dinoprost and Encephalitis

The neuroinflammatory response has received increasing attention as a key factor in the pathogenesis of Alzheimer's disease (AD). Microglia, the innate immune cells and resident phagocytes of the brain, respond to accumulating Aβ peptides by generating a nonresolving inflammatory response. While this response can clear Aβ peptides from the nervous system in some settings, its failure to do so in AD accelerates synaptic injury, neuronal loss, and cognitive decline. The complex molecular components of this response are beginning to be unraveled, with identification of both damaging and protective roles for individual components of the neuroinflammatory response. Even within one molecular pathway, contrasting effects are often present. As one example, recent studies of the inflammatory cyclooxygenase-prostaglandin pathway have revealed both beneficial and detrimental effects dependent on the disease context, cell type, and downstream signaling pathway. Nonsteroidal anti-inflammatory drugs (NSAIDs), which inhibit cyclooxygenases, are associated with reduced AD risk when taken by cognitively normal populations, but additional clinical and mouse model studies have added complexities and caveats to this finding. Downstream of cyclooxygenase activity, prostaglandin E2 signaling exerts both damaging pro-inflammatory and protective anti-inflammatory effects through actions of specific E-prostanoid G-protein coupled receptors on specific cell types. These complexities underscore the need for careful study of individual components of the neuroinflammatory response to better understand their contribution to AD pathogenesis and progression.

Topics: Alzheimer Disease; Animals; Dinoprost; Encephalitis; Humans; Microglia; Signal Transduction

Neuroinflammatory responses are triggered by diverse ethiologies and can provide either beneficial or harmful results. Microglial cells are the major cell type involved in neuroinflammation, releasing several mediators, which contribute to the neuronal demise in several diseases including cerebral ischemia and neurodegenerative disorders. Attenuation of microglial activation has been shown to confer protection against different types of brain injury. Recent evidence suggests that resveratrol has anti-inflammatory and potent antioxidant properties. It has been also shown that resveratrol is a potent inhibitor of cyclooxygenase (COX)-1 activity. Previous findings have demonstrated that this compound is able to reduce neuronal injury in different models, both in vitro and in vivo. The aim of this study was to examine whether resveratrol is able to reduce prostaglandin E2 (PGE2) and 8-iso-prostaglandin F2alpha (8-iso-PGF2 alpha) production by lipopolysaccharide (LPS)-activated primary rat microglia.. Primary microglial cell cultures were prepared from cerebral cortices of neonatal rats. Microglial cells were stimulated with 10 ng/ml of LPS in the presence or absence of different concentrations of resveratrol (1-50 microM). After 24 h incubation, culture media were collected to measure the production of PGE2 and 8-iso-PGF2 alpha using enzyme immunoassays. Protein levels of COX-1, COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) were studied by Western blotting after 24 h of incubation with LPS. Expression of mPGES-1 at the mRNA level was investigated using reverse transcription-polymerase chain reaction (RT-PCR) analysis.. Our results indicate that resveratrol potently reduced LPS-induced PGE2 synthesis and the formation of 8-iso-PGF2 alpha, a measure of free radical production. Interestingly, resveratrol dose-dependently reduced the expression (mRNA and protein) of mPGES-1, which is a key enzyme responsible for the synthesis of PGE2 by activated microglia, whereas resveratrol did not affect the expression of COX-2. Resveratrol is therefore the first known inhibitor which specifically prevents mPGES-1 expression without affecting COX-2 levels. Another important observation of the present study is that other COX-1 selective inhibitors (SC-560 and Valeroyl Salicylate) potently reduced PGE2 and 8-iso-PGF2 alpha production by LPS-activated microglia.. These findings suggest that the naturally occurring polyphenol resveratrol is able to reduce microglial activation, an effect that might help to explain its neuroprotective effects in several in vivo models of brain injury.

Topics: Animals; Animals, Newborn; Antioxidants; Cells, Cultured; Cyclooxygenase 1; Cyclooxygenase Inhibitors; Dinoprost; Dinoprostone; Down-Regulation; Encephalitis; Free Radical Scavengers; Free Radicals; Gliosis; Inflammation Mediators; Lipopolysaccharides; Microglia; Oxidative Stress; Rats; Resveratrol; Stilbenes

