[A case of pulmonary arteriovenous fistula beneath the surface of the lung]

A 19-year-old woman complaining of exertional dyspnea was admitted to our hospital with an abnormal shadow on the left side of the chest. Laboratory examination revealed polycythemia and hypoxemia. Pulmonary angiogram demonstrated a pulmonary arteriovenous fistula beneath the surface of the left S10. Partial resection of the left S10 was performed. The wall of the arteriovenous fistula was flimsy and seemed to rupture easily. The sister of this patient also had a peripheral pulmonary arteriovenous fistula and suffered from repeating epistaxis. Rendu-Osler-Weber disease was diagnosed in both, and the sister underwent partial resection of the right S7, which contained the fistula. Their postoperative courses were uneventful. Hemothorax and hemoptysis are lethal complications of arteriovenous fistulae. In order to avoid the rupture of fistulae, surgical resection is the most reliable treatment. Pulmonary arteriovenous fistulae beneath the surface of the lung should be resected.

Down-regulation of cholesterol biosynthesis in sitosterolemia: diminished activities of acetoacetyl-CoA thiolase, 3-hydroxy-3-methylglutaryl-CoA synthase, reductase, squalene synthase, and 7-dehydrocholesterol delta7-reductase in liver and mononuclear leukocytes

Sitosterolemia is a recessively inherited disorder characterized by abnormally increased plasma and tissue plant sterol concentrations. Patients have markedly reduced whole body cholesterol biosynthesis associated with suppressed hepatic, ileal, and mononuclear leukocyte 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-controlling enzyme in cholesterol biosynthetic pathway, coupled with significantly increased low density lipoprotein (LDL) receptor expression. To investigate the mechanism of down-regulated cholesterol biosynthesis, we assayed several other key enzymes in the cholesterol biosynthetic pathway including acetoacetyl-CoA thiolase, HMG-CoA synthase, squalene synthase, and 7-dehydrocholesterol delta7-reductase activities in liver and freshly isolated mononuclear leukocytes from four sitosterolemic patients and 19 controls. Hepatic acetoacetyl-CoA thiolase, HMG-CoA synthase, reductase, and squalene synthase activities were significantly decreased (P < 0.05) -39%, -54%, -76%, and -57%, respectively, and 7-dehydrocholesterol delta7-reductase activity tended to be lower (-35%) in the sitosterolemic compared with control subjects. The reduced HMG-CoA synthase, reductase, and squalene synthase activities were also found in mononuclear leukocytes from a sitosterolemic patient. Thus, reduced cholesterol synthesis is caused not only by decreased HMG-CoA reductase but also by the coordinate down-regulation of entire pathway of cholesterol biosynthesis. These results suggest that inadequate cholesterol production in sitosterolemia is due to abnormal down-regulation of early, intermediate, and late enzymes in the cholesterol biosynthetic pathway rather than a single inherited defect in the HMG-CoA reductase gene.

Bone structural and metabolic changes at the end of pregnancy and lactation in rats

OBJECTIVE

The objective of this study was to elucidate the net change of bone structure and metabolism in the lumbar trabecular bone of rats at the end of the pregnancy and lactation.

STUDY DESIGN

Female virgin Sprague-Dawley rats aged 200 days were mated, and bone mineral density by dual-energy x-ray absorptiometry, bone histomorphometry, and serum bone metabolic markers were measured at the end of pregnancy (day 22 of pregnancy), after delivery (day 5 post partum), and at the end of lactation (day 21 post partum).

RESULTS

At the end of pregnancy bone mineral density, bone volume, trabecular thickness, and serum calcium decreased; serum parathyroid hormone increased; and the histomorphometric parameters indicated that bone resorption were higher than those variables in nonpregnant rats, but bone formation was suppressed, as demonstrated by the low histomorphometric parameters and by the low serum alkaline phosphatase levels. After delivery the bone mineral density of nonlactating rats recovered rapidly, as in nonpregnant rats, but nonlactating rats showed more bone formation by histomorphometry than nonpregnant rats did. At the end of lactation, bone mineral density and serum calcium levels decreased considerably, and lactating rats showed substantial bone formation, bone resorption, and high serum alkaline phosphatase levels. The correlation between the number of pups (x) of the lactating and nonlactating groups and the bone mineral density (y, in grams per square centimeter) showed simple linear regression (y = -0.0067 . x +0.2517, r = 0.949, p < 0.0001).

