This study was conducted to evaluate the effectiveness of fucoidan in ameliorating hydrogen peroxide (H₂O₂)-induced oxidative stress to porcine intestinal epithelial cell line (IPEC-1). The cell viability test was initially performed to screen out appropriate concentrations of H₂O₂ and fucoidan. After that, cells were exposed to H₂O₂ in the presence or absence of pre-incubation with fucoidan. Hydrogen peroxide increased the apoptotic and necrotic rate, boosted reactive oxygen species (ROS) generation, and disturbed the transcriptional expression of genes associated with antioxidant defense and apoptosis in IPEC-1 cells. Pre-incubation with fucoidan inhibited the increases in necrosis and ROS accumulation induced by H₂O₂. Consistently, in the H₂O₂-treated IPEC-1 cells, fucoidan normalized the content of reduced glutathione as well as the mRNA abundance of NAD(P)H quinone dehydrogenase 1 and superoxide dismutase 1 while it prevented the overproduction of malondialdehyde. Moreover, H₂O₂ stimulated the translocation of nuclear factor-erythroid 2-related factor-2 to the nucleus of IPEC-1 cells, but this increase was further promoted by fucoidan pre-treatment. The results suggest that fucoidan is effective in protecting IPEC-1 cells against oxidative damage induced by H₂O₂, which may help in developing appropriate strategies for maintaining the intestinal health of young piglets.

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp) is the causative agent of mycoplasma pneumonia of swine (MPS). M. hyopneumoniae infection causes inflammation in pigs and leads to considerable economic losses in the pig industry. Pregnane X receptor (PXR) is a pluripotent gene regulatory protein that plays an important role in regulating cytochrome P-450 (CYP) in pigs in the context of inflammatory responses, drug metabolism, homeostasis, etc. We previously reported that cytochrome P450 3A29 (CYP3A29) expression was significantly upregulated in pigs infected with M. hyopneumoniae compared with healthy control pigs. This experiment mainly focused on identifying the role of PXR in the regulation of CYP3A29 and inflammatory factors after M. hyopneumoniae infection by establishing pig alveolar macrophage (PAM) cells in which PXR was overexpressed or silenced. Our results showed that the overexpression of PXR could significantly improve the protein and the mRNA expression levels of CYP3A29 with and without M. hyopneumoniae infection in PAM cells. After the expression of PXR was inhibited, protein and mRNA expression levels of CYP3A29 were significantly reduced with and without M. hyopneumoniae infection in PAM cells. Moreover, PXR can regulate the mRNA expression levels of IL-6 and IL-8 during M. hyopneumoniae infection of PAM cells. In conclusion, these results suggest that PXR positively regulates CYP3A29 expression during the inflammatory response caused by M. hyopneumoniae infection.