Eugenia García-Zaragozá

Inhibition of mitochondrial respiration by endogenous nitric oxide: A critical step in Fas signaling

We have found that activation of human adult T cell leukemia (Jurkat) cells with anti-Fas Ab leads, in a concentration-dependent manner, to an early burst of production of nitric oxide (NO), which inhibits cell respiration. This results in mitochondrial hyperpolarization, dependent on the hydrolysis of glycolytic ATP by the F1Fo-ATPase acting in reverse mode. During this early phase of activation, there is a transient release of superoxide anion. All these processes can be prevented by an inhibitor of NO synthase. Approximately 2 h after stimulation with anti-Fas Ab, a distinct second phase can be detected. This comprises a concentration-dependent collapse in mitochondrial membrane potential, a second wave of free radical production, and activation of caspase-8 leading to apoptosis. This second phase is abolished by an inhibitor of caspase activation. In contrast, inhibition of NO synthesis leads to an enhancement and acceleration of these latter processes, suggesting that the early NO-dependent phase represents a protective mechanism. The significance of the two phases in relation to cell survival and death remains to be studied.

A cerebral nitrergic pathway modulates endotoxin-induced changes in gastric motility

This study analyses the neural pathway involved in the modulation of gastric motor function by stress. Systemic administration of low doses of endotoxin (40 μg kg−1, i.v.) prevents the increase in gastric tone induced by 2‐deoxy‐D‐glucose (200 mg kg−1, i.v., 2‐DG) in urethane‐anaesthetized rats. Functional inhibition of afferent neurones by systemic administration of capsaicin (20+30+50 mg kg−1, i.m.) in adult rats prevented the inhibitory effects of endotoxin. Pre‐treatment with the nitric oxide synthase (NOS) inhibitor, NG‐nitro‐L‐arginine methyl ester (L‐NAME), both i.v. (10 mg kg−1) and i.c. (200 μg rat−1), prevented the inhibitory effects of endotoxin on gastric tone induced by 2‐DG. Immunohistochemical studies show Fos expression in the dorsal vagal complex (DVC) of the brainstem of 2‐DG‐treated animals. Peripheral administration of endotoxin (40 μg kg−1, i.p.) increased the number of Fos‐immunoreactive cells induced by 2‐DG, both in the nucleus tractus solitarii (NTS) and in the dorsal motor nucleus (DMN) of the DVC. Pre‐treatment with L‐NAME prevented the increase in Fos expression induced by endotoxin in both nuclei. Endotoxin (40 μg kg−1, i.p.) increased Ca2+‐dependent nitric oxide synthase (cNOS) activity in the brainstem. Addition of 7‐nitroindazole (600 μM, 7‐NI) to the assay significantly inhibited the increase in cNOS activity caused by endotoxin. No change in NOS activity of any isoform was observed in the stomach of animals treated with endotoxin. The present study suggests that inhibition of gastric motor function by low doses of endotoxin involves activation of capsaicin‐sensitive afferent neurones and neuronal NOS in the brainstem.

Role of central glutamate receptors, nitric oxide and soluble guanylyl cyclase in the inhibition by endotoxin of rat gastric acid secretion

This study examines the role of a central pathway involving glutamate receptors, nitric oxide (NO) and cyclic GMP in the acute inhibitory effects of low doses of peripheral endotoxin on pentagastrin‐stimulated acid production. Vagotomy or intracisternal (i.c.) microinjections of the NO‐inhibitor, NG‐nitro‐L‐arginine methyl esther (L‐NAME; 200 μg rat−1) restored acid secretory responses in endotoxin (10 μg kg−1, i.v.)‐treated rats. The acid‐inhibitory effect of i.v. endotoxin (10 μg kg−1, i.v.) was prevented by prior i.c. administration of the NMDA receptor antagonists, dizocilpine maleate (MK‐801; 10 nmol rat−1) and D‐2‐amino‐5‐phosphono‐valeric acid (AP‐5; 20 nmol rat−1), or the AMPA/kainate antagonist 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX; 10 nmol rat−1). However, the competitive metabotropic glutamate receptor antagonist (+)‐α‐methyl‐4‐carboxyphenylglycine (MCPG; 20–1000 nmol rat−1) did not antagonize the effects of endotoxin. I.c. administration of L‐glutamate (0.1 nmol rat−1) inhibited pentagastrin‐stimulated gastric acid secretion. Coadministration with L‐NAME (200 μg rat−1) prevented the inhibition of gastric acid secretion by the aminoacid. I.c. administration of 1H‐[1,2,4]Oxazodiolo[4,3‐a]quinoxalin‐1‐one (ODQ; 100 nmol rat−1), a soluble guanylyl cyclase (sGC) blocker, reversed the hyposecretory effect of endotoxin. I.c. administration of the cyclic GMP analogue 8‐Bromoguanosine‐3,5‐cyclic monophosphate (8‐Br‐cGMP; 100–300 nmol rat−1) reduced gastric acid production in a dose‐dependent manner. We conclude that central NMDA and AMPA/kainate receptors are involved in the acid inhibitory effect of peripherally administered endotoxin. This central pathway involves synthesis of NO, which acts on the enzyme sGC.