CONCLUSIONS

These results indicate that significant decreases occur in the trabecular bone of rats at the end of pregnancy and lactation and that lactational intensity is related to bone mineral density.

Regulation of early cholesterol biosynthesis in rat liver: effects of sterols, bile acids, lovastatin, and BM 15.766 on 3-hydroxy-3-methylglutaryl coenzyme A synthase and acetoacetyl coenzyme A thiolase activities

Cytosolic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase catalyzes the formation of HMG-CoA, the substrate for the rate-controlling enzyme in the cholesterol biosynthetic pathway. To explore the regulation in liver, we developed a new, accurate, and reliable reversed-phase ion-pair chromatographic assay that uses nonradioactive substrates and n-propionyl coenzyme A as an internal recovery standard. The hepatic activities were measured in rats treated with cholesterol, sitosterol, cholic acid, deoxycholic acid, ursodeoxycholic acid, cholestyramine, bile fistula, lovastatin, and BM 15.766, an inhibitor of 7-dehydrocholesterol delta7-reductase, and were compared with microsomal HMG-CoA reductase and cytosolic acetoacetyl coenzyme A (AcAc-CoA) thiolase activities. HMG-CoA synthase activity was effectively suppressed in synchrony with HMG-CoA reductase activity by treatments with cholesterol (-41%, P < .05), cholic acid (-72%, P < .005), and deoxycholic acid (-62%, P < .05). However, ursodeoxycholic acid increased activity 84% (P < .05) and intravenous sitosterol did not change activity. AcAc-CoA thiolase activities also paralleled HMG-CoA reductase and HMG-CoA synthase activities, but differences were not statistically significant. In contrast to inhibition, up-regulation of hepatic HMG-CoA synthase activities by cholestyramine, bile fistula, and lovastatin was much less than HMG-CoA reductase activities. In addition, BM 15.766 did not stimulate synthase activity, whereas lovastatin increased activity 2.4-fold. Thus, hepatic HMG-CoA synthase activity was regulated coordinately with HMG-CoA reductase, and responded more forcefully to regulatory stimuli than acetoacetyl-CoA thiolase activity but usually less than HMG-CoA reductase.

Synthesis of [3 alpha-3H]7-dehydrocholesterol via stable tritiated 4-phenyl-1,2,4-triazoline-3,5-dione derivative

Synthesis of [3 alpha-3H]7-dehydrocholesterol is described via protection of the 5,7-diene system in 7-dehydrocholesterol as the Diels-Alder adduct with 4-phenyl-1,2,4-triazoline-3,5-dione followed by oxidation of the hydroxyl group to give the 3-oxo adduct. Reduction of the keto adduct with [3H]sodium borohydride produced the adduct of [3 alpha-3H]7-dehydrocholesterol from which the radiolabeled sterol was obtained via treatment with lithium aluminum hydride. The advantage of the method is that highly labeled [3 alpha-3H]7-dehydrocholesterol can be prepared. Further, unlike 7-dehydrocholesterol, its adduct with 4-phenyl-1,2,4-triazoline-3,5-dione is stable and can be stored. This allows the preparation of small batches of [3 alpha-3H]7-dehydrocholesterol for immediate use in biological experiments, and losses due to decomposition of excess radiolabeled 7-dehydrocholesterol are minimized.

[A case of successful treatment with ganciclovir for cytomegalovirus pneumonia after pulmonary lobectomy]

The premortem diagnosis of cytomegalovirus (CMV) pneumonia is usually difficult, and mortality of it is high. A case of successful treatment with ganciclovir for cytomegalovirus pneumonia after pulmonary lobectomy is reported. The patient was a 76-year-old man. Under diagnosis as lung cancer, the right lower lobectomy was performed. After operation, pneumonia occurred on the nonoperated side and in a few days reticular shadows rapidly spread to the whole lung. Although pulse steroid therapy was performed, the interstitial pneumonitis improved only a little. Then intranuclear inclusion body-bearing giant cells were found in sputum obtained by bronchoscopy. So we diagnosed the interstitial pneumonitis as CMV pneumonia and ganciclovir was administrated. CMV pneumonia had improved for two weeks and the patient has no recurrence. When interstitial pneumonitis develop in patients after operation or steroid therapy, the differential diagnosis should include the possibility of CMV pneumonia.

[Transcription and replication of influenza virus genome]

The genome of influenza virus is composed of eight RNA segments of negative polarity. The RNA-dependent RNA polymerase is associated with each viral RNA (vRNA) segment and after infection, involved in both transcription (vRNA-directed synthesis of viral mRNA) and vRNA replication (vRNA-dependent synthesis of complementary RNA(cRNA) and cRNA-dependent synthesis of vRNA). The RNA polymerase is composed of three viral proteins, PB1, PB2 and PA. PB1 is the core subunit for not only the RNA synthesis but also the assembly of PB2 and PA into this multifunctional enzyme complex. PB1 alone is able to catalyze vRNA-dependent RNA synthesis, but PB2 is required for capped RNA-dependent transcription, both together forming the transcriptase. The third P protein, PA, and an as yet unidentified host factor(s) are involved for the conversion of RNA polymerase from transcriptase to replicase. The functional map including both subunit-subunit contact sites and catalytic sites for capped RNA endonuclease and RNA polymerization is being made for both PB1 and PB2 proteins.

[Morphological reversion of tumor cells by histone deacetylase inhibitors and radicicol]

Trichostatins and trapoxins, structurally unrelated microbial metabolites, are specific inhibitors of histone deacetylases. Radicicol inhibits Src family protein-tyrosine kinases. Recently, these agents were found to induce morphological reversion and enhanced expression of gelsolin, an actin regulatory protein, in a variety of transformed cells. Microinjection of an anti-gelsolin antibody that neutralizes the gelsolin function caused inhibition of the morphological change, suggesting that gelsolin expression is associated with the suppression of transformation.

Short-term effects of 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor on cholesterol and bile acid synthesis in humans

Competitive inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase improve hypercholesterolemia. However, reports about the effects of these agents on bile acid synthesis, the metabolic pathway of cholesterol, are conflicting. We studied the short-term effect on one of these agents, pravastatin, on bile acid synthesis. Six male volunteers were given 40 mg of pravastatin. Plasma mevalonate level (which reflects cholesterol synthesis) and 7 alpha-hydroxy-4-cholesten-3-one level (which reflects bile acid synthesis) were measured every 2 h for 8 h. These plasma levels were compared to those of the same volunteers without pravastatin. Plasma mevalonate level after 2 h was lower than control (3.0 +/- 1.1 ng/mL vs. 6.7 +/- 2.5, mean +/- SD; P < 0.05). This decrease continued for 8 h (2.5 +/- 0.8 vs. 5.2 +/- 1.5; P < 0.05). On the other hand, plasma 7 alpha-hydroxy-4-cholesten-3-one level did not change until after 6 h; then at 8 h it was lower than control (15.7 +/- 11.8 ng/mL vs. 24.7 +/- 16.9; P < 0.05). According to three-way layout analysis of variance, mevalonate level was influenced by both pravastatin treatment (P < 0.01) and time-course (P < 0.01). On the other hand, the 7 alpha-hydroxy-4-cholesten-3-one level was affected by both individual difference (P < 0.01) and time course (P < 0.01), but pravastatin treatment did not influence this compound. This indicates that bile acid synthesis was influenced by pravastatin, although cholesterol synthesis was inhibited. The short-term inhibition of cholesterol synthesis did not affect bile acid synthesis.

Rapid identification of Smith-Lemli-Opitz syndrome homozygotes and heterozygotes (carriers) by measurement of deficient 7-dehydrocholesterol-delta 7-reductase activity in fibroblasts

To extend the enzyme deficiency in Smith-Lemli-Opitz syndrome (SLOS) to extrahepatic tissues, 7-dehydrocholesterol-delta 7-reductase activity was measured in fibroblasts from 10 controls, five SLOS homozygotes, and five obligate heterozygotes. In cells grown almost to confluence in cholesterol-containing medium (4 mg/dL), the conversion of [1,2-3H]7-dehydrocholesterol to cholesterol (7-dehydrocholesterol-delta 7-reductase activity) was 3.8 times higher in control than in homozygote cells and 2.2 times higher than in heterozygote cells. After 24 hours' exposure of the fibroblasts to cholesterol-deficient medium supplemented with lovastatin, 7-dehydrocholesterol-delta 7-reductase activity increased twofold in controls, but did not change significantly in either heterozygous or homozygous cells. In contrast, the activities of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and lathosterol 5-dehydrogenase, two key enzymes that precede 7-dehydrocholesterol-delta 7-reductase in the cholesterol biosynthetic pathway, and low-density lipoprotein (LDL) receptor-mediated binding were equal in control, homozygote, and heterozygote fibroblasts. Further, HMG-CoA reductase activity and LDL receptor-mediated binding increased after exposure of the cells to cholesterol-deficient medium. Fibroblast cholesterol concentrations were approximately equal, although homozygote cells contained 30 times more 7-dehydrocholesterol. Thus, markedly reduced 7-dehydrocholesterol-delta 7-reductase activity that cannot be upregulated after exposure of the cells to cholesterol-deficient medium is diagnostic for the biochemical defect in SLOS. Significantly reduced enzyme activity between the levels in controls and homozygotes without accumulation of 7-dehydrocholesterol in fibroblasts identified heterozygotes.

The molecular anatomy of influenza virus RNA polymerase

The genome of influenza virus is composed of eight RNA segments of negative polarity. The RNA-dependent RNA polymerase is associated with each viral RNA (vRNA) segment and in virus-infected cells, involved in both transcription, i.e. vRNA-directed synthesis of viral mRNA, and two step reactions of vRNA replication, i.e. vRNA-dependent synthesis of complementary RNA (cRNA) and cRNA-dependent synthesis of vRNA. The RNA polymerase is composed of three viral proteins, PB1, PB2 and PA. PB1 is the core subunit for not only the RNA synthesis but also the assembly of PB2 and PA into this multifunctional enzyme complex. PB1 alone is able to catalyze vRNA-dependent RNA synthesis, but PB2 is required for capped RNA-dependent transcription, both together forming the transcriptase. The third P protein, PA, and an as yet unidentified host factor(s) are involved in the conversion of RNA polymerase from transcriptase to replicase. The functional map is being made for both PB1 and PB2 proteins.

Sodium phenobarbital-enhanced mutation frequency in the liver DNA of lacZ transgenic mice treated with diethylnitrosamine

To investigate how a carcinogenic promoter acts on cells mutated by an initiator, we used as a model, lacZ transgenic mouse and a positive selection system. Preliminary data for the mutational events in liver DNA of the mice was generated using diethylnitrosamine (DEN) and sodium phenobarbital (S-PB) as initiator and promoter, respectively. In our first experiment, male MutaMice received a single i.p. injection of saline or 100 mg/kg DEN and were fed a normal diet for 7 days and 500 p.p.m. S-PB in the diet for 21 days. Liver DNA was harvested after a 1 night fast on days 7 and 28 post-DEN treatment. In our second experiment, male mice received a single i.p. injection of phosphate buffered saline or 50 mg/kg DEN and were fed a normal diet for 7 days, a diet with S-PB for 14 days and then a normal diet for 7 days. Liver DNA was harvested after a 1 night fast on days 7, 21 and 28 post-DEN treatment. The S-PB diet enhanced absolute and relative liver weights in all groups. The single intraperitoneal dose of 50 or 100 mg/kg DEN induced high mutation frequencies (MF) in liver, lacZ genes on days 7, 21 and 28. There were no remarkable differences of the MF among any sampling days for animals receiving DEN and a normal diet. S-PB feeding at 500 p.p.m. for 21 days failed to affect the MF in groups given saline or 100 mg/kg DEN. On the other hand, when 50 mg/kg DEN was given, S-PB feeding at 500 p.p.m. for 14 days elevated the MF in liver DNA on days 21 and 28 to approximately 1.8 and 4.0 times the MF, respectively, of the mice fed the normal diet. Consequently, S-PB might preferentially promote certain initiated cells participating in a balance between cell death and proliferation.

