An assessment of the carcinogenic potential of ezetimibe using nonclinical data in a weight-of-evidence approach

Ezetimibe blocks intestinal absorption of sterols via interaction with the Neimann-Pick C1-Like 1 (NPC1L1) transporter and is approved for use in the treatment of primary hyperlipidemia (heterozygous familial and non-familial), homozygous familial hypercholesterolemia, and homozygous sitosterolemia. A recently completed randomized clinical trial [simvastatin and ezetimibe in aortic stenosis (SEAS)] testing the effectiveness of Vytorin (a combination of simvastatin and ezetimibe) in patients with aortic stenosis reported an unexpected safety finding: an increase in overall cancer incidence and cancer-associated mortality (all types) in the treated groups relative to the placebo control. A subsequent meta-analysis utilizing a much larger database from two ongoing clinical trials indicated that the observed findings in the SEAS trial were likely due to chance and not a true drug-induced effect. Nonetheless, it has been suggested by various commentators on the SEAS trial that ezetimibe may be carcinogenic. The extensive nonclinical database for ezetimibe was used to test the hypothesis that ezetimibe may be a direct or indirect carcinogen. Using two different in silico approaches, ezetimibe showed no structural alerts for genetic toxicity or carcinogenicity. Ezetimibe was not genotoxic in two reverse mutation assays, one in vitro clastogenicity assay, and two mouse micronucleus assays. No evidence of proliferative lesions was observed in three species in studies of 1-12 months in duration. Ezetimibe was not carcinogenic in standard 2-year bioassays in mice and rats. Additionally, in these 2-year bioassays, no drug-related non-neoplastic lesions were noted. The absence of drug-induced non-neoplastic or proliferative lesions in these studies indicates that ezetimibe treatment was not associated with findings characteristic of carcinogens (i.e., DNA reactivity or cell proliferation) Administration of pharmacologic doses of ezetimibe to mice did not alter hepatic expression patterns of genes associated with apoptosis, cell proliferation, or epithelial-mesenchymal transition. No evidence of drug-induced tumors was observed in mice in which the molecular target of ezetimibe (NPC 1L1) was knocked out over the life span of the animal. In conclusion, the nonclinical data do not support the proposed hypothesis based on the single observation from the SEAS trial and, rather, support the conclusion that ezetimibe does not represent a carcinogenic hazard to humans using this drug in a therapeutic setting.

Ezetimibe, a potent cholesterol absorption inhibitor, inhibits the development of atherosclerosis in ApoE knockout mice

Ezetimibe (SCH58235) is a potent, selective, cholesterol absorption inhibitor. The objective of this study was to determine whether ezetimibe reduces plasma cholesterol and inhibits atherogenesis in apolipoprotein E knockout (apoE-/-) mice. Cholesterol absorption was inhibited by >90% at doses of ezetimibe >3 mg/kg in apoE-/- mice. Atherosclerosis and lipoprotein changes were determined in apoE-/- mice fed a high-fat (0.15% cholesterol) "western" diet, a low-fat (0.15% cholesterol) diet, or a semisynthetic cholesterol-free diet with or without ezetimibe (5 mg/kg per day) for 6 months. Ezetimibe reduced plasma cholesterol levels from 964 to 374 mg/dL, from 726 to 231 mg/dL, and from 516 to 178 mg/dL in the western, low-fat, and cholesterol-free diet groups, respectively. The reductions occurred in the very low density and low density lipoprotein fractions, whereas high density lipoprotein cholesterol levels were increased by ezetimibe treatment. Ezetimibe reduced aortic atherosclerotic lesion surface area from 20.2% to 4.1% in the western diet group and from 24.1% to 7.0% in the low-fat cholesterol diet group. Ezetimibe reduced carotid artery atherosclerotic lesion cross-sectional area by 97% in the western and low-fat cholesterol groups and by 91% in the cholesterol-free group. Ezetimibe inhibits cholesterol absorption, reduces plasma cholesterol, increases high density lipoprotein levels, and inhibits the progression of atherosclerosis under western, low-fat, and cholesterol-free dietary conditions in apoE-/- mice. Although apoE-/- mice are more hypercholesterolemic than are humans and low density lipoprotein reductions with ezetimibe are not as pronounced clinically, ezetimibe may inhibit atherogenesis in individuals consuming restricted-fat or western diets.

The synergistic hypocholesterolemic activity of the potent cholesterol absorption inhibitor, ezetimibe, in combination with 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors in dogs

Ezetimibe (SCH 58235) and SCH 48461 are potent cholesterol absorption inhibitors, which cause significant decreases in plasma cholesterol levels in cholesterol-fed animals and in humans with hypercholesterolemia. These compounds selectively block intestinal uptake and absorption of cholesterol. These cholesterol absorption inhibitors cause modest, inconsistent reductions in plasma cholesterol levels in animals fed cholesterol-free chow diets. Although, these compounds block cholesterol absorption and increase neutral sterol excretion, chow-fed animals compensate for the loss of biliary cholesterol by increasing hepatic cholesterol synthesis. Therefore, we determined the effect of SCH 48461 and ezetimibe in combination with 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors in chow-fed dogs. A synergistic reduction in plasma cholesterol was observed in chow-fed dogs given SCH 48461 (0.1 mg/kg/d) and the HMG CoA reductase inhibitor, lovastatin (5 mg/kg/d). Neither SCH 48461 nor lovastatin alone affected plasma cholesterol levels. Their combination for 14 days caused a 36% reduction in plasma cholesterol levels from 129 mg/dL to 83 mg/dL (P <.05). Ezetimibe (0.007 mg/kg/d) also caused synergistic reductions in plasma cholesterol levels in chow-fed dogs when combined with HMG CoA reductase inhibitors for 2 weeks (5 mg/kg lovastatin -50%; 2.5 mg/kg pravastatin -41%; 5 mg/kg fluvastatin -60%, and -30% with low doses of simvastatin and atorvastatin 1 mg/kg). The combination of this class of cholesterol absorption inhibitors with an HMG CoA reductase inhibitor should be very effective clinically at reducing plasma cholesterol levels, even with reduced dietary intake of cholesterol.

