Chenodeoxycholic acid (CDCA), a primary bile acid, has been demonstrated to play important roles as a signaling molecule in various physiology functions. However, the role of CDCA in regulating intestinal barrier function remains largely unknown. This study aimed to investigate the effects of CDCA on the lipopolysaccharide (LPS)-impaired intestinal epithelial barrier function and explore the underlying mechanisms. In IPEC-J2 cells, CDCA reversed the LPS-induced increase in transepithelial electrical resistance and decrease in tight junction protein expression. In addition, we found that farnesoid X receptor (FXR) but not Takeda G-protein receptor 5 was responsible for the CDCA-improved epithelial barrier function impaired by LPS. Furthermore, CDCA blocked LPS-induced activation of the myosin light chain kinase (MLCK) pathway in a FXR-dependent manner and elicited similar effects to MLCK inhibition. In mice, CDCA supplementation restored LPS-induced elevation of intestinal permeability and MLCK expression and reduction of tight junction protein expression, thus alleviating LPS-induced intestinal barrier impairment. In conclusion, CDCA protected against the LPS-induced impairment of the intestinal epithelial barrier function via the FXR–MLCK pathway.

This study aimed to investigate the effects of exogenous H S on the proliferation of porcine mammary gland epithelial cells (PMECs) and explore the underlying mechanisms. We found that exposure of PMECs to NaHS, at concentrations ranging from 10 to 200 µM, stimulated cell proliferation. However, high concentration of NaHS (600 µM) inhibited PMECs proliferation. Accordingly, 10 µM NaHS significantly increased the percentage of cells undergoing DNA replication, elevated the mRNA and/or protein expression of Cyclin A2, Cyclin D1/3, Cyclin E2 and PCNA, and decreased p21 mRNA expression. In contrast, 600 µM NaHS elicited the opposite effects to that of 10 µM NaHS. In addition, PI3 K/Akt and mTOR signaling pathways were activated or inhibited in response to 10 or 600 µM NaHS, respectively. Furthermore, the promotion of PMECs proliferation, the change of proliferative genes expression, and the activation of mTOR signaling pathway induced by 10 µM NaHS were effectively blocked by PI3 K inhibitor Wortmannin. Similarly, inhibition of mTOR with Rapamycin totally abolished the 10 µM NaHS-induced stimulation of PMECs proliferation and alteration of proliferative genes expression, with no influence on PI3 K/Akt signaling pathway. Moreover, constitutive activation of Akt pathway via transfection of Akt-CA completely eliminated the inhibition of PMECs proliferation and mTOR signaling pathway, and the change of proliferative genes expression induced by 600 µM NaHS. In conclusion, our findings provided evidence that exogenous H S supplied by NaHS exerted biphasic effects on PMECs proliferation, with stimulation at lower doses and suppression at high dose, through the intracellular PI3 K/Akt-mTOR signaling pathway.

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The present study aimed to investigate the effects of exogenous H 2 S on mammary gland development in pubescent mice and to explore the underlying mechanism. The mouse mammary epithelial cell line Hc11, along with c57Bl/6J mice, were treated with different concentrations of sodium hydrosulfide (NaHS), which is a donor of H 2 S. The Hc11 cell viability, pubescent mammary gland development, and the involvement of proliferative proteins and pathways were assessed by ccK-8 assay, edu assay, whole mount staining, H&e staining, western blotting and reverse transcription-quantitative Pcr. Both in vitro and in vivo, a low concentration of NaHS (100 µM in vitro; 9 mg/kg in vivo) significantly promoted the viability of Hc11 cells and the development of mammary glands by increasing the expression of the proliferative markers cyclin d1/3 and proliferating cell nuclear antigen. However, a high concentration of NaHS (1,000 µM in vitro; 18 mg/kg in vivo) inhibited HC11 cell viability, mammary gland development and the expression levels of proteins involved in proliferation. Subsequent experiments revealed that naHS regulated the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway during this process. In vivo, intraperitoneal injection of low concentration NaHS (9 mg/kg) activated the Pi3K/akt-mTor pathway in mammary glands of pubescent mice, increased the secretion of insulin-like growth factor 1 (IGF-1) and estradiol (E2), and then stimulated mammary gland ductal development. Whereas a high concentration of NaHS (18 mg/kg) elicited the opposite effects to those of low-dose naHS. in conclusion, the present study demonstrated that exogenous H 2 S supplied by naHS may exert bidirectional effects on mammary gland ductal development; promoting ductal development at a low concentration and inhibiting it at a high concentration. The effects of H 2 S may occur via the intracellular Pi3K/akt-mTor signaling pathway, or by regulation of the secretion of IGF-1 and E2.