title: Low molecular weight hyaluronan activates cytosolic phospholipase A2α and eicosanoid production in monocytes and macrophages.
abstract: Hyaluronan (HA) is the major glycosaminoglycan in the extracellular matrix. During inflammation, there is an increased breakdown of HA, resulting in the accumulation of low molecular weight (LMW) HA and activation of monocytes and macrophages. Eicosanoids, derived from the cytosolic phospholipase A2 group IVA (cPLA2α) activation, are potent lipid mediators also attributed to acute and chronic inflammation. The aim of this study was to determine the effect of LMW HA on cPLA2α activation, arachidonic acid (AA) release, and subsequent eicosanoid production and to examine the receptors and downstream mechanisms involved in these processes in monocytes and differently polarized macrophages. LMW HA was a potent stimulant of AA release in a time- and dose-dependent manner, induced cPLA2α, ERK1/2, p38, and JNK phosphorylation, as well as activated COX2 expression and prostaglandin (PG) E2 production in primary human monocytes, murine RAW 264.7, and wild-type bone marrow-derived macrophages. Specific cPLA2α inhibitor blocked HA-induced AA release and PGE2 production in all of these cells. Using CD44, TLR4, TLR2, MYD88, RHAMM or STAB2 siRNA-transfected macrophages and monocytes, we found that AA release, cPLA2α, ERK1/2, p38, and JNK phosphorylation, COX2 expression, and PGE2 production were activated by LMW HA through a TLR4/MYD88 pathway. Likewise, PGE2 production and COX2 expression were blocked in Tlr4(-/-) and Myd88(-/-) mice, but not in Cd44(-/-) mice, after LMW HA stimulation. Moreover, we demonstrated that LMW HA activated the M1 macrophage phenotype with the unique cPLA2α/COX2(high) and COX1/ALOX15/ALOX5/LTA4H(low) gene and PGE2/PGD2/15-HETE(high) and LXA4(low) eicosanoid profile. These findings reveal a novel link between HA-mediated inflammation and lipid metabolism.
authors.affiliation: From the Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892 and.
authors.forename: Milena
authors.initials: M
authors.lastname: Sokolowska
authors.forename: Li-Yuan
authors.initials: LY
authors.lastname: Chen
authors.forename: Michael
authors.initials: M
authors.lastname: Eberlein
authors.forename: Asuncion
authors.initials: A
authors.lastname: Martinez-Anton
authors.forename: Yueqin
authors.initials: Y
authors.lastname: Liu
authors.forename: Sara
authors.initials: S
authors.lastname: Alsaaty
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Qi
authors.forename: Carolea
authors.initials: C
authors.lastname: Logun
authors.forename: Maureen
authors.initials: M
authors.lastname: Horton
authors.forename: James H
authors.initials: JH
authors.lastname: Shelhamer
mesh_terms: D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000235:genetics; D015777:Eicosanoids / Q000096:biosynthesis* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D054513:Group IV Phospholipases A2 / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D006820:Hyaluronic Acid / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D050356:Lipid Metabolism / Q000502:physiology*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
chemical_list: D015777:Eicosanoids; C507779:MYD88 protein, human; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C516390:Pla2g4a protein, mouse; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D006820:Hyaluronic Acid; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D054513:Group IV Phospholipases A2; C516389:PLA2G4A protein, human
keywords: Cyclooxygenase (COX) Pathway; Eicosanoid; Extracellular Matrix; Hyaluronan; Inflammation; Macrophage Polarization; Monocytes; Prostaglandin; Toll-like Receptors (TLR); cPLA2