Functional and histochemical analysis of MDR3 P-glycoprotein in a tetracycline-controlled gene expression system

Aim of the present study was to establish a cell system to study the physiological function of human MDR3 P-glycoprotein in cellular phosphatidylcholine (PC) secretion. MDR3 cDNA was expressed in HeLa cells using the tet-off system together with a luciferase reporter gene. MDR3 Pgp expression was turned on upon removal of doxycycline as shown by Western blot analysis. Immunohistochemistry using a specific anti human MDR3 Pgp antibody revealed a prominent staining of MDR3 Pgp covering the cytoplasm and the area of the plasma membrane. In presence of doxycycline MDR3 Pgp expression was turned off. For analysis of PC secretory activity, MDR3 Pgp expressing and non-expressing cells as well as control HeLa cells with low endogenous MDR3 were preincubated with [(3)H]choline for synthesis of cellular [(3)H]PC. Cells were then incubated for 2 h in media with 0-4 mM taurocholate (TC) and release of cellular [(3)H]PC was recorded. [(3)H]PC secretion was observed in presence of TC without impairing cell viability. There was a significant increase in [(3)H]PC excretion in MDR3 Pgp expressing cells compared to non-expressing controls (e.g. 4.5 fold at 4 mM TC), revealing a high efficiency of transport activity (turnover). From the data it is concluded that the MDR3 Pgp expressing cell system under control of a doxycycline responsive promotor is functionally active and provides a tool to further study MDR3 Pgp mediated transport.

[Pulmonal sarcoidosis: A rare side effect of interferon-alpha treatment for chronic hepatitis C infection]

This is a case report of a 44-year-old woman who received a 1-year-treatment with interferon-alpha for chronic hepatitis C virus infection. 3 months after cessation of the therapy she relapsed and was successfully retreated 12 months with a combination of interferon-alpha and ribavirin thereafter. During the treatment the patient developed a typical flue-like syndrome, dry cough with exertional dyspnea that was initially interpreted as a typical side effect of interferon-alpha treatment. Due to the persisting cough, further radiologic and histologic work up was done and results were significant for interstitial sarcoidosis. After interferon-treatment was stopped the pulmonary symptoms resolved completely while pathologic changes in radiographic imaging persisted. Interferon-alpha may have contributed to the development and progression of sarcoidosis by activation of cellular immunity. Although there are only few reports about pulmonary sarcoidosis associated with interferon-alpha treatment, this entity should be included in the differential diagnosis of putative side effects of interferon-alpha therapy.

Indications for the presence of an atypical protease-activated receptor on rat platelets

Activation of the protease-activated receptor (PAR)-1, one of four known PARs (PAR-1 to PAR-4), can be mimicked by thrombin receptor activating peptides (TRAPs) based on the PAR-1 tethered ligand. Interestingly, despite being activatable by thrombin, rodent platelets do not express PAR-1 and thus do not respond to PAR-1-derived TRAPs, indicating different activation mechanisms between human and rodent platelets. Using a rat platelet aggregation model, we determined that TRAPs based on the tethered ligand of PAR-1 fail to activate rat platelet aggregation at concentrations up to 1 mmol/l. In addition, TRAPs inhibit thrombin-mediated rat platelet aggregation, indicating the presence of a modified PAR-1 in this species. In order to determine characteristics of this putative receptor, we tested a panel of synthesized TRAPs based on the rat sequence (R) and human sequence (H) of the PAR-1 tethered ligand for their ability to inhibit thrombin-induced rat platelet aggregation. Peptides R1-9, R4-9, R4-10, and H4-10 inhibited rat platelet aggregation in response to alpha-thrombin [inhibitory concentration (IC) 50% 0.25-1.5 mmol/l]. None of these peptides blocked epinephrine-, collagen-, or arachidonic acid-induced platelet aggregation. Alanine substitution mapping of H4-10 indicated that both Leu4 and Arg5 are essential for inhibition. Inhibition of thrombin's catalytic activity required peptide concentrations tenfold higher than inhibition of platelet aggregation (IC50% 3-5 mmol/l). No prolongation of thrombin clotting time in response to TRAPs was detected at peptide concentrations up to 5 mmol/l. Our data suggest that (1) rat platelets express a PAR-1 subtype, (2) residues Leu4 and Arg5 of the tethered ligand peptide are required for binding to this new receptor, and (3) further analysis of peptide sequences might reveal a novel PAR-1 subtype.

