Anti-C1s humanized monoclonal antibody SAR445088: A classical pathway complement inhibitor specific for the active form of C1s

The objective of this study was to characterize the complement-inhibiting activity of SAR445088, a novel monoclonal antibody specific for the active form of C1s. Wieslab® and hemolytic assays were used to demonstrate that SAR445088 is a potent, selective inhibitor of the classical pathway of complement. Specificity for the active form of C1s was confirmed in a ligand binding assay. Finally, TNT010 (a precursor to SAR445088) was assessed in vitro for its ability to inhibit complement activation associated with cold agglutinin disease (CAD). TNT010 inhibited C3b/iC3b deposition on human red blood cells incubated with CAD patient serum and decreased their subsequent phagocytosis by THP-1 cells. In summary, this study identifies SAR445088 as a potential therapeutic for the treatment of classical pathway-driven diseases and supports its continued assessment in clinical trials.

Specific Inhibition of the Classical Complement Pathway Prevents C3 Deposition along the Dermal-Epidermal Junction in Bullous Pemphigoid

Deposition of autoantibodies (α-BP180 and BP230) and complement along the dermal-epidermal-junction is a hallmark of bullous pemphigoid and was shown to be important for pathogenesis. Given the adverse effects of standard treatment (glucocorticoids, immunosuppressants), there is an unmet need for safe and effective therapies. In this phase 1 trial, we evaluated the safety and activity of BIVV009 (sutimlimab, previously TNT009), a targeted C1s inhibitor, in 10 subjects with active or past bullous pemphigoid (NCT02502903). Four weekly 60 mg/kg infusions of BIVV009 proved sufficient for inhibition of the classical complement pathway in all patients, as measured by CH50. C3c deposition along the dermal-epidermal junction was partially or completely abrogated in 4 of 5 patients, where it was present at baseline. BIVV009 was found to be safe and tolerable in this elderly population, with only mild to moderate adverse events reported (e.g., headache, fatigue). One serious adverse event (i.e., fatal cardiac decompensation) occurred at the end of the post-treatment observation period in an 84-year-old patient with a history of diabetes and heart failure, but was deemed unlikely to be related to the study drug. This trial provides the first results with a complement-targeting therapy in bullous pemphigoid, to our knowledge, and supports further studies on BIVV009's efficacy and safety in this population.

Effect of a C1s Inhibitor on the Efficacy of Anti-Capsular Antibodies against Neisseria meningitidis and Streptococcus pneumoniae

Terminal complement pathway inhibition at the level of C5 alleviates symptoms of several diseases associated with complement overactivation. However, C5 blockade is associated with an increased risk of invasive meningococcal disease despite immunization. Targeting specific complement pathways proximal to C5 provides the theoretical advantage of leaving the other pathways (including the terminal pathway) intact for immune surveillance. We aimed to address the risk of Neisseria meningitidis and Streptococcus pneumoniae infections when inhibiting the classical pathway (CP) using a specific C1s inhibitor (TNT005). Addition of TNT005 to 20% normal human serum that contained anti-meningococcal capsular Ab decreased C4 deposition 8-fold and abrogated killing of N. meningitidis, despite leaving C3 deposition intact. TNT005 impaired killing of N. meningitidis in 78% nonimmune human plasma and 78% whole blood but permitted killing in both when specific anti-capsular Ab was added. Simultaneously inhibiting both the CP and alternative pathway (AP) blocked killing of Ab-coated N. meningitidis in whole blood. Blocking the AP alone abrogated C3 deposition, whereas TNT005 only partially inhibited (∼40% decrease) C3 deposition on S. pneumoniae coated with anti-capsular Ab. Blocking either the CP or AP alone did not impair killing of pneumococci in whole blood containing specific Ab (<10% survival at 3 h); however, blocking both pathways resulted in ∼35% bacterial survival. These data suggest that killing of N. meningitidis or S. pneumoniae in whole blood containing specific anti-capsular Abs is unimpeded by TNT005. Meningococcal and pneumococcal capsular conjugate vaccines may mitigate risk of these infections in patients receiving C1s inhibitors.

C1s Inhibition by BIVV009 (Sutimlimab) Prevents Complement-Enhanced Activation of Autoimmune Human B Cells In Vitro

The classical pathway of complement (CP) can mediate C3 opsonization of Ags responsible for the costimulation and activation of cognate B lymphocytes. In this manner, the complement system acts as a bridge between the innate and adaptive immune systems critical for establishing a humoral response. However, aberrant complement activation is often observed in autoimmune diseases in which C3 deposition on self-antigens may serve to activate self-reactive B cell clones. In this study, we use BIVV009 (Sutimlimab), a clinical stage, humanized mAb that specifically inhibits the CP-specific serine protease C1s to evaluate the impact of upstream CP antagonism on activation and proliferation of normal and autoimmune human B cells. We report that BIVV009 significantly inhibited complement-mediated activation and proliferation of primary human B cells. Strikingly, CP antagonism suppressed human Ig-induced activation of B cells derived from patients with rheumatoid arthritis. These results suggest that clinical use of CP inhibitors in autoimmune patients may not only block complement-mediated tissue damage, but may also prevent the long-term activation of autoimmune B cells and the production of autoantibodies that contribute to the underlying pathologic condition of these diseases.

Anti-C1s monoclonal antibody BIVV009 in late antibody-mediated kidney allograft rejection-results from a first-in-patient phase 1 trial

The classical pathway (CP) of complement may contribute to the pathogenesis of antibody-mediated rejection (ABMR). Selective CP blockade may be a promising strategy to counteract rejection. The objective of this first-in-patient phase 1b trial was to evaluate the safety/tolerability and CP-blocking potential of 4 weekly doses (60 mg/kg) of the anti-C1s antibody BIVV009 in complement-mediated disorders. Here we describe the results in a cohort of 10 stable kidney transplant recipients (median of 4.3 years posttransplantation) with late active ABMR and features of CP activation, such as capillary C4d or complement-fixing donor-specific antibodies (DSA). During 7 weeks follow-up, no severe adverse events were reported, and BIVV009 profoundly inhibited overall and DSA-triggered CP activation in serum. Five of 8 C4d-positive recipients turned C4d-negative in 5-week follow-up biopsies, while another 2 recipients showed a substantial decrease in C4d scores. There was, however, no change in microcirculation inflammation, gene expression patterns, DSA levels, or kidney function. In conclusion, we demonstrate that BIVV009 effectively blocks alloantibody-triggered CP activation, even though short-course treatment had no effect on indices of activity in late ABMR. This initial trial provides a valuable basis for future studies designed to clarify the therapeutic value of CP blockade in transplantation. ClinicalTrials.gov NCT#02502903.

Uncoupling complement C1s activation from C1q binding in apoptotic cell phagocytosis and immunosuppressive capacity

Complement activation contributes to inflammation in many diseases, yet it also supports physiologic apoptotic cells (AC) clearance and its downstream immunosuppressive effects. The roles of individual complement components in AC phagocytosis have been difficult to dissect with artificially depleted sera. Using human in vitro systems and the novel antibody complement C1s inhibitor TNT003, we uncoupled the role of the enzymatic activation of the classical pathway from the opsonizing role of C1q in mediating a) the phagocytosis of early and late AC, and b) the immunosuppressive capacity of early AC. We found that C1s inhibition had a small impact on the physiologic clearance of early AC, leaving their immunosuppressive properties entirely unaffected, while mainly inhibiting the phagocytosis of late apoptotic/secondary necrotic cells. Our data suggest that C1s inhibition may represent a valuable therapeutic strategy to control classical pathway activation without causing significant AC accumulation in diseases without defects in AC phagocytosis.

