Angiographic no-reflow phenomenon strongly predicts long-term cardiac complications after AMI; these complications are possibly associated with LV remodeling.

Abstract-We recently reported that angiotensin II (Ang II) induced IL-6 mRNA expression in cardiac fibroblasts, which played an important role in Ang II-induced cardiac hypertrophy in paracrine fashion. The present study investigated the regulatory mechanism of Ang II-induced IL-6 gene expression, focusing especially on reactive oxygen species (ROS)-mediated signaling in cardiac fibroblasts. Ang II increased intracellular ROS in cardiac fibroblasts, and the increase was completely inhibited by the AT-1 blocker candesartan and the NADH/NADPH oxidase inhibitor diphenyleneiodonium (DPI). We first confirmed that antioxidant N-acetylcysteine, superoxide scavenger Tiron, and DPI suppressed Ang II-induced IL-6 expression. Because we observed that exogenous H 2 O 2 also increased IL-6 mRNA, the signaling pathways downstream of Ang II and exogenous H 2 O 2 were compared. Ang II, as well as exogenous H 2 O 2 , activated ERK, p38 MAPK, and JNK, which were significantly inhibited by N-acetylcysteine and DPI. In contrast with exogenous H 2 O 2 , however, Ang II did not influence phosphorylation and degradation of IB-␣/␤ or nuclear translocation of p65, nor did it increase NF-B promoter activity. PD98059 and SB203580 inhibited Ang II-induced IL-6 expression. Truncation and mutational analysis of the IL-6 gene promoter showed that CRE was an important cis-element in Ang II-induced IL-6 gene expression. NF-B-binding site was important for the basal expression of IL-6, but was not activated by Ang II. Ang II phosphorylated CREB through the ERK and p38 MAPK pathway in a ROS-sensitive manner. Collectively, these data indicated that Ang II stimulated ROS production via the AT1 receptor and NADH/NADPH oxidase, and that these ROS mediated activation of MAPKs, which culminated in IL-6 gene expression through a CRE-dependent, but not NF-B-dependent, pathway in cardiac fibroblasts. Key Words: angiotensin II Ⅲ interleukin-6 Ⅲ reactive oxygen species Ⅲ mitogen-activated protein kinase Ⅲ cardiac fibroblast C linical, experimental, and genetic data have demonstrated that the renin angiotensin system is linked to the pathogenesis of a variety of cardiac diseases. Expression of angiotensin II (Ang II), the key effector molecule of the renin angiotensin system, is increased under various pathophysiological conditions and stimulates cardiomyocyte hypertrophy and interstitial fibrosis coinciding with accumulation of extracellular matrix. Recent reports had shown that Ang II stimulates membrane-bound NAD(P)H oxidase, which generates reactive oxygen species (ROS) in a variety of nonphagocytic cells. 1 ROS may act as a second messenger that regulates various intracellular signal transduction cascades and the activity of various transcription factors. NF-B and AP-1 are the best characterized transcription factors to be influenced by the cellular oxidation-reduction (redox) state. 2,3 The primary target of activation of NF-B by ROS appears to be the phosphorylation and subsequent degradation of IB. 4 Another well-characterized redox sensitive signali...

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 [ 3 H]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

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.A large number of studies have shown that cytokines share signaling pathways involving activation of protein tyrosine kinases which are required for subsequent cellular responses (1-3). Recent reports revealed that interleukin-6 related cytokines including interleukin-6, leukemia inhibitory factor (LIF), 1 ciliary neurotrophic factor, oncostatin M, and cardiotrophin-1 activate Janus kinase (JAK)/Tyk family kinases by the formation of homodimers or heterodimers of gp130 (4 -7). gp130 functions as a common cytokine signal transducer for the interleukin-6 family, and is reported to lead to cardiac hypertrophy. These signals might be essential in the physiologic regulation of myocardium by these cytokines (8,9). LIF is also a member of multifunctional cytokines, and induces one to one heterodimerization between the LIF receptor and gp130 (10,11). We have recently demonstrated that JAK signal transducer and activator of transcription (STAT) and mitogen-activated protein (MAP) kinase pathways are present at downstream of gp130 in cardiac myocytes and are rapidly activated by LIF both in vivo and in vitro (12).Activation of cell proliferation by several different cytokines has been shown to correlate with the intracellular activation of common protein kinase cascades. This may be explained by the functional pleiotropy and redundancy of cytokine receptor systems (13). It is very intriguing that growth factors (e.g. plateletderived growth factor and angiotensin II) and cytokines work through the JAK/Tyk and MAP kinases and lead to the activation of the same or different sets of signal transduction pathways.It is generally accepted that the tyrosine kinases of growth factor receptors and oncogene products specific...