Co-doped carbon materials synthesized with polymeric precursors as bifunctional electrocatalysts

The design of stable and high performance metal free bifunctional electrocatalysts is a necessity in alkaline zinc–air batteries for oxygen reduction and evolution reaction. In the present work co-doped carbon materials have been developed from polymeric precursors with abundant active sites to achieve bifunctional activity. A 3-dimensional microporous nitrogen–carbon (NC) and co-doped nitrogen–sulfur–carbon (NSC) and nitrogen–phosphorus–carbon (NPC) were synthesized using poly(2,5-benzimidazole) as an N containing precursor. The obtained sheet like structure shows outstanding ORR and OER performance in alkaline systems with excellent stability compared to Pt/C catalyst. The doped heteroatom in the carbon is expected to have redistributed the charge around heteroatom dopants lowering the ORR potential and modifying the oxygen chemisorption mode thereby weakening the O–O bonding and improving the ORR activity and overall catalytic performance. The bifunctional activity (ΔE = E_j=10 − E_1/2) of an air electrode for NPC, NSC, NC and Pt/C is 0.82 V, 0.87 V, 1.06 V and 1.03 V respectively, and the NPC value is smaller than most of the reported metal and non-metal based electrocatalysts. The ORR (from onset potential) and OER (10 mA cm⁻²) overpotential for NPC, NSC, and NC is (290 mV, 410 mV), (310 mV, 450 mV) and (340 mV, 600 mV) respectively. In the prepared catalyst the NPC exhibited higher ORR and OER activity (NPC > NSC > NC). The doping of P in NPC is found to have a great influence on the microstructure and therefore on the ORR and OER activity.

Metal free bifunctional catalysts based on co-doped carbon materials synthesized from polymeric precursors via a simple pyrolysis route with high cyclic stability and low polarization for Zn–air batteries.

Ionophores as Potent Anti-malarials: A Miracle in the Making

Plasmodium has a complex life cycle that spans between mosquito and human. For survival and pathogenesis it banks upon dynamic alterations in ionic transport across organelle and plasma membrane. Being a fundamental contributor of crucial biological processes in parasite, ionic balance facilitates parasite invasion, augmentation and transmission. Past few decades have witnessed tremendous advancement in understanding the relevance of ionic transit in parasites. Perhaps, not surprisingly, disruption of ionic homeostasis was thought to be detrimental for parasite. Compounds like ionophores are known to facilitate ionic transport across membrane down their electrochemical gradient. Despite continuous effort, malaria treatment is still a challenge particularly due to the development of resistance among parasites against existing therapeutic options. However, repurposing the existing drugs can be advantageous over de novo drug development programs in terms of cost and associated risk factors. Ionophores, being used in coccidiosis have proven to be of significance in the treatment of experimental models of malaria. Several recent reports have highlighted the attractive potential of ionophores such as Monensin, Maduramicin, Valinomycin, etc., that can act against multiple stages of malarial parasite's life cycle. Improved variety of these molecules may help in mitigating the drug resistance problems as well. This review is an attempt to examine the relevant literature and provide insight into the mechanism and prospects of different classes of ionophores as promising anti-malarial potpourri.

Efficacy of Liposomal Monensin on the Enhancement of the Antitumour Activity of Liposomal Ricin in Human Epidermoid Carcinoma (KB) Cells

The monensin, known to enhance the cytotoxicity of ricin and ricin-based immunotoxins is a very hydrophobic molecule and this limits its administration in optimum doses under in vivo conditions. In order to realise its full potential, monensin was intercalated into various liposomal formulations and its ability to potentiate the cytotoxicity of ricin liposomes in human epidermoid carcinoma (KB) cells was studied. It was observed that ricin cytotoxicity enhancing ability of monensin liposome depends on the surface charge as well as density and chain length of distearoyl phosphatidylethanolamine-methoxy polyethylene glycol present on the surface of liposomal monensin. Maximum potentiation on the cytotoxicity of liposomal ricin was observed by monensin entrapped in neutral liposome (106.5 fold) followed by negatively charged (94.2 fold) and positively charged liposome (90 fold). Studies on the effect of variation of density and chain length of distearoyl phosphatidylethanolamine-methoxy polyethylene glycol showed that neutral monensin liposomes having 2.5 mol% distearoyl phosphatidylethanolamine-methoxy polyethylene glycol with chain length of 2000 exhibits maximum potentiation (117.6 fold) on the cytotoxicity of ricin liposomes when the cellular uptake of monensin liposome was maximum (42.0%) and the zeta potential value on the surface of liposomes was -0.645. The present study has clearly shown that liposomal monensin is very effective in enhancing the cytotoxicity of liposomal ricin in human cancer cells and liposome can be used as in vivo deliver vehicle for monensin to potentiate the cytotoxicity of liposomal ricin to eliminate cancer cells.

