Gunnar Aberg

Effects of captopril on atherosclerosis in cynomolgus monkeys.

A study was performed to investigate if oral dosing of captopril could influence the development of atherosclerosis in cholesterol-fed cynomolgus monkeys. Twenty-four monkeys were divided into four groups: (a) a control group given a normal monkey diet and placebo medication; (b) a high cholesterol group given a high cholesterol diet and placebo medication: (c) a low-dose captopril group given the cholesterol diet and 25 mg/kg of captopril twice daily, and (d) a high-dose captopril group given the cholesterol diet and 50 mg/kg of captopril twice daily. The doses of captopril used in this study did not change the levels of total serum cholesterol, high-density lipoprotein (HDL), or triglycerides. The total cholesterol/HDL. ratio was also un-alfected by captopril. The animals were killed after 6 months of treatment. The progression of atherosclerosis was assessed by gross pathology, histopathology. and biochemical methods. The results showed a significantly reduced progression of arterial lesions in monkeys given captopril: the effects of captopril were most evident in the coronary arteries, which were practically free from atherosclerosis in captopril-treated animals.

Effects of albuterol enantiomers on in vitro bronchial reactivity.

Asthma is one of the most common diseases in the industrialised countries. The underlying mechanisms are complex and still not fully understood although inflammation of the airways plays an important role. There are to day several types of drugs used in the treatment of asthma such as anti-inflammatory drugs, specific antagonists for inflammatory mediators and bronchodilators. Beta-agonists are the main choice for relaxing airway constriction, however unwanted effects of beta-agonists on patients with asthma has been reported. The betaantagonists that are used for treatment of hypertension and various other conditions also is shown to be deleterious in asthmatics. In the present study we have used guinea pig airways to examine the proposed deleterious effects of beta-agonists and antagonists. We have shown that the (S)-enantiomeric forms of salbutamol and formoterol are able to potentiate cholinergic stimuli and we have shown that the potentiation was indomethacin sensitive in airway preparations of sensitised guinea pigs. We also showed and confirmed that the (R)-enantiomeric forms of salbutamol and formoterol were more potent in relaxing airway smooth muscle contracted with different stimuli compared to the (S)-enantiomers. The betaantagonists propranolol and pindolol were shown to be able to contract tracheal preparations if they had been pre-treated with a beta-agonist and the contraction was not simply a blockade of the beta-adrenoceptor induced relaxation. Propranolol contraction was stereo-selective and (S)-propranolol was more effective in inducing contraction than (R)-propranolol. Moreover, atenolol a betacselective antagonist induced significantly smaller contractions compared to general beta-antagonists. This indicates that the beta2-adrenocepor probably is involved in the beta-antagonist induced contraction. The cyclooxygenase inhibitor indomethacin, the 5-lipoxygenase inhibitor MK886 and a thromboxane A2 antagonist as well as capsaicin reduced the beta-antagonist induced contraction. This indicates that several arachidonic acid products as well as neuropeptides may be involved in the beta-antagonistinduced contraction.The worsening of asthma by beta-antagonists is well known and the risks associated with beta-agonists are discussed, but the mechanisms behind these effects need further clarification. In this thesis some of the possible mechanism have been discussed, further studies are needed in order to get more safe and effective asthma treatment regime.

Bi-directional chiral inversion of ketoprofen in CD-1 mice

The R enantiomers of some of the 2-arylpropionic acid non-steroidal antiinflammatory drugs (NSAIDs) are known to undergo metabolic chiral inversion to their more pharmacologically active antipodes. This process is drug and species dependent and usually unidirectional. The S to R chiral inversion, on the other hand, is rare and has been observed, in substantial extents, only for ibuprofen in guinea pigs and 2-phenylpropionic acid in dogs. After i.p. administration of single doses of racemic ketoprofen or its optically pure enantiomers to male CD-1 mice and subsequent study of the concentration time-course of the enantiomers, we noticed substantial chiral inversion in both directions. Following racemic doses, no stereoselectivity in the plasma-concentration time courses was observed. After dosing with optically pure enantiomer, the concentration of the administered enantiomer predominated during the absorption phase. During the terminal elimination phase, however, the enantiomers had the same concentrations. Our observation is suggestive of a rapid and reversible chiral inversion for ketoprofen enantiomers in mice.

