Biomedical subjects

S V Pizzo

Publications and source records attributed to S V Pizzo.

At least 163 records · Page 9Linked to original sources

PubMed1988

Use of anti-idiotypic antibodies to establish that monoclonal antibody 7H11D6 binds to the alpha 2-macroglobulin receptor recognition site.

Studies were performed to determine if monoclonal antibody 7H11D6 binds to the region of alpha 2-macroglobulin (alpha 2M) that interacts with cell-surface receptors. F(ab')2 fragments prepared from this antibody delayed the in vivo clearance of alpha 2M-trypsin complexes from the murine circulation and blocked the in vitro binding of 125I-labeled alpha 2M-trypsin to rat kidney fibroblasts. Chemical modification studies revealed that the epitope region for 7H11D6 is sensitive to modification of the inhibitor with cis-dichlorodiammineplatinum (II). To determine if the epitope for 7H11D6 is comprised of residues involved in the alpha 2M receptor determinant, anti-idiotypic antibodies against 7H11D6 were prepared. A competitive enzyme-linked immunosorbent assay demonstrated that the anti-idiotypic IgG competed with alpha 2M-trypsin complexes for binding to 7H11D6. The anti-idiotypic IgG inhibited the binding of 125I-labeled alpha 2M-trypsin complexes to normal rat kidney fibroblasts, and a Kd of 194 pM for the binding of the anti-idiotype to these cells was derived from a fit of the data to a model involving a single class of sites. Binding of the anti-idiotypic IgG to the alpha 2M receptor provides unequivocal evidence that 7H11D6 is binding to residues within the receptor recognition site on alpha 2M and not merely to residues sufficiently close to that region to cause steric hindrance.

Animals↗

PubMed1988

Evidence that the platinum-reactive methionyl residue of the alpha 2-macroglobulin receptor recognition site is not in the carboxyl-terminal receptor binding domain.

Digestion of human alpha 2-macroglobulin-methylamine (alpha 2M-CH3NH2) with papain prior to gel filtration resulted in the resolution of three distinct peaks. The material in peak I (Mr approximately 600,000) and peak II (Mr approximately 55,000) did not have any receptor binding ability as determined by in vivo clearance studies and in vitro competitive binding studies using mouse peritoneal macrophages. In contrast, the material in peak III (Mr approximately 20,000) bound to macrophage alpha 2-macroglobulin (alpha 2M) receptors with a Kd of 250 nM. This represents a 500-fold decrease in affinity relative to undigested alpha 2M-CH3NH2. Sequence analysis demonstrated that this material constituted the carboxyl-terminal fragment (COOH-terminal fragment) of alpha 2M. alpha 2M is known to possess a methionyl residue which is susceptible to modification by cis-dichlorodiammineplatinum (II) (cis-DDP) with the result being a loss of receptor binding ability by alpha 2M. For this reason, experiments were performed to determine if the platinum-reactive methionyl residue is located in the COOH-terminal receptor binding fragment of alpha 2M. The results of this investigation demonstrate that cis-DDP is not reactive with either the isolated COOH-terminal fragment or the COOH-terminal fragment isolated from alpha 2M-CH3NH2 which had been pretreated with cis-DDP. In addition, the COOH-terminal fragment did not bind to monoclonal antibody 7H11D6, a monoclonal antibody which binds to the platinum-reactive epitope of the alpha 2M-CH3NH2 receptor recognition site. In contrast, the 55-kDa fragment of alpha 2M bound approximately 1 mol platinum/mol of 55-kDa fragment and also bound to monoclonal antibody 7H11D6. Since the COOH-terminal fragment retains some receptor binding ability, the results of this investigation demonstrate that this fragment is not the complete receptor recognition site and suggest that a platinum-reactive methionyl residue located in the 55-kDa fragment of alpha 2M is another component of this site.

Animals↗

PubMed1988

Clearance and distribution of recombinant murine gamma-interferon in mice.

