Jana Kopincova

Endothelial dysfunction in spontaneously hypertensive rats: focus on methodological aspects

Despite the apparent consensus on the existence of endothelial dysfunction in conduit and resistance arteries of spontaneously hypertensive rats (SHR), a commonly employed experimental model of hypertension, there are a number of reports showing that endothelium-dependent vasodilatory responses are similar, or even increased, in SHR compared with their normotensive counterparts. The present paper aims to discuss the rationale for these apparent discrepancies, including the effect of age, type of artery and methodological aspects. Data from the literature indicate that the age of the animal is a contributing factor and that endothelial dysfunction is likely to be a consequence of hypertension. In addition, the use of antioxidant additives, such as ascorbic acid or ethylene diaminetetraacetic acid, and differences in the level of initial arterial stretch, might also be of importance because they may modify the oxidative status of the artery and the levels of vasoactive factors released by the endothelium.

L-NAME in the cardiovascular system – nitric oxide synthase activator?

L-arginine analogues are widely used inhibitors of nitric oxide synthase (NOS) activity both in vitro and in vivo, with N(ω)-nitro-L-arginine methyl ester (L-NAME) being at the head. On the one hand, acute and chronic L-NAME treatment leads to changes in blood pressure and vascular reactivity due to decreased nitric oxide (NO) bioavailability. However, lower doses of L-NAME may also activate NO production via feedback regulatory mechanisms if administered for longer time. Such L-NAME-induced activation has been observed in both NOS expression and activity and revealed considerable differences in regulatory mechanisms of NO production between particular tissues depending on the amount of L-NAME. Moreover, feedback activation of NO production by L-NAME seems to be regulated diversely under conditions of hypertension. This review summarizes the mechanisms of NOS regulation in order to better understand the apparent discrepancies found in the current literature.

Biochemical aspects of nitric oxide synthase feedback regulation by nitric oxide

Biochemical aspects of nitric oxide synthase feedback regulation by nitric oxide Nitric oxide (NO) is a small gas molecule derived from at least three isoforms of the enzyme termed nitric oxide synthase (NOS). More than 15 years ago, the question of feedback regulation of NOS activity and expression by its own product was raised. Since then, a number of trials have verified the existence of negative feedback loop both in vitro and in vivo. NO, whether released from exogenous donors or applied in authentic NO solution, is able to inhibit NOS activity and also intervenes in NOS expression processes by its effect on transcriptional nuclear factor NF-κB. The existence of negative feedback regulation of NOS may provide a powerful tool for experimental and clinical use, especially in inflammation, when massive NOS expression may be detrimental.

Meconium-induced inflammation and surfactant inactivation: specifics of molecular mechanisms.

This review summarizes neonatal meconium aspiration syndrome in light of meconium-induced inflammation and inflammatory surfactant inactivation, related to both endogenous and therapeutic exogenous surfactant. The wide effect of meconium on surfactant properties is divided into three points. Direct effect of meconium on surfactant properties refers mainly to fragmentation of dipalmitoylphosphatidylcholine and other surfactant phospholipids together with cleavage of surfactant proteins. Initiation of inflammatory response due to activation of receptors by yet unspecified compounds involves complement and Toll-like receptor activation. A possible role of lung collectins, surfactant proteins A and D, which can exert both pro- and anti-inflammatory reactions, is discussed. Initiation of inflammatory response by specified compounds in meconium reflects inflammatory functioning of cytokines, bile acids, and phospholipases contained in meconium. Unifying sketch of many interconnections in all these actions aims at providing integrated picture of inflammatory surfactant inactivation.

Comorbidity has no impact on eosinophil inflammation in the upper airways or on severity of the sinonasal disease in patients with nasal polyps

The study was designed to determine whether there is an association between the comorbidity as atopy, bronchial asthma, aspirin intolerance and eosinophil infiltration of the upper airways, severity of the sinonasal disease and rate of revision sinus surgery in patients with nasal polyps.

