Effect of hydroxylated fullerene C60(OH)25 on macrophage plasma membrane integrity

Our study has shown that the damaging effect of hydroxylated fullerene C60(OH)25 on mouse peritoneal macrophage plasma membranes increased when we enlarged the concentration of fullerene in the incubation media (from 0.005 to 0.5 mg/ml), the incubation temperature (from 22 degrees C to 37 degrees C) and the time of incubation (from 30 to 90 min). In conditions of the H2O2-induced membrane damage, fullerene was observed to intensify the H2O2-induced damaging effect at a concentration of 0.05 mg/ml and reduce it at a concentration of 0.5 mg/ml. In conditions of the UV-induced membrane damage, it was discovered that the damaging effect of UV increased when C60(OH)25 nanoparticles were added to the incubation media before irradiation and decreased when they were added after irradiation. Eventual participation of ROS in damaging effects of C60(OH)25 was discussed.     

Dehydroepiandrosterone protects human keratinocytes against apoptosis through membrane binding sites

Although the epidermis is importantly affected by steroid hormones, little is known about the effects of dehydroepiandrosterone (DHEA) on human keratinocytes, in spite of its abundance in human serum. Here, we demonstrate for the first time a protective role of DHEA against apoptosis in keratinocytes, using non-cancerous immortalized human HaCaT cells. We show that DHEA transmits its signal via specific G protein-coupled, membrane binding sites and inhibits apoptosis, through prevention of mitochondrial disruption and altered balance of Bcl-2 proteins. DHEA conjugated to the membrane impermeable molecule BSA, as well as DHEA-S, the most abundant form of DHEA in human serum exhibit similar anti-apoptotic effect. Our data provide new insights in the treatment of the epidermis with steroid hormones in apoptosis-related conditions.     

Nitric oxide-scavenging activity of polyhydroxylated fullerenol, C60(OH)24.

Investigation of the possible nitric oxide-scavenging activity of hydroxylated derivative of fullerene, fullerenol C60(OH)24, demonstrated that it expressed direct scavenging activity toward nitric oxide radical (NO) liberated within solution of sodium nitroprusside (SNP), a well known NO donor. In parallel, pre-treatment (30') with intratesticular injection of fullerenol (60 microg/each testis) prevented NO-induced decrease of catalase, glutathione transferase and glutathione peroxidase activities in the denucleated fraction of interstitial testicular cells of adult rats 2 h after intratesticular injection of SNP (20 microg/each testis). In addition, fullerenol decreased formation of thiobarbituric acid-reactive substances (TBA-RS) with similar efficiency as butylated hydroxy toluen (BHT), a well known antioxidant. Also, fullerenol expressed certain scavenging activity toward superoxide anion (O2-) in xanthine/xanthine oxidase system. In summary, results obtained in this study confirmed free radical-scavenging activity of fullerenol, and according to our knowledge, it is the first evidence of direct NO-quenching activity of hydroxylated C60 derivative in different milieu.     

Augmenter of liver regeneration (ALR) protects human hepatocytes against apoptosis

Augmenter of liver regeneration (ALR) is known to support liver regeneration and to stimulate proliferation of hepatocytes. However, it is not known if ALR exerts anti-apoptotic effects in human hepatocytes and whether this protective effect is cell type specific. This is relevant, because compounds that protect the liver against apoptosis without undesired effects, such as protection of metastatic tumour cells, would be appreciated in several clinical settings. Primary human hepatocytes (phH) and organotypic cancer cell lines were exposed to different concentrations of apoptosis inducers (ethanol, TRAIL, anti-Apo, TGF-β, actinomycin D) and cultured with or without recombinant human ALR (rhALR). Apoptosis was evaluated by the release of cytochrome c from mitochondria and by FACS with propidium iodide (PI) staining.ALR significantly decreased apoptosis induced by ethanol, TRAIL, anti-Apo, TGF-β and actinomycin D. Further, the anti-apoptotic effect of ALR was observed in primary human hepatocytes and in HepG2 cells but not in bronchial (BC1), colonic (SW480), gastric (GC1) and pancreatic (L3.6PL) cell lines.Therefore, the hepatotrophic growth factor ALR acts in a liver specific manner with regards to both its mitogenic and its anti-apoptotic effect. Unlike the growth factors HGF and EGF, rhALR acts in a liver specific manner. Therefore, ALR is a promising candidate for further evaluation as a possible hepatoprotective factor in clinical settings.     

