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Background: The risk for coronary events may rise during acute infection. Perturbation in coronary endothelial function emerges as one important link. We investigated whether simvastatin could protect the coronary arterial function from the adverse effects of acute infection in swine., Methods: Coronary endothelium-dependent and -independent vasomotor responses were assessed by Doppler velocimetry in 12 Chlamydia pneumoniae-infected and 6 sham-infected swine 2 weeks after intratracheal inoculation. Half of animals from the infection group were pre-treated with simvastatin (80 mg daily), while the remaining animals received placebo. The treatment was started 2 weeks prior to inoculation and continued until the end of the study. ANOVA was used for statistical calculations. Data are mean+/-S.D., Results: All animals inoculated with C. pneumoniae developed IgM antibodies against this organism. As compared to noninfected animals, peak-to-baseline coronary flow velocity (CFV) ratio after bradykinin was significantly decreased in infected animals regardless of statin treatment (p=0.01). Intracoronary 10(-6) M acetylcholine caused slight dilatory responses in both noninfected and infected-treated animals (CFV ratio: 1.6+/-0.2 and 1.4+/-0.2, respectively; p>0.1), while a velocity drop (CFV ratio: 0.7+/-0.1; p<0.01 versus noninfected-infected and treated), indicating constriction, was observed in infected-nontreated animals; 10(-5) M acetylcholine caused vasoconstriction in all animals, with a significantly more prolonged response in the infected-nontreated group (p<0.01). Intracoronary adenosine and SNP induced similar dilatory responses in all groups (p>0.5). There were no differences in markers of systemic inflammation (fibrinogen, amyloid, and CRP) and lipid profile (HDL, LDL and total cholesterol) between the groups (p>0.2)., Conclusion: Acute infection is associated with impairment of the muscarinic and kinin-related reactivity of coronary circulation. These functional abnormalities are in part prevented by simvastatin through mechanisms unrelated to lipid lowering.

Background: Arterial endothelial dysfunction is an important mechanism of tissue injury caused by ischemia-reperfusion (I/R). Earlier studies of I/R have shown that intracoronary preinfusion with 2.5-5 microg/mL bradykinin (BK) could alleviate the postischemic myocardial damage. Using an experimental human model of I/R, we investigated whether preceding infusion with BK could prevent the I/R-induced arterial endothelial dysfunction., Methods: The left radial artery (LRA) from 16 healthy male adults, 18 to 30 years old, was submitted to I/R by completely occluding the left brachial artery with a pressure tourniquet for 20 minutes (ischemia), followed by its release (reperfusion). Prior to I/R, half of the subjects were randomly assigned to receive either BK (5 microg/mL) or saline, both being infused into the left brachial artery (0.5 mL/min, 10 min). The infusion was followed by a 10-minute drug-free period. The endothelial function of the LRA was studied by measuring the flow-mediated dilation (FMD) at baseline (prior to drug infusion), and at 15 minutes of reperfusion. In addition, baseline radial artery diameter, plasma nitrate, and von Willebrand factor were measured at these time points, and immediately before I/R (pre-I/R)., Results: BK had no effect on the pre-I/R plasma nitrate (p > 0.5 vs. saline) and diameter of LRA (p > 0.5 vs. baseline). At 15 minutes of reperfusion, FMD was significantly decreased in the saline group as compared to baseline (absolute dilation: 0.08 +/- 0.03 vs. 3.02 +/- 0.8 mm, respectively, p < 0.01; percentage dilation: 3 +/- 0.6 vs. 8 +/- 0.6%, respectively, p < 0.001), but it remained unaffected in the BK group (absolute dilation: 3.06 +/- 0.9 vs. 3.27 +/- 0.8 mm, respectively, p > 0.5; percentage dilation: 7 +/- 0.7 vs. 8 +/- 0.8%, respectively, p > 0.5). A similar trend was observed with regard to plasma nitrate, which remained unchanged in the BK group (37.01 +/- 4.14 vs. 39.14 +/- 4.49 micromol/L, p > 0.5) but decreased in the saline group (35.91 +/- 3.03 vs. 28.91 +/- 2.81 micromol/L, p < 0.1)., Conclusion: Infusion of BK could protect the arterial endothelial function against I/R injury in humans, possibly in part by preserving the endothelial NO availability. The findings support the use of BK in the prevention of tissue injury due to I/R and might reveal an additional mechanism whereby ACE inhibitors exert their preconditioning effects on myocardium.

