Interpretations of SARS-CoV-2 IgM and IgG antibody titers in the seroepidemiological study of asymptomatic healthy volunteers.

INTRODUCTION: The usefulness of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody tests in asymptomatic individuals has not been well validated, although they have satisfied sensitivity and specificity in symptomatic patients. In this study, we investigated the significance of IgM and IgG antibody titers against SARS-CoV-2 in the serum of asymptomatic healthy subjects. METHODS: From June 2020, we recruited 10,039 participants to the project named the University of Tokyo COVID-19 Antibody Titer Survey (UT-CATS), and measured iFlash-SARS-CoV-2 IgM and IgG (YHLO IgM and IgG) titers in the collected serum. For the samples with increased IgM or IgG titers, we performed additional measurements using Elecsys Anti-SARS-CoV-2 Ig (Roche total Ig) and Architect SARS-CoV-2 IgG (Abbott IgG) and investigated the reactivity to N, S1, and receptor binding domain (RBD) proteins. RESULTS: After setting the cutoff value at 5 AU/mL, 61 (0.61%) were positive for YHLO IgM and 104 (1.04%) for YHLO IgG. Few samples with elevated YHLO IgM showed reactivity to S1 or RBD proteins, and IgG titers did not increase during the follow-up in any samples. The samples with elevated YHLO IgG consisted of two groups: one reacted to S1 or RBD proteins and the other did not, which was reflected in the results of Roche total Ig. CONCLUSIONS: In SARS-CoV-2 seroepidemiological studies of asymptomatic participants, sufficient attention should be given to the interpretation of the results of YHLO IgM and IgG, and the combined use of YHLO IgG and Roche total Ig might be more reliable.

Nonselective cation currents regulate membrane potential of rabbit coronary arterial cell: modulation by lysophosphatidylcholine.

BACKGROUND: The effects of lysophosphatidylcholine (LPC) on electrophysiological activities and intracellular Ca2+ concentration ([Ca2+]i) were investigated in coronary arterial smooth muscle cells (CASMCs). METHODS AND RESULTS: The patch clamp techniques and Ca2+ measurements were applied to cultured rabbit CASMCs. The membrane potential was -46.0+/-5.0 mV, and LPC depolarized it. Replacement of extracellular Na+ with NMDG+ hyperpolarized the membrane and antagonized the depolarizing effects of LPC. In Na+-, K+-, or Cs+-containing solution, the voltage-independent background current with reversal potential (E(r)) of approximately +0 mV was observed. Removal of Cl- failed to affect it. When extracellular cations were replaced by NMDG+, E(r) was shifted to negative potentials. La3+ and Gd3+ abolished the background current, but nicardipine and verapamil did not inhibit it. In Na+-containing solution, LPC induced a voltage-independent current with E(r) of approximately +0 mV concentration-dependently. Similar current was recorded in K+- and Cs+-containing solution. La3+ and Gd3+ inhibited LPC-induced current, but nicardipine and verapamil did not inhibit it. In cell-attached configurations, single-channel activities with single-channel conductance of approximately 32pS were observed when patch pipettes were filled with LPC. LPC increased [Ca2+]i as the result of Ca2+ influx, and La3+ completely antagonized it. CONCLUSIONS: These results suggest that (1) nonselective cation current (I(NSC)) contributes to form membrane potentials of CASMCs and (2) LPC activates I(NSC), resulting in an increase of [Ca2+]i. Thus, LPC may affect CASMC tone under various pathophysiological conditions such as ischemia.

Molecular and pharmacological characteristics of transient voltage-dependent K+ currents in cultured human pulmonary arterial smooth muscle cells.

The A-type voltage-dependent K(+) current (I(A)) has been identified in several types of smooth muscle cells including the pulmonary artery (PA), but little is known about the pharmacological and molecular characteristics of I(A) in human pulmonary arterial smooth muscle cells (hPASMCs). We investigated I(A) expressed in cultured PASMCs isolated from the human main pulmonary artery, using patch-clamp techniques, reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative real-time RT-PCR and immunocytochemical studies. With high EGTA and ATP in the pipette, the outward currents were dominated by a transient K(+) current (I(A)), followed by a relatively small sustained outward current (I(K)). I(A) was inhibited by 4-aminopyridine (4-AP) concentration-dependently, and could be separated pharmacologically into two components by tetraethylammonium (TEA) sensitivity. A component was sensitive to TEA, and the second component was insensitive to TEA. I(A) was inhibited by blood depressing substrate (BDS)-II, a specific blocker of K(V)3.4 subunit, and phrixotoxin-II, a specific blocker of K(V)4.2 and 4.3. Flecainide inhibited I(A) concentration-dependently, but it inhibited it preferentially in the presence of TEA (TEA-insensitive I(A)). Systematic screening of expression of K(V) genes using RT-PCR showed the definite presence of transcripts of the I(A)-encoding genes for K(V)3.4, K(V)4.1, K(V)4.2 and K(V)4.3 as well as the I(K)-encoding genes for K(V)1.1, K(V)1.5 and K(V)2.1. The real-time RT-PCR analysis showed that the relative abundance of the encoding genes of I(A) alpha-subunit and K(V) channel-interacting proteins (KChIPs) was K(V)4.2 > K(V)3.4 > K(V)4.3 (long) > K(V)4.1, and KChIP3 >> KChIP2, respectively. The presence of K(V)3.4, K(V)4.2 and K(V)4.3 proteins was also demonstrated by immunocytochemical studies, and confirmed by immunohistochemical staining using intact human PA sections. These results suggest that I(A) in cultured hPASMCs consists of two kinetically and pharmacologically distinct components, probably K(V)3.4 and K(V)4 channels.

Relationship between chronotropic incompetence and ß-blockers based on changes in chronotropic response during cardiopulmonary exercise testing.

BACKGROUND: Chronotropic incompetence (CI), an attenuated heart rate (HR) response to exercise, is common in patients with cardiovascular disease. The aim of this study was to assess changes in the chronotropic response (CR) during cardiopulmonary exercise testing (CPET) in patients undergoing cardiac rehabilitation and investigate the effects of ß-blockers. METHODS: Patients undergoing cardiac rehabilitation performed CPET. Failure to achieve 80% of the age-predicted maximal HR (APMHR) defined CI. Values of the metabolic chronotropic relationship (MCR) were calculated from the ratio of the HR reserve to metabolic reserve at 4 stages, warm-up (MCR-Wu), anaerobic threshold (MCR-AT), respiratory compensation (MCR-Rc), and peak point (MCR-Pk), using the Wilkoff model. In patients who showed an increase in MCR at ≥ 3 of the 4 exercise stages, CR was considered to have improved. RESULTS: Patients with high BNP levels (≥ 80 pg/ml) had a lower MCR at all stages compared with those with low BNP levels (< 80 pg/ml). Of the 80 patients, 47 showed an increase in both peak VO2 and AT, and of these 31 (66.0%) were taking ß-blockers. Improvement in CR was observed in 30 of 47 patients with CI, and 70% of these were taking ß-blockers. In patients not taking ß-blockers, MCR-AT was lower than MCR-Rc, whereas in those taking ß-blockers MCR-AT was higher than MCR-Rc. CONCLUSIONS: An attenuated HR response may occur during the early stages of exercise. The HR response according to the presence or absence of ß-blockers is clearly identifiable by comparing MCR-AT and MCR-Rc using the Wilkoff model.

Voltage-gated sodium channel expressed in cultured human smooth muscle cells: involvement of SCN9A.

