The von Willebrand Factor in Myocardial Infarction and Unstable Angina: A Kinetic Study

Recent studies have demonstrated elevations of von Willebrand Factor following acute myocardial infarction (AMI). In order to determine if this parameter may serve as a marker for AMI, we tested the blood levels of vWF and Factor VIII :C in 28 patients with AMI, 9 patients with unstable angina, 7 patients with atypical chest pain, and 25 healthy volunteers. The level of ristocetin cofactor activity of vWF was between 70 and 144% in the control group. In patients with AMI, the mean level of this activity was 175% on the first day following infarction, rose to a peak of 270% on the fifth and sixth days, and was still significantly greater than normal in all patients on the 14th day. The vWF: Ag level closely paralleled the rise of ristocetin cofactor activity of vWF, with a peak of 336% on day 5. FVIII :C was not significantly changed. No significant elevation of vWF was observed in patients with unstable angina. The ristocetin cofactor activity of vWF and vWF: Ag thus are sensitive biochemical indicators for recent AMI, and may serve as useful markers for up to 14 days following infarction, when the traditional enzymes have returned to normal levels.

EGFR and KRAS mutation status of lung adenocarcinomas in African Americans

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Background: The 2004 discovery of the tyrosine kinase inhibitor-sensitizing mutations in the epidermal growth factor receptor (EGFR) represents a major advance in the study and management of non-small cell lung cancer. Conversely, KRAS mutations in these cancers confer resistance to the EGFR tyrosine kinase inhibitors gefitinib and erlotinib. EGFR mutations occur almost exclusively in adenocarcinoma, and are more common in never smokers, women, and people born in East Asian (compared to Whites). No comprehensive studies exist of EGFR and KRAS mutations in lung cancers from African-American patients. Methods: We collected formalin-fixed paraffin-embedded material from 121 resected lung adenocarcinomas from African-American patients for DNA extraction. EGFR exon 19 deletions and exon 21 L858R point mutations were detected by sensitive mutation-specific PCR-based methods. KRAS codon 12 and 13 mutation testing was performed by mass-spectrometry (Sequenom)-based genotyping and direct sequencing. These data were compared to Memorial Sloan-Kettering data for EGFR and KRAS mutations in all resected adenocarcinomas in white patients. Results: EGFR mutations were detected in 23 of 121 cases (19%), while KRAS mutations were found in 21 (17%). Exon 19 deletions accounted for 18 of 23 of the EGFR mutations compared to 5 EGFR L858R mutations. KRAS mutations were primarily the transversion type mutations (17 of 21). When compared to data from Memorial Sloan-Kettering for White patients (81/273, 30%), the 17% rate of KRAS mutations in lung adenocarcinomas from African-Americans was significantly lower (p=0.01). EGFR mutation status was similar between African-Americans and Whites (19% vs 18%, p=0.9) and the proportion of exon 19 deletions and L858R mutations was comparable as well. Conclusions: This is the first large series reporting results of mutation testing in lung adenocarcinoma specimens from African-Americans. African-American patients are less likely than Whites to harbor KRAS mutations in their lung adenocarcinomas. There was no significant difference in the prevalence of EGFR mutations. Since biological characteristics underlie clinical factors, these differences may help explain differences in outcomes comparing African-Americans to other groups.

No significant financial relationships to disclose.

Angiostatin and angiostatin-related proteins

The study of angiogenesis, and the promise of angiogenesis inhibition as a means of cancer therapy, has dramatically accelerated in the last several years. The discovery and publication of angiostatin by O'Reilly and colleagues in Judah Folkman's lab in 1994 has greatly contributed to this progress. Angiostatin is a kringle-containing fragment of plasminogen, which is a potent inhibitor of angiogenesis in vivo, and selectively inhibits endothelial cell proliferation and migration in vitro. There have been a number of proposed proteolytic mechanisms by which plasminogen is cleaved to form angiostatin, and the resulting cleavage products contain different NH2 and COOH termini of the angiostatin. Therefore, it is possible that there are more than one angiostatin isoforms (or angiostatin-related proteins) which occur in one or more normal or pathophysiological situations. It is also possible that some of the proteolytic processes which can convert plasminogen to angiostatin-like proteins are simply laboratory artifacts. Angiostatin-related proteins exert potent endothelial cell inhibitory activity, including the induction of apoptosis, and inhibition of migration, and the intact kringle structures are believed to be necessary for the antiangiogenic activity. Efforts are now underway to translate the understanding of the biology of angiostatin to clinical practice, which includes phase 1 clinical trials with recombinant angiostatin K1-3 (kringles 1-3) as well as phase 1 trials of an Angiostatin Cocktail, which induces the direct in vivo conversion of plasminogen to angiostatin 4.5 (kringles 1-4, plus most of kringle 5). The translation of the basic science of angiostatin and angiostatin-related proteins to clinical trial promises to provide an important new tool in the treatment of cancer by inhibition of angiogenesis.

