Previous studies suggesting a link between Escherichia coli phylogenetic groups and extraintestinal virulence have been hampered by the difficulty in establishing the intrinsic virulence of a bacterial strain. Indeed, unidentified virulence factors do exist, and the susceptibility of the host to infection is highly variable. To overcome these difficulties, we have developed a mouse model of extraintestinal virulence to test the virulence of the strains under normalized conditions. We then assessed the phylogenetic relationships compared to the E. coli reference (ECOR) collection, the presence of several known virulence determinants, and the lethality to mice of 82 human adult E. coli strains isolated from normal feces and during the course of extraintestinal infections. Commensal strains belong mainly to phylogenetic groups A and B1, are devoid of virulence determinants, and do not kill the mice. Strains exhibiting the same characteristics as the commensal strains can be isolated under pathogenic conditions, thus indicating the role of host-dependent factors, such as susceptibility linked to underlying disease, in the development of infection. Some strains of phylogenetic groups A, B1, and D are able to kill the mice, their virulence being most often correlated with the presence of virulence determinants. Lastly, strains of the B2 phylogenetic group represent a divergent lineage of highly virulent strains which kill the mice at high frequency and possess the highest level of virulence determinants. The observed link between virulence and phylogeny could correspond to the necessity of virulence determinants in a genetic background that is adequate for the emergence of a virulent clone, an expression of the interdependency of pathogenicity and metabolic activities in pathogenic bacteria.

Endothelin-1 (ET-1), a 21-amino acid vasoactive peptide mainly produced by vascular endothelial cells, is involved in the regulation of vascular tone and smooth muscle cell proliferation. Peroxisome proliferator-activated receptors (PPARs), key players in lipid and glucose metabolism, have been implicated in metabolic disorders that are predisposing to atherosclerosis. Because of the potential role of ET-1 in vascular disorders such as hypertension and atherosclerosis, we investigated the regulation of ET-1 expression by PPAR activators. Western blot and reverse transcription-polymerase chain reaction analyses demonstrated that both PPARalpha and PPARgamma are expressed in human coronary artery endothelial cells as well as in endothelial cell lines such as HMEC-1 and ECV304. In bovine aortic endothelial cells and HMEC-1 cells, both PPARalpha and PPARgamma ligands inhibited thrombin-induced ET-1 secretion, whereas basal ET-1 secretion was only slightly suppressed. Reverse transcription-polymerase chain reaction experiments showed that this inhibition of ET-1 production occurs at the gene expression level. Using transient transfection assays, we demonstrated that PPARs downregulate thrombin-activated transcription of the human ET-1 promoter. Transactivation studies with c-Jun and c-Fos expression plasmids indicated that PPARs negatively interfere with the activator protein-1 signaling pathway, which mediates thrombin activation of ET-1 gene transcription. Furthermore, electrophoretic mobility shift assays demonstrated that PPAR activators reduce the thrombin-stimulated binding activity of bovine aortic endothelial cell nuclear extracts as well as c-Jun binding to an activator protein-1 consensus site. Taken together, these data indicate that (1) both PPARalpha and PPARgamma are expressed in human vascular endothelial cells and (2) PPAR activators inhibit thrombin-induced ET-1 biosynthesis, indicating a novel role for PPARs in vascular endothelial function.

Abstract-Large observational studies and atherosclerosis regression trials of lipid-modifying pharmacotherapy have established that intima-media thickness of the carotid and femoral arteries, as measured noninvasively by B-mode ultrasound, is a valid surrogate marker for the progression of atherosclerotic disease. To exploit fully the potential of ultrasound imaging in atherosclerosis research, standardized and strictly implemented imaging protocols should be used in both observational studies and applied clinical research. This article describes such a protocol developed at the Academic Medical Center of the University of Amsterdam, the Netherlands. Results are presented from a study that estimated atherosclerosis progression from childhood into old age by measuring intima-media thickness in subjects with familial hypercholesterolemia compared with healthy controls. Key Words: B-mode ultrasound Ⅲ familial hypercholesterolemia Ⅲ intima-media thickness Ⅲ surrogate markers A therosclerosis is a generalized disease of the arterial wall, which may progress or regress depending on a plethora of factors. [1][2][3][4][5][6] This dynamic process is characterized by arterial wall remodeling that may go unnoticed for a lifetime, but may also present as acute vascular disease and become clinically manifest. 2 Because atherosclerosis progresses over decades, epidemiological studies and intervention trials with clinical end points require long-term follow-up, participation of large populations, or both. [3][4][5][6] These requirements have to be met to provide data from which valid conclusions about the determinants of disease or the efficacy of a therapeutic intervention can be drawn. 7 As a consequence, such studies consume precious time and financial resources. 8 To overcome these challenges, surrogate markers became the focus of intense attention. 8 Such markers might be used to investigate determinants of atherosclerosis at an early stage of the process and can, subsequently, assess modifiers of atherosclerotic disease progression, such as lifestyle and pharmacological interventions.Boissel and coworkers have proposed criteria for the validity of surrogate markers as a substitute for clinical end points. 9 These investigators stipulated 3 conditions for the determination of validity. First, a surrogate marker should be more sensitive and more readily available (sensitivity and availability) than the clinical end point. Also, the surrogate marker should be easy to evaluate (convenient), preferably by noninvasive means. Second, the causal relationship between the surrogate marker and the clinical end point (proximity) should be established on the basis of epidemiological, pathophysiological, and clinical studies. It is a prerequisite that patients with and without vascular disease exhibit differences in surrogate marker measurements (specificity). Third, in intervention studies, anticipated clinical benefits (assessment of benefit) should be deducible from the observed changes in the surrogate marker. The latter argument ...