Anti-inflammatory Treatment in Dysfunction of Pulmonary Surfactant in Meconium-Induced Acute Lung Injury

Inflammation, oxidation, lung edema, and other factors participate in surfactant dysfunction in meconium aspiration syndrome (MAS). Therefore, we hypothesized that anti-inflammatory treatment may reverse surfactant dysfunction in the MAS model. Oxygen-ventilated rabbits were given meconium intratracheally (25 mg/ml, 4 ml/kg; Mec) or saline (Sal). Thirty minutes later, meconium-instilled animals were treated by glucocorticoids budesonide (0.25 mg/kg, i.t.) and dexamethasone (0.5 mg/kg, i.v.), or phosphodiesterase inhibitors aminophylline (2 mg/kg, i.v.) and olprinone (0.2 mg/kg, i.v.), or the antioxidant N-acetylcysteine (10 mg/kg, i.v.). Healthy, non-ventilated animals served as controls (Con). At the end of experiments, left lung was lavaged and a differential leukocyte count in sediment was estimated. The supernatant of lavage fluid was adjusted to a concentration of 0.5 mg phospholipids/ml. Surfactant quality was evaluated by capillary surfactometer and expressed by initial pressure and the time of capillary patency. The right lung was used to determine lung edema by wet/dry (W/D) weight ratio. Total antioxidant status (TAS) in blood plasma was evaluated. W/D ratio increased and capillary patency time shortened significantly, whereas the initial pressure increased and TAS decreased insignificantly in Sal vs. Con groups. Meconium instillation potentiated edema formation and neutrophil influx into the lungs, reduced capillary patency and TAS, and decreased the surfactant quality compared with both Sal and Con groups (p > 0.05). Each of the anti-inflammatory agents reduced lung edema and neutrophil influx into the lung and partly reversed surfactant dysfunction in the MAS model, with a superior effect observed after glucocorticoids and the antioxidant N-acetylcysteine.

Surfactant proteins A and D are related to severity of the disease, pathogenic bacteria and comorbidity in patients with chronic rhinosinusitis with and without nasal polyps.

Surfactant proteins (SP) A and D play a critical role in the innate defence of respiratory mucosa. Although numerous studies have focused on the importance of surfactant in the lower airways, relatively little is known about its role in the upper respiratory system.

Modified porcine surfactant enriched by recombinant human superoxide dismutase for experimental meconium aspiration syndrome

Aims: Combination of exogenous surfactant with antioxidant enzyme recombinant human superoxide dismutase (rhSOD) was tested in the treatment of experimental meconium aspiration syndrome as oxidative processes play key role in its pathogenesis. Material and methods: Young New Zealand rabbits were instilled by saline (Sal group) or by meconium suspension (Mec group). Some of meconium‐instilled animals were treated by surfactant alone (Surf group) or surfactant in combination with rhSOD (Surf + SOD group) and oxygen‐ventilated for 5 h. PaO2/FiO2, oxygenation index, oxygen saturation, PaCO2, ventilation efficiency index and alveolar‐arterial gradient were evaluated every hour; post mortem, cells in bronchoalveolar lavage were counted, inflammatory and oxidative markers were assessed using ELISA in lung tissue homogenates. Key findings: Exogenous surfactant combined with rhSOD improved oxygenation during the first hour after the treatment more than surfactant alone (p = 0.039 to 0.0001 vs. Mec and Surf group). Amelioration was also seen in CO2 elimination (p = 0.049 to 0.0096 vs. Mec group), alveolar‐arterial gradient diminution (p = 0.024 to 0.0019 vs. Mec and Surf group), prevention of oxidative damage and cytokine production (p = 0.049 to 0.002 vs. Mec group). Significance: It seems that inhibition of oxidative signalization may be strong supporting factor in surfactant treatment of MAS.

