Long QT syndrome-associated calmodulin mutations and their interactions with the Kv7.1 voltage-gated potassium channel

Introduction

Calmodulin (CaM) is a highly conserved mediator of calcium (Ca2+) dependent signalling. Its flexible structure allows CaM to bind and modulate many targets, including cardiac ion channels. Genotyping has revealed several CaM mutations associated with congenital disorders of heart rhythm, known as long QT-syndrome (LQTS). LQTS patients suffer from prolonged ventricular recovery times (QT-interval) which increases their risk of significant cardiac events. Loss of function KV7.1 mutations are the largest cause of LQTS, accounting for >50% of cases. CaM facilitates Ca2+-sensitivity to KV7.1 in producing IKs, Kv7.1 mutations which reduce CaM binding promote LQTS pathology. However, the effects of LQTS-associated CaM mutations on Kv7.1 function remain unknown.

Purpose

To determine the biophysical consequences of congenital LQTS-associated CaM mutations and how they alter modulation of Kv7.1 in producing the ventricular repolarising IKs current.

Methods

WT and mutant CaM proteins were recombinantly expressed and purified for biophysical characterisation. Using circular dichroism, secondary structures and thermostability of proteins were quantified. Isothermal titration calorimetry was used to quantitatively measure interactions between CaM proteins and binding sites of KV7.1 (Helix B). NMR was employed to study the conformations of target-bound WT and mutant proteins. Whole cell currents were determined using voltage clamp electrophysiology in HEK cells.

Results

Mutations significantly changed the thermostability and secondary structure distributions of CaM, and also caused site-dependent increases in susceptibility to protease digestion. CaM interacted with Helix B (KV7.1) via both Ca2+-dependent and independent mechanisms. Ca2+ dependent binding to Helix B was much higher affinity than Ca2+-independent binding, with >2000-fold reduction in dissociation constant measured. LQTS-CaM variants reduced Helix B affinity with the largest reductions found in EF-hand IV mutants. These mutants also adopted most distinct conformations when Helix B-bound. Calmodulation of the KV7.1 channel produced larger (IKs) currents without altering channel activation kinetics. IKs exhibited Ca2+-sensitivity, in response to increased cytosolic Ca2+, larger currents were generated. Modulation by CaM mutants reduced current density at systolic Ca2+-concentrations (1000 nM), within physiological time periods (0.35 s), revealing a direct QT-prolonging modulatory effect.

Conclusions

Provided here are mechanistic insights as to how LQTS-associated CaM variants contribute to electrical disease of the heart. Mutations in the highly conserved structure of CaM disrupt protein conformation and perturb complex formation with KV7.1. This results in aberrant Ca2+-sensitivity of Kv7.1, reducing IKs generation. This ultimately decreases the repolarisation capacity of cells and would extend the QT interval of myocytes.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Intermediate Basic Science Research Fellowship

Disease-associated calmodulin mutations disrupt L-type Ca2+ channel (Cav1.2) activity and CaMKIIdelta phosphorylation in long QT syndrome

Introduction

Long QT Syndrome (LQTS) is a major inherited arrhythmia syndrome that can cause sudden cardiac death. Using genome sequencing in human patients, mutations in the ubiquitous calcium (Ca2+) sensor protein calmodulin (CaM) have been associated to LQTS. CaM is an ion channel regulator and can modulate the activity of the voltage-gated calcium channel (Cav1.2) and Ca2+/CaM-dependent protein kinase II (CaMKIIδ), involved in cardiac muscle contraction. However the molecular mechanism by which CaM mutations contribute to irregular heartbeats remains unclear.

Methods

Interaction of CaM proteins with Cav1.2 and CaMKIId synthetic peptides (Cav1.2-NSCaTE51–68, Cav1.2-IQ1665–1685, Cav1.2-C1627–1652, CaMKIIδ294–315,) was investigated using Isothermal Titration Calorimetry (ITC) and X-ray crystallography. Whole-cell patch clamp electrophysiology was used to determine the effect of CaM mutations on L-type Ca2+ currents and Ca2+-dependent inactivation (CDI). CaMKIIδ phosphorylation activity was determined by western blot and fluorescence kinase assay.