Plasmodium falciparum erythrocyte membrane protein 3 (PfEMP3) destabilizes erythrocyte membrane skeleton

Plasmodium falciparum erythrocyte membrane protein 3 (PfEMP3) is a parasite-derived protein that appears on the cytoplasmic surface of the host cell membrane in the later stages of the parasite's development where it associates with membrane skeleton. We have recently demonstrated that a 60-residue fragment (FIa1, residues 38-97) of PfEMP3 bound to spectrin. Here we show that this polypeptide binds specifically to a site near the C terminus of alpha-spectrin at the point that spectrin attaches to actin and protein 4.1R in forming the junctions of the membrane skeletal network. We further show that this polypeptide disrupts formation of the ternary spectrin-actin-4.1R complex in solution. Importantly, when incorporated into the cell, the PfEMP3 fragment causes extensive reduction in shear resistance of the cell. We conjecture that the loss of mechanical cohesion of the membrane may facilitate the exit of the mature merozoites from the cell.     

Ascorbate protects against tert-butyl hydroperoxide inhibition of erythrocyte membrane Ca2+ + Mg2(+)-ATPase

The incubation of erythrocyte suspensions or isolated membranes containing a residual amount of hemoglobin (0.04% of original cellular hemoglobin) with tert-butyl hydroperoxide (tBHP, 0.5 mM) caused significant inhibition of basal and calmodulin-stimulated Ca2+ + Mg2(+)-ATPase activities and the formation of thiobarbituric acid reactive products measured as malondialdehyde. In contrast, the treatment of white ghosts (membranes not containing hemoglobin) with tBHP (0.5 mM) did not lead to appreciable enzyme inhibition within the first 20 min and did not result in malondialdehyde (MDA) formation. However, the addition of either 10 microM hemin or 100 microM ferrous chloride + 1 mM ADP to white ghosts produced hydroperoxide effects similar to those in pink ghosts (membranes with 0.04% hemoglobin). The concentrations of hemin and ferrous chloride which caused half-maximal inhibition of Ca2+ + Mg2(+)-ATPase activity at 10 min were 0.5 and 30 microM, respectively. The effects of several antioxidants (mannitol, thiourea, hydroxyurea, butylated hydroxytoluene, and ascorbate) were investigated for their protective effects against oxidative changes resulting from tBHP treatment. Over a 30-min incubation period only ascorbate significantly reduced the enzyme inhibition, MDA formation, and protein polymerization. Thiourea and hydroxyurea decreased MDA formation and protein polymerization but failed to protect against the enzyme inhibition. Butylated hydroxytoluene was similar to thiourea and hydroxyurea but with better protection at 10 min. Mannitol, under these conditions, was an ineffective antioxidant for all parameters tested.     

A new human erythrocyte variant (Ph) containing an abnormal membrane sialoglycoprotein

1. A new human erythrocyte variant (Ph) is described. The variant contains an unusual sialic acid-rich glycoprotein in addition to the blood-group-MN([unk])- and blood-group-Ss(δ)-active sialoglycoproteins found in normal erythrocytes. 2. The unusual component Ph has an apparent mol.wt. of 32000 on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The Ph component is not degraded during trypsin treatment of intact erythrocytes. 3. The Ph component was labelled by lacto-peroxidase-mediated radioiodination of intact erythrocytes and was found to be present in amounts approximately equimolar to α-sialoglycoprotein in the variant erythrocytes. 4. The Ph component had receptors for the lectins from Maclura aurantiaca (osage orange) and Triticum vulgaris (wheat-germ), but lacked a receptor for the Phaseolus vulgaris (red kidney bean) lectin, suggesting that it carries only O-linked oligosaccharides. 5. The presence of the Ph component in these erythrocytes does not correspond to any of the known blood-group-MNSs-related antigens examined. 6. We suggest that this component may be a hybrid polypeptide containing the N-terminal portion derived from normal δ-sialoglycoprotein, and the C-terminal portion from normal α-sialoglycoprotein, in a manner similar to the anti-Lepore haemoglobin.     

Isolation and partial characterization of human erythrocyte membrane NADH: (Acceptor) oxidoreductase

Gengliosides generally provide a small portion of the complex carbohydrate content of cell surfaces. An exception is the central nervous system where they comprise up to 5–10% of the total lipid of some membranes. This tissue is unique in that the quantity of lipid-bound sialic acid exceeds that of the protein-bound fraction. Over 30 different molecular species have been characterized to date. These range in complexity from sialosylgalactosyl ceramide with 2 sugars to the pentasialoganglioside of fish brain with 9 carbohydrate units. Virtually all cellular and subcellular fractions of brain that have been carefully examined contain gangliosides to one degree or another, but the majority of brain ganglioside is located in the neurons. Their mode of distribution within the neuron has not been entirely clarified by subcellular studies. Calculations based on reported values for axon terminal density and synaptosomal ganglioside concentration in the rat reveal that nerve endings contribute less than 12% of total cerebral cortical ganglioside. It is concluded that the plasma membranes of neuronal processes contain most of the neuronal ganglioside. These and other considerations suggest the possibility that gangliosides may be distributed over the entire neuronal surface.     

