Atherogenic effects of TNF-α and IL-6 via up-regulation of scavenger receptors

Patients with chronic inflammatory disorders such as rheumatoid arthritis (RA) have a high risk of developing cardiovascular disease. We evaluated the effects of TNF-α and IL-6 on foam cell formation, a pivotal process in atherogenesis. Accumulation of intracellular oxidized LDL (oxLDL) was induced when THP-1/macrophages were stimulated with TNF-α or IL-6. TNF-α induced the expressions of scavenger receptors SR-A and LOX-1, and IL-6 induced SR-A expression. Inhibition of the NF-κB signaling markedly decreased TNF-α-induced foam cell formation and SR-A expression. Serum from RA patients, but not healthy subjects, induced foam cell formation, which was partially reversed by either IL-6 or TNF-α blockade in conjunction with inhibiting the induction of scavenger receptors. The present study clearly showed that in patients with chronic inflammation mediated by TNF-α and IL-6, these cytokines are directly implicated in atherosclerotic plaque formation.

► TNF-α and IL-6 each promoted foam cell formation, a pivotal process of oxLDL-mediated atherogenesis.
► αIL-6R Ab partially inhibited TNF-α-induced oxLDL accumulation.
► Serum from RA patients, but not serum of healthy subjects, induced foam cell formation.
► Foam cell formation induced by serum from RA serum was partially reverse by either αIL-6R Ab or TNF-α receptor (p75)-Fc.
► TNF-α, IL-6 and serum from RA patients each up-regulated the expression of SR-A, LOX-1 which uptake oxLDL.