Disorder-induced pseudodiffusive transport in graphene nanoribbons.

We study the transition from ballistic to diffusive and localized transport in graphene nanoribbons in the presence of binary disorder, which can be generated by chemical adsorbates or substitutional doping. We show that the interplay between the induced average doping (arising from the nonzero average of the disorder) and impurity scattering modifies the traditional picture of phase-coherent transport. Close to the Dirac point, intrinsic evanescent modes produced by the impurities dominate transport at short lengths giving rise to a regime analogous to pseudodiffusive transport in clean graphene, but without the requirement of heavily doped contacts. This intrinsic pseudodiffusive regime precedes the traditional ballistic, diffusive, and localized regimes. The last two regimes exhibit a strongly modified effective number of propagating modes and a mean free path which becomes anomalously large close to the Dirac point

NADPH Oxidase–Dependent Superoxide Production Is Associated With Carotid Intima-Media Thickness in Subjects Free of Clinical Atherosclerotic Disease

Objective—Oxidative stress plays a critical role in the pathogenesis of atherosclerosis. The NADPH oxidase constitutes the main source of superoxide in phagocytic and vascular cells. This study aimed to investigate the levels of NADPH oxidase–mediated superoxide production in phagocytic cells and the association between phagocytic superoxide production and carotid intima-media thickness (IMT), a surrogate marker of asymptomatic atherosclerosis. Methods and Results—NADPH oxidase–mediated superoxide production was determined by a chemiluminescence assay using lucigenin and associated with IMT for 184 asymptomatic subjects free of overt clinical atherosclerotic disease. Compared with individuals in the lowest tertile of superoxide production, those in the upper tertile ( 20 counts/sec) showed significantly higher IMT (P 0.05). In correlation analysis, a positive relationship was found between superoxide production and carotid IMT. Superoxide production also correlated positively (P 0.05) with body mass index (BMI). In multivariate analysis, the association of superoxide production with carotid IMT remained significant after adjustment for age, sex, systolic blood pressure, BMI, triglycerides, glucose, and smoking. Conclusions—In a population sample of adults without clinically overt atherosclerotic disease, increased NADPH oxidase activity was associated with enhanced carotid IMT, suggesting a relationship between phagocytic NADPH oxidase– mediated oxidative stress and the development of atherosclerosis

Increased phagocytic nicotinamide adenine dinucleotide phosphate oxidase–dependent superoxide production in patients with early chronic kidney disease

Background. Oxidative stress has been implicated in the pathogenesis of atherosclerosis that develops in patients with advanced chronic kidney disease (CKD). This study was designed to investigate whether a relationship exists between phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase–dependent superoxide anion (•O2 −) production and subclinical atherosclerosis in patients with early CKD. Methods. Superoxide production was assayed by chemiluminescence under baseline and stimulated conditions on mononuclear cells obtained from asymptomatic patients with stage 1 to 2 CKD (N = 22) and healthy controls (N = 21). Ultrasonographic determination of carotid intima-media thickness (IMT) was used to assess the presence of atherosclerosis. Results. Although there were no differences in baseline •O2 − production between controls and patients, the •O2 − production in phorbol myristate acetate–stimulated mononuclear cells was increased (P < 0.05) in patients compared with controls. The phorbol myristate acetate–induced •O2 − production was completely abolished by apocynin, a specific inhibitor of NADPH oxidase. A direct correlation (r = 0.441, P < 0.05) was found between plasma insulin levels and NADPH oxidase–mediated •O2 − production in patients. Carotid IMT was higher (P < 0.005) in patients than in controls. CarotidIMTvalues above the upper normal limit in controls were found in 70% and 40% of patients with increased or normal NADPH oxidase–mediated •O2 − production, respectively. Conclusion. Generation of •O2 − that is mainly dependent on NADPH oxidase is abnormally enhanced in patients with early CKD. It is suggested that this alteration could be related to the development of subclinical atherosclerosis in these patients

Mutational screening of splicing factor genes in cases with autosomal dominant retinitis pigmentosa.

