Roles of Protein S-Nitrosylation in Endothelial Homeostasis and Dysfunction

Significance: Nitric oxide (NO) plays several distinct roles in endothelial homeostasis. Except for activating the guanylyl cyclase enzyme-dependent cyclic guanosine monophosphate signaling pathway, NO can bind reactive cysteine residues in target proteins, a process known as S-nitrosylation (SNO). SNO is proposed to explain the multiple biological functions of NO in the endothelium. Investigating the targets and mechanism of protein SNO in endothelial cells (ECs) can provide new strategies for treating endothelial dysfunction-related diseases. Recent Advances: In response to different environments, proteomics has identified multiple SNO targets in ECs. Functional studies confirm that SNO regulates NO bioavailability, inflammation, permeability, oxidative stress, mitochondrial function, and insulin sensitivity in ECs. It also influences EC proliferation, migration, apoptosis, and transdifferentiation. Critical Issues: Single-cell transcriptomic analysis of ECs isolated from different mouse tissues showed heterogeneous gene signatures. However, litter research focuses on the heterogeneous properties of SNO proteins in ECs derived from different tissues. Although metabolism reprogramming plays a vital role in endothelial functions, little is known about how protein SNO regulates metabolism reprogramming in ECs. Future Directions: Precisely deciphering the effects of protein SNO in ECs isolated from different tissues under different conditions is necessary to further characterize the relationship between protein SNO and endothelial dysfunction-related diseases. In addition, identifying SNO targets that can influence endothelial metabolic reprogramming and the underlying mechanism can offer new views on the crosstalk between metabolism and post-translational protein modification. Antioxid. Redox Signal. 40, 186-205.

L-Arginine-eNOS-NO Functional System in Brain Damage and Cognitive Impairments in Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) is a significant cause of cognitive impairment (CI), disability, and mortality. The insufficient effectiveness of antihypertensive therapy in curbing the disease justifies the search for potential targets for modifying therapy and indicators supporting its use. Using a laser-assisted optical rotational cell analyzer (LORRCA, Mechatronics, The Netherlands), the rheological properties and deformability of erythrocytes before and after incubation with 10 μmol/L of L-arginine, the nitric oxide (NO) donor, blood-brain barrier (BBB) permeability assessed by dynamic contrast-enhanced MRI, clinical, and MRI signs were studied in 73 patients with CSVD (48 women, mean age 60.1 ± 6.5 years). The control group consisted of 19 volunteers (14 women (73.7%), mean age 56.9 ± 6.4 years). The erythrocyte disaggregation rate (y-dis) after incubation with L-arginine showed better performance than other rheological characteristics in differentiating patients with reduced NO bioavailability/NO deficiency by its threshold values. Patients with y-dis > 113 s-1 had more severe CI, arterial hypertension, white matter lesions, and increased BBB permeability in grey matter and normal-appearing white matter (NAWM). A test to assess changes in the erythrocyte disaggregation rate after incubation with L-arginine can be used to identify patients with impaired NO bioavailability. L-arginine may be part of a therapeutic strategy for CSVD with CI.

A Critical Review on Vasoactive Nutrients for the Management of Endothelial Dysfunction and Arterial Stiffness in Individuals under Cardiovascular Risk

Pathophysiological conditions such as endothelial dysfunction and arterial stiffness, characterized by low nitric oxide bioavailability, deficient endothelium-dependent vasodilation and heart effort, predispose individuals to atherosclerotic lesions and cardiac events. Nitrate (NO₃^-), L-arginine, L-citrulline and potassium (K⁺) can mitigate arterial dysfunction and stiffness by intensifying NO bioavailability. Dietary compounds such as L-arginine, L-citrulline, NO₃^- and K⁺ exert vasoactive effects as demonstrated in clinical interventions by noninvasive flow-mediated vasodilation (FMD) and pulse-wave velocity (PWV) prognostic techniques. Daily L-arginine intakes ranging from 4.5 to 21 g lead to increased FMD and reduced PWV responses. Isolated L-citrulline intake of at least 5.6 g has a better effect compared to watermelon extract, which is only effective on endothelial function when supplemented for longer than 6 weeks and contains at least 6 g of L-citrulline. NO₃^- supplementation employing beetroot at doses greater than 370 mg promotes hemodynamic effects through the NO₃^--NO2-/NO pathway, a well-documented effect. A potassium intake of 1.5 g/day can restore endothelial function and arterial mobility, where decreased vascular tone takes place via ATPase pump/hyperpolarization and natriuresis, leading to muscle relaxation and NO release. These dietary interventions, alone or synergically, can ameliorate endothelial dysfunction and should be considered as adjuvant therapies in cardiovascular diseases.

