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OBJECTIVES: To develop and validate an outcome measure for assessing fears in patients with rheumatoid arthritis (RA) and axial spondyloarthritis (axSpA). METHODS: Fears were identified in a qualitative study, and reformulated as assertions with which participants could rate their agreement (on a 0-10 numeric rating scale). A cross-sectional validation study was performed including patients diagnosed with RA or axSpA. Redundant items (correlation >0.65) were excluded. Internal consistency (Cronbach's α) and factorial structure (principal component analysis) were assessed. Patients were classified into fear levels (cluster analysis). Associations between patient variables and fear levels were evaluated using multiple logistic regression. RESULTS: 672 patients were included in the validation study (432 RA, 240 axSpA); most had moderate disease activity and were prescribed biologics. The final questionnaire included 10 questions with high internal consistency (α: 0.89) and a single dimension. Mean scores (±SD) were 51.2 (±25.4) in RA and 60.5 (±22.9) in axSpA. Groups of patients with high (17.2%), moderate (41.1%) and low (41.7%) fear scores were identified. High fear scores were associated with high Arthritis Helplessness Index scores (OR 6.85, 95% CI (3.95 to 11.87)); high Hospital Anxiety and Depression Scale anxiety (OR 5.80, 95% CI (1.19 to 4.22)) and depression (OR 2.37, 95% CI (1.29 to 4.37)) scores; low education level (OR 3.48, 95% CI (1.37 to 8.83)); and high perceived disease activity (OR 2.36, 95% CI (1.10 to 5.04)). CONCLUSIONS: Overall, 17.2% of patients had high fear scores, although disease was often well controlled. High fear scores were associated with psychological distress. This questionnaire could be useful both in routine practice and clinical trials.
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Artrite Reumatoide/psicologia , Medo/psicologia , Medidas de Resultados Relatados pelo Paciente , Psicometria/métodos , Espondilartrite/psicologia , Adulto , Idoso , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Pesquisa Qualitativa , Inquéritos e QuestionáriosRESUMO
OBJECTIVE: RA and axial SpA have an important impact on patients' lives. The objective of this study was to explore the reporting of different aspects of that impact in publications, with a focus on differences between diseases and over time. METHODS: A systematic literature review retrieved all articles reporting on the life impact of RA or axial radiographic SpA in adults published within the last 10 years and issued from European research. The data were classified into physical impact (including pain, functional assessment and fatigue), psychological impact (including psychological distress and coping) and social impact (including relationships, family and social life). The number of articles published over time was analysed by linear regression. RESULTS: In all, 1352 abstracts were screened and 149 publications (40,056 patients) were analysed: 129 articles (86.5%) concerned RA and 16 (10.7%) concerned axial SpA. The mean number of articles reporting on the physical aspects of impact was 11.4 (s.d. 4.8) per 2-year period, but increased more than 2-fold (from 7 articles in 2001-3 to 15 in 2010-11), in particular due to recent publications on fatigue, whereas the number of articles on psychological aspects [mean 12.4 (s.d. 4.0)] decreased markedly after 2006. Publications reporting on social aspects [mean 8.2 (s.d. 4.1)] remained globally stable. CONCLUSION: In the era of biologics, there is an interest in the patient-perceived life impact of RA and axial SpA in the European literature, but the impact of RA has been the subject of greater exploration. There are clearly trends over time in the reporting of impact.
