Identification and characterization of diacylglycerol kinase ζ as a novel enzyme producing ceramide-1-phosphate.

Ceramide-1-phosphate (C1P) is a sphingolipid formed by the phosphorylation of ceramide; it regulates various physiological functions, including cell survival, proliferation, and inflammatory responses. In mammals, ceramide kinase (CerK) is the only C1P-producing enzyme currently known. However, it has been suggested that C1P is also produced by a CerK-independent pathway, although the identity of this CerK-independent C1P was unknown. Here, we identified human diacylglycerol kinase (DGK) ζ as a novel C1P-producing enzyme and demonstrated that DGKζ catalyzes the phosphorylation of ceramide to produce C1P. Analysis using fluorescently labeled ceramide (NBD-ceramide) demonstrated that only DGKζ among ten kinds of DGK isoforms increased C1P production by transient overexpression of the DGK isoforms. Furthermore, an enzyme activity assay using purified DGKζ revealed that DGKζ could directly phosphorylate ceramide to produce C1P. Furthermore, genetic deletion of DGKζ decreased the formation of NBD-C1P and the levels of endogenous C18:1/24:1- and C18:1/26:0-C1P. Interestingly, the levels of endogenous C18:1/26:0-C1P were not decreased by the knockout of CerK in the cells. These results suggest that DGKζ is also involved in the formation of C1P under physiological conditions.

Effects of ceramide kinase knockout on lipopolysaccharide-treated sepsis-model mice: Changes in serum cytokine/chemokine levels and increased lethality.

Ceramide, a central molecule of sphingolipid metabolism, is phosphorylated to ceramide-1-phosphate (C1P) by ceramide kinase (CerK). The CerK/C1P pathway regulates many cellular functions, but its roles in immune/inflammation-related (IIR) diseases in vivo are not well known. Sepsis is an acute systemic inflammatory disease accompanied by damage/dysfunction in multiple organs. In the present study, we investigated the effects of CerK knockout on the onset/progression of sepsis-related events in lipopolysaccharide (LPS)-treated sepsis-model mice. In CerK-null mice, the lethality at 48 h after i.v. injection of LPS was significantly increased compared with that in wild-type (WT) mice. The increased lethality by CerK knockout was reproduced in mice treated with i.p. injections of LPS. Changes in serum levels of 23 IIR molecules, including cytokines and chemokines, were measured. In WT mice, levels of these molecules increased 4 and/or 20 h after i.v. injection of LPS. Although the basal levels of IIR molecules were not affected, LPS-induced increases in interleukin-17 (IL-17), C-C motif chemokine ligands (CCL-2 and CCL-11), and tumor necrosis factor-α were significantly up-regulated, whereas IL-2 levels were slightly down-regulated by CerK knockout. Putative mechanisms for the CerK/C1P pathway-mediated regulation of IIR molecules and increased lethality in LPS-treated mice are discussed.

Down-regulation of ceramide kinase via proteasome and lysosome pathways in PC12 cells by serum withdrawal: Its protection by nerve growth factor and role in exocytosis.

Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P). CerK is highly expressed in the brain, and its association with the neuronal function has been reported. Previous reports showed that the activity of CerK is regulated by post-translational modifications including phosphorylation, whereas the cellular fate of CerK protein and its role in neuronal functions have not been clearly elucidated. Therefore, we investigated these issues in PC12 cells. Treatment with nerve growth factor (NGF) for 6 h increased the formation of C1P but not CerK mRNA. Knockdown of CerK and overexpression of HA-tagged CerK down- and up-regulated the formation of C1P, respectively. In PC12-CerK-HA cells, serum withdrawal caused ubiquitination of CerK-HA protein and down-regulated both CerK-HA protein and C1P formation within 6 h, and these down-regulations were abolished by co-treatments with NGF or proteasome inhibitors such as MG132 and clasto-lactacystin. Microscopic analysis showed that treatment with the proteasome inhibitors increased CerK-HA in puncture structures, possibly endosomes and/or vesicles, in cells. Treatment with the lysosome inhibitors reduced serum withdrawal-induced down-regulation of CerK-HA protein but not C1P formation. When knockdown or overexpression of CerK was performed, Ca2+-induced release of [3H] noradrenaline was reduced or enhanced, respectively, but neurite extension was not modified. There was a positive correlation between noradrenaline release and formation of C1P and/or CerK-HA levels in NGF- and clasto-lactacystin-treated cells. These results suggest that levels of CerK were down-regulated by the ubiquitin/proteasome and lysosome pathways and the former pathway-sensitive pool of CerK was suggested to be linked with exocytosis in PC12 cells.

