A novel series of 2,6,7-substituted 2,3-dihydro-1,4-benzodioxin and 2,6,7-substituted 1,4-benzodioxin derivatives as lipid peroxidation inhibitors. Structure-activity relationships for high inhibition of human low-density lipoprotein peroxidation.

A series of 6- or 7-substituted 2-carboxamido- or 2-(aminomethyl)-1,4-benzodioxin and -2,3-dihydro-1,4-benzodioxin derivatives were synthesized and evaluated to determine the necessary structural requirements for a high inhibition of human low-density lipoprotein copper-induced peroxidation. The most active compounds (21, 25, 28, 36, and 37) were found between 5 and >45 times more active than probucol itself. Due to both their potency and their structural features, compounds 25 and 36 were selected with others for complementary in vitro and in vivo investigations. Both of them exhibit calcium antagonist properties in the same range of potency as flunarizine itself. Compound 36 was also found to have significant hypolipaemic activity in mice at 100 and 300 mg/kg po, while compound 25 proved to be clearly active in a normobar hypoxia test.

Synthesis and pharmacological evaluation of analgesic 6-substituted 2(3H)-benzothiazolones.

A series of novel 6-substituted-2(3H)-benzothiazolones were synthesized and studied as analgesic agents. Among these compounds, two of them were found to exhibit potent analgesic activity in several in vivo tests (acetic acid writhing, Koster, carrageenan and PGE2 hyperalgesia). In these tests the most active compound of this series, i.e. 6-benzoyl-2(3H)-benzothiazolone (4a) was found to be superior to acetylsalicylic acid and equivalent to glafenine. The present study allows to conclude that 4a represents a new type of antinociceptive agent acting in periphery by inhibiting the cyclo-oxygenase pathway and promoting the release of an opioid peptide.

Effect of intravenous administration of melatonin on the efferent activity of the adrenal nerve.

The effect of intravenous administration of melatonin on the efferent activity of the adrenal nerve was investigated in the rat. Intravenous infusion of 1 or 2 ng melatonin resulted in a decrease, and 10 or 20 ng or larger amount of melatonin caused an increase in the efferent activity of the adrenal nerve. The least effective dose for the suppressive activity of melatonin was 100 pg and the response is dose-related. Administration of either 1 ng or 10 ng of melatonin did not change the plasma glucose concentration until 30 min after the administration. Hepatic vagotomy eliminates the inhibitory effect of melatonin. These results suggest that melatonin sensors in the hepato-portal region and melatonin receptors in the SCN play important roles in the regulation of sympathetic outflow to the adrenal medulla.

Diurnal rhythms in plasma glucose, insulin, growth hormone and melatonin levels in fasted and hyperglycaemic rats.

As the data on circadian variations in plasma glucose or insulin are rather controversial due to interactions with food intake, this work attempted to characterize more precisely the daily rhythm of plasma glucose, insulin, growth hormone and melatonin in rats and to determine whether hormone rhythms occur independently of glucose variations. Plasma glucose, insulin, growth hormone and melatonin were investigated in rats infused for 24 h with a saline (fasted rats) or glucose solution (hyperglycaemic rats). Samples were taken every 2 h during a 24-h period. In fasted rats, both a glucose and an insulin diurnal rhythm were observed. The glucose rhythm was mainly characterized by an increase at the beginning of the night period, similar to that of the dawn phenomenon in humans but in opposite circumstances. Insulin rhythm appeared to be independent of glucose variations as it was still observed in rats maintained in stable hyperglycaemia (13.5 mM). A nycthemeral rhythmicity of growth hormone was observed in fasted and hyperglycaemic rats, with higher fluctuating values during the day period. As expected, plasma melatonin levels were characterized by a rise during the night period in both groups, although the rise was shifted in hyperglycaemic as compared to fasted rats. The main results of this study are the presence of an insulin secretion rhythmicity independent of glucose variations and the existence of a diurnal plasma glucose rhythm, with an increase occurring at the beginning of the night in fasted rats.

Substituted pyrido[3,2-b]oxazin-3(4H)-ones: synthesis and evaluation of antinociceptive activity.

