Direct protective effects of poly-unsaturated fatty acids, DHA and EPA, against activation of cardiac late sodium current

Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic and eicosapentaenoic acids (DHA, EPA) exert ischemic anti-arrhythmic effects. However, their mechanism of action remains unknown. The present study was designed to investigate their potential effect on the regulation of the late sodium current as the basis for their ischemic anti-arrhythmic activity. Human isoforms of wild-type SCN5A and DeltaKPQ-mutated cardiac sodium channels were stably transfected in HEK 293 cells and, the resulting currents were recorded using the patch clamp technique in whole cell configuration. In addition to their effect to inhibit peak I(Na), acute application of DHA and EPA blocked veratridine-induced late sodium current (late I(Na-Verat)) in a concentration--dependent manner with IC(50) values of 2.1 +/- 0.5 microM and 5.2 +/- 0.8 microM,for DHA and EPA, respectively. Channels availability was reduced, resulting in a significant leftward shift of the steadystate inactivation curve by -10.0 +/- 2.1 mV and -8.5 +/- 0.2 mV for DHA and EPA, respectively. Similar inhibitory effects of DHA and EPA were also observed on late I(Na-KPQ). In addition to their role as blocking agents of peak I(Na), DHA and EPA reduced human late I(Na). These results could explain the antiarrhythmic properties of DHA and EPA during ischemia or following ischemia-reperfusion.

Direct Effect of F12511, A Systemic Inhibitor of Acyl-CoA Cholesterol Acyltransferase on Bovine Aortic Endothelial Cells

F12511(S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-alpha-phenylacetanilide (F12511) is a new Acyl-CoA cholesterol acyltransferase (ACAT) inhibitor that not only reduces the plasma cholesterol levels but also has anti-atherosclerotic actions in animals models. The study's aim was to analyze if F12511 may directly modify the ability of tumor necrosis factor--alpha (TNF-alpha)-incubated bovine aortic endothelial cells (BAEC) to express endothelial nitric oxide synthase (eNOS) protein and inflammatory-related proteins such as platelet endothelial cell adhesion molecule (PECAM) and CD40 ligand (CD40L). The addition of increasing concentrations of F12511 (10 to 10 mol/L) failed to modify the level of eNOS protein expressed in control BAEC. TNF-alpha (10 ng/mL) reduced the expression of eNOS protein. In TNF-alpha--incubated BAEC, F12511 protected eNOS expression in a concentration-dependent manner. TNF-alpha stimulated the expression of both CD40L and PECAM in cultured BAEC. F12511 (10 mol/L) failed to modify the expression of CD40L and PECAM in control and TNF-alpha-incubated BAEC. Reverse transcriptase polymerase chain reaction showed a marked expression of the ACAT-2 isoform and absent of expression of the ACAT-1 isoform in BAEC. The presence of ACAT-2 isoform in BAEC was further confirmed by Western blot. F12511 failed to modify the expression of the proinflammatory associated proteins PECAM and CD40L in the endothelium but protected eNOS expression in the endothelial cells exposed to inflammatory conditions.

Regulation of the scavenger receptor BI and the LDL receptor by activators of aldosterone production, angiotensin II and PMA, in the human NCI-H295R adrenocortical cell line

In human adrenal cells, cholesterol for steroidogenesis is derived from both high-density lipoproteins (HDL) via the Scavenger Receptor Class B Type I (SR-BI) and low-density lipoproteins (LDL) via the LDL receptor pathway. We have previously shown that, in the human adrenocortical carcinoma cell line, NCI-H295R, SR-BI and LDL receptor expression and steroidogenesis are coordinately regulated by activators of protein kinase A (PKA) leading to glucocorticoid synthesis. In the present study, we studied whether SR-BI and LDL receptor expression are regulated by activators of the protein kinase C (PKC) signaling pathway, such as angiotensin II, which stimulate mineralocorticoid synthesis. First, it is shown that, in NCI-H295R cells, aldosterone synthesis is stimulated by a phorbol ester (phorbol-12-myristate-13 acetate, PMA), a potent PKC activator. Northern blot analysis indicated that both angiotensin II and PMA stimulated SR-BI expression in a time-dependent manner. LDL receptor expression is slightly stimulated by PMA. The induction of SR-BI gene expression occurs at the transcriptional level, via an activation of the human SR-BI promoter, as shown by transient transfection experiments. Finally, SR-BI protein level was increased in angiotensin II- and PMA-stimulated cells, resulting in higher lipoprotein binding and specific cholesteryl ester (CE) uptake from HDL, as well from LDL after angiotensin II and PMA stimulation.