Tumor-host interactions in the gallbladder suppress distal angiogenesis and tumor growth: involvement of transforming growth factor beta1

Angiogenesis inhibitors produced by a primary tumor can create a systemic anti-angiogenic environment and maintain metastatic tumor cells in a state of dormancy. We show here that the gallbladder microenvironment modulates the production of transforming growth factor (TGF)-beta1, a multifunctional cytokine that functions as an endogenous anti-angiogenic and anti-tumor factor in a cranial window preparation. We found that a wide variety of human gallbladder tumors express TGF-beta1 irrespective of histologic type. We implanted a gel impregnated with basic fibroblast growth factor or Mz-ChA-2 tumor in the cranial windows of mice without tumors or mice with subcutaneous or gallbladder tumors to study angiogenesis and tumor growth at a secondary site. Angiogenesis, leukocyte-endothelial interaction in vessels and tumor growth in the cranial window were substantially inhibited in mice with gallbladder tumors. The concentration of TGF-beta1 in the plasma of mice with gallbladder tumors was 300% higher than that in the plasma of mice without tumors or with subcutaneous tumors. In contrast, there was no difference in the plasma levels of other anti- and pro-angiogenic factors. Treatment with neutralizing antibody against TGF-beta1 reversed both angiogenesis suppression and inhibition of leukocyte rolling induced by gallbladder tumors. TGF-beta1 also inhibited Mz-ChA-2 tumor cell proliferation. Our results indicate that the production of anti-angiogenesis/proliferation factors is regulated by tumor-host interactions.

Angiostatin inhibits endothelial and melanoma cellular invasion by blocking matrix-enhanced plasminogen activation

Angiostatin, a kringle-containing fragment of plasminogen, is a potent inhibitor of angiogenesis. The mechanism(s) responsible for the anti-angiogenic properties of angiostatin are unknown. We now report that human angiostatin blocks plasmin(ogen)-enhanced in vitro invasion of tissue plasminogen activator (t-PA)-producing endothelial and melanoma cells. Kinetic analyses demonstrated that angiostatin functions as a non-competitive inhibitor of extracellular-matrix (ECM)-enhanced, t-PA-catalysed plasminogen activation, with a Ki of 0.9+/-0.03 microM. This mechanism suggests that t-PA has a binding site for the inhibitor angiostatin, as well as for its substrate plasminogen that, when occupied, prevents ternary complex formation between t-PA, plasminogen and matrix protein. Direct binding experiments confirmed that angiostatin bound to t-PA with an apparent Kd [Kd(app)] of 6.7+/-0.7 nM, but did not bind with high affinity to ECM proteins. Together, these data suggest that angiostatin in the cellular micro-environment can inhibit matrix-enhanced plasminogen activation, resulting in reduced invasive activity, and suggest a biochemical mechanism whereby angiostatin-mediated regulation of plasmin formation could influence cellular migration and invasion.

Potentiation of the antitumor effect of ionizing radiation by brief concomitant exposures to angiostatin

