bm-15766 and Disease-Models--Animal

We showed previously that 3 distal inhibitors of cholesterol synthesis are highly teratogenic in rats. AY 9944 and BM 15766 inhibit 7-dehydrocholesterol reductase, which catalyzes the last step of cholesterol synthesis, and triparanol inhibits Delta(24)-dehydrocholesterol reductase, which catalyzes the last step in another pathway. These molecules cause holoprosencephalic brain anomalies. Under certain experimental conditions, other anomalies (of the limbs and male genitalia) are also observed. Assays performed by gas chromatography-mass spectrometry (GC-MS) show hypocholesterolemia and an accumulation of precursors. These data indicate that this animal model can be considered a model of Smith-Lemli-Opitz syndrome. Smith-Lemli-Opitz syndrome is a recessive autosomal genetic disease characterized by malformations (microcephaly, corpus callosum agenesis, holoprosencephaly, and mental retardation), male pseudohermaphroditism, finger anomalies, and failure to thrive. The syndrome has been attributed to a deficit in 7-dehydrocholesterol reductase. As assayed by GC-MS, the sterol status of these patients indicates severe hypocholesterolemia and an accumulation of precursors: 7-dehydrocholesterol, 8-dehydrocholesterol, and oxidized derivatives. The presence of 7-dehydrocholesterol in the serum of patients is pathognomonic of the disease. The developmental gene Shh (sonic hedgehog) plays a key role in brain, limb, and genital development; it was shown recently that the Shh protein has to be covalently linked to cholesterol to be active. This is the first time that a posttranslational function has been attributed to cholesterol. There is an obvious relation between Shh dysfunction and the malformations observed in our experiments and in patients with Smith-Lemli-Opitz syndrome. However, the exact relation remains to be clarified. It is clear, however, that the role of cholesterol in embryonic development must be taken into account.

Topics: Animals; Anticholesteremic Agents; Cholesterol; Dehydrocholesterols; Disease Models, Animal; Embryonic and Fetal Development; Fetus; Piperazines; Rats; Smith-Lemli-Opitz Syndrome; trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride; Triparanol

Topics: Animals; Cholestadienols; Cholesterol; Dehydrocholesterols; Disease Models, Animal; Enzyme Inhibitors; Humans; Liver; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Piperazines; Smith-Lemli-Opitz Syndrome

Clinical, epidemiological, and laboratory studies suggest that cholesterol may play a role in the pathogenesis of Alzheimer's disease (AD). Transgenic mice exhibiting an Alzheimer's beta-amyloid phenotype were treated with the cholesterol-lowering drug BM15.766 and tested for modulation of beta-amyloid levels. BM15.766 treatment reduced plasma cholesterol, brain Abeta peptides, and beta-amyloid load by greater than twofold. A strong, positive correlation between the amount of plasma cholesterol and Abeta was observed. Furthermore, drug treatment reduced the amyloidogenic processing of the amyloid precursor protein, suggesting alterations in processing in response to cholesterol modulation. This study demonstrates that hypocholesterolemia is associated with reduced Abeta accumulation suggesting that lowering cholesterol by pharmacological means may be an effective approach for reducing the risk of developing AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Anticholesteremic Agents; Aspartic Acid Endopeptidases; Brain Chemistry; Cholesterol; Disease Models, Animal; Drug Evaluation, Preclinical; Endopeptidases; Enzyme Inhibitors; Female; Humans; Male; Membrane Proteins; Mice; Mice, Transgenic; Nerve Tissue Proteins; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Piperazines; Presenilin-1; Protein Processing, Post-Translational; Serum Amyloid P-Component

The fact that Smith-Lemli-Opitz syndrome (SLOS), a syndrome comprising major malformations involving a number of organ systems, results from an abnormality in cholesterol biosynthesis, was discovered only recently. Utilizing a drug (BM 15.766) to inhibit the same step in cholesterol biosynthesis as is abnormal in those affected with SLOS, we have developed a rat model that presents with abnormalities observed as early as gestational day 12 that appear to be consistent with some of those subsequent malformations that comprise the human syndrome. Abnormalities of the brain and face include deficiency in the midline region of the upper face, narrowing of the forebrain hemispheres and of the cerebral aqueduct, and deficiency in the developing lower jaw. Associated pathogenesis, as observed on gestational day 11 in histological sections and with scanning electron microscopy, involves abnormal cell populations at the rim of the developing forebrain and in the alar plate of the lower midbrain and hind-brain. The affected cells appear abnormally rounded up, having apparently lost their normal cell contacts. The potential basis for the selective vulnerability of this cell population and the impact of its vulnerability relative to subsequent dysmorphogenesis is discussed.

Topics: Animals; Cholesterol; Disease Models, Animal; Embryo, Mammalian; Female; Piperazines; Pregnancy; Rats; Rats, Wistar; Smith-Lemli-Opitz Syndrome; Teratogens

