Effects of acute and chronic endurance exercise on intracellular nitric oxide in putative endothelial progenitor cells: role of NAPDH oxidase

Endothelial progenitor cell mobilization based on exercise volume in patients with cardiovascular disease and healthy individuals: a systematic review and meta-analysis

Endothelial progenitor cells (EPCs) play a vital role in protecting endothelial dysfunction and cardiovascular disease (CVD). Physical exercise stimulates the mobilization of EPCs, and along with vascular endothelial growth factor (VEGF), promotes EPC differentiation, and contributes to vasculogenesis. The present meta-analysis examines the exercise-induced EPC mobilization and has an impact on VEGF in patients with CVD and healthy individuals. Database research was conducted (PubMed, EMBASE, Cochrane Library of Controlled Trials) by using an appropriate algorithm to indicate the exercise-induced EPC mobilization studies. Eligibility criteria included EPC measurements following exercise in patients with CVD and healthy individuals. A continuous random effect model meta-analysis (PROSPERO-CRD42019128122) was used to calculate mean differences in EPCs (between baseline and post-exercise values or between an experimental and control group). A total of 1460 participants (36 studies) were identified. Data are presented as standard mean difference (Std.MD) and 95% confidence interval (95% CI). Aerobic training stimulates the mobilization of EPCs and increases VEGF in patients with CVD (EPCs: Std.MD: 1.23, 95% CI: 0.70-1.76; VEGF: Std.MD: 0.76, 95% CI:0.16-1.35) and healthy individuals (EPCs: Std.MD: 1.11, 95% CI:0.53-1.69; VEGF: Std.MD: 0.75, 95% CI: 0.01-1.48). Acute aerobic exercise (Std.MD: 1.40, 95% CI: 1.00-1.80) and resistance exercise (Std.MD: 0.46, 95%CI: 0.10-0.82) enhance EPC numbers in healthy individuals. Combined aerobic and resistance training increases EPC mobilization (Std.MD:1.84, 95% CI: 1.03-2.64) in patients with CVD. Adequate exercise volume (>60%VO2max >30 min; P = 0.00001) yields desirable results. Our meta-analysis supports the findings of the literature. Exercise volume is required to obtain clinically significant results. Continuous exercise training of high-to-moderate intensity with adequate duration as well as combined training with aerobic and resistance exercise stimulates EPC mobilization and increases VEGF in patients with CVD and healthy individuals.

Changes in Circulating Stem and Progenitor Cell Numbers Following Acute Exercise in Healthy Human Subjects: a Systematic Review and Meta-analysis

Despite of the increasing number of investigations on the effects of acute exercise on circulating stem and progenitor cell (SC) numbers, and in particular on respective subgroups, i.e. endothelial (ESC), hematopoietic (HSC), and mesenchymal (MSC) stem and progenitor cells, a consensus regarding mechanisms and extent of these effects is still missing. The aim of this meta-analysis was to systematically evaluate the overall-effects of acute exercise on the different SC-subgroups and investigate possible subject- and intervention-dependent factors affecting the extent of SC-mobilization in healthy humans. Trials assessing SC numbers before and at least one timepoint after acute exercise, were identified in a systematic computerized search. Compared to baseline, numbers were significantly increased for early and non-specified SCs (enSCs) until up to 0.5 h after exercise (0–5 min: +0.64 [Standardized difference in means], p < 0.001; 6–20 min: +0.42, p < 0.001; 0.5 h: +0.29, p = 0.049), for ESCs until 12–48 h after exercise (0–5 min: +0.66, p < 0.001; 6–20 min: +0.43 p < 0.001; 0.5 h: +0.43, p = 0.002; 1 h: +0.58, p = 0.001; 2 h: +0.50, p = 0.002; 3–8 h: +0.70, p < 0.001; 12–48 h: +0.38, p = 0.003) and for HSCs at 0–5 min (+ 0.47, p < 0.001) and at 3 h after exercise (+ 0.68, p < 0.001). Sex, intensity and duration of the intervention had generally no influence. The extent and kinetics of the exercise-induced mobilization of SCs differ between SC-subpopulations. However, also definitions of SC-subpopulations are non-uniform. Therefore, finding a consensus with a clear definition of cell surface markers defining ESCs, HSCs and MSCs is a first prerequisite for understanding this important topic.

