Usefulness of a novel Caco-2 cell perfusion system II. Characterization of monolayer properties and peptidase activity.

In this study, the enzymatic activity and the influence of support filters and extracellular matrix proteins on the differentiation of Caco-2 cells grown in a perfusion system (Minucells and MinutissueTM) were examined and compared to traditional culturing approaches. Differences were observed regarding the differentiation of Caco-2 cells using the traditional approach and perfusion system such that the cell monolayers grown in a perfusion system showed a significant increase in dipeptidase activities (18.20 +/- 0.43nmol x min(-1) x cm(-2)) compared to the cells cultivated using the 21-day protocol (9.45 +/- 0.50 nmol x min(-1) x cm(-2)). The peptidase activity of Caco-2 cells was strikingly inhibited when Matrigel extracellular protein was used for coating polycarbonate support filters. While the enzymatic activities of the cell monolayers differentiated in the perfusion system were up-regulated, the transepithelial electrical resistance values of the cell monolayers (171 +/- 52 and 251 +/- 62 omega x cm2 for polycarbonate and polyester, respectively) decreased compared to the traditional Snapwell inserts (644 +/- 119 omega x cm2). The results suggested that the perfusion systems were useful permeability models which reduce workload, resources and manpower needed to obtain useful Caco-2 monolayers. In addition, the approach offers an efficient tool for long-term culturing of highly differentiated Caco-2 cell monolayers.

Parallel artificial membrane permeability assay (PAMPA) combined with a 10-day multiscreen Caco-2 cell culture as a tool for assessing new drug candidates.

The parallel artificial membrane permeability assay (PAMPA) is extensively used for the evaluation of early drug candidates. It is high throughput, low cost and is amenable to automation. This method has been shown useful in assessing transmembrane, non-energy dependent, diffusion of drugs such that reasonable predictability with in vivo (passive) absorption is possible. Cell cultures mimicking the gastrointestinal tract such as the CACO-2 cultures have the advantage of taking into account other transport mechanism including paracellular and carrier-mediated uptake but are lower throughput and labor-intensive. In this study, the applicability of two high throughput permeability assays namely PAMPA (PSR4p, pION Inc.) and 96-well Caco-2 cell assay (MultiScreen, Millipore) were used to rank drug permeability as well as to predict passive and active drug absorption/secretion for a series of marketed drugs as well as a collection of structurally diverse drug candidates. CACO-2 cells were cultured using MultiScreen hardware over a period of 10 days with the integrity of the cells assessed using transepithelial electrical resistance (TEER) and by the ability of the monolayer to the transport a paracellular marker, sodium fluorescence. Effective permeability (Peff) data were calculated using spectrophotometric data and were binned based on a pre-defined cut-off values as either highly and poorly permeable. A comparison of a well characterized drug training set indicate at least 85% concordance between the data generated from PAMPA and Caco-2 MultiScreen. The values obtained using the MultiScreen approach were also similar to data obtained from the literature using the conventional 21-day Caco-2 cell assay. Differences between PAMPA and CACO-2 ranking were useful indicators of either drug efflux (PAMPA (Peff) > CACO-2 (Peff)) or absorptive transport (CACO-2 (Peff) > PAMPA (Peff)). These results indicate that PAMPA combined with the MultiScreen Caco-2 cell culture may be a useful high throughput screening for predicting passive diffusion and active transport of new drugs.

Delivery of a DNAzyme targeting c-myc to HT29 colon carcinoma cells using a gold nanoparticulate approach.

