Acute endocapillary proliferative glomerulonephritis associated with human parvovirus B19 infection.

A 36-year-old female developed acute nephritic syndrome associated with human parvovirus B19 (HPVB19) infection. Laboratory data showed proteinuria, hypocomplementemia, mild pancytopenia, the presence of immunoglobulin (Ig) M and IgG antibodies to HPVB 19 and positive reaction of serum HPVB19 DNA using a polymerase chain reaction (PCR). A renal biopsy showed endocapillary hypercellularity mainly of mononuclear cells with segmental apparent mesangiolytic change; fine granular IgM, IgG and C3 deposits were noted by immunofluorescence microscopy; relatively small electron-dense deposits were observed in the widened subendothelial spaces and the mesangium, and loosening of the mesangial matrix varied from place to place electron microscopically. PCR of HPVB19 DNA in the renal biopsy tissue was positive as well as in the peripheral blood. The histological findings suggested that immune-complex-mediated endocapillary proliferative glomerulonephritis is caused by acute HPVB 19 infection. We discuss the differences from poststreptococcal glomerulonephritis and the possible pathogenesis of acute endocapillary proliferative glomerulonephritis associated with HPVB19 infection.

Right ventricular cardiomyopathy accompanied by protein-losing enteropathy and chylous effusion.

Severe right-side heart failure developed in a 47-year-old Japanese woman who suffered from hypoalbuminemia and a massive right side chylous pleural effusion. She had been diagnosed as having protein-losing enteropathy with right ventricular cardiomyopathy. Autopsy showed congenital anomalies of the lymph ducts and abnormal deposition of fibrous and fatty tissue in the right ventricular myocardium. The clinical and pathological findings are consistent with the nonarrythmogenic form of the arrythmogenic right ventricular dysplasia.

Activation of signal transducer and activator of transcription 3 protects cardiomyocytes from hypoxia/reoxygenation-induced oxidative stress through the upregulation of manganese superoxide dismutase.

BACKGROUND: Mice with cardiac-specific overexpression of signal transducer and activator of transcription 3 (STAT3) are resistant to doxorubicin-induced damage. The STAT3 signal may be involved in the detoxification of reactive oxygen species (ROS). METHODS AND RESULTS: The effects of leukemia inhibitory factor (LIF) or adenovirus-mediated transfection of constitutively activated STAT3 (caSTAT3) on the intracellular ROS formation induced by hypoxia/reoxygenation (H/R) were examined using rat neonatal cardiomyocytes. Either LIF treatment or caSTAT3 significantly suppressed the increase of H/R-induced ROS evaluated by 2',7'-dichlorofluorescin diacetate fluorescence. To assess whether ROS are really involved in H/R-induced cardiomyocyte injury, the amount of creatine phosphokinase in cultured medium was examined. Both LIF treatment and caSTAT3 significantly decreased H/R-induced creatine phosphokinase release. These results indicate that the gp130/STAT3 signal protects H/R-induced cardiomyocyte injury by scavenging ROS generation. To investigate the mechanism of scavenging ROS, the effects of LIF on the induction of antioxidant enzymes were examined. LIF treatment significantly increased the expression of manganese superoxide dismutase (MnSOD) mRNA, whereas the expression of the catalase and glutathione peroxidase genes were unaffected. This induction of MnSOD mRNA expression was completely blocked by adenovirus-mediated transfection of dominant-negative STAT3. Moreover, caSTAT3 augmented MnSOD mRNA and its enzyme activity. In addition, the antisense oligodeoxyribonucleotide to MnSOD significantly inhibited both LIF and caSTAT3-mediated protective effects. CONCLUSIONS: The activation of STAT3 induces a protective effect on H/R-induced cardiomyocyte damage, mainly by inducting MnSOD. The STAT3-mediated signal is proposed as a therapeutical target of ROS-induced cardiomyocyte injury.

Bone morphogenetic protein-2 inhibits serum deprivation-induced apoptosis of neonatal cardiac myocytes through activation of the Smad1 pathway.

