prostaglandin-d2 and Alzheimer-Disease

Prostaglandins (PGs) are produced via cyclooxygenases, which are enzymes that play a major role in neuroinflammation. Epidemiological studies show that chronic treatment with low levels of cyclooxygenase inhibitors (nonsteroidal anti-inflammatory drugs (NSAIDs)) lowers the risk for Alzheimer's disease (AD) and Parkinson's disease (PD) by as much as 50%. Unfortunately, inhibiting cyclooxygenases with NSAIDs blocks the synthesis of downstream neuroprotective and neurotoxic PGs, thus producing adverse side effects. We focus on prostaglandin J2 (PGJ2) because it is highly neurotoxic compared to PGA1, D2, and E2. Unlike other PGs, PGJ2 and its metabolites have a cyclopentenone ring with reactive α,β-unsaturated carbonyl groups that form covalent Michael adducts with key cysteines in proteins and GSH. Cysteine-binding electrophiles such as PGJ2 are considered to play an important role in determining whether neurons will live or die. We discuss in vitro and in vivo studies showing that PGJ2 induces pathological processes relevant to neurodegenerative disorders such as AD and PD. Further, we discuss our work showing that increasing intracellular cAMP with the lipophilic peptide PACAP27 counteracts some of the PGJ2-induced detrimental effects. New therapeutic strategies that neutralize the effects of specific neurotoxic PGs downstream from cyclooxygenases could have a significant impact on the treatment of chronic neurodegenerative disorders with fewer adverse side effects.

Topics: Alzheimer Disease; Animals; Disease Models, Animal; Humans; Inflammation; Lipopolysaccharides; Neurodegenerative Diseases; Neurons; Parkinson Disease; Prostaglandin D2; Prostaglandins; Protein Binding; Protein Processing, Post-Translational; Receptors, Prostaglandin; Signal Transduction

We investigated the relevance of the prostaglandin D2 pathway in Alzheimer's disease, because prostaglandin D2 is a major prostaglandin in the brain. Thus, its contribution to Alzheimer's disease merits attention, given the known impact of the prostaglandin E2 pathway in Alzheimer's disease. We used the TgF344-AD transgenic rat model because it exhibits age-dependent and progressive Alzheimer's disease pathology. Prostaglandin D2 levels in hippocampi of TgF344-AD and wild-type littermates were significantly higher than prostaglandin E2. Prostaglandin D2 signals through DP1 and DP2 receptors. Microglial DP1 receptors were more abundant and neuronal DP2 receptors were fewer in TgF344-AD than in wild-type rats. Expression of the major brain prostaglandin D2 synthase (lipocalin-type PGDS) was the highest among 33 genes involved in the prostaglandin D2 and prostaglandin E2 pathways. We treated a subset of rats (wild-type and TgF344-AD males) with timapiprant, a potent highly selective DP2 antagonist in development for allergic inflammation treatment. Timapiprant significantly mitigated Alzheimer's disease pathology and cognitive deficits in TgF344-AD males. Thus, selective DP2 antagonists have potential as therapeutics to treat Alzheimer's disease.

Topics: Alzheimer Disease; Animals; Dinoprostone; Disease Models, Animal; Lipopolysaccharide Receptors; Male; Prostaglandin D2; Prostaglandins; Rats; Rats, Transgenic; Receptors, Immunologic; Receptors, Prostaglandin

Topics: Administration, Intranasal; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Anilides; Animals; Behavior, Animal; Brain; Cytokines; Fluorodeoxyglucose F18; Glucose; Glucose Transporter Type 4; Hippocampus; Immunologic Factors; Mice; Mice, Transgenic; Morris Water Maze Test; Neurons; Peptide Fragments; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Positron-Emission Tomography; PPAR gamma; Presenilin-1; Prostaglandin D2; Radiopharmaceuticals; Signal Transduction

Regulation of the amyloid precursor protein (APP) processing by α- and β-secretases is of special interest to Alzheimer's disease (AD), as these proteases prevent or mediate amyloid beta formation, respectively. Neuroinflammation is also implicated in AD. Our data demonstrate that the endogenous mediator of inflammation prostaglandin J2 (PGJ2) promotes full-length APP (FL-APP) processing by α- and β-secretases. The decrease in FL-APP was independent of proteasomal, lysosomal, calpain, caspase, and γ-secretase activities. Moreover, PGJ2-treatment promoted cleavage of secreted APP, specifically sAPPα and sAPPβ, generated by α and β-secretase, respectively. Notably, PGJ2-treatment induced caspase-dependent cleavage of sAPPβ. Mechanistically, PGJ2-treatment selectively diminished mature (O- and N-glycosylated) but not immature (N-glycosylated only) FL-APP. PGJ2-treatment also increased the overall levels of protein O-GlcNAcylation, which occurs within the nucleocytoplasmic compartment. It is known that APP undergoes O-GlcNAcylation and that the latter protects proteins from proteasomal degradation. Our results suggest that by increasing protein O-GlcNAcylation levels, PGJ2 renders mature APP less prone to proteasomal degradation, thus shunting APP toward processing by α- and β-secretases.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Caspases; Cells, Cultured; Cytoplasm; Female; Glycosylation; Humans; Inflammation; Male; Prostaglandin D2; Proteasome Endopeptidase Complex; Proteolysis; Rats, Sprague-Dawley; Tumor Cells, Cultured