Mitochondrial dysfunction in skeletal muscle of fukutin-deficient mice is resistant to exercise- and 5-aminoimidazole-4-carboxamide ribonucleotide-induced rescue

NEW FINDINGS

What is the central question of this study? Does fukutin deficiency in skeletal muscle cause mitochondrial dysfunction, and if so, can AMP-activated protein kinase (AMPK) stimulation via 5-aminoimidazole-4-carboxamide ribonucleotide attenuate this through regulation of mitochondrial biogenesis and autophagy? What is the main finding and its importance? Mitochondrial dysfunction is associated with fukutin deficiency and AMPK stimulation may benefit muscle contractility to a greater extent than mitochondrial function.

ABSTRACT

Disruptions in the dystrophin-glycoprotein complex (DGC) are clearly the primary basis underlying various forms of muscular dystrophies and dystroglycanopathies, but the cellular consequences of DGC disruption are still being investigated. Mitochondrial abnormalities are becoming an apparent consequence and contributor to dystrophy disease pathology. Herein, we demonstrate that muscle-specific deletion of the fukutin gene (Myf5/fktn-KO mice (Fktn KO)), a model of secondary dystroglycanopathy, results in ∼30% lower muscle strength (P < 0.001) and 16% lower mitochondrial respiratory function (P = 0.002) compared to healthy littermate controls (LM). We also observed ∼80% lower expression of the gene for peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) (P = 0.004), a primary transcription factor for mitochondrial biogenesis, in Fktn KO mice that likely contributes to the mitochondrial defects. PGC-1α is post-translationally regulated via phosphorylation by AMP-activated protein kinase (AMPK). Treatment with the AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) failed to rescue mitochondrial deficits in Fktn KO mice (P = 0.458) but did have beneficial (∼30% greater) effects on recovery of muscle contractility following injury in both LM and Fktn KO mice compared to saline treatment (P = 0.006). The beneficial effects of AMPK stimulation via AICAR on muscle contractile function may be partially explained by AMPK's other role of regulating skeletal muscle autophagy, a cellular process critical for clearance of damaged and/or dysfunctional organelles. Two primary conclusions can be drawn from this data: (1) fukutin deletion produces intrinsic muscular metabolic defects that likely contribute to dystroglycanopathy disease pathology, and (2) AICAR treatment accelerates recovery of muscle contractile function following injury suggesting AMPK signalling as a possible target for therapeutic strategies.

Establishment of optimal exercise therapy using near-infrared spectroscopy monitoring of tissue muscle oxygenation after therapeutic angiogenesis for patients with critical limb ischemia: A multicenter, randomized, controlled trial

Critical limb ischemia (CLI) is a potentially life-threatening condition that involves severely reduced blood flow to the peripheral arteries due to arteriosclerosis obliterans (ASO) of the limbs or a similar condition. CLI patients must undergo revascularization to avoid amputation of the lower limbs and improve their survival prognosis. However, the outcomes of conventional surgical revascularization or endovascular therapy are inadequate; therefore, establishing further effective treatment methods is an urgent task. We perform therapeutic angiogenesis using autologous bone marrow-derived mononuclear cells in clinical practice and demonstrated its safety and efficacy for CLI patients for whom conventional treatments failed or are not indicated. Exercise therapies must be devised for CLI patients who have undergone therapeutic angiogenesis to save their limbs and improve survival. Because evidence regarding the efficacy and safety of exercise therapy for CLI patients is lacking, we plan to perform a prospective trial of the efficacy and safety of optimal exercise therapy following therapeutic angiogenesis for CLI patients.The trial will enroll 30 patients between 20 and 79 years with Rutherford category 4 or 5 CLI caused by ASO who will undergo therapeutic angiogenesis. Participants will be randomly allocated to receive either optimal exercise therapy or fixed exercise therapy. Those receiving optimal exercise therapy will undergo tissue muscle oxygen saturation monitoring using near-infrared spectroscopy while performing exercises and will be prescribed optimal exercise therapy. The optimal amount of exercise will be determined on day 8, 31, 61, 91 and 181 after therapeutic angiogenesis.

ETHICS AND DISSEMINATION

This protocol was approved by the Institutional Review Boards of Kyoto Prefectural University of Medicine. In accordance with the Helsinki Declaration, written informed consent has been obtained from all participants prior to enrollment. The results of this trial will be disseminated by publication in a peer-reviewed journal.

TRIAL REGISTRATION

This trial is registered at http://www.umin.ac.jp/ctr/index.htm (identifier: UMIN000035288).

Adult Stem Cells: Beyond Regenerative Tool, More as a Bio-Marker in Obesity and Diabetes

Obesity, diabetes, and cardiovascular diseases are increasing rapidly worldwide and it is therefore important to know the effect of exercise and medications for diabetes and obesity on adult stem cells. Adult stem cells play a major role in remodeling and tissue regeneration. In this review we will focus mainly on two adult stem/progenitor cells such as endothelial progenitor cells and mesenchymal stromal cells in relation to aerobic exercise and diabetes medications, both of which can alter the course of regeneration and tissue remodelling. These two adult precursor and stem cells are easily obtained from peripheral blood or adipose tissue depots, as the case may be and are precursors to endothelium and mesenchymal tissue (fat, bone, muscle, and cartilage). They both are key players in maintenance of cardiovascular and metabolic homeostasis and can act also as useful biomarkers.