A novel HSP70 gene of Schizosaccharomyces pombe that confers K-252a resistance

A new gene encoding a heat shock protein 70 family protein of Schizosaccharomyces pombe (Sp), named sks2+, was cloned as a weak suppressor for the K-252a-sensitive mutation, ucm1. The nucleotide sequence of sks2+ revealed an open reading frame of a 613-amino-acid (aa) protein. The deduced aa sequence of sks2+ showed significant homology with Saccharomyces cerevisiae (Sc) Ssb1p and Ssb2p responsible for protein synthesis by non-organelle-localized ribosomes, as well as with other proteins of the HSP70 family. The cells lacking the functional sks2+ gene were viable and showed no increased sensitivity to K-252a but grew slowly with an elongated morphology. These results suggest that the sks2+ gene product plays a role in the cell cycle progression and is able to confer drug resistance in a multicopy state.

[An operative case of bilateral peripheral pulmonary arterial aneurysms]

An operative case of bilateral peripheral pulmonary arterial aneurysms is described. Nine cases of bilateral peripheral pulmonary arterial aneurysms reported in Japan are reviewed. The patient was a 26-year-old woman complaining of massive hemoptysis. Her chest X-ray showed coin lesions in the bilateral hilus region. After admission, body CT and pulmonary arteriography revealed saccular dilatation of the bilateral peripheral pulmonary artery. We diagnosed as bilateral peripheral pulmonary arterial aneurysms. Bronchoscopic examination revealed bleeding from the left lower lobe bronchus. She underwent left lower lobectomy. Histological examination of the resected specimen demonstrated a marked destruction of the wall of the aneurysm. This patient died of recurrence of hemoptysis from bilateral lung on the 42nd postoperative day.

[Pleural B cell lymphoma presenting as paraplegia]

A 54-year-old man felt pain on the right side of his chest. Two months later, paraplegia developed. A chest CT scan revealed a pleural effusion and a mass lesion along the right parietal pleura. The lesion extended directly into the adjacent part of the spinal canal and compressed the spinal cord. Cytologic examination of the pleural effusion revealed atypical lymphoid cells, and examination of a transcutaneous biopsy specimen showed monotonous atypical B lymphocytes. The diagnosis was pleural malignant lymphoma. Chemotherapy induced a partial remission, but 14 months after the first examination he died of central nervous system involvement. Pleural lymphoma can directly compress the spinal cord and cause paraplegia. Early diagnosis and therapy greatly affect the outcome in patients with spinal cord compression.

Sterol concentrations in cultured Smith-Lemli-Opitz syndrome skin fibroblasts: diagnosis of a biochemically atypical case of the syndrome

The Smith-Lemli-Opitz syndrome is a common birth defect syndrome caused by a deficiency of 7-dehydrocholesterol delta 7-reductase, an essential enzyme in the biosynthesis of cholesterol. The syndrome can usually be diagnosed easily from the plasma markers of markedly elevated 7-dehydrocholesterol and reduced cholesterol concentrations. However, atypical cases with normal plasma levels of cholesterol with only moderately elevated 7-dehydrocholesterol have been reported. To establish a sensitive method for the biochemical diagnosis of the atypical cases of the syndrome, we measured sterol concentrations of cultured skin fibroblasts. 7-Dehydrocholesterol concentrations in patients' fibroblasts grown in the presence of 10% fetal bovine serum were significantly higher than those in controls and parents (P < 0.0005), but they were not elevated proportionately as much as in plasma. To re-produce the accumulation of 7-dehydrocholesterol, the cells were exposed to delipidated medium to induce sterol biosynthesis. After 4 weeks, 7-dehydrocholesterol concentrations in patients' fibroblasts increased from 2.8 +/- 0.3% to 34 +/- 3% of total sterols (cholesterol + 7-dehydrocholesterol + 8-dehydrocholesterol). The increase was also observed in fibroblasts from an atypical patient who has a normal plasma cholesterol level and a 7-dehydrocholesterol concentration of only 0.15 mg/dl. In contrast, cells from parents and controls accumulated very little 7-dehydrocholesterol (< 1% of total sterols). These results demonstrate that cultured fibroblasts exhibit abnormally high accumulation of 7-dehydrocholesterol after cells are exposed to delipidated medium not only in typical patients, but also in an atypical case. The present method is a sensitive procedure for the biochemical diagnosis of this syndrome.