Fatty acid transporters in plasma membranes of cardiomyocytes in patients with dilated cardiomyopathy

BACKGROUND

Long-chain fatty acids are one of the major cardiac energy substrates. Although the exact mechanism of myocardial fatty acid uptake is not known, several proteins, including the integral membrane proteins FATP1 (fatty acid transport protein 1) and FAT (fatty acid translocase), are being implicated in this process. The aim of this study was to further investigate FATP1 and FAT in the heart and its potential role in myocardial fatty acid utilization. -

METHODS

The expression of FATP1 and FAT in mouse myocardium and in myocardial biopsies of 14 patients with different cardiomyopathies was detected by immunocytochemistry and visualized with a laser scanning microscope. -

RESULTS

FAT and FATP1 are co-expressed on the plasma membrane of cardiac endothelial cells and on the sarcolemma of cardiomyocytes. The staining-pattern and the intensity of signal for both transport proteins was constant in different cardiomyopathies compared with the expression in biopsies of patients with other cardiac diseases and the expression in the myocardium of healthy mice. -

CONCLUSION

Cardiac endothelial cells and cardiomyocytes express FAT and FATP1 in vivo, suggesting an active part of these proteins in the uptake process of long-chain fatty acids. However, we did not find evidence for an altered expression of fatty acid transport proteins in patients with dilated cardiomyopathy, suggesting that these proteins are of minor importance in this kind of heart failure.

Analysis of Qa-1(b) peptide binding specificity and the capacity of CD94/NKG2A to discriminate between Qa-1-peptide complexes

The major histocompatibility complex class Ib protein, Qa-1(b), serves as a ligand for murine CD94/NKG2A natural killer (NK) cell inhibitory receptors. The Qa-1(b) peptide-binding site is predominantly occupied by a single nonameric peptide, Qa-1 determinant modifier (Qdm), derived from the leader sequence of H-2D and L molecules. Five anchor residues were identified in this study by measuring the peptide-binding affinities of substituted Qdm peptides in experiments with purified recombinant Qa-1(b). A candidate peptide-binding motif was determined by sequence analysis of peptides eluted from Qa-1 that had been folded in the presence of random peptide libraries or pools of Qdm derivatives randomized at specific anchor positions. The results indicate that Qa-1(b) can bind a diverse repertoire of peptides but that Qdm has an optimal primary structure for binding Qa-1(b). Flow cytometry experiments with Qa-1(b) tetramers and NK target cell lysis assays demonstrated that CD94/NKG2A discriminates between Qa-1(b) complexes containing peptides with substitutions at nonanchor positions P4, P5, or P8. Our findings suggest that it may be difficult for viruses to generate decoy peptides that mimic Qdm and raise the possibility that competitive replacement of Qdm with other peptides may provide a novel mechanism for activation of NK cells.

Spontaneous regression of intrahepatic lesions mimicking metastatic disease

This is a case report of a 53-year-old male with chronic hepatitic C infection presenting with weight loss and elevated liver function tests. Repeated ultrasonography, computed tomography and magnet resonance imaging showed multiple intrahepatic lesions suggestive of metastatic disease. Repeated ultrasound-guided biopsies from the lesions as well as from the adjacent normal appearing liver tissue revealed no malignancy but showed inflammation and significant fibrotic tissue, consistent with chronic hepatitis C. 2 years after the first admission liver function tests were all within the normal range and remained so until today. Computed tomography at that time showed complete remission of all intrahepatic lesions. The exact diagnosis remained elusive but the rare case of reversible focal fibrosis is the most likely cause of these spontaneously regressive lesions.