Inhibitory effects of ceramide kinase on Rac1 activation, lamellipodium formation, cell migration, and metastasis of A549 lung cancer cells.

Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P), a bioactive sphingolipid. Since the mechanisms responsible for regulating the proliferation and migration/metastasis of cancer cells by the CerK/C1P pathway remain unclear, we conducted the present study. The knockdown of CerK in A549 lung and MCF-7 breast cancer cells (shCerK cells) increased the formation of lamellipodia, which are membrane protrusions coupled with cell migration. Mouse embryonic fibroblasts prepared from CerK-null mice also showed an enhanced formation of lamellipodia. The overexpression of CerK inhibited lamellipodium formation in A549 cells. The knockdown of CerK increased the number of cells having lamellipodia with Rac1 and the levels of active Rac1-GTP form, whereas the overexpression of CerK decreased them. CerK was located in lamellipodia after the epidermal growth factor treatment, indicating that CerK functioned there to inhibit Rac1. The migration of A549 cells was negatively regulated by CerK. An intravenous injection of A549-shCerK cells into nude mice resulted in markedly stronger metastatic responses in the lungs than an injection of control cells. The in vitro growth of A549 cells and in vivo expansion after the injection into mouse flanks were not affected by the CerK knockdown. These results suggest that the activation of CerK/C1P pathway has inhibitory roles on lamellipodium formation, migration, and metastasis of A549 lung cancer cells.

Effect of low-dose French maritime pine bark extract on climacteric syndrome in 170 perimenopausal women: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To evaluate the efficacy of a relatively low daily dosage of Pycnogenol French maritime pine bark extract for improvement of climacteric symptoms. STUDY DESIGN: In a double-blind, placebo-controlled study 170 perimenopausal women were enrolled and treated with 30 mg Pycnogenol or placebo twice daily over a period of 3 months. Climacteric symptoms were evaluated by the Women's Health Questionnaire (WHQ) and by the Kupperman index, accompanied by an investigation of sex hormones and routine blood chemistry. RESULTS: Seven women dropped out of each group due to noncompliance or personal reasons, but not as a result of treatment. A significant placebo effect was apparent in this study, suggesting an improvement of a majority of the WHQ categories. Compared to baseline, Pycnogenol significantly (p < 0.05) improved all symptoms with the exception of formication sensation and abnormal perceptions. Pycnogenol was found to be especially effective for improving vasomotor and insomnia/sleep problem symptoms, which were significantly better after 4 and 12 weeks than with placebo (p < 0.05). Total Kupperman's index for perimenopausal symptom severity score decreased significantly by 56% as compared to placebo (-39%) after 12 weeks of treatment (p < 0.05). Symptom score was also significantly better already after 4 weeks of treatment with Pycnogenol as compared to placebo. CONCLUSION: This study, applying a relatively low daily dose, allows identification of those climacteric symptoms which respond particularly well to supplementation with Pycnogenol.

Ceramide kinase deficiency improves diet-induced obesity and insulin resistance.

Ceramide kinase (CERK) is an enzyme that phosphorylates ceramide to produce ceramide 1-phosphate. Recently, evidence has emerged that CERK has a role in inflammatory signaling of immune cells. Since obesity is accompanied by chronic, low-grade inflammation, we examined whether CERK might be involved using CERK-null mice. We determined that CERK deficiency suppresses diet-induced increases in body weight, and improves glucose intolerance. Furthermore, we demonstrated that CERK deficiency attenuates MCP-1/CCR2 signaling in macrophages infiltrating the adipose tissue, resulting in the suppression of inflammation in adipocytes, which might otherwise lead to obesity and diabetes.

Ceramide kinase is not essential but might act as an Ca2+-sensor for mast cell activation.