Voltage-gated Na(+) channel (I(Na)) is expressed under culture conditions in human smooth muscle cells (hSMCs) such as coronary myocytes. The aim of this study is to clarify the physiological, pharmacological and molecular characteristics of I(Na) expressed in cultured hSMCs obtained from bronchus, main pulmonary and coronary artery. I(Na), was recorded in these hSMCs and inhibited by tetrodotoxin (TTX) with an IC(50) value of approximately 10 nM. Reverse transcriptase/polymerase chain reaction (RT-PCR) analysis of mRNA showed the prominent expression of transcripts for SCN9A, which was consistent with the results of real-time quantitative RT-PCR. These results provide novel evidence that TTX-sensitive Na(+) channel expressed in cultured hSMCs is mainly composed of Na(v)1.7.

Amlodipine increases nitric oxide production in exhaled air during exercise in patients with essential hypertension.

BACKGROUND: Endothelial production of nitric oxide (NO) is attenuated in patients with essential hypertension. We investigated whether treatment with amlodipine increased exhaled NO output (VNO) at rest and during exercise in patients with essential hypertension. METHODS: We studied the effect of amlodipine in seven untreated hypertensive patients. Cardiopulmonary exercise testing and NO measurement of exhaled air were performed on these patients before and after 2 months of amlodipine treatment. RESULTS: Amlodipine decreased blood pressure (BP) both at rest and during exercise (at rest: 147.1 +/- 6.4 [SEM]/89.9 +/- 4.4 v 133.6 +/- 5.4/82.7 +/- 3.9 mm Hg, P <.05; at peak exercise: 224.9 +/- 8.0/113.1 +/- 5.3 v 207.0 +/- 6.0/100.7 +/- 5.0 mm Hg, P <.05) without affecting heart rate (at rest: 67.6 +/- 3.9 v 70.4 +/- 4.5 beats/min, P =.33; peak exercise: 146.4 +/- 7.4 v 144.0 +/- 7.2 beats/min, P =.49). Amlodipine did not affect minute ventilation (VE) at rest or during exercise. It did not alter anaerobic threshold, peak oxygen uptake (peak VO(2)), or peak workload. However, after amlodipine treatment, VNO was significantly greater both at rest (130.8 +/- 19.4 v 180.4 +/- 24.8 nL/min, P <.05) and at peak exercise (380.0 +/- 47.5 v 582.6 +/- 74.3 nL/min, P <.05). CONCLUSIONS: Amlodipine increased NO production, at least in the pulmonary circulation, in patients with essential hypertension. In addition to its antihypertensive effect, the enhancement of NO production by amlodipine in the vasculature of other organs may contribute to its beneficial effects on the cardiovascular system.

Inhibitory effects of ursodeoxycholic acid on the induction of nitric oxide synthase in vascular smooth muscle cells.

The expression of inducible nitric oxide synthase (iNOS) and the resultant increased nitric oxide production are associated with endotoxemia and atherosclerotic lesions observed in transplant hearts or balloon-injured artery. Ursodeoxycholic acid has been shown to have cardiovascular protective effects, such as inhibition of the development of transplant arteriosclerosis, but its mechanism remains unclear. Here, we investigated the effects of ursodeoxycholic acid on nitric oxide production and the expression of iNOS in vascular smooth muscle cells isolated from adult rat aorta and rabbit coronary artery. Nitrite released from cells in the culture medium was measured with the Griess reaction. iNOS mRNA and protein were measured by Northern and Western blot analyses. Treatment with ursodeoxycholic acid (30-1000 microM) significantly inhibited lipopolysaccharide plus interferon-gamma-induced nitric oxide production in a concentration-dependent manner, but ursodeoxycholic acid showed only small inhibitory effects on nitric oxide production that had already been induced by lipopolysaccharide plus interferon-gamma. Ursodeoxycholic acid by itself did not affect basal nitric oxide production. Ursodeoxycholic acid also suppressed lipopolysaccharide plus interferon-gamma-induced expression of iNOS mRNA and protein. Ursodeoxycholic acid had the most potent inhibitory effect among various kinds of bile acids examined, i.e. chenodeoxycholic acid, deoxycholic acid, cholic acid and conjugated bile acids such as tauroursodeoxycholic acid. These results suggest that ursodeoxycholic acid inhibits the induction of iNOS and then nitric oxide production in aortic and coronary artery smooth muscle cells, suggesting a possible mechanism for the cardiovascular protective effect of ursodeoxycholic acid under various pathophysiological conditions such as endotoxemia and atherosclerosis.

