Formation of methionine sulfoxide by peroxynitrite at position 1606 of von Willebrand factor inhibits its cleavage by ADAMTS-13: A new prothrombotic mechanism in diseases associated with oxidative stress

An enhanced formation of reactive oxygen species and peroxynitrite occurs in several clinical settings including diabetes, coronary artery disease, stroke, sepsis, and chronic inflammatory diseases. Peroxynitrite oxidizes methionine and tyrosine residues to methionine sulfoxide (MetSO) and 3-nitrotyrosine (NT), respectively. Notably, ADAMTS-13 cleaves von Willebrand factor (VWF) exclusively at the Tyr1605–Met1606 peptide bond in the A2 domain. We hypothesized that peroxynitrite could oxidize either or both of these amino acid residues, thus potentially affecting ADAMTS-13-mediated cleavage. We tested our hypothesis using synthetic peptide substrates based on: (1) VWF Asp1596–Ala1669 sequence (VWF74) and (2) VWF Asp1596–Ala1669 sequence containing nitrotyrosine (VWF74-NT) or methionine sulfoxide (VWF74-MetSO) at position 1605 or 1606, respectively. The peptides were treated with recombinant ADAMTS-13 and the cleavage products analyzed by RP-HPLC. VWF74 oxidized by peroxynitrite underwent a severe impairment of its hydrolysis. Likewise, VWF74-MetSO was minimally hydrolyzed, whereas VWF74-NT was hydrolyzed slightly more efficiently than VWF74. Oxidation by peroxynitrite of purified VWF multimers inhibited ADAMTS-13 hydrolysis, but did not alter their electrophoretic pattern nor their ability to induce platelet agglutination by ristocetin. Moreover, VWF purified from type 2 diabetic patients showed oxidative damage, as revealed by enhanced carbonyl, NT, and MetSO content and was partially resistant to ADAMTS-13 hydrolysis. In conclusion, peroxynitrite may contribute to prothrombotic effects, hindering the proteolytic processing by ADAMTS-13 of high-molecular-weight VWF multimers, which have the highest ability to bind and activate platelets in the microcirculation.     

Survivin and Cyclooxygenase-2 are co-expressed in human and mouse colon carcinoma and in terminally differentiated colonocytes

In the evolution of colon rectal cancer (CRC) the imbalance between cell proliferation and apoptosis is considered one of the prominent causes of tumor induction and/or progression. In order to establish the role of anti apoptotic proteins in colon cancer development, we studied with immunohistochemical techniques the expression of Survivin in a mouse model of colon carcinogenesis induced by 1,2-dimethyl-hydrazine treatment. In this mouse model Survivin was over-expressed during tumor development, showing a distribution mimicking that described in the correspondent human malignancies. We also correlated Survivin distribution with COX-2 and beta-Catenin expression patterns. The co-localization of COX-2/beta-Catenin/Survivin in the same epithelial cells in tumor samples lends credence to possible in vivo regulatory effects of COX-2 and beta-Catenin on the intracellular Survivin levels in mouse and human colon cancer.     

Application of 2-D DIGE to formalin-fixed, paraffin-embedded tissues

The ability to investigate the proteome of formalin-fixed, paraffin-embedded (FFPE) tissues can be considered a major recent achievement in the field of clinical proteomics. However, gel-based approaches to the investigation of FFPE tissue proteomes have lagged behind, mainly because of insufficient quality of full-length protein extracts. Here, the 2-D DIGE technology was investigated for applicability to FFPE proteins, for internal reproducibility among replicate FFPE extracts, and for comparability between FFPE and fresh-frozen tissue profiles. The 2-D DIGE patterns obtained upon labeling and electrophoresis of replicate FFPE tissue extracts were highly reproducible, with satisfactory resolution and complexity. Moreover, the implementation of DIGE enabled to highlight and characterize the consistent differences found in the FFPE profiles compared with fresh-frozen profiles, represented by an acidic shift, directly correlated to the protein pI value, and by a reduction in spot signal intensity, directly correlated to molecular weight and percentage of lysine residues. Being constantly and reproducibly present in all FFPE tissue extract replicates at similar extents, these modifications do not appear to hinder the comparative analysis of FFPE tissue extracts by 2-D DIGE, opening the way to its application for the differential proteomic investigation of archival tissue repositories.     

Increased plasma levels of adrenomedullin, a vasoactive peptide, in patients with end-stage pulmonary disease

AIM: To study adrenomedullin (AM) plasma levels in patients with severe lung disease and to analyze the relationship between AM and heart changes, hemodynamics and blood gases. METHODS: Case control study of 56 patients (36 men, 20 women) with severe lung disease and 9 control subjects (7 men, 2 women). Patients with end-stage pulmonary disease, including chronic obstructive pulmonary disease (COPD, n=11), cystic fibrosis (CF, 26), idiopatic pulmonary fibrosis (ILD, n=9), and idiopatic pulmonary arterial hypertension (PAH, n=10), who were evaluated for lung trasplantation between January 1997 and September 2000, and nine patients who underwent lung surgery for a solitary benign nodule. AM plasma levels in pulmonary artery (mixed venous blood, vein) and aorta or femoral artery (arterial, art), art and vein blood gases, pulmonary hemodynamics, systemic hemodynamics, two-dimensional transthoracic echocardiography and echo-Doppler study. RESULTS: Plasma AM (art and ven) levels were higher among patients' group compared to the controls (AMart p<0.02 and AMven p<0.04) for CF, ILD, PAH (AMart, pg ml(-1) Controls 13.7+/-3.6, COPD 22.8+/-6.2, CF 28.1+/-11.4, ILD 34.1+/-14.3, PAH 35.1+/-18.9; AMven, pg ml(-1) Controls 14.2+/-4.8, COPD 28.1+/-12.6, CF 31.7+/-14.1, ILD 38.7+/-16.5, PAH 40.1+/-4.4). We found with a trend towards higher concentration in ILD and PAH patients compared to COPD and CF but no statistical significant differences. Mixed-venous AM was higher than arterial AM in all groups resulting in AM uptake (AMPulmUp pg min(-1) Controls 4.8+/-22.6, COPD 21.1+/-44.9, CF 20.6+/-45.1, ILD 23.7+/-38.5, PAH 29.9+/-49.7). The univariate analysis showed a weak but significant correlation between AMart and mean systemic arterial pressure, heart rate, mean pulmonary arterial pressure and systemic vascular resistance. In the multivariate analysis, four variables emerged as independent factors of AMart including mean pulmonary arterial pressure, heart rate, mean systemic arterial pressure and left ventricular diastolic diameter (F=8.6, p<0.00001, r=0.60, r2=0.32). A similar weak correlation was apparent between AMven, systemic vascular resistance, and mean pulmonary arterial pressure. The results of multivariate analysis identify right atrial enlargement, mean right atrial pressure, heart rate and left ventricular dimensions as the only independent variables related to AMven (F=4.3, p<0.0004 r=0.56, r2=0.26). AM pulmonary uptake was significantly correlated with AMven (r=0.65), but not with hemodynamic, blood gas and echocardiographic variables. CONCLUSIONS: AM plasma levels are elevated in patients with severe lung disease in face of a preserved pulmonary uptake. These results suggest that the high AM plasma levels in patients with severe lung disease are not caused by a reduced pulmonary clearance, instead suggesting a systemic production.     

Substrate-induced conformational changes of the mitochondrial oxoglutarate carrier: a spectroscopic and molecular modelling study

The structural and dynamic properties of the oxoglutarate carrier were investigated by introducing a single tryptophan in the Trp-devoid carrier in position 184, 190 or 199 and by monitoring the fluorescence spectra in the presence and absence of the substrate oxoglutarate. In the absence of substrate, the emission maxima of Arg190Trp, Cys184Trp and Leu199Trp are centered at 342, 345 and 348 nm, respectively, indicating that these residues have an increasing degree of solvent exposure. The emission intensity of the Arg190Trp and Cys184Trp mutants is higher than that of Leu199Trp. Addition of substrate increases the emission intensity of Leu199Trp, but not that of Cys184Trp and Arg190Trp. A 3D model of the oxoglutarate carrier was built using the structure of the ADP/ATP carrier as a template and was validated with the experimental results available in the literature. The model identifies Lys122 as the most likely candidate for the quenching of Trp199. Consistently, the double mutant Lys122Ala-Leu199Trp exhibits a higher emission intensity than Leu199Trp and does not display further fluorescence enhancement in response to substrate addition. Substitution of Lys122 with Cys and evaluation of its reactivity with a sulphydryl reagent in the presence and absence of substrate confirms that residue 122 is masked by the substrate, likely through a substrate-induced conformational change.     

