Hemodynamic reactivity to laboratory stressors in healthy subjects: influence of gender and family history of cardiovascular diseases.

Although laboratory stressor tests have been applied as a preliminary protocol in some cardiovascular studies, there is a lack of data comparing the pressor and chronotropic responses among the main stressor tests. Therefore, the aim of this study was to evaluate the variability in hemodynamic responsiveness to the main stressor tests, establish a hyperresponsiveness cutoff criterion and analyze the influence of gender and family history of cardiovascular diseases (CVDs) in healthy subjects. We examined hemodynamic responses to physical (cold pressor and handgrip tests) and mental (Stroop color-word test) stressors in 98 subjects (48 males and 50 females) without CVDs. All stressor tests resulted in increased blood pressure (BP) levels, which were lower and less dispersed in the handgrip test compared to the cold pressor test. Adopting the 75(th) percentile as the cutoff in our data, we classified subjects exhibiting absolute pressor changes equal to or higher than 14, 24 and 36 mmHg in systolic and 9, 13 and 24 mmHg in diastolic BP during the handgrip, Stroop and cold pressor test, respectively, as hyperresponsives. Males exhibited greater (p<0.05) increases in systolic BP in the handgrip (11% vs. 8%) and cold pressor (25% vs. 21%) tests and in diastolic BP in the handgrip (12% vs. 7%) and Stroop (22% vs. 19%) tests than females. A positive association between family history of CVDs and pressor hyperreactivity to stressor tests was observed. We propose using the 75(th) percentile of hemodynamic sample values as a cutoff criterion to classify individuals as pressor or chronotropic hyperreactives. We conclude that hemodynamic responsiveness to stressor tests in healthy subjects is positively influenced by male gender and family history of CVDs.

Renovascular hypertension leads to DNA damage and apoptosis in bone marrow cells.

Angiotensin II (Ang II), which plays a pivotal role in the pathophysiology of the two-kidney, one-clip (2K1C) Goldblatt hypertension, has been associated with augmented generation of reactive oxygen species (ROS) in some cells and tissues. In the present study, we evaluated the influence of 2K1C hypertension on oxidative stress, DNA fragmentation, and apoptosis of bone marrow (BM) cells. Two weeks after the renal artery clipping or Sham operation, flow cytometry analysis showed a higher production of superoxide anions (approximately sixfold) and hydrogen peroxide (approximately twofold) in 2K1C hypertensive than in Sham normotensive mice. 2K1C mice also showed an augmented DNA fragmentation (54%) and apoptotic cells (21%). Our data show that the 2K1C renovascular hypertension is characterized by an increased production of ROS, DNA damage, and apoptosis of BM, which is a fundamental source of the cells involved in tissue repair.

DNA damage and augmented oxidative stress in bone marrow mononuclear cells from Angiotensin-dependent hypertensive mice.

It has been proposed that the nonhemodynamic effects of angiotensin II are important for the damage observed in the two-kidney, one-clip (2K1C) renovascular hypertension model. Much evidence confirms that angiotensin II is directly involved in NAD(P)H oxidase activation and consequent superoxide anion production, which can damage DNA. The current study was performed to examine the effects of angiotensin-II-dependent hypertension in bone marrow mononuclear cells (BM-MNC); dihydroethidium staining was used to assess reactive oxygen species (ROS) production, and the comet assay was used to assess DNA fragmentation in 2K1C hypertensive mice 14 days after renal artery clipping. In this study we demonstrated that 2K1C hypertensive mice have an elevated lymphocyte count, while undifferentiated BM-MNC counts were diminished. 2K1C mice also showed an augmented ROS production and marked BM-MNC DNA fragmentation. In conclusion, endogenous renin angiotensin system activation-induced arterial hypertension is characterized by excessive ROS production in BM-MNC, which might cause marked DNA damage.

Effects of Aging and Hypercholesterolemia on Oxidative Stress and DNA Damage in Bone Marrow Mononuclear Cells in Apolipoprotein E-deficient Mice.

