Significance of cytoreductive surgery including bowel resection for patients with advanced ovarian cancer

The aim of this study was to determine the significance of bowel resection in advanced ovarian cancer. A total of 64 women with stage IIIc or IV epithelial ovarian cancer, who consecutively received primary treatment between 1991 and 1995, were entered in this prospective study. The outcome of the patients undergoing bowel resection was evaluated. Thirty-nine patients underwent cytoreductive surgery at initial surgery. Of them, 16 patients could undergo optimal operation without bowel resection. Twenty-three patients received bowel resection at initial surgery. Of these 23 patients, 16 underwent optimal operation and 7 did not. Among 25 patients judged as inoperable cases at initial surgery, 21 responded to chemotherapy and underwent second surgery. Of 21 patients receiving second surgery, 15 underwent optimal operation (7 without bowel resection and 8 with bowel resection). The 3-year survival rate for 24 patients undergoing optimal operation with bowel resection (46.8%) was not significantly different from that for 23 patients without bowel resection (59.1%). Postoperative complications were seen in 8 patients (21.6%) of the patients receiving bowel resection and 3 (13.0%) of those without bowel resection. Cytoreductive surgery including bowel resection is effective for an improvement of the survival in patients with advanced ovarian cancer, if an optimal operation can be performed.

[Pharmaco-dynamic study of methotrexate (MTX) during intraperitoneal MTX/5-FU sequential therapy after gastric surgery]

A pharmaco dynamic study of Methotrexate (MTX) during intraperitoneal MTX/5-FU sequential therapy was carried out after gastric surgery. A comparative study of the route of MTX administration and its dose was also done. 1) Comparative study of the serum concentration of MTX between i.p. and i.v. administration revealed a similar MTX concentration except immediately after administration. 2) A comparative study of the serum concentration of MTX administered i.p. between patients with and without malignant ascites was conducted. Immediate elevation of the serum concentration of MTX was observed in patients without malignant ascites. On the other hand, the MTX concentration was slowly elevated and washed out in patients with malignant ascites. 3) The MTX concentration in the intraperitoneal fluid was compared between patient with and without malignant ascites. In patients without malignant ascites, MTX disappeared quickly from the intraperitoneal fluid. However, the MTX concentration lasted long in the malignant ascites cases. These results were similar with a low-dose MTX (30 mg/body) or moderate dose (100 mg/body). MTX/5-FU sequential i.p. therapy can thus be an effective treatment for patients after gastric surgery, though clearance of MTX was slow in cases with malignant ascites.

[Intrabiliary administration of doxorubicin for pancreaticobiliary cancer]

The effect and drug absorbtion of intrabiliary chemotherapy with Doxorubicin for pancreaticobiliary cancer with PTCD was investigated. Doxorubicin (DXR: 20 mg) was administered intrabiliary for 3 hours by PTCD catheter. Radiographic evaluation of the bile duct before and after chemotherapy and measurement of DXR concentration in the serum and bile were carried out.

RESULTS

Intrabiliary administration of DXR was completed without any significant complications other than epigastric pain. Radiographic study of the bile duct of a patient with pancreatic cancer who could successfully complete DXR administration showed improvement of bile duct passage. The placement of biliary stent could be achieved. Concentration of DXR in the serum after administration was below the lowest determinable level while those in the bile maintained a considerably high concentration 4 hours after the administration. With negligible absorption from bile, intrabiliary chemotherapy with DXR was thought to be an acceptable palliative treatment for pancreaticobiliary cancer.

Vascular access system for continuous arterial infusion of a protease inhibitor in acute necrotizing pancreatitis

We used a vascular access system (VAS) for continuous arterial infusion (CAI) of a protease inhibitor in two patients with acute necrotizing pancreatitis. The infusion catheter was placed into the dorsal pancreatic artery in the first patient and into the gastroduodenal artery in the second, via a femoral artery approach. An implantable port was then connected to the catheter and was secured in a subcutaneous pocket prepared in the right lower abdomen. No complications related to the VAS were encountered. This system provided safe and uncontaminated vascular access for successful CAI for acute pancreatitis.