Effect of an 8-Week Individualized Training Program on Blood Biomarkers, Adipokines and Endothelial Function in Obese Young Adolescents with and without Metabolic Syndrome

Obesity is a chronic condition whose incidence is growing due to lack of exercise and frequent nutrition disorders. Childhood obesity has reached epidemic proportions worldwide. One of the best treatment methods is physical training. However, conflicting results have been reported regarding its clinical effectiveness. These contrasting findings may be due to the type and intensity of the adopted physical training program. Therefore, the purpose of the current study was to investigate the effect of an 8-week individualized physical training program on endothelial function, blood biomarkers and adipokine levels in obese children with and without metabolic syndrome (MS). One-hundred-and-twenty-two obese adolescents (71 obese without MS and 51 obese with MS) aged 14 ± 2 years were included in this study. The 8-week individualized training program decreased glucose, triglycerides, total cholesterol, low-density lipoprotein cholesterol and leptin in obese subjects with and without MS. However, adiponectin and endothelial-dependent vasodilatation increased in the follow-up study in both groups. Taken together, the findings suggest that individualized training program is an effective means for the treatment of obesity and MS in pediatric populations.

Glucose and acute exercise influence factors secreted by circulating angiogenic cells in vitro

Circulating angiogenic cells (CAC) influence vascular repair through the secretion of proangiogenic factors and cytokines. While CAC are deficient in patients with diabetes and exercise has a beneficial effect on CACs, the impact of these factors on paracrine secretion from CAC is unknown. We aimed to determine whether the in vitro secretion of selected cytokines and nitric oxide (NO) from CAC is influenced by hyperglycemia and acute exercise. Colony‐forming unit CAC (CFU‐CAC) were cultured from young active men (n = 9, 24 ± 2 years) at rest and after exercise under normal (5 mmol/L) and elevated (15 mmol/L) glucose. Preliminary relative multiplex cytokine analysis revealed that CAC conditioned culture media contained three of six measured cytokines: transforming growth factor‐beta‐1 (TGFβ1), tumor necrosis factor alpha (TNFα), and monocyte chemotactic protein‐1 (MCP‐1). Single quantitative cytokine analysis was used to determine the concentration of each cytokine from the four conditions. NO was measured via Griess assay. There was a significant effect of CAC exposure to in vivo exercise on in vitro TGFβ1 secretion (P = 0.024) that was independent of glucose concentration. There was no effect of glucose or acute exercise on TNFα or MCP‐1 concentration (both P > 0.05). The concentration of NO from CFU‐CAC cultured in elevated glucose was lower following acute exercise (P = 0.002) suggesting that exercise did not maintain NO secretion under hyperglycemic conditions. Our results identify paracrine signaling factors that may be responsible for the proangiogenic function of CFU‐CAC and an influence of acute exercise and elevated glucose on CFU‐CAC soluble factor secretion.

Vascular Ageing and Exercise: Focus on Cellular Reparative Processes

Ageing is associated with an increased risk of developing noncommunicable diseases (NCDs), such as diabetes and cardiovascular disease (CVD). The increased risk can be attributable to increased prolonged exposure to oxidative stress. Often, CVD is preceded by endothelial dysfunction, which carries with it a proatherothrombotic phenotype. Endothelial senescence and reduced production and release of nitric oxide (NO) are associated with “vascular ageing” and are often accompanied by a reduced ability for the body to repair vascular damage, termed “reendothelialization.” Exercise has been repeatedly shown to confer protection against CVD and diabetes risk and incidence. Regular exercise promotes endothelial function and can prevent endothelial senescence, often through a reduction in oxidative stress. Recently, endothelial precursors, endothelial progenitor cells (EPC), have been shown to repair damaged endothelium, and reduced circulating number and/or function of these cells is associated with ageing. Exercise can modulate both number and function of these cells to promote endothelial homeostasis. In this review we look at the effects of advancing age on the endothelium and these endothelial precursors and how exercise appears to offset this “vascular ageing” process.