Results

Binding affinity of CaMKIId and Cav1.2 peptides to the LQTS-associated CaM variants was significantly reduced, up to 7-fold. Interestingly, the Cav1.2-IQ1665–1685 peptide showed a stronger binding, up to 2-fold, towards LQTS-CaM mutants. Crystal structures of Ca2+-CaM:CaMKIId294–315 showed structural alterations induced by LQTS associated mutations. In addition, we demonstrated that CaMKIIδ autophosphorylation and kinase activity can be significantly reduced by LQTS-associated CaM mutants. Electrophysiological examination of Cav1.2 function revealed that CaM mutations significantly impaired channel CDI, without affecting the voltage dependence of activation and inactivation.

Conclusions

These data demonstrate a strong correlation between LQTS-associated CaM mutations and Cav1.2 activity. We provide molecular insights into the diverse factors contributing to CaM-mediated arrhythmias.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Intermediate Basic Science Research Fellowship

A National Equity Initiative to Address Noncommunicable Diseases and Injuries: Findings and Recommendation from the Nepal NCDI Poverty Commission

We aimed to assess the burden of NCDIs across socioeconomic groups, their economic impact, existing health service readiness and availability, current policy frameworks and national investment, and planned programmatic initiatives in Nepal through a comprehensive literature review. Secondary data from Global Burden of Disease estimates from GBD 2015 and National Living Standard Survey 2011 were used to estimate the burden of NCDI and present the relationship of NCDI burden with socioeconomic status. The Commission used these data to define priority NCDI conditions and recommend potential cost-effective, poverty-averting, and equity-promoting health system interventions. NCDIs disproportionately affect the health and well-being of poorer populations in Nepal and cause significant impoverishment. The Commission found a high diversity of NCDIs in Nepal, with approximately 60% of the morbidity and mortality caused by NCDIs without primary quantified behavioral or metabolic risk factors, and nearly half of all NCDI-related DALYs occurring in Nepalese younger than 40 years. The Commission prioritized an expanded set of twenty-five NCDI conditions and recommended introduction or scale-up of twenty-three evidence-based health sector interventions. Implementation of these interventions would avert an estimated 9680 premature deaths per annum by 2030 and would cost approximately $8.76 per capita. The Commission modelled potential financing mechanisms, including increased excise taxation on tobacco, alcohol, and sugar-sweetened beverages, which would provide significant revenue for NCDI-related expenditures. Overall, the Commission's conclusions are expected to be a valuable contribution to equitable NCDI planning in Nepal and similar resource-constrained settings globally.

Kyasanur forest disease: a state-of-the-art review

Kyasanur forest disease (KFD) virus is a flavivirus that can be transmitted to humans from monkeys or other mammals through hard ticks (Haemaphysalis spinigera). The disease is endemic to 16 districts in 5 states of Southern India and is reported in the dry season, most commonly in humans travelling to the forests in these areas. The aim of this systematic review is to raise awareness of the clinical and laboratory manifestation of KFD among physicians and travel medicine practitioners. A total of 153 articles were screened of which 16 articles that met the inclusion and exclusion criteria were included for qualitative analysis. KFD is an acute haemorrhagic fever with a biphasic component in some individuals. The second phase is usually marked by neurological symptoms. Leucopoenia, thrombocytopenia and elevated transaminases are the hallmarks of the first phase of KFD. The diagnostic modality of choice in the first few days of illness is polymerase chain reaction assay, whereas serology is used in the late phase. In the absence of a specific antiviral treatment, the clinical management of patients is limited to supportive care. Avoidance of exposure and vaccination is recommended to prevent this infection.

Hedonic perception of odors in children aged 5-8 years is similar across 18 countries: Preliminary data

OBJECTIVE

Olfactory preference emerges very early in life, and the sense of smell in children rapidly develops until the second decade of life. It is still unclear whether hedonic perception of odors is shared in children inhabiting different regions of the globe.

METHODS

Five-hundred ten healthy children (N = 510; n_girls = 256; n_boys = 254) aged from 5 to 8 years from 18 countries rated the pleasantness of 17 odors.