Emerin increase in regenerating muscle fibers

The fate of emerin during skeletal muscle regeneration was investigated in an animal model by means of crush injury. Immunofluorescence, immunoblotting and mRNA analysis demonstrated that emerin level is increased in regenerating rat muscle fibers with respect to normal mature myofibers. This finding suggests an involvement of emerin during the muscle fiber regeneration process, in analogy with its reported involvement in muscle cell differentiation in vitro. The impairment of skeletal muscle physiological regeneration or reorganization could be a possible pathogenetic mechanism for Emery Dreifuss muscular dystrophy.     

High-resolution whole-genome association study of Parkinson disease

We performed a two-tiered, whole-genome association study of Parkinson disease (PD). For tier 1, we individually genotyped 198,345 uniformly spaced and informative single-nucleotide polymorphisms (SNPs) in 443 sibling pairs discordant for PD. For tier 2a, we individually genotyped 1,793 PD-associated SNPs (P<.01 in tier 1) and 300 genomic control SNPs in 332 matched case-unrelated control pairs. We identified 11 SNPs that were associated with PD (P<.01) in both tier 1 and tier 2 samples and had the same direction of effect. For these SNPs, we combined data from the case-unaffected sibling pair (tier 1) and case-unrelated control pair (tier 2) samples and employed a liberalization of the sibling transmission/disequilibrium test to calculate odds ratios, 95% confidence intervals, and P values. A SNP within the semaphorin 5A gene (SEMA5A) had the lowest combined P value (P=7.62 x 10(-6)). The protein encoded by this gene plays an important role in neurogenesis and in neuronal apoptosis, which is consistent with existing hypotheses regarding PD pathogenesis. A second SNP tagged the PARK11 late-onset PD susceptibility locus (P=1.70 x 10(-5)). In tier 2b, we also selected for genotyping additional SNPs that were borderline significant (P<.05) in tier 1 but that tested a priori biological and genetic hypotheses regarding susceptibility to PD (n=941 SNPs). In analysis of the combined tier 1 and tier 2b data, the two SNPs with the lowest P values (P=9.07 x 10(-6); P=2.96 x 10(-5)) tagged the PARK10 late-onset PD susceptibility locus. Independent replication across populations will clarify the role of the genomic loci tagged by these SNPs in conferring PD susceptibility.     

Structural dynamics of the mitochondrial ADP/ATP carrier revealed by molecular dynamics simulation studies

The mitochondrial adenosine diphosphate/adenosine triphosphate (ADP/ATP) carrier has been recently crystallized in complex with its specific inhibitor carboxyatractyloside (CATR). In the crystal structure, the six-transmembrane helix bundle that defines the nucleotide translocation pathway is closed on the matrix side due to sharp kinks in the odd-numbered helices. The closed conformation is further sealed by the loops protruding into the matrix that interact through an intricate network of charge-pairs. To gain insight into its structural dynamics we performed molecular dynamics (MD) simulation studies of the ADP/ATP carrier with and without its cocrystallized inhibitor. The two trajectories sampled a conformational space around two different configurations characterized by distinct salt-bridge networks with a significant shift from inter- to intrarepeat bonding on the matrix side in the absence of CATR. Analysis of the geometrical parameters defining the transmembrane helices showed that even-numbered helices can undergo a face rotation, whereas odd-numbered helices can undergo a change in the wobble angle with a conserved proline acting as molecular hinge. Our results provide new information on the dynamical properties of the ADP/ATP carrier and for the first time yield a detailed picture of a stable carrier conformation in absence of the inhibitor.