Angiostatin, a proteolytic fragment of plasminogen, inhibits the growth of primary and metastatic tumors by suppressing angiogenesis. When used in combination with ionizing radiation (IR), angiostatin demonstrates potent antitumor synergism, largely caused by inhibition of the tumor microvasculature. We report here the temporal interaction of angiostatin and IR in Lewis lung carcinoma (LLC) tumors growing in the hind limbs of syngeneic mice. Tumors with an initial mean volume of 510 +/- 151 mm3 were treated with IR alone (20 Gy x 2 doses on days 0 and 1), angiostatin alone (25 mg/kg/day divided twice daily) on days 0 through 13, or a combination of the two as follows: (a) IR plus angiostatin (days 0 through 13); (b) IR plus angiostatin (days 0 and 1); and (c) IR followed by angiostatin beginning on the day after IR completion and given daily thereafter (days 2 through 13). By day 14, tumors in untreated control mice had grown to 6110 +/- 582 mm3, whereas in mice treated with: (a) IR alone, tumors had grown to 2854 +/- 338 mm3 (P < 0.05 compared with untreated controls); and (b) angiostatin alone, tumors had grown to 3666 +/- 453 mm3 (P < 0.05 compared with untreated controls). In combined-treatment groups, in mice treated with: (a) IR plus longer-course angiostatin, tumors reached 2022 +/- 282 mm3 (P = 0.036 compared with IR alone); (b) IR followed by angiostatin, tumors reached 2677 +/- 469 mm3 (P > 0.05 compared with IR alone); and (c) IR plus short-course angiostatin, tumors reached 1032 +/- 78 mm3 (P < 0.001 compared with IR alone). These findings demonstrate that the efficacy of experimental radiation therapy is potentiated by brief concomitant exposure of the tumor vasculature to angiostatin.

Multiple forms of angiostatin induce apoptosis in endothelial cells

Angiostatin is a circulating inhibitor of angiogenesis generated by proteolytic cleavage of plasminogen. In this study we have used recombinant human and murine angiostatins (kringles 1-4) as well as native human angiostatin (prepared by elastase digestion of plasminogen [kringles 1-3] or by plasmin autocatalysis in the presence of a free sulfhydryl donor [kringles 1-4]). We report that angiostatin reduces endothelial cell number in a 4-day proliferation assay without affecting cell cycle progression into S-phase (as determined by bromodeoxyuridine labeling). This suggested that the reduction in cell number in the proliferation assay might in part be due to cytotoxicity. This was confirmed by the observation that ethidium homodimer incorporation (a measure of plasma membrane integrity) into endothelial cells was increased by angiostatin in a manner similar to that seen with tumor necrosis factor- (TNF-) and transforming growth factor-beta1 (TGF-beta1), both of which induce apoptosis in endothelial cells. In contrast to TNF- and TGF-beta1, angiostatin did not induce cytotoxicity in human MRC-5 fibroblast, rat smooth muscle, canine MDCK epithelial, or murine B16-F10 melanoma cell lines. Angiostatin-induced apoptosis was confirmed by endothelial cell nuclear acridine orange incorporation as well as by annexin V and TUNEL staining. These in vitro findings point to endothelial cell apoptosis as a mechanism for the antiangiogenic effect of angiostatin in vivo.

Nitric oxide--cyclic GMP pathway regulates vascular smooth muscle cell phenotypic modulation: implications in vascular diseases

The role of cGMP-dependent protein kinase (PKG) in the regulation of rat aortic vascular smooth muscle cells (VSMC) phenotype was examined using a transfected cell culture system. Repetitively passaged VSMC do not express PKG and exist in the synthetic phenotype. Transfection of PKG-l alpha cDNA, or the active catalytic domain of PKG-l alpha, resulted in the appearance of VSMC having a morphology consistent with the contractile phenotype. PKG-expressing cells also contained markers for the contractile phenotype (for example, smooth muscle specific myosin heavy chain, calponin, alpha-actin) and reduced levels of synthetic phenotype markers (osteopontin, thrombospondin). PKG-transfected VSMC have also reduced the levels of fibroblast growth factor receptors 1 and 2, consistent with the establishment of a more contractile phenotype. The regulation of PKG expression in VSMC is largely undefined; however, continuous exposure of cultured bovine aortic smooth muscle cells with nitric oxide (NO)-donor drugs or cyclic nucleotide analogues reduced the expression of PKG. These results suggest that PKG occupies a critical role in VSMC phenotype and that suppression of PKG expression during inflammation or injury promotes a more synthetic state of the VSMC.

