A membrane-associated phosphoswitch in Rad controls adrenergic regulation of cardiac calcium channels.

The ability to fight or flee from a threat relies on an acute adrenergic surge that augments cardiac output, which is dependent on increased cardiac contractility and heart rate. This cardiac response depends on ß-adrenergic-initiated reversal of the small RGK G protein Rad-mediated inhibition of voltage-gated calcium channels (CaV) acting through the Cavß subunit. Here, we investigate how Rad couples phosphorylation to augmented Ca2+ influx and increased cardiac contraction. We show that reversal required phosphorylation of Ser272 and Ser300 within Rad's polybasic, hydrophobic C-terminal domain (CTD). Phosphorylation of Ser25 and Ser38 in Rad's N-terminal domain (NTD) alone was ineffective. Phosphorylation of Ser272 and Ser300 or the addition of 4 Asp residues to the CTD reduced Rad's association with the negatively charged, cytoplasmic plasmalemmal surface and with CaVß, even in the absence of CaVα, measured here by FRET. Addition of a posttranslationally prenylated CAAX motif to Rad's C-terminus, which constitutively tethers Rad to the membrane, prevented the physiological and biochemical effects of both phosphorylation and Asp substitution. Thus, dissociation of Rad from the sarcolemma, and consequently from CaVß, is sufficient for sympathetic upregulation of Ca2+ currents.

A Genetically Encoded Actuator Selectively Boosts L-type Calcium Channels in Diverse Physiological Settings.

L-type Ca 2+ channels (Ca V 1.2/1.3) convey influx of calcium ions (Ca 2+ ) that orchestrate a bevy of biological responses including muscle contraction and gene transcription. Deficits in Ca V 1 function play a vital role in cardiac and neurodevelopmental disorders. Yet conventional pharmacological approaches to upregulate Ca V 1 are limited, as excessive Ca 2+ influx leads to cytotoxicity. Here, we develop a genetically encoded enhancer of Ca V 1.2/1.3 channels (GeeC) to manipulate Ca 2+ entry in distinct physiological settings. Specifically, we functionalized a nanobody that targets the Ca V macromolecular complex by attaching a minimal effector domain from a Ca V enhancer-leucine rich repeat containing protein 10 (Lrrc10). In cardiomyocytes, GeeC evoked a 3-fold increase in L-type current amplitude. In neurons, GeeC augmented excitation-transcription (E-T) coupling. In all, GeeC represents a powerful strategy to boost Ca V 1.2/1.3 function in distinct physiological settings and, in so doing, lays the groundwork to illuminate new insights on neuronal and cardiac physiology and disease.

Shorter Duration Hepatitis C Virus Treatment is Associated with Better Persistence to Prescription Refills in People Who Inject Drugs: A Real-World Study.

INTRODUCTION: Direct-acting antiviral (DAA) therapy is highly effective in curing hepatitis C virus (HCV) infection in people who inject drugs (PWID). Previous studies showed declining persistence to DAA therapy over the course of treatment. This study compares real-world medication persistence to prescription refills for 8- versus 12-week DAA in treatment-naïve PWID with chronic HCV with compensated cirrhosis or without cirrhosis. METHODS: Symphony Health's claims database was used to collect data from patients with chronic HCV aged ≥ 12 years who were prescribed 8- or 12-week DAA therapy between August 2017 and November 2020 and had a diagnosis of addicted drug use within 6 months prior to index date. Eligible patients had medical/pharmacy claims in the 6 months before and 3 months after the first index medication fill date (i.e., index date). Patients completing all refills (8-week = 1 refill, 12-week = 2 refills) were deemed persistent. The percentage of persistent patients in each group, and at each refill step, was determined; outcomes were also assessed in a subgroup of Medicaid-insured patients. RESULTS: This study assessed 7203 PWID with chronic HCV (8-week, 4002; 12-week, 3201). Patients prescribed 8-week DAA treatment were younger (42.9 ± 12.4 vs 47.5 ± 13.2, P < 0.001) and had fewer comorbidities (P < 0.001). Patients receiving 8- versus 12-week DAA had greater refill persistence (87.9% vs 64.4%, P < 0.001). Similar percentages of patients missed their first refill (8-week, 12.1% vs 12-week, 10.8%); nearly 25% of patients receiving 12-week DAA missed their second refill. After baseline characteristics were controlled, patients prescribed 8- versus 12-week DAA were more likely to be persistent (odds ratio [95% confidence interval] 4.3 [3.8, 5.0]). Findings in the Medicaid-insured subgroup were consistent. CONCLUSION: Patients prescribed 8- vs 12-week DAA therapy had significantly greater prescription refill persistence. Most nonpersistence was due to missed second refills, highlighting the potential benefit of shorter treatment durations in this population.

