Beyond STEMI-NSTEMI Paradigm: Dante Pazzanese's Proposal for Occlusion Myocardial Infarction Diagnosis. / Além do Paradigma IAMCSST-IAMSSST: Proposta do Instituto Dante Pazzanese para o Diagnóstico de Oclusão Coronariana Aguda.

Although the existing framework for classifying acute myocardial infarction (AMI) into STEMI and NSTEMI has been beneficial, it is now considered to be falling short in addressing the complexity of acute coronary syndromes. The study aims to scrutinize the current STEMI-NSTEMI paradigm and advocate for a more nuanced framework, termed as occlusion myocardial infarction (OMI) and non-occlusion myocardial infarction (NOMI), for a more accurate diagnosis and management of AMI. A comprehensive analysis of existing medical literature was conducted, with a focus on the limitations of the STEMI-NSTEMI model. The study also outlines a new diagnostic approach for patients presenting with chest pain in emergency settings. The traditional STEMI-NSTEMI model falls short in diagnostic precision and effective treatment, especially in identifying acute coronary artery occlusions. The OMI-NOMI framework offers a more anatomically and physiologically accurate model, backed by a wealth of clinical research and expert opinion. It underscores the need for quick ECG assessments and immediate reperfusion therapies for suspected OMI cases, aiming to improve patient outcomes. The OMI-NOMI framework offers a new avenue for future research and clinical application. It advocates for a more comprehensive understanding of the underlying mechanisms of acute coronary syndromes, leading to individualized treatment plans. This novel approach is expected to ignite further scholarly debate and research, particularly in the Brazilian cardiology sector, with the goal of enhancing diagnostic accuracy and treatment effectiveness in AMI patients.

Embora o modelo existente de classificação do infarto agudo do miocárdio (IAM) em IAMCSST e IAMSSST tenha sido benéfico, considera-se hoje que ele falha em abordar a complexidade das síndromes coronarianas agudas. O estudo tem como objetivo examinar o atual paradigma IAMCSST-IAMSSST e defender um modelo mais detalhado, chamado de oclusão coronariana aguda (OCA) e Ausência de Oclusão Coronária Aguda (NOCA), para um diagnóstico e um manejo do IAM mais precisos. Realizou-se uma análise abrangente da literatura médica existente, com foco nas limitações do modelo IAMCSST-IAMSSST. O estudo também descreve uma nova abordagem diagnóstica para pacientes apresentando do torácica nos departamentos de emergência. O modelo IAMCSST-IAMSSST tradicional falha em prover um diagnóstico preciso e um tratamento efetivo, principalmente na identificação de oclusões da artéria coronária. O modelo OCA-NOCA é mais preciso em termos anatômicos e fisiológicos, e apoiado por pesquisa clínica extensa e opiniões de especialistas. Ele destaca a necessidade de rápida realização de eletrocardiogramas (ECGs) e terapias de reperfusão para casos suspeitos de OCA, visando melhorar os desfechos dos pacientes. O modelo OCA-NOCA abre um novo caminho para pesquisas e aplicações clínicas futuras. Ele defende um entendimento mais abrangente dos mecanismos subjacentes das síndromes coronarianas agudas, levando a planos individualizados de tratamentos. Espera-se que essa nova abordagem incite novos debates e pesquisas acadêmicas, principalmente na área de cardiologia no Brasil, com o objetivo de aumentar a precisão diagnóstica e a eficácia do tratamento de pacientes com IAM.

Interações complexas na hipercolesterolemia familiar: um estudo de caso de aterosclerose multivascular e variantes genéticas / Complex interactions in familial hypercholesterolemia: a case study of multivascular atherosclerosis and genetic variants

