Identification of cardiac myocytes as the target of interleukin 11, a cardioprotective cytokine

Interleukin (IL)-6 family cytokines, which share glycoprotein 130 (gp130) as a signal-transducing receptor component, play important roles in the maintenance of cardiac homeostasis. IL-11, a member of IL-6 family cytokines, is expressed in cardiac myocytes, though it remains to be elucidated how IL-11 functions in the hearts. In the present study, first, we showed that IL-11 administration reduced the ischemia/reperfusion injury in the hearts. IL-11 receptor alpha was expressed in cardiomyocytes. IL-11 treatment rapidly activated signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase (ERK) 1/2 in cardiac myocytes. IL-11 stimulation resulted in the translocation of phosphorylated STAT3 into nuclei. Immunofluorescence microscopic analyses revealed that IL-11 treatment led to the cell elongation, as is the case with other cardiotrophic members of IL-6 family, such as leukemia inhibitory factor. Finally we showed that IL-11 treatment conferred the resistance to cell death induced by hydrogen peroxide, which was abrogated by adenoviral transfer of dominant negative STAT3, but not by the inhibition of ERK1/2 with U0126. These findings indicate that IL-11 mediates cytoprotective signals in cardiomyocytes, proposing that IL-11 has the potential to exhibit cardioprotection as a novel biological function.

Regulation of Cytochrome P450 2E1 under Hypertonic Environment through TonEBP in Human Hepatocytes

Whereas the liver as well as the other organs are continually exposed to the change of osmotic status, it has never been investigated whether activities and gene expressions of drug-metabolizing enzymes, including cytochromes P450, are dependent on osmotic change in the liver. In the present study, we determined that CYP2E1 is induced under hypertonic environments at a transcriptional level in human primary hepatocytes, as assessed by cDNA microarray and real time-reverse transcription-polymerase chain reaction analyses. Both a protein level and the catalytic activity of CYP2E1 were consistently increased in response to hypertonic conditions. In promoter-reporter assay, it was demonstrated that -586 to -566 in the CYP2E1 5'-flanking region was necessary for 2E1 promoter activation by hypertonic stimulation. It is noteworthy that tonicity-response element (TonE) consensus sequence was found at -578 to -568 in human CYP2E1 5'-flanking region, and electrophoretic mobility shift assay demonstrated the interaction of TonE binding protein (TonEBP) with TonE motif of CYP2E1 promoter. Furthermore, cotransfection of a CYP2E1 promoter construct with wild-type TonEBP expression vector enhanced promoter activity under both isotonic and hypertonic conditions, whereas dominant-negative TonEBP suppressed an induction of CYP2E1 promoter activity. These results indicate that the level of CYP2E1 is induced by hypertonic condition via TonEBP transactivation. The present study suggests that osmotic status may influence individual responses to the substrate of CYP2E1.

Determination of single nucleotide polymorphisms in N-acetyltransferase2 gene using an electrochemical DNA chip and an automated DNA detection system

An electrochemical DNA chip using an electrochemically active intercalator and DNA probe immobilized on a gold electrode has been developed for genetic analysis. In this study, N-acetyltransferase2 (NAT2) gene polymorphisms (C481T G590A G857A) were determined by the electrochemical DNA chip and the automated DNA detection system that performs hybridization reaction, washing, detection, and data analysis. Human genomic DNAs were extracted from blood and DNA fragments containing the three polymorphisms were amplified by the polymerase chain reaction (PCR) method. Double-stranded PCR products were treated with T7 exonuclease and single-stranded target DNAs were obtained. A sample containing the single-stranded target DNAs was injected into a cassette including the electrochemical DNA chip and set in an automated system. The turnaround time for genotyping with this system was 90 min. A total of 38 samples were automatically genotyped by an SNP determination algorithm. The results of genotype were completely consistent with those determined by the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. Consequently, this method requires no labeling step and has the advantage of realizing a compact and automatic system, and so the system is expected to contribute to personalized medicine based on genotype.