Real-World Effectiveness of 8-Week Glecaprevir/Pibrentasvir in Treatment-Naïve, Compensated Cirrhotic HCV Patients.

INTRODUCTION: The EXPEDITION-8 clinical trial has demonstrated that treatment-naïve patients with compensated cirrhosis (TN/CC) of HCV genotypes 1-6 can achieve a 98% intent-to-treat sustained virologic response rate 12 weeks post-treatment with an 8-week glecaprevir/pibrentasvir (G/P) regimen. Further real-world evidence is needed to support the effectiveness of 8-week G/P in a clinical practice setting and to consolidate these treatment recommendations. The aim of this study is to contribute real-world evidence for the effectiveness of an 8-week G/P treatment in TN/CC patients with HCV genotypes 1-6. METHODS: Retrospective real-world data from 494 TN/CC patients with HCV genotypes 1-6 were collected between August 2017 to December 2020 from the Symphony Health Solutions administrative claims database. Demographic and clinical characteristics were collected at baseline. Patients were required to have a follow-up HCV ribonucleic acid level at least 8 weeks or more after the end of treatment. The percentage of patients achieving a sustained virologic response (SVR) is reported. RESULTS: The majority of patients were male (58%) and Caucasian (40%), with a mean age of 58 years; 74%, 12%, 12%, and 1% of patients were HCV genotype 1, 2, 3, and 4-6 infected, respectively. SVR was achieved in 95.5% of all patients. Across patient subgroups, SVR was achieved in 95.6% of patients with HCV genotype 3 and in 93% of HCV patients with a recent diagnosis of illicit drug use or abuse (within 6 months prior to G/P initiation). CONCLUSION: Early real-world evidence indicates high effectiveness of the 8-week G/P regimen in TN/CC patients of HCV genotypes 1-6 from a large US claims database.

5-Year Outcomes After Bioresorbable Coronary Scaffolds Implanted With Improved Technique.

BACKGROUND: Bioresorbable vascular scaffolds (BVS) were designed to improve late event-free survival compared with metallic drug-eluting stents. However, initial trials demonstrated worse early outcomes with BVS, in part due to suboptimal technique. In the large-scale, blinded ABSORB IV trial, polymeric everolimus-eluting BVS implanted with improved technique demonstrated noninferior 1-year outcomes compared with cobalt chromium everolimus-eluting stents (CoCr-EES). OBJECTIVES: This study sought to evaluate the long-term outcomes from the ABSORB IV trial. METHODS: We randomized 2,604 patients at 147 sites with stable or acute coronary syndromes to BVS with improved technique vs CoCr-EES. Patients, clinical assessors, and event adjudicators were blinded to randomization. Five-year follow-up was completed. RESULTS: Target lesion failure at 5 years occurred in 216 (17.5%) patients assigned to BVS and 180 (14.5%) patients assigned to CoCr-EES (P = 0.03). Device thrombosis within 5 years occurred in 21 (1.7%) BVS and 13 (1.1%) CoCr-EES patients (P = 0.15). Event rates were slightly greater with BVS than CoCr-EES through 3-year follow-up and were similar between 3 and 5 years. Angina, also centrally adjudicated, recurred within 5 years in 659 patients (cumulative rate 53.0%) assigned to BVS and 674 (53.3%) patients assigned to CoCr-EES (P = 0.63). CONCLUSIONS: In this large-scale, blinded randomized trial, despite the improved implantation technique, the absolute 5-year rate of target lesion failure was 3% greater after BVS compared with CoCr-EES. The risk period for increased events was limited to 3 years, the time point of complete scaffold bioresorption; event rates were similar thereafter. Angina recurrence after intervention was frequent during 5-year follow-up but was comparable with both devices.(Absorb IV Randomized Controlled Trial; NCT02173379).