A new series of N-substituted pyrido[3,2-b]oxazinones has been synthesized, pharmacologically evaluated, and compared with acetyl salicylic acid. The compound with the maximal combination of safety and analgesic efficacy was 4-¿3-[4-(4-fluorophenyl-1-piperazinyl)propyl]¿-2H-pyrido[3,2-b]-1, 4-oxazin-3(4H)-one (6c) with ED50 values of 12.5 mg/kg po (mouse: phenylquinone writhing test) and 27.8 mg/kg po (rat: acetic acid writhing test), respectively. Compound 6c proved to be more active than aspirin with a safety index of 5.1.

Lack of melatonin effects on insulin action in normal rats.

Despite a large number of studies, the role of melatonin on glucose metabolism is still controversial. The aim of the present work was to further characterize the effect of melatonin on insulin action during: i) intravenous insulin tolerance test performed at different times of the day using melatonin, a melatonin agonist (S-20304), a melatonin antagonist (S-20928) or in pinealectomized rats. ii) euglycemic-hyperinsulinemic clamp performed in melatonin agonist-treated as well as in pinealectomized rats. The fall in glycemia after the insulin injection was not significantly affected by melatonin and melatonin agonist (S-20304) at ZT6, nor by the melatonin antagonist (S-20928) at ZT13 nor in pinealectomized animals at ZT6 in comparison to their respective control. Acute treatment with S-20304 or chronic suppression of melatonin by pinealectomy did not significantly alter basal plasma glucose and insulin levels or hepatic glucose production and whole body or individual tissue glucose utilization. These data do not give support to a crucial role of melatonin on insulin action in normal rats.

6-aminoalkyloxazolo[4,5-b]pyridin-2(3H)-ones: synthesis and evaluation of antinoceptive activity.

Series of 6-aminoalkyloxazolo[4,5-b]pyridin-2(3H)-ones incorporating structural modifications both in the alkyl chain and basic amino moiety were tested for their analgesic efficacy and safety in mice and rats. Two of the synthesised compounds, 4a (3-methyl-6-[(4-phenyl-1-piperazinyl)methyl]oxazolo[4,5-b]pyridin-2(3H)-one) and 12a (3-methyl-6¿1-[2-(4-phenyl-1-piperazinyl)ethan-1-ol]¿oxazolo[4,5-b]pyridin- 2(3H)-one) were found to be more potent than aspirin with ED50 values of 26 (16.1-42.4) and 15.5 (11.4-21.2) mg/kg po (mouse, phenylquinone writhing test) respectively and 6 (3.1-9.8) and 5.5 (3.5-8.8) mg/kg po (rat, acetic acid writhing test). Compounds 4a and 12a proved to be potent nonopioid nonantiinflammatory analgesics but unfortunately have sedative properties at relatively low doses (respectively 64 and 16 mg/kg po, mice).

Melatonin suppresses hyperglycemia caused by intracerebroventricular injection of 2-deoxy-D-glucose in rats.

To elucidate the role of melatonin (MT), we examined the effects of intracranial injection of MT and an MT-antagonist (S20928) on the hyperglycemic response to intracranial injection of 2-deoxy-D-glucose (2DG) in rats. The hyperglycemic and hyperglucagonemic responses caused by intracerebroventricular injection of 2DG were inhibited by intracerebroventricular co-injection of MT, but enhanced by co-injection of the MT-antagonist. Intraperitoneal injection of MT also inhibited the hyperglycemic response, though the inhibition seemed to be less than that after intracranial injection of MT. These results suggest that MT plays an endogenously suppressive role in the hyperglycemia caused by 2DG, possibly through a brain site.

Novel indole-2-carboxamide and cycloalkeno[1,2-b]indole derivatives. Structure-activity relationships for high inhibition of human LDL peroxidation.

