Cell type specific and glucose responsive expression of interleukin-4 by using insulin promoter and water soluble lipopolymer.

For gene therapy, tissue targeting of gene delivery systems is required for the maximum efficiency. In this study, we constructed pRIP-IL4 in which the expression of interleukin-4 (IL-4) was driven by the rat insulin promoter. WSLP-pRIP-IL4 complex was characterized by pancreas beta-cell specific and glucose responsive expression of IL-4. pRIP-IL4 was completely retarded at a 6:1 or higher N/P (nitrogen atom of WSLP/phosphate of plasmid) ratio in 1% agarose gel. In addition, WSLP protected plasmid DNA from DNase I for more than 1 h. In cytotoxicity assay, WSLP showed less cytotoxicity than PEI (25000 Da) to mouse insulinoma (MIN6) cells. ELISA showed that pRIP-IL4 expressed much higher levels of IL-4 in MIN6 cells than in NIH3T3 cells. The expression level of IL-4 by pRIP-IL4 increased with increasing concentration of glucose. Also, IL-4 was expressed in a dose-dependent manner. This WSLP-pRIP-IL4 system will be useful in the development of a pancreas specific expression system for the prevention of diabetes without systemic side effects.