The effects of ��-MSH on TUNEL staining and cell viability in the macrophages must be post-caspase activity in the apoptotic pathway. It has been shown that inhibiting phosphorylation of p38 MAPK inhibits the apoptosis pathway before DNA fragmentation. It is not clear if p38 MAPK AbMole Metaproterenol Sulfate activation is directly involved in the activation of DNA fragmentation, or that its activation is a bystander indicator of Caspase 3 activation of MAP kinase kinases that initiates the process of DNA fragmentation. While the intracellular pathways of ��-MSH mediated signaling are not fully understood, it is known that ��MSH suppresses the activation of both NF-kB and p38 MAPK AbMole Terbuthylazine through its melanocortin receptors MC1r and MC3r. This suppresses inflammatory activity in the macrophages stimulated through Toll-like receptors and proinflammatory cytokines. The suppression of NF-kB is ��-MSH promoting IRAK-M binding to IRAK-1 to inhibit TLR signaling. The suppression of p38 MAPK is though ��-MSH activation of cAMP-dependent PKA. Therefore, since the results show no effect of ��-MSH on the initial steps and the caspase steps of apoptosis, and that ��-MSH is known to suppress p38 MAPK phosphorylation, it suggests that the effects of ��-MSH are on the post-caspase steps of apoptosis to promote cell survival. The survival of such affected macrophages may be part of immune-homeostasis mediated by ��-MSH within localized tissue microenvironments. We know that macrophages treated with ��-MSH are suppressed in inflammatory activity, and may promote regulatory or tolerogenic immunity. In the retina, ��-MSH is part of RPE mediated induction of suppressor macrophages and similar characteristics in the retinal microglial cells. However, the signaling pathways that result in activation of genes and functions of inflammation within macrophages are also signals of survival and resistance to apoptosis. Therefore, in the healthy retina ��-MSH must be providing an anti-inflammatory signal, and a necessary survival signal for the immunosuppressive microglial to function and survive in the retina. Moreover, ��-MSH may be part of a selective mechanism mediated by the RPE to exclude macrophages that are unresponsive to ��-MSH immunosuppressive activity. In this way macrophages and possibly dendritic cells migrating into the retina would encounter the soluble apoptotic signal from RPE and will have to respond to ��-MSH to survive, but by doing so makes them immunosuppressive. This selective process could explain why in the healthy retina the microglial cells are found to be characteristically uniform as myeloid suppressor cell-like. Some of the caspases also have non-apoptotic activities. The diversion of the caspases to other non-apoptotic activities could be the effects of ��-MSH with saving the macrophages from apoptosis. A non-apoptotic activity of Caspase 8 is to activate NF-��B. The suppression of Caspase 8 that was detected could be ��-MSH suppressing another pathway to NF-��B activation. Maintaining nonapoptotic activities of Caspase 3 has benefits to ocular immunobiology. The non-apoptotic functions of Caspase 3 include suppression of MHC class II antigen expression and dendritic cell maturation. This would greatly contribute to the immune privileged and immunosuppressive microenvironment of the retina. Since ��-MSH can have a role in immune-homeostasis to resolve inflammation, it could mediate more than immunosuppression by maintaining in surviving cells caspase functionalities that contribute to resolving inflammation and promoting wound repair. The neuropeptide ��-MSH is not just an anti-inflammatory factor. It modulates the functionality of immune cells.