Factors affecting membrane-controlled drug release for an osmotic pump tablet (OPT) utilizing (SBE)(7m)-beta-CD as both a solubilizer and osmotic agent

PURPOSE

The purpose of this study was to define membrane controlling factors responsible for drug release from a controlled-porosity osmotic pump tablet (OPT) that utilizes a sulfobutyl ether-beta-cyclodextrin, (SBE)(7m)-beta-CD, as both a solubilizing and osmotic agent.

METHOD

The OPT was spray coated with cellulose acetate solutions varying the amount and size of micronized lactose, the amount of triethyl citrate (TEC) and the composition ratio of dichlormethane to ethanol. Chlorpromazine (CLP) was used as a model drug. The release of CLP from the OPTs was studied using the Japanese Pharmacopoeia dissolution method. The membrane surface area of the OPTs were measured with multi-point analysis by the gas absorption method.

RESULTS

The release rate of CLP from OPTs containing (SBE)(7m)-beta-CD increased with increasing amounts of micronized lactose and decreasing amounts of TEC and lactose particle size in the membrane. Also, the CLP release rates from the spray-coated OPTs using mixtures of varying ratios of dichlormethane to ethanol were almost identical. The membrane surface area of the OPTs following release of membrane components had a linear relationship to CLP release rates from the OPTs.

CONCLUSION

The present results confirmed that the membrane controlling factors responsible for the drug release were the amount and size of micronized lactose and the amount of TEC in the membrane.

Mitochondrial DNA replication in human T lymphocytes is regulated primarily at the H-strand termination site

The most unique feature in the replication of mitochondrial DNA (mtDNA) is that most of the newly synthesized heavy strands (H-strands) terminate prematurely, resulting in the formation of displacement loop (D-loop) strands. Only the H-strand which proceeds past the termination site is a true nascent H-strand leading to the overall replication on a circular mtDNA molecule. The physiological significance of the D-loop formation has long been unclear. To examine the role of premature termination in mtDNA replication, we therefore developed a method for selectively measuring both the total amount of nascent H-strands and the amount of true nascent H-strands using ligation-mediated polymerase chain reaction, which, for the first time, enabled us to estimate the frequency of premature termination. The stimulation of cell proliferation with interleukin 2 and phytohemagglutinin in human peripheral T lymphocytes caused an increase in the net replication rate of mtDNA. In stimulated cells, in comparison to resting ones, the amount of true nascent H-strands increased approx. 2.6-fold while the total amount of nascent H-strands remained unchanged, indicating that premature termination decreased while the initiation of replication remained the same. Our findings thus demonstrate the first clear example that premature termination plays a primary role in the up-regulation of the net rate of mtDNA replication in human cells.

Inhibition of attachment and chemotactic invasion of uterine endometrial cancer cells by a new vinca alkaloid, conophylline

The effect of conophylline, a new vinca alkaloid that inhibits ras expression, on tumour cell adhesion and infiltration was evaluated using a human endometrial cancer cell line. When SNG-II, a highly differentiated human endometrial cancer cell line, was exposed to conophylline, the cells developed filamentous processes at concentrations which did not affect cell proliferation (0.03-0.3 microgram/ml). After exposure to conophylline (0.3 microgram/ml), cells adherent to matrigel- and type IV collagen-coated wells respectively decreased to 26.9% and 33.3% of the number in the untreated control culture (p < 0.01). In an in vitro invasion assay using a Boyden chamber, infiltration of cells exposed to conophylline decreased to 19.4% (0.3 microgram/ml) (p < 0.01) of the control. In a wound assay, conophylline inhibited the movement of cells at 24 hr after wounding. Flow cytometric analysis revealed that expression of integrin beta 1 was not altered by conophylline, but E-cadherin and CD44 were decreased. The expression of E-cadherin and CD44 could be changed by conophlline.