Microglia are the major cell type involved in neuroinflammatory events in brain diseases such as encephalitis, stroke, and neurodegenerative disorders, and contribute significantly to the release of prostaglandins (PGs) during neuronal insults. In this report, we studied the immediate-early intracellular signalling pathways in microglia, following bacterial lipopolysaccharide (LPS) stimulation, leading to the synthesis and release of PGE2. Here we show that LPS induces cyclooxygenase (COX) 2 by activating sphingomyelinases leading to the release of ceramides, which in turn, activate the p38 mitogen-activated protein kinases (MAPK), but not the p42/44 MAPK. We further show that exogenously added ceramide analogue (C2-ceramide) also induce PGE2 synthesis through a p38 MAPK-dependent pathway. This potential nature of ceramides in activating microglia suggests that endogenously produced ceramides during neuronal apoptosis in ischemia or neurodegenerative diseases could also contribute to the amplification of neuroinflammatory events. In contrast to protein kinase C (PKC) and phosphocholine-specific phospholipase C (PC-PLC), which transcriptionally regulate LPS-induced COX-2 synthesis, inhibition of phospholipase A2 (PLA2) has no effect on COX-2 transcription, although it inhibits the release of PGE2. Transcriptional regulation of LPS-induced COX-2 by PKC is further proved by the ability of the PKC inhibitor, Gö 6976, to inhibit LPS-induced 8-isoprostane synthesis, but not affecting LPS-induced COX-2 activity. Our data with 8-isoprostane also indicates that COX-2 plays a major role in ROS production in LPS-activated microglia. This detailed view of the intracellular signaling pathway in microglial activation and COX-2 expression opens a new therapeutic window in the search for new and more effective central anti-inflammatory agents.

Topics: Animals; Animals, Newborn; Brain; Cells, Cultured; Ceramides; Cyclooxygenase 2; Dinoprost; Dinoprostone; Encephalitis; Enzyme Activation; Enzyme Inhibitors; Gliosis; Lipopolysaccharides; Microglia; p38 Mitogen-Activated Protein Kinases; Prostaglandin-Endoperoxide Synthases; Protein Kinase C; Rats; Rats, Sprague-Dawley; Signal Transduction; Transcriptional Activation; Type C Phospholipases

This study was designed to test the hypothesis that the sphingomyelin-ceramide signaling pathway may be important in proinflammatory-like responses in the intact brain. Effects of neutral sphingomyelinase (N-SMase), ceramide analogs, phosphorylcholine and ceramide metabolites were studied on rat brain cerebral (cortical) venule lumen sizes, leukocyte rolling, velocity and endothelial cell wall adhesion, microvessel permeability, microvessel rupture and focal hemorrhages using in vivo high resolution TV microscopy. Perivascular and close intra-arterial administration of N-SMase, C(2)-, C(8)-, and C(16)-ceramide, but not either phosphorylcholine, C(6)-ceramide, nervonic (C(24):1) ceramide, lignoceric (C(24):0) ceramide, C(8)-ceramide-1-phosphate, glucosylceramide or 1-0-acylceramide, resulted in potent, concentration-dependent constriction (and spasm) of cortical venules, followed by increased leukocyte rolling, decreased leukocyte velocities, increased leukocyte-endothelial wall adhesion, increased venular wall permeability, postcapillary venule rupture and, often, micro-hemorrhaging at high concentrations; angiotensin II, serotonin and PGF(2alpha) didn't demonstrate these characteristics. Pretreatment with either one of three different antioxidants, including inhibitors of NF-kappaB activation, or two different Ca(2+) channel blockers either prevented or attenuated the adverse venular effects of N-SMase and the ceramides. Likewise, pretreatment with either a PKCalpha-beta antagonist or a MAP kinase antagonist also attenuated the adverse venular effects. These results suggest that N-SMase and several ceramides can result in potent venular cerebrovasospasm, leukocyte-endothelial chemoattraction, and microvessel wall permeability changes in the intact rat brain. These proinflammatory-like actions suggest that N-SMase and ceramides could produce brain-vascular damage by reperfusion injury triggering lipid peroxidation, release of reactive oxygen species and activation of diverse signaling pathways: PKCalpha-beta isozymes, MAP kinase and NF-kappaB.

Topics: Angiotensin II; Animals; Brain Injuries; Capillary Permeability; Cell Communication; Ceramides; Cerebral Veins; Dinoprost; Dose-Response Relationship, Drug; Encephalitis; Endothelium, Vascular; Leukocytes; Male; Rats; Rats, Wistar; Serotonin; Signal Transduction; Sphingomyelin Phosphodiesterase; Sphingomyelins; Stroke; Vasoconstriction; Venules

Fractalkine is a chemokine widely and constitutively expressed in the brain and, as suggested by in vitro studies, it is involved in brain inflammatory responses. In this study, we have investigated the in vivo anti-inflammatory potential of fractalkine in a model of neuroinflammation induced by intracerebroventricular injection of lipopolysaccharide (LPS) in rats. LPS induces a rapid and acute production of the pro-inflammatory cytokine, TNFalpha, in hippocampus and cerebrospinal fluid (CSF), and an increase of 8-isoprostane levels, a marker of oxidative stress, in hippocampus. Although intracerebroventricular injection of fractalkine has no effect on TNFalpha and 8-isoprostane production, neutralization of endogenous fractalkine within the brain with a specific anti-fractalkine antibody potentiates LPS effects. These data emphasize the involvement of constitutive brain fractalkine in the control of inflammatory reaction in CNS.

Topics: Animals; Antibodies; Brain; Chemokine CX3CL1; Chemokines, CX3C; Chemokines, CXC; Dinoprost; Disease Models, Animal; Encephalitis; F2-Isoprostanes; Hippocampus; Injections, Intraventricular; Lipopolysaccharides; Male; Membrane Proteins; Oxidative Stress; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha