A central role of plasmin in cardiac injury initiated by fetal exposure to maternal anti-Ro autoantibodies.

OBJECTIVE: Cardiac neonatal lupus (cardiac-NL), initiated by surface binding of anti-Ro60 autoantibodies to apoptotic cardiocytes during development, activates the urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) system. Subsequent accumulation of apoptotic cells and plasmin generation facilitates increased binding of anti-Ro60 by disrupting and cleaving circulating ß2-glycoprotein I (ß2GPI) thereby eliminating its protective effect. The association of soluble levels of components of the uPA/uPAR system with cardiac-NL was examined. METHODS: Levels of the uPA/uPAR system were assessed by ELISA in cord blood and immunohistological evaluation of autopsies. RESULTS: uPA, uPAR and plasminogen levels were each significantly higher in cord blood from cardiac-NL (n = 35) compared with non-cardiac-NL (n = 26) anti-Ro-exposed neonates: 3.3 ± 0.1 vs 1.9 ± 0.05 ng/ml (P < 0.0001), 6.6 ± 0.3 vs 2.1 ± 0.2 ng/ml (P < 0.0001) and 435 ± 34 vs 220 ± 19 ng/ml (P < 0.0001), respectively. In three twin pairs discordant for cardiac-NL, the twin with cardiac-NL had higher levels of uPA, uPAR and plasminogen than the unaffected twin (3.1 ± 0.1 vs 1.9 ± 0.05 ng/ml; P = 0.0086, 6.2 ± 1.4 vs 2.2 ± 0.7 ng/ml; P = 0.147 and 412 ± 61 vs 260 ± 27 ng/ml; P = 0.152, respectively). Immunohistological evaluation of three hearts from fetuses dying with cardiac-NL revealed macrophages and giant cells expressing uPA and plasminogen in the septal region. CONCLUSION: Increased soluble uPA, uPAR and plasminogen in cord blood and expression in affected tissue of fetuses with cardiac-NL supports the hypothesis that fetal cardiac injury is in part mediated by plasmin generation initiated by anti-Ro binding to the apoptotic cardiocyte.

Binding of anti-SSA antibodies to apoptotic fetal cardiocytes stimulates urokinase plasminogen activator (uPA)/uPA receptor-dependent activation of TGF-ß and potentiates fibrosis.

In congenital heart block (CHB), binding of maternal anti-SSA/Ro Abs to fetal apoptotic cardiocytes impairs their removal by healthy cardiocytes and increases urokinase plasminogen activator (uPA)/uPA receptor (uPAR)-dependent plasmin activation. Because the uPA/uPAR system plays a role in TGF-ß activation, we evaluated whether anti-Ro binding to apoptotic cardiocytes enhances plasmin-mediated activation of TGF-ß, thereby promoting a profibrosing phenotype. Supernatants from cocultures of healthy cardiocytes and apoptotic cardiocytes bound by IgG from a mother whose child had CHB (apoptotic-CHB-IgG [apo-CHB-IgG]) exhibited significantly increased levels of active TGF-ß compared with supernatants from cocultures of healthy cardiocytes and apoptotic cardiocytes preincubated with IgG from a healthy donor. Treatment of the culture medium with anti-TGF-ß Ab or TGF-ß inhibitor (SB431542) abrogated the luciferase response, thereby confirming TGF-ß dependency. Increased uPA levels and activity were present in supernatants generated from cocultures of healthy cardiocytes and apo-CHB-IgG cardiocytes compared with healthy cardiocytes and apoptotic cardiocytes preincubated with IgG from a healthy donor, respectively. Treatment of apo-CHB-IgG cardiocytes with anti-uPAR or anti-uPA Abs or plasmin inhibitor aprotinin prior to coculturing with healthy cardiocytes attenuated TGF-ß activation. Supernatants derived from cocultures of healthy cardiocytes and apo-CHB-IgG cardiocytes promoted Smad2 phosphorylation and fibroblast transdifferentiation, as evidenced by increased smooth muscle actin and collagen expression, which decreased when fibroblasts were treated with supernatants from cocultures pretreated with uPAR Abs. These data suggested that binding of anti-Ro Abs to apoptotic cardiocytes triggers TGF-ß activation, by virtue of increasing uPAR-dependent uPA activity, thus initiating and amplifying a cascade of events that promotes myofibroblast transdifferentiation and scar.

Identification of Stk6/STK15 as a candidate low-penetrance tumor-susceptibility gene in mouse and human.

Linkage analysis and haplotype mapping in interspecific mouse crosses (Mus musculus x Mus spretus) identified the gene encoding Aurora2 (Stk6 in mouse and STK15 in human) as a candidate skin tumor susceptibility gene. The Stk6 allele inherited from the susceptible M. musculus parent was overexpressed in normal cells and preferentially amplified in tumor cells from F(1) hybrid mice. We identified a common genetic variant in STK15 (resulting in the amino acid substitution F31I) that is preferentially amplified and associated with the degree of aneuploidy in human colon tumors. The Ile31 variant transforms rat1 cells more potently than the more common Phe31 variant. The E2 ubiquitin-conjugating enzyme UBE2N was a preferential binding partner of the 'weak' STK15 Phe31 variant form in yeast two-hybrid screens and in human cells. This interaction results in colocalization of UBE2N with STK15 at the centrosomes during mitosis. These results are consistent with an important role for the Ile31 variant of STK15 in human cancer susceptibility.

A novel role of endothelin-1 in linking Toll-like receptor 7-mediated inflammation to fibrosis in congenital heart block.

Autoimmune associated congenital heart block (CHB) may result from pathogenic cross-talk between inflammatory and profibrosing pathways. Incubation of macrophages with immune complexes (IC) composed of Ro60, a target of the pathologic maternal autoantibodies necessary for CHB, hY3 ssRNA, and affinity-purified anti-Ro60 antibody induces the Toll-like receptor 7 (TLR7)-dependent generation of supernatants that provoke a fibrosing phenotype in human fetal cardiac fibroblasts. We show herein that these cells are a major source of TGFß and that endothelin-1 (ET-1) is one of the key components responsible for the profibrosing effects generated by stimulated macrophages. Supernatants from macrophages incubated with IC induced the fibroblast secretion of TGFß, which was inhibited by treating the macrophages with an antagonist of TLR7. Under the same conditions, the induced fibroblast secretion of TGFß was decreased by inhibitors of the ET-1 receptors ETa or ETb or by an anti-ET-1 antibody but not by an isotype control. Exogenous ET-1 induced a profibrosing phenotype, whereas fibroblasts transfected with either ETa or ETb siRNA were unresponsive to the profibrosing effects of the IC-generated macrophage supernatants. Immunohistochemistry of the hearts from two fetuses dying with CHB revealed the presence of ET-1-producing mononuclear cells in the septal region in areas of calcification and fibrosis. In conclusion, these data support a novel role of ET-1 in linking TLR7 inflammatory signaling to subsequent fibrosis and provide new insight in considering therapeutics for CHB.

Role of the urokinase plasminogen activator receptor in mediating impaired efferocytosis of anti-SSA/Ro-bound apoptotic cardiocytes: Implications in the pathogenesis of congenital heart block.

RATIONALE: Binding of maternal anti-Ro/La antibodies to cognate antigen expressed on apoptotic cardiocytes decreases clearance by healthy cardiocytes, which may contribute to the development of autoimmune associated congenital heart block and fatal cardiomyopathy. OBJECTIVE: Given recent evidence implicating the urokinase plasminogen activator receptor (uPAR) as a "don't eat me" signal during efferocytosis, experiments addressed whether surface bound anti-Ro antibodies inhibit apoptotic cell removal via an effect on the expression/function of the urokinase-type plasminogen activator protease uPA/uPAR system. METHODS AND RESULTS: As assessed by flow cytometry and confocal microscopy, uPAR colocalizes and interacts with Ro60 on the surface of apoptotic human fetal cardiocytes. Blocking of uPAR enhances phagocytosis of apoptotic cardiocytes by healthy cardiocytes and reverses the anti-Ro60-dependent impaired clearance of apoptotic cardiocytes. Binding of anti-Ro60 antibodies to apoptotic cardiocytes results in increased uPAR expression, as well as enhanced uPA activity. The binding of anti-Ro60 did not alter other surface molecules involved in cell recognition (calreticulin, CD31, or CD47). CONCLUSIONS: These data suggest that increased uPAR expression and uPA activity induced by anti-Ro60 binding to the apoptotic fetal cardiocyte provide a molecular basis by which these antibodies inhibit efferocytosis and ultimately lead to scar of the fetal conduction system and working myocardium.

