Secretory Functions of Macrophages in the Human Pancreatic Islet are Regulated by Endogenous Purinergic Signaling.

Endocrine cells of the pancreatic islet interact with their microenvironment to maintain tissue homeostasis. Communication with local macrophages is particularly important in this context, but the homeostatic functions of human islet macrophages are not known. Here we show that the human islet contains macrophages in perivascular regions that are the main local source of the anti-inflammatory cytokine Il-10 and the metalloproteinase MMP9. Macrophage production and secretion of these homeostatic factors is controlled by endogenous purinergic signals. In obese and diabetic states, macrophage expression of purinergic receptors, MMP9, and Il-10 is reduced. We propose that in those states exacerbated beta cell activity due to increased insulin demand and increased cell death produces high levels of ATP that downregulate purinergic receptor expression. Loss of ATP sensing in macrophages may reduce their secretory capacity.