Use of a membrane potential-sensitive probe to assess biological expression of the cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis is caused by defects in a chloride-transporting protein termed cystic fibrosis transmembrane conductance regulator (CFTR). This study presents an innovative procedure to evaluate expression of functional CFTR. The technique uses the potential-sensitive probe bis-(1,3-diethylthiobarbituric acid) trimethine oxonol or DiSBAC2(3), by single-cell fluorescence imaging. The DiSBAC2(3) method was first validated on the mouse mammary tumor cell line C127, stably expressing wild-type CFTR. Activation of protein kinase A by the cAMP-permeable analogue 8-Br-cAMP induced cell membrane depolarization consistent with expression of wild-type CFTR. The DiSBAC2(3) method is quick, simple, and reproducible, and does not require invasive cell loading procedures. The system was then applied to the cell model of the human lung tumor cell line A549, in which exogenous CFTR was expressed by infecting with the replication-deficient recombinant adenovirus AdCFTR. DiSBAC2(3) was able to detect the fraction of cells in which the expression of CFTR protein was confirmed by immunocytochemistry. The DiSBAC2(3) probe was also used in human nasal respiratory cells cultured in vitro, in which it efficiently discriminated between endogenous CFTR in normal and CF cells. Functional evaluation of CFTR function by the described method can be a useful tool to detect the expression of the CF gene transferred by adenoviral vectors for use in gene therapy trials.

Effect of modulation of protein kinase C on the cAMP-dependent chloride conductance in T84 cells.

The regulation of chloride conductance was investigated in the T84 human colon carcinoma cell line by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl)quinolinium. The permeable cAMP analog 8-Br-cAMP (100 microM) and the calcium ionophore ionomycin (1 microM) activate a chloride conductance. A prolonged (4 h) preincubation of cells with phorbol 12-myristate 13-acetate (100 nM) or with the diacylglycerol analog 1-oleoyl-2-acetyl-glycerol (100 microM): (i) down-modulates to almost zero the protein kinase C activity in the membranes; (ii) inhibits the activation of the chloride conductance mediated by 8-Br-cAMP but not by calcium; (iii) reduces the mRNA without changing the expression of the protein product of the cystic fibrosis gene. The data suggest that PKC is essential for the activation of the cAMP-dependent chloride conductance in T84 cells.

Alternative splicing of a previously unidentified CFTR exon introduces an in-frame stop codon 5' of the R region.

The cystic fibrosis transmembrane conductance regulator (CFTR) has been extensively characterized as the carrier of the basic defect in cystic fibrosis. CFTR is part of a growing family of proteins encoded by a single gene, the variant isoforms of which are generated by alternative splicing or RNA editing. We have analyzed the CFTR mRNA in the region of exons 10-11 in T84 cells and detected an alternatively spliced exon (10b) accounting for about 5% of the CFTR mRNA. The exon 10b found in both the human and mice genomes, introduces an in-frame stop codon. The resulting mRNA is translated into a truncated CFTR protein, identified in T84 cells by immunoprecipitation with the CFTR-specific monoclonal antibody MATG 1061. The insertion of a differentially spliced exon carrying an in-frame stop codon is a novel cellular mechanism for the production of a protein sharing common sequences with another, but having different properties and functions.

[Internal carotid bilateral occlusion, meningovascular syphilis and AIDS: case report]. / Oclusão bilateral das artérias carótidas internas, sífilis meningovascular e SIDA. Relato de caso.

We report a case of bilateral occlusion of internal carotid arteries, presenting with right hemiparesis and hypoesthesia, associated to meningovascular syphilis in a patient with AIDS. CT scan showed few small hypodense lesions, with a predominance on the left side, and the angiography showed bilateral occlusion of the carotid arteries. The association between syphilis and AIDS is not unusual, but the paucity of symptoms, probably due to a slow and gradual occlusion is not commonly reported.

Targeting transcription factor activity as a strategy to inhibit pro-inflammatory genes involved in cystic fibrosis: decoy oligonucleotides and low-molecular weight compounds.

The development of drugs able to inhibit the expression of pro-inflammatory genes is of great interest in the treatment of cystic fibrosis (CF). Chronic pulmonary inflammation in the lungs of patients affected by CF is characterized by massive intra-bronchial infiltrates of neutrophils. This process is initiated upon interaction of pathogens (including Pseudomonas aeruginosa) with surface bronchial cells. Consequently, they release cytokines, the most represented being the potent neutrophilic chemokine Interleukin (IL)-8 and the pro-inflammatory cytokine IL-6. The chronic inflammatory process is crucial, since it leads to progressive tissue damage and severe respiratory insufficiency. In order to reduce the adverse effects of the excessive inflammatory response, one of the approaches leading to inhibition of IL-8 and IL-6 gene expression is the transcription factor (TF) decoy approach, based on intracellular delivery of double stranded oligodeoxynucleotides (ODNs) mimicking the binding sites of TFs and causing inhibition of binding of TF-related proteins to regulatory sequences identified in the promoters of specific genes. Since the promoters of IL-8 and IL-6 contain consensus sequences for NF-κ B and Sp1, double stranded TF "decoy" ODNs targeting NF-κB and Sp1 can be used. Alternatively, screening of drugs targeting relevant TFs can be performed using drug cocktails constituted by extracts from medicinal plants inhibiting TF/DNA interactions. Finally, virtual screening might lead to identification of putative bioactive molecules to be validated using molecular and cellular approaches. By these means, low-molecular drugs targeting NF-κB and inhibiting IL-8 gene expression are available for pre-clinical testing using experimental systems recapitulating chronic pulmonary inflammation of patients affected by CF.

