Peripheral artery disease, redox signaling, oxidative stress - Basic and clinical aspects.

Reactive oxygen and nitrogen species (ROS and RNS, e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. At higher concentrations, ROS and RNS lead to oxidative stress and oxidative damage of biomolecules (e.g. via formation of peroxynitrite, fenton chemistry). Peripheral artery disease (PAD) is characterized by severe ischemic conditions in the periphery leading to intermittent claudication and critical limb ischemia (end stage). It is well known that redox biology and oxidative stress play an important role in this setting. We here discuss the major pathways of oxidative stress and redox signaling underlying the disease progression with special emphasis on the contribution of inflammatory processes. We also highlight therapeutic strategies comprising pharmacological (e.g. statins, angiotensin-converting enzyme inhibitors, phosphodiesterase inhibition) and non-pharmacological (e.g. exercise) interventions. Both of these strategies induce potent indirect antioxidant and anti-inflammatory mechanisms that may contribute to an improvement of PAD associated complications and disease progression by removing excess formation of ROS and RNS (e.g. by ameliorating primary complications such as hyperlipidemia and hypertension) as well as the normalization of the inflammatory phenotype suppressing the progression of atherosclerosis

Supervised exercise training in peripheral arterial disease increases vascular shear stress and profunda femoral artery diameter.

Background Arteriogenesis is promoted by flow- and pressure-related forces such as tangential wall stress and laminar shear stress. Exercise training (ET) is known to promote arteriogenesis in peripheral arterial disease (PAD) patients. It remains unclear whether supervised ET (SET) promotes arteriogenesis more efficiently than non-SET (nSET). Methods and results Forty PAD patients participated in a SET or nSET training programme ( n = 20 each) and were compared to 20 healthy individuals without any history of cardiovascular events. Femoral artery diameter, flow and velocity were measured by ultrasound. Tangential wall stress and laminar shear stress were calculated for femoral arteries. Follow-up was performed after a mean of 7.65 ± 1.62 months. At follow-up, only the SET group showed a significant increase in lumen diameter of the profunda femoral artery ( p = 0.03), accompanied by an increase of tangential wall stress ( p = 0.002). Laminar shear stress decreased, but remained higher for the SET group compared to controls ( p < 0.01). Individual changes in walking distance were higher for SET patients ( p = 0.01) than nSET patients ( p = 0.07). Profunda femoral lumen diameter and tangential wall stress correlated directly with walking distance ( r = 0.446; p < 0.001), as well as with each other ( r = 0.743; p < 0.0001). Conclusions Our results indicate that SET promotes arteriogenesis more efficiently than nSET. Femoral lumen diameter and flow might help with the monitoring of ET efficiency and potential arteriogenesis

Supervised exercise training in peripheral arterial disease increases vascular shear stress and profunda femoral artery diameter

Background Arteriogenesis is promoted by flow- and pressure-related forces such as tangential wall stress and laminar shear stress. Exercise training (ET) is known to promote arteriogenesis in peripheral arterial disease (PAD) patients. It remains unclear whether supervised ET (SET) promotes arteriogenesis more efficiently than non-SET (nSET). Methods and results Forty PAD patients participated in a SET or nSET training programme ( n = 20 each) and were compared to 20 healthy individuals without any history of cardiovascular events. Femoral artery diameter, flow and velocity were measured by ultrasound. Tangential wall stress and laminar shear stress were calculated for femoral arteries. Follow-up was performed after a mean of 7.65 ± 1.62 months. At follow-up, only the SET group showed a significant increase in lumen diameter of the profunda femoral artery ( p = 0.03), accompanied by an increase of tangential wall stress ( p = 0.002). Laminar shear stress decreased, but remained higher for the SET group compared to controls ( p < 0.01). Individual changes in walking distance were higher for SET patients ( p = 0.01) than nSET patients ( p = 0.07). Profunda femoral lumen diameter and tangential wall stress correlated directly with walking distance ( r = 0.446; p < 0.001), as well as with each other ( r = 0.743; p < 0.0001). Conclusions Our results indicate that SET promotes arteriogenesis more efficiently than nSET. Femoral lumen diameter and flow might help with the monitoring of ET efficiency and potential arteriogenesis

Phenotypic and functional characterization of neutrophils and monocytes from patients with myelodysplastic syndrome by flow cytometry.

