Subcellular Propagation of Cardiomyocyte ß-Adrenergic Activation of Calcium Uptake Involves Internal ß-Receptors and AKAP7.

ß-adrenergic receptor (ß-AR) signaling in cardiac myocytes is central to cardiac function, but spatiotemporal activation within myocytes is unresolved. In rabbit ventricular myocytes, ß-AR agonists or high extracellular [Ca] were applied locally at one end, to measure ß-AR signal propagation as Ca-transient (CaT) amplitude and sarcoplasmic reticulum (SR) Ca uptake. High local [Ca]o, increased CaT amplitude under the pipette faster than did ISO, but was also more spatially restricted. Local isoproterenol (ISO) or norepinephrine (NE) increased CaT amplitude and SR Ca uptake, that spread along the myocyte to the unexposed end. Thus, local [Ca]i decline kinetics reflect spatio-temporal progression of ß-AR end-effects in myocytes. To test whether intracellular ß-ARs contribute to this response, we used ß-AR-blockers that are membrane permeant (propranolol) or not (sotalol). Propranolol completely blocked NE-dependent CaT effects. However, blocking surface ß-ARs only (sotalol) suppressed only ∼50% of the NE-induced increase in CaT peak and rate of [Ca]i decline, but these changes spread more gradually than NE alone. We also tested whether A-kinase anchoring protein 7γ (AKAP7γ; that interacts with phospholamban) is mobile, such that it might contribute to intracellular spatial propagation of ß-AR signaling. We found AKAP7γ to be highly mobile using fluorescence recovery after photobleach of GFP tagged AKAP7γ, and that PKA activation accelerated AKAP7γ-GFP wash-out upon myocyte saponin-permeabilization, suggesting increased AKAP7γ mobility. We conclude that local ß-AR activation can activate SR Ca uptake at remote myocyte sites, and that intracellular ß-AR and AKAP7γ mobility may play a role in this spread of activation.

Synergistic FRET assays for drug discovery targeting RyR2 channels.

A key therapeutic target for heart failure and arrhythmia is the deleterious leak through sarcoplasmic reticulum (SR) ryanodine receptor 2 (RyR2) calcium release channels. We have previously developed methods to detect the pathologically leaky state of RyR2 in adult cardiomyocytes by monitoring RyR2 binding to either calmodulin (CaM) or a biosensor peptide (DPc10). Here, we test whether these complementary binding measurements are effective as high-throughput screening (HTS) assays to discover small molecules that target leaky RyR2. Using FRET, we developed and validated HTS procedures under conditions that mimic a pathological state, to screen the library of 1280 pharmaceutically active compounds (LOPAC) for modulators of RyR2 in cardiac SR membrane preparations. Complementary FRET assays with acceptor-labeled CaM and DPc10 were used for Hit prioritization based on the opposing binding properties of CaM vs. DPc10. This approach narrowed the Hit list to one compound, Ro 90-7501, which altered FRET to suggest increased RyR2-CaM binding and decreased DPc10 binding. Follow-up studies revealed that Ro 90-7501 does not detrimentally affect myocyte Ca2+ transients. Moreover, Ro 90-7501 partially inhibits overall Ca2+ leak, as assessed by Ca2+ sparks in permeabilized rat cardiomyocytes. Together, these results demonstrate (1) the effectiveness of our HTS approach where two complementary assays synergize for Hit ranking and (2) a drug discovery process that combines high-throughput, high-precision in vitro structural assays with in situ myocyte assays of the pathologic RyR2 leak. These provide a drug discovery platform compatible with large-scale HTS campaigns, to identify agents that inhibit RyR2 for therapeutic development.

Beat-to-beat dynamic regulation of intracellular pH in cardiomyocytes.

The mammalian heart beats incessantly with rhythmic mechanical activities generating acids that need to be buffered to maintain a stable intracellular pH (pHi) for normal cardiac function. Even though spatial pHi non-uniformity in cardiomyocytes has been documented, it remains unknown how pHi is regulated to match the dynamic cardiac contractions. Here, we demonstrated beat-to-beat intracellular acidification, termed pHi transients, in synchrony with cardiomyocyte contractions. The pHi transients are regulated by pacing rate, Cl-/HCO3 - transporters, pHi buffering capacity, and ß-adrenergic signaling. Mitochondrial electron-transport chain inhibition attenuates the pHi transients, implicating mitochondrial activity in sculpting the pHi regulation. The pHi transients provide dynamic alterations of H+ transport required for ATP synthesis, and a decrease in pHi may serve as a negative feedback to cardiac contractions. Current findings dovetail with the prevailing three known dynamic systems, namely electrical, Ca2+, and mechanical systems, and may reveal broader features of pHi handling in excitable cells.