Ezetimibe selectively inhibits intestinal cholesterol absorption in rodents in the presence and absence of exocrine pancreatic function

1. Ezetimibe potently inhibits the transport of cholesterol across the intestinal wall, thereby reducing plasma cholesterol in preclinical animal models of hypercholesterolemia. The effect of ezetimibe on known absorptive processes was determined in the present studies. 2. Experiments were conducted in the hamster and/or rat to determine whether ezetimibe would affect the absorption of molecules other than free cholesterol, namely cholesteryl ester, triglyceride, ethinylestradiol, progesterone, vitamins A and D, and taurocholic acid. In addition, to determine whether exocrine pancreatic function is involved in the mechanism of action of ezetimibe, a biliary anastomosis model, which eliminates exocrine pancreatic function from the intestine while maintaining bile flow, was established in the rat. 3. Ezetimibe reduced plasma cholesterol and hepatic cholesterol accumulation in cholesterol-fed hamsters with an ED(50) of 0.04 mg kg(-1). Utilizing cholesteryl esters labelled on either the cholesterol or the fatty acid moiety, we demonstrated that ezetimibe did not affect cholesteryl ester hydrolysis and the absorption of fatty acid thus generated in both hamsters and rats. The free cholesterol from this hydrolysis, however, was not absorbed (92 - 96% inhibition) in the presence of ezetimibe. Eliminating pancreatic function in rats abolished hydrolysis of cholesteryl esters, but did not affect the ability of ezetimibe to block absorption of free cholesterol (-94%). Ezetimibe did not affect the absorption of triglyceride, ethinylestradiol, progesterone, vitamins A and D, and taurocholic acid in rats. 4. Ezetimibe is a potent inhibitor of intestinal free cholesterol absorption that does not require exocrine pancreatic function for activity. Ezetimibe does not affect the absorption of triglyceride as a pancreatic lipase inhibitor (Orlistat) would, nor does it affect the absorption of vitamin A, D or taurocholate, as a bile acid sequestrant (cholestyramine) would.

Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study

OBJECTIVE

To quantify developmental abnormalities in cerebral and cerebellar volume in autism.

METHODS

The authors studied 60 autistic and 52 normal boys (age, 2 to 16 years) using MRI. Thirty autistic boys were diagnosed and scanned when 5 years or older. The other 30 were scanned when 2 through 4 years of age and then diagnosed with autism at least 2.5 years later, at an age when the diagnosis of autism is more reliable.

RESULTS

Neonatal head circumferences from clinical records were available for 14 of 15 autistic 2- to 5-year-olds and, on average, were normal (35.1 +/- 1.3 cm versus clinical norms: 34.6 +/- 1.6 cm), indicative of normal overall brain volume at birth; one measure was above the 95th percentile. By ages 2 to 4 years, 90% of autistic boys had a brain volume larger than normal average, and 37% met criteria for developmental macrencephaly. Autistic 2- to 3-year-olds had more cerebral (18%) and cerebellar (39%) white matter, and more cerebral cortical gray matter (12%) than normal, whereas older autistic children and adolescents did not have such enlarged gray and white matter volumes. In the cerebellum, autistic boys had less gray matter, smaller ratio of gray to white matter, and smaller vermis lobules VI-VII than normal controls.

CONCLUSIONS

Abnormal regulation of brain growth in autism results in early overgrowth followed by abnormally slowed growth. Hyperplasia was present in cerebral gray matter and cerebral and cerebellar white matter in early life in patients with autism.

Ezetimibe, a potent cholesterol absorption inhibitor, normalizes combined dyslipidemia in obese hyperinsulinemic hamsters

Ezetimibe potently and selectively inhibits cholesterol absorption in the intestine, thereby reducing plasma cholesterol in preclinical models of hypercholesterolemia. Clinical trials have demonstrated that ezetimibe lowers LDL cholesterol and raises HDL cholesterol in humans. The effect of ezetimibe on other dyslipidemias, particularly hypertriglyceridemia, is not yet known. In the present studies, we assessed the effect of ezetimibe on combined hypercholesterolemia and hypertriglyceridemia in obese hyperinsulinemic hamsters. Hamsters were fed chow, chow with cholesterol (0.12%), or the same cholesterol diet containing different dietary triglycerides (15%) in the absence or presence of 1 mg/kg ezetimibe (in diet) for up to 84 days. Body weight, serum insulin, leptin, glucose, cholesterol, and triglyceride levels were analyzed. Cholesterol and triglyceride levels were also determined in VLDL+IDL, LDL, and HDL. Hamsters maintained on high-fat diets became obese, hyperinsulinemic, hyperleptinemic, hypercholesterolemic, and hypertriglyceridemic. Ezetimibe did not affect body weight, insulin, or leptin, but ablated the combined hypercholesterolemia and hypertriglyceridemia induced by high-fat diets. Ezetimibe normalized VLDL+IDL cholesterol and triglyceride and significantly decreased LDL cholesterol to below chow-fed levels. The ratio of HDL to LDL cholesterol increased significantly with the addition of ezetimibe. Ezetimibe completely eliminated the accumulation of cholesteryl ester and free cholesterol in liver that was induced under the various dietary conditions in the absence of drug. In conclusion, ezetimibe is very effective in correcting the combined dyslipidemia in diet-induced obese hyperinsulinemic hamsters and may be an effective therapy for ameliorating combined dyslipidemia in obese insulin-resistant and/or type 2 diabetic humans.

The cholesterol absorption inhibitor, ezetimibe, decreases diet-induced hypercholesterolemia in monkeys

Ezetimibe (1-(4-fluorophenyl)-(3R)-[3-(4-fluorophenyl)-(3S)-hydroxypropyl]-(4S)-(4-hydroxyphenyl)-2-azetidinone) potently and selectively inhibits the intestinal absorption of cholesterol, thereby reducing plasma cholesterol in preclinical models of hypercholesterolemia. In rhesus monkeys fed a diet containing 375 mg/day of cholesterol, 0.1 mg/kg of ezetimibe completely prevented the doubling of plasma cholesterol normally induced under these dietary conditions (ED(50)=0.0005 mg/kg). Low-density lipoprotein cholesterol (LDL) was dose-dependently reduced, while high-density lipoprotein cholesterol (HDL) and plasma triglyceride were unchanged. A single dose of an ezetimibe analog administered to cynomolgus monkeys fed a single cholesterol-containing meal caused a significant reduction (-69%) of cholesterol in chylomicrons during the postprandial phase without affecting triglyceride content. In rhesus monkeys, apolipoprotein (apo) B(48) concentrations in chylomicrons did not differ between control and the ezetimibe analog, but apo B(100) was significantly reduced in LDL (-41%). These data indicate that these cholesterol absorption inhibitors reduce cholesterol content in chylomicrons, which indirectly leads to a decrease in LDL cholesterol and particle number.

