Nitroarginine Methyl Ester Research Articles

The renal resistive index is associated with microvascular remodeling in patients with severe obesity.

Renal hemodynamics is impaired since the early stage of cardiometabolic disease. However, in obesity, its noninvasive ultrasound assessment still fails to provide pathophysiologic and clinical meaningfulness. We aimed to explore the relationship between peripheral microcirculation and renal hemodynamics in severe obesity. We enrolled fifty severely obese patients with an indication for bariatric referring to our outpatient clinic. Patients underwent an extensive reno-metabolic examination, paired with Doppler ultrasound and measurement of the renal resistive index (RRI). On the day of the surgery, visceral fat biopsies were collected to perform an ex-vivo complete microcirculatory assessment. Media-to-lumen ratio (M/L) and vascular response to acetylcholine (ACh), alone or co-incubated with N G -nitro arginine methyl ester (L-NAME), were measured. Patients were stratified according to their normotensive (NT) or hypertensive (HT) status. HT had lower estimated glomerular filtration rate and higher RRI compared to NT, while the presence and extent of albuminuria were similar between the two groups. Concerning microcirculatory assessment, there were no differences between groups as regards the microvascular structure, while the vasorelaxation to ACh was lower in HT ( P = 0.042). Multivariable analysis showed a relationship between M/L and RRI ( P = 0.016, St. β 0.37) and between albuminuria and the inhibitory response of L-NAME to Ach vasodilation ( P = 0.036, St. β = -0.34). Notably, all these correlations were consistent also after adjustment for confounding factors. The RRI and albuminuria relationship with microvascular remodeling in patients affected by severe obesity supports the clinical implementation of RRI to improve risk stratification in obesity and suggests a tight pathophysiologic connection between renal haemodynamics and microcirculatory disruption.

Berberine promotes the viability of random skin flaps via the PI3K/Akt/eNOS signaling pathway.

Random skin flaps are often used in reconstruction operations. However, flap necrosis is still a common postoperative complication. Here, we investigated whether berberine (C20 H19 NO5 , BBR), a drug with antioxidant activity, improves the survival rate of random flaps. Fifty-four rats were divided into three groups: control, BBR and BBR +L -NAME groups (L -NAME, L -NG -Nitro-arginine methyl ester). The survival condition and the percentage of survival area of the flaps were evaluated on the seventh day after surgery. After animals were sacrificed, angiogenesis, apoptosis, oxidative stress and inflammation levels were assessed by histological and protein analyses. Our findings suggest that berberine promotes flap survival. The level of angiogenesis increased; the levels of oxidative stress, inflammation and apoptosis decreased; the levels of phosphoinositide 3-kinase (PI3K), phospho-Akt (p-Akt) and phospho-endothelial nitric oxide synthase (p-eNOS) increased in the flap tissue; and L -NAME reversed the effects of berberine on random skin flaps. Statistical analysis showed that the BBR group results differed significantly from those of the control and the BBR +L -NAME groups (p< .05). Our results confirm that berberine is an effective drug for significantly improving the survival rate of random skin flaps by promoting angiogenesis, inhibiting inflammation, attenuating oxidative stress, and reducing apoptosis through the PI3K/Akt/eNOS signaling pathway.

Characterization of Endothelium-Dependent Relaxation in the Saphenous Artery and Its Caudal Branches in Young and Old Adult Sprague Dawley Rats.

Ageing is associated with reduced endothelium-derived nitric oxide (NO) production in the femoral artery of Sprague Dawley (SD) rats. In the current study, we examined endothelium-dependent relaxation (EDR) in the saphenous artery and its caudal branches. We used acetylcholine and the Proteinase-Activated receptor-2 (PAR2)-specific agonist (2fLIGRLO) with nitroarginine methylester (L-NAME) to assess EDR in two groups of male SD rats (age in weeks: young, 10–12; old, 27–29). Acetylcholine and 2fLIGRLO were potent NO-dependent relaxant agents in all arteries. For all arteries, EDR by acetylcholine decreased significantly in old compared to young SD rats. Interestingly, PAR2-induced EDR of proximal saphenous artery segments and caudal branches decreased significantly in old compared to young, but did not differ for the in-between middle and distal ends of the saphenous artery. L-NAME treatment increased subsequent contractions of proximal and middle segments of saphenous arteries by phenylephrine and U46619 in young, but not in old, SD rats. We conclude the SD saphenous artery and caudal branches exhibit regional characteristics that differ in response to specific EDR agonists, endothelial NO synthase inhibitor, and changes to endothelium function with increased age, which are, in part, attributed to decreased sensitivity of vascular smooth muscle to the gaseous transmitter NO.