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Artrite Reumatoide/psicologia , Qualidade de Vida/psicologia , Autoimagem , Espondilartrite/psicologia , Fadiga/epidemiologia , Fadiga/psicologia , Humanos , Modelos Lineares , Estudos Longitudinais , Dor/epidemiologia , Dor/psicologia , PrevalênciaRESUMO
Nitric oxide is implicated in the pathogenesis of various neuropathologies characterized by oxidative stress. Although nitric oxide has been reported to be involved in the exacerbation of oxidative stress observed in several neuropathologies, existent data fail to provide a holistic description of how nitrergic pathobiology elicits neuronal injury. Here we provide a comprehensive description of mechanisms contributing to nitric oxide induced neuronal injury by global transcriptomic profiling. Microarray analyses were undertaken on RNA from murine primary cortical neurons treated with the nitric oxide generator DETA-NONOate (NOC-18, 0.5 mM) for 8-24 hrs. Biological pathway analysis focused upon 3672 gene probes which demonstrated at least a ±1.5-fold expression in a minimum of one out of three time-points and passed statistical analysis (one-way anova, P < 0.05). Numerous enriched processes potentially determining nitric oxide mediated neuronal injury were identified from the transcriptomic profile: cell death, developmental growth and survival, cell cycle, calcium ion homeostasis, endoplasmic reticulum stress, oxidative stress, mitochondrial homeostasis, ubiquitin-mediated proteolysis, and GSH and nitric oxide metabolism. Our detailed time-course study of nitric oxide induced neuronal injury allowed us to provide the first time a holistic description of the temporal sequence of cellular events contributing to nitrergic injury. These data form a foundation for the development of screening platforms and define targets for intervention in nitric oxide neuropathologies where nitric oxide mediated injury is causative.
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Apoptose/fisiologia , Perfilação da Expressão Gênica , Neurônios/patologia , Neurônios/fisiologia , Óxido Nítrico/metabolismo , Transdução de Sinais/fisiologia , Transcriptoma , Animais , Sobrevivência Celular , Células Cultivadas , Biologia Computacional , Regulação da Expressão Gênica , Camundongos , Dados de Sequência Molecular , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Estresse Oxidativo/fisiologia , Fatores de TempoRESUMO
The original version of this article was revised due to a retrospective Open Access order.
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Misinterpretation of patient beliefs may complicate shared decision-making in rheumatoid arthritis (RA) or axial spondyloarthritis (axSpA). The objective of this study was to develop a questionnaire to assess patients' beliefs about their disease and its treatment, and to identify patient characteristics associated with these beliefs. All beliefs reported by > 5% of 50 patients in a previous study were reformulated with a partnering patient organization into statements with which participants could rate their agreement on a scale of 0-10 (totally disagree to totally agree). The resulting Questionnaire for Arthritis Dialogue (QuAD) was made available to patients with RA or axSpA. A score ≥ 7 was considered a strongly held belief. Associations between patient characteristics and individual lifestyle beliefs were assessed using multiple logistic regression. The 21-item QuAD was completed by 672 patients (432 RA, 240 axSpA; mean [±SD] age 54.2 [± 14.2]; 63.7% female). The most widely held beliefs were related to uncertainty about progression (n = 354, 54.0%), heredity (n = 309, 47.8%), and flare triggers (n = 283, 42.7%). The unwarranted belief that physical activity is deleterious to disease activity was associated with markers of psychological distress and lower educational levels. The beliefs of patients with RA or axSpA about their disease are wide-ranging. Since these may be unwarranted and may lead to inappropriate behaviors, physicians should discuss these beliefs with their patients. The QuAD may facilitate this dialogue, and may also be useful in population studies to standardize the assessment and evolution of beliefs over time. People with long-term inflammatory conditions such as rheumatoid arthritis (RA; inflammation of the joints) and axial spondyloarthritis (axSpA; inflammation of the spine) may hold a number of beliefs about their disease, including some that are not supported by current scientific evidence (e.g., "I think that my disease was triggered by a vaccination"). Some beliefs, especially those relating to the role of lifestyle factors (such as exercise, diet, smoking, and drinking alcohol), may encourage people living with severe diseases to change their behavior in a way that has an effect on their disease. Within this project, we developed a questionnaire to identify the most common beliefs held by people living with RA or axSpA, which is called the "Questionnaire for Arthritis Dialogue (QuAD)." We also examined whether certain characteristics (or traits) of people living with RA or axSpA are linked to beliefs not currently supported by scientific evidence. A total of 672 people living with RA or axSpA in France were asked to complete the questionnaire (QuAD). The questionnaire included 21 opinion statements that they scored from 0 (totally disagree) to 10 (totally agree). A score of more than 7 was interpreted to mean that the person significantly agreed with the opinion. Based on the responses to specific opinion statements in the questionnaire, we were able to identify possible links between beliefs that are not supported by scientific evidence (e.g., "I think that flare-ups of my disease are triggered by physical effort"), and characteristics of people living with severe diseases. Our findings suggested that beliefs about lifestyle and inflammatory diseases varied from person to person, were sometimes inconsistent (the most widely held beliefs were sometimes contradictory), and were often not supported by scientific evidence. The belief that physical activity had negative effects on the disease was linked to poor education and psychological issues (such as anxiety and helplessness). People living with axSpA were more likely to believe their disease was a result of their genetic make-up, whereas those with RA more often believed their disease was caused by emotional issues. People living with axSpA were also more likely to believe that physical activity could be beneficial for their disease, and less likely to believe that their disease was caused by smoking. Our results suggest that doctors need to discuss with their patients how they might believe lifestyle is associated with their disease. This will help to dispel any unnecessary concerns, and to encourage their patients to take up healthy lifestyles and habits that are beneficial for their disease management. It may also be beneficial for health care providers to discuss the beliefs identified in this study during educational programs about inflammatory diseases, for the benefit of people living with RA or axSpA.
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Artrite Reumatoide/psicologia , Conhecimentos, Atitudes e Prática em Saúde , Inquéritos Epidemiológicos , Espondilartrite/psicologia , Ansiedade , Artrite Reumatoide/tratamento farmacológico , Feminino , França , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Annexin A8 is a relatively infrequent and poorly studied member of this large family of calcium-binding and membrane-binding proteins. It is, however, associated with a specific disease, acute promyelocytic leukemia. We have solved its three-dimensional structure, which includes a moderately long and intact N terminus. The structure is closest to that of annexin A3 and highlights several important regions of inherent flexibility in the annexin molecule. The N terminus resembles that of annexin A3, as it lies along the concave surface of the molecule and inserts partially into the hydrophilic channel in its centre. Since both annexins A3 and A8 are expressed in promyelocytic cells during their differentiation, the similarity in their structures might suggest a functional relationship.
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Anexina A3/química , Anexinas/química , Anexinas/genética , Anexinas/metabolismo , Sítios de Ligação , Cálcio/farmacologia , Cristalografia por Raios X , Lisina/genética , Lisina/metabolismo , Modelos Moleculares , Mutação/genética , Conformação ProteicaRESUMO
The glucocorticoid-inducible protein annexin (ANXA) 1 is an anti-inflammatory mediator that down-regulates the host response. Endogenously, ANXA1 is released in large amounts from adherent polymorphonuclear neutrophils (PMN) and binds to their cell surface to inhibit their extravasation into inflamed tissues. The present study determined the effects of exogenous ANXA1 on several functions of human PMN in vitro. Addition of 0.1-1 microM human recombinant ANXA1 to the PMN provoked rapid and transient changes in intracellular Ca2+ concentrations that were blocked by the Ca2+ channel inhibitor SKF-96365. Although ANXA1 did not affect oxidant production and only minimally affected PMN chemotactic properties, the ANXA1-promoted Ca2+ influx was associated with two important functional effects: shedding of L-selectin and acceleration of PMN apoptosis. The latter effect was confirmed using three distinct technical procedures, namely, cell cycle, Hoechst staining, and ANXA5 binding assay. ANXA1-induced PMN apoptosis was insensitive to inhibitors of L-selectin shedding, whereas it appeared to be associated with dephosphorylation of the proapoptotic intracellular mediator BAD. In conclusion, exogenous ANXA1 displayed selective actions on human PMN. We propose that the new proapoptotic effect reported here may be part of the spectrum of ANXA1-mediated events involved in the resolution of acute inflammation.