Positron emission tomographic measurement of acetylcholinesterase activity reveals differential loss of ascending cholinergic systems in Parkinson's disease and progressive supranuclear palsy

We measured brain acetylcholinesterase activity in 16 patients with Parkinson's disease (PD), 12 patients with progressive supranuclear palsy (PSP), and 13 age-matched controls, using N-methyl-4-[11C]piperidyl acetate and positron emission tomography. Kinetic analysis was performed to calculate k3, an index of acetylcholinesterase activity. In PD patients, there was a significant reduction (-17%) of cerebral cortical k3 compared with normal controls, whereas there was only a nonsignificant reduction (-10%) of cortical k3 in PSP patients. However, there was a prominent reduction (-38%) of thalamic k3 in PSP patients compared with normal controls, whereas there was only a nonsignificant reduction (-13%) of thalamic k3 in PD patients. The results suggest that there is a loss of cholinergic innervation to the cerebral cortex in association with cholinergic innervation to the thalamus in PD, whereas there is a preferential loss of cholinergic innervation to the thalamus in PSP. When the thalamic to cerebral cortical k3 ratio was taken for each subject, PD and PSP were separated, suggesting that positron emission tomography measurement of acetylcholinesterase activity may be useful for differentiating the two similar disorders.

Design and evaluation of an osmotic pump tablet (OPT) for chlorpromazine using (SBE)7m-beta-CD

PURPOSE

The purpose of this study was to develop a controlled-porosity osmotic pump tablet (OPT) which exhibits pH-independent release profiles for a basic drug using a sulfobutyl ether-beta-cyclodextrin, (SBE)7m-beta-CD, which acts as both a solubilizer and as an osmotic agent.

METHODS

Chlorpromazine free base (CLP) was chosen as a model drug for this study. The release of CLP from osmotic pump tablets was studied in vitro. In vivo absorption of CLP from the OPT was evaluated in male beagle dogs.

RESULTS

The CLP release profile from an OPT prepared from a core tablet composed of a 1:10 molar ratio of CLP to (SBE)7m-beta-CD was pH-independent, and was controlled by modulating the membrane thickness of the OPT. Another cyclodextrin, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and a sugar mixture of lactose and fructose resulted in pH-dependent release at the same molar ratio. An in vivo absorption study in dogs with an OPT containing (SBE)7m-beta-CD correlated very well with the in vitro release profiles using the Japanese Pharmacopoeia dissolution method.

CONCLUSIONS

In addition to serving as a solubilizer and osmotic agent, (SBE)7m-beta-CD can also serve as the controlling agent for pH independent release of CLP from OPTs. This system successfully modified the in vivo input rate of CLP without compromising oral bioavailability.

Characterization of itraconazole/2-hydroxypropyl-beta-cyclodextrin inclusion complex in aqueous propylene glycol solution

The interaction of itraconazole, a triazole antifungal agent, with 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) in water and 10% v/v propylene glycol/water solution at pH 2.0 was investigated by the solubility method and ultraviolet and 1H-nuclear magnetic resonance (NMR) spectroscopies. The solubility of itraconazole in water significantly increased as the concentrations of HP-beta-CyD were augmented, showing an AP type phase solubility diagram. The upward curvature closely corresponded to the simulation curve which was calculated on the basis of the 1:2 (guest:host) complexation model. The 1:2 complex was formed even in the presence of 10% v/v propylene glycol, although the co-solvent system made the interaction with HP-beta-CyD weaker due to the competitive inclusion. The ultraviolet spectroscopic studies also supported the 1:2 complex formation of itraconazole with HP-beta-CyD in 10% v/v propylene glycol/water solution at pH 2.0. The 1H-NMR spectroscopic studies suggested that the triazole and triazolone moieties of itraconazole are involved in the 1:2 inclusion complexation.

Lithium decreases Cl--ATPase activity and increases intracellular Cl- concentration in cultured rat hippocampal neurons

Under the conditions of stimulated phosphatidylinositol turnover (0. 1 mM carbachol plus 20 mM KCl), LiCl (0.1-10 mM) reduced the activity of Cl--ATPase in cultured rat hippocampal neurons without affecting Na+/K+- or anion-insensitive Mg2+-ATPase. This inhibition of Cl--ATPase was attenuated by the addition of 0.5 mM inositol to culture media. The intracellular Cl- concentrations of the LiCl-treated neurons increased in an inositol-sensitive manner.

