Effects of Apelin on RAW264.7 cells under both normal and hypoxic conditions

• Apelin decreased the mRNA expression of VEGFA, Ang2, TNFα and chemokines in normoxia.
• Apelin decreased supernatant concentrations of chemokines and TNFα in normoxia.
• Hypoxia up-regulated the chemokines and TNFα expression at mRNA and protein levels.
• Apelin suppressed the hypoxia-induced increases of MCP1, MCP3, MIP2, MIP1β and TNFα.
• Apelin can protect macrophages from apoptosis and can enhance cell migration during hypoxia.

Macrophages are an important source of pro-inflammatory and pro-angiogenic factors, which can promote pathological processes involving inflammation and angiogenesis. This study investigated the effects of Apelin on macrophages under both normal and hypoxic conditions. Under normal culture conditions, Apelin down-regulated the mRNA expression levels of monocyte chemotactic protein 1 (MCP1), monocyte chemotactic protein 3 (MCP3), macrophage inflammatory protein 1 (MIP1α, MIP1β), vascular endothelial growth factor A (VEGFA), Angiopoietin 2 (Ang2) and tumor necrosis factor α (TNFα). The supernatant concentrations of MCP1, MCP3, MIP1α, MIP1β, macrophage inflammatory protein 2 (MIP2) and TNFα proteins were significantly decreased in the Apelin treated group. Hypoxia induced profound up-regulations of the angiogenic, chemokine, and inflammatory factors at both the mRNA and protein levels. Apelin suppressed the hypoxia-induced increases in MCP1, MCP3, MIP2, MIP1β and TNFα expression. The underlying mechanism of Apelin inhibit inflammation is regulating NF-κB/JNK signal pathway. Additionally, Apelin can protect macrophages from apoptosis and can enhance cell migration during hypoxia. And cleaved Caspase9/3 pathways were involved in Apelin inhibiting RAW264.7 apoptosis. In conclusion, we showed the effect of Apelin on RAW264.7 macrophage under normal and hypoxic condition, which could further influence the angiogenesis and inflammation process that promoted by macrophages.