Biomedical subjects
Publications and source records attributed to J Damas.
A fraction of the vascular endothelial cells may synthetised and release acetylcholine. This release is enhanced by mechanical stimuli such as shear stress or increased blood flow. The physiological role of this release of acetylcholine is explained taking the vasodilatory response to mental stress of blood vessels in skeletal muscles as an example.
A series of 6-substituted 2-alkylaminoquinazolin-4(3H)-ones structurally related to 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides were synthesized and tested as putative K(ATP) channel openers on isolated pancreatic endocrine tissue as well as on isolated vascular, intestinal, and uterine smooth muscle. Most of the 6-halogeno-2-alkylaminoquinazolin-4(3H)-ones were found to inhibit insulin release from pancreatic B-cells and to exhibit vasorelaxant properties. In contrast to their pyridothiadiazine dioxide isosteres previously described as more active on the endocrine than on the smooth muscle tissue, quinazolinones cannot be considered as tissue selective compounds. Biological investigations, including measurements of (86)Rb, (45)Ca efflux from pancreatic islet cells and measurements of vasodilator potency in rat aortic rings exposed to 30 or 80 mM KCl in the presence or the absence of glibenclamide, were carried out with 6-chloro- and 6-iodo-3-isopropylaminoquinazolin-4(3H)-ones. Such experiments showed that, depending on the tissue, these new compounds did not always express the pharmacological profile of pure K(ATP) channel openers. Analyzed by X-ray crystallography, one example of quinazolinones appeared to adopt a double conformation. This only suggests a partial analogy between the 2-alkylaminoquinazolin-4(3H)-ones and the 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides. In conclusion, the newly synthesized quinazolinones interfere with insulin secretion and smooth muscle contractile activity. Most of the compounds lack tissue selectivity, and further investigations are required to fully elucidate their mechanism(s) of action.
The chemical modification of clozapine (1) has permitted the finding of new analogues, e.g., olanzapine (2), quetiapine (3), 5-(4-methylpiperazin-1-yl)-8-chloropyrido[2,3-b][1,5]benzoxazepine fumarate (9), with a clinical or psychopharmacological profile similar to that of clozapine. However, when developing new derivatives, the designers are discouraged by the development of clozapine-induced agranulocytosis. Different researchers have raised the role played by the oxidizability of the molecule in such a deleterious effect. In the present paper, we examined the oxidation profile (direct scavenging abilities, efficacy in inhibiting lipid peroxidation, and electrooxidation potential) of newly developed methoxy and trifluoromethylsulfonyloxy analogues related to clozapine, some of them being described as putative antipsychotic. The oxazepine derivative 7, unlike the other diazepine derivatives (6, 10--12), was not readily oxidized. Using a statistical predictive model for hematotoxicity previously described, 7 was found in the cluster of potentially nontoxic compounds while diazepine derivatives 6 and 10-12 were classified as potentially toxic compounds. Among these original compounds, 7, which presents a preclinical clozapine-like profile and a low sensitivity to oxidation, could be a promising antipsychotic candidate with low side effects. Considering the tricyclic derivatives examined so far, some elements of structure-oxidation relationship (SOR) might be pointed out. Regarding the nature of the tricyclic ring substituent, from the most to the least sensitive to oxidation, the sequence was as follows: HO > Cl > CH(3)O > CF(3)SO(2)O. The nature of the tricyclic ring influenced also the sensitivity to oxidation; the diazepine moiety appeared to be the most reactive ring compared to oxa- and thiazepine congeners. These parameters could be advantageously integrated in the early design of new safer clozapine-like analogues.
1. The influence of bradykinin (BK) on blood glucose and plasma insulin levels was investigated in anaesthetized rats. 2. Blood glucose level was dose-dependently increased by intravenous infusion of BK. This effect of BK was enhanced by captopril, an inhibitor of angiotensin-converting enzyme (ACE). Des-Arg9-bradykinin (DABK), a kinin B1 receptor agonist, did not modify blood glucose levels while the effect of BK was inhibited by Hoe-140, a kinin B2 receptor antagonist. 3. The effect of BK was reduced by the NO-synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), and by the cyclo-oxygenase inhibitor, indomethacin. The effect of BK was suppressed by the association of propranolol with phentolamine or phenoxybenzamine. It was also reduced by hexamethonium, a ganglion-blocking drug. In adrenalectomized rats, the infusion of BK slightly decreased blood glucose levels. 4. The hyperglycaemic effect of adrenaline was suppressed by propranolol associated with phentolamine or phenoxybenzamine, but it was not modified by L-NAME. 5. Infusion of BK did not modify plasma insulin levels. However, after phentolamine and propranolol, BK induced a transient 2 fold rise in plasma insulin levels. The release of insulin was dose-dependent and inhibited by Hoe-140. 6. We conclude that infusion of BK induces, via a stimulation of B2 receptors, the release of NO and of prostanoids. The latter agents activate through a reflex pathway the release of catecholamines from the adrenal medulla. This release increases blood glucose levels and reduces plasma insulin levels. After adrenoceptor inhibition, BK induces a secretion of insulin, via the stimulation of B2 receptors.
