Antithrombotic therapy in atrial fibrillation: guidelines translated for the clinician

Genome-Wide RNA-Sequencing Reveals Massive Circular RNA Expression Changes of the Neurotransmission Genes in the Rat Brain after Ischemia-Reperfusion

Ischemic brain stroke is one of the most serious and socially significant diseases. In addition to messenger RNAs (mRNAs), encoding protein, the study of regulatory RNAs in ischemic has exceptional importance for the development of new strategies for neuroprotection. Circular RNAs (circRNAs) have a closed structure, predominantly brain-specific expression, and remain highly promising targets of research. They can interact with microRNAs (miRNAs), diminish their activity and thereby inhibit miRNA-mediated repression of mRNA. Genome-wide RNA-Seq analysis of the subcortical structures of the rat brain containing an ischemic damage focus and penumbra area revealed 395 circRNAs changed their expression significantly at 24 h after transient middle cerebral artery occlusion model (tMCAO) conditions. Furthermore, functional annotation revealed their association with neuroactive signaling pathways. It was found that about a third of the differentially expressed circRNAs (DECs) originate from genes whose mRNA levels also changed at 24 h after tMCAO. The other DECs originate from genes encoding non-regulated mRNAs under tMCAO conditions. In addition, bioinformatic analysis predicted a circRNA–miRNA–mRNA network which was associated with the neurotransmission signaling regulation. Our results show that such circRNAs can persist as potential miRNA sponges for the protection of mRNAs of neurotransmitter genes. The results expanded our views about the neurotransmission regulation in the rat brain after ischemia–reperfusion with circRNA action.

Novel Insights into the Protective Properties of ACTH(4-7)PGP (Semax) Peptide at the Transcriptome Level Following Cerebral Ischaemia-Reperfusion in Rats

Cerebral ischaemia is the most common cause of impaired brain function. Biologically active peptides represent potential drugs for reducing the damage that occurs after ischaemia. The synthetic melanocortin derivative, ACTH_(4-7)PGP (Semax), has been used successfully in the treatment of patients with severe impairment of cerebral blood circulation. However, its molecular mechanisms of action within the brain are not yet fully understood. Previously, we used the transient middle cerebral artery occlusion (tMCAO) model to study the damaging effects of ischaemia-reperfusion on the brain transcriptome in rats. Here, using RNA-Seq analysis, we investigated the protective properties of the Semax peptide at the transcriptome level under tMCAO conditions. We have identified 394 differentially expressed genes (DEGs) (>1.5-fold change) in the brains of rats at 24 h after tMCAO treated with Semax relative to saline. Following tMCAO, we found that Semax suppressed the expression of genes related to inflammatory processes and activated the expression of genes related to neurotransmission. In contrast, ischaemia-reperfusion alone activated the expression of inflammation-related genes and suppressed the expression of neurotransmission-related genes. Therefore, the neuroprotective action of Semax may be associated with a compensation of mRNA expression patterns that are disrupted during ischaemia-reperfusion conditions.

RNA Sequencing for Gene Expression Profiles in a Rat Model of Middle Cerebral Artery Occlusion

Gene expression regulatory mechanisms in models of middle cerebral artery occlusion (MCAO) have been assessed in some studies, but questions remain. The discovery of differentially expressed genes (DEGs) between MCAO and control rats analyzed by next-generation RNA sequencing is of particular interest. These DEGs may help guide the clinical diagnosis of stroke and facilitate selection of the optimal treatment strategy. Twenty rats were equally divided into control and MCAO groups. Three rats from each group were randomly selected for RNA sequencing analysis. Sequence reads were obtained from an Illumina HiSeq2500 platform and mapped onto the rat reference genome RN6 using Hisat2. We identified 1,007 significantly DEGs with p<0.05, including 785 upregulated (fold change [FC]>2) and 222 downregulated (FC<0.5) DEGs, in brain tissue from MCAO rats compared with that from control rats, and numerous immune response genes were identified. Gene ontology (GO) analysis revealed that the majority of the most enriched and meaningful biological process terms were mainly involved in immune response, inflammatory response, cell activation, leukocyte migration, cell adhesion, response to external stimulus, cell migration, and response to wounding. Also enriched were immune-related pathways and neural-related pathways. Similar to GO molecular function terms, the enriched terms were mainly related to cytokine receptor activity. Six DEGs were verified by quantitative real-time polymerase chain reaction (qRT-PCR). Protein-protein interaction analysis of these hits revealed that MCAO affects complement and coagulation cascades and chemokine signaling pathway. Our study identified novel biomarkers that could help further elucidate MCAO mechanisms and processes.