Adenosine 3':5'-monophosphate-dependent protein kinase from human placenta: characterization of the catalytic subunit.

The catalytic subunit of cAMP-dependent protein kinase (EC 2.7.1.37) was purified for the first time from human placenta by DEAE-cellulose and HTP chromatography. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis showed a single band of average molecular weight of 42 kDa (SEM = 0.52). Kinetic experiments showed a Km for ATP of 12.6 +/- 1.2 mumol/l, for histone II-AS of 1.3 +/- 0.05 mg.ml-1, for kemptide of 11.4 +/- 4.4 mumol/l. The synthetic inhibitor IP20-amide showed a competitive mechanism of inhibition with a Ki of 5.0 nmol/l. The protein kinase inhibitors H7 and H9 showed an apparent Ki of 8.3 and 4.9 mumol/l respectively. Preparative isoelectric focusing revealed the presence of 5 different isoforms with an average pI of 6.17, 6.70, 7.15, 7.67, 8.9.

Protracted neonatal hypertrypsinogenaemia, normal sweat chloride, and cystic fibrosis.

The cystic fibrosis (CF) clinical spectrum has greatly expanded in the past few years, including atypical forms with low sweat chloride concentrations. Two cases are presented which suggest that children detected by neonatal CF screening whose trypsinogen concentrations are still raised by the second month of age could, despite a negative sweat test, be affected by an atypical CF with fully expressed pulmonary involvement.

Heparan sulfate glycosaminoglycans are involved in adenovirus type 5 and 2-host cell interactions.

Gene therapy vectors derived from subgroup C adenoviruses of the serotype 5 (Ad5) and 2 (Ad2) resulted in inefficient infection of well differentiated respiratory cells, both in vitro and in vivo. The level of expression and localization of the primary receptor for Ad5 and Ad2, termed CAR, do not completely explain why the infection efficiency varies greatly in different experimental conditions. The possibility that additional receptors like proteoglycans are involved in the infection of Ad5 and Ad2 was investigated, because several pathogenic microorganisms use heparan sulfate-glycosaminoglycans (HS-GAGs) as coreceptors for multistep attachment to target cells. The HS-GAG analog heparin decreased Ad5- and Ad2-mediated infection and binding starting from the concentration of 0.1 microgram/ml, up to a maximum of 50%. A similar reduction in Ad5 binding and infection was obtained by treatment of cells with heparin lyases I, II, and III but not with chondroitin ABC lyase. The effect of heparin on Ad5 binding has not been observed in surface GAG-defective Raji cells and after treating A549 cells with heparin lyases I, II,and III. The binding of Ad5 was completely abolished when both CAR was blocked with RmcB antibody and HS-GAGs were competitively inhibited by heparin. Parallel experiments demonstrate that HS-GAGs are irrelevant to binding and infection of the subgroup B adenovirus type 3. Collectively, these results demonstrate for the first time that HS-GAGs expressed on the cell surface are involved in the binding of Ad5 and Ad2 to host cells.

Protein A, hydroxyapatite and diethylaminoethyl: evaluation of three procedures for the preparative purification of monoclonal antibodies by high-performance liquid chromatography.

Three rapid, reproducible and feasible monoclonal antibody purification procedures by means of high-performance liquid chromatography have been evaluated. The stationary phases employed were high-performance hydroxyapatite, high-performance Protein A and high-performance anion-exchange resin. The purity of the final immunoglobulin preparations was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions and, subsequently, by high-performance gel permeation chromatography. The immunoreactivity of purified monoclonal antibodies was determined by the radioimmunoassay method.

Protein kinase C activates chloride conductance in C127 cells stably expressing the cystic fibrosis gene.