Does resection of small liver metastases from colorectal cancer improve survival of patients?

Because the size of metastases greatly affects their detection, we retrospectively investigated the influence of the size of liver metastases on survival after hepatic surgery. The subject group study consisted of 77 patients who underwent liver surgery for metastases from colorectal cancer. The survival rate after hepatic surgery was analysed using multivariate Cox's proportional hazards model with the following variables: (1) size of dominant metastases (Small: < 3 cm; Medium: > or = 3 cm and < 6 cm; Large: > or = 6 cm); (2) synchronous versus metachronous resection; (3) solitary versus multiple metastases. The size of dominant metastases (p = 0.035) and synchronous versus metachronous resection (p = 0.0009) were independently associated with survival after liver resection. No association was found, however, for solitary versus multiple metastases. The survival of the Large group was much poorer than that of the Small group (p = 0.0168) and that of the Medium group (p = 0.0205), with statistically significant differences. No statistically significant difference was seen between the Small and the Medium groups (p = 0.7963). This study showed that long-term survival following resection of metastases was much poorer when metastases were 6 cm or greater in diameter. With regard to metastases less than 6 cm in diameter, resection of the smallest of these (less than 3 cm) did not appear to improve survival.

Human cerebral acetylcholinesterase activity measured with positron emission tomography: procedure, normal values and effect of age

The regional cerebral metabolic rate of [11C]N-methyl-4-piperidyl acetate, which is nearly proportional to regional cerebral acetylcholinesterase (AChE) activity, was measured by dynamic positron emission tomography in 20 healthy subjects with a wide age range (24-89 years). Quantitative measurement was achieved using a kinetic model which consisted of arterial plasma and cerebral tissue compartments. The plasma input function was obtained using thin-layer chromatography and an imaging phosphor plate system at frequent sampling intervals to catch the rapid metabolism of the tracer in the blood. The distribution of the rate constant k3, an index of AChE activity, agreed well with reported post-mortem AChE distribution in the cerebral cortex (0.067-0.097 min-1) and thalamus (0.268 min-1), where AChE activity was low to moderate. The k3 values in the striatum and cerebellum, where AChE activity was very high, did not respond linearly to AChE activity because of increased flow dependency. No significant effect of age was found on AChE activity of the cerebral cortex, suggesting that the ascending central cholinergic system is preserved in normal aging. This study has shown that quantitative measurement of enzyme activity in the living brain is possible through appropriate modelling of tracer kinetics and accurate measurement of the input function. The method should be applicable to patients with Alzheimer's disease and those with other kinds of dementia whose central cholinergic system has been reported to be disturbed.

Enhanced absorption of cyclosporin A by complexation with dimethyl-beta-cyclodextrin in bile duct-cannulated and -noncannulated rats

The enhancing effects of dimethyl-beta-cyclodextrin (DM-beta-CyD) on the absorption of cyclosporin A (CsA) after oral administration to rats under bile duct-cannulated and -noncannulated conditions were investigated. The dissolution rate of CsA was markedly augmented by complexation with DM-beta-CyD. In a closed loop in situ study, DM-beta-CyD considerably increased the cumulative amounts of CsA in the mesenteric venous blood after injection of the aqueous CsA suspension into the small intestinal sac of rats. In addition, the cumulative amount ratio of M1, the dominant metabolite of CsA in rats, to CsA in the mesenteric venous blood for up to 40 min after the injection of the CsA-DM-beta-CyD suspension into the sac was lower than that of the CsA suspension alone. DM-beta-CyD inhibited the bioconversion of CsA in the small intestinal microsomes of rats. These results indicate that the bioconversion of CsA was abated by complexation with DM-beta-CyD. An in vivo study revealed that DM-beta-CyD increased the transfer of CsA to blood, not lymph, with low variability in the absorption after oral administration of the CsA suspension to rats. The variability of bioavailability of DM-beta-CyD complex was lower than that of Sandimmune, although the extent of bioavailability of DM-beta-CyD was only a little higher than that of Sandimmune. The bioavailability of CsA or its DM-beta-CyD complex was appreciably decreased by the cannulation of the bile duct of rats, and the extent of the lowering in the bioavailability in the presence of DM-beta-CyD was much less serious than that of CsA alone. The present results suggest that DM-beta-CyD is particularly useful in designing oral preparations of CsA with an enhanced bioavailability and a reduced variability in absorption.