An Anti-C1s Monoclonal, TNT003, Inhibits Complement Activation Induced by Antibodies Against HLA

Antibody-mediated rejection (AMR) of solid organ transplants (SOT) is characterized by damage triggered by donor-specific antibodies (DSA) binding donor Class I and II HLA (HLA-I and HLA-II) expressed on endothelial cells. While F(ab')2 portions of DSA cause cellular activation and proliferation, Fc regions activate the classical complement cascade, resulting in complement deposition and leukocyte recruitment, both hallmark features of AMR. We characterized the ability of an anti-C1s monoclonal antibody, TNT003, to inhibit HLA antibody (HLA-Ab)-induced complement activation. Complement deposition induced by HLA-Ab was evaluated using novel cell- and bead-based assays. Human aortic endothelial cells (HAEC) were cultured with HLA-Ab and human complement; production of activated complement proteins was measured by flow cytometry. Additionally, C3d deposition was measured on single antigen beads (SAB) mixed with HLA-Ab and human complement. TNT003 inhibited HLA-Ab mediated complement deposition on HAEC in a concentration-dependent manner; C3a, C4a and C5a anaphylatoxin production was also diminished by TNT003. Finally, TNT003 blocked C3d deposition induced by Class I (HLAI-Ab)- and Class II (HLAII-Ab)-specific antibodies on SAB. These data suggest TNT003 may be useful for modulating the effects of DSA, as TNT003 inhibits complement deposition and split product formation generated by HLA-I/II-Ab in vitro.

Inhibition of tumor cell migration by LD22-4, an N-terminal fragment of 24-kDa FGF2, is mediated by Neuropilin 1

LD22-4, an 86-amino acid fragment of the basic fibroblast growth factor, is an inhibitor of cell migration. LD22-4 inhibits the migration of various tumor cells, endothelial cells, and fibroblasts in vitro and suppresses tumor growth and angiogenesis in vivo. LD22-4 is effective in the presence of multiple growth factors, either alone or in combination, as well as haptotactic factors. LD22-4 inhibits the rate of malignant gliomas prepared from U87MG cells in an orthotopic mouse model by 90% compared with untreated mice. Using U87MG cells, we identified the LD22-4 membrane receptor as neuropilin 1 (NRP1). The identification of NRP1 as the LD22-4 receptor was based upon mass spectrometric analysis of proteins that bind to LD22-4, immunoprecipitation of an NRP1-LD22-4 complex formed during incubation of LD22-4 with U87MG cells, LD22-4-NRP1 coimmunoprecipitation studies, and binding of LD22-4 to HEK293 cells expressing NRP1. In contrast, NRP1 binding of an inactive mutant of LD22-4 was substantially reduced. As is typical of NRP1-binding proteins, LD22-4 itself binds to heparin and requires heparan sulfate for binding to cells. The addition of heparin to migration assays increased the inhibitory activity of LD22-4. In addition to a heparin-binding region, LD22-4 contains a 5-amino acid C-terminus that matches an NRP1 consensus binding sequence. Thus, direct binding experiments, dependence on heparan sulfate, and the presence of a NRP1 consensus binding sequence indicate that NRP1 is the binding site of LD22-4 and mediates inhibition of cell migration.

NF-κB Mediated Transcription in Human Monocytic Cells and Endothelial Cells

Monocytes and endothelial cells become activated at sites of inflammation and contribute to the pathology of many diseases, including septic shock and atherosclerosis. In these cells, induction of genes expressing various inflammatory mediators, such as adhesion molecules, cytokines, and growth factors, is regulated by NF-κB/Rel transcription factors. Recent studies have identified components of the signal transduction pathways leading to the activation of NF-κB/Rel proteins. Inhibition of these signaling pathways provides a novel therapeutic approach to prevent inducible gene expression in both monocytes and endothelial cells. (Trends Cardiovasc Med 1998;8:138-142). © 1998, Elsevier Science Inc.

Crystal structures of two human vitronectin, urokinase and urokinase receptor complexes

The urokinase receptor (uPAR) can recognize several ligands. The structural basis for this multiple ligand recognition by uPAR is unknown. This study reports the crystal structures of uPAR in complex with both urokinase (uPA) and vitronectin and reveal that uPA occupies the central cavity of the receptor, whereas vitronectin binds at the outer side of the receptor. These results provide a structural understanding of one receptor binding to two ligands.

A non-RGD-based integrin binding peptide (ATN-161) blocks breast cancer growth and metastasis in vivo

PURPOSE

Integrins are expressed by numerous tumor types including breast cancer, in which they play a crucial role in tumor growth and metastasis. In this study, we evaluated the ability of ATN-161 (Ac-PHSCN-NH2), a 5-mer capped peptide derived from the synergy region of fibronectin that binds to alpha5beta1 and alphavbeta3 in vitro, to block breast cancer growth and metastasis.

EXPERIMENTAL DESIGN

MDA-MB-231 human breast cancer cells were inoculated s.c. in the right flank, or cells transfected with green fluorescent protein (MDA-MB-231-GFP) were inoculated into the left ventricle of female BALB/c nu/nu mice, resulting in the development of skeletal metastasis. Animals were treated with vehicle alone or by i.v. infusion with ATN-161 (0.05-1 mg/kg thrice a week) for 10 weeks. Tumor volume was determined at weekly intervals and tumor metastasis was evaluated by X-ray, microcomputed tomography, and histology. Tumors were harvested for histologic evaluation.

RESULT

Treatment with ATN-161 caused a significant dose-dependent decrease in tumor volume and either completely blocked or caused a marked decrease in the incidence and number of skeletal as well as soft tissue metastases. This was confirmed histologically as well as radiographically using X-ray and microcomputed tomography. Treatment with ATN-161 resulted in a significant decrease in the expression of phosphorylated mitogen-activated protein kinase, microvessel density, and cell proliferation in tumors grown in vivo.

CONCLUSION

These studies show that ATN-161 can block breast cancer growth and metastasis, and provides a rationale for the clinical development of ATN-161 for the treatment of breast cancer.

Structure of human urokinase plasminogen activator in complex with its receptor

The urokinase plasminogen activator binds to its cellular receptor with high affinity and initiates signaling cascades that are implicated in pathological processes including tumor growth, metastasis, and inflammation. We report the crystal structure at 1.9 angstroms of the urokinase receptor complexed with the urokinase amino-terminal fragment and an antibody against the receptor. The three domains of urokinase receptor form a concave shape with a central cone-shaped cavity where the urokinase fragment inserts. The structure provides insight into the flexibility of the urokinase receptor that enables its interaction with a wide variety of ligands and a basis for the design of urokinase-urokinase receptor antagonists.

