Developmental Role of Macrophage Cannabinoid-1 Receptor Signaling in Type 2 Diabetes.

ABSTRACT: Islet inflammation promotes ?-cell loss and type 2 diabetes (T2D), a process replicated in Zucker Diabetic Fatty (ZDF) rats in which ?-cell loss has been linked to cannabinoid-1 receptor (CB₁R)-induced proinflammatory signaling in macrophages infiltrating pancreatic islets. Here, we analyzed CB₁R signaling in macrophages and its developmental role in T2D. ZDF rats with global deletion of CB₁R are protected from ?-cell loss, hyperglycemia, and nephropathy that are present in ZDF littermates. Adoptive transfer of CB₁R^-/- bone marrow to ZDF rats also prevents ?-cell loss and hyperglycemia but not nephropathy. ZDF islets contain elevated levels of CB₁R, interleukin-1?, tumor necrosis factor-?, the chemokine CCL2, and interferon regulatory factor-5 (IRF5), a marker of inflammatory macrophage polarization. In primary cultured rodent and human macrophages, CB₁R activation increased Irf5 expression, whereas knockdown of Irf5 blunted CB₁R-induced secretion of inflammatory cytokines without affecting CCL2 expression, which was p38MAPK? dependent. Macrophage-specific in vivo knockdown of Irf5 protected ZDF rats from ?-cell loss and hyperglycemia. Thus, IRF5 is a crucial downstream mediator of diabetogenic CB₁R signaling in macrophages and a potential therapeutic target.

SUBMITTER: Jourdan T 

PROVIDER: S-EPMC5360301 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature