l-Arginine attenuates acute pulmonary embolism-induced oxidative stress and pulmonary hypertension

L-arginine mitigates bleomycin-induced pulmonary fibrosis in rats through regulation of HO-1/PPAR-γ/β-catenin axis

Pulmonary fibrosis is a chronic and progressively deteriorating lung condition that can be replicated in laboratory animals by administering bleomycin, a chemotherapeutic antibiotic known for its lung fibrosis-inducing side effects. L-arginine, a semi-essential amino acid, is recognized for its diverse biological functions, including its potential to counteract fibrosis. This study aimed to evaluate the antifibrotic properties of L-arginine on bleomycin-induced pulmonary fibrosis in rats. The administration of a single intratracheal dose of bleomycin resulted in visible and microscopic damage to lung tissues, an uptick in oxidative stress markers, and an elevation in inflammatory, apoptotic, and fibrotic indicators. A seven-day treatment with L-arginine post-bleomycin exposure markedly improved the gross and histological architecture of the lungs, prevented the rise of malondialdehyde and carbonyl content, and enhanced total antioxidant capacity alongside the activities of antioxidant enzymes. Also, L-arginine attenuated the expression of the pro-fibrotic factors, transforming growth factor-β and lactate dehydrogenase in bronchoalveolar lavage fluid. In the lung tissue, L-arginine reduced collagen deposition, hydroxyproline concentration, and mucus production, along with decreasing expression of α-smooth muscle actin, tumor necrosis factor-α, caspase-3, matrix metalloproteinase-9, and β-catenin. Moreover, it boosted levels of nitric oxide and upregulated the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ), heme oxygenase-1 (HO-1), and E-cadherin and downregulating the expression of β-catenin. These findings suggest that L-arginine has preventive activities against bleomycin-induced pulmonary fibrosis. This effect can be attributed to the increased production of nitric oxide, which modulates the HO-1/PPAR-γ/β-catenin axis.

Oxidative stress in acute pulmonary embolism: emerging roles and therapeutic implications

Oxidative stress is an imbalance between the body's reactive oxygen species and antioxidant defense mechanisms. Oxidative stress is involved in the development of several cardiovascular diseases, such as pulmonary hypertension, atherosclerosis, and diabetes mellitus. A growing number of studies have suggested the potential role of oxidative stress in the pathogenesis of pulmonary embolism. Biomarkers of oxidative stress in pulmonary embolism have also been explored, such as matrix metalloproteinases, asymmetric dimethylarginine, and neutrophil/lymphocyte ratio. Here, we comprehensively summarize some oxidative stress mechanisms and biomarkers in the development of acute pulmonary embolism and summarize related treatments based on antioxidant stress to explore effective treatment strategies for acute pulmonary embolism.

Antiseptic mouthwash inhibits antihypertensive and vascular protective effects of L-arginine

L-arginine supplementation increases nitric oxide (NO) formation and bioavailability in hypertension. We tested the possibility that many effects of L-arginine are mediated by increased formation of NO and enhanced nitrite, nitrate and nitrosylated species concentrations, thus stimulating the enterosalivary cycle of nitrate. Those effects could be prevented by antiseptic mouthwash. We examined how the derangement of the enterosalivary cycle of nitrate affects the improvement of endothelial dysfunction (assessed with isolated aortic ring preparation), the antihypertensive (assessed by tail-cuff blood pressure measurement) and the antioxidant effects (assessed with the fluorescent dye DHE) of L-arginine in two-kidney, one-clip hypertension model in rats by using chlorhexidine to decrease the number of oral bacteria and to decrease nitrate reductase activity assessed from the tongue (by ozone-based chemiluminiscence assay). Nitrite, nitrate and nitrosylated species concentrations were assessed (ozone-based chemiluminiscence). Chlorhexidine mouthwash reduced the number of oral bacteria and tended to decrease the nitrate reductase activity from the tongue. Antiseptic mouthwash blunted the improvement of the endothelial dysfunction and the antihypertensive effects of L-arginine, impaired L-arginine-induced increases in plasma nitrite and nitrosylated species concentrations, and blunted L-arginine-induced increases in aortic nitrate concentrations and vascular antioxidant effects. Our results show for the first time that the vascular and antihypertensive effects of L-arginine are prevented by antiseptic mouthwash. These findings show an important new mechanism that should be taken into consideration to explain how the use of antibacterial mouth rinse may affect arterial blood pressure and the risk of developing cardiovascular and other diseases.

Development and validation of a novel risk assessment model to estimate the probability of pulmonary embolism in postoperative patients

Pulmonary embolism (PE) is a leading cause of mortality in postoperative patients. Numerous PE prevention clinical practice guidelines are available but not consistently implemented. This study aimed to develop and validate a novel risk assessment model to assess the risk of PE in postoperative patients. Patients who underwent Grade IV surgery between September 2012 and January 2020 (n = 26,536) at the Affiliated Dongyang Hospital of Wenzhou Medical University were enrolled in our study. PE was confirmed by an identified filling defect in the pulmonary artery system in CT pulmonary angiography. The PE incidence was evaluated before discharge. All preoperative data containing clinical and laboratory variables were extracted for each participant. A novel risk assessment model (RAM) for PE was developed with multivariate regression analysis. The discrimination ability of the RAM was evaluated by the area under the receiver operating characteristic curve, and model calibration was assessed by the Hosmer–Lemeshow statistic. We included 53 clinical and laboratory variables in this study. Among them, 296 postoperative patients developed PE before discharge, and the incidence rate was 1.04%. The distribution of variables between the training group and the validation group was balanced. After using multivariate stepwise regression, only variable age (OR 1.070 [1.054–1.087], P < 0.001), drinking (OR 0.477 [0.304–0.749], P = 0.001), malignant tumor (OR 2.552 [1.745–3.731], P < 0.001), anticoagulant (OR 3.719 [2.281–6.062], P < 0.001), lymphocyte percentage (OR 2.773 [2.342–3.285], P < 0.001), neutrophil percentage (OR 10.703 [8.337–13.739], P < 0.001), red blood cell (OR 1.872 [1.384–2.532], P < 0.001), total bilirubin (OR 1.038 [1.012–1.064], P < 0.001), direct bilirubin (OR 0.850 [0.779–0.928], P < 0.001), prothrombin time (OR 0.768 [0.636–0.926], P < 0.001) and fibrinogen (OR 0.772 [0.651–0.915], P < 0.001) were selected and significantly associated with PE. The final model included four variables: neutrophil percentage, age, malignant tumor and lymphocyte percentage. The AUC of the model was 0.949 (95% CI 0.932–0.966). The risk prediction model still showed good calibration, with reasonable agreement between the observed and predicted PE outcomes in the validation set (AUC 0.958). The information on sensitivity, specificity and predictive values according to cutoff points of the score in the training set suggested a threshold of 0.012 as the optimal cutoff value to define high-risk individuals. We developed a new approach to select hazard factors for PE in postoperative patients. This tool provided a consistent, accurate, and effective method for risk assessment. This finding may help decision-makers weigh the risk of PE and appropriately select PE prevention strategies.