Alzheimer's disease (AD) is characterized by the loss of neurogenesis and excessive induction of apoptosis. The induction of neurogenesis and inhibition of apoptosis may be a promising therapeutic approach to combating the disease. Celecoxib (CB), a cyclooxygenase-2 specific inhibitor, could offer neuroprotection. Specifically, the CB-encapsulated erythrocyte membranes (CB-RBCMs) sustained the release of CB over a period of 72 h in vitro and exhibited high brain biodistribution efficiency following intranasal administration, which resulted in the clearance of aggregated β-amyloid proteins (Aβ) in neurons. The high accumulation of the CB-RBCMs in neurons resulted in a decrease in the neurotoxicity of CB and an increase in the migratory activity of neurons, and alleviated cognitive decline in APP/PS1 transgenic (Tg) mice. Indeed, COX-2 metabolic products including prostaglandin E2 (PGE

Topics: 14-3-3 Proteins; Adaptor Proteins, Signal Transducing; Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; Apoptosis Regulatory Proteins; beta-Arrestin 1; Brain; Celecoxib; Cell Line, Tumor; Cell Movement; Cognitive Dysfunction; Dinoprostone; Erythrocyte Membrane; HEK293 Cells; Humans; Liposomes; Mice, Transgenic; Mitochondrial Proteins; Models, Biological; Neural Stem Cells; Neurogenesis; Neurons; Phospholipids; Presenilin-1; Prostaglandin D2; Rats, Wistar; Superoxide Dismutase; Tissue Distribution; Up-Regulation

Neurofibrillary tangles (NFT) are a hallmark of Alzheimer's disease. The major neurofibrillary tangle component is tau that is truncated at Asp421 (Deltatau), hyperphosphorylated and aggregates into insoluble paired helical filaments. Alzheimer's disease brains also exhibit signs of inflammation manifested by activated astrocytes and microglia, which produce cytotoxic agents among them prostaglandins. We show that prostaglandin (PG) J2, an endogenous product of inflammation, induces caspase-mediated cleavage of tau, generating Deltatau, an aggregation prone form known to seed tau aggregation prior to neurofibrillary tangle formation. The initial event observed upon PGJ2-treatment of human neuroblastoma SK-N-SH cells was the build-up of ubiquitinated (Ub) proteins indicating an early disruption of the ubiquitin-proteasome pathway. Apoptosis kicked in later, manifested by caspase activation and caspase-mediated cleavage of tau at Asp421 and poly (ADP-ribose) polymerase. Furthermore, cathepsin inhibition stabilized Deltatau suggesting its lysosomal clearance. Upon PGJ2-treatment tau accumulated in a large perinuclear aggregate. In rat E18 cortical neuronal cultures PGJ2-treatment also generated Deltatau detected in dystrophic neurites. Levels of Deltatau were diminished by caspase 3 knockdown using siRNA. PGD2, the precursor of PGJ2, produced some Deltatau. PGE2 generated none. Our data suggest a potential sequence of events triggered by the neurotoxic product of inflammation PGJ2 leading to tau pathology. The accumulation of Ub proteins is an early response. If cells fail to overcome the toxic effects induced by PGJ2, including accumulation of Ub proteins, apoptosis kicks in triggering caspase activation and tau cleavage, the clearance of which by cathepsins could be compromised culminating in tau pathology. Our studies are the first to provide a mechanistic link between inflammation and tau pathology.

Topics: Alzheimer Disease; Animals; Apoptosis; Caspases; Cathepsins; Cell Line, Tumor; Cells, Cultured; Encephalitis; Enzyme Activation; Humans; Lysosomes; Neurofibrillary Tangles; Prostaglandin D2; Proteasome Endopeptidase Complex; Rats; Signal Transduction; tau Proteins; Tauopathies; Ubiquitination

It has been proposed that neuroinflammation, among other factors, may trigger an aberrant neuronal cell cycle re-entry leading to neuronal death. Cell cycle disturbances are also detectable in peripheral cells from Alzheimer's disease (AD) patients. We previously reported that the anti-inflammatory 15- deoxy-Delta(12,14)-prostaglandin J (2) (15d-PGJ (2)) increased the cellular content of the cyclin-dependent kinase inhibitor p27, in lymphoblasts from AD patients. This work aimed at elucidating the mechanisms of 15d-PGJ (2)-induced p27 accumulation. Phosphorylation, half-life, and the nucleo-cytoplasmic traffic of p27 protein were altered by 15d-PGJ2 by mechanisms dependent on PI3K/Akt activity. 15d-PGJ (2) prevents the calmodulin-dependent Akt overactivation in AD lymphoblasts by blocking its binding to the 85-kDa regulatory subunit of PI3K. These effects of 15d-PGJ (2) were not mimicked by 9,10-dihydro-15-deoxy-Delta(12,14)- prostaglandin J (2), suggesting that 15d-PGJ (2) acts independently of peroxisome proliferator-activated receptor gamma activation and that the alpha,beta-unsaturated carbonyl group in the cyclopentenone ring of 15d-PGJ (2) is a requisite for the observed effects.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Calmodulin; Cell Cycle; Cells, Cultured; Cyclin-Dependent Kinase Inhibitor p27; Half-Life; Humans; Lymphocytes; Nerve Tissue Proteins; Phosphatidylinositol 3-Kinases; Phosphorylation; Prostaglandin D2; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Protein Transport; Proto-Oncogene Proteins c-akt