Screening for abnormal cholesterol biosynthesis in the Smith-Lemli-Opitz syndrome: rapid determination of plasma 7-dehydrocholesterol by ultraviolet spectrometry

The Smith-Lemli-Opitz syndrome (SLOS) is a common condition caused by deficiency of 7-dehydrocholesterol delta 7-reductase. The syndrome can usually be diagnosed by demonstrating markedly increased plasma concentrations of the cholesterol precursor, 7-dehydrocholesterol. We describe a simple and rapid method for detection of plasma 7-dehydrocholesterol by use of ultraviolet (UV) spectrometry. Lipids were extracted from plasma by addition of ethanol and n-hexane, and the n-hexane phase was directly subjected to spectrometry. The absorption maxima characteristics of 7-dehydrocholesterol (lambda max 271, 282, and 294 nm) were observed in patients' plasma but not in controls. For quantitative measurements, absorbance at 282 nm was used. Since this absorbance is the sum of the absorbance derived from 7-dehydrocholesterol and background absorbance, the concentrations of 7-dehydrocholesterol in various plasma samples were quantified by subtracting estimated background absorbance at 282 nm from observed absorbance at 282 nm. The results correlated well with total (free plus esterified) 7-dehydrocholesterol concentrations measured by gas-liquid chromatographic method. The UV spectrometric assay was sensitive enough to detect increased 7-dehydrocholesterol in cultured skin fibroblasts from patients grown in delipidated medium. The present method will make it possible to screen plasma or fibroblasts to detect the syndrome rapidly in general clinical laboratories.

[Primary pulmonary lymphoma diagnosed from monoclonality of lymphocytes in a transbronchial biopsy specimen]

A 57-year-old man was found on a routine chest X-ray examination to have three infiltrative shadows: two in the right lung field and one in the left. Examination of a transbronchial biopsy specimen revealed infiltration of many small lymphocytes under the bronchial mucosa. In situ hybridization showed that they were monoclonal, and primary pulmonary lymphoma was diagnosed. The patient also had liver cirrhosis, diabetes mellitus, and hypertension. He was treated with a combination of pirarubein, cyclo-phosphamide, vindesine, prednisolone, and etoposide, but the tumors did not shrink. Therefore, as of the time of this writing he was being given only etoposide.

[Eosinophilic pneumonia presenting as a mass shadow]

A 35-year-old man underwent routine chest roentgenography and a mass shadow was seen in the left lung field. Examination of a transbronchial lung biopsy specimen revealed that many eosinophils had infiltrated under the bronchial mucosa and into the alveolar septum. The total serum IgE concentration was high, and skin tests with Aspergillus antigen and serum precipitating antibodies against Aspergillus were positive. The mass lesion disappeared without any therapy, and a cystic lesion remained. Mediators released from eosinophils were thought to have damaged the lung tissue. We should have administrated corticosteroids as soon as possible.

Measurement of 3 beta-hydroxysteroid delta 7-reductase activity in cultured skin fibroblasts utilizing ergosterol as a substrate: a new method for the diagnosis of the Smith-Lemli-Opitz syndrome

A new sensitive and specific method for the evaluation of 3 beta-hydroxysteroid delta 7-reductase activity, the defective enzyme in the Smith-Lemli-Opitz (SLO) syndrome, is described. The assay is based on the use of gas chromatography-mass spectrometry with selected-ion monitoring to measure the mass of brassicasterol (ergosta-5,22-dien-3 beta-ol) produced by the incubation of ergosterol (ergosta-5,7,22-trien-3 beta-ol) with cultured human skin fibroblasts. Although the conversion of ergosterol to brassicasterol was slower than the transformation of [3H]7-dehydrocholesterol to [3H] cholesterol, cells from control subjects produced brassicasterol efficiently. In contrast, cells form SLO patients produced very little brassicasterol (P < 0.0001, patients vs. parents or vs. controls). These results indicate that the reduction of ergosterol can be used as an assay for 3 beta-hydroxysteroid delta 7-reductase in human skin fibroblasts, which avoids the many problems caused by the instability and lack of availability of radiolabeled 7-dehydrocholesterol. The present method made it possible to diagnose the SLO syndrome with high sensitivity and reliability using a commercially available compound.

