Pharmacological support to anti-arthritic prospective of physostigmine: a new approach

Rheumatoid arthritis (RA) is a slowly progressing inflammatory autoimmune disease. Several features are involved in the RA pathogenesis in addition to environmental and genetic factors. Previously it has been reported that acetyl cholinesterase (AChE) activity is enhanced in old age and may contribute in the progression of RA. The current experimental work was projected to assess the activity of physostigmine (a cholinesterase inhibitor) for treatment of RA. In vitro and in vivo approaches were used for such evaluation. However, enzyme linked immunosorbent assays (ELISA) was performed to determine the concentrations of Prostaglandins E2 (PGE2) and tumor necrosis factor-α in arthritic rats after treatment with physostigmine. Moreover, anti-oxidant assays were employed to calculate the level of super oxide dismutase (SOD) and catalase peroxidase (CAT) in tissue of treated animals. The results claimed the dose dependent protective and stabilizing effect of physostigmine on denaturation of albumin (egg and bovine serum) protein and human red blood cell membrane, respectively, through in vitro studies. Furthermore, the physostigmine (10 and 20 mg/kg) significantly (p < 0.001) reduced the swelling of paw after induction of arthritis with formaldehyde or complete Freund's adjuvant (CFA) as compared to arthritic control animals. Moreover, significant (p < 0.001) reduction in the levels of inflammatory markers (PGE2 and TNF-α) at doses of 10 and 20 mg/kg of physostigmine has been observed in ELISA test. Likewise, there was a prominent rise in levels of SOD and CAT in animals treated with physostigmine. These findings pharmacologically conclude the anti-arthritic effect of physostigmine.

Serum Protein Adsorption Modulates the Toxicity of Highly Positively Charged Hydrogel Surfaces

Hydrogels formed from peptide self-assembly are a class of materials that are being explored for their utility in tissue engineering, drug and cell delivery, two- and three-dimensional cell culture, and as adjuvants in surgical procedures. Most self-assembled peptide gels can be syringe-injected in vivo to facilitate the local delivery of payloads, including cells, directly to the targeted tissue. Herein, we report that highly positively charged peptide gels are inherently toxic to cells, which would seem to limit their utility. However, adding media containing fetal bovine serum, a common culture supplement, directly transforms these toxic gels into cytocompatible materials capable of sustaining cell viability even in the absence of added nutrients. Multistage mass spectrometry showed that at least 40 serum proteins can absorb to a gel's surface through electrostatic attraction ameliorating its toxicity. Further, cell-based studies employing model gels having only bovine serum albumin, fetuin-A, or vitronectin absorbed to the gel surface showed that single protein additives can also be effective depending on the identity of the cell line. Separate studies employing these model gels showed that the mechanism(s) responsible for mitigating apoptosis involve both the pacification of gel surface charge and adsorbed protein-mediated cell signaling events that activate both the PI3/Akt and MAPK/ERK pathways which are known to facilitate resistance to stress-induced apoptosis and overall cell survival.

Human topoisomerase inhibition and DNA/BSA binding of Ru(II)-SCAR complexes as potential anticancer candidates for oral application

Three ruthenium(II) phosphine/diimine/picolinate complexes were selected aimed at investigating anticancer activity against several cancer cell lines and the capacity of inhibiting the supercoiled DNA relaxation mediated by human topoisomerase IB (Top 1). The structure-lipophilicity relationship in membrane permeability using the Caco-2 cells have also been evaluated in this study. SCAR 5 was found to present 45 times more cytotoxicity against breast cancer cell when compared to cisplatin. SCAR 4 and 5 were both found to be capable of inhibiting the supercoiled DNA relaxation mediated by Top 1. Interaction studies showed that SCAR 4 and 5 can bind to DNA through electrostatic interactions while SCAR 6 is able to bind covalently to DNA. The complexes SCAR were found to interact differently with bovine serum albumin (BSA) suggesting hydrophobic interactions with albumin. The permeability of all complexes was seen to be dependent on their lipophilicity. SCAR 4 and 5 exhibited high membrane permeability (P _app  > 10 × 10^-6 cm·s^-1) in the presence of BSA. The complexes may pass through Caco-2 monolayer via passive diffusion mechanism and our results suggest that lipophilicity and interaction with BSA may influence the complexes permeation. In conclusion, we demonstrated that complexes have powerful pharmacological activity, with different results for each complex depending on the combination of their ligands.