Inactivation of aldophosphamide by human aldehyde dehydrogenase isozyme 3

Tumors resistant to chemotherapeutic oxazaphosphorines such as cyclophosphamide often overexpress aldehyde dehydrogenase (ALDH), some isozymes of which catalyze the oxidization of aldophosphamide, an intermediate of cyclophosphamide activation, with formation of inert carboxyphosphamide. Since resistance to oxazaphosphorines can be produced in mammalian cells by transfecting them with the gene for human ALDH isozyme 3 (hALDH3), it seems possible that patients receiving therapy for solid tumors with cyclophosphamide might be protected from myelosuppression by their prior transplantation with autologous bone marrow that has been transduced with a retroviral vector causing overexpression of hALDH3. We investigated whether retroviral introduction of hALDH3 into a human leukemia cell line confers resistance to oxazaphosphorines. This was examined in the polyclonal transduced population, that is, without selecting out high expression clones. hALDH3 activity was 0.016 IU/mg protein in the transduced cells (compared with 2x10(-5) IU/mg in untransduced cells), but there was no detectable resistance to aldophosphamide-generating compounds (mafosfamide or 4-hydroperoxycyclophosphamide). The lack of protection was due, in part, to low catalytic activity of hALDH3 towards aldophosphamide, since, with NAD as cofactor, the catalytic efficiency of homogeneous, recombinant hALDH3 for aldophosphamide oxidation was shown to be about seven times lower than that of recombinant hALDH1. The two polymorphic forms of hALDH3 had identical kinetics with either benzaldehyde or aldophosphamide as substrate. Results of initial velocity measurements were consistent with an ordered sequential mechanism for ALDH1 but not for hALDH3; a kinetic mechanism for the latter is proposed, and the corresponding rate equation is presented.

cAMP-dependent protein kinase inhibits mGluR2 coupling to G-proteins by direct receptor phosphorylation

One of the primary physiological roles of group II and group III metabotropic glutamate receptors (mGluRs) is to presynaptically reduce synaptic transmission at glutamatergic synapses. Interestingly, previous studies suggest that presynaptic mGluRs are tightly regulated by protein kinases. cAMP analogs and the adenylyl cyclase activator forskolin inhibit the function of presynaptic group II mGluRs in area CA3 of the hippocampus. We now report that forskolin has a similar inhibitory effect on putative mGluR2-mediated responses at the medial perforant path synapse and that this effect of forskolin is blocked by a selective inhibitor of cAMP-dependent protein kinase (PKA). A series of biochemical and molecular studies was used to determine the precise mechanism by which PKA inhibits mGluR2 function. Our studies reveal that PKA directly phosphorylates mGluR2 at a single serine residue (Ser(843)) on the C-terminal tail region of the receptor. Site-directed mutagenesis combined with biochemical measures of mGluR2 function reveal that phosphorylation of this site inhibits coupling of mGluR2 from GTP-binding proteins

Survival of nurse-managed centers: the importance of cost analysis

Despite the explosive growth in nurse-managed centers (NMC) in the past 20 years, most have been unable to achieve financial self-sufficiency, and many have closed. Combining costing techniques with outcome measures provides essential information needed by NMC for making operating decisions and for marketing NMC performance. These outcome data can be persuasive to policy makers and institutional decision makers and are crucial for NMC to improve their competitiveness in the health care market place.

Spatial information transfer from virtual to real versions of the Kiel locomotor maze

The Kiel locomotor maze requires participants to choose five targets from among 20 locations marked by small red lights on the floor of a dimly lit circular environment having four wall-mounted extramaze cues and two intramaze cues at floor level. In the present study, acquisition of the real task was examined in 11-year-old children following prior accurate training in a virtual version, following misleading virtual training, or following no training. The virtual version was displayed on a desk-top computer monitor. Acquisition testing in the real maze was either locomotor or non-locomotor. Good transfer was achieved from virtual to real versions. Children's exploration of the real maze prior to real maze acquisition training revealed a clear transfer of spatial information previously learned in the virtual version. Children taught the correct target configuration in the simulation made fewer errors and more rapid, confident responses to targets in the real maze than children given no training. However, acquisition was also better following misleading training than no training, suggesting that a non-specific components of performance also transferred. Male superiority was only seen following misleading training, which was interpreted in terms of male superiority in mental rotation. After acquisition, a single probe trial was performed, in which proximal cues and participants' starting position were rotated, but this had equivalent effects on all groups' performance. It is clear that transfer of spatial information occurs from the simulated Kiel maze to the real version. This has implications for its use in diagnosis and training.

Modulation of endometrial steroid receptors and growth regulatory genes by tamoxifen

OBJECTIVE

We investigated tamoxifen's effects on the expression of growth regulatory genes in the endometrium to identify the mechanism by which tamoxifen induces proliferation.