A New Glycoprotein Allergen/Antigen with the Protease Activity from Aspergillus fumigatus

BACKGROUND

Aspergillus fumigatus is an opportunistic fungus causing allergic and invasive aspergillosis in humans and animals. It secretes an array of complex biologically active glycoprotein antigens and allergens. It is important to identify and characterize probable potential virulent factors playing a major role in the pathogenesis of aspergillosis.

METHODS

Using protein purification techniques (lectin affinity chromatography, gel filtration, electroelution and high-pressure liquid chromatography), a major antigen/allergen with a molecular weight of 56 kD (gp56) from A. fumigatus was purified to homogeneity. The protein was characterized by immunoblot, ELISA and protease assays. The N-terminal amino acid sequencing was performed.

RESULTS

The gp56 protein showed a single band on silver staining and isoelectric focussing. The protein to carbohydrate ratio was 1.5:1 and gp56 gave a protein band at a molecular weight of 34 kD on enzymatic deglycosylation. It also exhibited IgG and IgE immunobinding with antibodies present in sera of allergic bronchopulmonary aspergillosis patients. The gp56 exhibited protease activity and N-terminal seven-amino acid sequence showed homology with fungal serine proteases.

CONCLUSIONS

The gp56 protein by virtue of its proteolytic activity could be one of the virulent factors of A. fumigatus involved in establishing infection in the host along with other factors.

Altered immune response to liposomal allergens of Aspergillus fumigatus in mice

Aspergillus fumigatus has been implicated as the major pathogenic fungus causing Aspergillus-mediated disorders. It secretes complex glycoprotein antigens and allergens, which induce type I and type III mediated hypersensitivity reactions. The immune response to these allergens/antigens in allergic disorders is characterized by elevated levels of specific IgE, Th2 cytokines and eosinophilia. In the current study, the ability of negatively charged liposomes entrapped with glycoprotein antigens and allergens of A. fumigatus to modulate the immune response was studied. Immune response in mice was evaluated with both free and liposomal formulations. Liposome entrapped glycoprotein antigens/allergens of A. fumigatus elicited a Th1 type response with increased levels of TNF-alpha (5.5-folds), IFN-gamma (four-folds), specific IgG (three-folds) and IgG2a (2.4-folds), low titers of specific IgG1 (2.2-folds decrease) and IgE (three-folds decrease), and decreased peripheral eosinophilia by four-folds in comparison to mice receiving free glycoprotein allergens/antigens of A. fumigatus. Histopathological examination of lung tissue sections clearly indicated reduced eosinophil infiltration in mice immunized with liposomal formulations. These results suggest potential of liposomal formulations for A. fumigatus allergens/antigens for exploration in immunotherapy.

Characterization of Aspergillus fumigatus protein disulfide isomerase family gene

Aspergillus fumigatus is an opportunistic fungus which causes pulmonary complications in humans and animals. The clinical spectrum observed with A. fumigatus is attributed to the multifunctional nature of its antigens. Lack of understanding on the molecular processes and complexity of the fungus have spurred interest in the identification and characterization of its antigens/allergens with biological activities and virulence functions. For identification of some of these antigens/allergens, a cDNA library of A. fumigatus was screened with antibodies of allergic bronchopulmonary aspergillosis (ABPA) patients. One of the reactive clones was sequenced and observed to have an open reading frame of 1095 nucleotides corresponding to a polypeptide of 364 amino acids. The nucleotide and deduced amino acid sequence showed significant homology with the protein disulfide isomerase (PDI) superfamily. The expressed recombinant fusion protein exhibited specific IgG and IgE binding with antibodies present in ABPA patients' sera. The recombinant protein in vitro catalyzed folding of scrambled RNase. The probable epitopic regions of the deduced amino acid sequence were mapped by algorithmic analysis. This is the first report of isolation of a gene encoding a member of the PDI family from A. fumigatus. The PDI superfamily of proteins may play an important role in the protein folding mechanisms of A. fumigatus antigens/allergens for their interaction with the host.

