Forkhead box protein A2 alleviates toll-like receptor 4-mediated inflammation, endoplasmic reticulum stress, autophagy, and apoptosis induced by lipopolysaccharide in bovine hepatocytes

Lipopolysaccharide (LPS) is an important stimulus of inflammation via binding to toll-like receptor 4 (TLR4), but the role of TLR4 in LPS-induced cellular homeostasis disruption indicated by the increased level of endoplasmic reticulum (ER) stress, autophagy, and apoptosis is unknown in the liver of dairy cows. Previous studies show that forkhead box protein A2 (FOXA2) is an important transcriptional factor to maintain cel-lular metabolic homeostasis, but the mechanisms by which FOXA2 mediates cellular homeostasis disruption in response to LPS remains unclear. To achieve the aims, hepatocytes separated from dairy cows at similar to 160 d in milk were pretreated with a specific TLR4 inhibi-tor TAK-242 for 12 h, followed by LPS treatment for another 12 h to investigate the role of TLR4 in LPS-induced disruption of cellular homeostasis. The results indicated that LPS-induced nuclear factor-kappa B (NF-kappa B)-mediated inflammatory cascades, ER stress, autophagy, and apoptosis via activating TLR4 and downregulating FOXA2 expression in bovine hepatocytes. The ap-plication of TLR4 inhibitor alleviated LPS-induced inflammation through inactivating NF-kappa B proinflam-matory pathway, restored cell homeostasis by decreas-ing the level of ER stress, autophagy, and apoptosis, and upregulated FOXA2 expression. Furthermore, we also elevated FOXA2 expression with an overexpres-sion plasmid to clarify its molecular role in response to LPS challenge. FOXA2 overexpression reduced LPS-caused inflammation by inhibiting NF-kappa B signaling pathway. Also, FOXA2 could alleviate ER stress to block unfolded protein response and suppress autopha-gic flux. In addition, FOXA2 enhanced mitochondrial membrane potential via reducing pro-ap optotic protein BAX, CASPASE3, and Cleaved CASPASE3 expression and elevating anti-apoptotic protein BCL-2 expression to mitigate LPS-induced apoptosis. Taken together, these findings suggested that FOXA2 is a mediator to alleviate TLR4-controlled inflammation, ER stress, autophagy, and apoptosis in LPS-treated bovine hepa-tocytes, it could serve as a potential target to intervene cell homeostasis disruption caused by LPS in the liver of dairy cows.

Automated summary

This study found that LPS activates TLR4 and inhibits FOXA2 expression, leading to NF-kappa B-mediated inflammation, ER stress, autophagy, and apoptosis. Inhibiting TLR4 and increasing FOXA2 expression can alleviate LPS-induced inflammation, ER stress, autophagy, and apoptosis, maintaining cellular homeostasis.