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

Abstract

Myeloperoxidase aids in clearance of microbes by generation of peroxidase-mediated oxidants that kill leukocyte-engulfed pathogens. In this review, we will examine 1) strategies for in vitro evaluation of myeloperoxidase function and its inhibition, 2) ways to monitor generation of certain oxidant species during inflammation, and 3) how these methods can be used to approximate the total polymorphonuclear neutrophil chemotaxis following insult. Several optical imaging probes are designed to target reactive oxygen and nitrogen species during polymorphonuclear neutrophil inflammatory burst following injury. Here, we review the following 1) the broad effect of myeloperoxidase on normal physiology, 2) the difference between myeloperoxidase and other peroxidases, 3) the current optical probes available for use as surrogates for direct measures of myeloperoxidase-derived oxidants, and 4) the range of preclinical options for imaging myeloperoxidase accumulation at sites of inflammation in mice. We also stress the advantages and drawbacks of each of these methods, the pharmacokinetic considerations that may limit probe use to strictly cell cultures for some reactive oxygen and nitrogen species, rather than in vivo utility as indicators of myeloperoxidase function. Taken together, our review should shed light on the fundamental rational behind these techniques for measuring myeloperoxidase activity and polymorphonuclear neutrophil response after injury toward developing safe myeloperoxidase inhibitors as potential therapy for chronic obstructive pulmonary disease and rheumatoid arthritis.

Macrophage Apoptosis and Efferocytosis in the Pathogenesis of Atherosclerosis

“…Accumulation of oxidized LDL (oxLDL), formation of dysfunctional high-density lipoprotein (HDL) and increased inflammation caused by peroxidase-derived oxidants and reactive oxygen species (ROS) contribute to the formation of vulnerable plaques by enhancing macrophage apoptosis and defective efferocytosis, causing increased size of the necrotic core (NC), a key feature of vulnerable plaques. 3,4 Plaque rupture promotes thrombosis, blocking the blood flow in the artery and resulting in acute ischemic atherosclerotic cardiovascular events.…”

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.…”

Pharmacological Therapeutics Targeting RNA-Dependent RNA Polymerase, Proteinase and Spike Protein: From Mechanistic Studies to Clinical Trials for COVID-19

“…Recent studies demonstrate that excessive recruitment of neutrophils and formation of neutrophil extracellular traps results in acute lung injury of influenza pneumonitis [127]. In addition, neutrophil-derived myeloperoxidase (MPO) serves as a potent tissue damage factor and also contributes to influenza pneumonia in mice infected with influenza virus [128][129][130][131]. In addition, coronavirus infection is able to induce stress response, autophagy, apoptosis, and activate innate immunity [40].…”