Aerobic interval exercise improves parameters of nonalcoholic fatty liver disease (NAFLD) and other alterations of metabolic syndrome in obese Zucker rats

Metabolic syndrome (MS) is a group of metabolic alterations that increase the susceptibility to cardiovascular disease and type 2 diabetes. Nonalcoholic fatty liver disease has been described as the liver manifestation of MS. We aimed to test the beneficial effects of an aerobic interval training (AIT) protocol on different biochemical, microscopic, and functional liver alterations related to the MS in the experimental model of obese Zucker rat. Two groups of lean and obese animals (6 weeks old) followed a protocol of AIT (4 min at 65%-80% of maximal oxygen uptake, followed by 3 min at 50%-65% of maximal oxygen uptake for 45-60 min, 5 days/week, 8 weeks of experimental period), whereas 2 control groups remained sedentary. Obese rats had higher food intake and body weight (P < 0.0001) and suffered significant alterations in plasma lipid profile, area under the curve after oral glucose overload (P < 0.0001), liver histology and functionality, and antioxidant status. The AIT protocol reduced the severity of alterations related to glucose and lipid metabolism and increased the liver protein expression of PPARγ, as well as the gene expression of glutathione peroxidase 4 (P < 0.001). The training protocol also showed significant effects on the activity of hepatic antioxidant enzymes, although this action was greatly influenced by rat phenotype. The present data suggest that AIT protocol is a feasible strategy to improve some of the plasma and liver alterations featured by the MS.

Exercise and Stem Cells

Stem cells are traditionally studied in the context of embryonic development, yet studies confirm that a fraction remains in the adult organism for the purpose of daily remodeling and rejuvenation of multiple tissues following injury. Adult stem cells (ASCs) are found in close proximity to vessels and respond to tissue-specific cues in the microenvironment that dictate their fate and function. Exercise can dramatically alter strain sensing, extracellular matrix composition, and inflammation, and such changes in the niche likely alter ASC quantity and function postexercise. The field of stem cell biology is still in its infancy and identification and terminology of ASCs continues to evolve; thus, current information regarding exercise and stem cells is lacking. This chapter summarizes the literature that reports on the ASC response to acute exercise and exercise training, with particular emphasis on hematopoietic stem cells, endothelial progenitor cells, and mesenchymal stem cells.

Chronic endurance exercise affects paracrine action of CD31+ and CD34+ cells on endothelial tube formation

We aimed to determine if chronic endurance-exercise habits affected redox status and paracrine function of CD34(+) and CD34(-)/CD31(+) circulating angiogenic cells (CACs). Subjects were healthy, nonsmoking men and women aged 18-35 yr and categorized by chronic physical activity habits. Blood was drawn from each subject for isolation and culture of CD34(+) and CD34(-)/CD31(+) CACs. No differences in redox status were found in any group across either cell type. Conditioned media (CM) was generated from the cultured CACs and used in an in vitro human umbilical vein endothelial cell-based tube assay. CM from CD34(+) cells from inactive individuals resulted in tube structures that were 29% shorter in length (P < 0.05) and 45% less complex (P < 0.05) than the endurance-trained group. CD34(-)/CD31(+) CM from inactive subjects resulted in tube structures that were 26% shorter in length (P < 0.05) and 42% less complex (P < 0.05) than endurance-trained individuals. Proteomics analyses identified S100A8 and S100A9 in the CM. S100A9 levels were 103% higher (P < 0.05) and S100A8 was 97% higher in the CD34(-)/CD31(+) CM of inactive subjects compared with their endurance-trained counterparts with no significant differences in either protein in the CM of CD34(+) CACs as a function of training status. Recombinant S100A8/A9 treatment at concentrations detected in inactive subjects' CD34(-)/CD31(+) CAC CM also reduced tube formation (P < 0.05). These findings are the first, to our knowledge, to demonstrate a differential paracrine role in CD34(+) and CD34(-)/CD31(+) CACs on tube formation as a function of chronic physical activity habits and identifies a differential secretion of S100A9 by CD34(-)/CD31(+) CACs due to habitual exercise.

Circulating angiogenic cell population responses to 10 days of reduced physical activity

Circulating angiogenic cells (CACs) are a diverse group that have been identified as predictors of cardiovascular health and are inversely proportional to cardiovascular disease (CVD) outcomes. Inactivity is a growing concern in industrialized nations and is an independent risk factor for CVD. There is limited evidence regarding the impact of reduced physical activity (rPA) on different CAC populations. The purpose of this study was to evaluate the effect of objectively monitored rPA with maintained energy balance on two CAC populations (CFU and CD34(+) cells), intracellular nitric oxide (NOi), and genes related to NO production in active, healthy men. Participants (age 25 ± 2.9 yr) refrained from structured physical activity for 10 days, which was reflected by a significant reduction in time in vigorous + very vigorous intensity activity (P = 0.03). Sedentary time tended to increase (P = 0.06) with rPA. CFU CACs have been characterized as mainly monocytic and lymphocytic cells. We found significant reductions in both the number of CFU CACs (-35.69%, P = 0.01) and CFU CAC NOi (-33.84%, P = 0.03). Neither NOi nor the number of CD34(+) cells, which are hematopoietic and endothelial progenitors, changed with rPA. We found no significant differences in NO-related gene expression or oxidative stress-related gene expression with rPA in either CAC type. Therefore, we conclude that although various CAC populations have been related to vascular health, regular physical activity is necessary to maintain CAC NOi and the vulnerability of CACs to short-term reductions in physical activity is population specific.