Nitrite and tempol combination promotes synergic effects and alleviates right ventricular wall stress during acute pulmonary thromboembolism

INTRODUCTION

The mechanical obstruction and pulmonary vasoconstriction are major determinants of the sudden right ventricular (RV) afterload increases observed during acute pulmonary thromboembolism (APT). Vasodilators and antioxidants agents have been shown to mitigate pulmonary hypertension. We examined whether sodium nitrite and the antioxidant tempol combination could be advantageous in an APT sheep model.

METHODS

APT was induced in anesthetized sheep by autologous blood clots (250 mg/kg) into the right atrium. Thirty minutes after APT induction, the animals received a continuous infusion of tempol (1.0 mg/kg/min), increasing sodium nitrite infusion (5, 15, and 50 μmol/kg), or a simultaneous combination of both drugs. Saline was used as a control treatment. Hemodynamic measurements were carried out every 15 min. Also, whole blood nitrite and serum 8-isoprostanes levels were measured.

RESULTS

APT induced sustained pulmonary hypertension, increased dp/dt_max, and rate pressure product (RPP). Nitrite or tempol treatments attenuated these increases (P < 0.05). When both drugs were combined, we found a robust reduction in the RV RPP compared with the treatments alone (P < 0.05). The sole nitrite infusion increased blood nitrite concentrations by 35 ± 6 μM (P < 0.05), whereas the nitrite and tempol combination produced higher blood nitrite concentrations by approximately 54 ± 7 μM. Tempol or nitrite infusions, both alone or combined, blunted the increases in 8-isoprostane concentrations observed after APT.

CONCLUSIONS

Nitrite and tempol combination protects against APT-induced RV wall stress. The association of both drugs may offer an advantage to treat RV failure during severe APT.

Hydrogen sulfide and vascular regulation - An update

BACKGROUND

Hydrogen sulfide (H₂S) is considered to be the third gasotransmitter after carbon monoxide (CO) and nitric oxide (NO). It plays an important role in the regulation of vascular homeostasis. Vascular remodeling have has proved to be related to the impaired H₂S generation.

AIM OF REVIEW

This study aimed to summarize and discuss current data about the function of H₂S in vascular physiology and pathophysiology as well as the underlying mechanisms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Endogenous hydrogen sulfide (H₂S) as a third gasotransmitter is primarily generated by the enzymatic pathways and regulated by several metabolic pathways. H₂S as a physiologic vascular regulator, inhibits proliferation, regulates its apoptosis and autophagy of vascular cells and controls the vascular tone. Accumulating evidence shows that the downregulation of H₂S pathway is involved in the pathogenesis of a variety of vascular diseases, such as hypertension, atherosclerosis and pulmonary hypertension. Alternatively, H₂S supplementation may greatly help to prevent the progression of the vascular diseases by regulating vascular tone, inhibiting vascular inflammation, protecting against oxidative stress and proliferation, and modulating vascular cell apoptosis, which has been verified in animal and cell experiments and even in the clinical investigation. Besides, H₂S system and angiotensin-converting enzyme (ACE) inhibitors play a vital role in alleviating ischemic heart disease and left ventricular dysfunction. Notably, sulfhydryl-containing ACEI inhibitor zofenopril is superior to other ACE inhibitors due to its capability of H₂S releasing, in addition to ACE inhibition. The design and application of novel H₂S donors have significant clinical implications in the treatment of vascular-related diseases. However, further research regarding the role of H₂S in vascular physiology and pathophysiology is required.

Plasma irisin level associated with hemodynamic parameters and predict clinical outcome in patients with acute pulmonary embolism

BACKGROUND

The purpose of the present study is to investigate the correlation of plasma irisin level and hemodynamic parameters in patients with acute pulmonary embolism (APE) and to estimate clinical outcome prediction value of plasma irisin level.

METHODS

We prospectively recruited 86 adult patients with APE in the present study. All recruited patients conduct measurement of plasma irisin levels using ELISA kits. Baseline clinical characteristics, hemodynamic parameters and prognostic conditions were evaluated according to different plasma irisin levels.

RESULTS

According to median values of irisin levels, APE patients were divided into high irisin group (irisin≥6.9 μg/ml) and low irisin group (irisin<6.9 μg/ml). Plasma NT-proBNP (P = 0.044), mean pulmonary artery pressure (mPAP, P = 0.013), systolic pulmonary artery pressure (sPAP, P = 0.001), mean right ventricular pressure (mRVP, P = 0.021) and systolic right ventricular pressure (sPVP, P = 0.003) were higher in low irisin group compared with high irisin group. Hemodynamic parameters of mPAP, sPAP, mRVP and sRVP were negatively correlated with plasma irisin levels. Kaplan- Meier survival analysis showed that APE patients with lower plasma irisin levels had significantly higher clinical worsening event rate (P = 0.026) and could be the independent predictor of prognosis in multivariate analysis (P = 0.035).

CONCLUSION

Plasma irisin level was negatively correlated with hemodynamic parameters in patients with APE. Low irisin group patients had significantly higher clinical worsening event rate and could be the independent predictor of clinical outcome in multivariate analysis.

Treatment with new organic nitrites in pulmonary hypertension of acute experimental pulmonary embolism

Acute pulmonary embolism may cause right heart failure due to increased pulmonary vascular resistance and arterial hypoxemia. Effective vasodilator therapy of the pulmonary hypertension is highly needed. Therefore, we investigated the effects of a newly developed effective pulmonary vasodilator, the organic mononitrites of 1,2-propanediol (PDNO), in a rabbit model of acute pulmonary embolism. In anesthetized and ventilated rabbits, systemic and pulmonary hemodynamics, exhaled nitric oxide (NO), plasma nitrite concentration, and blood gases were monitored. First, dose-response experiments with intravenous and left heart ventricle infusions of PDNO and inorganic nitrite were done in naive animals and in pulmonary hypertension induced by a thromboxane A2 analogue. Second, acute pulmonary embolism was induced and either PDNO or placebo were administered intravenously within 20 minutes and evaluated within 1 hour after pulmonary embolization. PDNO intravenously, in contrast to inorganic nitrite intravenously, increased exhaled NO and counteracted pulmonary hypertension and vasodilated the systemic circulation, dose-dependently, thereby showing efficient NO donation. Pulmonary embolization induced pulmonary hypertension and gas exchange disturbances. PDNO significantly decreased and normalized pulmonary vascular resistance and the right ventricle rate-pressure product, without causing tolerance, with no significant side effects on the systemic circulation, nor on blood-gas values or on methemoglobin formation. In conclusion, PDNO is a NO donor and an efficient vasodilator in the pulmonary circulation. Treatment with this or similar organic nitrites intravenously may be a future option to avoid right heart failure in life-threatening acute pulmonary embolism.

