Search

Acute myelogenous leukemia (AML) is an aggressive hematologic cancer characterized by infiltration of proliferative, clonal, abnormally differentiated cells of myeloid lineage in the bone marrow and blood. Malignant cells in AML often exhibit chromosomal and other genetic or epigenetic abnormalities that are useful in prognostic risk assessment. In this study, the relative expression and novel single-stranded DNA (ssDNA) binding function of purine-rich element binding proteins A and B (Purα and Purβ) were systematically evaluated in established leukemia cell lines and in lineage committed myeloid cells isolated from patients diagnosed with a hematologic malignancy. Western blotting revealed that Purα and Purβ are markedly elevated in CD33+ /CD66b+ cells from AML patients compared to healthy subjects and to patients with other types of myeloid cell disorders. Results of in silico database analysis of PURA and PURB mRNA expression during hematopoiesis in conjunction with the quantitative immunoassay of the ssDNA-binding activities of Purα and Purβ in transformed leukocyte cell lines pointed to Purβ as the more distinguishing biomarker of myeloid cell differentiation status. Purβ ssDNA-binding activity was significantly increased in myeloid cells from AML patients but not from individuals with other myeloid-related diseases. The highest levels of Purβ activity were detected in myeloid cells from primary AML patients and from AML patients displaying other risk factors forecasting a poor prognosis. Collectively, these findings suggest that the enhanced ssDNA-binding activity of Purβ in transformed myeloid cells may serve as a unique and measurable phenotypic trait for improving prognostic risk stratification in AML.

Elaboration of tumor necrosis factor (TNF) is a very early event in development of ischemia/reperfusion injury pathophysiology. Therefore, TNF may be a prominent mediator of endothelial cell and vascular wall dysfunction in sickle cell anemia, a hypothesis we addressed using NY1DD, S+SAntilles, and SS‐BERK sickle transgenic mice. Transfusion experiments revealed participation of abnormally activated blood monocytes exerting an endothelial activating effect, dependent upon Egr‐1 in both vessel wall and blood cells, and upon NFκB(p50) in a blood cell only. Involvement of TNF was identified by beneficial impact from TNF blockers, etanercept and infliximab, with less benefit from an IL‐1 blocker, anakinra. In therapeutic studies, etanercept ameliorated multiple disturbances of the murine sickle condition: monocyte activation, blood biomarkers of inflammation, low platelet count and Hb, vascular stasis triggered by hypoxia/reoxygenation (but not if triggered by hemin infusion), tissue production of neuro‐inflammatory mediators, endothelial activation (monitored by tissue factor and VCAM‐1 expression), histopathologic liver injury, and three surrogate markers of pulmonary hypertension (perivascular inflammatory aggregates, arteriolar muscularization, and right ventricular mean systolic pressure). In aggregate, these studies identify a prominent—and possibly dominant—role for an abnormal monocyte‐TNF‐endothelial activation axis in the sickle context. Its presence, plus the many benefits of etanercept observed here, argue that pilot testing of TNF blockade should be considered for human sickle cell anemia, a challenging but achievable translational research goal.

Peri-transplant surgical trauma and ischemia/reperfusion injury in accepted murine heterotopic heart grafts has been associated with myofibroblast differentiation, cardiac fibrosis and biomechanical-stress activation of the fetal myocardial smooth muscle α-actin (SMαA) gene. The wound-healing agonists, transforming growth factor β1 and thrombin, are known to coordinate SMαA mRNA transcription and translation in activated myofibroblasts by altering the subcellular localization and mRNA-binding affinity of the Y-box binding protein-1 (YB-1) cold-shock domain (CSD) protein that governs a variety of cellular responses to metabolic stress. YB-1 accumulated in polyribosome-enriched regions of the sarcoplasm proximal to cardiac intercalated discs in accepted heart grafts. YB-1 binding to a purine-rich motif in exon 3 of SMαA mRNA that regulates translational efficiency increased substantially in perfusion-isolated, rod-shaped adult rat cardiomyocytes during phenotypic de-differentiation in the presence of serum-derived growth factors. Cardiomyocyte de-differentiation was accompanied by the loss of a 60 kDa YB-1 variant that was highly expressed in both adult myocardium and freshly isolated myocytes and replacement with the 50 kDa form of YB-1 (p50) typically expressed in myofibroblasts that demonstrated sequence-specific interaction with SMαA mRNA. Accumulation of p50 YB-1 in reprogrammed, de-differentiated myocytes was associated with a 10-fold increase in SMαA protein expression. Endomyocardial biopsies collected from patients up to 14 years after heart transplant showed variable yet coordinately elevated expression of SMαA and p50 YB-1 protein and demonstrable p50 YB-1:SMαA mRNA interaction. The p60 YB-1 variant in human heart graft samples, but neither mouse p60 nor mouse or human p50, reacted with an antibody specific for the phosphoserine 102 modification in the YB-1 CSD. Modulation of YB-1 subcellular compartmentalization and mRNA-binding activity may be linked with reprogramming of contractile protein gene expression in ventricular cardiomyocytes that could contribute to maladaptive remodeling in accepted, long-term heart grafts.

