Restoration of Cardiac Myosin Light Chain Kinase Ameliorates Systolic Dysfunction by Reducing Superrelaxed Myosin

Circulation, Ahead of Print. Background:Cardiac-specific myosin light chain kinase (cMLCK), encoded byMYLK3, regulates cardiac contractility through phosphorylation of ventricular myosin regulatory light chain. However, the pathophysiological and therapeutic implications of cMLCK in human heart failure remain unclear. We aimed to investigate whether cMLCK dysregulation causes cardiac dysfunction and whether the restoration of cMLCK could be a novel myotropic therapy for systolic heart failure.Methods:We generated the knock-in mice (Mylk3+/fsandMylk3fs/fs) with a familial dilated cardiomyopathy–associatedMYLK3frameshift mutation (MYLK3+/fs) that had been identified previously by us (c.1951-1G >T; p.P639Vfs*15) and the human induced pluripotent stem cell–derived cardiomyocytes from the carrier of the mutation. We also developed a new small-molecule activator of cMLCK (LEUO-1154).Results:Both mice (Mylk3+/fsandMylk3fs/fs) showed reduced cMLCK expression due to nonsense-mediated messenger RNA decay, reduced MLC2v (ventricular myosin regulatory light chain) phosphorylation in the myocardium, and systolic dysfunction in a cMLCK dose–dependent manner. Consistent with this result, myocardium from the mutant mice showed an increased ratio of cardiac superrelaxation/disordered relaxation states that may contribute to impaired cardiac contractility. The phenotypes observed in the knock-in mice were rescued by cMLCK replenishment through the AAV9_MYLK3vector.MYLK3+/fsinduced pluripotent stem cell–derived cardiomyocytes reduced cMLCK expression by 50% and contractile dysfunction, accompanied by an increased superrelaxation/disordered relaxation ratio. CRISPR-mediated gene correction, or cMLCK replenishment by AAV9_MYLK3vector, successfully recovered cMLCK expression, the superrelaxation/disordered relaxation ratio, and contractile dysfunction. LEUO-1154 increased human cMLCK activity ≈2-fold in theVmaxfor ventricular myosin regulatory light chain phosphorylation without affecting theKm. LEUO-1154 treatment of humanMYLK3+/fsinduced pluripotent stem cell–derived cardiomyocytes restored the ventricular myosin regulatory light chain phosphorylation level and superrelaxation/disordered relaxation ratio and improved cardiac contractility without affecting calcium transients, indicating that the cMLCK activator acts as a myotrope. Finally, human myocardium from advanced heart failure with a wide variety of causes had a significantly lowerMYLK3/PPP1R12Bmessenger RNA expression ratio than control hearts, suggesting an altered balance between myosin regulatory light chain kinase and phosphatase in the failing myocardium, irrespective of the causes.Conclusions:cMLCK dysregulation contributes to the development of cardiac systolic dysfunction in humans. Our strategy to restore cMLCK activity could form the basis of a novel myotropic therapy for advanced systolic heart failure.

Leggi
Maggio 2023

Views of leaders in under-represented and equity-denied communities on organ and tissue donation in Nova Scotia, Canada, in light of the Human Organ and Tissue Donation Act: a qualitative descriptive study

Objective
To explore the views of underserved and equity-denied communities in Nova Scotia, Canada, regarding organ and tissue donation and deemed consent legislation.

Design
A qualitative descriptive study was undertaken, employing both interviews and focus groups.

Setting
The province of Nova Scotia, Canada—the first jurisdiction in North America to implement deemed consent legislation for organ and tissue donation.

Participants
Leaders of African Nova Scotian, Lesbian, Gay, Bisexual, Trans, Queer, Two Spirit (LGBTQ2S+) and Faith-based communities (Islam and Judaism) were invited to participate (n=11). Leaders were defined as persons responsible for community organisations or in other leadership roles, and were purposively recruited by the research team.

Results
Through thematic analysis, four main themes were identified: (1) alignment with personal values as well as religious beliefs and perspectives; (2) trust and relationships, which need to be acknowledged and addressed in the context of deemed consent legislation; (3) cultural competence, which is essential to the roll-out of the new legislation and (4) communication and information to combat misconceptions and misinformation, facilitate informed decision-making, and mitigate conflict within families.

Conclusions
Leaders of African Nova Scotian, LGBTQ2S+ and Faith-based communities in Nova Scotia are highly supportive of deemed consent legislation. Despite this, many issues exemplify the need for cultural competence at all levels. These findings should inform ongoing implementation of the legislation and other jurisdictions considering a deemed consent approach to organ and tissue donation.