Anti-atherosclerotic properties of the acyl-coenzyme A:cholesterol acyltransferase inhibitor F 12511 in casein-fed New Zealand rabbits

SUMMARY

The anti-atherosclerotic properties of F 12511, a novel acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibitor, were studied in rabbits that were fed a cholesterol-free casein-rich diet and developed endogenous hypercholesterolemia and fibrofatty preatheroma lesions. After 6 weeks of casein feeding, an endothelial abrasion was performed in the abdominal aorta; at week 8, a control group was maintained on this diet while F 12511 (8 mg/kg/d) was administered as a diet admixture for the subsequent 24 weeks. Total plasma cholesterol level rose to 250-300 mg/dl in both groups before starting the treatment; F 12511 time-dependently reduced total plasma cholesterol by 50%, and also decreased by 50% the incidence of lesions and macrophage accumulation in uninjured aorta (thoracic arch, celiac bifurcation). Residual lesions in the treated group were characterized by few macrophages, essentially under the endothelium, and by a larger content of smooth muscle cells. Quantitative image analysis of serial sections of mechanically injured abdominal aorta revealed a 20% surface covered by preatheroma lesions in the placebo group; F 12511 significantly reduced this surface. These data suggest that the combination of endogenous hypercholesterolemia with endothelial injury in the rabbit may offer a useful model to study atherosclerosis; lipid lowering by F 12511 reduces the incidence of vascular lesions and macrophage infiltration and may reinforce the fibrous skeleton of the atheroma.

Pharmacological analysis of wild-type alpha, gamma and delta subtypes of the human peroxisome proliferator-activated receptor

Three distinct peroxisome proliferator-activated receptor (PPAR) cDNAs were isolated from human brain RNA. Whereas the PPARdelta subtype perfectly matched the amino acid sequences reported in the Genbank database, several differences were found for the PPARalpha (Lys(123)Met, Ala(268)Val, Gly(296)Ala and Val(444)Ala) and PPARgamma2 (Met(8)Ile, Pro(9)Ala, Met(186)Ile, Pro(187)Ala and the deletion of a Gln(213) residue) subtypes. A pharmacological analysis was undertaken by co-expressing each PPAR subtype with a reporter plasmid containing a luciferase gene under the transcriptional control of a synthetic, triplicated PPAR response element in either HepG2 or Cos-7 cells. Whereas fenofibrate unselectively activated the PPARalpha and PPARdelta subtypes, the related BM-17.0744 compound was more potent and selective for PPARalpha. The thiazolidine dione derivatives rosiglitazone and pioglitazone were potent and selective PPARgamma2 agonists. L-165041, reported as a selective and potent PPARdelta ligand, displayed in this specified transactivation system, apart from its highly efficacious PPARdelta agonist activity, partial and full agonism at, respectively, PPARalpha and PPARgamma2 subtypes. In conclusion, transcriptional control of a luciferase gene by wild-type PPAR subtypes provides powerful recombinant assays to evaluate ligand's efficacy at these nuclear receptors.

PPARalpha and PPARdelta activators inhibit cytokine-induced nuclear translocation of NF-kappaB and expression of VCAM-1 in EAhy926 endothelial cells

Endothelium injury is a primary event in atherogenesis, which is followed by monocyte infiltration, macrophage differentiation, and smooth muscle cell migration. Peroxisome proliferator-activated receptors (PPARs) are transcription factors now recognized as important mediators in the inflammatory response. The aim of this study was to develop a human endothelial model to evaluate anti-inflammatory properties of PPAR activators. PPAR proteins (alpha, delta and gamma) are expressed in EAhy926 endothelial cells (ECs). Pirinixic acid (Wy-14643), fenofibrate, fenofibric acid, the Merck ligand PPARdelta activator L-165041, 15-deoxy-Delta(12,14)-prostaglandin J2, but not rosiglitazone (BRL-49653) inhibited the induced expression of vascular cell adhesion molecule-1 (VCAM-1), as measured by enzyme linked immunosorbent assay (ELISA), and monocyte binding to activated-EAhy926 cells. The PPARdelta activator L-165041 had the greatest potency to reduce cytokine-induced monocyte chemotactic protein-1 (MCP-1) secretion. All PPAR activators tested which impaired VCAM-1 expression reduced significantly nuclear p65 amount. These results show that EAhy926 endothelial cells are an adequate tool to substantiate and characterize inflammatory impacts of PPAR activators.

Overexpression of SR-BI in hamsters treated with a novel ACAT inhibitor (F12511)

The effect of a novel acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor on cholesterol metabolism was studied in hamsters. Oral administration of F12511 (10 mg/kg/d) for 4 weeks produced a decrease in dietary cholesterol absorption (-18%) and in the liver concentration of esterified cholesterol (-75%), as compared with control values in untreated hamsters. While the hepatic expression of LDLr was unchanged by the treatment, that of SR-BI was increased (+142%), which suggests that the hepatic expression of SR-BI could be upregulated by a depletion of the cholesterol stores, due to ACAT inhibition. This SR-BI overexpression, however, did not induce a fall in plasma HDL-cholesterol concentration, in contrast with previous reports in transgenic mice overexpressing SR-BI at a higher extent.