Series of indole-2-carboxamide and cycloalkeno[1,2-b]indole derivatives were synthesized and evaluated in order to determine the necessary structural requirements for a high inhibition of human LDL copper-induced peroxidation. Various modulations were systematically performed on the indole and cycloalkeno[1,2-b]indole nuclei as well as on the carboxamide moiety. The best compounds (3c, 3e, 7c, 7f, 7h, 7g, and 7o) are between 5 and 30 times more active than probucol itself. Two of these compounds (3c and 7o) were selected for complementary in vitro and in vivo investigations, which have shown additional properties of interest for the treatment and the prevention of atherosclerosis injuries. Compound 3c was found to have some antiinflammatory properties while compound 7o was proved to protect endothelial cells from the direct cytotoxicity of oxidized LDL with some additional calcium channel blocking properties.

Oxidative degradation of cholesteryl esters in low-density lipoproteins: analysis by liquid chromatography-light scattering and protection by a new synthetic antioxidant, S20478.

Cholesteryl esters in the hydrophobic core of low-density lipoprotein (LDL) particles constitute a major molecular target during copper-mediated oxidation. To facilitate the rapid analysis and quantitation of the oxidative degradation of LDL cholesteryl esters, we describe a new approach based on light scattering detection following separation by HPLC. We have applied this approach to the evaluation of the protective capacity of a new synthetic antioxidant, S20478, during oxidation of LDL in the presence of copper ions. HPLC separation of cholesterol and the four major molecular species of cholesteryl esters (C16:0, C18:1, C18:2 and C20:4) of LDL was achieved in a single run of 20 min with high sensitivity (50 ng) and low background. Time course studies of the oxidative modification of LDL (ratio LDL protein: copper, 100 micrograms/mL: 1 microM) revealed that the content of unsaturated cholesteryl esters (C20:4 and C18:2) decreased (-30% and -15%, respectively) within 90 min of copper-mediated oxidation, while only minor degradation (up to 15%) of monounsaturated (C18:1) and saturated (C16:0) esters occurred. At 24 hours of oxidation, only traces (< 5%) of the C20:4 and C18:2 esters were detectable; whereas 52% of the C18:1 ester remained (P < 0.01). Of the saturated esters, only minor proportions (35% or less) underwent oxidative modification. In addition, some 81% of free cholesterol was conserved as the native sterol. The synthetic antioxidant, S20478 (50 microM) was capable of inhibiting the initiation and the propagation of copper-mediated LDL oxidation as determined by the time- and dose-dependent inhibition of the formation of conjugated dienes and thiobarbituric acid-reactive substances, as well as the conservation of the net electrical charge of LDL; indeed S20478 conserved cholesteryl esters in their native form up to 24 hours. However, after prolonged exposure to copper ions (48 hours), only 47% of the unsaturated esters remained (C18:2, P < 0.05). Nonetheless, S20478 (10 microM) was more efficient in inhibiting copper-mediated LDL oxidation as compared to probucol at the same concentration. These findings suggest that S20478 may be of potential interest in a new antioxidant approach to therapeutic stabilisation and regression of atherosclerotic plaques. Moreover, this method should prove useful in the assessment of the integrity of native LDL, and provides a new chemical marker of the degree of LDL oxidation.

N-substituted aminohydroxypyridines as potential non-opioid analgesic agents.

A series of new N-substituted aminohydroxypyridines have been synthesized, pharmacologically evaluated and compared with their N-substituted oxazolopyridone analogs. The compound with the maximal combination of safety and analgesic efficacy was 3-[2-[4-(4-fluorophenyl)-1-piperazinyl]ethyl]amino-2-hydroxypyridine (compound 10a), with ED50 values 0.4 mg kg-1 po (mouse: phenylquinone writhing test) and 0.5 mg kg-1 po (rat: acetic acid writhing test). Compound 10a possesses a potent non-opioid antinociceptive activity with moderate anti-inflammatory properties.

N-substituted oxazolo[5,4-b]pyridin-2(1H)-ones: a new class of non-opiate antinociceptive agents.