Tumour targeted delivery of encapsulated dextran-doxorubicin conjugate using chitosan nanoparticles as carrier

Doxorubicin (DXR) commonly used in cancer therapy produces undesirable side effects such as cardiotoxicity. To minimize these, attempts have been made to couple the drug with dextran (DEX) and then to encapsulate this drug conjugate in hydrogel nanoparticles. By encapsulation of the drug conjugate in biodegradable, biocompatible long circulating hydrogel nanoparticles, we further improved the therapeutic efficacy of the conjugate. The size of these nanoparticles as determined by quasi-elastic light scattering, was found to be 100+/-10 nm diameter, which favors the enhanced permeability and retention effect (EPR) as observed in most solid tumors. The antitumor effect of these DEX-DXR nanoparticles, was evaluated in J774A.1 macrophage tumor cells implanted in Balb/c mice. The in vivo efficacy of these nanoparticles as antitumor drug carriers, was determined by tumor regression and increased survival time as compared to drug conjugate and free drug. These results suggest that encapsulation of the conjugate in nanoparticles not only reduces the side effects, but also improves its therapeutic efficacy in the treatment of solid tumors.

Biodistribution of amphotericin B when delivered through cholesterol hemisuccinate vesicles in normal and A. fumigatus infected mice

PURPOSE

This study compared the biodistribution of two amphotericin B formulations in normal and Aspergillus infected mice. Amphotericin B cholesterol hemisuccinate vesicles (ABCV) which reduces the toxicity of amphotericin B and thereby enhances its therapeutic efficacy in a murine model of aspergillosis was compared with conventional amphotericin B deoxycholate suspension (AmB(DOC)).

METHODS

ABCV (12 mg/kg wt) and AmB(DOC) (2 mg/kg wt) were intravenously administered to normal and A. fumigatus infected mice. The concentration of amphotericin B in plasma and other organs was determined at different time points.

RESULTS

It was observed that ABCV had a significantly different pharmacokinetic profile compared to conventional amphotericin B. In comparison to AmB(DOC) significantly lower levels of amphotericin B were observed in kidneys and plasma, the major target organs of toxicity. Animals receiving ABCV demonstrated high levels of amphotericin B in liver (38% retention till 48 h) and spleen (2.6% retention till 48 h) in comparison to AmB(DOC) (7.3% and 0.21% retention in liver and spleen respectively till 48 h). Biodistribution studies of ABCV in infected mice demonstrated that there was a moderate enhancement in levels of amphotericin B in liver, spleen, lungs and kidneys as compared to normal mice and the plasma levels were reduced. However, such observations were not made after AmB(DOC) administration to infected mice except for kidneys in which there was a marked increase in uptake as compared to normal mice.

CONCLUSIONS

Our results suggest that prolonged retention of high concentrations of ABCV in reticuloendothelial system organs is the reason for its reduced toxicity. Enhanced localization of the drug at the infected site may lead to improvement in therapeutic efficacy.

Assessment of targeting potential of galactosylated and mannosylated sterically stabilized liposomes to different cell types of mouse liver

Galactose and Mannose residues were tagged on the surface of n-glutaryl-phosphatidylethanolamine (NGPE) containing liposomes with and without polyethylene glycol of molecular weight 2000 Da conjugated to distearoyl phosphatidylethanolamine (PEG-2000-DSPE). Biodistribution studies showed that sugar bearing liposomes were cleared more rapidly from circulation than those not bearing the sugar moieties. However, the rate of clearance of glycosylated conventional liposomes was much faster than the sugar bearing sterically stabilized liposomes. Intrahepatic distribution studies showed that a substantial amount of conventional liposomes without sugar residues were taken up by both parenchymal (P) (40%) and non-parenchymal (NP) cells (60%). However, incorporation of PEG-2000-DSPE shifted this uptake slightly in favour of parenchymal cells (47%). While ratio of distribution of galactosylated conventional liposomes to P and NP cells was found to be 74:26, galactosylation of sterically stabilized liposomes further enhanced the affinity of these vesicles towards P cells (P:NP ratio being 93:7). Thus, reduced uptake by Kupffer cells was observed with galactosylated sterically stabilized liposomes as compared to conventional liposomes. Whereas, mannosylation of both the liposomes shifted the distribution towards Kupffer cells in an analogous manner. These findings indicate that sterically stabilized liposomes tagged with galactose residues on their surface are more effective in targeting the entrapped material to hepatocytes as compared to conventional liposomes. This approach can therefore be employed for delivering therapeutic agents like drugs, enzymes, genetic materials, anti-sense oligonucleotides selectively to liver P cells for treatment of hepatic disorders.