We previously observed gross hemorrhage in plasminogen activator inhibitor type-1 (PAI-1) knockout (PKO) mice with induced myocardial infarction (MI). We hypothesized that it reflected degradation of vessels - a phenomenon we termed vascular rhexis. Accordingly, in the present study we characterized vascular rhexis in C57BL6 mice. MI was induced in 10- to 12-week-old mice by coronary artery ligation for 24, 48, 72 or 96 h. Hemorrhage was quantified by non-cross-reacting enzyme-linked immunosorbent assay of left ventricular (LV) hemoglobin corrected for myoglobin. Degradation of vasculature was quantified by the appearance of alpha smooth muscle actin (alphaSMA) in low salt soluble fractions of LV homogenates (Western blotting) and by immunohistochemistry (residual alphaSMA). Co-staining for CD31 (endothelial cells) and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) (a marker of cell death) was used to identify capillary rhexis. PKO mice (n = 9) had marked hemorrhage in infarct zones (432 +/- 27 standard error of mean microL blood/g). Hemorrhage was evident in C57BL6 mice as well (n = 6): 51 +/- 8 microL/g LV 96 h after coronary occlusion compared with 10 +/- 5 microL /g, n = 13 in normal LVs. Residual intact vasculature was reduced 48 h after infarction. Thus, an average of 16 +/- 1.6 small- and medium-sized vessels (n = 5 hearts) were seen compared with 84 +/- 4.8 in normal LVs (n = 3, Por = 0.05). An approximately three-fold increase in soluble alphaSMA 48 h after MI (2.68 +/- 0.28, n = 6) was seen relative to that in normal LVs defined as 1.0 +/- 0.04, n = 10, Por = 0.05. Capillary degradation was evident as well, as judged from CD31 and TUNEL co-localization. Vascular rhexis occurs within 48 h after the onset of MI. It may contribute to the early no-reflow phenomenon and to late negative LV remodeling.

Sickle cell anemia is accompanied by the activation of coagulation and thrombosis. We have studied the abnormal expression of tissue factor (TF) by the pulmonary vein endothelium of the mild-phenotype NY1DD sickle transgenic. As detected by immunofluorescence microscopy, this occurs only after the NY1DD mouse is exposed to hypoxia/reoxygenation (H/R), which actually causes ischemia/reperfusion in the sickle cell disease—but not the normal—mouse model. We tested the hypothesis that the nuclear factor-kappa B (NFκB)-activating inflammation that develops in post-H/R NY1DD mice is responsible for this phenotype switch. Various NFκB inhibitors (including p50-specific andrographolide) demonstrated that endothelial TF positivity is NFκB dependent. Several systemic inflammatory stimulators (tumor necrosis factor [TNFα], lipopolysaccharide, thioglycollate, and carageenan) given to control mice showed that the inflammatory promotion of TF expression by only pulmonary vein endothelium is not specific to the sickle cell disease model. We bred the NFκB(p50)-/- state into the NY1DD mouse. Combined with marrow transplantation, this allowed the creation of NY1DD mice that were NFκB(p50)-/- only in peripheral blood cells (and marrow) versus only in vessel walls (and tissues). This process revealed that endothelial TF expression in the NY1DD mouse is highly dependent on NFκB(p50) in peripheral blood mononuclear cells—but not in the vessel wall. In confirmation, the infusion of post-H/R sickle mouse blood mononuclear cells into naive NY1DD mice stimulated endothelial TF expression; the infusion of such cells from unstimulated sickle cell disease mice at ambient air did not stimulate TF expression. We conclude that peripheral blood mononuclear cells indirectly promote endothelial TF expression via a NFκB(p50)-dependent mechanism. This approach may be relevant to the role of coagulopathy in clinical sickle cell disease.

The vascular pathobiology of sickle cell anemia involves inflammation, coagulation, vascular stasis, reperfusion injury, iron-based oxidative biochemistry, deficient nitric oxide (NO) bioavailability, and red cell sickling. These disparate pathobiologies intersect and overlap, so it is probable that multimodality therapy will be necessary for this disease. We have, therefore, tested a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), for efficacy in reducing endothelial activation. We found that pulmonary vascular endothelial VCAM-1 and tissue factor (TF) expression (both are indicators of endothelial activation) are powerfully and significantly inhibited by TSA. This is seen both with pretreatment before the inducing stress of hypoxia/reoxygenation (NY1DD sickle transgenic mouse), and upon longer-term therapy after endothelial activation has already occurred (hBERK1 sickle mouse at ambient air). In addition, TSA prevented vascular stasis in sickle mice, it exhibited activity as an iron chelator, and it induced expression of the antisickling hemoglobin, hemoglobin F. Notably, the TSA analog SAHA (suberoylanilide hydroxaminc acid) that is already approved for human clinical use exhibits the same spectrum of biologic effects as TSA. We suggest that SAHA possibly could provide true, multimodality, salubrious effects for prevention and treatment of the chronic vasculopathy of sickle cell anemia.

Gonadotropin-releasing hormone-1 (GnRH1) controls reproduction by stimulating the release of gonadotropins from the pituitary. To characterize regulatory factors governing GnRH1 gene expression, we employed biochemical and bioinformatics techniques to identify novel GnRH1 promoter-binding proteins from the brain of the cichlid fish, Astatotilapia burtoni (A. burtoni). Using an in vitro DNA-binding assay followed by mass spectrometric peptide mapping, we identified two members of the purine-rich element-binding (Pur) protein family, Puralpha and Purbeta, as candidates for GnRH1 promoter binding and regulation. We found that transcripts for both Puralpha and Purbeta colocalize in GnRH1-expressing neurons in the preoptic area of the hypothalamus in A. burtoni brain. Furthermore, we confirmed in vivo binding of endogenous Puralpha and Purbeta to the upstream region of the GnRH1 gene in A. burtoni brain and mouse neuronal GT1-7 cells. Consistent with the relative promoter occupancy exhibited by endogenous Pur proteins, overexpression of Purbeta, but not Puralpha, significantly downregulated GnRH1 mRNA levels in transiently transfected GT1-7 cells, suggesting that Purbeta acts as a repressor of GnRH1 gene transcription.

