M. A. Martínez-Cuesta

The role of nitric oxide and platelet-activating factor in the inhibition by endotoxin of pentagastrin-stimulated gastric acid secretion.

Administration of E. coli endotoxin (1 mg/kg i.v.) abolished the acid secretory response induced by a bolus injection of pentagastrin (100 micrograms/kg i.v.) in the continuously perfused stomach of the anaesthetized rat. Endotoxin administration did not modify mean systemic arterial blood pressure. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME; 5-20 mg/kg i.v.), but not dexamethasone (5 mg/kg s.c. twice) or indomethacin (5 mg/kg i.m.), substantially restored the secretory responses to pentagastrin. The actions of L-NAME were reversed by the prior administration of L-arginine (100 mg/kg i.v.), but not by its enantiomer D-arginine (100 mg/kg i.v.). L-NAME (10 mg/kg i.v.) increased blood pressure but this does not seem to be the mechanism by which endotoxin-induced acid inhibition was prevented, since similar systemic pressor responses induced by noradrenaline (15 micrograms/kg per min i.v.) had no such effect. The platelet-activating factor (PAF) receptor antagonist, WEB 2086 (2 mg/kg), induced a partial reversal of the inhibition by endotoxin of acid responses to pentagastrin. In endotoxin-treated rats, the combined administration of L-NAME (10 mg/kg) and WEB 2086 (2 mg/kg) completely restored the degree of H+ output induced by pentagastrin to levels similar to those of control, vehicle-treated animals. These findings suggest that endotoxin-induced acute inhibition of acid responses to pentagastrin involves NO synthesis and the release of PAF.

Analgesic and central depressor effects of the dichloromethanol extract from Schinus molle L.

The analgesic and central depressor effects of the dichloromethanol extract of Schinus molle L. were analysed in in vivo models. This extract showed low acute toxicity, CNS depressor activity and analgesic effect. Following further fractionation, the hexane/dichloromethane (75/25) fraction showed the most interesting results. Thus, this fraction caused a total inhibition of motor activity and significantly reduced the threshold of pain to chemical stimulus.

Anatomical differences in responsiveness to vasoconstrictors in the mesenteric veins from normal and portal hypertensive rats

The present study evaluates the effects of pre-hepatic portal hypertension, induced in rats by partial portal vein ligation, on the responsiveness of rostral (proximal) and caudal (distal) rings from the mesenteric vein. The anatomical origin of the sample influenced the response to vasoconstrictors in sham-operated animals, and this pattern of reactivity was specifically modified in portal-ligated rats. In veins from sham-operated rats, contraction induced by a submaximal concentration of KCl (60 mM) was greater in proximal than in distal rings. Vasopressin and 5-hydroxytryptamine contracted mainly distal rings, methoxamine showed a greater effect on proximal rings, and endothelin-1 and angiotensin-II contracted vein rings independently of their anatomical origin. In veins from portal hypertensive rats, responses to KCl (60 mM) were increased in distal rings, and all rings exhibited enhanced reactivity to vasopressin and 5-hydroxyptyptamine as well as attenuation of the response to methoxamine. Responses to endothelin-1 were decreased in proximal vein rings from portal hypertensive rats whereas responses to angiotensin-II were not influenced by the anatomical origin. Incubation with atropine, propranolol or indomethacin, did not modify the responses to vasopressin and 5-hydroxytryptamine in tissues from either sham-operated or portal hypertensive animals. Likewise, the hyporeactivity to methoxamine and endothelin-1 in rings from portal hypertensive rats persisted in the presence of the nitric oxide inhibitor NG-nitro-l-arginine methyl ester. These results suggest the physiological existence of anatomical differences in the responsiveness to vasoconstrictors throughout the mesenteric vein and that changes in the responsiveness of the mesenteric vein induced by portal hypertension are specific for each agonist and possibly result from individual variations at a receptor or post-receptor level.

Differential effects of anti-TNF-α and anti-IL-12/23 agents on human leukocyte-endothelial cell interactions.