Anti-IL-8 antibody potentiates the effect of exogenous surfactant in respiratory failure caused by meconium aspiration

ABSTRACT Aim: Meconium aspiration syndrome (MAS) is life-threatening respiratory failure of newborns which can be treated by exogenous surfactant. In response to meconium, increased levels of chemokine IL-8 (CXCL8) stimulate massive neutrophil infiltration of the lungs. Local accumulation and activation of neutrophils, on-going inflammation, lung edema, and oxidative damage contribute to inactivation of endogenous and therapeutically given surfactants. Therefore, we have hypothesized that addition of monoclonal anti-IL-8 antibody into exogenous surfactant can mitigate the neutrophil-induced local injury and the secondary surfactant inactivation and may finally result in improvement of respiratory functions. Methods: New Zealand rabbits with intratracheal meconium-induced respiratory failure (meconium 25 mg/ml, 4 ml/kg) were divided into three groups: untreated (M), surfactant-treated (M + S), and treated with combination of surfactant and anti-IL-8 antibody (M + S + anti-IL-8). Surfactant therapy consisted of two lung lavages with diluted porcine surfactant Curosurf (10 ml/kg, 5 mg phospholipids (PL)/ml) followed by undiluted Curosurf (100 mg PL/kg) delivered by means of asymmetric high-frequency jet ventilation (f. 300/min, Ti 20%). In M + S + anti-IL-8 group, anti-IL-8 antibody (100 µg/kg) was added directly to Curosurf dose. Animals were oxygen-ventilated for additional 5 h, respiratory parameters were measured regularly. Subsequently, cell counts in bronchoalveolar lavage fluid (BAL), lung edema formation, oxidative damage, levels of interleukins (IL)-1β and IL-6 in the lung homogenate were evaluated. Results: Surfactant instillation significantly improved lung function. Addition of anti-IL-8 to surfactant further improved gas exchange and ventilation efficiency and had longer-lasting effect than surfactant-only therapy. Combined treatment showed the trend to reduce neutrophil count in BAL fluid, local oxidative damage, and levels of IL-1β and IL-6 more effectively than surfactant-alone, however, these differences were not significant. Conclusion: Addition of anti-IL-8 antibody to surfactant could potentiate the efficacy of Curosurf on the gas exchange in experimental model of MAS.

INCREASED NITRIC OXIDE-DEPENDENT COMPONENT OF VASORELAXATION IN NORMOTENSIVE RATS AFTER CHRONIC STRESS: PP.6.233

Objective: Previously we showed increased endothelium-dependent vasorelaxation in stressed Wistar-Kyoto (WKY) rats (1) when ascorbic acid (AsA) was present in working physiological salt solution (PSS). The aim of study was to examine endothelium-dependent vasodilatation in the femoral artery (FA) of WKY rats exposed to chronic social stress produced by crowding in absence of AsA in PSS. Design and Method: Adult, male rats were divided into control (480 cm2/rat) or stressed (200 cm2/rat) group for 8 weeks. Blood pressure (BP) and heart rate (HR) were determined using tail-cuff plethysmography. Nitric oxide synthase (NOS) activity was determined by conversion of [3H]-L-arginine. Conjugated dienes (CD) and thiobarbituric acid-reactive substances (TBARS) concentrations were measured in the left ventricle and liver. NO-dependent component of acetylcholine (ACh)-induced, endothelium-dependent relaxation was investigated in the FA pre-constricted with serotonin using the wire myograph as a difference between ACh-induced relaxation before and after acute NOS inhibitor NG-Nitro-L-arginine methyl ester (300 umol/l) pre-treatment. Results: BP and HR were not influenced by chronic stress. NOS activity in the aorta was significantly increased in stressed rats by 80% (p < 0.01) vs. control. ACh-induced relaxation of the FA of stressed rats exceeded that of the controls, which was associated with significant increase of NO-dependent component of relaxation. Similar extent of vasorelaxation was observed when expressed as absolute tension, which indicates an enhancement of NO release after chronic stress. Stress failed to alter sodium nitroprusside-induced relaxation. Additionally, CD and TBARS concentrations were similar in stressed and control rats in both tissues investigated. Conclusions: Data showed better NO bioavailability in the FA of stressed rats resulting in improved vasorelaxation in spite of the absence of AsA in PS S. Thus, the results proved that elevation of NO production during stress exposure is an important way of adaptation preventing normotensive rats from the development of the stress-induced hypertension.