Ageing and endothelium-mediated vascular dysfunction: the role of the NADPH oxidases

The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Endothelium-dependent [intraluminal flow- and acetylcholine (ACh)-induced] vasodilatation in human skeletal muscle feed arteries (SMFAs) of young (24 ± 1 years, n = 16), middle aged (45 ± 1 years, n = 18) and old (76 ± 2 years, n = 21) subjects was assessed in vitro with and without the inhibition of NOX1 (ML090), NOX2 (gp91) and NOX4 (plumbagin). To identify the role of nitric oxide (NO) bioavailability in these responses, NO synthase blockade (l-NG -monomethyl arginine citrate) was utilized. SMFA NOX1, NOX2 and NOX4 protein expression was determined by western blotting. Age related endothelium-dependent vasodilatory dysfunction was evident in response to flow (young: 69 ± 3; middle aged: 51 ± 3; old: 27 ± 3%, P < 0.05) and ACh (young: 89 ± 2; middle aged: 72 ± 3; old: 45 ± 4%, P < 0.05). NOX1 inhibition had no effect on SMFA vasodilatation, whereas NOX2 inhibition restored flow- and ACh-induced vasodilatation in the middle aged and the old SMFAs (middle aged + gp91: 69 ± 3; 86 ± 3, old + gp91: 65 ± 5; 83 ± 2%, P < 0.05) and NOX4 inhibition tended to restore these vasodilatory responses in these two groups, but neither achieved statistical significance (P ≈ 0.06). l-NG -monomethyl arginine citrate negated the restorative effects of NOX2 and NOX4 blockade. Only NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function (r = 0.48 to 0.93, P < 0.05). NOX2 and, to a lesser extent, NOX4 appear to play an important, probably NO-mediated, role in age-related endothelial dysfunction. KEY POINTS: The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Age related endothelium-dependent vasodilatory dysfunction was evident in skeletal muscle feed arteries in response to both flow and acetylcholine. NOX2 inhibition (gp91) restored endothelium-dependent vasodilatation in the middle aged and the old skeletal muscle feed arteries, and NOX4 inhibition (plumbagin) tended to restore these vasodilatory responses in these two groups. Nitric oxide synthase inhibition negated the restorative effects of NOX2 and NOX4 blockade. NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function. NOX2 and, to a lesser extent, NOX4 appear to play an important, probably nitric oxide-mediated, role in age-related endothelial dysfunction and could be important therapeutic targets to maintain vascular health with ageing.