Recombinant murine gamma-interferon (rIFN-gamma) was radiolabeled by a novel procedure which does not require the use of preiodinated Bolton-Hunter reagent (specific activities of 0.5-3.0 microCi/micrograms). Gel filtration chromatography of the radiolabeled preparation yielded two peaks. The early eluting peak contained disulfide stabilized aggregates with minimal interferon antiviral activity. The second peak contained activity that was consistently greater than or equal to that of the nonradiolabeled rIFN-gamma. Two bands with apparent molecular weights of 17,000 and 34,000 were observed when the second peak was analyzed by SDS gel electrophoresis. Fractions comprising each of the two chromatography peaks were pooled separately and subjected to gel filtration again on identical columns 24 h after completion of the first column run. The elution volumes of each peak remained unchanged suggesting that the two forms are not in rapid equilibrium. The plasma clearance rates of [125I]rIFN-gamma before and after purification by chromatography were initially rapid but multiphasic. The slower phases of clearance did not result from stable association of the rIFN-gamma with plasma proteins. In organ distribution studies, the liver and spleen sequestered significant amounts of [125I]rIFN-gamma; however, the highest concentration of rIFN-gamma was recovered in the kidneys. A functional nephrectomy procedure was used to further study the role of the kidneys in rIFN-gamma clearance. Eliminating the kidneys significantly increased the amount of rIFN-gamma retained in the circulation, particularly at later times when the vascular [125I]rIFN-gamma levels were approximately threefold higher than in nonnephrectomized mice.

Animals↗

PubMed1988

Intersubunit cross-linking by cis-dichlorodiammineplatinum(II) stabilizes an alpha 2-macroglobulin "nascent" state: evidence that thiol ester bond cleavage correlates with receptor recognition site exposure.

Treatment of human alpha 2-macroglobulin (alpha 2M) with proteinase results in cleavage of the alpha 2M subunits and subsequently in a conformational change in the inhibitor. This change irreversibly traps the proteinase and is accompanied by the generation of four thiol groups as well as exposure of receptor recognition sites. cis-Dichlorodiammineplatinum(II) (cis-DDP) causes extensive intersubunit cross-linking of alpha 2M. Incubation of alpha 2M or cis-DDP-treated alpha 2M with trypsin results in complete subunit cleavage; however, trypsin treatment of cis-DDP-alpha 2M does not result in a conformational change as determined by nondenaturing polyacrylamide gel electrophoresis (PAGE), receptor recognition site exposure, or appearance of thiol groups from the inhibitor. These results are in marked contrast to previous studies which demonstrated that incubation of cis-DDP-treated alpha 2M with CH3NH2 resulted in thiol ester bond cleavage and receptor recognition site exposure. cis-DDP-treated alpha 2M bound only 0.13 mol of 125I-trypsin/mol of cis-DDP-alpha 2M. Incubation of trypsin-treated cis-DDP-alpha 2M with diethyldithiocarbamate (DDC), a potent chelator of platinum compounds, results in the removal of the intersubunit cross-links and completion of the alpha 2M conformational change as determined by nondenaturing PAGE. Complete receptor recognition site exposure and the appearance of 3.3 thiol groups/mol of alpha 2M also occur following this treatment. These results demonstrate that cross-linking of alpha 2M by cis-DDP prevents a conformational change in the inhibitor which is necessary for thiol ester bond activation and cleavage.(ABSTRACT TRUNCATED AT 250 WORDS)

Cisplatin↗

PubMed1988

cis-dichlorodiammineplatinum (II) as a selective modifier of the oxidation-sensitive reactive-center methionine in alpha 1-antitrypsin.

Methionine 358 in the plasma protein alpha 1-antitrypsin (alpha 1AT) is an oxidation-sensitive reactive-center residue critical for proteinase-inhibitory activity. Reaction of alpha 1AT with 20 microM to 1.67 mM cis-dichlorodiammineplatinum (II) (cis-DDP) or trans-DDP afforded concentration-dependent loss of trypsin-inhibitory activity. This effect, studied by gel electrophoresis and activity assays, is essentially independent of pH over the range 4.9-8.6. Binding assays showed covalent incorporation of 1 mol of cis-DDP into each mol of alpha 1AT. cis-DDP protected a single methionine residue from oxidation and made alpha 1AT resistant to degradation by papain, which cleaves alpha 1AT at Met358. These findings strongly suggest that cis-DDP inactivates alpha 1AT by binding exclusively to its reactive-center methionine. alpha 1AT bound twice as much platinum when reacted with trans-DDP. Because carboxamidomethylated alpha 1AT incorporated nearly 1 mol of both cis- and trans-DDP, the trans isomer apparently binds to both the reactive-center methionine and to the single cysteine residue of alpha 1AT. Because of its greater selectivity, cis-DDP is the superior reagent for modification of the alpha 1AT reactive-center methionine.

