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1.  Exercise-Mediated Wall Shear Stress Increases Mitochondrial Biogenesis in Vascular Endothelium 
PLoS ONE  2014;9(11):e111409.
Enhancing structural and functional integrity of mitochondria is an emerging therapeutic option against endothelial dysfunction. In this study, we sought to investigate the effect of fluid shear stress on mitochondrial biogenesis and mitochondrial respiratory function in endothelial cells (ECs) using in vitro and in vivo complementary studies.
Methods and Results
Human aortic- or umbilical vein-derived ECs were exposed to laminar shear stress (20 dyne/cm2) for various durations using a cone-and-plate shear apparatus. We observed significant increases in the expression of key genes related to mitochondrial biogenesis and mitochondrial quality control as well as mtDNA content and mitochondrial mass under the shear stress conditions. Mitochondrial respiratory function was enhanced when cells were intermittently exposed to laminar shear stress for 72 hrs. Also, shear-exposed cells showed diminished glycolysis and decreased mitochondrial membrane potential (ΔΨm). Likewise, in in vivo experiments, mice that were subjected to a voluntary wheel running exercise for 5 weeks showed significantly higher mitochondrial content determined by en face staining in the conduit (greater and lesser curvature of the aortic arch and thoracic aorta) and muscle feed (femoral artery) arteries compared to the sedentary control mice. Interestingly, however, the mitochondrial biogenesis was not observed in the mesenteric artery. This region-specific adaptation is likely due to the differential blood flow redistribution during exercise in the different vessel beds.
Taken together, our findings suggest that exercise enhances mitochondrial biogenesis in vascular endothelium through a shear stress-dependent mechanism. Our findings may suggest a novel mitochondrial pathway by which a chronic exercise may be beneficial for vascular function.
PMCID: PMC4222908  PMID: 25375175
2.  Increased Oxidative Metabolism in the Li–Fraumeni Syndrome 
The New England journal of medicine  2013;368(11):1027-1032.
There is growing evidence that alterations in metabolism may contribute to tumorigenesis. Here, we report on members of families with the Li–Fraumeni syndrome who carry germline mutations in TP53, the gene encoding the tumor-suppressor protein p53. As compared with family members who are not carriers and with healthy volunteers, family members with these mutations have increased oxidative phosphorylation of skeletal muscle. Basic experimental studies of tissue samples from patients with the Li–Fraumeni syndrome and a mouse model of the syndrome support this in vivo finding of increased mitochondrial function. These results suggest that p53 regulates bioenergetic homeostasis in humans. (Funded by the National Heart, Lung, and Blood Institute and the National Institutes of Health; number, NCT00406445.)
PMCID: PMC4123210  PMID: 23484829
3.  Racial differences in oxidative stress and inflammation: in vitro and in vivo 
African American race is an independent risk factor for enhanced oxidative stress and inflammation. We sought to examine whether oxidative stress and inflammatory markers that are typically measured in human also differ by race in cell culture. We compared levels between African American and Caucasian young adults and then separately in human umbilical vein endothelial cells (HUVECs) from both races. We found heightened oxidative stress and inflammation in the African Americans both in vitro and in vivo. African American HUVECs showed higher nitric oxide (NO) levels (10.8±0.4 vs 8.8±0.7umol/L/mg, P=0.03), IL-6 levels (61.7±4.2 vs 23.9±9.0pg/mg, P=0.02), and lower superoxide dismutase activity (15.6±3.3 vs. 25.4±2.8U/mg, P=0.04), and also higher protein expression (p<0.05) of NADPH oxidase subunit p47phox, isoforms NOX2 and NOX4, endothelial nitric oxide synthase, inducible NOS, as well as IL-6. African American adults had higher plasma protein carbonyls (1.1±0.1 vs 0.8±0.1nmol/mg, P=0.01) and antioxidant capacity (2.3±0.2 vs 1.1±0.3mM, P=0.01). This preliminary translational data demonstrates a racial difference in HUVECs much like that in humans, but should be interpreted with caution given its preliminary nature. It is known that racial differences exist in how humans respond to development and progression of disease, therefore these data suggest that ethnicity of cell model may be important to consider with in vitro clinical research.
