Ryanodine receptor cluster fragmentation and redistribution in persistent atrial fibrillation enhance calcium release

In atrial fibrillation (AF), abnormalities in Ca(2+) release contribute to arrhythmia generation and contractile dysfunction. We explore whether RyR cluster ultrastructure is altered and is associated with functional abnormalities in AF.status: publishe

The application of selective reaction monitoring confirms dysregulation of glycolysis in a preclinical model of schizophrenia.

BACKGROUND: Establishing preclinical models is essential for novel drug discovery in schizophrenia. Most existing models are characterized by abnormalities in behavioral readouts, which are informative, but do not necessarily translate to the symptoms of the human disease. Therefore, there is a necessity of characterizing the preclinical models from a molecular point of view. Selective reaction monitoring (SRM) has already shown promise in preclinical and clinical studies for multiplex measurement of diagnostic, prognostic and treatment-related biomarkers. METHODS: We have established an SRM assay for multiplex analysis of 7 enzymes of the glycolysis pathway which is already known to be affected in human schizophrenia and in the widely-used acute PCP rat model of schizophrenia. The selected enzymes were hexokinase 1 (Hk1), aldolase C (Aldoc), triosephosphate isomerase (Tpi1), glyceraldehyde-3-phosphate dehydrogenase (Gapdh), phosphoglycerate mutase 1 (Pgam1), phosphoglycerate kinase 1 (Pgk1) and enolase 2 (Eno2). The levels of these enzymes were analyzed using SRM in frontal cortex from brain tissue of PCP treated rats. RESULTS: Univariate analyses showed statistically significant altered levels of Tpi1 and alteration of Hk1, Aldoc, Pgam1 and Gapdh with borderline significance in PCP rats compared to controls. Most interestingly, multivariate analysis which considered the levels of all 7 enzymes simultaneously resulted in generation of a bi-dimensional chart that can distinguish the PCP rats from the controls. CONCLUSIONS: This study not only supports PCP treated rats as a useful preclinical model of schizophrenia, but it also establishes that SRM mass spectrometry could be used in the development of multiplex classification tools for complex psychiatric disorders such as schizophrenia.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Hyperactive ryanodine receptors in human heart failure and ischaemic cardiomyopathy reside outside of couplons

Aims In ventricular myocytes from humans and large mammals, the transverse and axial tubular system (TATS) network is less extensive than in rodents with consequently a greater proportion of ryanodine receptors (RyRs) not coupled to this membrane system. TATS remodelling in heart failure (HF) and after myocardial infarction (MI) increases the fraction of non-coupled RyRs. Here we investigate whether this remodelling alters the activity of coupled and non-coupled RyR sub-populations through changes in local signalling. We study myocytes from patients with end-stage HF, compared with non-failing (non-HF), and myocytes from pigs with MI and reduced left ventricular (LV) function, compared with sham intervention (SHAM).Methods and resultsSingle LV myocytes for functional studies were isolated according to standard protocols. Immunofluorescent staining visualized organization of TATS and RyRs. Ca2+ was measured by confocal imaging (fluo-4 as indicator) and using whole-cell patch-clamp (37°C). Spontaneous Ca2+ release events, Ca2+ sparks, as a readout for RyR activity were recorded during a 15 s period following conditioning stimulation at 2 Hz. Sparks were assigned to cell regions categorized as coupled or non-coupled sites according to a previously developed method. Human HF myocytes had more non-coupled sites and these had more spontaneous activity than in non-HF. Hyperactivity of these non-coupled RyRs was reduced by Ca2+/calmodulin-dependent kinase II (CaMKII) inhibition. Myocytes from MI pigs had similar changes compared with SHAM controls as seen in human HF myocytes. As well as by CaMKII inhibition, in MI, the increased activity of non-coupled sites was inhibited by mitochondrial reactive oxygen species (mito-ROS) scavenging. Under adrenergic stimulation, Ca2+ waves were more frequent and originated at non-coupled sites, generating larger Na+/Ca2+ exchange currents in MI than in SHAM. Inhibition of CaMKII or mito-ROS scavenging reduced spontaneous Ca2+ waves, and improved excitation–contraction coupling.ConclusionsIn HF and after MI, RyR microdomain re-organization enhances spontaneous Ca2+ release at non-coupled sites in a manner dependent on CaMKII activation and mito-ROS production. This specific modulation generates a substrate for arrhythmia that appears to be responsive to selective pharmacologic modulation

Chronic intra-uterine Ureaplasma parvum infection induces injury of the enteric nervous system in ovine fetuses