Leggi
Aprile 2023

Tacrolimus-binding protein FKBP8 directs myosin light chain kinase-dependent barrier regulation and is a potential therapeutic target in Crohns disease

Objective
Intestinal barrier loss is a Crohn’s disease (CD) risk factor. This may be related to increased expression and enzymatic activation of myosin light chain kinase 1 (MLCK1), which increases intestinal paracellular permeability and correlates with CD severity. Moreover, preclinical studies have shown that MLCK1 recruitment to cell junctions is required for tumour necrosis factor (TNF)-induced barrier loss as well as experimental inflammatory bowel disease progression. We sought to define mechanisms of MLCK1 recruitment and to target this process pharmacologically.

Design
Protein interactions between FK506 binding protein 8 (FKBP8) and MLCK1 were assessed in vitro. Transgenic and knockout intestinal epithelial cell lines, human intestinal organoids, and mice were used as preclinical models. Discoveries were validated in biopsies from patients with CD and control subjects.

Results
MLCK1 interacted specifically with the tacrolimus-binding FKBP8 PPI domain. Knockout or dominant negative FKBP8 expression prevented TNF-induced MLCK1 recruitment and barrier loss in vitro. MLCK1-FKBP8 binding was blocked by tacrolimus, which reversed TNF-induced MLCK1-FKBP8 interactions, MLCK1 recruitment and barrier loss in vitro and in vivo. Biopsies of patient with CD demonstrated increased numbers of MLCK1-FKBP8 interactions at intercellular junctions relative to control subjects.

Conclusion
Binding to FKBP8, which can be blocked by tacrolimus, is required for MLCK1 recruitment to intercellular junctions and downstream events leading to immune-mediated barrier loss. The observed increases in MLCK1 activity, MLCK1 localisation at cell junctions and perijunctional MLCK1-FKBP8 interactions in CD suggest that targeting this process may be therapeutic in human disease. These new insights into mechanisms of disease-associated barrier loss provide a critical foundation for therapeutic exploitation of FKBP8-MLCK1 interactions.

Leggi
Aprile 2023

Health visiting in the UK in light of the COVID-19 pandemic experience (RReHOPE): a realist review protocol

Introduction
Health visiting services, providing support to under 5s and their families, are organised and delivered in very different ways in different parts of the UK. While there has been attention to the key components of health visiting practice and what works well and how, there is little research on how health visiting services are organised and delivered and how that affects their ability to meet their objectives. The COVID-19 pandemic rapidly disrupted service delivery from March 2020. This realist review aims to synthesise the evidence on changes during the pandemic to identify the potential for improving health visiting services and their delivery.

Methods and analysis
This review will follow the RAMESES (Realist And Meta-narrative Evidence Syntheses: Evolving Standards) quality standards and Pawson’s five iterative stages to locate existing theories, search for evidence, select literature, extract data, synthesise evidence and draw conclusions. It will be guided by stakeholder engagement with practitioners, commissioners, policymakers, policy advocates and people with lived experience. This approach will consider the emerging strategies and evolving contexts in which the services are delivered, and the varied outcomes for different groups. A realist logic of analysis will be used to make sense of what was happening to health visiting services during and following the pandemic response through the identification and testing of programme theories. Our refined programme theory will then be used to develop recommendations for improving the organisation, delivery and ongoing postpandemic recovery of health visiting services.

Ethics and dissemination
General University Ethics Panel approval has been obtained from University of Stirling (reference 7662). Dissemination will build on links to policymakers, commissioners, providers, policy advocates and the public. A range of audiences will be targeted using outputs tailored to each. A final stakeholder event focused on knowledge mobilisation will aid development of recommendations.

PROSPERO registration number
CRD42022343117.

Leggi
Marzo 2023

Abstract TMP117: Housing Light Cycle Impacts Metabolic Profile, Stroke Survival, And Cognitive Outcomes In Diabetic Rats

Stroke, Volume 54, Issue Suppl_1, Page ATMP117-ATMP117, February 1, 2023. Diabetes worsens stroke outcomes and cognitive function, but the underlying reasons are not understood. Long-term experimental studies had been limited by greater mortality in diabetic cohorts. Recent studies suggested circadian rhythms may modulate brain ischemia and hence mortality/recovery. The goal of this study was to determine the impact of stroke timing and housing light cycle conditions on survival and cognitive outcomes in control and diabetic rats.Methods:Control (C) and diabetic (D) male rats (n=7/group) were randomly grouped into normal light cycle (NLC 6 am/6 pm) or reverse light cycle (RLC 12 am/12 pm) starting at 4 w of age. At 12 w of age, rats were subjected to 60 min middle cerebral artery occlusion (MCAO, night stroke in NLC and morning stroke in RLC). A battery of behavioral tests was performed up to W8 post-stroke to assess motor, cognitive, and psychosocial status.Results:(Table). RLC conditions improved stroke surgery mortality and long-term survival in diabetic animals. Pre- and post-stroke body weight gain was affected only in the NLC/D group. High mortality in the NLC/D prevented 2×2 comparisons at W8 but suggested the worst performance the in NLC/D cohort. Comparisons of C and D rats in RLC showed a decline in recognition memory in both groups over time with trends for worse performance in diabetic animals. There was no difference in aversive learning or anxiety status.Conclusions:These results suggest that the light cycle and timing of MCAO affect the circadian rhythm, overall health state, and cognitive outcomes, especially in diabetes. RLC experiments may refine and improve the long-term studies in comorbid disease models.