Enhanced leukocyte recruitment is an inflammatory process that occurs during early phases of the vascular dysfunction that characterises atherosclerosis. We evaluated the impact of anti-TNF-α (adalimumab, infliximab and etanercept) and anti-IL-12/23 (ustekinumab) on interactions between human leukocytes and endothelial cells in a flow chamber that reproduced in vivo conditions. Clinical concentrations of anti-TNF-α were evaluated on the leukocyte recruitment induced by a variety of endothelial (TNF-α, interleukin-1β, lymphotoxin-α and angiotensin-II) and leukocyte (PAF, IL-12 and IL-23) stimuli related to inflammation and atherosclerosis. Treatment with anti-TNF-α, even before or after establishing the inflammatory situation induced by TNF-α, diminished leukocyte-endothelial cell interactions induced by this stimuli. Our results also implicated adhesion molecules (ICAM-1, VCAM-1 and E-selectin) in the actions of anti-TNF-α in terms of leukocyte adhesion to endothelium. However, anti-TNF-α drugs did not influence the actions of interleukin-1β, but prevented those of lymphotoxin-α and angiotensin-II. However, once established, inflammatory response elicited by the latter three stimuli could not be reversed. Pre-treatment with anti-TNF-α, also prevented leukocyte actions induced by IL-23 on PBMC rolling flux and rolling velocity and by IL-12 on PMN adhesion. Ustekinumab exhibited a more discreet profile, having no effect on leukocyte recruitment induced by any of the endothelial stimuli, while blocking the effects of IL-23 on leukocyte activation and those of IL-12 on PMN adhesion and PAF on PBMC rolling velocity. These findings endorse the idea that biological anti-inflammatory drugs, in particular anti-TNF-α, have the capacity to influence cardiovascular risk accompanying psoriasis and rheumatoid arthritis by ameliorating vascular inflammation.

Nitric oxide modulates the acute increase of gastrointestinal transit induced by endotoxin in rats: a possible role for tachykinins.

Because of the evidence that endogenous nitric oxide (NO) plays an essential role in the physiological regulation of gastrointestinal motility we have investigated, by use of the NO synthase inhibitor, NG‐nitro‐l‐arginine methyl ester (l‐NAME), the role of endogenous NO in the acute endotoxin‐induced changes of gastrointestinal transit.

Efavirenz induces interactions between leucocytes and endothelium through the activation of Mac-1 and gp150,95

OBJECTIVES The potential cardiovascular (CV) toxicity associated with combined antiretroviral therapy (cART) has been attributed mainly to the nucleoside reverse transcriptase inhibitors abacavir and didanosine. However, the other two components of cART--non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs)--may also be implicated, either directly or by influencing the action of the other drugs. This study evaluates the acute direct effects of the NNRTIs efavirenz and nevirapine and one of the most widely employed PIs, lopinavir, on leucocyte-endothelium interactions, a hallmark of CV disease. METHODS Drugs were analysed in vitro in human cells (interactions of peripheral blood polymorphonuclear or mononuclear cells with human umbilical vein endothelial cells) using a flow chamber system, and in vivo in rat mesenteric vessels by means of intravital microscopy. The expression of adhesion molecules in leucocytes and endothelial cells was studied by flow cytometry, and the role of these molecules in white cell recruitment was evaluated by pre-treating human cells or rats with blocking antibodies. RESULTS Efavirenz and nevirapine, but not lopinavir, increased the rolling flux and adhesion of leucocytes in vitro and in vivo while inducing emigration in rat venules. Efavirenz, but not nevirapine, augmented the levels of CD11b, CD11c and CD18 in neutrophils and monocytes. The actions of efavirenz, but not of nevirapine, were reversed by antibodies against Mac-1 (CD11b/CD18), gp150,95 (CD11c/CD18) or ICAM-1 (CD54). CONCLUSIONS NNRTIs, but not PIs, interfere with leucocyte-endothelial interactions. However, differences between efavirenz and nevirapine suggest a specific CV profile for each compound.

Differential effects of locally-applied capsaicin on distension-stimulated gastric acid secretion in the anesthetized rat.

