A cross-sectional study on smartphone uses among pregnant women attending childbirth classes in the Metropolitan Area of Palermo, Italy: The Stop-Phone study.

Background: Prevalence of mobile device addiction has increased over the years; both women and men have assimilated the mobile phone as a central component of their personal existence: integrating it into their lifestyle or becoming so dependent on it that life without it has become unimaginable. Smartphones generate radio-frequency electromagnetic fields. While short-term exposure in adults was considered quite safe, effects of long-term exposure or exposure during pregnancy on fetuses or during breastfeeding on newborns are not well studied yet. The objective of the present study was to investigate the prevalence and usage characteristics of smartphones among a sample of pregnant women, and promote the correct and conscious use of the smartphone. Methods: A cross-sectional study was conducted, with a questionnaire administered during childbirth classes and - after the questionnaire administration - an educational intervention focused on promoting the correct and conscious use of smartphones was carried out by psychologists and psychotherapists. Results: The findings of our study suggest that a significant number of the participants suffered addiction to mobile phone usage, but were not aware of it. More than two third of the sample (67.2%) have not changed their smartphone use habits since the beginning of their pregnancy and even more significant data shows that almost all future moms (98.3%) never speak with their doctor about smartphone use during pregnancy. Conclusions: Data collected suggest a lack of attention to the proposed topic, especially in relation to pregnancy. It seems necessary to sensitize future mothers on this topic. The promotion of a more conscious and controlled use of electronic devices can help reduce the radiation to which the unborn child may be exposed, but has a fundamental role even after birth, to ensure an adequate psychomotor and relational development of the child and do not affect, due to uncontrolled use of smartphones, the mother-child relationship.

Loss of cell surface TFII-I promotes apoptosis in prostate cancer cells stimulated with activated α2 -macroglobulin.

Receptor-recognized forms of α2 -macroglobulin (α2 M) bind to cell surface-associated GRP78 and initiate pro-proliferative and anti-apoptotic signaling. Ligation of GRP78 with α2 M also upregulates TFII-I, which binds to the GRP78 promoter and enhances GRP78 synthesis. In addition to its transcriptional functions, cytosolic TFII-I regulates agonist-induced Ca(2+) entry. In this study we show that down regulation of TFII-I gene expression by RNAi profoundly impairs its cell surface expression and anti-apoptotic signaling as measured by significant reduction of GRP78, Bcl-2, and cyclin D1 in 1-Ln and DU-145 human prostate cancer cells stimulated with α2 M. In contrast, this treatment significantly increases levels of the pro-apoptotic proteins p53, p27, Bax, and Bak and causes DNA fragmentation. Furthermore, down regulation of TFII-I expression activates agonist-induced Ca(2+) entry. In plasma membrane lysates p-PLCγ1, TRPC3, GRP78, MTJ1, and caveolin co-immunoprecipitate with TFII-I suggesting multimeric complexes of these proteins. Consistent with this hypothesis, down regulating TFII-I, MTJ1, or GRP78 expression by RNAi greatly attenuates cell surface expression of TFII-I. In conclusion, we demonstrate that not only does cell surface GRP78 regulate apoptosis, but it also regulates Ca(2+) homeostasis by controlling cell surface localization of TFII-I.

Modulation of the unfolded protein response in prostate cancer cells by antibody-directed against the carboxyl-terminal domain of GRP78.

Receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) bind to cancer cell surface GRP78, which functions as a signaling receptor promoting proliferation and survival. Patients with prostate, ovary, and skin cancer may develop auto-antibodies to the alpha(2)M* binding site which are receptor agonists whose presence indicates a poor prognosis. By contrast, antibodies directed against the COOH-terminal domain of GPR78 (anti-CTD antibody), are antagonists which down regulate pro-proliferative signaling and upregulate p53. Unfolded protein response (UPR) signaling plays an important role in cell survival and proliferation as well as apoptosis. We, therefore, studied the effect of anti-CTD antibody on UPR signaling in 1-LN and DU-145 prostate cancer cells. Treatment of these cells, which express GRP78 on their cell surface, with this antibody significantly downregulated IRE1-alpha, PERK, and ATF6alpha-dependent UPR signaling. By contrast, the pro-apoptotic protein GADD153 was elevated. Anti-CTD antibody treatment also elevated apoptotic components, cleaved PARP-1, and Erdj5. In general, a two to threefold effect was observed for the parameters which were studied. These studies suggest that anti-CTD antibody induces growth inhibitory and pro-apoptotic effects by modulating UPR signaling in human prostate cancer cells.

