Possible role of increased oxidative stress in pulmonary hypertension in experimental diaphragmatic hernia.

PURPOSE: Congenital diaphragmatic hernia (CDH) is one of the causes of respiratory failure in newborns due to lung hypoplasia and pulmonary abnormalities leading to pulmonary hypertension (PH). NAD(P)H oxidase (Nox) is a family of isoenzymes that generate reactive oxygen species (ROS) which can contribute to PH-induced vascular dysfunction. On the other hand, superoxide dismutase (SOD) 1-2 and catalase are the antioxidant enzymes that eliminate the excess of ROS in pulmonary vascular cells. Our aim is to examine whether PH-associated with CDH is due to a dysregulation of ROS production in lungs from CDH fetuses. METHODS: Pregnant rats received either 100 mg nitrofen or vehicle on E9.5. Fetuses were recovered on E21. (1) Nox activity, (2) H2O2 production and (3) mRNA levels of Nox1, Nox2, Nox4, SOD1, SOD2 and catalase were analyzed in fetal lungs. RESULTS: Nox activity and Nox1 and Nox2 mRNA levels were increased in the lungs of fetuses with CDH. However, there were no changes in H2O2 production and Nox4 mRNA levels. SOD1, SOD2 and catalase were decreased. CONCLUSIONS: The raised oxidative stress due to increase in ROS generation by Nox isoenzymes and dysfunction of antioxidant enzymes seems to be a potential mechanism responsible on PH-associated with CDH.

Abnormal development of lung innervation in experimental esophageal atresia.

BACKGROUND/AIM: Patients with esophageal atresia and tracheo-esophageal fistula (EA-TEF) have chronic respiratory tract disease and deficient tracheal innervation. This study tests the hypothesis in rats with EA-TEF that deficient lung innervation could be one of the causes of respiratory disease. MATERIAL AND METHODS: Pregnant rats were treated with either 2 mg/kg i.p. adriamycin or vehicle on E7, E8 and E9. Lungs and tracheas were retrieved on E15, E18 and E21 (term: E22). Innervation was examined by regular (PGP 9.5 and GDNF) and whole-mount (PGP 9.5 and α-actin) immunohistochemistry. PGP 9.5 and GDNF mRNA were measured by real-time, quantitative RT-PCR and the levels of PGP 9.5 protein by immunoblot. Embryonic lung primordia harvested on E13 were cultured for 72 h and airway peristalsis was assessed under an inverted microscope. PGP 9.5 expression was then examined in explants by whole-mount immunohistochemistry and RT-PCR. Values were compared with non-parametric tests. RESULTS: Neural networks were present in both EA-TEF and control fetuses on E15, E18 and E21, but the neural network was obviously disorganized in whole-mount immunohistochemistry of EA-TEF. The pan-neural marker PGP 9.5 protein was increased at term whereas the neural chemo-attractant GDNF protein was unchanged. PGP 9.5 mRNA significantly increased from subnormal levels on E15 to very increased ones on E18 compared with controls. GDNF mRNA levels followed the same trend. Airway peristalsis of explanted embryonal lungs was similar in both groups. The neural networks were underdeveloped in these primordia, as assessed by whole-mount PGP 9.5 immunohistochemistry and RT-PCR. CONCLUSIONS: The development of respiratory tract innervation in adriamycin-induced EA-TEF was delayed and abnormally controlled in rats compared with controls. However, these deficiencies were apparently compensated for at term and had no effect on airway peristalsis. The possible significance of innervation anomalies for respiratory sequelae in EA-TEF patients deserves further investigation.

The myenteric plexus of the esophagus is abnormal in an experimental congenital diaphragmatic hernia model.