Increasing complexity and interactions of oxidative stress in chronic respiratory diseases: An emerging need for novel drug delivery systems

Oxidative stress is intensely involved in enhancing the severity of various chronic respiratory diseases (CRDs) including asthma, chronic obstructive pulmonary disease (COPD), infections and lung cancer. Even though there are various existing anti-inflammatory therapies, which are not enough to control the inflammation caused due to various contributing factors such as anti-inflammatory genes and antioxidant enzymes. This leads to an urgent need of novel drug delivery systems to combat the oxidative stress. This review gives a brief insight into the biological factors involved in causing oxidative stress, one of the emerging hallmark feature in CRDs and particularly, highlighting recent trends in various novel drug delivery carriers including microparticles, microemulsions, microspheres, nanoparticles, liposomes, dendrimers, solid lipid nanocarriers etc which can help in combating the oxidative stress in CRDs and ultimately reducing the disease burden and improving the quality of life with CRDs patients. These carriers improve the pharmacokinetics and bioavailability to the target site. However, there is an urgent need for translational studies to validate the drug delivery carriers for clinical administration in the pulmonary clinic.

Effect of simvastatin on the SIRT2/NF-κB pathway in rats with acute pulmonary embolism

CONTEXT

Statins have been widely used in acute pulmonary embolism (APE), while simvastatin has been well-established for the prevention of pulmonary hypertension, which was supposed to be an attractive recommendation for APE treatment.

OBJECTIVE

The current article studies the effect of simvastatin on the SIRT2/NF-κB pathway in rats with APE.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into four groups (n = 24 per group): control group, rats were treated with saline once daily for 14 days before administration of saline (sham group) or a suspension of autologous emboli (APE group), or rats were treated with simvastatin (10 mg/kg) for 14 days before administration of autologous emboli (APE + simvastatin) group. The RVSP, mPAP and the arterial blood gas was analyzed. Besides, plasma inflammatory cytokines and MMPs levels, as well as the expression of SIRT2/NF-κB pathway were determined.

RESULTS

Compared with the control and sham groups, the levels of mPAP (31.06 ± 3.47 mmHg), RVSP (35.12 ± 6.02 mmHg), A-aDO₂ (33.14 ± 6.16 mmHg) and MMP-9 (6.89 ± 0.84 ng/mL) activity were significantly elevated, but PaO₂ (66.87 ± 7.85 mmHg) was highly decreased in rats from APE group at 24 h after APE. Meanwhile, the inflammatory changes were aggravated by the enhanced levels of TNF-α (138.85 ± 22.69 pg/mL), IL-1β (128.47 ± 22.14 pg/mL), IL-6 (103.16 ± 13.58 pg/mL) and IL-8 (179.28 ± 25.79 pg/mL), as well as increased NF-κB (5.29 ± 0.47 fold), but reduced SIRT2 (59 ± 6% reduction), and eNOS (61 ± 5% reduction) mRNA in APE rats. APE rats treated with simvastatin led to a significant opposite trend of the above indexes.

CONCLUSIONS

Simvastatin protects against APE-induced pulmonary artery pressure, hypoxemia and inflammatory changes probably due to the regulation of SIRT2/NF-κB signalling pathway, which suggest that simvastatin may have promising protective effects in patients with APE.

Novel microspheres reduce the formation of deep venous thrombosis and repair the vascular wall in a rat model

L-Arginine (L-arg), widely known as a substrate for endogenous nitric oxide synthesis, can improve endothelial function associated with the vasculature, inhibit platelet aggregation, and alter the activity of vascular smooth muscle cells. P-selectin is a membrane component of the platelet alpha-granule and the endothelial cell-specific Wiebel–Palade body that plays a central role in mediating interactions between platelets and both leukocytes and the endothelium. The experiment was designed to evaluate the effect of novel microspheres with L-arg targeting P-selectin on the formation of deep vein thrombosis and repair of vascular wall in a rat model. Thrombosis of the inferior vena cava was induced by applying a piece of filter paper (5 mm × 10 mm) saturated with 10% FeCl₃ solution for 5 min. Targeted microspheres with L-arg, targeted microspheres with water, and saline were injected into the tail veins of the rats after 30 min of applying the filter paper saturated with 10% FeCl₃ solution. The dry weight and length of the thrombus isolated from the inferior vena cava were significantly decreased in the group with L-arg in microsphere after 24 h. No significant differences in prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen among the groups were indicated. Images revealed that apoptosis in the vascular wall was less in the group injected with targeted microspheres with L-arg than in the other two groups at 1 and 8 d postsurgery. Meanwhile, cell proliferation was considerably excessive in the group injected with L-arg wrapped in targeted microspheres. Therefore, these novel microspheres could decrease the formation of thrombus in the early stages and in the subsequent periods of thrombosis. The microspheres can also enhance the vitality of impaired endothelial cells and reduce cell apoptosis.

Effects of grape seed extract supplementation on exercise-induced oxidative stress in rats

The aim of the present study was to investigate the effects of grape seed extract (GSE) supplementation on exercise performance and oxidative stress in acutely and chronically exercised rats. A total of sixty-four male rats were used in the study. Rats were divided into six groups: control, chronic exercise control, acute exercise control (AEC), GSE-supplemented control, GSE-supplemented chronic exercise and GSE-supplemented acute exercise groups. Chronic exercise consisted of treadmill running at 25 m/min, 45 min/d, 5 d a week for 6 weeks. Rats in the acute exercise groups were run on the treadmill at 30 m/min until exhaustion. GSE were given at 100 mg/kg of body weight with drinking water for 6 weeks. Plasma was separated from blood samples for the analysis of oxidative stress markers. There was no significant difference in time of exhaustion between the acute exercise groups. Plasma malondialdehyde (MDA) levels were higher in the acute exercise groups and lower in the chronic exercise groups. GSE supplementation decreased MDA levels. Xanthine oxidase and adenosine deaminase activities were higher in the AEC group compared to all the other groups. NO levels were increased with both chronic exercise and GSE supplementation. Superoxide dismutase and glutathione peroxidase activities were lower in the acute exercised groups and higher in the chronic exercised groups. GSE supplementation caused an increase in antioxidant enzyme activities. In conclusion, GSE supplementation prevents exercise-induced oxidative stress by preventing lipid peroxidation and increasing antioxidant enzyme activities.