PFT-alpha inhibits antibody-induced activation of p53 and pro-apoptotic signaling in 1-LN prostate cancer cells.

Antibodies against the COOH-terminal domain of cell surface GRP78 induce apoptosis in cancer cell lines via activation of p53 signaling. We now have studied the effects of PFT-alpha, an inhibitor of p53-mediated apoptotic pathways, on anti-GRP78 antibody-induced activation of p53 and pro-apoptotic signaling in 1-LN prostate cancer cells. Pretreatment of 1-LN cancer cells with this agent significantly inhibited antibody or doxorubicin-induced upregulation of p53. Concomitantly, PFT-alpha treatment prevented down regulation of ERK1/2 activation by either antibody or doxorubicin. Likewise, PFT-alpha prevented increases in the pro-apoptotic proteins BAD, BAK, BAX, PUMA, and NOXA as well as activation of caspases-3, -7, and -9. We conclude that antibody-induced apoptosis in prostate cancer cells is mediated predominantly by p53 using the mitochondrial pathway of apoptosis.

Inhibition of NF-kappaB1 and NF-kappaB2 activation in prostate cancer cells treated with antibody against the carboxyl terminal domain of GRP78: effect of p53 upregulation.

Ligation of cancer cell surface GRP78 by activated alpha2-macroglobulin (alpha2M*) triggers pro-proliferative and anti-apoptotic signaling pathways. Cancer patients who develop autoantibodies to the alpha2M* binding site in GRP78 have a poor prognosis since these antibodies are receptor agonists. The NF-kappaB family of transcription factors induces expression of genes affecting cell growth and differentiation. NF-kappaB1 plays a major regulatory role in controlling innate immunity and inflammation, whereas NF-kappaB2 plays a greater role in cancer cell proliferation. Here we report that treatment of prostate cancer cells with antibody directed against the carboxyl terminal domain of GRP78 inhibits alpha2M*-induced activation of NF-kappaB2 by approximately 50% while exerting a lesser effect of approximately 20% on NF-kappaB1 activation. Treatment of these cells nearly abolished alpha2M*-induced activation of IKKalpha involved in the activation of NF-kappaB2. This antibody also suppressed alpha2M*-induced phosphorylation of IKKalpha, IKKalpha/beta, IkappaBalpha, and IkappaBbeta as well as levels of NIK. Antibody treatment of cancer cells elevated pro-apoptotic p21WAF and p27kip while reducing cyclin D1 levels. These studies demonstrate that antibody directed against the carboxyl terminal domain of GRP78 inhibits the pro-proliferative NF-kappaB signaling cascade in cancer cells.

Transcription factor TFII-I causes transcriptional upregulation of GRP78 synthesis in prostate cancer cells.

Receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) bind to cell surface-associated GRP78 and induce proliferative and survival signaling in prostate cancer cells. As part of the cellular response to alpha(2)M*, GRP78 expression is itself upregulated. In response to other stimuli, the transcription factor TFII-I upregulates GRP78 by binding to its gene promoter. We have, therefore, studied the role of TFII-I in transcriptional upregulation of GRP78 in 1-LN human prostate cancer cells stimulated with alpha(2)M*. This treatment caused a two- to threefold increase in TFII-I and GRP78 synthesis from [(35)S]-labeled precursor amino acids. Synthesis of both TFII-I and GRP78 were significantly reduced by silencing TFII-I gene expression or pretreatment of cells with genistein or actinomycin D. Confocal microscopy was employed to demonstrate relocation of TFII-I to the nucleus. In alpha(2)M*-stimulated cells, moreover, TFII-I bound to the GRP78 promoter as determined by CHIP assay. We also demonstrate binding of TFII-I to the c-fos promoter, consistent with its role in upregulating c-fos gene expression. In non-lymphoid cells, phosphorylated c-Src is an activator of TFII-I. Ligation of GRP78 on 1-LN cells with alpha(2)M* was followed by tyrosine phosphorylation of c-Src as well as TFII-I. We conclude that alpha(2)M*-induced increase in GRP78 synthesis is caused by transcriptional upregulation of TFII-I which binds to the GRP78 promoter and thus potentiates its cell survival and antipoptotic functions in 1-LN prostate cancer cells.