Genetic Polymorphism of Bile acid CoA: Amino acid N-acyltransferase in Japanese Individuals

In the present study, we identified three novel single nucleotide polymorphisms (SNPs), 147C>T in exon 2 (silent), 602G>C in exon 3 (Arg201Pro), and 1134C>T in exon 4 (silent), in the gene of bile acid CoA: amino acid N-acyltransferase (BAAT) by resequencing the entire coding region and the exon-intron junctions of 100 Japanese individuals. The allelic frequencies were 0.005 for 147C>T, 0.095 for 602G>C, and 0.015 for 1134C>T. The two known SNPs, 59G>A (Arg20Gln, rs1572983) and UTR1513G>A (rs2229594), were detected at a frequency of 0.500 and 0.425, respectively. In the haplotype analysis for the 59G>A and 602G>C polymorphisms, the allelic frequency of 59G-602G, 59G-602C, 59A-602G and 59A-602C was 0.405, 0.095, 0.500 and 0.000, respectively. On the other hand, the allelic frequency of the nonsynonymous SNP 602G>C was 0.194 in a Caucasian population.

Rac1 activity is required for cardiac myocyte alignment in response to mechanical stress

Mechanical stretch is essential for the cardiac growth. The exposure of cardiac myocytes to the mechanical stretch leads to the cell alignment in parallel to the stretch direction, determining the cell polarity, though it remains to be addressed how mechanical stretch regulates cell orientation. In the present study, we investigated the signal transduction pathways responsible for the cell orientation response to mechanical stretch, focusing on Rho family proteins. Neonatal rat cardiomyocytes were cultured on silicon chambers and exposed to artificial uniaxial cyclic stretch. The pull-down assays revealed that Rac1 was rapidly activated by stretch, but not RhoA. To analyze the roles of Rho family proteins in cardiomyocyte orientation, adenoviral vectors expressing dominant-negative (dn) RhoA and Rac1 were generated. The transfection with adenovirus vector expressing dnRac1, but not dnRhoA, inhibited stretch-induced cell alignment. In conclusion, Rac1 activity is necessary for cardiomyocyte alignment in response to directional stretch.

Degradation of NFAT5, a transcriptional regulator of osmotic stress-related genes, is a critical event for doxorubicin-induced cytotoxicity in cardiac myocytes

Nuclear factor-activated T cell 5 (NFAT5), a novel member of the NFAT family of proteins, was originally identified as a transcriptional factor responsible for adaptation to hyperosmotic stress. Though NFAT5 is ubiquitously expressed, the biological functions of NFAT5 remain to be clarified, especially in the tissues that are not exposed to hypertonicity, including hearts. In the present study, we focused on the cardioprotective roles of NFAT5 against the cardiotoxic anti-tumor agent doxorubicin (Dox). In cultured cardiomyocytes, transcripts of the hypertonicity-inducible genes, such as taurine transporter (TauT) and sodium/myo-inositol transporter, were down-regulated by Dox. Interestingly, NFAT5 protein, but not mRNA, was decreased in cardiomyocytes exposed to Dox. Treatment of proteasome inhibitors, MG-132 or proteasome-specific inhibitor 1, prevented the Dox-mediated decrease of NFAT5 protein. Further, ubiquitin-conjugated NFAT5 was not detected in cultured cardiomyocytes treated with MG-132 and/or Dox, as assessed by immunoprecipitation assay, suggesting Dox-induced degradation through ubiquitin-independent proteasome pathway. Importantly, inhibition of NFAT5 with overexpression of dominant-negative NFAT5 decreased cell viability and increased creatine kinase leakage into culture medium. Consistently, small interfering RNA targeting NFAT5 gene enhanced myocyte death. These findings suggest that Dox promoted the degradation of NFAT5 protein, reducing cell viability in cardiomyocytes. This is the first demonstration that NFAT5 is a positive regulator of cardiomyocyte survival.

MTHFR gene polymorphism and diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of catastrophic loss of vision. Each year, DR darkens the lives of 12,000 to 24,000 diabetic patients in the United States, and more than 4,000 patients in Japan. Clinically, hyperglycemia induces proliferative changes in DR synergistically with other risk factors for vascular diseases. Methyl- enetetrahydrofolate reductase (MTHFR) is an enzyme involved in remethylation of homocysteine to methionine. A polymorphic mutation (C677T) in the MTHFR gene leads to impaired enzyme activity, resulting in hyper- homocysteinemia as an independent risk factor for macroangiopathy. Recently, more and more attention has been paid to the involvement of hyperhomocysteinemia in the progression of DR, a serious microangiopathic complication of diabetes. Clinical studies have demonstrated that MTHFR gene polymorphism can contribute to the progression of DR, especially in the patients with blood glucose poorly controlled. Furthermore, accumulating evidence suggests that homocysteine activates vascular inflammation through inflammatory cytokines, including VEGF. These data imply that the decrease in plasma homocysteine could prevent the development and progression of DR. We also propose the possibility of personalized medicine for diabetes mellitus based on a better understanding of MTHFR gene polymorphism and its ramifications, which might cast new light on diabetic retinopathy.

Effects of the serotonin type 2A, 3A and 3B receptor and the serotonin transporter genes on paroxetine and fluvoxamine efficacy and adverse drug reactions in depressed Japanese patients

In this study, we tested the influence of the serotonin type 2A, 3A and 3B receptor genes (HTR2A, HTR3A, HTR3B) in addition to a polymorphism in the promoter region of the serotonin transporter (SERTPR), and investigated the different characteristics of clinical responses to paroxetine and fluvoxamine. A total of 100 Japanese patients affected by major recurrent depression were enrolled in a randomized 6-week study. The clinical response was evaluated using the Hamilton Rating Scale for Depression (HAM-D), and adverse drug reactions were assessed at each visit. Patients with the l allele of SERTPR showed a better response to SSRIs than s/s genotype carriers (p = 0.015-0.042), more significantly to fluvoxamine. The -1438G/G genotype of HTR2A was associated with a good response to SSRIs (p = 0.010-0.039), especially to fluvoxamine, and significantly with severe nausea in paroxetine-treated patients (p = 0.013). The 178C/C genotype of the HTR3A was associated with an antidepressant response (p = 0.022-0.042), and more significantly in paroxetine-treated patients (p = 0.002-0.042). These effects were independent of one another. We replicated the finding that the SERPTR polymorphism was associated with a response to SSRIs. We additionally found that HTR2A and HTR3A polymorphisms are associated with the efficacy, and the HTR2A polymorphism is also associated with adverse drug reactions. Furthermore, the effects of these polymorphisms varied from one SSRI to another and thus may depend on the characteristics of each SSRI.

No positive association between adrenergic receptor variants of alpha2cDel322-325, beta1Ser49, beta1Arg389 and the risk for heart failure in the Japanese population

AIMS

We investigated the correlation of adrenergic receptor polymorphisms, alpha(2c)Del322-325, beta(1)Ser49Gly and beta(1)Arg389Gly, with the risk of heart failure in the Japanese population.

METHODS

These polymorphisms were analysed by polymerase chain reaction-restriction fragment length polymorphism in patients with chronic heart failure due to idiopathic dilated cardiomyopathy (DCM) and compared with the control group.

RESULTS

There were no differences or any trends in the allele and genotype frequencies of the beta(1)Ser49Gly and beta(1)Arg389Gly polymorphisms. The allele frequency of the alpha(2c)Del322-325 variant was lower in patients than in controls (0.11 vs. 0.04, P = 0.011 < 0.017, by Bonferroni correction), while the genotype frequency just failed to reach significance (P = 0.022 > 0.017, by Bonferroni correction).

