Identification of free nitric oxide radicals in rat bone marrow: implications for progenitor cell mobilization in hypertension

Dietary intake of anthocyanins improves arterial stiffness, but not endothelial function, in volunteers with excess weight: A randomized clinical trial

Excess body weight has been associated with endothelial dysfunction and increased arterial stiffness. Foods rich in polyphenols and anthocyanins such as açaí-juçara (Euterpe edulis Martius) fruit may have protective vascular effects. Thus, we examined the effect of dietary intake of anthocyanins (açaí-juçara fruit) on endothelial function (flow-mediated dilation [FMD]) and arterial stiffness (pulse wave velocity [PWV]) in individuals with excess body weight. Fifty-five individuals with BMI ≥25 kg/m² were randomized into non-anthocyanin (N-ATH, n = 25) or anthocyanin (ATH, n = 30) intake groups. A 12-week individualized diet plan (20% reduction in total energy intake) was prescribed and included daily intake of açaí-juçara 200 g (anthocyanins 293.6 mg) in the ATH diet plan. We evaluated anthropometric and biochemical parameters, FMD, PWV, and peripheral vascular resistance (PVR). A GEE (Bonferroni post-hoc) was used (p ≤ 0.05). No change in FMD was observed. However, PWV showed a reduction from baseline in the ATH (p = 0.002) and vs. N-ATH (p = 0.036). Both groups showed reduced peripheral vascular resistance (N-ATH, p = 0.005; ATH, p = 0.040) with no significant differences between them. In conclusion, dietary intake of anthocyanins proved effective in protecting against arterial stiffness (by PWV) in individuals with excess weight. PVR was reduced in both diet groups regardless of dietary intake of anthocyanins.

Biomechanical cues as master regulators of hematopoietic stem cell fate

Hematopoietic stem cells (HSCs) perceive both soluble signals and biomechanical inputs from their microenvironment and cells themselves. Emerging as critical regulators of the blood program, biomechanical cues such as extracellular matrix stiffness, fluid mechanical stress, confined adhesiveness, and cell-intrinsic forces modulate multiple capacities of HSCs through mechanotransduction. In recent years, research has furthered the scientific community's perception of mechano-based signaling networks in the regulation of several cellular processes. However, the underlying molecular details of the biomechanical regulatory paradigm in HSCs remain poorly elucidated and researchers are still lacking in the ability to produce bona fide HSCs ex vivo for clinical use. This review presents an overview of the mechanical control of both embryonic and adult HSCs, discusses some recent insights into the mechanisms of mechanosensing and mechanotransduction, and highlights the application of mechanical cues aiming at HSC expansion or differentiation.

Individuals with controlled hypertension show endothelial integrity following a bout of moderate-intensity exercise: randomized clinical trial

To examine the acute effects of aerobic exercise (AE), resistance exercise (RE) or combined exercise (CE) on flow-mediated dilation (FMD), progenitor cells (PCs), endothelial progenitor cells (EPCs), oxidative stress markers and endothelial-cell derived microvesicles (EMVs) in patients with hypertension. This is a randomized, parallel-group clinical trial involving an intervention of one session of three different modalities of exercise. Thirty-three males (43 ± 2y) were randomly divided into three groups: a session of AE (n = 11, 40 min, cycle ergometer, 60% HRR); a session of RE (n = 11, 40 min, 4 × 12 lower limb repetitions, 60% 1-RM); or a session of CE (n = 11, 20-min RE + 20-min AE). FMD was assessed 10 min before and 10, 40 and 70 min post-intervention. Blood samples were collected at the same time points (except 40 min). FMD were similar in all groups and from baseline (within each group) after a single exercise bout (AE, RE or CE). At 70 min, RE group showed higher levels of PCs compared to the AE (81%) and CE group (60%). PC levels were reduced from baseline in all groups (AE: 32%, p = 0.037; RE: 15%, p = 0.003; CE: 17%, p = 0.048). The levels of EPCs, EMVs and oxidative stress were unchanged. There were no acute effects of moderate-intensity exercise on FMD, EPCs, EMVs and oxidative stress, but PCs decreased regardless of the exercise modality. Individuals with controlled hypertension do not seem to have impaired vascular function in response to a single exercise bout.

Endothelial LRP1 protects against neurodegeneration by blocking cyclophilin A

The low-density lipoprotein receptor–related protein 1 (LRP1) is an endocytic and cell signaling transmembrane protein. Endothelial LRP1 clears proteinaceous toxins at the blood–brain barrier (BBB), regulates angiogenesis, and is increasingly reduced in Alzheimer’s disease associated with BBB breakdown and neurodegeneration. Whether loss of endothelial LRP1 plays a direct causative role in BBB breakdown and neurodegenerative changes remains elusive. Here, we show that LRP1 inactivation from the mouse endothelium results in progressive BBB breakdown, followed by neuron loss and cognitive deficits, which is reversible by endothelial-specific LRP1 gene therapy. LRP1 endothelial knockout led to a self-autonomous activation of the cyclophilin A–matrix metalloproteinase-9 pathway in the endothelium, causing loss of tight junctions underlying structural BBB impairment. Cyclophilin A inhibition in mice with endothelial-specific LRP1 knockout restored BBB integrity and reversed and prevented neuronal loss and behavioral deficits. Thus, endothelial LRP1 protects against neurodegeneration by inhibiting cyclophilin A, which has implications for the pathophysiology and treatment of neurodegeneration linked to vascular dysfunction.