Myelodysplastic syndrome (MDS) is a clonal stem cell disorder frequently associated with inefficient granulopoiesis showing dysplastic polymorphonuclear neutrophils (PMNs). To assess PMN functionality in MDS in a clinical routine setting, 30 MDS patients and ten healthy volunteers were analyzed for PMN and monocyte phenotype and function (degranulation, CD62L shedding, oxidative burst and phagocytosis) upon stimulation with lipopolysaccharide by multi-color flow cytometry (MCFC). Our data show a heterogeneous pattern for CD66, CD16 and CD64 expression on PMNs of MDS patients. CD62L shedding rate and CD66 degranulation were reduced. Interestingly, we detected correlations between the WHO adapted prognostic scoring system (WPSS) and CD16 expression on PMNs as well as the international prognostic scoring system (IPSS) and CD11b degranulation by MCFC, suggesting clinical relevance of MCFC based function testing. In conclusion, MCFC of myelodysplastic immunophenotypes and PMN functionality are applicable in clinical settings, but further prospective studies are needed to assess the practical clinical value of such analyses

Serum Ceramides and Type 2 Diabetes Are Mutually Independent Predictors of Cardiovascular Events in Patients With Peripheral Artery Disease

Abstract Introduction: Ceramides are enriched in atherosclerotic plaques, and a set of circulating ceramides including Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/24:1), and Cer(d18:1/24:0) has recently emerged as predictors of cardiovascular outcomes in coronary artery disease patients. Hypothesis: We hypothesize that they have the power to predict cardiovascular events in patients with peripheral artery disease (PAD). Methods: We measured the serum concentrations of the above mentioned ceramides in a cohort of 380 patients with sonographically proven PAD, of whom 107 had type 2 diabetes (T2DM). Prospectively, we recorded 221 cardiovascular events over a mean follow-up time of 6.3±2.3 years. Results: Cardiovascular event risk was higher in T2DM patients than in those who did not have diabetes (69 vs. 52%, p=0.001). The ceramides Cer(18:1/16:0) and Cer(18:1/24:1) and the respective ratios Cer(18:1/16:0) / Cer(18:1/24:0) and Cer(18:1/24:1) / Cer(18:1/24:0) were significant predictors of cardiovascular events both univariately and after multivariate adjustment including the presence of T2DM (figure). Conversely, T2DM predicted cardiovascular events independently from the investigated ceramides (adjusted HR 1.76 [1.31-2.35], p<0.001). Conclusions: We conclude that the investigated ceramides and T2DM are mutually independent predictors of cardiovascular events in PAD patients

Leukocyte-platelet aggregates-a phenotypic characterization of different stages of peripheral arterial disease.

The formation of monocyte-platelet aggregates and neutrophil-platelet aggregates (MPA and NPA, respectively) is influenced by inflammation, but also might contribute to an exacerbation of inflammatory responses in atherosclerotic plaque. The purpose of this study was to analyze MPA and NPA proportions in regard to different stages of peripheral arterial disease (PAD). Forty-five patients with intermittent claudication (IC) (3 groups: Rutherford (R)-1, R-2, and R-3; each n = 15), 20 patients with critical limb ischemia (CLI) (Rutherford 5 (40%) and 6 (60%)), and 20 healthy controls were studied. Analyses of monocyte (Mon) subpopulations (CD14++CD16- (classical) Mon1, CD14++CD16+ (intermediate) Mon2, CD14+CD16++ (non-classical) Mon3), MPA, and NPA was performed from whole blood by flow cytometry. Controls showed an increased proportion of the Mon1 subpopulation (p < 0.001), whereas CLI patients showed a significant increase of the Mon2 subpopulation compared to controls, R-1, or R-2 patients (p < 0.0001). For the Mon3 subpopulation, CLI and R-3 patients showed an increased proportion (p < 0.05). MPA formation with the proinflammatory Mon2 and Mon3 subpopulations was increased in CLI patients (both p < 0.01). Similarly, NPA was significantly increased in CLI patients (p < 0.05). Serological markers of inflammation and procoagulation (fibrinogen [r = 0.459, p < 0.001], soluble triggering receptor expressed on myeloid cells (sTREM-1) [r = 0.237, p < 0.05] and P-Selectin [r = 0.225, p < 0.05]) correlated directly with MPA formation on the Mon2 subpopulation. We found an association of inflammatory and procoagulatory markers with increased formation of MPA on the Mon2 subpopulation. Since R-3 patients also had significantly increased MPA, one can speculate that the inflammatory burden might promote an aggravation of the disease

Reasons for Disparity in Statin Adherence Rates between Clinical Trials and Real World Observations. A Review.

With statins, the reported rate of adverse events differs widely between randomized clinical trials (RCTs) and observations in clinical practice, the rates being 1-2% in RCTs versus 10-20% in the so-called real world. One possible explanation is the claim that RCTs mostly use a run-in period with a statin. This would exclude intolerant patients from being included into RCTs and therefore favor a bias towards lower rates of intolerance.We here review data from RCTs with more than 1000 participants with and without a run-in period, which were included in the Cholesterol Treatment Trialists collaboration (CTTC). Two major conclusions arise: 1) The majority of RCTs did not have a test dose of a statin in the run-in phase. 2) A test dose in the run-in phase was not associated with a significantly improved adherence rate within that trial when compared to trials without a test dose. Taken together, the RCTs of statins reviewed here do not suggest a bias towards an artificially higher adherence rate because of a run-in period with a test dose of the statin.Other possible explanations for the apparent disparity between RCTs and real world observations are also included in this review albeit mostly not supported by scientific data