Inhibition of Advanced Glycation End Products (AGEs) Accumulation by Pyridoxamine Modulates Glomerular and Mesangial Cell Estrogen Receptor α Expression in Aged Female Mice

Age-related increases in oxidant stress (OS) play a role in regulation of estrogen receptor (ER) expression in the kidneys. In this study, we establish that in vivo 17β-estradiol (E2) replacement can no longer upregulate glomerular ER expression by 21 months of age in female mice (anestrous). We hypothesized that advanced glycation end product (AGE) accumulation, an important source of oxidant stress, contributes to these glomerular ER expression alterations. We treated 19-month old ovariectomized female mice with pyridoxamine (Pyr), a potent AGE inhibitor, in the presence or absence of E2 replacement. Glomerular ERα mRNA expression was upregulated in mice treated with both Pyr and E2 replacement and TGFβ mRNA expression decreased compared to controls. Histological sections of kidneys demonstrated decreased type IV collagen deposition in mice receiving Pyr and E2 compared to placebo control mice. In addition, anti-AGE defenses Sirtuin1 (SIRT1) and advanced glycation receptor 1 (AGER1) were also upregulated in glomeruli following treatment with Pyr and E2. Mesangial cells isolated from all groups of mice demonstrated similar ERα, SIRT1, and AGER1 expression changes to those of whole glomeruli. To demonstrate that AGE accumulation contributes to the observed age-related changes in the glomeruli of aged female mice, we treated mesangial cells from young female mice with AGE-BSA and found similar downregulation of ERα, SIRT1, and AGER1 expression. These results suggest that inhibition of intracellular AGE accumulation with pyridoxamine may protect glomeruli against age-related oxidant stress by preventing an increase of TGFβ production and by regulation of the estrogen receptor.

Nε-(carboxymethyl) lysine-induced mitochondrial fission and mitophagy cause decreased insulin secretion from β-cells

Nε-(carboxymethyl) lysine-conjugated bovine serum albumin (CML-BSA) is a major component of advanced glycation end products (AGEs). We hypothesised that AGEs reduce insulin secretion from pancreatic β-cells by damaging mitochondrial functions and inducing mitophagy. Mitochondrial morphology and the occurrence of autophagy were examined in pancreatic islets of diabetic db/db mice and in the cultured CML-BSA-treated insulinoma cell line RIN-m5F. In addition, the effects of α-lipoic acid (ALA) on mitochondria in AGE-damaged tissues were evaluated. The diabetic db/db mouse exhibited an increase in the number of autophagosomes in damaged mitochondria and receptor for AGEs (RAGE). Treatment of db/db mice with ALA for 12 wk increased the number of mitochondria with well-organized cristae and fewer autophagosomes. Treatment of RIN-m5F cells with CML-BSA increased the level of RAGE protein and autophagosome formation, caused mitochondrial dysfunction, and decreased insulin secretion. CML-BSA also reduced mitochondrial membrane potential and ATP production, increased ROS and lipid peroxide production, and caused mitochondrial DNA deletions. Elevated fission protein dynamin-related protein 1 (Drp1) level and mitochondrial fragmentation demonstrated the unbalance of mitochondrial fusion and fission in CML-BSA-treated cells. Additionally, increased levels of Parkin and PTEN-induced putative kinase 1 protein suggest that fragmented mitochondria were associated with increased mitophagic activity, and ALA attenuated the CML-BSA-induced mitophage formation. Our study demonstrated that CML-BSA induced mitochondrial dysfunction and mitophagy in pancreatic β-cells. The findings from this study suggest that increased concentration of AGEs may damage β-cells and reduce insulin secretion.

Inhibition of antithrombin and bovine serum albumin native state aggregation by heparin

Protein native state aggregation, a major problem in pharmaceutical and biological processes, has been addressed pharmacologically by the addition of protein-binding excipients. Heparin (Hp), a highly sulfated polysaccharide, interacts with numerous proteins with moderate to high affinity, but reports about its effect on protein aggregation are contradictory. We studied the pH dependence of the aggregation of antithrombin (AT) and bovine serum albumin (BSA) in the presence and absence of heparin. High-precision turbidimetry showed strong aggregation for both AT and BSA in I = 10 mM NaCl, conditions at which electrostatically driven Hp binding and aggregation both occur, with more obvious aggregation of heparin-free AT appearing as larger aggregate size. Aggregation of AT was dramatically inhibited at Hp: protein 6:1 (mole ratio); however, the effect at 0.5:1 Hp:protein was greater for BSA. Frontal analysis capillary electrophoresis showed a much larger equilibrium association constant Kobs between Hp and AT, in accord with the onset of Hp binding at a higher pH; both effects are explained by the higher charge density of the positive domain for AT as revealed by modeling with DelPhi. The corresponding modeling images showed that these domains persist at high salt only for AT, consistent with the 160-fold drop in Kobs at 100 mM salt for BSA-Hp binding. The smaller inhibition effect for AT arises from the tendency of its uncomplexed monomer to form larger aggregates more rapidly, but the stronger binding of Hp to AT does not facilitate Hp-induced aggregate dissolution which occurs more readily for BSA. This can be attributed to the higher density of AT aggregates evidenced by higher fractal dimensions. Differences between inhibition and reversal by Hp arise because the former may depend on the stage at which Hp enters the aggregation process and the latter on aggregate size and morphology.