Effects of F2833 on cholesterol metabolism in the genetically hyperlipidemic rat

The effects of the new hypolipidemic agent, F2833 or (chloro 2' (1-1') biphenyl-4)-2 propanol-2, on cholesterol metabolism were studied in genetically hyperlipidemic rats (RICO). Cholesterolemia decreased after 2 days of treatment to 60% of its initial value (1.20+/-0.10 g/l vs. 1.99+/-0.08, P < 0.001) and then stabilised within 10 days. This hypocholesterolemic action was effective for as long as 3 months. Concerning the different classes of lipoproteins, a significant drop was observed in HDL (high density lipoproteins) (25%, 0.49 +/- 0.02 g/l vs. 0.66 +/- 0.007, P < 0.01) and particularly in LDL (low density lipoproteins) (70%, 0.30 +/- 0.04 g/l vs. 0.92 +/- 0.05, P < 0.001). Whole body cholesterol showed a higher fractional catabolic rate (0.25 +/- 0.02 vs. 0.17 +/- 0.005 day(-1), P < 0.01) together with an increased cholesterol synthesis (60 +/- 5 vs. 36 +/- 4 mg/day, P < 0.01). LDL kinetics showed that the decrease in these lipoproteins is essentially caused by an increase in the fractional catabolic rate (10.6 +/-0.1%/h vs. 5.2 +/- 0.1%/h, P < 0.001) and by a lesser decrease in the LDL production rate. This cholesterol metabolic profile created by treatment suggests an effect through stimulation of cholesterol output (biliary cholesterol elimination or cholesterol transformation into bile acids).

F 12511, a novel ACAT inhibitor, and atorvastatin regulate endogenous hypercholesterolemia in a synergistic manner in New Zealand rabbits fed a casein-enriched diet

F 12511, a novel ACAT inhibitor, lowers plasma cholesterol levels in New Zealand rabbits fed a cholesterol-free casein-rich diet. In rabbits endogenous hypercholesterolemia pre-established for 8 weeks was used to compare treatments with F 12511 and atorvastatin for a further 8-week period, and to determine whether both agents act synergistically. F 12511 appears to be 3-4-fold more potent than atorvastatin in reducing total plasma cholesterol (active doses ranging from 0.16 to 2.5 and from 1.25 to 10 mg/kg per day, respectively) while the hypocholesterolemic efficacy of both compounds at 2.5 mg/kg per day amounted to 70 and 45%, respectively. A reduction by as much as 75% of esterified cholesterol in liver mediated by F 12511 could account for the decrease of plasma VLDL, LDL and apo B-100, whereas a reduction of the LDL production rate has been described as the main mechanism underlying the atorvastatin effect. F 12511 modified adrenal cholesterol balance only at the largest dose studied. In a further experiment the co-administration of threshold doses of F 12511 and atorvastatin (0.63 and 1.25 mg/kg per day, respectively) lowered plasma total cholesterol and apo B-100 containing lipoproteins to a greater extent and more rapidly than either agent alone. In the liver a decrease by atorvastatin in free cholesterol substrate for ACAT may amplify the effect of F 12511 on cholesteryl ester content leading to a diminution, in at least an additive manner, of the assembly and secretion of atherogenic lipoproteins in New Zealand rabbits which have developed an endogenous hypercholesterolemia. Thus, the combination of the ACAT inhibitor F 12511 with atorvastatin can represent a better approach than either agent alone to regulate lipoprotein metabolism in certain pathophysiological situations.

Lack of toxic effects of F 12511, a novel potent inhibitor of acyl-coenzyme A: cholesterol O-acyltransferase, on human adrenocortical cells in culture

Inhibition of acyl-coenzyme A: cholesterol O-acyltransferase (EC 2.3.1.26; ACAT) reduces intracellular cholesteryl esters that are substrates for steroidogenesis in adrenal cells. The adrenal side effects of ACAT inhibitors remain a key point for their development as antiatherosclerotic agents. The aim of this study was to characterize the effects of a novel and powerful ACAT inhibitor, F 12511 (S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-phenylacetanilide, on the NCI-H295R cell line, which has functional properties comparable to those of normal human adrenal cells. F 12511 incubated with cultured cells for 4-72 hr strongly inhibited cholesteryl oleate formation. The concentrations required to produce 50% inhibition (IC50) values) ranged from 20 to 50 nM; in the presence of low-density lipoproteins (LDL), this effect was paralleled by a decrease in cholesteryl ester mass and an increase in intracellular free cholesterol. At concentrations 100-fold larger than the IC(50) value for up to 48 hr, F 12511 reduced neither the basal release of cortisol and aldosterone nor the production of cortisol stimulated by forskolin. F 12511 did not modify the mRNA levels of the steroidogenic enzyme genes cytochrome P450 cholesterol side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17), or cytochrome P450 21-hydroxylase (P450c21) or those of the LDL receptor and high-density lipoprotein scavenger receptor class B, type I (SR-BI) genes, either in the presence or absence of adenosine 3',5'-cyclic monophosphate stimulation for 24 hr. Exposure to F 12511 at up to 3 microM for 24 or 48 hr did not result in significant change in morphological and ultrastructural characteristics; the cytoplasm contained large numbers of mitochondria with intact crystae, and the same typical features of secretory activity were observed in NCI-H295R control cells. Exposure to 3 microM of F 12511 for 96 hr also did not affect cell viability. These data demonstrate that reduction of the substrate for steroidogenesis by the ACAT inhibitor F 12511 impairs neither steroid production nor transcription of genes involved in steroidogenesis and lipoprotein uptake in the pluripotent human adrenal cell line NCI-H295R.

