Oxidative stress in cardiovascular disease: successful translation from bench to bedside?

The association of plasma fluorescent oxidation products and chronic kidney disease: a case-control study

BACKGROUND/AIMS

Plasma fluorescent oxidation products (FLOP) constitute a stable and easily measured biomarker of cumulative oxidative stress. However, their association with chronic kidney disease (CKD) has not been studied.

METHODS

We examined the association of FLOP and CKD in 201 CKD patients and 201 controls without CKD from the community. CKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) or the presence of albuminuria.

RESULTS

Adjusted median (interquartile range) FLOP levels were significantly higher in patients with CKD than in controls [FLOP1 (lipid oxidation products): 215.2 (181.3-268.7) vs. 156.6 (139.6-177.3) fluorescent intensity units/ml, p < 0.0001; FLOP2 (DNA oxidation products): 534.8 (379.3-842.4) vs. 269.9 (232.4-410.5) fluorescent intensity units/ml, p < 0.0001; FLOP3 (protein and phospholipid oxidation products): 51.4 (44.4-66.0) vs. 45.2 (38.3-51.7) fluorescent intensity units/ml, p = 0.002]. Compared with those with a FLOP level below the 75th percentile, participants with a FLOP level above the 75th percentile had increased odds of CKD after adjustment for covariables (FLOP1: odds ratio 13.1, 95% confidence interval 6.2-27.6; FLOP2: odds ratio 5.7, 95% confidence interval 2.9-11.1; FLOP3: odds ratio 2.4, 95% confidence interval 1.2-4.7). Levels of FLOP1, FLOP2 and FLOP3 were related to eGFR (p < 0.0001 for all) and log-transformed urine albumin (p < 0.005 for all) in multivariable-adjusted linear regression models.

CONCLUSION

These data indicate that an elevated FLOP level is associated with CKD status and severity. Future studies are warranted to elucidate its role in the development and progression of CKD.

Noninvasive vascular function measurement in the community: cross-sectional relations and comparison of methods

BACKGROUND

Several methods of noninvasive vascular function testing have been suggested for cardiovascular risk screening in the community. A direct comparison of the different methods and their relation to classical cardiovascular risk factors in a large cohort is missing.

METHODS AND RESULTS

In 5000 individuals (mean age, 55.5 ± 10.9 years; age range, 35 to 74 years; women, 49.2%) of the population-based Gutenberg Heart Study, we performed simultaneous measurement of flow-mediated dilation (FMD) and peripheral arterial volume pulse determined by infrared photo (reflection index) and pneumatic plethysmography (PAT) and explored their associations. All function measures were recorded at baseline and after reactive hyperemia induced by 5-minute brachial artery occlusion. Correlations between different measures of vascular function were statistically significant but moderate. The strongest association for hyperemic response variables was observed for PAT ratio and FMD (Spearman r = 0.17; age- and sex-adjusted partial correlation, 0.068). Classical risk factors explained between 15.8% (baseline reflection index) and 58.4% (brachial artery diameter) of the baseline values but only accounted for 3.2% (reflection index), 15.4% (FMD), and 13.9% (PAT ratio) of the variability of reflective hyperemic response. Regression models varied in their relations to classical risk factors for the individual vascular function measures. Consistently associated with different vascular function methods were age, sex, body mass index, and indicators of hypertension. Peripheral tonometry also showed a relation to fasting glucose concentrations.

CONCLUSIONS

Noninvasive measures of conduit artery and peripheral arterial function are modestly correlated, differ in their relation to classical cardiovascular risk factors, and may thus reflect different pathologies.

Kynurenine pathway - a new link between endothelial dysfunction and carotid atherosclerosis in chronic kidney disease patients

PURPOSE

The endothelium dysfunction is an important component of atherosclertic cardiovascular disease. It has been also suggested that kynurenine pathway activation may be involved in the pathogenesis of this disease.