SummaryThe effects induced by the local administration of capsaicin on acid production have been investigated in the continuously perfused stomach of the anesthetized rat. Basal acid secretion was not influenced by 10 min intragastric perfusion with capsaicin (300 μg min−1). Acid responses elicited by distension of the stomach with increases in intragastric pressure of 5 and 10 cm H2O were not modified after a 10 min intraluminal infusion with 80 or 300 μg min−1 of capsaicin. H+ output stimulated by higher intraluminal pressure (20 cm H2O) were significantly decreased by intraluminal infusion of capsaicin (20, 80, 300 and 600 μg min−1). Acid responses to carbachol (4 μg kg−1, i.p.) were not influenced by intragastric (300 μg min−1), or systemic neonatal, treatment with capsaicin.Intraluminal infusion of the neurotoxin tetrodotoxin (0.12 μg min−1, 10 min) decreased acid responses to an increase in intragastric pressure of 20 cm H2O but not those elicited by distention with a pressure of 10 cm H2O. Neonatal systemic treatment (s. c.) with capsaicin or local gastric serosal application of either capsaicin or tetrodotoxin abolished acid responses to gastric distension (+ 20 cm H2O). Capsaicin (80 μg min−1) and tetrodotoxin (0.12 μg min−1) infused concurrently into the lumen did not inhibit gastric acid secretion stimulated by an increase of 20 cm H2O in intragastric pressure to any greater extent than did either drug given alone. The inhibition of acid secretion cannot be attributed to an increase in H+ loss, since intragastric infusion of capsaicin (300 μg min−1) did not cause any significant acid loss in rats pretreated with omeprazole and undergoing luminal perfusion with acid saline during gastric distension (+ 20 cm H2O). Neither the intragastric perfusion nor the serosal application of capsaicin modified the H+ production induced by electrical stimulation of the vagus. This acid response was, however, abolished following 10 min intraluminal perfusion with tetrodotoxin (0.12 μg min−1).These observations confirm that capsaicin-sensitive sensory fibers located in the stomach wall mediate the acid secretory responses to intragastric distension. Such fibers are susceptible to the effects of capsaicin when administered systemically or through the gastric serosa, but only partially if capsaicin is infused intraluminally.

Involvement of endogenous nitric oxide in the inhibition by endotoxin and interleukin‐1β of gastric acid secretion

Abstract Administration of Escherichia coli endotoxin abolished the acid secretory response induced by a bolus injection of pentagastrin in the continuously perfused stomach of the anaesthetized rat. Likewise, acid secretion stimulated by the continuous intravenous perfusion of pentagastrin was inhibited by administration of interleukin‐1β (IL‐1β). In both cases pretreatment with Ng‐nitro‐l‐arginine methyl ester (l‐Name) but not dexamethasone or indomethacin substantially restored the secretory responses to pentagastrin. The actions of l‐Name were reversed by the prior administration of l‐arginine but not by its enantiomer d‐arginine. Even though l‐Name increased blood pressure, this does not seem to be the mechanism by which endotoxin‐induced acid inhibition was prevented, since similar systemic pressor responses induced by phenylephrine had no such effect. The secretory response elicited by pentagastrin in the isolated lumen perfused stomach of the rat was not influenced by incubation (100 min) with IL‐1β. These observations suggest that the acute inhibition of acid responses to pentagastrin by endotoxin and IL‐1β involves nitric oxide (NO) synthesis from l‐arginine.

Influence of Cholecystitis State on Pharmacological Response to Cholecystokinin of Isolated Human Gallbladder with Gallstones

We studied the influence of the inflammatory state of the gallbladder with gallstones on its response to cholecystokinin (CCK). Responses to CCK were evaluated in isolated human gallbladder strips incubated with pharmacological antagonists. Gallbladders from patients with gallstones were classified as having mild and severe chronic cholecystitis. Healthy gallbladders were collected from liver donors. In donor gallbladders, the CCK contraction was abolished with the CCK-A receptor antagonist, L-364718, and significantly reduced by indomethacin. In gallbladders with gallstones, only mild cholecystitis showed a decreased contraction to CCK. In gallbladders with gallstones, no involvement of prostaglandins in the CCK response was observed. In severe cholecystitis, CCK contractile effect was reduced by the serotonin receptor antagonist methysergide. In healthy gallbladder, the contraction provoked by CCK is mediated by CCK-A receptors and modulated by prostaglandins. The presence of gallstones in the gallbladder is correlated with a loss of prostaglandins-modulated CCK contraction. However, the excessive release of serotonin in advanced cholecystitis normalizes the contraction to CCK, suggesting that the state of cholecystitis affects the pool of inflammatory mediators responsible for gallbladder CCK-altered motility.

Involvement of Prostaglandins and 5‐Hydroxytryptamine in the Contractile Effect of Platelet‐activating Factor in Rat Isolated Gastric Corpus

The present study characterizes the nature of the response to the platelet‐activating factor (PAF) in isolated gastric corpus with and without mucosa.