Reframing Adolescent Development: Identifying Communications Challenges and Opportunities.

Understanding Americans' deeply held and widely shared assumptions about adolescents and their development can reveal key opportunities and challenges for developmental science communicators. Twenty-nine in-depth interviews were conducted with adolescents and adults about adolescence. We analyzed the cultural models the public use to make meaning about what adolescence is, what development involves, what adolescents need, and how adolescents can be supported. The analysis revealed several cultural models that may impede public engagement around youth issues. These dominant ways of thinking include a strong focus on the vulnerability of adolescence and a narrow understanding of how environments affect adolescent development. The findings have important implications for communicators seeking to expand and deepen public thinking about adolescence.

Cardiomyocyte Na+ and Ca2+ mishandling drives vicious cycle involving CaMKII, ROS, and ryanodine receptors.

Cardiomyocyte Na+ and Ca2+ mishandling, upregulated Ca2+/calmodulin-dependent kinase II (CaMKII), and increased reactive oxygen species (ROS) are characteristics of various heart diseases, including heart failure (HF), long QT (LQT) syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). These changes may form a vicious cycle of positive feedback to promote cardiac dysfunction and arrhythmias. In HF rabbit cardiomyocytes investigated in this study, the inhibition of CaMKII, late Na+ current (INaL), and leaky ryanodine receptors (RyRs) all attenuated the prolongation and increased short-term variability (STV) of action potential duration (APD), but in age-matched controls these inhibitors had no or minimal effects. In control cardiomyocytes, we enhanced RyR leak (by low [caffeine] plus isoproterenol mimicking CPVT) which markedly increased STV and delayed afterdepolarizations (DADs). These proarrhythmic changes were significantly attenuated by both CaMKII inhibition and mitochondrial ROS scavenging, with a slight synergy with INaL inhibition. Inducing LQT by elevating INaL (by Anemone toxin II, ATX-II) caused markedly prolonged APD, increased STV, and early afterdepolarizations (EADs). Those proarrhythmic ATX-II effects were largely attenuated by mitochondrial ROS scavenging, and partially reduced by inhibition of CaMKII and pathological leaky RyRs using dantrolene. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) bearing LQT3 mutation SCN5A N406K, dantrolene significantly attenuated cell arrhythmias and APD prolongation. Targeting critical components of the Na+-Ca2+-CaMKII-ROS-INaL arrhythmogenic vicious cycle may exhibit important on-target and also trans-target effects (e.g., INaL and RyR inhibition can alter INaL-mediated LQT3 effects). Incorporating this vicious cycle into therapeutic strategies provides novel integrated insight for treating cardiac arrhythmias and diseases.

A Survivor-Derived Approach to Addressing Trafficking in the Pediatric ED.

OBJECTIVES: Our objective was to elicit the perspectives of survivors of child trafficking on addressing trafficking in the pediatric emergency department (ED) and, secondarily, to provide a survivor-derived framework to help pediatric emergency medicine (PEM) providers discuss trafficking with their patients. METHODS: We conducted in-depth, semistructured interviews with young adults who experienced trafficking as children and/or as adolescents. In the interviews, we employed a novel video-elicitation method designed by the research team to elicit detailed participant feedback and recommendations on the pediatric ED through an interactive, immersive discussion with the interviewer. A grounded theory approach was employed. RESULTS: Seventeen interviews were conducted revealing the following themes, which we present in an integrated framework for PEM providers: (1) fear is a significant barrier; (2) participants do want PEM providers to ask about trafficking, and it is not harmful to do so; (3) PEM providers should address fear through emphasizing confidentiality and privacy and encouraging agency; (4) PEM providers should approach the patient in a direct, sensitive, and nonjudgmental manner; and (5) changes to the ED environment may facilitate the conversation. Suggested wordings and tips from survivors were compiled. CONCLUSIONS: Trafficking survivors feel that the pediatric ED can be a place where they can be asked about trafficking, and that when done in private, it is not harmful or retraumatizing. Fear is a major barrier to disclosure in the pediatric ED setting, and PEM providers can mitigate this by emphasizing privacy and confidentiality and increasing agency by providing choices. PEM providers should be direct, sensitive, and nonjudgmental in their approach to discussing trafficking.