Genome-wide transcriptome analysis using RNA-Seq reveals a large number of differentially expressed genes in a transient MCAO rat model

Background

The transient middle cerebral artery occlusion (tMCAO) model is used for studying the molecular mechanisms of ischemic damage and neuroprotection. Numerous studies have demonstrated the role of individual genes and associated signaling pathways in the pathogenesis of ischemic stroke. Here, the tMCAO model was used to investigate the genome-wide response of the transcriptome of rat brain tissues to the damaging effect of ischemia and subsequent reperfusion.

Results

Magnetic resonance imaging and histological examination showed that the model of focal ischemia based on endovascular occlusion of the right middle cerebral artery for 90 min using a monofilament, followed by restoration of the blood flow, led to reproducible localization of ischemic damage in the subcortical structures of the brain. High-throughput RNA sequencing (RNA-Seq) revealed the presence of differentially expressed genes (DEGs) in subcortical structures of rat brains resulting from hemisphere damage by ischemia after tMCAO, as well as in the corresponding parts of the brains of sham-operated animals. Real-time reverse transcription polymerase chain reaction expression analysis of 20 genes confirmed the RNA-Seq results. We identified 469 and 1939 genes that exhibited changes in expression of > 1.5-fold at 4.5 and 24 h after tMCAO, respectively. Interestingly, we found 2741 and 752 DEGs under ischemia–reperfusion and sham-operation conditions at 24 h vs. 4.5 h after tMCAO, respectively. The activation of a large number of genes involved in inflammatory, immune and stress responses, apoptosis, ribosome function, DNA replication and other processes was observed in ischemia–reperfusion conditions. Simultaneously, massive down-regulation of the mRNA levels of genes involved in the functioning of neurotransmitter systems was recorded. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that dozens of signaling pathways were associated with DEGs in ischemia–reperfusion conditions.

Conclusions

The data obtained revealed a global profile of gene expression in the rat brain sub-cortex under tMCAO conditions that can be used to identify potential therapeutic targets in the development of new strategies for the prevention and treatment of ischemic stroke.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5039-5) contains supplementary material, which is available to authorized users.

Is Appropriate Management of Atrial Fibrillation in Primary Care a Utopia?

Objective:

The authors aimed at reporting on whether or not primary care doctors follow atrial fibrillation (AF) treatment protocols, and on the mental distress of such patients.

Methods:

A total of 138 patients with first detected or recurrent AF were examined in a health center. Demographic data were collected and their lifestyle and medical history for rhythm-related pathologies and chronic medication were investigated. Physical examination, electrocardiogram (EKG), and in selected cases, lab analysis were carried-out. CHADS2 index was used for assessing the stroke risk in patients with AF, while the General Health Questionnaire-12 (GHQ-12) for personal health perception was performed in all patients.

Results:

According to CHADS2 the majority of the patients had at least 1 risk factor and half of those receiving oral vitamin K antagonists presented an out-of-range international normalized ratio (INR). In 24 cases, patients used both aspirin and oral anticoagulants, while in 41 cases, medication was corrected according to index. GHQ-12 seemed to be significantly worse in paroxysmal and persistent cases, as well as in women with recurrent AF. Many paroxysmal AF patients under 75 years continued caffeine intake, whereas an extensive use of benzodiazepines was noticed in the majority of patients.