Biodistribution of fluoresceinated dextran using novel nanoparticles evading reticuloendothelial system

The rapid clearance of circulating nanoparticles from the blood stream coupled with their high uptake by liver and spleen has thus far been overcome by reducing the particle size, and by making the particle surface hydrophilic with poloxamers and poloxamines. We have prepared hydrogel nanoparticles of polyvinylpyrrolidone of a size less than 100 nm diameter with precise size distribution. Since the inner cores of these particles are also hydrophilic, these particles are capable of encapsulating water-soluble compounds. Biodistribution of these particles shows practically negligible (<1%) uptake by the macrophages in liver and spleen, and approximately 5-10% of these particles remain in circulation even 8 h after i.v. injection. Increasing the surface hydrophobicity as well as particle size can increase the RES uptake of these particles. Because of longer residence in blood, the hydrogel nanoparticles have potential therapeutic applications particularly in cancer: the water-soluble cytotoxic agents encapsulated in these particles can be targeted to tumors while minimizing the likelihood of toxicity to reticuloendothelial system (RES).

Effect of amphotericin B lipid formulation on immune response in aspergillosis

The immune response against Aspergillus fumigatus has been studied during infection and therapy in order to understand the mechanism of pathogenesis and the effect of treatment with amphotericin B. With this in view an animal model of aspergillosis was developed in Balb/c mice by intravenous injection of an optimized dose of 3. 6x10(6) A. fumigatus spores. Infection due to Aspergillus was well established by histopathological examination and fungal load in the animal. Lesions and eosinophil infiltration was observed in the infected tissues which indicated the involvement of a Type I hypersensitivity response. Evaluation of serological parameters indicated high levels of interleukin-4 (IL-4) and A. fumigatus specific IgG antibodies. The reduction in fungal load and modulation of immune response in the infected mice was studied following treatment with amphotericin B/cholesterol hemisuccinate vesicles (ABCV). The results clearly indicated significant reduction in the fungal load, disappearance of eosinophils and lesions with the appearance of macrophages and neutrophils in the infected lung tissue, a decrease in IL-4 (fourfold) and a concomitant increase of interferon-gamma (IFN-gamma; twofold) with an improvement in general condition of mice. In the non-treated mice, the rise of IL-4 level indicated the association of T(H)2 cell response with susceptibility to infection while the increase of IFN-gamma in the treated group suggested that T(H)1 cell response may be involved in resistance to Aspergillus infection.

Toxicity and therapeutic efficacy of amphotericin B delivered through cholesterol hemisuccinate vesicles in the treatment of experimental murine aspergillosis

We have studied the toxicity and therapeutic efficacy of amphotericin B in cholesterol hemisuccinate vesicles (ABCV) in the treatment of invasive aspergillosis in Balb/c mice. The toxicity of amphotericin B was significantly reduced when delivered through cholesterol hemisuccinate vesicles as compared to deoxycholate suspension (AmB(DOC)) as evidenced by reduced nephrotoxicity in Balb/c mice, lower in-vitro toxicity to erythrocytes and higher maximum tolerated dose. The latter increased from 2 mg/kg wt for AmB(DOC) to 17 mg/kg wt for ABCV. The vesicles had a mean diameter of 252 nm. In order to evaluate the therapeutic efficacy of ABCV, Aspergillus fumigatus-infected mice were treated with ABCV 2, 4, 8 or 12 mg/kg or AmB(DOC) 1 mg/kg wt. The antifungal activity was highly dependent on the dosage of ABCV on the basis of survival of treated mice and cfu in lung, liver, spleen and kidney. This study found that ABCV had dose-dependent antifungal activity and therapeutic efficacy in the treatment of invasive aspergillosis in Balb/c mice.

A colorimetric estimation of polyethyleneglycol-conjugated phospholipid in stealth liposomes

The paper describes a colorimetric method for estimation of polyethyleneglycol (PEG)-conjugated phospholipid in either form, free or bound to liposomes. It provides a rapid, highly reproducible, and sensitive tool to detect PEG-coupled phospholipid in amounts as low as 1 microg giving a linear response over a range of 1-100 microg. The method makes use of the biphasic system comprising aqueous ammonium ferrithiocyanate and chloroform, developed by Stewart for estimation of phospholipids. The same system was also applied for quantitation of PEG in PEG-protein conjugates in a recent report. The samples were digested with phospholipase-C, prior to analysis, in order to eliminate the contributions from liposomal phospholipids other than the PEG-conjugated phospholipid. The technique can give valuable information regarding the retention of PEG coating on the surface of the vesicles when employed in combination with markers for the aqueous compartment. In addition, it does not suffer from interference by proteins. This makes it particularly suitable for monitoring the pharmacokinetics of stealth liposomes, using PEG-phospholipid as a lipid probe. Since it does not involve handling hazardous radioisotopes, the suggested technique could even be utilized in clinical trials.

