VIP modulates human macrophages phenotype via FPRL1 via activation of RhoA-GTPase and PLC pathways

Objective and design This study is aimed at uncovering the signaling pathways activated by vasoactive intestinal peptide in human macrophages Materials Human peripheral blood mononuclear cell-derived macrophages were used for the in vitro investigation of the VIP-activated signaling pathways. Methods and treatment Time-course and dose-response experiments and siRNA were used in human macrophages co-challenged with various concentrations of VIP and different MAPK pharmacologic inhibitors to investigate signaling pathways activated by VIP. Flow analysis was performed to assess the levels of CD11b, CD35 and CD66. Luminescence spectrometry was used to measure the levels of the released hydrogen peroxide and the intracellular calcium levels in the media. Results Macrophages incubated with VIP showed increased phospho-AKT and phospho-ERK1/2 levels in a GTP-RhoA-GTPase-dependent manner. Similarly, VIP increased intracellular release of H2O2 and calcium via PLC and GTP-RhoA-GTPase, in addition to inducing the expression of CD11b, CD35, CD66 and MMP9. Furthermore, VIP activated P38 MAPK through the cAMP/PKA pathway but was independent of both PLC and RhoA signaling. The above-mentioned VIP effects were mediated via activation of the FPRL1 receptor. Conclusion VIP/FPRL1/VPAC/GTP-RhoA-GTPase signaling modulated macrophages phenotype through activation of multiple signaling pathways including ERK1/2, AKT, P38, ROS, cAMP and calcium.

Automated summary

The study revealed that VIP induced activation of phospho-AKT and phospho-ERK1/2 levels in macrophages in a GTP-RhoA-GTPase-dependent manner. VIP also increased intracellular release of H2O2 and calcium through PLC and GTP-RhoA-GTPase, and induced the expression of CD11b, CD35, CD66, and MMP9. Furthermore, VIP activated P38 MAPK through the cAMP/PKA pathway but independently of PLC and RhoA signaling, with these effects mediated via the FPRL1 receptor.