METHODS

Using immunohistochemical techniques, we analyzed 39 endometrial specimens for expression of Ki-67, lactoferrin, transforming growth factor-alpha, tumor necrosis factor receptor-II, adrenomedullin, estrogen receptors, and progesterone receptors. Twenty specimens were obtained from postmenopausal breast cancer patients treated with tamoxifen (20 mg/day) for at least 6 months to include two endometrial adenocarcinoma specimens. Five secretory phase, three proliferative phase, and seven atrophic endometrial specimens were used as controls. In addition, four endometrial adenocarcinoma specimens were reviewed from patients not treated with tamoxifen. Intensity of immunostaining was quantified using digitized imaging techniques.

RESULTS

Overexpression of both estrogen receptors and progesterone receptors, and an elevated proliferative index were the most consistent effects observed in benign endometrial specimens from tamoxifen-treated patients compared with atrophic controls (P <. 003). This staining pattern was also evident in adenocarcinomas from patients who received tamoxifen. Benign endometrium from tamoxifen-treated patients also expressed transforming growth factor-alpha, tumor necrosis factor receptor-II, lactoferrin, and adrenomedullin at levels comparable with those found in proliferative endometrial specimens.

CONCLUSION

These data provide further documentation that the uterotropic effects of tamoxifen may be due, at least in part, to the induction of estrogen receptors and progesterone receptors, as well as other genes associated with the proliferative phase. Furthermore, analysis of estrogen receptors, progesterone receptors, and Ki-67 may be useful in identifying postmenopausal individuals on tamoxifen, who are at increased risk for developing endometrial cancer.

Mechanistic aspects of the cytotoxic activity of glufosfamide, a new tumour therapeutic agent

Beta-D-glucosyl-ifosfamide mustard (D 19575, glc-IPM, INN = glufosfamide) is a new agent for cancer chemotherapy. Its mode of action, which is only partly understood, was investigated at the DNA level. In the breast carcinoma cell line MCF7 glufosfamide inhibited both the synthesis of DNA and protein in a dose-dependent manner, as shown by the decreased incorporation of [3H-methyl]-thymidine into DNA and [14C]-methionine into protein of these cells. Treatment of MCF7 cells with 50 microM glufosfamide was sufficient to trigger poly(ADP-ribose) polymerase (PARP) activation, as revealed by immunofluorescence analysis. Both CHO-9 cells, which are O6-methylguanine-DNA methyltransferase (MGMT)-deficient, and an isogenic derivative, which has a high level of MGMT, showed the same cytotoxic response to beta-D-glc-IPM, indicating that the O6 position of guanine is not the critical target for cytotoxicity. By contrast, a sharp decrease in survival of cross-link repair deficient CL-V5 B cells was observed already at concentrations of 0.1 mM beta-D-glc-IPM, whereas the wild-type V79 cells showed a 90% reduction in survival only after treatment with 0.5 mM of this compound. The therapeutically inactive beta-L-enantiomer of glufosfamide also showed genotoxic effects in the same assays but at much higher doses. This was probably due to small amounts of ifosfamide mustard formed under the conditions of incubation. The results indicate that the DNA crosslinks are the most critical cytotoxic lesions induced by beta-D-glc-IPM.

[Megaloblastic anemia in a psychogenic eating disorder]

HISTORY AND ADMISSION FINDINGS

A 68-year-old woman had progressively lost strength over the past 5 years and become bed-ridden. She reported gradually reducing her diet during the last few years, for the last two years restricting herself to oatmeal, biscuits and water. Acute exacerbation of dyspnoea, dizziness, tachycardia and cardiac arrhythmias for the last 3 month necessitated her emergency admission when she was found to have oedema of the limbs and definite jaundice, as well as predominantly distal sensory deficits in the legs, a slightly ataxic gait and poor reflexes in the limbs.

INVESTIGATIONS

She was found to have pancytopenia with marked megaloblastic anaemia (haemoglobin 4.8 mg/dl, mean red cell volume 141.8 fl, leukocytopenia 41/nl), marked haemolysis (lactate dehydrogenase 1629 U/l, haptohaemoglobin < 0.1 g/l, total bilirubin concentration 4.5 mg/dl). Pernicious anaemia was excluded: no antibodies against parietal cells and intrinsic factor, and no atrophic gastritis in a gastric biopsy.