RESULTS

The hedonic perception of odors in children aged between 5 and 8 years was rather consistent across 18 countries and mainly driven by the qualities of an odor and the overall ability of children to label odorants.

CONCLUSION

Conclusions from this study, being a secondary analysis, are limited to the presented set of odors that were initially selected for the development of U-Sniff test and present null findings for the cross-cultural variability in hedonic perception of odors across 18 countries. These two major issues should be addressed in the future to either contradict or replicate the results presented herewith. This research lays fundament for posing further research questions about the developmental aspects of hedonic perception of odors and opens a new door for investigating cross-cultural differences in chemosensory perception of children.

MR Imaging Differences in the Circle of Willis between Healthy Children and Adults

BACKGROUND AND PURPOSE

Asymmetries in the circle of Willis have been associated with several conditions, including migraines and stroke, but they may also be age-dependent. This study examined the impact of age and age-dependent changes in cerebral perfusion on circle of Willis anatomy in healthy children and adults.

MATERIALS AND METHODS

We performed an observational, cross-sectional study of bright and black-blood imaging of the proximal cerebral vasculature using TOF-MRA and T2 sampling perfection with application-optimized contrasts by using different flip angle evolution (T2-SPACE) imaging at the level of the circle of Willis in 23 healthy children and 43 healthy adults (4-74 years of age). We compared arterial diameters measured manually and cerebral perfusion via pseudocontinuous arterial spin-labeling between children and adults.

RESULTS

We found that the summed cross-sectional area of the circle of Willis is larger in children than in adults, though the effect size was smaller with T2-SPACE-based measurements than with TOF-MRA. The circle of Willis is also more symmetric in children, and nonvisualized segments occur more frequently in adults than in children. Moreover, the size and symmetry of the circle of Willis correlate with cerebral perfusion.

CONCLUSIONS

Our results demonstrate that the circle of Willis is different in size and symmetry in healthy children compared with adults, likely associated with developmental changes in cerebral perfusion. Further work is needed to understand why asymmetric vasculature develops in some but not all adults.

Systematic review of health workforce surge capacity during COVID-19 and other viral pandemics

Background

Healthcare decision-makers need comprehensive evidence to mitigate surges in the demand for human resources for health (HRH) during infectious disease outbreaks, in terms of both short- and longer-term impacts. This study aimed to assess the state of the evidence to address HRH surge capacity during COVID-19 and other outbreaks of global significance in the 21st century.

Methods

We systematically searched eight bibliographic databases to extract primary research articles published between 01/2000-06/2020, capturing temporal changes in HRH requirements and responses surrounding viral respiratory infection pandemics. A systems approach was used, considering providers in hospitals, out-of-hospital systems, emergency medical services, and public health. We narratively synthesized the evidence following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) standard.

Results

Of the 1,155 retrieved records, 16 studies met our inclusion criteria; of these, 5 focused on COVID-19, 3 on H1N1, and 8 on a hypothetical pandemic. Different training, mobilization, and redeployment options to address pandemic-time health system capacity were assessed. Few governance scenarios drew on observational HRH data allowing for comparability across contexts. Notable evidence gaps included occupational and psychosocial factors affecting healthcare workers' absenteeism and risk of burnout, gendered considerations of HRH capacity, evaluations in low- and lower-middle income countries, and policy-actionable assessments to inform post-pandemic recovery and sustainability of services for noncommunicable disease management.

Conclusions

This research emphasized the critical need for timely, internationally comparable, and equity-informative HRH data and research to enhance preparedness, response, and recovery policies for this and future pandemics. Full paper is available at: https://doi.org/10.1002/hpm.3137

Key messages

The COVID-19 pandemic has highlighted the critical need for enhanced health workforce data and research, including better tracking of demographics, exposures, infections and deaths of health workers. Although women comprise 70% of the health workforce in many countries, gender-blindness persists in the global literature on health workforce research and governance in public health emergencies./bodyt

639 Emergency Surgical Approach to A Bleeding Pseudoaneurysm Of the Posterior Inferior Pancreaticoduodenal Artery After Failed Embolisation

Background

Pseudoaneurysms of visceral arteries are uncommon, with a prevalence of 0.01% to 0.2%1. Initial treatment is radiological embolisation (RE)2. If this fails, surgical access to the pseudoaneurysm is extremely difficult. They are associated with major complications such as rupture, ischaemia and shock2, with a 20-70% mortality rate3. We report the case of a patient admitted with a life-threatening bleed from an aberrant inferior pancreaticoduodenal artery (IPDA) with failed RE.