Targeting of urokinase plasminogen activator receptor in human pancreatic carcinoma cells inhibits c-Met- and insulin-like growth factor-I receptor-mediated migration and invasion and orthotopic tumor growth in mice

Pancreatic carcinomas express high levels of urokinase-type plasminogen activator (uPA) and its receptor (uPAR), both of which mediate cell migration and invasion. We investigated the hypotheses that (a) insulin-like growth factor-I (IGF-I)- and hepatocyte growth factor (HGF)-mediated migration and invasion of human pancreatic carcinoma cells require uPA and uPAR function and (b) inhibition of uPAR inhibits tumor growth, retroperitoneal invasion, and hepatic metastasis of human pancreatic carcinomas in mice. Using transwell assays, we investigated the effect of IGF-I and HGF on L3.6pl migration and invasion. We measured the induction of uPA and uPAR following treatment of cells with IGF-I and HGF using immunoprecipitation and Western blot analysis. The importance of uPA and uPAR on L3.6pl cell migration and invasion was studied by inhibiting their activities with amiloride and antibodies before cytokine treatment. In an orthotopic mouse model of human pancreatic carcinoma, we evaluated the effect of anti-uPAR monoclonal antibodies with and without gemcitabine on primary tumor growth, retroperitoneal invasion, and hepatic metastasis. IGF-I and HGF mediated cell migration and invasion in L3.6pl cells. In addition, IGF-I and HGF induced uPA and uPAR expression in L3.6pl cells. In vitro, blockade of uPA and uPAR activity inhibited IGF-I- and HGF-mediated cell migration and invasion. Treatment of mice with anti-uPAR monoclonal antibody significantly decreased pancreatic tumor growth and hepatic metastasis and completely inhibited retroperitoneal invasion. Our study shows the importance of the uPA/uPAR system in pancreatic carcinoma cell migration and invasion. These findings suggest that uPAR is a potential target for therapy in patients with pancreatic cancer.

Insulinlike growth factor-I-mediated migration and invasion of human colon carcinoma cells requires activation of c-Met and urokinase plasminogen activator receptor

OBJECTIVE

To determine whether insulinlike growth factor-I (IGF-I) and hepatocyte growth factor (HGF) cooperate to induce migration and invasion of human colorectal carcinoma (CRC) cells and whether the effects of IGF-I and/or HGF are mediated through activation of the urokinase plasminogen activator (uPA)/uPA receptor (uPAR) system, a central mediator of tumor-cell migration and invasion.

SUMMARY BACKGROUND DATA

CRC cells must invade through the basement membrane of the colon and migrate to form metastases. CRC cells are known to overexpress IGF-I receptor (IGF-IR), c-Met, and uPAR, 3 cell-surface receptors known to mediate cell migration and invasion. We hypothesized that IGF-IR and c-Met cooperate to induce migration and invasion in CRC cells and that this signaling is dependent on uPAR.

METHODS

KM12L4 human CRC cells were treated with IGF-I, HGF, or IGF-I + HGF in transwell migration and invasion chambers; cells that had migrated or invaded were counted. To determine the role of c-Met in IGF-I-induced migration and invasion, c-Met was inhibited by infection of cells with an adenovirus containing a c-Met ribozyme; transwell assays were then repeated. To determine the role of the uPA/uPAR system in IGF-I-induced CRC cell migration and invasion, transwell assays were repeated after pretreating cells with the uPA inhibitor amiloride or with neutralizing antibodies to uPA and uPAR.

RESULTS

IGF-I and HGF, alone or in combination, increased cell migration and invasion. The c-Met ribozyme inhibited IGF-I- and HGF-mediated migration and invasion, indicating that c-Met is essential for these processes. uPA and uPAR inhibition blocked IGF-I- and HGF-mediated migration and invasion, suggesting that uPAR is downstream of IGF/IGF-IR and HGF/c-Met in the signaling pathways that mediate cell migration and invasion.

CONCLUSIONS

IGF-I and HGF cooperate to induce migration and invasion of CRC cells, and c-Met and uPA/uPAR are required for IGF-I-mediated migration and invasion. In our in vitro model of CRC migration and invasion, uPA and uPAR appear to be downstream of IGF-IR and c-Met and are required for migration and invasion. Elucidation of the pathways that contribute to tumor progression and metastasis should provide a foundation for the rational development and use of targeted therapies for CRC.

Critical role of integrin alpha 5 beta 1 in urokinase (uPA)/urokinase receptor (uPAR, CD87) signaling

Urokinase-type plasminogen activator (uPA) induces cell adhesion and chemotactic movement. uPA signaling requires its binding to uPA receptor (uPAR/CD87), but how glycosylphosphatidylinositol-anchored uPAR mediates signaling is unclear. uPAR is a ligand for several integrins (e.g. alpha 5 beta 1) and supports cell-cell interaction by binding to integrins on apposing cells (in trans). We studied whether binding of uPAR to alpha 5 beta 1 in cis is involved in adhesion and migration of Chinese hamster ovary cells in response to immobilized uPA. This process was temperature-sensitive and required mitogen-activated protein kinase activation. Anti-uPAR antibody or depletion of uPAR blocked, whereas overexpression of uPAR enhanced, cell adhesion to uPA. Adhesion to uPA was also blocked by deletion of the growth factor domain (GFD) of uPA and by anti-GFD antibody, whereas neither the isolated uPA kringle nor serine protease domain supported adhesion directly. Interestingly, anti-alpha 5 antibody, RGD peptide, and function-blocking mutations in alpha 5 beta 1 blocked adhesion to uPA. uPA-induced cell migration also required GFD, uPAR, and alpha 5 beta 1, but alpha 5 beta 1 alone did not support uPA-induced adhesion and migration. Thus, binding of uPA causes uPAR to act as a ligand for alpha 5 beta 1 to induce cell adhesion, intracellular signaling, and cell migration. We demonstrated that uPA induced RGD-dependent binding of uPAR to alpha 5 beta 1 in solution. These results suggest that uPA-induced adhesion and migration of Chinese hamster ovary cells occurs as a consequence of (a) uPA binding to uPAR through GFD, (b) the subsequent binding of a uPA.uPAR complex to alpha 5 beta 1 via uPAR, and (c) signal transduction through alpha 5 beta 1.

Inhibition of integrin alpha5beta1 function with a small peptide (ATN-161) plus continuous 5-FU infusion reduces colorectal liver metastases and improves survival in mice

Integrin alpha(5)beta(1) is expressed on activated endothelial cells and plays a critical role in tumor angiogenesis. We hypothesized that a novel integrin alpha(5)beta(1) antagonist, ATN-161, would inhibit angiogenesis and growth of liver metastases in a murine model. We further hypothesized that combining ATN-161 with 5-fluorouracil (5-FU) chemotherapy would enhance the antineoplastic effect. Murine colon cancer cells (CT26) were injected into spleens of BALB/c mice to produce liver metastases. Four days thereafter, mice were given either ATN-161 (100 mg/kg, every 3rd day) or saline by intraperitoneal injection, with or without combination of continuous-infusion 5-FU (100 mg/kg/2 weeks), which was started on day 7. On day 20 after tumor cell inoculation, mice were killed and liver weights and number of liver metastases were determined. A follow-up study on survival was also conducted in which mice were randomized to receive ATN-161, 5-FU or ATN-161+5-FU. Combination therapy with ATN-161+5-FU significantly reduced tumor burden (liver weight) and number of liver metastases (p<0.02). Liver tumors in the ATN-161 and ATN-161+5-FU groups had significantly fewer microvessels (p<0.05) than tumors in the control or 5-FU-treated groups. Unlike treatment with either agent alone, ATN-161+5-FU significantly increased tumor cell apoptosis and decreased tumor cell proliferation (p<0.03) and improved overall survival (p<0.03, log-rank test). Targeting integrin alpha(5)beta(1) in combination with 5-FU infusion reduced liver metastases formation and improved survival in this colon cancer model. The enhancement of antineoplastic activity from the combination of anti-angiogenic therapy and chemotherapy may be a promising approach for treating metastatic colorectal cancer.