Nitric Oxide Therapy Attenuates Heart Failure with Preserved Ejection Fraction

IntroductionNitric oxide (NO) based therapeutics have proven to exert cardioprotective actions in the setting of heart failure with reduced ejection fraction (HFrEF). However, NO therapy has failed to exert beneficial effects in clinical studies of heart failure with preserved ejection fraction (HFpEF).We investigated (1) the effects of the NO donor, sodium nitrite, as a monotherapy, (2) hydralazine monotherapy, a known vasodilator and antioxidant, and (3) combination therapy with both drugs in a murine model of HFpEF. We assessed left ventricular (LV) function, oxidative/nitrosative stress, exercise tolerance, and cardiac fibrosis.Materials and MethodsMale, C57/BL6N (n=15 per group) were placed on a Western high fat diet (60% kCal from fat) and treated with L‐NG‐Nitro arginine methyl ester (L‐NAME, 0.5 g/L/day) in the drinking water beginning at 10 weeks of age. At 15 weeks of age, mice were randomly assigned to four separate groups for five additional weeks: HFpEF control, sodium nitrite in drinking water (75 mg/L), hydralazine (2 mg/kg/day, i.p., b.i.d.), or the combination of sodium nitrite and hydralazine.Plasma was collected to measure circulating 8‐isoprostane and 3‐nitrotyrosine levels, biomarkers of oxidative and nitrosative stress respectively. In addition, cardiac tissue was harvested at 20 weeks for Masson’s Trichrome staining and to measure cardiac nitrite levels. Echocardiography and exercise tolerance testing was performed at 10, 15, and 20 weeks of age.ResultsThere was a significant increase in circulating nitrite levels (p &lt; 0.05) in the sodium nitrite + hydralazine group compared to the control and either monotherapy groups. There was no significant difference in the cardiac tissue nitrite levels between the combination therapy and the control group. Plasma 8‐isoprostane and 3‐nitrotyrosine levels were significantly (p &lt; 0.05) reduced in the sodium nitrite + hydralazine group compared to the HFpEF control group, indicating a reduction in oxidative and nitrosative stress. Although there was no significant difference in the extent of interstitial cardiac fibrosis between groups, there was a significant decrease (p &lt; 0.05) in myocardial perivascular fibrosis in the sodium nitrite + hydralazine group compared to control. Left ventricular end‐diastolic pressure (LVEDP) was significantly reduced in all treatment groups, and LVEDP was reduced to the greatest extent in the nitrite + hydralazine group vs. HFpEF control. Furthermore, we observed a significant (p &lt; 0.01) improvement in LV diastolic function (i.e., E/e’) in the sodium nitrite and hydralazine group that was superior to either of the treatments alone. There was no significant difference in the exercise distance or duration among the various groups.ConclusionThese data demonstrate that the combination of a powerful antioxidant with NO donor therapy significantly enhances the beneficial effects NO therapy in the setting of severe HFpEF.

Caveolar disruption with methyl-β-cyclodextrin causes endothelium-dependent contractions in Wistar rat carotid arteries.

Caveolae are organizing centers for cellular signal transduction in endothelial cells (ED) and smooth muscle cells (SMCs) in the blood vessels. Myography was used to investigate the effects of a caveolar disruption using methyl-β-cyclodextrin (MBCD) on maxi-K channels in rat carotid arteries. Incubation of carotid segments with MBCD augmented contractions in response to BaK (chemical channel agonist) but not those induced by depolarizing high potassium physiological saline (KPSS). In contrast, incubation with cholesterol-saturated MBCD (Ch-MBCD) abolished the effects of MBCD. Mechanical removal of endothelial cells by MBCD triggered a small contraction in response to BaK. Incubation with nitroarginine methyl ester (L-NAME) inhibited nitric oxide (NO) release, causing increased contractions in response to BaK, and this effect was reversed by pretreatment with MBCD. These results suggest that MBCD inhibits endothelial NO release. Contrastingly, inhibition of maxi-K channels with iberiotoxin enhanced contractions in response to BaK. Likewise, L-NAME decreased the contractile effect of iberiotoxin, as in the ED-denuded arteries. Transmission electron microscopy (TEM) showed the presence and absence of caveolae in intact blood vessels before and after MBCD treatment, respectively, whereas histology confirmed ED removal after the treatment. Caveolar disruption using MBCD impairs ED-dependent relaxation by inhibiting the release of NO from the ED and altered the contractility of SMCs independent of the ED due to reduced contribution of maxi-K channels to the SMC membrane potential, causing depolarization and increasing carotid artery contraction. These findings might help to understand the physiological role of the maxi-K channels in rat carotid arteries.