Unlabelled: Although clinical manifestations of atherosclerotic coronary heart disease occur in adult life, the initial stages of its development commence in childhood. Therefore, elucidating the pathogenesis of early atherosclerosis and identifying the network of risk factors have become fundamental priorities for both cardiovascular healthcare providers and scientists. There is mounting evidence from both human studies and animal experiments that infectious pathogens could be implicated in atherosclerosis development. The vulnerability of the arterial wall to the adverse effects of infection is probably augmented when additional risk factors and/or certain proatherogenic genetic profiles are also present. The precise mechanisms whereby infection, alone or in synergy with conventional cardiovascular risk factors, could contribute to atherosclerosis are not fully understood., Conclusion: Injury to the vascular endothelium, which could be elicited by infection through inflammatory, metabolic, autoimmune, and pathogen-related mechanisms, might be a central link between infection and early atherosclerosis.

Atherosclerosis is regarded as a chronic disease that begins in early life. While the main underlying mechanism of atherosclerosis is nowadays unequivocally attributed to a low-grade inflammatory reaction, the spectrum of aetiological conditions is far from being fully elucidated. Both viruses and bacteria have been suggested to intervene at various stages of atherosclerosis development, although a clear pathogenic link between infection and atherosclerosis remains debatable. As one key event in atherogenesis involves a perturbation of the protective mechanisms normally posed by the arterial endothelium, a number of studies have enquired into the possible detrimental effects of microbes and their components on the endothelial cells. This review aims to scrutinize the current literature in this regard, and to suggest several possible directions for future studies.

Formerly viewed as a bland lipid storage disease mainly affecting adults, atherosclerosis is nowadays recognized to be a chronic inflammatory disease that begins much earlier, probably already during fetal life. There has inevitably been reorientation from the traditional risk factor cholesterol to a broad category of factors, including those triggering chronic inflammation, such as infections. In addition, major advances in the field of vascular biology have led to a reassessment of our perception and understanding of the pathogenesis of atherosclerosis. A key role in this process is now attributed to vascular endothelium.

Background: Coronary endothelial dysfunction contributes to the pathogenesis of acute coronary syndromes (ACSs). Acute Chlamydia pneumoniae infection has been epidemiologically associated with ACS. In this study, we investigated whether acute C. pneumoniae infection could alter the endothelial vasomotor function of porcine coronary vessels., Methods and Results: Twenty pigs, 7-9 kg in weight, were inoculated intratracheally with C. pneumoniae (n=12) or saline (n=8), and investigated at 3 days (five infected/four non-infected) and 2 weeks (5+2 infected/four non-infected) after inoculation. The endothelium-dependent reactivity of coronary microcirculation was assessed at both time points by measuring peak coronary flow velocity (CFV) in response to bradykinin, before and after infusions with glutathione, an antioxidant, and L-arginine, a substrate for nitric oxide synthase (NOS). CFV after bradykinin was significantly decreased in infected animals at both time points. At 2 weeks, both glutathione and L-arginine significantly improved CFV after bradykinin. CFV after sodium nitroprusside (SNP) was similar in both groups. At 3 days, the relaxation responses of bradykinin-induced pre-contracted left anterior descending (LAD) coronary rings to bradykinin were significantly less in infected animals. N(G)-nitro-L-arginine-methyl-ester, an NOS inhibitor, had significantly greater inhibitory effect on bradykinin-induced relaxation in infected animals. Plasma nitrate-nitrite and fibrinogen, and NOS activity from LAD coronary samples were significantly increased in infected animals., Conclusion: Acute C. pneumoniae infection causes endothelial dysfunction of both resistance and epicardial coronary vessels, and favours a pro-coagulant status. These effects could in part account for the epidemiologically suggested association between acute infection and ACS.