BM-531 (N-tert-butyl-N'-[(2-cyclohexylamino-5-nitrobenzene)sulfonyl]urea), a torasemide derivative, is a novel noncarboxylic thromboxane receptor antagonist and thromboxane synthase inhibitor. Indeed, its affinity for human washed platelet TXA2 receptors labeled with [3H]SQ-29548 (IC50 = 0.0078 microM) is higher than sulotroban (IC50 = 0.93 microM) and SQ-29548 (IC50 = 0.021 microM). Moreover, BM-531 is characterized by a potent antiaggregatory property. Indeed, on one hand, in human citrated platelet-rich plasma BM-531 prevents platelet aggregation induced by arachidonic acid (600 microM) (ED100 = 0.125 microM), U-46619, a stable TXA2 agonist (1 microM) (ED50 = 0.482 microM) or collagen (1 microgram/mL) (percentage of inhibition: 42.9% at 10 microM) and inhibits the second wave of ADP (2 microM)-induced aggregation. On the other hand, when BM-531 is incubated in whole blood from healthy donors, the closure time measured by the recently developed platelet function analyser (PFA-100) is significantly prolonged. In addition, at the concentrations of 10 and 1 microM, BM-531 totally prevents the production of TXB2 by human platelets activated by arachidonic acid. Finally, at 10 microM, BM-531 significantly prevents rat fundus contractions induced by U-46619 but not by prostacyclin. These results suggest that BM-531, which is devoid of the diuretic property of torasemide, can be regarded as a promising antiplatelet agent.
We recall the works of Bacq, Lecomte and Goffart, three physiologists from the University of Liège, on neurohumoral transmission, autacoids, sloths and monkeys in order to stress first that Physiology is a natural science of its own, and secondly that physiological studies aim at the understanding of the general mechanisms concurring to homeostasis.
In man, three kinds of sympathetic neurons reach the skin. Some cholinergic neurons stimulate the sweat glands, they are excited by temperature-regulating centers. Adrenergic neurons release noradrenaline and ATP to reduce cutaneous blood flow while cholinergic neurons release acetylcholine and a co-transmitter to dilate skin blood vessels. The excitation of both latter types of nerve cells depends on influences from temperature-regulating centers, baroreceptors and exercise. Moreover, in cutaneous blood vessels, a synthesis of NO is enhanced by an increase of body temperature and overall by direct heating of the skin. Burns are associated with axon reflexes and release of inflammatory mediators. The involvement of these various influences is described.
A series of 3-alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides structurally related to diazoxide and pinacidil were synthesized and tested as possible K(ATP) channel openers on isolated pancreatic endocrine tissue as well as on isolated vascular, intestinal, and uterine smooth muscle. In contrast to previously described 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1, 1-dioxides, most of the new compounds were found to be poorly active on B-cells but exhibited clear vasorelaxant properties. 3-(3, 3-Dimethyl-2-butylamino)-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxide (4d) and 7-chloro-3-(3, 3-dimethyl-2-butylamino)-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxide (5d), two compounds bearing the alkyl side chain of pinacidil, were found to be the most active representatives of their respective series on rat aorta rings. 3-Cycloalkylalkylamino- and 3-aralkylamino-7-chloro-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides also expressed myorelaxant activity on electrically stimulated guinea pig ileum and on oxytocin-induced contractions of the rat uterus. Further biological investigations ((86)Rb efflux measurements, vasodilator potency on 30 and 80 mM KCl-induced contractions in the absence and presence of glibenclamide) revealed that compounds 4d and 5d, but not compound 5f, expressed the pharmacological profile of classical K(ATP) channel openers. In conclusion, by changing the position of the nitrogen atom in the pyridine ring, we now have obtained a family of drugs expressing an opposite tissue selectivity. Taken as a whole, the present findings also suggest that 3-alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides such as 4c, 4d, 5c, and 5d may be considered as new examples of K(ATP) channel openers expressing a pharmacological profile similar to that of pinacidil and diazoxide.