INTRODUÇÃO: A hipercolesterolemia familiar (HF) é um distúrbio genético bem reconhecido que se manifesta como níveis significativamente elevados de LDL-c sérico devido a aberrações no metabolismo das lipoproteínas. A maioria dos casos de HF, especificamente 85-90%, está associada a mutações patogênicas no gene do receptor de LDL (LDLR). Além disso, a presença de mutações de perda de função (LOF) no gene PCSK9 tem sido associada a um risco reduzido de doença cardiovascular, um fenômeno observado mesmo quando variantes patogênicas de LDLR coexistem. MÉTODOS: Este estudo incluiu um homem de 46 anos com dislipidemia e uso inconsistente de rosuvastatina. Na história familiar consta uma irmã (caso índice) e um sobrinho diagnosticados com HF portadores de variante patogênica de LDLR (c.313+1G>A, heterozigoto). RESULTADOS: O paciente relatou o aparecimento de dor precordial típica um mês antes da consulta. O exame físico revelou arco corneano. Os resultados laboratoriais iniciais mostraram colesterol total em 254 mg/dL, LDL-c em 191 mg/dL, HDL-c em 49 mg/dL e triglicerídeos em 69 mg/dL. Um escore Dutch MedPed de 11 confirmou HF. A ecocardiografia transtorácica indicou função ventricular esquerda normal. A angiografia coronária revelou calcificação significativa e estenose da artéria coronária direita (RCA) e da artéria circunflexa esquerda proximal (LCx). A intervenção incluiu angioplastia LCx e manejo conservador da RCA. Medicamentos pós-alta incluíram AAS 100mg/dia, Clopidogrel 75mg/dia, Rosuvastatina 40mg/ dia e Ezetimibe 10mg/dia. O nível de LDL-c diminuiu para 76 mg/dL no acompanhamento. A análise genética confirmou a variante familiar de LDLR e identificou uma mutação LOF coexistente de PCSK9 (R46L, heterozigoto). CONCLUSÃO: Este caso destaca a gravidade e complexidade da aterosclerose multivascular associada à HF. Embora a variante LOF de PCSK9 seja potencialmente protetora, sua influência nos resultados clínicos permanece incerta. Essa ambiguidade reforça a progressão multifatorial da aterosclerose e a resposta variável ao tratamento em pacientes com HF. Isso ressalta a importância de identificar fatores genéticos e não genéticos adicionais que contribuem para a doença, além dos loci genéticos conhecidos para entender e gerenciar melhor essa condição clínica.

Troca valvar aórtica transcateter e doença arterial coronária ­ experiência de um centro terciário de cardiologia / Transcatheter aortic valve replacement and coronary artery disease ­ experience from a tertiary cardiology center

INTRODUÇÃO: A troca valvar aórtica transcateter (TAVI) está estabelecida para o tratamento da estenose aórtica, independente do risco cirúrgico. Estudos demonstram prevalência variável de doença arterial coronária (DAC) nesta população, podendo chegar a até 81% dos pacientes tratados. A presença de DAC em concomitância com a estenose aórtica oferece um pior prognóstico a estes pacientes e o melhor momento para o tratamento da doença coronária ainda é controverso. OBJETIVO: Avaliar a incidência de DAC com angio-tomografia (angio-TC) em pacientes submetidos a TAVI em um hospital terciário de cardiologia e o impacto prognóstico da presença de DAC após um ano de seguimento. MÉTODOS: Estudo longitudinal, retrospectivo, com inclusão de pacientes submetidos consecutivamente a TAVI entre set/2020 a Dez/2023. A indicação de TAVI esteve baseada em diretriz da Sociedade Brasileira de Cardiologia, corroborada pelo Heart Team institucional. A investigação de DAC seguiu as recomendações mais recentes da mesma diretriz. Dados demográficos, comorbidades e eventos adversos foram computados para análise estatística. Análise multivariada foi realizada para avaliar fatores preditivos associados a ocorrência de eventos cardiovasculares (EC) em 1 ano. RESULTADOS: Um total de 268 pacientes submetidos a TAVI, com idade média de 79 anos, a maioria do sexo feminino (66%), com STS mortalidade médio de 3,1 ( 2.1 ­ 4.1) e alta prevalência de comorbidades associadas (tabela 1). As lesões foram avaliadas por angio-TC (Tabela 2). 96 pacientes possuíam dados após 1 ano de acompanhamento para análise de desfechos (tabela 3), com incidência de eventos cardiovasculares de 9% (tabela 4). Após análise multivariada, a presença de lesão de tronco da coronária esquerda e coronária direita foram fatores preditores para ocorrência de EC (Figura 1). Conclusão: Os resultados de nossa experiência estão alinhados aos resultados dos mais recentes ensaios clínicos randomizados. Apesar da alta incidência de DAC detectada através de angio-TC, a incidência de EC na população foi baixa durante o seguimento. A presença lesão em tronco da coronária esquerda e coronária direita, foram associados a maior prevalência de eventos adversos no seguimento de 1 ano.