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Anexina A1/farmacologia , Apoptose , Cálcio/metabolismo , Neutrófilos/citologia , Bloqueadores dos Canais de Cálcio/farmacologia , Humanos , Imidazóis/farmacologia , Modelos Biológicos , Ativação de Neutrófilo/efeitos dos fármacos , Neutrófilos/efeitos dos fármacos , Neutrófilos/metabolismoRESUMO
OBJECTIVE: Annexins are Ca(2+)-dependent phospholipid binding proteins. Externalized annexin A5 has been recently suggested to have a proapoptotic effect. Our aim was to determine whether annexin A5, which is intracellular in cardiomyocytes, could be translocated and/or externalized and play a role during the apoptotic process. METHODS: Apoptosis was induced in rat cardiomyocytes by continuous incubation with staurosporine or 30 min treatment with H(2)O(2) and was measured by phosphatidylserine (PS) externalization, TUNEL staining and DNA ladder. Immunofluorescence labeling of annexin A5 was performed on permeabilized or nonpermeabilized cardiomyocytes. RESULTS: Staurosporine or H(2)O(2) treatment of neonatal cardiomyocytes resulted in significant increases of apoptosis at 24 h, but H(2)O(2) treatment led to a faster and higher PS externalization than that observed with ST. In both neonatal and adult cardiomyocytes, annexin A5 was intracellular in control conditions but was found at the external face of sarcolemma during apoptosis. Furthermore, neonatal cardiomyocytes with externalized annexin A5 have apoptotic characteristics and their number increased with time. Interestingly, immediately after H(2)O(2) induction, the number of annexin A5-positive cells was higher than that of PS-positive cells (p=0.05) and colabeling showed that half annexin A5-positive cells were PS-negative. We further demonstrated by immunoblots that free annexin A5 was absent from the media and could not be released from cardiomyocytes by washes at 1.8 mM Ca(2+). Removing annexin A5 by Ca(2+)-free washes 15 or 30 min after H(2)O(2) treatment or blocking externalized annexin A5 by antibodies lead to a significant decrease of apoptotic cardiomyocytes, cytochrome c release and caspase 3 activity. CONCLUSION: This study indicated for the first time that annexin A5 was externalized at a very early stage of apoptosis and could have a proapoptotic effect in cardiomyocytes.
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Anexina A5/metabolismo , Miócitos Cardíacos/metabolismo , Animais , Anexina A5/análise , Anexina A5/imunologia , Anticorpos Monoclonais/farmacologia , Apoptose , Caspase 3 , Caspases/metabolismo , Células Cultivadas , Citocromos c/metabolismo , Inibidores Enzimáticos/farmacologia , Peróxido de Hidrogênio/farmacologia , Marcação In Situ das Extremidades Cortadas , Microscopia Confocal , Miócitos Cardíacos/patologia , Proteína Quinase C/antagonistas & inibidores , Ratos , Ratos Wistar , Sarcolema/metabolismo , Estaurosporina/farmacologiaRESUMO
Annexin 3 (ANX A3) represents approximately 1% of the total protein of human neutrophils and promotes tight contact between membranes of isolated specific granules in vitro leading to their aggregation. Like for other annexins, the primary molecular events of the action of this protein is likely its binding to negatively charged phospholipid membranes in a Ca(2+)-dependent manner, via Ca(2+)-binding sites located on the convex side of the highly conserved core of the molecule. The conformation and dynamics of domain III can be affected by this process, as it was shown for other members of the family. The 20 amino-acid, N-terminal segment of the protein also could be affected and also might play a role in the modulation of its binding to the membranes. The structure and dynamics of these two regions were investigated by fluorescence of the two tryptophan residues of the protein (respectively, W190 in domain III and W5 in the N-terminal segment) in the wild type and in single-tryptophan mutants. By contrast to ANX A5, which shows a closed conformation and a buried W187 residue in the absence of Ca(2+), domain III of ANX A3 exhibits an open conformation and a widely solvent-accessible W190 residue in the same conditions. This is in agreement with the three-dimensional structure of the ANX A3-E231A mutant lacking the bidentate Ca(2+) ligand in domain III. Ca(2+) in the millimolar concentration range provokes nevertheless a large mobility increase of the W190 residue, while interaction with the membranes reduces it slightly. In the N-terminal region, the W5 residue, inserted in the central pore of the protein, is weakly accessible to the solvent and less mobile than W190. Its amplitude of rotation increases upon binding of Ca(2+) and returns to its original value when interacting with membranes. Ca(2+) concentration for half binding of the W5A mutant to negatively charged membranes is approximately 0.5 mM while it increases to approximately 1 mM for the ANX A3 wild type and to approximately 3 mM for the W190 ANX A3 mutant. In addition to the expected perturbation of the W190 environment at the contact surface between the protein and the membrane bilayer, binding of the protein to Ca(2+) and to membranes modulates the flexibility of the ANX A3 hinge region at the opposite of this interface and might affect its membrane permeabilizing properties.