Effects of aegeline, a main alkaloid of Aegle Marmelos Correa leaves, on the histamine release from mast cells

Aegeline or N-[2-hydroxy-2(4-methoxyphenyl) ethyl]-3-phenyl-2-propenamide is a main alkaloid isolated from Aegle marmelos Correa collected in Yogyakarta Indonesia. In our study, we investigated the effects of aegeline on the histamine release from mast cell. The study was performed by using (1) rat basophilic leukemia (RBL-2H3) cell line, and (2) rat peritoneal mast cells (RPMCs). DNP(24)-BSA, thapsigargin, ionomycin, compound 48/80 and PMA were used as inducers for histamine release from mast cell. In our study, aegeline inhibited the histamine release from RBL-2H3 cells induced by DNP(24)-BSA. Indeed, aegeline showed strong inhibition when RBL-2H3 cells induced by Ca(2+) stimulants such as thapsigargin and ionomycin. Aegeline is suggested to influence the intracellular Ca(2+) pool only since could not inhibit the (45)Ca(2+) influx into RBL-2H3 cells. Aegeline showed weak inhibitory effects on the histamine release from RPMCs, even though still succeed to inhibit when the histamine release induced by thapsigargin. These findings indicate that aegeline altered the signaling pathway related to the intracellular Ca(2+) pool in which thapsigargin acts. Based on the results, the inhibitory effects of aegeline on the histamine release from mast cells depended on the type of mast cell and also involved some mechanisms related to intracellular Ca(2+) signaling events via the same target of the action of thapsigargin or downstream process of intracellular Ca(2+) signaling in mast cells.

Advanced glycation end products downregulates peroxisome proliferator-activated receptor γ expression in cultured rabbit chondrocyte through MAPK pathway

Accumulation of advanced glycation end products (AGEs) which are known to adversely affect cartilage turnover and mechanical properties, provides a molecular mechanism by which aging contributes to the development of osteoarthritis. The objective of the present study was to investigate the role of peroxisome proliferator-activated receptor γ (PPARγ) in AGEs-mediated chondrocytes damage. In the cultured rabbit chondrocytes, our results show that the PPARγ agonist pioglitazone can concentration-dependently inhibit the AGEs-induced expression of TNF-α and MMP-13. Several studies have shown that activation of PPARγ may interfere with several signaling pathways regulating the proinflammatory genes in vivo and vitro experiments, but little is known regarding their expression and regulation in cartilage. Thus the effect of AGEs on PPARγ expression was next examined. Reverse transcription (RT)-PCR analysis revealed that AGEs treatment of chondrocytes downregulated PPARγ expression in a time- and concentration-dependent manner. AGEs-induced a significant downregulation in PPARγ mRNA at 48 h and the maximum effect was found at 100 μg/ml AGEs. This effect was significantly depressed by the anti-RAGE antibody. Specific inhibitors of the mitogen-activated protein kinases (MAPK) p38 (SB203580) and c-Jun N-terminal kinase (SP600125), but not of extracellular signal-regulated kinase (PD98059), prevented AGEs-induced downregulation of PPARγ expression. In conclusion, AGEs may be responsible for PPARγ downregulation via a mechanism involving activation of the MAPK (p38 and JNK), and this downregulation might play a key role in AGEs-induced production of TNF-α and MMP-13.

Flavan-3-ols from Ulmus davidiana var. japonica with inhibitory activity on protein glycation

Four flavan-3-ols, (+)-catechin ( 1), (+)-catechin 7- O- beta- D-apiofuranoside ( 2), (+)-catechin 7- O- beta- D-xylopyranoside ( 3), (+)-catechin 7- O- beta- D-glucopyranoside ( 4), and proanthocyanidin A-1 ( 5) as well as three other constituents, isolated from an EtOAc-soluble extract of the stem barks of Ulmus davidiana var. japonica, were evaluated for inhibitory activity against the formation of AGEs. Compounds 1 - 5 exhibited a significant inhibitory activity on the formation of AGEs in an AGEs-BSA assay by specific fluorescence and this was confirmed by an indirect AGEs-ELISA. Moreover, compounds 1 and 5 markedly reduced AGEs-BSA cross-linking to collagen in a dose-dependent manner. AGEs:advanced glycation end products BSA:bovine serum albumin CC:column chromatography CD:circular dichroism.

Effect of protocatechualdehyde on receptor for advanced glycation end products and TGF-β1 expression in human lens epithelial cells cultured under diabetic conditions and on lens opacity in streptozotocin-diabetic rats

Advanced glycation end products and transforming growth factor-beta (TGF-beta) have been implicated in the development of diabetic complications such as cataract. The diverse metabolic effects of protocatechualdehyde (PCA, 3, 4-dihydroxybenzaldehyde) include the inhibition of aldose reductase and oxidation, two processes that are involved in the development of complications in diabetic patients. Here, the potential therapeutic effects of PCA in the treatment of diabetic complications were studied by determining this compound's ability to inhibit the formation of advanced glycation end products-bovine serum albumin (BSA) and the expression of receptor for advanced glycation end products and TGF-beta1 in human lens epithelial cells cultured under diabetic conditions. In addition, the ability of PCA to suppress lens opacification in streptozotocin-diabetic rats was analyzed. PCA significantly reduced advanced glycation end products-BSA formation in vitro and was more effective than aminoguanidine. In human lens epithelial cells, PCA significantly inhibited the induction of receptor for advanced glycation end products protein and mRNA expression by the receptor for advanced glycation end products-specific ligand S100b. Moreover, PCA inhibited high glucose- or S100b-induced TGF-beta1 protein and mRNA expression as well as nuclear accumulation of phosphorylated Smad2/3. In streptozotocin-induced diabetic cataract in rats, oral administration of PCA (25 mg/kg body weight) for 8 weeks significantly ameliorated the development of lens opacity (cataract) with effect on glycemic control. These results suggest that PCA is of therapeutic interest with respect to the prevention of diabetic complications such as diabetic cataract.

Enhancement of thermal stability and inhibition of protein aggregation by osmolytic effect of hydroxyproline

A combination of spectroscopic, calorimetric, and microscopic studies to understand the effect of hydroxyproline on the thermal stability, conformation, biological activity, and aggregation of proteins has been investigated. Significantly increased protein stability and suppression of aggregation is achieved in the presence of hydroxyproline. For example, exceptional increase in the thermal stability of lysozyme up to 26.4 degrees C and myoglobin up to 31.8 degrees C is obtained in the presence of hydroxyproline. The increased thermal stability of the proteins is observed to be accompanied with significant rise of the catalytic activity. Hydroxyproline is observed to prevent lysozyme fibril formation in vitro. Fluorescence and circular dichroism studies indicate induction of tertiary structures of the studied proteins in the presence of hydroxyproline. Preferential hydration of the native state is found to be crucial for the mechanism of protein stabilization by hydroxyproline. We compared the effect of hydroxyproline to that of proline and observed similar increase in the activity and suppression of protein aggregation. The results demonstrate the use of hydroxyproline as a protein stabilizer and in the prevention of protein aggregation and fibril formation.

Effect of antibodies against serotonin, bovine serum albumin, and complete Freund's adjuvant on mice subjected to acute immobilization stress

Nonspecific immunomodulators (complete Freund's adjuvant and bovine serum albumin) produced an antistress effect on mice during immobilization stress. Immunization with a serotonin-protein conjugate produced no antistress effect.

Study of the disulfide reduction of denatured proteins by liquid chromatography coupled with on-line cold-vapor-generation atomic-fluorescence spectrometry (LC-CVGAFS)

Hydrophobic-interaction chromatography coupled on-line with chemical-vapor-generation atomic-fluorescence spectrometry (HIC-CVGAFS), optimized recently for the analysis of thiol-containing proteins under denaturing conditions, has been used to study the chemical reduction of denatured proteins. Four proteins chosen as models (human serum albumin (HSA), bovine serum albumin (BSA), alpha-lactalbumin (alpha-Lac) from bovine milk, and lysozyme from chicken egg (Lys)) were denatured with urea and reduced with dithiothreitol (DTT), with selenol as catalyst. The method is based on derivatization of the -SH groups of proteins with p-hydroxymercurybenzoate (PHMB), followed by HIC separation and post-column on-line reaction of the derivatized reduced, denatured proteins with bromine generated in situ. HgII, derived from rapid conversion of uncomplexed and protein-complexed PHMB, is selectively detected by AFS in an Ar/H2 miniaturized flame after sodium borohydride (NaBH4) reduction to Hg degrees . The yield of the reduction was studied as a function of reductant concentration, reduction time (tred), and urea concentration. Results showed that the optimum values for DTT and selenol concentrations and for tred were between 1 and 100 mmol L(-1) and between 1 and 20 min, respectively, depending on the protein studied. The percentage disulfide bond reduction increases as the urea concentration used for protein denaturation increases, giving a single-step sigmoid increment for single-domain, low-MW proteins (alpha-Lac and Lys), and a two-step sigmoid increment for multi-domain, high MW proteins (HSA and BSA). The shapes of plots of percentage reduced disulfide against urea concentration are characteristic of each protein and are correlated with the location of S-S in the protein. Under the adopted conditions complete protein denaturation is the conditio sine qua non for obtaining 100% S-S reduction. The detection limit for denatured, reduced proteins examined under the optimized conditions was found to be in the range 1-5 x 10(-12) mol L(-1) (10-30 pg), depending on the protein considered.

