Evaluation of the anti-diarrheal activity of the hydromethanolic root extract of Rhus tripartita (Ucria) (Anacardiacae)

INTRODUCTION

Rhus tripartita (Anacardiacae) is a plant which is traditionally used for the treatment of ulcer and diarrhea in Tunisia. However, the scientific basis for this usage has not been well established. The core aim of the present study is to evaluate the antidiarrheal activity of Rhus tripartita root methanolic extract (RRE).

MATERIAL AND METHODS

The antidiarrheal activity of RRE oral doses (50, 100, 200 and 300mg/kg) was evaluated using the castor oil-induced diarrhea, the intestinal fluid emptying method and the normal intestinal transit test. The antibacterial activity was tested against four pathogenic bacteria using two methods. The RRE was also phytochemical studied.

RESULTS

Diarrhea experiments showed a protective effect of the RRE which produced a significant (p<0.05) and dose-dependent reduction of all the diarrhea parameters. It delayed the onset of diarrhea, produced a significant decrease in the frequency of defecation and the diarrhea score severity and decreased the volume of intestinal fluid induced by castor oil as well as the propulsion intestinal transit. The effect of the extract at the highest dose (300mg/kg) was similar to that of loperamide, the standard anti-diarrheal drug (10mg/kg). The anti-bacterial activity test showed that RRE exhibited a great inhibition activity against four pathogenic bacteria strains (Esherichia coli, Salmonella typhimurium, Salmonella argenosa, Staphylococcus aureus). Oral administration of the extract up to 3g/kg did not produce any acute toxicity in rats. The preliminary phytochemical screening of the RRE revealed the presence of flavonoids, tannins, and polyphenols.

CONCLUSION

Results showed that RRE at 300mg/kg possesses the highest anti-diarrheal activity possibly mediated by the inhibitory effects on gastrointestinal propulsion and intestinal fluid accumulation.

Epigenetic properties of the diarrhetic marine toxin okadaic acid: inhibition of the gap junctional intercellular communication in a human intestine epithelial cell line

Okadaic acid (OA) is produced by several types of dinoflagellates (marine plankton) and has been implicated as the causative agent of diarrhetic shellfish syndrome. Previous studies have shown that okadaic acid is a tumor promoter and a specific potent inhibitor of protein phosphatases and protein synthesis. These effects in turn affect intracellular processes such as metabolism, contractility, gene transcription, and the maintenance of cytoskeletal structure. Gap junctional intercellular communication (GJIC) is a means of maintaining cellular homeostasis in organs, the disruption of which favors tumor cell growth. The GJIC involves the transfer of small water-soluble molecules through intercellular channels (gap junctions), composed of proteins called connexins. OA disrupts cellular homeostasis in Caco-2 cells through several mechanisms including protein synthesis inhibition, apoptosis, and clastogenic effects. The aim of this study was then to evaluate the expression of the connexin 43 (Cx 43) mRNA in relation with the cytotoxicity induced by OA (3.75-60 ng/ml) in a human colonic epithelial cell line in culture (Caco-2 cells). OA produced a dose-dependent inhibition of GJIC in Caco-2 cells, along with a parallel decrease in the expression of Cx 43 as shown by immunohistochemistry using anti-Cx 43 antibody. Since Cx 43 is implicated in the suppression of tumors and OA is a tumor promoter, the inhibition of GJIC may play an important role in its carcinogenesis. These data are discussed in relation to the toxicity of OA, total RNA synthesis, and possible specificity of Cx 43 inhibition in the GJIC.

Indirect cytotoxicity evaluation of pseudowollastonite

This study aimed to evaluate the cytotoxicity of substances leached by pseudowollastonite (CaSiO(3)). It has been previously shown that calcium (Ca(2+)) and silicate (SiO(3)(-)) ions are released from pseudowollastonite into biological solutions. Both of these ions are known to influence the biological metabolism of osteoblastic cells essential in the mineralization process and bone-bonding mechanism. The indirect toxicity evaluation was performed by extraction method, according to International Standard Organization (ISO). Pseudowollastonite pellets obtained by solid-state reaction were incubated, in culture medium, during 24, 48, 72 or 168 h at different concentrations (5, 10, 15, 50, 100, 200 mg/ml). The cytotoxicity of each extract in presence of human osteoblastic cell line (SaOS-2) was quantitatively assessed by measuring the viability (succinate dehydrogenase activity, MTT), the membrane integrity (the uptake of the neutral red by viable cells, NR) as well as the cell necrosis by measuring the lactate dehydrogenase (LDH) released in the culture medium. No significant alteration of membrane integrity or cell suffering was detectable. However, increased cell metabolism was observed for cells exposed to pseudowollastonite extract with longest extraction time (168 h). In conclusion, mineral elements leached by pseudowollastonite do not significantly affect the metabolism of osteoblastic cells.

Physical and chemical processing for a human dura mater substitute

OBJECT

Allogenic human fascia lata used in neurosurgery, as dura mater substitute, can be associated with a risk of viral and bacterial transmission. Chemical and physical procedures, developed to inactivate virus and bacteria, have been applied to fascia lata. The aim of this study consists in the evaluation of the biological properties of this treated graft.

METHODS

Grafts were treated with solvent detergents, freeze-dried for conservation and gamma irradiated (25,000 Gy) for sterilization. The indirect toxicity evaluation was performed by extraction method, according to the International Standard Organization (ISO). First, the cytotoxic effect of each extracts incubated in the presence of human fibroblasts (WI38) was quantitatively assessed by measuring the cell growth, the viability (succinate dehydrogenase activity, MTT), the membrane integrity (uptake of the neutral red by viable cells, NR) as well as the release of lactate dehydrogenase in the culture medium. Second, confocal laser scanning microscopy (CLSM) was used to assess the direct contact between human primary fibroblasts and graft. CLSM was performed at days 3 and 7 after cells loading.

RESULTS

No acute cytotoxicity was observed for chemically processed allografts. Cells loaded on the graft have demonstrated a good growth and spreading.

CONCLUSIONS

Human fascia lata secured against conventional and non-conventional agents is a fully biocompatible alternative to the available dural graft materials.

Design of an efficient medium for insect cell growth and recombinant protein production

We report the development of a new serum-free medium based on the use of factorial experiments. At first, a variety of hydrolysates were screened using a fractional factorial approach with High-Five cells. From this experiment yeastolate ultrafiltrate was found to have, by far, the most important effect on cell growth. Furthermore, Primatone RL was found to remarkably prolong the stationary phase of Sf-9 and High-Five cell cultures. The optimal concentrations for yeastolate and Primatone were determined to be 0.6 and 0.5%, respectively, on the basis of a complete factorial experiment. This new medium, called YPR, supported good growth of both Sf-9 and High-Five cells in batch cultures, with maximal densities of 5.4 and 6.1 x 10(6) cells/ml, respectively. In addition, both cell lines achieved good growth in bioreactor batch culture and had a prolonged stationary phase of 3-4 d in YPR medium compared to Insect-XPRESS medium. The ability of the new medium to support recombinant protein expression was also tested by infecting Sf-9 or High-Five cells at high density (2 x 10(6) cells/ml) with a baculovirus expressing secreted placental alkaline phosphatase (SEAP). The maximum total SEAP concentration after 7 d was about 43 lU/ml (58 mg/L) and 28 lU/ml (39 mg/L) for High-Five and Sf-9 cells, respectively.