Five-Year Follow-up after Transcatheter Repair of Secondary Mitral Regurgitation.

BACKGROUND: Data from a 5-year follow-up of outcomes after transcatheter edge-to-edge repair of severe mitral regurgitation, as compared with outcomes after maximal doses of guideline-directed medical therapy alone, in patients with heart failure are now available. METHODS: We randomly assigned patients with heart failure and moderate-to-severe or severe secondary mitral regurgitation who remained symptomatic despite the use of maximal doses of guideline-directed medical therapy to undergo transcatheter edge-to-edge repair plus receive medical therapy (device group) or to receive medical therapy alone (control group) at 78 sites in the United States and Canada. The primary effectiveness end point was all hospitalizations for heart failure through 2 years of follow-up. The annualized rate of all hospitalizations for heart failure, all-cause mortality, the risk of death or hospitalization for heart failure, and safety, among other outcomes, were assessed through 5 years. RESULTS: Of the 614 patients enrolled in the trial, 302 were assigned to the device group and 312 to the control group. The annualized rate of hospitalization for heart failure through 5 years was 33.1% per year in the device group and 57.2% per year in the control group (hazard ratio, 0.53; 95% confidence interval [CI], 0.41 to 0.68). All-cause mortality through 5 years was 57.3% in the device group and 67.2% in the control group (hazard ratio, 0.72; 95% CI, 0.58 to 0.89). Death or hospitalization for heart failure within 5 years occurred in 73.6% of the patients in the device group and in 91.5% of those in the control group (hazard ratio, 0.53; 95% CI, 0.44 to 0.64). Device-specific safety events within 5 years occurred in 4 of 293 treated patients (1.4%), with all the events occurring within 30 days after the procedure. CONCLUSIONS: Among patients with heart failure and moderate-to-severe or severe secondary mitral regurgitation who remained symptomatic despite guideline-directed medical therapy, transcatheter edge-to-edge repair of the mitral valve was safe and led to a lower rate of hospitalization for heart failure and lower all-cause mortality through 5 years of follow-up than medical therapy alone. (Funded by Abbott; COAPT ClinicalTrials.gov number, NCT01626079.).

Engineered cardiac tissue model of restrictive cardiomyopathy for drug discovery.

Restrictive cardiomyopathy (RCM) is defined as increased myocardial stiffness and impaired diastolic relaxation leading to elevated ventricular filling pressures. Human variants in filamin C (FLNC) are linked to a variety of cardiomyopathies, and in this study, we investigate an in-frame deletion (c.7416_7418delGAA, p.Glu2472_Asn2473delinAsp) in a patient with RCM. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with this variant display impaired relaxation and reduced calcium kinetics in 2D culture when compared with a CRISPR-Cas9-corrected isogenic control line. Similarly, mutant engineered cardiac tissues (ECTs) demonstrate increased passive tension and impaired relaxation velocity compared with isogenic controls. High-throughput small-molecule screening identifies phosphodiesterase 3 (PDE3) inhibition by trequinsin as a potential therapy to improve cardiomyocyte relaxation in this genotype. Together, these data demonstrate an engineered cardiac tissue model of RCM and establish the translational potential of this precision medicine approach to identify therapeutics targeting myocardial relaxation.

Sympathetic Nervous System Regulation of Cardiac Calcium Channels.