The anti-inflammatory properties of hydrophilic extracts of the capsular polymers of twelve cyanobacterial strains belonging to the genera Phormidium and Nostoc from marine and terrestrial habitats were tested topically on croton oil-induced oedema in mice ear skin. The screening program identified several strains as producers of anti-inflammatory products (up to 56% inhibition of the oedema). The inhibition response was dose-dependent. The application of trichloroacetic acid-treated extracts reduced the oedema by about 60%. On the other hand, one of the strains enhanced the inflammatory response. Analysis of five of the extracts showed the presence of neutral sugars (from 34.3% to 47.1%, w/w), uronic acids (from 7.1% to 26.7%, w/w) and proteins (from 30.1% to 57.0%, w/w) in the crude polymer. Rhamnose, fucose, arabinose, xylose, mannose, glucose, galactose, galacturonic acid and glucuronic acid were detected as well as sulphate groups (from 9.6% to 21.5%, w/w of sugars). The main components found were glucose and mannose.
Using in vitro electrophysiological procedures, we confirm the inhibitory effect of 10-(4-methylpiperazin-1-yl)pyrido[4,3-b][1, 4]benzothiazepine (JL 3), on dorsal raphe serotonergic (IC(50)=14 microM) and noradrenergic neurons (IC(50)=4.5 microM). The effect on dorsal raphe neurons was reduced by N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl- cyclohexanecarboxamide (WAY-100635), suggesting the importance of 5-HT(1A) receptor stimulation. Yohimbine, and ritanserin, to a lesser extent, blocked the inhibitory effect of JL 3 on locus coeruleus neurons indicating that alpha(2)-adrenoceptors and 5-HT(2A) receptors may be implicated in the effects. Because of its negligible alpha(2)-adrenoceptor affinity, the effect of JL 3 on locus coeruleus neurons, would have to be indirect. JL 3 may interfere with the norepinephrine transporter site (IC(50)=0.34 microM). JL 3 tended to reinforce the hypertensive effect of norepinephrine, while it strongly inhibited the hypertensive effect of tyramine, further indicating an interaction at the norepinephrine transporter site level.
Centaurea cyanus flower-heads are used in European phytotherapy for the treatment of minor ocular inflammations. Different pharmacological experiments (inhibition of carrageenan, zymosan and croton oil-induced oedemas, inhibition of plasma haemolytic activity, induction of anaphylatoxin activity) showed that polysaccharides extracted from C. cyanus flower-heads had anti-inflammatory properties and interfered with complement. Moreover, these polysaccharides were found to be mainly composed of galacturonic acid, arabinose, glucose, rhamnose and galactose.
Some antipsychotic agents have been found to produce agranulocytosis and aplastic anemia. The oxidation phenomena and/or the formation of free radicals has been suggested to be causally related to various hematological disorders, e.g., agranulocytosis. Using five experimental conditions, we tested the oxidative potential of compounds with and without a history of hematological side effects, e.g., agranulocytosis and aplastic anemia. A statistical analysis was undertaken for each experimental condition and a multivariate analysis combining all results was performed. Two peroxidase-induced free radical models did not successfully discriminate between drugs with and without a history of causing hematologic problems (<70%). The lipid peroxidation system provided even less satisfactory discrimination, with only 56.25% correct classification. However, an 87.5% correct classification was obtained when using the oxidation potentials of these drugs determined at pH 4.7 and at pH 7.4. A multivariate analysis taking into account the five variables provided 87.5% success in classification. The two clusters were better discriminated in terms of a "distance coefficient." In a second analysis, the putative antipsychotic pyridobenzodiazepine analogues (JL5, JL8, JL18, and JL25) were classified in the cluster of toxic compounds, while the oxa- and thiazepine analogues (JL2, JL3, and JL13) were classified as nontoxic compounds. On the other hand, a few metabolites of clozapine and fluperlapine were classified in the toxic compound group. The procedure described herein is, to our knowledge, the first which classifies molecules of different structures as well as different pharmacological profiles according to their hematotoxic potential. Such a procedure could be used to predict drug-induced hematological side effects.