Conclusions:

Shortages and limitations of the peripheral or rural units and health centers and inadequate knowledge and application of the guidelines, seemed to be major factors responsible for mismanaging AF patients. More education in prehospital cardiology may contribute in improving management of arrhythmias in primary care.

Global gene expression profile of cerebral ischemia-reperfusion injury in rat MCAO model

It is well-established that reperfusion following cerebral ischemic injury gives rise to secondary injury accompanied by structural and functional damage. However, it remains unclear how global genes changes in cerebral ischemia-reperfusion injury (IRI). This study investigated global gene expression in the hippocampi of Wistar rats following transient cerebral IRI using an RNA-sequencing strategy. The results revealed ≥2-fold up-regulation of 156 genes and ≥2-fold down-regulation of 26 genes at 24 h post-reperfusion. Fifteen differentially expressed genes were selected to confirm the RNA-sequencing results. Gene expression levels were dynamic, with the peak expression level of each gene occurring at different time points post-reperfusion. Gene Ontology (GO) analysis classified the differentially expressed genes as mainly involved in inflammation, stress and immune response, glucose metabolism, proapoptosis, antiapoptosis, and biological processes. KEGG pathway analysis suggested that IRI activated different signaling pathways, including focal adhesion, regulation of actin cytoskeleton, cytokine-cytokine receptor interaction, MAPK signaling, and Jak-STAT signaling. This study describes global gene expression profiles in the hippocampi of Wistar rats using the middle cerebral artery occlusion (MCAO) model. These findings provide new insights into the molecular pathogenesis of IRI and potential drug targets for the prevention and treatment of IRI in the future.

Review of challenges in optimizing oral anticoagulation therapy for stroke prevention in atrial fibrillation

Oral anticoagulant therapy is the mainstay of stroke prevention in patients with atrial fibrillation; it is highly effective at reducing stroke risk, but its use can be limited by increased risk of bleeding. As new oral anticoagulants are available, barriers to optimal use of oral anticoagulation therapy warrant consideration by healthcare professionals and administrators who are seeking to optimize the quality of care for patients with atrial fibrillation. Suboptimal use of oral anticoagulation therapy constitutes an important health problem with significant humanistic and economic consequences. Based on a review of the medical literature published between 2000 and 2011, this article summarizes the literature on the barriers to optimal use of oral anticoagulation therapy, describes the clinical and economic burdens that these barriers add to the burden of atrial fibrillation, and discusses how well the new oral anticoagulants may address some of these issues.

Highlights from the IV International Symposium of Thrombosis and Anticoagulation (ISTA), October 20-21, 2011, Salvador, Bahia, Brazil

To discuss and share knowledge about advances in the care of patients with thrombotic disorders, the Fourth International Symposium of Thrombosis and Anticoagulation was held in Salvador, Bahia, Brazil, from October 20-21, 2011. This scientific program was developed by clinicians for clinicians and was promoted by three major clinical research institutes: the Brazilian Clinical Research Institute, the Duke Clinical Research Institute of the Duke University School of Medicine, and Hospital do Coração Research Institute. Comprising 2 days of academic presentations and open discussion, the symposium had as its primary goal to educate, motivate, and inspire internists, cardiologists, hematologists, and other physicians by convening national and international visionaries, thought-leaders, and dedicated clinician-scientists. This paper summarizes the symposium proceedings.

Highlights from the III International Symposium of Thrombosis and Anticoagulation (ISTA), October 14-16, 2010, São Paulo, Brazil

To discuss and share knowledge around advances in the care of patients with thrombotic disorders, the Third International Symposium of Thrombosis and Anticoagulation was held in São Paulo, Brazil, from October 14-16, 2010. This scientific program was developed by clinicians for clinicians, and was promoted by four major clinical research institutes: the Brazilian Clinical Research Institute, the Duke Clinical Research Institute of the Duke University School of Medicine, the Canadian VIGOUR Centre, and the Uppsala Clinical Research Center. Comprising 3 days of academic presentations and open discussion, the symposium had as its primary goal to educate, motivate, and inspire internists, cardiologists, hematologists, and other physicians by convening national and international visionaries, thought-leaders, and dedicated clinician-scientists. This paper summarizes the symposium proceedings.