Rosa centifolia petal extract induces endothelium-dependent and endothelium-independent vasorelaxation in rat aorta and prevents accumulation of inflammatory factors in human umbilical vein endothelial cells.

This study aims to investigate the vasorelaxation effects of a Rosa centifolia petal extract (ROSE CRYSTA®-70: ROSE-70) on the isolated aorta and the protective effect of ROSE-70 on human umbilical vein endothelial cells (HUVECs) dysfunction. ROSE-70 inhibited phenylephrine (PE) -induced contraction in an endothelium-dependent and endothelium-independent manner; however, this relaxation was lower in the endothelium-denuded aorta. ROSE-70-induced relaxation was attenuated by L-NG -nitroarginine methyl ester (L-NAME), a nitric oxide synthase inhibitor in the endothelium-intact aorta. Moreover, the relaxation in the endothelium-denuded aorta in response to increases in cAMP was inhibited by SQ22536, an adenylate cyclase inhibitor, and this relaxation was also attenuated by 4-aminopyridine, a voltage-activated K+ channel inhibitor. ROSE-70 contains high concentrations of quercetin, rutin, and other compounds. Pure quercetin and rutin also inhibited PE-induced contraction in an endothelium-dependent manner, although rutin-induced relaxation was milder in the endothelium-denuded aorta. ROSE-70 significantly increased the phosphorylation (at Ser1177) of eNOS in HUVECs. Moreover, ROSE-70 potently suppressed high glucose- and H2 O2 -induced accumulation of tumor necrosis factor-α (TNF-α) and nuclear factor-kappa B (NF-κB) were investigated in human umbilical vein endothelial cells (HUVECs). In this study, we defined the mechanism of ROSE-70-induced vasorelaxation in rat aorta and demonstrated that ROSE-70 has anti-inflammatory effects in endothelial cells. PRACTICAL APPLICATIONS: Endothelial cells play a role in vascular homeostasis. Endothelial dysfunction is caused by a variety of risk factors such as hypertension, arteriosclerosis, hyperglycemia, and oxidative stress. ROSE-70 is a food ingredient and the powdered form of an extract from the rose petal with >70% of the content corresponding to rose petal polyphenols such as rutin, quercetin, and protocatechuic acid. This study revealed that vasorelaxation effects of ROSE-70 and the protective role of ROSE-70 on the dysfunction of endothelial cells by high glucose and superoxides were investigated for the first time. We showed the mechanisms of ROSE-70- induced endothelium-dependent vasorelaxation and the protective effects of endothelial cells from high glucose and superoxide. ROSE-70 has been shown to have antiaging, skin elasticity-enhancing, skin-lightening, anti-allergic, sugar-absorbing, and lipolytic effects (URL: https://www.toyohakko-healthcare. com/en/rose_crysta70/). Therefore, the authors believe that ROSE-70 is an excellent food ingredient that has preventive and antiaging effects on lifestyle-related diseases.

Potential Benefits of Omega 3.5.7 on Cardiovascular and Reproductive Functions of Male Rats Administered L-N G -Nitro Arginine Methyl Ester (L-NAME)

Background: Dietary interventions and lifestyle changes are some of the ways to manage hypertension and its complications. Males with hypertension report infertility and erectile dysfunction. Objective: This study determined the role of Omega 3.5.7 enriched diet on cardiovascular and reproductive functions in male rats administered L-N G -Nitro arginine methyl ester (L-NAME; a nitric oxide synthase inhibitor). Materials and Methods: Twenty-four male rats were divided into four groups of six rats each: Group 1 (control), Group 2 received L-NAME (50 mg/kg b.w. intraperitoneally), Group 3 received L-NAME + Omega 3.5.7, and Group 4 received 1.5% omega 3.5.7 enriched diet. Rats were fed for two weeks and blood pressure parameters were obtained under anaesthesia using a Power Lab system. Blood was withdrawn from the carotid arteries for biochemical and hormonal assays and the caudal epididymis was collected for the assessment of sperm parameters. Results: Systolic, diastolic, mean arterial blood pressure, and rate pressure products were increased in the L-NAME and group while levels of antioxidants (GSH, SOD, CAT) were decreased. Omega 3.5.7 supplementation with L-NAME increased GSH and CAT levels when compared with the L-NAME group. Plasma NO and sperm count, sperm motility, and testosterone levels were decreased by L-NAME. The Omega 3.5.7 + L-NAME group increased NO and testosterone levels. Conclusions: Improved antioxidant status, testosterone, and NO levels are indicators that omega 3.5.7 enriched diet could reverse blood pressure and increase the decrease in sperm count and motility induced by L-NAME.