Effect of YM 9429, a potent teratogen, on cholesterol biosynthesis in cultured cells and rat liver microsomes

YM 9429 (cis-1-[4-(p-menthan-8-yloxy)phenyl]piperidine) is a hypolipidemic agent with a potent and specific teratogenicity, inducing cleft palate and skeletal variations in rats. Since cleft palate is generally observed in the Smith-Lemli-Opitz syndrome, a common syndrome of multiple congenital anomalies caused by reduced activity of 7-dehydrocholesterol delta 7-reductase (3 beta-hydroxysteroid delta 7-reductase), the final enzyme in the cholesterol biosynthetic pathway, YM 9429 was suspected of being an inhibitor of this enzyme. To prove this hypothesis, YM 9429 was added to cultured human skin fibroblasts and to cultured Morris hepatoma cells and incubated with [5-3H]mevalonolactone. After 24 h, radiolabeled 7-dehydrocholesterol accumulated in the cells, whereas the formation of radiolabeled cholesterol was markedly reduced. The results indicate that YM 9429 inhibits the conversion of 7-dehydrocholesterol to cholesterol catalyzed by the microsomal enzyme 7-dehydrocholesterol delta 7-reductase. In rat liver microsomes, the mode of inhibition was found to be noncompetitive, with a Ki of 40 microM. These results suggest that YM 9429 induced developmental abnormalities in rats by the same mechanism as the Smith-Lemli-Opitz syndrome. This compound might be useful for studying the pathogenesis of anomalies in animal models of the Smith-Lemli-Opitz syndrome.

Regulation of the last two enzymatic reactions in cholesterol biosynthesis in rats: effects of BM 15.766, cholesterol, cholic acid, lovastatin, and their combinations

The Smith-Lemli-Opitz syndrome is a common inherited birth disorder caused by markedly reduced 7-dehydrocholesterol delta 7-reductase activity, the final enzyme in the cholesterol biosynthetic pathway. BM 15.766 (4-[2-[1-(4-chlorocinnamyl)piperazin-4-yl]ethyl]-benzoic acid) inhibits 7-dehydrocholesterol delta 7-reductase activity, reduces plasma cholesterol levels, and increases 7-dehydrocholesterol levels to reproduce the biochemical abnormalities of the syndrome in rats. Cholesterol, cholic acid, and lovastatin, alone or in combinations, were fed to rats given BM 15.766, and hepatic activities of the last two enzymes in the cholesterol biosynthetic pathway, lathosterol 5-dehydrogenase and 7-dehydrocholesterol delta 7-reductase, were measured. After feeding BM 15.766, hepatic 7-dehydrocholesterol delta 7-reductase activity decreased by 77% while lathosterol 5-dehydrogenase activity tended to increase, so that the ratio of 5-dehydrogenase to delta 7-reductase activities increased from 0.33 to 2.8. In BM 15.766-fed rats, treatment with cholesterol suppressed both 5-dehydrogenase and delta 7-reductase activities by 76% and 66%, respectively, and decreased the 5-dehydrogenase: delta 7-reductase activities ratio from 2.8 to 2.2. In contrast, treatment with cholic acid and BM 15.766 further inhibited delta 7-reductase activity by 67% without changing significantly the 5-dehydrogenase activity that had increased the ratio to 5.5. Combining BM 15.766 with lovastatin increased 5-dehydrogenase activity fivefold but did not change delta 7-reductase activity, raising the ratio to 14.3. In BM 15.766-treated rats, the first and last two enzymatic reactions in the cholesterol biosynthetic pathway catalyzed by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, lathosterol 5-dehydrogenase, and 7-dehydrocholesterol delta 7-reductase are down-regulated by cholesterol. Thus, only cholesterol and not cholic acid or lovastatin could reduce elevated plasma 7-dehydrocholesterol levels induced by BM 15.766.