Changes in disease burden and treatment reality in patients with severe asthma

BACKGROUND

Biologics are clinically available for patients with severe asthma, but changes in asthma control over time are unknown. We examined changes in disease burden and treatment in severe asthma patients.

METHODS

This retrospective study used a Japanese health insurance database (Cross Fact) and included patients aged ≥16 years treated continuously with an inhaled corticosteroid (ICS) for a diagnosis of asthma in each calendar year from 2015 to 2019. Severe asthma was defined as annual use of high-dose ICS plus one or more asthma controller medications four or more times, oral corticosteroids for ≥183 days, or biologics for ≥16 weeks. Changes in asthma exacerbations, prescriptions, and laboratory testing were examined.

RESULTS

Demographic characteristics were similar throughout the study. The number and proportion of patients with severe asthma among those with asthma increased (2724; 15.3% in 2015 vs 4485; 19.0% in 2019). The proportion of severe asthma patients with two or more asthma exacerbations decreased from 24.4% to 21.5%. Odds ratios (95% confidence interval) of ≥2 asthma exacerbations in each year compared with 2015 were 0.96 (0.85-1.08) in 2016 and 0.86 (0.76-0.97) in 2017, with significant reductions observed in subsequent years. Short-acting beta agonists and oral corticosteroid prescriptions for asthma exacerbations decreased and long-acting muscarinic antagonist and biologic prescriptions for maintenance treatment increased.

CONCLUSIONS

This study showed improvements in disease burden and treatment in severe asthma patients. There remains an unmet medical need for patients with severe asthma, given the proportion who continue to have asthma exacerbations.

A Retrospective Claims Database Study to Clarify Treatment Reality of Asthma Patients Before and After Referral to a Specialist

Purpose

Japanese guidelines recommend that patients with uncontrolled asthma be referred by non-specialists to specialists (allergists and/or pulmonologists). This study investigated the reality of clinical practice in asthma patients referred to specialists in Japan.

Patients and Methods

This was a retrospective, observational cohort study of asthma patients in a health insurance claim database (Cross Fact) referred from facilities with non-specialists to those with specialists from January 2016 to December 2018. The referred asthma patients were defined as patients with ≥4 inhaled corticosteroid (ICS)-containing prescriptions during a 1-year baseline period, with an asthma diagnosis, and who had visited a facility with specialists. Asthma exacerbation, maintenance treatment, laboratory tests, and medical procedures before and after referral were analyzed.

Results

Data for 2135 patients were extracted, of which 420 with referral codes were analyzed. The proportion of patients with asthma exacerbations was 50.2% (95% confidence interval [CI]: 45.4-55.1%) before referral and 37.4% (95% CI: 32.7-42.2%) after, a significant decrease (P<0.001; McNemar test). The proportions of patients prescribed ICS alone, long-acting beta-agonists (LABA), and ICS/LABA were lower after referral than before, but the proportions of patients prescribed long-acting muscarinic antagonists (LAMA), ICS/LABA/LAMA, and biologics increased after referral. More asthma-related laboratory tests were performed after referral, and spirometry incidence increased from 16.4% before referral to 51.4% after referral.

Conclusion

This study shows a decrease in asthma exacerbations, change in asthma treatments, and increase in laboratory tests after referral to a specialist, suggesting that referrals to specialists lead to better management of asthma.

Exacerbation rates in Japanese patients with obstructive lung disease: A subanalysis of the prospective, observational NOVELTY study

BACKGROUND

Although clinical trials including asthma and COPD patients have revealed much about exacerbation frequencies, most studies are limited in that they recruited patients only with a clear diagnosis of one disease or the other, based on conventional diagnostic criteria, which may exclude many real-world patients with mixed symptoms.

METHODS

NOVELTY is a global prospective observational study of patients with asthma and/or COPD from real-world practice. In this subanalysis, we compared patient characteristics of obstructive pulmonary diseases between the Japanese population (n = 820) and the overall population excluding Japanese patients (n = 10,406).

RESULTS

The Japanese population had fewer exacerbations than the overall population across most of the physician-assessed disease severities and all diagnoses. The difference in exacerbation frequencies was more prominent in patients with COPD and asthma + COPD. The Japanese population was older, had higher former smoking rates, lower BMI, fewer respiratory symptoms, and better health-related quality of life compared with the overall population across all diagnoses.

CONCLUSIONS

We clarified differences in patient characteristics among patients with asthma and/or COPD in Japan compared with non-Japanese patients. Importantly, we found that Japanese patients with asthma and/or COPD had significantly fewer exacerbations compared with patients overall. The results from our study may contribute to the development of precision medicine and guidelines specific to Japan.

[Mechanism of action of tezepelumab (TEZSPIRE®) and clinical trial results in ‍asthma]

Tezepelumab (TEZSPIRE® Subcutaneous Injection 210 ‍mg), a biologic medicine with a novel mechanism, was approved in Japan in September 2022 for the treatment of bronchial asthma. Tezespire auto-injector was approved in Japan in August 2023 as an additional dosage. It is indicated for severe or refractory patients whose asthmatic symptoms cannot be controlled by currently available treatment. Tezepelumab binds to the epithelial cytokine thymic stromal lymphopoietin (TSLP) and disrupts TSLP signaling via the heterodimeric receptor. In the Phase 3 NAVIGATOR trial, the annual asthma exacerbation rate was significantly reduced by tezepelumab when administered subcutaneously every 4 weeks over a 52-week period to patients with uncontrolled, severe asthma who had received medium- or high-dose inhaled glucocorticoids. Its efficacy in reducing asthma exacerbations was observed regardless of blood eosinophil (bEOS) count, fractional exhaled nitric oxide (FeNO) levels, or serum total IgE at baseline. Significant improvements were noted in lung function, health-related quality of life, and change from baseline in asthma control. Reductions in the levels of inflammatory biomarkers (bEOS, FeNO, and IgE) was also noted. Clinical pharmacology trials demonstrated the efficacy of tezepelumab in improving airway hyperresponsiveness. In this article, we reviewed pharmacological characteristics, pharmacokinetics, clinical efficacy, and the safety profile of tezepelumab.

Oral Corticosteroid Reduction Between Biologics Initiated and Non-Initiated Patients with Severe Asthma

Purpose

The oral corticosteroid (OCS)-sparing effect of several biologics (BIOs) has been shown in clinical trials. To date, no study has evaluated differences in OCS dose reduction between BIO-initiated and BIO-non-initiated patients in real-world clinical practice. We compared dose reductions in maintenance OCS between BIO-initiated and BIO-non-initiated severe asthma patients in a real-world setting.

Patients and Methods

This retrospective cohort study used the data from the Diagnosis Procedure Combination database of Medical Data Vision in Japan. Severe asthma patients with continuous use of OCS were selected from December 2015 to February 2020. The primary endpoint was the proportion reduction in daily maintenance OCS dose from Week 0 to Week 24. Analyses were performed using inverse probability treatment weighting.

Results

In total, 2927 patients were included (BIO-initiated: 239 patients, BIO-non-initiated: 2688 patients). Adjusted median (quartile [Q] 1-Q3) proportion reduction in daily maintenance OCS dose at Week 24 from the index date was 25.0% (0.0-100.0%) and 0.0% (0.0-83.3%) in the BIO-initiated and BIO-non-initiated groups, respectively (Hodges-Lehmann estimate [95% confidence interval], 0.0000% [0.0000-0.3365%]). Respective proportions of patients in the BIO-initiated and BIO-non-initiated groups achieving dose reductions from the index date in the daily maintenance OCS dose at Week 24 were >0% reduction, 56.6% and 44.1% (odds ratio [OR] 1.6554); ≥25% reduction, 50.5% and 40.6% (OR 1.4888); ≥50% reduction, 42.8% and 33.7% (OR 1.4714); and 100% reduction, 26.2% and 24.4% (OR 1.1005).

Conclusion

Among severe asthma patients, the daily dose of maintenance OCS was reduced with BIO treatment. Although a higher percentage of patients in the BIO-initiated group had an OCS reduction of ≤75% than the BIO-non-initiated group, we found no clear difference in OCS reduction. Our findings will be justified by further research that incorporates a longer observation period and variables excluded from this study.