Transpelvic Magnetic Stimulation Enhances Penile Microvascular Perfusion in a Rat Model: A Novel Interventional Strategy to Prevent Penile Fibrosis after Cavernosal Nerve Injury.

PurposePenile microvascular dysfunction is a known contributor to erectile dysfunction (ED) and penile fibrosis has been shown to impair microvascular perfusion (MVP). Our objectives were to: (i) determine beneficial effects of TPMS to modulate penile MVP, (ii) determine its mechanism, (iii) evaluate impact of cavernosal nerve injury (CNI) on penile MVP, and (iv) determine time-course of cavernosal tissue elastin changes after CNI in rats.Materials and MethodsAdult male rats (n=5) were anesthetized and subjected to TPMS (13%, 15%, and 17%) and MVP changes were recorded using laser speckle contrast imaging (LSCI). Another group of male rats were subjected to either bilateral cavernosal nerve injury (CNI; n=7) or sham surgery (n=7). After recovery, animals were monitored for MVP using LSCI before and after TPMS. Rat penile tissues were harvested and analyzed for fibrosis using a marker for elastin.ResultsRat TPMS resulted in a stimulus dependent increase in MVP; maximal perfusion was observed at 17%. L-N(G)-Nitroarginine methyl ester (L-NAME) resulted in a marked decrease in TPMS induced MVP increase (393.33 AU vs. 210.67 AU). CNI resulted in 40% to 50% decrease in MVP. CNI produced a remarkable increase in elastin deposits that are noticeable throughout the cavernosal tissues post injury.ConclusionsTPMS is a novel and non-invasive intervention to improve penile MVP after CNI. Potential application includes treatment of ED and sexual function preservation following cancer treatment, possibly through improved penile hemodynamics that might help prevent penile hypoxia and fibrosis.

Y-016. Interaction between previous preeclampsia and inter-pregnancy chronic hypertension development on preeclampsia risk in the subsequent pregnancy

Our recent study demonstrates the beneficial effect of a combined supplementation of vitamin B12, folic acid, and docosahexaenoic acid in reducing the severity of pregnancy induced hypertension (PIH). It is also known to be associated with angiogenic imbalance and inflammation. The current study examines whether the individual/combined supplementation of folic acid, vitamin B12 and omega-3 fatty acid during pregnancy can ameliorate the inflammatory markers and restore the angiogenic balance in a rat model of PIH.There were total of six groups, control and five treatment groups: PIH Induced; PIH+vitamin B12; PIH+folic acid; PIH+Omega-3 fatty acids and PIH+combined micronutrient supplementation (vitamin B12+folic acid+omega-3 fatty acids). Hypertension during pregnancy was induced using L- Nitroarginine methylester (L-NAME; 50 mg/kg body weight/day). Dams were dissected at d20 of gestation and placental tissues were collected for further analysis.Animals from the PIH induced group demonstrated lower (p<0.01 for both) IL-10 and VEGF levels as compared to control. However, PIH induction did not alter the protein levels of eNOS, IL-6, Flt and mRNA levels of VEGF and VEGFR-1/ Flt-1. Individual micronutrient supplementation of vitamin B12 and folate did not offer benefit. In contrast individual omega-3 fatty acid as well as combined micronutrient supplementation showed IL-10 and VEGF levels comparable to that of control.Omega 3 fatty acid supplementation plays a key role in reducing inflammation in pregnancy induced hypertension.

The potential relationship between gasotransmitters and oxidative stress, inflammation and apoptosis in lead-induced hepatotoxicity in rats

The interrelationship between gasotransmitters and oxidative stress, inflammation and apoptosis in lead-induced hepatotoxicity was investigated in this study. On prolonged exposure, lead was accumulated in liver tissue of rats and impaired liver function and structure as assessed by measurement of the serum hepatic function markers and by histopathological examination. The accumulated metal induced oxidative stress, inflammation and apoptosis in the liver. Also, it increased nitric oxide (NO) production and decreased hydrogen sulfide (H2S) level and heme oxygenase (HO-1) concentration in liver tissue. Decreasing of NO production by L-N(G)-nitroarginine methyl ester (L-NAME) and increasing of H2S level by sodium hydrosulfide (NaHS) and carbon monoxide (CO) level by carbon monoxide-releasing molecule-A1 (CORM-A1) inhibited lead-induced impairment of liver function and structure. Concomitantly, these agents inhibited lead intoxication-induced oxidative stress, inflammation, apoptosis, nitrosative stress and reduction of HO-1 concentration and H2S level. Furthermore, concurrent treatment with these agents inhibited lead intoxication-induced increase in the protein expressions of inducible NO synthase, tumor necrosis factor-alpha, interleukin-1beta and caspase-3 as well as decrease in protein expressions of HO-1 and cystathionine-γ-lyase in the liver. NO donor, l-arginine and H2S and CO biosynthesis inhibitors, trifluoro-DL-alanine and zinc deutroporphyrin, respectively aggravated the toxic effects of lead. These results indicate, for the first time, that there is an interrelationship between gasotransmitters and lead-induced hepatotoxicity. The ability of L-N AME, NaHS and CORM-A1 to provide protective effects against lead-induced hepatotoxicity may positively correlate, to their ability to suppress hepatic oxidative stress, nitrosative stress, inflammation and apoptosis.