Losartan exerts no protective effects against acute pulmonary embolism-induced hemodynamic changes

The acute obstruction of pulmonary vessels by venous thrombi is a critical condition named acute pulmonary embolism (APE). During massive APE, severe pulmonary hypertension may lead to death secondary to right heart failure and circulatory shock. APE-induced pulmonary hypertension is aggravated by active pulmonary vasoconstriction. While blocking the effects of some vasoconstrictors exerts beneficial effects, no previous study has examined whether angiotensin II receptor blockers protect against the hemodynamic changes associated with APE. We examined the effects exerted by losartan on APE-induced hemodynamic changes. Hemodynamic evaluations were performed in non-embolized lambs treated with saline (n = 4) and in lambs that were embolized with silicon microspheres and treated with losartan (30 mg/kg followed by 1 mg/kg/h, n = 5) or saline (n = 7) infusions. The plasma and lung angiotensin-converting enzyme (ACE) activity were assessed using a fluorometric method. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 21 ± 2 mmHg and 375 ± 20 dyn s cm⁻⁵ m⁻², respectively (P < 0.05). Losartan decreased MPAP significantly (by approximately 15%), without significant changes in PVRI and tended to decrease cardiac index (P > 0.05). Lung and plasma ACE activity were similar in both embolized and non-embolized animals. Our findings show evidence of lack of activation of the renin-angiotensin system during APE. The lack of significant effects of losartan on the pulmonary vascular resistance suggests that losartan does not protect against the hemodynamic changes found during APE.

Pulmonary hypertension in dogs: diagnosis and therapy

Pulmonary hypertension (PH) has been recognized as a clinical syndrome for many years in veterinary medicine, but routine accurate clinical diagnosis in dogs was greatly enhanced by widespread use of echocardiography and Doppler echocardiography. Most cases of PH in veterinary medicine can be categorized as precapillary or postcapillary. These subsets of patients often differ with regard to clinical presentation, response to therapy, and prognosis. Effective medical therapy is now available to treat this often-devastating clinical complication of common chronic diseases, making accurate diagnosis even more important to patient longevity and quality of life.

Hemodynamic effects of inducible nitric oxide synthase inhibition combined with sildenafil during acute pulmonary embolism

While endogenous nitric oxide (NO) may be relevant to the beneficial hemodynamic effects produced by sildenafil during acute pulmonary embolism (APE), huge amounts of inducible NO synthase (iNOS)-derived NO may contribute to lung injury. We hypothesized that iNOS inhibition with S-methylisothiourea could attenuate APE-induced increases in oxidative stress and pulmonary hypertension and, therefore, could improve the beneficial hemodynamic and antioxidant effects produced by sildenafil during APE. Hemodynamic evaluations were performed in non-embolized dogs treated with saline (n=4), S-methylisothiourea (0.01 mg/kg followed by 0.5 mg/kg/h, n=4), sildenafil (0.3 mg/kg, n=4), or S-methylisothiourea followed by sildenafil (n=4), and in dogs that received the same drugs and were embolized with silicon microspheres (n=8 for each group). Plasma nitrite/nitrate (NOx) and thiobarbituric acid reactive substances (TBARS) concentrations were determined by Griess and a fluorometric assay, respectively. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 25±1.7 mm Hg and by 941±34 dyn s cm(-5) m(-2), respectively. S-methylisothiourea neither attenuated APE-induced pulmonary hypertension, nor enhanced the beneficial hemodynamic effects produced by sildenafil after APE (>50% reduction in pulmonary vascular resistance). While sildenafil produced no change in plasma NOx concentrations, S-methylisothiourea alone or combined with sildenafil blunted APE-induced increases in NOx concentrations. Both drugs, either alone or combined, produced antioxidant effects. In conclusion, although iNOS-derived NO may play a key role in APE-induced oxidative stress, our results suggest that the iNOS inhibitor S-methylisothiourea neither attenuates APE-induced pulmonary hypertension, nor enhances the beneficial hemodynamic effects produced by sildenafil.

The immediate effect of nitric oxide on the rabbit bladder after ovariectomy

Ovariectomy resulted in decreased blood flow and hypoxia to the bladder mucosa and smooth muscle. Nitric oxide (NO) played an important role in regulating bladder function during bladder ischemia and reperfusion. This study was designed to evaluate the role of NO on bladder function in the first few days after ovariectomy. Female rabbits were separated into three groups, one which received no medication, premedicated with N(omega)-nitro-L-arginine methyl ester (L-NAME) and the third treated with L-arginine. Non-ovariectomized controls and at 1 and 3 days post-ovariectomy, animals from each group were euthanized. Cystometry and in vitro isometric contractile responses were recorded and the oxidative stress markers, nitrotyrosine and protein carbonylation were determined. L-NAME treatment did not significantly alter bladder function after ovariectomy. L-Arginine fed, ovariectomized rabbits had lower intravesical pressure and better contractile responses to all forms of stimulation than the ovariectomized rabbits with or without L-NAME. Furthermore, the ovariectomized ones with or without L-NAME had higher oxidative stress markers than L-arginine fed rabbits. This study clearly demonstrates that feeding rabbits with L-arginine can protect the bladder from oxidative free radical damage following short-term ovariectomy.