A colorimetric assay for estimation of polyethylene glycol and polyethylene glycolated protein using ammonium ferrothiocyanate

A colorimetric method for quantitative assay of polyethylene glycol (PEG) described here is based on partitioning of a chromophore present in ammonium ferrothiocyanate reagent from an aqueous to a chloroform phase in the presence of PEG. The method is simple, reproducible, and can detect PEG in amounts as low as 5 microg. It gives a linear response over a range of 5-100 microg. The absence of any interference by proteins makes the assay equally suitable for the estimation of PEG in PEG-protein conjugates. The method was employed to monitor the separation profile of a mixture of free and PEG-5000 coupled to bovine serum albumin during purification through a gel filtration column. In this report we have also demonstrated for the first time an assay method which permits a critical evaluation of pharmacokinetic properties of any PEG-protein conjugate under in vivo conditions.

Potentiation of ricin cytotoxicity by liposomal monensin under in vitro and in vivo conditions

Effect of monensin, intercalated in liposomes on the cytotoxicities of ricin, Pseudomonas exotoxin A and diphtheria toxin in phagocytic and non-phagocytic cells as well as in mice has been studied. Intercalation does not disturb the integrity of the liposomal bilayer and substantially enhances the cytotoxicities of ricin and Pseudomonas exotoxin A in both phagocytic and non-phagocytic cells while it has no effect on diphtheria toxin. The observed effect is highly dependent on the liposomal lipid composition as well as cell types. The potentiating ability of monensin in neutral vesicle is 2.2-fold higher than in negatively charged vesicles in non-phagocytic cells while no difference was observed in phagocytic cells. Incorporation of stearylamine in liposomes reduces the potentiating effect of monensin. Liposomal monensin has also been found to enhance the cytotoxicity of ricin in mouse in vivo in a dose-dependent manner and is maximal when ricin is injected within 60 min of monensin injection. Liposomal monensin remains in circulation for 2 hr while free monensin remains only for 15 min. Tissue distribution studies reveal that liposomal monensin is present mainly in the liver and spleen which are also the major sites for ricin accumulation. Thus liposome is found to be an effective delivery vehicle for monensin to potentiate the cytotoxicity of immunotoxins or hormonotoxins and could prove useful for selective elimination of cancer cells.

Enhancing potency of liposomal monensin on ricin cytotoxicity in mouse macrophage tumor cells

Monensin, a carboxylic ionophore, which is known to disrupt intracellular trafficking of proteins was intercalated in liposomes and its effect on the stability of liposomes and cytotoxicities of ricin and Pseudomonas exotoxin A in mouse macrophage tumor cells J774A.1 was studied. Stability of liposomes containing monensin was comparable to liposomes without monensin. The cytotoxicity of ricin and Pseudomonas exotoxin A was significantly enhanced by 1nM liposomal monensin (15.7 and 3.6 fold respectively). The enhancing potency of monensin in neutral and negative vesicles was found to be similar, while it was drastically reduced in positive vesicles. The specific uptake of 125I-gelonin from neutral and negative vesicles was not significantly different, whereas from positive vesicles no uptake was observed. Serum strongly influenced the binding at 4 degrees C of positive vesicles as well as the enhancing potency of monensin in these vesicles. Monensin in neutral and negative vesicles significantly reduced the lag period of ricin action, while in positive vesicles, it had no effect. These studies clearly indicate that liposomes could be used as a delivery vehicle for monensin.

Monensin intercalation in liposomes: effect on cytotoxicities of ricin, Pseudomonas exotoxin A and diphtheria toxin in CHO cells

Monensin, a carboxylic ionophore was intercalated in liposomes (liposomal monensin) and its effect on cytotoxicities of ricin, Pseudomonas exotoxin A and diphtheria toxin in CHO cells was studied. Intercalation of monensin in liposomal bilayer is found to have no effect on its stability and interaction with cells. Liposomal monensin (1 nM) substantially enhance the cytotoxicities of ricin (62-fold) and Pseudomonas exotoxin A (11.5-fold) while it has no effect on diphtheria toxin. This observed effect is highly dependent on the liposomal lipid composition. The potentiating ability of monensin (1 nM) in neutral vesicles is significantly higher (2.2-fold) as compared to negatively charges vesicles. This ability is drastically reduced by incorporation of stearylamine in liposomes and is found to be dependent on the density of stearylamine as well as on the concentration of serum in the medium. Monensin in liposomes containing 24 mol% stearylamine has a very marginal effect on the cytotoxicity of ricin (7.5-fold) which is further reduced (1.5-fold) in the presence of 20% serum. The uptake of 125I-gelonin from neutral vesicles is significantly higher (approximately 2.0-fold) than that from the negative vesicles. The uptake from positive vesicles is highly dependent on the concentration of stearylamine. The reduction in the lag period (30 min) of ricin action by monensin in neutral and negative vesicle is comparable with free monensin. However, monensin in positive vesicle has no effect on it. These studies have suggested that liposomes could be used as a delivery vehicle for monensin for selective elimination of tumor cells in combination with hybrid toxins.