Comparison of the activity and disposition of the novel cholesterol absorption inhibitor, SCH58235, and its glucuronide, SCH60663

Previous studies described the metabolism-based discovery of a potent, selective inhibitor of intestinal absorption of cholesterol, SCH58235 (Ezetimibe). Here we demonstrate that the phenolic glucuronide (SCH60663) of SCH58235, was more potent at inhibiting cholesterol absorption in rats than SCH58235, when administered by the intraduodenal route. To understand the increased potency of the glucuronide, the metabolism and distribution of SCH58235 and SCH60663 were studied in bile duct-cannulated rats. One minute after intraduodenal delivery of SCH58235, significant levels of compound were detected in portal plasma; >95% was glucuronidated, indicating that the intestine was metabolizing SCH58235 to its glucuronide. When intraduodenally delivered as SCH58235, the compound was glucuronidated, moved through the intestinal wall, into portal plasma, through the liver, and into bile. However, when delivered as SCH60663, >95% of the compound remained in the intestinal lumen and wall, which may explain its increased potency. Significant inhibition of cholesterol absorption and glucuronidation of SCH58235 occurred when SCH58235 was intravenously injected into bile duct-cannulated rats. Autoradiographic analysis demonstrated that drug related material was located throughout the intestinal villi, but concentrated in the villus tip. These data indicate that (a) SCH58235 is rapidly metabolized in the intestine to its glucuronide; (b) once glucuronidated, the dose is excreted in the bile, thereby delivering drug related material back to the site of action and (c) the glucuronide is more potent than the parent possibly because it localizes to the intestine. Taken together, these data may explain the potency of SCH58235 in the rat (ID(50) = 0.0015 mg kg(-1)) and rhesus monkey (ID(50) = 0.0005 mg kg(-1)).

2-Azetidinone cholesterol absorption inhibitors: increased potency by substitution of the C-4 phenyl ring

SAR studies directed towards the optimization of 2-azetidinone cholesterol absorption inhibitors led to the discovery of 11a, the most potent cholesterol absorption inhibitor yet identified.

Discovery of 1-(4-fluorophenyl)-(3R)-[3-(4-fluorophenyl)-(3S)-hydroxypropyl]-(4S)-(4 -hydroxyphenyl)-2-azetidinone (SCH 58235): a designed, potent, orally active inhibitor of cholesterol absorption

(3R)-(3-Phenylpropyl)-1,(4S)-bis(4-methoxyphenyl)-2-azetidinone (2, SCH 48461), a novel inhibitor of intestinal cholesterol absorption, has recently been described by Burnett et al. and has been demonstrated to lower total plasma cholesterol in man. The potential sites of metabolism of 2 were considered, and the most probable metabolites were prepared. The oral cholesterol-lowering efficacy of the putative metabolites was evaluated in a 7-day cholesterol-fed hamster model for the reduction of serum total cholesterol and liver cholesteryl esters versus control. On the basis of our analysis of the putative metabolite structure-activity relationship (SAR), SCH 58235 (1, 1-(4-fluorophenyl)-(3R)-[3-(4-fluorophenyl)-(3S)-hydroxypropyl]-(4S)- (4-hydroxyphenyl)-2-azetidinone) was designed to exploit activity enhancing oxidation and to block sites of potential detrimental metabolic oxidation. Additionally, a series of congeners of 2 were prepared incorporating strategically placed hydroxyl groups and fluorine atoms to further probe the SAR of 2-azetidinone cholesterol absorption inhibitors. Through the SAR analysis of a series of putative metabolites of 2, compound 1 was targeted and found to exhibit remarkable efficacy with an ED50 of 0.04 mg/kg/day for the reduction of liver cholesteryl esters in a 7-day cholesterol-fed hamster model.

Effect of chronic central administration of glucagon-like peptide-1 (7-36) amide on food consumption and body weight in normal and obese rats

Glucagon-like peptide (7-36) amide (GLP-1) acutely inhibits food and water consumption in rats after intracerebroventricular (icv) administration. To assess the potential for desensitization of these effects, we investigated the effects of chronic icv administration of GLP-1 on food consumption and body weight in Sprague-Dawley (SD) rats and Zucker (fa/fa) obese rats. In vitro functional densensitization of the GLP-1 receptor was not observed after overnight exposure of Rin m5F insulinoma cells to GLP-1 at concentrations up to 10 nM. Administration of GLP-1 to SD rats (30 microg icv twice a day for 6 days) resulted in significant reductions in 24-hour food consumption each day (25 +/- 1%). Continuous icv infusion of GLP-1 for 7 and 14 days significantly inhibited cumulative food consumption and reduced body weight in SD rats. In the genetically obese Zucker rat, chronic dosing with GLP-1 (30 microg icv) once a day for 6 days caused significant reductions in food consumption each day and a reduction in body weight. These results indicate that the GLP-1 pathways in the central nervous system controlling food consumption do not desensitize after chronic exposure to GLP-1 and suggest that agonists of the central GLP-1 receptor may be effective agents for the treatment of obesity.

Sugar-substituted 2-azetidinone cholesterol absorption inhibitors: enhanced potency by modification of the sugar

A glucuronide conjugate of the potent 2-azetidinone cholesterol absorption inhibitor Sch 58235 was synthesized to confirm the structure of a metabolite isolated from in vivo sources. A series of 2-azetidinone glycosides was prepared via Schmidt trichloroimidate methodology. Enhanced cholesterol absorption inhibition was achieved by modification of the sugar moiety.

Carboxy-substituted 2-azetidinones as cholesterol absorption inhibitors

Metabolism initiated SAR studies led to the discovery of a new class of potent 2-azetidinone cholesterol absorption inhibitors. These studies found that a heteroatom at the para position of the C-4 phenyl ring is not a requirement for cholesterol absorption inhibition as was suggested by earlier findings. Substitution of Ph-linker-COOR for PhOMe at the C-4 position enhanced cholesterol absorption inhibition.

Sugar-substituted 2-azetidinones as cholesterol absorption inhibitors

The asymmetric synthesis of a glucuronide conjugate of the 2-azetidinone cholesterol absorption inhibitor Sch 48461 was accomplished to confirm the structure of a metabolite isolated from in vivo sources. Key features of this article include the asymmetric synthesis of 2-azetidinones by Evan's chiral oxazolidinone methodology and glucuronide formation by a Mitsunobu protocol.

In vivo metabolism-based discovery of a potent cholesterol absorption inhibitor, SCH58235, in the rat and rhesus monkey through the identification of the active metabolites of SCH48461

SCH48461 is a selective and highly potent inhibitor of cholesterol absorption. In rats, SCH48461 is rapidly and completely metabolized in the first pass through the body. To compare the activity of the metabolites of SCH48461 with SCH48461 itself, an intestinally cannulated, bile duct-cannulated rat model for cholesterol absorption was developed. SCH48461 inhibited the absorption of cholesterol by 70%, whereas bile containing the metabolites of SCH48461 (henceforth, "metabolite bile") inhibited the absorption by greater than 95%. Very little of the recovered radioactive dose of SCH48461 was located in the intestinal lumen (7%) or wall (4%), whereas 85% appeared in bile. However, in rats treated with metabolite bile, 62% of the dose remained in the lumen, 13% was associated with the wall and only 24% reappeared in bile, which suggests that the activity of the metabolite bile may be related to its higher retention in the intestinal wall. Rats treated with metabolite bile had 64% and 84% less drug-related radioactivity in their plasma and livers, respectively, compared with animals treated with SCH48461, which indicates that the metabolites are systemically less available than SCH48461. The metabolites in bile were separated by high-performance liquid chromatography; the most active fraction in the bile duct-cannulated rat model was identified by mass spectrometry as the glucuronide of the C4-phenol of SCH48461. The other fractions had moderate or no activity. Through the identification of the most active biliary metabolites of SCH48461 in the rat, we have discovered SCH58235, a novel cholesterol absorption inhibitor which is 400 times more potent than SCH48461 in the cholesterol-fed rhesus monkey.