Amyloid precursor protein and amyloid beta-peptide bind to ATP synthase and regulate its activity at the surface of neural cells.

Amyloid precursor protein (APP) and amyloid beta-peptide (Abeta) have been implicated in a variety of physiological and pathological processes underlying nervous system functions. APP shares many features with adhesion molecules in that it is involved in neurite outgrowth, neuronal survival and synaptic plasticity. It is, thus, of interest to identify binding partners of APP that influence its functions. Using biochemical cross-linking techniques we have identified ATP synthase subunit alpha as a binding partner of the extracellular domain of APP and Abeta. APP and ATP synthase colocalize at the cell surface of cultured hippocampal neurons and astrocytes. ATP synthase subunit alpha reaches the cell surface via the secretory pathway and is N-glycosylated during this process. Transfection of APP-deficient neuroblastoma cells with APP results in increased surface localization of ATP synthase subunit alpha. The extracellular domain of APP and Abeta partially inhibit the extracellular generation of ATP by the ATP synthase complex. Interestingly, the binding sequence of APP and Abeta is similar in structure to the ATP synthase-binding sequence of the inhibitor of F1 (IF(1)), a naturally occurring inhibitor of the ATP synthase complex in mitochondria. In hippocampal slices, Abeta and IF(1) similarly impair both short- and long-term potentiation via a mechanism that could be suppressed by blockade of GABAergic transmission. These observations indicate that APP and Abeta regulate extracellular ATP levels in the brain, thus suggesting a novel mechanism in Abeta-mediated Alzheimer's disease pathology.

Receptors for maleylated proteins regulate secretion of neutral proteases by murine macrophages.

Receptors for maleylated or acetylated proteins as well as for alpha-2-macroglobulin-protease complexes on macrophages serve as scavengers by mediating the uptake of macromolecules from the extracellular compartment. Described in this report is a novel function of these receptors on macrophages: regulation of neutral protease secretion. The binding of maleylated bovine serum albumin to macrophages triggered secretion of three neutral proteases: neutral caseinases, plasminogen activator, and cytolytic proteinase. Release of acid phosphatase, however, was not induced. An important biological consequence of protease secretion by macrophages, tumor-cytolysis, was also triggered by engagement of the receptor for maleylated bovine serum albumin. By contrast, the binding of alpha-2-macroglobulin-protease complexes to the macrophages suppressed secretion of all three proteases. Thus two receptors heretofore believed to serve principally as scavengers also regulate secretory functions of macrophages.

Regulation of factor Xa in vitro in human and mouse plasma and in vivo in mouse. Role of the endothelium and plasma proteinase inhibitors.

The regulation of human Factor Xa was studied in vitro in human and mouse plasma, and in vivo in mouse. In human plasma, 125I-Factor Xa bound to alpha 1-proteinase inhibitor, antithrombin III, and alpha 2-macroglobulin in a ratio of 4.9:1.9:1 as determined by gel electrophoresis and by adsorption to IgG-(antiproteinase inhibitor)-Sepharose beads. The distribution of Factor Xa in mouse plasma was similar. The clearance of Factor Xa in mice was rapid (50% clearance in 3 min) and biphasic. alpha 1-Proteinase inhibitor-trypsin, even at a 2,000-fold molar excess, failed to inhibit the clearance of Factor Xa, while alpha 2-macroglobulin-trypsin inhibited only the later phase of clearance. The plasma clearance of diisopropylphosphoryl-Factor Xa was more rapid than native Factor Xa (50% clearance in 2.5 min), and the clearance was blocked by diisopropylphosphoryl-thrombin. Electrophoresis experiments confirmed that by 2 min after injection into the murine circulation, 90% of the bound Factor Xa was on alpha 2-macroglobulin, in marked contrast to the in vitro results. Organ distribution studies at 3 and 15 min with 125I-Factor Xa demonstrated that the majority of radioactivity was in the liver, with significant radioactivity also present in lung and kidney. Autopsies performed 30 s after injection of 125I-Factor Xa also demonstrated significant binding to the aorta and vena cava. These studies indicate that Factor Xa binds to specific thrombin-binding sites on endothelial cells, and that this binding alters its proteinase inhibitor specificity. Factor Xa binds to alpha 2-macroglobulin in vivo, whereas the predominant in vitro inhibitor of Factor Xa is alpha 1-proteinase inhibitor.