DIAGNOSIS, TREATMENT AND COURSE

Megaloblastic anaemia due to dietary deficiencies with early funicular myelosis was suspected. After infusion of four erythrocyte concentrates and vitamin B12 administration the symptoms and blood picture improved within days.

CONCLUSION

Although dietary causes of megaloblastic anaemia are rare in Central Europe, they must be considered in the differential diagnosis, especially in the elderly and those with psychogenic disorders.

Chemical stability and fate of the cytostatic drug ifosfamide and its N-dechloroethylated metabolites in acidic aqueous solutions

31P NMR spectroscopy was used to study the products of the decomposition of the antitumor drug ifosfamide (IF, 1d) and its N-dechloroethylated metabolites, namely, 2,3-didechloroethylIF (1a) and 2- (1b) and 3-dechloroethylIF (1c), in buffered solutions at acidic pH. The first stage of acid hydrolysis of these four oxazaphosphorines is a P-N bond cleavage of the six-membered ring leading to the phosphoramidic acid monoesters (2a-d) of type R'HN(CH(2))(3)OP(O)(OH)NHR, with R and/or R' = H or (CH(2))(2)Cl. The electron-withdrawing chloroethyl group at the endocyclic and/or exocyclic nitrogens counteracts the endocyclic P-N bond hydrolysis. This effect is even more marked when the N-chloroethyl group is in the exocyclic position since the order of stability is 1d > 1c > 1b > 1a. In the second stage of hydrolysis, the remaining P-N bond is cleaved together with an intramolecular attack at the phosphorus atom by the non-P-linked nitrogen of the compounds 2a-d. This leads to the formation of a 2-hydroxyoxazaphosphorine ring with R = H (3a coming from compounds 2a,c) or (CH(2))(2)Cl (3b coming from compounds 2b,d) and to the release of ammonia or chloroethylamine. The third step is the P-N ring opening of the oxazaphosphorines 3a,b leading to the phosphoric acid monoesters, H(2)N(CH(2))(3)OP(O)(OH)(2) (4a) and Cl(CH(2))(2)HN(CH(2))(3)OP(O)(OH)(2) (4b-1), respectively. For the latter compound, the chloroethyl group is partially (at pH 5.5) or totally (at pH 7.0) cyclized into aziridine (4b-2), which is then progressively hydrolyzed into an N-hydroxyethyl group (4b-3). Compounds 3a,b are transient intermediates, which in strongly acidic medium are not observed with (31)P NMR. In this case, cleavage of the P-N bond of the type 2 phosphoramidic acid monoesters leads directly to the type 4 phosphoric acid monoesters. The phosphate anion, derived from P-O bond cleavage of these latter compounds, is only observed at low levels after a long period of hydrolysis. Compounds 1a-c and some of their hydrolytic degradation products (4b-1, 4b-2, diphosphoric diester [Cl(CH(2))(2)NH(CH(2))(3)OP(O)(OH)](2)O (5), and chloroethylamine) did not exhibit, as expected, any antitumor efficacy in vivo against P388 leukemia. (31)P NMR determination of the N-dechloroethylated metabolites of IF or its structural isomer, cyclophosphamide (CP), and their degradation compounds could provide an indirect and accurate estimation of chloroacetaldehyde amounts formed from CP or IF.

Modulation of expression of endothelial nitric oxide synthase by nordihydroguaiaretic acid, a phenolic antioxidant in cultured endothelial cells

Retrospective epidemiological studies have suggested that antioxidant therapy may decrease cardiovascular morbidity and mortality rates, although the mechanisms for this effect remain unclear. In the present study, we demonstrate that selective antioxidants can enhance expression of endothelial nitric oxide synthase (eNOS). We found that the antioxidants nordihydroguaiaretic acid (NDGA), catechol, glutaryl probucol, and N-acetylcysteine increased eNOS expression in cultured bovine aortic endothelial cells (BAECs). NDGA seemed to be the most potent of the phenolic antioxidants, producing a 3-fold increase in eNOS mRNA. This effect of NDGA was enhanced by nonphenolic antioxidants such as N-acetylcysteine and ascorbic acid. Nuclear run-on studies indicated that NDGA increased eNOS transcription. A similar increase in eNOS protein content was observed with Western blot analysis after treating BAECs or human aortic endothelial cells with NDGA. Exposure of BAECs to NDGA enhanced NO production, as measured by electron paramagnetic resonance spin trapping and eNOS activity, as measured by [14C]arginine-to-[14C]citrulline assay. Methylation of the phenolic hydroxyl groups completely inhibited the NDGA effect on eNOS mRNA levels. This effect of NDGA was not due to inhibition of lipoxygenase because cis-5,8,11,14-eicosatetraynoic acid did not alter eNOS expression. We conclude that antioxidants may not only increase the bioactivity of nitric oxide but also enhance expression of the eNOS enzyme. Such an effect may prove useful in conditions such as hypertension and atherosclerosis, in which nitric oxide production and/or biological activity is impaired.