Diet-induced obese mice develop peripheral, but not central, resistance to leptin

Leptin administration reduces obesity in leptin-deficient ob/ob mice; its effects in obese humans, who have high circulating leptin levels, remain to be determined. This longitudinal study was designed to determine whether diet-induced obesity in mice produces resistance to peripheral and/or central leptin treatment. Obesity was induced in two strains of mice by exposure to a 45% fat diet. Serum leptin increased in proportion to body weight (P < 0.00001). Whereas C57BL/6 mice initially responded to peripherally administered leptin with a marked decrease in food intake, leptin resistance developed after 16 d on high fat diet; mice on 10% fat diet retained leptin sensitivity. In AKR mice, peripheral leptin significantly decreased food intake in both 10 and 45% fat-fed mice after 16 d of dietary treatment. However, after 56 d, both groups became resistant to peripherally administered leptin. Central administration of leptin to peripherally leptin-resistant AKR mice on 45% fat diet resulted in a robust response to leptin, with a dose-dependent decrease in food intake (P < 0.00001) and body weight (P < 0.0001) after a single intracerebroventricular infusion. These data demonstrate that, in a diet-induced obesity model, mice exhibit resistance to peripherally administered leptin, while retaining sensitivity to centrally administered leptin.

The relationship of tissue localization, distribution and turnover to feeding after intraperitoneal 125I-leptin administration to ob/ob and db/db mice

Brain and whole body localization and distribution of 125I-leptin was determined after intraperitoneal administration to ob/ob and db/db mice, and was compared to inhibition of food intake. Food intake was not significantly inhibited at3 hours post-injection, but was decreased significantly at 6 h (p < 0.0007) and 24 h (p < 0.02) in ob/ob mice, times at which > 97 % of the radioactive dose was found in the urine. The highest concentrations of 125I-leptin at all time-points were found in the serum, liver and kidneys. These findings were verified by whole body autoradiography. Virtually no 125I-leptin was found in the CNS at later timepoints in either ob/ob or db/db mice. Coronal sectioning of entire brains from ob/ob and db/db mice revealed 125I radioactivity localized to the choroid plexus and in the ventricular space, but not in other CNS regions. No differences in localization, accumulation, or clearance of 125I-leptin in ob/ob vs. db/db mice were found in any of the tissues studied. The present studies demonstrate that the inhibitory effect of leptin on food intake in the ob/ob mouse persists for up to 24 hours after a single dose, despite the complete degradation and elimination of the labeled leptin during the first several hours after injection.

2-Azetidinone cholesterol absorption inhibitors: structure-activity relationships on the heterocyclic nucleus

A series of azetidinone cholesterol absorption inhibitors related to SCH 48461 ((-)-6) has been prepared, and compounds were evaluated for their ability to inhibit hepatic cholesteryl ester formation in a cholesterol-fed hamster model. Although originally designed as acyl CoA: cholesterol acyltransferase (ACAT) inhibitors, comparison of in vivo potency with in vitro activity in a microsomal ACAT assay indicates no correlation between activity in these two models. The molecular mechanism by which these compounds inhibit cholesterol absorption is unknown. Despite this limitation, examination of the in vivo activity of a range of compounds has revealed clear structure-activity relationships consistent with a well-defined molecular target. The details of these structure-activity relationships and their implications on the nature of the putative pharmacophore are discussed.

Amides of piperidine, morpholine and piperazine substituted 1-phenylethylamines: inhibitors of acylCoA:cholesterol acyltransferase (ACAT) activity in vitro and in vivo

Amides of some substituted 1,2-diarylethylamines have been shown to exhibit potent acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) inhibitory activity in vitro in microsomal ACAT assays but show poor in vivo activity in a cholesterol-fed hamster model. In an effort to design ACAT inhibitors that are potent in both our in vitro and in vivo assays a series of amides of piperidine, morpholine and piperazine substituted 1-phenylethylamines were synthesized. Compounds of this series were found to be very potent inhibitors of ACAT in a microsomal ACAT assay and also exhibited potent activity in a cholesterol-fed hamster model.

Substituted (1,2-diarylethyl)amide acyl-CoA:cholesterol acyltransferase inhibitors: effect of polar groups on in vitro and in vivo activity

Substituted (1,2-diarylethyl)amides have been prepared and evaluated for their ability to inhibit microsomal acyl-CoA:cholesterol acyltransferase activity in vitro and to lower hepatic cholesteryl ester content in vivo in a cholesterol-fed hamster. Simple unsubstituted (diarylethyl)amides were potent inhibitors in vitro but showed poor activity in vivo. Introduction of polar groups at specific locations on the diarylethylamine moiety decreased in vitro activity but increased in vivo activity. Both effects were highly structure dependent, suggesting specific interactions which were mediating activity in each model. Optimization of these opposing effects led to compounds which were potent in both models.

Hypocholesterolemic activity of a novel inhibitor of cholesterol absorption, SCH 48461

The amount of cholesterol that circulates in the plasma as lipoproteins can be affected by the balance of cholesterol metabolism within and between the intestines and liver. In the present report, we describe a novel hypocholesterolemic agent and document its pharmacological effects in animal models of hypercholesterolemia. The oral administration of (3R,4S)-1,4-bis-(4-methoxyphenyl)-3-(3-phenylpropyl)-2-azetidinone (SCH 48461) reduced plasma cholesterol concentrations in cholesterol-fed hamsters, rats and rhesus monkeys with ED50s of 1, 2 and 0.2 mg/kg per day, respectively, SCH 48461 was also highly effective in reducing hepatic cholesteryl ester accumulation in cholesterol-fed hamsters and rats after 7 days of treatment. In one 3 week study, rhesus monkeys were fed a 0.25% cholesterol/22% saturated fat diet with or without SCH 48461. At the end of the 3 week period the control group's VLDL + LDL-cholesterol increased to 180 Mg/dl from a baseline of approximately 65 mg/dl while plasma apolipoprotein B levels had doubled. Animals treated daily with 1 mg/kg SCH 48461 maintained their baseline levels of VLDL + LDL-cholesterol, HDL-cholesterol, and plasma apolipoproteins B and A-I. After 3 weeks the diets of the two groups were switched. Within 1 week SCH 48461 (1 mg/kg per day) rapidly reversed the elevated VLDL + LDL-cholesterol levels of the previous control group to near baseline values. SCH 48461 exerted its hypocholesterolemic effect through the inhibition of cholesterol absorption. A dose of 10 mg/kg per day inhibited cholesterol absorption in cholesterol-fed hamsters by 68% while a similar reduction was achieved in chow-fed monkeys with 3 mg/kg per day. This latter dose inhibited cholesterol absorption in cholesterol-fed monkeys by 95%. Treatment of cholesterol-fed monkeys with 10 mg/kg per day SCH 48461 significantly increased fecal neutral sterol excretion (52 vs. 32 mg/kg) but had no effect on acidic sterol excretion. Using a 2-h absorption model in cholesterol-fed hamsters, SCH 48461 caused a 46% inhibition of unesterified [14C]cholesterol accumulation in the intestinal wall and a 90% inhibition of cholesteryl ester formation at a dose of 10 mg/kg. Similar data were observed when the plasma radioactivity was assessed, indicating inhibition of both free (61%) and esterified (85%) cholesterol appearance. In contrast, CI-976, a potent acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, did not affect the uptake of free cholesterol into the intestines while inhibiting cholesterol esterification (98% inhibition).(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of acyl CoA: cholesterol acyltransferase inhibition on the uptake, esterification and secretion of cholesterol by the hamster small intestine