Demonstration and characterization of specific binding sites for factor VIII/von Willebrand factor on human platelets.

The presence of specific Factor VIII/von Willebrand factor (FVIII/vWF) binding sites on human platelets has been demonstrated by using 125I-FVIII/vWF and washed human platelets. Binding is ristocetin-dependent and increases in proportion to the concentration of ristocetin from 0.2 to 1 mg/ml. Binding of 125I-FVIII/vWF to platelets can be competitively inhibited by unlabeled human or bovine FVIII/vWF, but not by human thrombin, fibrinogen, alpha 2-macroglobulin, equine collagen, or a lectin of Ricinus communis. Scatchard analysis of binding data indicated that the dissociation constant of FVIII/vWF receptors is 0.45--0.5 nM. There are 31,000 binding sites per platelet at 1 mg/ml of ristocetin concentration. The optimal pH range for binding is from 7.0 to 7.5. At a concentration of 2 mM, EGTA inhibits 86% of the binding; however, 20 mM of Ca++, Mg++, or EDTA have little effect. Binding sites for FVIII/vWF were found only on platelets, and no significant binding was detected with human erythrocytes or polymorphonuclear leukocytes.

Catabolic pathways for streptokinase, plasmin, and streptokinase activator complex in mice. In vivo reaction of plasminogen activator with alpha 2-macroglobulin.

The catabolic pathways of streptokinase, plasmin, and activator complex prepared with human plasminogen were studied in mice. (125)I-streptokinase clearance occurred in the liver and was 50% complete in 15 min. Incubation with mouse plasma had no effect on the streptokinase clearance rate. Complexes of plasmin and alpha(2)-plasmin inhibitor were eliminated from the plasma by a specific and saturable pathway. Competition experiments demonstrated that this pathway is responsible for the clearance of injected plasmin. Streptokinase-plasminogen activator complex formed with either (125)I-plasminogen or (125)I-streptokinase cleared in the liver at a significantly faster rate than either of the uncomplexed proteins (50% clearance in <3 min). Streptokinase incubated with human plasma also demonstrated this accelerated clearance. p-Nitrophenyl-p'-guanidinobenzoate-HCl or pancreatic trypsin inhibitor-treated complex cleared slowly compared with untreated complex independent of which protein was radiolabeled. Significant competition for clearance was demonstrated between alpha(2)-macroglobulin-trypsin and activator complex only when the plasmin(ogen) was the radiolabeled moiety. Large molar excesses of alpha(2)-plasmin inhibitor-plasmin failed to retard the clearance of activator complex. Hepatic binding of streptokinase-plasmin, in liver perfusion experiments, was dependent upon prior incubation with plasma (8-10% uptake compared to a background of approximately 2.5%). Substitution of human alpha(2)-macroglobulin for plasma also resulted in binding when the incubation was performed for 10 min at 37 degrees C (7.5%). Electrophoresis experiments confirmed the transfer of 0.8 mol plasmin/mol alpha(2)-macroglobulin when activator complex was incubated at 37 degrees C with alpha(2)-macroglobulin for 40 min. Streptokinase transfer from activator complex to alpha(2)-macroglobulin was negligible. The in vivo clearance of activator complex is proposed to involve active attack of the complex on the alpha(2)-macroglobulin "bait region," resulting in facilitated plasmin transfer. Dissociated streptokinase is rapidly bound and cleared by sites in the liver.