Leggi
Febbraio 2023

Abstract TP49: The Pupillary Light Reflex Detects Large Vessel Occlusion

Stroke, Volume 54, Issue Suppl_1, Page ATP49-ATP49, February 1, 2023. Introduction:The pupillary light reflex (PLR) is a well-validated biomarker for neurologic monitoring and a decision-making tool for traumatic brain injury patients. We studied a machine learning-based mobile pupillometry platform in patients with acute ischemic stroke (AIS) with a large-vessel occlusion (LVO) prior to thrombectomy, compared to healthy volunteers.Methods:Pupillometry measurements were conducted with a mobile pupillometry platform (PupilScreen) and a digital infrared pupillometer (NeurOptics) for both pre-thrombectomy AIS subjects and healthy volunteers at an academic medical center. To correct for subject age differences, comparisons used the absolute inter-eye difference in each parameter for each subject by measuring the right:left (R:L) eye ratio absolute distance away from 1. Inter-eye difference means across subjects between AIS and healthy cohorts were analyzed for PLR changes in the presence of acute LVO using a t-test for independent means.Results:Seven AIS patients (4 female, 3 male; 1 Hispanic, 6 Caucasian; mean age 60.9 years) and 32 healthy patients (19 female, 13 male; 1 Hispanic, 2 African American, 3 Native American, 5 Asian, 21 Caucasian; mean age 34.4) were enrolled. All LVOs were of the middle cerebral artery, with 3 on the left and 4 on the right. NPi value was above 3 (briskly reactive) for all subjects. However, the smartphone pupillometer demonstrated a statistically significant (p

Leggi
Febbraio 2023

Abstract 10310: Sudden Cardiac Death in Recently Diagnosed Patients With Light-Chain Cardiac Amyloidosis

Circulation, Volume 146, Issue Suppl_1, Page A10310-A10310, November 8, 2022. Introduction:Untreated, light-chain (AL) cardiac amyloidosis is associated with a median survival of 6-months when diagnosed in advanced stage. However, current plasma cell-targeting therapies have drastically improved end-organ function and life expectancy. Yet, a portion still die despite appropriate treatment. We hypothesize this is from sudden cardiac death (SCD).Aim:To determine the incidence of and clinical characteristics associated with 90-day SCD after diagnosis of AL amyloidosis.Methods:Clinical, electrocardiographic, imaging, treatment, and outcomes were abstracted from consecutive patients diagnosed with AL amyloidosis from 2014-2022 at UT Southwestern Medical Center. Statistics were reported as mean and standard deviation.Results:In our study cohort (N=189) patients with AL amyloidosis, 18 patients (66% male, age 65 ± 9.5 y) died by 90-days (9.5%). Of these, 14 patients died by 60-days (7.3%), and 10 patient died by 30-days (5.2%). There were 7 cardiac deaths (3.6%): including one PEA arrest (0.5%), one in-hospital cardiac arrest (0.5%) and five unwitnessed out-of-hospital cardiac arrests (2.6%). Among cardiac deaths, 3 patients had endomyocardial tissue consistent with AL. Revised Mayo Stage was 66% III, 33% IV. Six patients had at least one dose of chemotherapy with bortezomib, cyclophosphamide and dexamethasone (CyBorD), Velcade/Dexamethasone, or Daratumumab/CyBorD, and 5 had at least one full cycle. The LVEF was 48.9 ± 8.1, QTc 483 ± 50 ms, interventricular septal thickness was 1.2 cm ± 0.4 cm. CMR was obtained in 4 of 7 patients, with late gadolinium enhancement present in a diffuse pattern in 75%, average LVEDV 59 ± 9.5 mL. Mean time to death was 37.2 ± 21 days.Conclusions:Sudden cardiac death may be a significant contributor to mortality among patients with newly diagnosed AL amyloidosis. These observations warrant confirmation in larger cohorts and may identify an unmet need to enhance risk stratification for SCD in this population.

