Inflammation is associated with the pathogenesis of coronary atherosclerosis, although the mechanisms remain unclear. We investigated whether cytokine secretion by innate immune responses could contribute to the production of proarteriosclerotic Th1-type cytokines in human coronary atherosclerosis. Cytokines were measured by ELISA in the plasma of patients with coronary atherosclerosis undergoing cardiac catheterization. IL-18 was detected in all subjects, whereas a subset of patients demonstrated a coordinated induction of other IFN-γ-related cytokines. Specifically, elevated plasma levels of IL-12 correlated with that of IFN-γ and IFN-γ-inducible chemokines, defining an IFN-γ axis that was activated independently of IL-6 or C-reactive protein. Systemic inflammation triggered by cardiopulmonary bypass increased plasma levels of the IFN-γ axis, but not that of IL-18. Activation of the IFN-γ axis was not associated with acute coronary syndromes, but portended increased morbidity and mortality after 1-year follow-up. IL-12 and IL-18, but not other monokines, elicited secretion of IFN-γ and IFN-γ-inducible chemokines in human atherosclerotic coronary arteries maintained in organ culture. T cells were the principal source of IFN-γ in response to IL-12/IL-18 within the arterial wall. This inflammatory response did not require, but was synergistic with and primed for TCR signals. IL-12/IL-18-stimulated T cells displayed a cytokine-producing, nonproliferating, and noncytolytic phenotype, consistent with previous descriptions of lymphocytes in stable plaques. In contrast to cognate stimuli, IL-12/IL-18-dependent IFN-γ secretion was prevented by a p38 MAPK inhibitor and not by cyclosporine. In conclusion, circulating IL-12 may provide a mechanistic link between inflammation and Th1-type cytokine production in coronary atherosclerosis.
Despite a higher level of comorbidity, elderly, ambulatory patients with chronic atrial fibrillation demonstrate similar exercise tolerance and report similar quality of life to a group of age-matched control patients in sinus rhythm. There is a cohort of patients in chronic atrial fibrillation in whom a strategy of rate control and anticoagulation may be appropriate.
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