Arf1 promotes porcine intestinal epithelial cell proliferation via the mTORC1 signaling pathway.

The promotion of gut health, a pervasive problem in modern animal husbandry, positively affects organismal health, productivity, and economics. Porcine intestinal epithelial cells (IPEC-J2) continuously proliferate to maintain intestinal homeostasis, including barrier, immune, and absorptive functions. Gut homeostasis is fundamental to organismal health. ADP-ribosylation factor 1 (Arf1), a small GTPase, plays a crucial role in coordinating mTORC1 in response to nutrients, especially amino acid availability in the gut. mTORC1 is the central hub of proliferation. Thus, it seems likely that Arf1 promotes IPEC-J2 cell proliferation. However, the exact role of Arf1 in the porcine gut remains unclear. Therefore, we evaluated the functional role and possible mechanisms of Arf1 in the porcine intestine through Arf1 overexpression and knockdown in IPEC-J2 cells. Arf1 overexpression and knockdown significantly enhanced and inhibited, respectively, IPEC-J2 cell viability, and PCNA expression varied with Arf1 expression. Moreover, the proportion of Ki67-positive cells was significantly greater in the Arf1-overexpressing group than in the control group. These results suggest that Arf1 improves IPEC-J2 cell proliferation. The underlying mechanism was explored by Western blotting. Arf1 overexpression and knockdown significantly enhanced and suppressed, respectively, the levels of p-S6K1 and p-RPS6, which are key downstream targets of the mTORC1 signaling pathway. Collectively, our findings reveal the role of the Arf1-mTORC1 axis in IPEC-J2 cell proliferation and its potential function in regulating intestinal homeostasis and health.

Dihydroquercetin improves the proliferation of porcine intestinal epithelial cells via the Wnt/ß-catenin pathway.

Dihydroquercetin (DHQ), also known as Taxifolin (TA), is a flavanonol with various biological activities, such as anticancer, anti-inflammatory, and antioxidative properties. It has been found to effectively increase the viability of porcine intestinal epithelial cells (IPEC-J2). However, the precise mechanism by which DHQ increases the proliferation of IPEC-J2 cells is not entirely understood. This study aimed to explore the potential pathways through which DHQ encourages the proliferation of IPEC-J2 cells. The findings indicated that DHQ significantly improved the protein expression of tight junction proteins (ZO-1, Occludin, and Claudin1) and a molecular biomarker of proliferation (PCNA) in IPEC-J2 cells. Furthermore, DHQ was found to increase the Wnt/ß-catenin pathway-associated ß-catenin, c-Myc, and cyclin D1 mRNA expression, and promote the protein expression of ß-catenin and TCF4. To confirm the involvement of the Wnt/ß-catenin signaling pathway in the DHQ-promoted proliferation of IPEC-J2 cells, the inhibitor LF3, which targets ß-catenin/TCF4 interaction, was used. It was found that LF3 inhibited the protein expressions upregulated by DHQ and blocked the promotion of cell proliferation. These results indicate that DHQ positively regulates IPEC-J2 cell proliferation through the Wnt/ß-catenin pathway, providing constructive insights into the role of DHQ in regulating intestine development.

The Alleviating Effect of Taxifolin on Deoxynivalenol-Induced Damage in Porcine Intestinal Epithelial Cells.

Deoxynivalenol (DON) contamination in feed is a global concern that severely threatens the health of animals and humans. Taxifolin (TA) is a natural flavonoid, a member of the polyphenols, that possesses robust antioxidant properties. This study aimed to investigate the effect of TA on DON-induced damage in porcine intestinal epithelial cells (IPEC-J2). The cells were pre-incubated with a series of concentrations of TA for 24 h and exposed to DON (0.5 µg/mL) for another 24 h. The results showed that pretreatment with TA (150 µM) significantly inhibited the DON-induced decline in cell viability (p < 0.05) and cell proliferation (p < 0.01). Additionally, 150 µM TA also alleviated DON-induced apoptosis (p < 0.01). Moreover, TA decreased the production of reactive oxygen species (ROS) induced by DON (p < 0.01). In addition, TA attenuated DON-induced cell junction damage (p < 0.05). Further experiments showed that TA reversed the DON-induced reduction in antioxidant capacity in the IPEC-J2 cells, probably via activating the Nrf2 signaling pathway (p < 0.05). Collectively, these findings suggest that 150 µM TA can protect against 0.5 µg/mL DON-induced damage to IPEC-J2 cells, potentially via the activation of the Nrf2 signaling pathway. This study provides insight into TA's potential to act as a green feed additive in the pig farming industry and its efficacy in counteracting DON-induced intestinal damage.