Recent evidence from apolipoprotein E-deficient (apoE-/-) mice shows that aging and atherosclerosis are closely associated with increased oxidative stress and DNA damage in some cells and tissues. However, bone marrow cells, which are physiologically involved in tissue repair have not yet been investigated. In the present study, we evaluated the influence of aging and hypercholesterolemia on oxidative stress, DNA damage and apoptosis in bone marrow cells from young and aged apoE-/- mice compared with age-matched wild-type C57BL/6 (C57) mice, using the comet assay and flow cytometry. The production of both superoxide and hydrogen peroxide in bone marrow cells was higher in young apoE-/- mice than in age-matched C57 mice, and reactive oxygen species were increased in aged C57 and apoE-/- mice. Similar results were observed when we analyzed the DNA damage and apoptosis. Our data showed that both aging and hypercholesterolemia induce the increased production of oxidative stress and consequently DNA damage and apoptosis in bone marrow cells. This study is the first to demonstrate a functionality decrease of the bone marrow, which is a fundamental extra-arterial source of the cells involved in vascular injury repair.

Mononuclear cell therapy reverts cuff-induced thrombosis in apolipoprotein E-deficient mice.

BACKGROUND: Stem/progenitor cell-based therapy has successfully been used as a novel therapeutic strategy for vascular diseases triggered by endothelial dysfunction. The aim of this study was to investigate the effects of mononuclear cell (MNC) therapy in situ on carotid cuff-induced occlusive thrombus in the apolipoprotein E knockout (apoE-/-) mouse. METHODS: Spleen-derived MNCs were isolated from green fluorescent protein (GFP)-transgenic mice for cell treatment. A cuff-induced thrombus model was produced by placing a nonconstrictive silastic collar around the left common carotid artery in 20-week-old female apoE-/- mice. After 10 days, the cuff was removed, and the animals received in situ MNCs (Cuff-MNC) or vehicle (Cuff-Vehicle) and were compared with sham-operated animals (Sham). RESULTS: The histological analysis showed that the MNC treatment reverted occlusive thrombus formation compared to the vehicle and the vessel lumen area to that observed in the Sham group (MNC, 50 ± 4; Vehicle, 20 ± 4; Sham, 55 ± 2 x10³ µm²; p < 0.01). The animals that underwent the carotid cuff placement developed compensatory vessel enlargement, which was reduced by the MNC therapy. In addition, the treatment was able to reduce superoxide anion production, which likely contributed to the reduced apoptosis that was observed. Lastly, the immunofluorescence analysis revealed the presence of endothelial progenitor cells (EPCs) in the carotid endothelia of the apoE-/- mice. CONCLUSION: In situ short-term MNC therapy was able to revert cuff-induced occlusive thrombi in the carotid arteries of apoE-/- mice, possibly through the homing of EPCs, reduction of oxidative stress and decreased apoptosis.

Mononuclear cell therapy attenuates atherosclerosis in apoE KO mice.

BACKGROUND: Recent studies have highlighted the potential of cell therapy for atherosclerosis. The aim of this study was to evaluate the effects of mononuclear cell (MNC) therapy on the development of atherosclerotic lesions in the apolipoprotein E knockout (apoE KO) mouse. METHODS: We investigated vascular lipid deposition, vascular remodeling, oxidative stress, and endothelial nitric oxide synthase (eNOS) expression in apoE KO mice treated with spleen MNCs isolated from lacZ transgenic mice (apoE KO-MNC) for 8 weeks compared to untreated control mice (apoE KO). RESULTS: Histological analysis of aortas showed a significant reduction in the lipid deposition area in apoE KO-MNC mice compared to apoE KO mice (0.051 ± 0.004 vs 0.117 ± 0.016 mm², respectively, p < 0.01). In addition, vessel morphometry revealed that MNC therapy prevented the outward (positive) remodeling in apoE KO mice that is normally observed (apoE KO-MNC: 0.98 ± 0.07 vs apoE KO: 1.37 ± 0.09), using wild-type mice (C57BL/6J) as a reference. ApoE KO-MNC mice also have reduced production of superoxide anions and increased eNOS expression compared to apoE KO mice. Finally, immunohistochemistry analysis revealed a homing of endothelial progenitor cells (EPCs) in the aortas of apoE KO-MNC mice. CONCLUSION: MNC therapy attenuates the progression of atherosclerosis in the aortas of apoE KO mice. Our data provide evidence that the mechanism by which this attenuation occurs includes the homing of EPCs, a decrease in oxidative stress and an upregulation of eNOS expression.