Antiatherosclerotic effects of the angiotensin-converting enzyme inhibitors captopril and fosinopril in hypercholesterolemic minipigs

We evaluated the two angiotensin-converting enzyme (ACE) inhibitors captopril and fosinopril with regard to possible antiatherosclerotic effects in minipigs. Experimental hypercholesterolemia and atherosclerosis was produced in 33 minipigs of the Gottingen strain by an egg yolk/cholesterol-enriched diet for 1 year. One group (n = 11) was fed the atherogenic diet alone and served as a control. A second group (n = 11) received captopril (80 mg/kg/day) added to the atherogenic diet, and a third group (n = 11) was treated in the same manner but with fosinopril (8 mg/kg/day). The drug treatments produced significant reduction in serum ACE activity associated with a reactive increase in plasma renin activity (PRA), but had only minor effects on plasma lipids and lipoproteins. At the end of the treatment period, all animals were killed and examined for degree of atherosclerosis. The percentage of atherosclerotic area in the abdominal aorta was significantly lower in both drug-treated groups as compared with controls. Furthermore, accumulation of cholesterol in the thoracic and abdominal aorta was inhibited by drug treatment. Finally, the percentage of intimal thickening in abdominal aorta was significantly reduced in the drug-treated groups. In conclusion, the ACE inhibitors captopril and fosinopril inhibited development of atherosclerosis in hypercholesterolemic minipigs.

Enhanced reduction of atherosclerosis in hamsters treated with Pravastatin and captopril : ACE in atheromas provides cellular targets for captopril

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and angiotensin-converting enzyme (ACE) reduce experimental atherosclerosis by different mechanisms. To determine whether dual-drug therapy additively retards the progression of early lesions, control hyperlipidemic hamsters were compared with those treated with pravastatin, captopril, and pravastatin plus captopril. After 8 weeks of treatment, pravastatin (34 mg/kg/day) reduced plasma total cholesterol and triglycerides by 41 and 84%, respectively, whereas captopril (100 mg/kg/day) reduced normal blood pressure by 21%. The combination of pravastatin and captopril (33 and 100 mg/kg/day) decreased plasma total cholesterol and triglycerides by 44 and 84%, and blood pressure was decreased by 14%. In the aortic arch, pravastatin reduced macrophage-foam cell size and fatty streak area by 21 and 31%, respectively, whereas captopril decreased macrophage-foam cell number and fatty streak area by 34 and 35%. Pravastatin plus captopril decreased macrophage-foam cell number, foam cell size, and fatty streak area by 38, 24, and 67%. ACE inhibitors were previously reported to retard atherosclerosis without affecting blood pressure, suggesting that these agents acted on the artery wall. Therefore the expression of arterial ACE was determined in normal and atherosclerotic hamster aortas. ACE messenger RNA (mRNA) and protein were detected in endothelial cells, intimal macrophage-foam cells and medial smooth-muscle cells of atherosclerotic arteries indicating an upregulation of ACE expression with hyperlipidemia and atherosclerosis. In conclusion, dual-therapy with pravastatin and captopril produced an additive reduction in fatty streak area compared with either drug alone and suggested that atherogenesis can be retarded beyond the level achieved with monotherapy. The presence of ACE in endothelial cells and intimal macrophage-foam cells provides cellular targets for captopril to directly modify the formation of early atherosclerotic lesions.

Enantioselective sulfation of β2-receptor agonists by the human intestine and the recombinant M-form phenolsulfotransferase

The beta 2-receptor agonist class of drugs is metabolized in humans almost exclusively by sulfate conjugation. The objective of this investigation was to determine the influence of chemical structure on the stereoselectivity of the sulfoconjugation of these chiral drugs. The pure enantiomers of six beta 2-agonists, including those clinically most widely used, were all effectively sulfated both by the cytosol of the human intestine and the recombinant human M-form phenolsulfotransferase (PST). Whereas the apparent Km values (Km,app) for the sulfation of the individual drug enantiomers by the intestinal cytosol varied widely, ranging from 4.8 microM for (S)-isoproterenol to 889 microM for (S)-albuterol, these Km,app values were highly correlated with those obtained with M-PST (correlation coefficient 0.994). In contrast, the M-PST Vmax,app values were similar for all drug enantiomers, ranging from 276 to 914 pmol min-1 mg-1 protein, implying that substrate binding to M-PST by far is the main determinant of the sulfation activity. For isoproterenol, the Km,app for M-PST was 6.1 times higher for the active (R)- than for the inactive (S)-enantiomer. For other beta 2-agonists, the stereoselectivity decreased towards unity as the Km,app increased. However, for albuterol, containing a hydroxymethyl substituent at the aromatic ring, the stereoselectivity was dramatically reversed, with 10 times higher Km,app for the inactive (S)- than for the active (R)-enantiomer.