Bone morphogenetic protein (BMP)-2 has been shown to induce ectopic expression of cardiac transcription factors and beating cardiomyocytes in non-precardiac mesodermal cells, suggesting that BMP-2 is an inductive signaling molecule that participates in cardiac development. However, direct evidence of the effects of BMP-2 on cardiac myocytes has not been reported. To examine the role of BMP-2 and its receptors, we studied the ability of BMP-2 to promote survival of isolated neonatal rat cardiac myocytes. BMP receptors IA, IB, and II and activin receptor I were found to be expressed in myocytes, and BMP-2 phosphorylated Smad1 and p38 MAPK. Interestingly, BMP-2 promoted survival and inhibited apoptosis of serum-deprived myocytes, although it did not strongly induce hypertrophic growth. To explore the mechanisms for this protective effect, an adenovirus-based vector system was used. Similar to BMP-2, Smad1 promoted survival that was repressed by Smad6. Moreover, BMP-2 and Smad1 enhanced the expression of the anti-apoptotic molecule Bcl-x(L). Antisense oligonucleotides to bcl-x(L) attenuated the survival effected by BMP-2. Overall, our findings suggest that BMP-2 prevents apoptosis of myocytes by induction of Bcl-x(L) via a Smad1 pathway and might be a novel survival factor without any hypertrophic effect on myocytes.

Glycoprotein 130 regulates cardiac myocyte survival in doxorubicin-induced apoptosis through phosphatidylinositol 3-kinase/Akt phosphorylation and Bcl-xL/caspase-3 interaction.

BACKGROUND: We recently reported that the activation of glycoprotein (gp) 130 by leukemia inhibitory factor (LIF) upregulates Bcl-xL and exerts antiapoptotic effects in cardiac myocytes. In addition, LIF induces activation of phosphatidylinositol (PI) 3-kinase and Akt, which are known to be required for cell survival. However, their regulatory roles in cell death remain unknown. METHODS AND RESULTS: We investigated the fate of these proteins and the cytoprotective effects of LIF on doxorubicin (DOX)-induced apoptosis in cultured neonatal rat cardiac myocytes. Myocyte apoptosis increased significantly in DOX-treated cells but was significantly reduced by LIF pretreatment. The kinase activities of PI 3-kinase and Akt declined below basal levels but were partially recovered with LIF. Moreover, DOX-induced caspase-3 activation and decrease in Bcl-xL abundance are completely inhibited by LIF and caspase inhibitor. LIF phosphorylates Bad through PI 3-kinase and reduces the heterodimerization of Bad with Bcl-xL. Adenovirus transfer of the constitutively active form of Akt to cardiac myocytes restored cardiac myocyte survival after DOX treatment. Conversely, the dominant-negative form of Akt inhibited LIF-induced increase in cell viability and suppression of caspase-9 activation. CONCLUSIONS: Activation of gp130 inhibits DOX-induced cell death in cardiac myocytes, resulting in the restoration of PI 3-kinase/Akt activities and in the inactivation of caspase-3, leading to facilitation of the protective function of Bcl-xL.

gp130-Dependent signalling pathway is not enhanced in gp130 transgenic heart after LIF stimulation.

Activation of gp130 transduces a hypertrophic signal in the heart, but it is not clear whether signalling through gp130 is enhanced when gp130 is overexpressed in vivo. We generated gp130 transgenic mice (TG) and examined the activation of signalling pathways downstream of gp130 in the hearts. The tyrosine phosphorylation of gp130 was enhanced, the phosphorylation of STAT3 and ERK (extracellular signal regulated kinase) 1/2 was increased and induction of the beta-myosin heavy chain (MHC) gene was observed in TG hearts without significant phenotypic changes. Intravenous administration of leukaemia inhibitory factor (LIF) induced tyrosine phosphorylation of STAT3 and ERK 1/2 and expression of c-fos and beta-MHC mRNAs in wild-type littermates' (WT) hearts. However, enhancement of STAT3 and ERK 1/2 phosphorylation or augmented mRNA expressions was not observed in TG hearts after LIF stimulation. Next, STAT-induced STAT inhibitor (SSI) mRNA expression was examined. The expression of SSI-1, SSI-2, and SSI-3 mRNAs was significantly augmented in TG hearts after LIF stimulation. These results indicate that overexpressed gp130 does not always enhance downstream signals in the hearts and suggest that the SSI family plays a role in the regulation of the gp130-dependent signalling pathway in the hearts.

Activation of JAK/STAT pathway transduces cytoprotective signal in rat acute myocardial infarction.

OBJECTIVES: We reported that the activation of gp130 transduced hypertrophic and cytoprotective signals via Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in cardiac myocytes. Recent in vivo experiments have demonstrated that the JAK/STAT pathway is activated in acute pressure overload hearts. The present study was designed to examine whether the JAK/STAT pathway is also activated in acute myocardial infarction (AMI) and to determine its pathophysiological roles in ischemic heart disease. METHODS AND RESULTS: AMI model was generated by the ligation of proximal left anterior descending coronary artery of male Wistar rat. They were sacrificed at various time points ranging from 1 to 24 h after coronary ligation and their hearts were examined. Tyrosine phosphorylation of STAT3 was observed in the myocardium obtained from both the ischemic area and the healthy border area adjacent to the infarcted area. The AMI rats were next randomly assigned to two groups, one with coronary ligation only (group M), and the other with coronary ligation with AG-490 treatment (1 mg/kg i.v., every 4 h), a specific JAK2 inhibitor (group A). In group A, phosphorylation of STAT3 was significantly suppressed and caspase-3 activity and Bax expression were significantly increased in the myocardium after AMI. In group M, few apoptotic myocytes were identified in the border area by means of TUNEL assay. However, a significant increase in apoptotic cells was observed in group A. CONCLUSIONS: Administration of JAK2 inhibitor resulted in deterioration of myocardial viability in AMI hearts. The JAK/STAT pathway is activated in AMI myocardium and plays a pivotal role in cytoprotective signaling.

Isolation and characterization of the murine cardiotrophin-1 gene: expression and norepinephrine-induced transcriptional activation.

Cardiotrophin-1 (CT-1) is a novel cytokine capable of inducing hypertrophy in cardiac myocytes and belongs to the interleukin-6 family that exert their biological effects through gp130. To clarify the involvement and pathophysiological role of CT-1 in myocardial diseases, it is important to characterize the regulation of CT-1 gene expression. In this study, we isolated and characterized the mouse CT-1 gene and studied the expression of CT-1 mRNA under norepinephrine (NE) stimulation. The mouse CT-1 gene constitutes 5.4 kilobases (kb) in length and consists of three exons and two introns. When nucleotide sequences of the coding regions of exons were compared with those of human, exon 1, 2 and 3 share 96%, 84% and 81% homology, respectively. The 2.2 kb of 5; flanking lesion of the mouse CT-1 gene contains a variety of transcription factor binding motif (e.g. CREB, MyoD, NF-IL6, Nkx2.5, GATA). Fluorescent in situ hybridization (FISH) analysis demonstrated that the mouse CT-1 gene was located on chromosome 7F3. The expression of CT-1 mRNA in cardiac myocytes was markedly augmented by NE stimulation, both in vivo and in vitro. Promoter analysis using deletion constructs of the CT-1 gene indicated that the NE responsive element located between -2174/-1540 and this region contained the cAMP responsive element (CRE). Electrophoretic gel mobility shift assays showed enhanced binding activity to the CRE motif in the nuclear extracts from NE-stimulated cardiac myocytes. These studies indicate that CT-1 is abundantly expressed in the heart and that the CRE is a possible cis -acting element of the CT-1 gene under NE-stimulation. These data suggest that the CT-1 gene expression is regulated, at least partially, by transcriptional machinery.

Detection of occult tumor cells in peripheral blood from patients with small cell lung cancer by reverse transcriptase-polymerase chain reaction.

The reverse transcriptase-polymerase chain reaction (RT-PCR) of tumor-specific or -associated genes is a sensitive assay for detecting a minimal number of tumor cells in peripheral blood (PB) or bone marrow (BM). In this study, we determined whether mRNA of bombesin receptors is detectable in PB or peripheral blood progenitor cell (PBPC) samples from patients with small cell lung cancer. Among three bombesin-like peptide receptors, we used the neuromedin B receptor (NMB-R) gene as a target, because of the most frequent expression on SCLC cell lines. The lower limit of detection was one tumor cell in one million normal PB cells and there was no detection in normal PB or BM cells unlike a cytokeratin 19 gene. The NMB-R gene was detected in 14 (31.8%) of 44 PB samples from patients with SCLC at diagnosis and 2 (15.4%) of 13 samples of PBPC collected during a recovery phase after chemotherapy followed by administration of G-CSF (filgrastim). At diagnosis, patients whose PB was positive for the NMB-R gene had a significantly shorter survival than those who were negative. Our observation suggests that this assay may be useful in diagnosing metastatic disease and monitoring minimal residual disease in patients with SCLC.

Signal transducer and activator of transcription 3 is required for glycoprotein 130-mediated induction of vascular endothelial growth factor in cardiac myocytes.

Activation of glycoprotein (gp) 130 transduces hypertrophic and cytoprotective signals in cardiac myocytes. In the present study, we have demonstrated that signals through gp130 increase the expression of vascular endothelial growth factor (VEGF) in cardiac myocytes via the signal transducer and activator of transcription (STAT) 3 pathway. After activation of gp130 with leukemia inhibitory factor (LIF), expression of VEGF mRNA rapidly increased with a peak at 3 h in cultured cardiac myocytes. Cardiotrophin-1 also enhanced VEGF mRNA expression in a dose-dependent manner. VEGF protein production and secretion to the medium were also enhanced by LIF and cardiotrophin-1 but not by interleukin-6. Adenovirus transfer of the dominant-negative form of STAT3 to cultured cardiac myocytes inhibited induction of VEGF expression induced by LIF, but neither PD98059 nor wortmannin was affected. In murine hearts, intravenous administration of LIF augmented expression of VEGF mRNA; however, the hearts of transgenic mice overexpressing dominant-negative STAT3 showed reduced expression of VEGF mRNA that was not induced after LIF stimulation. These data provide the first evidence that a STAT family protein functions as a regulator of angiogenic growth factors and suggest that gp130/STAT signaling in cardiac myocytes can control vessel growth during cardiac remodeling.

Signal transducer and activator of transcription 3 in the heart transduces not only a hypertrophic signal but a protective signal against doxorubicin-induced cardiomyopathy.

The signal transducer and activator of transcription (STAT) 3, a transcriptional factor downstream of several cytokines, is activated by Janus kinase families and plays a pivotal role in cardiac hypertrophy through gp130. To determine the physiological significance of STAT3 in vivo, transgenic mice with cardiac-specific overexpression of the Stat3 gene (STAT3-TG) were generated. STAT3-TG manifested myocardial hypertrophy at 12 wk of age with increased expression of the atrial natriuretic factor (ANF), beta-myosin heavy chain (MHC), and cardiotrophin (CT)-1 genes. The animals were injected i.p. with 15 mg/kg doxorubicin (Dox), an antineoplastic drug with restricted use because of its cardiotoxicity. The survival rates after 10 days were 25% (5/20) for control littermates (WT), but 80% (16/20) for STAT3-TG (P < 0.01). WT showed increased expression of beta-MHC and ANF mRNAs in the hearts 1 day after Dox treatment; this expression peaked at 3 days, suggesting that the WT suffered from congestive heart failure. Although the expression of these mRNAs was elevated in STAT3-TG hearts before Dox treatment, no additional increase was observed after the treatment. Dox administration significantly reduced the expression of the cardiac alpha-actin and Stat3 genes in WT hearts but not in STAT3-TG. These results provide direct evidence that STAT3 transduces not only a hypertrophic signal but also a protective signal against Dox-induced cardiomyopathy by inhibiting reduction of cardiac contractile genes and inducing cardiac protective factors.

Hypoxic stress induces cardiotrophin-1 expression in cardiac myocytes.

Cardiotrophin-1 (CT-1), a novel cytokine that belongs to the interleukin-6 cytokine family, activates gp130 dependent signaling pathway to transduce hypertrophic and cytoprotective signals in cardiac myocytes. To investigate the pathophysiological significance of CT-1 in myocardial disease, the expression of CT-1 was examined after hypoxic stimulation in cardiac myocytes. Highly expressed CT-1 mRNA was observed in embryonic and adult hearts by RNase protection assay. Cardiac myocytes subjected to hypoxic stimulation augmented CT-1 mRNA expression. Although CT-1 mRNA was expressed to a higher extent in non-myocardial cells, the expression was not affected with the stimulation. Conditioned medium from cultured cardiac myocytes presented the ability to tyrosine phosphorylate STAT3 through gp130 and that was further augmented with hypoxic conditioned medium. These results demonstrated for the first time that CT-1 expression is augmented after hypoxic stimulation and hypoxic conditioned medium presented enhanced ability to activate STAT3 in cardiac myocytes. CT-1 might play an important role in the pathogenesis of ischemic heart disease.