Pharmacological profile of F 12511, (S)-2',3', 5'-trimethyl-4'-hydroxy-alpha-dodecylthioacetanilide a powerful and systemic acylcoenzyme A: cholesterol acyltransferase inhibitor

The pharmacological profile of F 12511 (S)-2',3', 5'-trimethyl-4'-hydroxy-alpha-dodecylthio-phenylacetanilide, a new inhibitor of acyl-CoA: cholesterol acyltransferase (EC 2.3.1.26; ACAT), was evaluated by using different in vitro and in vivo models. In vitro, F 12511 was shown to be a highly potent inhibitor of ACAT activity in microsomal preparations from various animal species as well as of cholesterol esterification in relevant human cell lines in culture. The concentrations of F 12511 required to produce 50% inhibition of ACAT activity (IC(50) values) in microsomal preparations ranged from 41nM for hypercholesterolemic rabbit intestine to 223 nM for normocholesterolemic hamster liver. In whole cell assays using hepatic (Hep G2), intestinal (CaCo-2) and macrophagic (THP-1) cell lines, F 12511 inhibited ACAT activity with IC(50) values of 3, 7, and 71 nM, respectively. In vivo, orally administered F 12511 displayed high potency and efficacy as an antihypercholesterolemic compound in different cholesterol-fed animals (rat, guinea-pig, rabbit). For instance, in guinea-pigs the dose required to reduce plasma cholesterol levels by 30% (ED(30) value) was 0.008 mg.kg(-1.) In rabbits, an animal species prone to atherosclerosis, the hypocholesterolemic effect was accompanied by a dose-related reduction in the incidence of aortic fatty streaks that reached asymptote at 2.5 mg.kg(-1) and by an improvement of the impaired endothelial function. When given orally to chow-fed hamsters, F 12511 elicited a dose-related decrease in plasma cholesterol from 9% at 0.63 mg.kg(-1) up to 31% at 40 mg.kg(-1) associated with a preferential reduction in atherogenic lipoproteins, very low density lipoproteins (VLDL) and low density lipoproteins (LDL). Moreover, in the same dose range, F 12511 decreased hepatic cholesteryl ester concentrations and reduced liver ex vivo ACAT activity. By using a bioassay, ACAT inhibitory activity was present in plasma of treated hamsters 1 hr after oral administration of F 12511. Hence, the results in chow-fed hamsters are consistent with systemic and direct hepatic effects of F 12511. In guinea-pigs, an adreno-sensitive species, F 12511 did not impair the adrenal function (adrenocorticotrophic hormone challenge) at doses up to 2.5 mg.kg(-1,) far higher than those eliciting hypocholesterolemic effects in the same species. In conclusion, the results suggest that F 12511, a powerful and systemic ACAT inhibitor, constitutes an appropriate tool to determine whether the inhibition of ACAT constitutes an effective therapy for the treatment of hypercholesterolemia and of atherosclerosis in man.

Immunological quantitation and localization of ACAT-1 and ACAT-2 in human liver and small intestine

By using specific anti-ACAT-1 antibodies in immunodepletion studies, we previously found that ACAT-1, a 50-kDa protein, plays a major catalytic role in the adult human liver, adrenal glands, macrophages, and kidneys but not in the intestine. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in the intestine may be largely derived from a different ACAT protein. To test this hypothesis, we produced specific polyclonal anti-ACAT-2 antibodies that quantitatively immunodepleted human ACAT-2, a 46-kDa protein expressed in Chinese hamster ovary cells. In hepatocyte-like HepG2 cells, ACAT-1 comprises 85-90% of the total ACAT activity, with the remainder attributed to ACAT-2. In adult intestines, most of the ACAT activity can be immunodepleted by anti-ACAT-2. ACAT-1 and ACAT-2 do not form hetero-oligomeric complexes. In differentiating intestinal enterocyte-like Caco-2 cells, ACAT-2 protein content increases by 5-10-fold in 6 days, whereas ACAT-1 protein content remains relatively constant. In the small intestine, ACAT-2 is concentrated at the apices of the villi, whereas ACAT-1 is uniformly distributed along the villus-crypt axis. In the human liver, ACAT-1 is present in both fetal and adult hepatocytes. In contrast, ACAT-2 is evident in fetal but not adult hepatocytes. Our results collectively suggest that in humans, ACAT-2 performs significant catalytic roles in the fetal liver and in intestinal enterocytes.

Sulfonamide derivatives of benzylamine block cholesterol biosynthesis in HepG2 cells: a new type of potent squalene epoxidase inhibitors

Sulfonamide derivatives of ene-yne benzylamine 1 have been prepared and identified as a new class of potent SE inhibitors having demonstrated activity in HepG2 cells as cholesterol biosynthesis inhibitors.