Combined effects of angiostatin and ionizing radiation in antitumour therapy

Angiogenesis, the formation of new capillaries from pre-existing vessels, is essential for tumour progression. Angiostatin, a proteolytic fragment of plasminogen that was first isolated from the serum and urine of tumour-bearing mice, inhibits angiogenesis and thereby growth of primary and metastatic tumours. Radiotherapy is important in the treatment of many human cancers, but is often unsuccessful because of tumour cell radiation resistance. Here we combine radiation with angiostatin to target tumour vasculature that is genetically stable and therefore less likely to develop resistance. The results show an antitumour interaction between ionizing radiation and angiostatin for four distinct tumour types, at doses of radiation that are used in radiotherapy. The combination produced no increase in toxicity towards normal tissue. In vitro studies show that radiation and angiostatin have combined cytotoxic effects on endothelial cells, but not tumour cells. In vivo studies show that these agents, in combination, target the tumour vasculature. Our results provide support for combining ionizing radiation with angiostatin to improve tumour eradication without increasing deleterious effects.

Human angiostatin inhibits murine hemangioendothelioma tumor growth in vivo

Angiostatin inhibits angiogenesis and metastatic tumor growth; however, its usefulness in treating primary nonmetastasizing tumors is less well understood. We now report the effectiveness of human angiostatin administration in a mouse hemangioendothelioma model. Human angiostatin was administered to mice with s.c. hemangioendothelioma and associated disseminated intravascular coagulopathy (Kasabach-Merritt syndrome). Angiostatin significantly reduced tumor volume in comparison to nontreated controls, increased survival, and prevented the profound thrombocytopenia and anemia of Kasabach-Merritt syndrome. Apoptosis of tumor cells was induced by angiostatin, but tumor cell proliferation was not inhibited. These data suggest angiostatin as a novel treatment for nonmetastasizing vascular tumors and for Kasabach-Merritt syndrome.

Smooth muscle cell expression of type I cyclic GMP-dependent protein kinase is suppressed by continuous exposure to nitrovasodilators, theophylline, cyclic GMP, and cyclic AMP

A key component of the nitric oxide-cyclic guanosine monophosphate (cGMP) pathway in smooth muscle cells (SMC) is the type I GMP-dependent protein kinase (PK-G I). Activation of PK-G I mediates the reduction of cytoplasmic calcium concentrations and vasorelaxation. In this manuscript, we demonstrate that continuous exposure of SMC in culture to the nitrovasodilators S-nitroso-N-acetylpenicillamine (SNAP) or sodium nitroprusside (SNP) results in approximately 75% suppression of PK-G I mRNA by 48 h. PK-G I mRNA and protein were also suppressed by continuous exposure to cGMP analogues 8-bromo- and 8-(4-chlorophenylthio) guanosine-3,5-monophosphate or the cAMP analogue dibutyryl cAMP. These results suggest that activation of one or both of the cyclic nucleotide-dependent protein kinases mediates PK-G I mRNA suppression. Using isoform-specific cDNA probes, only the PK-G I alpha was detected in SMC, either at baseline or after suppression, while PK-G I beta was not detected, indicating that isoform switch was not contributing to the gene regulation. Using the transcription inhibitor actinomycin D, the PK-G I mRNA half-life in bovine SMC was observed to be 5 h. The half-life was not affected by the addition of SNAP to actinomycin D, indicating no effect on PK-G I mRNA stability. Nuclear runoff studies indicated a suppression of PK-G I gene transcription by SNAP. PK-G I suppression was also observed in vivo in rats given isosorbide dinitrate in the drinking water, with a dose-dependent suppression of PK-G I protein in the aorta. PK-G I antigen in whole rat lung extract was also suppressed by administration of isosorbide or theophylline in the drinking water. These data may contribute to our understanding of nitrovasodilator resistance, a phenomenon resulting from continuous exposure to nitroglycerin or other nitrovasodilators.

The mechanism of cancer-mediated conversion of plasminogen to the angiogenesis inhibitor angiostatin

