Search

Aims Smokers are at increased risk of cardiovascular events. However, the exact mechanisms through which smoking influences cardiovascular disease resulting in accelerated atherosclerosis and vascular calcification are unknown. The aim of this study was to investigate effects of nicotine on initiation of vascular smooth muscle cell (VSMC) calcification and to elucidate underlying mechanisms. Methods and results We assessed vascular calcification of 62 carotid lesions of both smoking and non-smoking patients using ex vivo micro-computed tomography (µCT) scanning. Calcification was present more often in carotid plaques of smokers (n = 22 of 30, 73.3%) compared to non-smokers (n = 11 of 32, 34.3%; P Conclusion In this study, we provide evidence that nicotine induces Nox5-mediated pro-calcific processes as novel mechanism of increased atherosclerotic calcification. We identified that activation of α7 and α3 nAChR by nicotine increases intracellular Ca2+ and initiates calcification of hVSMCs through increased Nox5 activity, leading to oxidative stress-mediated EV release. Identifying the role of Nox5-induced oxidative stress opens novel avenues for diagnosis and treatment of smoking-induced cardiovascular disease.

Pharmacogenomics (PGx) is a clinically significant factor in the safe and efficacious use of medicines. While PGx knowledge is abundant for other populations, there are scarce PGx data on African populations and is little knowledge on drug-gene interactions for medicines used to treat diseases common in Africa. The aim of this study was to use a custom-designed open array to genotype clinically actionable variants in a Zimbabwean population. This study also identified some of the commonly used drugs in Zimbabwe and the associated genes involved in their metabolism.A custom-designed open array that covers 120 genetic variants was used to genotype 522 black Zimbabwean healthy volunteers using TaqMan-based single nucleotide polymorphism genotyping. Data were also accessed from Essential Drugs' List in Zimbabwe (EDLIZ), and the medicines were grouped into the associated biomarker groups based on their metabolism. We also estimated the national drug procurement levels for medicines that could benefit from PGx-guided use based on the data obtained from the national authorities in Zimbabwe.The results demonstrate the applicability of an open-array chip in simultaneously determining multiple genetic variants in an individual, thus significantly reducing cost and time to generate PGx data. There were significantly high frequencies of African-specific variants, such as the CYP2D6*17 and *29 variants and the CYP2B6*18 variant. The data obtained showed that the Zimbabwean population exhibits PGx variations in genes important for the safe and efficacious use of drugs approved by the EDLIZ and are procured at significantly large amounts annually. The study has established a cohort of genotyped healthy volunteers that can be accessed and used in the conduct of clinical pharmacogenetic studies for drugs entering a market of people of predominantly African ancestry.Our study demonstrated the potential benefit of integrating PGx in Zimbabwe for the safe and efficacious use of drugs that are commonly used.

Impaired angiogenesis in ischemic tissue is a hallmark of diabetes. Thioredoxin-interacting protein (TXNIP) is an exquisitely glucose-sensitive gene that is overexpressed in diabetes. As TXNIP modulates the activity of the key angiogenic cytokine vascular endothelial growth factor (VEGF), we hypothesized that hyperglycemia-induced dysregulation of TXNIP may play a role in the pathogenesis of impaired angiogenesis in diabetes. In the current study, we report that high glucose–mediated overexpression of TXNIP induces a widespread impairment in endothelial cell (EC) function and survival by reducing VEGF production and sensitivity to VEGF action, findings that are rescued by silencing TXNIP with small interfering RNA. High glucose–induced EC dysfunction was recapitulated in normal glucose conditions by overexpressing either TXNIP or a TXNIP C247S mutant unable to bind thioredoxin, suggesting that TXNIP effects are largely independent of thioredoxin activity. In streptozotocin-induced diabetic mice, TXNIP knockdown to nondiabetic levels rescued diabetes-related impairment of angiogenesis, arteriogenesis, blood flow, and functional recovery in an ischemic hindlimb. These findings were associated with in vivo restoration of VEGF production to nondiabetic levels. These data implicate a critical role for TXNIP in diabetes-related impairment of ischemia-mediated angiogenesis and identify TXNIP as a potential therapeutic target for the vascular complications of diabetes.

Background. Circulating progenitor cells (PC) can positively influence the healing of ischaemic myocardium. Cardiovascular risk factors including diabetes mellitus (DM) may have a negative influence on both number and recruitment of PC. Recent evidence suggests that less differentiated CD133+PC contribute to myocardial healing and are promising candidates for therapy. Therefore, we investigated whether DM affects CD133+PC. Methods. CD133+PC were analyzed in patients following acute myocardial infarction and successful reperfusion [acute myocardial infarction (AMI, n = 45) with/without non-insulin-requiring type 2 DM (T2DM)]. Stable coronary artery disease patients (CAD, n = 45) served as stable controls. Number and phenotype of CD133+PC were assessed by flow cytometry. CD133+PC chemotaxis was assessed towards vascular endothelial growth factor, an angiogenic stimulus upregulated in AMI. The expression of anti-oxidant enzymes in CD133+PC was detected by reverse-transcriptase PCR. Results. In non-DM patients, the number of CD133+PC increased on day 3 following AMI (P = 0.0001). In contrast, no changes were observed in AMI patients with T2DM. Regarding the function of CD133+PC, an enhanced chemotactic response was observed following AMI in both non-DM (P = 0.0001) and T2DM (P = 0.007). However, the AMI-related functional activation was significantly weaker in diabetic patients (P = 0.001). Moreover, the expression of catalase was lower in CD133+PC from T2DM. Conclusions. Our results show that T2DM not only limits the abundance of CD133+PC following AMI, but also limits their activation. This might be explained by a lower resistance of CD133+PC to oxidative stress. Our data provide a possible explanation for the delayed postischaemic vascular healing and myocardial recovery in DM.