Influencing receptor-ligand binding mechanisms with multivalent ligand architecture

Multivalent ligands can function as inhibitors or effectors of biological processes. Potent inhibitory activity can arise from the high functional affinities of multivalent ligand-receptor interactions. Effector functions, however, are influenced not only by apparent affinities but also by alternate factors, including the ability of a ligand to cluster receptors. Little is known about the molecular features of a multivalent ligand that determine whether it will function as an inhibitor or effector. We envisioned that, by altering multivalent ligand architecture, ligands with preferences for different binding mechanisms would be generated. To this end, a series of 28 ligands possessing structural diversity was synthesized. This series provides the means to explore the effects of ligand architecture on the inhibition and clustering of a model protein, the lectin concanavalin A (Con A). The structural parameters that were varied include scaffold shape, size, valency, and density of binding elements. We found that ligands with certain architectures are effective inhibitors, but others mediate receptor clustering. Specifically, high molecular weight, polydisperse polyvalent ligands are effective inhibitors of Con A binding, whereas linear oligomeric ligands generated by the ring-opening metathesis polymerization have structural properties that favor clustering. The shape of a multivalent ligand also influences specific aspects of receptor clustering. These include the rate at which the receptor is clustered, the number of receptors in the clusters, and the average interreceptor distance. Our results indicate that the architecture of a multivalent ligand is a key parameter in determining its activity as an inhibitor or effector. Diversity-oriented syntheses of multivalent ligands coupled with effective assays that can be used to compare the contributions of different binding parameters may afford ligands that function by specific mechanisms.

Malondialdehyde-acetaldehyde-adducted bovine serum albumin activates protein kinase C and stimulates interleukin-8 release in bovine bronchial epithelial cells

Previous study results have demonstrated that cigarette smoke or acetaldehyde rapidly stimulates protein kinase C (PKC)-mediated release of interleukin-8 (IL-8) in bovine bronchial epithelial cells (BECs). Low concentrations of acetaldehyde combine synergistically with malondialdehyde to increase significantly maximal BEC PKC activity at 48 to 96 h stimulation. Because more than 95% of alcoholics are cigarette smokers, we hypothesized that malondialdehyde, an inflammation product of lipid peroxidation, and acetaldehyde, both a product of ethanol metabolism and a component of cigarette smoke, might stimulate PKC-mediated IL-8 release in BECs by malondialdehyde-acetaldehyde (MAA) adduct formation, rather than as free aldehydes. Protein kinase C activity is maximally elevated in BECs treated with 50 microg/ml of BSA-MAA from approximately 1 to 3 h. This activity subsequently begins to decrease by 4 to 6 h, with a return to baseline unstimulated kinase activity levels by 24 h. No activation of cyclic AMP-dependent protein kinase (PKA) or cyclic GMP-dependent protein kinase (PKG) was observed in BSA-MAA-treated BECs. The MAA adduct activation of PKC was followed by a fourfold to tenfold greater release of IL-8 over that observed for both BECs exposed to media only and BSA control-treated BECs. Protein kinase C activation and IL-8 release were blocked by pretreating BECs with 1 microM calphostin C or 100 nM of the PKC alpha-specific inhibitor, Go 6976. Isoform-specific inhibitors to PKC beta, PKC delta, and PKC zeta failed to inhibit completely MAA adduct-stimulated PKC or IL-8 release. Results of these studies indicate that metabolites derived from ethanol and cigarette smoke, such as acetaldehyde and malondialdehyde, form adducts that stimulate airway epithelial cell PKC alpha-mediated release of promigratory cytokines.

Advanced glycation end products impair protein turnover in LLC-PK1: amelioration by trypsin

BACKGROUND

Advanced glycation end products (AGEs) are assumed to play a key role in the pathogenesis of diabetic nephropathy (DN) and other diabetic complications. While AGEs have been shown to exert marked effects on mesangial and endothelial cells as well as on monocytes/macrophages, little is known about their effects on tubule cells. Therefore, we addressed the questions of (1) whether AGE-bovine serum albumin (AGE-BSA) impairs the protein metabolism in the tubule cells, and if so, (2) whether the AGE-induced effects are mediated via a protease sensitive mechanism.

METHODS

Arrested LLC-PK1 cells were exposed to a medium containing the vehicle (control, serum free), AGE-BSA (38 micromol/L), or BSA (38 micromol/L) in the presence or absence of trypsin (2.5 microg/mL) for 24 hours. We evaluated cell number, cell size, and cell protein content, as well as protein synthesis and protein degradation.

RESULTS

After an incubation period of 24 hours, AGE-BSA decreased the cell number to 84.5 +/- 5.5% of control and 82.5 +/- 5.6% of BSA-treated cells (P < 0.05). [3H]-thymidine incorporation declined to 66% of control (P < 0.05), while BSA was without any effect. The same AGE-BSA dose reduced protein degradation (P < 0.05) and stimulated total protein synthesis slightly, as determined by L-[14C]Phe incorporation into acidic-insoluble proteins. These effects resulted in a rise in cell protein content (AGE-BSA vs. control, 21.9 +/- 6.7%; AGE-BSA vs. BSA, 11.1 +/- 6.0%, P < 0.05) and cell volume (AGE-BSA vs. control 9.4 +/- 3.2%, AGE-BSA vs. BSA 18.4 +/- 3.7%, P < 0.05). Coincubation with AGE-BSA and trypsin was associated with an amelioration of all investigated parameters concerning cell number, cell proliferation, raised cell protein content, decreased protein degradation, and enhanced protein synthesis.