Sarcolemmal fragility secondary to the degradation of dystrophin in dilated cardiomyopathy, as estimated by electron microscopy.

A common gene deletion or mutation of delta-sarcoglycan (delta-SG) in dystrophin-related proteins (DRPs) is identified in both TO-2 strain hamsters and human families with dilated cardiomyopathy. We have succeeded in the long-lasting in vivo supplementation of a normal delta-SG gene by recombinant adeno-associated virus vector, restoration of the morphological and functional degeneration, and improvement in the prognosis of the TO-2 hamster. To evaluate the integrity of the sarcolemma (SL) and the subsequent change of organelles in cardiomyocytes of the TO-2 strain hamster, we examined electron microscopy (EM) images focusing on the sarcolemmal stability at the end stage of heart failure. Two types of sarcolemmal degradation were detected: the widened and locally thickened SL, and blurred and discontinuous SL. Bizarrely formed mitochondria of varying sizes were also observed. Immuno-EM revealed clear expression of dystrophin in the SL and intense expression at the costamere as well as at the T-tubules in the control F1B strain hearts, but a patchy deposition of dystrophin was observed along the SL without the transgene of delta-SG. In contrast to the previous reports that dystrophin's integrity was intact, the present results suggest that the gene deletion of delta-SG and the loss of delta-SG protein in the SL cardioselectively cause the morphological and functional deterioration of dystrophin and the resultant instability of the SL. The sarcolemmal fragility may be similar to Duchenne-type progressive muscular dystrophy in skeletal muscle. In addition to the mechanical role, another aspect of DRPs for the intracellular signal transmission is also discussed.

[T-type calcium channel blockers].

T-type calcium channels play an important role in regulating cell function in various kinds of organs, especially in cardiovascular systems. They have been recently clarified to be involved in various pathophysiological conditions, and clinically used for treatment of a variety of diseases. This review reports the usefulness and safety of the T-type calcium channel blockers.

High-frequency powers hidden within QRS complex as an additional predictor of lethal ventricular arrhythmias to ventricular late potential in post-myocardial infarction patients.

BACKGROUND: Ventricular late potentials (VLPs) have been known to be a predictor of lethal ventricular arrhythmias (L-VAs); however, detection of other arrhythmogenic signals within the QRS complex remains obscure. OBJECTIVE: The aim of this study was to evaluate whether abnormal intra-QRS high-frequency powers (IQHFP) within the QRS complex become a new predictor of L-VAs in addition to VLPs. METHODS: Both 12-lead electrocardiograms (ECG) and VLPs were recorded from 142 subjects, including 37 patients without heart diseases, 97 patients post-myocardial infarction (MI), and 45 post-MI patients with L-VAs. Time-frequency analysis of ECG (leads V(1) or II) using wavelet transform with the Morlet function was performed. After the time-frequency powers were calculated, the ratios of the peak of signal power during the QRS complex in high-frequency bands against the peak power at 80 Hz (b/a ratio; P100, P150, P200, P250, or P300Hz/P80Hz) were measured. Abnormal IQHFP was defined when the b/a ratio exceeded the optimal cut-off values estimated by receiver-operator characteristic curves. RESULTS: The combination of abnormal IQHFP appearing at 200, 250, and 300 Hz with positive VLPs increased the sensitivity for prediction of L-VAs from 53.3% by VLPs to 89.5%, and the negative predictive value from 74.7% by VLPs to 87.7%. CONCLUSION: The combined use of VLPs and IQHFP hidden within the QRS complex improved the prediction of L-VAs in post-MI patients.