Effects of physical activity on endothelial progenitor cells (EPCs)

Physical activity has a therapeutic role in cardiovascular disease (CVD), through its beneficial effects on endothelial function and cardiovascular system. Circulating endothelial progenitor cells (EPCs) are bone marrow (BM) derived cells that represent a novel therapeutic target in CVD patients, because of their ability to home to sites of ischemic injury and repair the damaged vessels. Several studies show that physical activity results in a significant increase in circulating EPCs, and, in particular, there are some evidence of the beneficial exercise-induced effects on EPCs activity in CVD settings, including coronary artery disease (CAD), heart failure (HF), and peripheral artery disease (PAD). The aim of this paper is to review the current evidence about the beneficial effects of physical exercise on endothelial function and EPCs levels and activity in both healthy subjects and patients with CVD.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Low clonogenic potential of circulating angiogenic cells is associated with lower density of capillaries in skeletal muscle in patients with impaired glucose tolerance

BACKGROUND

Reduced density of capillaries in skeletal muscle can limit insulin, glucose, and oxygen supply to the muscle, thereby contributing to worsening metabolism in older adults. The lower skeletal muscle capillarization in impaired glucose tolerance (IGT) may partially be due to circulating angiogenic cell dysfunction. Circulating angiogenic cells maintain the vasculature and promote angiogenesis, but circulating angiogenic cell number and function may be reduced in IGT. The goal of this study was to determine whether the clonogenic potential of circulating angiogenic cells is lower in IGT compared with normal-glucose-tolerant (NGT) controls and is associated with skeletal muscle capillarization.

METHODS

Glucose tolerance, endothelial cell colony-forming unit (CFU-EC) number, and vastus lateralis capillary density were measured in sedentary, older (62 ± 1 years, mean ± SEM) men and women with NGT (n = 16) and IGT (n = 12).

RESULTS

Adults with IGT had 43% lower CFU-EC number (11.4 ± 2.3 versus 20.1 ± 2.0 colonies, p < 0.01) and 12% lower capillary density (291 ± 11 versus 330 ± 9 capillaries/mm², p < 0.01) compared with those with NGT. In regression analyses, CFU-EC number inversely correlated with 120-min postprandial glucose in all subjects (r = -0.47, p < 0.05), and capillary density was directly associated with CFU-EC number (r = 0.53, p < 0.05).

CONCLUSIONS

We conclude that the clonogenic potential of circulating angiogenic cells is lower in sedentary older adults with IGT and is associated with lower skeletal muscle capillarization. Low circulating angiogenic cell clonogenic potential in IGT suggests a state of impaired angiogenesis occurring prior to overt type 2 diabetes that may mediate early microvascular changes in the development and progression of IGT to type 2 diabetes.

Beneficial effects of statins on endothelial progenitor cells

In recent years, endothelial progenitor cells (EPCs) have been demonstrated to play an important role during tissue vascularization and endothelium homeostasis in adults. In addition, EPCs have been implicated in the pathophysiology of cardiovascular and cerebrovascular disease, such that a decreased number of EPCs may not only be a risk indicator but also a potential therapeutic target. Of the many agents that have been examined to increase EPCs and enhance their function, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors or statins are one of the most intriguing. Accumulated evidence has demonstrated that statins promote EPC mobilization, proliferation, migration, adhesion, differentiation and reduce senescence and apoptosis independent of their serum lipid-lowering effect. This review summarizes the understanding of current mechanisms explaining the myriad of beneficial effects of statins on EPCs and discusses future challenges for studies involving statins and subpopulations of EPCs. However, the pharmacologic mechanisms of action of statins on EPCs remain at the cellular level, whereas the putative molecular mechanisms await further studies.

Exercise-induced Signals for Vascular Endothelial Adaptations: Implications for Cardiovascular Disease

This article reviews recent advances in our understanding of hemodynamic signals, external/compressive forces, and circulating factors that mediate exercise training-induced vascular adaptations, with particular attention to the roles of these signals in prevention and treatment of endothelial dysfunction and cardiovascular (CV) diseases.