Revisão sistemática e meta-análise da acurácia diagnóstica do Supradesnivelamento do segmento ST para diagnóstico de oclusão coronária aguda / Systematic review and meta-analysis of the diagnostic accuracy of ST segment elevation for diagnosing acute coronary occlusion

OBJETIVO: Avaliar a sensibilidade diagnóstica e a especificidade do supradesnivelamento do segmento ST em um ECG de 12 derivações na detecção de oclusão coronária aguda em qualquer artéria coronariana, desafiando o atual paradigma IAMCSST-IAMSSST. MÉTODOS: Estudos do MEDLINE e Scopus (2012-2023) comparando achados de ECG com angiogramas coronários foram revisados e analisados sistematicamente seguindo as diretrizes PRISMA-DTA. O risco de viés foi avaliado pelo QUADAS-2. SELEÇÃO DE ESTUDOS: Os estudos incluídos focaram em pacientes com síndrome coronária aguda e forneceram dados que permitiram a construção de tabelas de contingência para cálculo de sensibilidade e especificidade, excluindo aqueles com condições não-SCA, critérios desatualizados de STEMI ou foco específico em bloqueios de ramo ou artérias coronárias específicas. Os dados foram extraídos sistematicamente e as estimativas de precisão dos testes agrupadas foram calculadas usando o software MetaDTA, empregando análises bivariadas para variação intra e inter-estudos. Os desfechos primários medidos foram a sensibilidade e especificidade do supradesnivelamento do segmento ST na detecção de OCA. RESULTADOS: Três estudos com 23704 participantes foram incluídos. A sensibilidade agrupada do supradesnivelamento do segmento ST para detecção de OCA foi de 43,6% (IC 95%: 34,7%-52,9%), indicando que mais da metade dos casos de OCA pode não apresentar critérios de supradesnivelamento do segmento ST. A especificidade foi de 96,5% (IC 95%: 91,2%-98,7%). Uma análise adicional usando a estratégia OMI-NOMI mostrou sensibilidade melhorada (78,1%, IC 95%: 62,7%-88,3%) mantendo especificidade semelhante (94,4%, IC 95%: 88,6%-97,3%). CONCLUSÃO: Os achados revelam uma lacuna diagnóstica significativa no atual paradigma IAMCSST-IAMSSST, com mais da metade dos casos de OCA potencialmente ausentes de supradesnivelamento do segmento ST. A estratégia OMI-NOMI poderia oferecer uma abordagem diagnóstica aprimorada. A alta heterogeneidade e o número limitado de estudos exigem interpretação cautelosa e mais pesquisas em ambientes diversos.

Systematic review and meta-analysis of diagnostic test accuracy of ST-segment elevation for acute coronary occlusion.

OBJECTIVE: To evaluate the diagnostic sensitivity and specificity of ST-segment elevation on a 12­lead ECG in detecting ACO across any coronary artery, challenging the current STEMI-NSTEMI paradigm. METHODS: Studies from MEDLINE and Scopus (2012-2023) comparing ECG findings with coronary angiograms were systematically reviewed and analyzed following PRISMA-DTA guidelines. QUADAS-2 assessed the risk of bias. STUDY SELECTION: Studies included focused on AMI patients and provided data enabling the construction of contingency tables for sensitivity and specificity calculation, excluding those with non-ACS conditions, outdated STEMI criteria, or a specific focus on bundle branch blocks or other complex diagnoses. Data were extracted systematically and pooled test accuracy estimates were computed using MetaDTA software, employing bivariate analyses for within- and between-study variation. The primary outcomes measured were the sensitivity and specificity of ST-segment elevation in detecting ACO. RESULTS: Three studies with 23,704 participants were included. The pooled sensitivity of ST-segment elevation for detecting ACO was 43.6% (95% CI: 34.7%-52.9%), indicating that over half of ACO cases may not exhibit ST-segment elevation. The specificity was 96.5% (95% CI: 91.2%-98.7%). Additional analysis using the OMI-NOMI strategy showed improved sensitivity (78.1%, 95% CI: 62.7%-88.3%) while maintaining similar specificity (94.4%, 95% CI: 88.6%-97.3%). CONCLUSION: The findings reveal a significant diagnostic gap in the current STEMI-NSTEMI paradigm, with over half of ACO cases potentially lacking ST-segment elevation. The OMI-NOMI strategy could offer an improved diagnostic approach. The high heterogeneity and limited number of studies necessitate cautious interpretation and further research in diverse settings.

