Background: Although epithelial cells in ulcerative colitis may be metabolically deficient, it remains unknown whether epithelial cells modulate energy metabolism in inflamed mucosa. The purpose of the present study is to investigate whether inflammatory mediators such as lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) alter energy metabolism in epithelial cells.
Methods: Adenosine 5'-triphosphate (ATP) levels in HT29 cells cultured with LPS, IL-1beta, IL-6, or TNF-alpha were measured with high-performance liquid chromatography, using a reversed-phase chromatography column. Cellular and mitochondrial (antimycin A-sensitive) respiration rates were determined polarographically, using a Clark-type oxygen electrode.
Results: When the cells were cultured with LPS, IL-6, and TNF-alpha but not IL-1beta, ATP levels increased significantly at 6 h, followed by a decrease at 24 h. Enhancement of oxygen consumption, which was completely blocked by antimycin A, was also shown at 3 h by the exposure to these substrates.
Conclusion: LPS and proinflammatory cytokines induced cellular ATP generated by mitochondrial phosphorylation. An active energy production in epithelial cells on the exposure to inflammatory mediators may be critical for escape from chronic mucosal inflammation.