Trial Registration

ClinicalTrials.gov (NCT05136547).

Characterization of Severe Uncontrolled Asthma in Japan: Analysis of Baseline Data from the PROSPECT Study

Purpose

Treatment patterns and patient characteristics are not well elucidated among Japanese patients with severe uncontrolled asthma who currently have various treatment options, including biologics. We analyzed baseline characteristics of patients who did/did not initiate biologic treatment in PROSPECT, a 24-month observational study.

Patients and Methods

Patients with severe uncontrolled asthma were prospectively enrolled at 34 sites in Japan from December 2019 to September 2021. The enrolled population was divided based on initiation/non-initiation of biologic treatment within 12 weeks after enrollment. Patient demographics, clinical characteristics, biomarker levels, and asthma-related treatment were assessed at enrollment.

Results

Of 289 patients meeting the enrollment criteria, 127 patients initiated biologic treatment (BIO group: omalizumab, n = 16; mepolizumab, n = 10; benralizumab, n = 41; and dupilumab, n = 60) and 162 patients did not (non-BIO group). The proportion of patients with ≥2 asthma exacerbations was higher in the BIO group than the non-BIO group (65.0% vs 47.5%). Patients receiving omalizumab had the highest frequency of allergic rhinitis (87.5% vs other BIOs: 40.0%-53.3%). Patients receiving benralizumab and dupilumab had the highest incidence of nasal polyps (benralizumab: 19.5%, dupilumab: 23.3%, other BIOs: 0.0%). The proportion of patients with blood eosinophils ≥300 cells/μL was higher with benralizumab (75.6%) than other BIOs (26.7%-42.9%).

Conclusion

This analysis of baseline data from the PROSPECT study is the first to clarify the characteristics of Japanese patients with severe uncontrolled asthma. BIOs were not necessarily prescribed to patients in whom they were indicated; however, for patients who received them, selection appeared to be made appropriately based on asthma phenotypes.

Real-World Evidence on the Diagnostic and Clinical Characteristics of Asthma in Japanese Patients with COPD: The ACO Japan Cohort Study

Introduction

The ACO Japan Cohort Study, a multicenter observational study, investigated the proportion of patients with chronic obstructive pulmonary disease (COPD) who met the Japanese Respiratory Society (JRS) asthma-COPD overlap (ACO) diagnostic criteria, characteristics of ACO and non-ACO patients, and the patient transitions between ACO/non-ACO diagnosis over 2 years.

Patients and Methods

Patients with COPD were consecutively enrolled between June and December 2018 and followed up continuously for 2 years. All participating study sites were medical institutions where respiratory specialists routinely conducted medical examinations/tests required for ACO diagnosis.

Results

Among 708 patients with COPD, 101 (14.3%), 118 (16.7%), and 125 (17.7%) were diagnosed with ACO at registration, 1 year, and 2 years, respectively. In total, 22.6% of patients lacked the data necessary for ACO diagnosis throughout the 2 years. Among patients who had the necessary data for ACO diagnosis, 24.7% were diagnosed with ACO at 2 years. More ACO patients had moderate or severe exacerbations in the past year than non-ACO patients at registration (15.8% vs 6.3%, p = 0.049) and 1 year (19.4% vs 7.6%, p = 0.025). ACO patients had a greater decrease in mean forced expiratory volume in one second over 2 years than non-ACO patients (-92.0 vs 43.4 mL). Among patients diagnosed with ACO at registration, 21.4% transitioned to non-ACO after 1 year. Conversely, almost all non-ACO patients at registration remained non-ACO after 1 year.

Conclusion

COPD patients with ACO determined by the JRS criteria had a high risk of exacerbations and a rapid decline in respiratory function, indicating that the JRS criteria for ACO are useful for identifying high-risk COPD patients. Testing necessary for ACO diagnosis is insufficiently performed even in real-world clinical practice of COPD specialists.

A Retrospective Claims Database Study to Clarify Disease Burden of Severe Asthma Patients with Type 2 High or Low Inflammation

Purpose

The disease burden of severe asthma patients stratified by type 2 (T2) biomarkers is not well studied in large patient samples, especially for T2-low severe asthma patients. Using a Japanese medical record database, we investigated disease and economic burdens in T2-high and T2-low severe asthma patients.

Patients and Methods

Data of severe asthma patients (receiving high-dose inhaled corticosteroids and additional asthma-related controller medications or oral corticosteroids [OCS] prescription [≥183 days] during the 1-year baseline period) were analyzed in the Real World Data database, comprising electronic medical records from Japanese medical institutions. Severe asthma patients were stratified into a T2-high population with higher eosinophils (≥150 cells/μL) and/or higher total immunoglobulin E (IgE, ≥75 IU/mL) or a T2-low population with lower eosinophils (<150 cells/μL) and lower total IgE (<75 IU/mL). The incidence of asthma exacerbation events and drug costs were analyzed for each population. Different T2 thresholds were explored, including eosinophil count 300 cells/μL and/or IgE 150 IU/mL.

Results

Of the 732 severe asthma patients, 599 (81.8%) patients had T2-high type, and 133 (18.2%) had T2-low type. Proportions of the T2-high patients (30.6%) with asthma exacerbations, defined as a composite outcome, including OCS burst, injectable steroid use, and hospitalization, were similar to those of T2-low type (34.6%). The annual drug cost was similar between T2-high (175,487 JPY) and T2-low (165,322 JPY) populations.

Conclusion

In this large-scale study, both T2-high and T2-low severe asthma patients in Japan were shown to have a high disease burden and high economic burden, suggesting an unmet treatment need.

History of Respiratory Events Prior to a First COPD Diagnosis and Future Exacerbations: A Longitudinal Observational Cohort Database Study in Japan

Background

Little is known about the association between respiratory events prior to diagnosis of chronic obstructive pulmonary disease (COPD) and future clinical outcomes in Japan. We investigated the association between pre-COPD diagnosis respiratory events and the incidence of exacerbations in a cohort of newly diagnosed COPD patients in Japan.

Patients and Methods

Data were retrieved from the JMDC claims database. Patients ≥40 years old with a first COPD diagnosis (≥1 hospitalization or ≥2 outpatient claims for COPD) between 2010 and 2016 were included. The incidence rate (IR) of exacerbations in patients with or without any respiratory event (including lower respiratory tract infection and respiratory failure) in the year preceding diagnosis was compared. A negative binomial model explored the association between pre-diagnosis respiratory event and IR ratio (IRR) of exacerbations.

Results

A total of 20,212 patients newly diagnosed with COPD were identified: 61% male, mean age 55 years (SD 9); of these, 955 (4.7%) had experienced ≥1 respiratory event in the year preceding diagnosis. Median duration of follow-up was 3.3 years during which the IR of exacerbations was 0.31 per patient-year (95% confidence interval [CI] 0.29-0.33) in patients with respiratory event, and 0.11 (95% CI 0.10-0.13) in patients without. The IR for severe exacerbation was nearly 10 times greater in patients with respiratory event versus without. Experiencing respiratory event pre-diagnosis was independently associated with an increased IRR of future moderate-to-severe exacerbation (adjusted IRR, 2.7; 95% CI 2.3-3.1).

Conclusion

Patients experiencing respiratory events in the year preceding COPD diagnosis should be considered at-risk of worse clinical COPD outcomes.

Syndromic cardiac disorder is associated with a non-coding deletion that induces a 3D chromatin remodeling and PITX2 expression dysregulation

 

In a first family (family#1), we identified 53 members of whom 17 present a syndromic cardiac disorder characterized by electrical disorders (sinus node dysfunction, atrial fibrillation...) and developmental defects (atrial septal defect, valvopathy, left ventricle non-compaction...) following an autosomal dominant model. Among the affected family members, 6 are implanted with a pacemaker and one experienced a sudden death at 43yo. Despite a strong linkage pointing to the 4q25 region, exome sequencing failed to identify causal variant. Interestingly, 6 additional non-related families presenting the same phenotype have been also identified.

Our aims are to identity the causal mutation and the molecular mechanism underlying this complex cardiac syndrome.

