The PPAR‐γ Agonist 15‐Deoxy‐Δ12,14‐Prostaglandin J2 Attenuates Microglial Production of IL‐12 Family Cytokines: Potential Relevance to Alzheimer′s Disease

Abstract

Accumulation of amyloid-β peptide (Aβ) appears to contribute to the pathogenesis of Alzheimer's disease (AD). Therapeutic hope for the prevention or removal of Aβ deposits has been placed in strategies involving immunization against the Aβ peptide. Initial Aβ immunization studies in animal models of AD showed great promise. However, when this strategy was attempted in human subjects with AD, an unacceptable degree of meningoencephalitis occurred. It is generally believed that this adverse outcome resulted from a T-cell response to Aβ. Specifically, CD4+ Th1 and Th17 cells may contribute to severe CNS inflammation and limit the utility of Aβ immunization in the treatment of AD. Interleukin (IL)-12 and IL-23 play critical roles in the development of Th1 and Th17 cells, respectively. In the present study, Aβ 1−42 synergistically elevated the expression of IL-12 and IL-23 triggered by inflammatory activation of microglia, and the peroxisome proliferator-activated receptor (PPAR)-γ agonist 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2) effectively blocked the elevation of these proinflammatory cytokines. Furthermore, 15d-PGJ2 suppressed the Aβ-related synergistic induction of CD14, MyD88, and Toll-like receptor 2, molecules that play critical roles in neuroinflammatory conditions. Collectively, these studies suggest that PPAR-γ agonists may be effective in modulating the development of AD.