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.

Diphlorethohydroxycarmalol (DPHC) is a known to modulate the expression of extracellular matrix (ECM) components in 3T3-L1. However, the possible role of DPHC in integument stability during obesity induction is not clear yet. We evaluated the effects of DPHC on collagen or elastic fiber quantity in integument during obesity induction with high-fat diet. The dorsal back integument sections were stained with hematoxylin–eosin, Masson trichrome, and Verhoff-Van Gieson. The intensities of collagen fibers and elastin fibers were analyzed with ImageJ. The number of fibroblasts was counted at ×1,000 fields. The number of fibroblast was increased by obesity induction, but DPHC suppressed it in a concentrationdependent manner both in lean and obese mice. On the other hand, the intensities of collagen fibers were increased by DPHC treatment in obese mice groups but not in lean mice groups. The intensities of collagen fibers of obese mice were lower than that of the lean mice in 0% group. However, the number became similar between lean and obese mice by the treatment of DPHC. The intensity of elastic fibers was increased in the lean mice with the concentration of DPHC. In the obese mice group, there were increasing patterns but only significant at 10% DPHC group. The intensity of elastic fibers of obese mice was higher than lean mice in 0%, 1%, and 10% groups. Histologically epithelial cells and follicle cells which were diffused nuclear staining forms were increased by DPHC treatment. The results suggest that the activity of integument cells during obesity induction can be modulated by DPHC.