Genetic study has been performed using whole genome sequencing (WGS). Based on transgenic mouse strains, we assessed the impact of Family#1 mutation on the phenotype and on gene expression. Then, we generated human cardiomyocytes derived iPS cells (CM-iPS) isogenic models to evaluate the epigenome (CUT&RUN and ATAC-seq), transcriptome (RNA-seq) and topological associated domain (TAD) remodelling (Hi-C).

By WGS we uncovered a deletion of 15kb in a gene desert area on 4q25, segregating in all affected relatives of Family#1. The 6 other families present overlapping deletions. Mouse model recapitulates the cardiac phenotype and exhibit a dysregulation of Pitx2 expression in cardiac specific compartments. Based on human CM-iPS models, epigenetic data highlight among the 15kb deletion a unique open region containing a CTCF binding site, crucial for delimiting TAD boundaries. Hi-C assay reveals the fusion of 2 TADs and highlights new interactions between PITX2 and atrial specific regulatory elements.

We identified a deletion located within a gene desert area associated with a complex cardiac disorder. The CTCF binding site contained in the deletion seems key in the TAD border. The TAD remodelling leads to new (regulatory) interactions and expression dysregulation of PITX2. We describe a new molecular mechanism implying a yet unidentified non-coding regulatory element of PITX2 and responsible for a complex electrical and developmental cardiac syndrome.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Nantes UniversitéFrench national reserch agency (ANR)

Effect of timing of bronchodilator therapy initiation on exacerbations in patients with chronic obstructive pulmonary disease: a retrospective cohort study

Background

The benefit of prompt vs delayed treatment initiation with inhaled long-acting bronchodilators in reducing exacerbations in chronic obstructive pulmonary disease (COPD) is unclear. This study aimed to investigate if long-acting bronchodilator therapy initiation within 30 days of COPD diagnosis reduces exacerbation risk in patients with COPD.

Methods

This was a retrospective cohort study of patients with COPD based on claims and electronic medical records data extracted from the Real World Data database. The index date (day 0) was the date of the first confirmed inpatient or outpatient COPD diagnosis between January 1, 2005, and December 31, 2018. Patients with COPD without an asthma diagnosis and aged ≥ 40 years at the index date were included. Patients who initiated inhaled long-acting bronchodilator therapy within the first 30 days (day 0 to day 29) were categorized into the “prompt therapy” group and the rest into the “delayed therapy” group. Time from day 30 post-diagnosis to the first exacerbation and annual exacerbation rate (AER) were evaluated for the overall population and those stratified by COPD phenotype, including chronic bronchitis (CB) and emphysema.

Results

Compared with the delayed therapy group (n = 1516), time to first exacerbation was prolonged (hazard ratio 0.78; 95% confidence interval [CI] [0.70, 0.87]) and annual rates of moderate or severe exacerbations were lower (rate ratio 0.74; 95% CI [0.65, 0.84]) in the prompt therapy group (n = 1466). Similarly, time to first exacerbation was prolonged and AERs were lower in the prompt therapy group in the subgroups of patients with CB or emphysema.

Conclusions

This is the first study to demonstrate a prolonged time to first exacerbation upon initiation of long-acting bronchodilators within 30 days of COPD diagnosis. A beneficial effect was also observed in patients with CB and emphysema. Our data support advising patients to initiate long-acting bronchodilators soon after COPD diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02184-6.

Massive calcification around large joints in a patient subsequently diagnosed with adult-onset hypophosphatasia

We report a 64-year-old Japanese woman with a history of progressive loss of motor function and painful swelling of large joints. At the age of 54, profound calcification appeared around the shoulder and hip joints, which did not heal after repeated surgical resections. Iliac bone biopsy revealed osteomalacic changes. Laboratory data showed low serum alkaline phosphatase (ALP) activity and a high urine phosphoethanolamine (PEA) concentration with normal serum calcium, phosphate, and fibroblast growth factor 23 (FGF23) levels. Subsequent genetic analysis of the ALPL gene confirmed the diagnosis of hypophosphatasia (HPP) with the identification of a heterozygous single nucleotide deletion, c.1559delT (p.Leu520ArgfsX86). We started a mineral-targeted enzyme replacement therapy, asfotase alfa (AA), to treat the patient's musculoskeletal symptoms. A follow-up bone biopsy after 12 months of AA treatment showed improvement of osteomalacia. Calcified deposits around the large joints were unchanged radiographically. To our knowledge, this is the first report of a patient with an adult-onset HPP who presented with profound calcification around multiple joints. Nonspecific clinical signs and symptoms in patients with adult-onset HPP often result in delayed diagnosis or misdiagnosis. We propose that bone biopsy and genetic analysis should be considered along with laboratory analysis for all patients with ectopic calcification around joints of unknown etiology for accurate diagnosis and better treatment.

Real-World Status of Medical Care and Treatment of Chronic Obstructive Pulmonary Disease by Respiratory Specialists in Japan

INTRODUCTION

The ACO Registry Study was a multicenter, prospective, observational cohort study aiming to clarify the situation of asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) within the COPD population using the Japanese Respiratory Society (JRS) criteria. We reported the proportion of patients who met the ACO criteria among the COPD population at study registration.

METHODS

Using data collected at registration, we investigated the implementation of each diagnostic examination/test required for ACO diagnosis in the full analysis set. Among patients with data necessary for ACO diagnosis, ACO/non-ACO patients with/without asthma diagnosed by a physician and proportions of inhaled corticosteroid (ICS) treatments for COPD were calculated.

RESULTS

Of 708 patients analyzed, 396 (55.9%) had the data necessary for ACO diagnosis, and 312 (44.1%) did not. The proportions of patients who underwent laboratory and respiratory function tests (peripheral blood eosinophil count [79.8%], fractional exhaled nitric oxide [63.7%], airway reversibility [46.8%], and total immunoglobulin [Ig] E/specific IgE [33.3%]) were lower than those who underwent subjective examinations (perennial allergic rhinitis [100%], asthma before age 40 years [97.2%], and variable/paroxysmal respiratory symptoms [94.5%]). Among patients with the data necessary for ACO diagnosis and without asthma complications according to the physician's diagnosis, 15.1% (33/219) met the ACO criteria. Of patients who met the ACO criteria, 74.3% (75/101) received ICS, and 25.7% (26/101) did not. By comparison, among patients who did not meet the ACO criteria, 35.6% (105/295) were receiving ICS, and 64.4% (190/295) were not.

CONCLUSIONS

The proportion of objective laboratory and physiological tests was lower than expected, despite study sites having the clinical resources for objective tests. Most ACO patients were being treated with ICS as recommended in the JRS treatment guidelines. Attempts should be made to further increase the proper use of ICS among these patients in Japan.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03577795.

Regional differences in the incidence of asthma exacerbations in Japan: A heat map analysis of healthcare insurance claims data

BACKGROUND

In Japan, regional differences in asthma mortality have been reported; however, regional differences in asthma exacerbations have not been studied extensively. Therefore, using a health insurance claims database, we investigated the regional differences in the incidence of asthma exacerbations in Japan.

METHODS

This study used data from Medi-Scope (Japan Medical Information Research Institute Inc., Japan)-a nationwide health insurance claims database. Patients with asthma at the index date (the latest date of an asthma-related prescription with an asthma diagnosis before October 1, 2018) were included in the analysis. The pre-index period was defined as 1 year before the index date, and the follow-up period as 1 year after the index date. The incidence of asthma exacerbation events was analyzed for each region.

RESULTS

The primary analysis population comprised 24,883 patients who were continuously prescribed ICS or ICS/LABA at least four times during the pre-index period. The incidence rate of asthma exacerbations with hospitalization was the highest in Chugoku (2.95/100 person-years [95% CI, 1.97-4.43]) and the lowest in Kanto (1.52/100 person-years [95% CI, 1.26-1.83]). The incidence rate of asthma exacerbations for the composite outcome of hospitalization, injectable corticosteroid prescription, and oral corticosteroid burst was the highest in Fukui (105.00/100 person-years [95% CI, 64.53-170.85]) and the lowest in Nagasaki (15.69/100 person-years [95% CI, 10.84-22.72]).

CONCLUSIONS

Regional differences in the incidence of asthma exacerbations as well as their treatments were observed in Japan.