JNK2, a Newly-Identified SERCA2 Enhancer, Augments an Arrhythmic [Ca2+]SR Leak-Load Relationship.

RATIONALE: We recently discovered pivotal contributions of stress kinase JNK2 (c-Jun N-terminal kinase isoform 2) in increased risk of atrial fibrillation through enhanced diastolic sarcoplasmic reticulum (SR) calcium (Ca2+) leak via RyR2 (ryanodine receptor isoform 2). However, the role of JNK2 in the function of the SERCA2 (SR Ca2+-ATPase), essential in maintaining SR Ca2+ content cycling during each heartbeat, is completely unknown. OBJECTIVE: To test the hypothesis that JNK2 increases SERCA2 activity SR Ca2+ content and exacerbates an arrhythmic SR Ca2+ content leak-load relationship. METHODS AND RESULTS: We used confocal Ca2+ imaging in myocytes and HEK-RyR2 (ryanodine receptor isoform 2-expressing human embryonic kidney 293 cells) cells, biochemistry, dual Ca2+/voltage optical mapping in intact hearts from alcohol-exposed or aged mice (where JNK2 is activated). We found that JNK2, but not JNK1 (c-Jun N-terminal kinase isoform 1), increased SERCA2 uptake and consequently elevated SR Ca2+ content load. JNK2 also associates with and phosphorylates SERCA2 proteins. JNK2 causally enhances SERCA2-ATPase activity via increased maximal rate, without altering Ca2+ affinity. Unlike the CaMKII (Ca2+/calmodulin-dependent kinase II)-dependent JNK2 action in SR Ca2+ leak, JNK2-driven SERCA2 function was CaMKII independent (not prevented by CaMKII inhibition). With CaMKII blocked, the JNK2-driven SR Ca2+ loading alone did not significantly raise leak. However, with JNK2-CaMKII-driven SR Ca2+ leak present, the JNK2-enhanced SR Ca2+ uptake limited leak-induced reduction in SR Ca2+, normalizing Ca2+ transient amplitude, but at a higher arrhythmogenic SR Ca2+ leak. JNK2-specific inhibition completely normalized SR Ca2+ handling, attenuated arrhythmic Ca2+ activities, and alleviated atrial fibrillation susceptibility in aged and alcohol-exposed myocytes and intact hearts. CONCLUSIONS: We have identified a novel JNK2-induced activation of SERCA2. The dual action of JNK2 in CaMKII-dependent arrhythmic SR Ca2+ leak and a CaMKII-independent uptake exacerbates atrial arrhythmogenicity, while helping to maintain normal levels of Ca2+ transients and heart function. JNK2 modulation may be a novel therapeutic target for atrial fibrillation prevention and treatment.

Route Choices and Adolescent-Adult Connections in Mitigating Exposure to Environmental Risk Factors During Daily Activities.

While adolescent-adult connections have been shown to be protective against violence perpetration and victimization, mechanisms through which these connections confer protection from violence are poorly understood. We assessed whether adolescent-adult connections protected youth in lower resource urban neighborhoods from exposure to environmental risk factors for violence during daily activities. We overlaid on the city landscape minute-by-minute activity paths from 274 randomly sampled predominantly African American male youth, ages 10 to 24, enrolled in a population-based study of daily activities in Philadelphia, PA, to calculate environmental exposures and to compare exposures along actual versus shortest potential travel routes. Adolescent-adult connections were defined using brief survey questions and detailed family genograms. Analyses demonstrated that youth's selected travel routes resulted in significantly lower exposure to several types of crime, including vandalism, narcotics arrests, and disorderly conduct, than would have occurred on shortest potential routes. On average, youth with adolescent-adult connections spent less time outdoors than youth without connections, although these differences did not reach statistical significance (p = .06). There were no significant differences in environmental risk factors encountered by youth with versus without adolescent-adult connections. Future mixed-methods research combining qualitative and geographic information systems (GIS) approaches should investigate which factors shape travel decisions during daily activities to guide multimodal violence prevention interventions.

Metabolic Maturation Media Improve Physiological Function of Human iPSC-Derived Cardiomyocytes.