Background: Chorioamnionitis, inflammation of the fetal membranes during pregnancy, is often caused by intra-amniotic (IA) infection with single or multiple microbes. Chorioamnionitis can be either acute or chronic, and is associated with adverse postnatal outcomes of the intestine, including necrotizing enterocolitis (NEC). Neonates with NEC have structural and functional damage to the intestinal mucosa and the enteric nervous system (ENS), with loss of enteric neurons and glial cells. Yet, the impact of acute, chronic or repetitive antenatal inflammatory stimuli on the development of the intestinal mucosa and ENS has not been studied. The aim of this study is therefore to investigate the effect of acute, chronic and repetitive microbial exposure on the intestinal mucosa, submucosa and ENS in premature lambs. Materials and Methods: A sheep model of pregnancy was used in which the ileal mucosa, submucosa and ENS were assessed following IA exposure to lipopolysaccharide (LPS) for 2 or 7 days (acute), Ureaplasma parvum (UP) for 42 days (chronic) or repetitive microbial exposure (42 days UP with 2 or 7 days LPS). Results: IA LPS exposure for 7 days or IA UP exposure for 42 days caused intestinal injury and inflammation in the mucosal and submucosal layer of the gut. Repetitive microbial exposure did not further aggravate injury of the terminal ileum. Chronic IA UP exposure caused significant structural ENS alterations characterized by loss of PGP9.5 and S100β immunoreactivity whereas these changes were not found after re-exposure of chronic UP-exposed fetuses to LPS for 2 or 7 days. Conclusion: The in utero loss of PGP9.5 and S100β immunoreactivity following chronic UP exposure corresponds with intestinal changes in neonates with NEC, and may therefore form a novel mechanistic explanation for the association of chorioamnionitis and NEC

Atrial remodeling during persistent atrial fibrillation: focus on nitric oxide and calcium homeostasis

AF is the most common arrhythmia with a life time risk of developing AF of 1 out of 4 in people over 40. Only a minority of patients has AF without underlying heart disease, including arterial hypertension, valvular heart disease, congestive heart failure or coronary artery disease. AF is associated with a significant morbidity and mortality. Stroke resulting from embolization of atrial thrombi is the major determinant of this morbidity. Recent studies have suggested an important role for oxidative stress, induced by production of free radicals, in the development of AF. The production of free radicals is physiologically balanced by its degradation by anti-oxidants. Different pathologies can disrupt the equilibrium, leading to induction of oxidative stress. Increased production of free oxygen radicals can influence bioavailability of NO, which plays an important role in controlling vascular tone and thrombogenesis, and modulates myocardial contraction. The general aim of this thesis was to further investigate the underlying atrial remodeling induced by AF. More specifically, we focused on changes in the NO and oxidative stress pathways, as well as on alterations in Ca2+ handling properties. We used a sheep model, in which AF is induced by continuous rapid atrial pacing.In a first part, we showed that persistent AF was accompanied by increased superoxide production, indicating the presence of oxidative stress. This overproduction was associated with marked accumulation of peroxynitrite, which is produced by the reaction of superoxide with NO. In addition, we have demonstrated decreased expression of NOS3, and significantly lower levels of circulating NO metabolites in AF than in control. These data indicate that persistent AF is associated with oxidativestress and a decreased availability of NO. Second, we hypothesized that increasing the availability of NO may reduce electrical remodeling induced by atrial tachycardia. Short-term electrical remodeling was induced by 4 hours of rapid atrial pacing. Treatment with an NO-donor delayed electrical remodeling. This was accompanied by a significant decrease in systolic blood pressure. To exclude that the effect on electrical remodeling could be explained by this difference in blood pressure, additional experimentswere performed with urapidil, a vasodilator. Despite a similar decrease in blood pressure, treatment with urapidil was unable to prevent or delay the induced electrical remodeling. We could furthermore demonstrate that this delay was based on increased Ca2+ influx induced by NO-donors. On the long term this could therefore be detrimental due to cytotoxic Ca2+ overload of atrial myocytes. In a last part of the study we studied the changes in Ca2+ homeostasis and the link to atrial contractiledysfunction during AF. Reduced fractional Ca2+ release from the SR was observed, but was accompanied by preserved SR Ca2+ content. When Ca2+ release was maximal, however, cell contraction normalized to control levels. These data indicate that alterations in Ca2+ homeostasis, and not deficits in myofilament properties, were responsible for the decreased atrial contraction during AF. The decreased Ca2+ release from the SR was related to a loss in T-tubule density, which results ina decreased number of functional links between L-type Ca2+ channels and RyRs. Finally, we demonstrated that if functional links were present, their efficiency was affected in AF. In summary, persistent AF is associated with increased oxidative stress and attenuated NO availability. Pharmacologically increased NO levels in vivo transiently delayed short-term electrical remodeling induced by atrial tachypacing. The underlying mechanism, however, increases Ca2+ influx in atrial myocytes and therefore might be detrimental on the long term. In persistent AF, reduced fractional Ca2+ release is a major factor in the decreased atrial cell contraction. This is due to a combinationof reduced numbers of Ca2+channel-RyR couplings, due to loss of T-tubules, and decreased efficiency of these subsarcolemmal couplings. Importantly, it may further reduce the actual availability of Ca2+to the myofilaments, which further depresses atrial contraction during AF. These insights may help to optimize the treatment options for patients suffering from AF.nrpages: 126status: publishe

De rol van de wil en het gedrag van partijen bij de bevrijdende verjaring

status: publishe

How Pathological Gait Kinematics, Increased Femoral Anteversion and Neck Shaft Angle Adversely Affect the Loading Conditions of the Femoral Head During Gait in Children With Cerebral Palsy

status: publishe

Altered Ryanodine Receptor Function in Ischemic Heart Disease: Is there a Role for Mitochondria?

status: publishe

Altered CamkII and Ros Microdomains Favor Sparks in Orphaned RyR After Myocardial Infarction

status: publishe