Novel variant of the glycerol-3-phosphate dehydrogenase-1 Like (GPD1-L) gene in Japanese Brugada syndrome patients

Background

The incidence of Brugada syndrome (BrS) varies among racial groups. Several studies reported Glycerol-3-Phosphate Dehydrogenase 1-Like (GPD1-L) gene is associated with BrS. However, most of these studies were reported from Western countries, so the evidence about GPD1-L mutation is limited especially among Asian BrS patients. This study aimed to search for rare variants in GPD1-L among Japanese BrS patients and to investigate the pathogenicity.

Method

We performed whole-exome sequencing for patients with Brugada type 1 ECG pattern from Japanese multicenter BrS cohort consisting of SCN5A-negative BrS probands (n=288) and controls (n=372). We conducted patch-clamp study in human embryonic kidney (HEK) 293 cells cotransfected with the wild-type sodium channel (SCN5A) and wild-type or mutant GPD1-L expression plasmid.

Results

We identified a rare variant in GPD1-L, p.D262N (c.784g&gt;a) in 2 of 288 BrS probands, which was not identified in 372 controls. The minor allele frequency of the variant is 0.0014% in the Genome Aggregation Database. One proband was a 49-year-old man and the other was 34-year-old man who both developed a ventricular fibrillation. ECGs of both probands showed Brugada Type 1 pattern after administration of the pilsicainide. In functional study, coexpression of D262N GPD1-L with SCN5A in HEK293 cells significantly reduced inward sodium currents compared with wild-type GPD1-L. Additionally, inward sodium currents with D262N were similar to those with A280V GPD1-L, which was associated with BrS in previous reports (Figure). Also, several pathogenicity prediction programs, such as SIFT (score: 0.031) and PolyPhen2 (score: 0.937) predicted deleterious effects of GPD1-L D262N.

Conclusion

We identified a rare variant in GPD1-L at the rate of 0.7% in Japanese BrS patients without SCN5A mutations. GPD1-L, p.D262N reduces inward sodium currents and may be a novel susceptible variant for BrS in the Japanese population.

Funding Acknowledgement

Type of funding sources: None. Figure 1. Current–voltage curve

Primary bone adult T cell lymphoma with multiple skeletal lesions and debilitating painful osteolysis: a case report

There have been only a limited number of reports on primary adult T cell lymphoma/leukemia (ATL) in the bone. This is a case report of a 75-year-old patient initially reporting multiple bone pains that were attributed to osteolytic ATL. The patient developed spontaneous chest/back pain and visited a local hospital. Laboratory tests showed high levels of alkaline phosphatase (ALP), and computed tomography (CT) revealed skeletal lesions with osteolysis. Although multiple myeloma was initially suspected, the results of bone marrow aspiration and bone biopsy were inconsistent. After he was referred to our hospital, mild hypercalcemia (10.4 mg/dL) with low-normal intact parathyroid hormone (PTH) (27 pg/mL), low parathyroid hormone-related protein (PTHrP), and elevated 1,25-dihydroxy vitamin D (1,25OH₂D) levels (136 pg/mL) narrowed the differential diagnosis down to lymphomatous and granulomatous diseases, and then, the high serum soluble IL-2 receptor (3,450 U/mL) and the flower cells recognized in the peripheral blood sample suggested the involvement of ATL. Finally, the reevaluation of the iliac bone biopsy sample led us to the histological diagnosis of ATL infiltration in the bone. The subsequent two courses of chemotherapy in addition to denosumab resulted in an objective partial metabolic response indicated in 18-fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). Although very rare, the bone involvement of ATL could be used for the differential diagnosis for local osteolytic bone pain in addition to multiple myeloma and metastatic bone diseases.

Preclinical proof-of-concept study: antisense-mediated knockdown of CALM as a therapeutic strategy for calmodulinopathy

Background

Calmodulin (CaM) is a ubiquitous Ca2+ sensor molecule encoded by three distinct calmodulin genes, CALM1–3, and has an important role for cardiac ion channel function. Recently, heterozygous missense mutations in CALM genes were reported to cause a new category of life-threatening genetic arrhythmias such as long-QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT), which is called as “calmodulinopathy”. The patients with calmodulinopathy show poor prognosis and there is no effective treatment for them.

Purpose

Considering the dominant-negative effect of mutant calmodulin proteins produced by heterozygous missense mutations in CALMs, we aimed to prove the concept of antisense-based therapy to treat calmodulinopathy using human iPS cell-derived cardiomyocyte (hiPSC-CM) model.

Methods

We designed multiple locked nucleic acid (LNA) gapmer-antisense oligonucleotides (ASOs) targeting CALM2 and analyzed the silencing efficiency and toxicity in cultured cells to select the most potent ASO. Using CMs differentiated from hiPSCs which were generated form a 12-year-old boy with LQTS carrying a heterozygous CALM2-N98S mutation, CALM2 expression and action potentials (APs) were analyzed to evaluate the efficacy of ASOs.

Results

We identified several ASOs which reduced CALM2 expression without affecting cell viability in human cultured cells (HepG2) (ASO 50 nM, n=2; Figure 1A). Considering further experiments in vivo mouse model, we investigated the CALM2 silencing activity in mouse cultured cells (3T3-L1) without transfection (free-uptake) (ASO 1 μM, n=2; †ASOs have homologous sequence between human and mouse; Figure B). After free-uptake CALM2 silencing analysis in 3T3-L1 cells, we identified that ASO #2 has the most potent CALM2 silencing activity and low cytotoxicity (Figure 1B). ASO #2 effectively reduced CALM2 expression even in hiPSC-CMs (ASO(−): n=3, lipofection: n=4, free-uptake: n=3; P&lt;0.05; Figure 1C). In action potential recordings, we demonstrated that ASO #2 ameliorated prolonged AP durations (APD90) in N98S-hiPSC-CMs at 0.5 Hz pacing (ASO(−): 666±123 ms (n=7), lipofection: 329±21 ms (n=8), free-uptake: 388±34 ms (n=12); P&lt;0.05; Figure 1D).

Conclusion

Our results using patient-derived hiPSC-CM model suggest that ASO-based therapy might be a promising strategy for the treatment of calmodulinopathy.

Figure 1

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Nissan Chemical Corporation

Molecular mechanism of a new cardiac syndrome associated with a regulatory element deletion of chromosome 4q25

Introduction

We identified a large family of 53 members of whom 22 present a new cardiac syndrome characterized by electrical disorders and developmental defects following an autosomal dominant model. Among the affected family members 6 are implanted with a pacemaker, 2 experienced syncope and one a sudden death at 43yo. Linkage analysis points, with high confidence, to the chromosome 4q25 region. This region is associated with the Ankyrin syndrome (mutation in ANK2) sharing partly the electrical defects observed in the affected family members. No mutation was found in the coding region of the 4q25 region as well as in the coding and non-coding part of the ANK2.

Objective

Our aims are first to identity the responsible mutation present in this family and understand the molecular mechanisms leading to this new syndrome.

Method

Whole genome sequencing (WGS) has been employed to identify genetic variants responsible for this syndrome. ChIP-seq and ATAC-seq were used for functional annotation and genome editing (CRISPR-Cas9) to generate iPS cellular models.

Results

By WGS we uncovered a deleted region of 15kb in a gene desert area on 4q25, segregating in all affected relatives. Five other families (3 French and 2 Japanese) presenting the same phenotype show overlapping deletions. We generated human cardiac epigenetic data and identified among the 15kb deleted region a unique active enhancer region within the presence of a transcript factor CTCF binding site. Isogenic cell lines where the 15kb and the CTCF binding have been deleted are under investigation.

Conclusion

We identified a new cardiac syndrome and for the first time a mutation located within a gene desert area leading to severe and complex cardiac disorders. We demonstrated the presence of a likely gene regulatory element. Experiments are ongoing to characterize the molecular mechanisms and consequence of the deletion on gene expression.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Pays de la loire - Etoiles montantes

Systematic Evaluation of KCNQ1 variant using ACMG/AMP Guidelines and Risk Stratification in Long QT Syndrome Type 1

Background

Mutation/variant-site specific risk stratification in long-QT syndrome type 1 (LQT1) has been well investigated, but it is still challenging to adopt current enormous genomic information to clinical aspects caused by each mutation/variant. We assessed a novel variant-specific risk stratification in LQT1 patients.