Angiostatin, a potent naturally occurring inhibitor of angiogenesis and growth of tumor metastases, is generated by cancer-mediated proteolysis of plasminogen. Human prostate carcinoma cells (PC-3) release enzymatic activity that converts plasminogen to angiostatin. We have now identified two components released by PC-3 cells, urokinase (uPA) and free sulfhydryl donors (FSDs), that are sufficient for angiostatin generation. Furthermore, in a defined cell-free system, plasminogen activators [uPA, tissue-type plasminogen activator (tPA), or streptokinase], in combination with one of a series of FSDs (N-acetyl-L-cysteine, D-penicillamine, captopril, L-cysteine, or reduced glutathione] generate angiostatin from plasminogen. An essential role of plasmin catalytic activity for angiostatin generation was identified by using recombinant mutant plasminogens as substrates. The wild-type recombinant plasminogen was converted to angiostatin in the setting of uPA/FSD; however, a plasminogen activation site mutant and a catalytically inactive mutant failed to generate angiostatin. Cell-free derived angiostatin inhibited angiogenesis in vitro and in vivo and suppressed the growth of Lewis lung carcinoma metastases. These findings define a direct mechanism for cancer-cell-mediated angiostatin generation and permit large-scale production of bioactive angiostatin for investigation and potential therapeutic application.

Activated-protein-C resistance in cancer patients

BACKGROUND

Resistance to activated protein C (aPC) is usually linked to factor V Leiden, but may occur in other disorders associated with hypercoagulability. In this study, we investigated the frequency of resistance to aPC in patients with advanced cancer and examined the relationship of aPC resistance to other markers of coagulation activation.

METHODS

Patients (n = 39) had established diagnosis of advanced cancer; controls (n = 20) were healthy persons. aPC resistance was measured as the ratio of activated partial thromboplastin times with and without aPC (aPC-sensitivity ratio, aPC-SR). The factor V Leiden mutation was detected by a polymerase-chain-reaction based technique. Other assays were performed by standard laboratory methods. Data were analyzed using t tests and the Pearson correlation.

RESULTS

aPC-SR was below 2 SD for 5 of the cancer patients (13%), but none of the controls; only 1 of the 5 had the factor V Leiden mutation. aPC-SR was inversely correlated (p < 0.01) with factor VIII and fibrinogen in patients and with prothrombin activation fragment 1.2 (F1.2) in controls. Patient factor VIII, von Willebrand factor, (vWF), fibrinogen, F1.2 and D dimer were all significantly increased (p < 0.01; antithrombin III, protein C and proteins were similar to controls. Factor VIII correlated with vWF (p < 0.001) and F1.2 with d-dimer (p < 0.001). Other associations (p < 0.05) were observed between factor V and protein C, fibrinogen and protein C, factor V and antithrombin III and protein C and antithrombin III. Four cancer patients had a history of thromboembolism; their aPC-SR was similar to that of patients without thrombosis. Of the several coagulation measures examined, only vWF was higher in the patients with thrombosis (p = 0.01).

INTERPRETATION

Cancer patients have evidence of intravascular coagulation and increases in procoagulants and may have aPC resistance. The aPC resistance is not due to factor V Leiden, but is rather associated with elevated levels of factor VIII and fibrinogen, and in itself does not predict thrombosis.

Human prostate carcinoma cells express enzymatic activity that converts human plasminogen to the angiogenesis inhibitor, angiostatin

Angiostatin is an inhibitor of angiogenesis and metastatic growth that is found in tumor-bearing animals and can be generated in vitro by the proteolytic cleavage of plasminogen. The mechanism by which angiostatin is produced in vivo has not been defined. We now demonstrate that human prostate carcinoma cell lines (PC-3, DU-145, and LN-CaP) express enzymatic activity that can generate bioactive angiostatin from purified human plasminogen or plasmin. Affinity purified PC-3-derived angiostatin inhibited human endothelial cell proliferation, basic fibroblast growth factor-induced migration, endothelial cell tube formation, and basic fibroblast growth factor-induced corneal angiogenesis. Studies with proteinase inhibitors demonstrated that a serine proteinase is necessary for angiostatin generation. These data indicate that bioactive angiostatin can be generated directly by human prostate cancer cells and that serine proteinase activity is necessary for angiostatin generation.