Morbidity prevalence rate of kawasaki disease assessed by single cross-sectional history-taking.

The need for long-term follow-up in Kawasaki disease is poorly recognized although cardiac sudden death attacks asymptomatic young people with past illness after a long latent period. Therefore, in order to prevent cardiac disasters, high risk groups should be identified and the prevalence rate of the disease should be determined for crisis management. A total of 9,965 consecutive freshmen at the University of Tokyo were the subject of a questionnaire. Their parents/guardians who were briefed on the diagnostic criteria of the acute phase of Kawasaki disease actually completed the questionnaire. Students with a positive diagnosis underwent rest and exercise-stress electrocardiography and routine echocardiography. The overall prevalence rate was 0.57%. The rate in males (0.63%) was greater than that in females (0.32%) (P < 0.05). Electrocardiography and routine echocardiography identified no indices specific to a past illness of Kawasaki disease. The prevalence rate indicated that about 6 in 1000 students were high risk students who needed special care while at university. Since there are few symptoms and no signs indicating a past illness of Kawasaki disease, intensive history-taking from parents/guardians who are familiar with their acute symptoms during childhood is required in order to identify those at high risk of a coronary event.

Acute and chronic effects of eicosapentaenoic acid on voltage-gated sodium channel expressed in cultured human bronchial smooth muscle cells.

This study investigated acute and chronic effects of eicosapentaenoic acid (EPA) on voltage-gated Na+ current (I(Na)) expressed in cultured human bronchial smooth muscle cells (hBSMCs). The whole-cell voltage clamp technique and quantitative real-time RT-PCR analysis were applied. The alterations in the fatty acid composition of phospholipids after treatment with EPA were also examined. Extracellular application of EPA produced a rapid and concentration-dependent suppression of tetrodotoxin-sensitive I(Na) with the half-maximal inhibitory concentration of 2 microM. After washing out EPA with albumin, I(Na) returned to the control level. Similar inhibitory effects were observed regarding other fatty acids (docosahexaenoic, arachidonic, stearic, and oleic acids), but EPA was the most potent inhibitor. The effect of EPA on I(Na) was not blocked by nordihydroguaiaretic acid and indometacin, and was accompanied by a significant shift of the steady-state inactivation curve to more negative potentials. In cells chronically treated with EPA, the EPA content of the cell lipid fraction (mol%) increased time-dependently, while arachidonic acid (AA) decreased, resulting in an increase of EPA to AA ratio. Then, the level of mRNA (SCN9A) encoding I(Na) decreased significantly. These results provide novel evidence that EPA not only rapidly inhibits I(Na), but also reduces the mRNA levels of the Na+ channel after cellular incorporation of EPA in cultured hBSMCs.

Inhibitory effects of carvedilol on calcium channels in vascular smooth muscle cells.

Carvedilol has hypotensive effects and inhibits agonist-induced cell proliferation of vascular smooth muscle and then prevents vascular remodeling. However, the basic mechanisms have not been clarified. We examined the effects of carvedilol on [Ca2+]i mobilization and voltage-dependent L-type Ca2+ current (ICa.L) in vascular smooth muscle cells, and compared them with metoprolol. [Ca2+]i was measured using fura-2 AM and patch clamp techniques in rat embryonic aortic smooth muscle cells (A7r5). In the presence of extracellular Ca2+, vasopressin and endothelin-1 increased [Ca2+]i due first to the Ca2+ release from store sites, and subsequently Ca2+ entry. Carvedilol did not inhibit the Ca2+ release, but significantly suppressed the sustained rise due to Ca2+ entry concentration-dependently. Nilfedipine and nicardipine (10 microM) partly inhibited the sustained rise, but carvedilol inhibited it more effectively than the Ca2+ channel blockers. Under voltage clamp conditions, carvedilol (0.2-10 microM) reversibly inhibited the ICa.L concentration-dependently without any changes in the current-voltage relationships of ICa.L. Carvedilol shifted the steady-state inactivation for ICa.L to more negative potentials and inhibited ICa.L in a voltage-dependent manner. In addition, carvedilol did not inhibit Ca2+ release from store sites induced by thapsigargin, but significantly inhibited the sustained rise due to capacitative Ca2+ entry unrelated to ICa.L. In contrast, metoprolol did not mimic these effects of carvedilol. These results provide evidence that carvedilol inhibits ICa.L and may also inhibit the channels for agonist (vasopressin and endothelin-1)-induced Ca2+ entry in vascular smooth muscle cells, which might contribute to the vasorelaxing and antiproliferative effects of carvedilol.