Epidemiologic studies indicated that non-steroidal anti-inflammatory drugs (NSAIDs) might prevent or delay the clinical features of Alzheimer disease (AD). The pharmacological activity of NSAIDs is generally attributed to inhibition of cyclooxygenase and peroxisome proliferator-activated receptor gamma (PPARgamma) activation. Based on the antineoplastic and apoptotic effects of PPARgamma activation in a number of cell types, we hypothesized that NSAIDs could protect neurons by controlling the regulation of cell cycle. Recent work suggests that uncoordinated expression of cell cycle molecules and perturbation of cell cycle checkpoints may be one of the mechanisms by which post-mitotic neurons die. Since cell cycle dysfunction is not restricted to neurons in AD, we found it interesting to study the role of PPARgamma activation on cell proliferation in immortalized lymphocytes from AD patients. We report here that 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), but not NSAIDs or thiazolidinediones inhibited the serum-mediated enhancement of cell proliferation in AD by blocking the events critical for G1/S transition. The cyclopentenone induced a partial inhibition of retinoblastoma protein phosphorylation and increased levels of the CDK inhibitor p27kip1.

Topics: Aged; Alzheimer Disease; Analysis of Variance; Apoptosis; Case-Control Studies; Cell Cycle; Cell Line; Cell Proliferation; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Drug Interactions; Electrophoretic Mobility Shift Assay; Female; Gene Expression Regulation; Humans; Leupeptins; Lymphocytes; Male; Peroxisome Proliferator-Activated Receptors; Phosphorylation; PPAR gamma; Prostaglandin D2; Retinoblastoma Protein; Time Factors

Prostaglandins (PGs) and cytokines, such as interleukin-1 (IL-1) and interleukin-6 (IL-6), have been implicated in the etiopathology of various inflammatory and degenerative disorders, including Alzheimer's disease (AD). Previously, we detected the presence of IL-6 in cortices of AD patients. On the other hand, non-steroidal antiinflammatory drugs (NSAIDs), potent inhibitors of prostaglandin synthesis, have been shown to be beneficial in the treatment of AD. Until now, it remained unclear whether and how these two observations were functionally connected. Here, we show that PGs are able to induce IL-6 synthesis in a human astrocytoma cell line. PGE1 and PGE2, but not PGD2 and PGF2 alpha, led to a rapid and transient induction of astrocytic IL-6 mRNA, followed by IL-6 protein synthesis. Furthermore, PGE2 potentiated IL-1 beta-induced IL-6 mRNA synthesis. These results suggest a possible link between the release of PGs from activated microglia and the astrocytic synthesis of IL-6, which itself may affect neuronal cells, as hypothesized for Alzheimer's disease. Finally we demonstrate that microglia are a strong source of PGE2 synthesis indicating that these cells may act as the origin of the pathogenic cascade.

Topics: Alprostadil; Alzheimer Disease; Arachidonic Acid; Astrocytoma; Dinoprost; Dinoprostone; Humans; Interleukin-1; Interleukin-6; Microglia; Models, Immunological; Models, Neurological; Prostaglandin D2; Prostaglandins; RNA, Messenger; Transcription, Genetic; Tumor Cells, Cultured

The syntheses of prostaglandin (PG) F2 alpha, E2 and D2, and thromboxane (TX) B2 from [14C]arachidonic acid were studied in frontal cortex of human control and Alzheimer's disease (AD) brains using the microsomal fractions. Under the assay conditions employed, it was found that the major metabolite of [14C]arachidonic acid was PGE2 accounting for 63% of total prostanoid production; PGF2 alpha accounted for 21.5%, TXB2 for 9%, and PGD2 for 6.5%. When AD samples were compared to control samples, microsomal PG synthesis was significantly decreased, with reduced production of PGE2, PGF2 alpha and PGD2. Such decreases in AD brain seem unrelated to age, sex, postmortem delay and, as far as could be determined, antemortem state. In both control and Alzheimer groups, a history of anti-inflammatory therapy seemed to correlate with increased PG synthesis.

Topics: Aged; Alzheimer Disease; Animals; Arachidonic Acid; Carbon Radioisotopes; Cerebral Cortex; Choline O-Acetyltransferase; Dinoprost; Dinoprostone; Female; Glutaminase; Humans; Kinetics; Male; Microsomes; Postmortem Changes; Prostaglandin D2; Prostaglandins; Rats; Rats, Sprague-Dawley; Reference Values; Thromboxane B2