Expression of plasminogen activator inhibitor type 1 by human prostate carcinoma cells inhibits primary tumor growth, tumor-associated angiogenesis, and metastasis to lung and liver in an athymic mouse model

Expression of urokinase-type plasminogen activator (uPA) by malignant cells correlates with an aggressive phenotype, including increased invasiveness, tumor-associated angiogenesis, and metastases. Plasminogen activator inhibitor type 1 (PAI-1) is undetectable in cells of some aggressive malignancies, but present in the stroma of tumor-associated microvasculature. This analysis of an athymic mouse model of prostate carcinoma further defines the role of the uPA/PAI-1/plasmin system in primary growth and metastasis. A marked increase in PAI-1 expression was induced in clones of the aggressive human prostate carcinoma line, PC-3, by stable transfection. Primary PC-3 tumors, in mice, were significantly smaller when derived from PAI-1 expressing versus control cells. PAI-1 expression reduced the density of tumor-associated microvasculature by 22-38%. Microscopic metastases were quantitated using stable expression of the chromogenic label (beta-galactosidase) in control and PAI-1 expressing cells. PAI-1 expression resulted in a significant inhibition of lung metastases, and liver metastases. Expression of PAI-1 by malignant prostate cells resulted in a less aggressive phenotype, presumably by inhibition of uPA activity, suggesting pharmacologic or molecular inhibition of uPA activity as a potential therapeutic target.

The potential role of basic fibroblast growth factor in the transformation of cultured primary human fetal astrocytes and the proliferation of human glioma (U-87) cells

Basic fibroblast growth factor (bFGF) is a potent stimulator of angiogenesis, proliferation, and invasion in human gliomas. To test the hypothesis that bFGF is important in the development of the malignant phenotype of human gliomas, bFGF expression was prospectively modulated in primary human fetal astrocytes and in an established human glioma cell line. Fetal astrocytes were transfected with a vector expressing bFGF modified by the addition of a secretory signal peptide sequence. Two of these bFGF astrocyte clones examined in vitro demonstrated anchorage-independent growth, loss of contact inhibition, and decreased glial fibrillary acidic protein immunoreactivity, changes consistent with cellular transformation. To analyze the inhibition of bFGF expression, phosphorothioated bFGF antisense oligodeoxynucleotides were added to cultures of the U-87 human glioma cell line. The U-87 cell proliferation was inhibited to 70.6 +/- 0.4% of control at 10 mumol/L and to 53.2 +/- 5.6% of control at 20 mumol/L (P < 0.05). Both the 7.0- and 4.0-kilobase bFGF messenger ribonucleic acid transcripts were reduced after exposure to the antisense oligodeoxynucleotide, and cell-associated bFGF protein was reduced by 44%. The sense oligodeoxynucleotide, a negative control, failed to inhibit U-87 proliferation. These data support the concept that bFGF expression could be a key event in glial tumorigenesis that may be necessary for the sustained growth of human gliomas.

cAMP influence on transcription of thrombomodulin is dependent on de novo synthesis of a protein intermediate: evidence for cohesive regulation of myogenic proteins in vascular smooth muscle

We have previously shown that cyclic adenosine monophosphate (cAMP) increases thrombomodulin (TM) mRNA and protein in vascular smooth muscle cells (VSMCs). The mechanism of that enhancement is now further defined. A time course evaluation of this effect by Northern blot analysis showed that exposure to the cAMP analog dibutyryl-cAMP and theophylline (CT) amplified TM mRNA sixfold by 3 hours. This effect was sustained through 9 hours and began to decline by 24 hours of CT exposure. In vitro exposure of VSMCs either to CT and actinomycin D or to actinomycin D alone showed equivalent half-lives for TM mRNA. This indicates that the increase in TM mRNA with CT supplementation was not the result of enhanced mRNA stability. Nuclear run-off analysis of VSMCs grown in the presence of control or CT-supplemented medium showed that the increase in TM mRNA in VSMCs with CT exposure was transcriptional. CT exposure was associated with an eightfold increase in measured TM transcription at 90 minutes. As previously reported, cAMP induced a decrease in tropomyosin and in alpha-actin mRNA species, a change that paralleled the enhancement of TM. Thus cAMP enhances transcription of this antithrombotic species while simultaneously causing diminished expression of these myogenic mRNA species. Addition of cycloheximide prevented the cAMP-mediated increase in TM mRNA and curtailed the down-regulation of myogenic mRNA species, alpha-actin, and tropomyosin. This suggests that the cAMP-mediated down-regulation of some smooth muscle-specific mRNA, including tropomyosin mRNA and alpha-actin mRNA, like the enhancement of TM transcription, is dependent on de novo protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of the expression of cyclic GMP-dependent protein kinase by cell density in vascular smooth muscle cells