Methods

We classified a pathogenicity of 142 KCNQ1 variants among 927 LQT1 patients (536 probands and 391 family members) based on the American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines and evaluated whether the ACMG/AMP-based classification was associated with arrhythmic risk in LQT1 patients.

Results

Among 142 KCNQ1 variants, 60 (42.3%), 58 (40.8%), and 24 (16.9%) variants were classified into pathogenic (P), likely pathogenic (LP), and variant of unknown significance (VUS), respectively. The ACMG/AMP guideline-based classification was significantly associated with syncopal events (particularly those during exercise) and LQT risk score (Schwartz score) in overall population. On the other hand, arrhythmic risk was completely different between probands and families even in the same variants. The baseline QTc interval and variant location could stratify the risk in family members but not in probands, however, the ACMG/AMP-based KCNQ1 variant classification stratified the risk in LQT1 probands as well as family members. Multivariate analysis showed that proband (HR=2.52; 95% CI: 1.93–3.30; p&lt;0.0001), longer QTc interval (≥500ms) (HR=1.41; 95% CI: 1.11–1.79; p&lt;0.0001), variants at membrane spanning (MS) (vs. those at N/C terminus) (HR=1.40; 95% CI: 1.07–1.85; p=0.02), C-loop (vs. N/C terminus) (HR=1.58; 95% CI: 1.11–2.24; p=0.01), and P variants [(vs. LP) (HR=1.71; 95% CI: 1.33–2.23; p&lt;0.0001), (vs. VUS) (HR=1.96; 95% CI: 1.19–3.46; p=0.007)] were significantly associated with syncopal events. A clinical score (0–4) based on the proband, QTc (≥500ms), variant location (MS or C-loop) and P variant by the ACMG/AMP guidelines allowed identification of patients more likely to have arrhythmic events (Figure A and B).

Conclusion

Comprehensive evaluation of clinical findings and pathogenicity of KCNQ1 variants based on the ACMG/AMP-based evaluation may stratify arrhythmic risk of congenital long-QT syndrome type 1.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Health Science Research Grant from the Ministry of Health,Labor and Welfare of Japan for Clinical Research on Measures for Intractable Diseases (H24-033, H26-040, H27-032) and a research grant from the Japan Agency for Medical Research and Development (AMED) (15km0305015h0101, 16ek0210073h0001)

299 The prevalence and role of SCN10A variants in Han Chinese patients with Brugada syndrome: the SADS-TW BrS registry

On Behalf

SADS-TW BrS registry

Background

Brugada syndrome (BrS) is an inheritable arrhythmic disease responsible for sudden cardiac death. Information on the prevalence and role of SCN10A variants in BrS is limited and equivocal.

Purpose

We aimed to investigate the prevalence and role of SCN10A variants in BrS in Han Chinese.

Methods

From 2000 to 2017, we prospectively and consecutively enrolled 176 unrelated BrS patients from the Han Chinese population in Taiwan (the SADS-TW BrS registry). Thirty-four BrS-related genes were screened by next-generation sequencing, using Taiwan Biobank as the population reference. The pathogenicity was evaluated by literature review and in silico analyses, including the SKAT-O algorithm.

Results

The SKAT-O algorithm showed that rare variants of SCN10A, but not common variants, were significantly different between BrS patients and healthy controls in the additive and dominant models (p-value &lt;0.001), suggesting that rare SCN10A variants may play a role in BrS. Six likely pathogenic SCN10A variants were found in 6 patients and were compared to 25 pathogenic or likely pathogenic SCN5A variants found in 29 patients. The patients with likely pathogenic SCN10A variants tended to exhibit sudden death in older age and have a shorter QRS interval than those carrying pathogenic or likely pathogenic SCN5A variants or no variants in either gene (p = 0.06, 0.07, respectively). Collectively, the prevalence of likely pathogenic SCN10A variants was 3.4% in Han Chinese patients with BrS in Taiwan.

Conclusions

SCN10A likely pathogenic variants were present in 3.4% of Han Chinese BrS patients. Rare SCN10A variants may play a role in BrS, and may have impact on clinical and electrocardiographic manifestations.

Table 1. Patient Nucleotide Amino acid TWB gnomAD_EA REVEL CADD PHRED SIFT Polyphen-2 GERP++ 1 c.5789A &gt; T p.D1930V 0.001318 0.0008700 0.479 24.5 Damaging Possibly damaging 4.22 2 c.2341G &gt; A p.G781R 0 0.00005301 0.866 33 Damaging Probably damaging 4.83 3 c.5587C &gt; T p.R1863W 0.000502 0 0.832 27.8 Damaging Probably damaging 1.97 4 c.2161C &gt; T p.P721S 0.000989 0.0009016 0.933 28.5 Damaging Probably damaging 4.19 5 c.3749G &gt; A p.R1250Q 0 0 0.907 31 Damaging Probably damaging 4.23 6 c.1825A &gt; T p.R609W 0.000659 0.0001591 0.811 32 Damaging Probably damaging 4.28 Clinical and predicted functional characteristics of 6 likely pathogenic SCN10A variants. EA = East Asian; GERP = Genomic Evolutionary Rate Profiling; TWB = Taiwan Biobank. Transcript: NM_006514.3.

Abstract 299 Figure. Location of the SCN10A variants

Abstract B095: Novel anti-CD147 antibodies inducing activation of SMAD signaling and tumor shrinkage in intractable cancer models

CD147, a type I membrane protein, is highly expressed in various cancers and is involved in the growth, metastasis, and activation of inflammatory signals in cancer cells via interaction with various molecules, such as integrins, CD44, and monocarboxylate transporters. Additionally, the expression of CD147 in tumors positively correlates with poor prognosis in various cancers. Therefore, CD147 is an attractive target for cancer therapy. However, there have been no successful drugs targeting CD147 so far, possibly because it is a multifunctional protein interacting with multiple molecules, making it challenging to discover a relevant CD147-targeting drug candidate by general in vitro screening methodologies. In this study, we developed novel anti-CD147 antibodies, which showed significant antitumor efficacy in immune-deficient mice bearing human pancreatic cancer cell lines, PANC-1 or MIA PaCa-2. Six anti-CD147 antibodies showing in vivo anti-tumor efficacy were obtained; one mouse IgG3, two rat IgG2b, two rat IgG1, and one rat IgG2a antibodies. Analysis of antibody dependent cellular toxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity of chimeric and humanized antibodies with human IgG2 or IgG4P derived from the obtained 6 anti-CD147 antibodies, #147A/B/C/D/E/F, suggested no significant immune-effector function for these antibodies. Despite lacking effector function, these antibodies exhibited significant in vivo antitumor activity, suggesting that the mechanism underlying their anti-tumor efficacy did not involve their effector function. We also found that the anti-tumor efficacy of antibodies #147A and #147B positively correlated with SMAD4 protein expression rather than CD147 protein expression in 10 pancreatic cancer xenograft models (correlation coefficient of #147B: anti-tumor efficacy vs. CD147, 0.245; vs. SMAD4, 0.9328). Moreover, the administration of anti-CD147 antibodies upregulated rhoB expression in an anti-CD147 antibody-sensitive SMAD4-positive MIA PaCa-2 graft mouse model. The stable expression of SMAD4 increased the sensitivity to the anti-CD147 antibody, ch4#147A (chimeric IgG4P derived from #147A) in xenograft mice inoculated with the BxPC-3 pancreatic cancer cell line, which is originally negative for SMAD4 and has low sensitivity to anti-CD147 antibodies. These data suggest that the expression of SMAD4 and activation of SMAD signaling are functionally important for susceptibility to anti-CD147 antibody treatment. The humanized anti-CD147 IgG4P antibody, h4#147D, derived from #147D with cross reactivity to monkey CD147, showed superior anti-tumor efficacy with complete tumor reduction, compared to standard anticancer drugs, including gemcitabine, imatinib, and sorafenib, in xenograft mice bearing corresponding cancer cell lines, MIA PaCa-2, KU812 chronic myeloid leukemia, and HepG2 liver cancer cell lines, respectively. No toxicity of h4#147D was observed in cynomolgus monkeys at a single dose of 100 mg/kg. These data suggest that h4#147D might be a novel anti-CD147 antibody, which could induce SMAD activation and tumor shrinkage in multiple xenograft models. Therefore, it has potential as a promising antitumor therapeutic antibody with superior anti-tumor efficacy to existing therapy.