Smooth muscle cells influence monocyte response to LDL as well as their adhesion and transmigration in a coculture model of the arterial wall

We investigated the possible interference of smooth muscle cells with monocyte response to LDL as well as with their adhesion and transmigration in a coculture of porcine endothelial and smooth muscle cells. Lysophosphatidylcholine (LPC), a component of oxidized LDL (oxLDL), stimulated the adhesion of THP-1 cells to endothelial cells both in mono- and in coculture with smooth muscle cells. When THP-1 cells were incubated with endothelial cells in the presence of copper oxLDL, their adhesion was increased, but only in coculture. The addition of sodium nitroprusside (SNP) together with oxLDL markedly increased the adhesion of THP-1 cells in coculture. Close proximity between endothelial and smooth muscle cells was necessary to observe that effect. Furthermore, this increase in adhesion of THP-1 cells can, at least in part, be attributed to the augmented production of monocyte chemoattractant protein-1 (MCP-1) observed in coculture under the influence of oxLDL and SNP. The passage of THP-1 cells through the coculture was stimulated by MCP-1 and LPC. These results show that physical contacts or close proximity between endothelial and smooth muscle cells play a key role in the adhesion of monocytes and their infiltration into the intima in response to oxLDL.

S-nitrosothiols do not induce oxidative stress, contrary to other nitric oxide donors, in cultures of vascular endothelial or smooth muscle cells

Nitric oxide (NO) has been described to exert various anti-atherogenic actions. However, NO, in some cases, has been shown to stimulate the oxidation of low-density lipoprotein (LDL), which constitute an important triggering event in atherosclerosis. Thus, some NO donors, despite their advantages, might also induce oxidative stress. Therefore, the purpose of this study is to examine the effect of three different NO donors on LDL oxidation, in acellular system as well as in cultures of normal endothelial cells or smooth muscle cells, which constitute the two major cellular components of the arterial wall. Sodium nitroprusside oxidized strongly LDL in medium alone as well as in endothelial or smooth muscle cell cultures. Sydnonimine-1 (SIN-1) oxidized LDL already in the absence of cells and enhanced clearly the LDL oxidation in the cultures. S-nitroso-N-acetylpenicillamine was unable to oxidize LDL in synthetic medium alone as well as in the presence of cells, showing that the amount of superoxide and other reactive oxygen species released by these cells did not suffice, contrary to those liberated by macrophages, to combine to NO providing oxidant activity.

Adhesion and growth of CaCo2 cells on surface-modified PEEK substrata

A series of surface-functionalized poly(ether ether ketone) (PEEK) films has been prepared by selective wet-chemistry; they are hydroxylated polymer (PEEK-OH) obtained by reduction, aminated polymer (PEEK-[]-NH2) prepared by coupling a diisocyanate reagent to PEEK-OH (PEEK-[]-NCO) followed by hydrolysis, and carboxylated and aminocarboxylated polymers (PEEK-[]-GABA and PEEK-Lysine) resulting from the coupling of aminoacids to PEEK-[]-NCO. The aminated and carboxylated substrata promoted the adhesion and growth of CaCo2 cells in the presence of serum. Fibronectin (FN), an extra-cellular matrix protein, has been covalently fixed and/or adsorbed on various PEEK substrata, in the presence or not of a polymeric surfactant (Pluronic F68). The performances of the FN-grafted substrata (PEEK-[]-FN(1) and PEEK-[]-FN(2)) were significantly higher than those of reference substrata simply coated with FN (PEEK-OH(+FN)(1) and (2), PEEK-[]-NH2(+FN)(1) and (2)), considering the adhesion and spreading of CaCo2 cells in the absence of serum. Moreover, the stability of the adherent cells on the FN-adsorbed substrata dramatically depended on the experimental conditions applied during the PEEK coating with FN.

In vitro evaluation of acute cytotoxicity of human chemically treated allografts

In order to minimize the risk of contamination associated with tissue transplantation, tissue banks commonly chemically treat the tissues whenever possible. As viral inactivation uses agents lethal to microorganisms, it is imperative to assure that chemically inactivated tissue remains biocompatible. In vitro assays can be an effective means to assess the acute cytotoxicity of chemically treated human allografts. We have used different types of cells cultured in the presence of treated tissue extract. A standard cell line, a human fibroblast (WI38), which was the same for all the samples, was chosen. In addition, as the banked tissues (bone and fascia lata) were prepared to be used in bone or as a dura mater substitute, two other cell types were also used: an osteoblastic cell line (SaOS-2) and a neuronal cell line (Neuro 2A). Cytotoxic assessment was performed by qualitative evaluation of cell morphology based on confluence, granulation, vacuolization and swelling analysis. In addition, quantitative methods based on the use of neutral red (NR) and 3- (4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) were assayed. Qualitative and quantitative evaluation of fascia lata and bone extracts did not show deleterious effects on cell cultures. These results show that in vitro methods can be appropriate to select a non-toxic procedure before it is used in the human body and that several strong chemical treatments can result in a tissue suitable for human.

Transport mechanisms of the large neutral amino acid L-phenylalanine in the human intestinal epithelial caco-2 cell line

The transepithelial transport and the intracellular accumulation of the large neutral amino acid L-phenylalanine (L-Phe) were studied in monolayers of Caco-2 cells, cultivated in a bicameral insert system, to characterize the mechanisms involved in the absorption of this essential amino acid by the human intestinal mucosa. In our model, L-Phe was transported selectively in the apical (AP)-to-basolateral (BL) direction. AP-to-BL transport of L-Phe was temperature dependent and Na(+) independent, increased in the absence of protein synthesis and showed competition with large neutral and cationic amino acids. By contrast, transport in the BL-to-AP direction mainly resulted from passive movement (probably paracellular passage and transcellular diffusion). L-Phe accumulation into Caco-2 cells was higher from the BL pole than from the AP pole and characterized by the incorporation of most of the accumulated molecules into newly synthesized proteins. In addition, L-Phe accumulation was Na(+) dependent from both poles, whereas only accumulation from the AP pole was sensitive to inhibition by both large neutral and cationic amino acids. These results suggest that the processes involved in AP-to-BL transport and AP accumulation of this amino acid are very different from those involved in BL-to-AP transport and BL accumulation.

Transport mechanisms of the imino acid L-proline in the human intestinal epithelial caco-2 cell line

The intestinal transport of L-proline (L-Pro) has been investigated in various animal species with the use of different tissue preparations. Because major qualitative differences have been observed among the species, it is difficult to extent the results obtained with animal models to humans. In addition, studies on human tissue are lacking because of difficulties in obtaining material for experiments. To characterize the mechanisms involved in the intestinal absorption of L-Pro in humans, the transport of this nonessential imino acid was studied in monolayers of human intestinal Caco-2 cells that were cultivated on microporous membranes. In this model, L-Pro was transported selectively in the apical (AP)-to-basolateral (BL) direction. This transport was significantly reduced by metabolic inhibitors and by an incubation at 4 degrees C; it was Na(+) dependent and showed competition with (methylamino)-alpha-isobutyric acid and L-hydroxyproline. By contrast, transport in the BL-to-AP direction resulted to a large extent from passive movement (paracellular passage and transcellular diffusion). L-Pro accumulation by Caco-2 cells was significantly greater from the AP pole than from the BL pole. About 30-50% of the accumulated molecules were incorporated into newly synthesized proteins in a process inhibited by cycloheximide, whereas the remainder were extensively metabolized into non-amino acid compounds. L-Pro accumulations from the AP and BL poles were both Na(+) dependent, but they exhibited different characteristics. AP accumulation was inhibited by competition with (methylamino)-alpha-isobutyric acid, L-hydroxyproline and, to a lesser extent, D-Pro, whereas BL accumulation was inhibited by competition with L-hydroxyproline, (methylamino)-alpha-isobutyric acid, alpha-aminoisobutyric acid, L-histidine and small neutral amino acids. The results indicate that AP-to-BL transport and AP accumulation of L-Pro exhibited very different characteristics than BL-to-AP transport and BL accumulation.