Acyl CoA: cholesterol acyltransferase (ACAT) inhibitors are known to inhibit cholesterol absorption and are under investigation to reduce hypercholesterolemia. These studies examine the effect of an ACAT inhibitor 2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)-dodecanamide (PD128042) on the uptake, metabolism and secretion of cholesterol by the hamster intestinal wall in a short-term model. Preliminary studies in this model indicated that the uptake of 14C-cholesterol and its subsequent esterification 2 hr postoral dosing occurs primarily in the duodenal and jejunal segments of the small intestine and most of the radiolabeled cholesterol and cholesteryl ester in the plasma was associated with chylomicrons. In both single- and multiple-dose studies, PD128042 (50 mg kg-1 day-1) did not inhibit intestinal uptake of [14C]-cholesterol but [14C]-cholesteryl ester formation was inhibited. The free [14C]-cholesterol appearing in plasma was not affected despite a large reduction in [14C]-cholesteryl ester. In contrast, cholestyramine (1 g kg-1 day-1) inhibited the uptake of the radiolabeled free cholesterol and the appearance of cholesteryl ester in the intestine and plasma. The effects of PD128042 on cholesterol and cholesteryl ester mass associated with scraped intestinal mucosa were consistent with the effects observed with the use of the radiolabeled cholesterol. In addition, PD128042 did not affect the uptake of appearance of radiolabeled triglyceride in the intestinal wall after oral gavage of 3H-trioleoylglycerol. Taken together, the data suggest that ACAT inhibition reduces cholesterol absorption by limiting cholesteryl ester incorporation into chylomicrons and has no effect on the intestinal processing of free cholesterol to be secreted into plasma.

Inhibition of PDGF receptor binding and PDGF-stimulated biological activity in vitro and of intimal lesion formation in vivo by 2-bromomethyl-5-chlorobenzene sulfonylphthalimide

The proliferation of vascular smooth muscle cells (SMCs) is a key event in the development of atherosclerotic lesions and in the restenosis of arteries after angioplasty. Polypeptide growth factors are potent SMC mitogens in vitro and are believed to be involved in SMC proliferation in vivo. Strong data exist linking platelet-derived growth factor (PDGF) activity to human atherosclerosis. However, no low-molecular-weight antagonists of this growth factor have been discovered. We identified a compound, SCH 13929 (2-bromomethyl-5-chlorobenzene sulfonylphthalimide), which inhibits binding of 125I-PDGF BB to cell surface receptors with an IC50 of 0.13 mumol/L. This compound has a lesser effect on the binding of 125I-epidermal growth factor (EGF), 125I-basic fibroblast growth factor (bFGF), or 125I-endothelin to specific cell surface receptors. Exposure of cultured SMCs to SCH 13929 inhibits PDGF BB- and PDGF AA-stimulated DNA synthesis but not EGF- or bFGF-stimulated DNA synthesis. PDGF BB-stimulated SMC division is also inhibited by exposure to SCH 13929. Chemotaxis assays indicate that SCH 13929 inhibits PDGF-stimulated directional migration and suggest that the compound interacts with PDGF rather than with the receptor. Oral administration of SCH 13929 (100 mg/kg per day) to Sprague-Dawley rats or spontaneously hypertensive rats results in significant inhibition of lesion formation in the balloon catheter-deendothelialized carotid artery. These results suggest that SCH 13929 may be a useful tool for understanding the role of PDGF in intimal lesion formation.

Demonstration of a direct effect on hepatic acyl CoA: cholesterol acyl transferase (ACAT) activity by an orally administered enzyme inhibitor in the hamster

Orally active inhibitors of acyl CoA:cholesterol acyl transferase (ACAT), such as Lederle CL277082 (LE), are known to reduce plasma and hepatic cholesteryl ester levels, although the mechanisms are not well understood. Several groups have reported the inhibition of cholesterol absorption upon oral ACAT inhibitor administration. In this study, we used 7-day dietary and drug treatments of hamsters to examine the possible effects of LE on hepatic ACAT. ACAT assays were performed using liver homogenates in the absence and presence of a saturating level of exogenously added cholesterol. LE (100 mg/kg/day) treatment of chow or 0.5% cholesterol-fed animals caused reductions in ACAT activity without additional cholesterol as compared with non-treated animals. When a saturating level of cholesterol was added to the assays, reductions in ACAT activity upon LE treatment of chow- or cholesterol-fed animals were also observed. Treatment of cholesterol-fed animals with cholestyramine in the diet reduced ACAT activity in the absence of added cholesterol. However, ACAT activities similar to those of non-treated animals were observed at a saturating level of cholesterol. This latter effect demonstrates that inhibition of cholesterol absorption reduces cholesterol delivery to the liver but does not reduce cholesterol esterifying capacity since cholestyramine is not absorbed and has no direct effect on the liver. The decreased ACAT activity in homogenates from LE-treated animals could also be mimicked in a dose-dependent manner by the addition of exogenous LE to liver homogenates from non-treated animals. These results indicate that hepatic ACAT activity is regulated by the availability of free cholesterol, and that orally administered LE has a direct effect on hepatic ACAT activity in the liver. In addition, the data are consistent with LE activity in the liver as being responsible, in part, for the reduced hepatic and plasma cholesteryl esters in treated animals.

NG-nitro-L-arginine methyl ester does not affect balloon catheter-induced intimal hyperplasia in rats

The L-arginine derived NO-cGMP pathway's role in the response of the arterial wall to balloon catheter injury was examined. Rats were given the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg po twice daily) or vehicle for 6 days before and 2 weeks after balloon catheter injury. NG-nitro-L-arginine methyl ester treatment increased blood pressure and inhibited acetylcholine responses in aortic rings but did not alter the lesions produced by balloon injury. Our results suggest that the L-arginine derived NO-cGMP pathway does not play a significant role in the response of the artery wall to balloon injury in the rat.

