The isoprostane 8-iso-PGF2alpha suppresses monocyte adhesion to human microvascular endothelial cells via two independent mechanisms.
Isoprostanes, produced in vivo by non-enzymatic free-radical-induced lipid peroxidation, are markers of oxidative stress. Elevated serum and urine levels of 8-iso-PGF2alpha have been reported in a variety of diseases, many of which are characterized by early perivascular inflammatory infiltrates. It has been suggested that, in addition to being markers of oxidative stress, isoprostanes may have pathogenic functions. In this study, we investigated the potential role of 8-iso-PGF2alpha in inflammation, focusing on its effects on adhesion of monocytes to microvascular endothelial cells, an early event in the inflammatory response. In monocyte adhesion assays, 8-iso-PGF2alpha (>10(-8) M) suppressed both basal and TNF-alpha-induced monocyte adhesion to quiescent or proliferating human dermal (HMEC) and rat renal microvascular endothelial cells. In contrast, 8-iso-PGF2alpha stimulated monocyte adhesion to human umbilical vein endothelial cells (HUVEC) as also reported by others. 8-Iso-PGF2alpha had no effect on the viability (Trypan Blue exclusion) of U937 monocytes or HMEC. 8-Iso-PGF2alpha also had no effect on HMEC surface expression of ICAM-1 or VCAM-1. Exposure of HMEC to 8-iso-PGF2alpha for 1-2 h was sufficient to reduce monocyte adhesion to the cell surface, and this effect was independent of de novo protein synthesis by HMEC. The effect of 8-iso-PGF2alpha was mimicked by a thromboxane receptor (TP) agonist (U46619) and blocked by a TP antagonist (SQ29548), indicating a TP-mediated process. Signal transduction pathway inhibitors (SB203580, curcumin, and PD98059) implicated p38 and JNK, but not ERK, in 8-iso-PGF2alpha-induced suppression of monocyte adhesion. In addition to a direct effect, conditioned medium (CM) transfer experiments suggest that 8-iso-PGF2alpha induces a secondary mediator, which also suppresses monocyte adhesion but via an alternative mechanism initiated between 3-4 h, which is TP-independent, requires new protein synthesis, and is primarily dependent on activation of p38. The data show that 8-iso-PGF2alpha can suppress the attachment of monocytes to HMECs via two independent pathways, indicating a potential anti-inflammatory effect of 8-iso-PGF2alpha in the microvasculature.
Kumar
Anila
A
Centre for Nephrology, Division of Medicine, Royal Free and University College Medical School, London, UK.
Kingdon
Edward
E
Norman
Jill
J
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002448:Cell Adhesion / Q000187:drug effects*; D002460:Cell Line; D017077:Culture Media, Conditioned; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000737:chemistry / Q000502:physiology*; D005231:Fatty Acids, Unsaturated; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D007249:Inflammation / Q000473:pathology; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007668:Kidney / Q000098:blood supply; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009000:Monocytes / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction; D012867:Skin / Q000098:blood supply; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells; D014471:Umbilical Veins; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D019086:Bridged Bicyclo Compounds, Heterocyclic; D017077:Culture Media, Conditioned; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D011500:Protein Synthesis Inhibitors; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; C075750:8-epi-prostaglandin F2alpha; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C045749:SQ 29548; D015237:Dinoprost; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases