By aid of microarray analysis, we have previously reported that long-term exposure of SV40-immortalized human urothelial cells (HUC-1) to low dose (0.5 μM) of inorganic arsenite (iAs) resulted in enhanced or suppressed expression of a variety of genes. Among them, the expression of type 2 interleukin-1 receptor (IL1R2) was significantly enhanced in iAs-exposed HUC-1 cells, designated as (HUC-iAs). The enhanced expression of IL1R2 at mRNA and protein levels in HUC-iAs cells and cultural medium was confirmed by quantitative real time PCR, Western blot analysis and ELISA assay, respectively. IL1R2 was known as an IL-1 decoy receptor acting as an antagonist to block IL1-activated signaling. Although HUC-iAs also expressed higher levels of IL-1α and IL-1β as compared to the parental HUC-1 cells, HUC-iAs cells, as expectedly, did not response to IL-1β stimulation by using NF-κB-dependent promoter luciferase assay system. However, recent report has shown that IL1R2 could interact with intracellular pre-IL-1α and subsequently enhanced several IL-1α-regulated genes. We further explored the biological effects of IL1R2 overexpression in urothelial cells by transfection of IL1R2 expression vector into HUC-1 cells. IL1R2 expression vector was constructed by inserting IL1R2 cDNA into plasmid pFLAG-myc-CMV-22. NF-κB-dependent promoter luciferase assay was adopted to evaluate the function of transfected IL1R2 gene. Our results showed that in IL1R2-overexpressed HUC-1 cells, TNF-α, but not IL-1β, could activate NF-κB-mediated luciferase activity, indicating that IL1R2 specifically blocks IL-1β-activated signaling. Interestingly, IL1R2-overespressed HUC-1 cells showed significant changes of cellular morphology. As compared to parental HUC-1 cells, they became more diffuse without tight contact. By aid of Phalloidin staining, F-actin stress fibers were apparently increased in IL1R2-overexpressed cells. These observations suggest that in addition to serve as a negative regulator of IL-1 signaling, the involvement of IL1R2 on other cellular functions, such as migration, cell adhesion, and extracellular matrix interaction, warrants our further investigation.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA