Native LDL potentiate TNFα and IL-8 production by human mononuclear cells

Abstract

Native LDL (nLDL) increases expression of adhesion molecules on endothelial cells through induction of Ca2+ mobilization. Ca2+ mobilization is also involved in the induction of proinflammatory cytokines, important mediators involved in atherogenesis. The aim of the study was to evaluate the capacity of nLDL to affect spontaneous and lipopolysaccharide (LPS)-stimulated cytokine production. Preincubation of human peripheral blood mononuclear cells (PBMC) with nLDL for 24 h did not influence spontaneous production of tumor necrosis factor α (TNFα) or interleukin-8 (IL-8), but significantly potentiated LPS-induced production of these cytokines. nLDL preincubation of PBMC did not increase the expression of the LPS receptors Toll-like receptor-4, CD14, or CD11c/CD18. Potentiation of cytokine production by nLDL was mediated through induction of Ca2+ mobilization, because: a) nLDL induced a sustained pattern of repetitive Ca2+ transients in human PBMC; b) the Ca2+ chelator fura 2-acetoxymethyl ester, 1,2-bis(2-aminophenoxy)ethane-N,N, N′,N′-tetraacetic acid, an intracellular Ca2+ chelator, inhibited the potentiating effect of nLDL on LPS-induced cytokine synthesis; c) induction of Ca2+ mobilization by thapsigargin potentiated LPS-induced cytokine production. nLDL are able to potentiate LPS-induced production of cytokines by human PBMC, and this effect is probably mediated through induction of Ca2+ mobilization. This may represent an important pathogenetic mechanism in atherogenesis induced by hyperlipoproteinemia.