PURPOSE: Mutations in genes encoding proteins from the tri-snRNP complex of the spliceosome account for more than 12% of cases of autosomal dominant retinitis pigmentosa (adRP). Although the exact mechanism by which splicing factor defects trigger photoreceptor death is not completely clear, their role in retinitis pigmentosa has been demonstrated by several genetic and functional studies. To test for possible novel associations between splicing factors and adRP, we screened four tri-snRNP splicing factor genes (EFTUD2, PRPF4, NHP2L1, and AAR2) as candidate disease genes. METHODS: We screened up to 303 patients with adRP from Europe and North America who did not carry known RP mutations. Exon-PCR and Sanger methods were used to sequence the NHP2L1 and AAR2 genes, while the sequences of EFTUD2 and PRPF4 were obtained by using long-range PCRs spanning coding and non-coding regions followed by next-generation sequencing. RESULTS: We detected novel missense changes in individual patients in the sequence of the genes PRPF4 and EFTUD2, but the role of these changes in relationship to disease could not be verified. In one other patient we identified a novel nucleotide substitution in the 5' untranslated region (UTR) of NHP2L1, which did not segregate with the disease in the family. CONCLUSIONS: The absence of clearly pathogenic mutations in the candidate genes screened in our cohort suggests that EFTUD2, PRPF4, NHP2L1, and AAR2 are either not involved in adRP or are associated with the disease in rare instances, at least as observed in this study in patients of European and North American origin

Polymorphisms and promoter overactivity of the p22(phox) gene in vascular smooth muscle cells from spontaneously hypertensive rats

In a previous study, we found that the p22(phox) subunit of the NADH/NADPH oxidase is overexpressed in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHRs) with enhanced vascular production of superoxide anion ((.)O(2)(-)). Thus, we have investigated whether changes in the sequence or activity of the promoter region of p22(phox) gene are present in SHRs. To carry out this analysis, first of all, we characterized the rat gene structure and promoter region for the p22(phox) subunit. The p22(phox) gene spans approximately 10 kb and contains 6 exons and 5 introns. Primer extension analysis indicated the transcriptional start site 100 bp upstream from the translational start site. The immediate promoter region of the p22(phox) gene does not contain a TATA box, but there are a CCAC box and putative recognition sites for nuclear factors, such as SP1, gamma-interferon, and nuclear factor-kappaB. Using reporter-gene transfection analysis, we found that this promoter was functional in VSMCs. Furthermore, we observed that p22(phox) promoter activity was significantly higher in VSMCs from SHRs than from normotensive Wistar-Kyoto rats. In addition, we found that there were 5 polymorphisms in the sequence of p22(phox) promoter between Wistar-Kyoto rats and SHRs and that they were functional. The results obtained in this study provide a tool to explore the mechanisms that regulate the expression of p22(phox) gene in rat VSMCs. Furthermore, our findings show that changes in the sequence of p22(phox) gene promoter and in the degree of activation of VSMCs are responsible for upregulated expression of p22(phox) in SHRs

Functional Effect of the p22phox -930A/G Polymorphism on p22phox Expression and NADPH Oxidase Activity in Hypertension

Oxidative stress induced by superoxide is implicated in hypertension. NADPH oxidase is the main source of superoxide in phagocytic and vascular cells, and the p22phox subunit is involved in NADPH oxidase activation. Recently we reported an association of 930A/G polymorphism in the human p22phox gene promoter with hypertension. This study was designed to investigate the functional role of this polymorphism in hypertension. We thus investigated the relationships between the 930A/G polymorphism and p22phox expression and NADPH oxidase–mediated superoxide production in phagocytic cells from 70 patients with essential hypertension and 70 normotensive controls. Genotyping of the polymorphism was performed by restriction fragment length polymorphism. NADPH oxidase activity was determined by chemiluminescence assays, and p22phox mRNA and protein expression was measured by Northern and Western blotting, respectively. Compared with hypertensive subjects with the AA/AG genotype, hypertensive subjects with the GG genotype exhibited increased (P 0.05) phagocytic p22phox mRNA (1.26 0.06 arbitrary unit [AU] versus 0.99 0.03 AU) and protein levels (0.58 0.05 AU versus 0.34 0.04 AU) and enhanced NADPH oxidase activity (1998 181 counts/s versus 1322 112 counts/s). No differences in these parameters were observed among genotypes in normotensive cells. Transfection experiments on vascular smooth muscle cells showed that the A-to-G substitution of this polymorphism produced an increased reporter gene expression in hypertensive cells. Nitric oxide production, as assessed by measurement of serum nitric oxide metabolites, was lower in GG hypertensive subjects than in AA/AG hypertensive subjects. In conclusion, these results suggest that hypertensive subjects carrying the GG genotype of the p22phox 930A/G polymorphism are highly exposed to NADPH oxidase-mediated oxidative stress