Biological Assessment of the NO-Dependent Endothelial Function

Nitric oxide (NO) is implicated in numerous physiological processes, including vascular homeostasis. Reduced NO bioavailability is a hallmark of endothelial dysfunction, a prequel to many cardiovascular diseases. Biomarkers of an early NO-dependent endothelial dysfunction obtained from routine venous blood sampling would be of great interest but are currently lacking. The direct measurement of circulating NO remains a challenge due by its high reactivity and short half-life. The current techniques measure stable products from the NO signaling pathway or metabolic end products of NO that do not accurately represent its bioavailability and, therefore, endothelial function per se. In this review, we will concentrate on an original technique of low temperature electron paramagnetic resonance spectroscopy capable to directly measure the 5-α-coordinated heme nitrosyl-hemoglobin in the T (tense) state (5-α-nitrosyl-hemoglobin or HbNO) obtained from fresh venous human erythrocytes. In humans, HbNO reflects the bioavailability of NO formed in the vasculature from vascular endothelial NOS or exogenous NO donors with minor contribution from erythrocyte NOS. The HbNO signal is directly correlated with the vascular endothelial function and inversely correlated with vascular oxidative stress. Pilot studies support the validity of HbNO measurements both for the detection of endothelial dysfunction in asymptomatic subjects and for the monitoring of such dysfunction in patients with known cardiovascular disease. The impact of therapies or the severity of diseases such as COVID-19 infection involving the endothelium could also be monitored and their incumbent risk of complications better predicted through serial measurements of HbNO.

Nitric oxide synthase inhibition with N(G)-monomethyl-l-arginine: Determining the window of effect in the human vasculature

Nitric oxide synthase (NOS) inhibition with N(G)-monomethyl-l-arginine (L-NMMA) is often used to assess the role of NO in human cardiovascular function. However, the window of effect for L-NMMA on human vascular function is unknown, which is critical for designing and interpreting human-based studies. This study utilized the passive leg movement (PLM) assessment of vascular function, which is predominantly NO-mediated, in 7 young male subjects under control conditions, immediately following intra-arterial L-NMMA infusion (0.24 mg⋅dl^-1⋅min^-1), and at 45-60 and 90-105 min post L-NMMA infusion. The leg blood flow (LBF) and leg vascular conductance (LVC) responses to PLM, measured with Doppler ultrasound and expressed as the change from baseline to peak (ΔLBF_peak and ΔLVC_peak) and area under the curve (LBF_AUC and LVC_ACU), were assessed. PLM-induced robust control ΔLBF_peak (1135 ± 324 ml⋅min^-1) and ΔLVC_peak (10.7 ± 3.6 ml⋅min^-1⋅mmHg^-1) responses that were significantly attenuated (704 ± 196 ml⋅min^-1 and 6.7 ± 2 ml⋅min^-1⋅mmHg^-1) immediately following L-NMMA infusion. Likewise, control condition PLM ΔLBF_AUC (455 ± 202 ml) and ΔLVC_AUC (4.0 ± 1.4 ml⋅mmHg^-1) were significantly attenuated (141 ± 130 ml and 1.3 ± 1.2 ml⋅mmHg^-1) immediately following L-NMMA infusion. However, by 45-60 min post L-NMMA infusion all PLM variables were not significantly different from control, and this was still the case at 90-105 min post L-NMMA infusion. These findings reveal that the potent reduction in NO bioavailability afforded by NOS inhibition with L-NMMA has a window of effect of less than 45-60 min in the human vasculature. These data are particularly important for the commonly employed approach of pharmacologically inhibiting NOS with L-NMMA in the human vasculature.

Mathematical relationships of patterns of 35 rat haemodynamic parameters for conditions of hypertension resulting from decreased nitric oxide bioavailability

NEW FINDINGS

What is the central question of this study? Can the cross-relationship between 35 rat arterial pulse waveform (APW) parameters be described by known mathematical functions and can mathematical parameters be obtained for conditions in a model of hypertension resulting from decreased NO bioavailability? What is the main finding and its importance? Mathematical functions and their parameters were obtained that approximate the cross-relationships of 35 APW parameters to systolic blood pressure and to the augmentation index in conditions of decreased NO bioavailability. The results enable APW parameters to be assigned to decreased NO bioavailability, which may have predictive or diagnostic value.