The involvement of bradykinin and some other inflammatory mediators in formalin-induced oedema and plasma extravasation was examined. Formalin was injected in rat paws at two doses, 1.75% or 5%. The lower dose induced the development of an immediate oedema associated with a progressive accumulation of 125I-labelled albumin in the paws. These changes were suppressed by pretreatment with capsaicin or xylocaine. They were abolished by RP67580, a NK1 receptor antagonist, and increased by phosphoramidon or diprotin A. They were not affected by HOE140, a bradykinin B2 antagonist, captopril, methysergide, mepyramine, indomethacin, ketoprofen or L-N(G)-nitroarginine. The higher dose of formalin induced a swelling of the paws which took place in two phases associated with two periods of increase in vascular permeability. This oedema was reduced by pretreatment with capsaicin but not with xylocaine. It was reduced by RP67580 injected before or 30 min after formalin. It was inhibited by mepyramine, methysergide, indomethacin and NS-398, a cyclooxygenase-2 inhibitor. It was not modified by HOE140. Its development was similar in normal and kininogen-deficient rats. We concluded that formalin administered at a low dose induces an oedema which mainly results from a neurogenic inflammation mediated by neuropeptides such as substance P. At higher doses, formalin induces an oedema which mainly depends on the release of substance P, prostanoids, 5-hydroxytryptamine and histamine. Bradykinin plays no significant role in the vascular changes whereas this peptide has been reported to participate in the stimulation of nociceptive afferent neurons. This discrepancy could be explained by a difference in the threshold of stimulation of the nociceptive neurons and that of the cells of the vascular walls, or by a formation of kinins in close contact of the neurons.
We prepared solutions of human IgM and IgG to various lipopolysaccharide (LPS) species. These were then tested, along with solutions of non-LPS specific human IgG or IgM, for their ability to confer passive immunity against experimental endotoxemia in two animal models. The immunoglobulins were first tested for an effect on the lethality induced by seven different LPSs in actinomycin-D sensitized mice, or by three different bacteria in normal mice. When the immunoglobulins were administered 1 h before challenge, a small protective effect was observed. This protection was dependent upon both the anti-LPS agent, the chemical composition of the LPS, or the strain of gram-negative bacteria used for injection. The anti-LPS IgM and IgG preparations reduced the mortality induced by Escherichia coli but not by Serratia marcescens or Klebsiella pneumoniae, indicating protection by strain-specific antibodies. When the antibodies were preincubated with LPS or bacteria for 30 min before administration, almost complete protection was seen. The influence of these immunoglobulin preparations or of human albumin (as a control) on the hypotensive and vascular-permeabilizing effects of LPS in rats was then studied. A dose-dependent inhibitory effect was observed with IgG preparations and albumin. At 200 mg/kg, anti-LPS IgG reduced the effects of LPS, while at 400 mg/kg, both anti-LPS and normal IgG preparations showed protection, as did human albumin used at the same dose. The IgM-enriched preparation worsened the initial hypotensive phase after LPS, whereas the anti-LPS IgM significantly reduced the second phase of the hypotension, but only at the largest dose of 400 mg/kg. In this second model using the rat, a clear difference between the activity of IgG and IgM was thus observed. We conclude that pretreatment with human immunoglobulins from large plasma pools modestly, but significantly, attenuated the effects of murine and rat Gram-negative sepsis, but that protection was incomplete. Our results suggest that single regimen intervention strategies may not be sufficient to influence the course of the disease.
To examine the influence of passive immunization on the biological fate of injected lipopolysaccharide (LPS), we used a human IgG preparation (anti-LPS IgG) rich in antibodies to a large panel of smooth and rough purified LPS extracts as well as a normal IgG preparation (standard IgG). Our approach was to compare the uptake of 125I-labeled LPS by the tissues of saline or IgG-treated rats. After intravenous injection, one fraction of 125I-labeled Escherichia coli O55:B5 LPS is rapidly taken up by tissues, while another fraction remained in the blood. Uptake of 125I-labeled LPS was principally observed into the liver and spleen. In rats treated prophylactically with standard IgG, these tissues accumulated significantly larger amount of LPS than the tissues of rats treated with anti-LPS IgG. Nevertheless, both IgG preparations increased the specific binding of LPS by the liver and spleen. High levels of homologous unlabeled LPS decreased the uptake of LPS by the liver, presumably by occupying tissue receptors, whereas in the presence of E. coli O127:B8 LPS, an increase of the uptake of 125I-labeled LPS by the liver and lungs was observed. The pharmacokinetics and tissue distribution of LPS-IgG complexes pre-formed in vitro were compared. In the presence of standard IgG, a unexpected increase of the uptake of LPS by the tissues was recorded, whereas LPS-anti-LPS IgG complexes decreased the binding of 125I-labeled LPS to the tissues. On the other hand, the vascular effects induced by LPS did not appear to be modified in rats pretreated with either IgG preparation. In conclusion, although passive immunization against LPS slightly modified the uptake and clearance of LPS, neither in vitro nor in vivo formation of LPS-anti-LPS IgG complexes afforded a very significant protection against the toxic effects of LPS.