Slowing of brain atrophy with teriflunomide and delayed conversion to clinically definite MS.

BACKGROUND: We explored the effect of teriflunomide on cortical gray matter (CGM) and whole brain (WB) atrophy in patients with clinically isolated syndrome (CIS) from the phase III TOPIC study and assessed the relationship between atrophy and risk of conversion to clinically definite MS (CDMS). METHODS: Patients (per McDonald 2005 criteria) were randomized 1:1:1 to placebo, teriflunomide 7 mg, or teriflunomide 14 mg for ⩽108 weeks (core study). In the extension, teriflunomide-treated patients maintained their original dose; placebo-treated patients were re-randomized 1:1 to teriflunomide 7 mg or 14 mg. Brain volume was assessed during years 1-2. RESULTS: Teriflunomide 14 mg significantly slowed annualized CGM and WB atrophy versus placebo during years 1-2 [percent reduction: month 12, 61.4% (CGM; p = 0.0359) and 28.6% (WB; p = 0.0286); month 24, 40.2% (CGM; p = 0.0416) and 43.0% (WB; p < 0.0001)]. For every 1% decrease in CGM or WB volume during years 1-2, risk of CDMS conversion increased by 14.5% (p = 0.0004) and 47.3% (p < 0.0001) during years 1-2, respectively, and 6.6% (p = 0.0570) and 35.9% (p = 0.0250) during years 1-5. In patients with the least (bottom quartile) versus most (top quartile) atrophy during years 1-2, risk of CDMS conversion was reduced by 58% (CGM; p = 0.0024) and 58% (WB; p = 0.0028) during years 1-2, and 42% (CGM; p = 0.0138) and 29% (WB; p = 0.1912) during years 1-5. CONCLUSION: These findings support the clinical relevance of CGM and WB atrophy and early intervention with teriflunomide in CIS.

Aurora-A regulation of nuclear factor-kappaB signaling by phosphorylation of IkappaBalpha.

The Aurora-A/STK15 gene encodes a kinase that is frequently amplified in cancer. Overexpression of Aurora-A in mammalian cells leads to centrosome amplification, genetic instability, and transformation. In this study, we show that Aurora-A activates nuclear factor-kappaB (NF-kappaB) via IkappaBalpha phosphorylation. Inhibition of endogenous Aurora-A reduces tumor necrosis factor alpha (TNFalpha)-induced IkappaBalpha degradation. We analyzed primary human breast cancers, and 13.6% of samples showed Aurora-A gene amplification, all of which exhibited nuclear localization of NF-kappaB. We propose that this subgroup of patients with breast cancer might benefit from inhibiting Aurora-A. We also show that down-regulation of NF-kappaB via Aurora-A depletion can enhance cisplatin-dependent apoptosis. These data define a new role for Aurora-A in regulating IkappaBalpha that is critical for the activation of NF-kappaB-directed gene expression and may be partially responsible for the oncogenic effect of Aurora-A when the gene is amplified and overexpressed in human tumors.

Serum Biomarkers of Inflammation, Fibrosis, and Cardiac Function in Facilitating Diagnosis, Prognosis, and Treatment of Anti-SSA/Ro-Associated Cardiac Neonatal Lupus.

BACKGROUND: Cardiac manifestations of neonatal lupus (cardiac NL) include congenital heart block and cardiomyopathy. Several candidate biomarkers were evaluated in cases at risk for cardiac NL on the basis of potential roles in inflammation, fibrosis, and cardiac dysfunction: C-reactive protein (CRP); NT-pro-B-type natriuretic peptide (NT-proBNP); troponin I; matrix metalloproteinase (MMP)-2; urokinase plasminogen activator (uPA); urokinase plasminogen activator receptor (uPAR); plasminogen; and vitamin D. OBJECTIVES: Identification of maternal and fetal biomarkers associated with development and morbidity of cardiac NL should provide clues to pathogenesis with translational implications for management. METHODS: Cord (139) and maternal (135) blood samples collected during pregnancies at risk for cardiac NL were available for study. Levels of cord and maternal CRP, cord NT-proBNP, and cord troponin I were evaluated using multiplex assays. Cord and maternal vitamin D were assessed by liquid chromatography-mass spectrometry. MMP-2, uPA, uPAR, and plasminogen were evaluated using ELISA. RESULTS: Cord CRP, NT-proBNP, MMP-2, uPA, uPAR, and plasminogen levels were higher in cardiac NL-affected fetuses than in unaffected cases, independent of maternal rheumatic disease, season at highest risk of cardiac NL development, and medications taken during pregnancy. These biomarkers were positively associated with a disease severity score derived from known risk factors for mortality in cardiac NL. Maternal CRP and cord troponin I levels did not differ between the groups. Cord and maternal vitamin D levels were not significantly associated with cardiac NL, but average maternal vitamin D level during pregnancy was positively associated with longer time to postnatal pacemaker placement. CONCLUSIONS: These data support the association of fetal reactive inflammatory and fibrotic components with development and morbidity of cardiac NL. Following CRP and NT-proBNP levels after birth can potentially monitor severity and progression of cardiac NL. MMP-2 and the uPA/uPAR/plasminogen cascade provide therapeutic targets to decrease fibrosis. Although decreased vitamin D did not confer increased risk, given the positive influence on postnatal outcomes, maternal levels should be optimized.