ABSTRACT

Information obtained from the arterial pulse waveform (APW) using haemodynamic parameters (HPs) is useful for characterization of the cardiovascular system in particular (patho)physiological conditions. Our goal was to find out whether the relationships between rat HPs could be described by simple mathematical functions and to find mathematical parameters for conditions of high blood pressure (BP) resulting from decreased NO bioavailability. The right jugular vein of anaesthetized Wistar rats was cannulated for i.v. administration of N^ω -nitro-l-arginine methyl ester (l-NAME). The left common carotid artery was cannulated to detect the APW. From 10 points on the rat APW we defined 35 HPs (some were known already) and found 595 cross-relationships between HPs showing unique patterns for particular cardiovascular conditions. Here we show parallel time-dependent changes of 35 HPs and some of their cross-relationships in condition of high BP induced by l-NAME. We found that most of the time-dependent changes of 35 HPs and their relationships were very well fitted by simple mathematical functions, e.g. a linear function, exponential growth, exponential decay or exponential rise to maximum. The results may enable the mathematical functions to be assigned for decreased NO bioavailability, which may have predictive or diagnostic value for conditions of high BP. Using this approach, it may be possible to find unique cross-relationship patterns of HPs and mathematical functions between HPs for different cardiovascular (patho)physiological or drug-modulating conditions. This knowledge can be used in studying the molecular mechanisms of particular (patho)physiological conditions or drug actions and may have predictive or diagnostic value.

Lancemaside A from Codonopsis lanceolata prevents hypertension by inhibiting NADPH oxidase 2-mediated MAPK signalling and improving NO bioavailability in rats

OBJECTIVES

This study investigated whether lancemaside A (LMA) can prevent hypertension and assessed the mechanisms of action of LMA in rats.

METHODS

Hypertension was induced by chronic immobilization stress and nicotine administration. Hypertensive vehicle rats were treated with LMA (1, 20, or 40 mg/kg) or nifedipine (10 mg/kg) as a positive control daily for 3 weeks.

KEY FINDINGS

In hypertensive vehicle rats, LMA dose-dependently reduced systolic blood pressure. LMA doses of 20 and 40 mg/kg reduced the aortic expression of nicotinamide adenine dinucleotide phosphate oxidase (NOX)2 (both P < 0.01), and 40 mg/kg LMA reduced serum malondialdehyde (P < 0.01). Serum nitrite levels were significantly higher in LMA treated rats than in hypertensive vehicle rats, with LMA doses of 20 and 40 mg/kg reducing the expression of endothelial nitric oxide synthase in rat aortas (P < 0.001 and P < 0.01, respectively). LMA also reduced the aortic levels of nuclear factor kappa B and the activation of the three isoforms of mitogen-activated protein kinase (MAPK).

CONCLUSIONS

Lancemaside A prevents hypertension in rats by inhibiting the activation of MAPK signalling and the impairment in nitric oxide bioavailability due to NOX2-mediated oxidative stress. Thus, LMA may act as a preventive agent for hypertension.

Vasodilatory function in human skeletal muscle feed arteries with advancing age: the role of adropin

KEY POINTS

The present study aimed to determine the impact of ageing on endogenous adropin levels in human skeletal muscle feed arteries (SMFAs) and the role of adropin in age-related vascular dysfunction. Adropin protein expression falls progressively with advancing age in the human peripheral vasculature. Endothelial-dependent vasodilatation, typically attenuated with age, was strongly correlated with SMFA adropin protein levels. Adropin incubation restored age-related endothelial-dependent vasodilatory dysfunction and increased the phosphorylated endothelial nitric oxide synthase (eNOS)/eNOS ratio in an age-dependent manner in the SMFAs. The role of nitric oxide bioavailability was additionally indicated by NOS blockade ablating both the positive vascular effects of adropin incubation and the relationship between endothelial function and adropin protein expression. Additional evidence of a mechanistic link between declining adropin and age-related endothelial dysfunction was documented by a progressively increasing magnitude of effect of adropin-induced eNOS-mediated vasodilatation with ageing. Adropin appears to be a novel therapeutic target for facilitating the restoration of endothelial function with ageing.

