Abstract: The aim of this study was to establish an inflammation model of yak rumen epithelial cells induced by lipopolysaccharide (LPS), and to investigate whether there is intracellular complement C3 activation in rumen epithelial cells as non-immune cells, and its influence on the production of adenosine triphosphate (ATP). To provide experimental basis for nutrition regulation techniques of rumen health. Different concentrations of LPS were used to treat yak rumen epithelial cell line. Cell viability was determined by CCK-8 method. ELISA kit was used to determine the concentrations of C3 activation products C3a and C3b in cells and the concentrations of interleukin-1β (IL-1), interleukin 6 (IL-6), tumor necrosis factor (TNF-α) in the cell culture; The intracellular ATP concentration was detected by chemical method, and the number of mitochondria and membrane potential were detected by mitochondrial red fluorescent probe and flow cytometry. The relative expression of IL-1β, IL-6, TNF-α, complement C3, cathepsin B (CTSB), cathepsin L (CTSL), and ATP synthase subunits (ATP5A and ATP5C1) were determined by q-PCR. The results showed that: 1) After different concentrations of LPS treatment, the activity of yak rumen epithelial cells was significantly decreased (P<0.01), and the gene expression and concentration of proinflammatory factors, such as TNF-α, IL-1β and IL-6 were significantly increased (P<0.01). The inflammatory model of yak rumen epithelial cells was established successfully when the concentration of LPS was 10 μg·mL^-1; 2) Under inflammation, the gene expression of complement C3 and its key activating enzyme CTSB increased significantly in yak rumen epithelial cells (P<0.01), and the concentration of activated complement fragments C3a and C3b increased significantly (P<0.01); 3) Under inflammation, the ATP content (P<0.01) and mitochondrial membrane potential (P<0.01) in yak rumen epithelial cells decreased significantly, and the gene expression of ATP synthase subunits ATP5A and ATP5C1 decreased significantly with the increasing of LPS concentration (P<0.01). In summary, the inflammation model of yak rumen epithelial cells was established by LPS. The LPS stimulation can activate the intracellular complement C3, and inhibit the gene expression of mitochondrial ATP synthase subunits ATP5A, ATP5C1 and key enzyme ME1 of aerobic respiration, thus reducing mitochondrial membrane potential and inhibiting ATP production in the yak rumen epithelial cells. LPS-induced inflammation can inhibit ATP production of rumen epithelial cells, leading to rumen health problems.

Key words: yak, rumen epithelial cells, immune inflammation, complement C3, ATP