Binding Sites↗

PubMed1988

Defective release of tissue plasminogen activator in patients with sickle cell anemia.

Recent studies suggest that intravascular coagulation occurs in sickle cell anemia. There is also some evidence that decreased fibrinolytic activity may be associated with the disorder. In the current study we measured tissue plasminogen activator levels (t-PA) in seven asymptomatic patients with sickle cell anemia. The mean level of releasable t-PA was only 0.01 IU/mL +/- 0.005 (SEM) as compared to 118 healthy volunteers with levels of 0.70 +/- 0.10 (SEM). Despite the small sample size, the difference between the two groups was statistically significant (P less than .001). These data suggest that defective release of t-PA may contribute to a hypercoagulable state in sickle cell anemia.

Anemia, Sickle Cell↗

PubMed1988

Methionine sulfoxide and the oxidative regulation of plasma proteinase inhibitors.

The sensitivity of methionine residues to oxidation is a mechanism by which many proteins, including plasma proteinase inhibitors, may be oxidatively inactivated. Much evidence suggests that methionine oxidation and concurrent losses of protein activity not only occur widely in living systems but are physiologic, homeostatic processes. Neutrophils, macrophages and other leukocytes secrete large quantities of powerful oxidants at sites of inflammation and may readily bring about methionine oxidative inactivation of proteins. In particular, oxidation of proteinase inhibitors may favorably alter the proteinase-antiproteinase balance to facilitate tissue remodeling and protection from invading organisms. Leukocyte-mediated inhibitor oxidation also appears to regulate local immunosuppressive activity. Pathophysiologic processes such as emphysema and rheumatoidal disease involve derangements of these homeostatic mechanisms.

Animals↗

PubMed1988

Alpha 2 macroglobulin-proteinase complexes stimulate prostaglandin E2 synthesis by peritoneal macrophages.

alpha 2-Macroglobulin is a proteinase inhibitor which is converted from its native form into an electrophoretically "fast" form by reaction with a proteinase or methylamine. All alpha 2M "fast" forms bind to a specific high-affinity receptor on macrophages. alpha 2M "fast" forms inhibit the interferon-gamma (IFN)-induced increase in macrophage Ia expression. This study examined whether alpha 2M-proteinase complexes alter prostaglandin (PG) E2 synthesis, and whether PGE2 mediates alpha 2M "fast" forms effects on macrophage Ia expression. Culture with alpha 2M "fast" forms increased PGE2 accumulation in the medium over control values in a dose-dependent manner. Culture with IFN alone did not increase PGE2 levels, but potentiated the effect of alpha 2M-proteinase complexes on PGE2 levels. Inhibition of PGE2 synthesis did not alter the inhibitory effect of alpha 2M-proteinase complexes on IFN-induced Ia expression. However, exogenous PGE2 did suppress IFN-induced Ia expression. Thus, alpha 2M-proteinase complexes increase macrophage PGE2 synthesis, but increased synthesis of PGE2 or other cyclooxygenase products is not the mediator of antagonism of IFN-induced Ia expression by alpha 2M-proteinase complexes.

Animals↗

PubMed1988

In vivo catabolism of heparin cofactor II and its complex with thrombin: evidence for a common receptor-mediated clearance pathway for three serine proteinase inhibitors.