Previous studies from our laboratories have implicated two members of the Pur family of single-stranded DNA/RNA-binding proteins, Purα and Purβ, in transcriptional repression of the smooth muscle α-actin gene in vascular cell types. Although Purα and Purβ share substantial sequence homology and nucleic acid binding properties, genomic promoter and cis-element occupancy studies reported herein suggest that Purβ is the dominant factor in gene regulation. To dissect the molecular basis of Purβ repressor activity, site-directed mutagenesis was used to map amino acids critical to the physical and functional interaction of Purβ with the smooth muscle α-actin promoter. Of all the various acidic, basic, and aromatic residues studied, mutation of positionally conserved arginines in the class I or class II repeat modules significantly attenuated Purβ repressor activity in transfected vascular smooth muscle cells and fibroblasts. DNA binding and protein-protein interaction assays were conducted with purified recombinant Purβ and selected mutants to reveal the physical basis for loss-of-function. Mutants R57E, R57E/R96E, and R57A/R96A each exhibited reduced single-stranded DNA binding affinity for an essential promoter element and diminished interaction with corepressor YB-1/MSY1. Structural analyses of the R57A/R96A and R57E/R96E double mutants in comparison to the wild-type Purβ homodimer revealed aberrant self-association into higher order oligomeric complexes, which correlated with decreased α-helical content and defective DNA and protein binding in vitro. These findings point to a previously unrecognized structural role for certain core arginine residues in forming a conformationally stable Purβ protein capable of physical interactions necessary for smooth muscle α-actin gene repression.

Adult skeletal muscle retains the capability of transcriptional reprogramming. This attribute is readily observable in the non-weight-bearing (NWB) soleus muscle, which undergoes a slow-to-fast fiber type transition concurrent with decreased beta-myosin heavy chain (betaMyHC) gene expression. Our previous work showed that Sp3 contributes to decreased betaMyHC gene expression under NWB conditions. In this study, we demonstrate that physical and functional interactions between Sp3, Puralpha, and Purbeta proteins mediate repression of betaMyHC expression under NWB conditions. Binding of Puralpha or Purbeta to the single-stranded betaMyHC distal negative regulatory element-sense strand (dbetaNRE-S) element is markedly increased under NWB conditions. Ectopic expression of Puralpha and Purbeta decreased betaMyHC reporter gene expression, while mutation of the dbetaNRE-S element increased expression in C2C12 myotubes. The dbetaNRE-S element conferred Pur-dependent decreased expression on a minimal thymidine kinase promoter. Short interfering RNA sequences specific for Sp3 or for Puralpha and Purbeta decreased endogenous Sp3 and Pur protein levels and increased betaMyHC reporter gene expression in C2C12 myotubes. Immunoprecipitation assays revealed an association between endogenous Puralpha, Purbeta, and Sp3, while chromatin immunoprecipitation assays demonstrated Puralpha, Purbeta, and Sp3 binding to the betaMyHC proximal promoter region harboring the dbetaNRE-S and C-rich elements in vivo. These data demonstrate that Pur proteins collaborate with Sp3 to regulate a transcriptional program that enables muscle cells to remodel their phenotype.

Platelet endothelial cell adhesion molecule-1 (PECAM-1) (CD31) is known to inhibit platelet function and thrombus formation. The mechanisms involved in PECAM-1's roles as a modulator of hemostasis are still not completely understood. We examined the role of PECAM-1 as a regulator of tissue factor (TF) expression, a known important inducer of thrombosis. Wildtype and CD31KO mice underwent transient (30 min) renal ischemia followed by 24 h re-perfusion and their kidneys assessed for apoptosis, fibrin formation, and tissue factor expression. CD31KO mice exhibited increased tubular epithelial and endothelial apoptosis, increased fibrin deposition, and tissue factor expression. Human umbilical vein endothelial cells (HUVEC) transfected with antisense (AS) PECAM-1 oligonucleotides to downregulate PECAM-1 expression, exhibited greater induction of TF mRNA and protein expression as well as increased expression and nuclear localization of the transcription factor Egr-1 compared to scrambled AS PECAM-1 (Scr)-treated HUVEC following thrombin stimulation. TF induction was found to be mediated through thrombin receptor PAR-1 and the Galphai/o subunit of G-protein, confirmed by PAR-1 antagonist and pertussis toxin inhibition respectively. Thrombin-mediated TF induction was dependent on Rho Kinase activity, phosphorylation of p38(MAPK) and p85 & Akt dephosphorylation. The inverse correlation of PI3K-Akt phosphorylation with p38 (MAPK) phosphorylation was confirmed by pharmacological inhibition. These studies suggest that PECAM-1 is involved in regulating a signaling pathway, affecting PI3K and Akt activation, p38 (MAPK) phosphorylation, which in turn, affects Egr-1 expression and nuclear translocation, ultimately affecting TF expression. These findings provide new insights into the action of PECAM-1 as a modulator of thrombosis.

Objective— Proliferation of vascular smooth muscle cells (VSMCs) contributes to restenosis after coronary intervention. We have shown previously that increased expression of plasminogen activator inhibitor type 1 (PAI-1) limits VSMC apoptosis. Because apoptosis and proliferation appear to be linked, we sought to determine whether increased PAI-1 would affect VSMC proliferation. Methods and Results— VSMCs were explanted from control and transgenic mice (SM22-PAI + ) in which VSMC expression of PAI-1 was increased. Increased growth of SM22-PAI + -VSMCs (2.3±0.4-fold) reflected, at least partially, increased proliferation. Greater expression of FLICE-like inhibitory protein (FLIP; 2.7-fold) and its cleaved active form were seen in SM22-PAI + -VSMCs. The balance between caspase-8 and FLIP favored proliferation in SM22-PAI + -VSMCs. Increased expression of NF-κB and activation of extracellular signal-regulated kinase (ERK) were demonstrated in SM22-PAI + -VSMCs (fold=NF-κB=2.2±0.1, fold=phosphorylated-ERK=1.6±0.1). Results were confirmed when expression of PAI-1 was increased by transfection. Inhibition of NF-κB and ERK attenuated proliferation in SM22-PAI + -VSMCs. Increased expression of PAI-1 promoted proliferation when VSMCs were exposed to tumor necrosis factor (TNF). Conclusions— Increased expression of PAI-1 is associated with greater activity of FLIP that promotes VSMC proliferation through NF-κB and ERK. Thus, when vascular wall expression of PAI-1 is increased, restenosis after coronary intervention is likely to be potentiated by greater proliferation of VSMC and resistance to apoptosis.

