Mechanisms of oxidative stress in human aortic aneurysms — association with clinical risk factors for atherosclerosis and disease severity

Aortic abdominal aneurysms (AAA) are important causes of cardiovascular morbidity and mortality. Oxidative stress may link multiple mechanisms of AAA including vascular inflammation and increased metalloproteinase activity. However, the mechanisms of vascular free radical production remain unknown. Accordingly, we aimed to determine sources and molecular regulation of vascular superoxide (O2radical dot−) production in human AAA. Methods and results: AAA segments and matched non-dilated aortic samples were obtained from 40 subjects undergoing AAA repair. MDA levels (determined by HPLC/MS) were greater in plasma of AAA subjects (n = 16) than in risk factor matched controls (n = 16). Similarly, superoxide production, measured by lucigenin chemiluminescence and dihydroethidium fluorescence, was increased in aneurysmatic segments compared to non-dilated aortic specimens. NADPH oxidases and iNOS are the primary sources of O2radical dot− in AAA. Xanthine oxidase, mitochondrial oxidases and cyclooxygenase inhibition had minor or no effect. Protein kinase C inhibition had no effect on superoxide production in AAA. NADPH oxidase subunit mRNA levels for p22phox, nox2 and nox5 were significantly increased in AAAs while nox4 mRNA expression was lower. Superoxide production was higher in subjects with increased AAA repair risk Vanzetto score and was significantly associated with smoking, hypercholesterolemia and presence of CAD in AAA cohort. Basal superoxide production and NADPH oxidase activity were correlated to aneurysm size. Conclusions: Increased expression and activity of NADPH oxidases are important mechanisms underlying oxidative stress in human aortic abdominal aneurysm. Uncoupled iNOS may link oxidative stress to inflammation in AAA. Oxidative stress is related to aneurysm size and major clinical risk factors in AAA patients

GTP cyclohydrolase I gene polymorphisms are associated with endothelial dysfunction and oxidative stress in patients with type 2 diabetes mellitus

Background: The genetic background of atherosclerosis in type 2 diabetes mellitus (T2DM) is complex and poorly understood. Studying genetic components of intermediate phenotypes, such as endothelial dysfunction and oxidative stress, may aid in identifying novel genetic components for atherosclerosis in diabetic patients.<p></p> Methods: Five polymorphisms forming two haplotype blocks within the GTP cyclohydrolase 1 gene, encoding a rate limiting enzyme in tetrahydrobiopterin synthesis, were studied in the context of flow and nitroglycerin mediated dilation (FMD and NMD), intima-media thickness (IMT), and plasma concentrations of von Willebrand factor (vWF) and malondialdehyde (MDA).<p></p> Results: Rs841 was associated with FMD (p = 0.01), while polymorphisms Rs10483639, Rs841, Rs3783641 (which form a single haplotype) were associated with both MDA (p = 0.012, p = 0.0015 and p = 0.003, respectively) and vWF concentrations (p = 0.016, p = 0.03 and p = 0.045, respectively). In addition, polymorphism Rs8007267 was also associated with MDA (p = 0.006). Haplotype analysis confirmed the association of both haplotypes with studied variables.<p></p> Conclusions: Genetic variation of the GCH1 gene is associated with endothelial dysfunction and oxidative stress in T2DM patients

Relationship between rs841 polymorphism in the 3'-UTR of GCH1 gene and vascular function measured as endothelium dependent FMD (panel A) and endothelium independent NMD) (panel B).

<p>AA indicates frequent homozygote, Aa - heterozygote, aa - rare homozygote.</p

Clinical characteristics of the studied T2DM patients.

<p>Clinical characteristics of the studied T2DM patients.</p

Association of individual GCH1 gene polymorphisms with outcome variables.

<p>Association of individual GCH1 gene polymorphisms with outcome variables.</p

Relationship between studied polymorphisms and plasma vWF concentration.

<p>Relationship to polymorphisms forming haplotype block 1 (panel A) and haplotype block 2 (panel B) is demonstrated. Statistical significance of linear regression: * p<0.05.</p

Models of association of GCH1 gene polymorphisms with outcome variables, accounting for current smoking, kidney dysfunction^* and diabetes duration covariates.

<p>Models of association of GCH1 gene polymorphisms with outcome variables, accounting for current smoking, kidney dysfunction^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108587#nt104" target="_blank">*</a>} and diabetes duration covariates.</p

Relationship between studied polymorphisms and plasma MDA concentration measured by mass-spec analysis.

<p>Relationship to polymorphisms forming haplotype block 1 (panel A) and haplotype block 2 (panel B) is demonstrated. Statistical significance of linear regression: * p<0.05; ** p<0.01.</p