Inward rectifier K(+) current in human bronchial smooth muscle cells: inhibition with antisense oligonucleotides targeted to Kir2.1 mRNA.

Inward rectifier K(+) (Kir) channels play an important role in forming membrane potential and then modulating muscle tone in certain types of smooth muscles. In cultured human bronchial smooth muscle cells (hBSMCs), Kir current was identified using whole-cell voltage clamp techniques and explored by using RT-PCR analysis of mRNA, Western blotting, and antisense oligonucleotide methods to block the synthesis of Kir channel protein. The K(+) current with strong inward rectification and high K(+) ion selectivity was observed. The current was unaffected by 4-aminopyridine, glibenclamide, and charybdotoxin, and hardly inhibited by tetraethylammonium, but was potently inhibited by extracellular Ba(2+). The IC(50) value of external Ba(2+) was approximately 1.3 microm. RT-PCR analysis of mRNA showed transcripts for Kir2.1, but not Kir1.1, Kir2.2, or Kir2.3. Treatment of cells with antisense oligonucleotides targeted to Kir2.1 resulted in a decrease in the current density of the Kir current and Kir protein expression, as compared with the mismatch-treated cells, whereas the current density of 4-AP-sensitive K(+) currents (K(V)) remained unaffected. The application of Ba(2+) markedly depolarized the membrane. These results demonstrate that Kir channel is present in human bronchial smooth muscle cells, and the Kir2.1 gene encodes the Kir channel protein in these cells.

Gene therapy prevents disruption of dystrophin-related proteins in a model of hereditary dilated cardiomyopathy in hamsters.

BACKGROUND: The TO-2 hamster is an animal model of dilated cardiomyopathy (DCM). It has genetic and clinical features in common with humans who carry the gene deletion or mutation of the delta-sarcoglycan (SG) gene, a component in dystrophin-related proteins (DRP). DRP stabilise the sarcolemma during cardiac contraction. We performed in vivo gene therapy of the TO-2 hamster, whose heart is defective in all four SG proteins, to determine its potential as a model for therapy for DCM. In addition to the hereditary origin, heart failure is aggravated by treatment with catecholamines and ameliorated by the administration of some kinds of beta-antagonist both in humans and in TO-2 hamsters. METHODS: Gene therapy for DCM was achieved by supplementing the delta-SG gene with rAAV vector and intramurally delivering rAAV-delta-SG into the cardiac apex and left ventricle. RESULTS: This treatment resulted in: (i) a sustained and non-pathogenic expression of both the transcript and transgene of delta-SG and all other SG proteins; (ii) improvement to both morphological and physiological deterioration; and (iii) rescued prognosis compared with untreated TO-2 hamsters, and TO-2 hamsters transfected with reporter gene alone. Another acute heart-failure model was prepared by high-dose isoproterenol treatment in Wistar rats, which resulted in: (i) translocation of dystrophin, but not delta-SG, from the cardiac sarcolemma to the myoplasm; and (ii) fragmentation of dystrophin, probably due to the activation of endogenous protease(s) or proteasome(s) that contributed to muscular dystrophy-like degeneration occurring specifically in cardiomyocytes. CONCLUSIONS: Both the TO-2 hamster and the isoproterenol-treated Wistar rat models commonly experience disruption of dystrophin or DRP. Targeting the responsible gene with the use of a potent vector may provide a novel strategy for the treatment of advanced heart failure.