Profibrotic regulatory mechanisms for tissue repair after traumatic injury have developed under strong evolutionary pressure to rapidly stanch blood loss and close open wounds. We have examined the roles played by two profibrotic mediators, transforming growth factor beta1 (TGFbeta1) and thrombin, in directing expression of the vascular smooth muscle alpha-actin (SMalphaA) gene, an important determinant of myofibroblast differentiation and early protein marker for stromal cell response to tissue injury. TGFbeta1 is a well known transcriptional activator of the SMalphaA gene in myofibroblasts. In contrast, thrombin independently elevates SMalphaA expression in human pulmonary myofibroblasts at the posttranscriptional level. A common feature of SMalphaA up-regulation mediated by thrombin and TGFbeta1 is the involvement of the cold shock domain protein YB-1, a potent repressor of SMalphaA gene transcription in human fibroblasts that also binds mRNA and regulates translational efficiency. YB-1 dissociates from SMalphaA enhancer DNA in the presence of TGFbeta1 or its Smad 2, 3, and 4 coregulatory mediators. Thrombin does not effect SMalphaA gene transcription but rather displaces YB-1 from SMalphaA exon 3 coding sequences previously shown to be required for mRNA translational silencing. The release of YB-1 from promoter DNA coupled with its ability to bind RNA and shuttle between the nucleus and cytoplasm is suggestive of a regulatory loop for coordinating SMalphaA gene output in human pulmonary myofibroblasts at both the transcriptional and translational levels. This loop may help restrict organ-destructive remodeling due to excessive myofibroblast differentiation.

Objective: Chronic rejection in cardiac allografts depletes vascular smooth muscle (VSM) α-actin from the coronary arterial smooth muscle bed while promoting its abnormal accumulation in cardiomyocytes and myofibroblasts. The objective was to determine if the newly discovered TEF1, MSY1, Purα and Purβ VSM α-actin transcriptional reprogramming proteins (TRPs) were associated with development of chronic rejection histopathology in accepted murine cardiac allografts. Methods: A mouse heterotopic cardiac transplant model was employed using H2 locus-mismatched mouse strains (DBA/2 or FVB/N to C57BL/6). Recipients were immunosuppressed to promote long-term allograft acceptance and emergence of chronic rejection. Explanted grafts and isolated heart cells were evaluated for changes in the DNA-binding activity and subcellular distribution of VSM α-actin transcriptional regulatory proteins. Results: The DNA-binding activity of all four TRPs was high in the developing mouse ventricle, minimal in adult donor hearts and increased substantially within 30 days after transplantation. Immunohistologic analysis revealed nuclear localization of Purβ and MSY1 particularly in fibrotic areas of the allograft myocardium demonstrating extravascular accumulation of VSM α-actin. Cardiomyocytes isolated from adult, non-transplanted mouse hearts not only exhibited less VSM α-actin expression and lower levels of TRPs compared to isolated cardiac fibroblasts or neonatal cardiomyocytes, but also contained a novel size variant of the MSY1 protein. Conclusion: Accumulation of TRPs in cardiac allografts, particularly within the fibroblast-enriched myocardial interstitium, was consistent with their potential role in VSM α-actin gene reprogramming, fibrosis and dysfunctional remodeling following transplant. These nuclear protein markers could help stage peri-transplant cellular events that precede formation of graft-destructive fibrosis and coronary vasculopathy during chronic rejection.

Tissue factor, the cellular initiator of blood coagulation, has been implicated as a determinant of metastatic potential in human melanoma cells. Here, we report that differential expression of tissue factor in murine melanoma cell lines of known metastatic behavior is mediated by AP-1-dependent and 12S E1A oncoprotein-repressible gene transcription. When compared to weakly metastatic C10 cells, highly metastatic M4 cells possessed elevated levels of tissue factor cofactor activity, transfected promoter activity, and heterodimeric AP-1 DNA-binding complexes containing Fra-1. Transient co-expression of the adenovirus E1A 12S oncoprotein strongly repressed transcription of an AP-1-driven tissue factor reporter gene indicating the additional requirement of N-terminal E1A-interacting coactivators. Stable expression of E1A mutants defective in CBP/p300-binding failed to suppress tissue factor expression and experimental metastasis by M4 cells while clones expressing wild type E1A exhibited greatly reduced tissue factor cofactor activity and metastatic potential in vivo. Overexpression of functional tissue factor in cells containing wild type E1A failed to restore the highly metastatic M4 phenotype suggesting that additional E1A-responsive and CBP/p300-dependent genes are required to facilitate metastasis of murine melanoma cells demonstrating high tissue factor expression and cofactor activity. J. Cell. Biochem. 85: 54–71, 2002. © 2002 Wiley-Liss, Inc.

Transcriptional activity of the mouse vascular smooth muscle alpha-actin gene in fibroblasts is regulated, in part, by a 30-base pair asymmetric polypurine-polypyrimidine tract containing an essential MCAT enhancer motif. The double-stranded form of this sequence serves as a binding site for a transcription enhancer factor 1-related protein while the separated single strands interact with two distinct DNA binding activities termed VACssBF1 and 2 (Cogan, J. G., Sun, S., Stoflet, E. S., Schmidt, L. J., Getz, M. J., and Strauch, A. R. (1995) J. Biol. Chem. 270, 11310-11321; Sun, S., Stoflet, E. S., Cogan, J. G., Strauch, A. R., and Getz, M. J. (1995) Mol. Cell. Biol. 15, 2429-2936). VACssBF2 has been recently cloned and shown to consist of two closely related proteins, Puralpha and Purbeta (Kelm, R. J., Elder, P. K., Strauch, A. R., and Getz, M. J. (1997) J. Biol. Chem. 272, 26727-26733). In this study, we demonstrate that Puralpha and Purbeta interact with each other via highly specific protein-protein interactions and bind to the purine-rich strand of the MCAT enhancer in the form of both homo- and heteromeric complexes. Moreover, both Pur proteins interact with MSY1, a VACssBF1-like protein cloned by virtue of its affinity for the pyrimidine-rich strand of the enhancer. Interactions between Puralpha, Purbeta, and MSY1 do not require the participation of DNA. Combinatorial interactions between these three single-stranded DNA-binding proteins may be important in regulating activity of the smooth muscle alpha-actin MCAT enhancer in fibroblasts.