PMCID: PMC3077905  PMID: 21348953
African American; NADPH oxidase; HUVECs
5.  Racial differences in tumor necrosis factor-α-induced endothelial microparticles and interleukin-6 production 
African Americans (AA) tend to have heightened systemic inflammation and endothelial dysfunction. Endothelial microparticles (EMP) are released from activated/apoptotic endothelial cells (EC) when stimulated by inflammation. The purpose of our study was to assess EMP responses to inflammatory cytokine (TNF-α) and antioxidant (superoxide dismutase, SOD) conditions in human umbilical vein ECs (HUVECs) obtained from AA and Caucasians. EMPs were measured under four conditions: control (basal), TNF-α, SOD, and TNF-α + SOD. Culture supernatant was collected for EMP analysis by flow cytometry and IL-6 assay by ELISA. IL-6 protein expression was assessed by Western blot. AA HUVECs had greater EMP levels under the TNF-α condition compared to the Caucasian HUVECs (6.8 ± 1.1 vs 4.7% ± 0.4%, P = 0.04). The EMP level increased by 89% from basal levels in the AA HUVECs under the TNF-α condition (P = 0.01) compared to an 8% increase in the Caucasian HUVECs (P = 0.70). Compared to the EMP level under the TNF-α condition, the EMP level in the AA HUVECs was lower under the SOD only condition (2.9% ± 0.3%, P = 0.005) and under the TNF-α + SOD condition (2.1% ± 0.4%, P = 0.001). Basal IL-6 concentrations were 56.1 ± 8.8 pg/mL/μg in the AA and 30.9 ± 14.9 pg/mL/μg in the Caucasian HUVECs (P = 0.17), while basal IL-6 protein expression was significantly greater (P < 0.05) in the AA HUVECs. These preliminary observational results suggest that AA HUVECs may be more susceptible to the injurious effects of the proinflammatory cytokine, TNF-α.
Video abstract
PMCID: PMC3180509  PMID: 21966220
endothelium; inflammation; endothelial microparticles; African Americans
6.  Racial differences in the responses to shear stress in human umbilical vein endothelial cells 
African American ethnicity is an independent risk factor for exaggerated oxidative stress, which is related to inflammation, hypertension, and cardiovascular disease. Recently, we reported that in vitro oxidative stress and inflammation levels differ between African American and Caucasian human umbilical vein endothelial cells (HUVECs), African American HUVECs having higher levels of both. However, it remains to be shown whether the cells would respond differently to external stimuli.
We used a cone and plate viscometer to apply laminar shear stress (LSS) as an aerobic exercise mimetic to compare the responses by race. HUVECs were exposed to static conditions (no LSS), low LSS (5 dyne/cm2), and moderate LSS (20 dyne/cm2).
It was found that African American HUVECs had higher levels of oxidative stress under static conditions, and when LSS was applied protein expression levels (NADPH oxidase NOX2, NOX4 and p47phox subunits, eNOS, SOD2, and catalase) and biomarkers (NO, SOD, and total antioxidant capacity) were modulated to similar levels between race.
African American HUVECs may be more responsive to LSS stimulus indicating that aerobic exercise prescriptions may be valuable for this population since the potential exists for large in vivo improvements in oxidative stress levels along the endothelial layer in response to increased shear flow.
PMCID: PMC3141915  PMID: 21796257
shear stress; African American; NADPH oxidase; HUVECs; oxidative stress
7.  Plasma Nitrate/Nitrite Levels are Unchanged after Long-Term Aerobic Exercise Training in Older Adults 
Reduced nitric oxide (NO) production and bioactivity is a major contributor to endothelial dysfunction. Animal data suggests that improvements in endothelial function in response to aerobic exercise training may depend on the duration of the training program. However, no studies have examined changes in NO (as assessed by the major NO metabolites, nitrate and nitrite, NOx) after long-term training in humans. In addition, aging may impair the ability of the vasculature to increase NO with exercise. Thus, we determined whether 24 weeks of aerobic exercise training increases plasma NOx levels in sedentary older adults. We also examined changes in forearm blood flow (FBF) at rest and during reactive hyperemia as a measure of vasomotor function. Plasma NOx levels were measured in 82 men and women using a modified Griess assay. FBF was assessed in a subset of individuals (n=15) using venous occlusion plethysmography. After 24 weeks of exercise training, there were significant improvements in maximum oxygen consumption, HDL cholesterol, triglycerides, and body fat. Changes in plasma NOx levels ranged from −14.83 to +16.69 μmol/L; however, the mean change overall was not significant (−0.33±6.30 μmol/L, p=0.64). Changes in plasma NOx levels were not associated with age, gender, race, HDL cholesterol, triglycerides, body weight, body fat, or maximal oxygen consumption. There were also no significant changes in basal FBF, peak FBF, hyperemic response, total hyperemic flow, or minimum forearm vascular resistance with exercise training. In conclusion, improvements in plasma NOx levels and FBF are not evident after long-term training in older adults.