Systematic review and meta-analysis of diagnostic test accuracy of ST-segment elevation for acute coronary occlusion

OBJECTIVE: To evaluate the diagnostic sensitivity and specificity of ST-segment elevation on a 12­lead ECG in detecting ACO across any coronary artery, challenging the current STEMI-NSTEMI paradigm. METHODS: Studies from MEDLINE and Scopus (2012-2023) comparing ECG findings with coronary angiograms were systematically reviewed and analyzed following PRISMA-DTA guidelines. QUADAS-2 assessed the risk of bias. STUDY SELECTION: Studies included focused on AMI patients and provided data enabling the construction of contingency tables for sensitivity and specificity calculation, excluding those with non-ACS conditions, outdated STEMI criteria, or a specific focus on bundle branch blocks or other complex diagnoses. Data were extracted systematically and pooled test accuracy estimates were computed using MetaDTA software, employing bivariate analyses for within- and between-study variation. The primary outcomes measured were the sensitivity and specificity of ST-segment elevation in detecting ACO. RESULTS: Three studies with 23,704 participants were included. The pooled sensitivity of ST-segment elevation for detecting ACO was 43.6% (95% CI: 34.7%-52.9%), indicating that over half of ACO cases may not exhibit ST-segment elevation criteria. The specificity was 96.5% (95% CI: 91.2%-98.7%). Additional analysis using the OMI-NOMI strategy showed improved sensitivity (78.1%, 95% CI: 62.7%-88.3%) while maintaining similar specificity (94.4%, 95% CI: 88.6%-97.3%). CONCLUSION: The findings reveal a significant diagnostic gap in the current STEMI-NSTEMI paradigm, with over half of ACO cases potentially lacking ST-segment elevation. The OMI-NOMI strategy could offer an improved diagnostic approach. The high heterogeneity and limited number of studies necessitate cautious interpretation and further research in diverse settings.

Além do Paradigma IAMCSST-IAMSSST: Proposta do Instituto Dante Pazzanese para o Diagnóstico de Oclusão Coronariana Aguda / Beyond STEMI-NSTEMI Paradigm: Dante Pazzanese's Proposal for Occlusion Myocardial Infarction Diagnosis

Resumo Embora o modelo existente de classificação do infarto agudo do miocárdio (IAM) em IAMCSST e IAMSSST tenha sido benéfico, considera-se hoje que ele falha em abordar a complexidade das síndromes coronarianas agudas. O estudo tem como objetivo examinar o atual paradigma IAMCSST-IAMSSST e defender um modelo mais detalhado, chamado de oclusão coronariana aguda (OCA) e Ausência de Oclusão Coronária Aguda (NOCA), para um diagnóstico e um manejo do IAM mais precisos. Realizou-se uma análise abrangente da literatura médica existente, com foco nas limitações do modelo IAMCSST-IAMSSST. O estudo também descreve uma nova abordagem diagnóstica para pacientes apresentando do torácica nos departamentos de emergência. O modelo IAMCSST-IAMSSST tradicional falha em prover um diagnóstico preciso e um tratamento efetivo, principalmente na identificação de oclusões da artéria coronária. O modelo OCA-NOCA é mais preciso em termos anatômicos e fisiológicos, e apoiado por pesquisa clínica extensa e opiniões de especialistas. Ele destaca a necessidade de rápida realização de eletrocardiogramas (ECGs) e terapias de reperfusão para casos suspeitos de OCA, visando melhorar os desfechos dos pacientes. O modelo OCA-NOCA abre um novo caminho para pesquisas e aplicações clínicas futuras. Ele defende um entendimento mais abrangente dos mecanismos subjacentes das síndromes coronarianas agudas, levando a planos individualizados de tratamentos. Espera-se que essa nova abordagem incite novos debates e pesquisas acadêmicas, principalmente na área de cardiologia no Brasil, com o objetivo de aumentar a precisão diagnóstica e a eficácia do tratamento de pacientes com IAM.