Semi-mechanistic modelling platform to assess cardiac contractility and haemodynamics in preclinical cardiovascular safety profiling of new molecular entities.

Cardiovascular safety is one of the most frequent causes of safety-related attrition both preclinically and clinically. Preclinical cardiovascular safety is routinely assessed using dog telemetry monitoring key cardiovascular functions. The present research was to develop a semi-mechanistic modelling platform to simultaneously assess changes in contractility (dPdtmax ), heart rate (HR) and mean arterial pressure (MAP) in preclinical studies. Data from dPdtmax , HR, preload (left ventricular end-diastolic pressure [LVEDP]) and MAP were available from dog telemetry studies after dosing with atenolol (n = 27), salbutamol (n = 5), L-NG -nitroarginine methyl ester (L-NAME; n = 4), milrinone (n = 4), verapamil (n = 12), dofetilide (n = 8), flecainide (n = 4) and AZ001 (n = 14). Literature model for rat CV function was used for the structural population pharmacodynamic model development. LVEDP was evaluated as covariate to account for the effect of preload on dPdtmax . The model was able to describe drug-induced changes in dPdtmax , HR and MAP for all drugs included in the developed framework adequately, by incorporating appropriate drug effects on dPdtmax , HR and/or total peripheral resistance. Consistent with the Starling's law, incorporation of LVEDP as a covariate on dPdtmax to correct for the preload effect was found to be statistically significant. The contractility and haemodynamics semi-mechanistic modelling platform accounts for diurnal variation, drug-induced changes and inter-animal variation. It can be used to hypothesize and evaluate pharmacological effects and provide a holistic cardiovascular safety profile for new drugs.

Comparative Effects of Aqueous Leaf Extracts of Thymus schimperi and Moringa stenopetala on Regional Blood Flow Velocity and Vascular Resistance of Pre-eclampsia Rat Models

Background: Pre-eclampsia (PE) is a common hypertensive disorder of pregnancy with a prevalence rate of 3-5%. There is no modern drug which cures PE so far. On the other hand, plant medicines are claimed to cure this disease. Exploring potential plant medicines for their therapeutic and/or prophylactic uses in this disease, therefore has paramount importance. In Ethiopia, there is a strong claim that leaves of Moringa stenopetala and Thymus schimperi have anti-hypertension activities. Thus, the current study was supposed to prove the potential therapeutic effects of the two plants against PE. PE reduces organ blood flow and increasesvascular resistance. Assessing these variables has widely been accepted when monitoring high-risk pregnancies and evaluating therapeutic and/or prophylactic uses of drugs.&#x0D; Methods: A comparative experimental case control study was employed to determine the effects of aqueous crude extracts of Thymus schimperi and Moringa stenopetala on regional blood flow velocities and vascular resistance of PE Albino-Wistar rat models induced by a potent vasoconstrictor, nitro-arginine methyl ester(L-NAME). A Doppler flow meter (Atys, Directive 93/42/EEC/CEE, Model, BASIC123LP) was used to measure the systolic and diastolic regional blood flow velocities through abdominal aorta, uterine, renal and common carotid arteries. The peripheral vascular resistance for the respective vessels were evaluated using resistivity and pulsatility indices.&#x0D; Results: Aqueous leaf extracts of T. schimperi (ALETS) and M. stenopetala (ALEMS) significantly increased regional blood flow velocities and decreased peripheral vascular resistance in PE rat modelsin a dose dependent pattern compared with untreated controls. For example, ALETS treated PE groups showed increased diastolic blood velocity (DBV) (cm/sec) of uterine arteries 3.8±0.4 (p&lt;0.05), 4.2±0.4 (p&lt;0.01), 7.3±0.5 (p&lt;0.01), while ALEMS treated PE group had uterine arterial DBV of 2.8±0.3 (p&lt;0.01), 3.5±0.8 (p&lt;0.05), 6.6±0.8 (p&lt;0.01) with daily doses of 250 mg/kg, 500 mg/kg and 1 gm/kg, respectively. Moreover, the vascular resistances (measured by resistivity and pulsatility indices), of the respective vessels were significantly lower in a dose dependent pattern.&#x0D; Conclusion: Both ALETS and ALEMS could increaseregional blood flow velocities and decrease vascular resistances of PE rat models. Further investigation should, however, be carried out to confirm their therapeutic merits.