Biochemical changes and morphological alterations of liver and kidney in hamsters after administration of the HMG-coenzyme A reductase inhibitor, simvastatin: prevention and reversibility by mevalonate

The present study analyses the effects of simvastatin, a specific inhibitor of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA reductase) in male Syrian hamsters fed a standard diet or a diet supplemented with 0.12% cholesterol and 20% coconut oil. In hamsters fed the standard diet, gastric administration of simvastatin (10 mg/kg/day) during 12 days was found to be lethal and to have hepatotoxic and nephrotoxic effects. This toxicity was exacerbated in hamsters fed a hyperlipidaemic diet and was preceded by a progressive anorexia and loss of body weight. Marked elevations in serum aspartate and alanine aminotransferase activities were associated with the organ lesions. All elevated biochemical changes and morphological alterations were prevented or reversed by coadministration of mevalonate, the product of the HMG-CoA reductase. It is suggested that the dramatic effect of simvastatin could result from depletion of a non-sterol metabolite of mevalonate in spite of a lack of protective effects of farnesol and geranylgeraniol in the following study. The toxicity of simvastatin could indeed result from the low basal activity of HMG-CoA reductase in hamster liver coupled with a prolonged inhibition of mevalonate synthesis.

(Aryloxy)methylsilane derivatives as new cholesterol biosynthesis inhibitors: synthesis and hypocholesterolemic activity of a new class of squalene epoxidase inhibitors

A series of 3-substituted (aryloxy)silane derivatives of benzylamine (4, 4', or 4") was synthesized and evaluated for hypocholesterolemic activity. Most of the new silane derivatives were identified as potent inhibitors of pig liver squalene epoxidase with IC50 values in the submicromolar range. In vitro inhibition of cholesterol biosynthesis in Hep-G2 cells was observed with a very good potency for the ene-yne derivatives 4a, 4i, 4n, 4q, and 4u as well as for the yne-yne compound 4". In vivo, 4i, 4u, 4', and 4" were found to decrease cholesterol biosynthesis in rats upon oral administration with ED50 values in the range of 2-7 mg/kg. Therefore, these new (aryloxy)methylsilane derivatives of benzylamine represent a new class of potent squalene epoxidase inhibitors with promising hypocholesterolemic properties.

Intrinsic activity of the non-prostanoid thromboxane A2 receptor antagonist, daltroban (BM 13,505), in human platelets in vitro and in the rat vasculature in vivo

1. We evaluated the effects of daltroban on (i) human platelet shape change and aggregation in vitro, and (ii) mean systemic and pulmonary arterial pressures (MAP and MPAP, respectively) as well as haematocrit, in anaesthetized, open-chest Sprague-Dawley rats, compared with those of a chemically distinct prostanoid thromboxane A2 (TxA2) receptor antagonist, SQ 29,548, and agonist, U-46619. 2. In human platelets in vitro, daltroban (10 nM-100 microM; n = 6 per group) concentration-dependently induced shape change, attaining at 50 microM, a maximum amplitude of 0.83 +/- 0.09 mV representing 46.4 +/- 4.8% of that evoked by U-46619 (1.78 +/- 0.20 mV at 0.2 microM; n = 9); and inhibited U-46619-induced platelet aggregation with an IC50 of 77 (41-161)nM. SQ 29,548 (10 nM-100 microM; n = 6 per group) failed to evoke any platelet shape change, but potently inhibited U-46619-induced platelet aggregation with an IC50 < 10 nM. 3. In anaesthetized rats in vivo, daltroban (10-2500 micrograms kg-1, i.v. infused over 2 min; n = 4-8 per group) produced a bell-shaped dose-response curve for MPAP and haematocrit, and evoked maximal increases of 12.7 +/- 2.1 mmHg and 5.8 +/- 1.5% at 80 micrograms kg-1 (n = 6) and 630 micrograms kg-1 (n = 8), respectively (both P < 0.05) with ED50s of 20 (16-29) and 217 (129-331) micrograms kg-1, respectively. By comparison, U-46619(0.16-20 microg kg-1, i.v.), induced dose-dependent increases in MPAP and haematocrit (25.4 +/- 1.0 mmHg and 16.1 +/- 2.9% at the highest dose; n = 12, both P<0.01), with ED50s of 1.8 (1.3-2.5) and 3.9(3.5- 5.4) microg kg- 1, respectively. Daltroban dose-dependently increased MAP with a maximum amplitude of 42.2 +/- 4.4 mmHg at a dose of 80 microg kg-1 [ED50 = 94 (64-125) microg kg-1], similar to that induced by U-46619 (41.3 +/- 9.6 mmHg) at a dose of 0.63 microg kg-1 [ED50= 0.22 (0.13-0.24) microg kg-1]. SQ 29,548(10-2500 microg kg-1, i.v.; n =4 per group) failed to modify significantly any of these parameters.4. Our results clearly demonstrate that daltroban, in a similar manner to the TxA2 analogue, U-46619,but unlike the TxA2 receptor antagonist, SQ 29,548, exhibits significant intrinsic activity in human platelets in vitro and in the rat vasculature in vivo, possibly through TxA2 receptor activation.