Objective—The involvement of transition metals in atherosclerosis is controversial. Some epidemiological studies have reported a relationship between iron (Fe) and cardiovascular disease, whereas others have not. Experimental studies have reported elevated levels of iron and copper (Cu) in diseased human arteries but have often used methods that release metal ions from proteins.Methods and Results—In this study, we have used the minimally invasive technique of electron paramagnetic resonance (EPR) spectroscopy and inductively coupled plasma mass spectroscopy (ICPMS) to quantify iron and copper in ex vivo healthy human arteries and carotid lesions. The EPR spectra detected are characteristic of nonheme Fe(III) complexes. Statistically elevated levels of iron were detected in the intima of lesions compared with healthy controls (0.370 versus 0.022 nmol/mg tissue for EPR, 0.525 versus 0.168 nmol/mg tissue by ICPMS,PPConclusions—These data support the hypothesis that iron accumulates in human lesions and may contribute to disease progression.

Objective— Oxidized lipids and proteins, as well as decreased antioxidant levels, have been detected in human atherosclerotic lesions, with oxidation catalyzed by iron and copper postulated to contribute to lesion development. Zinc has been postulated to displace iron from critical sites and thereby protect against damage. In this study, metal ion and protein oxidation levels were quantified in human carotid and abdominal artery specimens containing early-to-advanced lesions, to determine whether zinc concentrations correlate inversely with iron levels and protein oxidation. Methods and Results— Metal ions were quantified by EPR and inductively coupled plasma mass spectroscopy. Native and oxidized protein side-chains were quantified by high-performance liquid chromatography. Elevated levels of zinc (≈6-fold) were detected in advanced lesions compared to healthy tissue or early lesions. Zinc did not correlate negatively with iron or copper levels suggesting that zinc does not displace these metal ions. Highly significant positive correlations ( P Conclusions— Zinc did not correlate with low iron levels and reduced protein oxidation. These data indicate that zinc does not prevent protein oxidation in advanced lesions. The reported protective effect of zinc accumulation is proposed to be associated with lesion calcification.

Objective— The role of antioxidants in preventing vascular disease remains controversial. Vascular endothelial growth factor (VEGF-A) is important for endothelial and monocyte function. This study investigated the negative effects of smoking on monocyte migratory responsiveness to VEGF-A and the usefulness of vitamin C to prevent smoking-induced monocyte dysfunction. Methods and Results— The chemotactic response of isolated monocytes from a cohort of 17 non-smokers and 10 smokers toward VEGF-A was assessed. VEGF-A significantly stimulated the migration of monocytes in non-smokers; the monocytes from smokers failed to respond to VEGF-A. Repeated analysis after 2 weeks of vitamin C intake (2g/d) showed a fully restored VEGF-A-induced monocyte migration in smokers. VEGF-A serum levels were not altered by vitamin C. VEGF-A-inducible kinase activity was intact in monocytes from smokers as assessed by in vitro kinase assay. Monocyte dysfunction can be mimicked in vitro by challenging monocytes with a range of reactive oxygen species (ROS). Conclusions— Stimulation of monocyte migration by VEGF-A was severely attenuated in smokers, and the deficit observed was surmounted by vitamin C supplementation. The negative effects of smoking on monocyte function may translate into adverse impacts on VEGF-A-dependent repair processes such as arteriogenesis. These results propose a causative role of oxidative stress in smoking-induced monocyte dysfunction.

Previous studies have provided compelling evidence for the presence of oxidized proteins and lipids in advanced human atherosclerotic lesions. The catalyst responsible for such oxidation is unknown and controversial. We have previously provided evidence for elevated levels of iron in lesions. In this study we hypothesized that if iron ions catalyzed protein and lipid oxidation in the artery wall, then there should be a positive correlation between these parameters. Iron concentrations in ex vivo healthy human arteries and advanced carotid lesions were quantified by electron paramagnetic resonance spectroscopy. Four specific side-chain oxidation products of proteins, and the lipid oxidation products 7-ketocholesterol and cholesterol ester alcohols and hydroperoxides, were quantified by HPLC in the same samples used for the iron measurements. Parent amino acids, cholesterol, and cholesterol esters were also quantified. Statistically elevated levels of iron, cholesterol, cholesterol esters, 7-ketocholesterol, and cholesterol ester alcohols and hydroperoxides were detected in advanced lesions compared with healthy control tissue. Iron levels correlated positively and strongly with all four markers of protein oxidation, but not with either marker of lipid oxidation. These data support the hypothesis that elevated levels of iron contribute to the extent of protein, but not lipid, oxidation in advanced human lesions.