GPD1-L is a novel gene that may affect trafficking of the cardiac Na+ channel to the cell surface. A GPD1-L mutation decreases SCN5A surface membrane expression, reduces inward Na+ current, and causes Brugada syndrome.

Rationale: Mutations in glycerol-3-phosphate dehydrogenase 1-like (GPD1-L) protein reduce cardiac Na ؉ current (I Na ) and cause Brugada Syndrome (BrS). GPD1-L has >80% amino acid homology with glycerol-3-phosphate dehydrogenase, which is involved in NAD-dependent energy metabolism.Objective: Therefore, we tested whether NAD(H) could regulate human cardiac sodium channels (Na v 1.5).

Abstract-Heart failure (HF) is associated with reduced cardiac Na ϩ channel (SCN5A) current. We hypothesized that abnormal transcriptional regulation of this ion channel during HF could help explain the reduced current. Using human hearts explanted at the transplantation, we have identified 3 human C-terminal SCN5A mRNA splicing variants predicted to result in truncated, nonfunctional channels. As compared with normal hearts, the explanted ventricles showed an upregulation of 2 of the variants and a downregulation of the full-length mRNA transcript such that the E28A transcript represented only 48.5% (PϽ0.01) of the total SCN5A mRNA. This correlated with a 62.8% (PϽ0.01) reduction in Na ϩ channel protein. Lymphoblasts and skeletal muscle expressing SCN5A also showed identical C-terminal splicing variants. Variants showed reduced membrane protein and no functional current. Transfection of truncation variants into a cell line stably transfected with the full-length Na ϩ channel resulted in dose-dependent reductions in channel mRNA and current. Introduction of a premature truncation in the C-terminal region in a single allele of the mouse SCN5A resulted in embryonic lethality. Embryonic stem cell-derived cardiomyocytes expressing the construct showed reductions in Na ϩ channel-dependent electrophysiological parameters, suggesting that the presence of truncated Na ϩ channel mRNA at levels seen in HF is likely to be physiologically significant. In summary, chronic HF was associated with an increase in 2 truncated SCN5A variants and a decrease in the native mRNA. These splice variations may help explain a loss of Na Key Words: sodium channels Ⅲ transcriptional regulation Ⅲ mRNA splice variations Ⅲ heart failure Ⅲ arrhythmia H uman heart failure (HF) is associated with decreased cardiac voltage-gated sodium channel current. 1,2 Genetically mediated decreases in Na ϩ current have been implicated in the risk for sudden death, [3][4][5] and Na ϩ channel changes may contribute to the increased risk of sudden death in HF. 6,7 Because transcriptional alterations in other ion channels have been noted to contribute to current changes in HF, 8,9 we investigated Na ϩ channel protein and mRNA abundance in hearts explanted during cardiac transplantation to determine whether there were changes that might explain the reduced Na ϩ current previously reported in this tissue. Materials and Methods Detection of Human SCN5A 3UTR Variants by Rapid Amplification of cDNA Ends PCRTotal human RNA from normal fetal and adult whole hearts was purchased from Clontech (Mountain View, Calif). The RNA ligasemediated rapid amplification of cDNA ends (RACE) method was used to characterize the 3Ј ends of the human SCN5A mRNA using the GeneRacer kit (Invitrogen, Carlsbad, Calif). Primary and nested PCR reactions were performed with primers HE26F (on exon 26) and HE27F (on exon 27) specific to the human SCN5A gene and the GeneRacer 3Ј primer for amplifying the 3Ј-end fragment. The nested PCR products were cloned into pCR4-TOPO vector (Invitrogen) and se...

