Oxidative stress and cardiovascular risk: the role of vascular NAD(P)H oxidase and its genetic variants

Several risk factors for coronary artery disease (CAD) induce atherosclerosis through endothelial activation and dysfunction, and ample evidence now suggests that the balance between production and removal of reactive oxygen species (ROS) - a condition termed oxidative stress - is implicated in such processes. A main source of ROS in vascular cells is the reduced nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase system. This is a membrane-associated enzyme, composed of five subunits, catalyzing the one-electron reduction of oxygen, using NADH or NADPH as the electron donor. One of the system subunits, termed p22-phox, has a polymorphic site on exon 4, associated with variable enzyme activity. This polymorphism is generated by a point mutation (C(242)T) producing a substitution of histidine with tyrosine at position 72, which affects one of the heme binding sites essential for the NAD(P)H enzyme activity. The consequent decrease of superoxide production thus characterizes a phenotype candidate for conferring to the carrier a reduced susceptibility to CAD. At present, however, the body of evidence from current literature is not yet sufficient to confirm or exclude the hypothesis that the C(242)T polymorphism protects from CAD. The functional effects of this polymorphism and the potential and its pathophysiological consequences also need further investigation.

[The IL-6 soluble receptors in hemodialyzed patients]

Pro-inflammatory cytokines, in addition to their role in host defence, can be considered a disease mediator; therefore, a reduction in cytokine synthesis or its effects is becoming a target of many diseases. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that could play a role in several clinical problems related to dialysis treatment. Biological activities of IL-6 could be modulated by two soluble circulating receptors, namely sIL-6R and sgp130. sIL-6R can enhance the inflammatory effects of IL-6 and; therefore, is an "agonistically" acting molecule. On the contrary, sgp130 efficiently binds the IL-6/sIL-6R complex with "antagonistic" effects. In this study we evaluated sgp130 release by peripheral blood mononuclear cells (PBMC) harvested from 10 healthy controls (CON) and 11 end-stage renal disease (ESRD) patients undergoing renal dialysis therapy RDT) with cellulosic hemophan membrane (HD). We also evaluated gp130 gene expression by reverse transcriptase polymerase chain reaction (RT-PCR). gp130 is the membrane bound receptor of IL-6 that could be proteolytically cleaved to generate soluble sgp130. Our results demonstrated that HD. at basal conditions, showed a higher release of sgp130 as compared with CON. We also demonstrated by RT-PCR at basal conditions a higher gene expression of gp130 in HD, as compared with CON. These results took place in the absence of any mitogenic stimulation and suggest that in HD patients an inflammatory subclinical status increases sgp130 release. The results obtained after lipopolysaccharide (LPS) stimulation confirm the role of inflammation on the increased release of sgp130 in HD patients.

[Chronic inflammation and cardiovascular risk in hemodialysis]

Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in patients with end-stage renal disease (ESRD). Traditional risk factors are common in ESRD patients, but they alone may not be sufficient to account for the high prevalence of CVD in this population. Recent clinical evidence demonstrates that chronic inflammation, a non traditional risk factor which is commonly observed in ESRD patients, may be associated with the presence of poor nutritional parameters and progressive atherosclerotic CVD. Based on these observations, the presence in ESRD patients of a syndrome consisting in malnutrition, signs of systemic chronic inflammation and atherosclerosis (MIA syndrome) has recently been suggested. A central role in this syndrome is played by the proinflammatory cytokines generated in response to factors such as chronic renal failure and infectious-inflammatory co-morbid disease. It is now clear that the immune response, both innate and adaptive, is the main cause of inflammation characterising atherosclerosis. As there is as yet no recognized, or even proposed, treatment for ESRD patients with chronic inflammation, it would be of obvious interest to study the long-term effect of various inflammatory treatment strategies on the nutritional and cardiovascular status as well as the outcome in these patients.

Aspects of gene polymorphisms in cardiovascular disease: the renin-angiotensin system

The renin-angiotensin system (RAS) plays a central role in cardiovascular homeostasis. Angiotensin is the key peptide of the RAS, and exerts its influence on the heart and blood vessels both through its haemodynamic effects (via its influence on after-load and pre-load and determining coronary vasoconstriction) and through its direct cellular effects (via its actions on cell proliferation). Numerous studies in the past 10 years have demonstrated that the pharmacological inhibition of angiotensin converting enzyme (ACE), one of the two critical enzymes of the RAS, improves the outcome in patients with several cardiovascular disorders (hypertension, heart failure, ischaemic heart disease). These studies suggest a role of the RAS as a major determinant of cardiovascular risk. Recent data suggest that genetics may in turn contribute to modulating the effects of angiotensin on coronary vascular biology and ischaemia. This paper reviews the physiologic characteristics of the RAS and recent research developments related to angiotensin cell biology and pathobiology in heart disease. In particular, this review will cover the genetic aspects of RAS and their implications in cardiovascular disease.