In vivo potentiation of ricin toxicity by monensin delivered through liposomes

Monensin, a carboxylic ionophore, which is known to raise intravesicular pH, was intercalated in liposomes and its effect on the toxicity of ricin in mice was studied. The toxicity of ricin in vivo was found to be significantly enhanced by the administration of monensin intercalated in liposomes (liposomal monensin). The observed enhancement of the toxicity of ricin by monensin was highly dose-dependent and was maximal when ricin was injected within 60 min of monensin injection. The survival time was found to be reduced in the range of 8-20 h, depending on the dose of ricin used, by liposomal monensin. Stability of liposomes containing monensin as inferred from the release of entrapped calcein or FITC-dextran under both in vivo and in vitro conditions was comparable to that observed for liposomes without monensin. Liposomal monensin remains in circulation for 2 h and was cleared from the blood stream after 4 h. In contrast, 15 min was required for the clearance of monensin when administered in free form. Studies on the distribution of liposomal monensin and 125I-ricin in various tissues have revealed that monensin is mainly localized in the liver and spleen which are also the major sites for ricin accumulation. Our observation on the substantial enhancement of ricin toxicity in vivo by liposomal monensin strongly supports the potential usefulness of the latter as a potentiating agent in the enhancement of the toxicity of immunotoxin or hormonotoxin for selective elimination of cancer cells.

Liposome immune lysis assay (LILA) for gelonin

A complement-mediated liposome immune lysis assay using entrapped calcein was developed for a plant toxin gelonin. Gelonin was covalently coupled to DPPE, and then adsorbed on to the surface of liposomes. Such antigen-bearing liposomes when incubated with anti-gelonin antibody in the presence of guinea pig complement undergo lysis. The detection range is from 3 ng to 60 ng. The method was used to monitor isolation of gelonin by affinity chromatography. It was observed that a minor peak in addition to the major one comes with gelonin, shared common epitopes/epitope with gelonin in immunological reaction. This was further confirmed by SDS-gel electrophoresis indicating the former being an isoform of gelonin. A comparative study of the immunocross-reactivity of ricin and ricin A chain with anti-gelonin antibody was carried out. It was found that while ricin A chain cross-reacted extensively with gelonin antibody and intact ricin elicited little or no cross-reactivity. It is suggested that the present LILA may be employed for the detection and quantitation of ricin A chain by this LILA method.

Interaction of gelonin with macrophages: effect of lysosomotropic amines

The cytotoxic effects of gelonin on various phagocytic and nonphagocytic cells were studied. Peritoneal exudate cells (PEC) are found to be more sensitive to gelonin compared to P388D1 and J774A.1 cells, nonphagocytic cells being the least sensitive. While chloroquine markedly enhances the cytotoxicity of gelonin in macrophages (greater than 100-fold) ammonium chloride confers protection. A higher rate of uptake of 125I-gelonin in PEC (7 times the rate observed in other cells) is probably mediated by an interaction of terminal mannose residues of gelonin with mannose receptors on PEC plasma membrane as inferred from a pronounced inhibitory effect of mannan. In contrast to a pronounced inhibitory effect of mannan on the uptake of gelonin in PEC (7-fold), the cytotoxicity is reduced only by 2-fold. On the other hand, mannan has little or no effect on enhancement of the toxicity of gelonin by chloroquine. The studies have suggested that the internalization of gelonin in PEC may involve two pathways: (a) mannose receptor-mediated endocytosis, which plays a minor role in the intoxication process, and (b) nonspecific fluid phase pinocytosis, which is susceptible to enhancement by chloroquine and has a major role to play in the manifestation of the toxic effect of gelonin. In macrophage-like cells only the latter pathway operates.

Design of liposomes for circumventing the reticuloendothelial cells

Two different aspects of liposomal drug delivery to non-RES cells have been described. In one of the systems, by incorporating neutral glycolipids, with terminal beta-galactoside residue into liposomes, it is possible to target liposomes to the liver parenchymal cells, partially bypassing the RES. Asialoganglioside seems to be the most suited for this purpose. In another approach, various factors that prolong the lifespan of circulating liposomes have been discussed. It is possible to design such liposomes by imparting hydrophilicity to the liposomal surface. The effectiveness of a number of possible candidates, such as dextran, GM1 ganglioside and PEG, has been discussed in this context.