Human and monkey corneal endothelium expression of low-density lipoprotein receptors

Receptors for low-density lipoprotein are necessary for high-affinity uptake of lipid and protein essential to cell structure and function. Distinct receptors for acetoacetylated low-density lipoprotein internalize oxidized or enzymatically modified low-density lipoprotein and extracellular matrix components. We identified low-density lipoprotein receptors on cultured human and monkey corneal endothelial cells by the avid incorporation of fluorescently labeled low-density lipoprotein that was competitively inhibited by excess unlabeled low-density lipoprotein but not by unlabeled acetoacetylated low-density lipoprotein. Specific uptake of labeled low-density lipoprotein was greatest in nonconfluent, growing cells and increased after low-density lipoprotein deprivation. Intact endothelial monolayers of whole human cornea also incorporated low-density lipoprotein but not acetoacetylated low-density lipoprotein. After scratch injury of human corneas, spreading endothelium adjacent to areas of cell loss internalized more fluorescent low-density lipoprotein than cells distant from the injury. Blood-aqueous barrier breakdown occurring in ocular diseases and after surgical and nonsurgical trauma may allow leakage of circulating low-density lipoprotein, which provides a rich supply of lipid and protein for endothelial use. Efficient, receptor-mediated, low-density lipoprotein uptake may facilitate repair of damaged corneal endothelial membranes and regeneration of intact, functional cell monolayers.

Development of atherosclerosis in genetically hyperlipidemic rabbits during chronic fish-oil ingestion

The evidence for a reduction in cardiovascular mortality from fish oil is based on epidemiologic observations. To test whether fish-oil supplementation influences the development of atherosclerosis, we treated Watanabe heritable hyperlipidemic rabbits (WHHL), an inbred strain that spontaneously develops atherosclerosis, with 2.5 ml of MaxEPA fish-oil concentrate daily and compared them to a control group fed unsupplemented rabbit chow. Serial cholesterol and triglyceride levels were monitored as were plasma lipid hydroperoxides. The animals were given fish oil from the time of weaning until 1 year of age, when they were sacrificed and their aortas were compared for the extent of atherosclerosis. No significant differences in the cholesterol or triglyceride levels were noted between the two groups. Fatty acid hydroperoxide levels were also similar and were noted to increase from weaning (1.0 +/- 0.7 microM) to the time of sacrifice (1.8 +/- 1.5 microM, p less than 0.01). Fish oil had no influence on the extent of aortic atherosclerosis (25% +/- 14% surface area for controls vs. 28% +/- 19% for treated, p = NS), plaque thickness, or plaque volume after 1 year. We conclude that fish oil does not reduce the levels of serum cholesterol, lipid hydroperoxides, or aortic atherosclerosis in WHHL rabbits. The hypothesis that fish oil protects against atherosclerosis was not supported by this study.

Aortic wall metabolism in relation to susceptibility and resistance to experimental atherosclerosis

Different segments of the aorta and its branches show differing susceptibilities to atherosclerosis. To identify metabolic features that may account for plaque formation and sparing, we studied aortic wall respiration and glycolysis proximal and distal to an aortic coarctation in 30 rabbits fed a standard or atherogenic diet. Three months after coarctation, blood pressure in the proximal aorta was elevated, and plaque occupied 98% +/- 28% of the intimal surface compared with 57% +/- 26% for control animals (p less than 0.05). Aortic pressure distal to the stenosis remained normal, but plaque formation was markedly decreased (5% +/- 4%) compared with controls (30% +/- 27%, p less than 0.05). Metabolic studies included measurement of oxygen consumption of proximal and distal aortic walls, lactic acid production, and 2-deoxyglucose uptake. Elevated pressure or hyperlipidemia increased respiration (22.6 +/- 4.0 or 16.3 +/- 6.0 pmol oxygen consumed/min/microgram deoxyribonucleic acid [DNA] vs 5.8 +/- 5.2 for controls; p values less than 0.05) without increasing glycolytic metabolism. The coexistence of hypertension and hyperlipidemia resulted in maximal plaque formation and a sevenfold increase in both oxidative metabolism (46.6 +/- 27.2 pmol oxygen consumed/min/microgram DNA vs 5.8 +/- 5.2 for controls, p less than 0.004) and glycolytic metabolism (44 +/- 10 ng lactic acid produced/90 min/microgram DNA vs 6 +/- 3 for controls, p less than 0.004). In the spared aortic segment distal to coarctation, glycolytic metabolism was increased (10 +/- 8 ng lactic acid produced/90 min/microgram DNA vs 2 +/- 1 for controls, p less than 0.05) but oxidative metabolism remained normal.(ABSTRACT TRUNCATED AT 250 WORDS)

The sympathetic nervous system and atherosclerosis

Morphometric and chemical changes in the arterial wall were studied after 12 months of diet-induced atherosclerosis in rhesus monkeys treated with either bilateral surgical thoracic sympathectomy or propranolol. There was a marked reduction in the progression of atherosclerosis in the carotid arteries and a moderate reduction in the disease found in the thoracic aorta of monkeys treated initially with a sympathectomy, in comparison to control monkeys fed an atherogenic diet alone. Propranolol at a dose of 40 mg/12 hrs also seemed to reduce the progression of atherosclerosis in the carotid arteries and thoracic aorta, although the differences were less dramatic. There were minimal differences in the extent of atherosclerosis in the abdominal aorta or femoral arteries of animals in either treatment group as compared with the control group. Similarly, the chemical composition of these same major vessels showed no significant differences. Therefore, in the face of severe atherogenic stimuli, chemical or surgical sympathectomy may be useful in controlling atherosclerosis in specific arterial beds.

Effect of an elastin growth substrate on cholesteryl ester synthesis and foam cell formation by cultured aortic smooth muscle cells

Exposure of smooth muscle cells cultured on plastic or glass to hyperlipidemic serum did not result in the formation of foam cells. Since elastin binds serum lipids, and vascular smooth muscle cells are normally closely associated with elastin, we investigated the effects of an elastin substrate on lipid metabolism and on the accumulation of lipid vacuoles by rabbit aortic smooth muscle cells in culture. When cells were grown in plastic petri dishes, cholesteryl ester synthesis, as measured by [14C]oleate incorporation into cholesteryl esters, was 3 times greater in rabbit hyperlipidemic serum (HLS) than in normolipemic serum (NLS) (P less than 0.001). For cells of the same subculture grown on the elastin substrate, the synthetic rate was 6-fold greater in HLS compared to NLS (P less than 0.005). The cells grown on the elastin membranes in the presence of HLS contained large numbers of Oil red O stainable lipid vacuoles and resembled foam cells, while those grown in petri dishes and exposed to HLS showed only an occasional cell containing a few vacuoles. Pre-incubation in lipoprotein-deficient serum markedly enhanced the stimulatory effect of HLS on cholesteryl ester synthesis for cells growing in plastic petric dishes but had much less stimulatory effect on the cells growing on elastin membranes. These studies indicate that close association with elastin modulates the response of smooth muscle cells to hyperlipidemia and suggest a role for elastin in the formation of foam cells of smooth muscle origin during atherogenesis.