Biological evaluation of RGD peptidomimetics, designed for the covalent derivatization of cell culture substrata, as potential promotors of cellular adhesion

Our aim was to replace the proteins and peptides, generally used for the biocompatibilization of polymer substrata, with synthetic molecules mimicking the RGD (Arg-Gly-Asp) active sequence. Based on the (L)-tyrosine template, RGD peptidomimetics were constructed; one molecule 3 was equipped with an anchorage arm that allowed its covalent grafting on a culture substratum made from poly(ethylene terephthalate) (PET) microporous membrane. The amount of fixed molecules was readily determined by XPS, using a fluorine tag incorporated in the peptidomimetic structure. The binding of peptidomimetics 1-3 to the vitronectin (VN) and fibronectin (FN) receptors could not be revealed in a test of inhibition of MSC 80 cells adhesion, by the synthetic compounds in solution placed in competition with the adhesive proteins (VN and FN) coating polystyrene plates. However, the cell-attachment activity of peptidomimetic 3 was shown by culturing CaCo2 cells, in the absence of serum, on the PET substratum grafted with 3. The performance of this support was similar to that of PET grafted with the reference peptide RGDS (Arg-Gly-Asp-Ser), and only reduced by half comparatively to the PET grafted with FN.

Fibronectin adsorption or/and covalent grafting on chemically modified PEEK film surfaces

Poly(ether ether ketone) (PEEK) films were chemically modified, by surface wet chemistry, into PEEK-OH, PEEK-NH2, and PEEK-NCO. Fibronectin (FN) adsorption, in the presence or absence of two non-ionic surfactants, was compared onto PEEK, PEEK-OH, and PEEK-NH2 on which the protein can only be adsorbed, and onto PEEK-NCO on which FN could be covalently grafted. The amounts of FN present on the various supports were assayed by ELISA and LSC (with 125I-labeled FN). The remarkable effect of Pluronic F68 in preventing non-specific protein adhesion on the less hydrophilic surfaces was pointed out. Accordingly, a procedure could be proposed that allows minimal FN adhesion vs FN fixation on PEEK-NCO. The resulting PEEK-FN film, which immobilized 120-150 ng FN cm(-2), constitutes a new substratum for cell cultivation.

Competitive adsorption of proteins: key of the relationship between substratum surface properties and adhesion of epithelial cells

The adhesion of Hep G2 cells was investigated using different substrata (commercial substrata, polystyrene modified by oxygen or ammonia plasma discharge), the surface properties of which were characterized (surface chemical composition, water contact angle, zeta potential). Some substrata were pre-conditioned with solutions of extracellular matrix (ECM) protein (collagen, laminin, fibronectin), solutions of albumin or polylysin, fetal calf serum or culture medium. The culture medium contained the surfactant Pluronic F68; cycloheximide was added in certain tests to inhibit protein synthesis. Cells spread within 1.5 h provided ECM proteins were present at the surface. Adsorption of ECM proteins was subject to competition with adsorption of Pluronic F68. When the substratum was exposed simultaneously to ECM protein and Pluronic F68, either by pre-conditioning or through protein cell secretion, a weaker substratum hydrophobicity favored adsorption of the proteins and subsequent cell adhesion. On the other hand, when ECM proteins were pre-adsorbed, they were not displaced by Pluronic F68 and cell adhesion was not influenced by substratum hydrophobicity. When ECM proteins were present, no difference was observed between substrata of similar hydrophobicity carrying positive or negative charges, respectively. In absence of ECM proteins, the presence of cationic sites at the substratum surface (NH3 plasma treatment, adsorption of polylysine) allowed cell attachment but no spreading within 1.5 h.

Adsorption of albumin, collagen, and fibronectin on the surface of poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and of poly (epsilon-caprolactone) (PCL) films modified by an alkaline hydrolysis and of poly(ethylene terephtalate) (PET) track-etched membranes

The effect of alkaline hydrolysis on several surface properties of poly(hydroxybutyrate-hydroxyvalerate) (92/8) (PHB/HV) and poly(epsilon-caprolactone) (PCL) films and of poly(ethylene terephtalate) (PET) track-etched membranes have been characterized, as well as the adsorption of three proteins normally encountered by mammalian cells in vivo, namely albumin, collagen, and fibronectin. The water contact angle decreases and the number of -COOH functions accessible to a chemical reaction at the surface of PCL increases with alkaline hydrolysis. Analysis by atomic force microscopy pictures reveals a change in surface morphology. The modifications of surface properties are correlated with a two times increase of the adsorption of three radiolabelled proteins. The hydrolysis results in a slight increase in the water contact angle of one face of the PHB/HV film and a sharp increase in the number of -COOH functions. Important morphology changes are also induced. The adsorption of the radiolabelled proteins is almost 100 times higher on the hydrolyzed polymer than on the native surface. The increase in hydrophilicity of different PET batches correlates to an increase in the number of -COOH functions. Nevertheless, the surface chemical composition and rugosity are constant and no significant difference in the amount of radiolabelled fibronectin adsorbed on the different surfaces is detectable. In conclusion, the effect of hydrolysis on the surface properties of each of the polyesters studied as well as the proteins adsorption on the different surfaces are different. The results strongly support the hypothesis that, in the system studied, parameters other than hydrophilicity influence protein adsorption: the main parameters that might play a role are the total surface area accessible to the proteins, as well as the surface chemical composition.

Adhesion of mammalian cells to polymer surfaces: from physical chemistry of surfaces to selective adhesion on defined patterns

The study of the adsorption of type I collagen from a solution containing Pluronic F68 has shown that the latter prevents collagen adsorption on polystyrene and does not prevent it on surface-oxidized polystyrene. This explains the control of mammalian cell adhesion by substrate surface hydrophobicity and composition of pre-conditioning solution. On that basis, selective adhesion of different types of mammalian cells (PC12 pheochromocytoma, MSC80 schwannoma, Hep G2 hepatoblastoma, rat hepatocytes) on patterned surfaces was achieved. Therefore tracks (width in the range of a few tens of microm) of reduced hydrophobicity were produced on polystyrene by photolithography and oxygen plasma treatment. After conditioning by a solution containing both Pluronic F68 and extracellular matrix protein (collagen, fibronectin), the latter adsorbed selectively on these paths thus allowing selective adhesion of the cells.

Influence of Substrate Hydrophobicity on the Adsorption of Collagen in the Presence of Pluronic F68, Albumin, or Calf Serum

The influence of Pluronic F68 [a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer surfactant], serum albumin (HSA), and fetal calf serum (FCS) on the adsorption of type I collagen by polymer substrates was investigated using radiolabeling and XPS analysis. Three different kinds of polystyrene substrates with increasing level of hydrophobicity were used. Change in the state of hydration of the sorbent and protein surfaces appears to be the main driving force for collagen adsorption. Pluronic F68 strongly reduces collagen adsorption, the reduction being more pronounced with higher substrate hydrophobicity. This explains why epithelial cell adhesion on substrates preconditioned with a solution of Pluronic F68 and collagen is strongly influenced by substrate hydrophobicity. Collagen adsorption is also reduced in the presence of HSA and FCS, but the reduction and its sensitivity to substrate hydrophobicity are lower than with Pluronic F68.

Compartmentalized coculture of porcine arterial endothelial and smooth muscle cells on a microporous membrane

Endothelial and smooth muscle cells were harvested from porcine pulmonary arteries and grown to two passages from primary culture in serum-containing medium. Thereafter, the cells were plated on the opposite sides of microporous poly-(ethylene terephthalate) membrane and cultivated in a chemically defined, serum-free medium. The membrane with pores of 1 microgram diameter allowed the passage of molecules and the extension of cell processes, while maintaining separate homogeneous cell populations. Pores of 3 microgram diameter permitted the crossing of smooth muscle cells through the membrane. The coating of the polymer with constituents of the extracellular matrix optimized cell adhesion. Morphological analysis of the model showed typical cobblestone pattern and ultrastructure of endothelial cells, which lost rapidly the expression of von Willebrand factor but kept that of angiotensin-converting enzyme. Smooth muscle cells were spindle shaped and specific alpha-actin was revealed by immunochemistry and quantitated by enzyme-linked immunosorbent assay (ELISA). Their ultrastructure featured an intermediate contractile-synthetic phenotype. Permeability studies to different molecules showed a marked reduction of the albumin clearance. Finally, in coculture in the presence of endothelial cells, the smooth muscle cells proliferation was increased, whereas it was not the case in autologous cocultures. In conclusion, such a coculture model may help to a better understanding of the interactions between endothelial and smooth muscle cells that may be important in the pathogenesis of vascular diseases.

