Cytosolic Phospholipase A2α Promotes Pulmonary Inflammation and Systemic Disease during Streptococcus pneumoniae Infection.

Pulmonary infection by Streptococcus pneumoniae is characterized by a robust alveolar infiltration of neutrophils (polymorphonuclear cells [PMNs]) that can promote systemic spread of the infection if not resolved. We previously showed that 12-lipoxygenase (12-LOX), which is required to generate the PMN chemoattractant hepoxilin A3 (HXA3) from arachidonic acid (AA), promotes acute pulmonary inflammation and systemic infection after lung challenge with S. pneumoniae As phospholipase A2 (PLA2) promotes the release of AA, we investigated the role of PLA2 in local and systemic disease during S. pneumoniae infection. The group IVA cytosolic isoform of PLA2 (cPLA2α) was activated upon S. pneumoniae infection of cultured lung epithelial cells and was critical for AA release from membrane phospholipids. Pharmacological inhibition of this enzyme blocked S. pneumoniae-induced PMN transepithelial migration in vitro Genetic ablation of the cPLA2 isoform cPLA2α dramatically reduced lung inflammation in mice upon high-dose pulmonary challenge with S. pneumoniae The cPLA2α-deficient mice also suffered no bacteremia and survived a pulmonary challenge that was lethal to wild-type mice. Our data suggest that cPLA2α plays a crucial role in eliciting pulmonary inflammation during pneumococcal infection and is required for lethal systemic infection following S. pneumoniae lung challenge.

Neuroinflammation in Alzheimer's Disease: The Preventive and Therapeutic Potential of Polyphenolic Nutraceuticals.

Brain inflammation, characterized by increased microglia and astrocyte activation, increases during aging and is a key feature of neurodegenerative diseases, such as Alzheimer's disease (AD). In AD, neuronal death and synaptic impairment, induced by amyloid-ß (Aß) peptide, are at least in part mediated by microglia and astrocyte activation. Glial activation results in the sustained production of proinflammatory cytokines and reactive oxygen species, giving rise to a chronic inflammatory process. Astrocytes are the most abundant glial cells in the central nervous system and are involved in the neuroinflammation. Astrocytes can be activated by numerous factors, including free saturated fatty acids, pathogens, lipopolysaccharide, and oxidative stress. Activation of astrocytes produces inflammatory cytokines and the enzyme cyclooxygenase-2, enhancing the production of Aß. Furthermore, the role of the receptor for advanced glycation end products/nuclear factor-κB (NF-κB) axis in neuroinflammation is in line with the nonenzymatic glycosylation theory of aging, suggesting a central role of the advanced glycation end products in the age-related cognitive and a possible role of nutraceuticals in the prevention of neuroinflammation and AD. However, modulation of P-glycoprotein, rather than antioxidant and anti-inflammatory effects, could be the major mechanism of polyphenolic compounds, including flavonoids. Curcumin, resvertrol, piperine, and other polyphenols have been explored as novel therapeutic and preventive agents for AD. The aim of this review is to critically analyze and discuss the mechanisms involved in neuroinflammation and the possible role of nutraceuticals in the prevention and therapy of AD by targeting neuroinflammation.

Glucocorticoids sensitize rat placental inflammatory responses via inhibiting lipoxin A4 biosynthesis.

Inflammation dysregulation in placenta is implicated in the pathogenesis of numerous pregnancy complications. Glucocorticoids (GCs), universally considered anti-inflammatory, can also exert proinflammatory actions under some conditions, whereas whether and how GCs promote placental inflammation have not been intensively investigated. In this paper we report the opposing regulation of rat placental inflammation by synthetic GC dexamethasone (Dex). When Dex was subcutaneously injected 1 h after we administered an intraperitoneal lipopolysaccharide (LPS) challenge, neutrophil infiltration and proinflammatory Il1b, Il6, and Tnfa expression in rat placenta were significantly reduced. In contrast, Dex pretreatment for 24 h potentiated rat placental proinflammatory response to LPS and delayed inflammation resolution, which involved MAPKs and NF-kappaB activation. Mechanically, Dex pretreatment promoted 5-lipoxygenase (ALOX5) activation and increased leukotriene B4 production, whereas it inhibited the anti-inflammatory and proresolving lipid mediator lipoxin A4 (LXA4) biosynthesis in rat placenta via downregulating ALOX15 and ALOX15B expression. Moreover, LXA4 supplementation dampened Dex-potentiated placental inflammation and suppressed Dex-mediated ALOX5 activation in vivo and in vitro. Taken together, these findings suggest that GCs exposure could promote placental inflammation initiation and delay resolution via disrupting LXA4 biosynthesis.

Regulation of inflammation in cancer by eicosanoids.

Inflammation in the tumor microenvironment is now recognized as one of the hallmarks of cancer. Endogenously produced lipid autacoids, locally acting small molecule lipid mediators, play a central role in inflammation and tissue homeostasis, and have recently been implicated in cancer. A well-studied group of autacoid mediators that are the products of arachidonic acid metabolism include: the prostaglandins, leukotrienes, lipoxins and cytochrome P450 (CYP) derived bioactive products. These lipid mediators are collectively referred to as eicosanoids and are generated by distinct enzymatic systems initiated by cyclooxygenases (COX 1 and 2), lipoxygenases (5-LOX, 12-LOX, 15-LOXa, 15-LOXb), and cytochrome P450s, respectively. These pathways are the target of approved drugs for the treatment of inflammation, pain, asthma, allergies, and cardiovascular disorders. Beyond their potent anti-inflammatory and anti-cancer effects, non-steroidal anti-inflammatory drugs (NSAIDs) and COX-2 specific inhibitors have been evaluated in both preclinical tumor models and clinical trials. Eicosanoid biosynthesis and actions can also be directly influenced by nutrients in the diet, as evidenced by the emerging role of omega-3 fatty acids in cancer prevention and treatment. Most research dedicated to using eicosanoids to inhibit tumor-associated inflammation has focused on the COX and LOX pathways. Novel experimental approaches that demonstrate the anti-tumor effects of inhibiting cancer-associated inflammation currently include: eicosanoid receptor antagonism, overexpression of eicosanoid metabolizing enzymes, and the use of endogenous anti-inflammatory lipid mediators. Here we review the actions of eicosanoids on inflammation in the context of tumorigenesis. Eicosanoids may represent a missing link between inflammation and cancer and thus could serve as therapeutic target(s) for inhibiting tumor growth.

