GABAergic compensation in connexin36 knock-out mice evident during low-magnesium seizure-like event activity

Gap junctions within the cerebral cortex may facilitate cortical seizure formation by their ability to synchronize electrical activity. To investigate this, one option is to compare wild-type (WT) animals with those lacking the gene for connexin36 (Cx36 KO); the protein that forms neuronal gap junctions between cortical inhibitory cells. However, genetically modified knock-out animals may exhibit compensatory effects; with the risk that observed differences between WT and Cx36 KO animals could be erroneously attributed to Cx36 gap junction effects. In this study we investigated the effect of GABAA-receptor modulation (augmentation with 16 μM etomidate and blockade with 100 μM picrotoxin) on low-magnesium seizure-like events (SLEs) in mouse cortical slices. In WT slices, picrotoxin enhanced both the amplitude (49% increase, p = 0.0006) and frequency (37% increase, p = 0.005) of SLEs; etomidate also enhanced SLE amplitude (18% increase, p = 0.003) but reduced event frequency (25% decrease, p < 0.0001). In Cx36 KO slices, the frequency effects of etomidate and picrotoxin were preserved, but the amplitude responses were abolished. Pre-treatment with the gap junction blocker mefloquin in WT slices did not significantly alter the drug responses, indicating that the reduction in amplitude seen in the Cx36 KO mice was not primarily mediated by their lack of interneuronal gap junctions, but was rather due to pre-existing compensatory changes in these animals. Conclusions from studies comparing seizure characteristics between WT and Cx36 KO mice must be viewed with a degree of caution because of the possible confounding effect of compensatory neurophysiological changes in the genetically modified animals

Connexin36 knockout mice display increased sensitivity to pentylenetetrazol-induced seizure-like behaviors

Large-scale synchronous firing of neurons during seizures is modulated by electrotonic coupling between neurons via gap junctions. To explore roles for connexin36 (Cx36) gap junctions in seizures, we examined the seizure threshold of connexin36 knockout (Cx36KO) mice using a pentylenetetrazol (PTZ) model

Role of Cx36 gap junction modulation in general anaesthetic anticonvulsant action

Many GABAergic anaesthetics reduce gap junction coupling but it is currently unknown whether this effect contributes to anaesthetic anticonvulsant action. In this study we examined the possible role of connexin36 gap junctions in the anticonvulsant action of isoflurane and compared this to etomidate, an anaesthetic known for having proconvulsant effects. We compared the effect of anaesthetic concentrations of isoflurane (1 MAC) and etomidate (16 μM) on low-magnesium-induced interictal-like activity in isolated neocortical slices. The effect of connexin36 gap junction blockade was explored by comparing effects in slices from wild-type mice and from a transgenic mouse strain lacking the gene for connexin36. In slices from wild-type mice, both isoflurane (1 MAC) and etomidate (16 μM) reduced interictal-like event frequency; mean(S.D.) reduction of 44(13)% (P < 0.0001) and 25(24)% (P < 0.0001), respectively. The reduction in event frequency was greater for isoflurane (P < 0.005). Isoflurane had no effect on the amplitude of interictal-like events, but event amplitude was enhanced by etomidate (18(28)% increase, P < 0.005). The capacity for isoflurane to reduce event frequency was significantly reduced, but not eliminated in slices from connexin36 knock-out mice (33(15)% reduction, P < 0.05 for the difference with wild-type), while that of etomidate remained unchanged (23(39)% reduction). The etomidate-mediated increase in event amplitude was eliminated in connexin36 knock-out slices. The results from this study support the hypothesis that the anticonvulsant effect of isoflurane is in part mediated by gap junction blockade. The role of gap junction modulation by etomidate is more complicated and may be important in the mechanism of action of etomidate's proconvulsant effects

The role of connexin36 gap junctions in modulating the hypnotic effects of isoflurane and propofol in mice

Gap junction blockade is a possible mechanism by which general anaesthetic drugs cause unconsciousness. We measured the sensitivity of connexin36 knockout mice to the hypnotic effects of isoflurane and propofol. The experimental endpoint was recovery of the righting reflex of the anaesthetised animals during 0.2% step-reductions in isoflurane concentration, or following intraperitoneal injection of propofol (100 mg.kg⁻¹). Connexin36 knockout animals were more sensitive to the hypnotic effects of isoflurane than ‘normal’ wild-type animals. The half maximal effective concentration (EC50) for recovery of righting reflex was 0.37% for connexin36 knockout vs 0.49% for wild-type animals (p < 0.001). For propofol, connnexin36 knockout animals showed more rapid loss of righting reflex than wild-type animals (mean (SD) 2.8 (0.13) vs 3.8 (0.27) min); and young (< 60 days) connexin36 knockout animals remained anaesthetised for longer than young wild-type mice (47.2 (2.9) vs 30.5 (1.7) min; p < 0.00001). These findings suggest that the hypnotic effects of anaesthetic drugs may be moderately enhanced by gap junction blockade