ABSTRACT

The present study aimed to determine the impact of advancing age on endogenous adropin levels in human skeletal muscle feed arteries (SMFAs) and the role of adropin in age-related vascular dysfunction. Adropin protein expression and vasodilatory capacity was assesed in SMFAs from Young (27 ± 2 years, n = 10), Middle Aged (54 ± 2 years, n = 10) and Old (75 ± 2 years, n = 16) subjects. Endothelial-dependent vasodilatation, with and without adropin incubation, was assessed in response to flow-induced shear stress and ACh. Both SMFA adropin protein expression and endothelial-dependent vasodilatory function exhibited a progressive, age-related, reduction (Flow: Y: 65 ± 3%; Middle Aged: 36 ± 3%; Old: 15 ± 2%; ACh: Young: 63 ± 2%, Middle Aged: 34 ± 3%; Old: 23 ± 3%, P < 0.05). There was a strong positive correlation between SMFA adropin protein expression and both flow (r = 0.81, P < 0.05) and ACh (r = 0.78, P < 0.05). Adropin incubation in the Middle Aged and Old SMFAs restored the vasodilatory response to flow (Middle Aged + Adropin: 59 ± 3%; Old + Adropin: 47 ± 3%, P < 0.05) and ACh (Middle Aged + Adropin: 59 ± 3%; Old + Adropin: 49 ± 2%, P < 0.05). A mechanistic link between adropin and nitric oxide (NO) biovavailabilty was supported by (i) increased phosphorylated endothelial NO synthase (eNOS)/eNOS protein expression with adropin incubation only in the Middle Aged and Old SMFAs; (ii) eNOS blockade ablating both the positive vascular effects of adropin incubation and the relationship between endothelial function and adropin protein expression and (iii) a progressive increase in the magnitude of effect of adropin-induced eNOS-mediated vasodilatation with advancing age. Adropin could be a novel therapeutic target for facilitating the restoration of endothelial function via increased NO bioavailability, with advancing age.

Oral Nitrate Supplementation Differentially Modulates Cerebral Artery Blood Velocity and Prefrontal Tissue Oxygenation During 15 km Time-Trial Cycling in Normoxia but Not in Hypoxia

Background: Nitrate is a precursor of nitric oxide (NO), an important regulator of cerebral perfusion in normoxic and hypoxic conditions. Nitrate supplementation could be used to improve cerebral perfusion and oxygenation during exercise in hypoxia. The effects of dietary nitrate supplementation on cerebral haemodynamics during exercise in severe hypoxia (arterial O₂ saturation < 70%) have not been explored.

Methods: In twelve trained male cyclists, we measured blood pressure (BP), middle cerebral artery blood velocity (MCAv), cerebrovascular resistance (CVR) and prefrontal oxyhaemoglobin and deoxyhaemoglobin concentration (O₂Hb and HHb, respectively) during 15 km cycling time trials (TT) in normoxia and severe hypoxia (11% inspired O₂, peripheral O₂ saturation ∼66%) following 3-day oral supplementation with placebo or sodium nitrate (0.1 mmol/kg/day) in a randomised, double-blinded manner. We tested the hypothesis that dietary nitrate supplementation increases MCAv and cerebral O₂Hb during TT in severe hypoxia.

Results: During TT in normoxia, nitrate supplementation lowered MCAv by ∼2.3 cm/s and increased cerebral O₂Hb by ∼6.8 μM and HHb by ∼2.1 μM compared to normoxia placebo (p ≤ 0.01 for all), while BP tended to be lowered (p = 0.06). During TT in severe hypoxia, nitrate supplementation elevated MCAv (by ∼2.5 cm/s) and BP (by ∼5 mmHg) compared to hypoxia placebo (p < 0.01 for both), while it had no effect on cerebral O₂Hb (p = 0.98), HHb (p = 0.07) or PETCO₂ (p = 0.12). Dietary nitrate had no effect of CVR during TT in normoxia or hypoxia (p = 0.19).

Conclusion: Our findings indicate that during normoxic TT, the modulatory effect of dietary nitrate on regional and global cerebral perfusion is heterogeneous. Meanwhile, the lack of major changes in cerebral perfusion with dietary nitrate during hypoxic TT alludes to an exhausted cerebrovascular reserve.