Abstract Although the existing framework for classifying acute myocardial infarction (AMI) into STEMI and NSTEMI has been beneficial, it is now considered to be falling short in addressing the complexity of acute coronary syndromes. The study aims to scrutinize the current STEMI-NSTEMI paradigm and advocate for a more nuanced framework, termed as occlusion myocardial infarction (OMI) and non-occlusion myocardial infarction (NOMI), for a more accurate diagnosis and management of AMI. A comprehensive analysis of existing medical literature was conducted, with a focus on the limitations of the STEMI-NSTEMI model. The study also outlines a new diagnostic approach for patients presenting with chest pain in emergency settings. The traditional STEMI-NSTEMI model falls short in diagnostic precision and effective treatment, especially in identifying acute coronary artery occlusions. The OMI-NOMI framework offers a more anatomically and physiologically accurate model, backed by a wealth of clinical research and expert opinion. It underscores the need for quick ECG assessments and immediate reperfusion therapies for suspected OMI cases, aiming to improve patient outcomes. The OMI-NOMI framework offers a new avenue for future research and clinical application. It advocates for a more comprehensive understanding of the underlying mechanisms of acute coronary syndromes, leading to individualized treatment plans. This novel approach is expected to ignite further scholarly debate and research, particularly in the Brazilian cardiology sector, with the goal of enhancing diagnostic accuracy and treatment effectiveness in AMI patients.

Discovery and structural characterization of chicoric acid as a SARS-CoV-2 nucleocapsid protein ligand and RNA binding disruptor.

The nucleocapsid (N) protein plays critical roles in coronavirus genome transcription and packaging, representing a key target for the development of novel antivirals, and for which structural information on ligand binding is scarce. We used a novel fluorescence polarization assay to identify small molecules that disrupt the binding of the N protein to a target RNA derived from the SARS-CoV-2 genome packaging signal. Several phenolic compounds, including L-chicoric acid (CA), were identified as high-affinity N-protein ligands. The binding of CA to the N protein was confirmed by isothermal titration calorimetry, 1H-STD and 15N-HSQC NMR, and by the crystal structure of CA bound to the N protein C-terminal domain (CTD), further revealing a new modulatory site in the SARS-CoV-2 N protein. Moreover, CA reduced SARS-CoV-2 replication in cell cultures. These data thus open venues for the development of new antivirals targeting the N protein, an essential and yet underexplored coronavirus target.

Structural dynamics of SARS-CoV-2 nucleocapsid protein induced by RNA binding.

The nucleocapsid (N) protein of the SARS-CoV-2 virus, the causal agent of COVID-19, is a multifunction phosphoprotein that plays critical roles in the virus life cycle, including transcription and packaging of the viral RNA. To play such diverse roles, the N protein has two globular RNA-binding modules, the N- (NTD) and C-terminal (CTD) domains, which are connected by an intrinsically disordered region. Despite the wealth of structural data available for the isolated NTD and CTD, how these domains are arranged in the full-length protein and how the oligomerization of N influences its RNA-binding activity remains largely unclear. Herein, using experimental data from electron microscopy and biochemical/biophysical techniques combined with molecular modeling and molecular dynamics simulations, we show that, in the absence of RNA, the N protein formed structurally dynamic dimers, with the NTD and CTD arranged in extended conformations. However, in the presence of RNA, the N protein assumed a more compact conformation where the NTD and CTD are packed together. We also provided an octameric model for the full-length N bound to RNA that is consistent with electron microscopy images of the N protein in the presence of RNA. Together, our results shed new light on the dynamics and higher-order oligomeric structure of this versatile protein.