Changes in oxidative stress haemostatic parameters during the thrombolytic treatment of pulmonary embolism

A pulmonalis embolia a harmadik leggyakoribb cardiovascularis halálok. A masszív tüdőembólia thrombolysiskezelése kapcsán vérzéses szövődmény, reembólia léphet fel, a kórállapotot oxidatív stressz kíséri. Célok: Vizsgálatunkban az akut tüdőembólia rögoldó kezelése során elemeztük a thrombocytaaggregáció, a haemostaseologiai paraméterek, a leukocytaaktiváció és az oxidatív stressz markereinek változásait. Módszer: 15 beteget választottunk be, akik ultranagy dózisú sztreptokináz- ( n = 8) vagy altepláz- ( n = 7) kezelésben részesültek. Artériás vérmintát vettünk a thrombolysis előtt, azt követően pedig az első 24 órában 4 óránként, majd a 36. órában, és a 2., 3., 4., 5. és 30. napon. Mértük a spontán és az adrenalin, a kollagén és az adenozin-difoszfát indukálta thrombocytaaggregációt. A D-dimer- és fibrinogénszinteket az első napon 8 óránként, majd a fenti időpontokban egy alkalommal vizsgáltuk. Az oxidatív stressz és a leukocytaaktiváció elemzésére a thrombolysis előtt, a kezelést követően a 8. órában, majd az 1., 3., 5. és 30. napon vettünk vérmintákat. Az oxidatív stressz változásának nyomon követésére plazmából és teljes vérből malondialdehid, redukált glutation-, plazmaszulfhidrilcsoport-szinteket, szuperoxid-dizmutáz- és mieloperoxidázenzim-aktivitást mértünk. A teljes vér gyöktermelő kapacitását, vizsgálatát kemilumineszcenciával végeztük. Áramláscitometriával mértük a leukocyták által expresszált CD11a, CD18 és CD97 felszíni antigéneket. Eredmények: Az adrenalin indukálta thrombocytaaggregáció a 4. és a 8. órában csökkent ( p < 0,03), és szignifikánsan alacsony tartományban maradt a 36. órától a 3. napig az alteplázcsoporthoz képest. A sztreptokinázzal kezelteknél az adenozin-difoszfát indukálta aggregáció a 4. órában csökkent a kiindulási értékhez képest ( p < 0,05), kollagén esetében ugyanez a csökkenés a 4. és a 8. órában szignifikáns. A fibrinogénszintek a thrombolysist követően mindkét kezelési csoportban szignifikánsan csökkentek, míg a D-dimer a 8. órában szignifikánsan megemelkedett. Spontán thrombocytaaggregációt egyetlen mérési időpontban sem találtunk, jelentős vérzés, reembólia nem lépett fel. Az emelkedett malondialdehid-, reaktívoxigéngyök- és mieloperoxidáz-szintek, a csökkent redukált glutation- és plazmaszulfhidril-szintek a tüdőembóliás betegekben jelen lévő fokozott oxidatív stresszre utalnak. A thrombolysist követően a malondialdehid szignifikánsan emelkedik, a redukált glutation pedig csökken. A reaktív oxigéngyökök termelése a 3. és 5. nap között a legmagasabb. A thrombolysist kifejezett granulocyta és monocyta CD11a- és CD18-, valamint granulocyta CD97-expresszió-csökkenés kíséri ( p < 0,05). Következtetések: A masszív/szubmasszív pulmonalis embolia és az alkalmazott thrombolysis károsítja a thrombocytafunkciókat. A tüdőembólia reperfúziója során a fibrinogénszint csökkenése szignifikáns korrelációt mutat a tüdőperfúzió javulásával, ezek alapján a fibrinogénszint változása jól alkalmazható marker lehet a thrombolysis eredményességének akut felmérésére. Masszív/szubmasszív pulmonalis emboliás betegeknél a thrombolysis előtt fokozott oxidatív stressz állt fenn. Igazoltuk, hogy TL-t követően az oxidatív stressz és a leukocytaaktiváció még kifejezettebb, és e paraméterek csak a 30. napra normalizálódnak.

Dose-dependent beneficial hemodynamic effects of BAY 41-2272 in a canine model of acute pulmonary thromboembolism

The current therapy of acute pulmonary embolism is focused on removing the mechanical obstruction of the pulmonary vessels. However, accumulating evidence suggests that pulmonary vasoconstriction drives many of the hemodynamic changes found in this condition. We examined the effects of stimulation of soluble guanylate cyclase with BAY 41-2272 (5-Cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrim idin-4-ylamine) in an anesthetized dog model of acute pulmonary embolism. Hemodynamic and arterial blood gas evaluations were performed in non-embolized dogs treated with vehicle (N=5), and in embolized dogs (intravenous injections of microspheres) that received BAY 41-2272 intravenously in doses of 0.03, 0.1, 0.3, and 1 mg/kg/h or vehicle (1 ml/kg/h of 1.13% ethanol in saline, volume/volume). Plasma cGMP and thiobarbituric acid reactive substances concentrations were determined using a commercial enzyme immunoassay and a fluorometric method, respectively. The infusion of BAY 41-2272 resulted in a decrease in pulmonary artery pressure by approximately 29%, and in pulmonary vascular resistance by approximately 46% of the respective increases induced by lung embolization (both P<0.05). While the higher doses of BAY 41-2272 produced no additional effects on the pulmonary circulation, they caused significant arterial hypotension and reduction in systemic vascular resistance (both P<0.05). Although BAY 41-2272 increased cGMP concentrations (P<0.05), it did not affect the hypoxemia and the increased oxidative stress caused by lung embolization. These results suggest that stimulation of soluble guanylate cyclase with low (but not high) doses of BAY 41-2272 produces selective pulmonary vasodilation during acute pulmonary embolism. The dose-dependent systemic effects produced by BAY 41-2272, however, may limit its usefulness in larger doses.

Aminoguanidine produces beneficial haemodynamic effects in a canine model of acute pulmonary thromboembolism

AIM

Activating the nitric oxide (NO)-cyclic guanosine 3',5'-monophosphate (cGMP) pathway improves haemodynamics following acute pulmonary thromboembolism (APT). However, the role of NO synthase (NOS) isoforms in the responses to APT has not been determined. We examined the effects of selective and non-selective inducible NOS (iNOS) inhibition.

METHODS

Haemodynamic evaluations were performed in non-embolized dogs treated with saline (control group; n = 4), L-NAME (NAME group; n = 3), or aminoguanidine (AG group; n = 3), and in dogs that received the same drugs and were embolized with 5 mL kg(-1) of clots made with autologous blood (Emb group, n = 9; NAME + Emb group, n = 4 and AG + Emb group, n = 7). The lung concentrations of nitrite/nitrate (NOx) and cGMP were determined by chemiluminescence and ELISA respectively.

RESULTS

Acute pulmonary thromboembolism increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 21.4 +/- 1.7 mmHg and by 843 +/- 34 dyn s cm(-5) m(-2), respectively, in Emb group. MPAP and PVRI increased to higher levels in the NAME + Emb group 15 min after APT and all dogs in this group died 15-30 min after APT. Conversely, lower MPAP and PVRI levels were found in the AG + Emb group 2 h after APT compared with the Emb group (both P < 0.05). Higher NOx concentrations were found in the Emb group compared with the other groups (all P < 0.05). Higher cGMP concentrations were found in the Emb and AG + Emb groups compared with the other groups (all P < 0.05).