Background— Delineating the role of microRNAs (miRNAs) in the posttranscriptional gene regulation offers new insights into how the heart adapts to pathological stress. We developed a knockout of miR-22 in mice and investigated its function in the heart. Methods and Results— Here, we show that miR-22 –deficient mice are impaired in inotropic and lusitropic response to acute stress by dobutamine. Furthermore, the absence of miR-22 sensitized mice to cardiac decompensation and left ventricular dilation after long-term stimulation by pressure overload. Calcium transient analysis revealed reduced sarcoplasmic reticulum Ca 2+ load in association with repressed sarcoplasmic reticulum Ca 2+ ATPase activity in mutant myocytes. Genetic ablation of miR-22 also led to a decrease in cardiac expression levels for Serca2a and muscle-restricted genes encoding proteins in the vicinity of the cardiac Z disk/titin cytoskeleton. These phenotypes were attributed in part to inappropriate repression of serum response factor activity in stressed hearts. Global analysis revealed increased expression of the transcriptional/translational repressor purine-rich element binding protein B, a highly conserved miR-22 target implicated in the negative control of muscle expression. Conclusion— These data indicate that miR-22 functions as an integrator of Ca 2+ homeostasis and myofibrillar protein content during stress in the heart and shed light on the mechanisms that enhance propensity toward heart failure.

Osteonectin is an adhesive, cell, and extracellular matrix-binding glycoprotein found primarily in the matrix of bone and in blood platelets in vivo. Osteonectins isolated from these two sources differ with respect to the complexity of their constituent N-linked oligosaccharide. In this study, osteonectin synthesized by bone-forming cells (osteoblasts) and platelet-producing cells (megakaryocytes) in vitro was analyzed to determine if the proteins produced were analogous in terms of glycosylation to those isolated from bone and platelets, respectively. Immunoblot analyses of osteonectin produced by the osteoblast-like cell lines, SaOS-2 and MG-63, indicated that secreted and intracellular forms of the molecule are structurally distinct. Endoglycosidase treatment and immunoblotting of osteonectin secreted from SaOS-2 and MG-63 cells, under serum-deprived conditions, suggested that the molecule possessed a complex type oligosaccharide unlike the high-mannose moiety found on bone matrix-derived osteonectin. Biosynthetic labeling of SaOS-2 cells and human megakaryocytes indicated that both cell types synthesize osteonectin de novo. Electrophoretic and glycosidase sensitivity analyses of [35S]-osteonectin isolated from lysates of metabolically labeled SaOS-2 cells and megakaryocytes indicated that these two cell types synthesize osteonectin molecules that are identical in oligosaccharide structure to the isolated bone and platelet proteins. These data suggest that the intracellular form of the osteonectin molecule is glycosylated differently in SaOS-2 cells and megakaryocytes but that the extracellular form which is secreted from platelets in vivo and osteoblasts in vitro is characterized by the presence of a complex type N-linked oligosaccharide.

Activation of the coagulation system is a characteristic feature of sickle cell anemia, which also includes clinical thrombosis. The sickle transgenic mouse abnormally expresses tissue factor (TF) on the pulmonary vein endothelium. Knowing that this aberrancy is stimulated by inflammation, we sought to determine whether nitric oxide (NO) contributes to regulation of endothelial TF expression in the sickle mouse model. We used the NY1DD sickle mouse, which exhibits a low-TF to high-TF phenotype switch on exposure to hypoxia/reoxygenation. Manipulations of NO biology, such as breathing NO or addition of arginine or L-NAME (N-nitro-L-arginine-methyl-ester) to the diet, caused significant modulations of TF expression. This was also seen in hBERK1 sickle mice, which have a different genetic background and already have high-TF even at ambient air. Study of NY1DD animals bred to overexpress endothelial nitric oxide synthase (eNOS; eNOS-Tg) or to have an eNOS knockout state (one eNOS(-/-) animal and several eNOS(+/-) animals) demonstrated that eNOS modulates endothelial TF expression in vivo by down-regulating it. Thus, the biodeficiency of NO characteristic of patients with sickle cell anemia may heighten risk for activation of the coagulation system.

Mouse hearts subjected to repeated transplant surgery and ischemia-reperfusion injury develop substantial interstitial and perivascular fibrosis that was spatially associated with dysfunctional activation of fetal smooth muscle alpha-actin (SM alpha A) gene expression in graft ventricular cardiomyocytes. Compared with cardiac fibroblasts in which nuclear levels of the Sp1 and Smad 2/3 transcriptional-activating proteins increased markedly after transplant injury, the most abundant SM alpha A gene-activating protein in cardiomyocyte nuclei was serum response factor (SRF). Additionally, cardiac intercalated discs in heart grafts contained substantial deposits of Pur alpha, an mRNA-binding protein and known negative modulator of SRF-activated SM alpha A gene transcription. Activation of fetal SM alpha A gene expression in perfusion-isolated adult cardiomyocytes was linked to elevated binding of a novel protein complex consisting of SRF and Pur alpha to a purine-rich DNA element in the SM alpha A promoter called SPUR, previously shown to be required for induction of SM alpha A gene transcription in injury-activated myofibroblasts. Increased SRF binding to SPUR DNA plus one of two nearby CArG box consensus elements was observed in SM alpha A-positive cardiomyocytes in parallel with enhanced Pur alpha:SPUR protein:protein interaction. The data suggest that de novo activation of the normally silent SM alpha A gene in reprogrammed adult cardiomyocytes is linked to elevated interaction of SRF with fetal-specific CArG and injury-activated SPUR elements in the SM alpha A promoter as well as the appearance of novel Pur alpha protein complexes in both the nuclear and cytosolic compartments of these cells.