Leggi
Ottobre 2022

Abstract 13258: Myosin Light Chain Dephosphorylation by Ppp1r12c Promotes Atrial Hypocontractility in Atrial Fibrillation

Circulation, Volume 146, Issue Suppl_1, Page A13258-A13258, November 8, 2022. Introduction:Atrial fibrillation (AF) is the most common sustained arrhythmia, with an estimated prevalence in the U.S. of 6.1 million . AF increases the risk of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. We have recently identified protein phosphatase 1 subunit 12c (PPP1R12C) as a key molecule targeting myosin light chain phosphorylation in AF.ObjectiveWe hypothesize that the overexpression of PPP1R12C causes hypophosphorylation of atrial myosin light chain 2 (MLC2a), thereby decreasing atrial contractility in AF.Methods and ResultsLeft and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluate the role of the PP1c-PPP1R12C interaction in MLC2a de-phosphorylation, we utilized Western blots, co-immunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12CPP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A) PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls.ConclusionThe overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, associated with a reduction in atrial contractility and increase in AF inducibility. All these discoveries suggest that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

Leggi
Ottobre 2022

Abstract 12887: Lightning Strikes Twice – A Case of Light Chain and Attr Amyloidosis

Circulation, Volume 146, Issue Suppl_1, Page A12887-A12887, November 8, 2022. The most common subsets of amyloidosis that affect the heart include light chain (AL) and transthyretin (ATTR). While both types cause diffuse amyloid fibril deposition within the interstitial space of the myocardium, they arise from two different precursors. AL amyloidosis results from misfolded monoclonal light chains, whereas ATTR amyloidosis results from misfolded transthyretin monomers. This distinction is essential as it suggests that a diagnosis of one disease does not exclude the existence of the other. We present a unique case of a patient with evidence of both systemic ATTR and AL amyloidosis occurring concurrently.An 80-year-old male with a past medical history of severe mitral regurgitation S/p mechanical mitral valve replacement, rotator cuff tear, bilateral carpal tunnel syndrome, and multiple hospitalizations for decompensated systolic heart failure was referred to cardiomyopathy clinic. He presented with class III New York Heart Association (NYHA) symptoms, including significant limitations in activity due to dyspnea. An echocardiogram demonstrated severe left ventricular hypertrophy with a low global longitudinal strain, an apical sparing pattern suspicious of amyloidosis. Monoclonal gammopathy workup showed an elevated lambda free light chain. Subsequent bone marrow biopsy demonstrated plasma cell dyscrasia and amyloid deposition in hypocellular bone marrow. Mass spectrometry showed both lambda light chain and transthyretin amyloid protein. He had elevated cardiac biomarkers, speaking for advanced cardiac involvement, together with nephrotic range proteinuria. He was started on chemotherapy/immunotherapy, with daratumumab, bortezomib and dexamethasone. He was in end stage heart failure requiring inotropic support. Few weeks after chemotherapy, he transitioned toward hospice care.In conclusion, we present a rare case of ATTR and AL amyloidosis coinciding simultaneously that demonstrates the importance of having high index of suspicion for this disease, a stepwise and thorough diagnostic approach highlighting the importance of mass spectroscopy after amyloid protein detection.

Leggi
Ottobre 2022

Abstract 13860: Heart Failure With Preserved Ejection Fraction Induced by Amyloid Light Chain Amyloidosis: A Case Report

Circulation, Volume 146, Issue Suppl_1, Page A13860-A13860, November 8, 2022. Introduction:Cardiac amyloidosis is a clinical disorder defined as an extracellular deposition of protein in the heart. Typically, signs and symptoms of heart failure develop in the advanced disease. High index of suspicion is required for the diagnosis of this disorder.Results:A 62 years old male came to the cardiology clinic due to lower extremity edema, fatigue, dyspnea on exertion. He had a 3 month history of progressive lower leg edema. On physical examination he had a positive S4; lung sounds were diminished and there was dullness to percussion over the lower two thirds; and bilateral lower extremity edema. Hospital admission was decided for management of decompensated heart failure. On admission, the surface ECG showed normal sinus rhythm with low QRS voltage in the limb leads, a RBBB and LPFB. Initial laboratory reported elevated NT-proBNP: 13,816 pg/mL. Chest x-ray demonstrated right interstitial infiltration and bilateral pleural effusion. The echocardiogram revealed severe concentric hypertrophy of the left ventricle, an apical sparing left ventricle longitudinal strain, and an ejection fraction of 68%. A cardiac MRI showed concentric biventricular hypertrophy associated with extensive diffuse late gadolinium enhancement, suggestive of cardiac amyloidosis. Screening resulted in a Perugini score of 1 on Tc-PYP scintigraphy, elevated Kappa and Lambda light chains on serum, and kidney biopsy positive for amyloidosis. Hematology-oncology consultation was done and a daratumumab-CyBorD protocol was started.Conclusions:This case elucidated a stepwise diagnostic approach of cardiac amyloidosis in a patient presenting with signs and symptoms of heart failure. Amyloid AL cardiac amyloidosis and its repercussions are severe because it not only compromises by being infiltrative but also by its toxic capacity. A high index of suspicion and a multidisciplinary approach is needed in order to improve quality of life and prolong survival.

Leggi
Ottobre 2022