Cyclic GMP-dependent protein kinase (cGMP kinase) is the major receptor protein for cGMP in vascular smooth muscle. Vascular smooth muscle cells (VSMC) isolated from the rat aorta express type I cGMP kinase at high levels, but expression decreases markedly upon passage of the cells. In primary or early passage, the expression of cGMP kinase is lowest when cells are plated at low density as assessed by immunological and Northern analyses. Expression increases at confluence and is maintained in postconfluent cultures. With repeated passaging, however, the levels of cGMP kinase decrease even in confluent and postconfluent cultures so that after several passages enzyme levels are undetectable. The decrease in expression in passaged cells is not due to exposure to serum-derived growth factors, but rather on the repeated exposure of cells to conditions in which cell density is reduced (i.e., subculturing). These results indicate that aortic VSMC grown at low density or those repetitively passaged have reduced expression of cGMP kinase, and thus may not represent appropriate cultures with which to investigate the role of nitric oxide and cGMP in VSMC function.

Autoantibody to von Willebrand factor in systemic lupus erythematosus

A 17-year old woman (patient 1) was found to have severe bleeding as the initial manifestation of systemic lupus erythematosus. Profound deficiencies of factor VIII coagulation activity (10%), von Willebrand factor (vWF) antigen (< 10%), and ristocetin cofactor (< 1%), and a disproportionate loss of large molecular weight multimers of vWF were observed. An antibody to vWF was suspected, and an enzyme-linked immunoadsorbent assay (ELISA) was devised to detect and quantify such antibody. The ELISA measured the binding of anti-vWF antibody from sample plasma to surface-bound vWF antigen. Binding was detected by a conjugate of alkaline phosphatase with affinity-purified anti-human immunoglobulin G, A, or M and a chromogenic substrate for alkaline phosphatase. Controls included plasma from normal subjects, from patients with von Willebrand's disease, and from a patient (patient 2) with type III von Willebrand's disease who had developed an inhibitor to vWF. Analysis of our patient's plasma revealed immunoglobulin G, A, and M anti-vWF antibodies. Preincubation of the plasma from patient 1 and patient 2 with pure vWF antigen completely inhibited antibody binding, confirming antibody specificity. These antibodies were quantitatively titered by determining the volume ratio of normal pooled plasma (a source of vWF antigen) to test plasma required to inhibit 50% of the antibody binding to immobilized vWF antigen. The value was 0.8 +/- 0.3 (mean +/- SD of three determinations) for the immunoglobulin G of our patient as compared with 15.6 +/- 2.9 for the immunoglobulin G of patient 2. The titers of the immunoglobulin A and M were less than 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of thrombomodulin by smooth muscle cells in culture: different effects of tumor necrosis factor and cyclic adenosine monophosphate on thrombomodulin expression by endothelial cells and smooth muscle cells in culture

Thrombomodulin (TM), a critical component of the protein C anticoagulant pathway, has previously been localized to endothelial cells (EC), but not smooth muscle cells (SMC) of the blood vessel wall. We demonstrate that cultured rat, bovine, as well as human SMC, but not blood vessel wall smooth muscle tissue, possess significant functional levels of TM and TM mRNA. Cyclic adenosine monophosphate stimulates TM expression in cultured SMC, but not EC, while tumor necrosis factor suppresses TM expression in EC but not cultured SMC. We postulate that following acute or chronic EC injury, luminal SMC can express TM, and are therefore able to protect the damaged blood vessel from thrombosis.

Thrombocytopenia associated with repletion of iron in iron-deficiency anemia

Two patients with iron deficiency experienced rapid decreases in their platelet levels following initiation of replacement therapy with oral ferrous sulfate or ferrous gluconate. The first patient, whose pretreatment platelet count was 168,000 per mm3, developed marked thrombocytopenia (platelet count, 21,000 per mm3) on the sixth day of iron repletion. The second patient's platelet level fell from 725,000 to 105,000 per mm3 on the tenth day of therapy. In both instances, platelet levels gradually returned to normal levels. The data suggest that the administration of oral iron resulted in an acute reduction in platelet production. The mechanism(s), prevalence, and clinical significance of thrombocytopenia following iron repletion in patients with iron deficiency anemia remain unknown.