Quantitative mass spectrometry to study inflammatory cartilage degradation and resulting interactions with the complement system

Joint diseases are often characterized by inflammatory processes that result in pathological changes in joint tissues, including cartilage degradation and release of components into the synovial fluid. The complement system plays a central role in promoting the inflammation. Because several cartilage proteins are known to interact with complement, causing either activation or inhibition of the system, we aimed to investigate these interactions comprehensively. Bovine cartilage explants were cultured with IL-1α to induce cartilage degradation, followed by incubation with human serum. Label-free selected reaction monitoring mass spectrometry was used to specifically quantify complement proteins interacting with the cartilage explant. In parallel, the time-dependent degradation of cartilage was detected using mass spectrometry analysis (liquid chromatography-tandem mass spectrometry). Complement proteins resulting from activation of the classical, alternative, and terminal pathways were detected on IL-1α-stimulated cartilage at time points when clear alterations in extracellular matrix composition had occurred. Increased levels of the complement activation product C4d, as detected by ELISA in serum after incubation with IL-1α-stimulated cartilage, confirmed the selected reaction monitoring results indicating complement activation. Further, typical activated (cleaved) C3 fragments were detected by Western blotting in extracts of IL-1α-stimulated cartilage. No complement activation was triggered by cartilage cultured in the absence of IL-1α. Components released from IL-1α-stimulated cartilage during culture had an inhibitory effect on complement activation. These were released after a longer incubation period with IL-1α and may represent a feedback reaction to cartilage-triggered complement activation observed after a shorter incubation period

Sacubitril/valsartan eligibility and outcomes in the ESC-EORP-HFA Heart Failure Long-Term Registry: bridging between European Medicines Agency/Food and Drug Administration label, the PARADIGM-HF trial, ESC guidelines, and real world

Aims: To assess the proportion of patients with heart failure and reduced ejection fraction (HFrEF) who are eligible for sacubitril/valsartan (LCZ696) based on the European Medicines Agency/Food and Drug Administration (EMA/FDA) label, the PARADIGM-HF trial and the 2016 ESC guidelines, and the association between eligibility and outcomes. Methods and results: Outpatients with HFrEF in the ESC-EORP-HFA Long-Term Heart Failure (HF-LT) Registry between March 2011 and November 2013 were considered. Criteria for LCZ696 based on EMA/FDA label, PARADIGM-HF and ESC guidelines were applied. Of 5443 patients, 2197 and 2373 had complete information for trial and guideline eligibility assessment, and 84%, 12% and 12% met EMA/FDA label, PARADIGM-HF and guideline criteria, respectively. Absent PARADIGM-HF criteria were low natriuretic peptides (21%), hyperkalemia (4%), hypotension (7%) and sub-optimal pharmacotherapy (74%); absent Guidelines criteria were LVEF>35% (23%), insufficient NP levels (30%). and sub-optimal pharmacotherapy (82%); absent label criteria were absence of symptoms (New York Heart Association class I). When a daily requirement of ACEi/ARB ≥ 10 mg enalapril (instead of ≥ 20 mg) was used, eligibility rose from 12% to 28% based on both PARADIGM-HF and guidelines. One-year heart failure hospitalization was higher (12% and 17% vs. 12%) and all-cause mortality lower (5.3% and 6.5% vs. 7.7%) in registry eligible patients compared to the enalapril arm of PARADIGM-HF. Conclusions: Among outpatients with HFrEF in the ESC-EORP-HFA HF-LT Registry, 84% met label criteria, while only 12% and 28% met PARADIGM-HF and guideline criteria for LCZ696 if requiring ≥ 20 mg and ≥ 10 mg enalapril, respectively. Registry patients eligible for LCZ696 had greater heart failure hospitalization but lower mortality rates than the PARADIGM-HF enalapril group

Hyponatraemia and changes in natraemia during hospitalization for acute heart failure and associations with in-hospital and long-term outcomes - from the ESC HFA EORP Heart Failure Long-Term Registry

