Cytoprotective effect of 1-nitro-2-phenylethane in mice pancreatic acinar cells subjected to taurocholate: putative role of guanylyl cyclase-derived 8-nitro-cyclic-GMP.

The nitroderivative 1-nitro-2-phenylethane (NPE) was recently described as a compound possessing heme-dependent soluble guanylyl cyclase (sGC) stimulating properties in vascular smooth muscle cells. In this study, we tested such pharmacological property of NPE in mice pancreatic acinar cells subjected to the bile salt taurocholate, a type of pathological stimulus that simulates pancreatitis. Here, isolated acinar cells were treated with NPE in order to assess the role of sGC on the detrimental effects induced by taurocholate. NPE reduced taurocholate-elicited Ca(2+) overload, production of reactive oxygen species (ROS), apoptosis, necrosis, and exerted a protective effect against mitochondrial membrane potential (ΔΨm) dissipation. These NPE-induced effects were abolished by pretreatment with ODQ and KT 5823, and after the blockade of nitric oxide (NO) synthase with l-NAME, inhibitors of key components of the sGC pathway. Contrarily to cGMP that alone increased ΔΨm collapse and cell damage, the cytoprotective effect of NPE on ΔΨm and cell necrosis was almost reproduced by 8-nitro-cGMP, a second messenger generated by sGC under oxidative stress conditions. In conclusion, putative sGC stimulation with NPE reveals its cytoprotective profile on pancreatic cells subjected to taurocholate. Moreover, ROS and NO conjunctly appear to drive sGC activity in pancreatic acinar cells to implement an adaptive mechanism in response to oxidative and Ca(2+) stress through 8-nitro-cGMPsynthesis.

Antispasmodic and myorelaxant effects of the flavoring agent methyl cinnamate in gut: potential inhibition of tyrosine kinase.

Methyl cinnamate (MC) is a safe flavoring agent useful to food industry. Although chemically analog to tyrosine kinase inhibitors, there is little information regarding its biological actions. Here, we aimed at assessing the MC effects on gastrointestinal contractility and the putative involvement of tyrosine kinase in the mediation of these effects. Isometric contractions were recorded in rat isolated strips from stomach, duodenum and colon segments. In gastric strips, MC (3-3000 µM) showed antispasmodic effects against carbachol-induced contractions, which remained unchanged by either l-NAME or tetraethylammonium pretreatment and occurred with potency similar to that obtained against contractions evoked by potassium or U-46619. In colon strips, MC was four times more potent than in gastric ones. MC and the positive control genistein inhibited phasic contractions induced by acetylcholine in Ca2+-free medium, an effect fully prevented by sodium orthovanadate. Both MC and genistein decreased the spontaneous contractions of duodenal strips and shortened the time necessary for gastric fundic tissues to reach 50% of maximal relaxation. In freshly isolated colon myocytes, MC decreased the basal levels of cytoplasmic Ca2+, but not the potassium-elicited cytoplasmic Ca2+ elevation. Colon strips obtained from rats subjected to intracolonic acetic acid instillation showed reduced contractility to potassium, which was partially recovered in MC-treated rats. Inhibitory effect of nifedipine against cholinergic contractions, blunted in acetic acid-induced colitis, was also recovered in MC-treated rats. In conclusion, MC inhibited the gastrointestinal contractility with a probable involvement of tyrosine kinase pathways. In vivo, it was effective to prevent the deleterious effects of colitis resulting from acetic acid injury.

Gastric contractility in experimental gastroschisis.

BACKGROUND/PURPOSE: The mechanism of fetal gastric dilation in gastroschisis is controversial. This study was designed to characterize changes in the contractile profile of strips of stomach from rats following experimental gastroschisis. METHODS: Pregnant Wistar rats were operated on day 18.5. Fetuses were divided into three groups: gastroschisis (G), sham (S), and control (C). On day 21.5, gastric fundus and antrum strips were obtained and suspended to a force transducer connected to a digital data acquisition system. They were submitted to increasing concentrations of carbachol (CCh) and weighed at the end of each procedure. Frequency and amplitude of each contraction were evaluated. RESULTS: Under basal conditions, spontaneous oscillatory contractions of antrum and fundus strips of G, S, and C were similar (P>0.05; ANOVA). However, cumulative concentrations of CCh (0.01-100 µM) produced different effects in all groups and were characterized by a significant increase in amplitude and frequency of spontaneous contractions in antral smooth muscle and a sustained increase in tonus in fundic strips. Upon analysis, no significant difference in frequency or amplitude was noted in antral tissues comparing C to G and to S (P>0.05). No significant contractility difference was noted in fundic smooth muscle (comparing all groups, P>0.05), with the CCh-induced curve following a typical sigmoidal format, dependent on increasing concentrations (P<0.001). CONCLUSIONS: Gastric contractile responses to CCh are preserved in experimental gastroschisis. These results do not support the theory that gastric dilation occurs secondary to intestinal inflammation alone.