Ceramide kinase (CerK) catalyzes the conversion of ceramide to ceramide 1-phosphate (C1P). We previously revealed that CerK is involved in the activation of mast cells. In this study, we performed an advanced investigation into the role of CerK on the activation of mast cells using CERK-/- mice. Although CERK-/- mice were less prone to exhibiting a passive cutaneous anaphylactic shock (PCA)-reaction compared to wild type (WT) mice, the differences were not significant. In bone marrow-derived mast cells (BMMC) activated by cross-linking antigen (Ag)/IgE, not high, but low concentrations of Ag had a reduced effect on degranulation in BMMC from CERK-/- mice compared to effects on BMMC from WT mice. Similarly, when the BMMCs were activated with calcium ionophore to focus on the downstream signaling of Ca(2+)-elevation, only a low concentration of ionophore had a reduced effect on degranulation in the BMMC from CERK-/- mice compared to the effect on BMMC from WT mice. Furthermore, the CerK inhibitor K1 reduced the differences in degranulation observed between the BMMC from CERK-/- and WT mice in a dose-dependent manner, demonstrating a contribution for CerK and its product C1P in degranulation. Although CerK is not essential for activation of mast cells, especially a potent and acute activation such as a PCA reaction, CerK might act as an modulator for mild and chronic activation of mast cells, thus increasing sensitivity to cytoplasmic Ca(2+).

Association between the incidence of premature rupture of membranes in pregnant women and seismic intensity of the Noto Peninsula earthquake.

OBJECTIVES: The Noto Peninsula earthquake struck the coast of the Noto Peninsula, Japan on March 25, 2007, resulting in the death of one woman and injury to 356 people. A total of 684 houses were totally destroyed by this earthquake, and more than 2,500 people were forced to live at shelters. In this study, we have evaluated the association between the incidence of peripartum abnormalities and seismic intensity of the Noto Peninsula earthquake. METHODS: Demographic data, births, seismic intensity of the earthquake and the incidence of peripartum abnormalities between June 25, 2007 and January 31, 2008 were surveyed. The dataset included 126 pregnant women who lived in the disaster area. The seismic intensity of the earthquake was expressed on the scale (0-7, with 7 being the strongest measure) used by the Japan Meteorological Agency. The subjects of the analysis included 19.7% of the pregnant women affected by the disaster. RESULTS: Of the pregnant women included in this study, 7.9% had a premature rupture of membranes (PROM), with the percentage being significantly higher in the group that experienced a seismic intensity of 6 than in that experienced a seismic intensity of 5. CONCLUSIONS: Our epidemiologic study shows that the PROM among our study cohort was associated with seismic intensity, suggesting that the physical outcome was due to aftershocks of the earthquake at a seismic intensity ≥6. This outcome may result from the psychological stress caused by the earthquakes.

Sphingosine kinase 1 inhibition sensitizes hormone-resistant prostate cancer to docetaxel.

It has recently been shown that docetaxel chemotherapy is effective in prolonging life in patients with prostate cancer (PCa). We have investigated potential ways of increasing the effectiveness of chemotherapy in this disease. We have previously reported that sphingosine kinase 1 (SphK1) inhibition is a key step in docetaxel-induced apoptosis in the PC-3 PCa cell line and that pharmacologicalSphK1 inhibition is chemosensitizing in the docetaxel-resistant PCa LNCaP cell line. In this study we have addressed the mechanism of docetaxel-induced apoptosis of PC-3 cells and identified SphK1-dependent and -independent components. We have shown that SphK1 inhibition by docetaxel is a two-step process involving an initial loss of enzyme activity followed by a decrease in SphK1 gene expression. Using hormoneresistant PC-3 and DU145 PCa cells we have demonstrated that both pharmacological and siRNA-mediated SphK1 inhibition leads to a four-fold decrease in the docetaxel IC50 dose. This work points out to potential ways of increasing the effectiveness of chemotherapy for PCa by SphK1 inhibition.

Chemosensitizing effects of sphingosine kinase-1 inhibition in prostate cancer cell and animal models.