Redox biology of exercise: an integrative and comparative consideration of some overlooked issues

The central aim of this review is to address the highly multidisciplinary topic of redox biology as related to exercise using an integrative and comparative approach rather than focusing on blood, skeletal muscle or humans. An attempt is also made to re-define ‘oxidative stress’ as well as to introduce the term ‘alterations in redox homeostasis’ to describe changes in redox homeostasis indicating oxidative stress, reductive stress or both. The literature analysis shows that the effects of non-muscle-damaging exercise and muscle-damaging exercise on redox homeostasis are completely different. Non-muscle-damaging exercise induces alterations in redox homeostasis that last a few hours post exercise, whereas muscle-damaging exercise causes alterations in redox homeostasis that may persist for and/or appear several days post exercise. Both exhaustive maximal exercise lasting only 30 s and isometric exercise lasting 1–3 min (the latter activating in addition a small muscle mass) induce systemic oxidative stress. With the necessary modifications, exercise is capable of inducing redox homeostasis alterations in all fluids, cells, tissues and organs studied so far, irrespective of strains and species. More importantly, ‘exercise-induced oxidative stress’ is not an ‘oddity’ associated with a particular type of exercise, tissue or species. Rather, oxidative stress constitutes a ubiquitous fundamental biological response to the alteration of redox homeostasis imposed by exercise. The hormesis concept could provide an interpretative framework to reconcile differences that emerge among studies in the field of exercise redox biology. Integrative and comparative approaches can help determine the interactions of key redox responses at multiple levels of biological organization.

Prior endurance exercise prevents postprandial lipaemia-induced increases in reactive oxygen species in circulating CD31+ cells

We hypothesized that prior exercise would prevent postprandial lipaemia (PPL)-induced increases in intracellular reactive oxygen species (ROS) in three distinct circulating angiogenic cell (CAC) subpopulations. CD34(+), CD31(+)/CD14(-)/CD34(-), and CD31(+)/CD14(+)/CD34(-) CACs were isolated from blood samples obtained from 10 healthy men before and 4 h after ingesting a high fat meal with or without ∼50 min of prior endurance exercise. Significant PPL-induced increases in ROS production in both sets of CD31(+) cells were abolished by prior exercise. Experimental ex vivo inhibition of NADPH oxidase activity and mitochondrial ROS production indicated that mitochondria were the primary source of PPL-induced oxidative stress. The attenuated increases in ROS with prior exercise were associated with increased antioxidant gene expression in CD31(+)/CD14(-)/CD34(-) cells and reduced intracellular lipid uptake in CD31(+)/CD14(+)/CD34(-) cells. These findings were associated with systemic cardiovascular benefits of exercise, as serum triglyceride, oxidized low density lipoprotein-cholesterol, and plasma endothelial microparticle concentrations were lower in the prior exercise trial than the control trial. In conclusion, prior exercise completely prevents PPL-induced increases in ROS in CD31(+)/CD14(-)/CD34(-) and CD31(+)/CD14(+)/CD34(-) cells. The mechanisms underlying the effects of exercise on CAC function appear to vary among specific CAC types.

Critical role of the nitric oxide/reactive oxygen species balance in endothelial progenitor dysfunction

Endothelial injury and dysfunction are critical events in the pathogenesis of cardiovascular disease. During these processes, an impaired balance of nitric oxide bioavailability and oxidative stress is mechanistically involved. Circulating angiogenic cells (including early and late outgrowth endothelial progenitor cells (EPC)) contribute to formation of new blood vessels, neovascularization, and homeostasis of the vasculature, and are highly sensitive for misbalance between NO and oxidative stress. We here review the role of the endothelial nitric oxide synthase and oxidative stress producing enzyme systems in EPC during cardiovascular disease. We also focus on the underlying molecular mechanisms and potential emerging drug- and gene-based therapeutic strategies to improve EPC function in cardiovascular diseased patients.