Histidine-proline-rich glycoprotein has potent antiangiogenic activity mediated through the histidine-proline-rich domain

Histidine-proline-rich glycoprotein (HPRG) is an abundant multidomain plasma protein evolutionarily related to high-molecular-weight kininogen. The cleaved form of high-molecular-weight kininogen has recently been demonstrated to exhibit antiangiogenic activities in vitro (J. C. Zhang et al., FASEB J., 14: 2589-2600, 2000), mediated primarily through domain 5. HPRG contains a histidine-proline-rich (H/P) domain with sequence and functional similarities to HKa-D5. We hypothesized that HPRG may also have antiangiogenic properties, localized within its H/P domain. The H/P domain is highly conserved among species, and because rabbit H/P domain is more resistant to internal proteolytic cleavage than the human domain, the rabbit HPRG (rbHPRG) was primarily used to assess the antiangiogenic activity of HPRG. Rabbit HPRG inhibited human umbilical vein endothelial cell (HUVEC) tube formation stimulated by fibroblast growth factor-2 (FGF-2) or vascular endothelial growth factor on a Matrigel surface as well as cell proliferation of FGF-2 stimulated HUVECs. The antiangiogenic activity of rbHPRG was localized to the H/P domain by use of proteolytic fragments of rbHPRG and was further confirmed and characterized in two in vivo models of angiogenesis: the chorioallantoic membrane of the chick assay and the mouse Matrigel plug assay. Caspase-3 activation was observed in HUVECs stimulated with FGF-2 in the presence of rbHPRG, suggesting that apoptosis of activated endothelial cells may be one of the mechanisms underlying its antiangiogenic activity. Finally, the H/P domain of rbHPRG reduced tumor cell number when tumor cells were co-inoculated in the Matrigel plug assay. In conclusion, the H/P domain within HPRG induces the apoptosis of activated endothelial cells leading to potent antiangiogenic effects.

Progressive and transient expression of tissue plasminogen activator during fetal development

In previous studies of the role of tissue plasminogen activator (tPA) in the lung inflammatory response, we observed that tPA expression was present exclusively in the small arteries and arterioles within the lung and absent from the capillaries, veins, and large pulmonary arteries. To define more completely the expression pattern of tPA, we evaluated the distribution of this protein during prenatal and postnatal development. tPA was first observed in the rat fetus at day 13 in the large arteries of both the thoracic and cranial cavities, including the dorsal aortas and pulmonary arteries in the former and the internal carotid and middle cerebral arteries in the latter. By day 15, tPA was no longer detectable in the aortas but appeared throughout the pulmonary, subclavian, vertebral, and basilar arteries. At day 17, tPA had disappeared from the subclavian artery and the proximal portion of the vertebral artery but was found in the smaller arterial branches of these 2 large vessels. By the end of gestation, tPA had also disappeared from the main pulmonary arteries but remained in the branches at the hilus of the lung. At birth, tPA was concentrated in the endothelia of arteries within the pia mater, the basilar and superficial cerebral arteries, and the lung arterial system. As the animals reached maturity, tPA disappeared from the larger cerebral arteries and their cortical branches but continued to be expressed in the vessels of the pia mater and lung. This study indicates that tPA expression is a dynamic process that responds to a changing arterial environment during vascular development.

Mouse embryogenesis requires the tissue factor extracellular domain but not the cytoplasmic domain

Recent studies indicate that tissue factor (TF) acts in embryogenesis, metastasis, and angiogenesis. Three independent groups showed that targeted disruption of the murine TF (mTF) gene results in 90% lethality of mTF null embryos at embryonic days 9. 5-10.5. We have demonstrated that expression of wild-type human TF (hTF) from a minigene rescues the embryonic lethality of mTF null embryos. To investigate the role of TF in embryogenesis, we made mutant hTF minigenes whose products either bound FVII/VIIa at a reduced level or lacked the cytoplasmic domain. Two independent transgenic lines expressing the hTF extracellular domain mutant failed to rescue the embryonic lethality of mTF null embryos, suggesting that FVII/VIIa binding by TF, proteolytic activity by the TF/FVIIa complex, or both were required for embryogenesis. In contrast, two transgenic lines expressing the hTF cytoplasmic domain mutant rescued the embryonic lethality of mTF null embryos, indicating that the cytoplasmic domain of TF was not required for embryogenesis. We propose that TF/FVIIa-dependent extracellular protease activity is required for embryogenesis.

Tissue factor is required for uterine hemostasis and maintenance of the placental labyrinth during gestation

We employed a novel mouse line that expresses low levels of human tissue factor (TF) in the absence of murine TF to analyze the role of TF in gestation. Low-TF female mice had a 14-18% incidence of fatal postpartum uterine hemorrhage, suggesting that TF plays an important role in uterine hemostasis. Low-TF female mice mated with low-TF male mice had a 42% incidence of fatal midgestational hemorrhage (n = 41), whereas no fatal midgestational hemorrhages were observed in low-TF female mice mated with wild-type male mice (n = 43). Placentas of low-TF embryos from both low-TF and normal (+/-) TF females were abnormal and contained numerous maternal blood pools in the labyrinth. Placentas of TF null embryos surviving beyond embryonic day 10.5 exhibited similar defects. The mouse maternal-embryonic placental barrier consists of four cellular layers (layers I, II, and III and endothelial cells), where layer I lines the maternal lacunae. Comparison of TF-deficient placentas with control placentas by immunohistochemical and ultrastructural analyses revealed thinning of layer I and a reduction in the number of cellular contacts of layer I trophoblasts spanning the maternal blood space between adjacent trabeculae. These structural changes in low-TF and TF null placentas result in enlarged maternal lacunae, as determined by morphometric analysis, and placental hemorrhage, which leads to midgestational death of low-TF female mice. This study demonstrated that TF is required for uterine hemostasis and revealed an unexpected role of TF in the maintenance of the placental labyrinth.

Regulation of an essential innate immune response by the p50 subunit of NF-kappaB

Recognition of bacterial endotoxin (LPS) elicits multiple host responses, including activation of cells of the innate immune system. LPS exposure occurs repeatedly during septicemia, making strict regulation of gene expression necessary. Such regulation might prevent, for example, the continuous production of proinflammatory cytokines such as tumor necrosis factor (TNF), which could lead to severe vascular collapse. Tolerance to LPS is characterized by a diminished production of TNF during prolonged exposure to LPS, and is therefore likely to represent an essential control mechanism during sepsis. In the present study, which uses mice with genetic deletions of the proteins of NF-kappaB complex, we provide data demonstrating that increased expression of the p50 subunit of NF-kappaB directly results in the downregulation of LPS-induced TNF production. This contention is supported by the following observations: (1) tolerance to LPS is not induced in macrophages from p50-/- mice; (2) long-term pretreatment with LPS does not block synthesis of TNF mRNA in p50-/- macrophages (in contrast to wild-type macrophages); (3) ectopic overexpression of p50 reduces transcriptional activation of the murine TNF promoter; and (4) analysis of the four kappaB sites from the murine TNF promoter demonstrates that binding of p50 homodimers to the positively acting kappaB3 element is associated with development of the LPS-tolerant phenotype. Thus, p50 expression plays a key role in the development of LPS tolerance.

