Abstract: Objective · To investigate the effect of insulin-like growth factor 1 (IGF-1) on phagocytosis and production of interleukin-10 (IL-10) in the murine alveolar epithelial cell line MLE-12. Methods · After treatment with IGF-1 for 48 h, MLE-12 cells were incubated with fluorescent microspheres for 2 h in the presence or absence of wortmannin (phosphatidylinositol-3-kinase inhibitor). Flow cytometry was then used to assess cell phagocytosis of fluorescent microspheres. Enzyme linked immunosorbent assay (ELISA) was used to detect the content of IL-10 in MLE-12 cells culture supernatant stimulatedIGF-1 for 24 h. After pretreatment with IGF-1 for 2 h, MLE-12 cells were stimulatedlipopolysaccharides (LPS) for 24 h, and the of phosphorylated signal transduction and activator of transcription 3 (p-STAT3) in cytoplasm was detectedWestern blotting. Results · With the increase of IGF-1 stimulation concentration, the ability of MLE-12 cells to phagocytose fluorescent microspheres increased, and the ability to phagocytose fluorescent microspheres reached the peak in the presence of IGF-1 at 50 ng/mL. However, the ability of IGF-1 to phagocytose fluorescent microspheres was completely blockedwortmannin in MLE-12 cells. IGF-1 promoted IL-10 secretion and inhibited LPS-induced enhancement of STAT3 activation in MLE-12 cells. Conclusion · IGF-1 promotes phagocytosis of MLE-12 cells via the PI3K/protein kinase B (Akt) pathway and exhibits anti-inflammatory properties.

Key words: insulin-like growth factor 1 (IGF-1), MLE-12 cell, phagocytosis, interleukin-10 (IL-10), signal transduction and activator of transcription 3 (STAT3)