oxLDL downregulates the dendritic cell homing factors CCR7 and CCL21.

INTRODUCTION: Dendritic cells (DCs) and oxLDL play an important role in the atherosclerotic process with DCs accumulating in the plaques during plaque progression. Our aim was to investigate the role of oxLDL in the modulation of the DC homing-receptor CCR7 and endothelial-ligand CCL21. METHODS AND RESULTS: The expression of the DC homing-receptor CCR7 and its endothelial-ligand CCL21 was examined on atherosclerotic carotic plaques of 47 patients via qRT-PCR and immunofluorescence. In vitro, we studied the expression of CCR7 on DCs and CCL21 on human microvascular endothelial cells (HMECs) in response to oxLDL. CCL21- and CCR7-mRNA levels were significantly downregulated in atherosclerotic plaques versus non-atherosclerotic controls [90% for CCL21 and 81% for CCR7 (P < 0.01)]. In vitro, oxLDL reduced CCR7 mRNA levels on DCs by 30% and protein levels by 46%. Furthermore, mRNA expression of CCL21 was significantly reduced by 50% (P < 0.05) and protein expression by 24% in HMECs by oxLDL (P < 0.05). CONCLUSIONS: The accumulation of DCs in atherosclerotic plaques appears to be related to a downregulation of chemokines and their ligands, which are known to regulate DC migration. oxLDL induces an in vitro downregulation of CCR7 and CCL21, which may play a role in the reduction of DC migration from the plaques.

Immunomodulatory effects of aerobic training in obesity.

INTRODUCTION: Physical inactivity and obesity are independent risk factors for atherosclerosis. We analyzed the immunomodulatory capacity of 10-week intensified exercise training (ET) in obese and lean athletes. Markers of the innate immune response were investigated in obese (ONE: ET≤40 km/week) and lean athletes (LNE: ET≤40 km/week and LE: ET≥55 km/week). METHODS: Circulating dendritic cells (DC) were analyzed by flow-cytometry for BDCA-1/-2-expression. TLR-2/-4/-7 and MyD88 were analyzed by RT-PCR and Western blot. Circulating oxLDL levels were analyzed by ELISA. RESULTS: BDCA-1 expression at baseline was lower in ONE compared to both other groups (ONE 0.15%; LNE 0.27%; LE 0.33%; P < .05), but significantly increased in ONE after training (+50%; P < .05). In contrast, BDCA-2 expression at baseline was higher in ONE (ONE 0.25%; LNE 0.11%; LE 0.09%; P < .05) and decreased in ONE after the 10-week training period (-27%; P < .05). Gene activations of TLR-4 and TLR-7 with corresponding protein increase were found for all three groups (P < .01/P < .05) compared to pre training. A reduction of oxLDL levels was seen in ONE (-61%; P < .05). CONCLUSIONS: Intensified exercise induces an increase of BDCA-1+ DCs and TLR-4/-7 in obese athletes. We hereby describe new immune modulatory effects, which-through regular aerobic exercise-modulate innate immunity and pro-inflammatory cytokines in obesity.

Immunoregulatory effects of the flavonol quercetin in vitro and in vivo.

PURPOSE: Atherosclerosis is known to be an inflammatory disease. Dendritic cells (DCs) are essential for the regulation of the immune system. Up to 10% of the cells in atherosclerotic plaques are DCs. The cardiovascular protective effects of flavonoids (tea, wine) may be mediated by anti-inflammatory mechanisms that affect DC regulation. We aimed to characterize the impact of the flavonol quercetin on DC activity and differentiation in vitro and in vivo. METHODS: For the in vitro experiments, we used murine DCs and endothelial cells to study adhesion properties. For all other experiments (DC phagocytosis capacity, DC maturation, DC differentiation (BDCA-1/-2) and NF-kB-activation), human monocyte-derived DCs were used. The cells were incubated with quercetin (10 µmol/L) ± oxLDL (10 µg/mL) between 24 and 48 h. For in vivo experiments, eight healthy male volunteers took 500 mg of quercetin twice daily over 4 weeks, five healthy male volunteers served as control. Before and after intake, blood samples were collected. Peripheral blood leukocytes were isolated (analyses of DC differentiation), and plasma was immediately frozen. RESULTS: Quercetin reduced DC adhesion (-42%; p < 0.05) and expression of CD11a (-21%; p < 0.05). OxLDL-induced DC differentiation was partially inhibited by quercetin (BDCA-1-29%; BDCA-2-33%; p < 0.05). These effects were achieved by compensation of oxLDL-induced up-regulation of NF-kB by quercetin. The 4-week treatment with quercetin resulted in relevant plasma levels (2.47 µmol/L) and reduced BDCA-2 + DCs in the peripheral blood by 42% (p < 0.05) as well as systemic levels of the NO-synthase inhibitor asymmetric dimethylarginine (-31%, p < 0.05). CONCLUSION: In vitro, quercetin reduced DC adhesion and oxLDL-induced DC differentiation. In vivo, quercetin reduced circulating plasmacytoid DCs and systemic ADMA-levels. The immunoregulatory effects of quercetin may contribute to the anti-atherosclerotic potential of flavonols.

oxLDL uptake by dendritic cells induces upregulation of scavenger-receptors, maturation and differentiation.

BACKGROUND: Several studies have proposed a pathogenic role for oxidized LDL (oxLDL) in atherosclerosis. We tested the hypothesis whether oxLDL modulates dendritic cells (DCs), since these important antigen-presenting cells have been implicated in atherogenesis. We investigated the uptake of oxLDL by DCs, the scavenger-receptors involved and the resulting changes in phenotype and cytokine-spectra. In addition, we analyzed the impact of oxLDL on the nuclear transcription factor-kappa B (NF-kappaB)-pathway. METHODS AND RESULTS: oxLDL (10microg/ml) increased the expression of the scavenger-receptors CD205 and CD36 and decreased the mannose-receptor expression. The lectin-like oxLDL-receptor (LOX-1)-expression was not affected. The endocytotic capacity of dextran and lucifer-yellow was moderately decreased by oxLDL. Blockage of the scavenger-receptors CD36, LOX-1 and CD205 reduced oxLDL uptake. Furthermore, oxLDL induced DC-maturation and triggered differentiation of DCs in myeloid and plasmacytoid DCs. oxLDL decreased IL-10 secretion and increased IL-6 release. Finally, oxLDL induced an activation of the NF-kappaB-pathway. Inhibition of IkappaBalpha-phosphorylation diminished the oxLDL-induced DC-maturation and -differentiation. CONCLUSION: oxLDL uptake by DCs is mediated by the scavenger-receptors LOX-1, CD36, and CD205. oxLDL induces a proinflammatory cytokine profile in human DCs leading to DC-maturation and -differentiation which can, in part, be explained by an activation of the NF-kappaB-pathway. These results support the hypothesis that vascular inflammation may be aggravated by oxLDL induced DC-activation.