Eosinophil cationic protein induces insulin-like growth factor I receptor expression on bronchial epithelial cells

Although the biologic activity of eosinophil-specific granule proteins, e.g. eosinophil cationic protein (ECP) has been attributed to cytotoxic properties, it has also been shown to be attributable to non-cytotoxic activation of various inflammatory cells. In addition, airway epithelial cells have been reported to express insulin-like growth factor I (IGF-I) receptor and proliferate in response to IGF-I. The present study examined the regulation of expression of IGF-I receptor on bronchial epithelial cells by eosinophil granule proteins was examined. ECP significantly induced IGF-I receptor expression on bronchial epithelial cells compared with unstimulated cells. These findings suggest that eosinophils participate in the repair process of injured bronchial epithelial cells in the inflamed focus through augmentation of IGF-I receptor expression by suboptimal degranulation of eosinophil granule proteins, e.g. ECP.