The Effect of Inhibition of Interleukin-6 Activity on Vascular, Endothelial and Left Ventricular Function in Patients With Rheumatoid Arthritis

The inflammatory processes observed in patients with rheumatoid arthritis (RA) are strongly linked to enhanced interleukin-6 (IL-6) activity. Increased IL-6 activity causes myocardial cell damage and endothelial dysfunction. The adverse effects of IL-6 on myocardial and endothelial cells are mediated by an enhanced nitrooxidative stress and the promotion of apoptotic cardiomyocyte death through increased nitrooxidative stress and inflammation. Tocilizumab, a recombinant form of human IL-6 receptor antagonist, is commonly used for the treatment of RA. However it has not been defined whether inhibition of IL-6 activity by tocilizumab shows beneficial effects on endothelial, coronary, arterial and LV systolic and diastolic function in patients with RA.

For this purpose, we studied 60 patients with RA (American Rheumatism Association criteria). All the above subjects had an inadequate response to disease modifying antirheumatic drugs (DMARDs) and corticosteroids and were going to initiate treatment with IL-6 activity inhibitor (tocilizumab). All patients were on treatment with statins and cardioactive medications respectively, for the last 6 months.

All patients were randomized to receive a single injection of tocilizumab (150 mg s.c.), or other biological agent (TNFa inhibitor, abatacept, rituximab, IL-1Ra) or enhanced treatment with corticosteroid and non-biological agents.

Twenty asymptomatic subjects matched for age and sex as the RA patients and with a normal ECG, echocardiogram, and treadmill test were selected as healthy control subjects among subjects attending the cardiology outpatients' clinic.

At baseline in all RA subjects and controls as well as 3 months after the single injection of tocilizumab in RA subjects, we assessed the following parameters a)carotid-femoral pulse wave velocity (PWV), b) the LV dimensions,fractional shortening and wall motion score index (WMSI) c) the systolic (Sm), early diastolic (Em) and late diastolic (Am) myocardial velocities of the mitral annulus by using of tissue Doppler (TDI) as well as the ratio of E wave of the mitral inflow measured by pulsed wave Doppler to the mean Em as an index of LV diastolic filling pressures d) the LV longitudinal, circumferential and radial strain and strain rate, as well as Global Longitudinal strain and Torsion using speckle tracking echocardiography e) the coronary flow reserve (CFR)after adenosine infusion to assess coronary vasomotor function f) the flow-mediated endothelial-dependent dilation of the brachial artery (FMD) to assess peripheral endothelial function g) the diameters of aorta at systole and diastole to calculate the aortic strain as an index of local aortic properties, h) perfused boundary region (PBR) of the sublingual arterial microvessels (ranged from 5-25μm) using Sideview, Darkfield imaging (Microscan, Glycocheck). Increased PBR is considered an accurate index of reduced endothelial glucocalyx thickness because of a deeper red blood cells (RBC) penetration in the glucocalyx. At the same time periods, we measured in blood samples a) nitrotyrosine (NT), protein carbonyls (PC) and malondialdehyde (MDA) to assess oxidative stress, b) soluble Fas and Fas-ligand to assess apoptosis, and c) interleukin-6 and tumor necrosis factor-a to assess inflammation.