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Anexina A3/metabolismo , Cálcio/metabolismo , Anexina A3/química , Sítios de Ligação , Cristalografia por Raios X , Polarização de Fluorescência , Proteínas de Membrana/metabolismo , Mutação , Conformação Proteica , Estrutura Terciária de Proteína , Triptofano/metabolismoRESUMO
Phosphorylation of the Ca2+ and membrane-binding protein annexin 1 by epidermal growth factor (EGF) receptor tyrosine kinase has been thought to be involved in regulation of the EGF receptor trafficking. To elucidate the interaction of annexin 1 during EGF receptor internalization, we followed the distribution of annexin 1-GFP fusion proteins at sites of internalizing EGF receptors. The observed association of annexin 1 with EGF receptors was confirmed by immunoprecipitation. We found that this interaction was independent of a functional phosphorylation site in the annexin 1 N-terminal domain but mediated through the Ca2+ binding core domain.
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Anexina A1/metabolismo , Membrana Celular/metabolismo , Receptores ErbB/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Anexina A1/química , Anexina A1/genética , Cálcio/metabolismo , Endocitose/fisiologia , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HeLa , Humanos , Imunoprecipitação , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genéticaRESUMO
OBJECTIVES: To explore beliefs and apprehensions about disease and its treatment in patients with rheumatoid arthritis and spondyloarthritis. METHODS: 25 patients with rheumatoid arthritis and 25 with spondyloarthritis participated in semi-structured interviews about their disease and its treatment. The interviews were performed by trained interviewers in participants' homes. The interviews were recorded and the main themes identified by content analysis. RESULTS: Patients differentiated between the underlying cause of the disease, which was most frequently identified as a hereditary or individual predisposition. In patients with rheumatoid arthritis, the most frequently cited triggering factor for disease onset was a psychological factor or life-event, whereas patients with spondyloarthritis tended to focus more on an intrinsic vulnerability to disease. Stress and overexertion were considered important triggering factors for exacerbations, and relaxation techniques were frequently cited strategies to manage exacerbations. The unpredictability of the disease course was a common source of anxiety. Beliefs about the disease and apprehensions about the future tended to evolve over the course of the disease, as did treatment expectations. CONCLUSIONS: Patients with rheumatoid arthritis and spondyloarthritis hold a core set of beliefs and apprehensions that reflect their level of information about their disease and are not necessarily appropriate. The physician can initiate discussion of these beliefs in order to dispel misconceptions, align treatment expectations, provide reassurance to the patient and readjust disease management. Such a dialogue would help improve standards of care in these chronic and incapacitating diseases.
