Paola Di Meglio

Hydroxytyrosol, a phenolic compound from virgin olive oil, prevents macrophage activation

We investigated the effect of hydroxytyrosol (HT), a phenolic compound from virgin olive oil, on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in J774 murine macrophages stimulated with lipopolysaccharide (LPS). Incubation of cells with LPS caused an increase in iNOS and COX-2 mRNA and protein level as well as ROS generation, which was prevented by HT. In addition, HT blocked the activation of nuclear factor-κB (NF-κB), signal transducer and activator of transcription-1α (STAT-1α) and interferon regulatory factor-1 (IRF-1). These results, showing that HT down-regulates iNOS and COX-2 gene expression by preventing NF-κB, STAT-1α and IRF-1 activation mediated through LPS-induced ROS generation, suggest that it may represent a non-toxic agent for the control of pro-inflammatory genes.

Neutralization of Interleukin-18 Inhibits Neointimal Formation in a Rat Model of Vascular Injury

Background— Studies in humans and animal models suggest that interleukin-18 (IL-18) plays a crucial role in vascular pathologies. IL-18 is a predictor of cardiovascular death in angina and is involved in atherotic plaque destabilization. Higher IL-18 plasma levels also are associated with restenosis after coronary artery angioplasty performed in patients with acute myocardial infarction. We investigated the effective role of IL-18 in neointimal formation in a balloon-induced rat model of vascular injury. Methods and Results— Endothelial denudation of the left carotid artery was performed by use of a balloon embolectomy catheter. Increased expression of IL-18 and IL-18Rα/β mRNA was detectable in carotid arteries from days 2 to 14 after angioplasty. The active form of IL-18 was highly expressed in injured arteries. Strong immunoreactivity for IL-18 was detected in the medial smooth muscle cells at days 2 and 7 after balloon injury and in proliferating/migrating smooth muscle cells in neointima at day 14. Moreover, serum concentrations of IL-18 were significantly higher among rats subjected to vascular injury. Treatment with neutralizing rabbit anti-rat IL-18 immunoglobulin G significantly reduced neointimal formation (by 27%; P<0.01), reduced the number of proliferating cells, and inhibited interferon-γ, IL-6, and IL-8 mRNA expression and nuclear factor-&kgr;B activation in injured arteries. In addition, in vitro data show that IL-18 affects smooth muscle cell proliferation. Conclusions— These results identify a critical role for IL-18 in neointimal formation in a rat model of vascular injury and suggest a potential role for IL-18 neutralization in the reduction of neointimal development.

A novel lipid A from Halomonas magadiensis inhibits enteric LPS-induced human monocyte activation.

Lipopolysaccharide (LPS) endotoxin is the bacterial product responsible for the clinical syndrome of Gram‐negative septicemia and endotoxic shock. During sepsis, microbial antigens, such as LPS, activate monocytes and macrophages to produce several pro‐inflammatory cytokines, among which tumor necrosis factor‐α (TNF‐α) appears to be very important for the development of endotoxic shock. The endotoxic properties of LPS principally reside in the lipid A (LIP A) component, which is the primary immunostimulatory center of Gram‐negative bacteria. In recent years there has been a continuous effort to identify molecules able to antagonize the deleterious effects of endotoxic shock. In this study we show that a novel LIP A fraction from the LPS of Halomonas magadiensis (Hm), a Gram‐negative extremophilic and alkaliphilic bacterium, significantly inhibits the synthesis of TNF‐α by human monocytes activated by Escherichia coli LPS. LIP A from Hm exerts these effects by interfering with E. coli LPS for activation of Toll‐like receptor 4 expressed in human cells. This result defines Hm LIP A as a novel class of LPS antagonist whose structural features could be utilized for the design of compounds for the treatment of Gram‐negative sepsis.

The IκB Kinase Inhibitor Nuclear Factor-κB Essential Modulator–Binding Domain Peptide for Inhibition of Injury-Induced Neointimal Formation

Objective—The activation of nuclear factor-&kgr;B (NF-&kgr;B) is a crucial step in the arterial walls response to injury. The identification and characterization of the NF-&kgr;B essential modulator-binding domain (NBD) peptide, which can block the activation of the I&kgr;B kinase complex, have provided an opportunity to selectively abrogate the inflammation-induced activation of NF-&kgr;B. The aim of the present study was to evaluate the effect of the NBD peptide on neointimal formation. Methods and Results—In the rat carotid artery balloon angioplasty model, local treatment with the NBD peptide (300 &mgr;g/site) significantly reduced the number of proliferating cells at day 7 (by 40%; P<0.01) and reduced injury-induced neointimal formation (by 50%; P<0.01) at day 14. These effects were associated with a significant reduction of NF-&kgr;B activation and monocyte chemotactic protein-1 expression in the carotid arteries of rats treated with the peptide. In addition, the NBD peptide (0.01 to 1 &mgr;mol/L) reduced rat smooth muscle cell proliferation, migration, and invasion in vitro. Similar results were observed in apolipoprotein E−/− mice in which the NBD peptide (150 &mgr;g/site) reduced wire-induced neointimal formation at day 28 (by 47%; P<0.01). Conclusion—The NBD peptide reduces neointimal formation and smooth muscle cell proliferation/migration, both effects associated with the inhibition of NF-&kgr;B activation.