PMCID: PMC2796424  PMID: 19825427
exercise training; nitric oxide; forearm blood flow; aging
8.  p53 Improves Aerobic Exercise Capacity and Augments Skeletal Muscle Mitochondrial DNA Content 
Circulation research  2009;105(7):705-712.
Exercise capacity is a physiological characteristic associated with protection from both cardiovascular and all-cause mortality. p53 regulates mitochondrial function and its deletion markedly diminishes exercise capacity, but the underlying genetic mechanism orchestrating this is unclear. Understanding the biology of how p53 improves exercise capacity may provide useful insights for improving both cardiovascular as well as general health.
To understand the genetic mechanism by which p53 regulates aerobic exercise capacity.
Methods and Results
Using a variety of physiological, metabolic and molecular techniques, we further characterized maximum exercise capacity and the effects of training, measured various non-mitochondrial and mitochondrial determinants of exercise capacity, and examined putative regulators of mitochondrial biogenesis. As p53 did not affect baseline cardiac function or inotropic reserve, we focused on the involvement of skeletal muscle and now report a wider role for p53 in modulating skeletal muscle mitochondrial function. p53 interacts with Mitochondrial Transcription Factor A (TFAM), a nuclear-encoded gene important for mitochondrial DNA (mtDNA) transcription and maintenance, and regulates mtDNA content. The increased mtDNA in p53+/+ compared to p53−/− mice was more marked in aerobic versus glycolytic skeletal muscle groups with no significant changes in cardiac tissue. These in vivo observations were further supported by in vitro studies showing over-expression of p53 in mouse myoblasts increases both TFAM and mtDNA levels while depletion of TFAM by shRNA decreases mtDNA content.
Our current findings indicate that p53 promotes aerobic metabolism and exercise capacity by utilizing different mitochondrial genes and mechanisms in a tissue-specific manner.
PMCID: PMC2761626  PMID: 19696408
aerobic; exercise; mitochondrial DNA; p53; TFAM
9.  Independent and combined influence of AGTR1 variants and aerobic exercise on oxidative stress in hypertensives 
Blood pressure  2009;18(4):204-212.
Angiotensin II (AngII), via the AngII type 1 receptor (AT1R), contributes to oxidative stress. Aerobic exercise training (AEXT) reduces the risk of cardiovascular (CV) disease, presumably by reducing the grade of oxidative stress. We investigated the independent and combined influence of the AGTR1 A1166C and −825 T/A polymorphisms on oxidative stress and plasma AngII responses to AEXT in pre- and stage 1 hypertensives. Urinary 8-iso-PGF2α significantly increased with AEXT (p=0.002); however, there were no significant changes in superoxide dismutase activity or AngII levels. There was a significant difference in the change in AngII levels with AEXT between A1166C genotype groups (p=0.04) resulting in a significant interactive effect of the A1166C polymorphism and AEXT on the change in AngII (p<0.05). Only the TT genotype group of the −825 T/A polymorphism had a significant reduction in plasma AngII (p=0.02). Risk allele analysis revealed a significant reduction in plasma AngII (p=0.04) and a significant increase in urinary 8-iso-PGF2α (p=0.01) with AEXT in individuals with two risk alleles only. Our findings suggest that variation in the AGTR1 gene is associated with differential changes in plasma AngII but not oxidative stress.
PMCID: PMC2922402  PMID: 19593696
AGTR1; angiotensin II; exercise; isoprostanes; oxidative stress
10.  Exercise Training, NADPH Oxidase p22phox Gene Polymorphisms, and Hypertension 
Oxidative stress that is mediated through NADPH oxidase activity plays a role in the pathology of hypertension, and aerobic exercise training reduces NADPH oxidase activity. The involvement of genetic variation in the p22phox (CYBA) subunit genes in individual oxidative stress responses to aerobic exercise training has yet to be examined in Pre and Stage 1 hypertensives.
Ninety-four sedentary Pre and Stage 1 hypertensive adults underwent 6 months of aerobic exercise training at a level of 70% V̇O2max to determine whether the CYBA polymorphisms, C242T and A640G, were associated with changes in urinary 8-iso-prostaglandin F2α (8-iso-PGF2α), urinary nitric oxide metabolites (NOx), and plasma total antioxidant capacity (TAC).
Demographic and subject characteristics were similar among genotype groups for both polymorphisms. At baseline, a significant (P = 0.03) difference among the C2424T genotype groups in 8-iso-PGF2α levels was detected, with the TT homozygotes having the lowest levels and the CC homozygotes having the highest levels. However, no differences were found at baseline between the A640G genotype groups. After 6 months of aerobic exercise training, there was a significant increase in V̇O2max (P < 0.0001) in the entire study population. In addition, there were significant increases in both urinary 8-iso-PGF2α (P = 0.002) and plasma TAC (P = 0.03) levels and a significant decrease in endogenous urinary NOx (P < 0.0001). Overall, aerobic exercise training elicited no significant differences among genotype groups in either CYBA variant for any of the oxidative stress variables.