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have enormous potential for the study of human cardiac disorders. However, their physiological immaturity severely limits their utility as a model system and their adoption for drug discovery. Here, we describe maturation media designed to provide oxidative substrates adapted to the metabolic needs of human iPSC (hiPSC)-CMs. Compared with conventionally cultured hiPSC-CMs, metabolically matured hiPSC-CMs contract with greater force and show an increased reliance on cardiac sodium (Na+) channels and sarcoplasmic reticulum calcium (Ca2+) cycling. The media enhance the function, long-term survival, and sarcomere structures in engineered heart tissues. Use of the maturation media made it possible to reliably model two genetic cardiac diseases: long QT syndrome type 3 due to a mutation in the cardiac Na+ channel SCN5A and dilated cardiomyopathy due to a mutation in the RNA splicing factor RBM20. The maturation media should increase the fidelity of hiPSC-CMs as disease models.

Disease-associated mutations in Niemann-Pick type C1 alter ER calcium signaling and neuronal plasticity.

Niemann-Pick type C1 (NPC1) protein is essential for the transport of externally derived cholesterol from lysosomes to other organelles. Deficiency of NPC1 underlies the progressive NPC1 neurodegenerative disorder. Currently, there are no curative therapies for this fatal disease. Given the Ca2+ hypothesis of neurodegeneration, which posits that altered Ca2+ dynamics contribute to neuropathology, we tested if disease mutations in NPC1 alter Ca2+ signaling and neuronal plasticity. We determine that NPC1 inhibition or disease mutations potentiate store-operated Ca2+ entry (SOCE) due to a presenilin 1 (PSEN1)-dependent reduction in ER Ca2+ levels alongside elevated expression of the molecular SOCE components ORAI1 and STIM1. Associated with this dysfunctional Ca2+ signaling is destabilization of neuronal dendritic spines. Knockdown of PSEN1 or inhibition of the SREBP pathway restores Ca2+ homeostasis, corrects differential protein expression, reduces cholesterol accumulation, and rescues spine density. These findings highlight lysosomes as a crucial signaling platform responsible for tuning ER Ca2+ signaling, SOCE, and synaptic architecture in health and disease.

The role of resilience in healthcare transitions among adolescent kidney transplant recipients.

PURPOSE: AYAs with KTs experience high rates of premature allograft loss during the HCT. There is a critical need to identify protective factors associated with stable HCT. Resilience-the ability to adapt and thrive in the setting of adversity-has known positive impact on health outcomes. This study explored the novel role of resilience constructs as protective factors in securing stable HCT among AYA with KT. METHODS: We conducted semi-structured interviews of adolescents and young adults who transitioned from a single pediatric transplant center to multiple adult nephrology centers between 2010 and 2017. Interviews explored the role of key resilience constructs in participants' lives around the time of HCT. Participants were stratified into stable or unstable HCT groups based on biological markers of allograft function and clinical data from chart review. Content analyses of interview transcripts were reviewed and compared among HCT groups. RESULTS: Thirty-two participants enrolled (17 stable; 15 unstable). Key resilience constructs more salient in the stable versus unstable HCT group were confidence in and connection to one's healthcare team. Reports of healthcare self-management competencies were similar across both HCT groups. CONCLUSIONS: Confidence in and connection to one's healthcare team appear to be linked with a stable HCT among AYA with KT. This suggests that interdependence, the ability to foster connections with and elicit support from healthcare providers, as opposed to complete independence or autonomy, which is often advised in the HCT process, is a critical component of resilience linked to stable HCT.

The Role of Patient and Parental Resilience in Adolescents with Chronic Musculoskeletal Pain.

OBJECTIVES: To assess the level of resilience among patients with chronic musculoskeletal pain and their parents and to determine factors associated with patient and parental resilience. STUDY DESIGN: Cross-sectional cohort study of children aged 13-17 years diagnosed with chronic musculoskeletal pain and their parents. Patient-parent pairs were seen for initial consultation in the pediatric rheumatology pain clinic at Children's Hospital of Philadelphia between March and May 2018 and were administered a series of questionnaires including measures of resilience (Connor-Davidson Resilience Scale 10 item, The 14-item Resilience Scale, and the 7Cs of Resilience Tool). We calculated Pearson correlation coefficients to examine the relationship between the variables of interest and resilience. RESULTS: According to all resilience measures, patients and parents had low to moderate levels of resilience. These levels were lower than those previously reported among healthy populations, as well as those with chronic medical conditions. According to the Connor-Davidson Resilience Scale 10 item, patient-level resilience was negatively correlated with pain level (r = -0.48), physical disability (r = -0.54), and symptom severity (r = -0.53). The level of resilience among patients was positively correlated with energy level (r = 0.57) and health-related quality of life (r = 0.64). Parental resilience was positively correlated with parental mental health (r = 0.61). CONCLUSIONS: Higher patient resilience was correlated with reduced disease severity among adolescents with chronic musculoskeletal pain. Future research should explore whether fostering resilience in adolescents with chronic musculoskeletal pain via the application of resilience-training interventions mitigates disease burden in this vulnerable patient population.