Insulin sensitivity of kininogen-deficient rats was compared with that of normal rats using euglycaemic hyperinsulinaemic glucose clamping. Anaesthetized animals were infused with 2-50 mU kg-1 min-1 of insulin and the glucose infusion rates needed to maintain euglycaemia were determined. Maximum glucose uptake, insulin sensitivity index and insulin clearance were reduced in kininogen-deficient rats. Captopril increased the amount of glucose needed to maintain euglycaemia during infusion of 2 and 10 mU kg-1 min-1 of insulin in normal rats, but had no effect in kininogen-deficient rats. Anaesthetized rats of both strains were given an intraperitoneal injection of glucose and the evolution of blood glucose was followed for 120 min. The peak increase was higher in kininogen-deficient rats. Similar larger increases in blood glucose were observed after glucose injection in normal rats previously treated with HOE 140, a bradykinin B2 receptor antagonist. After glucose injection, plasma insulin increased in both groups of rats but reached lower levels in kininogen-deficient animals. These results suggest that bradykinin is involved not only in the clearance of glucose and insulin by the tissues during insulin infusion but also that bradykinin can affect the release of insulin after a glucose load.
Torasemide, a loop diuretic, has been reported to relax dog coronary artery precontracted by thromboxane A2 (TXA2), an endogenous prostanoid involved in cardiovascular and pulmonary diseases. N-cyano-N'-[[4-(3'-methylphenylamino)pyrid-3-yl]sulphonyl] homopiperidinoamidine (BM-144) and N-isopropyl-N'-[5-nitro-2-(3'-methylphenylamino)-benzenesulphon yl]urea (BM-500), chemically related to torasemide, have been examined for their TXA2 antagonism. The affinity (IC50, the concentration resulting in 50% inhibition) of BM-144 and BM-500 for the TXA2 receptor of washed platelets from man was 0.28 and 0.079 microM, respectively. This is better than for sulotroban (IC50 = 0.93 microM) but less than for SQ-29548 (IC50 = 0.021 microM), two TXA2 antagonists used as reference. The aggregation of platelets from man induced by arachidonic acid was prevented by BM-144 (IC50 = 9.0 microM) and by BM-500 (IC50 = 14.2 microM). Similar results were obtained by use of U-46619, a TXA agonist, as aggregating agent (BM-144, IC50 = 12.9 microM and BM-500, IC50 = 9.9 microM). The contracting effect of U-46619 on rat stomach strip was abolished by BM-144 (IC50 = 1.01 microM) and BM-500 (IC50 = 2.54 microM). Both drugs (BM-144: IC50 = 0.12 microM and BM-500: IC50 = 0.19 microM) also relaxed rat aorta precontracted by U-46619; both were more potent than sulotroban (IC50 = 1.62 microM). The two torasemide derivatives (100 microM) did not significantly affect the myo-stimulating effect of some prostaglandins (PGE2, PGI2, PGF2alpha) or aorta contraction elicited by KCl (30 mM). They did not modify rat diuresis after administration of a 30-mg kg(-1) dose. In conclusion, BM-144 and BM-500 can be regarded as novel non-carboxylic TXA2 receptor antagonists and offer a novel template for the design of more potent molecules.
In the face of the tissue injury, the human organism builds three kinds of responses: inflammation, acute phase phenomena and stress. These responses correspond to three lines of a gradual defense against aggressive stimuli. However, the stress can be induced in the absence of any kind of inflammation. As the effects of these responses are often confounded, we think it was useful to recall the main repercussions of these responses, the links between them and the aspects which separate them.