1-Methyl-4-phenylpyridinium ion (MPP+) selectively inhibits the replication of mitochondrial DNA

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine is known to cause Parkinsonism in its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+). We have previously reported that MPP+ decreases the content of mitochondrial DNA (mtDNA) independently of the inhibition of complex I in human cells [Miyako, K., Kai, Y., Irie, T., Takeshige, K., and Kang, D. (1997) J. Biol. Chem. 272, 9605-9608]. Here we study the mechanism causing the decrease in mtDNA. MPP+ inhibits the incorporation of 5-bromo-2'-deoxyuridine into mtDNA but not into nuclear DNA, indicating that MPP+ inhibits the replication of mtDNA but not that of the nuclear genome. The replication of mtDNA is initiated by the synthesis of the heavy strand switched from the transcription of the light strand. MPP+ decreases the nascent heavy strands per mtDNA and increases the transcript of the ND6 gene, encoded on light strand, per mtDNA. The amount of mitochondrial transcription factor A is not decreased. These data suggest that the transcription is not inhibited and therefore the transition from transcription to replication of mtDNA is lowered in the MPP+-treated cells. Electron microscopy shows that the number of mitochondria is not decreased in the MPP+-treated cells, suggesting that MPP+ does not affect the overall biogenesis of mitochondria. Thus, MPP+ selectively inhibits the replication of mtDNA.

[Clinical outcomes in low grade follicular lymphoma]

Twenty-six patients with follicular small-cleaved lymphoma (FSCL) and 16 patients with follicular mixed lymphoma (FML) were treated at the Nichidai Itabashi Hospital between 1981 and 1995. The 5-year overall survival rate was 74.3% and 70.0% for the FSCL and FML patients, respectively. Of the patients with stage III-IV FSCL, 9 were assigned to a "watchful waiting" follow-up course and 13 were treated with a single alkylating agent or CHOP therapy. The 5-year failure-free survival rate was 66.7% and 33.0%, respectively. Of the patients with stage II-IV FML, 6 were treated with CHOP or MACOP-B protocol. The complete response rate for this group was only 33.3%, and none of the patients were in remission for more than 2 years. Histological transformation into diffuse aggressive lymphoma was observed in 7 patients, with the median time from diagnosis to transformation at 50 months. Three of those patients were successfully treated with intensive chemotherapy after transformation.

Residual disease and presence of human papillomavirus after conization

The objective of this study was to evaluate the incidence of residual disease and the presence of human papillomavirus (HPV) after conization. Data on 53 patients with carcinoma in situ or microinvasive carcinoma who underwent hysterectomy less than 2 months after conization were examined. Seven of 53 patients (13%) had positive margins. In 4 of these 7 patients (57%), residual disease was found in the postconization hysterectomy specimen. Two of 46 patients (4%) with negative margins also had residual disease. HPV DNA was detected by PCR in 27 of 53 conization specimens and in 2 postconization hysterectomy specimens. Of 2 patients, 1 did not have residual disease. Residual disease could be present even with a negative conization margin, and HPV DNA may be found in a histologically normal cervix after conization.