PRAK, a novel protein kinase regulated by the p38 MAP kinase

We have identified and cloned a novel serine/ threonine kinase, p38-regulated/activated protein kinase (PRAK). PRAK is a 471 amino acid protein with 20-30% sequence identity to the known MAP kinase-regulated protein kinases RSK1/2/3, MNK1/2 and MAPKAP-K2/3. PRAK was found to be expressed in all human tissues and cell lines examined. In HeLa cells, PRAK was activated in response to cellular stress and proinflammatory cytokines. PRAK activity was regulated by p38alpha and p38beta both in vitro and in vivo and Thr182 was shown to be the regulatory phosphorylation site. Activated PRAK in turn phosphorylated small heat shock protein 27 (HSP27) at the physiologically relevant sites. An in-gel kinase assay demonstrated that PRAK is a major stress-activated kinase that can phosphorylate small heat shock protein, suggesting a potential role for PRAK in mediating stress-induced HSP27 phosphorylation in vivo.

PRAK, a novel protein kinase regulated by the p38 MAP kinase

We have identified and cloned a novel serine/ threonine kinase, p38-regulated/activated protein kinase (PRAK). PRAK is a 471 amino acid protein with 20-30% sequence identity to the known MAP kinase-regulated protein kinases RSK1/2/3, MNK1/2 and MAPKAP-K2/3. PRAK was found to be expressed in all human tissues and cell lines examined. In HeLa cells, PRAK was activated in response to cellular stress and proinflammatory cytokines. PRAK activity was regulated by p38alpha and p38beta both in vitro and in vivo and Thr182 was shown to be the regulatory phosphorylation site. Activated PRAK in turn phosphorylated small heat shock protein 27 (HSP27) at the physiologically relevant sites. An in-gel kinase assay demonstrated that PRAK is a major stress-activated kinase that can phosphorylate small heat shock protein, suggesting a potential role for PRAK in mediating stress-induced HSP27 phosphorylation in vivo.

IL-1beta-induced monocyte chemoattractant protein-1 gene expression in endothelial cells is blocked by proteasome inhibitors

Human monocyte chemoattractant protein-1 (MCP-1) is expressed by a variety of cell types in response to various stimuli. MCP-1 expressed by the endothelium plays an important role in cell migration and activation. MCP-1 is a major chemoattractant for monocytes, T lymphocytes, and basophils. In the present study, we present evidence that the proteasome complex is involved in mediating the interleukin (IL)-1beta induction of MCP-1 in endothelial cells. We present evidence that a proteasome inhibitor, N-acetyl-leucinyl-leucinyl-norleucinal (norLeu), and the protease inhibitor tosyl-Phe-chloromethylketone (TPCK) block IL-1beta induction of MCP-1 protein expression. norLeu and TPCK also blocked IL-1beta-induced MCP-1 promoter-driven reporter gene expression as well as nuclear factor (NF)-kappaB-mediated reporter gene expression. The effects of norLeu were due to its inhibition of the proteasome rather than calpain, because other calpain inhibitors had no effect on MCP-1 expression. In contrast to TPCK, which blocked NF-kappaB translocation to the nucleus, norLeu had no effect on NF-kappaB nuclear translocation or IL-1beta-induced phosphorylation of p65. This study demonstrates that the proteasome pathway is involved in IL-1beta-induced MCP-1 gene expression in human endothelial cells.

Low levels of tissue factor are compatible with development and hemostasis in mice

Tissue factor (TF) expression is associated with life-threatening thrombosis in a variety of human diseases, including sepsis, cancer, and atherosclerosis. Recently, it was shown that inactivation of the murine TF (mTF) gene results in embryonic lethality. To date, despite extensive studies on the regulation of the TF promoter in vitro, no studies have examined the cis-acting regulatory elements that control TF gene expression in vivo. Here we report that a human TF (hTF) minigene containing the human TF promoter and human TF cDNA directed a low level (approximately 1% relative to mouse TF) of both constitutive and LPS-inducible human TF expression in transgenic mice. Importantly, the human TF minigene rescued the embryonic lethality of murine TF null embryos, suggesting that human TF substituted for murine TF during embryogenesis. Rescued mice (mTF-/-, hTF+), which expressed low levels (approximately 1%) of TF activity, developed normally with no signs of a bleeding diathesis, suggesting that low TF expression can maintain hemostasis compatible with normal survival. These studies establish a novel mouse model system that can be used to examine the regulation of the human TF gene in vivo and the impact of low TF levels on the hemostatic balance in various thrombotic diseases.

Role of cyclic AMP response element-binding protein in cyclic AMP inhibition of NF-kappaB-mediated transcription

The NF-kappaB family of transcription factors regulates the inducible expression of a variety of genes. Recently, we showed that elevation of intracellular cyclic AMP inhibits NF-kappaB-mediated transcription in human monocytes and endothelial cells without preventing nuclear translocation of NF-kappaB complexes. The present study examined the molecular mechanism of this inhibition. We hypothesized that activation of the protein kinase A signaling pathway may inhibit NF-kappaB-mediated transcription by phosphorylating proteins, such as cAMP response element-binding protein (CREB), which compete for limiting amounts of the coactivator CBP. Here, we show that the amino-terminal region (amino acids 1-450) of CBP specifically interacts with the carboxyl-terminal region (amino acids 286-551) of NF-kappaB p65 (RelA) both in vitro and in vivo. Functional studies using human endothelial cells demonstrated that overexpression of CBP rescued cAMP inhibition of NF-kappaB-mediated transcription and transcription mediated by a chimeric protein, GAL4-p65(286-551), which contained the GAL4 DNA binding domain fused to the carboxyl-terminal region of p65 (amino acids 286-551). In contrast, overexpression of CREB inhibited GAL4-p65(286-551)-mediated transcription. These results suggest that activation of the protein kinase A pathway inhibits NF-kappaB transcription by phosphorylating CREB, which competes with p65 for limiting amounts of CBP.

Role of cyclic AMP response element-binding protein in cyclic AMP inhibition of NF-kappaB-mediated transcription

The NF-kappaB family of transcription factors regulates the inducible expression of a variety of genes. Recently, we showed that elevation of intracellular cyclic AMP inhibits NF-kappaB-mediated transcription in human monocytes and endothelial cells without preventing nuclear translocation of NF-kappaB complexes. The present study examined the molecular mechanism of this inhibition. We hypothesized that activation of the protein kinase A signaling pathway may inhibit NF-kappaB-mediated transcription by phosphorylating proteins, such as cAMP response element-binding protein (CREB), which compete for limiting amounts of the coactivator CBP. Here, we show that the amino-terminal region (amino acids 1-450) of CBP specifically interacts with the carboxyl-terminal region (amino acids 286-551) of NF-kappaB p65 (RelA) both in vitro and in vivo. Functional studies using human endothelial cells demonstrated that overexpression of CBP rescued cAMP inhibition of NF-kappaB-mediated transcription and transcription mediated by a chimeric protein, GAL4-p65(286-551), which contained the GAL4 DNA binding domain fused to the carboxyl-terminal region of p65 (amino acids 286-551). In contrast, overexpression of CREB inhibited GAL4-p65(286-551)-mediated transcription. These results suggest that activation of the protein kinase A pathway inhibits NF-kappaB transcription by phosphorylating CREB, which competes with p65 for limiting amounts of CBP.