Covalent grafting of fibronectin and asialofetuin at surface of poly(ethylene terephthalate) track-etched membranes improves adhesion but not differentiation of rat hepatocytes

The adhesion and differentiation of rat hepatocytes onto track-etched poly(ethylene terephthalate) (PET) membranes were studied. Native or [3H]methylated fibronectin (FN) or asialofetuin (ASF) were immobilized onto oxidized PET membranes, preactivated or not with carbodiimide (WSC). Radiochemical assay and ELISA indicated that upon washing in SDS or in serum-containing medium, significantly less FN was released from WSC-activated membranes that from unactivated ones. These differences were abolished when the NH2 functions of FN were fully acetylated, suggesting that part of FN was covalently grafted on WSC-activated PET. Although weaker, a comparable effect was observed with ASF. Hepatocytes adhered faster on membranes on which FN was grafted than adsorbed, reaching values comparable to collagen-coated PET; after 24 h these differences decreased. Experiments with cycloheximide or at 4 degrees C suggested that this results from secretion of extracellular matrix adsorbing on PET. Phase I or II biotransformation activities of cells cultured for 1-4 days on FN-, ASF-, or collagen-treated substrates were not significantly different. These results indicate that stable immobilization of FN (covalent grafting) onto PET membranes significantly accelerates adhesion of hepatocytes but does not affect their differentiation. This may result from a progressive surface reconditioning by neosynthesized extracellular matrix.

Coupled influence of substratum hydrophilicity and surfactant on epithelial cell adhesion

The influence of substratum surface hydrophilicity and of a surfactant on human epithelial cell adhesion and protein adsorption was investigated. Therefore, tissue culture grade polystyrene (TCPS) and bacteriological grade polystyrene (BGPS) substrata were treated with different media, with or without Pluronic F68 [a poly(ethylene oxide) and poly(propylene oxide) triblock copolymer surfactant], and with or without type I collagen as a typical extracellular matrix protein. The conditioned substrata were submitted to XPS analysis and assayed for cell adhesion by inoculating Hep G2 cells in a chemically defined nutritive medium. The presence of collagen at the substratum surface is required to obtain attachment and spreading of Hep G2 cells. With PS substrata, treating with a solution of collagen does not promote cell adhesion if the solution contains Pluronic; XPS data show that this is due either to prevention of collagen adsorption or to its desorption by rinsing. With less hydrophobic TCPS substrata, the presence of Pluronic in the conditioning solution does not preclude cell adhesion, nor collagen adsorption. The effect of BGPS and TCPS substrata on Hep G2 cell adhesion is thus mediated by the presence of a surfactant that affects the adsorption of collagen.

Surface Functionalization of Polyethylene Terephthalate Film and Membranes by Controlled Wet Chemistry

Surface functionalization of polyethylene terephthalate film and track-etched microporous membranes was performed using organic synthesis at the solid-liquid interface. The hydroxyl chain ends, naturally occurring in the membranes or created by basic hydrolysis in the film, were activated by reaction with p-toluenesulfonyl chloride and then coupled to [4,5-(3)H]lysine used as a model of water-soluble bioactive molecules. The ratios of derivatization were determined by liquid scintillation counting of the radioactivity associated with the samples. The hydroxyl chain ends were further reacted with 4,4'-methylene di(phenyl isocyanate); the resulting surfaces equipped with sensitive isocyanate spacers were assayed as before using [4,5-(3)H]lysine. The ranges of derivatization were from 5 to 60 pmol of fixed amino acid per open surface unit (cm(2)). Some samples were also analyzed by X-ray photoelectron spectroscopy.

Human and rat macrophages mediate fungistatic activity against Rhizopus species differently: in vitro and ex vivo studies

Both rat alveolar macrophages and a human macrophages cell line with characteristics of human tissue (e.g., alveolar) macrophages (THP-1) were found to inhibit the germination of Rhizopus spores. However, the conditions under which fungistatic activity occurs are different for these two cell types. The inhibition of Rhizopus spore germination by rat alveolar macrophages requires the activation of macrophages and the presence of serum and L-arginine. During rat alveolar macrophage-mediated fungistatic activity, L-arginine is oxidized to nitric. Human macrophage-mediated fungistatic activity is similar to that mediated by rat macrophages in terms of the serum requirement, but it does not require L-arginine. Human macrophages did not produce any nitrite detectable by the colorimetric assay. Their ability to inhibit germination was enhanced by the combination of endotoxin and gamma interferon. The inhibition of Rhizopus spore germination by rat alveolar macrophages is thus mediated by the generation of nitric oxide, whereas the mechanism of similar inhibition by human macrophages remains poorly understood. Serum samples from diabetic rats as well as from patients with diabetes or uremia decreased the inhibitory effect of macrophages on spore germination. Dialysis of the serum samples against a buffered salt solution antagonized this phenomenon, indicating that a low-molecular-weight factor in the sera of patients with diabetes or uremia may modulate local antifungal defense mechanisms. The absence of L-arginine-dependent nitrogen oxidation in human macrophages, compared with its presence in rat alveolar macrophages, under conditions during which fungistatic activity occurs suggests that this phenomenon is species specific.

Iron uptake from ferrioxamine and from ferrirhizoferrin by germinating spores of Rhizopus microsporus

Mucormycosis caused by the fungus Rhizopus has been documented in iron overloaded patients and more particularly in dialysis patients, both when treated with desferrioxamine B (DFO). This iron and aluminium chelator is thought to play a role in the pathogenesis of this infection. We therefore investigated in vitro the cellular pharmacology of iron chelated by DFO in the fungus Rhizopus. In a medium, designed for fungal cultivation, Rhizopus microsporus var. rhizopodiformis takes up iron from ferric-DFO complex (55Fe.DFO) and from 55Fe.rhizoferrin, the siderophore synthesized and secreted by Rhizopus [Drechsel et al., Biol. Metals 4: 238-243, 1991]. In both cases, iron accumulation is partially saturable with the duration of exposure and the chelator concentration. Fe.DFO binds to Rhizopus; iron becomes trapped and remains associated with the fungus, whereas the iron-depleted siderophore is released in the extracellular medium. In a medium designed for mammalian cell cultivation and in the absence of human serum, the fungal iron accumulation both from 55Fe.DFO and from 55Fe.rhizoferrin is proportional to the chelator concentration. Human serum at 40% does not influence the iron accumulation from Fe.DFO but it significantly affects that from Fe.rhizoferrin which, in the presence of serum, only occurs at concentration > 5 microM. This difference finds its explanation in the iron transfer observed between Fe.rhizoferrin and seric apotransferrin, the latter making the metal unavailable to Rhizopus. By contrast, no iron transfer takes place between Fe.DFO and apotransferrin, allowing fungal iron utilization from this complex, even at very low concentrations. The iron uptake, being inhibited by NaN3 and KCN, is energy-dependent; being inhibited by bipyridyl, it requires prior reduction of ferric iron; being unaffected by the covalent linkage of Fe.DFO to albumin, it does not require the entry of Fe.DFO within the fungus. These in vitro results strongly suggest that, upon administration of DFO to iron overloaded or dialysis patients, the formed Fe.DFO is efficiently used as an iron source by Rhizopus, even in the presence of serum apotransferrin or rhizoferrin. The consequent promotion of the growth of Rhizopus helps explain the increased risk of mucormycosis in DFO-treated patients.

