Prostaglandin J2 (PGJ2) is an endogenous product of inflammation in humans. It induces neuronal death and the accumulation of ubiquitinated proteins into distinct aggregates. It may play a role in neurodegenerative disorders inducing a chain of events that culminates in neuronal cell death. An altered expression of enzymes in PGJ2 synthesis may represent a novel pathogenic mechanism in human obesity. The peroxisome proliferator-activated receptor gamma (PPARγ) has a fundamental role in glucose homeostasis and adipocyte differentiation. Besides linoleate, linolenate and arachidonate, the most notable PPAR ligand is 15-deoxy-delta12-14-prostaglandin J2, a natural derivative of prostaglandin D2 and PGJ2. It is therefore plausible that the production of 15d-PGJ2 within adipose tissue may act as an endogenous mediator of adipocyte differentiation. PGJ2 disrupts the cytoskeleton in neuronal cells. This cyclopentenone prostaglandin triggered endoplasmic reticulum (ER) collapse and the redistribution of ER proteins, such as calnexin and catechol-O-methyltransferase, into a large centrosomal aggregate containing ubiquitinated proteins and alpha-synuclein. The PGJ2-dependent cytoskeletal rearrangement paralleled the development of the large centrosomal aggregate. Supporting a mechanism by which, upon PGJ2 treatment, cytoskeleton/ER collapse coincides with the relocation of ER proteins, other potentially neighboring proteins, and ubiquitinated proteins into centrosomal aggregates. Development of these large perinuclear aggregates is associated with disruption of the microtubule/ER network. This aberrant protein deposition, triggered by a product of inflammation, may be common to other compounds that disrupt microtubules and induce protein aggregation, such as MPP+ and rotenone, found to be associated with neurodegeneration. Many neurodegenerative disorders, such as Parkinson disease, exhibit inclusion bodies containing ubiquitinated proteins. Concentrations of PGJ2 in biofluids have not been established, since this prostaglandin is further metabolized into delta12-PGJ2, and 15-deoxy-delta12,14-PGJ2. Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.