title: Interleukin-1β inhibits synthesis of 5-lipooxygenase in lipopolysaccharide-stimulated equine whole blood.
abstract: Interleukin-1β (IL-1β) is a pro-inflammatory cytokine. It induces the synthesis of prostaglandin E2 (PGE2) catalyzed by cyclooxygenase (COX) and microsomal prostaglandin E synthase (m-PGES). Besides its pro-inflammatory properties, PGE2 also exhibits anti-inflammatory properties by inhibiting synthesis of 5-lipooxygenase (5-LO) products which are in themselves, pro-inflammatory mediators. Thus, inhibition of 5-LO products is beneficial in regulating immune-responses and pro-inflammatory processes. To investigate the hypothesis that IL-1β is responsible for the increase in the synthesis of PGE2 and in the reduction of 5-LO products, equine whole blood (EWB) was treated with lipopolysaccharide (LPS). In vitro treatment of EWB with LPS resulted in increased expression of IL-1β while expression of 5-LO was suppressed. Quantification of eicosanoids using liquid-chromatography-mass spectrometry/multiple reaction monitoring (LC-MS/MRM) showed increased concentrations of prostaglandins and decreased 5-LO products in LPS-treated EWB. Pretreatment of EWB with IL-1β followed by calcium ionophore A23187 (CI) reduced synthesis of 5-LO products. However, pretreatment of EWB with COX-2 inhibitor (NS-398) or m-PGES-1 inhibitor (CAY 10526) and IL-1β followed with CI resulted in a significant (p<0.0001) increase in 5-LO products. Pretreatment of EWB with phospholipase C inhibitor (U73122) followed with LPS reduced PGE2 production but increased 5-LO products. The result of this study indicated that increased PGE2 production led to reduction in 5-LO products in LPS-treated EWB via IL-1β. However, other pathways, cytokines and mediators may be involved in inhibiting 5-LO products but the present study did not include those other potential pathways. Inhibition of 5-LO products by PGE2 in EWB may regulate the initiation and pathogenesis of inflammatory responses in the horse.
authors: University of Pennsylvania School of Veterinary Medicine, Department of Clinical Studies, New Bolton Center Campus, 382 West Street Road, Kennett Square, PA 19348, USA.
authors: Dipti
authors: D
authors: Mangal
authors: University of Pennsylvania School of Veterinary Medicine, Department of Clinical Studies, New Bolton Center Campus, 382 West Street Road, Kennett Square, PA 19348, USA; PA Equine Toxicology & Research Center, West Chester University, Department of Chemistry, 220 East Rosedale Avenue, West Chester, PA 19382, USA. Electronic address: ubohcorn@vet.upenn.edu.
authors: Cornelius E
authors: CE
authors: Uboh
authors: University of Pennsylvania School of Veterinary Medicine, Department of Clinical Studies, New Bolton Center Campus, 382 West Street Road, Kennett Square, PA 19348, USA.
authors: Zibin
authors: Z
authors: Jiang
authors: University of Pennsylvania School of Veterinary Medicine, Department of Clinical Studies, New Bolton Center Campus, 382 West Street Road, Kennett Square, PA 19348, USA.
authors: Lawrence R
authors: LR
authors: Soma
mesh_terms: D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000096:biosynthesis* / Q000235:genetics; D061207:Calcium Ionophores / Q000494:pharmacology; D015777:Eicosanoids / Q000096:biosynthesis / Q000097:blood; D004794:Enzyme Repression; D004963:Estrenes / Q000494:pharmacology; D006736:Horses; D053583:Interleukin-1beta / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
chemical_list: D061207:Calcium Ionophores; D015777:Eicosanoids; D004963:Estrenes; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D001094:Arachidonate 5-Lipoxygenase; D010738:Type C Phospholipases
keywords: 5-Lipooxygenase; Equine whole blood; Interleukin-1β; LC–MS/MRM; Lipopolysaccharide; Prostaglandin E(2)