prostaglandin-a2 and Inflammation

The role of prostaglandin A2 (PGA2) in modulation of vascular endothelial function is unknown. We investigated effects of PGA2 on pulmonary endothelial cell (EC) permeability and inflammatory activation and identified a receptor mediating these effects. PGA2 enhanced the EC barrier and protected against barrier dysfunction caused by vasoactive peptide thrombin and proinflammatory bacterial wall lipopolysaccharide (LPS). Receptor screening using pharmacological and molecular inhibitory approaches identified EP4 as a novel PGA2 receptor. EP4 mediated barrier-protective effects of PGA2 by activating Rap1/Rac1 GTPase and protein kinase A targets at cell adhesions and cytoskeleton: VE-cadherin, p120-catenin, ZO-1, cortactin, and VASP. PGA2 also suppressed LPS-induced inflammatory signaling by inhibiting the NFκB pathway and expression of EC adhesion molecules ICAM1 and VCAM1. These effects were abolished by pharmacological or molecular inhibition of EP4. In vivo, PGA2 was protective in two distinct models of acute lung injury (ALI): LPS-induced inflammatory injury and two-hit ALI caused by suboptimal mechanical ventilation and injection of thrombin receptor-activating peptide. These protective effects were abolished in mice with endothelial-specific EP4 knockout. The results suggest a novel role for the PGA2-EP4 axis in vascular EC protection that is critical for improvement of pathological states associated with increased vascular leakage and inflammation.

Topics: Animals; Antigens, CD; Cadherins; Capillary Permeability; Cell Adhesion; Cell Line; Cell Membrane Permeability; Cyclic AMP-Dependent Protein Kinases; Endothelial Cells; Endothelium, Vascular; Guanine Nucleotide Exchange Factors; Humans; Inflammation; Intercellular Adhesion Molecule-1; Lipopolysaccharides; Lung; Mice; NF-kappa B; Permeability; Prostaglandins A; Receptors, Prostaglandin E, EP4 Subtype; Signal Transduction

Dendritic cells (DC) are professional antigen-presenting cells playing a pivotal role in the induction of immunological responses. There is evidence that DC survival during ongoing immune responses is finite. However, little is known about the mechanisms regulating apoptosis in these cells. Here, we have investigated the effects of the anti-inflammatory cyclopentenone prostaglandins on human monocyte-derived DC.. Phenotype of DC was determined by flow cytometry and their allostimulatory potential in mixed leukocyte reaction. Induction of apoptosis in DC was monitored by staining with annexin-V-FITC and propidium iodide, propidium iodide staining of cell nuclei, and fluorimetric assay of caspase activity. Induction of maturation in DC was obtained by stimulation with TNF-alpha, LPS, IFN-gamma, CD40-ligand, or different combinations of these stimuli. PPAR-gamma expression in DC was determined by RT-PCR.. Exposure of immature DC to cyclopentenone prostaglandins blunted their allostimulatory capacity and skewed their phenotype by downregulating CD1a and costimulatory molecules. These effects were due to activation of caspases and induction of apoptotic cell death in DC by cyclopentenone prostaglandins. Mature DC showed enhanced susceptibility to apoptosis via cyclopentenone prostaglandins as compared with immature DC. Although DC express PPAR-gamma, the corresponding receptor for some of these metabolites, PPAR-gamma activation by a synthetic high-affinity agonist failed to impair DC viability.. Cyclopentenone prostaglandins induce apoptosis of human DC by a PPAR-gamma-independent mechanism. Since these compounds are released during an inflammatory event and show anti-inflammatory properties, they may contribute to the downregulation of DC function through apoptotic cell death.

Topics: Amino Acid Chloromethyl Ketones; Antigens, CD1; Apoptosis; Caspases; CD40 Ligand; Cell Differentiation; Cells, Cultured; Cyclooxygenase 2; Cysteine Proteinase Inhibitors; Dendritic Cells; Dinoprostone; Drug Resistance; Enzyme Activation; Enzyme Inhibitors; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Inflammation; Interferon-gamma; Interleukin-4; Isoenzymes; Lipopolysaccharides; Membrane Proteins; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Prostaglandins A; Receptors, Cytoplasmic and Nuclear; T-Lymphocytes; Transcription Factors; Tumor Escape; Tumor Necrosis Factor-alpha