A series of 1-(aminoalkyl)- and 1-[(4-aryl-1-piperazinyl)alkyl]oxazolo[5,4-b]pyridin-2(1H)-one derivatives of oxazolo[5,4-b]pyridin-2(1H)-one, incorporating modifications to the length of the alkyl side chain and to the amino or 4-aryl-1-piperazinyl substituents, were tested for safety and analgesic efficacy in mice and rats. Some compounds with 4-(substituted or nonsubstituted phenyl)-1-piperazinyl substituents and a 3-4-carbon alkyl side chain had significantly greater analgesic activity than that of the oxazolo[4,5-b]pyridin-2(3H)-one analogs. To reduce the metabolic N-dealkylation of the piperazine observed in our previous work on oxazolo[4,5-b]-pyridin-2(3H)-ones, analogs of the most active compounds with steric hindrance on the alkyl side chain were prepared and tested. The compound with the maximal combination of safety and analgesic efficacy was 1-[[4-(4-fluorophenyl)-1-piperazinyl]propyl]oxazolo[5,4-b]pyridin- 2(1H)-one (compound 3b), with ED50 values of 5.6 mg/kg po (mouse, phenylquinone writhing test) and 0.5 mg/kg po (rat, acetic acid writhing test). Compound 3b is a potent, rapid-acting, non-opioid, nonantiinflammatory analgesic with low acute toxicity and sustained effect.

[First intention treatment of arterial hypertension. Effectiveness and safety of perindopril]. / Traitement de première intention de l'hypertension artérielle. Efficacité et sécurité d'emploi du perindopril.

Inhibitors of the angiotensin conversion enzyme (ICE) represent an effective and well tolerated therapeutic class, for the treatment of arterial hypertension. The antihypertensive efficacy or perindopril, an ICE active in one single daily dose, is at least equal to that of reference antihypertensive drugs administered at usual doses. The possibility of occurrence of some side-effects while using ICE, has resulted in a particular attention in evaluating the safety of perindopril. First, the renal function was monitored. During essential hypertension, no significant variation of the creatininemia was observed with long-term administration of the drug (12 months). In elderly hypertensive patients or patients with chronic renal insufficiency, the glomerular filtration is also preserved, except during rare occurrences of decreased creatinine clearance, especially after adjunction of hydrochlorothiazide. A discrete elevation of the kaliemia without clinical significance is observed when perindopril is used as a single drug. Reports of symptomatic hypotension with perindopril are rare (0.2%), even in situations of water and sodium depletion. Among other side-effects of ICE, cough, more recent, was thoroughly investigated. Its frequency was determined during a double blind trial comparing perindopril (1.2%) with captopril (2.4%). It was also evaluated during a long-term study concerning 632 hypertensive patients (391 patients treated in 1 year); its incidence is the 2.9 p. cent and it resulted in discontinuation of the treatment in 8 cases. In this study, 36 patients interrupted the treatment prematurily because of an adverse reaction (5.7%). Finally no harmful drug interaction was reported. The favorable tolerance profile of perindopril is combined with a beneficial effect on the functional and structural modifications of the heart and large vessels related to hypertension.

[Ambulatory registration of arterial pressure during treatment with perindopril. Effects on systolic pressure and hemodynamic implications]. / Enregistrement ambulatoire de la pression artérielle lors d'un traitement par le perindopril. Effets sur la pression systolique et implications hémodynamiques.

The effects of perindopril on the 24-hour arterial pressure levels were evaluated by ambulatory recording in 21 patients (mean age 48 +/- 2 years) with mild to moderate hypertension. At the end of a 3 months treatment with perindopril (4 to 8 mg per day in one dose), comparison by variance analysis of the mean values of arterial pressure over 24 hours before and after treatment showed a significant decrease of SAP (from 144 +/- 3 to 133 +/- 3 mmHg, p less than 0.01) and DAP (from 95 +/- 2 to 87 +/- 2 mmHg, p less than 0.01). The fall in arterial pressures was more pronounced during day-time (7 a.m. to 10 p.m.) than at night. Particular attention was paid to the reduction of systolic pressure owing to its relation with arterial compliance. There was a significant correlation between ambulatory recordings of SAP and DAP before and after treatment (r = 0.82 and 0.76 respectively, p less than 0.001). Calculation and comparison of the corresponding regression slope showed that for any given level of DAP, SAP was lower after than before treatment. This effect is related to the increase of arterial compliance observed after treatment with perindopril, as already reported by other authors.