Gene Therapy for Cardiac Arrhythmias.

UNLABELLED: Morbidity and mortality caused by cardiac arrhythmias are a major issue in developed countries. Although conventional therapeutic options including pharmacological therapy, catheter ablation, and implantable devices have shown extensive advances to help reduce morbidity and mortality, a certain segment of these arrhythmias is still refractory to treatment. Therefore, gene therapy was explored as a potential additional or alternative therapy. Gene therapy trials have been developed for bradycardia, atrial fibrillation, and ventricular tachycardia. For the treatment of bradycardia, "biological pacemaker" attempts have been examined utilizing virus vectors to eliminate inward rectifier potassium current, or to overexpress the If current to convert quiescent myocytes into spontaneously active cells. These gene therapy attempts were soon followed by gene and cell hybrid therapies, and cell transplantation therapies utilizing pacemaker cells derived from stem cells. For the treatment of tachycardia, two major strategies were conceived: 1) to increase the effective refractory period, or 2) to recover the conduction velocity. The establishment of a selective and highly efficient gene transfer method would enable us to apply these concepts into the atrial fibrillation and ventricular tachycardia models. Both concepts resulted in an elimination or reduction of tachyarrhythmias in large animal models. Although these trials proved the concept of gene therapy as an adjuvant or alternative approach for the treatment of cardiac arrhythmias, the limitation of these studies is the long-term efficacy and safety. Consequently, an improvement in the gene delivery method is required to overcome these issues. KEY WORDS: Atrial fibrillation; Biological pacemaker; Gene therapy; Ion channel; Ventricular tachycardia.

Ectopic expression of an esterase, which is a candidate for the unidentified plant cutinase, causes cuticular defects in Arabidopsis thaliana.

Cutinase is an esterase that degrades the polyester cutin, a major component of the plant cuticle. Although cutinase activity has been detected in pollen, the genes encoding this enzyme have not been identified. Here, we report the identification and characterization of Arabidopsis CDEF1 (cuticle destructing factor 1), a novel candidate gene encoding cutinase. CDEF1 encodes a member of the GDSL lipase/esterase family of proteins, although fungal and bacterial cutinases belong to the alpha/beta hydrolase superfamily which is different from the GDSL lipase/esterase family. According to the AtGenExpress microarray data, CDEF1 is predominantly expressed in pollen. The ectopic expression of CDEF1 driven by the 35S promoter caused fusion of organs, including leaves, stems and flowers, and increased surface permeability. Ultrastructural analysis revealed that the cuticle of the transgenic plants was often disrupted and became discontinuous. Subcellular analysis with green fluorescent protein (GFP)-tagged CDEF1 showed that the protein is secreted to the extracellular space in leaves. The recombinant CDEF1 protein has esterase activity. These results are consistent with cutinase being secreted from cells and directly degrading the polyester in the cuticle. CDEF1 promoter activity was detected in mature pollen and pollen tubes, suggesting that CDEF1 is involved in the penetration of the stigma by pollen tubes. Additionally, we found CDEF1 expression at the zone of lateral root emergence, which suggests that CDEF1 degrades cell wall components to facilitate the emergence of the lateral roots. Our findings suggest that CDEF1 is a candidate gene for the unidentified plant cutinase.

Odd variation of 75 g oral glucose tolerance test results in a Japanese patient with polycystic ovary syndrome: a case report.

We report a young woman of normal body weight who was diagnosed with polycystic ovary syndrome (PCOS) and had an odd variation of 75 g oral glucose tolerance test (OGTT). This woman underwent the 75 g OGTT to evaluate the association between PCOS and insulin secretion capacity. Although the blood sugar levels were within normal range before the OGTT load test, we noted an odd variation of insulin response in which a condition of hyperinsulinemia after the load test was followed suddenly by hypoglycemia. Hyperandrogenism in the PCOS patient and insulin resistance indicated by 75 g OGTT suggest that insulin may influence the ovary and that there could be an association between this disease and insulin resistance. The insulinogenic index in this case showed higher than normal values, demonstrating that there was a positive correlation between hyperinsulinemia and insulin resistance. This patient experienced ovulation followed by pregnancy after treatment with an herbal medicine called Shakuyaku-Kanzo-To. We believed that identifying the subset of PCOS woman who is insulin resistant may be useful, as this resistance could be import in terms of follow-up and future exploration.

Nitric oxide-dependent modulation of the delayed rectifier K+ current and the L-type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea-pig cardiomyocytes.

1 Ginsenoside Re, a major ingredient of Panax ginseng, protects the heart against ischemia-reperfusion injury by shortening action potential duration (APD) and thereby prohibiting influx of excessive Ca2+. Ginsenoside Re enhances the slowly activating component of the delayed rectifier K+ current (IKs) and suppresses the L-type Ca2+ current (I(Ca,L)), which may account for APD shortening. 2 We used perforated configuration of patch-clamp technique to define the mechanism of enhancement of IKs and suppression of I(Ca,L) by ginsenoside Re in guinea-pig ventricular myocytes. 3 S-Methylisothiourea (SMT, 1 microm), an inhibitor of nitric oxide (NO) synthase (NOS), and N-acetyl-L-cystein (LNAC, 1 mm), an NO scavenger, inhibited IKs enhancement. Application of an NO donor, sodium nitroprusside (SNP, 1 mm), enhanced IKs with a magnitude similar to that by a maximum dose (20 microm) of ginseonside Re, and subsequent application of ginsenoside Re failed to enhance IKs. Conversely, after IKs had been enhanced by ginsenoside Re (20 microm), subsequently applied SNP failed to further enhance IKs. 4 An inhibitor of guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 microm), barely suppressed IKs enhancement, while a thiol-alkylating reagent, N-ethylmaleimide (NEM, 0.5 mm), clearly suppressed it. A reducing reagent, di-thiothreitol (DTT, 5 mm), reversed both ginsenoside Re- and SNP-induced IKs enhancement. 5 I(Ca,L) suppression by ginsenoside Re (3 microm) was abolished by SMT (1 microm) or LNAC (1 mm). NEM (0.5 mm) did not suppress I(Ca,L) inhibition and DTT (5 mm) did not reverse I(Ca,L) inhibition, whereas in the presence of ODQ (10 microm), ginsenoside Re (3 microm) failed to suppress I(Ca,L). 6 These results indicate that ginsenoside Re-induced IKs enhancement and I(Ca,L) suppression involve NO actions. Direct S-nitrosylation of channel protein appears to be the main mechanism for IKs enhancement, while a cGMP-dependent pathway is responsible for I(Ca,L) inhibition.