The regulatory domain (R domain) of the cystic fibrosis transmembrane conductance regulator (CFTR) is phosphorylated by protein kinase A and protein kinase C (PKC) in vivo (Picciotto, M. R., Cohn, J. A., Bertuzzi, G., Greengard, P., and Nairn, A. C. (1992) J. Biol. Chem. 267, 12742-12752), but so far the functional effect of the PKC-dependent phosphorylation has not been clarified. We investigated the effect of PKC on the CFTR-mediated Cl- transport by treating with phorbol 12-myristate 13-acetate (PMA), the cell line C127i stably expressing CFTR wild type (C127 CFTRw/t), or CFTR bearing the most common mutation deltaF508 (C127 CFTRdF508). We show that PMA activates Cl- efflux in C127 CFTRw/t, but not in C127 CFTRdF508 and C127i. The PMA-dependent activation of CFTR is not mediated by increase of intracellular [cAMP] and is not the result of a primary activation of a K+ conductive pathway. These results strongly suggest that PKC activates directly CFTR-mediated Cl- transport.

cAMP-dependent protein kinase inhibits the chloride conductance in apical membrane vesicles of human placenta.

The role of adenosine 3',5'-monophosphate (cAMP) dependent protein kinase (PK-A) on the Cl- conductance has been studied in the apical membrane vesicles purified from the chorionic villi of human placenta. In order to phosphorylate the cytosolic side of the membranes, vesicles have been hypotonically lysed, loaded with 100 nM catalytic subunit of PK-A purified from human placenta and 1 mM of the phosphatase resistant adenosine 5'-thiotriphosphate (ATP-gamma-S) and resealed. Cl- conductance has been measured by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ) at 23 degrees C with membrane potential clamped at 0 mV. The actual volume of the resealed vesicles was measured in each experiment by trapping an impermeable radioactive molecule ([14C]-sucrose) and included in each Cl- flux calculation. In 19 independent experiments, the mean Cl- conductance in placental membranes in the absence of phosphorylation was 3.67 +/- 3.18 whereas with the addition of PK-A and ATP-gamma-S it was 1.97 +/- 1.75 nmol.sec-1. (mg protein)-1 (mean +/- SD). PK-A dependent phosphorylation reduced the Cl- conductance in 14/19 experiments. The same protocol applied to the apical membranes of bovine trachea, where PK-A is known to activate the Cl- channels, confirmed that the PK-A dependent phosphorylation increased in Cl- conductance in 11/13 experiments, from 1.01 +/- 0.61 to 1.85 +/- 0.99 nmol.sec-1.(mg protein)-1 (mean +/- SD). These studies indicate that the PK-A dependent phosphorylation inhibits one or more Cl- channel(s) of the apical membranes of human placenta.

Activation of NF-kB mediates ICAM-1 induction in respiratory cells exposed to an adenovirus-derived vector.

Gene transfer to the respiratory tract by replication-deficient adenoviruses is limited by the induction of inflammatory and immune responses. We previously demonstrated that a E1-E3-deleted recombinant adenovirus carrying the expression cassette for the cystic fibrosis gene (Ad.CFTR) upregulates the expression of the pro-inflammatory intercellular adhesion molecule-1 (ICAM-1) both in vitro and in vivo. In the present work we suggest a role for the nuclear factor-kB (NF-kB) in Ad.CFTR-dependent up-regulation of ICAM-1 in respiratory epithelial A549 cells. Specifically, Ad.CFTR induced translocation of NF-kB into the nucleus and binding to the proximal -228/-218 NF-kB consensus sequence on the ICAM-1 promoter. Ad.CFTR also stimulated a 13-fold increase in NF-kB-dependent expression of the CAT reporter gene under the control of a region of the ICAM-1 promoter, including the proximal NF-kB consensus sequence. The Ad.CFTR-dependent increase of ICAM-1 mRNA was abolished by inhibitors of NF-kB, such as N-acetyl-L-cysteine, pyrrolidine dithiocarbamate, parthenolide and the synthetic peptide SN50. All these inhibitors abolished both Ad.CFTR-induced NF-kB DNA binding and transactivating activities. These results indicate a critical role of NF-kB in the pro-inflammatory response elicited by replication-deficient adenoviral vectors in respiratory cells.

ICAM-1 induction in respiratory cells exposed to a replication-deficient recombinant adenovirus in vitro and in vivo.

Administration of replication-deficient recombinant adenoviruses (Ad) designed as vectors for gene transfer to the airway tract of rats and monkeys has been associated with a dose-dependent inflammatory process a few days after viral exposure. Among the cellular mechanisms possibly involved, we investigated the expression of intercellular adhesion molecule-1 (ICAM-1), which is known to be induced by parainfluenza, adenovirus type 5 and respiratory syncytial viruses in vitro. To test this hypothesis, an Ad type 5-derived replication-deficient recombinant vector carrying the expression cassette for the cystic fibrosis gene (Ad.CFTR) was either incubated with A549 cells (a human-derived lung epithelial cell line) or instilled by bronchoscopic procedures into the airways of Rhesus monkeys. Ad.CFTR induced expression of ICAM-1 in A549 cells and up-regulated with time the basal levels of ICAM-1 mRNA in lung portions of Rhesus monkeys. These observations indicate that E1-E3-deleted replication-deficient adenoviral vectors are capable of inducing adhesion molecules known to play a role in inflammation.