Low Molecular Weight Hyaluronan Activates Cytosolic Phospholipase A2α and Eicosanoid Production in Monocytes and Macrophages

• Published in: The Journal of biological chemistry 2014-02, Vol.289 (7), p.4470-4488
• Main Authors: Sokolowska, Milena, Chen, Li-Yuan, Eberlein, Michael, Martinez-Anton, Asuncion, Liu, Yueqin, Alsaaty, Sara, Qi, Hai-Yan, Logun, Carolea, Horton, Maureen, Shelhamer, James H.
• Format: Article
• Language: English
• Subjects: Animals; Cell Line; cPLA2; Cyclooxygenase (COX) Pathway; Cyclooxygenase 2 - biosynthesis; Cyclooxygenase 2 - genetics; Eicosanoid; Eicosanoids - biosynthesis; Eicosanoids - genetics; Enzyme Activation - drug effects; Extracellular Matrix; Extracellular Signal-Regulated MAP Kinases - genetics; Extracellular Signal-Regulated MAP Kinases - metabolism; Female; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Enzymologic - genetics; Group IV Phospholipases A2 - biosynthesis; Group IV Phospholipases A2 - genetics; Humans; Hyaluronan; Hyaluronic Acid - genetics; Hyaluronic Acid - metabolism; Hyaluronic Acid - pharmacology; Inflammation; Inflammation - genetics; Inflammation - metabolism; Lipid Metabolism - physiology; Lipids; Macrophage Polarization; Macrophages - cytology; Macrophages - metabolism; Male; Mice; Mice, Knockout; Monocytes; Monocytes - cytology; Monocytes - metabolism; Myeloid Differentiation Factor 88 - genetics; Myeloid Differentiation Factor 88 - metabolism; Prostaglandin; Toll-Like Receptor 4 - genetics; Toll-Like Receptor 4 - metabolism; Toll-like Receptors (TLR)
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.515106

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/COX2high and COX1/ALOX15/ALOX5/LTA4Hlow gene and PGE2/PGD2/15-HETEhigh and LXA4low eicosanoid profile. These findings reveal a novel link between HA-mediated inflammation and lipid metabolism. Fragmented hyaluronan (a major extracellular matrix component) and eicosanoids (potent lipid mediators) are associated with chronic inflammatory diseases and cancer. Fragmented hyaluronan stimulates lipid mediator production in human monocytes and macrophages and influences macrophage differentiation toward a distinct activation pattern. These findings reveal a novel link between hyaluronan-mediated inflammation and lipid metabolism. This link may provide new targets for disease therapeutics.