). Results: We found a significant decrease in CSIc viability and TEER values after treatment with AFB1 at concentrations of 20 μM or higher. Quantitative polymerase chain reaction analysis indicated a downregulation of OCLN, CLDN3, and TJP1 in CSIc treated with 20 μM or higher concentrations of AFB1. Additionally, AFB1 treatment downregulated CAT , GPX1, and BCL2. Conclusions: Acute exposure of CSIc to AFB1 induces toxicity, and exposure to AFB1 above a certain threshold compromises the barrier integrity of CSIc.

ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
    Cell culture
    Cell viability assay
    Transepithelial-transendothelial electrical resistanceassay
    RNA extraction and quantitative reverse transcriptionpolymerasechain reaction (qPCR)
    Statistical analysis
RESULTS
    Aflatoxin B1 decreased the viability of CSIc andimpaired barrier integrity
    AFB1 downregulated antioxidant and apoptosisrelatedgenes
DISCUSSION
CONCLUSION
REFERENCES

• Hyun-Woo Cho(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Kangmin Seo(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Min Young Lee(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Sang-Yeob Lee(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Kyoung Min So(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Ki Hyun Kim(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea)
• Ju Lan Chun(National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea) Corresponding author