The neuropeptides α-MSH and NPY modulate phagocytosis and phagolysosome activation in RAW 264.7 cells

• The neuropeptides α-MSH and NPY suppress phagocytosis of unopsonized bioparticles.
• The neuropeptides α-MSH and NPY do not suppress FcR-mediated phagocytosis.
• α-MSH and NPY suppress phagolysosome activation of FcR-mediated phagosomes.
• α-MSH and NPY suppress FcR-mediated generation of reactive oxygen species.

Within the immunosuppressive ocular microenvironment, there are constitutively present the immunomodulating neuropeptides alpha-melanocyte stimulating hormone (α-MSH) and neuropeptide Y (NPY) that promote suppressor functionality in macrophages. In this study, we examined the possibility that α-MSH and NPY modulate phagocytic activity in macrophages. The macrophages treated with α-MSH and NPY were significantly suppressed in their capacity to phagocytize unopsonized Escherichia coli and Staphylococcus aureus bioparticles, but not antibody-opsonized bioparticles. The neuropeptides significantly suppressed phagolysosome activation, and the FcR-associated generation of reactive oxidative species as well. This suppression corresponds to neuropeptide modulation of macrophage functionality within the ocular microenvironment to suppress the activation of immunogenic inflammation.