[Insulin-like growth factor 1 (IGF-1) promotes phagocytic activity of mouse BV-2 microglial cells via activating...

Objective To investigate the effect of insulin-like growth factor 1 (IGF-1) on the phagocytic activity of mouse BV-2 microglial cells. Methods Western blotting was performed to detect the protein levels of IGF-1 and IGF-1 receptor (IGF-1R) in the murine brain after the establishment of acute central nervous system inflammation models by intraperitoneal lipopolysaccharide (LPS) injection (10 mg/kg). The protein level of IGF-1R on BV-2 microglial cells that had been stimulated by 500 ng/mL LPS for 4, 12 and 24 hours was measured by Western blotting. To assess the phagocytic activity of microglial cells in response to IGF-1, BV-2 microglial cells were stimulated by IGF-1 at different concentrations for 24 hours after pretreated with or without wortmannin (PI3K/AKT signaling pathway blocker), and then incubated with fluorescent microbeads for 2 hours followed by measurement of phagocytosis of the fluorescent microbeads by flow cytometry. After treatment of IGF-1 (50 ng/mL), p-AKT and AKT signaling pathways in the BV-2 microglial cells were detected by Western blotting. Results Intraperitoneal LPS injection caused increased levels of IGF-1 and IGF-1R in the mouse brain. LPS upregulated the protein expression of IGF-1R on BV-2 microglial cells. The activity of BV-2 microglial cells to phagocytose fluorescent microbeads gradually increased with IGF-1 concentration rising and peaked in the IGF-1 treatment at 50 ng/mL, and gradually decreased thereafter. And IGF-1 induced the phosphorylation of AKT in BV-2 microglial cells. However, after the PI3K/AKT signaling pathway was blocked via wortmannin, the effect of IGF-1 on the activity of BV-2 microglial cells to phagocytose fluorescent microbeads was significantly alleviated. Conclusion IGF-1 can promote phagocytic activity of BV-2 cells via activating PI3K/AKT signaling pathway, which suggests a potential role of IGF-1 in regulating the cerebral inflammation.