The anti-sickling drug lawsone (2-OH-1,4-naphthoquinone) protects sickled cells against membrane damage

The ability of an anti-sickling drug lawsone, 2-OH-1,4-naphthoquinone, and two related compounds to inhibit the haematoporphyrin-sensitised photohaemolysis of normal and sickle cell erythrocytes has been investigated. The compounds appear to protect the erythrocyte membranes by reaction with transient oxidative species. Differential effects between normal and sickle cells are shown and these are attributed to the different membrane composition of irreversibly sickled erythrocytes. This report describes a possible basis for the decreased formation of irreversibly sickled cells in the presence of lawsone.     

Relative biological effectiveness of high-energy photons (up to 50 MV) and electrons (50 MeV)

In vitro studies of the relative biological effectiveness (RBE) of 50-MV X rays have shown an RBE of 1.1 relative to 4-MV X rays. This will be important in clinical radiotherapy. The aim of this study was to verify these results and to investigate whether photonuclear processes might cause the difference in RBE. To do so, 50- and 20-MV X rays and 50-MeV electrons were investigated with respect to RBE. Chinese hamster V79 cells were irradiated in a specially designed system which allows for a high reproducibility of geometry and dosimetry. Fractionation experiments were also carried out to establish the RBE at the clinically relevant dose level, 2 Gy. Fricke dosimetry was used, and the results were confirmed with ionization chamber measurements. The RBE for 50-MV X rays was estimated to be 1.14 at a surviving fraction of 0.1 and 1.12 at a surviving fraction of 0.01. The RBEs for the other qualities were equal to one. The RBE calculated for the 2 Gy/fraction experiments was 1.17.     

Localization of the C termini of the Rh (rhesus) polypeptides to the cytoplasmic face of the human erythrocyte membrane.

We have raised a rabbit antiserum to a synthetic peptide corresponding to the C terminus (residues 400-416) of the Rh30A polypeptide. The rabbit antiserum reacted with the Rh30B (D30) polypeptide in addition to the Rh30A (C/c and/or E/e) polypeptide(s), indicating that these proteins share homology at their C termini. The antiserum did not react with erythrocyte membranes from an individual with Rh(null) syndrome. The rabbit antiserum immunoprecipitated Rh polypeptides from erythrocyte membranes and alkali-stripped membranes, but not from intact erythrocytes. Treatment of intact red cells with carboxypeptidase Y did not affect the reactivity of the antiserum, whereas treatment of alkali-stripped and unsealed erythrocyte ghost membranes resulted in the loss of antibody binding. Carboxypeptidase A treatment of intact erythrocytes and alkali-stripped membranes had no effect on antibody binding, indicating that the C-terminal domains of the Rh polypeptides contain lysine, arginine, proline, or histidine residues. These results show that the C termini of the Rh polypeptides are located toward the cytoplasmic face of the erythrocyte membrane. Treatment of intact radioiodinated erythrocytes with bromelain followed by immunoprecipitation with monoclonal anti-D gave a band of M(r) 24,000-25,000, indicating that the Rh30B (D30) polypeptide is cleaved at an extracellular domain close to the N or C terminus, with loss of the major radioiodinated domain. Immunoblotting of bromelain treated D-positive erythrocyte membranes with the rabbit antiserum to the C-terminal peptide revealed a new band of M(r) 6000-6500, indicating that the extracellular bromelain cleavage site is located near the C terminus of the molecule. The band of M(r) 6000-6500 was not obtained in erythrocyte membranes derived from bromelain treated D-negative erythrocytes. Erythrocytes of the rare -D- phenotype appear to either totally lack, or have gross alterations in, the Cc/Ee polypeptide(s), since the bromelain treatment of these cells resulted in the total loss of staining in the M(r) 35,000-37,000 region and the concomitant appearance of the new band of M(r) 6000-6500.     

Nature of cerium(III)- and lanthanum(III)-induced aggregation of human erythrocyte membrane proteins

To clarify the nature of the aggregation of membrane proteins (MP) induced by lanthanide cations (Lns), the interaction of cerium(III) (Ce3+) and lanthanum(III)(La3+) with erythrocyte membrane proteins was studied by means of SDS-PAGE, light scattering measurement, fluorescence, CD and FTIR spectra. The results showed that Ce3+ and La3+ induce protein aggregation not only by Lns non-covalent binding and cross-linking, but also by oxidative cross-linking through disulfide bond formation. As demonstrated by intrinsic fluorescence, CD and FTIR spectra studies, the aggregation was accompanied by the conformation changes with tryptophane residues exposing to more hydrophobic environment and the decreasing alpha-helix and beta-sheet contents. By stopped-flow studies, protein aggregation was shown to be a slow change, which is initiated by rapid Lns binding and then followed by subsequent conformational changes.     