A nonantigenic covalent streptokinase-polyethylene glycol complex with plasminogen activator function.

A series of new, covalent polyethylene glycol (PEG)-streptokinase adducts were synthesized and characterized. PEGs with average molecular weights of 2,000, 4,000, and 5,000 were activated with carbonyldiimidazole and coupled to the protein under standardized reaction conditions. Steady-state kinetic analysis demonstrated comparable Km values for the activation of plasminogen by streptokinase, PEG-2-streptokinase, and PEG-4-streptokinase. The kcat values were somewhat decreased when PEG-2 or PEG-4 was coupled to the streptokinase. Activation by the PEG-5 adduct did not follow Michaelis-Menten kinetics under the conditions employed in this study. Plasmin activity obtained by incubating streptokinase derivatives with plasminogen also was studied as a function of time with each of the PEG-streptokinase derivatives. By this assay, incubations containing PEG-5-streptokinase and unmodified streptokinase demonstrated comparable activity while reaction mixtures containing PEG-2-streptokinase and PEG-4-streptokinase were slightly more active. Streptokinase incubated with plasminogen at a 1:1 molar ratio was extensively degraded after 30 min whereas PEG-2-streptokinase was resistant to plasmin cleavage. The derivatized proteins were radioiodinated and incubated in plastic microtiter plates that were coated with an immunoglobulin fraction containing antibodies to streptokinase. Binding of the PEG-streptokinase adducts was decreased by greater than 95% compared with unmodified streptokinase. Plasminogen activator complexes were formed by reacting the streptokinases with human plasminogen in vitro and the clearance studied in mice. Radioiodinated plasmin in complex with the PEG-streptokinase adducts cleared at a slower rate than did plasmin complexed with unmodified streptokinase. Catabolism of the protease still occurred by a mechanism that involved reaction with alpha 2-macroglobulin as has been described for nonderivatized streptokinase-plasminogen complex (Gonias, S. L., M. Einarsson, and S. V. Pizzo, 1982, J. Clin. Invest., 70:412-423). When more extensive derivatization procedures were utilized, PEG-2-streptokinase preparations were obtained that further prolonged the clearance of complexed 125I-plasmin; however, these adducts did not uniformly retain comparable activity. It is suggested that PEG-streptokinase complexes with greatly reduced antigenicity may be useful in the treatment of thrombotic disorders.

The effect of fibrin-stabilizing factor on the subunit structure of human fibrin.

The formation of human fibrin from fibrinogen has been examined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, a method which separates a mixture of proteins on the basis of differences in molecular weight. It has been found that the plasma from a patient with a congenital deficiency of fibrin-stabilizing factor forms clots lacking the cross links among the alpha- and gammachains found in normal, cross-linked human fibrin. The addition of purified fibrin-stabilizing factor or normal plasma to the deficient plasma results in extensive cross-linking of the chains. Thus, the fibrinogen in the fibrin-stabilizing factor deficient plasma appears to be normal and forms fibrin which contains dimeric, cross-linked gamma-chains and polymeric, high molecular weight forms of alpha-chains. By the use of these electrophoretic methods, it has also been possible to develop a highly sensitive method for measuring the content of fibrin-stabilizing factor in plasma. This method depends upon the use of urea-treated fibrinogen, which is completely devoid of fibrin-stabilizing factor, but which forms the usual cross-linked subunits after conversion to fibrin by thrombin in the presence of fibrin-stabilizing factor.

The subunit structure of normal and hemophilic factor VIII.