Effects of the new hypolipidemic agent F 2833 on plasma lipoprotein levels in normal and hyperlipidemic hamsters

The present study analyzed the effects of the new hypolipidemic agent, F 2833, in male golden Syrian hamsters fed a standard diet or a diet supplemented with 0.06% cholesterol and 20% coconut oil. F 2833 did not detectably modify the blood lipid parameters studied in hamsters receiving the standard diet. After 28 days, the hyperlipidemic diet in untreated animals significantly increased plasma cholesterol, triglycerides and phospholipids (by 91, 138 and 61%, respectively) and in the different lipoprotein classes. Treatment with F 2833 (150 and 300 mg/kg/day) caused a dose-dependent reduction of the blood lipid parameters studied. At the higher dose, this decrease was significant for cholesterol (27%), triglycerides (48%) and plasma phospholipids (27%). With regard to the different classes of lipoproteins, a significant drop in cholesterol was observed in VLDL (38%) and LDL (29%), while that in HDL (22%) was not significant. Triglycerides were significantly lowered in all lipoprotein classes with a more pronounced effect in the VLDL pool (53%). F 2833 thus decreased plasma lipids in hamsters that were fed on hyperlipidemic diet to normal values observed in animals fed a standard diet. These results confirm and extend findings previously obtained in other animal species in which F 2833 was also shown to be an effective hypolipidemic drug.

Synthesis and pharmacological study of new N-methyl 1,2,3-triazole derivatives of 2-cyano chromones

The reaction of various 2-cyano chromones with diazomethane generated a series of 21 N-methyl triazoles, with a benzopyrone moiety and divided into three isomeric groups. The anti-inflammatory, psychotropic and anti-allergic effects of these new compounds were evaluated. The results obtained did not confirm their expected potentialities.

Antiallergic and anti-inflammatory action of tioxamast in rats. II. Anti-inflammatory action in vivo

Tioxamast is an antiallergic drug that inhibits anaphylaxis in various models in rats, and it inhibits the release and synthesis of certain mediators of inflammation [see Tarayre et al., this issue]. Here we report that the drug also has an anti-inflammatory effect in vivo in various nonimmunological models in rats. It reduces zymosan-induced inflammation in the paw and pleural cavity, starting at doses from 1.5625 to 3.125 mg/kg given intraperitoneally. In pleurisy, tioxamast lowers the concentration of leukotriene B4 (LTB4) in the exudate, at doses from 50 mg/kg i.p. Also, at doses from 12.5 mg/kg i.p., the compound reduced PAF-acether-induced pleurisy and the concentrations of LTB4 and peptidoleukotrienes in the exudate. An anti-inflammatory action against carrageenin-induced edema of the paw was seen only at doses of 50 mg/kg i.p. or more. The anti-inflammatory and antiallergic effect of tioxamast makes it a potentially useful drug in the treatment of allergies in humans.

Antiallergic and anti-inflammatory action of tioxamast in rats. I. Antiallergic activity in vivo and in vitro

Tioxamast (F 1865) is an antiallergic drug that, administered systemically, reduces anaphylaxis in various models in rats. This action is due mainly to the inhibition of the synthesis and release of certain mediators. Orally or intraduodenally administered tioxamast inhibits IgE-dependent passive cutaneous anaphylaxis (ED50 = 0.8 mg/kg), IgE-dependent passive pulmonary anaphylaxis (ED50 = 0.5 mg/kg), and IgG-dependent passive cutaneous anaphylaxis (ED50 = 0.6 mg/kg). It has little or not effect on the increase of cutaneous capillary permeability induced by various mediators. In IgE-dependent passive peritoneal anaphylaxis in rats, tioxamast reduces the release of histamine (IC50 = 0.024 micrograms/ml) and of beta-glucuronidase (IC50 = 0.102 micrograms/ml). Also, histamine release is inhibited in IgG-dependent peritoneal anaphylaxis (IC50 = 0.103 micrograms/ml). The antiallergic compound has less effect on the release of histamine induced by the compound 48/80 in the peritoneal cavity of rats (IC50 = 1.67 micrograms/ml). Tioxamast inhibits the synthesis in vitro of leukotriene B4 (LTB4) by peritoneal neutrophils from rats stimulated by A23187 (IC50 = 8.88 micrograms/ml). At higher tioxamast concentrations, metabolites of the cyclo-oxygenase pathway are inhibited at concentrations of the same order of magnitude as those that inhibit Naja naja phospholipase A2 (IC50 = 144 micrograms/ml). Tioxamast also reduces the production of free radicals by leukocytes from the pleural cavity of rats which had phagocytosed opsonized zymosan (IC50 = 5.21 micrograms/ml).