Deferoxamine augments growth and pathogenicity of Rhizopus, while hydroxypyridinone chelators have no effect

Deferoxamine (DFO), when used in dialysis patients, is a well recognized risk factor for the development of mucormycosis caused by Rhizopus. This study compares, both in vivo and in vitro, the effects produced on Rhizopus by DFO and by two chelators of the hydroxypyridinone class, L1 and CP94. Experimental systemic mucormycosis was induced in the guinea pig by an i.v. injection of two different strains of Rhizopus: R. microsporus and R. arrhizus. Concomitant i.p. administration of DFO for four days shortened animal survival (P < 0.05), whereas concomitant administration of either L1 or CP94 did not. In vitro radioiron uptake by R. microsporus was 100-fold higher from the 55ferric complex of DFO than of L1 or CP94. In vitro fungal growth was stimulated sevenfold by the ferric complex of DFO (P < 0.0001) but not significantly by the ferric complex of either L1 or CP94. These results indicate that the ferric complex of DFO but not that of L1 or CP94 specifically stimulates both the iron uptake and the growth of Rhizopus. They suggest that the risk of developing mucormycosis should be minimal with L1 or CP94, as opposed to DFO.

Iron absorption by CaCo 2 cells cultivated in serum-free medium as in vitro model of the human intestinal epithelial barrier

A cell culture system consisting of confluent monolayer of human enterocyte-like CaCo 2 cells, cultivated in a serum-free nutritive medium, on microporous synthetic membranes has been used as an in vitro model of the intestinal epithelial barrier. The uptake of 55ferric citrate, as well as the transepithelial passage from the apical to the basolateral pole, have been studied. CaCo 2 cells accumulate iron in a time- and concentration-dependent process, largely specific from the apical pole. When 55ferric citrate is added at the apical pole, radioiron appears at the basal pole and the clearance rate is approximately four times higher than in the opposite direction; the amounts of 55Fe increase with the concentration in iron citrate and the duration of incubation. At least two concurrent mechanisms could be involved in iron absorption across monolayers of CaCo 2 cells. A first route would correspond to a paracellular passage of the metal from the apical to the basal pole. The second route would involve a selective intake of iron at the apical pole and could require a reduction of ferric iron, prior to the entry. Iron accumulated by the cells would, for a minor part, be stored within ferritin, whereas the major part would be excreted at the basolateral pole, either as low molecular weight material of undetermined chemical composition but from which iron is easily mobilized by apotransferrin or associated with neosynthesized apotransferrin. Vesicular transport and protein synthesis seem to be required.

Phase I and II biotransformations in living CaCo 2 cells cultivated under serum-free conditions. Selective apical excretion of reaction products

CaCo 2 cells, cultivated in a synthetic, serum-free nutritive medium on poly (ethylene terephthalate) membranes, form a confluent monolayer of differentiated cells, with the apical and basolateral poles exposed to the upper and lower compartments, respectively, of bicameral culture inserts (Halleux and Schneider, In Vitro Cell Dev Biol, 27A: 293-302, 1991). This cell culture system allows the passage of intact mannitol by the paracellular route and the transcellular diffusion of testosterone which appears mainly as a biotransformed unconjugated metabolite. When ethoxyresorufin is added to either the apical or basolateral poles of living CaCo 2 cells, resorufin is formed, and more than 80% is excreted at the apical pole. Under our experimental conditions, no detectable amounts of glucurono- or sulfconjugates are found. Methylcholanthrene and phenobarbital increase the biotransformation of ethoxyresorufin 50 and 3 times, respectively, and induce that of benzoxyresorufin, but not of pentoxyresorufin which remains absent under all conditions. These substances do not affect the proportion of resorufin recovered at the apical role. Verapamil inhibits by 25% the release of resorufin but does not affect its distribution. Chlorodinitrobenzene is conjugated with glutathione and at least two-thirds of the product is excreted at the apical pole; methylcholanthrene and phenobarbital do not increase this activity. These results demonstrate that differentiated CaCo 2 cells, under serum-free conditions, perform phase I and II reactions and that the biotransformation products are selectively excreted at the apical pole.

Mucormycosis during deferoxamine therapy is a siderophore-mediated infection. In vitro and in vivo animal studies

This study investigates the pathophysiology of mucormycosis caused by Rhizopus, which has been reported in 46 dialysis patients, while treated with deferoxamine (DFO). This drug aggravates mucormycosis, which we experimentally induced in guinea pigs and which lead to a shortened animal survival (P < or = 0.01). The drug's effect on Rhizopus is not mediated through the polymorphonuclear cells. Fe.DFO, the iron chelate of DFO, abolishes the fungistatic effect of serum on Rhizopus and increases the in vitro growth of the fungus (P < or = 0.0001). This effect is present at Fe.DFO concentrations > or = 0.01 microM, at which fungal uptake of radioiron from 55Fe.DFO is observed. A 1,000-fold higher concentration of iron citrate is required to achieve a similar rate of radioiron uptake and of in vitro growth stimulation as observed with Fe.DFO. These in vitro effects of Fe.DFO (1 microM) in serum on radioiron uptake and on growth stimulation are more striking for Rhizopus than for Aspergillus fumigatus and are practically absent for Candida albicans. For these three fungal species, the rates of radioiron uptake from 55Fe.DFO and of growth stimulation in the presence of Fe.DFO in serum are directly related (r = 0.886). These results underscore the major role of Fe.DFO in the pathogenesis of DFO-related mucormycosis. Pharmacokinetic changes in uremia lead to a prolonged accumulation of Fe.DFO after DFO administration, which helps explain the increased sensitivity of dialysis patients to DFO-related mucormycosis.

Estrogen and insulin modulation of intracellular insulin-like growth factor binding proteins in human breast cancer cells: possible involvement in lysosomal hydrolases oversecretion

Differences in insulin-like growth factor binding proteins (IGFBPs) expressed within estrogen receptor positive (ER+, MCF-7/6) and negative (ER-, MDA-MB-231) human breast cancer cells cultured in chemically defined medium were observed. In the absence of insulin, 17 beta-estradiol affects this expression in ER+ cells by significantly reducing 34 and 28 kDa species. In ER+ cells, insulin appears to minimize the estrogen induced reduction of these 34 and 28 kDa IGFBPs and stimulates a 24 kDa type. We suggest that through its association with a given IGFBP, insulin-like growth factor-II (IGF-II) directs lysosomal enzymes to secretion by its binding to the mannose-6-phosphate/IGF-II receptors present in the Golgi apparatus. Alternatively, the association of IGF-II with another IGFBP would inhibit this binding and lead to its autocrine or intracrine mitogenic action via the IGF-I receptor.

Iron absorption by intestinal epithelial cells: 1. CaCo2 cells cultivated in serum-free medium, on polyethyleneterephthalate microporous membranes, as an in vitro model

Iron absorption by intestinal epithelial cells, passage onto plasmatic apotransferrin, and regulation of the process remain largely misunderstood. To investigate this problem, we have set up an in vitro model, consisting in CaCo2 cells (a human colon adenocarcinoma line, which upon cultivation displays numerous differentiation criteria of small intestine epithelial cells). Cells are cultivated in a serum-free medium, containing 1 microgram/ml insulin, 1 ng/ml epidermal growth factor, 10 micrograms/ml albumin-linoleic acid, 100 nM hydrocortisone, and 2 nM T3 on new, transparent, Cyclopore polyethyleneterephthalate microporous membranes coated with type I collagen. Cells rapidly adhere, grow, and form confluent monolayers; after 15 days, scanning electron microscopy reveals numerous uniform microvilli. Domes, which develop on nonporous substrata, are absent on high porosity membranes. Culture medium from upper and lower compartments of microplate inserts and cell lysates were immunoprecipitated after labeling with [3H]glucosamine and leucine; analysis was done by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), followed by autoradiography. [3H]transferrin is found mainly in the lower compartment and in cells; [3H]apolipoprotein B is released in both compartments, and fibronectin almost entirely recovered in the lower compartment; [3H]transferrin receptors and ferritin are only present in cell lysates. Binding experiments also show that transferrin receptors are accessible from the lower compartment. These results suggest that CaCo2 cells, cultivated in synthetic medium on membranes of appropriate porosity, could provide an in vitro model of the intestinal barrier, with the upper compartment of the culture insert corresponding to the apical pole facing the intestinal lumen and the lower one to the basal pole in contact with blood.