Citation Format: Keisuke Fukuchi, Kayoko Nanai, Shoji Yamamoto, Jun Tsukada, Yusuke Totoki, Koichiro Inaki, Masato Ishigami, Naoyuki Makita, Yoko Nakano, Chigusa Yoshimura, Kozo Yoneda, Masato Amano, Kensuke Nakamura, Yoshiyuki Kanari, Yoko Oda, Haruyuki Nishigohri, Rika Nakano, Atsuko Nishida, Kenji Murakami, Yumi Matsui, Naomi Kasanuki, Shoji Midori, Satoko Funo, Sayako Takahashi, Hironobu Komori, Toshiaki Ohtsuka, Toshinori Agatsuma. Novel anti-CD147 antibodies inducing activation of SMAD signaling and tumor shrinkage in intractable cancer models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B095. doi:10.1158/1535-7163.TARG-19-B095

Genome-wide siRNA screening in mouse bone marrow-derived macrophages revealed that knockdown of ribosomal proteins suppresses IL-10 and enhances TNF-α production

Macrophages play a central role in the immune response, and their diverse functions are attributed to the spectrum of their functional states. To elucidate molecules involved in modulating the balance between the anti-inflammatory cytokine IL-10 and the pro-inflammatory cytokine TNF-α, we conducted genome-wide siRNA screening. First, we established an siRNA screening system using mouse bone marrow-derived macrophages, which are a suitable model for studying functional states of macrophages in vitro. In the primary screen and the subsequent reproducibility assay, 112 siRNA pools demonstrated enhancement of IL-10 production and 497 siRNA pools suppressed IL-10 production. After a deconvolution assay for IL-10-up-regulating siRNA pools, 8 genes were identified as IL-10 repressors, including Cnot1 and Rc3h1, components of the CCR4-NOT complex known to degrade cytokine mRNAs. On the other hand, siRNA pools targeting ribosomal proteins were frequently found among those that down-regulated IL-10 production and up-regulated TNF-α production. Four pools were assayed using deconvoluted siRNAs and identified as high-confidence hits. Thus, we found that the genome-wide knockdown of 19 ribosomal proteins resulted in decreased IL-10 and increased TNF-α production.

Dichloroacetate induces regulatory T-cell differentiation and suppresses Th17-cell differentiation by pyruvate dehydrogenase kinase-independent mechanism

OBJECTIVES

Recently, there has been a growing interest in the mechanism of action of dichloroacetate (DCA) for T-cell differentiation; however, this mechanism has not been elucidated in detail. Therefore, this study aimed to investigate the mechanism of action of DCA for Treg and Th17 differentiation with pyruvate dehydrogenase kinase (PDHK) inhibitor (AZD7545) and PDHK knockdown.

METHODS

Inhibitory activity of DCA and AZD7545 against recombinant PDHK and intracellular PDH phosphorylation was measured. The effects of DCA and AZD7545 on T-cell differentiation were assessed by analysing Foxp3⁺ T-cell populations for Treg differentiation and IL-17A production for Th17 differentiation. For reactive oxygen species (ROS) production, DCFDA was used as an indicator.

KEY FINDINGS

Dichloroacetate and AZD7545 inhibited PDHK activity of recombinant PDHK and intracellular PDH phosphorylation. DCA was capable of inducing Treg differentiation and suppressing Th17 differentiation. The effects of DCA were independent of PDHK because neither AZD7545 nor knockdown of PDHK1 or PDHK3 affected T-cell differentiation. DCA was determined to be capable of inducing ROS production, and the effects of DCA on T-cell differentiation were shown to be dependent on ROS production.

CONCLUSIONS

Dichloroacetate possesses Treg induction and Th17 suppression, which is independent of PDHK and dependent on ROS production.

Quantitative analysis of cadherin-11 and β-catenin signalling during proliferation of rheumatoid arthritis-derived synovial fibroblast cells

Objectives

Cadherin-11 (CDH11) is an adhesion molecule that anchors β-catenin and is involved with various functions of synovial fibroblast cells (SFCs) during the development of rheumatoid arthritis (RA). However, the mechanism of CDH11 during RA-SFC proliferation is unclear. The aim of our study was to clarify the involvement of CDH11 and β-catenin signalling during proliferation.

Methods

IL-1β-induced and tumour necrosis factor-α (TNF-α)-induced cell proliferation, with CDH11 siRNAs, β-catenin-specific siRNAs and a CDH11-neutralizing antibody, were assessed by 5-Bromo-2'-deoxy-uridine ELISA.

Key findings

Using CDH11 siRNAs, there were a 42% reduction in IL-1β-induced proliferation and a 64% reduction in β-catenin protein. When β-catenin siRNAs were applied, there was a 63% reduction in IL-1β-induced proliferation. The median effective concentration (EC50) values for IL-1β-induced proliferation via CDH11-mediated β-catenin-dependent, total β-catenin-dependent and β-catenin-independent signalling were 0.0015, 0.016 and 0.18 ng/ml, respectively. Blocking CDH11 ligation with a CDH11-neutralizing antibody did not decrease IL-1β-induced proliferation.

Conclusions

CDH11-mediated β-catenin signalling was 42% involved in IL-1β-induced proliferation and had the highest susceptibility to IL-1β among the proliferative signallings analysed in this study. The mode of action for CDH11 during the cell proliferation was likely associated with a pool of β-catenin protein. In contrast, CDH11 and β-catenin were not involved in TNF-α-induced RA-SFC proliferation.

DNA compaction in a crowded environment with negatively charged proteins

We studied the conformational properties of DNA in a salt solution of the strongly charged protein bovine serum albumin. DNA is compacted when a suitable amount of bovine serum albumin is added to the solution due to a crowding effect and strong electrostatic repulsion between DNA and bovine serum albumin, both of which carry negative charges. However, DNA undergoes an unfolding transition with an increase in the salt concentration. This observation contradicts the current understanding of polymer- and salt-induced condensation, ψ condensation. We propose a simple theoretical model by taking into account the competition between the translational entropy of ions and electrostatic interaction.

Two of four alternatively spliced isoforms of RUNX2 control osteocalcin gene expression in human osteoblast cells

Runx2 is a Runt domain transcription factor that transcriptionally regulates osteoblast differentiation and bone formation. In this study, we show that human chondro- and osteosarcoma cell lines, human mesenchymal stem cells (hMSC) and a human primary chondrocytes (HC), osteoblst cells (HOb) express an intact isoform (RUNX2wt) and 3 alternatively spliced isoforms (RUNX2Delta5, Delta7, and Delta5Delta7) that are generated by skipping exon 5 and/or exon 7. Two of the truncated forms of RUNX2 (RUNX2Delta5 and RUNX2Delta5Delta7) did not localize in the nucleus and had lost their DNA binding activity. In cotransfection experiments with an osteocalcin (OC) promoter construct, we confirmed that only RUNX2wt and RUNX2Delta7 could upregulate the OC promoter activity in the osteosarcoma cell line. In addition, the coactivator CBP/p300 enhanced the transcriptional activity of the OC promoter when coexpressed with RUNX2wt or RUNX2Delta7, but not when coexpressed with RUNX2Delta5 or RUNX2Delta5Delta7. In contrast, the corepressor HDAC3 only repressed the activation from the OC promoter when coexpressed with RUNX2wt. These results support the hypothesis that RUNX2 both up- and downregulates its target gene promoters, as exemplified by the OC gene, using various isoforms and context-dependent formation of transcriptional complexes.

Moderate increase of mean daily temperature adversely affects fruit set of Lycopersicon esculentum by disrupting specific physiological processes in male reproductive development

BACKGROUND AND AIMS

Global warming is gaining significance as a threat to natural and managed ecosystems since temperature is one of the major environmental factors affecting plant productivity. Hence, the effects of moderate temperature increase on the growth and development of the tomato plant (Lycopersicon esculentum) were investigated.