Calcium influx through voltage-gated calcium channels, Cav1.2, in cardiomyocytes initiates excitation-contraction coupling in the heart. The force and rate of cardiac contraction are modulated by the sympathetic nervous system, mediated substantially by changes in intracellular calcium. Norepinephrine released from sympathetic neurons innervating the heart and epinephrine secreted by the adrenal chromaffin cells bind to ß-adrenergic receptors on the sarcolemma of cardiomyocytes initiating a signaling cascade that generates cAMP and activates protein kinase A, the targets of which control calcium influx. For decades, the mechanisms by which PKA regulated calcium channels in the heart were not known. Recently, these mechanisms have been elucidated. In this chapter, we will review the history of the field and the studies that led to the identification of the evolutionarily conserved process.

Effect of mechanical unloading on genome-wide DNA methylation profile of the failing human heart.

Heart failure (HF) is characterized by global alterations in myocardial DNA methylation, yet little is known about the epigenetic regulation of the noncoding genome and potential reversibility of DNA methylation with left ventricular assist device (LVAD) therapy. Genome-wide mapping of myocardial DNA methylation in 36 patients with HF at LVAD implantation, 8 patients at LVAD explantation, and 7 nonfailing (NF) donors using a high-density bead array platform identified 2,079 differentially methylated positions (DMPs) in ischemic cardiomyopathy (ICM) and 261 DMPs in nonischemic cardiomyopathy (NICM). LVAD support resulted in normalization of 3.2% of HF-associated DMPs. Methylation-expression correlation analysis yielded several protein-coding genes that are hypomethylated and upregulated (HTRA1, FBXO16, EFCAB13, and AKAP13) or hypermethylated and downregulated (TBX3) in HF. A potentially novel cardiac-specific super-enhancer long noncoding RNA (lncRNA) (LINC00881) is hypermethylated and downregulated in human HF. LINC00881 is an upstream regulator of sarcomere and calcium channel gene expression including MYH6, CACNA1C, and RYR2. LINC00881 knockdown reduces peak calcium amplitude in the beating human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). These data suggest that HF-associated changes in myocardial DNA methylation within coding and noncoding genomes are minimally reversible with mechanical unloading. Epigenetic reprogramming strategies may be necessary to achieve sustained clinical recovery from heart failure.

Rad regulation of CaV1.2 channels controls cardiac fight-or-flight response.

Fight-or-flight responses involve ß-adrenergic-induced increases in heart rate and contractile force. In the present study, we uncover the primary mechanism underlying the heart's innate contractile reserve. We show that four protein kinase A (PKA)-phosphorylated residues in Rad, a calcium channel inhibitor, are crucial for controlling basal calcium current and essential for ß-adrenergic augmentation of calcium influx in cardiomyocytes. Even with intact PKA signaling to other proteins modulating calcium handling, preventing adrenergic activation of calcium channels in Rad-phosphosite-mutant mice (4SA-Rad) has profound physiological effects: reduced heart rate with increased pauses, reduced basal contractility, near-complete attenuation of ß-adrenergic contractile response and diminished exercise capacity. Conversely, expression of mutant calcium-channel ß-subunits that cannot bind 4SA-Rad is sufficient to enhance basal calcium influx and contractility to adrenergically augmented levels of wild-type mice, rescuing the failing heart phenotype of 4SA-Rad mice. Hence, disruption of interactions between Rad and calcium channels constitutes the foundation toward next-generation therapeutics specifically enhancing cardiac contractility.

Bleeding and Ischemic Outcomes With Ticagrelor Monotherapy According to Body Mass Index.