BACKGROUND/AIM: Infants surviving congenital diaphragmatic hernia (CDH) suffer from anatomical and functional esophageal abnormalities. Previous work in the nitrofen animal model of CDH demonstrated malformations in neural crest-derived structures, including the vagus and recurrent laryngeal nerves. The aim of the present study was to assess whether the esophageal myenteric plexus is abnormal in rats with CDH. METHODS: We used the nitrofen-induced CDH fetal rat model. Two sections of the proximal, medium and distal esophagus from both groups were processed for immunohistochemical staining with anti-neuron specific enolase and anti-S-100 antibodies; the number of stained areas was recorded for each group. Whole-mount preparations of the entire esophagus of Control and CDH animals were histochemically stained for acetylcholinesterase; the density and area of the ganglia and the number of cells/ganglia were determined. Comparisons between groups were made by standard statistical methods. RESULTS: The number of immunohistochemically stained areas in transversal sections were decreased in CDH animals for anti-enolase (11.5+/-6.06 vs. 1.93+/-1.49, control vs. CDH, p<0.001) and anti S-100 antibodies (8.57+/-4.1 vs. 4.06+/-2.82, p<0.001). In whole-mount preparations the number of ganglia per high power field (35.16+/-6.57 vs. 29.29+/-10.26, p<0.05), the number of cells per ganglia (11.85+/-3.52 vs. 2.28+/-4.61, p<0.0001) and the relative area of the ganglia (0.35+/-0.32 vs. 0.18+/-0.42%, p<0.001), were also significantly decreased in CDH animals compared with Controls. CONCLUSIONS: Esophageal intrinsic innervation is defective in rat fetuses with CDH. If patients with CDH bear the same anomalies, this may explain some of their esophageal motility disorders. Finally, these findings support the concept of neural crest involvement in the pathogenic pathways of CDH.

Chronic ouabain treatment increases the contribution of nitric oxide to endothelium-dependent relaxation.

The aim of this study was to analyze the contribution of nitric oxide, prostacyclin and endothelium-dependent hyperpolarizing factor to endothelium-dependent vasodilation induced by acetylcholine in rat aorta from control and ouabain-induced hypertensive rats. Preincubation with the nitric oxide synthase inhibitor N-omega-nitro-L-arginine methyl esther (L-NAME) inhibited the vasodilator response to acetylcholine in segments from both groups but to a greater extent in segments from ouabain-treated rats. Basal and acetylcholine-induced nitric oxide release were higher in segments from ouabain-treated rats. Preincubation with the prostacyclin synthesis inhibitor tranylcypromine or with the cyclooxygenase inhibitor indomethacin inhibited the vasodilator response to acetylcholine in aortic segments from both groups. The Ca2+-dependent potassium channel blocker charybdotoxin inhibited the vasodilator response to acetylcholine only in segments from control rats. These results indicate that hypertension induced by chronic ouabain treatment is accompanied by increased endothelial nitric oxide participation and impaired endothelium-dependent hyperpolarizing factor contribution in acetylcholine-induced relaxation. These effects might explain the lack of effect of ouabain treatment on acetylcholine responses in rat aorta.

Chronic ouabain treatment increases the contribution of nitric oxide to endotheliumdependent relaxation

The aim of this study was to analyze the contribution of nitric oxide, prostacyclinand endothelium-dependent hyperpolarizing factor to endothelium-dependentvasodilation induced by acetylcholine in rat aorta from control and ouabain-inducedhypertensive rats. Preincubation with the nitric oxide synthase inhibitor N-omeganitro-L-arginine methyl esther (L-NAME) inhibited the vasodilator response toacetylcholine in segments from both groups but to a greater extent in segments fromouabain-treated rats. Basal and acetylcholine-induced nitric oxide release were higherin segments from ouabain-treated rats. Preincubation with the prostacyclin synthesisinhibitor tranylcypromine or with the cyclooxygenase inhibitor indomethacininhibited the vasodilator response to acetylcholine in aortic segments from bothgroups. The Ca2+-dependent potassium channel blocker charybdotoxin inhibited thevasodilator response to acetylcholine only in segments from control rats. Theseresults indicate that hypertension induced by chronic ouabain treatment is accompaniedby increased endothelial nitric oxide participation and impaired endotheliumdependenthyperpolarizing factor contribution in acetylcholine-induced relaxation.These effects might explain the lack of effect of ouabain treatment on acetylcholineresponses in rat aorta (AU)

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Aldosterone induces endothelial dysfunction in resistance arteries from normotensive and hypertensive rats by increasing thromboxane A2 and prostacyclin.