Pharmacological studies on zymosan inflammation in rats and mice. 2: Zymosan-induced pleurisy in rats

Injection of zymosan in rat pleural cavity provokes an exudate which is already detectable at 15 min and which is maximum at 24 h. The leucocyte count (mostly neutrophils) increases at 2-4 h and is maximum at 48 h. In this paper the reaction has been studied up to 6 h. Evidence of histamine release, of mast cell degranulation and of reduction of the exudate by anti-H1 compounds, as well as by sodium cromoglycate, proves the active role played by histamine in the early stage of pleurisy. Serotonin (whose role was studied exclusively using antagonists) seems to have only a minor part in the early phase of the reaction. Some metabolites of arachidonic acid were determined in the pleural exudate at 1 h and 6 h. The concentration of leukotriene B4 was high at 1 h and decreased at 6 h. The thromboxane B2 level was already high at 1 h and was neatly augmented at 6 h while the amount of prostaglandin F1 alpha was high at both times. The non-steroidal anti-inflammatory substances studied all reduced the pleural exudate at 1 h but their activity then varied from each other at 6 h. Cyclooxygenase and lipoxygenase inhibitors (phenidone, BW755C) induced a reduction of the exudate at both times. Zymosan-induced pleurisy seemed thus to be an excellent model for the investigation of antiallergic and anti-inflammatory compounds active on histamine and cyclooxygenase and lipoxygenase pathways.

Pharmacological studies on zymosan inflammation in rats and mice. 1: Zymosan-induced paw oedema in rats and mice

Injections of zymosan in mouse and rat paws provoke inflammatory reactions, the kinetics of which are different. In both models, inflammation occurs at an early stage but oedema is maximal at 30 min in rat paw and 6 h in mouse paw. In this study the two reactions have been studied up to 6 h. The reduction of oedema by anti-H1 compounds, as well as by disodium cromoglycate, proves the active role played by histamine in rat paw oedema. In mouse its role appears to be minor or non-existent. Serotonin seems to be clearly implicated in the early stages of the oedema in mouse, somewhat less in rat. In the two species, non-steroidal anti-inflammatory compounds only reduce the 4-6 h phase. BW755C and phenidone reduce the early and late phase of paw oedema in both species, with the exception of phenidone which is inactive on the 4-6 h phase in the mouse. We can hypothesize that in the two species some leukotrienes seem to be implicated principally in the early phases, while derivatives of cyclooxygenase play a more important role in the late phases. Theophylline reduces inflammation in the two models, hydrocortisone acetate, however, is only active on the late phases. These results indicate that there are important differences in the participation of the various mediators studied in the two models.

Pharmacological modulation of PAF-acether-induced pleurisy in rats

Injection of platelet-activating factor (PAF-acether) into the pleural cavity of rats induced the accumulation of a moderately intense exudate within 30 to 60 minutes. By comparison with animals given injections of the vehicle alone, the animals given this mediator had elevated levels of leukotriene C4-immunoreactive material (LTC4 im) in the exudate and decreased quantities of thromboxane B2 (TxB2) and of 6-Keto-F1 alpha-prostaglandin (6-Keto PGF1 alpha). Nifedipine, verapamil, and diltiazem reduced the pleural exudate with no major effect on the mediators. Both salbutamol and theophylline reduced the exudate and the levels of LTC4 im. Acetylsalicylic acid, phenylbutazone and indomethacin significantly inhibited the exudate, greatly lowered the quantities of cyclooxygenase derivatives and tended to increase LTC4 im. Phenidone, which inhibits the cyclooxygenase and lipoxygenase pathways, decreased the exudate and the three mediators. The phospholipase A2 inhibitor, chloroquine, decreased both the amount of exudate and moderately the concentration of LTC4 im. The glucocorticoids studied had no effect on the exudate or on the mediators. These results suggest that the role of the increased LTC4 im in the induction of the pleurisy is not clear.

Exudative, cellular and humoral reactions to platelet-activating factor (PAF-acether) in the pleural cavity of rats

The reactions to platelet-activating factor (PAF-acether) injected into the pleural cavity of rats were compared with the reactions in animals injected with 0.9% NaCl. PAF-acether induced a maximum exudate after 30-60 min, which then decreased and disappeared after 24 h. The number of pleural leukocytes in the exudate was clearly decreased 30 min after the injection, was slightly increased after 6 h and was unchanged at other times. The estimation of lipid mediators in the pleural exudate obtained 30 and 60 min after the injection of PAF-acether revealed an increase in type-C4 leukotriene (LTC4) and a decrease in thromboxane B2 (TxB2) and in 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha). In addition, the amount of histamine was found to be lower after 30 min. These results confirm in vivo that some biological effects of PAF-acether seem to involve the participation of other mediators.

Pharmacokinetic and metabolic study of itanoxone in the crab Pachygrapsus marmoratus (Decapoda, Brachyura): comparative study with clofibric acid

The LD50 of itanoxone injected i.v. in the crab Pachygrapsus marmoratus is 144 mg/kg. Hypolipidemic drug distribution is distinct according to organ and sex. The fixation power of muscle is comparatively low. Ovary radioactivity is higher than in the testicles. Itanoxone storage is large in the hepatopancreas. Metabolism, increasing over time, is not noticeably different according to sex. Two metabolites, chlorobiphenylcarboxylic acid and chlorobiphenylacetic acid, found in crab, are also identified in rat and man. The pharmacokinetic and metabolic study of itanoxone and clofibric acid in the crab shows a difference between the two drugs. Itanoxone metabolism and fixation is higher than clofibric acid.

