Effects of a Novel Pharmacologic Inhibitor of Myeloperoxidase in a Mouse Atherosclerosis Model

Abstract

Inflammation and oxidative stress play fundamental roles in the pathogenesis of atherosclerosis. Myeloperoxidase has been extensively implicated as a key mediator of inflammatory and redox-dependent processes in atherosclerosis. However, the effect of synthetic myeloperoxidase inhibitors on atherosclerosis has been insufficiently studied. In this study, ApoE−/− mice were randomized to low- and high-dose INV-315 groups for 16 weeks on high-fat diet. INV-315 resulted in reduced plaque burden and improved endothelial function in response to acetylcholine. These effects occurred without adverse events or changes in body weight or blood pressure. INV-315 treatment resulted in a decrease in iNOS gene expression, superoxide production and nitrotyrosine content in the aorta. Circulating IL-6 and inflammatory CD11b+/Ly6Glow/7/4hi monocytes were significantly decreased in response to INV-315 treatment. Acute pretreatment with INV-315 blocked TNFα-mediated leukocyte adhesion in cremasteric venules and inhibited myeloperoxidase activity. Cholesterol efflux was significantly increased by high-dose INV-315 via ex-vivo reverse cholesterol transport assays. Our results suggest that myeloperoxidase inhibition may exert anti-atherosclerotic effects via inhibition of oxidative stress and enhancement of cholesterol efflux. These findings demonstrate a role for pharmacologic modulation of myeloperoxidase in atherosclerosis.

Methods for measuring myeloperoxidase activity toward assessing inhibitor efficacy in living systems

“…Therefore, MPO is considered a druggable target with small-molecule inhibitors already identified and more expected for limiting ROS/RNS production. In preclinical study, several MPO inhibitors have limited inflammation in diseases, including thioxanthine-2 in chronic obstructive pulmonary disease studies [15], PF-1355 in vasculitis and glomerulonephritis [24], and INV315 in atherosclerosis [25]. In this review, we will mainly discuss the recent, emerging tools for in vivo assessment of MPO as a target with the goal of monitoring disease progression, tracking PMN migration, and detecting inflammatory sites for preclinical or clinical applications.…”

N-acetyl lysyltyrosylcysteine amide inhibits myeloperoxidase, a novel tripeptide inhibitor

“…A signifi cant amount of effort has gone into designing and testing agents that block MPO activity. Recent reports show that 2-thioxanthine and INV-315 inhibit MPO in vivo ( 45,46 ). It is well-known that MPO oxidizes the phenol side chain of Tyr in small peptides ( 47,48 ) /ml) were resuspended in DPBS with glucose.…”

“…Likewise, when cholesterol-fed rabbits were treated with 4-aminobenzoic acid hydrazide, which is highly effective for inhibiting MPO activity in vitro, the treatments actually increased intimal hyperplasia by over 43% ( 69 ). Recent reports indicate that 2-thioxanthine and INV-315 may be effective for inhibiting MPO in vivo ( 45,46 ). In the case of KYC, a detoxifi cation mechanism was purposely incorporated into the inhibitor to prevent the secondary oxidation that may be induced by oxidation of the inhibitor itself by MPO.…”

Scavenging dicarbonyls with 5’-O-pentyl-pyridoxamine increases HDL net cholesterol efflux capacity and attenuates atherosclerosis and insulin resistance

“…Our studies show that reactive dicarbonyl scavenging reduced the IL-1β levels and decreased the number of inflammatory macrophages as evidenced by the reduced expression of MPO and CCR2 in Ldlr-/-mice( Figure 5 and Figure 6). Pharmacologic inhibition of MPO decreases atherosclerosis [45,46] and MPO promotes plaque instability by modifying extracellular matrix protein, inhibiting NO availability, and reducing endothelial glycocalyx thickness [47][48][49]. CCR2 deficiency also reduces atherosclerosis [50], which is consistent with CCR2 being required for Ly6C hi monocyte recruitment to atherosclerotic lesions.…”