Human factor VIII from normals and hemophiliacs was partially purified by ethanol and polyethylene glycol precipitations. Final purification was achieved by gel filtration on 2 or 4% agarose or ion exchange chromatography on diethylaminoethyl cellulose. Comparable amounts of highly purified protein were obtained from normal and hemophilic plasma following the agarose chromatography step. Highly purified factor VIII was not dissociated by 6 M guanidine hydrochloride or 1% sodium dodecyl sulfate. However, when reduced by beta-mercaptoethanol and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, a single subunit species with an estimated 195,000 molecular weight was found for both normal and hemophilic factor VIII. By sedimentation equilibrium analysis, the normal factor VIII subunit was homogeneous and had an estimated molecular weight of 202,000. The subunit polypeptides from normal or hemophilic factor VIII contained carbohydrate. Each was homogeneous by isoelectric focusing. Immunodiffusion of purified normal and hemophilic factor VIII against rabbit antiserum to purified normal human factor VIII showed a single line of precipitation. Very low concentrations of purified human thrombin initially increased the activity of normal factor VIII about threefold and then progressively destroyed activity by 3 h. Only minimal activation occurred with hemophilic factor VIII. Both the activation and inactivation of normal and hemophilic factor VIII were unaccompanied by detectable changes in subunit molecular weight. These findings may have implications for the definition of the molecular defect in hemophilic factor VIII.

Mechanism of ancrod anticoagulation. A direct proteolytic effect on fibrin.

Fibrin formed in response to ancrod, reptilase, or thrombin was reduced by beta-mercaptoethanol and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It was found that ancrod progressively and totally digested the alpha-chains of fibrin monomers at sites different than plasmin; however, further digestion of fibrin monomers by either reptilase or thrombin was not observed. Highly purified ancrod did not activate fibrin-stabilizing factor (FSF); however, the reptilase preparation used in these experiments, like thrombin, activated FSF and thereby promoted cross-link formation. Fibrin, formed by clotting purified human fibrinogen with ancrod, reptilase, or thrombin for increasing periods of time in the presence of plasminogen, was incubated with urokinase and observed for complete lysis. Fibrin formed by ancrod was strikingly more vulnerable to plasmin digestion than was fibrin formed by reptilase or thrombin. The lysis times for fibrin formed for 2 hr by ancrod, reptilase, or thrombin were 18, 89, and 120 min, respectively. Evidence was also obtained that neither ancrod nor reptilase activated human plasminogen. These results indicate that fibrin formed by ancrod is not cross-linked and has significantly degraded alpha-chains: as expected, ancrod-formed fibrin is markedly susceptible to digestion by plasmin.

Altered interaction of Cis-dichlorodiammineplatinum(II)--modified alpha 2-macroglobulin (alpha 2M) with the low density lipoprotein receptor-related protein/alpha 2M receptor but not the alpha 2M signaling receptor.

Receptor-recognized forms of alpha 2-macroglobulin (alpha 2M*) bind to two macrophage receptors: an endocytic receptor, the low density lipoprotein receptor-related protein/alpha 2M receptor (LRP/alpha 2MR), and a G protein-coupled receptor, the alpha 2M signaling receptor (alpha 2MSR). Binding of alpha 2M* to LRP/alpha 2MR but not alpha 2MSR is inhibited by receptor-associated protein. We now present binding characteristics of alpha 2MSR (kD approximately 50 pm; 1,530 sites/cell) using Scatchard analysis. We also demonstrate that chemical modification of alpha 2M* with cis-dichlorodiammineplatinum (cis-DDP) does not significantly alter binding to either receptor or signaling characteristics as compared with unmodified alpha 2M*. However, internalization by LRP/alpha 2MR is greatly affected. Cis-DDP-modified alpha 2M* (cis-DDP-alpha 2M*) and alpha 2M* show comparable internalization during a single round of endocytosis; however, cis-DDP modification of alpha 2M* results in a > or = 82% reduction in internalization involving receptor recycling and multiple rounds of endocytosis. Results from pH 5.0 dissociation and receptor recycling experiments suggest that the mechanism of decreased internalization of cis-DDP-alpha 2M* involves poor dissociation from the receptor in endosomes and a decrease in available surface receptors over the time of exposure to the ligand.

Neonatal plasminogen displays altered cell surface binding and activation kinetics. Correlation with increased glycosylation of the protein.