Induction of interleukin (IL)-6 by hypoxia is mediated by nuclear factor (NF)-kappa B and NF-IL6 in cardiac myocytes.

OBJECTIVES: We have previously reported that interleukin (IL)-6 is induced by hypoxic stimulation in cardiac myocytes. In the present study, we examined the induction of potent transcription factors of IL-6, nuclear factor (NF)-kappa B and NF-IL6, in cardiac myocytes subjected to hypoxia. METHODS: Five different lengths of IL-6 promoter-luciferase reporter plasmids and three mutant plasmids, in which the binding sites of NF-kappa B and/or NF-IL6 were disrupted, were transfected into neonatal rat cardiac myocytes. Luciferase activities after hypoxic stimulation were measured. Electrophoretic mobility shift assays were performed using oligonucleotides containing the binding site for NF-kappa B or NF-IL6 as a probe. RESULTS: Hypoxic stimulation for 4 h increased luciferase activity by 5.7 fold in -179/+12-luciferase reporter plasmid, whereas no significant increase was observed in -60/+12-luciferase plasmid. Decrease in luciferase activity was more prominent when the NF-kappa B binding site was disrupted rather than when the NF-IL6 binding site was disrupted. Moreover, when both sites were disrupted, luciferase activity increased only by 1.5 fold. Electrophoretic mobility shift assays demonstrated enhanced binding activity to oligonucleotides containing the NF-kappa B binding site in hypoxic cardiac myocytes, which displayed a supershift with antibody to its subunit, p50 or p65. The binding activity to the NF-IL6 probe also enhanced and displayed a supershift with antibody to NF-IL6. CONCLUSIONS: Although hypoxic stimulation induced NF-kappa B and NF-IL6 in cardiac myocytes, NF-kappa B may be the primary positive regulator of transcriptional activation of the IL-6 gene in the context of hypoxia.

Activation of gp130 transduces hypertrophic signals via STAT3 in cardiac myocytes.

BACKGROUND: gp130, a signal transducer of the IL-6-related cytokines, is expressed ubiquitously, including in the heart. The activation of gp130 in cardiac myocytes was reported to induce myocardial hypertrophy. The downstream side of gp130 consists of two distinct pathways in cardiac myocytes, one a Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, the other a mitogen-activated protein kinase (MAPK) pathway. In the present study, we examined whether the JAK/STAT pathway, especially the STAT3-mediated pathway, plays a critical role in gp130-dependent myocardial hypertrophy by transfecting wild-type and mutated-type STAT3 cDNA to cardiac myocytes. METHODS AND RESULTS: We constructed three kinds of replication-defective adenovirus vectors carrying wild-type (AD/WT) or mutated-type (AD/DN) STAT3 cDNA or adenovirus vector itself (AD). Cultured murine cardiac myocytes infected with adenovirus were stimulated with leukemia inhibitory factor (LIF), and the expression of c-fos and atrial natriuretic factor (ANF) mRNAs and [3H]leucine incorporation were examined. There were no significant differences in MAPK activity among the three groups. Compared with AD-transfected cardiac myocytes, induction of c-fos and ANF mRNAs and protein synthesis after LIF stimulation were significantly augmented in AD/WT-transfected cells. In contrast, induction of c-fos and ANF mRNA expression and protein synthesis were attenuated after LIF stimulation in cardiac myocytes transfected with AD/DN. CONCLUSIONS: These results suggest that the STAT3-dependent signaling pathway downstream of gp 130 promotes cardiac myocyte hypertrophy under stimulation with LIF.

Activation of phosphatidylinositol 3-kinase through glycoprotein 130 induces protein kinase B and p70 S6 kinase phosphorylation in cardiac myocytes.