We have previously reported that, in prostate cancer, inhibition of the oncogenic sphingosine kinase-1/sphingosine 1-phosphate (SphK1/S1P) pathway is a key element in chemotherapy-induced apoptosis. Here, we show that selective pharmacologic inhibition of SphK1 triggers apoptosis in LNCaP and PC-3 prostate cancer cells, an effect that is reversed by SphK1 enforced expression. More importantly, we show for the first time that the up-regulation of the SphK1/S1P pathway plays a crucial role in the resistance of prostate cancer cells to chemotherapy. Importantly, pharmacologic SphK1 inhibition with the B-5354c compound sensitizes LNCaP and PC-3 cells to docetaxel and camptothecin, respectively. In vivo, camptothecin and B-5354c alone display a limited effect on tumor growth in PC-3 cells, whereas in combination there is a synergy of effect on tumor size with a significant increase in the ceramide to S1P sphingolipid ratio. To conclude, our study highlights the notion that drugs specifically designed to inhibit SphK1 could provide a means of enhancing the effects of conventional treatment through the prosurvival antiapoptotic SphK1/S1P pathway.

Role of ceramide kinase in peroxisome proliferator-activated receptor beta-induced cell survival of mouse keratinocytes.

Ceramide (Cer) is known to be a lipid mediator in apoptosis and to have an important role in cell fate, via control of intracellular Cer levels. Recently, ceramide kinase (CerK) was identified as an enzyme that converts Cer to ceramide 1-phosphate (C1P). We examined potential functions of CerK in the regulation of keratinocyte survival, and the possible involvement of peroxisome proliferator-activated receptor beta (PPARbeta). PPARbeta is known to be a nuclear receptor acting as a ligand-inducible transcription factor and has been implicated in the control of keratinocyte survival. In the mouse keratinocyte cell line SP1, serum starvation induced cell death and the accumulation of intracellular Cer, an apoptotic event. However, apoptosis was inhibited by activation of PPARbeta. Interestingly, activation of PPARbeta enhanced the mRNA expression of CerK and CerK activity. Furthermore, the cell survival effect of PPARbeta was greatly diminished in keratinocytes isolated from CerK-null mice. Chromatin immunoprecipitation revealed that, in vivo, PPARbeta binds to the CerK gene via a sequence located in the first intron. Electrophoretic mobility-shift assays confirmed that PPARbeta associates with this sequence in vitro. These findings indicated that CerK gene expression was directly regulated by PPARbeta. In conclusion, our results demonstrate that PPARbeta-mediated upregulation of CerK gene expression is necessary for keratinocyte survival against serum starvation-induced apoptosis.

French maritime pine bark extract significantly lowers the requirement for analgesic medication in dysmenorrhea: a multicenter, randomized, double-blind, placebo-controlled study.

OBJECTIVE: A previous open study demonstrated that French maritime pine bark extract (Pycnogenol) may soothe menstrual pain in dysmenorrhea. We thus investigated the effects of Pycnogenol on menstrual pain in a double-blind study. STUDY DESIGN: Subjects were 116 women aged 18-48 years. The first 2 menstrual cycles served as a control period; during the subsequent 2 menstrual cycles women received either a Pycnogenol supplement (60 mg/day) or a placebo in identical capsule form. One further cycle was monitored after cessation of capsule administration. Women were assigned to either a group with low menstrual pain or a group with dysmenorrhea. The criterion for assignment to the first group was absence of analgesic medication. RESULTS: In women with low menstrual pain, no significant difference for lowering of pain scores was found. In contrast, women with dysmenorrhea had a significantly lower pain score and required statistically significantly less analgesic medication during supplementation with Pycnogenol. The number of days women required analgesic medication was likewise found to be statistically significantly lowered in the Pycnogenol group. Even after discontinuation of Pycnogenol supplementation, the required analgesic medication remained significantly decreased. CONCLUSION: The analgesic-sparing effect of Pycnogenol increases with duration of supplementation and benefits persist even after discontinuation.

The generation and behavioral analysis of ceramide kinase-null mice, indicating a function in cerebellar Purkinje cells.

The discovery of ceramide kinase (CerK), which phosphorylates ceramide (Cer) to ceramide 1-phisphate (C1P), established a new pathway for Cer metabolism. Among mouse tissues, brain contains the highest CerK activity. In this study, we found that CerK is highly expressed in cerebellar Purkinje cells. Since Purkinje cells are important for motor-related behaviors, we generated CerK-null mice and performed behavioral analyses. The CerK-null mice were healthy, and displayed no histological abnormalities. The mice lost CerK activity completely, suggesting that CerK is the only enzyme that phosphorylate Cer. However, cellular C1P levels were not different between the CerK-null and wild-type mice, indicating the presence of other C1P-producing pathway. The general motor-coordination was not impaired in the CerK-null mice, but emotional behavior was slightly affected. Our findings suggest that CerK is not necessary for survival at an individual level, but might be involved in higher brain function related to emotion.