MATERIAL/METHODS

This is a cross-sectional study in chronic kidney disease (CKD) patients (n=106; 60 Males). The plasma markers of endothelial dysfunction and kynurenine (KYN), 3-hydroxykynurenine (3-HKYN), kynurenic acid (KYNA), anthranilic acid (AA) and quinolinic acid (QA) were measured in relation to an early indicator of the systemic atherosclerosis - intima-media thickness (IMT).

RESULTS

Kynurenines, von Willebrand factor (vWF), thrombomodulin (TM), soluble adhesion molecules (sICAM-1, sVCAM-1) and IMT in each uraemic group were significantly higher than in healthy people. In contrast, no significant differences in sE-selectin and sP-selectin concentrations were observed between CKD patients and controls. Kynurenines were positively associated with vWF, TM, sICAM-1 and sVCAM-1, whereas sP-selectin was inversely associated with the most of kynurenines. IMT was positively correlated both with kynurenines: KYN, 3-HKYN, QA as well as with endothelial markers: TM, vWF, sICAM-1 and sVCAM-1 (all p<0.01). Finally, multiple regression analysis identified age, vWF, sVCAM-1 and QA levels as the independent variables significantly associated with increased IMT in this population (adjusted r² = 0.51).

CONCLUSIONS

This study suggests a relationship between kynurenine pathway activation, endothelial dysfunction and the progression of atherosclerosis in CKD patients. It opens a new idea that the inhibition of kynurenine pathway may provide an effective strategy to slow down endothelial dysfunction and thereby the prevalence of atherosclerosis in this population.

Kynurenine and its metabolites--kynurenic acid and anthranilic acid are associated with soluble endothelial adhesion molecules and oxidative status in patients with chronic kidney disease

BACKGROUND

Cellular adhesion molecules and oxidative stress play a role in the pathogenesis of atherosclerosis in patients with chronic kidney disease (CKD). Recently, it has been postulated that the kynurenine (KYN) pathway could be involved in the pathogenesis of atherosclerosis.

METHODS

We evaluated the KYN, kynurenic acid (KYNA), anthranilic acid (AA), and their relations with cellular adhesion molecules: soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular adhesion molecule-1 (sVCAM-1), sE-selectin, sP-selectin, and Cu/Zn superoxide dismutase (Cu/Zn SOD) levels as the markers of oxidative stress in the population of 132 patients with CKD and 28 healthy controls.

RESULTS

Compared with the controls, 2 groups of dialyzed patients had significantly increased KYN (both P < 0.01), KYNA, AA, sICAM-1, sVCAM-1, and Cu/Zn SOD levels (all P < 0.001, respectively). KYN, AA, sICAM-1, and sVCAM-1 concentrations were significantly higher in undialyzed patients with CKD compared with healthy subjects (P < 0.001, P < 0.01, and both P < 0.05, respectively). sICAM-1 and sVCAM-1 were positively associated with KYN (P < 0.0001 and P < 0.01), KYNA (P < 0.05 and P < 0.0001), AA (P < 0.01 and P < 0.0001), and with Cu/Zn SOD (both P < 0.0001, respectively) in the whole CKD group. The positive relationship existed between sICAM-1, sVCAM-1 and age, high-sensitivity C-reactive protein, creatinine, and the duration of dialysis therapy. Multivariable analysis showed that KYN was a strong independent correlate of sICAM-1, whereas Cu/Zn SOD and platelets independently and significantly predicted sVCAM-1 in patients with CKD.

CONCLUSIONS

This study demonstrated that KYN is independently and significantly associated with elevated sICAM-1, whereas oxidative status and platelets independently and significantly predicted increased sVCAM-1 levels in patients with CKD.