CONCLUSION

These data indicate that AGE-BSA impairs cell proliferation and protein turnover in LLC-PK1 cells with a consequent rise in cell protein. Since these alterations were abrogated by coincubation with trypsin, an interference of this serine protease with the AGE-binding proteins on cell surfaces is assumed.

A vanadyl sulfate-bovine serum albumin complex stimulates the release of lipoprotein lipase activity from isolated rat fat pads through an increase in the cellular content of cAMP and myo-inositol 1,4,5-trisphosphate

A vanadyl sulfate-bovine serum albumin complex (vanadyl-BSA) prolonged the stability of the V4+ oxidation state, although vanadyl alone can readily change the oxidation state from V4+ to V5+ under physiological conditions. Vanadyl-BSA stimulated the release of lipoprotein lipase (LPL) activity from isolated rat fat pads and increased the cellular LPL activity in a time-dependent manner. These effects were independent of protein synthesis. Propranolol, quin 2-AM, ruthenium red, and neomycin all inhibited LPL release more potently than the increase in activity. In contrast, potent inhibition of the increase effect was observed with genistein and wortmannin. Short-term incubation of the fat pads with vanadyl-BSA showed a transient increase in the cellular content of cAMP and myo-inositol 1,4,5-trisphosphate (IP3), which was inhibited by propranolol and neomycin, respectively. These results suggest that vanadyl-BSA stimulates the release of LPL activity through an increase in the cellular content of cAMP and IP3, leading to an increased intracellular Ca2+ concentration, and that it also increases cellular LPL activity via process(es) sensitive to genistein and wortmannin.

Renin inhibits the vasorelaxation induced by nitroso albumin

Nitrosated proteins exhibit actions characteristic of free NO. As the vasorelaxation effect of nitrosated albumin is rapidly inactivated in plasma, we postulated that a protease could remove or modify the NO attached to albumin. We found that the ability of plasma to inactivate the vasorelaxing action of NO-bovine serum albumin (NO-BSA) is restricted to a plasma fraction containing macromolecules. We also found that a crude preparation of renal renin also inactivated the vasorelaxation action of NO-BSA and UV-spectrophotometric analysis showed that the 335-nm signal of NO-BSA was significantly decreased by renin. This decrease could be prevented by a renin inhibitor or by immunodepleting the renin preparation with a monoclonal antibody to renin. The data suggest that renin accelerates the uncoupling of NO to albumin. Such a function may be important in the control of vascular tone and blood pressure.

Role of a copper (I)-dependent enzyme in the anti-platelet action of S-nitrosoglutathione

1. S-nitrosoglutathione (GSNO) is a potent and selective anti-platelet agent, despite the fact that its spontaneous rate of release of nitric oxide (NO) is very slow. Our aim was to investigate the mechanism of the anti-aggregatory action of GSNO. 2. The biological action of GSNO could be mediated by NO released from S-nitrosocystylglycine, following enzymatic cleavage of GSNO by gamma-glutamyl transpeptidase. The anti-aggregatory potency of GSNO was not, however, altered by treatment of target platelets with the gamma-glutamyl transpeptidase inhibitor acivicin (1 mM). gamma-Glutamyl transpeptidase is not, therefore, involved in mediating the action of GSNO. 3. The rate of breakdown of S-nitrosoalbumin was increased from 0.19 +/- 0.086 nmol min-1 to 1.52 +/- 0.24 nmol min-1 (mean +/- s.e.mean) in the presence of cysteine (P < 0.05, n = 4). Inhibition of platelet aggregation by S-nitrosoalbumin was also significantly increased by cysteine (P < 0.05, n = 4), suggesting that the biological activity of S-nitrosoalbumin is mediated by exchange of NO from the protein carrier to form the unstable compound cysNO. Breakdown of GSNO showed a non-significant acceleration in the presence of cysteine, from 0.56 +/- 0.22 to 1.77 +/- 0.27 nmol min-1 (mean +/- s.e.mean) (P = 0.064, n = 4), and its ability to inhibit platelet aggregation was not enhanced by cysteine. This indicates that the anti-platelet action of GSNO is not dependent upon transnitrosation to form cysNO. 4. Platelets pretreated with the copper (I)-specific chelator bathocuproine disulphonic acid (BCS), then resuspended in BCS-free buffer, showed resistance to the inhibitory effect of GSNO. These findings suggest that BCS impedes the action of GSNO by binding to structures on the platelet, rather than by chelating free copper in solution. 5. Release of NO from GSNO was catalysed enzymatically by ultrasonicated platelet suspensions. This enzyme had an apparent K(m) for GSNO of 12.4 +/- 2.64 microM and a Vmax of 0.21 +/- 0.03 nmol min-1 per 10(8) platelets (mean +/- s.e.mean, n = 5). It was inhibited by BCS, but not by the iron chelator bathophenathroline disulphonic acid, nor by acivicin. 6. We conclude that the stable S-nitrosothiol compound GSNO may exert its anti-platelet action via enzymatic, rather than spontaneous release of NO. This is mediated by a copper-dependent mechanism. The potency and platelet-selectivity of GSNO may result from targeted NO release at the platelet surface.