Smoking-Induced Inhibition of Number and Activity of Endothelial Progenitor Cells and Nitric Oxide in Males Were Reversed by Estradiol in Premenopausal Females

Objectives

The number and activity of circulating EPCs were enhanced in premenopausal women contrast to postmenopausal females and age-matched males. Here, we investigated whether this favorable effect exists in premenopausal women and age-matched men with cigarette smoking.

Methods

In a cross-sectional study, the number and activity of circulating EPCs and nitric oxide production (NO) as well as flow-mediated vasodilation (FMD) in both premenopausal women and age-matched men with or without cigarette smoking were studied.

Results

Compared with age-matched men with or without smoking, the number and function of circulating EPCs as well as NO level in premenopausal women were obviously higher than that in the former and not affected by smoking. The number and function of circulating EPCs as well as NO level in male smokers were shown to be the most strongly inhibited. Furthermore, there was significant correlation between EPC number and activity, plasma NO level, and NO secretion by EPCs and FMD.

Conclusions

Estradiol was deemed to play an important role in enhancing the number and activity of EPCs and NO production in premenopausal women even when affected by smoking, which may be the important mechanisms underlying vascular protection of estradiol in premenopausal women, but not in age-matched men.

NOS2 deficiency has no influence on the radiosensitivity of the hematopoietic system

Objective

Previous studies have shown that inhibition of inducible NO synthase (NOS2 or iNOS) with an inhibitor can selectively protect several normal tissues against radiation during radiotherapy. However, the role of NOS2 in ionizing radiation (IR)-induced bone marrow (BM) suppression is unknown and thus was investigated in the present study using NOS2⁻/⁻ and wild-type mice 14 days after they were exposed to a sublethal dose of total body irradiation (TBI).

Methods

The effects of different doses of IR (1, 2 and 4 Gy) on the apoptosis and colony-forming ability of bone marrow cells from wild-type (WT) and NOS2⁻/⁻ mice were investigated in vitro. In addition, we exposed NOS2⁻/⁻ mice and WT mice to 6-Gy TBI or sham irradiation. They were euthanized 14 days after TBI for analysis of peripheral blood cell counts and bone marrow cellularity. Colony-forming unit-granulocyte and macrophage, burst-forming unit-erythroid and CFU-granulocyte, erythroid, macrophage in bone marrow cells from the mice were determined to evaluate the function of hematopoietic progenitor cells (HPCs), and the ability of hematopoietic stem cells (HSCs) to self-renew was analysed by the cobblestone area forming cell assay. The cell cycling of HPCs and HSCs were measured by flow cytometry.

Results

Exposure to 2 and 4 Gy IR induced bone marrow cell apoptosis and inhibited the proliferation of HPCs in vitro. However, there was no difference between the cells from WT mice and NOS2⁻/⁻ mice in response to IR exposure in vitro. Exposure of WT mice and NOS2⁻/⁻ mice to 6 Gy TBI decreased the white blood cell, red blood cell, and platelet counts in the peripheral blood and bone marrow mononuclear cells, and reduced the colony-forming ability of HPCs (P < 0.05), damaged the clonogenic function of HSCs. However, these changes were not significantly different in WT and NOS2⁻/⁻ mice.

Conclusion

These data suggest that IR induces BM suppression in a NOS2-independent manner.

Reprogramming Bone Marrow Stem Cells to Functional Endothelial Cells in a Mini Pig Animal Model

Background

The aims of this study were to compare the morphological, biochemical, and functional properties of reprogrammed bone marrow stem cell (BMSC)-derived arterial endothelial cells (AECs) and venous endothelial cells (VECs), following adenosine triphosphate (ATP)-stimulation in a mini pig animal model.

Material/Methods

Bone marrow aspiration was performed in six adult mini pigs. Harvested mononuclear cells were isolated, cultured, and treated with vascular endothelial growth factor (VEGF) (16 μg/ml). Transformed cells were characterized using immunofluorescence staining for CD31 and von Willebrandt factor (vWF) and expression of endothelial nitric oxide synthase (eNOS). Cell release of nitric oxide (cNO) was measured using spectrophotometry. Matrigel assays were used to investigate angiogenesis in transformed BMSCs.