Interleukin 1β-induced inhibition of gastric acid secretion involves glutamate, NO and cGMP synthesis in the brain

Abstract. This study examines the role of a central pathway involving glutamate receptors, nitric oxide (NO) and cGMP in the acute inhibitory effects of central interleukin 1β on pentagastrin-stimulated acid production.The acid-inhibitory effect of central interleukin 1β was prevented by intracisternal (i.c.) microinjections of interleukin 1β together with the NMDA receptor antagonist, dizocilpine maleate (MK-801). Intracisternal co-administration of the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl esther (L-NAME) or 1H-[1,2,4]oxazodiolo[4,3-a]quinoxalin-1-one (ODQ), a soluble guanylyl cyclase (sGC) blocker, both reversed the hyposecretory effect of central interleukin 1β. Peripheral administration of endotoxin significantly reduced pentagastrin-stimulated gastric acid secretion. I.c. pre-treatment with the interleukin 1 receptor antagonist, IL-1ra, failed to restore acid secretory responses in these rats. In addition, endotoxin did not modify the levels of endogenous mRNA for IL-1β in the brainstem.We conclude that central glutamate receptors are involved in the acid inhibitory effect of centrally administered interleukin 1β. This central pathway involves synthesis of NO, which acts on the enzyme sGC. However, endogenous interleukin 1β does not seem to be involved in the inhibition of gastric acid secretion elicited by peripheral endotoxin.

Opposite vascular activity of (R)-apomorphine and its oxidised derivatives. Endothelium-dependent vasoconstriction induced by the auto-oxidation metabolite

We have synthetised a series of oxidised apomorphine derivatives (orto and para quinones 2-5), in order to analyse their vascular activity. We have performed radioligand binding assays on rat cortical membranes and functional studies on rat aortic rings. Instead the relaxant activity exhibited by (R)-apomorphine, o-quinones 2, 4, show contractile activity dependent on endothelium in rat aortic rings. Compound 2, the main metabolite of (R)-apomorphine auto-oxidation, was the product which showed enhanced contractile activity by a complex mechanism related to activation of Ca(2+) channels through release and/or inhibition of endothelial factors. Moreover, this compound disrupts the endothelial function as shows the lack of response to acetylcholine observed in vessels pretreated with it.

Biopharmaceutics: Changes in Gastric Mucosal Permeability Induced by Haemorrhagic Shock in the Anaesthetized Rat: Modulation by Acid

Gastric mucosal damage induced by haemorrhagic shock in the anaesthetized rat has been evaluated by studying changes in capillary‐to‐lumen clearance of fluorescein isothiocyanate (FITC)‐labelled dextran.

Importancia farmacológica y clínica de los receptores serotoninérgicos del tracto gastrointestinal

La serotonina (5-hidroxitriptamina, 5HT) es una amina biógena ampliamente distribuida en el organismo. Fruto de esta ubicuidad es el hecho de que sus receptores controlen numerosos procesos celulares, participando en funciones fisiológicas tan diferentes como el control de la temperatura, comportamiento sexual y alimentario, movilidad gastrointestinal (GI) y vascular, secreción intestinal y pancreática, nocicepción, emesis y otros. Más del 90% de la serotonina del organismo se sintetiza y almacena en las células enterocromafines de la mucosa GI. Estas células endocrinas y las neuronas serotoninérgicas entéricas constituyen los dos únicos depósitos de 5HT en el tracto GI. El 10% restante se reparte entre las neuronas del SNC y las plaquetas, las cuales se limitan a cumplir una función de almacén. Dejando a un lado las acciones derivadas de sus receptores centrales, las posibles aplicaciones de los fármacos serotoninérgicos incluyen un amplio abanico de alteraciones del tracto GI, entre otros, náuseas y vómitos, dispepsia funcional, reflujo gastroesofágico, dolor torácico no cardíaco, distintas alteraciones de la secreción intestinal como los que se originan durante las diarreas secretoras, síndrome de intestino irritable y enfermedad inflamatoria intestinal.