Cytokine induction of monocyte chemoattractant protein-1 gene expression in human endothelial cells depends on the cooperative action of NF-kappa B and AP-1

Chemokines are potent mediators of cell migration and activation and therefore play an essential role in early events of inflammation. In conjunction with cell adhesion molecules, chemokines help to localize cells to a specific site and enhance the inflammatory reaction at the site. Clinically, elevated levels of chemokines have been found in a variety of inflammatory diseases. The prototype C-C chemokine is monocyte chemoattractant protein-1 (MCP-1) which is synthesized by variety of cell types including endothelial cells in response to a variety of stimuli. MCP-1 is a major chemoattractant for monocytes, T lymphocytes, and basophils. In the present study, we investigated the factors involved in cytokine-induced MCP-1 gene expression in human endothelial cells. We present evidence that the nuclear factor (NF)-kappa B-like binding site and the AP-1 binding site located 90 and 68 base pairs upstream of the transcriptional start site, respectively, are required for maximal induction of the human MCP-1 promoter by interleukin-(IL)-1 beta. Site-directed mutagenesis or deletion of the NF-kappa B-like site decreased the cytokine-induced activity of the promoter. Site-directed mutagenesis of the AP-1 binding site also decreased the cytokine-induced activity of the promoter. We show that the NF-kappa B-like site located at-90 in the MCP-1 promoter binds to the p50/p65 heterodimer of the NF-kappa B/Rel family in IL-1 beta-stimulated human endothelial cells. Overexpression of p65 results in the transactivation of the MCP-1 promoter as well. The data presented in this study suggest that cytokine-induced MCP-1 gene expression in human endothelial cells depends on the cooperative action of NF-kappa B and AP-1.

Inhibition of 5-lipoxygenase blocks IL-1 beta-induced vascular adhesion molecule-1 gene expression in human endothelial cells

Inflammation is characterized by the recruitment of leukocytes and their subsequent migration from the vasculature into the tissue, where they often cause severe damage. Endothelial cells play a major role in this cascade by expressing cell surface adhesion molecules, such as VCAM-1 and ICAM-1, and chemokines, in response to cytokines. Many of these genes are under the control of inflammatory response transcription factors such as nuclear factor (NF)-kappa B. In this study, we examined the effects of 5-lipoxygenase inhibitors (nordihydroguaiaretic acid and AA861) on IL-1 beta-induced VCAM-1 gene expression in HUVECs. We demonstrated that 5-lipoxygenase inhibitors, but not cyclooxygenase inhibitors, block IL-1 beta-induced VCAM-1 cell surface expression and promoter activity. In transiently transfected HUVECs, NF-kappa B-dependent gene expression was inhibited by 5-lipoxygenase inhibitors. These inhibitors did not block IL-1 beta-induced nuclear translocation of NF-kappa B, inhibitor of kappa B-alpha proteolytic degradation, or significantly reduce phosphorylation of p65. These studies indicate that inhibition of 5-lipoxygenase blocks cytokine-induced VCAM-1 gene expression by reducing the functional activity of NF-kappa B/Rel proteins in HUVECs.

Inhibition of 5-lipoxygenase blocks IL-1 beta-induced vascular adhesion molecule-1 gene expression in human endothelial cells

Inflammation is characterized by the recruitment of leukocytes and their subsequent migration from the vasculature into the tissue, where they often cause severe damage. Endothelial cells play a major role in this cascade by expressing cell surface adhesion molecules, such as VCAM-1 and ICAM-1, and chemokines, in response to cytokines. Many of these genes are under the control of inflammatory response transcription factors such as nuclear factor (NF)-kappa B. In this study, we examined the effects of 5-lipoxygenase inhibitors (nordihydroguaiaretic acid and AA861) on IL-1 beta-induced VCAM-1 gene expression in HUVECs. We demonstrated that 5-lipoxygenase inhibitors, but not cyclooxygenase inhibitors, block IL-1 beta-induced VCAM-1 cell surface expression and promoter activity. In transiently transfected HUVECs, NF-kappa B-dependent gene expression was inhibited by 5-lipoxygenase inhibitors. These inhibitors did not block IL-1 beta-induced nuclear translocation of NF-kappa B, inhibitor of kappa B-alpha proteolytic degradation, or significantly reduce phosphorylation of p65. These studies indicate that inhibition of 5-lipoxygenase blocks cytokine-induced VCAM-1 gene expression by reducing the functional activity of NF-kappa B/Rel proteins in HUVECs.

Shear stress induction of the tissue factor gene

Using flow channel, we report that the application of a laminar shear stress induced a transient increase of tissue factor (TF) procoagulant activity in human umbilical vein endothelial cells (HUVEC), which was accompanied by a rapid and transient induction of the TF mRNA in the HUVEC. Functional analysis of the 2.2 kb TF 5' promoter indicated that a GC-rich region containing three copies each of the EGR-1 and Sp1 sites was required for induction. Mutation of the Sp1 sites, but not the EGR-1 sites, attenuated the response of TF promoter to shear stress. Thus, Sp1 is a newly defined shear stress responsive element. Electrophoretic mobility shift assays showed there was no increase in binding of nuclear extracts from sheared cells to an Sp1 consensus site. In contrast, immunoblotting of these nuclear extracts with antibody against transcription factor Sp1 demonstrated that shear stress increased the phosphorylation of Sp1. We also showed that shear stress, like the phosphatase inhibitor okadaic acid, increased the transcriptional activity of Sp1. These findings suggest that the shear stress induction of TF gene expression is mediated through an increased Sp1 transcriptional activity with a concomitant hyperphosphorylation of Sp1.

Regulation of the tissue factor gene in human monocytic cells. Role of AP-1, NF-kappa B/Rel, and Sp1 proteins in uninduced and lipopolysaccharide-induced expression

Tissue factor (TF) expression by peripheral blood monocytes during sepsis initiates intravascular thrombosis. Bacterial lipopolysaccharide (LPS) rapidly induces TF gene transcription in monocytes. The human TF promoter contains binding sites for the transcription factors AP-1, c-Rel/p65, Egr-1, and Sp1. NF-kappa B/Rel proteins have been shown to physically interact with both AP-1 and Sp1 proteins. In this study, we investigated the role of these transcription factors in uninduced and LPS-induced TF gene expression in human monocytic THP-1 cells. Deletional analysis indicated that five Sp1 sites mediated basal expression in uninduced cells. The two AP-1 sites bound c-Fos/c-Jun heterodimers in both unstimulated and LPS-stimulated cells. Maximal LPS induction of the TF promoter required the two AP-1 sites and the kappa B site within the LPS response element. Disruption of the conserved spacing between the proximal AP-1 site and the kappa B site abolished LPS induction. Replacement of the two AP-1 sites with intrinsically bent DNA partially restored LPS induction, suggesting an additional structural role for the AP-1 sites. Synergistic transactivation of the LPS response element in Drosophila Schneider cells by coexpression of c-Fos, c-Jun, c-Rel, and p65 or c-Jun and p65 required the transactivation domains of c-Jun and p65. These data indicated that c-Fos/c-Jun, c-Rel/p65, and Sp1 regulate TF gene expression in human monocytic cells.