The objective of the current study was to develop cellular delivery approaches for catalytic DNA enzymes (DNAzymes) which cleave targeted messenger RNA, using vectors based on colloidal gold. The model DNAzyme was a 32mer oligonucleotide designed to specifically interact with and cleave c-myc mRNA. Colloidal gold particles were prepared by reduction of tetrachlororauric [III] acid with sodium citrate. Particles could be produced in the 1-90 nm range. A cationic substrate linked to transferrin was electrostatically/hydrophobically bound to the gold particle. These vectors were then treated with the DNAzyme to yield the condensed DNA-cationic polymer-particulate product. The pH (4-11.5), the quantity of the DNAzymes (0.079-0.567 microg/probe), the cationic polymer (polylysine (PL) or polyethylenimine (PEI)) as well as the surfactant (PVP) concentration (0-0.5%) were varied to give stable constructs which decomplexed under the desired conditions (i.e., in lysosomes and at lower pH values). Cellular uptake of the FITC-labelled c-myc DNAzyme incorporated in this vector was measured using FACS analysis in human HT29 colon carcinoma cells. Data suggested that PEI gave better delivery efficiencies than PL. The use of PVP to stabilize the formed dispersions was detrimental to DNAzyme delivery when PL was used but had little effect in the PEI systems. In the best cases, delivery to 77% of the cells was possible using PEI with the PVP stabilizer and completing the DNA condensation at pH 5.5 with 0.118 microg of DNAzyme/probe. In contrast, the best conditions for PL gave only transfection to 43% of the cells (no PVP, condensed at pH 5.7 and with a loading of 0.079 microg DNAzyme/probe). The PL probe tended to be more toxic than the PEI-based systems (65% cell death in PL transfected cells compared to 22% for PEI). These results suggest that cellular targeting using colloidal gold appears feasible for DNAzyme delivery.

Passive diffusion of polymeric surfactants across lipid bilayers.

Self-assembling polymeric surfactant, mmePEG(750)P(CL-co-TMC) [monomethylether poly(ethylene glycol)(750)-poly(caprolactone-co-trimethylene carbonate)], increases drug solubility and crosses an enterocyte monolayer both in vitro and in vivo. The aims of the present work were to investigate whether mmePEG(750)P(CL-co-TMC) polymers can diffuse passively through lipid bilayer using parallel artificial membrane permeability assay (PAMPA) and affect membrane properties using liposomes as model. The mmePEG(750)P(CL-co-TMC) polymer was able to cross by passive diffusion an enterocyte-mimicking membrane in PAMPA at concentration which did not perturb membrane integrity. A weak rigidification associated with a low increase in permeability of liposomal lipid bilayers was observed. These data suggest that polymeric surfactants can cross the lipid membrane by passive diffusion and interact with lipid bilayers.

Stable ciliary activity in human nasal epithelial cells grown in a perfusion system.

PURPOSE: Explore the usefulness of a perfusion system in order to establish human nasal epithelial cell cultures suitable for long-term in vitro ciliary beat frequency (CBF) and cilio-toxicity studies. METHODS: The cells were obtained by protease digestion of nasal biopsy material. The cells were plated at a density of 0.8-1 x 10(6)/cm2 on Vitrogen-coated polyethylene terephthalate membranes, and cultured under submerged conditions in a CO2 incubator or in a perfusion system (initiated on days 8-9 after plating). The CBF was determined at 24.1 +/- 0.8 degrees C by a computerized microscope photometry system. The morphology of the cultured cells was characterized by transmission electron microscopy (TEM). RESULTS: Under CO2 incubator culture conditions, stable ciliary activity was expressed and maintained from day 2 to day 24. Under perfusion system culture conditions, the CBF (mean+/-S.D., n = 4) amounted to 8.4 +/- 0.9 and 8.8 +/- 0.4 Hz on days 7 and 14, respectively. These values were lower as compared to the corresponding CBF obtained in the CO2 incubator cultures (9.5 +/- 0.6 and 9.9 +/- 1.0 Hz, respectively). Reference cilio-stimulatory (glycocholate) and cilio-inhibitory (chlorocresol) compounds were used to assess CBF reactivity. In the CO2 incubator and 7- and 14-days perfusion system cultures, glycocholate (0.5%) showed a reversible cilio-stimulatory effect of 23, 26 and 21%, respectively, while chlorocresol (0.005%) exerted a reversible cilio-inhibitory effect of 36, 40 and 36%, respectively. TEM revealed polarized cuboidal to columnar epithelial morphology, with well-differentiated ciliated cells under CO2 and perfusion system conditions (up to day 23). CONCLUSION: Culturing human nasal epithelial cells on Vitrogen-coated polyethylene terephthalate membranes in submerged conditions in a CO2 incubator and in a perfusion system offers the possibility for long-term preservation (up to 22-24 days) of stable and reactive CBF in vitro.

The use of human nasal in vitro cell systems during drug discovery and development.