The vasorelaxant effects of 1-nitro-2-phenylethane involve stimulation of the soluble guanylate cyclase-cGMP pathway.

1-Nitro-2-phenylethane is the first organic NO2-containing molecule isolated from plants. It possesses interesting hypotensive, bradycardic, and vasodilator properties, but the mode by which it induces vasorelaxation is still unknown. The underlying mechanism involved in the vasodilator effect of 1-nitro-2-phenylethane was investigated in rat aorta. The vasorelaxant effects of 1-nitro-2-phenylethane did not depend on endothelial layer integrity, and the effects were refractory to L-N(G)-nitroarginine methyl ester (L-NAME)-induced nitric oxide synthase inhibition. Vasorelaxation was similarly resistant to treatment with indomethacin, cis-N-(2-phenylcyclopentyl)-azacyclotridec-1-en-2-amine hydrochloride (MDL-12330A), and KT5720, indicating that neither prostaglandin release nor adenylyl cyclase activation is involved. Conversely, methylene blue- and ODQ-induced guanylate cyclase inhibition reduced the vasorelaxation induced by 1-nitro-2-phenylethane. The pharmacological blockade of K(+) channels with tetraethylammonium, glybenclamide, and 4-aminopyridine also blunted vasorelaxation induced by 1-nitro-2-phenylethane. The effects of 1-nitro-2-phenylethane were reversed by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and comparable to the effects induced by sodium nitroprusside. In silico analysis using an Ns H-NOX subunit of guanylate cyclase revealed a pocket on the macromolecule surface where 1-nitro-2-phenylethane preferentially docked. In vitro, 1-nitro-2-phenylethane increased cyclic guanosine 3',5'-monophosphate (cGMP) levels in rat aortic rings, an effect also reversed by ODQ. In conclusion, 1-nitro-2-phenylethane produces vasodilator effects by stimulating the soluble guanylate cyclase-cGMP pathway.

In-vitro characterization of the pharmacological effects induced by (-)-α-bisabolol in rat smooth muscle preparations.

The present study deals with the pharmacological effects of the sesquiterpene alcohol (-)-α-bisabolol on various smooth-muscle preparations from rats. Under resting tonus, (-)-α-bisabolol (30-300 µmol/L) relaxed duodenal strips, whereas it showed biphasic effects in other preparations, contracting endothelium-intact aortic rings and urinary bladder strips, and relaxing these tissues at higher concentrations (600-1000 µmol/L). In preparations precontracted either electromechanically (by 60 mmol/L K(+)) or pharmacomechanically (by phenylephrine or carbachol), (-)-α-bisabolol showed only relaxing properties. The pharmacological potency of (-)-α-bisabolol was variable, being higher in mesenteric vessels, whereas it exerted relaxing activity with a lesser potency on tracheal or colonic tissues. In tissues possessing spontaneous activity, (-)-α-bisabolol completely decreased spontaneous contractions in duodenum, whereas it increased their amplitude in urinary bladder tissue. Administered in vivo, (-)-α-bisabolol attenuated the increased responses of carbachol in tracheal rings of ovalbumin-sensitized rats challenged with ovalbumin, but was without effect in the decreased responsiveness of urinary bladder strips in mice treated with ifosfamide. In summary, (-)-α-bisabolol is biologically active in smooth muscle. In some tissues, (-)-α-bisabolol preferentially relaxed contractions induced electromechanically, especially in tracheal smooth muscle. The findings from tracheal rings reveal that (-)-α-bisabolol may be an inhibitor of voltage-dependent Ca(2+) channels.

Inhaled 1,8-cineole reduces inflammatory parameters in airways of ovalbumin-challenged Guinea pigs.