Isolation, culture, and immunostaining of neonatal rat ventricular myocytes.

Isolation and culture of ventricular cardiomyocytes from neonatal rats (NRVMs) is a powerful model to study neonatal cardiac development, cell cycle regulation, and cardiac physiology and pathology in vitro. Here, we present our modified enzymatic digestion protocol followed by two-step discontinuous Percoll gradient centrifugation to isolate a high yield of viable ventricular cardiomyocytes from neonatal rats. Finally, here we describe an immunostaining protocol for cytosolic and nuclear staining of NRVMs. For complete details on the use and execution of this protocol, please refer to Pereira et al. (2020).

Molecular and cellular basis of hyperassembly and protein aggregation driven by a rare pathogenic mutation in DDX3X.

Current studies estimate that 1-3% of females with unexplained intellectual disability (ID) present de novo splice site, nonsense, frameshift, or missense mutations in the DDX3X protein (DEAD-Box Helicase 3 X-Linked). However, the cellular and molecular mechanisms by which DDX3X mutations impair brain development are not fully comprehended. Here, we show that the ID-linked missense mutation L556S renders DDX3X prone to aggregation. By using a combination of biophysical assays and imaging approaches, we demonstrate that this mutant assembles solid-like condensates and amyloid-like fibrils. Although we observed greatly reduced expression of the mutant allele in a patient who exhibits skewed X inactivation, this appears to be enough to sequestrate healthy proteins into solid-like ectopic granules, compromising cell function. Therefore, our data suggest ID-linked DDX3X L556S mutation as a disorder arising from protein misfolding and aggregation.

Mechanistic insights revealed by a UBE2A mutation linked to intellectual disability.

Ubiquitin-conjugating enzymes (E2) enable protein ubiquitination by conjugating ubiquitin to their catalytic cysteine for subsequent transfer to a target lysine side chain. Deprotonation of the incoming lysine enables its nucleophilicity, but determinants of lysine activation remain poorly understood. We report a novel pathogenic mutation in the E2 UBE2A, identified in two brothers with mild intellectual disability. The pathogenic Q93E mutation yields UBE2A with impaired aminolysis activity but no loss of the ability to be conjugated with ubiquitin. Importantly, the low intrinsic reactivity of UBE2A Q93E was not overcome by a cognate ubiquitin E3 ligase, RAD18, with the UBE2A target PCNA. However, UBE2A Q93E was reactive at high pH or with a low-pKa amine as the nucleophile, thus providing the first evidence of reversion of a defective UBE2A mutation. We propose that Q93E substitution perturbs the UBE2A catalytic microenvironment essential for lysine deprotonation during ubiquitin transfer, thus generating an enzyme that is disabled but not dead.

Adenosine Kinase couples sensing of cellular potassium depletion to purine metabolism.

Adenosine Kinase (ADK) regulates the cellular levels of adenosine (ADO) by fine-tuning its metabolic clearance. The transfer of γ-phosphate from ATP to ADO by ADK involves regulation by the substrates and products, as well as by Mg2+ and inorganic phosphate. Here we present new crystal structures of mouse ADK (mADK) binary (mADK:ADO; 1.2 Å) and ternary (mADK:ADO:ADP; 1.8 Å) complexes. In accordance with the structural demonstration of ADO occupancy of the ATP binding site, kinetic studies confirmed a competitive model of auto-inhibition of ADK by ADO. In the ternary complex, a K+ ion is hexacoordinated between loops adjacent to the ATP binding site, where Asp310 connects the K+ coordination sphere to the ATP binding site through an anion hole structure. Nuclear Magnetic Resonance 2D 15N-1H HSQC experiments revealed that the binding of K+ perturbs Asp310 and residues of adjacent helices 14 and 15, engaging a transition to a catalytically productive structure. Consistent with the structural data, the mutants D310A and D310P are catalytically deficient and loose responsiveness to K+. Saturation Transfer Difference spectra of ATPγS provided evidence for an unfavorable interaction of the mADK D310P mutant for ATP. Reductions in K+ concentration diminish, whereas increases enhance the in vitro activity of mADK (maximum of 2.5-fold; apparent Kd = 10.4 mM). Mechanistically, K+ increases the catalytic turnover (Kcat) but does not affect the affinity of mADK for ADO or ATP. Depletion of intracellular K+ inhibited, while its restoration was accompanied by a full recovery of cellular ADK activity. Together, this novel dataset reveals the molecular basis of the allosteric activation of ADK by K+ and highlights the role of ADK in connecting depletion of intracellular K+ to the regulation of purine metabolism.

