Increased SR Ca2+ cycling contributes to improved contractile performance in SERCA2a-overexpressing transgenic rats

OBJECTIVE: Heart failure is associated with reduced function of sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a) but increased function of sarcolemmal Na+/Ca2+ exchanger (NCX), leading to decreased SR Ca2+ content and loss of frequency-potentiation of contractile force. We reported that SERCA2a-overexpression in transgenic rat hearts (TG) results in improved contractility. However, it was not clear whether TG have improved contractility due to frequency-dependent improved SR Ca2+ handling. METHODS: Therefore, we characterized TG (n=35) vs. wild-type (WT) control rats (n=39) under physiological conditions (37 degrees C, stimulation rate <8 Hz). Twitch force, intracellular Ca2+ transients ([Ca2+]i), and SR Ca2+ content were measured in isolated muscles. The contribution of transsarcolemmal Ca2+ influx (I(Ca)) through L-type Ca2+ channels (LTCC) and reverse mode NCX (I(Na/Ca)) to Ca2+ cycling were studied in isolated myocytes. RESULTS: With increasing frequency, force increased in TG muscles by 168+/-35% (8 Hz; P<0.05) and SR Ca2+ content increased by maximally 118+/-31% (4 Hz; P<0.05). In WT, there was a flat force-frequency response without changes in SR Ca2+ content. Relaxation parameters of force and [Ca2+]i decay were accelerated at each frequency in TG vs. WT by approximately 10%. At prolonged rest intervals (<240 s), force and SR Ca2+ content increased significantly more in TG. Consequently, absolute SR Ca2+ content measured in myocytes was increased approximately 2-fold in TG. Transsarcolemmal Ca2+ fluxes estimated by I(Ca) (at 0 mV -10.2+/-1.1 vs. -16.9+/-1.3 pA/pF) and I(Na/Ca) (0.17+/-0.02 vs. 0.46+/-0.05 pA/pF) were decreased in TG vs. WT (P<0.05), whereas NCX and LTCC protein expression was only slightly reduced (P=n.s.). CONCLUSION: In summary, SERCA2a-overexpression improved contractility in a frequency-dependent way due to increased SR Ca2+ loading whereas transsarcolemmal Ca2+ fluxes were decreased.     

N-cadherin haploinsufficiency affects cardiac gap junctions and arrhythmic susceptibility

Cardiac-specific deletion of the murine gene (Cdh2) encoding the cell adhesion molecule, N-cadherin, results in disassembly of the intercalated disc (ICD) structure and sudden arrhythmic death. Connexin 43 (Cx43)-containing gap junctions are significantly reduced in the heart after depleting N-cadherin, therefore we hypothesized that animals expressing half the normal levels of N-cadherin would exhibit an intermediate phenotype. We examined the effect of N-cadherin haploinsufficiency on Cx43 expression and susceptibility to induced arrhythmias in mice either wild-type or heterozygous for the Cx43 (Gja1)-null allele. An increase in hypophosphorylated Cx43 accompanied by a modest decrease in total Cx43 protein levels was observed in the N-cadherin heterozygous mice. Consistent with these findings N-cadherin heterozygotes exhibited increased susceptibility to ventricular arrhythmias compared to wild-type mice. Quantitative immunofluorescence microscopy revealed a reduction in size of large Cx43-containing plaques in the N-cadherin heterozygous animals compared to wild-type. Gap junctions were further decreased in number and size in the N-cad/Cx43 compound heterozygous mice with increased arrhythmic susceptibility compared to the single mutants. The scaffold protein, ZO-1, was reduced at the ICD in N-cadherin heterozygous cardiomyocytes providing a possible explanation for the reduction in Cx43 plaque size. These data provide further support for the intimate relationship between N-cadherin and Cx43 in the heart, and suggest that germline mutations in the human N-cadherin (Cdh2) gene may predispose patients to increased risk of cardiac arrhythmias.     