Enhancement of cytotoxicity of modeccin by nigericin in modeccin-resistant mutant cell lines

We have isolated a Chinese hamster ovary cell mutant (DMPR-2) simultaneously resistant to diphtheria toxin and modeccin. In addition to the increased resistance to these two toxins used in the selection, this mutant is more resistant to Pseudomonas toxin and hypersensitive to ricin than the parental cell line. In contrast to the wild-type cells in which nigericin protects cells from modeccin, the cytotoxicity of modeccin in the DMPR-2 mutant is enhanced by nigericin. We have also studied the effects of nigericin and NH4Cl on the cytotoxicity of modeccin in a modeccin-resistant mutant of HeLa cells (ModRI). The cytotoxicity of modeccin is enhanced by nigericin in ModRI mutant cells, in contrast to the protection of modeccin cytotoxicity by nigericin in the parental HeLa cells. Our results suggest that modeccin can reach the cytosol of mammalian cells by two distinct routes; the major route requires endosomal acidification and the minor route is activated by nigericin.

Perturbation of N-linked oligosaccharide structure results in an altered incorporation of [3H]palmitate into specific proteins in Chinese hamster ovary cells

Increased [3H]palmitate incorporation into specific cellular proteins has been reported to occur in Chinese hamster ovary (Wellner, R. B., Ray, B., Ghosh, P. C., and Wu, H. C. (1984) J. Biol. Chem. 259, 12788-12793) and yeast (Wen, D., and Schlesinger, M. J. (1984) Mol. Cell. Biol. 4, 688-694) mutant cells. In this paper we report studies concerning the relationship between N-linked oligosaccharide structure and [3H]palmitate incorporation into proteins of Chinese hamster ovary (CHO) cells. We have compared the incorporation of [3H]palmitate into proteins of wild-type and four different mutant CHO cell lines defective in various steps of N-linked protein glycosylation. Sodium dodecyl sulfate-gel electrophoretic analysis showed that three of the mutants exhibited increased [3H]palmitate incorporation into several CHO cellular proteins (approximately 30,000-38,000 molecular weight) as compared to the wild-type cells. One of the affected mutants which accumulates the Man5Gn2Asn intermediate structure was examined in detail. In agreement with earlier reports, virtually all of the [3H] palmitate-labeled proteins of both wild-type and mutant cell lines are membrane-bound. Pretreatment of the mutant cell line with tunicamycin blocked the increased [3H]palmitate incorporation into the two specific proteins (both of approximately 30,000 molecular weight) observed in untreated cells; the decreased incorporation of [3H]palmitate into the 30,000 molecular weight species was accompanied by a concomitant increase in the incorporation of [3H]palmitate into two proteins of approximately 20,000 molecular weight. Pretreatment of wild-type cells with tunicamycin also caused increased [3H]palmitate incorporation into the 20,000 molecular weight species. Endoglycosidase H treatment of [3H]palmitate-labeled extracts from the mutant cell line resulted in the disappearance of the heavily labeled 30,000 molecular weight species and the appearance of intensely labeled 20,000 molecular weight species. Pretreatment of the mutant cell line with either castanospermine or deoxynojirimycin reduced the [3H]palmitate incorporation in to the 30,000 molecular weight species increased in untreated cells, but did not cause increased [3H]palmitate incorporation into the 20,000 molecular weight species. Our results indicate that perturbation of N-linked oligosaccharide structure results in altered incorporation of [3H]palmitate into specific proteins in CHO cells.

Enhancement of ricin cytotoxicity in Chinese hamster ovary cells by depletion of intracellular K+: evidence for an Na+/H+ exchange system in Chinese hamster ovary cells

Depletion of intracellular K+ has been reported to result in an arrest of the formation of coated pits in human fibroblasts (Larkin, J.M., M.S. Brown, J.L. Goldstein, and R.G.W. Anderson, 1983, Cell, 33:273-285). We have studied the effects of K+ depletion on the cytotoxicities of ricin, Pseudomonas exotoxin A, and diphtheria toxin in Chinese hamster ovary (CHO) cells. The cytotoxicities of ricin and Pseudomonas toxin were enhanced in K+-depleted CHO cells whereas the cytotoxicity of diphtheria toxin was reduced by K+ depletion. The effects of NH4Cl on the cytotoxicities of ricin, Pseudomonas toxin, and diphtheria toxin were found to be similar to those of K+ depletion, and there were no additive or synergistic effects on ricin cytotoxicity by NH4Cl in K+-depleted medium. The enhancement of ricin cytotoxicity by K+ depletion could be completely reversed by the addition of K+, Rb+, and partially by the addition of Cs+, before the ricin treatment, whereas Li+ was ineffective. These protective effects of K+ or Rb+ requires a functional Na+/K+ ATPase. CHO cells grown in K+-depleted media were found to contain 6.3-fold increase in intracellular Na+ level, concomitant with a 10-fold reduction in intracellular K+ level. The enhanced cytotoxicity of ricin in K+-free medium and the increased uptake of Na+ could be abolished by amiloride or amiloride analogues, which are known to be potent inhibitors of the Na+/H+ antiport system. Our results suggest that a depletion of intracellular K+ results in an influx of Na+, which is accompanied by the extrusion of H+. Consequently, there is an alkalinization of the cytosol and the ricin-containing endosomes. As a result, ricin is more efficiently released from the endosomes in-K+-depleted cells. Results from the studies of the binding, internalization, and degradation of 125I-ricin, and the kinetics of inhibition of protein synthesis by ricin in K+-depleted cells are consistent with this working hypothesis.