BACKGROUND: There is a paucity of data regarding the safety and efficacy of different antiplatelet regimens according to standardized body mass index (BMI) categories. OBJECTIVES: The aim of this study was to investigate bleeding and ischemic outcomes according to BMI in the TWILIGHT (Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention) trial. METHODS: The TWILIGHT trial randomized high-risk patients to ticagrelor plus aspirin or ticagrelor plus placebo at 3 months after percutaneous coronary intervention. In this secondary analysis, patients were stratified by standard BMI categories, as recommended by the European Society of Cardiology Working Group on Thrombosis (normal weight [BMI 18.5-24.99 kg/m2], overweight [BMI 25-29.99 kg/m2], and obese [BMI ≥30 kg/m2]) and by median BMI, as prespecified in the protocol. RESULTS: Among 7,038 patients randomized and with available BMI, 1,807 (25.7%) were normal weight, 2,927 (41.6%) were overweight, and 2,304 (32.7%) were obese. In normal-weight, overweight, and obese patients, ticagrelor monotherapy, compared with ticagrelor plus aspirin, reduced the primary endpoint of Bleeding Academic Research Consortium type 2, 3, or 5 bleeding (normal weight: HR: 0.48 [95% CI: 0.32-0.73]; overweight: HR: 0.57 [95% CI: 0.41-0.78]; obese: HR: 0.63 [95% CI: 0.44-0.91]; P for interaction = 0.627), without any increase in the composite ischemic endpoint of all-cause death, myocardial infarction, or stroke (normal weight: HR: 1.36 [95% CI: 0.84-2.19]; overweight: HR: 0.92 [95% CI: 0.63-1.35]; obese: HR: 0.84 [95% CI: 0.56-1.25]; P for interaction = 0.290). These findings were consistent with the prespecified analysis by median BMI. CONCLUSIONS: Among high-risk patients undergoing percutaneous coronary intervention, ticagrelor monotherapy, compared with ticagrelor plus aspirin, reduced bleeding events without any increase in ischemic risk across different BMI categories.

Ticagrelor with and without aspirin in patients with a prior coronary artery bypass graft undergoing percutaneous coronary intervention: the TWILIGHT-CABG study.

BACKGROUND: Prior coronary artery bypass graft surgery (CABG) patients undergoing percutaneous coronary intervention (PCI) are often older and present with multiple comorbidities. Ticagrelor monotherapy after a short course of dual antiplatelet therapy (DAPT) has emerged as an effective bleeding-avoidance strategy among high-risk patients. AIMS: We aimed to examine the effects of ticagrelor with or without aspirin in prior CABG patients undergoing PCI within the TWILIGHT trial. METHODS: After 3 months of ticagrelor plus aspirin, patients were randomised to either aspirin or placebo, in addition to ticagrelor, for 12 months and compared by prior CABG status. The primary endpoint was Bleeding Academic Research Consortium (BARC) type 2, 3 or 5 bleeding. The key secondary endpoint was all-cause death, myocardial infarction (MI), or stroke. RESULTS: Out of 7,119 patients, a total of 703 (10.8%) patients had prior CABG within the randomised cohort. Prior CABG patients had more comorbidities and a higher incidence of BARC type 2, 3, or 5 bleeding and death, MI or stroke at 1 year after randomisation, compared with patients without prior CABG. Ticagrelor monotherapy was associated with significantly less BARC 2, 3, or 5 bleeding among prior CABG patients compared with DAPT (4.9% vs 9.6%, hazard ratio [HR] 0.50, 95% confidence interval [CI]: 0.28 to 0.90; pinteraction=0.676) and similar rates of death, MI or stroke (10.0% vs 8.7%, HR 1.14, 95% CI: 0.70 to 1.87; pinteraction=0.484). When comparing target vessel type, treatment effects were consistent among graft- and native-vessel interventions. CONCLUSIONS: In high-risk patients with prior CABG, ticagrelor monotherapy reduced bleeding without compromising ischaemic outcomes compared with ticagrelor plus aspirin.

Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

Voltage-gated sodium (Nav1.5) channels support the genesis and brisk spatial propagation of action potentials in the heart. Disruption of NaV1.5 inactivation results in a small persistent Na influx known as late Na current (I Na,L), which has emerged as a common pathogenic mechanism in both congenital and acquired cardiac arrhythmogenic syndromes. Here, using low-noise multi-channel recordings in heterologous systems, LQTS3 patient-derived iPSCs cardiomyocytes, and mouse ventricular myocytes, we demonstrate that the intracellular fibroblast growth factor homologous factors (FHF1-4) tune pathogenic I Na,L in an isoform-specific manner. This scheme suggests a complex orchestration of I Na,L in cardiomyocytes that may contribute to variable disease expressivity of NaV1.5 channelopathies. We further leverage these observations to engineer a peptide-inhibitor of I Na,L with a higher efficacy as compared to a well-established small-molecule inhibitor. Overall, these findings lend insights into molecular mechanisms underlying FHF regulation of I Na,L in pathophysiology and outline potential therapeutic avenues.

Polymer-Based Versus Polymer-Free Stents in High Bleeding Risk Patients: Final 2-Year Results From Onyx ONE.

BACKGROUND: Resolute Onyx polymer-based zotarolimus-eluting stents (ZES) were noninferior in safety and effectiveness to BioFreedom polymer-free biolimus A9-coated stents (DCS) in high-bleeding-risk (HBR) patients treated with 1-month dual antiplatelet therapy (DAPT) followed by single antiplatelet therapy (SAPT) at 1 year. OBJECTIVES: This study reports the final 2-year results of the randomized Onyx ONE trial. METHODS: The Onyx ONE (A Randomized Controlled Trial With Resolute Onyx in One Month Dual Antiplatelet Therapy (DAPT) for High-Bleeding Risk Patients) trial randomly assigned HBR patients to treatment with ZES or DCS. Following 1-month DAPT, event-free patients received SAPT (either aspirin or a P2Y12 inhibitor at physician discretion). The primary safety endpoint, a composite of cardiac death, myocardial infarction, or stent thrombosis at 1 year, was determined at 1 year. Rates of primary and secondary endpoints were calculated after final follow-up at 2 years. RESULTS: A total of 1,003 patients were randomly allocated to ZES and 993 patients to DCS. Follow-up was complete in 980 (97.7%) ZES patients and 962 (96.9%) DCS patients at 2 years. The primary safety endpoint occurred in 208 (21.2%) patients in the ZES group and 199 (20.7%) patients in the DCS group (risk difference: 0.5%; 95% CI: -3.1% to 4.2%; P = 0.78) at 2 years without significant differences in individual components of the composite endpoint. The secondary effectiveness endpoint occurred in 217 (22.1%) patients in the ZES group and 202 (21.0%) patients in the DCS group (risk difference: 1.1%; 95% CI: -2.5% to 4.8%; P = 0.54). CONCLUSIONS: Among patients at HBR treated with 1-month DAPT followed by SAPT, the Resolute Onyx polymer-based ZES had similar 2-year outcomes for the primary safety and secondary effectiveness endpoint compared with the BioFreedom polymer-free DCS. (A Randomized Controlled Trial With Resolute Onyx in One Month Dual Antiplatelet Therapy [DAPT] for High-Bleeding Risk Patients [Onyx ONE]; NCT03344653).

Increased Ca2+ influx through CaV1.2 drives aortic valve calcification.

Calcific aortic valve disease (CAVD) is heritable, as revealed by recent GWAS. While polymorphisms linked to increased expression of CACNA1C - encoding the CaV1.2 L-type voltage-gated Ca2+ channel - and increased Ca2+ signaling are associated with CAVD, whether increased Ca2+ influx through the druggable CaV1.2 causes CAVD is unknown. We confirmed the association between increased CaV1.2 expression and CAVD in surgically removed aortic valves from patients. We extended our studies with a transgenic mouse model that mimics increased CaV1.2 expression within aortic valve interstitial cells (VICs). In young mice maintained on normal chow, we observed dystrophic valve lesions that mimic changes found in presymptomatic CAVD and showed activation of chondrogenic and osteogenic transcriptional regulators within these valve lesions. Chronic administration of verapamil, a CaV1.2 antagonist used clinically, slowed the progression of lesion development in vivo. Exploiting VIC cultures, we demonstrated that increased Ca2+ influx through CaV1.2 drives signaling programs that lead to myofibroblast activation of VICs and upregulation of genes associated with aortic valve calcification. Our data support a causal role for Ca2+ influx through CaV1.2 in CAVD and suggest that early treatment with Ca2+ channel blockers is an effective therapeutic strategy.