The nasal route is widely used for the administration of drugs for both topical and systemic action. At an early stage in drug discovery and during the development process, it is essential to gain a thorough insight of the nasal absorption potential, metabolism and toxicity of the active compound and the components of the drug formulation. Human nasal epithelial cell cultures may provide a reliable screening tool for pharmaco-toxicological assessment of potential nasal drug formulations. The aim of this review is to give an overview of the information relevant for the development of a human nasal epithelial cell culture model useful during drug discovery and development. A primary goal in the development of in vitro cell culture systems is to maintain differentiated morphology and biochemical features, resembling the original tissue as closely as possible. The potential and limitations of the existing in vitro human nasal models are summarized. The following topics related to cell culture methodology are discussed: (i) primary cultures versus cell lines; (ii) cell-support substrate; (iii) medium and medium supplements; and (iv) the air-liquid interface model versus liquid-liquid. Several considerations with respect to the use of in vitro systems for pharmaceutical applications (transport, metabolism, assessment of ciliary toxicity) are also discussed.

The use of polymer-based electrospun nanofibers containing amorphous drug dispersions for the delivery of poorly water-soluble pharmaceuticals.

Electrostatic spinning was applied to the preparation of drug-laden nanofiber for potential use in oral and topical drug delivery. While this technique is in its infancy with regard to pharmaceutical applications, a number of recent publications suggest that it may be of high value in the formulation of poorly water-soluble drugs by combining nanotechnology and solid solution/dispersion methodologies. The purpose of this article is to describe some of these recently published applications. For immediate release oral application, a water-soluble cellulose polymer was selected (i.e., hydroxypropylmethylcellulose, HPMC) while for topical application, a nonbiodegradable, water-insoluble polymer was investigated (i.e., a segmented polyurethane, SPU). Solutions of the polymer and the drugs in appropriate solvents could be spun across various potentials (16-24 kV) generating nanofibers with diameters ranging from 300 to 2000 nm. Dissolution studies found that the non-woven fabrics derived from HPMC and containing itraconazole dissolved over a time course of minutes to hours depending on the formulation used as well as the drug/polymer ratios. Drug release from the SPU samples was dependent on the incorporated drug as well as nanostructure obtained.

Safety-assessment of 3-methoxyquercetin as an antirhinoviral compound for nasal application: effect on ciliary beat frequency.

It has been shown that 5,7,3',4'-tetrahydroxy-3-O-methylflavone (3-MQ) exhibits antipicornaviral activity. In order to explore the potential of 3-MQ as an antirhinoviral compound for nasal application, the effect of 3-MQ on the ciliary beat frequency (CBF) of human nasal epithelial cells was studied in vitro in the absence or presence of solubility/absorption enhancers (hydroxypropyl-beta-cyclodextrin (HP-beta-CD) or polysorbate 80). Nasal epithelial cells were obtained by protease digestion of surgical specimens of human nasal polyps, and used at confluency. The effect of 3-MQ (2, 10, and 20 microg/ml), HP-beta-CD (1, 3, and 10% (w/v)), polysorbate 80 (0.1, 0.3, and 1% (w/v)), and of the combination of 3-MQ with 3% HP-beta-CD or 1% polysorbate 80, on the CBF was determined by computerized microscope photometry 15 min after incubation with the test compounds; recovery was determined 35 min after rinsing. HP-beta-CD at 1 and 3% did not affect CBF; a reversible decrease (by 37%) was observed at 10%. Polysorbate 80 caused a reversible cilio-inhibitory effect of 40, 53, and 49% at 0.1, 0.3, and 1%, respectively. At 2 and 10 microg/ml, 3-MQ showed a reversible cilio-stimulatory effect of 18 and 14%, respectively. Combined with 3% HP-beta-CD, the reversible cilio-stimulatory effect of 2 microg/ml 3-MQ was preserved, while 10 and 20 microg/ml 3-MQ did not affect the CBF. The combination of polysorbate 80 (1%) and 3-MQ decreased the CBF, which could be attributed to the presence of polysorbate 80. In conclusion, no ciliotoxic effect could be observed for 3-MQ (up to 20 microg/ml) in the absence or presence of HP-beta-CD (3%). The potential of this combination as an antirhinoviral formulation for nasal application will be further explored.

Value of glial fibrillary acidic protein determination in amniotic fluid for prenatal diagnosis of neural tube defects.