Requirement of receptor-bound urokinase-type plasminogen activator for integrin alphavbeta5-directed cell migration

The urokinase plasminogen activator (uPA) interacts with its cell surface receptor (uPAR), providing an inducible, localized cell surface proteolytic activity, thereby promoting cellular invasion. Evidence is provided for a novel function of cell surface-associated uPA.uPAR. Specifically, induction of cell surface expression of uPA. uPAR by growth factors or phorbol ester was necessary for vitronectin-dependent carcinoma cell migration, an event mediated by integrin alphavbeta5. Cell migration on vitronectin was blocked with either a soluble form of uPAR, an antibody that disrupts uPA binding to uPAR, or a monoclonal antibody to alphavbeta5. Moreover, plasminogen activator inhibitor type 2 blocked this migration event but did not affect adhesion, suggesting a direct role for uPA enzyme activity in this process and that migration but not adhesion of these cells is regulated by uPA.uPAR. Growth factor-mediated induction of uPA.uPAR on the carcinoma cell surface promotes a specific motility event mediated by integrin alphavbeta5, since cells transfected with the beta3 integrin subunit expressed alphavbeta3 and migrated on vitronectin independently of growth factors or uPA.uPAR expression. This relationship between alphavbeta5 and the uPA.uPAR system has significant implications for regulation of motility events associated with development, angiogenesis, and tumor metastasis.

Elevated cyclic AMP inhibits NF-kappaB-mediated transcription in human monocytic cells and endothelial cells

The NF-kappaB/Rel family of transcription factors regulates the inducible expression of many genes in activated human monocytes and endothelial cells. In this study, we examined the molecular mechanism by which agents that elevate intracellular cAMP inhibit the expression of the tumor necrosis factor alpha (TNFalpha), tissue factor, endothelial leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1 genes. Both forskolin and dibutyryl cAMP, which elevate intracellular cAMP by independent mechanisms, inhibited TNFalpha and tissue factor expression at the level of transcription. Induction of NF-kappaB-dependent gene expression in transiently transfected human monocytic THP-1 cells and human umbilical vein endothelial cells was inhibited by elevated cAMP and by overexpression of the catalytic subunit of protein kinase A (PKA). Elevated cAMP did not prevent nuclear translocation of p50/p65 and c-Rel/p65 heterodimers, decrease nuclear translocation of p65, or significantly modify TNFalpha-induced phosphorylation of p65. Functional studies demonstrated that transcriptional activation of a plasmid containing multimerized kappaB sites by p65 was inhibited by agents that elevate cAMP and by overexpression of the catalytic subunit of PKA. This study indicates that activation of PKA reduces the induction of a distinct set of genes in monocytes and endothelial cells by inhibiting NF-kappaB-mediated transcription.

D609, a phosphatidylcholine-specific phospholipase C inhibitor, blocks interleukin-1 beta-induced vascular cell adhesion molecule 1 gene expression in human endothelial cells

At sites of inflammation, endothelial cells play a major role in defining the types of leukocytes that are recruited to a specific area. This is accomplished, at least in part, through the cytokine induction of cell surface adhesion molecules, including vascular cell adhesion molecule 1 (VCAM-1). We investigated the role of phosphatidylcholine-specific phospholipase C in the induction of VCAM-1 gene expression by interleukin-1 beta. D609, a phosphatidylcholine-specific phospholipase C inhibitor, reduced VCAM-1 cell surface expression and VCAM-1 promoter activity in human endothelial cells in a dose-dependent manner. D609 did not affect nuclear translocation of nuclear factor-kappa B but inhibited nuclear factor-kappa B-mediated transcription. The results of this study indicate that phosphatidylcholine-specific phospholipase C is required for activation of nuclear factor-kappa B and cytokine induction of VCAM-1 gene expression in endothelial cells.

Proteasome inhibitors block VCAM-1 and ICAM-1 gene expression in endothelial cells without affecting nuclear translocation of nuclear factor-kappa B

Endothelial cells play a major role in recruiting leukocytes to sites of inflammation. This is accomplished, at least in part, by up-regulation of cell surface adhesion molecules, including VCAM-1 and ICAM-1, in response to cytokines. In this report, we investigated the role of the proteasome complex in mediating the interleukin (IL)- 1 beta induction of VCAM-1 and ICAM-1 gene expression in human endothelial cells. We present evidence that a proteasome inhibitor, n-acetyl-leucinyl-leucinyl-norleucinal (norLEU), as well as specific protease inhibitors, n-tosyl-Lys-chloromethylketone and N-tosyl-Phe-chloromethylketone, blocked IL-1 beta induction of VCAM-1 and ICAM-1 promoter-driven reporter gene expression in stably transfected endothelial cells. These inhibitors also blocked cytokine induced cell surface expression of VCAM-1 and ICAM-1 by human umbilical vein endothelial cells. As expected, the protease inhibitors blocked the activation of nuclear factor (NF)-kappa B in response to IL-1 beta stimulation. In contrast, norLEU did not prevent IL-1 beta-induced nuclear translocation of NF-kappa B. The effects of norLEU were specific because it did not inhibit the IL-1 beta induction of plasminogen activator inhibitor type 1 gene expression. This study demonstrates that inhibition of the proteolytic activity of the proteasome blocks IL-1 beta induction of VCAM-1 and ICAM-1 gene expression in human endothelial cells.

A benzothiophene-carboxamide is a potent inhibitor of IL-1beta induced VCAM-1 gene expression in human endothelial cells

Vascular endothelial cells respond to cytokines such as IL-1 beta or TNF-alpha by undergoing a number of functional alterations. Among these alterations is the induction of cell surface adhesion molecules, including VCAM-1. In this report, we investigated the effects of a 3-alkoxybenzo[beta]thiophene-2-carboxamide (BZT) on the cytokine induction of VCAM-1 expression and activation of the transcription factor NF-kappa B in human endothelial cells. BZT blocked the IL-1 beta induced cell surface expression of VCAM-1 in human endothelial cells but did not prevent nuclear translocation of NF-kappa B. This study demonstrates that BZT is a potent inhibitor of VCAM-1 expression in human endothelial cells.

Transcriptional regulation of the tissue factor gene in human epithelial cells is mediated by Sp1 and EGR-1

Tissue factor (TF) gene expression is rapidly induced in epithelial cells by phorbol 12-myristate 13-acetate and serum. We have shown that this induction is mediated by a novel serum response region (SRR) (-111 to +14 bp) within the human TF promoter. In this study, we characterized cis-acting genetic elements within the SRR that regulated basal and inducible expression of the TF gene in HeLa cells. Gel mobility shift assays using oligonucleotides spanning the entire SRR identified three 12-base pair (bp) motifs within subregions 1, 2, and 3 that bound constitutively expressed Sp1 and inducibly expressed EGR-1. Analysis of protein binding to these 12-bp motifs by competition with Sp1 and EGR-1 sites, mutation, and antibody supershift experiments indicated that they each contained distinct EGR-1 and Sp1 sites that overlapped by 6 bp. Functional studies using HeLa cells transfected with plasmids containing the wild-type TF promoter (-111 to +14 bp) or derivatives containing mutations in the three Sp1 and/or EGR-1 sites examined basal and inducible expression. The Sp1 sites mediated basal promoter activity, and both Sp1 and EGR-1 sites were required for maximal induction of the TF promoter by phorbol 12-myristate 13-acetate or serum. These data indicated that TF gene expression in HeLa cells was regulated by both Sp1 and EGR-1.