Decline of proteins C and S and factors II, VII, IX and X during the initiation of warfarin therapy

Oral anticoagulants achieve an antithrombotic effect only several days after initiation of treatment. A rapid decline of the vitamin-K dependent natural anticoagulants (proteins C and S) during this period might result in a prothrombic phase. We addressed this question by measuring the rates of decline of these proteins, as well as the vitamin K dependent procoagulants, in two groups of patients: A "high dose group" (n = 7), who received a single 40 mg dose of warfarin, and a "low dose group" (n = 20), who received daily individually adjusted doses. In the high dose group an early and marked decline of factor VII:C and protein C antigen was observed, while levels of the other vitamin K dependent factors were still relatively high. In the low dose group, all these proteins declined more gradually. Mean +/- SD of protein C antigen level at 46 hr was 56 +/- 12% in the low dose group, and only 44 +/- 6% (p less than 0.05) in the high dose group. We conclude that during the initiation of warfarin therapy there is a transient prothrombotic phase, which is less marked in patients given daily adjusted doses.

Tocainide-induced reversible agranulocytosis and anemia

Tocainide is an effective oral antiarrhythmic agent. We report a 77-year-old man who developed agranulocytosis and anemia while receiving tocainide therapy. These hematologic abnormalities were detected on routine evaluation six weeks after beginning tocainide therapy. The absolute granulocyte count decreased to 50/mm3 (0.05 X 10(9)/L). The anemia was mild; hemoglobin count, 10.9 g/dL (109 g/L). These abnormalities were associated with local and stromal adipocytic bone marrow damage, and decreased production of red blood cells and granulocytes. The platelet count was not affected. The patient had no evidence of infection. Hematologic values were restored to normal two weeks after discontinuation of tocainide therapy, indicating that bone marrow toxicity of tocainide is reversible.

The von Willebrand factor in myocardial infarction and unstable angina: a kinetic study

Recent studies have demonstrated elevations of von Willebrand Factor following acute myocardial infarction (AMI). In order to determine if this parameter may serve as a marker for AMI, we tested the blood levels of vWF and Factor VIII:C in 28 patients with AMI, 9 patients with unstable angina, 7 patients with atypical chest pain, and 25 healthy volunteers. The level of ristocetin cofactor activity of vWF was between 70 and 144% in the control group. In patients with AMI, the mean level of this activity was 175% on the first day following infarction, rose to a peak of 270% on the fifth and sixth days, and was still significantly greater than normal in all patients on the 14th day. The vWF:Ag level closely paralleled the rise of ristocetin cofactor activity of vWF, with a peak of 336% on day 5. FVIII:C was not significantly changed. No significant elevation of vWF was observed in patients with unstable angina. The ristocetin cofactor activity of vWF and vWF:Ag thus are sensitive biochemical indicators for recent AMI, and may serve as useful markers for up to 14 days following infarction, when the traditional enzymes have returned to normal levels.

Protein C levels in nephrotic syndrome: use of a new enzyme-linked immunoadsorbent assay for protein C antigen

Activated protein C is a potent, physiologic anticoagulant that inactivates the activated forms of factors V and VIII as well as facilitates in vivo fibrinolysis. We developed a competitive protein-binding enzyme-linked immunoadsorbent assay (ELISA) for protein C that was utilized to investigate if the hypercoagulability of the nephrotic syndrome is related to a deficiency of circulating plasma protein C. Protein C was measured in plasma of 11 patients with nephrotic syndrome (24 hr protein 8.4 +/- 1.6 g, SEM; serum creatinine 4.2 +/- .74 mg/dl, SEM). Ten azotemic nonnephrotic patients were employed as controls (serum creatinine 6.0 +/- 1.25 mg/dl, SEM). No significant reduction of protein C values was observed (mean 108%, range 65-200%) in nephrotic patients when compared with the controls (mean 127%, range 100-200%) even though protein C antigen was present in all nephrotic urine samples tested. Also, no correlation existed between blood levels of urea nitrogen, creatinine, albumin, total protein, or 24-hr urine protein excretion and the observed protein C values. These results suggest that in patients with the nephrotic syndrome, a hypercoagulable state may not be related to a deficiency of protein C and that the level of this zymogen in nephrotic syndrome reflects a dynamic balance between urinary losses and systemic production.