BACKGROUND AND PURPOSE: The present study was designed to assess whether cyclooxygenase-2 (COX-2) activation is involved in the effects of chronic aldosterone treatment on endothelial function of mesenteric resistance arteries (MRA) from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). EXPERIMENTAL APPROACH: Relaxation to acetylcholine was measured in MRA from both untreated and aldosterone-treated strains. Vasomotor responses to prostacyclin and U46619 were also analysed. Release of 6-oxo-prostaglandin (PG)F1alpha and thromboxane B2 (TxB2) was determined by enzyme immunoassay. COX-2 protein expression was measured by western blot. KEY RESULTS: Aldosterone reduced acetylcholine relaxation in MRA from both strains. In MRA from both aldosterone-treated strains the COX-1/2 or COX-2 inhibitor (indomethacin and NS-398, respectively), TxA2 synthesis inhibitor (furegrelate), prostacyclin synthesis inhibitor (tranylcypromine) or TxA2/ PGH2 receptor antagonist (SQ 29 548), but not COX-1 inhibitor SC-560, increased acetylcholine relaxation. In untreated rats this response was increased only in SHR. Prostacyclin elicited a biphasic vasomotor response: lower concentrations elicited relaxation, whereas higher concentrations elicited contraction that was reduced by SQ 29 548. Aldosterone increased the acetylcholine-stimulated production of 6-oxo-PGF(1alpha) and TxB2 in MRA from both strains. COX-2 expression was higher in both strains of rats treated with aldosterone. CONCLUSIONS AND IMPLICATIONS: Chronic treatment with aldosterone impaired endothelial function in MRA under normotensive and hypertensive conditions by increasing COX-2-derived prostacyclin and thromboxane A2. As endothelial dysfunction participates in the pathogenesis of many cardiovascular disorders we hypothesize that anti-inflammatory drugs, specifically COX-2 inhibitors, could ameliorate vascular damage in patients with elevated aldosterone production.

Orchidectomy increases the formation of non-endothelial thromboxane A2 and modulates its role in the electrical field stimulation-induced response in rat mesenteric artery.

The aim of this study was to analyze whether endogenous male sex hormones influence the release of thromboxane A2(TXA2) and its role in the electrical field stimulation (EFS)-induced response, as well as the mechanism involved. For this purpose, endothelium-denuded mesenteric arteries from control and orchidectomized male Sprague-Dawley rats were used to measure TXA2 release; EFS-induced response, nitric oxide (NO), norepinephrine (NA), and prostaglandin (PG) I2 release were also measured in the presence of the TXA2 synthesis inhibitor furegrelate. Orchidectomy increased basal and EFS-induced TXA2 release. Furegrelate decreased the EFS-induced contraction in arteries from control rats, but did not modify it in arteries from orchidectomized rats. The EFS-induced neuronal NO release and vasodilator response were increased by furegrelate in arteries from control rats, but were not modified in arteries from orchidectomized rats. Furegrelate did not modify the EFS-induced NA release or vasoconstrictor response in arteries from either control or orchidectomized rats. The EFS-induced PGI2 release was not modified by furegrelate in arteries from control rats, but was increased in arteries from orchidectomized rats. The results of the present study show that endogenous male sex hormone deprivation i) increases non-endothelial TXA2 release and ii) regulates the effect of endogenous TXA2 on the EFS-induced response through different mechanisms that, at the least, involve the NO and PGI2 systems. In arteries from control rats, inhibition of TXA2 formation decreases the EFS-induced response by increasing neuronal NO release. In arteries from orchidectomized rats, the EFS-induced response is unaltered after the inhibition of TXA2 formation, by increasing PGI2 release.

Orchidectomy increases beta-adrenoceptor activation-mediated neuronal nitric oxide and noradrenaline release in rat mesenteric artery.

BACKGROUND/AIMS: A previous study has demonstrated that endogenous male sex hormones do not alter neuronal nitric oxide (NO) release in rat mesenteric artery. However, the regulatory role of endogenous male sex hormones on noradrenaline (NA) release in rat mesenteric artery is not known. The present study was designed to analyze whether endogenous male sex hormones influence the NA release induced by electrical field stimulation (EFS), as well as the possible modification in NA and neuronal NO release by presynaptic beta-adrenoceptor activation. METHODS: For this purpose, mesenteric arteries from control and orchidectomized male Sprague-Dawley rats were used. Basal and EFS-induced neuronal NO and NA release, as well as the contractile effect induced by EFS, was measured. RESULTS: Basal and EFS-induced neuronal NO and NA release were similar in arteries from control and orchidectomized rats. The beta-adrenoceptor agonist clenbuterol did not modify EFS-induced neuronal NO and NA release in arteries from control rats. In contrast, in arteries from orchidectomized animals, clenbuterol increased both neuronal NO and NA release; this increase was prevented by incubation with the beta-adrenoceptor antagonist propranolol. However, the contractile response elicited by EFS was not modified by clenbuterol in either group of rats. CONCLUSIONS: These results show that orchidectomy does not alter the EFS-induced NA release. What is more, activation of presynaptic beta-adrenoceptors does not modify EFS-induced NA and neuronal NO release in arteries from control rats although it increases the release of both neurotransmitters in arteries from orchidectomized rats. Despite these modifications, the EFS-induced contractile response is preserved in arteries from orchidectomized rats.