Our laboratory has previously shown that osteonectin, an abundant noncollagenous bone protein, is contained in and secreted from human platelets. In this study, the distribution of osteonectin both in the supernatant and on the platelet surface after activation was measured by fluid-phase and solid-phase radioimmunoassay, respectively. Total cellular osteonectin was determined by RIA of guanidinium chloride extracted platelets and ranged from 0.65 to 2.2 micrograms/10(8) platelets or 135,000 to 457,000 molecules/platelet. Platelets treated with varying concentrations of collagen and thrombin released osteonectin in a dose-dependent fashion. Approximately 61% of the total platelet osteonectin was secreted at saturating concentrations of collagen and thrombin. A small fraction of platelet osteonectin is expressed on the surface of platelets in an activation-specific manner as evidenced by the specific and saturable binding of [125I]-anti- osteonectin monoclonal antibody, IIIA3A8, to thrombin-activated platelets. Based on a non-linear least squares regression analysis of the antibody binding, 2,200 IIIA3A8 molecules, or 0.8% of the total platelet osteonectin, is expressed on the platelet surface on activation. Platelet osteonectin was purified from the supernatant of thrombin-activated platelets by immunoaffinity chromatography. Western blotting of proteins secreted by washed, thrombin-stimulated platelets with IIIA3A8 indicated that the osteonectin molecule released from the platelet is a single chain polypeptide. Comparison of immunopurified platelet osteonectin with isolated bovine bone osteonectin and isolated human bone osteonectin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that platelet osteonectin has a greater apparent molecular weight than bone osteonectin. The NH2-terminal sequence of immunopurified platelet osteonectin was obtained by automated Edman degradation and is identical to the sequence of human bone osteonectin derived from the cDNA of SaOS-2 cells. Collectively, these data suggest that platelet osteonectin is structurally distinct from bone osteonectin in a region of the molecule at a distance from the NH2-terminus.

Clinically, the vascular pathobiology of human sickle cell disease includes an abnormal state of chronic inflammation and activation of the coagulation system. Since these biologies likely underlie development of vascular disease in sickle subjects, they offer attractive targets for novel therapeutics. Similar findings characterize the sickle transgenic mouse, which therefore provides a clinically relevant inflammation model.The authors tested two polyhydroxyphenyl hydroxamic acid derivatives, didox and trimidox, in sickle transgenic mice. Animals were examined by intravital microscopy (cremaster muscle and dorsal skin fold preparations) and by histochemistry before and after transient exposure to hypoxia, with versus without preadministration of study drug. Previous studies have validated the application of hypoxia/reoxygenation to sickle transgenic mice as a disease-relevant model.Animals pretreated with these agents exhibited marked improvements in leukocyte/ endothelial interaction, hemodynamics and vascular stasis, and endothelial tissue factor expression. Thus, these drugs unexpectedly exert powerful inhibition on both the inflammation and coagulation systems.Each of these changes is expected to be therapeutically beneficial in systemic inflammatory disease in general, and in sickle disease in particular. Thus, these novel compounds offer the advantage of having multiple therapeutic benefits in a single agent.

Abnormal tissue factor (TF) expression has been demonstrated on blood monocytes and circulating endothelial cells in humans with sickle cell anemia. We have now studied sickle transgenic mice to help define the biology of endothelial TF expression in sickle disease. Using immunostaining of tissue sections, we find that this is confined almost exclusively to the pulmonary veins. About 15% and 13% of these exhibit TF-positive endothelium in the wild-type normal mouse and the normal human hemoglobin (HbA)-expressing control transgenic mouse, respectively. The mild sickle mouse is indistinguishable from normal (approximately 14% positive), but TF expression is significantly elevated in the moderate and severe mouse models of sickle disease (approximately 29% and approximately 41% positive, respectively). Exposure of the mild sickle mouse to hypoxia for 3 hours, followed by reoxygenation, converted its TF expression phenotype to that of the severe sickle mouse (approximately 36% positive). Pretreatment with lovastatin eliminated excessive expression of TF in the posthypoxic mild sickle mouse (approximately 16% positive) and in the more severe mouse at ambient air (approximately 21% positive). In addition to identifying tissue expression of endothelial TF in the sickle lung, these studies implicate reperfusion injury physiology in its expression and suggest a rationale for use of statins in sickle disease.

Serum-stimulation of quiescent mouse fibroblasts results in transcriptional activation of tissue factor (TF), the cellular initiator of blood coagulation. This requires the rapid entry of c-Fos into specific AP-1 DNA-binding complexes and can be strongly inhibited by the adenovirus EIA 12S gene product. In this study, we utilized a panel of E1A mutants deficient in cellular protein binding to analyse the molecular basis for EIA inhibition of a minimal, c-Fos-dependent TF promoter/ reporter construct in mouse AKR-2B fibroblasts. Mutations which impaired binding of the retinoblastoma tumor suppressor protein family members pRB, p107, and p130 relieved E1A-mediated inhibition of transcription in response to serum-stimulation or c-Fos overexpression. Inhibition was restricted to the G0 to G1 transition, consistent with the specificity of E1A for hypophosphorylated forms of RB proteins. Although E1A mutants deficient in CBP/p300 binding retained the ability to inhibit TF transcription, deletion of the amino-terminal portion of the CBP/p300 interaction domain was required to permit rescue of TF promoter activity by coexpression of pRB. Moreover, ectopic p107 could effectively substitute for pRB in relieving E1A-mediated repression. In primary mouse embryo fibroblasts, activity of the minimal AP-1-dependent TF promoter was suppressed in Rb(-/-) cells compared to parallel Rb(+/-) and Rb(+/+) transfectants. Ectopic expression of either pRB or p107 markedly enhanced TF promoter activity in Rb(-/-) fibroblasts. Collectively, these data imply that pRB and p107 can cooperate with c-Fos to activate TF gene transcription in fibroblasts and suggest a requirement for another, as yet unidentified, E1A-binding protein.