Monoclonal antibody production in semi-continuous serum- and protein-free culture. Effect of glutamine concentration and culture conditions on cell growth and antibody secretion

We have recently shown that the semi-continuous cultivation of a mouse hybridoma line in spinner flasks, with a basal defined medium (BDM) devoid of serum and protein, increases the secretion of the immunoreactive monoclonal antibody (MAb) by a factor of ca. 2.4, compared to culture in flasks with serum-containing medium (Schneider, 1989). To further optimise MAb production, we have now investigated the composition of BDM and the mode of cultivation. Hybridoma cells were inoculated at 0.3 x 10(6) cells/ml in 200 ml of BDM containing 4, 6 or 8 mM glutamine; after 3-4 days (when the cell density reached greater than or equal to 10(6) cells/ml) 20, 40, 60 or 100% of the culture medium were replaced daily by fresh nutritive BDM with or without 33, 66 or 100% cell recycling. Daily, over a total period of 15-16 days, viable cells were counted and the concentration of the MAb, of glucose and glutamine (the main nutrients) and of lactate, alanine and ammonia (the main metabolites) were assayed. These experiments indicate that to provide optimal cell growth and MAb production: (i) the concentration of glutamine in the nutritive medium should be maintained at 8 mM, otherwise it falls on some days to 0 with a significant amount of cell death; at 25 mM, glucose concentration is not a limiting factor, whatever the culture conditions; (ii) with a semi-continuous mode of cultivation, a perfusion rate of 40%/day appears optimal; without cell recycling, a rate of 20% does not provide enough nutrients and/or does not remove enough metabolites, whereas a rate of 60% washes over the cells; with cell recycling, rates of 60 (moderately) or 100% (considerably) increase cellular metabolism without concurrent augmentation of MAb secretion; (iii) the recycling of the cells increases the mean cell densities and the rate of production of the MAb, as well as the rate of consumption of nutrients and of production of metabolites; recycling of 33-66% is optimal, since the total recycling progressively raises the number of dead cells and debris; (iv) there are maximal values for cell densities (ca. 2.5 X 10(6) cells/ml) and MAb production (ca. 26 micrograms/10(6) cells X day) as well as for nutrient consumption and metabolite production (except with a very high perfusion rate).(ABSTRACT TRUNCATED AT 400 WORDS)

Desferrithiocin and desferrioxamine B. Cellular pharmacology and storage iron mobilization

3H-Desferrithiocin (DFT) has been synthesized from desmethyl desferrithiocin. The uptake and release of this 3H siderophore and of its iron complex have been studied in cultured rat hepatocytes and systematically compared to 14C desferrioxamine B (DFO). At 37 degrees, the uptake of both chelators is strictly proportional to the extracellular concentration and no toxicity is observed up to, at least, 1 mM. Uptake of 3H DFT is rapid and reaches a plateau after ca. 1 hr. The accumulation of 3H DFT attains a maximum three times that of 14C DFO and the plateau is reached much more rapidly. Upon reincubation in a drug-free medium of cells that had accumulated 3H DFT, most of the 3H label is rapidly released in the culture medium. These kinetic parameters suggest that the accumulation of these two chelators results from their diffusion across cellular membranes, as a function of the gradient of concentration between the cellular compartment and the extracellular medium. Differential centrifugation of homogenates from hepatocytes incubated with 3H DFT shows that the bulk of cell associated 3H-label (82%) is found in the cytosol, whereas a small proportion (14.5%) is present in the particulate fraction. Isopycnic centrifugation on sucrose gradients suggests that 3H-label associated with the particulate fraction is localized within mitochondria. In contrast, 14C DFO distributes in almost equal proportions between cytosol and the particulate fraction (MLP). At least part of the 14C-label in MLP is associated with lysosomes. Rat hepatocytes cultivated for long term in synthetic culture medium have been used to study iron mobilization by chelators from 59Fe loaded cells. DFT mobilizes iron more rapidly than DFO. This effect is also observed in vitro with ferritin, where, in addition, DFT is much more efficient than DFO to mobilize iron at acidic pH. These results strongly suggest that different iron mobilization from cultured hepatocytes results from differences in the cellular pharmacology of these two chelators and, in particular, in their rate of uptake, cellular accumulation levels and subcellular localizations. DFT could mobilize iron from cytosol and, possibly, to a small extent from mitochondria, whereas DFO would do so from cytosol and lysosomes.

Antibiotic susceptibility of Salmonella spp. at different pH values

We have examined the effects of acidic pH, in the range of those prevailing within phagosomes and lysosomes, on the growth and the susceptibility to different antibiotics of several strains of Salmonella spp. The minimal inhibitory concentration and the minimal bactericidal concentration of several beta-lactams were increased considerably during culture at pH 5.2. The extent of the increase was a function of: (1) the beta-lactam structure and, more particularly, the hydrophobicity of the side-chain of the molecule; and (2) the bacterial serotype. This phenotypic resistance at acid pH was not due to beta-lactamase activity or to a lower growth rate. In contrast, rifamycin SV was more active at acidic pH than at neutral pH and chloramphenicol, another highly hydrophobic drug, was equally efficacious at both pH values. Membrane lipopolysaccharide mutants, but not porin mutants, cultivated at an acidic pH were inhibited by lower concentrations of the beta-lactams. This suggests that the increased resistance to beta-lactams, and the increased susceptibility to rifamycin SV, at acidic pH, could have resulted from modified permeability of the outer membrane to antibiotics.

Cytotoxic activity of daunorubicin or vindesin conjugated to a monoclonal antibody on cultured MCF-7 breast carcinoma cells

Conjugates were constructed between daunorubicin or vindesin and a monoclonal antibody to human milk fat globule membrane associated antigen. This antibody recognizes a high molecular weight glycoprotein present at the cell surface of human normal and tumour epithelial cells; after specific binding to plasma membrane of cultured MCF-7 human breast carcinoma cells, it is endocytosed and gains access to lysosomes, wherein it is broken down (Aboud-Pirak et al., Cancer Res 48: 3188-3196, 1988). Covalent linkage of daunorubicin (through a succinylated tetrapeptide arm) or of vindesin (through a hemisuccinate arm) yields conjugates with maximal molar ratios (drug molecule/specific IgG under monomeric form, i.e. unaggregated) or 2.0 and 4.5 respectively. The conjugate with daunorubicin inhibits the binding of the 3H labelled antibody to MCF-7 cells as efficiently as the native unconjugated antibody, whereas the conjugate with vindesin inhibits it only by 56%. Both conjugates are entirely stable in plasma and serum; after 24 hr incubation at pH 4.8 in the presence of rat liver lysosomal enzymes, 60 and 33% of daunorubicin and vindesin respectively are released from the conjugates. Adherent non-confluent cultures of cells recognized (MCF-7) or not (Hep-G2, human hepatocarcinoma cells) by the antibody were incubated from 1 hr to 6 days with different concentrations of daunorubicin or vindesin, free or conjugated to the specific or to a control monoclonal antibody. LD50, defined as the drug concentration required to reach 50% of the amount of cell associated protein obtained in the absence of drug were determined at the end of 6 days continuous incubation or after shorter incubation followed by reincubation in drug free medium up to 6 days. Both cell lines are almost equally susceptible to the free drugs. The conjugate between daunorubicin and the antibody appears inactive, even at saturating concentrations of antibody. This could result from the extrusion out of the cells of daunorubicin molecules released from the conjugate, impairing the drug to reach the intracellular concentration required for cytotoxicity. In contrast, conjugation of vindesin to the specific but not to a control antibody restricts the activity of the drug to cells selectively recognized by the specific antibody. However, even after corrections for the loss of immunoreactivity and for the incomplete release of vindesin from the conjugate, cytotoxicity is achieved at higher concentrations or requires longer exposure to the conjugated than to the free drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Optimisation of hybridoma cell growth and monoclonal antibody secretion in a chemically defined, serum- and protein-free culture medium