The effects of exercise on vascular endothelial function in type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Vascular endothelial dysfunction induced by hyperglycemia and elevated insulin resistance is a potent risk factor for cardiovascular disease and likely contributes to multiple chronic disease complications associated with aging. The aim of this study was to systematically review and quantify the effects of exercise on endothelial function (EF) in type 2 diabetes (T2D).

METHODS

Five electronic databases were searched (until June 2017) for studies that met the following criteria: (i) randomized controlled trials; (ii) T2D aged ≥ 18 years; (iii) measured EF by brachial artery flow-mediated dilation (FMD); (iv) structured and supervised exercise intervention for ≥ 8 weeks.

RESULTS

Thirteen cohorts, selected from eight studies (306 patients, average age 59 years), met the inclusion criteria. Exercise training significantly increased FMD (mean ES = 0.41, 95% CI 0.21-0.62, P < 0.001). Low to moderate intensity subgroups and aerobic exercise (AE) subgroups significantly increased FMD more than moderate to high intensity subgroups and combined AE and resistance exercise subgroups respectively (P < 0.01, P < 0.05). The Grading of Recommendations Assessment, Development and Evaluation (GRADE) assessments reported that quality of evidence for all outcomes was moderate except shear rate showing low. Egger's test showed no significant publication bias for all outcomes.

CONCLUSION

Our results suggest that in patients with T2D, lower intensity exercise has physiological meaningful effects on EF, in support of the emerging concept that the lower efforts of exercise are not necessarily less cardioprotective than higher intensity training.

Nitric oxide bioavailability dysfunction involves in atherosclerosis

The pathological characteristics of atherosclerosis (AS) include lipid accumulation, fibrosis formation and atherosclerotic plaque produced in artery intima, which leads to vascular sclerosis, lumen stenosis and irritates the ischemic changes of corresponding organs. Endothelial dysfunction was closely associated with AS. Nitric oxide (NO) is a multifunctional signaling molecule involved in the maintenance of metabolic and cardiovascular homeostasis. NO is also a potent endogenous vasodilator and enters for the key processes that suppresses the formation vascular lesion even AS. NO bioavailability indicates the production and utilization of endothelial NO in organisms, its decrease is related to oxidative stress, lipid infiltration, the expressions of some inflammatory factors and the alteration of vascular tone, which plays an important role in endothelial dysfunction. The enhancement of arginase activity and the increase in asymmetric dimethylarginine and hyperhomocysteinemia levels all contribute to AS by intervening NO bioavailability in human beings. Diabetes mellitus, obesity, chronic kidney disease and smoking, etc., also participate in AS by influencing NO bioavailability and NO level. Here, we reviewed the relationship between NO bioavailability and AS according the newest literatures.

Effects of betaine supplementation on nitric oxide metabolism, atherosclerotic parameters, and fatty liver in guinea pigs fed a high cholesterol plus methionine diet

OBJECTIVE

The aim of this study was to investigate the effect of high cholesterol (CHOL) and CHOL + methionine (MET) diets on atherogenic and oxidative index parameters and on the factors that influence nitric oxide (NO) bioavailability. Also, attempts were made to determine whether dietary betaine (BET) resulted in any improvement in the changes that occurred after CHOL + MET administration.

METHODS

Guinea pigs were fed chow containing 1.5% CHOL with or without 2% MET for 10 wk. A third group received the CHOL + MET + BET diet. Control groups were given standard chow or standard chow + BET. Arginine, NO, nitrotyrosine (NT), and asymmetric dimethylarginine (ADMA) levels; lipid profile; and dimethylarginine dimethylaminohydrolase (DDAH) activity were measured. The liver and aorta were subjected to histopathologic analysis.