Background: Upregulation of proinflammatory endothelial cell adhesion molecules and decreased bioactivity of endothelial nitric oxide (NO) are important in the pathogenesis of atherosclerosis. We investigated the effects of co-infection with Chlamydia pneumoniae and Helicobacter pylori on these two events in apoE-KO mice., Methods: Thirty-two apoE-KO mice, 8 weeks old, were equally divided into 4 groups. The first 2 groups were infected with either C. pneumoniae or H. pylori, while the 3rd group was infected with both C. pneumoniae and H. pylori. Mice from the 4th group and 4 wild-type mice served as controls. Thoracic and abdominal aortas were harvested after 10 weeks, and staining for vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 was analyzed by immunocytochemistry. The endothelial vasomotor responses of thoracic aortas to methacholine were studied in organ chambers in the absence and presence of L-NAME. The plasma levels of nitrate/nitrite were measured., Results: Staining for VCAM-1 was more intense at the branching sites of aortas from mice with co-infection than in mono-infected or noninfected apoE-KO mice. The relaxation responses to methacholine and the plasma levels of nitrate/nitrite were significantly less in the co-infected group than in the other groups (p < 0.05)., Conclusion: Co-infection of apoE-KO mice with C. pneumoniae and H. pylori seems to be associated with impaired bioactivity of endothelial NO and increased expression of VCAM-1 at branching sites. The findings may suggest an additive interaction of these pathogens in atherogenesis., (Copyright 2003 S. Karger AG, Basel)

Background: Atherosclerosis begins early in life. Infections might contribute to the pathogenesis of atherosclerosis. In this study, we investigated whether acute infections in children could alter the carotid wall morphology and the lipid profile., Methods: Mean carotid intima-media thickness (IMT) was measured by high-resolution ultrasound in 28 hospitalised children (mean age: 5+/-2 years), who fulfilled the diagnostic criteria of acute infections (body temperature, >38 degrees C; C-reactive protein, >15mg/ml, and clinical), and in 20 age- and gender-matched controls. Antibodies against oxidised low-density lipoprotein (anti-oxLDL antibodies), as well as total and high-density lipoprotein cholesterol (HDL-C) were analysed in all children. The infection group was investigated both during the acute illness and 3 months after clinical recovery (post-infection)., Results: During the acute illness, the infection group had elevated anti-oxLDL antibodies and decreased HDL-C, as compared to those obtained at 3 months and in controls (p<0.05). These changes in the infection group were followed, at 3 months, by thickening of carotid intima-media. Those who received antibiotics during their acute illness had less carotid thickening than those who were not treated with antibiotics (p<0.05)., Conclusion: Acute infections in children seem to be accompanied by enhanced oxidative modification of LDL and by decrease in HDL-C. These lipid changes may be followed by thickening of carotid artery intima-media. These findings suggest that, in childhood, acute infections could be associated with increased risk of atherosclerosis, and warrant further studies on this topic.

Background: Arterial relaxation is largely regulated by endothelial nitric oxide (NO). Its diminished activity has been associated with incipient atherosclerosis. We investigated the endothelium-dependent relaxation of aorta in apolipoprotein E-knockout (apoE-KO) mice exposed to single or repeated Chlamydia pneumoniae inoculation., Methods and Results: Forty-eight apoE-KO mice, 8 weeks old, were inoculated intranasally with C pneumoniae (n=24) or saline (n=24) every 2 weeks over a 6-week period. Twenty mice (10 infected and 10 controls) were killed at 2 weeks and 6 weeks, respectively, after the first inoculation. The smooth muscle tone of aortic rings was measured in vitro at both time points. The norepinephrine-precontracted thoracic aortic rings were successively exposed to methacholine in the absence and presence of N:(G)-nitro-L-arginine methyl ester (L-NAME) and diclofenac. The methacholine-induced relaxation was attenuated in the infected mice at 6 weeks in both the absence and presence of L-NAME (P:<0.05 and P:<0.01, respectively). When administered together with L-NAME, diclofenac enhanced the relaxation of the L-NAME-pretreated aortas in infected mice at 2 weeks (P:<0.05) but not in noninfected mice. The relaxation response from infected mice tended to differ in the same manner at 6 weeks (P:<0.1). No intimal thickening was detected at either time point., Conclusions: C pneumoniae impairs arterial endothelial function, and the NO pathway is principally involved. Cyclooxygenase-dependent vasoconstricting products may also account for the infection-induced impaired relaxation. These findings further support the role of C pneumoniae infection in atherosclerosis development.