Genetic and biochemical analysis of mutation(s) affecting ricin internalization in Chinese hamster ovary cells

We have previously reported the isolation and characterization of Chinese hamster ovary (CHO) cell mutants defective in the internalization of ricin (Ray, B., and Wu, H.C. (1982) Mol. Cell. Biol. 2, 535-544). These mutants also do not exhibit the enhancement of ricin internalization by nigericin pretreatment at a low concentration, which is observed in the wild-type CHO cells. An analysis of somatic cell hybrids between the mutant and the toxin-sensitive wild-type CHO cell line shows that all of the phenotypes associated with the toxin resistance mutation are dominant in the hybrid cell lines. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [3H]palmitic acid-labeled cell extracts from the mutant and toxin-resistant hybrid cell lines has revealed an increased incorporation of [3H] palmitic acid into two proteins with apparent molecular weights near 30,000 in the mutant and hybrid cells as compared to that in the wild-type cell line. Our studies indicate that these two fatty acyl proteins might be related to a dominant mutation(s) which results in a decreased uptake of ricin.

Osmotically induced microinjection of ricin bypasses a ricin internalization defect in a Chinese hamster ovary mutant cell line

By osmotic lysis of pinocytic vesicles we were able to inject ricin or ricin A chain directly into the cytosol of Chinese hamster ovary cells. The lag time of 1 to 2 h before the onset of the inhibition of protein synthesis by ricin in intact cells was reduced to 15 to 30 min by this method. Preincubation of cells with a low concentration of nigericin, which was shown earlier to enhance the cytotoxicity of ricin, had no effect under this condition. Direct transfer of either intact ricin or the ricin A subunit by osmotic lysis of pinocytic vesicles into the cytosol of the ricin-resistant CHO mutant cell line 4-10 rendered the mutant 4-10 cells as sensitive to ricin as the CHO pro wild-type cells. Both the lag time and the rate of inhibition of protein synthesis in the wild-type and mutant cell lines after the introduction of ricin by osmotic lysis of pinocytic vesicles were the same. These results indicate that injection of ricin into the cytosol by osmotic lysis of pinosomes bypasses the internalization defect in the mutant cell line.

Antitumor Plants. V. Constituents of Cinchona pubescens

The stem bark and stem wood of Cinchona pubescens were found to owe their weak cytotoxic activity to the presence of quinovic acid. This acid and its 3-rhamnoside were isolated and characterized through several derivatives, all of which were assayed for their cytotoxicity.

Antitumor plants. IV. Constituents of Simarouba versicolor

beta-Sitosterol, epilupeo, amarolide-11-acetate, amarolide-2,11-diacetate, ailanthinone and glaucarubinone have been isolated from S. versicolor. The cytotoxic and antileukemic activities of extracts of this plant are due chiefly to glaucarubinone.

Steroid excretion and metabolism by gonadal tissue from a subject with testicular feminization syndrome

The initial clinical, pathological, and hormonal investigation of a patient with testicular feminization syndrome is described. Incubation of gonadal tissue with various radioactive substrates, together with the isolation and identification of the resulting metabolites, was demonstrated a high capacity to synthesize testosterone. Two biosynthetic pathways were demonstrated, originating from progesterone and pregnenolone. These are essentially similar to those of the normal adult testes. Low levels of activity were found in the phenolic fractions and no measurable production of oestrone, oestradiol, or oestriol was found.

Abnormal excretion of corticosteroid sulphates in patients with breast cancer

In a preliminary study, the 24-hour urinary excretion of corticosteroid sulphates and free cortisol have been measured in a group of patients with breast cancer and compared with the excretion of the same compounds in a group of normal women of similar age. Excretion of corticosteroid sulphates in the breast cancer group was found to be markedly raised. In a small number of patients with localized cancer of sites other than the breast the level of corticosteroid sulphate was not raised. If proved metastases were present a noticeable rise was observed.