Effect of French maritime pine bark extract on endometriosis as compared with leuprorelin acetate.

OBJECTIVE: To clarify the effect of Pycnogenol (Horphag Research, Geneva, Switzerland), French maritime pine bark extract, on endometriosis. STUDY DESIGN: Fifty-eight women were included in this study. They were operated on conservatively for endometriosis and surgically diagnosed with the condition. All patients were followed at 4, 12, 24 and 48 weeks after starting treatment to check for endometriosis signs and symptoms, including changes in CA-125 and estrogen levels (E2). Thirty-two patients in the Pycnogenol treatment group took 60 mg Pycnogenol orally a day for 48 weeks. The 26 patients who received gonadotropin-releasing hormone agonist (Gn-RHa) were treated in the standard way. RESULTS: Treatment with Pycnogenol slowly but steadily reduced the symptom scores. Treatment with Gn-RHa reduced the scores more efficiently; however, 24 weeks after the end of treatment, the scores suggested a recurrence of signs. No influence of treatment on menstrual cycles or E2 was observed in the Pycnogenol group. CA-125 decreased in both treatment groups. Patients with smaller endometriomas responded better to treatment as compared to patients with larger endometriomas. In the Gn-RHa group, the lowering of CA-125 concentrations was far more pronounced; however, a clear rebound effect was observed. CONCLUSION: Pycnogenol is a therapeutic alternative to Gn-RHa in the treatment of endometriosis.

Angiopoietin-like protein3 regulates plasma HDL cholesterol through suppression of endothelial lipase.

OBJECTIVE: A low level of high-density lipoprotein (HDL) in plasma has been recognized as an aspect of metabolic syndrome and as a crucial risk factor of cardiovascular events. However, the physiological regulation of plasma HDL levels has not been completely defined. Current studies aim to reveal the contribution of angiopoietin-like protein3 (angptl3), previously known as a plasma suppressor of lipoprotein lipase, to HDL metabolism. METHODS AND RESULTS: Angptl3-deficient mice showed low plasma HDL cholesterol and HDL phospholipid (PL), and which were increased by ANGPTL3 supplementation via adenovirus. In vitro, ANGPTL3 inhibited the phospholipase activity of endothelial lipase (EL), which hydrolyzes HDL-PL and hence decreases plasma HDL levels, through a putative heparin-binding site in the N-terminal domain of ANGPTL3. Post-heparin plasma in Angptl3-knockout mice had higher phospholipase activity than did that in wild-type mice, suggesting that the activity of endogenous EL is elevated in Angptl3-deficient mice. Furthermore, we established an ELISA system for human ANGPTL3 and found that plasma ANGPTL3 levels significantly correlated with plasma HDL cholesterol and HDL-PL levels in human subjects. CONCLUSIONS: Angptl3 acts as an inhibitor of EL and may be involved in the regulation of plasma HDL cholesterol and HDL-PL levels in humans and rodents.

Novel non-systemic inhibitor of ileal apical Na+-dependent bile acid transporter reduces serum cholesterol levels in hamsters and monkeys.

1-{7-[(1-(3,5-Diethoxyphenyl)-3-{[(3,5-difluorophenyl)(ethyl)amino]carbonyl}-4-oxo-1,4-dihydroquinolin-7-yl)oxy]heptyl}-1-methylpiperidinium bromide, R-146224, is a potent, specific ileum apical sodium-dependent bile acid transporter (ASBT) inhibitor; concentrations required for 50% inhibition of [3H]taurocholate uptake in human ASBT-expressing HEK-293 cells and hamster ileum tissues were 0.023 and 0.73 microM, respectively. In bile-fistula rats, biliary and urinary excretion 48 h after 10 mg/kg [14C]R-146224, were 1.49+/-1.75% and 0.14+/-0.05%, respectively, demonstrating extremely low absorption. In hamsters, R-146224 dose-dependently reduced gallbladder bile [3H]taurocholate uptake (ED50: 2.8 mg/kg). In basal diet-fed hamsters, 14-day 30-100 mg/kg R-146224 dose-dependently reduced serum total cholesterol (approximately 40%), high density lipoprotein (HDL) cholesterol (approximately 37%), non-HDL cholesterols (approximately 20%), and phospholipids (approximately 20%), without affecting serum triglycerides, associated with reduced free and esterified liver cholesterol contents. In normocholesterolemic cynomolgus monkeys, R-146224 specifically reduced non-HDL cholesterol. In human ileum specimens, R-146224 dose-dependently inhibited [3H]taurocholate uptake. Potent non-systemic ASBT inhibitor R-146224 decreases bile acid reabsorption by inhibiting the ileal bile acid active transport system, resulting in hypolipidemic activity.