Phosphatidylinositol (PI) 3-kinase is known to be activated by cytokine stimulation through different types of receptors to transduce intracellular responses. We have previously reported that leukemia inhibitory factor (LIF) induces the activation of Janus kinase signal transducer and activator of transcription (JAK-STAT) and mitogen-activated protein (MAP) kinase pathways through glycoprotein (gp) 130 in cardiac myocytes. However, whether PI 3-kinase is involved in regulation of gp130 signaling and the activation mechanisms by which it associates with other tyrosine-phosphorylated proteins remain unknown. We found that LIF induced the activation of PI 3-kinase in cardiac myocytes. Moreover, JAK1 binds to PI 3-kinase, and LIF stimulation increases the PI 3-kinase activity in JAK1 immunoprecipitates. Activation of MAP kinase and protein kinase B by LIF was attenuated by wortmannin. LIF-induced p70 S6 kinase activation, protein synthesis, and c-fos mRNA expression were inhibited by wortmannin and rapamycin. Both inhibitors failed to appreciably affect the phosphorylation of STAT3. In conclusion, PI 3-kinase is activated with LIF in cardiac myocytes, and JAK1 is found to associate with this enzyme. PI 3-kinase provides a crucial link between gp130, MAP kinase, protein kinase B, and p70 S6 kinase in cardiac myocytes.

Angiotensin II interferes with leukemia inhibitory factor-induced STAT3 activation in cardiac myocytes.

Recently, we reported that leukemia inhibitory factor (LIF), a member of the interleukin (IL)-6 cytokine family, transduced hypertrophic and cytoprotective signals via Januas Kinase-signal transducer and activator of transcription (JAK-STAT) pathway in cardiac myocytes. Angiotensin II (AII) is also known to activate STATs and reported to induced apoptosis in adult rat ventricular myocytes. In the present study, we investigated potential interactions between gp130 dependent and AII signaling pathways, by examining AII regulation of LIF-induced anti-apoptotic effect and STAT3 activation in cardiac myocytes. Although LIF attenuated the DNA fragmentation induced by serum depletion, AII augmented the DNA fragmentation in cultured neonatal rat cardiac myocytes. Furthermore, LIF-mediated cytoprotective effect was inhibited by AII pretreatment. LIF rapidly and transiently tyrosine phosphorylated STAT3 in cardiac myocytes which was not observed by AII. AII pretreatment inhibited LIF-induced phosphorylation of STAT3 in a dose dependent manner. This inhibitory effect of AII on STAT3 activation was blocked by the AII type I (AT1) receptor antagonist CV11974. These results demonstrate that negative crosstalk between gp130 and AT1 receptor dependent signaling exists in cardiac myocytes. This crosstalk may contribute to the modulation of pathophysiological process in myocardial disease.

Signals through gp130 upregulate bcl-x gene expression via STAT1-binding cis-element in cardiac myocytes.

We described recently the activation of the Janus kinasesignal transducer and activator of transcription (JakSTAT) and mitogen-activated protein (MAP) kinase pathways by leukemia inhibitory factor (LIF) through gp130, a signal transducer of IL-6-related cytokines, that transduces hypertrophic signals in cardiac myocytes. In addition, stimulation of gp130 by IL-6-related cytokines is known to exert a cytoprotective effect. In the present study, we investigated the possibility that activation of gp130 initiates activation of the cytoprotective genes in cardiac myocytes. Incubation of cardiac myocytes with LIF induced the expression of bcl-x, and the isoform that was induced by LIF was identified as bcl-xL. Induction of bcl-xL protein was also identified by Western blotting. Antisense oligonucleotide against bcl-x mRNA inhibited protective effect of LIF accompanied with the reduction in bclxL protein. We constructed bcl-x promoter-luciferase reporter gene plasmids (-639/+10- or -161/+10-luciferase), and transfected them to cardiac myocytes. LIF stimulation increased the luciferase activity of -639/+10-luciferase plasmids. Although -161/+10-luciferase plasmids presented comparable responsiveness to LIF, the basal transcription level was impaired. The LIF-responsive cis-element was localized to a DNA fragment (positions -161 to +10) that contains an interferon-gamma activation site (GAS) motif (GGA) at position -41 of the bcl-x gene promoter. This motif bound to STAT1, not to STAT3, and site-directed mutagenesis revealed that this motif was essential for LIF-responsive promoter activity. These data suggest that LIF induces bcl-x mRNA via STAT1 binding cis-element in cardiac myocytes, presenting cytoprotective effect.