Role of neutrophil elastase in stress-induced gastric mucosal injury in rats

Activated neutrophils play an important role in tissue injury by releasing various inflammatory mediators capable of damaging endothelial cells. To investigate whether neutrophil elastase (NE) is involved in stress-induced gastric mucosal injury, we examined the effects of 2 NE inhibitors (ONO-5046 and L-658 758) as well as nitrogen mustard-induced leukocytopenia on the formation of gastric mucosal lesions, gastric mucosal blood flow, gastric mucosal microvascular permeability, and gastric neutrophil accumulation in rats subjected to water immersion-restraint stress (WIR). Gastric mucosal injury peaked 8 hours after WIR. Gastric mucosal blood flow, as measured by laser-Doppler flow cytometry, decreased to 45% of its initial level 8 hours after WIR. Gastric mucosal microvascular permeability, evaluated by Evans blue dye leakage to the gastric mucosa, showed an increase, peaking 8 hours after WIR. Gastric accumulation of neutrophils, determined by measuring gastric myeloperoxidase activity and by histologic examination, was also significantly increased 8 hours after WIR. Both of the NE inhibitors markedly prevented the formation of gastric mucosal lesions. They also decreased the reduction in gastric mucosal blood flow seen in animals subjected to WIR while preventing increases in gastric mucosal microvascular permeability. Gastric neutrophil accumulation was significantly reduced in animals given either inhibitor 8 hours after WIR. Leukocytopenia produced effects similar to those produced by the inhibitors. Taken together, these observations strongly suggest that NE promotes stress-induced gastric mucosal injury in rats by reducing gastric mucosal blood flow and increasing neutrophil accumulation.

The metabolic pathway of visual pigment chromophore formation in Drosophila melanogaster--all-trans (3S)-3-hydroxyretinal is formed from all-trans retinal via (3R)-3-hydroxyretinal in the dark

Carotenoid-depleted fruit flies, Drosophila melanogaster, were reared on yeast/glucose medium containing lipid-depleted white corn grits and cholesterol. After rearing for more than a year, the yield of flies remained constant and the content of 3-hydroxyretinal in a head was three logarithmic units less than that of normal flies reared on medium containing yellow corn grits. When all-trans retinal was supplied as the sole source of retinoids, the flies formed and accumulated all-trans 3-hydroxyretinal in the dark. To examine the metabolic pathway to produce (3S)-3-hydroxyretinal in Drosophila, all-trans retinal was supplemented for two hours to carotenoid-depleted flies in the dark, and the subsequent changes in the composition of 3-hydroxyretinal enantiomers were analyzed using a chiral column on HPLC. The results indicated initial formation of (3R)-3-hydroxyretinal followed by isomerization into the 3S enantiomer. In another set of experiments, the membrane fraction was obtained from the head homogenate of retinoid-depleted flies and an in vitro assay of 3-hydroxyretinal formation from retinal was performed. The 3-hydroxyretinal produced was the 3R enantiomer, supporting the result obtained from the in vivo experiment whereby (3S)-3-hydroxyretinal is produced from retinal via (3R)-3-hydroxyretinal. Addition of NADPH enhanced 3-hydroxyretinal formation and the presence of carbon monoxide inhibited it, suggesting that hydroxylation at the C3 position of retinal occurred via the monooxygenase activity of cytochrome P-450.

A newly developed adenovirus-mediated transfer of a wild-type p53 gene increases sensitivity to cis-diamminedichloroplatinum (II) in p53-deleted ovarian cancer cells

A new recombinant adenovirus carrying a wild-type p53 gene (AxCAp53) was developed and the combination effect of p53 gene transfer and cis-diamminedichloroplatinum (II) (CDDP) was examined in an ovarian cancer cell line, SK-OV-3, with deletion of the p53 gene. AxCAp53 showed a high efficiency of gene transduction and increased sensitivity to CDDP in the SK-OV-3 cells. It was found that the sensitivity of the cells to CDDP correlated with the amount of infectious units of virus per cell of AxCAp53 which correlated with p53 protein expression. The results suggest that the combination of CDDP and AxCAp53 may be a potential strategy for the therapy of CDDP-resistant ovarian cancer.

Design and evaluation of an osmotic pump tablet (OPT) for prednisolone, a poorly water soluble drug, using (SBE)7m-beta-CD

PURPOSE

The purpose of this study was to develop a controlled-porosity osmotic pump tablet (OPT) for poorly water soluble drugs using a sulfobutyl ether-beta-cyclodextrin, (SBE)7m-beta-CD or Captisol, which acted as both a solubilizer and as an osmotic agent.

METHODS

Prednisolone (PDL) was chosen as a model drug for this study. The release of PDL from osmotic pump devices and tablets was studied. In vivo absorption of PDL from OPT was evaluated in male beagle dogs.

