Gallic acid mitigates LPS-induced inflammatory response via suppressing NF-kappa B signalling pathway in IPEC-J2 cells

Gallic acid is a phenolic compound that exhibits antibacterial, antioxidative and anti-inflammatory functions. In a previous study, we found that dietary supplementation with gallic acid decreased incidence of diarrhoea and protected intestinal integrity in weaning piglets. However, the underlying mechanism remains unclear. Here, a pig intestinal epithelial cell line (IPEC-J2) was used as an in vitro model to explore the antioxidant and anti-inflammatory capacity of gallic acid. IPEC-J2 cells were stimulated with hydrogen peroxide (H2O2) and lipopolysaccharide (LPS) to establish oxidative and inflammatory models, respectively. Results showed that H2O2 significantly decreased catalase (CAT) secretion and CAT mRNA abundance in the cells (p < 0.05), while pretreatment with gallic acid did not prevent the decrease in CAT expression induced by H2O2. However, gallic acid pretreatment mitigated the increased expression of the tumour necrosis factor-alpha and interleukin-8 genes caused by LPS in IPEC-J2 cells (p < 0.05). In addition, pretreatment with gallic acid significantly suppressed phosphorylation of NF-kappa B and I kappa B alpha in LPS-stimulated IPEC-J2 cells. Moreover, LPS stimulation decreased the protein abundance of zona occludens 1 (ZO-1) and occludin, while pretreatment with gallic acid preserved expression level of tight junction proteins ZO-1 and occludin in LPS-stimulated IPEC-J2 cells (p < 0.05). In conclusion, gallic acid may mitigate LPS-induced inflammatory responses by inhibiting the NF-kappa B signalling pathway, exerting positive effects on the barrier function of IPEC-J2 cells.