Adverse effects of fullerenes on endothelial cells: fullerenol C60(OH)24 induced tissue factor and ICAM-I membrane expression and apoptosis in vitro

We studied the effects of a C60 water suspension at 4 microg/mL (nC60) and the water soluble fullerenol C60(OH)24 at final concentrations of 1-100 microg/mL on human umbilical vein endothelial cells (HUVECs) in culture. We found that a 24 hr treatment of HUVECs with C60(OH)24 at 100 microg/mL significantly increased cell surface expression of ICAM-1(CD54) (67 +/- 4% CD54+ cells vs. 19 +/- 2 % CD540 cells in control; p < 0.001). In addition, this treatment induced the expression of tissue factor (CD142) on HUVECs (54 +/- 20% CD142+ cells vs 4 +/- 2% CD142+ cells in control; p = 0.008) and increased exposure of phosphatidylserine (PS) (29 +/- 2% PS+ cells vs. 12 +/- 5% PS+ cells in control; p < 0.001). Analysis of cell cycle and DNA fragmentation (TUNEL) showed that both nC60 and C60(OH)24 caused G1 arrest of HUVECs and C60(OH)24 induced significant apoptosis (21 +/- 2% TUNEL+ cells at 100 microg/mL of C60(OH)24 vs. 4 +/- 2% TUNEL+ cells in control; p < 0.001). We also demonstrated that both nC60 and C60(OH)24 induced a rapid concentration dependent elevation of intracellular calcium [Ca2+]i. This could be inhibited by EGTA, suggesting that the source of [Ca2+]i in fullerene stimulated calcium flux is predominantly from the extracellular environment. In conclusion, fullerenol C60(OH)24 had both pro-inflammatory and pro-apoptotic effects on HUVECs, indicating possible adverse effects of fullerenes on the endothelium.     

Urea exchange across the human erythrocyte membrane measured using 13C NMR lineshape analysis

The ¹³C NMR spectrum of ¹³C-urea in a suspension of human red cells of reduced mean cell volume was observed to contain partially resolved resonances arising from the intra- and extracellular populations of the compound. It was shown that at 25°C and a magnetic field strength of 9.4 T, the rate of exchange of urea between the intra- and extracellular populations was such that the NMR lineshape was sensitive to a change in the rate of ¹³C-urea exchange, induced either by the addition of the urea transport inhibitor phloretin, or by the addition of ¹²C-urea. Total lineshape analysis of ^r3C NMR spectra of ¹³C-urea in red cell suspensions containing different concentrations of ¹²C-urea resulted in a weighted mean estimate for the K_m and V_max for urea equilibrium exchange from three experiments of 44 ± 18 mM and 3.1 ± 0.6 × 10^–8 molcm^–2 s^–1, respectively (the errors denote the weighted mean standard deviations). These estimates of K_m and V_max, were significantly lower than previous values reported in the literature and determined using other techniques. Correspondence to: P. W Kuchel     

1,25(OH)2D3 increases membrane associated protein kinase C in MDBK cells.

To determine whether 1,25-dihydroxycholecalciferol [1,25(OH)2D3] affects protein kinase C (PKC) activity in kidney, as has been demonstrated in HL-60 cells we measured 1,25(OH)2D3 binding, PKC activity and PKC immunoreactivity in Madin Darby bovine kidney (MDBK) cells, a normal renal epithelial cell line derived from bovine kidney. Our data demonstrate that MDBK cells exhibit specific high affinity binding for 1,25(OH)2D3, indicating the presence of the vitamin D receptor (VDR). Treatment of MDBK cells with 1,25(OH)2D3 for 24 h increased membrane PKC activity and immunoreactivity. The effect of 1,25(OH)2D3 was dose-dependent, with a peak effect observed at 10(-7)M 1,25(OH)2D3. The 1,25(OH)2D3 induced increase in membrane PKC was paralleled by a comparable decrease in cytosolic PKC activity and amount. Although time course studies were consistent with a VDR mediated effect of 1,25(OH)2D3 on PKC protein synthesis, total PKC activity was not increased by 1,25(OH)2D3, suggesting an effect on PKC translocation or localization. These results suggest that 1,25(OH)2D3 modulates PKC mediated events in kidney, a classic target for this steroid hormone.