Expression of ubiquitin in peripheral inflammatory cells from patients with coronary artery disease

In addition to its role in the removal of damaged and unneeded proteins, the ubiquitin-proteasome system (UPS) may play a key role in coronary artery disease (CAD). To investigate the expression of ubiquitin in monocytes and lymphocytes isolated from patients at different stages of CAD, 120 patients with CAD (40 with acute myocardial infarction [AMI], 40 with unstable angina pectoris [UAP] and 40 with stable angina pectoris [SAP]) were selected; 40 patients with normal coronary arteries served as controls. At both the mRNA and protein levels, ubiquitin expression was higher in patients with CAD than in controls, and patients with AMI had a much higher expression of ubiquitin (at both the mRNA and protein levels) than those with SAP and UAP. These data indicate that ubiquitin expression increased with increasing severity of CAD, suggesting that ubiquitin may play a critical role in the development and progression of CAD.

Expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in peripheral inflammatory cells from patients with coronary heart disease

: The increased expression of heme oxygenase-1 content, a stress-response protein, directly correlates with the incidence of coronary heart disease. Down-regulation of hypoxia inducible factor-1α activity, a major downstream effector of the signaling pathways activated by hypoxia, increases cell survival after hypoxia. The ubiquitin system, a non-lysosomal pathway of protein degradation, is involved in processes of coronary heart disease. The aim of this study was to investigate the expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in both monocytes and lymphocytes isolated from patients at the mRNA and protein levels in different stages of coronary heart disease and their possible correlation.

: A total of 90 patients with coronary heart disease (30 acute myocardial infarction, 30 unstable angina pectoris, and 30 stable angina pectoris) were selected, and 30 cases with normal coronary artery served as controls. The mRNA and protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in monocytes and lymphocytes were examined by semi-quantitative reverse transcriptase polymerase chain reaction and Western blotting, respectively.

: The mRNA expression of heme oxygenase-1 and ubiquitin was associated with the severity of coronary heart disease (p<0.05). There was no significant difference in hypoxia inducible factor-1α mRNA expression between the coronary heart disease patients and controls. The protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin was significantly stronger in patients with coronary heart disease than in controls, and the expression levels increased with the severity of the disease. There was a positive association between heme oxygenase-1 and hypoxia inducible factor-1α and ubiquitin, antioxidative therapy with adrenergic receptor blocker, angiotensin-converting enzyme inhibitor or statins up-regulated the expression of heme oxygenase-1 and hypoxia inducible factor-1α.

: These data suggest that heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin are involved in the development and progression of coronary heart disease and thus may be useful biomarkers for coronary heart disease.

Clin Chem Lab Med 2009;47:327–33.

Circulating endothelial progenitor cells and residual in vivo thromboxane biosynthesis in low-dose aspirin-treated polycythemia vera patients

Polycythemia vera (PV) is associated with high morbidity and mortality for thrombosis. We hypothesized that in PV altered sensitivity to aspirin might be related to dysfunction of the endothelial repair and/or of the nitric oxide (NO) system. Urinary thromboxane (TX) A2 metabolite (TXM), endothelial colony-forming cells (ECFCs), plasma asymmetric dimethylarginine (ADMA) and von Willebrand factor (VWF) were measured in 37 PV patients on low-dose aspirin and 12 healthy controls. Patients showed an approximately 2-fold increase in median TXM and plasma ADMA levels (P < .001), while ECFC numbers were reduced by approximately 7-fold (P < .001) as compared with nonaspirinated control. These differences were more pronounced in patients with previous thrombosis. An 8-week course of aspirin did not affect ECFCs in 6 controls. VWF and TXM correlated directly with ADMA, and inversely with ECFCs. By multiple regression analysis, lower ECFC quartiles (beta = −0.39; SE = 0.17; P = .028) and higher VWF levels (beta = 0.338, SE = 0.002, P = .034) were independent predictors of higher TXM quartiles (R2 = 0.39). Serum TXB2, measured in 22 patients, was approximat-ly 10-fold higher than aspirin-treated controls. PV patients appear to have an unbalanced ECFC/NO axis, and an apparent altered sensitivity of platelet TXA2 production, all potentially contributing to aspirin-insensitive TXM formation. Thus, additional antithrombotic strategies may be beneficial in PV.