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Artrite Reumatoide/psicologia , Medo , Conhecimentos, Atitudes e Prática em Saúde , Espondilartrite/psicologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pesquisa QualitativaRESUMO
Massive neuronal apoptosis and accumulation of protein aggregates in the cortex and hippocampus of the brain are hallmarks of several neurodegenerative disorders, indicating ubiquitin proteasome system (UPS) dysfunction. Lactacystin, a classical proteasome inhibitor, is used to simulate ubiquitin proteasome system dysfunction in neurons to mimic pathological features of neurodegenerative disorders. Based on Western blot analyses, we reported for the first time that annexin A3 (AnxA3) is not only endogenously expressed in mouse cortical neurons but also more importantly, by gene expression microarray and real-time RT-PCR that it is greatly transcriptional up-regulated to approximately 11- and 15-fold, respectively in murine primary cortical neurons with 1µM lactacystin for 24h. Up-regulation of AnxA3 expression occurred after 12-15h post-lactacystin treatment, which corresponded with the onset of neuronal injury, with approximately 25% of the neurons being non-viable by that time interval. Western blot analysis with anti-AnxA3 antibodies further validated that up-regulation of AnxA3 only occurs with onset of neuronal death, and not with the onset of proteasome inhibition, which occurs at 4.5h post-lactacystin treatment. Over-expression studies suggested AnxA3 might be involved in death promotion during lactacystin-mediated neuronal death, since caspase-3 activation was significantly stronger upon neuronal AnxA3 over-expression. We propose AnxA3 up-regulation may have significant relevance in the elucidation of neurodegenerative pathophysiology.
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Acetilcisteína/análogos & derivados , Anexina A3/fisiologia , Córtex Cerebral/metabolismo , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/patologia , Neurônios/patologia , Acetilcisteína/toxicidade , Animais , Anexina A3/biossíntese , Anexina A3/genética , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , Células Cultivadas , Córtex Cerebral/enzimologia , Córtex Cerebral/patologia , Camundongos , Doenças Neurodegenerativas/enzimologia , Regulação para Cima/fisiologiaRESUMO
The development of the devastating neurodegenerative condition, Alzheimer's disease, is strongly associated with amyloid-beta (Abeta) deposition, neuronal apoptosis, and cell loss. Here, we provide evidence that implicates these same mechanisms in the retinal disease glaucoma, a major cause of irreversible blindness worldwide, previously associated simply with the effects of intraocular pressure. We show that Abeta colocalizes with apoptotic retinal ganglion cells (RGC) in experimental glaucoma and induces significant RGC apoptosis in vivo in a dose- and time-dependent manner. We demonstrate that targeting different components of the Abeta formation and aggregation pathway can effectively reduce glaucomatous RGC apoptosis in vivo, and finally, that combining treatments (triple therapy) is more effective than monotherapy. Our work suggests that targeting the Abeta pathway provides a therapeutic avenue in glaucoma management. Furthermore, our work demonstrates that the combination of agents affecting multiple stages in the Abeta pathway may be the most effective strategy in Abeta-related diseases.
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Peptídeos beta-Amiloides/efeitos dos fármacos , Glaucoma/tratamento farmacológico , Animais , Glaucoma/patologia , Pressão Intraocular , Masculino , Ratos , Células Ganglionares da Retina/patologiaRESUMO
Annexin A5 is a Ca2+-dependent phospholipid binding protein well known for its high phosphatidylserine affinity. In vitro, translocation to sarcolemma and externalization of endogenous annexin A5 in the cardiomyocyte has recently been demonstrated to exert a proapoptotic effect. To determine whether these in vitro findings occurred in vivo, we performed myocardial infarction (MI) and studied the time course of apoptosis and annexin A5 localization (0.5 to 8 h) in the border zone around the infarcted area. This zone that was defined as Evans blue unstained and triphenyltetrazolium chloride (TTC) stained, represented 42.3 +/- 5.5% of the area at risk and showed apoptotic characteristics (significant increases in caspase 3 activity 2.3-fold at 0.5 h; P < 0.05), transferase-mediated dUTP nick-end labeling-positive cardiomyocytes (15.8 +/- 0.8% at 8 h), and DNA ladder. When compared with sham-operated rats, we found that in this area, annexin A5 was translocated to the sarcolemma as early as 0.5 h after MI and that translocation increased with time. Moreover, the amount of annexin A5 was unchanged in the border zone and decreased in the infarcted area after 1 h (77.1 +/- 4.8%; P < 0.01 vs. perfused area), suggesting a release in the latter but not in the former. In conclusion, we demonstrated that annexin A5 translocation is an early and rapid event of the whole border zone, likely due to Ca2+ increase. Part of this translocation occurred in areas where apoptosis was later detected and suggests that in vivo as in vitro annexin A5 might be involved in the regulation of early apoptotic events during cardiac pathological situations.
