Macrophage Activation by Heparanase Is Mediated by TLR-2 and TLR-4 and Associates With Plaque Progression

Abstract

Objective Factors and mechanisms that activate macrophages in atherosclerotic plaques are incompletely understood. We examined the capacity of heparanase to activate macrophages. Results/Methods Highly purified heparanase was added to mouse peritoneal macrophages (MPM) and macrophage-like J774 cells and the levels of TNFα, MMP-9, IL-1, and MCP-1 were evaluated by ELISA. Gene expression was determined by RT-PCR. Cells collected from Toll like receptor (TLR)-2 and -4 knockout mice (KO) were evaluated similarly. Heparanase levels in the plasma of patients with acute myocardial infarction (MI), stable angina (SA), and healthy subjects were determined by ELISA. Immunohistochemistry was applied to detect the expression of heparanase in control specimens and specimens of patients with SA or acute MI. Addition or over expression of heparanase variants resulted in marked increase in TNFα, MMP-9, IL-1 and MCP-1 levels. MPM harvested from TLR-2 or TLR-4 knockout mice were not activated by heparanase. Plasma heparanase level was higher in patients with acute MI, compared to patients with SA and healthy subjects. Pathologic coronary specimens obtained from vulnerable plaques showed increased heparanase staining compared to specimens of stable plaque and controls. Conclusion Heparanase activates macrophages, resulting in marked induction of cytokine expression associated with plaque progression towards vulnerability.

Reducing Macrophage Proteoglycan Sulfation Increases Atherosclerosis and Obesity through Enhanced Type I Interferon Signaling

“…It is conceivable that Sulfs or other HSPG modifying enzymes, such as matrix metalloproteases and heparanase, a heparan-degrading enzyme, might modulate the bioavailability of IFN-β in the macrophage microenvironment in a similar way. While we did no observe differences in heparanase expression in macrophages, increased heparanase expression has been linked to activation of innate immune cells, expression of inflammatory markers, such as CCL5, CCL2 and TNF-α, and plaque vulnerability (Blich et al, 2013; Osterholm et al, 2013). …”

Loss of Syndecan-1 Induces a Pro-inflammatory Phenotype in Endothelial Cells with a Dysregulated Response to Atheroprotective Flow

“…We also found increased heparanase expression in severe atherosclerotic plaques and in arterial segments of the coronary vessels with low shear stress in a diabetic, hyperlipidemic porcine model of atherosclerosis (27). This finding has recently been corroborated in atherosclerotic plaques from human patients (55). Another study has also identified heparanase to be key in controlling the inflammatory response in sepsis through degradation of the glycocalyx (56).…”

Microglial Heparan Sulfate Proteoglycans Facilitate the Cluster-of-Differentiation 14 (CD14)/Toll-like Receptor 4 (TLR4)-Dependent Inflammatory Response

“…Importantly, this effect was dependent on catalytic activity of the enzyme, and Lerner et al (48) proposed that heparanase relieves a HS-mediated inhibition of LPS-induced TLR4 signaling, supporting previous work by Brunn et al (49). In accord with these findings Blich et al reported loss of the pro-inflammatory activity of recombinant heparanase in peritoneal macrophages isolated from TLR2 and TLR4 knock-out mice (50). In a related context HS has also been considered an endogenous TLR4 agonist (51).…”