A systemic inflammatory state is a prominent feature of sickle cell anemia. Using sickle transgenic mice, we previously identified a blood monocyte-TNF-endothelium activation axis using multiple complementary approaches. For example, endothelial activation (identified by abnormal expression of VCAM-1 and tissue factor (TF) by pulmonary vessel endothelium) was evident in unstressed BERK and S+SAntilles sickle mice. In NY1DD sickle mice, this was triggered by transient enhanced sickling and vasoocclusion resulting from transient exposure to hypoxia/reoxygenation (H/R). Endothelial activation depended upon Egr-1 and NFkB(p50) in peripheral blood mononuclear cells, and transfusion experiments clarified that the peripheral blood monocytes (PBM) were the responsible effecter cells. Finally, interference with TNFa using etanercept (Etn) prevented this PBM-induced endothelial activation. Based on these background data, we have now tested the “clinical” efficacy of long-term, anti-inflammatory TNFa interference via treatment of S+SAntilles sickle mice with Etn (started at weaning, 3 mg/kg sc, once/wk x 6 wk). In parallel, littermate controls received equimolar scrambled peptide version of Etn's TNF-receptor moiety. In response we observed significant improvement in multiple parameters relevant to inflammation-induced vessel wall disease in this model, as follows (data shown in inset). Etn decreased blood markers of inflammation: plasma levels of sVCAM-1 and SAP (by ELISA), and MCP-1 and TNFa (by FACS cytobead assay). Etn also decreased the % of PBM positive for TNFa (by FACS). Etn diminished the abnormal pulmonary vessel endothelial expression of VCAM-1 and TF (by histochemical and immunofluorescent staining). Etn eliminated the enhanced vasoocclusion seen as dermal microvascular stasis in the live mouse (using the dorsal skin fold chamber) measured at 1 and 4 hours post-H/R (7%O2x1hr, followed by 21%O2x 1-4hr). Instructively, Etn did not significantly improve the similar stasis induced by heme infusion, a TNF-independent direct endothelial stressor. Finally, Etn diminished evidence for pulmonary hypertension, assessed via three of its hallmark features: elevated right ventricular mean systolic pressure (by RV catheterization), abnormal peri-vascular inflammatory cell aggregates (by immuno-histochemical staining for CD11b), and abnormal pulmonary arterial wall muscularization (by immuno-histochemical staining for SM actin). Remarkably, Etn actually normalized RVSP, and Etn's partial improvement in pulmonary arterial muscularization resulted not only from prevention of its progression over duration of this study but also from some reversal of the abnormal remodeling that had already developed by the time Etn was started. In parallel, Etn reduced the number of abnormal peri-vascular aggregates of CDllb+ cells in the pulmonary arterial system. These results enable several conclusions. In the S+SAntilles sickle model, endothelial activation and aspects of vascular wall pathobiology derive from TNFa produced by activated PBM, a monocyte-TNF-endothelial activation axis. Interference with TNFa using etanercept exerts multiple salubrious vascular effects that predict possible clinical benefit. And results suggest that inflammation involving TNFa plays a proximate, generative role in development of pulmonary hypertension in this model. Assuming these benefits are independently corroborated, a controlled test of etanercept's efficacy for aspects of human sickle vascular pathobiology perhaps should be considered. Table. Disclosures: No relevant conflicts of interest to declare.

Abstract 1048 Peripheral blood monocytes can be pathogenic participants in vascular disease, and they are abnormally activated in sickle patients. As shown earlier, sickle mice have abnormally increased expression of endothelial tissue factor (eTF) in pulmonary veins (PV), expressed as % of PV positive for eTF. For HbS-BERK (eTF 36%, vs 9% for HbA-BERK controls) and S+SAntilles (eTF 28%, vs 7% for C57BL6 controls), abnormal eTF expression is chronic. For NY1DD, however, eTF switches from 7% at ambient air to 23% after exposure to hypoxia/reoxygenation (post-H/R). Having now examined roles of transcription factors Egr-1 and NFkB(p50), we find that H/R triggered expression of eTF in post-H/R NY1DD is: [a] dependent upon both Egr-1 and NFkB(p50) within peripheral blood mononuclear cells (PBMC), and dependent upon Egr-1 butnot NFkB(p50) in vessel wall endothelium. To examine the roles of PBMC and their product TNF in activating eTF expression we used three strategies. [A] First, transfusion (Tx) of PBMC from donor mice (DM) induced eTF in recipient mice (RM) as follows. At-air NY1DD RM exhibited eTF of 7% from Tx of at-air NY1DD DM PBMC, and eTF of 19% from Tx of post-H/R NY1DD DM PBMC. C57BL6 RM exhibited eTF of 10% from Tx of C57BL6 DM PBMC, 31% from Tx of S+SAntilles DM PBMC, and only 15% from Tx of PBMC from S+SAntilles DM also having NFkB(p50)−/−. HbA-BERK RM exhibited eTF of 9% from Tx of HbA-BERK DM PBMC, and 36% from Tx of HbS-BERK DM PBMC. [B] Second, we examined effect of TNF+LT blocker etanercept on PBMC in transfusion experiments. As expected, HbA-BERK RM exhibited eTF 36% from Tx of HbS-BERK PBMC obtained from etanercept-treated (3 mg/kg × 2) DM, and 38% from Tx of HbS-BERK PBMC obtained from DM treated with inactive control TNF-R-scrambled-peptide. On the other hand, HbA-BERK RM pre-treated with etanercept (same dose) vs control TNF-R-scrambled-peptide exhibited eTF of 11% and 33%, respectively from Tx of HbS-BERK DM PBMC. [C] Third, direct TNF blocking pre-treatment of NY1DD mice prevented the eTF increase from subsequent H/R (to 23% for the no pre-treatment controls): eTF of 5% (P=.000013) for pre-treatment with high-etanercept (10 mg/kg × 2), 12% (P=.00059) for pre-treatment with low-etanercept (3 mg/kg × 2), 19% (P=.053) for pre-treatment with IL1-blocker anakinra (10 mg/kg ×2), and 7% (P=.0016) for pretreatment withTNF-specific blocker infliximab (10 mg/kg ×2). For HbS-BERK mice having pre-existing eTF of 36%, extended treatment with etanercept (3 mg/kg, twice weekly × 3) reduced eTF to 27% (P=.026) while those receiving scrambled-peptide remained at 34%. Higher or longer etanercept may be more effective. Other murine treatments have shown us reversal of pre-existing eTF requires extended treatment. Since regulation of TF expression in endothelial cells and blood monocytes is similar, it is likely that these eTF effects would be paralleled by similar effects on monocyte TF expression. Thus, these results suggest that TNF blocking strategies could be helpful in mitigating effects of coagulation activation in the sickle context. Disclosures: No relevant conflicts of interest to declare.