RESULTS

The CHOL + MET diet caused higher serum CHOL and homocysteine levels, but no further increases were seen in aortic CHOL and diene conjugate (DC) levels and histopathologic lesions as compared with the CHOL group. Hepatic lipids and DC levels were also higher, and histopathologic lesions were more severe. CHOL + MET feeding increased ADMA and NT levels as compared with those of the CHOL-fed group. When BET (1 g/kg body weight/d) was added to the CHOL + MET diet, homocysteine and lipid levels decreased and histopathologic changes were reversed. BET diet decreased serum ADMA and hepatic and aortic DC levels and partly restored DDAH activity.

CONCLUSIONS

BET supplementation may be effective in preventing hyperlipidemia, disturbed NO availability, oxidative stress, and the development of fatty liver and atherosclerotic lesions that might result from excess amounts of cholesterol and methionine in the diet.

Crocetin restores diabetic endothelial progenitor cell dysfunction by enhancing NO bioavailability via regulation of PI3K/AKT-eNOS and ROS pathways

AIMS

Endothelial progenitor cell (EPC) dysfunction underlies a critical risk factor in diabetic vascular complications due to function defect in restoring endothelium injury. Crocetin has attracted increasing attention in several vascular-related diseases. In present study, we aimed to explore the role of crocetin in diabetic EPC dysfunction.

MAIN METHODS

EPCs were isolated from bone marrow in diabetic mice and identified using the fluorescence staining and flow cytometry. After exposure to various doses of crocetin, cell viability was detected by MTT assy. Then, colony formation, lactate dehydrogenase (LDH) release, cell apoptosis and caspase-3 activity were assessed. The underlying mechanism was also investigated by western blotting.

KEY FINDINGS

EPCs from diabetic mice exhibited dysfunction under hyperglycemia condition. Interestingly, crocetin treatment alleviated the impairment in diabetic EPC proliferation and colony formation. Simultaneously, the increases in LDH release, cell apoptosis and caspase-3 activity were also restrained following crocetin stimulation. Additionally, EPC migration response to SDF-1 was also impaired under diabetic condition, which was partly restored by crocetin. Mechanism analysis manifested that administration with crocetin repaired the damage in the activation of PI3K/AKT-eNOS pathway and NO production, but attenuated ROS elevation in diabetic EPCs. Importantly, preconditioning with antagonist of LY294002 (for PI3K/AKT) or N^G-monomethyl-l-arginine (for eNOS) antagonized the beneficial effect of crocetin on diabetic EPC dysfunction.

SIGNIFICANCE

These data corroborated that crocetin could restore the dysfunction of diabetic EPCs by enhancing NO bioavailability via regulation of PI3K/AKT-eNOS and ROS pathways. Therefore, this research supports a potential promising therapeutic aspect for diabetic patients.

Mathematical relationships and their consequences between rat pulse waveform parameters and blood pressure during decreasing NO bioavailability

NEW FINDINGS

What is the central question of this study? We wanted to find out whether the relationship between rat arterial pulse waveform (APW) parameters and blood pressure could be described by known mathematical functions and find mathematical parameters for conditions of hypertension resulting from decreased NO bioavailability. What is the main finding and its importance? We found mathematical functions and their parameters that approximate the relationships of 12 APW parameters to systolic and diastolic blood pressure in conditions of decreased NO bioavailability. The results may assign APW parameters to decreased NO bioavailability, which may have predictive or diagnostic value. Information obtained from the arterial pulse waveform (APW) is useful for characterization of the cardiovascular system in particular (patho)physiological conditions. Our goal was to find out whether the relationships between rat APW parameters could be described by simple mathematical functions and to find mathematical parameters for conditions of hypertension resulting from decreased NO bioavailability. Therefore, we explored details of 14 left carotid APW parameters of anaesthetized male Wistar rats and mathematically characterized their relationship to systolic and diastolic blood pressure (BP) in conditions of a gradual reduction in NO bioavailability after administration of l-NAME. The right jugular vein of anaesthetized Wistar rats was cannulated for l-NAME administration. The left carotid artery was cannulated to detect the APW at high resolution. Here, we show the time-dependent parallel changes of 14 APW parameters before and after i.v. administration of l-NAME and present mathematical functions that approximate the relationships of 12 APW parameters to systolic and diastolic BP. Some APW parameters had minor (e.g. heart rate) or biphasic dependence on BP (e.g. relative level of the maximum rate of ventricular pressure decrease (dP/dt_min )), but all relationships, within a particular range of BP, could be approximated by known regression functions, as a linear function (e.g. pulse BP), exponential decay (e.g. relative level of the maximum rate of ventricular pressure increase (dP/dt_max )), exponential growth (systolic area), exponential rise to a maximum (relative augmentation index) or sigmoid function (e.g. increase of relative level of dP/dt_min ). The mathematical functions may assign APW parameters to decreased NO bioavailability. This may have predictive or diagnostic value.