Aims: To comprehensively assess hyponatraemia in acute heart failure (AHF) regarding prevalence, associations, hospital course, and post-discharge outcomes. Methods and results: Of 8,298 patients in the ESC-HF Long-Term Registry hospitalized for AHF with any ejection fraction, 20% presented with hyponatraemia (serum sodium <135 mmol/L). Independent predictors included lower systolic blood pressure, estimated glomerular filtration rate (eGFR) and haemoglobin, along with diabetes, hepatic disease, use of thiazide diuretics, mineralocorticoid receptor antagonists, digoxin, higher doses of loop diuretics, and non-use of angiotensin-converting-enzyme inhibitors/angiotensin receptor blockers and beta-blockers. In-hospital death occurred in 3.3%. The prevalence of hyponatraemia and in-hospital mortality with different combinations were: 9% hyponatraemia both at admission and discharge (hyponatraemia Yes/Yes, in-hospital mortality 6.9%), 11% Yes/No (in-hospital mortality 4.9%), 8% No/Yes (in-hospital mortality 4.7%), and 72% No/No (in-hospital mortality 2.4%). Correction of hyponatraemia was associated with improvement in eGFR. In-hospital development of hyponatraemia was associated with greater diuretic use and worsening eGFR but also more effective decongestion. Among hospital survivors, 12-month mortality was 19% and adjusted hazard ratios were for hyponatraemia Yes/Yes 1.60 (1.35-1.89), Yes/No 1.35 (1.14-1.59), and No/Yes 1.18 (0.96-1.45). For death or HF hospitalization they were 1.38 (1.21-1.58), 1.17 (1.02-1.33), and 1.09 (0.93-1.27), respectively. Conclusion: Among patients with AHF, 20% had hyponatraemia at admission, which was associated with more advanced HF and normalized in half of patients during hospitalization. Admission hyponatraemia (possibly dilutional), especially if it did not resolve, was associated with worse in-hospital and post-discharge outcomes. Hyponatraemia developing during hospitalization (possibly depletional) was associated with lower risk. This article is protected by copyright. All rights reserved

Performance of Prognostic Risk Scores in Chronic Heart Failure Patients Enrolled in the European Society of Cardiology Heart Failure Long-Term Registry

Objectives: This study compared the performance of major heart failure (HF) risk models in predicting mortality and examined their utilization using data from a contemporary multinational registry. Background: Several prognostic risk scores have been developed for ambulatory HF patients, but their precision is still inadequate and their use limited. Methods: This registry enrolled patients with HF seen in participating European centers between May 2011 and April 2013. The following scores designed to estimate 1- to 2-year all-cause mortality were calculated in each participant: CHARM (Candesartan in Heart Failure-Assessment of Reduction in Mortality), GISSI-HF (Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico-Heart Failure), MAGGIC (Meta-analysis Global Group in Chronic Heart Failure), and SHFM (Seattle Heart Failure Model). Patients with hospitalized HF (n = 6,920) and ambulatory HF patients missing any variable needed to estimate each score (n = 3,267) were excluded, leaving a final sample of 6,161 patients. Results: At 1-year follow-up, 5,653 of 6,161 patients (91.8%) were alive. The observed-to-predicted survival ratios (CHARM: 1.10, GISSI-HF: 1.08, MAGGIC: 1.03, and SHFM: 0.98) suggested some overestimation of mortality by all scores except the SHFM. Overprediction occurred steadily across levels of risk using both the CHARM and the GISSI-HF, whereas the SHFM underpredicted mortality in all risk groups except the highest. The MAGGIC showed the best overall accuracy (area under the curve [AUC] = 0.743), similar to the GISSI-HF (AUC = 0.739; p = 0.419) but better than the CHARM (AUC = 0.729; p = 0.068) and particularly better than the SHFM (AUC = 0.714; p = 0.018). Less than 1% of patients received a prognostic estimate from their enrolling physician. Conclusions: Performance of prognostic risk scores is still limited and physicians are reluctant to use them in daily practice. The need for contemporary, more precise prognostic tools should be considered

Performance of Prognostic Risk Scores in Chronic Heart Failure Patients Enrolled in the European Society of Cardiology Heart Failure Long-Term Registry

Objectives: This study compared the performance of major heart failure (HF) risk models in predicting mortality and examined their utilization using data from a contemporary multinational registry. Background: Several prognostic risk scores have been developed for ambulatory HF patients, but their precision is still inadequate and their use limited. Methods: This registry enrolled patients with HF seen in participating European centers between May 2011 and April 2013. The following scores designed to estimate 1- to 2-year all-cause mortality were calculated in each participant: CHARM (Candesartan in Heart Failure-Assessment of Reduction in Mortality), GISSI-HF (Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico-Heart Failure), MAGGIC (Meta-analysis Global Group in Chronic Heart Failure), and SHFM (Seattle Heart Failure Model). Patients with hospitalized HF (n = 6,920) and ambulatory HF patients missing any variable needed to estimate each score (n = 3,267) were excluded, leaving a final sample of 6,161 patients. Results: At 1-year follow-up, 5,653 of 6,161 patients (91.8%) were alive. The observed-to-predicted survival ratios (CHARM: 1.10, GISSI-HF: 1.08, MAGGIC: 1.03, and SHFM: 0.98) suggested some overestimation of mortality by all scores except the SHFM. Overprediction occurred steadily across levels of risk using both the CHARM and the GISSI-HF, whereas the SHFM underpredicted mortality in all risk groups except the highest. The MAGGIC showed the best overall accuracy (area under the curve [AUC] = 0.743), similar to the GISSI-HF (AUC = 0.739; p = 0.419) but better than the CHARM (AUC = 0.729; p = 0.068) and particularly better than the SHFM (AUC = 0.714; p = 0.018). Less than 1% of patients received a prognostic estimate from their enrolling physician. Conclusions: Performance of prognostic risk scores is still limited and physicians are reluctant to use them in daily practice. The need for contemporary, more precise prognostic tools should be considered