The plasma clearance of 125I-labeled human heparin cofactor II and its complex with thrombin was studied in mice to determine whether a specific mechanism exists for the catabolism of the inhibitor-proteinase complex. Initial studies demonstrated that murine plasma contains a heparin cofactor II-like inhibitor as shown by the presence of a dermatan sulfate-sensitive thrombin inhibitor. Human heparin cofactor II cleared from the circulation of mice with an apparent half-life of 80 min while heparin cofactor II-thrombin complexes cleared with an apparent half-life of only 10 min. The specificity of the clearance mechanism was investigated by clearance competition studies involving coinjection of excess unlabeled heparin cofactor II-alpha-thrombin, antithrombin III-alpha-thrombin, or alpha 1-proteinase inhibitor-elastase, and by tissue distribution studies. The results demonstrated that the clearance of 125I-labeled heparin cofactor II-alpha-thrombin is a receptor-mediated process, and that the same hepatocyte receptor system recognizes complexes containing heparin cofactor II, antithrombin III, and alpha 1-proteinase inhibitor.

Animals↗

PubMed1988

Characterization of the fibrin polymer structure that accelerates thrombin cleavage of plasma factor XIII.

The effect of plasmin-derived fibrin(ogen) degradation products on alpha-thrombin cleavage of plasma Factor XIII was studied to identify the fibrin polymer structure that promotes Factor XIIIa formation. Fibrin polymers derived from fibrinogen and Fragment X enhanced the rate of thrombin cleavage of plasma Factor XIII in plasma or buffered solutions. The concentrations of fibrinogen and Fragment X that promoted half-maximal rates of Factor XIIIa formation were 5 and 40 micrograms/ml, respectively. Fragments Y, D, E, D-dimer, and photooxidized fibrinogen did not enhance thrombin cleavage of Factor XIII. Although purified Fragment D1 inhibited fibrin gelation, the soluble protofibrils promoted thrombin activation of Factor XIII. Noncrosslinked fibrin fibers failed to enhance thrombin cleavage of Factor XIII. In conclusion, soluble fibrin oligomers function to promote thrombin cleavage of plasma Factor XIII during blood clotting.

Calcium↗

PubMed1988

Selectivity and stereospecificity of the reactions of dichlorodiammineplatinum(II) with three purified plasma proteins.

The reactions of cis- and trans-dichlorodiammineplatinum(II) (cis- and trans-DDP) with albumin and two plasma proteinase inhibitors were compared. Reaction with alpha 2-macroglobulin (alpha 2M) resulted in subunit crosslinking and loss of proteinase binding activity. The reaction also modified a receptor recognition site present on each alpha 2M subunit. While more trans-DDP was incorporated into alpha 2M than cis-DDP, cis-DDP was more effective at blocking receptor recognition, alpha 1-proteinase inhibitor was also inactivated by reaction with either cis- or trans-DDP. These reactions resulted in binding of platinum to methionine-358 at the reactive center of this inhibitor. Trans-DDP, however, was less selective and also bound to the single cysteine residue (Cys-232) of alpha 1PI. Reaction of albumin with cis-DDP resulted in incorporation of about 1 mol platinum per mol protein, and this platinum modified the single cysteine (Cys-34) in the molecule. Albumin incorporated twice as much trans-DDP, but the binding did not involve cysteine-34. In general, reactions of cis-DDP with proteins appear to be more selective than those observed for modification with the trans isomer.

Blood Proteins↗

PubMed1988

Large scale purification of factor X by hydrophobic chromatography.

Factor X is a critical enzyme in the blood coagulation cascade, however, in recent years the coagulation zymogen factor X has received additional interest as a selective proteinase to allow production of functional eukaryotic proteins in a prokaryotic expression system. Traditional factor X purification schemes suffer from low yields, low capacity, lengthy dialysis steps, and contamination by the autoproteolytic activated enzyme factor Xa. By incorporating a reversible inhibitor of factor X activation, we were able to recover 67% of the factor X present without any detectable activated enzyme. Six liters of plasma could be processed onto a 50 mL phenylalanine-Sepharose hydrophobic chromatography column without saturating the matrix. The final product is devoid of detectable proteolytic activity. At time of use, the zymogen is specifically activated with a Sepharose-bound activating enzyme isolated from Russell's Viper Venom, resulting in factor Xa free of other detectable proteinases.

Chromatography↗

PubMed1988

Primary undifferentiated sarcoma of the thoracic aorta.