High-resolution synchrotron-based X-ray microtomography as a tool to unveil the three-dimensional neuronal architecture of the brain.

The assessment of neuronal number, spatial organization and connectivity is fundamental for a complete understanding of brain function. However, the evaluation of the three-dimensional (3D) brain cytoarchitecture at cellular resolution persists as a great challenge in the field of neuroscience. In this context, X-ray microtomography has shown to be a valuable non-destructive tool for imaging a broad range of samples, from dense materials to soft biological specimens, arisen as a new method for deciphering the cytoarchitecture and connectivity of the brain. In this work we present a method for imaging whole neurons in the brain, combining synchrotron-based X-ray microtomography with the Golgi-Cox mercury-based impregnation protocol. In contrast to optical 3D techniques, the approach shown here does neither require tissue slicing or clearing, and allows the investigation of several cells within a 3D region of the brain.

Human mitochondrial pyruvate carrier 2 as an autonomous membrane transporter.

The active transport of glycolytic pyruvate across the inner mitochondrial membrane is thought to involve two mitochondrial pyruvate carrier subunits, MPC1 and MPC2, assembled as a 150 kDa heterotypic oligomer. Here, the recombinant production of human MPC through a co-expression strategy is first described; however, substantial complex formation was not observed, and predominantly individual subunits were purified. In contrast to MPC1, which co-purifies with a host chaperone, we demonstrated that MPC2 homo-oligomers promote efficient pyruvate transport into proteoliposomes. The derived functional requirements and kinetic features of MPC2 resemble those previously demonstrated for MPC in the literature. Distinctly, chemical inhibition of transport is observed only for a thiazolidinedione derivative. The autonomous transport role for MPC2 is validated in cells when the ectopic expression of human MPC2 in yeast lacking endogenous MPC stimulated growth and increased oxygen consumption. Multiple oligomeric species of MPC2 across mitochondrial isolates, purified protein and artificial lipid bilayers suggest functional high-order complexes. Significant changes in the secondary structure content of MPC2, as probed by synchrotron radiation circular dichroism, further supports the interaction between the protein and ligands. Our results provide the initial framework for the independent role of MPC2 in homeostasis and diseases related to dysregulated pyruvate metabolism.

FAK Forms a Complex with MEF2 to Couple Biomechanical Signaling to Transcription in Cardiomyocytes.

Focal adhesion kinase (FAK) has emerged as a mediator of mechanotransduction in cardiomyocytes, regulating gene expression during hypertrophic remodeling. However, how FAK signaling is relayed onward to the nucleus is unclear. Here, we show that FAK interacts with and regulates myocyte enhancer factor 2 (MEF2), a master cardiac transcriptional regulator. In cardiomyocytes exposed to biomechanical stimulation, FAK accumulates in the nucleus, binds to and upregulates the transcriptional activity of MEF2 through an interaction with the FAK focal adhesion targeting (FAT) domain. In the crystal structure (2.9 Å resolution), FAT binds to a stably folded groove in the MEF2 dimer, known to interact with regulatory cofactors. FAK cooperates with MEF2 to enhance the expression of Jun in cardiomyocytes, an important component of hypertrophic response to mechanical stress. These findings underscore a connection between the mechanotransduction involving FAK and transcriptional regulation by MEF2, with potential relevance to the pathogenesis of cardiac disease.

Immediate response of myocardium to pressure overload includes transient regulation of genes associated with mitochondrial bioenergetics and calcium availability.