(ANG II) increases oxidative stress and is associated with increased risk of sudden cardiac death. The cardiac Na ϩ channel promoter contains elements that confer redox sensitivity. We tested the hypothesis that ANG IImediated oxidative stress may modulate Na ϩ channel current through altering channel transcription. In H9c2 myocytes treated for 48 h with ANG II (100 nmol/l) or H2O2 (10 mol/l) showed delayed macroscopic inactivation, increased late current, and 59.6% and 53.8% reductions in Na ϩ current, respectively (P Յ 0.01). By quantitative real-time RT-PCR, the cardiac Na ϩ channel (scn5a) mRNA abundance declined by 47.3% (P Ͻ 0.01) in H9c2 myocytes treated for 48 h with 100 nmol/l ANG II. A similar change occurred with 20 mol/l H2O2 (46.9%, P Ͻ 0.01) after 48 h. Comparable effects were seen in acutely isolated ventricular myocytes. The effects of ANG II could be inhibited by prior treatment of H9c2 cells with scavengers of reactive oxygen species or an inhibitor of the NADPH oxidase. Mutation of the scn5a promoter NF-B binding site prevented decreased activity in response to ANG II and H2O2. Gel shift and chromosomal immunoprecipitation assays confirmed that nuclear factor (NF)-B bound to the scn5a promoter in response to ANG II and H2O2. Overexpression of the p50 subunit of NF-B in H9c2 cells reduced scn5a mRNA (77.3%, P Ͻ 0.01). In conclusion, ANG II can decrease scn5a transcription and current. This effect appears to be through production of H2O2 resulting in NF-B binding to the Na ϩ channel promoter. arrhythmia, gene expression; sodium channel; redox signaling; renin angiotensin system ACTIVATION of the renin-angiotensin system (RAS) has been implicated in arrhythmia associated with heart failure because inhibitors of this pathway reduce the incidence of sudden death (18,39,42,43). One major effecter of RAS activation is angiotensin II (ANG II), produced by enzymatic activity of angiotensin-converting enzyme (ACE) on angiotensin I. ANG II is known to increase oxidative stress through NADPH oxidase activation (7,20,31). Increased oxygen free radical production is associated with congestive heart failure (13, 21) and arrhythmias (6, 32). Nevertheless, the molecular basis whereby ANG II may cause arrhythmias and any role for ANG II-induced oxidative stress are not clear.Ion channel transcriptional regulation is implicated in increasing ventricular and atrial arrhythmic risk (1,9,25,29,44).Often referred to as electrical remodeling, the changes in myocyte electrical properties in states of increased arrhythmic risk are related to underlying changes in expression of several ion channel genes, including reductions in connexins and Na ϩ channels, and may be responsible for the arrhythmic effects of ANG II. Downregulations of Na ϩ channels and connexin 43 are seen in heart failure, a condition associated with increased RAS activation (4, 15, 37, 46). Moreover, forms of electrical remodeling can be inhibited by agents altering RAS signaling and by antioxidants (8,24,38), suggesting that ANG IImediated ion channe...

BACKGROUND-Brugada and Long QT type 3 syndromes are linked to sodium channel mutations and clinically cause arrhythmias that lead to sudden death. We have identified a novel threonine to isoleucine missense mutation at position 353 (T353I) adjacent to the pore-lining region of domain I of the cardiac sodium channel (SCN5a) in family with Brugada syndrome. Both male and female carriers are symptomatic at young ages, have typical Brugada-type ECG changes, and have relatively normal corrected QT intervals.

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bnormalities of the function of the autonomic nervous system are frequent and often serious complications in patients with diabetic mellitus (DM), 1 and may be exacerbated by cardiovascular dysfunction. Power spectral analysis of heart rate (HR) variability (HRV) has been shown to be a quantitative and non-invasive method for assessing the effects of the sympathetic and parasympathetic components of autonomic nervous activity of the cardiovascular system. 2 Power spectral analysis of HRV is also a powerful tool for determinating the autonomic nerve tone in patients with diabetic neuropathy, and fast Fourier transform is statistically more robust. 3 However, time domain measurement of the RR intervals is a possible weakness and bottleneck, 4 so we decided to measure frequency domain (power spectral analysis) alternatively with the time domain of RR intervals in order to investigate autonomic nervous function in rats. A telemetric monitoring system for ECG has been developed for small animals and, moreover, sophisticated software permits analysis of HRV for long-term ECG recording even for species with a rapid heart beat. Therefore, analysis of HRV in rats can provide specific information concerning the autonomic nervous activity underlying control of the cardiovascular system in diabetic conditions without any effects of anesthetic agents or changes in environment. Methods Animals and HousingThe study animals were 6 spontaneously diabetic male Circulation Journal Vol.66, March 2002Kob rats, 15-19 months old and weighing 300-320 g, and 9 male Wistar rats of the same age. All rats were purchased from Seac Yoshitomi Limited Ltd (Tokyo, Japan) and were cared for humanely in accordance with the Principles of Laboratory Animal Care formulated by the National Society for Medical Research and the Guide for the Care and Use of Laboratory Animals published by the National Institute of Health (NIH publication No. 85-23, revised 1996). The rats were housed in individual cages with wood shavings in a light-proof room (TB181 or TB182; National, Osaka, Japan) under a light -dark cycle (LD 12:12; lights on at 08.00 h) that was maintained under constant temperature (24°C). The animals had free access to water and a standard diet. The diabetic state of the Kob rats was confirmed by the cardinal symptoms of loss of body weight, polydipsia, polyuria, polyphagia, cataract, increased fasting blood sugar (FBS) and ruffled hair. Surgical ProcedureAnimals were anesthetized with 50 mg/kg of intraperitoneal pentobarbital and a telemetric ECG radio-transmitter (25×15×9 mm in size and 7 g in weight; TA11CTA-F40, Data Sciences International, St. Paul, MN, USA), was placed in a dorsal subcutaneous pouch. The paired wire electrodes for the pericardial bipolar leads (apex-base leads) were placed under the skin of the dorsal and ventral thorax and the skin was sutured. ECG records were initiated 3 days after surgery to avoid any possible effects of residual anesthetic or the surgery. ECG Recordings and Data AnalysesEach rat cage was placed on top...

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