Effect of hypercholesterolemia on hypertension-induced renal injury in rats: Insights in the possible mechanisms

The effect of hypercholesterolemia on hypertension-induced renal injury was investigated in rats. Hypertension was induced by L-N(G)-nitroarginine methyl ester (L-NAME) and Hypercholesterolemia was induced by feeding rats with a diet containing 1% cholesterol. In these animals L-NAME produced a progressive increase in the systolic, diastolic and mean arterial Blood Pressure (BP). Similarly, L-NAME with hypercholesterolemia produced, in addition to compromised serum lipid profile, a progressive increase in the systolic, diastolic and mean arterial BP.

The interrelationship between gasotransmitters and lead-induced renal toxicity in rats

This study explored the role of gasotransmitters in lead-induced nephrotoxicity. Long-term exposure of rats to lead resulted in its accumulation in kidney. The accumulated metal impaired kidney function and structure. Lead intoxication resulted in oxidative stress, inflammation and apoptosis in kidney. In addition, it resulted in nitric oxide (NO) overproduction and decrease in hydrogen sulfide (H2S) level and heme oxygenase (HO-1) concentration in kidney. Inhibition of NO overproduction by L–N(G)-nitroarginine methyl ester (L–NAME) and increasing of H2S level by sodium hydrosulfide (NaHS) and CO level by carbon monoxide-releasing molecule-A1 (CORM-A1) inhibited lead-induced impairment of kidney function and structure. These agents inhibited lead-intoxication induced oxidative stress, inflammation, apoptosis, nitrosative stress and reduction of H2S level and HO-1 concentration. Also, concomitant treatment with these agents inhibited lead intoxication-induced increase in protein expressions of inducible NO synthase (iNOS), tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and caspase-3 as well as decrease in protein expressions of HO-1 and cystathionine- γ-lyase (CSE) in kidney. The NO donor, L-arginine and the H2S and CO biosynthesis inhibitors, trifluoro-DL-alanine and zinc deutroporphyrin, respectively produced opposite effects and aggravated the toxic effects of lead. These results demonstrate, for the first time, that gasotransmitters play an important role in lead-induced nephrotoxicity.

Nitric Oxide Synthesis/Pathway Inhibitors in Daphnia magna Reverse Alcohol-Induced Heart Rate Decrease

Studies show that alcohol causes oxidative stress and heart rate (HR) depression in humans. Chronic alcohol consumption also causes cardiac myopathy, which afflicts about 500,000 Americans annually. The present study aims to understand how alcohol reduces HR and examine if select chemical agents with inhibitory effects on nitric oxide levels can reverse the effects of alcohol on HR. In this study, we used Daphnia magna, a water crustacean with a large and a transparent heart, as an in vitro model to study the effects of agents such as methylene blue (a guanylyl cyclase inhibitor), melatonin (a free radical scavenger and Phosphodiesterase E5 (PDE5) inhibitor), L-glutamate (N-methyl-D-Aspartate (NMDA)-ion channel stimulator), and L-N(gamma)-nitroarginine methyl ester (L-NAME, nitric oxide synthase inhibitor) on HR by alcohol. We also examined the ability of these agents to prevent a decrease in the HR by alcohol by changing the order in which we exposed the Daphnia to the substances. Alcohol exposure decreased HR by 27% after 30 minutes of exposure. The experiment measured the ability of various drugs to reverse this decrease in HR. Methylene blue, after 10 minutes of exposure, increased the HR by 15%. Melatonin, after 10 minutes exposure, increased the HR by 27%. Similarly, L-NAME and L-glutamate, after 10 minutes of exposure, increased the HR by 20% and 36%, respectively. These results showed that alcohol’s depressive effects on HR could be mediated through nitric oxide generation and confirmed the hypothesis that nitric oxide synthesis inhibitors can reverse alcohol-induced HR decrease in Daphnia magna.

Measurement of flow-mediated dilation of mouse femoral artery in vivo by optical coherence tomography.