Pycnogenol alleviates pain associated with pregnancy.

The effect of Pycnogenol was studied in women in the third trimester of pregnancy, complaining of lower back pain, hip joint pain, pelvic pain (pain in the inguinal region), pain due to varices or calf cramps. The women were supplemented with Pycnogenol at a dose of 30 mg/day without any other therapy. Alleviation of pain was evaluated by pain scores until delivery. A significant reduction of pain could be obtained compared with the control group, where no decrease in pain scores in any symptoms was reported. No unwanted effects were observed in the Pycnogenol group. These results indicate the potential of Pycnogenol to reduce pain associated with pregnancy.

The effect of soybeans on the anovulatory cycle.

We treated 36 outpatients, suffering from secondary amenorrhea, who had no menstruation or no ovulation for more than 6 months before consulting our clinic. After polycystic ovary syndrome, hyperprolactinemia, and other ovarian disorders that require medical treatment had been ruled out through smear test examinations of the uterine cervix and uterine myoma, ovarian tumor, and endometriosis had been checked for with ultrasonography and serum CA-125, the subjects began to take 6 g/day of black soybean in micropowder form for 6 months (S group). We estimated the ovular improvement of theses patients, observing basal body temperature (BBT) and follicular development with ultrasonography during the menstrual cycle as the indexes for ovulation and compared them with 34 patients with no treatment (C group). In the S group, improved ovulation was seen in 12 patients, four patients became pregnant, and three patients had anovular menstruation within 3 months after starting to take soybean powder. The periods of first ovulation were 66 +/- 12 days. After ovulation started, all subjects had regular menstruations and ovulation, with more than a 7-day high phase in BBT. On the other hand, in the C group, improved ovulation was seen in two patients, and two patients had anovular menstruation. In conclusion, black soybean has the potential to improve the anovular menstrual cycle.

Analgesic efficacy of French maritime pine bark extract in dysmenorrhea: an open clinical trial.

OBJECTIVE: To clarify the effect of Pycnogenol (Horphag Research, Switzerland), French maritime pine bark extract, on menstrual pain. STUDY DESIGN: We treated 47 patients with menstrual pain, aged 21-45 years, with Pycnogenol at 30 mg (2 capsules) orally twice a dysmenorrl day. The administration of Pycnogenol began on the eighth day of the first menstrual cycle and continued until the seventh day of the third menstrual cycle. Improvement was evaluated by measuring scores of symptoms during the first and second, and first and third menstrual cycle using the Wilcoxon rank sum test. RESULTS: Treatment with Pycnogenol lowered the pain scores for abdominal pain significantly (p < 0.05) as compared to pretreatment values. Pain relief in the second cycle of treatment was better as compared to the first cycle of treatment, as indicated by a higher level of significance (p < 0.01) and lower median pain score. The number of days with abdominal pain showed a trend toward fewer days with pain; however, the difference failed to reach significance. Relief of back pain was not that pronounced during the first cycle treated with Pycnogenol; the pain scores were not significantly different from those in the pretreatment period. However, continuation of treatment during the second cycle produced significant pain relief (p < 0.01). The number of days with back pain decreased. The number of days with pain was significantly lower (p < 0.01) in the second cycle of treatment with Pycnogenol. CONCLUSION: Pycnogenol has a potential analgesic effect on menstrual pain.

A novel class of apical sodium-dependent bile acid transporter inhibitors: the amphiphilic 4-oxo-1-phenyl-1,4-dihydroquinoline derivatives.

A series of 4-oxo-1-phenyl-1,4-dihydroquinolines possessing a linker and an ammonio moiety were synthesized and found to inhibit the apical sodium-dependent bile acid transporter (ASBT). The potency of ASBT inhibition varied with the position and length of the linking tether. Compound 21e effectively lowered the total serum cholesterol levels in hamsters.