Glial fibrillary acidic protein (GFAp), an intracellular protein specific to astrocytes of the central nervous system, was determined by 2-site immunoradiometric assay in amniotic fluid from 78 pregnancies with a normal, and 100 with an abnormal outcome. GFAp was not detectable in any of the normal pregnancies, but there were measurable, and so raised, levels in 23 out of 25 cases of anencephaly and 4 out of 7 cases of spina bifida, which therefore allowed prenatal diagnosis. GFAp was also increased in 4 of 6 cases of fetal intrauterine death, but not in other congenital malformations associated with elevated alphafetoprotein levels or abnormal acetylcholinesterase banding pattern, such as exomphalos, other gastrointestinal malformations or renal abnormalities. GFAp is therefore specific for diagnosing open neural tube defects. The determination of GFAp in amniotic fluid was slightly less efficient overall than AFP for the prenatal diagnosis of neural tube defects, but can be a useful ancillary test and has the advantage of specificity.

Increased GFAp levels in CSF as a marker of organicity in patients with Alzheimer's disease and other types of irreversible chronic organic brain syndrome.

Glial fibrillary acidic protein (GFAp), an astrocyte-specific protein, was determined in cerebrospinal fluid (CSF) of adults and children with global cognitive dysfunction. In children CSF-GFAp values were not closely associated with organic brain disease. However, GFAp values in CSF were increased in 65 of 121 samples of adults with dementia, independent of its cause. GFAp values were not correlated with the severity of the dementia. Increased levels in the CSF are believed to indicate reactive gliosis in most patients with dementia, whereas GFAp levels in encephalitic patients normalize after clinical recovery.

Determination in human cerebrospinal fluid of glial fibrillary acidic protein, S-100 and myelin basic protein as indices of non-specific or specific central nervous tissue pathology.

The nervous system specific proteins glial fibrillary acidic protein (GFAp), S-100 and myelin basic protein (MBP) were determined in 535 human cerebrospinal fluid (CSF) samples. The level of all three proteins was increased in CSF of patients with nonselective destructive central nervous tissue disease such as encephalitis, cerebrovascular disease or tumoural compression. The increases in GFAp were more constant, making it a better marker of CNS pathology. Increases in MBP in CSF of patients with acute demyelinating disease were confirmed. S-100 did not seem to give more information as GFAp. Isolated increases of GFAp could be demonstrated in patients with dementia (Alzheimer type or multi-infarct dementia) or syringomyelia. Since CNS of these patients is very rich in fibrillary astrocytes, containing large amounts of GFAp, it is suggested that GFAp is to be considered as a specific marker of fibrillary gliosis in CSF and can be used as a diagnostic tool in dementia and syringomyelia.

Primary cultures from defined brain areas; effects of seeding time on cell growth, astroglial content and protein synthesis.

The influence of seeding time on cell growth, astroglial content and on protein synthesis during cultivation was determined in primary cultures from 3 phylogenetically different brain areas from rat cerebral cortex, striatum and brainstem. Brainstem cultivated from 17-day-old embryos and all the cultures studied from the 3 brain areas of newborn and 7-day-old rat showed a similar increase in total and water-soluble protein during cultivation. Glial fibrillary acidic protein (GFAp, alpha-albumin) levels increased with age in all cultures studied. There was a rapid increase in GFAp (alpha-albumin) between 1 and 2 weeks in cultures from newborn and between 2 and 3 weeks in brainstem cultures from 17-day-old embryos, these increases being slower thereafter. Incorporation of [3H]valine into soluble protein was lower in 3-week-old cultures than in 1- and 2-week-old cultures derived from newborn and 7-day-old rat brain. The incorporation rates were similar in comparisons of the various cultures. Similar results were obtained from embryonic cultures, although the decrease in incorporation rate was between 3 and 4 weeks. The efficiency of incorporation (% TCA-precipitated material/total [3H]activity) was higher in 2- and 3-week-old than in 1-week-old cultures from newborn and 7-day-old rats and in 3- and 4-week-old cultures of brainstem from 17-day-old rat embryos. These findings suggest a cell differentiation during cultivation. The results show that seeding time has a variable influence on cultures from the different brain areas studied concerning cell growth, astroglial content and probably differentiation during cultivation. Embryonic cell cultures seem, in general, to develop one week later than neonatal and postnatal ones. Cultures of newborn rat cells from cerebral cortex, striatum and brainstem show many similarities in the above parameters during cultivation. This is also the case for brainstem cultures from embryonic rat.

A serum protein affecting the regulation of the immune system.