Adaptive cytoprotection against ethanol-induced small intestinal mucosal injury

Exposure of the small intestinal mucose to 6% ethanol (which is found in human jejunum during alcohol consumption) causes morphological alterations, and increased permeability of the mucosa and histamine release from intestinal mast cells. The released histamine is shown to mediate a significant component of the increased mucosal permeability (i.e., mucosal injury). In the present study, we have investigated whether adaptive cytoprotection occurs against the increased mucosal permeability and histamine release induced by 6% ethanol. Rabbits were used. In each animal, three adjacent segments of upper small intestine were pre-perfused for 30 min, and then perfused for 90 min in the following order control solution followed by control solution (control segment); control solution followed by 6% ethanol (ethanol segment); 1% ethanol followed by 6% ethanol (pretreated ethanol segment). During the 90-min perfusion, mucosal permeability of each segment was measured by analyzing the effluent for intraluminal clearance of i.v. administered 51Cr-labelled ethylenediaminetetraacetic acid (51Cr-EDTA) and 125I-labelled bovine serum albumin (125I-BSA). Mast cell histamine release was assessed by determining histamine concentration of the gut effluent. All measurements were higher in the ethanol segments than in the controls. These ethanol effects were significantly lower in the pretreated ethanol segments, indicating that adaptive cytoprotection occurs against the mucosal injury induced by 6% ethanol. These findings are discussed in relation to the literature on mucosal effects of intestinal intraluminal ethanol.

Heparin inhibits the progression phase of subcultured endothelial cell proliferation in rat aorta

The anti-proliferative effects of heparin on subcultured endothelial cells (EC) of rat aorta were investigated to determine whether heparin inhibits the competence phase or the progression phase in the cell cycle using the starting time and the rate of proliferation. Fetal bovine serum (FBS)-stimulated EC proliferation increased to 1.5-times in cell number, but decreased to 0.5-times in 3H-thymidine incorporation, compared with the proliferation of rat primary cultured smooth muscle cells (SMC). The FBS-effects on EC proliferation were attributed to the progression phase rather than the competence phase. Heparin (1, 10 or 100 micrograms/ml) significantly inhibited the proliferation of FBS (5%)-stimulated EC, and the extent of inhibition was the same in both cell number and 3H-thymidine incorporation. In the 3H-thymidine incorporation every 3 hr, heparin reduced the rate of incorporation into G0-arrested EC, but did not affect the starting time of DNA synthesis. When the index of competence phase, starting time, was plotted against that of progression phase, rate of proliferation, the inhibition of heparin was attributed to the progression phase. These results demonstrate that heparin selectively inhibits the progression phase in subcultured EC of rat aorta.

Biscoclaurine alkaloids inhibit receptor-mediated phospholipase A2 activation probably through uncoupling of a GTP-binding protein from the enzyme in rat peritoneal mast cells

The mechanism underlying the inhibitory effect of biscoclaurine (bisbenzylisoquinoline) alkaloids on phospholipase A2 activation in the signalling system of stimulated rat peritoneal mast cells was studied. Cepharanthine, berbamine and isotetrandrine inhibited antigen- and compound 48/80-induced arachidonic acid liberation, but not diacylglycerol formation or histamine release. They had no effect on A23187-induced arachidonic acid liberation, which was prevented by p-bromophenacyl bromide, a known phospholipase A2 inhibitor, and also did not affect phospholipase A2 activity in a cell-free system including an exogenous phospholipid substrate. Each alkaloid also inhibited arachidonic acid liberation induced by guanosine 5'-O-(3-thiotriphosphate) in saponin-permeabilized mast cells, and by mastoparan or NaF plus AlCl3 intact cells. Furthermore, each alkaloid abolished the inhibitory effect of islet-activating protein on the compound 48/80-induced arachidonic acid liberation. These data suggest that these alkaloids suppress the receptor-mediated phospholipase A2 activation through, at least in part, uncoupling of a GTP-binding protein from the enzyme, rather than by affecting the enzyme directly.

Spatial specificity of chromophore assisted laser inactivation of protein function

Chromophore assisted laser inactivation (CALI) is a new technique that selectively inactivates proteins of interest to elucidate their in vivo functions. This method has application to a wide array of biological questions. An understanding of aspects of the mechanism of CALI is required for its judicious application. A critical concern for CALI is its spatial specificity because nonspecific inactivation of neighboring unbound proteins by CALI is a possibility. We show here that CALI is very dependent on the distance between the chromophore and the protein such that there is no significant effect beyond 60 A. CALI using antibodies can inactivate other proteins through a complex but its efficacy decreases approximately fourfold for each intervening protein. These data imply that CALI is spatially specific and damage to neighboring proteins is unlikely.