Fish oil inhibits development of atherosclerosis in rhesus monkeys

The effect of feeding fish oil (Menhaden) on the progression of rhesus monkey atherosclerosis was determined by feeding diets containing 2% cholesterol and either 25% coconut oil (Group I), 25% fish oil/coconut oil (1:1) (Group II), or 25% fish oil/coconut oil (3:1) (Group III) for 12 months (n = 8/group). The average serum cholesterol levels were 875 mg/dl for Group I, 463 mg/dl for Group II, and 405 mg/dl for Group III. HDL cholesterol levels were 49 mg/dl for Group I, 29 mg/dl for Group II, and 20 mg/dl for Group III. An average of 79% of the aortic intima was involved with atherosclerosis in Group I, 48% in Group II, and 36% in Group III. The aortas of both fish-oil groups (II or III) contained significantly less cholesterol (total, free, and esterified), as well as less acid lipase, cholesteryl esterase, and ACAT activities when compared to the coconut-oil group (I) (p less than 0.05). Microscopically, the aortic and carotid artery lesions were smaller in cross-sectional area and in thickness, and contained less macrophages in the fish-oil groups (II and III) when compared to the coconut-oil group (I) (p less than 0.05). This protective effect was not consistently enhanced by increasing the proportion of fish oil to 3:1 (Group III) over 1:1 (Group II). The results indicate that fish oil-containing diets reduce serum cholesterol levels and inhibit atherosclerosis even in the face of lowered HDL cholesterol levels when compared to a pure coconut oil/cholesterol diet in rhesus monkeys. Therefore, fish-oil diets exert effective protective control of progression of atherosclerosis during severe atherogenic stimuli.

Lysosomal enzyme activities in cultured trabecular-meshwork cells

We examined the lysosomal enzyme levels in cultured trabecular meshwork cells. Histochemical studies revealed that bovine trabecular meshwork cells stained prominently for acid lipase, acid phosphatase, and acid esterase activities. Following phagocytic challenges, such as incubations with latex microspheres or zymosan particles, lysosomal enzyme staining was visibly enhanced. The uptake of foreign particles by trabecular-meshwork cells was evident. Data from biochemical assays for acid lipase, cholesteryl esterase, and acid esterase confirmed the histochemical findings. These results indicate that trabecular meshwork cells are actively phagocytic in culture and that lysosomal enzyme levels in these cells may be modulated by phagocytic challenge.

Protection from atherosclerotic lesion formation by reduction of artery wall motion

We have studied mechanical factors that could determine how stenosis protects against distal atherosclerosis in cynomolgus monkeys fed an atherogenic diet. Critical aortic stenosis was produced by coarctation of the thoracic aorta. After 3 months, coarcted monkeys had a mean aortic pressure gradient of 25 +/- 1 mm Hg and a 76% +/- 2% lumen stenosis. Aortic wall motion was measured by means of in vivo ultrasonic sonomicrometry. Dynamic tracings of aortic pressure and diameter were recorded simultaneously at standard locations proximal and distal to the stenosis and at comparable sites in noncoarcted control animals. In the proximal aorta, mean blood pressure and pulse pressure were increased (p less than 0.05), but wall motion and intimal lesion area were not different from those determined in control monkeys. In the aorta distal to the coarct, mean blood pressure was no different from that in control animals but pulse pressure was diminished; in addition, there was marked reduction of arterial wall motion (p less than 0.001). This was accompanied by a significant reduction of intimal plaque area (p less than 0.05) and acid lipase activity (p less than 0.001). Thus, inhibition of plaque formation in the distal aorta coincided with reduction of pulse pressure and aortic wall motion rather than with blood pressure or hypercholesterolemia. Inhibition of arterial wall motion may account for the sparing effect often encountered in human arteries distal to stenosing atherosclerotic plaques.

Lectin binding to distinguish cell types in fixed atherosclerotic arteries

In order to assess the possible utility of lectin binding to identify the cellular components of fixed arterial lesions we studied lectin binding in experimental rabbit and monkey vessels, as well as in human atherosclerotic arteries obtained at surgery. The avidin-biotin-peroxidase technique was used to localize the binding of the following biotinylated lectins: Concanavalin A (Con A), Dolicho biflorus agglutinin (DBA), soybean agglutinin (SBA), peanut agglutinin (PNA), Phaseolus vulgaris agglutinin (PHA), Ricinus communis agglutinin (RCA), wheat germ agglutinin (WGA), and Ulex europaeus agglutinin (UEA). PHA demonstrated specific cytoplasmic staining of macrophages in rabbit, monkey, and human tissues and differentiated macrophages from other cell types in atherosclerotic lesions. When morphometric comparisons were made between lesion PHA staining and another macrophage marker, acid lipase, very similar results were obtained. Con A, RCA, and WGA stained macrophages intensely and differentiated them from other cell types in normal reticuloendothelial tissues and lesions, but also stained smooth muscle cells and endothelial cells when these cells developed lipid vacuoles. UEA stained the endothelium of vasa vasorum consistently in human arteries, but staining of artery lumen endothelium was variable. Endothelial cells of rabbit or monkey vessels did not stain with UEA. DBA, PNA, and SBA did not consistently stain any cellular structures in arteries. PHA was found to be an excellent marker to differentiate and quantify macrophages in glutaraldehyde or formalin-fixed, paraffin-embedded experimental and human atherosclerotic lesions. Con A, RCA and WGA merit further detailed study in conjunction with other histochemical tests as possible markers of functional changes in arterial cells during lesion development.

Role of acid lipase in cholesteryl ester accumulation during atherogenesis. Correlation of enzyme activity with acid lipase-containing macrophages in rabbit and human lesions

Purified acid lipase was previously shown to hydrolyze the artificial substrate, alpha-naphthyl palmitate, as well as triglycerides and cholesteryl esters and to form cholesteryl esters. To determine to what extent these activities are associated with acid lipase-containing cells in atherosclerotic plaques, we examined rabbit aortas at different stages of experimental lesion induction and human atherosclerotic arteries. Assays of cholesteryl ester formation, and alpha-naphthyl palmitate and cholesteryl ester hydrolysis were performed on homogenates of lesions and the hydrolysis of the artificial fatty acid ester was used as a histochemical marker to identify acid lipase positive foam cells in sections of the same lesions. The volume of lesions occupied by cells stained for acid lipase correlated strongly with the enzyme activities of the arterial homogenates. These results suggest that acid lipase-containing cells may mediate the accumulation of cholesteryl ester during atherogenesis. Since acid lipase activity marks macrophages, these methods may be useful for relating macrophage distribution and function to lesion progression, regression, and complication.