A thermostable alpha 2 globulin inhibiting the immunoglobulin/anti-immunoglobulin reaction was demonstrated working with subacute sclerosing panencephalitis (SSPE) and control serum IgG. This protein was isolated from SSPE and normal human blood, it inhibits the immunoglobulin/anti-immunoglobulin reaction but no other antigen/antibody reactions when applying different immunochemical methods such as nitrocellulose immunofixation, 2 site immunoradiometric assay, solid phase radioimmunoassay in coated cups. This was demonstrated, working on the one hand with measles virus strain Edmonston or SSPE virus strain D.R. and SSPE serum and on the other hand with IgG from SSPE and control serum. This alpha 2 globulin, an inhibiting protein, appears to be related to "normal immunosuppressive protein".

Identification of several forms of the glial fibrillary acidic protein, or alpha-albumin, by a specific monoclonal antibody.

A monoclonal antibody (mAb), termed UIA/NEU/I/G1 (G1), that reacted with the astroglial marker glial fibrillary acidic protein (GFAP), or alpha-albumin, is described. It was directed against a structural determinant of GFAP. The G1 mAb could be used for quantitative determination of GFAP in two-site radiometric assays and for histoimmunological demonstration of GFAP. The G1 mAb reacted with the GFAP from rat as well as from man. The presence of several different molecular weight forms of GFAP in aqueous and detergent extracts from human brain was shown with the G1 mAb. The possible meaning of these forms is discussed.

Cellular composition of primary cultures from cerebral cortex, striatum, hippocampus, brainstem and cerebellum.

Primary cultures from newborn rat cerebral cortex, striatum, hippocampus, brainstem and cerebellum were grown for 14 days. There was a linear relationship between the amount of material seeded and the protein content of the respective culture. The amount of tissue material seeded was selected so that the different cultures reached confluence at 6-7 days and contained similar amounts of protein when 7 and 14 days old. The cellular content was evaluated by astroglial markers, such as the glial fibrillary acidic protein (GFAp; alpha-albumin) and the S-100 protein, and by markers for other cells expected to be in the cultures (14-3-2 protein, macrophage acidic protein (MAP), alkaline phosphatase, myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP]. Astroglial-like cells represented 60-70% of the cells present in the different cultures. Quantitation of GFAp (alpha-albumin) showed similar amounts to be present in cultures from cerebral cortex, hippocampus and striatum; however, on lower levels expressed in soluble proteins than in the corresponding brain regions of adult rats. Brainstem of adult rat contained large amounts of GFAp (alpha-albumin), while low levels were found in brainstem culture. Also, phagocytic cells (macrophages), endothelial-like cells, mesenchymal-like cells, ependymal-like cells and oligoblasts were found. Neither mature neurons, nor oligodendroglial cells were observed. It is concluded that although there might be some differences in the degree of maturation or in the cellular composition of the various cultures, they could serve as a good model system for studying the characteristics of astroglial cells from various brain regions.

Autoantibodies to brain specific proteins in human serum from normal and several pathological conditions.

Autoantibodies to three nervous tissue specific proteins [alpha Albumin (GFA, Eng et al., 1971), S100 (Moore et al., 1968) and MBP (Eylar et al., 1969)] were determined in sera from 270 neurological patients. Control values were established in sera from 21 blood donors. Differences between the control group and several pathological conditions were found, positive results were obtained in sera of patients affected with MS, polyneuropathy and astroglial tumors.

Glial cells identified by anti-alpha-albumin (anti-GFA) in human pineal gland.

Alpha-albumin, a CNS specific protein, identical to GFA protein and specific glial cells, has been found in the human pineal gland using histoimmunological and quantitative methods. The significance of its presence in the pineal gland is discussed.

Subacute sclerosing panencephalitis antibodies against measles virus polypeptides.

Antibodies to measles virus proteins in SSPE, MS and control human sera were compared using measles virus strain Edmonston, productive SSPE strain Mantooth and non-productive SSPE strain DR. The viral antigens were subjected to transfer electrophoresis, incubated with sera and localized after a second incubation with peroxidase labeled immunoglobulins. High levels of antibodies to all measles viral proteins are present in SSPE sera and CSF and to a lesser degree in MS and control sera although the non-productive SSPE strains lack one viral protein (M protein) present in wild type measles virus strains and the productive SSPE strains.