METHODS

Plants were grown at 32/26 degrees C as a moderately elevated temperature stress (METS) treatment or at 28/22 degrees C (day/night temperatures) as a control with natural light conditions. Vegetative growth and reproductive development as well as sugar content and metabolism, proline content and translocation in the androecium were investigated.

KEY RESULTS

METS did not cause a significant change in biomass, the number of flowers, or the number of pollen grains produced, but there was a significant decrease in the number of fruit set, pollen viability and the number of pollen grains released. Glucose and fructose contents in the androecium (i.e. all stamens from one flower) were generally higher in the control than METS, but sucrose was higher in METS. Coincidently, the mRNA transcript abundance of acid invertase in the androecium was decreased by METS. Proline contents in the androecium were almost the same in the control and METS, while the mRNA transcript level of proline transporter 1, which expresses specifically at the surface of microspores, was significantly decreased by METS.

CONCLUSIONS

The research indicated that failure of tomato fruit set under a moderately increased temperature above optimal is due to the disruption of sugar metabolism and proline translocation during the narrow window of male reproductive development.

The complete nucleotide sequence and multipartite organization of the tobacco mitochondrial genome: comparative analysis of mitochondrial genomes in higher plants

Tobacco is a valuable model system for investigating the origin of mitochondrial DNA (mtDNA) in amphidiploid plants and studying the genetic interaction between mitochondria and chloroplasts in the various functions of the plant cell. As a first step, we have determined the complete mtDNA sequence of Nicotiana tabacum. The mtDNA of N. tabacum can be assumed to be a master circle (MC) of 430,597 bp. Sequence comparison of a large number of clones revealed that there are four classes of boundaries derived from homologous recombination, which leads to a multipartite organization with two MCs and six subgenomic circles. The mtDNA of N. tabacum contains 36 protein-coding genes, three ribosomal RNA genes and 21 tRNA genes. Among the first class, we identified the genes rps1 and psirps14, which had previously been thought to be absent in tobacco mtDNA on the basis of Southern analysis. Tobacco mtDNA was compared with those of Arabidopsis thaliana, Beta vulgaris, Oryza sativa and Brassica napus. Since repeated sequences show no homology to each other among the five angiosperms, it can be supposed that these were independently acquired by each species during the evolution of angiosperms. The gene order and the sequences of intergenic spacers in mtDNA also differ widely among the five angiosperms, indicating multiple reorganizations of genome structure during the evolution of higher plants. Among the conserved genes, the same potential conserved nonanucleotide-motif-type promoter could only be postulated for rrn18-rrn5 in four of the dicotyledonous plants, suggesting that a coding sequence does not necessarily move with the promoter upon reorganization of the mitochondrial genome.

A cardiac sodium channel mutation identified in Brugada syndrome associated with atrial standstill

Mutations in the cardiac Na+ channel gene SCN5A are responsible for multiple lethal ventricular arrhythmias including Brugada syndrome and congenital long QT syndrome. Here we report a case of Brugada syndrome with ST elevation in the right precordial and inferior leads accompanied by atrial standstill and spontaneous ventricular fibrillation. Atrial standstill and J wave elevation were provoked by procainamide. Genetic analysis revealed a missense mutation (R367H) in SCN5A. The resultant mutant Na+ channel was nonfunctional when expressed heterologously in Xenopus oocytes. Our study suggests that genetic defects in SCN5A may be associated with atrial standstill in combination with ventricular arrhythmias.

Cold induces shifts of voltage dependence in mutant SCN4A, causing hypokalemic periodic paralysis

BACKGROUND

The authors reported a mutation, P1158S, of the human skeletal muscle sodium channel gene (SCN4A) in a family with cold-induced hypokalemic periodic paralysis (hypoKPP) and myotonia.

OBJECTIVE

To identify mechanisms of temperature dependency in this channelopathy.

METHODS

Using the amphotericin B perforated patch clamp method, sodium currents were recorded at 22 and 32 degrees C from the wild-type (WT) and P1158S mutant SCN4A expressed in tsA201 cells. Computer simulation was performed, incorporating the gating parameters of the P1158S mutant SCN4A.

RESULTS

P1158S mutant SCN4A exhibited hyperpolarizing shifts in voltage dependence of both activation and inactivation curves at a cold temperature and a slower rate of inactivation than the WT. Computer simulation reproduced the abnormal skeletal muscle electrical activities of both paralysis at a low potassium concentration in the cold and myotonia at a normal potassium concentration.

CONCLUSIONS

Both paralysis and myotonia are attributable to the biophysical properties of the SCN4A mutation associated with hypoKPP. This is the first report of an SCN4A mutation that exhibits temperature-dependent shifts of voltage dependence in sodium channel gating.

Cloning of a functional splice variant of L-type calcium channel beta 2 subunit from rat heart

L-type Ca(2+) channels are heteromultimeric and finely tuned by auxiliary subunits in different tissues and regions. Among auxiliary subunits, beta subunit has been shown to play important roles in many functional aspects of Ca(2+) channel. Rat heart was reported to specifically express beta(2a) subunit. However, the slow inactivation rates of Ca(2+) currents recorded from recombinant Ca(2+) channels with the beta(2a) subunit, and the reported inability to detect beta(2a) subunit in rabbit heart by reverse transcription-PCR analysis raise the possibility of the existence of other beta subunits. We cloned a splice variant of beta(2) subunit from rat heart, using rapid amplification of cDNA 5' ends. The splice variant is highly similar to human beta(2c) subunit that was cloned from human ventricle. Northern blot analysis detected the rat beta(2c) subunit abundantly in rat heart and brain. The deduced amino acid sequence of the beta(2c) subunit was different from that of the beta(2a) subunit only in the N-terminal region. When the beta(2c) subunit was expressed along with alpha(1c) and alpha(2)delta subunits in baby hamster kidney cells, the inactivation rates were comparable with those from native cardiac myocytes, although those with the beta(2a) subunit were slow. Taken together, these observations suggest that the beta(2c) subunit is a functional beta(2) subunit expressed in heart and that the short N-terminal region plays a major role in modifying inactivation kinetics.

Enhanced Na(+) channel intermediate inactivation in Brugada syndrome

Brugada syndrome is an inherited cardiac disease that causes sudden death related to idiopathic ventricular fibrillation in a structurally normal heart. The disease is characterized by ST-segment elevation in the right precordial ECG leads and is frequently accompanied by an apparent right bundle-branch block. The biophysical properties of the SCN5A mutation T1620M associated with Brugada syndrome were examined for defects in intermediate inactivation (I:(M)), a gating process in Na(+) channels with kinetic features intermediate between fast and slow inactivation. Cultured mammalian cells expressing T1620M Na(+) channels in the presence of the human beta(1) subunit exhibit enhanced intermediate inactivation at both 22 degrees C and 32 degrees C compared with wild-type recombinant human heart Na(+) channels (WT-hH1). Our findings support the hypothesis that Brugada syndrome is caused, in part, by functionally reduced Na(+) current in the myocardium due to an increased proportion of Na(+) channels that enter the I:(M) state. This phenomenon may contribute significantly to arrhythmogenesis in patients with Brugada syndrome. The full text of this article is available at http://www.circresaha.org.