Diterpenos en infl amación: las Labiadas como paradigma / Diterpenes in inflammation: Labiatae as paradigm

Esta revisión trata esencialmente sobre los diterpenos antiinflamatorios procedentes de especies de Labiadas. Se estudian las publicaciones posteriores a 2002 referentes a los cuatro tipos estructurales más importantes en esa familia: labdano, abietano, pimarano y kaurano. Además se incluyen algunas moléculas interesantes obtenidas de especies de diferente origen taxonómico. De entre los mecanismos implicados destaca la inhibición del metabolismo del ácido araquidónico a través de ciclooxigenasas y lipoxigenasas, así como el freno a la producción de NO o citocinas. Adicionalmente se ha descrito para algunos principios el aumento de la expresión de hemo-oxigenasa 1. Algunos de los géneros botánicos mejor representados son Lavandula, Isodon, Rosmarinus y Sideritis (AU)

This review is devoted to the antiinflammatory diterpenoids obtained from species of Labiatae. Basically, we study the post-2002 publications concerning the four major structural types in the family: labdane, abietane, pimarane and kaurane. Certain interesting diterpenes derived from plants of different taxonomic origin are also reported. Among the mechanisms involved in the pharmacological effect, we should highlight the inhibition of arachidonic acid metabolism through cyclo-oxygenases and lipoxygenases, and the decrease in the production of NO or cytokines. Additionally, some principles are described as enhancers of the expression of heme oxygenase 1. Some of the botanical genera best represented are Lavandula, Isodon, Rosmarinus or Sideritis (AU)

Long-chain polyunsaturated fat supplementation in children with low docosahexaenoic acid intakes alters immune phenotypes compared with placebo.

OBJECTIVES: The objectives of this study were to assess the effects of long-term supplementation with arachidonic acid (AA; 20:4n-6) and docosahexaenoic acid (DHA; 22:6n-3) on cell phenotypes and cytokine production in children. PATIENTS AND METHODS: This randomized, double-blind, placebo-controlled trial provided children, (ages 5-7 years; n = 37) who had low intakes of DHA, with a dietary supplement containing AA (20-30 mg daily) and DHA (14-21 mg daily) or a placebo supplement for 7 months. After the supplementation period, a series of stimulants (pokeweed mitogen, phytohemagluttinin, lipopolysaccharide, beta-lactoglobulin, and ibuprofen) was used to stimulate peripheral blood mononuclear cells ex vivo. Antigen expression on T cells (CD25 and CD80), B cells, and macrophages (CD54), as well as cytokine production (interleukin [IL]-4, IL-10, tumor necrosis factor, IL-2, IL-6, and interferon-gamma), were measured using flow cytometry, monoclonal antibodies, and cytometric bead array, respectively. RESULTS: Mononuclear cells from children provided long-chain polyunsaturated fatty acids (LCPUFAs) had fewer CD8+ cells expressing CD25 and CD80 compared with placebo after exposure to each mitogen. The LCPUFA group also exhibited lower proportions of CD14+ cells after stimulation with beta-lactoglobulin and ibuprofen. The proportion of CD54+ cells was 2-fold higher for the LCPUFA group compared with placebo after exposure to ibuprofen and beta-lactoglobulin (P < 0.05). Each of these immune effects related to the amount of AA and/or DHA in the plasma and erythrocyte phospholipids. CONCLUSIONS: Alterations in cell phenotypes were evident when children were supplemented with AA and DHA. The results of this study have important implications for immune development and sensitivity to antigens in children.

Polyunsaturated fatty acids, inflammation, and immunity.

The fatty acid composition of inflammatory and immune cells is sensitive to change according to the fatty acid composition of the diet. In particular, the proportion of different types of polyunsaturated fatty acids (PUFA) in these cells is readily changed, and this provides a link between dietary PUFA intake, inflammation, and immunity. The n-6 PUFA arachidonic acid (AA) is the precursor of prostaglandins, leukotrienes, and related compounds, which have important roles in inflammation and in the regulation of immunity. Fish oil contains the n-3 PUFA eicosapentaenoic acid (EPA). Feeding fish oil results in partial replacement of AA in cell membranes by EPA. This leads to decreased production of AA-derived mediators. In addition, EPA is a substrate for cyclooxygenase and lipoxygenase and gives rise to mediators that often have different biological actions or potencies than those formed from AA. Animal studies have shown that dietary fish oil results in altered lymphocyte function and in suppressed production of proinflammatory cytokines by macrophages. Supplementation of the diet of healthy human volunteers with fish oil-derived n-3 PUFA results in decreased monocyte and neutrophil chemotaxis and decreased production of proinflammatory cytokines. Fish oil feeding has been shown to ameliorate the symptoms of some animal models of autoimmune disease. Clinical studies have reported that fish oil supplementation has beneficial effects in rheumatoid arthritis, inflammatory bowel disease, and among some asthmatics, supporting the idea that the n-3 PUFA in fish oil are anti-inflammatory and immunomodulatory.