Impact of allicin on enzyme activity, cytokine secretion, and gene expression dynamics in oxidative- and endotoxin-stressed porcine intestinal epithelial cells
Environmental stress and endotoxins can negatively affect gastrointestinal function by influencing cellular antioxidant systems, tight junctions, and inflammatory mediators. Allicin is a botanical derived from garlic that has anti-inflammatory and antioxidant properties. The objective of the current study was to determine if allicin could mitigate oxidative and endotoxin stress using an IPEC cell model. The experiment was arranged as a 2 x 2 x 2 factorial of allicin (0 or 40 µM), oxidative stressor, hydrogen peroxide (0 or 100 µM), and endotoxin stressor, lipopolysaccharide (0 or 10 µg/ml). Cells were incubated with allicin or lipopolysaccharide (LPS) for 18 h or with hydrogen peroxide for 3 h approximately 1 wk following confluency. Trans-epithelial resistance (TER), reactive oxygen species (ROS), antioxidant enzymes, interleukin 8 and 1 beta (IL-8 and IL-1β), and tumor necrosis factor alpha (TNF-α) secretion were measured. Gene expression was measured by RT-PCR for cytokines IL-8, IL-1β, and TNF-α and tight junction proteins claudin 1 (CL-1), occludin (OC), and zonula occludens 1 (ZO-1). Treatment did not affect TER although addition of allicin to hydrogen peroxide- and LPS-treated cells reduced (P < 0.05) ROS. Allicin decreased superoxide dismutase (SOD) activity (P < 0.001), whereas hydrogen peroxide increased SOD activity (P = 0.02). Furthermore, addition of allicin to hydrogen peroxide-treated cells restored SOD activity similar to untreated cells (P < 0.05). Addition of allicin to hydrogen peroxide- and LPS-treated cells decreased catalase activity (P < 0.05). There was an increase in TNF-α and IL-8 gene expression due to LPS (P < 0.001) although there was no effect of hydrogen peroxide or allicin (P > 0.05). Experimental treatment had no effect on tight junction gene expression (P > 0.05). There was an increase (P < 0.001) in IL-8 secretion due to LPS which was further increased (P < 0.05) by addition of allicin to LPS-treated cells and hydrogen peroxide incubation increased (P = 0.01) TNF-α secretion. Based on the results from the current study, allicin can ameliorate oxidant effects of hydrogen peroxide and LPS as well as alter cytokine secretion in IPEC cells.
allicin, hydrogen peroxide, lipopolysaccharide