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: Milena Sokolowska, Li-Yuan Chen, Michael Eberlein, Asuncion Martinez-Anton, Yueqin Liu, Sara Alsaaty, Hai-Yan Qi, Carolea Logun, Maureen Horton, James H Shelhamer
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 7 Pg. 4470-88 (Feb 14 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 24366870 (Publication Type: Clinical Trial, Journal Article, Research Support, N.I.H., Intramural)

Chemical References

• Eicosanoids
• MYD88 protein, human
• Myd88 protein, mouse
• Myeloid Differentiation Factor 88
• Pla2g4a protein, mouse
• TLR4 protein, human
• Tlr4 protein, mouse
• Toll-Like Receptor 4
• Hyaluronic Acid
• Ptgs2 protein, mouse
• Cyclooxygenase 2
• PTGS2 protein, human
• Extracellular Signal-Regulated MAP Kinases
• Group IV Phospholipases A2
• PLA2G4A protein, human

Topics

• Animals
• Cell Line
• Cyclooxygenase 2 (biosynthesis, genetics)
• Eicosanoids (biosynthesis, genetics)
• Enzyme Activation (drug effects)
• Extracellular Signal-Regulated MAP Kinases (genetics, metabolism)
• Female
• Gene Expression Regulation, Enzymologic (drug effects, genetics)
• Group IV Phospholipases A2 (biosynthesis, genetics)
• Humans
• Hyaluronic Acid (genetics, metabolism, pharmacology)
• Inflammation (genetics, metabolism)
• Lipid Metabolism (physiology)
• Macrophages (cytology, metabolism)
• Male
• Mice
• Mice, Knockout
• Monocytes (cytology, metabolism)
• Myeloid Differentiation Factor 88 (genetics, metabolism)
• Toll-Like Receptor 4 (genetics, metabolism)