Posttranscriptional and transcriptional regulation of endothelial nitric-oxide synthase during hypoxia: the role of microRNAs

Understanding the cellular pathways that regulate endothelial nitric oxide (eNOS, NOS3) expression and consequently nitric oxide (NO) bioavailability during hypoxia is a necessary aspect in the development of novel treatments for cardiovascular disorders. eNOS expression and eNOS-dependent NO cellular signaling during hypoxia promote an equilibrium of transcriptional and posttranscriptional molecular mechanisms that belong to both proapoptotic and survival pathways. Furthermore, NO bioavailability results not only from eNOS levels, but also relies on the presence of eNOS substrate and cofactors, the phosphorylation status of eNOS, and the presence of reactive oxygen species (ROS) that can inactivate eNOS. Since both NOS3 levels and these signaling pathways can also be a subject of posttranscriptional modulation by microRNAs (miRNAs), this class of short noncoding RNAs contribute another level of regulation for NO bioavailability. As miRNA antagomirs or specific target protectors could be used in therapeutic approaches to regulate NO levels, either by changing NOS3 mRNA stability or through factors governing eNOS activity, it is critical to understand their role in governing eNOS activity during hypoxa. In contrast to a large number of miRNAs reported to the change eNOS expression during hypoxia, only a few miRNAs modulate eNOS activity. Furthermore, impaired miRNA biogenesis leads to NOS3 mRNA stabilization under hypoxia. Here we discuss the recent studies that define miRNAs’ role in maintaining endothelial NO bioavailability emphasizing those miRNAs that directly modulate NOS3 expression or eNOS activity.

Sustained nitric oxide (NO)-releasing compound reverses dysregulated NO signal transduction in priapism

We evaluated the therapeutic potential of a sustained nitric oxide (NO)-releasing compound to correct the molecular hallmarks and pathophysiology of priapism, an important but poorly characterized erectile disorder. 1,5-Bis-(dihexyl-N-nitrosoamino)-2,4-dinitrobenzene (C6') and an inactive form of the compound [1,5-bis-(dihexylamino)-2,4-dinitrobenzene (C6)] were tested in neuronal cell cultures and penile lysates for NO release (Griess assay) and biological activity (cGMP production). The effect of local depot C6' or C6 was evaluated in mice with a priapic phenotype due to double neuronal and endothelial NO synthase deletion (dNOS(-/-)) or human sickle hemoglobin transgenic expression (Sickle). Changes in NO signaling molecules and reactive oxygen species (ROS) surrogates were assessed by Western blot. The physiological response after C6' treatment was assessed using an established model of electrically stimulated penile erection. C6' generated NO, increased cGMP, and dose dependently increased NO metabolites. C6' treatment reversed abnormalities in key penile erection signaling molecules, including phosphodiesterase type 5, phosphorylated endothelial nitric oxide synthase, and phosphorylated vasodilator-stimulated phosphoprotein. In Sickle mice, C6' also attenuated the increased ROS markers gp91(phox), 4-hydroxynonenal, and 3-nitrotyrosine. Finally, C6' corrected the excessive priapic erection response of dNOS(-/-) mice. Exogenous sustained NO release from C6' corrects pathological erectile signaling in mouse models of priapism and suggests novel approaches to human therapy.