A case of a primary undifferentiated sarcoma of the descending thoracic aorta in a 75-year-old man is reported. Intraluminal growth and occlusion produced congestive heart failure and renal failure. The thoracic aorta was relatively normal on chest radiography so that the lesion was undiscovered until the autopsy. To our knowledge, it is the first case of a primary undifferentiated sarcoma of the thoracic aorta, and the first undifferentiated aortic sarcoma to be examined with immunohistochemistry and electron microscopy. Electron microscopy and immunohistochemistry verified the sarcomatous nature of the undifferentiated neoplasm.

Aged↗

PubMed1988

The role of endothelium in factor Xa regulation: the effect of plasma proteinase inhibitors and hirudin.

The role of endothelium in the inhibition of human factor Xa was studied in a plasma environment. Human factor Xa can bind to and function on bovine aortic endothelium in a manner similar to that of bovine factor Xa. Approximately 70% of the bound factor Xa is subject to inhibition by plasma proteinase inhibitors, and the remaining 30% is irreversibly bound as part of a 125 Kd membrane-associated complex not subject to proteolytic degradation. The proportion reversibly bound and its rate of release do not alter with changes in calcium, citrate, heparin, or active proteinase inhibitor concentrations. The principal plasma proteinase inhibitor of human factor Xa was antithrombin III, which accounted for 60% to 65% of factor Xa released from endothelium, with alpha 1-proteinase inhibitor inactivating 20% to 25% and alpha 2-macroglobulin approximately 15%. All of the reversibly bound factor Xa was identified in complex with one of these three proteinase inhibitors. The thrombin active-site inhibitor hirudin was found to markedly accelerate the displacement of reversibly bound factor Xa from the endothelium and to associate specifically with factor Xa without a loss of activity toward chromogenic substrates, perhaps accounting for a novel mechanism of anticoagulation.

Animals↗

PubMed1988

Preparation of polyethylene glycol-tissue plasminogen activator adducts that retain functional activity: characteristics and behavior in three animal species.

Conditions were defined for the derivatization of recombinant tissue plasminogen activator (rt-PA) with polyethylene glycol (PEG) so as to retain functional activity as a possible means of producing a t-PA species with a prolonged circulating lifetime. Derivatives with a wide range of retention of activities were prepared by varying the concentration and species of activated PEG. The specific activities of the PEG-rt-PA derivatives were dependent on the method of assay. Assays using preformed fibrin gave higher estimates of retention of activity than assays using soluble components. Plasma elimination studies in mice and rats indicated prolonged circulating lifetimes for the radiolabeled PEG-rt-PA derivatives after a rapid clearance and distribution phase; however, the disappearance of functional activity was much more rapid than the disappearance of radiolabeled material. The PEG-rt-PA derivatives appeared to accumulate in tissues above their interstitial fluid concentrations and were rapidly inactivated, apparently by reaction with the plasma protease inhibitors. These results were consistent with the inactivation of the PEG-rt-PA derivatives in rat plasma in vitro. A somewhat longer half-life (t1/2) of the one derivative studied was observed in dogs (t1/2, 16 minutes) as compared with the rat (t1/2, five minutes). This was sufficient to confer thrombolytic activity upon the derivative (administered by bolus injection) in contrast to native rt-PA. The potential of PEG-modified rt-PA as a long-lived thrombolytic agent in humans will depend, however, on whether there will be a further extension of the t1/2 because of a reduction in clearance and/or a reduction in the rate of inactivation.

Animals↗

PubMed1987

The role of inter-alpha-trypsin inhibitor and other proteinase inhibitors in the plasma clearance of neutrophil elastase and plasmin.