Results

Reprogrammed BMSCs in culture showed a typical cobblestone-like pattern of growth. Immunofluorescence staining was positive for CD31 and vWF expression. Expression of eNOS, using immunofluorescence staining and Western blot, showed no difference between the reprogrammed BMSCs and VECs. Spectrophotometric examination following stimulation with 10mmol/l ATP, showed comparable cNO release for reprogrammed BMSCs (10.87±1.76 pmol/10⁶ cells/min) and VECs (13.23±2.16 pmol/10⁶ cells/min), but reduced cNO release for AECS (3.44±0.75 pmol/10⁶ cells/min). Matrigel assay for angiogenesis showed vascular tube formation of differentiated BMSC endothelial cells (grade 3.25). BMSCs cultured without VEGF did not demonstrate vascular tube formation.

Conclusions

The findings of this study showed that eNOS expression and release of NO could be used to show that BMSCs can be reprogrammed to functional VECs and AECs.

Reliability of ROS and RNS detection in hematopoietic stem cells − potential issues with probes and target cell population

Many studies have provided evidence for the crucial role of the reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the regulation of differentiation and/or self-renewal, and the balance between quiescence and proliferation of hematopoietic stem cells (HSCs). Several metabolic regulators have been implicated in the maintenance of HSC redox homeostasis; however, the mechanisms that are regulated by ROS and RNS, as well as their downstream signaling are still elusive. This is partially owing to a lack of suitable methods that allow unequivocal and specific detection of ROS and RNS. In this Opinion, we first discuss the limitations of the commonly used techniques for detection of ROS and RNS, and the problem of heterogeneity of the cell population used in redox studies, which, together, can result in inaccurate conclusions regarding the redox biology of HSCs. We then propose approaches that are based on single-cell analysis followed by a functional test to examine ROS and RNS levels specifically in HSCs, as well as methods that might be used in vivo to overcome these drawbacks, and provide a better understanding of ROS and RNS function in stem cells.

Effects of nitric oxide on stem cell therapy

The use of stem cells as a research tool and a therapeutic vehicle has demonstrated their great potential in the treatment of various diseases. With unveiling of nitric oxide synthase (NOS) universally present at various levels in nearly all types of body tissues, the potential therapeutic implication of nitric oxide (NO) has been magnified, and thus scientists have explored new treatment strategies involved with stem cells and NO against various diseases. As the functionality of NO encompasses cardiovascular, neuronal and immune systems, NO is involved in stem cell differentiation, epigenetic regulation and immune suppression. Stem cells trigger cellular responses to external signals on the basis of both NO specific pathways and concerted action with endogenous compounds including stem cell regulators. As potency and interaction of NO with stem cells generally depend on the concentrations of NO and the presence of the cofactors at the active site, the suitable carriers for NO delivery is integral for exerting maximal efficacy of stem cells. The innovative utilization of NO functionality and involved mechanisms would invariably alter the paradigm of therapeutic application of stem cells. Future prospects in NO-involved stem cell research which promises to enhance drug discovery efforts by opening new era to improve drug efficacy, reduce drug toxicity and understand disease mechanisms and pathways, were also addressed.

Sympathetic predominance is associated with impaired endothelial progenitor cells and tunneling nanotubes in controlled-hypertensive patients

Early endothelial progenitor cells (early EPC) and late EPC are involved in endothelial repair and can rescue damaged endothelial cells by transferring organelles through tunneling nanotubes (TNT). In rodents, EPC mobilization from the bone marrow depends on sympathetic nervous system activity. Indirect evidence suggests a relation between autonomic derangements and human EPC mobilization. We aimed at testing whether hypertension-related autonomic imbalances are associated with EPC impairment. Thirty controlled-essential hypertensive patients [systolic blood pressure/diastolic blood pressure = 130(120-137)/85(61-88) mmHg; 81.8% male] and 20 healthy normotensive subjects [114(107-119)/75(64-79) mmHg; 80% male] were studied. Mononuclear cells were cultured on fibronectin- and collagen-coated dishes for early EPC and late EPC, respectively. Low (LF)- and high (HF)-frequency components of short-term heart rate variability were analyzed during a 5-min rest, an expiration/inspiration maneuver, and a Stroop color-word test. Modulations of cardiac sympathetic and parasympathetic activities were evaluated by LF/HF (%) and HF power (ms(2)), respectively. In controlled-hypertensive patients, the numbers of early EPC, early EPC that emitted TNT, late EPC, and late EPC that emitted TNT were 41, 77, 50, and 88% lower than in normotensive subjects (P < 0.008), respectively. In controlled-hypertensive patients, late EPC number was positively associated with cardiac parasympathetic reserve during the expiration/inspiration maneuver (rho = 0.45, P = 0.031) and early EPC with brachial flow-mediated dilation (rho = 0.655; P = 0.049); also, late TNT number was inversely related to cardiac sympathetic response during the stress test (rho = -0.426, P = 0.045). EPC exposure to epinephrine or norepinephrine showed negative dose-response relationships on cell adhesion to fibronectin and collagen; both catecholamines stimulated early EPC growth, but epinephrine inhibited late EPC growth. In controlled-hypertensive patients, sympathetic overactivity/parasympathetic underactivity were negatively associated with EPC, suggesting that reducing sympathetic/increasing parasympathetic activation might favor endothelial repair.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.