Histochemical detection and quantification of macrophages in rhesus and cynomolgus monkey atherosclerotic lesions

A detailed histochemical study of the macrophage involvement during experimental atherogenesis in rhesus and cynomolgus monkeys was performed. Aortic, carotid, and femoral artery lesions were examined in both species after 4, 8, and 12 months of atherogenic diet feeding. Macrophages were identified and quantified in the atherosclerotic lesions using acid lipase, acid esterase, beta-galactosidase, and cytochrome oxidase histochemical procedures. Morphometric quantitation revealed that the cynomolgus monkey arterial lesions were larger and consistently demonstrated a greater number of cells with characteristics of macrophages in the intimal, medial, and adventitial portion of the arteries when compared to the primarily intimal rhesus monkey lesions. Biochemical assays of aortic samples for acid lipase and acid esterase activity also showed consistently higher activities in the cynomolgus samples when compared to the rhesus samples. Average serum cholesterol levels were higher in the cynomolgus monkeys than in the rhesus monkeys, but the differences in the arterial lesions still existed when animals with overlapping cholesterol levels were compared. Macrophages and their associated activities predominated in experimental cynomolgus monkey atherosclerosis when it was compared to the rhesus disease process, which may be an explanation for some of the differences in atherogenesis reported in these two species.

Reticuloendothelial system response to hyperlipidemia in rhesus and cynomolgus monkeys

A detailed study of the effect of various periods of hyperlipidemia on the reticuloendothelial system (RES) lipid accumulation in rhesus and cynomolgus monkeys was conducted. The cynomolgus serum cholesterol and triglyceride levels were on the average more elevated than the rhesus levels throughout a 12-month period when both species were fed a diet containing 12.5% coconut oil, 12.5% butter fat, and 2% cholesterol. After cynomolgus monkeys were fed this diet, their reticuloendothelial system became more lipid laden than that of the rhesus monkeys, in both the liver and the spleen. This was also true for the circulating monocytes. Furthermore, the parenchymal cells of the cynomolgus livers also become more fat filled, and chemical analyses demonstrated more cholesterol (total, free, and esterified) and triglycerides in the liver and the spleen. Xanthomata development in the cynomolgus, although similar in type and distribution, was more extensive than that in the rhesus monkey after similar periods of experimental diet feeding. Therefore, the RES of two species of macaque monkeys are affected differently when challenged with the same high fat, high cholesterol diet, with the cynomolgus RES being much more involved with lipid and cholesterol storage than the rhesus RES.

Apoprotein B quantification in rhesus and cynomolgus monkey atherosclerotic lesions

The concept that much of the cholesterol deposition in atherosclerotic plaque development is provided by ingress of blood-derived apo B-rich lipoproteins into the arterial intima is given support by the study of arterial apo B accumulation. To compare the arterial wall level of immunoreactive apo B during the progression of diet-induced atherosclerosis in two widely used animal models of atherosclerosis, rhesus and cynomolgus monkeys were fed an atherogenic diet for 4, 8, and 12 months and their abdominal aortas quantitated for apo B. Apo B was extracted from aortic intima-media homogenates in two forms: Tris-buffer extractable or 'loosely bounds' and detergent (Triton X-100) extractable or 'tightly bound'. The aortic extracts were quantitated for apo B by radial immunodiffusion, using goat anti-rhesus apo B along with serum LDL standards of the appropriate species diluted in the two extract solutions. The control monkeys' aortas contained only buffer-extractable apo B. The atherosclerotic aortas of both species of monkeys progressively increased their levels of loosely bound and tightly bound apo B through 4, 8, and 12 months of atherogenic diet feeding, with the 8- and 12-month cynomolgus aortas containing much larger amounts of apo B than the rhesus aortas. These differences in aortic apo B content could be accounted for by the greater rate at which the cynomolgus atherosclerotic lesions developed at the later time points. When the total lesion apo B levels were correlated with representative morphometrically-quantitated histopathologic sections of the homogenized aortas, a highly significant correlation was seen between the total aortic apo B values and both the absolute area of the intimal lesions and the total area of oil red O stainable lipid in the lesions (P less than 0.001). These data indicate that as atherosclerotic lesions become larger and richer in lipid with progression of the disease, the amount of apo B-associated lipoproteins which are deposited unmetabolized in the lesions increases. These lipoproteins are increased in both the tightly bound and loosely bound forms.

An avidin-biotin-peroxidase method for Fc receptors on macrophages isolated from and in sections of rat lung

Receptors for the Fc region of immunoglobulin G (Fc receptors) were detected on pulmonary macrophages by adapting an avidin-biotin-peroxidase technique to isolated cells and sections of rat lung. After incubation with soluble rabbit immunoglobulin G (IgG), surface bound IgG was identified consistently and reproducibly on glass-adherent pulmonary macrophages and on macrophages in tissue sections made from incubated lung slices. Control experiments indicated that binding was specifically mediated by surface Fc receptors. This method may be useful for identifying macrophages in intact tissues.

Identification of macrophages in sections of rabbit lung using acetoacetylated lipoproteins

Macrophages were labeled in sections of rabbit lung with acetoacetylated low density lipoprotein (LDL), a marker internalized by cultured macrophages but not by other connective tissue cells. Using a modified technique, thin slices of fresh rabbit lung were incubated in 3,3'-dioctadecylindocarbocyanine (DiI)-labeled, acetoacetylated LDL, fixed in paraformaldehyde, and sectioned. Alveolar macrophages incorporated the fluorescently labeled, modified LDL, but surrounding stroma and parenchyma did not stain. Our results indicate that DiI-labeled, acetoacetylated LDL may be used to identify mononuclear phagocytes in tissue sections.

Studies with implantable artificial capillary units containing rat islets on diabetic dogs

An implantable artificial endocrine pancreas consisting of a coiled single acrylic copolymer capillary surrounded by a rat islets (1000/kg body weight) was implanted in 10 streptozotocin-alloxan diabetic dogs. About 5 h following implantation plasma glucose decreased from an initial mean value of 350 mg/dl to 150 mg/dl, and then to 100 mg/dl at 12 h. Plasma insulin increased to a mean of 39 mU/1 (range 23-83 mU/l) at 5 h in the recipient animals In addition a much improved plasma glucose disappearance rate (K = 1.9 plus or minus 0.3) with slightly delayed insulin responses was seen after intravenous glucose tolerance tests performed in 4 dogs at 7, 8, 10 and 18 h following implantation. These findings suggest that xenogeneic rat islets implanted as an artificial endocrine pancreas can improve glucose metabolism in the diabetic dog.

Management of innovation and change in mental health services

In recent years the mental health field has been characterized by innovation and change. All changes are not sound or necessary, and the most common approach to implementing change, that of power, can have unfortunate consequences. However, the incidence of innovation and change and the growing technology on planning for the adoption of innovations indicates that change can be managed more effectively. One approach to managing change is the decision determinants analysis model, a group of eight factors that influence whether a change will be successfully adopted; they are ability, values, information, circumstances, timing, obligation, resistance, and yield. The author discusses the factors and gives suggestions related to each for increasing the probability of successful adoption of a change.