Abstract 2586 Poster Board II-562 The chronic, inflammatory vasculopathy of sickle cell anemia accounts for much of the non-infectious morbidity and mortality of this disease. The pathogenesis of vasculopathy involves multiple sub-biologies (sickling, hemolysis, inflammation, adhesion, coagulation, NO deficiency, stasis, and reperfusion injury). Moreover, these various sub-biologies overlap and transactivate each other. So a single modality approach would very likely fail to be effective. For this reason, effective preventative and interventional therapy for sickle vasculopathy will very likely require true multi-modality therapy, preferably with as few drugs as possible. To this end, we have evaluated the histone deacetylase (HDAC) inhibitors TSA and SAHA for beneficial vascular effects in sickle transgenic mouse models. We used the hBERK1 mouse, which displays abnormal endothelial activation even at ambient air; and we used the NY1DD mouse which only acquires significant endothelial activation upon exposure to hypoxia/reoxygenation. Both drugs significantly inhibited the abnormal endothelial expression of tissue factor, predicting beneficial effects for sickle coagulopathy. Both drugs significantly inhibited abnormal endothelial expression of VCAM1, a molecule involved in both adhesion and inflammation sub-biologies. Both drugs worked in both mouse models. For these benefits, both drugs were effective when given as preventative therapy (NY1DD model) or as longer term therapy (hBERK1 model), although previously-established endothelial activation (e.g., the hBERK1 model) required long term (3 weeks) therapy to observe the most significant benefits. TSA markedly inhibited the vascular stasis in the dorsal skinfold chamber model of hBERK1 mice that is seen after their exposure to H/R; SAHA did so in S+SAntilles mice after H/R; our previous studies have implicated VCAM1 and abnormal cell/cell interaction as the etiology of stasis in this model. Both drugs induced gamma globin and levels of HbF in K562 cells in vitro. Both drugs exhibited activity as iron chelators, as detected by absorption spectra in vitro. Since both drugs are hydroxamic acids, they may promote NO formation by the same mechanism that hydroxyurea is said to work, although we did not test this. We suggest that SAHA, which is already approved for other human clinical use, should be considered for testing in a pilot study to determine drug tolerance and in vivo efficacy in sickle subjects. Disclosures: No relevant conflicts of interest to declare.

Matched samples of bone from the lumbar spine and tibia were obtained at autopsy from three adult males who had no known evidence of metabolic bone disease at the time of their demise. The soluble noncollagenous bone proteins were quantitatively extracted from these samples and assayed for the relative content of two bone-associated proteins, osteocalcin and osteonectin. When compared to trabecular bone, cortical bone had higher levels of osteocalcin and much lower levels of osteonectin. When concentration is expressed per gram of dried bone, the osteocalcin excess in cortical bone ranged from 30- to 32-fold, and the osteonectin excess in trabecular bone ranged from 21- to 47-fold. These differences were significant (P less than 0.01) using analysis of variance. We conclude that the human skeleton is not homogeneous with regard to these biochemical markers and that cortical and trabecular bone are biochemically quite distinct. This implies that these two types of bone may be subject to distinct regulatory mechanisms and that global assessments of skeletal function and bone quality based upon soluble markers should be applied with caution. The data also imply that a differential assessment of skeletal performance may be possible using biochemical serum markers.

Sickle cell anemia is accompanied by biochemical activation of the coagulation system and by clinical thromboses. Therefore, we have focused on the expression of tissue factor (TF), the trigger of the coagulation system, in this disease. Previous studies from our laboratories described abnormal TF expression by monocytes and by circulating endothelial cells in human sickle blood. More recently, we reported (Blood104:840, 2004) that severe-phenotype (BERK) sickle mice abnormally express TF on pulmonary vein endothelium; mild-phenotype (NY1DD) sickle mice are normal in this regard but assume the abnormal phenotype after exposure to hypoxia (3 hr at 8% O2) followed by reoxygenation for 18 hr at ambient air (H/R). Monitoring the % of pulmonary veins positive for TF on triple stained tissue sections (for nuclei, for murine TF, for murine CD31 to identify endothelial cells), we have now evaluated the role of NO in TF expression, employing these two models. In the NY1DD H/R model, NO inhalation (34 ppm) administered during the entire reoxygenation period led to 68±18% reduction (P