The plasma clearance of neutrophil elastase, plasmin, and their complexes with human inter-alpha-trypsin inhibitor (I alpha I) was examined in mice, and the distribution of the proteinases among the plasma proteinase inhibitors was quantified in mixtures of purified inhibitors, in human or murine plasma, and in murine plasma following injection of purified proteins. The results demonstrate that I alpha I acts as a shuttle by transferring proteinases to other plasma proteinase inhibitors for clearance, and that I alpha I modulates the distribution of proteinase among inhibitors. The clearance of I alpha I-elastase involved transfer of proteinase to alpha 2-macroglobulin and alpha 1-proteinase inhibitor. The partition of elastase between these inhibitors was altered by I alpha I to favor formation of alpha 2-macroglobulin-elastase complexes. The clearance of I alpha I-plasmin involved transfer of plasmin to alpha 2-macroglobulin and alpha 2-plasmin inhibitor. Results of distribution studies suggest that plasmin binds to endothelium in vivo and reacts with I alpha I before transfer to alpha 2-macroglobulin and alpha 2-plasmin inhibitor. Evidence for this sequence of events includes observations that plasmin in complex with I alpha I cleared faster than free plasmin, that plasma obtained after injection of plasmin contained a complex identified as I alpha I-plasmin, and that a murine I alpha I-plasmin complex remained intact following injection into mice. Plasmin initially in complex with I alpha I more readily associated with alpha 2-plasmin inhibitor than did free plasmin.

Alpha-Globulins↗

PubMed1987

Modulation of mouse peritoneal macrophage Ia and human peritoneal macrophage HLA-DR expression by alpha 2-macroglobulin "fast" forms.

alpha 2-Macroglobulin (alpha 2M) is converted from its native form into electrophoretically "fast" forms by reaction with proteinases or with methylamine. The "fast" forms both bind to specific receptors on macrophages (MP). We have previously shown that alpha 2M "fast" forms modulate effector functions of murine peritoneal MP. In the present study, alpha 2M "fast" forms antagonized the increase in MP HLA-DR and Ia expression induced in vitro by interferon-gamma (IFN-gamma). This effect was observed with human peritoneal MP, as well as MP from peptone-injected and bacillus Calmette-Guérin-infected mice of three strains. alpha 2M-trypsin, which had been reacted with aprotinin and alpha 2M-methylamine, both of which lack proteolytic activity, also antagonized interferon-induced Ia expression. alpha 2M "fast" forms also reduced the ability of MP to serve as accessory cells for lectin-induced lymphocyte proliferation. alpha 2M "fast" form is an immune modulator of human and murine MP function, probably through a specific receptor-mediated mechanism.

Animals↗

PubMed1987

Effects of bacterial lipopolysaccharide on the hydrolysis of phosphatidylinositol-4,5-bisphosphate in murine peritoneal macrophages.

LPS and lipid A initiated enhanced hydrolysis of PIP2 in macrophages. When murine peritoneal macrophages were labeled with [2-3H]myoinositol and stimulated with either LPS or lipid A, a rapid (within 10 sec) rise in Ins(1,4,5)P3 was observed. The breakdown pattern of Ins(1,4,5)P3 was complex; this included breakdown of Ins(1,4,5)P3 and formation of Ins(1,3,4,5)P4 (approximately 10 to 30 sec), and ultimately formation of Ins(1,3,4)P3 (approximately 60 sec). Within 10 sec after treatment, LPS caused an average increase of about fourfold to fivefold in Ins(1,4,5)P3, which declined over 5 min. When the total isomers of InsP3 were measured, levels rose about twofold in response to LPS or to lipid A and remained elevated for as long as 5 min. Lipid A, in the concentration range of 0.1 to 10 micrograms/ml, induced elevated intracellular levels of Ca2+ as quantified by fluorescence with Quin 2 or with Fura 2. When single, adherent Fura 2-loaded macrophages were treated with lipid A, basal levels of calcium rose over 10 sec from approximately 55 nM to almost 600 nM. LPS, paradoxically, did not cause such substantial increases in intracellular calcium (i.e., increases of approximately 26 nM) when judged by Fura 2 fluorescence. LPS treatment led to enhanced phosphorylation of a characteristic set of proteins, similar to those induced by stimulating protein kinase C (PKC) with phorbol myristate acetate as previously reported. The enhanced phosphorylation of pp28, pp33, and pp67 in macrophages was evident by 15 min and optimal by 30 min. Taken together, these observations indicate that LPS and lipid A cause increased breakdown of phosphatidylinositol 4,5-bisphosphate, which led to enhanced intracellular levels of calcium and also to enhanced protein phosphorylation, presumably mediated by PKC. The data thus suggest that one major intracellular signal transduction mechanism, initiated by LPS and lipid A in macrophages, is the rapid breakdown of PIP2.

Animals↗