[Comparative biochemical and ultrastructural study of the hepatic response induced in the rat by 2 hypolipemic agents: clofibrate and itanoxone]

A comparative biochemical and ultrastructural investigation o hepatic response induced in rats by clofibrate and itanoxone, a new hypolipemic agent, was performed. Normocholesterolemic Sprague-Dawley male rats were distributed into homogeneous groups and orally treated on 10 successive days either by the vehicle alone (1%--carboxymethylcellulose), or by clofibrate (300 mg/kg/day) or by itanoxone (100 and 300 mg/kg/day). On the eleventh day, a last dose was applied after about 16 hours fasting, one hour before sacrificing the animals. Biochemical parameters (total serum cholesterol, hepatic catalase activity) and morphological ones (liver weight, ultrastructural analysis of the hepatic cell with especially cytochemical evaluation and counting of peroxisomes) were studied. The treatment with clofibrate gave the following results: fall in total serum cholesterol (-25%), increase in liver weight (+89%) and hepatic catalase activity (+69%), high proliferation of hepatic peroxisomes (+246%). These data are in agreement with literature. The following observations were noted with itanoxone: a decrease in total serum cholesterol proportional to the dose applied and of higher intensity as compared to clofibrate (-36,5% at 100 mg/kg; -54% at 300 mg/kg), a moderate increase in liver weight (+25% at 100 mg/kg; +41% at 300 mg/kg) and hepatic peroxisomes (+12% at 100 mg/kg; +85% at 300 mg/kg), no effect on hepatic catalase activity. The moderate feature of the hepatic response induced by itanoxone in spite of a marked hypocholesterolemic activity was discussed: first in connection with the hypothesis about a relation between the proliferation of hepatic peroxisomes induced by many hypolipemic agents and the advent of tumors in rats, then, in connection with the association sometimes assumed between the increased number of hepatic peroxisomes and the effect on lipids of several hypolipemic substances related or not to clofibrate.

Hemorheological and biochemical parameters in the "fatty" rat

The essential part played by rheological factors in genesis of thrombosis and atherosclerosis has often been mentioned. Thus the authors have carried out a study of rheological and biochemical parameters on a genetic animal model with modifications in plasma lipids (homozygous obese "Fatty" rat) compared to the non obese heterozygous animal. The results obtained for the evolution of biochemical parameters (blood glucose, cholesterol, triglycerides) over a 16 months period confirm those published earlier. Further, a significant increase in fibrinogen level was observed in homozygous animals, and correlated with plasma viscosity. There results are also connected with changes in apparent blood viscosity which is considerably increased in homozygous rats, particularly at low shear rates (gamma less than 20 s-1). These results show the value of this animal model and the authors suggest the application of such a genetic animal model and of its heterozygous control population to both theoretical rheological and pharmacological studies on atherogenesis and hyperlipoproteinaemia.

Differential effects of itanoxone--a new hypolipidemic and hypouricemic drug--on platelet and vascular prostaglandin generation in rats

Itanoxone ((chloro-2'-diphenyl)-4-oxo-4 methylene 2-butyric acid), a newly developed, hypolipidemic and hypouricemic compound with moderate anti-inflammatory activity, showed a short-lived, dose-dependent (20--200 mg/kg, orally), apparently competitive inhibition of platelet malondialdehyde (MDA), stimulated by either thrombin or arachidonic acid. Repeated doses did not result in any cumulative effect. At doses which completely blocked MDA production, itanoxone also inhibited thrombin-stimulated thromboxane B2 production in platelets but had no measurable effect on vascular prostacyclin generation. Pretreatment with itanoxone partially prevented the inhibitory effect of aspirin on both platelet and vascular prostaglandin synthesis. This suggests that itanoxone--like aspirin--acts at the level of cyclo-oxygenase but with greater selectivity on the platelet enzyme. This pharmacological activity is of great theoretical interest for the potential use of this compound as an antithrombic drug.

Action of various drugs with anti-inflammatory or anti-rheumatic properties on pleurisy due to Bordetella pertussis hypersensitivity in the rat

The authors studied various drugs with anti-inflammatory or antirheumatic properties on pleurisy due to Bordetella pertussis hypersensitivity in the rat. The following compounds were studies according to various methods of treatment: indomethacin, phenylbutazone, cyclophosphamide, desonide, chloroquine, levamisole, D-penicillamine and sodium aurothiopropanol sulphonate. The action on the volume of pleural exudate and on cell events depended on the compounds and the conditions of treatment. Only gold salt produced no reduction in the pleural volume under all methods of treatment. All the compounds studied produced various degrees of significant modifications at the level of the cell events.

The influence of various methods of sensitization on delayed hypersensitivity to Bordetella pertussis in the Sprague Dawley Rat

In the rat, the injection of Bordetella pertussis produces, after prior sensitization, a delayed hypersensitivity inflammatory reaction within the pleural cavity. The influence of various methods of sensitization on this hypersensitivity was studied in the Sprague Dawley rat. The reaction was very variable according to the experimental conditions used. Optimal sensitization was obtained following the injection of antigen mixed with complete Freund's adjuvant into the dorsal surface of the paws.