RESULTS

PDL release from the osmotic pump tablet with (SBE)7m-beta-CD was complete. Another cyclodextrin, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and a sugar mixture of lactose and fructose resulted in incomplete release. Although PDL release from the OPT with (SBE)7m-beta-CD and the sugar formulation displayed mainly zero-order release characteristics, the tablet utilizing HP-beta-CD showed apparent first-order release characteristics. An in vivo absorption study in dogs correlated very well with the in vitro release profiles using the Japanese Pharmacopoeia dissolution method.

CONCLUSIONS

The present results confirm that (SBE)7m-gamma-CD can serve as both the solubilizer and the osmotic agent for OPT of PDL, and modify the input rate of PDL without compromising oral bioavailability.

Design, synthesis and evaluation of transition-state analogue inhibitors of Escherichia coli gamma-glutamylcysteine synthetase

Phosphinic acid-, sulfoximine- and sulfone-based transition-state analogues were synthesized and evaluated as inhibitors of Escherichia coli gamma-glutamylcysteine synthetase. These compounds have a carboxyl function at the beta-carbon to the tetrahedral central hetero atom so as to mimic the carboxyl group of the attacking cysteine in the transition state. The phosphinic acid- and the sulfoximine-based compounds were found to be potent ATP-dependent inactivators, both showing a slow-binding kinetics with overall affinities and second-order inactivation rates of one to two orders of magnitude greater than those of L-buthionine (SR)-sulfoximine (L-BSO). The sulfone was a simple reversible inhibitor without causing ATP-dependent enzyme inactivation, but its affinity toward the enzyme was still five times greater than that of L-BSO, indicating that the beta-carboxyl function plays a key role in the recognition of the inhibitors by the enzyme. The sulfoximine with (S)-beta-carbon to the sulfur was synthesized stereoselectively, and the two diastereomers with respect to the chiral sulfur atom were separated as a cyclic sulfoximine derivative. The sulfoximine with R-configuration around the sulfur served as an extremely powerful ATP-dependent inactivator with an overall inhibition constant of 39 nM and an inactivation rate of 6750 M-1 s-1, which correspond to 1260-fold higher affinity and almost 1400-fold greater inactivation rate as compared with L-BSO. The sulfoximine with (S)-sulfur was a simple reversible inhibitor with an inhibition potency comparable to that of the sulfone. The synthesis and inhibition profile of the N-phosphoryl sulfoximine is also described.

Chloride concentration in cultured hippocampal neurons increases during long-term exposure to ammonia through enhanced expression of an anion exchanger

The effects of long-term exposure to ammonia on [Cl-]i in cultured hippocampal neurons were examined. Ammonia increased the [Cl-]i time- (>/=24 h) and concentration- (>/=2 mM) dependently, resulting in a depolarizing shift of the equilibrium potential of the GABAA receptor-Cl- channel opening (EGABA). Such an effect of ammonia was diminished by the inhibitors of Cl-/HCO3- exchangers, 0.1 mM 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) and 0.1 mM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), and a carbonic anhydrase inhibitor, 2 mM acetazolamide, but not by a Na+/K+/2Cl-cotransport inhibitor, 50 microM bumetanide, suggesting an enhanced Cl-/HCO3- exchange activity by ammonia. The ammonia-induced increase in [Cl-]i was also abolished by the inhibitors of protein kinase C (PKC), 0.1 microM calphostin C and 10 microM 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine dihydrochloride (H-7), and of transcription and de novo protein synthesis, 1 microM actinomycin D and 0.5 microg/ml cycloheximide, while a PKC activator, 0.1 h microM phorbor 12-myristate 13-acetate (PMA), increased the [Cl-]i. The mRNA level of the AE3 Cl-/HCO3- exchanger was increased by ammonia in a calphostin C- and H-7-sensitive manner. The AE3-like immunoreactivity was also increased by ammonia. These findings suggest that long-term exposure to ammonia increases the expression of AE3 through the activation of PKC, resulting in an increase in [Cl-]i in neurons and a reduction of inhibitory postsynaptic potentials.