Glutamine Promotes Porcine Intestinal Epithelial Cell Proliferation through the Wnt/ß-Catenin Pathway.

Glutamine (Gln) is a critical nutrient required by neonatal mammals for intestinal growth, especially for newborn piglets. However, the mechanisms underlying the role of Gln in porcine intestinal epithelium development are not fully understood. The objective of the current study was to explore the possible signaling pathway involved in the promotion of porcine intestinal epithelial cell (IPEC-J2) proliferation by Gln. The results showed that 1 mM Gln promoted IPEC-J2 cell proliferation, and tandem mass tag proteomics revealed 973 differentially expressed proteins in Gln-treated IPEC-J2 cells, 824 of which were upregulated and 149 of which were downregulated. Moreover, gene set enrichment analysis indicated that the Wnt signaling pathway is activated by Gln treatment. Western blotting analysis further confirmed that Gln activated the Wnt/ß-catenin signaling pathway. In addition, Gln increased not only cytosolic ß-catenin but also nuclear ß-catenin protein expression. LF3 (a ß-catenin/TCF4 interaction inhibitor) assay and ß-catenin knockdown demonstrated that Gln-mediated promotion of Wnt/ß-catenin signaling and cell proliferation were blocked. Furthermore, the inhibition of TCF4 expression suppressed Gln-induced cell proliferation. These findings further confirmed that Wnt/ß-catenin signaling is involved in the promotion of IPEC-J2 cell proliferation by Gln. Collectively, these findings demonstrated that Gln positively regulated IPEC-J2 cell proliferation through the Wnt/ß-catenin pathway. These data greatly enhance the current understanding of the mechanism by which Gln regulates intestinal development.

Piceatannol Alleviates Deoxynivalenol-Induced Damage in Intestinal Epithelial Cells via Inhibition of the NF-κB Pathway.

Deoxynivalenol (DON) is a common mycotoxin that is widely found in various foods and feeds, posing a potential threat to human and animal health. This study aimed to investigate the protective effect of the natural polyphenol piceatannol (PIC) against DON-induced damage in porcine intestinal epithelial cells (IPEC-J2 cells) and the underlying mechanism. The results showed that PIC promotes IPEC-J2 cell proliferation in a dose-dependent manner. Moreover, it not only significantly relieved DON-induced decreases in cell viability and proliferation but also reduced intracellular reactive oxygen species (ROS) production. Further studies demonstrated that PIC alleviated DON-induced oxidative stress damage by increasing the protein expression levels of the antioxidant factors NAD(P)H quinone oxidoreductase-1 (NQO1) and glutamate-cysteine ligase modifier subunit (GCLM), and the mRNA expression of catalase (CAT), Superoxide Dismutase 1 (SOD1), peroxiredoxin 3 (PRX3), and glutathione S-transferase alpha 4 (GSTα4). In addition, PIC inhibited the activation of the nuclear factor-B (NF-κB) pathway, downregulated the mRNA expression of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) to attenuate DON-induced inflammatory responses, and further mitigated DON-induced cellular intestinal barrier injury by regulating the protein expression of Occludin. These findings indicated that PIC had a significant protective effect against DON-induced damage. This study provides more understanding to support PIC as a feed additive for pig production.

Extracellular Glutamine Promotes Intestinal Porcine Epithelial Cell Proliferation via Arf1-mTORC1 Pathway Independently of Rag GTPases.

Glutamine (Gln) is the major energy source of intestinal porcine epithelial cells (IPEC-J2 cells) and plays a critical role in the nutritional physiological function of the intestine. However, the underlying mechanism requires further investigation. Here, the Gln-sensing pathway in IPEC-J2 cells was investigated. The results showed that Gln increased the cell proliferation. Subsequently, an analysis of the phosphorylated proteome revealed that Gln markedly upregulated ribosomal protein S6 (RPS6) phosphorylation at serine 235/236, suggesting that Gln activated the mTORC1 pathway. mTOR inhibition revealed that Gln promotes cell proliferation through the mTORC1 pathway. Similarly, blocking ADP-ribosylation factor 1 (Arf1) activity indicated that Gln-induced mTORC1 activation promoted cell proliferation in an Arf1-dependent manner. Additionally, the RagA/B pathway did not participate in Gln-induced mTORC1 activation. Collectively, these findings suggest that Gln-induced mTORC1 activation promotes IPEC-J2 cell proliferation via Arf1, not Rag GTPases. These results broaden our understanding of functional-cell-sensing amino acids, particularly Gln, that are regulated by mTORC1.