Eucalyptol, also known as 1,8-cineole, is a monoterpene traditionally used to treat respiratory disorders due to its secretolytic properties. In addition to its myorelaxant effects, it also has anti-inflammatory actions in vitro. In this study, we aimed to evaluate the efficacy of acute treatment with 1,8-cineole on reducing airway inflammatory parameters. Ovalbumin (OVA)-sensitized guinea pigs were submitted to antigenic challenge (OVA) with or without pre-treatment with a single dose of 1,8-cineole administered by inhalation. Airway inflammatory parameters were reduced or absent in 1,8-cineole-treated animals as compared with untreated guinea pigs. Acute treatment with 1,8-cineole impaired the development of airway hyperresponsiveness to carbachol in isolated tracheal rings. Levels of the pro-inflammatory cytokines TNFα and IL-1ß was lower in bronchoalveolar lavage fluid (BALF) of 1,8-cineol-treated guinea pigs than in untreated animals. 1,8-Cineole impaired the OVA-induced increase of the myeloperoxidase activity in BALF. 1,8-Cineole also prevented the reduction of the mucociliary clearance induced by the antigen presentation. The present investigation provides evidence that inhaled 1,8-cineole prevents hyperresponsiveness and inhibits inflammation in airways of ovalbumin-challenged guinea pigs.

The essential oil of Eucalyptus tereticornis, and its constituents alpha- and beta-pinene, potentiate acetylcholine-induced contractions in isolated rat trachea.

The effects of the essential oil of Eucalyptus tereticornis (EOET), especially the effects of its constituents alpha- and beta-pinene, were studied on rat trachea in vitro. In tracheal rings, EOET, alpha- or beta-pinene potentiated the contractions induced by acetylcholine (ACh). Contractions induced by K(+) (60mM) were also potentiated by alpha- and beta-pinene, but were reduced by EOET. Our findings show that EOET has myorelaxant effects on rat airways, but potentiates ACh-induced contractions. Monoterpenes alpha- and beta-pinene are involved in its potentiating actions, but are not responsible for its myorelaxant effects. A putative inhibition of the acetylcholinesterase enzyme is involved.

Inhibitory effect of 1,8-cineole on guinea-pig airway challenged with ovalbumin involves a preferential action on electromechanical coupling.

1. 1,8-Cineole is a terpenoid constituent of essential oils with anti-inflammatory properties. It reduces the neural excitability, functions as an antinociceptive agent and has myorelaxant actions in guinea-pig airways. The aim of the present study was to investigate the mechanism underlying the myorelaxant effects of 1,8-cineole in guinea-pig isolated trachea from either naïve guinea-pigs or ovalbumin (OVA)-sensitized animals subjected to antigenic challenge. 2. Isometric recordings were made of the tone of isolated tracheal rings. Rings with an intact epithelium relaxed beyond basal tone in the presence of 1,8-cineole (6.5 x 10(-6) to 2 x 10(-2) mol/L) in a concentration-dependent manner (P < 0.001, anova) with a pD(2) value of 2.23 (95% confidence interval 2.10-2.37). Removal of the epithelium or pretreatment of intact tissue for 15 min with 50 micromol/L N(G)-nitro-l-arginine methyl ester, 5 mmol/L tetraethylammonium, 0.5 micromol/L tetrodotoxin or 5 micromol/L propranolol did not alter the potency (pD(2)) or the maximal myorelaxant effect (E(max)) of 1,8-cineole. 3. 1,8-Cineole also significantly decreased the Schultz-Dale contraction induced by OVA, mainly in preparations from OVA-sensitized animals submitted to antigen challenge. 1,8-Cineole decreased tracheal hyperresponsiveness to KCl and carbachol caused by antigen challenge and almost abolished the concentration-response curves to KCl, whereas it had little effect on the concentration-response curves to carbachol. Under Ca(2+)-free conditions and in the presence of 10(-4) mol/L acetylcholine, neither 1,8-cineole (6.5 x 10(-3) mol/L) nor verapamil (1 x 10(-5) mol/L) affected Ca(2+)-induced contractions, but they almost abolished Ba(2+)-induced contractions. 4. In conclusion, the findings of the present study show that 1,8-cineole is a tracheal myorelaxant that acts preferentially on contractile responses elicited electromechanically.