We found that compared with CYBA polymorphisms C242T and A640G, it was aerobic exercise training that had the greatest influence on the selected biomarkers; furthermore, our results suggest that the C242T CYBA variant influences baseline levels of urinary 8-iso-PGF2α but not the aerobic exercise-induced responses.
PMCID: PMC2871250  PMID: 19516159
11.  Differential aerobic exercise-induced changes in plasma aldosterone between African Americans and Caucasians 
Experimental physiology  2007;92(5):871-879.
Aldosterone influences the kidney’s regulation of blood pressure (BP), but aldosterone can contribute to the pathogenesis of hypertension. Blood pressure is reduced with aerobic exercise training (AEX), but the extent to which plasma aldosterone (PA) levels change is unclear. The purpose of this study was to determine whether 6 months of AEX changed PA levels, 24 h sodium (Na+) excretion and BP in prehypertensive and hypertensive subjects and whether these changes differed according to ethnicity. The study was performed in the Kinesiology Department at the University of Maryland, College Park, and 35 (22 Caucasian; 13 African American) sedentary prehypertensive and hypertensive subjects completed 6 months of AEX. Blood samples were collected under fasting and supine conditions, and PA was measured by radioimmunoassay. In total population aerobic exercise training increased maximal oxygen consumption (24 ± 0.8 versus 28 ± 1 ml kg−1 min−1, P < 0.001) and decreased PA levels (97 ± 11 versus 72 ± 6 pg ml−1, P = 0.01), body mass index (28 ± 0.5 versus 28 ± 0.5 kg m−2, P = 0.004) and weight (85 ± 2 versus 83 ± 2 kg, P = 0.003). Aerobic exercise training decreased PA levels (from 119 ± 16 to 81 ± 7 pg ml−1, P = 0.02) in the Caucasians but there was no change in BP or Na+ excretion. African American participants had no significant changes in PA levels, BP and Na+ excretion. Plasma aldosterone levels were 47% lower at baseline (P = 0.01) and 30% lower after AEX (P = 0.04) in African American participants compared with Caucasians. Baseline (P = 0.08) and final PA levels (P = 0.17) did not differ between the two groups after accounting for baseline and final intra-abdominal fat, respectively. The reduction in PA levels with AEX appeared to be driven by the change in PA levels in Caucasian participants. Fat distribution contributed to the ethnic differences in PA levels.
PMCID: PMC2729146  PMID: 17483200
12.  NFKB1 promoter variation implicates shear-induced NOS3 gene expression and endothelial function in prehypertensives and stage I hypertensives 
In endothelial cells, NF-κB is an important intracellular signaling molecule by which changes in wall shear stress are transduced into the nucleus to initiate downstream endothelial nitric oxide synthase (NOS3) gene expression. We investigated whether NF-κ light-chain gene enhancer in B cells 1 (NFKB1) promoter polymorphism (−94NFKB1 I/D, where I is the insertion allele and D is the deletion allele) was associated with 1) NOS3 gene expression in endothelial cells under physiological levels of unidirectional laminar shear stress (LSS) and 2) endothelial function in prehypertensive and stage I hypertensive individuals before and after a 6-mo supervised endurance exercise intervention. Competitive EMSAs revealed that proteins present in the nuclei of endothelial cells preferentially bound to the I allele NFKB1 promoter compared with the D allele. Reporter gene assays showed that the I allele promoter had significantly higher activity than the D allele. In agreement with these observations, homozygous II genotype cells had higher p50 expression levels than homozygous DD genotype cells. Cells with the homozygous II genotype showed a greater increase in NOS3 protein expression than did homozygous DD genotype cells under LSS. Functional experiments on volunteers confirmed higher baseline reactive hyperemic forearm blood flow, and, furthermore, the subgroup analysis revealed that DD homozygotes were significantly less prevalent in the exercise responder group compared with II and ID genotypes. We conclude that the −94NFKB1 I/D promoter variation contributes to the modulation of vascular function and adaptability to exercise-induced flow shear stress, most likely due to differences in NFKB1 gene transactivity.
PMCID: PMC2614625  PMID: 17644577
nuclear factor-κ light-chain gene enhancer in B cells 1; nitric oxide synthase 3; shear stress

Results 1-12 (12)