Effects of acute and chronic endurance exercise on intracellular nitric oxide and superoxide in circulating CD34⁺ and CD34⁻ cells

We investigated the influence of acute and chronic endurance exercise on levels of intracellular nitric oxide (NO), superoxide (O₂·⁻), and expression of genes regulating the balance between these free radicals in CD34⁺ and CD34⁻ peripheral blood mononuclear cells (PBMCs; isolated by immunomagnetic cell separation). Blood samples were obtained from age- and body mass index (BMI)-matched endurance-trained (n = 10) and sedentary (n = 10) men before and after 30 min of exercise at 75% maximal oxygen uptake (·VO(₂max)). Baseline levels of intracellular NO (measured by DAF-FM diacetate) and O₂·⁻ (measured by dihydroethidium) were 26% (P < 0.05) and 10% (P < 0.05) higher, respectively, in CD34⁺ PBMCs from the sedentary group compared with the endurance-trained group. CD34⁺ PBMCs from the sedentary group at baseline had twofold greater inducible nitric oxide synthase (iNOS) mRNA and 50% lower endothelial NOS (eNOS) mRNA levels compared with the trained group (P < 0.05). The baseline group difference in O₂·⁻ was eliminated by acute exercise. Experiments with apocynin indicated that the training-related difference in O₂·⁻ levels was explained by increased NADPH oxidase activity in the sedentary state. mRNA levels of additional angiogenic and antioxidant genes were consistent with a more angiogenic profile in CD34⁺ cells of trained subjects. CD34⁻ PBMCs, examined for exploratory purposes, also displayed a more angiogenic mRNA profile in trained subjects, with vascular endothelial growth factor (VEGF) and eNOS being more highly expressed in trained subjects. Overall, our data suggest an association between the sedentary state and increased nitro-oxidative stress in CD34⁺ cells.

Plasma fetuin-A concentrations in young and older high- and low-active men

Fetuin-A is a liver-derived factor that may play a role in insulin resistance and age-related chronic diseases (eg, type 2 diabetes mellitus and cardiovascular [CV] disease). Regular exercise improves CV risk and insulin sensitivity; however, it is unknown whether chronic exercise training is related to circulating levels of fetuin-A. Therefore, this study examined whether plasma fetuin-A levels were related to age and chronic physical activity in men. We hypothesized that chronic physical activity would be related to lower plasma fetuin-A levels in younger and older men. In healthy high-active (HI) and low-active (LO) young (HI, n = 7; LO, n = 8) and older (HI, n = 12, LO, n = 11) men, we determined cardiorespiratory fitness (maximal oxygen uptake), plasma fetuin-A levels, plasma insulin, insulin resistance (homeostasis model assessment of insulin resistance), and the standard risk factors for CV disease. Groups were matched for body mass index. Fetuin-A was significantly higher (~20%) in both young and older LO men compared with their HI counterparts, and fetuin-A was inversely related to maximal oxygen uptake (r = -0.40, P = .014). Plasma fetuin-A levels showed trends to be significantly correlated with insulin (r = -0.34, P = .052) and homeostasis model assessment of insulin resistance (r = 0.33, P = .058) in the older individuals. In younger participants, fetuin-A was related to blood pressure and cholesterol measures. These results indicate that low levels of fetuin-A are related to cardiorespiratory fitness and a number of conventional CV and metabolic disease risk factors independent of age and body mass index. Therefore, the maintenance of low levels of circulating fetuin-A may be a novel mechanism contributing to enhanced insulin sensitivity with regular physical activity.

Targeting stem cell niches and trafficking for cardiovascular therapy

Regenerative cardiovascular medicine is the frontline of 21st-century health care. Cell therapy trials using bone marrow progenitor cells documented that the approach is feasible, safe and potentially beneficial in patients with ischemic disease. However, cardiovascular prevention and rehabilitation strategies should aim to conserve the pristine healing capacity of a healthy organism as well as reactivate it under disease conditions. This requires an increased understanding of stem cell microenvironment and trafficking mechanisms. Engagement and disengagement of stem cells of the osteoblastic niche is a dynamic process, finely tuned to allow low amounts of cells move out of the bone marrow and into the circulation on a regular basis. The balance is altered under stress situations, like tissue injury or ischemia, leading to remarkably increased cell egression. Individual populations of circulating progenitor cells could give rise to mature tissue cells (e.g. endothelial cells or cardiomyocytes), while the majority may differentiate to leukocytes, affecting the environment of homing sites in a paracrine way, e.g. promoting endothelial survival, proliferation and function, as well as attenuating or enhancing inflammation. This review focuses on the dynamics of the stem cell niche in healthy and disease conditions and on therapeutic means to direct stem cell/progenitor cell mobilization and recruitment into improved tissue repair.