Block of sodium channels by divalent mercury: role of specific cysteinyl residues in the P-loop region

Divalent mercury (Hg(2+)) blocked human skeletal Na(+) channels (hSkM1) in a stable dose-dependent manner (K(d) = 0.96 microM) in the absence of reducing agent. Dithiothreitol (DTT) significantly prevented Hg(2+) block of hSkM1, and Hg(2+) block was also readily reversed by DTT. Both thimerosal and 2,2'-dithiodipyridine had little effect on hSkM1; however, pretreatment with thimerosal attenuated Hg(2+) block of hSkM1. Y401C+E758C rat skeletal muscle Na(+) channels (mu1) that form a disulfide bond spontaneously between two cysteines at the 401 and 758 positions showed a significantly lower sensitivity to Hg(2+) (K(d) = 18 microM). However, Y401C+E758C mu1 after reduction with DTT had a significantly higher sensitivity to Hg(2+) (K(d) = 0.36 microM) than wild-type hSkM1. Mutants C753Amu1 (K(d) = 8.47 microM) or C1521A mu1 (K(d) = 8.63 microM) exhibited significantly lower sensitivity to Hg(2+) than did wild-type hSkM1, suggesting that these two conserved cysteinyl residues of the P-loop region may play an important role in the Hg(2+) block of the hSkM1 isoform. The heart Na(+) channel (hH1) was significantly more sensitive to low-dose Hg(2+) (K(d) = 0.43 microM) than was hSkM1. The C373Y hH1 mutant exhibited higher resistance (K(d) = 1.12 microM) to Hg(2+) than did wild-type hH1. In summary, Hg(2+) probably inhibits the muscle Na(+) channels at more than one cysteinyl residue in the Na(+) channel P-loop region. Hg(2+) exhibits a lower K(d) value (<1. 23 microM) for inhibition by forming a sulfur-Hg-sulfur bridge, as compared to reaction at a single cysteinyl residue with a higher K(d) value (>8.47 microM) by forming sulfur-Hg(+) covalently. The heart Na(+) channel isoform with more than two cysteinyl residues in the P-loop region exhibits an extremely high sensitivity (K(d) < 0. 43 microM) to Hg(+), accounting for heart-specific high sensitivity to the divalent mercury.

A novel SCN5A mutation associated with idiopathic ventricular fibrillation without typical ECG findings of Brugada syndrome

Mutations in the human cardiac Na+ channel alpha subunit gene (SCN5A) are responsible for Brugada syndrome, an idiopathic ventricular fibrillation (IVF) subgroup characterized by right bundle branch block and ST elevation on an electrocardiogram (ECG). However, the molecular basis of IVF in subgroups lacking these ECG findings has not been elucidated. We performed genetic screenings of Japanese IVF patients and found a novel SCN5A missense mutation (S1710L) in one symptomatic IVF patient that did not exhibit the typical Brugada ECG. Heterologously expressed S1710L channels showed marked acceleration in the current decay together with a large hyperpolarizing shift of steady-state inactivation and depolarizing shift of activation. These findings suggest that SCN5A is one of the responsible genes for IVF patients who do not show typical ECG manifestations of the Brugada syndrome.

A case of mixed connective tissue disease (MCTD) complicated with MPO-ANCA-related necrotizing glomerulonephritis

Renal diseases of mixed connective tissue disease (MCTD) are not unusual. Although most of them are SLE-like renal impairment with immune complex deposits, systemic sclerosis- (SSc) like renal impairments with intimal thickening of interlobular arteries or arterioles are also encountered. Several cases of SSc complicated with MPO-ANCA-related necrotizing glomerulonephritis (nGN) are reported. Here we report a case which developed MPO-ANCA-related nGN 16 years after the diagnosis of MCTD. She exhibited pauci-immune focal nGN and significantly high titer of MPO-ANCA. She was successfully treated with prednisolone and cyclophosphamide. We believe this is the first case in which MPO-ANCA-related nGN was demonstrated in a patient with MCTD.

Selective block of late currents in the DeltaKPQ Na(+) channel mutant by pilsicainide and lidocaine with distinct mechanisms

The congenital long QT syndrome is an inherited disorder characterized by a delay in cardiac repolarization, leading to lethal cardiac arrhythmias such as torsade de pointes. One form of this disease involves mutations in the voltage-dependent cardiac Na(+) channel, which includes an in-frame deletion of three amino acids (Lys-1505, Pro-1506, and Gln-1507; DeltaKPQ). The potential for selective suppression of the mutant was examined by heterologous expression of DeltaKPQ-Na(+) channels in Chinese hamster fibroblast cells via single-channel recording. In a single-channel cell-attached patch study, DeltaKPQ-Na(+) channels yielded currents that peaked at approximately 1 ms after voltage steps to 0 mV with aberrant late currents, which were composed of burst and isolated openings. The affinity of certain anesthetics (pilsicainide and lidocaine) to the late currents of the mutant channels was examined. It was revealed that 1) pilsicainide (1 microM), an open channel blocker of voltage-dependent Na(+) channels, remarkably decreased the late currents primarily by the shortening of burst duration without suppressing the initial peak current; and 2) lidocaine (1 microM), an inactivated channel blocker, decreased the late currents primarily by the suppression of isolated channel openings. Because the late currents in DeltaKPQ mutants are mainly composed of the burst openings, we conclude that pilsicainide is capable of selectively blocking the late currents in the mutant Na(+) channels that show dominant abnormal burst openings such as in DeltaKPQ mutants.

Cardiac Na(+) channel dysfunction in Brugada syndrome is aggravated by beta(1)-subunit

BACKGROUND

Mutations in the gene encoding the human cardiac Na(+) channel alpha-subunit (hH1) are responsible for chromosome 3-linked congenital long-QT syndrome (LQT3) and idiopathic ventricular fibrillation (IVF). An auxiliary beta(1)-subunit, widely expressed in excitable tissues, shifts the voltage dependence of steady-state inactivation toward more negative potentials and restores normal gating kinetics of brain and skeletal muscle Na(+) channels expressed in Xenopus oocytes but has little if any functional effect on the cardiac isoform. Here, we characterize the altered effects of a human beta(1)-subunit (hbeta(1)) on the heterologously expressed hH1 mutation (T1620M) previously associated with IVF.

METHODS AND RESULTS

When expressed alone in Xenopus oocytes, T1620M exhibited no persistent currents, in contrast to the LQT3 mutant channels, but the midpoint of steady-state inactivation (V(1/2)) was significantly shifted toward more positive potentials than for wild-type hH1. Coexpression of hbeta(1) did not significantly alter current decay or recovery from inactivation of wild-type hH1; however, it further shifted the V(1/2) and accelerated the recovery from inactivation of T1620M. Oocyte macropatch analysis revealed that the activation kinetics of T1620M were normal.

CONCLUSIONS

It is suggested that coexpression of hbeta(1) exposes a more severe functional defect that results in a greater overlap in the relationship between channel inactivation and activation (window current) in T1620M, which is proposed to be a potential pathophysiological mechanism of IVF in vivo. One possible explanation for our finding is an altered alpha-/beta(1)-subunit association in the mutant.

Bone marrow transplantation attenuates murine IgA nephropathy: role of a stem cell disorder

BACKGROUND

The pathogenesis of IgA nephropathy is still obscure. The aim of this study was to investigate whether the fundamental pathogenesis of IgA nephropathy lies in bone marrow stem cells (BMCs).

METHODS

We used donors of two different strains for bone marrow transplantation (BMT) into mice with a high content of serum IgA (ddY strain, HIGA mice), a murine model of IgA nephropathy. One group (B6-->HIGA, N = 5) received BMCs of C57BL/6j (B6) mice, and the other (HIGA-->HIGA, N = 8) were reconstituted with BMCs of HIGA mice.

RESULTS

Twenty-six weeks after BMT, in B6-->HIGA mice, mesangial deposits of IgA and C3 were statistically milder than those in HIGA-->HIGA mice. Light microscopic observations disclosed that glomerular sclerosis and mesangial matrix expansion in B6-->HIGA mice were decreased compared with those in HIGA-->HIGA mice. These B6-->HIGA mice also excreted less urinary albumin than HIGA-->HIGA mice. Furthermore, serum levels of IgA in B6-->HIGA mice were markedly lower than those in HIGA-->HIGA mice. Size analysis of serum IgA revealed that macromolecular IgA were notably lower in B6-->HIGA mice than in HIGA-->HIGA mice.

CONCLUSIONS

Our results suggest that qualitative and quantitative changes of serum IgA are determined at the level of stem cells, and that BMT from normal donors can attenuate glomerular lesions in HIGA mice. This approach may offer a new avenue to study the pathogenesis of IgA nephropathy.

ATP/ADP switches the higher-order structure of DNA in the presence of spermidine

In the living cellular environment, DNAs exist in a compact state in the presence of a polyamine, such as spermidine. We found that the hydrolysis of ATP into ADP induces the folding of elongated DNAs, by the single-chain observation of individual T4 DNA molecules. This result is discussed in relation to the possible role of ATP as a regulatory factor in genetic activity, in addition to its well-established role as an energy source.