Oral anticoagulation in elderly patients as secondary prevention of cardioembolic strokes

Background

Stroke incidence increases with age. Atrial fibrillation (AF) is an important risk factor for ischemic stroke and its incidence also increases with age. However oral anticoagulant therapy (OAT) tends to be underused in the elderly population.

Methods

Elderly patients (> = 80 years) with an ischemic stroke admitted in our department between 1/7/2003 and 31/6/2005 were prospectively evaluated. Baseline characteristics, risk factors, treatment and etiology according to TOAST criteria were recorded. Patients treated with OAT were followed up in order to assess any side effect and stroke recurrence. Mean follow-up was of 19.5 months (7-45) from discharge.

Results

Sixty four out of a hundred and fifty nine elderly patients (40.25%) were classified as cardioembolic; mean age was 84.5 years (80-97) and 64.6% were women. AF had been previously identified in 60% of them (16.9% were on OAT and 40.6% on antiplatelet therapy). At discharge, 32 patients (49.2%) were on OAT. In the follow-up 4 patients (12.5%) suffered systemic haemorrhages (3 urinary, 1 gastrointestinal bleeding), with no change in their functional status. Mean INR in this group was 5.9 [3-11] and, in 3 of them, OAT was cancelled. No brain haemorrhages were recorded. Ischemic stroke recurred in 4 patients (INR < 1.8 in 3 of them; the other, INR 2.35). Three patients had died at the end of the follow-up, one of them as a consequence of ischemic stroke recurrence.

Discussion

Twenty eight point eight of stroke patients admitted in the period of study were >80 years. The high proportion of cardioembolic strokes in this age segment contrasts with the general underuse of OAT as antithrombotic prophylaxis. Our study suggests that OAT is a safe strategy when carefully prescribed, even for elderly patients.

Cardioembolic stroke in atrial fibrillation-rationale for preventive closure of the left atrial appendage

Atrial fibrillation is the most common cardiac arrhythmias, and a major cause of morbidity and mortality due to cardioembolic stroke. The left atrial appendage is the major site of thrombus formation in non-valvular atrial fibrillation. Loss of atrial systole in atrial fibrillation and increased relative risk of associated stroke point strongly toward a role for stasis of blood in left atrial thrombosis, although thrombus formation is multifactorial, and much more than blood flow irregularities are implicated. Oral anticoagulation with vitamin-K-antagonists is currently the most effective prophylaxis for stroke in atrial fibrillation. Unfortunately, this treatment is often contraindicated, particularly in the elderly, in whom risk of stroke is high. Moreover, given the risk of major bleeding, there is reason to be skeptical of the net benefit when warfarin is used in those patients. This work reviews the pathophysiology of cardioembolic stroke and critically spotlights the current status of preventive anticoagulation therapy. Various techniques to exclude the left atrial appendage from circulation were discussed as a considerable alternative for stroke prophylaxis.

Highlights from the I international symposium of thrombosis and anticoagulation in internal medicine, October 23-25, 2008, Sao Paulo, Brazil

The importance of thrombosis and anticoagulation in clinical practice is rooted firmly in several fundamental constructs that can be applied both broadly and globally. Awareness and the appropriate use of anticoagulant therapy remain the keys to prevention and treatment. However, to assure maximal efficacy and safety, the clinician must, according to the available evidence, choose the right drug, at the right dose, for the right patient, under the right indication, and for the right duration of time. The first International Symposium of Thrombosis and Anticoagulation in Internal Medicine was a scientific program developed by clinicians for clinicians. The primary objective of the meeting was to educate, motivate and inspire internists, cardiologists and hematologists by convening national and international visionaries, thought-leaders and dedicated clinician-scientists in Sao Paulo, Brazil. This article is a focused summary of the symposium proceedings.