Thrombin and exercise similarly influence expression of cell cycle genes in cultured putative endothelial progenitor cells

Acute exercise and exercise training may influence putative endothelial progenitor cell (EPC) number and colony forming units (CFU-ECs), although the mechanisms remain unclear. This study examined the effects of in vitro thrombin supplementation and acute exercise on CFU-EC gene expression, associated with cellular proliferation and differentiation. The effect of habitual physical activity was evaluated through analysis of EPCs from chronically high- and low-active men. Participants were healthy high- and low-active men (n=23), aged 55-80 yr. Circulating CD34+/VEGFR2+ number, CFU-ECs, plasma prothrombin fragment (F1+2), and thrombin-antithrombin III were measured at rest and after 30 min of exercise. Gene expression of cyclin A2, cyclin D1, p27, VE-cadherin, and VEGFR2 was assessed in postexercise CFU-ECs and resting CFU-ECs treated with 0, 1, 5, or 10 U/ml of thrombin. Outcomes were compared between high- and low-active participants. F1+2 and thrombin-antithrombin III, but not CD34+/VEGFR2+ number and CFU-ECs, increased with exercise. Exercise-induced changes in F1+2 correlated with changes in CD34+/VEGFR2+ number in both groups. Thrombin treatments and acute exercise increased cyclin A2 and cyclin D1 expression and decreased p27 expression. One unit per milliliter thrombin increased VEGFR2 and VE-cadherin expression, whereas 5 U/ml, 10 U/ml, and acute exercise did not elicit any changes. An exercise training effect was observed with greater decreases in p27 expression with 5 and 10 U/ml thrombin and greater increases in VEGFR2 and VE-cadherin expression with 1 U/ml thrombin in high-active men. Exercise-induced changes in putative EPC gene expression are associated with thrombin production and may be modulated by long-term exercise training.

Acute resistance exercise reduces blood pressure and vascular reactivity, and increases endothelium-dependent relaxation in spontaneously hypertensive rats

The aim of the present study was to assess the effects of acute dynamic resistance exercise on resting blood pressure (BP) and on endothelial function of vascular bed of spontaneously hypertensive rats. Hemodynamic measurements were performed before and after acute dynamic resistance exercise in conscious animals. After exercise, the tail artery was cannulated for mean perfusion pressure with constant flow measurement and for performing concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) and dose-response curves to phenylephrine (PHE). PHE protocol was also repeated with damaged endothelium and after L-NAME and indomethacin perfusion on the tail. The maximal response (E(max)) and sensitivity (pD(2)) were evaluated to these drugs. Exercise reduced resting systolic and diastolic BP (Delta -79 +/- 1.8; -23 +/- 2.3 mmHg, respectively; P < 0.05). ACh-induced relaxation increased in the exercise group (pD(2) = 9.8 +/- 0.06, P < 0.05) when compared with control rats (pD(2) = 8.7 +/- 0.1). The E(max) to PHE with intact endothelium decreased following exercise condition (439 +/- 18 mmHg, P < 0.05) when compared with control rats (276 +/- 22 mmHg). This response was abolished after L-NAME and indomethacin administration. After damage of the endothelium, PHE responses were not significantly different between the groups; however, E(max) and pD(2) increased when compared with responses obtained with intact endothelium. The results demonstrated that acute dynamic resistance exercise decreased resting BP and reactivity to PHE and increased endothelium-dependent relaxation. Nitric oxide and vasodilators prostanoids appear to be involved in post-exercise endothelial and pressor responses.

Perinatal changes in superoxide generation in the ovine lung: Alterations associated with increased pulmonary blood flow

Although alterations in ROS generating systems are well described in several vascular disorders, there is very limited information on the perinatal regulation of these systems in the lung both during normal development and in pulmonary hypertension. Thus, this study was undertaken to explore how the two predominant superoxide generating systems, nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) and xanthine oxidase (XO), are developmentally regulated in control lambs and in our established lamb model of increased pulmonary blood flow (Shunt) over the first 2months of life. We found that the levels of p47(phox), p67(phox), and Rac1 subunits of NADPH oxidase complex were altered. During the first two months of life there was no change in p47(phox) protein levels in either normal or Shunt lambs. However, both p67(phox) and Rac1 protein levels decreased over time. In addition, p47(phox) protein levels were significantly increased in shunt lambs at 2- and 4-, but not 8-weeks of age compared to age-matched controls while levels of the p67(phox) subunit were decreased at 8-weeks of age in the Shunts but unchanged at other time periods. Furthermore, Rac1 protein expression was significantly increased in the Shunts only at 4weeks of age. These data correlated with a significant increase in NADPH oxidase dependent superoxide generation at 2- and 4-, but not 8-weeks of age in the Shunts. During normal development XO levels significantly increased over time in normal lambs but significantly decreased in the Shunts. In addition, XO protein levels were significantly increased in the Shunt at 2- and 4-weeks of age but significantly decreased at 8-weeks. Again this correlated with a significant increase in XO dependent superoxide generation at 2- and 4-, but not 8-weeks of age in the Shunts. Collectively, our findings suggest that NADPH oxidase and XO are major contributors to superoxide generation both during the normal development and during the development of pulmonary hypertension.