Monoclonal antibodies (MAbs), for human use require chemical and biological purity. The best approach seems in vitro cultivation in a serum-, protein-free medium. A basal defined culture medium has been developed to sustain optimal hybridoma cell growth and MAb secretion. It consists of Iscove's Dulbecco's modified, Eagle's, Ham's F12 and NCTC 135 media in a 5:5:1 mixture (v/v/v), to which glucose is added to reach a final concentration of 25 mM, glutamine to 4-6 mM, 2-mercaptoethanol to 50 microM, Pluronic F68 to 0.01-0.1% (w/v), Hepes to 25 mM and NaHCO3 to 3 g/l. Hybridoma cells, derived from Sp 2/0 myeloma and secreting a MAb to a human milk fat globule membrane-associated high molecular weight glycoprotein, were cloned in this medium containing 1% (v/v) fetal calf serum and then sequentially adapted in serum-free medium further supplemented with transferrin and insulin, both at 10 micrograms/ml. Clones producing immunoreactive MAbs secrete a mean of 50 micrograms IgG/ml, i.e., ca. 80% of the concentration reached in Dulbecco's modified Eagle's medium containing 10% serum. When cells were cultured in spinner flasks with a semi-continuous mode of cultivation (with a daily removal of 20% of the volume and its replacement by fresh culture medium), in serum-free medium further supplemented with 10 nM estradiol, a mixture of trace elements and albumin (at 30 micrograms/ml) complexed to linoleic acid, MAb secretion reached 100 micrograms/ml and became equal or higher to that obtained in serum-containing medium. MAb secretion was not decreased and was even significantly increased during the growth phase, when transferrin was replaced by another iron source, i.e., ferric citrate at 500 microM associated with 20 microM ascorbic acid. Finally, deletion of insulin and of albumin-linoleic acid did not affect significantly cell density nor MAb secretion. In conclusion, it appears from this study that semi-continuous cultivation in spinner flasks of hybridoma cells, after cloning and progressive adaptation, in a chemically defined, serum- and protein-free medium, permitted MAb secretion to be increased to a mean of 144 micrograms/ml, i.e., multiplied by a factor of ca. 1.5 compared to culture of these cells in serum-containing medium under the same conditions and by a factor of ca. 2.4 compared to cultivation in serum-containing medium in flasks.

Binding and endocytosis of a monoclonal antibody to a high molecular weight human milk fat globule membrane-associated antigen by cultured MCF-7 breast carcinoma cells

The aim of this study was to analyze whether a monoclonal antibody to human milk fat globule membrane-associated antigens, recognized specifically and homogeneously by human breast carcinoma cells but also by normal epithelial cells active in secretion, could be used to restrict the access of antitumoral drugs to cells exposing the epitope. The drug-antibody conjugate to be used is constructed by means of a covalent peptidic linkage stable in extracellular medium but hydrolyzed by lysomal enzymes after endocytosis of the drug-carrier conjugate. This monoclonal antibody specifically immunoprecipitates radioactive material from MCF-7 cells biosynthetically radiolabeled with galactose, glucosamine, palmitic acid, or acetic acid but not with mannose, leucine, or methionine. Upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and dithiothreitol, the label migrates as two bands with apparent molecular weights of about 350,000 and 400,000. These bands disappear, or their molecular weight is affected, after treatment of the cells with cycloheximide or of cell lysates with trypsin, Pronase, or neuraminidase but not treatment of the immunoprecipitate with endoglycosidase F. This suggests that these antigens are glycoproteins with O-linked oligosaccharides containing sialic acid in the epitope. By analogy, they should be similar, if not identical, to those recognized by the monoclonal antibodies designated HMFG1 (H. Burchell, H. Durbin, and J. Taylor-Papadimitriou, J. Immunol., 131:508-513, 1983) and DF3 (H. Sekine, T. Ohno, and D.W. Kufe, J. Immunol., 135:3610-3615, 1985). Binding at 4 degrees C of the 3H-labeled antibody by MCF-7 cells indicates the specific attachment of about 1.2 X 10(6) IgG molecules per cells with a Kd of about 14 nM. At 37 degrees C, cells take up the 3H-labeled antibody in amounts much higher than the binding capacity. In addition to cell-associated material, labeled digestion products are released into the culture medium. Cell fractionation by differential centrifugation and isopycnic equilibration on sucrose gradient indicates that the bulk of cell-associated antibody is distributed like the marker enzyme of lysosomes. Although the total uptake of the antibody by the cells is unaffected by either 50 microM chloroquine or 3 micrograms/ml cycloheximide, the release of digestion products is completely inhibited by chloroquine. Antigen-antibody dissociation is pH dependent, since, respectively, 50 and 84% of membrane-bound antibody are released during washing at pH 4.6 and 4.1.(ABSTRACT TRUNCATED AT 400 WORDS)

Uptake, subcellular distribution and biotransformation of 3H-labelled astemizole in cultured rat hepatocytes

When incubated with 3H-astemizole, a potent antagonist of H1 receptor, cultured rat hepatocytes, which do not express specific receptors for this ligand, avidly take up 3H-label proportionally to the drug concentration. HPLC analysis indicates that at 10 ng 3H-astemizole/ml, cells almost entirely deplete the culture medium of the drug within 4 hr of incubation. At 37 degrees, astemizole is metabolized and released into the culture medium mainly under the form of glucuronoconjugated metabolites. Differential centrifugation of homogenates from hepatocytes incubated with 3H-astemizole indicates that astemizole and unconjugated metabolites are found in the particulate fraction, whereas astemizole and conjugated metabolites are present in the cytosol. Isopycnic centrifugation on sucrose gradient shows that the major part of the 3H-label in the particulate fraction distributes like phospholipids and NADPH cytochrome c reductase, suggesting an association with membranes and, in particular, with the endoplasmic reticulum. Chloroquine, a drug accumulating within lysosomes and acidic endosomes, decreases the uptake of 3H-astemizole by hepatocytes and induces, during isopycnic centrifugation of a particulate fraction, a shift of the 3H-label towards lower densities where it closely accompanies cathepsin B. This suggests that a minor part of astemizole accumulated in the hepatocytes could be trapped within lysosomes. These results could support the hypothesis that aspecific binding of astemizole to cellular membranes and, to a lesser extent, trapping in lysosomes could play a role in the pharmacokinetics of the drug.

Subcellular localization of transferrin protein and iron in the perfused rat liver. Effect of Triton WR 1339, digitonin and temperature

The subcellular localization of 3H-labelled 59Fe-loaded transferrin accumulated by the liver has been studied by means of cell fractionation techniques. More than 96% of the 59Fe present in the liver of rats perfused with 59Fe-labelled transferrin is recovered in the parenchymal cells. Rat livers were perfused with 10 micrograms/ml 3H-labelled 59Fe-saturated transferrin, homogenized separated in nuclear (N), mitochondrial (M), light mitochondrial (L), microsomal (P) and supernatant (S) fractions; M, L and P fractions were further analysed by isopycnic centrifugation in sucrose gradients. 3H label distributes essentially around densities of 1.13-1.14 g/ml overlapping to a large extent with the distribution of galactosyltransferase, the marker enzyme of the Golgi complex. However, after treatment with low concentrations of digitonin the 3H label dissociates from galactosyltransferase and is shifted to higher densities, suggesting an association of transferrin with cholesterol-rich endocytic vesicles which could derive from the plasma membrane. 59Fe is mostly found in the supernatant fraction largely in the form of ferritin, as indicated by its reaction with antiferritin antibodies. In the mitochondrial fraction the density distribution of 59Fe suggests an association with lysosomes and/or mitochondria. In contrast to the lysosomal enzyme cathepsin B, the density distribution of 59Fe was only slightly affected by pretreatment of the rats with Triton WR 1339, suggesting its association with the mitochondria. At 15 degrees C, 59Fe and 3H labels are recovered together in low-density endocytic vesicles. On the basis of our results we suggest that, at low extracellular transferrin concentration, iron uptake by the liver involves endocytosis of the transferrin protein. The complex is interiorized in low-density acidic vesicles where iron is released. The iron passes into the cytosol, where it is incorporated into ferritin and into the mitochondria. The iron-depleted transferrin molecule would then be returned to the extracellular medium during the recycling of the plasma membrane.

