LPS-Induced Intracellular Complement 3 Activation Regulated ATP Production in Yak Rumen Epithelial Cells

This study aimed to investigate whether intracellular complement 3 (C3) activation regulates ATP production in yak rumen epithelial cells under inflammatory conditions and its potential mechanism. An in vitro inflammation model was established by stimulating yak rumen epithelial cells with lipopolysaccharide (LPS). Then, protease inhibitors targeting C3 activation enzymes were added. Additionally, to explore the downstream signaling pathway, exogenous C3a and the C3a receptor (C3aR) inhibitor C3aRY were applied to the inflammation model. After treatment with different concentrations of LPS, the gene expression levels and concentrations of pro-inflammatory cytokines, such as TNF-α, IL-1β, and IL-6 were significantly up-regulated (p < 0.05), while a significant reduction in cellular ATP levels was observed (p < 0.05), along with a significant reduction in mitochondrial membrane potential (p < 0.05). After treating the inflammation model with different protease inhibitors, the ATP content and gene expression of the ATP synthase subunit ATP5A were significantly increased (p < 0.05). Exogenous addition of the C3aR inhibitor C3aRY in the inflammation model exhibited a significant increase in ATP content and ATP5A gene expression (p < 0.05) when compared to the inflammation model. These results demonstrated that intracellular C3 activation inhibited ATP production in yak rumen epithelial cells under inflammatory conditions, likely through C3a-C3aR signaling and the cAMP/PKA pathway.