CONCLUSIONS

These results indicate that endogenous NO protects against APT-induced cardiovascular responses. Moreover, iNOS-derived NO possibly produces unfavourable effects, which are counteracted by aminoguanidine. However, non-NO-related mechanisms may also be involved.

Oxidative stress in patients with COPD and pulmonary hypertension

OBJECTIVE

Oxidative stress plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Oxidant/antioxidant imbalance has also been reported in various forms of pulmonary hypertension. The present study aimed to assess systemic oxidative stress, as reflected by serum malondialdehyde (MDA) concentrations and activities of antioxidant enzymes in erythrocytes [glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT)] in patients with and without pulmonary hypertension secondary to COPD.

PATIENTS AND METHODS

Seventy-five patients (58 male) with COPD (mean age 65.1 +/- 1.2 years; mean smoking history 35.6 +/- 3.8 pack-years) were studied. Twenty-one healthy non-smokers served as a control group. Pulmonary function was evaluated with body plethysmography; mean and systolic pulmonary artery pressures (Ppa) were assessed with Doppler echocardiography. Serum concentrations of MDA and activities of GPX, SOD and CAT in washed red blood cells were measured using spectrophotometry.

RESULTS

Pulmonary hypertension was present in 28 patients with COPD (systolic Ppa: 46.4 +/- 2.3 mmHg; mean Ppa: 26.0 +/- 1.9 mmHg) and absent in 47 (systolic Ppa: 22.9 +/- 0.8 mmHg; mean Ppa: 13.4 +/- 0.6 mmHg). Compared with the healthy control group, all the patients (with or without pulmonary hypertension) had higher serum MDA concentrations (1.5 +/- 0.1 versus 2.3 +/- 0.1 versus 2.3 +/- 0.1 nmol/mL, ANOVA, P < 0.001) and lower erythrocyte GPX activity (51.3 +/- 3.2 versus 42.2 +/- 2.0 versus 41.3 +/- 2.5 U/g Hb, P = 0.029), whereas SOD (1121.1 +/- 29.0 versus 1032.6 +/- 21.8 versus 1032.7 +/- 36.2 U/g Hb, P = 0.063) and CAT activities (4.9 +/- 0.2 versus 4.6 +/- 0.1 versus 4.7 +/- 0.2 U/g Hb; P= 0.454) were similar. No differences were observed in serum MDA concentrations or activities of GPX, SOD and CAT in erythrocytes between COPD patients with and without pulmonary hypertension.

CONCLUSION

The study demonstrates the presence of oxidative/antioxidative imbalance in the systemic circulation in patients with COPD: compared with healthy subjects, COPD patients had higher serum MDA concentrations and lower GPX activity in erythrocytes. The magnitudes of the increase in MDA and reduction in GPX activity were similar in COPD patients with pulmonary hypertension and in those with normal pulmonary artery pressures.

A role for matrix metalloproteinase-9 in the hemodynamic changes following acute pulmonary embolism

BACKGROUND

Matrix metalloproteinases (MMPs) modulate vascular contractility and may affect acute pulmonary embolism (APE)-induced pulmonary hypertension. We examined the effects of the administration of doxycycline (a MMP inhibitor) following APE in anesthetized dogs.

METHODS

Sham operated dogs (N=5) received only saline. APE was induced by intravenous injections of microspheres in amounts to increase mean pulmonary artery pressure (MPAP) by 20 mm Hg, and embolized dogs received saline (Emb group, N=8), or doxycycline (10 mg/kg, i.v.) 5 or 30 min of APE (Emb+Doxy 5 and Emb+Doxy 30 groups, N=9 and 8, respectively). Hemodynamic evaluation was performed at baseline and 5-120 after APE. Gelatin zymography of MMP-2 and MMP-9 from plasma samples was performed.

RESULTS

No significant hemodynamic changes were found in Sham animals. Embolization increased MPAP by 218+/-16% and the pulmonary vascular resistance index (PVRI) by 289+/-42% in Emb group (both P<0.05). Doxycyline increased the cardiac index by 24+/-5% and reduced PVRI by 23+/-4% 120 min of APE in Doxy 30+Emb group. In addition, doxycyline reduced MPAP and PVRI 30 min after APE with maximum effects seen 120 min after APE (25+/-4% decrease in MPAP and 33+/-6% decrease in PVRI; both P<0.05) in Doxy+5 group. Plasma pro-MMP-9 and MMP-9 levels increased only in Emb group and MMP-2 remained unaltered.

CONCLUSIONS

Our study shows that doxycycline attenuates APE-induced pulmonary hypertension, and indicates that MMP-9 has a role in APE-induced pulmonary hypertension. MMP-9 may be a pharmacological target in APE.

Evaluation of oxidative stress in the thrombolysis of pulmonary embolism

BACKGROUND

To analyse leukocyte function parameters and oxidative stress (OS) in patients with acute pulmonary embolism (PE) treated with thrombolytics.

METHODS

Fifteen patients undergoing thrombolysis (TL) with ultra-high dose streptokinase (n = 8), or alteplase (tPA) (n = 7) treatment were studied. Blood samples were collected prior to TL, and then 8 h, 1, 3, 5 and 30 days after treatment. Malondialdehyde (MDA), reduced glutathione (GSH), plasma protein sulfhydryl groups (PSH) levels, superoxide dismutase (SOD) and myeloperoxidase enzyme (MPO) activities were measured in plasma or whole blood for monitoring of the OS markers. Production of reactive oxygen species (ROS) in whole blood was measured by luminol dependent chemiluminescence. Flow cytometry was used to determine CD11a, CD18, and CD97 surface antigen expression on leukocytes.

RESULTS

The elevated MDA, ROS and MPO, decreased GSH and PSH levels indicated the presence of OS in patients with PE. MDA significantly (P < 0.05) increased, GSH significantly (P < 0.05) decreased following thrombolysis. ROS production peaked on the 3rd and 5th days. TL was accompanied by significant decrease in granulocyte and monocyte CD11a and CD18 as well as in granulocyte CD97 expression (P < 0.05).

CONCLUSION

PE led to OS that was augmented following TL. Decreased adhesion molecule expression of circulating leukocytes in the early phase of TL reflects the pathological leukocyte endothelial cell interactions.