Aurora kinase inhibition downregulates NF-kappaB and sensitises tumour cells to chemotherapeutic agents.

We have identified that Aurora-A activates NF-kappaB via IkappaBalpha phosphorylation. Here, we analysed different human tumour cell types for their NF-kappaB activity. We found that there is an association between cell resistance to chemotherapeutic agents and NF-kappaB activation. A549 human lung adenocarcinoma cells and SKOV3 human ovarian cancer cells have high levels of NF-kappaB and are resistant to cytotoxic agents such as adriamycin and VP-16 (etoposide). We also found that in A549 and SKOV3 cells treated with a small molecule inhibitor towards Aurora kinases, the NF-kappaB activity was downregulated and the efficacy of cytotoxic drugs was enhanced. In addition, the transcriptional targets Bcl-XL and Bcl-2 were downregulated. This study provides evidence for a potential mechanism of chemoresistance and may be useful for the enhancement of certain chemotherapeutics regimens.

The N-terminal domain of the Aurora-A Phe-31 variant encodes an E3 ubiquitin ligase and mediates ubiquitination of IkappaBalpha.

Aurora-A is an important regulator of mitosis and is frequently amplified in human cancer. Ectopic expression of Aurora-A in mammalian cells induces centrosome amplification, genomic instability and transformation. A common genetic variant in Aurora-A (F31I) is preferentially amplified and is associated with the occurrence and the status of colon, oesophageal and breast cancers. Here we demonstrate that the N-terminal domain of Aurora-A Phe-31 variant exhibits an intrinsic ubiquitin ligase activity. Mutation of cysteines 8, 33 and 49 of Aurora-A abolishes the ubiquitin ligase activity of the protein. Aurora-A in a complex with UBE2N/MMS2 catalyses polyubiquitination of IkappaBalpha in vitro and in vivo.

Ecdysone-inducible expression of oncogenic Ha-Ras in NIH 3T3 cells leads to transient nuclear localization of activated extracellular signal-regulated kinase regulated by mitogen-activated protein kinase phosphatase-1.

The Ras family of GTP-binding proteins are key transducers of extracellular signals, particularly through the mitogen-activated protein kinase (MAPK) pathway. Constitutively active forms of Ras are found in a variety of tumours, suggesting an important role for this pathway in cancer. Here we report that initial cellular exposure to oncogenic Ras chronically activated the MAPK pathway in the cytoplasm, but transiently activated the same pathway in the nucleus. Nuclear-activated extracellular signal-regulated kinase (ERK) was rapidly dephosphorylated, with consequent short-term activation of the Elk-1 transcription factor and expression of the c-fos gene. Additional experiments suggested that the regulatory mechanism involved requires the calcium-dependent protein phosphotyrosine phosphatase MAPK phosphatase-1 (MKP-1). This is the first report on the ability of Ras, in the absence of growth factors, to transiently activate the MAPK pathway in the nucleus and show an involvement of MKP-1 in nuclear ERK2 regulation. In addition we show that transient activation of the MAPK pathway is sufficient to drive chronic cell-cycle progression. We conclude that, whereas the MAPK pathway is necessary to initiate cellular proliferation and transformation, the transient nature of the MAPK pathway activation suggests the involvement of additional signalling pathway(s) regulated by Ras.