Color duplex scanning for the identification of extracranial atherosclerosis in patients with suspected coronary artery disease

BACKGROUND

The presence of extracranial artery disease has been used as a predictor of coronary artery disease (CAD). The present study was conducted to test the prevalence of extracranial artery disease among patients with suspected CAD.

METHODS

Among candidates for coronary arteriography, 400 consecutive patients (mean age 63 +/- 11 years, 78% males, 22% females) underwent color duplex ultrasound of carotid arteries.

RESULTS

Extracranial artery disease was documented in 60 patients (15%), CAD in 309 patients (77%). Patients with extracranial artery disease were significantly older (p < 0.001), smoked a higher amount of pack-years (p < 0.001), showed a higher incidence of diabetes (p < 0.01), hypertension (p < 0.05) and CAD (p < 0.05) when compared to extracranial artery disease-free subjects. Plotting age against extracranial artery disease and CAD distribution, extracranial artery disease occurred later in life than CAD (p < 0.001). The best cut-off point of age for predicting extracranial artery disease was 68 years. Carotid angiography was performed in 114 patients after cardiac catheterization (k = 0.8044 with color duplex scanning).

CONCLUSIONS

Extracranial artery disease is frequent among patients undergoing coronary arteriography. Carotid ultrasound screening is useful in older patients.

[Carotid atherosclerosis in patients with suspected coronaropathy: the relationship to traditional risk factors in the 2 vascular areas]

In order to evaluate the prevalence of carotid atherosclerosis (CA) in patients with coronary artery disease (CAD) and to identify the differential role of traditional risk factors, we analyzed data concerning 290 patients aged 61.9 +/- 10.8 years who underwent color duplex ultrasound of extracranial arteries before coronary angiography. Significant CA (stenosis > or = 50% in at least one extracranial artery) was disclosed in 44 patients (15%); significant CAD (stenosis > or = 70% at least in a major epicardial vessel) was documented in 238 patients (82%). Age and smoking were significantly associated with both CAD (respectively, p = 0.034 and p = 0.050) and CA (respectively, p = 0.000 and p = 0.000), but a stronger correlation was documented with CA (r = 0.325 vs r = 0.125 for age; r = 0.218 vs r = 0.114 for smoking). Diabetes (p = 0.031) and male gender (p = 0.016) were significantly associated with CAD, and hypertension (p = 0.029) with CA.

CONCLUSIONS

Traditional risk factors play different roles in the pathogenesis of atherosclerotic disease of carotid and coronary circulation. Color duplex evaluation of the carotid arteries can be useful in high-risk patients, particularly if candidates for coronary surgery.

Effect of acute increase of interstitial myocardial fluid on ventricular function in isolated working rat hearts

An acute increase of myocardial interstitial fluid may affect ventricular function. In the present study we evaluated the effects of acute changes of myocardial tissue fluid on cardiac function and ultrastructural morphometry. Isolated rat hearts were perfused for 100 min in the working heart mode. Hearts were distributed into 5 groups: controls [perfused with Krebs-Henseleit (KH) isotonic buffer to rat plasma, KH, 287 mOsm], moderate hyposmotic perfusion (75% Hyposm: perfusion with 75% diluted KH, 216 mOsm), highly hyposmotic perfusion (60% Hyposm: perfusion with 60% diluted KH, 170 mOsm), afterload increase (Pre-over: isotonic perfused hearts subjected to an increase of afterload from 72 to 145 cm H2O) and ion dilution (Ion-dil: hearts perfused with a 60% KH with 115 mM sucrose, isotonic, 287 mOsm). We evaluated functional changes, markers of cellular necrosis or damage (CPK, LDH and purine release in coronary effluent), heart weight changes (weight gain and ww/dw ratio) and ultrastructural morphometry (analysis of cell damage, interstitial area, and mitochondrial alterations by a computerized image analysis system). The ww/dw ratio increased significantly only in 60% Hyposm (+140%, p < 0.001) and Pre-over (+63%, p < 0.001 vs control) groups. An impaired myocardial function in 60% Hyposm, Pre-over and Ion-dil groups was observed with cardiac failure at 50, 60 and 60 min, respectively. Enzyme release was significant higher in 60% Hyposm and Pre-over groups and was related to heart weight gain (r = 0.85, p < 0.001). Ultrastructural analysis confirmed a significant increase of interstitial space area (ISA) and mitochondrial damage in 60% Hyposm and Pre-over groups (p < 0.001); a significant (p < 0.05) increase was observed in the Ion-dil group; in 75% Hyposm group, a significant increase of mitochondrial damage was detected (p < 0.05). In brief, a higher functional and morphological deterioration was observed in hearts in which a more evident interstitial edema was detected (60% Hyposm and Pre-over groups). We conclude that, in the experimental condition, an acute increase of myocardial interstitial tissue fluid directly compromises left ventricular function and contributes to the ultrastructural damage to the myocardium.