Influence of L-arginine on the expression of eNOS and COX2 in experimental pulmonary thromboembolism

The influence of L-arginine on endothelial nitric oxide synthase (eNOS) and cyclooxygenase 2 (COX2) was observed in experimental pulmonary thromboembolism and the action mechanism on pulmonary thromboembolism was explored. Wistar rats were randomly divided into control group, model group and treatment group. Pulmonary thromboembolism models were established by auto-blood back transfusion, and L-Arg 100 mg/kg was intraperitoneally injected after successful model preparation. The animals were sacrificed at 3 h, 1 day, 3 days and 7 days after embolism. Plasma NO, TXB2 and 6-Keto-PGFla were detected. The expression of eNOS and COX2 protein and mRNA in pulmonary tissues was detected by immunohistochemistry and RT-PCR respectively. The results showed that pulmonary thrombosis could be seen post pulmonary embolism and inflammatory reaction was significant. Plasma NO was decreased (P<0.01), and the levels of TXB2, 6-Keto-PGF1alpha and T/P ratio were all elevated. The expression of eNOS protein and mRNA in the pulmonary tissue was down-regulated (P<0.05), while that of COX2 protein and mRNA was upregulated (P<0.01). In treatment group, the level of NO was increased, the levels of TXB2 and T/P ratio were decreased, but the level of 6-Keto-PGF1alpha was increased. The expression of eNOS protein and mRNA in pulmonary tissue was upregulated (P<0.05), while that of COX2 protein and mRNA was down-regulated (P<0.05). In conclusion, L-arginine can educe the role of pulmonary tissue protection through up-regulating the expression of intra-pulmonary NOS and down -regulating COX2 in pulmonary thromboembolism.

eNOS gene T-786C polymorphism modulates atorvastatin-induced increase in blood nitrite

Statins inhibit cholesterol synthesis and produce pleiotropic, cholesterol-independent effects including endothelial NO synthase (eNOS) stimulation and increased expression. However, a functional polymorphism in the promoter of the eNOS gene (T-786C) reduces its activity and could modulate the response to statins. Here, we examined whether this polymorphism modulates the effects of atorvastatin on the plasma levels of markers of NO formation and oxidative stress. We genotyped 200 healthy subjects for this polymorphism, and 15 subjects with the TT genotype and 15 with the CC genotype were selected to receive placebo or atorvastatin 10 mg/day po for 14 days. To assess NO bioavailability, the plasma concentrations of nitrate, nitrite, and cGMP and the whole blood nitrite concentrations were determined after placebo or atorvastatin using an ozone-based chemiluminescence assay and an enzyme immunoassay. Thiobarbituric acid-reactive species (TBA-RS) were measured in the plasma to assess oxidative stress. Atorvastatin decreased cholesterol concentrations independent of genotype. Whereas atorvastatin produced no significant changes in plasma nitrite, nitrate, or cGMP concentrations in both genotype groups, atorvastatin increased whole blood nitrite concentrations and decreased plasma TBA-RS concentrations in the CC (but not in the TT) genotype group. These findings suggest that the T-786C polymorphism modulates the effects of atorvastatin on NO bioavailability and oxidative stress.

Lercanidipine reduces matrix metalloproteinase-9 activity in patients with hypertension

Increased levels of metalloproteinase (MMP)-9 have been shown in hypertensive patients. Lercanidipine is a calcium channel blocker with antioxidant actions. We examined whether lercanidipine produces antioxidant effects and reduces MMP-9 activity in hypertensive patients in a placebo-controlled, crossover, single-blinded design study including 18 healthy volunteers (control group), and 14 hypertensive patients without (N = 7) or with (N = 7) diabetes mellitus. Hypertensive patients were randomized to treatment with placebo (15 days) or lercanidipine 20 mg/d (15 days). Arterial blood pressure was evaluated with ambulatory blood pressure monitoring. Plasma thiobarbituric acid reactive species (TBA-RS) levels were measured to assess oxidative stress, and plasma MMP-2 and MMP-9 were assayed by gel zymography before and after treatment with placebo or lercanidipine. Plasma concentrations of tissue inhibitor of metalloproteinases (TIMP)-1 were measured by ELISA. Lercanidipine reduced mean arterial pressure by 7% in hypertensive patients without diabetes (P < 0.05), but not in hypertensive patients with diabetes. It significantly decreased plasma TBA-RS levels in hypertensive patients without and with diabetes (95% confidence interval [CI], -26 to -46%, P = 0.048, and -22 to -33%, P = 0.036, respectively). In addition, lercanidipine decreased activated MMP-9 in hypertensive patients without and with diabetes (95% CI, -19 to -47%, P = 0.047, and -80 to -96%, P = 0.010, respectively). No effects were seen on MMP-2. No significant differences or changes in plasma TIMP-1 concentrations were found. Therefore, we demonstrate for the first time that lercanidipine consistently decreased MMP-9 activity and reduced oxidative stress in hypertensive patients, thus suggesting a mechanism probably involved in the pleotropic actions of lercanidipine.

Hemodynamic effects of sildenafil interaction with a nitric oxide donor compound in a dog model of acute pulmonary embolism

Sildenafil attenuates acute pulmonary embolism (APE)-induced pulmonary hypertension. However, the hemodynamic effects of sildenafil in combination with other vasodilators during APE have not been examined yet. In the present study, we examined the hemodynamic effects of combined diethylenetriamine/nonoate (DETA-NO, 1microMol kg(-1), i.v.) and sildenafil (0.25mg/kg, i.v.) in an anesthetized dog model of APE. Plasma nitrite/nitrate (NO(x)) and cyclic GMP concentrations were determined using an ozone-based chemiluminescence assay and a commercial enzyme immunoassay, respectively. We found that this dose of DETA-NO did not attenuate APE-induced pulmonary hypertension. However, significant decreases in mean pulmonary artery pressure were observed 15, 30 and 45min after the administration of sildenafil alone or after the combined administration of DETA-NO and sildenafil (all P<0.05). No significant differences among groups were observed in the respiratory parameters. While DETA-NO significantly increased NO(x) concentrations by approximately 4microM, cyclic GMP concentrations increased only when sildenafil was administered (all P<0.05). These results show that the combined administration of 1microMol kg(-1) of DETA-NO and sildenafil is not advantageous compared with sildenafil alone, thus suggesting that sildenafil alone produced maximum attenuation of APE-induced pulmonary hypertension, as far as the NO-cGMP pathway is concerned.

L-arginine attenuates acute pulmonary embolism-induced increases in lung matrix metalloproteinase-2 and matrix metalloproteinase-9

STUDY OBJECTIVES

To evaluate the effects of L-arginine on acute pulmonary embolism (APE)-induced pulmonary hypertension and increases in lung matrix metalloproteinase (MMP)-2 and MMP-9 activities.

DESIGN

Prospective trial.

SETTING

University laboratory.