Detecting Cardiovascular Protein-Protein Interactions by Proximity Proteomics.

Rapidly changing and transient protein-protein interactions regulate dynamic cellular processes in the cardiovascular system. Traditional methods, including affinity purification and mass spectrometry, have revealed many macromolecular complexes in cardiomyocytes and the vasculature. Yet these methods often fail to identify in vivo or transient protein-protein interactions. To capture these interactions in living cells and animals with subsequent mass spectrometry identification, enzyme-catalyzed proximity labeling techniques have been developed in the past decade. Although the application of this methodology to cardiovascular research is still in its infancy, the field is developing rapidly, and the promise is substantial. In this review, we outline important concepts and discuss how proximity proteomics has been applied to study physiological and pathophysiological processes relevant to the cardiovascular system.

Awareness and Epidemiology of Chronic Hepatitis C Virus Infections in Florida.

INTRODUCTION: Progress towards achieving hepatitis C virus (HCV) elimination in Florida has been hampered by barriers to screening, linkage to care, and treatment. This study aims to describe the HCV care cascade and patient characteristics in Florida. METHODS: This analysis combined HCV-related laboratory data and patient characteristics from two, large US laboratory datasets that included individuals tested for HCV antibody (Ab) and HCV ribonucleic acid (RNA) viral load between January 2015 and December 2019. A decline in sequential HCV RNA viral loads was used to impute HCV treatment. Machine-learning algorithms were used to identify cured patients. The actual number of individuals with HCV Ab screening, and the number and percentage of persons who were HCV RNA-positive and treated, were calculated. RESULTS: The number of persons in Florida diagnosed as HCV RNA-positive was 31,659 in 2019. The number of individuals HCV Ab screened in 2019 was 1,024,379, an increase of 82.5% from 2015. The percentage of HCV Ab-positive individuals was 4.1%, demonstrating a 16.2% decrease from 2015. The percentage of HCV RNA-positive patients who were treated was 27.0%, a 10.5% decrease from 2015 to 2019. CONCLUSION: An Ab positivity rate > 4-times higher than national estimates with increased screening among baby boomers, but decreased screening among younger individuals, suggests risk-based screening is still common practice in Florida, despite universal screening recommendations. Public health efforts to decrease barriers to screening, linkage to care, and treatment are needed to reduce the burden of HCV in Florida and to ensure progress toward virus elimination.

Adrenergic Regulation of Calcium Channels in the Heart.

Each heartbeat is initiated by the action potential, an electrical signal that depolarizes the plasma membrane and activates a cycle of calcium influx via voltage-gated calcium channels, calcium release via ryanodine receptors, and calcium reuptake and efflux via calcium-ATPase pumps and sodium-calcium exchangers. Agonists of the sympathetic nervous system bind to adrenergic receptors in cardiomyocytes, which, via cascading signal transduction pathways and protein kinase A (PKA), increase the heart rate (chronotropy), the strength of myocardial contraction (inotropy), and the rate of myocardial relaxation (lusitropy). These effects correlate with increased intracellular concentration of calcium, which is required for the augmentation of cardiomyocyte contraction. Despite extensive investigations, the molecular mechanisms underlying sympathetic nervous system regulation of calcium influx in cardiomyocytes have remained elusive over the last 40 years. Recent studies have uncovered the mechanisms underlying this fundamental biologic process, namely that PKA phosphorylates a calcium channel inhibitor, Rad, thereby releasing inhibition and increasing calcium influx. Here, we describe an updated model for how signals from adrenergic agonists are transduced to stimulate calcium influx and contractility in the heart.