Flow-mediated vasodilation (FMD) is used for assessment of vascular endothelial function in humans as a predictor of cardiovascular events. It has been challenging to carry it on preclinical murine models due to the diminutive size of the femoral artery. Here, we present a new approach to accurately measure the blood velocity and femoral artery diameters of mice by acquiring Doppler optical coherence tomography and optical coherence tomography angiography continuously within 1 single experimental scanning protocol. Using the 3-dimensional imaging and new velocity algorithm, the measurement precision of diameter, blood flow, velocity and wall shear stress are improved to 0.91%, 11.0%, 10.7% and 14.0%, respectively. FMD of healthy mouse femoral artery measured by this method was 11.96% ± 0.98%, which was blunted to 5.69% ± 0.4% by intravenous administration of endothelial nitric oxide synthase inhibitor (L-NG -Nitroarginine methyl ester), in agreement with that reported in the literature.

Deletion of endothelial arginase 1 does not improve vasomotor function in diabetic mice.

Endothelial arginase 1 was ablated to assess whether this prevents hyperglycemia‐induced endothelial dysfunction by improving arginine availability for nitric oxide production. Endothelial Arg1‐deficient mice (Arg1‐KOT ie2) were generated by crossing Arg1 fl/fl (controls) with Tie2Cre tg/− mice and analyzed by immunohistochemistry, measurements of hemodynamics, and wire myography. Ablation was confirmed by immunohistochemistry. Mean arterial blood pressure was similar in conscious male control and Arg1‐KOT ie2 mice. Depletion of circulating arginine by intravenous infusion of arginase 1 or inhibition of nitric oxide synthase activity with L‐NG‐nitro‐arginine methyl ester increased mean arterial pressure similarly in control (9 ± 2 and 34 ± 2 mmHg, respectively) and Arg1‐KOT ie2 mice (11 ± 3 and 38 ± 4 mmHg, respectively). Vasomotor responses were studied in isolated saphenous arteries of 12‐ and 34‐week‐old Arg1‐KOT ie2 and control animals by wire myography. Diabetes was induced in 10‐week‐old control and Arg1‐KOT ie2 mice with streptozotocin, and vasomotor responses were studied 10 weeks later. Optimal arterial diameter, contractile responses to phenylephrine, and relaxing responses to acetylcholine and sodium nitroprusside were similar in normoglycemic control and Arg1‐KOT ie2 mice. The relaxing response to acetylcholine was dependent on the availability of extracellular l‐arginine. In the diabetic mice, arterial relaxation responses to endothelium‐dependent hyperpolarization and to exogenous nitric oxide were impaired. The data show that endothelial ablation of arginase 1 in mice does not markedly modify smooth muscle and endothelial functions of a resistance artery under normo‐ and hyperglycemic conditions.

Capillary response to skeletal muscle contraction: evidence that redundancy between vasodilators is physiologically relevant during active hyperaemia.

The current theory behind matching blood flow to metabolic demand of skeletal muscle suggests redundant interactions between metabolic vasodilators. Capillaries play an important role in blood flow control given their ability to respond to muscle contraction by causing conducted vasodilatation in upstream arterioles that control their perfusion. We sought to determine whether redundancies occur between vasodilators at the level of the capillary by stimulating the capillaries with muscle contraction and vasodilators relevant to muscle contraction. We identified redundancies between potassium and both adenosine and nitric oxide, between nitric oxide and potassium, and between adenosine and both potassium and nitric oxide. During muscle contraction, we demonstrate redundancies between potassium and nitric oxide as well as between potassium and adenosine. Our data show that redundancy is physiologically relevant and involved in the coordination of the vasodilator response during muscle contraction at the level of the capillaries. We sought to determine if redundancy between vasodilators is physiologically relevant during active hyperaemia. As inhibitory interactions between vasodilators are indicative of redundancy, we tested whether vasodilators implicated in mediating active hyperaemia (potassium (K+ ), adenosine (ADO) and nitric oxide (NO)) inhibit one another's vasodilatory effects through direct application of pharmacological agents and during muscle contraction. Using the hamster cremaster muscle and intravital microscopy, we locally stimulated capillaries with one vasodilator in the absence and the presence of a second vasodilator (10-7 m S-nitroso-N-acetylpenicillamine (SNAP), 10-7 m ADO, 10mm KCl) applied sequentially and simultaneously, and observed the response in the associated upstream 4A arteriole controlling the perfusion of the stimulated capillary. We found that KCl significantly attenuated SNAP- and ADO-induced vasodilatations by ∼49.7% and ∼128.0% respectively and ADO significantly attenuated KCl- and SNAP-induced vasodilatations by ∼94.7% and ∼59.6%, respectively. NO significantly attenuated KCl vasodilatation by 93.8%. Further, during muscle contraction we found that inhibition of NO production using l-NG -nitroarginine methyl ester and inhibition of ADO receptors using xanthine amine congener was effective at inhibiting contraction-induced vasodilatation but only in the presence of K+ release channel inhibition. Thus, only when the inhibiting vasodilator K+ was blocked was the second vasodilator, NO or ADO, able to produce effective vasodilatation. Therefore, we show that there are inhibitory interactions between specific vasodilators at the level of the capillary. Further, these inhibitions can be observed during muscle contraction indicating that redundancies between vasodilators are physiologically relevant and influence vasodilatation during active hyperaemia.

