Characterization of IL-15 Expression for the Regulation to Cigarette Smoke Exposure in Human Airway Epithelial Cells

Abstract

P-279 Abstract: Interleukin 15 (IL-15) is a cytokine stimulate the proliferation, activation and recruitment of B cell, T cell and natural killer cell. In general, the level of IL-15 protein in human is relatively low. The IL-15 mRNA, however, is detectable in tissues or organs such as monocyte, epithelial cell, skeleton muscle, kidney, heart, and etc. Since the bronchial epithelium is the primary barrier forward the environmental air pollutants in lung, the expression of IL-15 in airway epithelial cells may reveal the association with the inflammatory process due to environmental tobacco exposure. In our experiment, we used cigarette smoke extract (CSE) and lipopolysaccharide (LPS) individually to induce the inflammatory process, and investigate the effect on the characterization of the expression of IL-15 and its variants. Human bronchial epithelial cells, BEAS-2B, were plated into 6-well plates for the subconfluent cultures, and then respectively treated with 10ug/ml LPS, 2.5% CSE or both for 24-hour exposure. Total RNA were harvested from treated BEAS-2B cells to determine the expression of IL-15 and its variant forms by complementary DNA PCR. Human BEAS-2B cells with CSE treatment had the IL-15 expression. In contrast to the IL-15 expression in BEAS-2B cells induced by LPS treatment only, the cells had more IL-15 expression with CSE treatment after LPS sensitized cells first. Although CSE induced IL-15 expression as well as LPS, there were different in the expression of IL-15 variant forms. We have demonstrated BEAS-2B cells mainly expressed IL-15 variant 1, and after CSE exposure, the cells decreased the expression of IL-15 variant 1 and switched to express the variant 2 for message of IL-15 no matter LPS sensitization or none. The expressions of variant 1- and 3-form messages are either low or not in BEAS-2B cells treated with CSE. However, BEAS-2B cells with LPS treatment expressed more the variant 3 message form besides variant 1 than the cell with CSE exposure. CSE dose increase the expression of IL-15, regardless of LPS sensitization. Furthermore, CSE may have different effect on the variant messages of IL-15 from LPS. The LPS also increases the IL-15 expression, but the mechanism in regulation is different from CSE due to the expression of IL-15 variant messages. Since LPS is an inflammatory stimulant, whereas, CSE is with oxidative damage potential, it suggests LPS and CSE stimulate the expression of IL-15 in different ways. The regulation mechanism of IL-15 variants needs to further investigate.