Increased ocular blood flow and 125I-albumin permeation in galactose-fed rats: inhibition by sorbinil

125I-Albumin permeation and blood flow (assessed with 15 micron, 85Sr-labelled microspheres) were determined in the retina, choroid, anterior uvea, and brain of male Sprague-Dawley rats fed diets containing 50% dextrin (control) or 50% galactose. Blood flow was increased in the retina, choroid, and anterior uvea but not in the brain of rats fed galactose for 3 weeks and 3 months versus controls, and was normalized by sorbinil (an inhibitor of aldose reductase) in the 3-week group. After 8 months of galactose feeding, blood flow was reduced to normal levels in the retina and was slightly below normal in the choroid; blood flow remained elevated in the anterior uvea but was significantly lower than that observed at 3 weeks and at 3 months. In rats fed galactose for 8 months, sorbinil completely normalized blood flow in the choroid, and decreased, but did not normalize, blood flow in the anterior uvea. 125I-Albumin permeation was increased in the retina, choroid, and anterior uvea of rats fed 50% galactose for 3 weeks, 3 months, and 8 months versus controls, but was unchanged in the brain. Sorbinil normalized 125I-albumin permeation in all three ocular tissues in 8-month galactose-fed rats. Polyol levels were increased significantly in all three ocular tissues of 3-week galactose-fed rats; sorbinil markedly decreased, but did not normalize, polyol levels in all three tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical charge and joint inflammation. Suppression of cationic aBSA-induced arthritis with a competitive polycation

Chronicity of murine allergic arthritis depends on the charge-mediated retention of the cationic antigen in the joint. The authors examined whether arthritis induced with the positively charged antigen amidated bovine serum albumin (aBSA) could be modulated with a nonimmunogenic polycation by competition for anionic retention sites in the joint. Concomitant intraarticular injection of aBSA with the cationic protein protamine chloride (pI approximately 10) strongly reduced the retention of aBSA. Detailed analysis revealed that the retention of aBSA in the noncartilaginous tissues was significantly reduced by protamine, whereas the retention in the highly negatively charged cartilage was completely prevented. Joint inflammation was already significantly suppressed at Day 3 and suppression was still demonstrable at Day 28. Protamine treatment also caused a highly significant reduction in cartilage damage and bone apposition. Control experiments indicated that the suppressive effect of protamine was related to its interference with antigen retention in the joint and not to a mere antiinflammatory action.

Aleutian disease of mink. Prevention of lesions by immunosuppression

Mink that were homozygous recessive for the Aleutian gene (aa) were inoculated with Aleutian disease virus (ADV) and simultaneously treated with cyclophosphamide (Cy). Control mink were inoculated with ADV. All mink were injected with bovine serum albumin (BSA) and their anti-BSA antibody response was measured to monitor the influence of drug therapy on the humoral antibody response. Formation of anti-BSA antibody was markedly suppressed and the hypergammaglobulinemia and development of AD lesions was inhibited in the Cy-treated mink. The non-Cy-treated control mink developed characteristic signs and lesions including glomerulonephritis and arteritis. The nontreated ADV-infected mink, but not the Cy-treated ADV-infected mink, had glomerular deposition of C3 and gamma globulin. Both groups had high titers of virus in their blood. These results indicate that the development of ADV lesions can be prevented by immunosuppressive treatment and further implicate host immune mechanisms in the pathogenesis of Aleutian disease.

Sepcific removal of in vivo antibody by extracorporeal circulation over an immunoadsorbent in gel

A method is described for preparation of a solid immunoadsorbent suspended in an agar gel. The immunoadsorbent in gel retains its specificity. Rabbits were injected with antibody or antigen, and an extracorporeal circulation was established through columns or funnels coated with such immunoadsorbents. It was shown that either antibody or antigen can be specifically and rapidly removed, and that no measurable amounts of antigen from the immunoadsorbent were released into the animals.

Transformation of human lymphocytes: inhibition by homologous alpha globulin

An alpha globulin fraction prepared from normal human plasma by column chromatography prevents homologous lymphocyte transformation and the stimulation of DNA, and also protein synthesis induced by phytohemagglutinin and specific antigens. These observations support the concept of a normal circulating immunosuppressant factor which prevents lymphoid cell proliferation.

Lysosomal acid proteinase of rabbit liver

1. Acid proteinase from rabbit liver lysosomes was purified about 1000-fold, on a protein basis. 2. The purification procedure involved isolation of a lysosomal-mitochondrial pellet and conversion of this into an acetone-dried powder. 3. The enzyme was extracted with an acidic buffer and subjected to column chromatography with DEAE-Sephadex and Sephadex G-100. 4. The molecular weight of the enzyme was 50000-52000. 5. Maximal activity against haemoglobin was obtained at pH3.2; serum albumin was attacked, but very much more slowly. 6. Several possible inhibitors of the enzyme were tested. Thiol-blocking reagents, several inhibitors of trypsin and chymotrypsin, and a chelating agent were without effect. 7. The enzyme was competitively inhibited by 3-phenylpyruvic acid at low concentrations. 8. Dithiothreitol caused rapid inactivation of the enzyme at pH8. 9. It is concluded that this enzyme is a form of cathepsin D, which may be widely distributed in lysosomes.