Monomeric C-Reactive Protein Binds to Circulating Microparticles and Deposits into Atherosclerotic Plaques in Patients with Stable Coronary Artery Disease

Objectives: quantitative evaluation of monomeric C-reactive protein (mCRP) bound to circulating microparticles in blood of patients with stable coronary artery disease (CAD) and detection of mCRP deposits in autopsy samples of coronary atherosclerotic plaques.
Materials and methods: Blood plasma of 7 patients with CAD and 5 healthy controls was screened by flow cytometry for blood-bourne annexin V-positive microparticles. mCRP was targeted with monoclonal antibody to mCRP (MOH CRP 328, IMTEK Limited, Russia) and native CRP (MOH CRP 372, IMTEK Limited, Russia). Count adjustment between samples for precise quantification of mCRP-bearing microparticles has been done by adjusting the sample volume to the known count of pre-added FITC-conjugated latex microparticles, 1 µm in diameter. Deposition of mCRP in atherosclerotic plaques was studied on autopsy samples of coronary arteries of 7 persons, died of cardiovascular events. Staining was performed by monoclonal antibody to mCRP and native CRP (nCRP) and polyclonal antibody to nCRP (POH CRP, IMTEK Limited, Russia). Control staining was performed by nonspecific mouse IgG.
Results: mCRP-bearing microparticles count was significantly higher in patients with CAD (9645+3573 particles per µl, n=7), than in healthy individuals (1365+250 particles per µl, n=5). mCRP deposits were detectable in all autopsy samples of coronary atherosclerotic plaques with predominant deposition in unstable plaques. We performed control tests with nCRP-specific antibodies to exclude cross-reactivity results in all experiments.
Conclusions: Elevated counts of circulating mCRP-bearing microparticles in patients with CAD and mCRP deposition into atherosclerotic plaques may suggest an important role of mCRP in development of coronary artery disease.
Sources of funding: This work was supported by the grant of the Russian Science Foundation (project #16-15-10098). The authors report no conflict of interests.