Case Summary

A 44-year-old patient presented with right upper quadrant pain, shock and low haemoglobin. His computerised tomography (CT) scan showed a large retroperitoneal haematoma with active bleeding from a 5x6mm IPDA pseudoaneurysm. After resuscitation, access to the IPDA during RE via the coeliac axis and superior mesenteric artery was unsuccessful and he deteriorated. He underwent an emergency laparotomy, which showed the retro-peritoneal haematoma had ruptured into the peritoneal cavity through the transverse mesocolon. Four-quadrant abdominal packing and supra-coeliac manual compression of the aorta was utilised. The right colon was mobilised with full kocherisation of the duodenum. The gastrocolic omentum was divided to enter the lesser sac. The haematoma was evacuated and bleeding branches from the IPDA were suture ligated. He required 26 units of blood throughout admission and underwent 24-hour damage control laparostomy on intensive care. CT mesenteric angiogram post-surgery and re-look laparotomy showed no further active bleeds. He had an uneventful recovery and discharged safely.

Conclusions

RE of visceral artery pseudoaneurysms is challenging. Surgery remains the last resort and should be performed by appropriately trained specialist surgeons.

Noncontrast MRI Protocol for Selected Pediatric Pituitary Endocrinopathies: A Procedure with High Diagnostic Yield and Potential to Reduce Anesthesia and Gadolinium-Based Contrast Exposure

BACKGROUND AND PURPOSE

Although many pediatric neuroradiology practices empirically use noncontrast brain and pituitary MR imaging for evaluation of growth hormone deficiency, central precocious puberty, and short stature, there are currently insufficient published data to support this practice in an evidence-based fashion. Therefore, the use of contrast-enhanced MR imaging for all pediatric pituitary endocrinopathies remains widespread. We evaluated whether noncontrast MR imaging has adequate diagnostic yield for the evaluation of pediatric growth hormone deficiency, central precocious puberty, and short stature.

MATERIALS AND METHODS

Pituitary MR imaging studies obtained for growth hormone deficiency, central precocious puberty, or short stature in patients 0-18 years of age from 2010 to 2019 were analyzed. Separate blinded review of noncontrast images in cases with abnormalities on the original radiology report was performed by 2 subspecialty-trained pediatric neuroradiologists, with discrepancies resolved by consensus.

RESULTS

Of the 134/442 MR imaging studies obtained for growth hormone deficiency, central precocious puberty, or short stature with hypothalamic-pituitary region abnormalities, there was 70% concordance with the original reports on blinded review of noncontrast images. Twenty-two of 40 discrepancies were deemed unrelated to the indication, and 9 cases originally interpreted as possible microadenoma were read as having normal findings on blinded review. Only 9 of 40 discrepancies required contrast for further characterization.

CONCLUSIONS

In our study, most relevant radiologic findings in patients with growth hormone deficiency, central precocious puberty, and short stature were detectable without contrast, providing evidence that contrast can be avoided in routine MR imaging evaluation of these indications. We propose a "rapid noncontrast pituitary" MR imaging protocol for pediatric patients presenting with growth hormone deficiency, central precocious puberty, or short stature, which may increase efficiency and decrease contrast and anesthesia exposure.

Medical publishing: a flawed model in dire need of reform

Recently, in the midst of the Covid-19 pandemic, high-profile retractions of some papers published in prestigious medical journals have highlighted the necessity for structural reform to the current model of medical publishing. We discuss what ails the current system and what can be done to remedy it.

Remission in Cushing's disease is predicted by cortisol burden and its withdrawal following pituitary surgery

AIM

To ascertain the predictors of remission and relapse in patients of Cushing's disease (CD) undergoing pituitary transsphenoidal surgery (TSS).