Regression of early atherosclerosis in hyperlipidemic hamsters induced by fosinopril and captopril

Summary We determined whether inhibiting angioten-sin-converting enzyme (ACE) with fosinopril or captopril induced the regression of atherosclerosis in hamsters. A pressor experiment demonstrated that 100 mg/kg fosinopril or captopril almost completely inhibited ACE activity in vivo. Another study established that feeding hamsters 0.05% cholesterol and 10% coconut oil resulted in rapid and progressive accumulation of oil red O-stained macrophage-foam cells in the aortic arch. In the regression study, three groups of hamsters were fed the same atherogenic diet for 4 weeks to induce fatty lesions in the arch. After 4 weeks, plasma lipids, blood pressure (BP), and atherosclerosis were quantified in control hamsters. Beginning at 4 weeks, the two remaining groups of hamsters were treated with 100 mg/kg/day fosinopril or 100 mg/kg/ day captopril for 6 more weeks while receiving the atherogenic diet. After 6-week treatment, plasma lipids, BP, and atherosclerosis were quantified in the two treated groups (i.e., study week 10), and they were compared with the 4-week controls. As compared with that in controls, fosinopril decreased plasma low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterols by ∼69%. High density lipoprotein (HDL) cholesterol decreased by 16% and total triglycerides decreased by 56% as compared with that of controls. Captopril did not alter LDL plus VLDL cholesterols or total triglycerides, but HDL cholesterol decreased by 24% as compared with that of the control group. As compared with that of control hamsters, mean arterial BP (MAP) decreased by 9% with captopril treatment, and heart rate (HR) was decreased by both fosinopril and captopril. The fosinopril group had 53% fewer macrophage-foam cells per square millimeter, the foam cells were 32% smaller, there was a 94% reduction in fatty streak area, and 63% less area of extracellular lipid as compared with 4 week controls. Captopril reduced foam cell number, size, and fatty streak area by 40, 21, and 56%, respectively; the area of extracellular lipid particles increased slightly. Fosinopril induced the regression of all parameters of early atherosclerosis, whereas captopril reversed foam cell accumulation and fatty streak formation.

Stereospecific pharmacokinetics and toxicodynamics of ketorolac after oral administration of the racemate and optically pure enantiomers to the rat

To determine the stereospecific pharmacokinetics and gastrointestinal permeability (GI) changes (surrogate measures of toxicity) in the rat following oral administration of S, R, and racemic ketorolac (KT), optically pure enantiomers (S and R 2.5 mg/kg), and racemic KT (5 mg/kg) were administered orally to male Sprague-Dawley rats and plasma samples were collected for 6 h post-dose for pharmacokinetic assessments. KT-induced changes in GI permeability were assessed using sucrose and 51Cr-EDTA as markers of gastroduodenal and distal intestinal permeability, respectively. After the racemate, R-KT was predominant in plasma (AUC S/R, 0.45). No significant differences in pharmacokinetic indices were evident following administration of the racemate as compared with individual enantiomers. In plasma, there was only negligible S-KT after administration of R-KT. After S-KT, on the other hand, AUC of R-KT was found to be 6.7% of that of S-KT. Both permeability markers showed considerable interanimal variability. Gastroduodenal permeability was significantly increased from baseline by the racemate but not by either of the two enantiomers administered alone. Permeability to 51Cr-EDTA was not significantly increased above baseline for any of the treatments. The plasma concentration of R-KT found after administration of S-KT may be from the < 2% chiral impurity which appears magnified due to its slower clearance as compared with its antipode. There is no evidence of a pharmacokinetic interaction between the enantiomers. Since 2.5 mg/kg S-KT is somewhat less toxic on the gastroduodenum than 5 mg/kg racemate, it may be a safer alternative to the latter, at least in the rat model.

The acute antiarrhythmic effects of droxicainide and lidocaine in unanesthetized dogs.

Two groups of unanesthetized dogs, each consisting of six animals with ventricular tachycardia caused by two-stage ligation of the anterior descending branch of the left coronary artery on the day before treatment, were given continuous intravenous infusions of 0.5 mg/kg/min of either droxicainide [DL N-(2-hydroxy-ethyl) pipecolinyl-2,6-dimethylanilide] hydrochloride or lidocaine hydrochloride until convulsions occurred. At low cumulative doses of either drug, the infusions produced a progressive reduction in the frequency of ventricular ectopic beats, but no significant changes in the sinus rate, the PR or QRS intervals of normal sinus beats, the arterial and central venous pressures, or the respiratory rate. At higher cumulative doses lidocaine produced sedation, and both drugs produced emesis and then convulsions that subsided soon after termination of treatment. With respect to both the cumulative doses and plasma concentrations at which they reduced the frequency of ectopic beats by 25, 50, and 75% and at which they produced convulsions, droxicainide was a more potent antiarrhythmic agent than lidocaine and had a wider margin of safety.

Characterization and Validation of a Canine Pruritic Model.

Preclinical Research