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Anexina A5/metabolismo , Apoptose/fisiologia , Infarto do Miocárdio/patologia , Miócitos Cardíacos/fisiologia , Sarcolema/patologia , Doença Aguda , Animais , Anexina A5/genética , Western Blotting , Caspase 3 , Caspases/metabolismo , Vasos Coronários/fisiologia , DNA/biossíntese , DNA/genética , Marcação In Situ das Extremidades Cortadas , Ligadura , Masculino , Ratos , Ratos Wistar , ATPase Trocadora de Sódio-Potássio/metabolismoRESUMO
Annexin A5 is a Ca2+ dependent phosphatidylserine binding protein mainly located in the T-tubules and sarcolemma of cardiomyocytes. Our objectives were to determine whether annexin A5 was associated with various protein(s) and whether such an association was modified in failing (F) hearts. The association between annexin A5 and the cardiac Na+/Ca2+ exchanger (NCX) was demonstrated by immunohistofluorescence, annexin A5-biotin overlay and co-immunoprecipitations (IPs) performed with microsomal preparations (MPs) from non-failing (NF) (n = 8) and F (dilated cardiomyopathy, n = 7) human hearts. We moreover found caveolin-3 in the immunoprecipitates, indicating the presence of multimolecular subsarcolemmal complexes. Surface plasmon resonance assays in NF MPs allowed us to demonstrate direct interaction between the NCX and caveolin-3 and immobilized annexin A5. Interaction was Ca2+-dependent and inhibited by the specific antibody. In addition, dissociation by zwittergent 3-14 (ZW 3-14) of the complexes from MPs increased specific interactions. In F hearts, specific interactions were blunted in native MPs but were fully recovered after treatment with ZW 3-14. In conclusion, we demonstrated that a direct interaction between annexin A5 and the cardiac NCX occurs in complexes including caveolin-3. In F hearts, despite the increase in the exchanger level, almost all of the NCX was involved in complexes. These interactions probably occurred in the intracytoplasmic regulatory loop of the exchanger, suggesting a different regulation of the exchanger in heart failure, consistent with a role in altered Ca2+ handling.
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Anexina A5/metabolismo , Caveolina 3/metabolismo , Insuficiência Cardíaca/metabolismo , Miocárdio/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Western Blotting , Humanos , Imunoprecipitação , Complexos Multiproteicos , Compostos de Amônio Quaternário/química , Valores de Referência , Ressonância de Plasmônio de SuperfícieRESUMO
Annexins are abundant and ubiquitous proteins that bind, by their four structurally identical domain cores, to phosphatidylserine-containing membranes in the presence of Ca2+. Using molecular simulation and mutagenesis, we have identified a new phosphatidylserine-binding site in annexin V domain 1 and established its structure. The residues involved in this site constitute a consensus sequence highly conserved in all annexins. Remarkably, this consensus sequence is exclusively found in domains 1 or 2, sometimes in both, but never in domains 3 and 4. Such a pattern actually delineates three classes of annexins, shedding new light on the role played by the four-domain core of annexins that could encode specific information discriminating the different annexins that compete within a given cell for membrane binding. Our findings thus provide new strategies for understanding the regulation of the cellular functions of annexins.