METHODS

Patients with CD subjected to TSS over 35 years at a tertiary care center were included. Patients were grouped into remission and persistent disease at 1 year after surgery, and were further followed up for relapse. Demographic, clinical, biochemical, histological, radiological and post-operative follow-up parameters were analyzed.

RESULTS

Of the 152 patients of CD, 145 underwent TSS. Remission was achieved in 95 (65.5%) patients at 1 year. Patients in remission had shorter duration of symptoms prior to presentation (p = 0.009), more frequent presence of proximal myopathy (p = 0.038) and a tumor size of < 2.05 cm (p = 0.016) in comparison to those with persistent disease. Post-TSS, immediate post-operative 0800-h cortisol (< 159.85 nmol/L; p = 0.001), histological confirmation of tumor (p = 0.045), duration of glucocorticoid replacement (median 90 days; p = 0.001), non-visualization of tumor on MRI (p = 0.003), new-onset hypogonadism (p = 0.001), 3-month 0800-h cortisol (< 384.9 nmol/L; p = 0.001), resolution of diabetes (p = 0.001) and hypertension (p = 0.001), and recovery of hypothalamic-pituitary-adrenal axis (p = 0.018) favored remission. In logistic regression model, requirement of glucocorticoid replacement (p = 0.033), and resolution of hypertension post-TSS (p = 0.003) predicted remission. None of the parameters could predict relapse.

CONCLUSION

The study could ascertain the predictors of remission in CD. Apart from the tumor characteristics, surgical aspects and low post-operative 0800-h cortisol, the results suggest that baseline clinical parameters, longer glucocorticoid replacement, and resolution of metabolic complications post-TSS predict remission in CD. Long-term follow-up is essential to look for relapse.

Serotype and genotype diversity of dengue viruses circulating in India: a multi-centre retrospective study involving the Virus Research Diagnostic Laboratory Network in 2018

OBJECTIVES

A retrospective study was undertaken to investigate the circulating dengue virus (DENV) serotypes and genotypes in India in 2018.

METHODS

In total, 4963 samples referred to virus research diagnostic laboratories (n=21), the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) and ICMR-NIV field units (n=2) for diagnosis of dengue in 2018 were tested using a real-time reverse transcription polymerase chain reaction assay for the presence of DENV serotypes. Representative samples were sequenced for the envelope (E) gene.

RESULTS

Regional diversity was observed with regard to the dominant circulating serotypes. DENV-2 was found to be the most common serotype in many states. Thrombocytopenia, petechiae and malaise were associated with DENV-2 infection. Phylogenetic analyses of DENV E gene sequences revealed the circulation of genotypes I and V of DENV-1, two lineages of DENV-2 genotype IV, DENV-3 genotype III and DENV-4 genotype I.

CONCLUSIONS

This study found regional differences in the prevalence of circulating DENV serotypes in India, and provides baseline data for continuous molecular surveillance. Molecular surveillance may have implications for predicting large-scale outbreaks of dengue if regional shifts in the predominantly circulating serotypes and genotypes are detected during the early phase of the dengue season.

Meagreness of Employees Is Symptomatic to Disease: A Case on Healthcare Industry

The main purpose of this study is to examine the existing workplace scenario in the healthcare industry. Furthermore, it analyses the causes and also uncovers the solutions to resolve the attrition problem confronted by the healthcare industry in India. The authors have explored the attrition phenomenon through a conceptual descriptive study conducted with the support of secondary data. The variables that play their noticeable role are lack of work-life balance, the absence of the feeling of achievement among the workers, substantial outstanding burden with nearly less remuneration and furthermore much repetitiveness of work. To conquer such situations, the organisation should work upon their inward strategies including the policies formed in consensus with the employees, increased employee participation in decision making and last but not the least, the organisation ought to introduce the mentoring programme with consistency, which will manufacture the trust among the lower level workers. The results of this study will be of interest to the modern HR world, HR and healthcare students, hospital administrators and to any HR consultant or agency wishing to study and resolve the herculean issue of attrition that obstructs the walls of organisational development.