Cellular pharmacology of deferrioxamine B and derivatives in cultured rat hepatocytes in relation to iron mobilization

Two radiolabelled derivatives of deferrioxamine B (DF) have been synthesized: methyl-DF and acetyl-DF. Both derivatives are non cytotoxic and stable in cell culture but they are degraded in human plasma and more extensively in rat plasma. Methyl-DF, acetyl-DF and DF mobilize radioiron to the same extent from hepatocytes loaded with 59Fe citrate in the same range of extracellular concentrations. The uptake and release of the 3H-labelled derivatives and their corresponding iron complexes have been measured and appear to represent a passive phenomenon resulting from the gradient of concentration between the cellular compartment and the extracellular medium. The results indicate that only a limited pool of cellular iron is accessible for chelation and that neither the permeability of the cellular membrane, nor the intracellular concentration of the chelators are the limiting factors for iron mobilization. On the basis of the subcellular distribution of the 3H-DF analogues, methylamine inhibition of iron chelation by siderophores in cell cultures and the positive effect of acidic pH and hydrolysis by lysosomal enzymes on in vitro iron mobilization from radiolabelled ferritin, we suggest that iron mobilization by DF and its derivatives occurs in lysosomes where they complex iron released from ferritin under the conjugate actions of acidic pH and lysosomal enzymes.

Receptor-mediated endocytosis of polymeric IgA and galactosylated serum albumin in rat liver. Evidence for intracellular ligand sorting and identification of distinct endosomal compartments

Rat polymeric IgA (pIgA) and galactosylated bovine serum albumin (GalBSA), once injected to rats, are avidly taken up by hepatocytes via receptor-mediated endocytosis. Of injected pIgA, 64% was transferred undigested into bile within 3 h, with a peak at 30-45 min. GalBSA was essentially digested in lysosomes. By electron microscopy using ligand-peroxidase conjugates, both ligands were internalized through coated pits/coated vesicles into similar electron-lucent vesicles and tubules. Subsequently, pIgA remained mostly associated with small vesicles clustering around and fusing with bile canaliculi, while GalBSA was predominantly found in large, heterogeneous endocytic structures and in lysosomes. By subcellular fractionation, they were associated at 3 min after injection with structures that similarly sedimented in the P fraction (250 000 - 3 X 10(6) X g X min) and equilibrated at densities of about 1.13 g/ml in sucrose gradients. At 10 min and 20 min, pIgA distribution remained mostly in the P fraction at the same equilibrium density. A minor component of the pIgA distribution was found at the density of lysosomes, but contrary to lysosomal enzymes, its distribution was not affected by Triton WR 1339. In contrast to pIgA, GalBSA was progressively recovered in the L fraction (33 000 - 250 000 X g X min) with organelles equilibrating around 1.11 g/ml, and, by 20-45 min, was found in the ML fraction (10 000 - 250 000 X g X min), around 1.20 g/ml, i.e. in lysosomes. Chloroquine did not reduce the efficiency but delayed the secretion of pIgA into bile. Similarly, it did not affect the uptake of GalBSA but apparently delayed GalBSA transfer along successive populations of host organelles. The low density, GalBSA-containing structures were devoid of proteolytic activity. Anti-secretory components IgG and F(ab')2 were selectively excreted into bile, partially or totally as compounds of lower molecular mass. These antibody fragments probably result from a disulfide reduction activity along the pIgA pathway. In conclusion, our data (a) strongly suggest that pIgA and GalBSA are sorted between 3 min and 10 min after injection in non-lysosomal acidic organelles, (b) identify two successive and physically distinct endosomal populations containing GalBSA, and (c) provide the first evidence for a disulfide reduction activity along the transcytotic pathway of rat hepatocytes.

Iron mobilization from cultured hepatocytes: effect of desferrioxamine B

When cultured rat hepatocytes prelabelled for different times at 37 degrees with 59Fe are reincubated for 1 hr in a fresh medium, radiolabelled iron is released in the washout medium as a function of the prelabelling time, and behaves like low molecular weight material on isokinetic centrifugation in sucrose gradients. When apotransferrin or desferrioxamine B are present in the reincubation medium, the kinetics of iron release are similar but the absolute amounts of radiolabelled iron found in the culture medium are much greater. In the presence of apotransferrin, most of the 59Fe released from the cells distributes as transferrin whereas with desferrioxamine B, almost all the 59Fe is extracted by benzyl alcohol indicating its chelation by the drug. Cell fractionation data indicate that iron accumulated by hepatocytes is rapidly incorporated into cytosol ferritin, and this seems to be a preferred source of iron for the chelator.

Transferrin protein and iron uptake by cultured hepatocytes

The binding and uptake of 59Fe-loaded 3H-labelled rat transferrin by cultured rat hepatocytes was investigated. At 4 degrees C, there is no evidence for a specific binding of transferrin which could be related to the association of neo-synthesized transferrin with plasma membrane receptors. At 37 degrees C, iron uptake is much more important than transferrin uptake; it proceeds linearly over the time of incubation, is largely proportional to the extracellular transferrin concentration, and is compatible with uptake by fluid phase endocytosis. The difference observed between iron and transferrin uptake implies the existence of a mechanism allowing the reutilization of transferrin after iron delivery.

Evidence for a continual exchange of 5'-nucleotidase between the cell surface and cytoplasmic membranes in cultured rat fibroblasts

Approximately 40% of the 5'-nucleotidase activity in cultured rat embryo fibroblasts was patent, as judged by enzymatic assays comparing the activity of intact cells with detergent-solubilized cells. The patent activity was inhibited when cells were incubated with anti-5'-nucleotidase serum at 2 degrees C, whereas latent activity (calculated as the difference between total and patent activity) was not. Latent activity was inhibited by antibody when the antiserum was added directly to detergent-solubilized cells or when cells were cultured in the presence of antiserum for several hours. Patent activity was inhibited by antibody, and cells were returned to culture in antibody-free medium; after 12 hr, 30% of the total activity was expressed in intact cells and 60% of the anti-5'-nucleotidase, assayed by the binding of sheep antirabbit antibodies to intact cells, was lost from the cell surface, indicating an exchange of 5'-nucleotidase between the latent and patent compartments. Cytochemical studies showed that the patent activity was located on the cell surface and that latent activity was present in cytoplasmic vacuoles and vesicles, and in the Golgi complex. Over 30% of the anti-5'-nucleotidase internalized during 6 hr in culture returned to the cell surface after a further 9 hr, indicating a continual exchange of the enzyme between the cell surface and cytoplasmic membranes.

Effect of chloroquine and methylamine on endocytosis of fluorescein-labelled controlled IgG and of anti-(plasma membrane) IgG by cultured fibroblasts

We report here the effect of chloroquine and methylamine two lysosomotropic drugs, on the binding, uptake and subcellular localization of fluorescein-labelled control immunoglobulin G (control IgG) a marker for non-specific adsorptive endocytosis and of anti-(plasma membrane) IgG (specific IgG), a specific ligand of cell-surface antigens. At 4 degrees C, methylamine and chloroquine inhibit the binding of control IgG to the cell surface, probably by a reversible competition. These two drugs, methylamine more than chloroquine, considerably slow down the rate at which control IgG is transferred from its binding sites on the phagosomal membrane to the lysosomal compartment; both drugs block almost completely the intralysosomal digestion of this IgG as well as the release of degradation products into the culture medium. They do not affect the binding and uptake of the specific IgG. In addition, methylamine seems to inhibit partially the return of the cell surface of membrane antigens and of membrane fragments bearing 5'-nucleotidase or binding sites for control IgG. We conclude that important steps (binding to cell surface, delivery to lysosomes, digestion and recycling of plasma membrane) involved in the uptake and the processing of IgG by fibroblasts are inhibited by these two substances. The effects of lysosomotropic agents on the regulation and function of the endocytic pathway and of lysosomes could have many pharmacological and therapeutic implications.