CONCLUSIONS

In this population, the variants beta(1)Ser49, beta(1)Arg389, and alpha(2c)Del322-325 do not appear to be risk factors for chronic heart failure due to DCM. The alpha(2c)Del322-325 variant may in fact confer some protection.

Myogenic differentiation induces taurine transporter in association with taurine-mediated cytoprotection in skeletal muscles

Skeletal muscle homoeostasis is maintained by a variety of cytoprotective mechanisms. Since ablation of the TauT (taurine transporter) gene results in susceptibility to exercise-induced muscle weakness in vivo, it has been suggested that TauT is essential for skeletal muscle function. However, the regulatory mechanisms of TauT expression remain to be elucidated. In the present study, we demonstrated that TauT was up-regulated during myogenesis in C2C12 cells. Treatment with bFGF (basic fibroblast growth factor), which inhibited muscle differentiation, abrogated myogenic induction of TauT. The promoter activities of TauT were up-regulated during muscle differentiation in C2C12 cells. Database analyses identified an MEF2 (myocyte enhancer binding factor 2) consensus sequence at -844 in the rat TauT gene. Truncation of the promoter region containing the MEF2 site significantly reduced the promoter activity, demonstrating the functional importance of the MEF2 site. Electrophoretic mobility-shift assays confirmed that MEF2 bound to the MEF2 consensus sequence and that DNA-protein complex levels were increased during differentiation. Promoter analyses using mutated promoter-reporter plasmids demonstrated that this site was functional. Importantly, transfection with a MyoD expression vector markedly enhanced TauT promoter activity in the (non-myogenic) 10T1/2 cells. Moreover, co-transfection with an MEF2 expression vector augmented MyoD-induced TauT promoter activity, suggesting that MEF2 is required for full activation of TauT expression. Finally, we examined the effects of taurine on myotube atrophy to clarify the biological significance of the up-regulation of TauT, and demonstrated that taurine attenuated muscle atrophy induced by dexamethasone. TauT expression is regulated under the control of the myogenic programme, and we propose that this is the mechanism for taurine-mediated resistance to muscle atrophy.

N-cadherin signals through Rac1 determine the localization of connexin 43 in cardiac myocytes

It has been proposed that the formation of gap junction is influenced by adherens junction in cardiac myocytes. To examine whether signals through N-cadherin are involved in the distribution of connexin 43 (Cx43), the distribution of cell-cell adhesion molecules, N-cadherin and Cx43, was analyzed in aligned cardiac myocytes. To induce cell orientation running in parallel to tension direction, neonatal rat cardiac myocytes were plated for 3 hours and exposed to 20% cyclic stretch for 24 hours on silicone dishes. The aligned cells cultured for 0-5 days were immunostained with anti- N-cadherin or anti-Cx43 antibody. After cultivation for 3-5 days, following the accumulation of N-cadherin, Cx43 was localized at the longitudinal cell termini. Adenoviral gene transfer of dominant negative N-cadherin significantly attenuated the localization of Cx43 at the longitudinal cell termini, suggesting that Cx43 localization is regulated downstream of N-cadherin. In the process of Cx43 localization, Rho family proteins, RhoA and Rac1, were activated, but not Cdc42. RhoA and Rac1 activation was inhibited by the transfection of dominant negative N-cadherin, indicating that RhoA and Rac1 were activated by N-cadherin in the oriented cardiac myocytes. The inhibition of Rho family proteins by Rho GDI significantly attenuated the accumulation of Cx43, but not that of N-cadherin. Furthermore, the translocation of Cx43 to longitudinal cell termini was prevented by the inhibition of Rac1, but not RhoA. Collectively, these findings suggest that the localization of Cx43 was determined through the Rac1 pathway downstream of N-cadherin in cardiac myocytes.