Protective effect of the standardized extract of ginkgo biloba (EGb761) against hypertension with hypercholesterolemia-induced renal injury in rats: Insights in the underlying mechanisms

The potential protective role of the standardized leaf extract of ginkgo biloba (EGb761) on hypertension with hypercholesterolemia-induced renal injury was investigated in rats. Hypertension was induced by L-N(G)-nitroarginine methyl ester (L-NAME) and hypercholesterolemia was induced by feeding rats with a diet containing 1% cholesterol. In these animals repeated treatment with EGb761 produced a progressive reduction in the systolic, diastolic and mean arterial blood pressure (BP). EGb761 increased the progressive reduction in the systolic, diastolic and mean arterial BP induced by repeated administration of losartan with simvastatin. EGb761 corrected the compromised serum lipid profile and enhanced the effect of losartan with simvastatin on lipid profile. EGb761 protected against hypertension with hypercholesterolemia-induced renal injury as assessed by measurement of serum renal function markers and by histopathological examination. EGb761 enhanced the renoprotective effect of losartan with simvastatin in these rats. Concomitantly, hypertension with hypercholesterolemia-induced elevation of renal tissue malondialdehyde (MDA) and nitrite levels and reduction of intracellular reduced glutathione (GSH) level were inhibited by repeated treatment with EGb761. In addition, hypertension with hypercholesterolemia-induced increases in tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) levels in renal tissues were inhibited by treatment with EGb761. Also, EGb761 inhibited hypertension with hypercholesterolemia-induced decrease in endothelial nitric oxide synthase (eNOS) protein expression and increase in the protein expressions of inducible NO synthase (iNOS), TNF-α, IL-6 and IL-1β in the kidney tissues. Losartan with simvastatin produced similar effects on renal tissues oxidative stress, nitrite and inflammatory markers levels and on protein expressions of eNOS, iNOS, TNF-α, IL-6 and IL-1β. EGb761 enhanced losartan with simvastatin effects. These results indicate that EGb761 has the ability to protect against hypertension with hypercholesterolemia-induced renal injury. The ability of EGb761 to provide this renoprotective effect may positively correlate, besides its antihypertensive and antihypercholesterolemic effects, to its ability to suppress renal oxidative stress, nitrosative stress and inflammation.

Shear stress-mediated upregulation of GTP cyclohydrolase/tetrahydrobiopterin pathway ameliorates hypertension-related decline in reendothelialization capacity of endothelial progenitor cells.

Guanosine triphosphate cyclohydrolase/tetrahydrobiopterin (GTPCH)/(BH4) pathway has been proved to regulate the function of endothelial progenitor cells (EPCs) in deoxycorticosterone acetate-salt hypertensive mice, indicating that GTPCH/BH4 pathway may be an important repair target for hypertension-related endothelial injury. Shear stress is an important nonpharmacologic strategy to modulate the function of EPCs. Here, we investigated the effects of laminar shear stress on the GTPCH/BH4 pathway and endothelial repair capacity of circulating EPCs in hypertension. Laminar shear stress was loaded on the human EPCs from hypertensive patients and normotensive patients. The in-vitro function, in-vivo reendothelialization capacity and GTPCH/BH4 pathway of human EPCs were evaluated. Both in-vitro function and reendothelialization capacity of EPCs were lower in hypertensive patients than that in normotensive patients. The GTPCH/BH4 pathway of EPCs was downregulated in hypertensive patients. Shear stress increased in-vitro function and reendothelialization capacity of EPCs from hypertensive patients and normotensive patients. Furthermore, shear stress upregulated the expression of GTPCH I and levels of BH4, nitric oxide, and cGMP of EPCs, and reduced thrombospondin-1 expression. With treatment of GTPCH knockdown or nitroarginine methyl ester inhibition, shear stress-induced increased levels of BH4, nitric oxide and cGMP of EPCs was suppressed. When GTPCH/BH4 pathway of EPCs was blocked, the effects of shear stress on in-vitro function and reendothelialization capacity of EPCs were inhibited. The study demonstrates for the first time that shear stress-induced upregulation of the GTPCH/BH4 pathway ameliorates hypertension-related decline in endothelial repair capacity of EPCs. These findings provide novel nonpharmacologic therapeutic approach for hypertension-related endothelial repair.