Transcriptional regulation of tissue factor expression in human endothelial cells

Tissue factor (TF) expression by endothelial cells is implicated in thrombotic episodes in patients with a variety of clinical disorders. In a baboon model of lethal sepsis, TF is expressed by endothelial cells in the splenic microvasculature. In vitro, endothelial cells are induced to express TF in response to tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and bacterial endotoxin (lipopolysaccharide [LPS]). Here, we identified cis-acting regulatory elements that control TF gene transcription in primary human endothelial cells. Functional studies showed that the TF promoter contained a 56-bp enhancer (-227 to -172 bp), which included two activator protein-1 (AP-1) sites and a kappa B-like site, that mediated induction by TNF-alpha, IL-1 beta, and LPS. Electrophoretic mobility shift assays demonstrated that endothelial cells contained constitutive AP-1 binding activity, whereas the kappa B-like site, 5'-CGGAGTTTCC-3', bound an inducible nuclear complex composed of c-Rel-p65 heterodimers. Taken together, our data suggest that induction of TF gene transcription in endothelial cells is mediated by functional interactions between Fos-Jun and c-Rel-p65 heterodimers.

Structural features of synthetic peptides of apolipoprotein E that bind the LDL receptor

Apolipoprotein (apo) E, via its receptor binding domain contained in residues 140-150, mediates hepatic and peripheral tissue binding of cholesterol-rich lipoproteins. Previously, we reported that a synthetic peptide representing a linear tandem repeat of amino acids 141-155, the 141-155 dimer, binds the low density lipoprotein (LDL) receptor. To define the structural features essential for LDL receptor binding of the 141-155 dimer, a series of modified peptides were synthesized. The secondary structure content of the modified apoE peptides was assessed by circular dichroism (CD) and the receptor activity was studied in cellular LDL receptor binding assays. alpha-Helix content was necessary but not sufficient for receptor activity because both a 129-162 monomer and the 141-155 dimer peptides had comparable CD spectra and helix contents, but only the 141-155 dimer was receptor active. Deletion of the charged amino terminal residues including arg142 and lys143 in the 145-155 or 144-150 dimers had no effect on alpha-helix content, yet abolished their receptor activities. Helical net models of all receptor active peptides indicated that the LDL-receptor binding activity of the 141-155 dimer is dependent on at least two clusters of basic amino acids present on the hydrophilic face of the amphipathic alpha-helix of the 141-155, 141-150, 141-155 (lys143-->ala) and 141-155 (arg150-->ala) dimer peptides.

A set of inducible genes expressed by activated human monocytic and endothelial cells contain kappa B-like sites that specifically bind c-Rel-p65 heterodimers

NF-kappa B/Rel proteins regulate the inducible expression of many genes in activated monocytes and endothelial cells that contain decameric kappa B and kappa B-like binding sites. In this study, we examined the binding of c-Rel-p65 heterodimers to non-consensus kappa B-like sites from several genes that do not bind prototypic NF-kappa B(p50-p65). c-Rel-p65 heterodimers from both monocytic and endothelial cells bound to the kappa B-like sites in the interleukin-8, granulocyte/macrophage colony-stimulating factor, intercellular adhesion molecule-1, and tissue factor genes but not to a closely related sequence in the granulocyte colony-stimulating factor gene. In contrast, kappa B sites in the endothelial-leukocyte adhesion molecule-1 and Ig kappa genes that match the kappa B consensus, 5'-GGGRNNYYCC-3' (where R indicates A or G, Y indicates C or T, and N indicates any base), bound NF-kappa B(p50-p65). Comparison of the kappa B-like sites indicated that c-Rel-p65 heterodimers bound to a consensus sequence, 5'-HGGARNYYCC-3' (where R indicates A or G, Y indicates C or T, H indicates A, C, or T, and N indicates any base), which differs at position 1 from the kappa B consensus established for binding NF-kappa B(p50-p65) and other members of the NF-kappa B/Rel family. The selective binding of c-Rel-p65 heterodimers to kappa B-like sites in this set of genes may play a central role in regulating inducible gene expression in monocytes and endothelial cells.

Lipopolysaccharide induction of tissue factor gene expression in monocytic cells is mediated by binding of c-Rel/p65 heterodimers to a kappa B-like site

Exposure of monocytic cells to bacterial lipopolysaccharide (LPS) activates the NF-kappa B/Rel family of proteins and leads to the rapid induction of inflammatory gene products, including tissue factor (TF). TF is the primary cellular initiator of the coagulation protease cascades. Here we report the characterization of a nuclear complex from human monocytic cells that bound to a kappa B-like site, 5'-CGGAGTTTCC-3', in the 5'-flanking region of the human TF gene. This nuclear complex was activated by LPS with kinetics that preceded induction of the TF gene. In vitro binding studies demonstrated that the TF site bound translated c-Rel and p65 homodimers but not p50/p65 heterodimers or p50 homodimers. Base-pair substitutions in the TF site indicated that the presence of a cytosine at position 1 precluded binding of NF-kappa B. In fact, under low-ionic-strength conditions, the TF complex did not migrate with translated p50/p65 dimers but instead comigrated with c-Rel/p65 dimers. Antibodies against the NF-kappa B and Rel proteins and UV cross-linking studies revealed the presence of c-Rel and p65 and the absence of p50 in the TF complex and further showed that c-Rel/p65 heterodimers selectively bound to the TF kappa B-like site. Functional studies indicated that the TF site conferred LPS inducibility on a heterologous promoter and was transactivated by c-Rel or p65. Taken together, our results demonstrated that binding of c-Rel/p65 heterodimers to a novel kappa B-like site mediated LPS induction of TF gene expression in monocytic cells.

Regulation of tissue factor gene expression in epithelial cells. Induction by serum and phorbol 12-myristate 13-acetate

Cell-specific expression of tissue factor (TF) in vivo is consistent with its primary role in hemostasis. In addition, TF expression is induced in cultured cells by a variety of agents, including serum and growth factors, which define the TF gene as a "primary response" gene. In this study we examined the signaling pathways and cis-acting regulatory elements required for induction of TF gene expression in HeLa cells in response to serum and the tumor promoter, phorbol 12-myristate 13-acetate (PMA). TF activity and mRNA were induced greater than sixfold in quiescent HeLa cells by serum and PMA. TF mRNA induction by both agonists required intracellular Ca2+ mobilization, whereas inhibition of protein kinase C abolished induction of the TF gene by PMA but had no effect on induction by serum. Functional studies demonstrated that a region of the human TF promoter between -96 and +121 bp contained regulatory elements required for serum and PMA induction. These data indicate that different signaling pathways regulate TF gene expression in response to serum and PMA, although the same cis-acting DNA elements may mediate induction.

A prospective study of human papillomavirus infection of the cervix

In a prospective study 42 women, diagnosed as having low grade cervical intraepithelial neoplasia (CIN), made a total of 281 clinic visits over a 45 month period. At each visit, they were subjected to cytological and colposcopical examination and samples were taken for human papillomavirus (HPV) DNA hybridization studies and for the detection of non-HPV infections. HPV types 16 and/or 18 were found in 25% of all the samples tested and these virus types were detected in five of six (83%) women whose lesions progressed compared to seven of 14 (50%) of those whose lesions regressed. The presence of HPV DNA was not a good prognostic indicator of progression since half of those whose disease regressed also harboured these viruses at some time. The recording of non-HPV infections almost 10 times more often in the women whose disease regressed than in those whose disease progressed could probably be accounted for by the former having a larger number of follow-up visits. Nevertheless, the significance of non-HPV infections also remains unclear.