Enhanced Depolarization Drive in Failing Rabbit Ventricular Myocytes: Calcium-Dependent and ß-Adrenergic Effects on Late Sodium, L-Type Calcium, and Sodium-Calcium Exchange Currents.

BACKGROUND: Heart failure (HF) is characterized by electrophysiological remodeling resulting in increased risk of cardiac arrhythmias. Previous reports suggest that elevated inward ionic currents in HF promote action potential (AP) prolongation, increased short-term variability of AP repolarization, and delayed afterdepolarizations. However, the underlying changes in late Na+ current (INaL), L-type Ca2+ current, and NCX (Na+/Ca2+ exchanger) current are often measured in nonphysiological conditions (square-pulse voltage clamp, slow pacing rates, exogenous Ca2+ buffers). METHODS: We measured the major inward currents and their Ca2+- and ß-adrenergic dependence under physiological AP clamp in rabbit ventricular myocytes in chronic pressure/volume overload-induced HF (versus age-matched control). RESULTS: AP duration and short-term variability of AP repolarization were increased in HF, and importantly, inhibition of INaL decreased both parameters to the control level. INaL was slightly increased in HF versus control even when intracellular Ca2+ was strongly buffered. But under physiological AP clamp with normal Ca2+ cycling, INaL was markedly upregulated in HF versus control (dependent largely on CaMKII [Ca2+/calmodulin-dependent protein kinase II] activity). ß-Adrenergic stimulation (often elevated in HF) further enhanced INaL. L-type Ca2+ current was decreased in HF when Ca2+ was buffered, but CaMKII-mediated Ca2+-dependent facilitation upregulated physiological L-type Ca2+ current to the control level. Furthermore, L-type Ca2+ current response to ß-adrenergic stimulation was significantly attenuated in HF. Inward NCX current was upregulated at phase 3 of AP in HF when assessed by combining experimental data and computational modeling. CONCLUSIONS: Our results suggest that CaMKII-dependent upregulation of INaL in HF significantly contributes to AP prolongation and increased short-term variability of AP repolarization, which may lead to increased arrhythmia propensity, and is further exacerbated by adrenergic stress.

Concerns and Expectations of Parents Seeking Subspecialist Care for Their Child's Short Stature.

INTRODUCTION: Parents (PP) of children in primary care clinics previously reported factors influencing their height-related medical decision making. However, patients seeking height-related care in endocrine subspecialty clinics and their parents (EP) differ demographically from the general population. OBJECTIVE: To determine EP height-related medical concerns and expectations, and to compare between EP and PP. METHODS: EP completed a survey assessing their concerns in seeking medical care for their child's height with identical questions previously asked of PP and two additional questions about growth hormone (GH) treatment. RESULTS: A greater proportion of the 166 EP (80% response rate) than the 1,820 PP (83% response rate) previously surveyed was Caucasian (75% EP, 41% PP) and privately insured (80% EP, 58% PP). Both groups rated treatment efficacy and risks most as having a bigor extreme impact on decision making (65% EP, 58% PP). The second most rated concern for EP was comparison of child's height to peers or growth chart (60% EP, 32% PP) versus child's health for PP (54% EP, 56% PP). Of the 166 EP surveyed, 76% rated GH treatment as potentially improving quality of life (QoL), with 88% reporting a minimum 3-inch height increase as necessary to improve QoL. CONCLUSIONS: Height comparisons were more likely to impact EP than PP in seeking height-related medical care for their children. EP had high expectations of QoL improvement with GH treatment, which are unlikely to be met with treatment of idiopathic short stature. Thus, clinicians should be prepared to support families in other ways that promote positive development in children with short stature.