Systematic Literature Review of Psychiatric Comorbidities in Adults with Epilepsy

Background and PurposeMental illness is disproportionately common in people with epilepsy (PWE). This systematic literature review identified original research articles that reported the prevalence of psychiatric comorbidities based upon clinical assessments in a sample of PWE and assessed the clinical features of the populations found in studies included in our review of mental health comorbidity.MethodsThe included articles were written in English and published from 2008 to 2018, and focused on adults aged ≥18 years who had psychiatric diagnoses determined in clinical assessments, such as those found in medical records, clinician psychiatric evaluations, structured diagnostic interviews, and mental health screening questionnaires specific for a psychiatric disorder. The primary outcome was the prevalence of psychiatric comorbidities as a percentage of the total sample of PWE. Additional data included the overall sample size, mean age, epilepsy type, study design, and method of diagnosis. A modified Newcastle Ottawa Scale was used to assess the quality of the studies. All 23 articles that were consistent with the inclusion criteria were related to observational studies.ResultsMood disorders and anxiety disorders were the most common psychiatric comorbidities, with prevalence rates of 35.0% and 25.6%, respectively. Major depressive disorder was the most common mood disorder, with a prevalence of 24.2%. Post-traumatic stress disorder (PTSD) had the highest reported prevalence among anxiety disorders, at 14.2%, followed by general anxiety disorder at 11.1%. Other comorbidities included psychosis (5.7%), obsessivecompulsive disorder (3.8%), schizophrenia (1.7%), bipolar disorder (6.2%), and substance abuse (7.9%). The pooled prevalence of suicidality, as reported for two studies, was 9.3%. Temporal lobe epilepsy (TLE) was associated with higher levels of psychiatric comorbidity. Two (8.7%) of the 23 studies compared psychiatric comorbidities in TLE with that of extratemporal lobe epilepsy (ETLE), and one of these two studies found that depression was more common in TLE (53.8%) than in ETLE (25%). Regarding seizure types, partial seizures were associated with a higher prevalence of depression vs generalized seizures.ConclusionsThis systematic literature review of recent original research found a relatively high prevalence of mental health comorbidities in PWE. Mood and anxiety disorders are the most common comorbidities, while psychotic spectrum conditions such as schizophrenia and bipolar disorder are much rarer. The prevalence of comorbidity may vary with the epilepsy type and treatment responsiveness. These findings suggest that screening tools for depression and anxiety should be included as part of the training for epilepsy care, while resources for other relatively common conditions such as PTSD and substance abuse disorders should be readily available to neurology specialists who treat PWE.     

Effectiveness of inhaled hypertonic saline application for sputum induction to improve Mycobacterium tuberculosis identification in patients with pulmonary tuberculosis

Wiener Medizinische Wochenschrift - This study assessed the effectiveness and diagnostic significance of hypertonic saline sputum induction for improving Mycobacterium tuberculosis (MTB) detection....     

Interaction between leukotoxin and Cu,Zn superoxide dismutase in Aggregatibacter actinomycetemcomitans

Aggregatibacter (Actinobacillus) actinomycetemcomitans is a gram-negative oral pathogen that is the etiologic agent of localized aggressive periodontitis and systemic infections. A. actinomycetemcomitans produces leukotoxin (LtxA), which is a member of the RTX (repeats in toxin) family of secreted bacterial toxins and is known to target human leukocytes and erythrocytes. To better understand how LtxA functions as a virulence factor, we sought to detect and study potential A. actinomycetemcomitans proteins that interact with LtxA. We found that Cu,Zn superoxide dismutase (SOD) interacts specifically with LtxA. Cu,Zn SOD was purified from A. actinomycetemcomitans to homogeneity and remained enzymatically active. Purified Cu,Zn SOD allowed us to isolate highly specific anti-Cu,Zn SOD antibody and this antibody was used to further confirm protein interaction. Cu,Zn SOD-deficient mutants displayed decreased survival in the presence of reactive oxygen and nitrogen species and could be complemented with wild-type Cu,Zn SOD in trans. We suggest that A. actinomycetemcomitans Cu,Zn SOD may protect both bacteria and LtxA from reactive species produced by host inflammatory cells during disease. This is the first example of a protein-protein interaction involving a bacterial Cu,Zn SOD.