The impaired conversion of 7-dehydrocholesterol to cholesterol, as a result of a permanent inhibition of the activity of 7-dehydrocholesterol-delta 7-reductase, has been reported in the Smith-Lemli-Opitz (SLO) syndrome (1, 2). For the purpose of experimental teratology, an animal disease model consisting of the offspring of pregnant rats treated with AY 9944 or BM 15766, inhibitors of 7-dehydrocholesterol-delta 7-reductase, was established. The present study compares the profiles of sterols in rat serum, obtained after transient treatment with inhibitors, with profiles of sterols obtained from patients with the permanent enzyme defect. AY 9944 (single dose of 50, 75, or 100 mg/kg) or BM 15766 (60, 75, or 90 mg/kg per day for 11 days) induces hypocholesterolemia and accumulation of 7-dehydrocholesterol and aberrant sterols in rat serum. The aberrant sterols in the treated rats are similar to those detected in human SLO patients by gas chromatography coupled to mass spectrometry (1, 3, 4) and were identified as 7- and 8-dehydrocholesterol, two trienols (I and II), and 19-nor-5,7,9(10)-cholestatrien-3 beta-ol. The time- and dose-dependences of the biochemical alterations are compared to the teratogenic abnormalities induced by inhibitors. The dietary cholesterol supplementation that suppresses embryo malformations induced by AY 9944 prevents severe hypocholesterolemia and decreases the aberrant sterol levels. As a function of time after intoxication, the 8-dehydrocholesterol to 7-dehydrocholesterol ratio increases, suggested that 8-dehydrocholesterol is derived from the gradual conversion of the accumulated 7-dehydrocholesterol. The ratio of 8-dehydrocholesterol to 7-dehydrocholesterol is higher in human SLO than in the animal disease model. This may be explained by a permanent block in 7-dehydrocholesterol-delta 7-reductase in SLO compared to a transient inhibition of this enzyme in the animal model.

Topics: Animals; Child; Cholestadienols; Cholesterol; Dehydrocholesterols; Disease Models, Animal; Enzyme Inhibitors; Female; Heterozygote; Humans; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Piperazines; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Wistar; Smith-Lemli-Opitz Syndrome; Sterols; trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride

The Smith-Lemli-Opitz syndrome is a recessive inherited disorder characterized by neurological developmental defects and dysmorphic features with a defect in cholesterol synthesis at the conversion of 7-dehydrocholesterol to cholesterol. BM 15.766 inhibits 7-dehydrocholesterol-delta 7-reductase and reproduces the biochemical defect. The aim of this study was to investigate the effects of cholesterol, cholic acid, and lovastatin feeding on rats fed BM 15.766.. Plasma cholesterol and 7-dehydrocholesterol concentrations were related to the hepatic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase.. With the inhibitor treatment, plasma cholesterol concentrations decreased 67%; 7-dehydrocholesterol concentrations increased from trace to 17 mg/dL; and hepatic HMG-CoA reductase activity and messenger RNA levels were stimulated 74% and two times, respectively. In inhibitor-treated rats, feeding cholesterol increased plasma cholesterol concentrations 3.7 times, decreased 7-dehydrocholesterol concentrations 88%, and reduced elevated HMG-CoA reductase activity and messenger RNA levels 74% and 49%. Feeding cholic acid increased plasma cholesterol without reducing 7-dehydrocholesterol concentrations. The combination of cholic acid and cholesterol enhanced plasma cholesterol 9.5 times without decreasing 7-dehydrocholesterol levels. Feeding lovastatin depressed plasma cholesterol further without reducing 7-dehydrocholesterol levels.. Cholesterol is essential to correct abnormal cholesterol synthesis induced by BM 15.766 in rats by expanding the pool and inhibiting HMG-CoA reductase. Neither cholic acid nor lovastatin are effective separately, but cholic acid plus cholesterol may offer some additional benefit.

Topics: Acyl Coenzyme A; Animals; Cholesterol; Cholic Acid; Cholic Acids; Dehydrocholesterols; Disease Models, Animal; Liver; Lovastatin; Male; Microsomes, Liver; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Piperazines; Rats; Rats, Sprague-Dawley; Smith-Lemli-Opitz Syndrome

Topics: Animals; Anticholesteremic Agents; Cholesterol; Dehydrocholesterols; Disease Models, Animal; Humans; Piperazines; Rats; Syndrome

The Smith-Lemli-Opitz syndrome is a recessive inherited disorder characterized by neurologic developmental defects and dysmorphic features in many organs. Recently, abnormal cholesterol biosynthesis with impaired conversion of 7-dehydrocholesterol to cholesterol has been discovered in homozygotes. To reproduce the biochemical abnormality, BM 15.766, a competitive inhibitor of 7-dehydrocholesterol-delta 7-reductase, the enzyme that catalyzes the conversion of 7-dehydrocholesterol into cholesterol was fed by gavage to rats. After 14 d, plasma cholesterol concentrations declined from 48 mg/dl to 16 mg/dl and 7-dehydro-cholesterol levels rose from trace to 17 mg/dl. Hepatocytes surrounding the central vein developed balloon necrosis. Stimulating cholesterol synthesis with cholestyramine followed by BM 15.766 produced an additional 40% decline (P < 0.05) in plasma cholesterol and 34% increase in 7-dehydrocholesterol levels compared to the inhibitor alone. Adding 2% cholesterol to the diet during the second week of BM 15.766 treatment increased plasma cholesterol threefold and decreased 7-dehydrocholesterol concentrations 55%. Hepatic 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase activity increased 73% with a 3.9-fold rise in mRNA levels but cholesterol 7 alpha-hydroxylase activity decreased slightly though mRNA levels increased 1.4 times with BM 15.766 treatment. These results demonstrate that BM 15.766 is a potent inhibitor of 7-dehydrocholesterol-delta 7-reductase. The model reproduces abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome and is useful to test different treatment strategies. Stimulating early steps of cholesterol synthesis worsens the biochemical abnormalities while feeding cholesterol inhibits abnormal synthesis, improves the biochemical abnormalities and prevents liver damage.

Topics: Abnormalities, Multiple; Animals; Anticholesteremic Agents; Bile; Bile Acids and Salts; Cholesterol; Cholesterol 7-alpha-Hydroxylase; Cholesterol, Dietary; Dehydrocholesterols; Disease Models, Animal; Homozygote; Hydroxymethylglutaryl CoA Reductases; Intellectual Disability; Liver; Male; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Piperazines; Rats; Rats, Sprague-Dawley; Syndrome