Cell density and growth-dependent down-regulation of both intracellular calcium responses to agonist stimuli and expression of smooth-surfaced endoplasmic reticulum in MC3T3-E1 osteoblast-like cells.

A two-dimensional intracellular Ca(2+) ([Ca(2+)](i)) imaging system was used to examine the relationship between [Ca(2+)](i) handling and the proliferation of MC3T3-E1 osteoblast-like cells. The resting [Ca(2+)](i) level in densely cultured cells was 1.5 times higher than the [Ca(2+)](i) level in sparsely cultured cells or in other cell types (mouse fibroblasts, rat vascular smooth muscle cells, and bovine endothelial cells). A high resting [Ca(2+)](i) level may be specific for MC3T3-E1 cells. MC3T3-E1 cells were stimulated with ATP (10 microM), caffeine (10 mM), thapsigargin (1 microM), or ionomycin (10 microM), and the effect on the [Ca(2+)](i) level of MC3T3-E1 cells was studied. The percentage of responding cells and the degree of [Ca(2+)](i) elevation were high in the sparsely cultured cells and low in densely cultured cells. The rank order for the percentage of responding cells and magnitude of the Ca(2+) response to the stimuli was ionomycin > thapsigargin = ATP > caffeine and suggests the existence of differences among the various [Ca(2+)](i) channels. All Ca(2+) responses in the sparsely cultured MC3T3-E1 cells, unlike in other cell types, disappeared after the cells reached confluence. Heptanol treatment of densely cultured cells restored the Ca(2+) response, suggesting that cell-cell contact is involved with the confluence-dependent disappearance of the Ca(2+) response. Immunohistological analysis of type 1 inositol trisphosphate receptors and electron microscopy showed distinct expression of inositol trisphosphate receptor proteins and smooth-surfaced endoplasmic reticulum in sparsely cultured cells but reduced levels in densely cultured cells. These results indicate that the underlying basis of confluence-dependent [Ca(2+)](i) regulation is down-regulation of smooth-surfaced endoplasmic reticulum by cell-cell contacts.

Translocation and cleavage of myocardial dystrophin as a common pathway to advanced heart failure: a scheme for the progression of cardiac dysfunction.

Advanced heart failure (HF) is the leading cause of death in developed countries. The mechanism underlying the progression of cardiac dysfunction needs to be clarified to establish approaches to prevention or treatment. Here, using TO-2 hamsters with hereditary dilated cardiomyopathy, we show age-dependent cleavage and translocation of myocardial dystrophin (Dys) from the sarcolemma (SL) to the myoplasm, increased SL permeability in situ, and a close relationship between the loss of Dys and hemodynamic indices. In addition, we observed a surprising correlation between the amount of Dys and the survival rate. Dys disruption is not an epiphenomenon but directly precedes progression to advanced HF, because long-lasting transfer of the missing delta-SG gene to degrading cardiomyocytes in vivo with biologically nontoxic recombinant adenoassociated virus (rAAV) vector ameliorated all of the pathological features and changed the disease prognosis. Furthermore, acute HF after isoproterenol toxicity and chronic HF after coronary ligation in rats both time-dependently cause Dys disruption in the degrading myocardium. Dys cleavage was also detected in human hearts from patients with dilated cardiomyopathy of unidentified etiology, supporting a scheme consisting of SL instability, Dys cleavage, and translocation of Dys from the SL to the myoplasm, irrespective of an acute or chronic disease course and a hereditary or acquired origin. Hereditary HF may be curable with gene therapy, once the responsible gene is identified and precisely corrected.