Novel structure of the CYP2D6 gene that confuses genotyping for the CYP2D6*5 allele

We encountered DNA samples which showed a positive product using a long PCR-based method for the detection of CYP2D6*5, indicating deletion of the entire CYP2D6 gene, but the samples did not show a band related to CYP2D6*5 in either XbaI- or EcoRI-RFLP analysis. To achieve genotyping with accuracy, we performed a further genetic analysis to clarify the discrepancy. An unknown 1.6-kb insert was identified in a region downstream from the CYP2D6 stop codon where a specific primer was designed for long-PCR analysis for CYP2D6*5 genotyping. This finding suggested that the CYP2D6 gene might not be deleted in the samples even if a positive product was detected by the long-PCR method. Furthermore, the allelic frequency of this type was found to be approximately 0.3% (4 heterozygous/771 samples) in a Japanese population. In conclusion, we found a novel structure of the CYP2D6 gene, which might lead to incorrect genotyping for CYP2D6*5. Although the long PCR-based strategy for the detection of CYP2D6*5 has been widely used due to its usefulness and convenience, we recommend caution when adopting this method and propose re-evaluating the method for detecting CYP2D6*5.

Leukemia inhibitory factor induces endothelial differentiation in cardiac stem cells

The importance of interleukin 6 (IL-6)-related cytokines in cardiac homeostasis has been studied extensively; however, little is known about their biological significance in cardiac stem cells. Here we describe that leukemia inhibitory factor (LIF), a member of IL-6-related cytokines, activated STAT3 and ERK1/2 in cardiac Sca-1+ stem cells. LIF stimulation resulted in the induction of endothelial cell-specific genes, including VE-cadherin, Flk-1, and CD31, whereas neither smooth muscle nor cardiac muscle marker genes such as GATA4, GATA6, Nkx-2.5, and calponin were up-regulated. Immunocytochemical examination showed that about 25% of total cells were positively stained with anti-CD31 antibody 14 days after LIF stimulation. Immunofluorescent microscopic analyses identified the Sca-1+ cells that were also positively stained with anti-von Willebrand factor antibody, indicating the differentiating process of Sca-1+ cells into the endothelial cells. IL-6, which did not activate STAT3 and ERK1/2, failed to induce the differentiation of cardiac stem cells into the endothelial cells. In cardiac stem cells, the transduction with dominant negative STAT3 abrogated the LIF-induced endothelial differentiation. And the inhibition of ERK1/2 with the MEK1/2 inhibitor U0126 also prevented the differentiation of Sca-1+ cells into endothelial cells. Thus, both STAT3 and ERK1/2 are required for LIF-mediated endothelial differentiation in cardiac stem cells. Collectively, it is proposed that LIF regulates the commitment of cardiac stem cells into the endothelial cell lineage, contributing to neovascularization in the process of tissue remodeling and/or regeneration.

Transposon-mediated insertional mutagenesis revealed the functions of animal cellulose synthase in the ascidian Ciona intestinalis

Tunicates are the only animals that perform cellulose biosynthesis. The tunicate gene for cellulose synthase, Ci-CesA, was likely acquired by horizontal transfer from bacteria and was a key innovation in the evolution of tunicates. Transposon-based mutagenesis in an ascidian, Ciona intestinalis, has generated a mutant, swimming juvenile (sj). Ci-CesA is the gene responsible for the sj mutant, in which a drastic reduction in cellulose was observed in the tunic. Furthermore, during metamorphosis, which in ascidians convert the vertebrate-like larva into a sessile filter feeder, sj showed abnormalities in the order of metamorphic events. In normal larvae, the metamorphic events in the trunk region are initiated after tail resorption. In contrast, sj mutant larvae initiated the metamorphic events in the trunk without tail resorption. Thus, sj larvae show a "swimming juvenile" phenotype, the juvenile-like trunk structure with a complete tail and the ability to swim. It is likely that ascidian cellulose synthase is required for the coordination of the metamorphic events in the trunk and tail in addition to cellulose biosynthesis.