Ventricular hypertrophy is one of the major myocardial responses to pressure overload (PO). Most studies on early myocardial response focus on the days or even weeks after induction of hypertrophic stimuli. Since mechanotransduction pathways are immediately activated in hearts undergoing increased work load, it is reasonable to infer that the myocardial gene program may be regulated in the first few hours. In the present study, we monitored the expression of some genes previously described in the context of myocardial hypertrophic growth by using the Northern blot technique, to estimate the mRNA content of selected genes in rat myocardium for the periods 1, 3, 6, 12 and 48 h after PO stimuli. Results revealed an immediate switch in the expression of genes encoding alpha and beta isoforms of myosin heavy chain, and up-regulation of the cardiac isoform of alpha actin. We also detected transitory gene regulation as the increase in mitochondrial cytochrome c oxidase 1 gene expression, parallel to down-regulation of genes encoding sarco(endo)plasmic reticulum Ca(+2) ATPase and sodium-calcium exchanger. Taken together, these results indicate that initial myocardial responses to increased work load include alterations in the contractile properties of sarcomeres and transitory adjustment of mitochondrial bioenergetics and calcium availability.

Immediate response of myocardium to pressure overload includes transient regulation of genes associated with mitochondrial bioenergetics and calcium availability

Ventricular hypertrophy is one of the major myocardial responses to pressure overload (PO). Most studies on early myocardial response focus on the days or even weeks after induction of hypertrophic stimuli. Since mechanotransduction pathways are immediately activated in hearts undergoing increased work load, it is reasonable to infer that the myocardial gene program may be regulated in the first few hours. In the present study, we monitored the expression of some genes previously described in the context of myocardial hypertrophic growth by using the Northern blot technique, to estimate the mRNA content of selected genes in rat myocardium for the periods 1, 3, 6, 12 and 48 h after PO stimuli. Results revealed an immediate switch in the expression of genes encoding alpha and beta isoforms of myosin heavy chain, and up-regulation of the cardiac isoform of alpha actin. We also detected transitory gene regulation as the increase in mitochondrial cytochrome c oxidase 1 gene expression, parallel to down-regulation of genes encoding sarco(endo)plasmic reticulum Ca+2 ATPase and sodium-calcium exchanger. Taken together, these results indicate that initial myocardial responses to increased work load include alterations in the contractile properties of sarcomeres and transitory adjustment of mitochondrial bioenergetics and calcium availability.

Analysis of adenosine by RP-HPLC method and its application to the study of adenosine kinase kinetics.

An RP-HPLC method for the analysis of adenosine (ADO) has been developed and validated. In the present study, we report an RP-HPLC-based method with modifications of mobile phase and shorter retention time that substantially improved the efficiency of ADO analysis. The HPLC separation of the ADO was achieved on a C18 column, using a mobile phase consisting of water, containing 7% v/v ACN, at a flow rate of 0.8 mL/min. The column effluent was monitored by UV detection at 260 nm. A linear response was achieved over the concentration range of 0.25-100.00 micromol/L. The analytical method inter- and intra-run accuracy and precision were better than +/- 15%. The LOQ was 0.25 micromol/L, with ADO detection in the range of 6.25 pmol per sample. The method has been applied to the study of adenosine kinase (AK) kinetics.

MEF2C DNA-binding activity is inhibited through its interaction with the regulatory protein Ki-1/57.

Myocyte enhancer factor (MEF2) are MADS box transcription factors that play important roles in the regulation of myogenesis and morphogenesis of muscle cells. MEF2 proteins are activated by mechanical overload in the heart. In this study, we found the interaction of MEF2C with the regulatory protein Ki-1/57 using yeast two-hybrid system. This interaction was confirmed by GST-pull down assay in vitro and by co-immunoprecipitation in vivo. This interaction is also dependent on pressure overload in the heart. Co-imunoprecipitation assay with anti-MEF2 and anti-Ki-1/57 antibodies demonstrated a basal association between these proteins in the left ventricles of control rats. Pressure overload caused a reduction in this association. Ki-1/57 co-localizes with MEF2 in the nucleus of myocytes of control rats. However, after submitting the animals to pressure overload Ki-1/57 leaves the nucleus thereby decreasing this co-localization. Ki-1/57 also exerts an inhibitory effect upon MEF2C DNA binding activity. These results suggest that Ki-1/57 is a new interacting partner of MEF2 protein and may be involved in the regulation of MEF2 at the onset of hypertrophy.