Neuroprotective effects of growth/differentiation factor 5 depend on the site of administration

Growth/differentiation factor 5 (GDF5) is a neurotrophin which protects the rat nigrostriatal dopaminergic pathway from 6-hydroxydopamine-induced damage. Here we used amphetamine-induced rotational testing, high-performance liquid chromatography and immunocytochemistry to investigate the minimum effective dose of GDF5. We also compared the effectiveness of injecting GDF5 into either the substantia nigra pars compacta (SNpc), the lateral ventricle (LV) or the striatum (or combinations of these sites).

Bone morphogenetic proteins and growth and differentiation factors in the human cornea

PURPOSE

To investigate transcription of members of the transforming growth factor (TGF)-beta superfamily and corresponding receptors in human corneal epithelium and stroma.

METHODS

Transcription of bone morphogenetic proteins (BMP)-2, BMP-3, BMP-4, BMP-5, and BMP-7; growth- differentiation factor (GDF)-5), and BMP receptors (BMPR) types I (BMPR-IA, BMPR-IB) and II (BMPR-II) was investigated by reverse transcription-polymerase chain reaction (RT-PCR) in ex vivo and cultured cells. For verification, PCR fragments were cloned and sequenced. DNA dot blot analysis was performed to estimate the level of transcription. RNA dot blots were performed to determine expression of GDF-5. Expression of BMP receptor proteins was investigated by immunohistochemistry. Single-cell clonal growth proliferation assays were performed using recombinant human GDF-5 and TGF-beta1.

RESULTS

Transcription of BMP-2, BMP-3, BMP-4, BMP-5, and BMP-7 and receptors of BMPR-IA, BMPR-IB and BMPR-II was detected in ex vivo and cultured epithelium and stroma. The level of transcription was higher in cultured stroma for all factors, but the level for the receptors was higher in cultured epithelium. In contrast GDF-5 was transcribed only in stromal cells, suggesting that this cytokine may be an important mediator between keratocytes and epithelial cells. Furthermore, GDF-5 inhibited proliferation of corneal epithelial and stromal cells.

CONCLUSIONS

Given the importance of the TGF-beta family during embryonic development, the results suggest that its members may be components of the corneal cytokine network and may participate in the regulation of cellular proliferation and differentiation.

Growth/differentiation factor 5 and glial cell line-derived neurotrophic factor enhance survival and function of dopaminergic grafts in a rat model of Parkinson's disease

Growth/differentiation factor 5 is a member of the transforming growth factor beta superfamily, which has neurotrophic and neuroprotective effects on dopaminergic neurons both in vitro and in vivo. Here we investigate the effects of growth/differentiation factor 5 on foetal mesencephalic grafts transplanted into a rat model of Parkinson's disease, and compare them with those of glial cell line-derived neurotrophic factor. Mesencephalic tissue was suspended in solutions containing either growth/differentiation factor 5 or glial cell line-derived neurotrophic factor prior to transplantation into the left striatum of rats with 6-hydroxydopamine lesions of the left medial forebrain bundle. Both proteins enhanced graft-induced compensation of amphetamine-stimulated rotations. Positron emission tomography studies showed that both neurotrophins increased graft-induced recovery of striatal binding of [11C]RTI-121, a marker for dopaminergic nerve terminals. Post mortem analysis at 8 weeks after transplantation showed that both neurotrophins significantly increased the survival of grafted dopaminergic neurons. This study shows that growth/differentiation factor 5 is at least as effective as glial cell line-derived neurotrophic factor in enhancing the survival and functional activity of mesencephalic grafts, and thus is an important candidate for use in the treatment of Parkinson's disease.