Plasminogen isolated from 60 full-term newborns differs from adult plasminogen in carbohydrate composition, kinetic activation constants, and cell binding. Amino acid composition and amino-terminal sequence analysis data indicate that the plasminogens of neonates and adults have the same amino acid sequence. Like the adult, the neonate has two glycoforms, but both have significantly more mannose and sialic acid than the adult forms. The difference in the neonatal glycosylation is probably responsible for the altered migration observed by isoelectric focusing. Moreover, the difference in carbohydrate composition appears to be the basis of the decreased functional activity of the neonatal plasminogen. The kcat/Km ratios indicate that the overall activation rates of the two neonatal plasminogen glycoforms are lower compared with the adult glycoforms. In addition, neonatal plasminogen does not bind as well to cellular receptors compared with adult plasminogen. These studies suggest a basis for the decreased fibrinolytic activity observed in neonates.

Regulation of factor IXa in vitro in human and mouse plasma and in vivo in the mouse. Role of the endothelium and the plasma proteinase inhibitors.

The regulation of human Factor IXa was studied in vitro in human and mouse plasma and in vivo in the mouse. In human plasma, approximately 60% of the 125I-Factor IXa was bound to antithrombin III (ATIII) by 2 h, with no binding to alpha 2-macroglobulin or alpha 1-proteinase inhibitor, as assessed by gel electrophoresis and IgG- antiproteinase inhibitor-Sepharose beads. In the presence of heparin, virtually 100% of the 125I-Factor IXa was bound to ATIII by 1 min. The distribution of 125I-Factor IXa in mouse plasma was similar. The clearance of 125I-Factor IXa was rapid (50% clearance in 2 min) and biphasic and was inhibited by large molar excesses of ATIII-thrombin and alpha 1-proteinase inhibitor-trypsin, but not alpha 2-macro-globulin-trypsin; it was also inhibited by large molar excesses of diisopropylphosphoryl - (DIP-) Factor Xa, DIP-thrombin, and Factor IX, but not by prothrombin or Factor X. The clearance of Factor IX was also rapid (50% clearance in 2.5 min) and was inhibited by a large molar excess of Factor IX, but not by large molar excesses of Factor X, prothrombin, DIP-Factor Xa, or DIP-thrombin. Electrophoresis and IgG- antiproteinase inhibitor-Sepharose bead studies confirmed that by 2 min after injection into the murine circulation, 60% of the 125I-Factor IXa was bound to ATIII. Organ distribution studies with 125I-Factor IXa demonstrated that most of the radioactivity was in the liver. These studies suggest that Factor IXa binds to at least two classes of binding sites on endothelial cells. One site apparently recognizes both Factors IX and IXa, but not Factor X, Factor Xa, prothrombin, or thrombin. The other site recognizes thrombin, Factor Xa, and Factor IXa, but not the zymogen forms of these clotting factors. After this binding, Factor IXa is bound to ATIII and the complex is cleared from the circulation by hepatocytes.

Modulation of murine B16F10 melanoma plasminogen activator production by a synthetic peptide derived from the laminin A chain.

Laminin is a large multidomain protein with diverse biological activities. We previously demonstrated that intact laminin as well as an A chain synthetic peptide (LamA2091-2108) stimulate tissue plasminogen activator (t-PA)-catalyzed plasminogen activation. Here we report that LamA2091-2108 increases t-PA production by the highly metastatic murine melanoma cell line B16F10, with no effect on the parental B16F1 line, which has a low metastatic capacity. Incubation of plasminogen with B16F10-conditioned medium results in direct activation of the zymogen to plasmin. Furthermore, following incubation of B16F10 cells with plasminogen, plasmin is eluted from the cell surface, suggesting that these cells contain binding sites for plasminogen/plasmin in close proximity to t-PA binding sites. Quantitation of t-PA activity using the synthetic substrate Val-Leu-Lys-p-nitroanilide indicates a minimal 10-fold increase in t-PA in the conditioned medium of B16F10 cells grown in the presence of LamA2091-2108, with no increased t-PA activity observed in B16F1-conditioned medium. Similar results were obtained in immunocapture experiments which are specific for t-PA antigen. In addition, B16F10 melanoma-associated t-PA catalyzes the plasminogen-dependent hydrolysis of laminin. Together these data suggest that degradation of basement membrane proteins by metastatic melanoma cells may release fragments (such as LamA2091-2108) which stimulate both the production and activity of metastasis-associated proteinases such as t-PA, providing a mechanism for augmentation of the metastatic capacity of B16F10 melanoma cells.

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.