INTERVENTIONS

Using an isolated lung perfusion rat model of APE, we examined whether L-arginine (0, 0.5, 3, and 10 mmol/L; five to seven rats per group) attenuates the pulmonary hypertension induced by the injection of 6.6 mg/kg of 300 microm microspheres into the pulmonary artery. In a second series of experiments (6 to 11 rats per group), we investigated whether nonselective inhibition of nitric oxide (NO) synthases with N(G)-nitro-L-arginine methyl ester (L-NAME; 4 mmol/L) decreases the effects produced by L-arginine. Lung MMP-2 and MMP-9 activities were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gelatin zymography.

RESULTS

L-arginine at 0.5, 3, and 10 mmol/L attenuated APE-induced pulmonary hypertension by 25 to 42% (all p < 0.05). The protective effect of L-arginine was completely reversed by inhibition of NO synthesis with L-NAME. APE was associated with increased lung MMP-2 and MMP-9 activities (both p < 0.05). While L-arginine at 0.5 mmol/L produced no effect on MMPs, L-arginine 3 at mmol/L and 10 mmol/L attenuated the increases in MMP-2 and MMP-9 activities after APE (both p < 0.05).

CONCLUSIONS

L-arginine attenuates APE-induced pulmonary hypertension through mechanisms involving increased NO synthesis and maybe attenuation of lung MMP-2 and MMP-9 activities.

eNOS genotype-dependent correlation between whole blood lead and plasma nitric oxide products concentrations

Experimental data indicate that lead exposure decreases nitric oxide (NO) availability. However, no previous study has examined whether lead exposure affects plasma nitrite/nitrate (NO(x)) concentrations in humans. In addition, the T(-786)C polymorphism affects endothelial NO synthase (eNOS) expression and endogenous NO release. Here, we investigated whether there is an association between the circulating concentrations of NO(x) and the concentrations of lead in whole blood (B-Pb) and in plasma (P-Pb) from lead-exposed subjects. In addition, we also evaluated whether eNOS genotype for the T(-786)C polymorphism affects NO(x) concentrations in lead-exposed subjects. We studied 104 subjects exposed to lead who were non-smokers, 18-60 years of age, and not alcohol consumers. Genomic DNA was isolated from blood samples and genotypes for the T(-786)C polymorphism were determined by PCR and restriction fragment length digestion. Circulating NO(x) was determined by chemiluminescence. B-Pb and P-Pb were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. No significant correlations were found between NO(x) and B-Pb and P-Pb measured in the 104 subjects (all P > 0.05). However, while no significant correlation was found in subjects with TT genotype, a negative correlation was found between plasma NO(x) and B-Pb (r = 0.230, P = 0.048) and P-Pb (r = 0.194, P = 0.110) in subjects from TC + CC genotypes group. Our study shows a negative correlation between plasma NO(x) concentrations and B-Pb in carriers of the "C" allele, thus suggesting a possible mechanism possibly involved in lead exposure-induced increase in the susceptibility to cardiovascular diseases.

Hemodynamic effects of combined sildenafil and L-arginine during acute pulmonary embolism-induced pulmonary hypertension

Sildenafil attenuates acute pulmonary embolism-induced pulmonary hypertension. However, the hemodynamic effects of sildenafil in combination with other vasodilators during acute pulmonary embolism have not been examined yet. In the present study, we examined the hemodynamic effects of combined sildenafil (0.25 mg/kg, i.v.) and L-arginine (100, 200, 500, and 1000 mg/kg/h, i.v.) in an anesthetized dog model of acute pulmonary embolism. Plasma nitrite/nitrate (NO(x)) and cGMP concentrations were determined using an ozone-based chemiluminescence assay and a commercial enzyme immunoassay, respectively. We found that L-arginine alone did not attenuate acute pulmonary embolism-induced pulmonary hypertension. However, significant decreases in mean pulmonary artery pressure were observed 30, 45, 60, and 75 min after the administration of sildenafil alone or after the combined administration of sildenafil and L-arginine (all P < 0.05). No significant differences among groups were observed in the respiratory parameters. While L-arginine significantly increased NO(x) concentrations, cGMP concentrations increased only when sildenafil was administered (all P < 0.05). These results suggest that while sildenafil attenuates acute pulmonary embolism-induced pulmonary hypertension, L-arginine does not enhance the beneficial hemodynamic effects of sildenafil. In addition, these findings suggest that stimulation of NO synthesis with L-arginine during acute pulmonary embolism does not produce beneficial effects.

L-Arginine-NO-cGMP signaling following acute liver injury in the rat

The incidence of liver diseases has increased over the past few years. For this reason, the consequences of induced nitric oxide (NO) synthesis in liver damages warrant further studies. To address this issue, we investigated the expression of key enzymes engaged in the control of NO signaling in the rat liver after carbon tetrachloride (CCl4) intoxication and subsequent regeneration. CCl4 intoxication resulted in up-regulation of the entire NO signal transduction machinery. Expression patterns of arginase, soluble guanylyl cyclase and cyclic nucleotide phosphodiesterase revealed striking parallels with that of NO synthase (NOS). Co-expression of the major components of the l-arginine-NO-cGMP signaling cascade both in hepatocytes and in nonparenchymal cells indicates an autocrine rather than a paracrine fashion of NO signaling in the liver. Up-regulation of NOS after CCl4 intoxication fell behind the oxidative stress and was found to be associated with the initiation of parenchymal regeneration implying a beneficial effect of NO.

Protective effects of L-arginine on pulmonary oxidative stress and antioxidant defenses during exhaustive exercise in rats

AIM

To assess the effects of L-arginine (L-Arg) supplementation on pulmonary oxidative stress and antioxidant defenses in rats after exhaustive exercise.

METHODS

Rats were randomly divided into four groups: sedentary control (SC), sedentary control with L-Arg treatment (SC+Arg), exhaustive exercise with control diet (E) and exhaustive exercise with L-Arg treatment (E+Arg). Rats in groups SC+Arg and E+Arg received a 2% L-Arg diet. Rats in groups E and E+Arg underwent an exhaustive running test on a motorized treadmill. Pulmonary oxidative stress indices [xanthine oxidase (XO), myeloperoxidase (MPO), and malondialdehyde (MDA)] and antioxidant defense systems [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione (GSH)] were investigated in this study.

RESULTS

L-Arg supplementation significantly reduced exercise-induced elevations of XO and MPO activities in lung. L-Arg reversed the exercise-induced increase in SOD and GR activities, but increased CAT and GPX activities. L-Arg administration also significantly increased the GSH levels in plasma.

CONCLUSION

L-Arg supplementation can prevent elevations of XO and MPO activities in the lung and favorably influence pulmonary antioxidant defense systems after exhaustive exercise.