Preliminary characterisation of the promoter of the human p22phox gene: identification of a new polymorphism associated with hypertension

The p22(phox) subunit is an essential protein in the activation of NAD(P)H oxidase. Here we report the preliminary characterisation of the human p22(phox) gene promoter. The p22(phox) promoter contains TATA and CCAC boxes and Sp1, gamma-interferon and nuclear factor kappaB sites. We screened for mutations in the p22(phox) promoter and identified a new polymorphism, localised at position -930 from the ATG codon, which was associated with hypertension. Mutagenesis experiments showed that the G allele had higher promoter activity than the A allele. These results suggest that the -930(A/G) polymorphism in the p22(phox) promoter may be a novel genetic marker associated with hypertension

Association of increased phagocytic NADPH oxidasedependent superoxide production with diminished nitric oxide generation in essential hypertension

Objective: Oxidative stress has been implicated in the pathogenesis of hypertension and its complications through alterations in nitric oxide (NO) metabolism. This study was designed to investigate whether a relationship exists between phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide anion (•O2-) production and NO generation in patients with essential hypertension. Methods: Superoxide production was assayed by chemiluminescence under baseline and stimulated conditions on mononuclear cells obtained from hypertensives (n = 51) and normotensives (n = 43). NO production was evaluated by determining serum NO metabolites, nitrate plus nitrite (NOx). Results: Although there were no differences in baseline •O2- production between normotensives and hypertensives, the •O2- production in phorbol myristate acetate (PMA)-stimulated mononuclear cells was increased (P < 0.05) in hypertensives compared with normotensives. The PMA-induced •O2- production was completely abolished by apocynin, a specific inhibitor of NADPH oxidase. Moreover, stimulation of •O2- production by angiotensin II and endothelin-1 was higher (P < 0.05) in cells from hypertensives than in cells from normotensives. In addition, diminished (P < 0.001) serum NOx was detected in hypertensives compared with normotensives. Interestingly, an inverse correlation (r = 0.493, P < 0.01) was found between •O2- production and NOx in hypertensives. Conclusions: Generation of •O2- mainly dependent on NADPH oxidase is abnormally enhanced in stimulated mononuclear cells from hypertensives. It is suggested that this alteration could be involved in the diminished NO production observed in these patients

Oxidative Stress in Arterial Hypertension: Role of NAD(P)H Oxidase

Increased vascular reactive oxygen species production, especially superoxide anion, contributes significantly in the functional and structural alterations present in hypertension. An enhanced superoxide production causes a diminished NO bioavailability by an oxidative reaction that inactivates NO. Exaggerated superoxide levels and a low NO bioavailability lead to endothelial dysfunction and hypertrophy of vascular cells. It has been shown that the enzyme NAD(P)H oxidase plays a major role as the most important source of superoxide anion in vascular cells. Several experimental observations have shown an enhanced superoxide generation as a result of the activation of vascular NAD(P)H oxidase in hypertension. Although this enzyme responds to stimuli such as vasoactive factors, growth factors, and cytokines, some recent data suggest the existence of a genetic background modulating the expression of its different components. New polymorphisms have been identified in the promoter of the p22(phox) gene, an essential subunit of NAD(P)H oxidase, influencing the activity of this enzyme. Genetic investigations of these polymorphisms will provide novel markers for determination of genetic susceptibility to oxidative stress in hypertension