Caffeic Acid Counteracts LPS-Induced Inflammatory Damage in Yak Mammary Epithelial Cells Associated with NF-κB-Mediated Autophagy Regulation

Mastitis limits yak dairy production and is associated with lipopolysaccharide (LPS)-mediated inflammation in yak mammary epithelial cells (YMECs). This study aimed to investigate the protective effect of caffeic acid (CA) against LPS-induced cellular injury and to elucidate the underlying mechanisms, with a particular focus on autophagy regulation via the NF-κB signaling pathway. LPS exposure strikingly reduced cellular viability and increased intracellular reactive oxygen species (ROS) levels, accompanied by activation of the NF-κB pathway. Furthermore, it increased the expression of pro-inflammatory cytokines (TNF-α, IL-8, and IL-1β). In addition, LPS enhanced endoplasmic reticulum (ER) stress and Ca2+ dysregulation, increased LC3-II/LC3-I ratio, and reduced synthesis of α-casein and β-casein. Pretreatment with CA resulted in the effective alleviation of these alterations by restoring cellular viability, suppressing inflammatory responses, and normalizing autophagy-related markers. Additionally, inhibition of Nrf2 reversed the partial reversal of the protective effects of CA, resulting in increased ROS accumulation and autophagy activation, but did not impact NF-κB suppression. These findings indicate that CA attenuates LPS-induced inflammatory injury in YMECs involved in both Nrf2-dependent and independent pathways. These findings provide a mechanistic analysis of yak mastitis pathogenesis and CA potential as a natural therapeutic for improving mammary health and milk quality in yak dairy systems.