Janus kinase-2 signaling mediates apoptosis in rat cardiomyocytes

Insight on the meat quality and carbonylation profile of breast muscle of broilers in response to chronic heat stress: A proteomic research

This study was conducted to explore the influences of carbonyl modification on proteins within the breast muscle of heat-stressed broilers and their correlations to decreased meat quality. The results showed that birds that suffered from heat stress had higher lightness, drip loss, shear force value, and hardness, and lower redness and springiness of breast meat than those under normal control and pair fed treatments. Proteomic analysis identified a total of 921 differentially carbonylated sites, which were allocated to 419 proteins. The modified sites included Lys, Pro, Arg, Trp, Cys, His, and Met. Seven motif sequences were detected, where five motifs neighbored Lys and two neighbored Pro. The differentially carbonylated proteins in heat-stressed birds mainly participated in the glycolytic process, collagen fibril organization, calcium homeostasis, and apoptosis. This study provided a unique landscape of the muscular carbonyl modification rule and unraveled the potential impact of carbonylated protein on meat quality.

Molecular Mechanisms of Action of Emodin: As an Anti-Cardiovascular Disease Drug

Emodin is a natural occurring anthraquinone derivative isolated from roots and barks of numerous plants, molds, and lichens. It is found to be an active ingredient in different Chinese herbs including Rheum palmatum and Polygonam multiflorum, and it is a pleiotropic molecule with diuretic, vasorelaxant, anti-bacterial, anti-viral, anti-ulcerogenic, anti-inflammatory, and anti-cancer effects. Moreover, emodin has also been shown to have a wide activity of anti-cardiovascular diseases. It is mainly involved in multiple molecular targets such as inflammatory, anti-apoptosis, anti-hypertrophy, anti-fibrosis, anti-oxidative damage, abnormal, and excessive proliferation of smooth muscle cells in cardiovascular diseases. As a new type of cardiovascular disease treatment drug, emodin has broad application prospects. However, a large amount of evidences detailing the effect of emodin on many signaling pathways and cellular functions in cardiovascular disease, the overall understanding of its mechanisms of action remains elusive. In addition, by describing the evidence of the effects of emodin in detail, the toxicity and poor oral bioavailability of mice have been continuously discovered. This review aims to describe a timely overview of emodin related to the treatment of cardiovascular disease. The emphasis is to summarize the pharmacological effects of emodin as an anti-cardiovascular drug, as well as the targets and its potential mechanisms. Furthermore, the treatment of emodin compared with conventional cardiovascular drugs or target inhibitors, the toxicity, pharmacokinetics and derivatives of emodin were discussed.

Lysine inhibits apoptosis in satellite cells to govern skeletal muscle growth via the JAK2-STAT3 pathway

Apoptosis is programmed cell death that can be stimulated by external stress or nutrition restrictions. However, the precise mechanism of apoptosis in skeletal muscle remains unknown. The objective of this study was to investigate whether apoptosis could be regulated by lysine (Lys) supplementation and the potential mechanism. In this study, an isobaric tag for relative and absolute quantification (iTRAQ) proteomics analysis of the longissimus dorsi muscle from piglets showed that the Janus family tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT) pathway was involved in Lys deficiency-induced apoptosis and inhibited skeletal muscle growth. Meanwhile, western blotting results demonstrated that Lys deficiency led to apoptosis in the longissimus dorsi muscle with the JAK2-STAT3 pathway inhibition. Interestingly, apoptosis was suppressed, and the JAK2-STAT3 pathway was reactivated after Lys re-supplementation. In addition, the results showed that Lys deficiency-induced apoptosis in satellite cells (SCs) was mediated by the JAK2-STAT3 pathway inhibition. Moreover, the JAK2-STAT3 pathway was reactivated by Lys re-supplementation and suppressed cell apoptosis, and this effect was inhibited after treatment with Tyrphostin B42 (AG 490). In conclusion, we found that Lys inhibits apoptosis in SCs to govern skeletal muscle growth via the JAK2-STAT3 pathway.

Retracted: Emodin protects H9c2 cells against hypoxia-induced injury via regulation of miR-26a/survivin and the JAK1/STAT3 pathway

BACKGROUND/AIM

Congenital heart disease (CHD) is a catastrophic disease. Emodin possesses biological properties in protecting against some diseases. Our study investigated to explore the effects of emodin on hypoxia-stimulated cardiomyocytes, which mimicked CHD in vitro.

METHODS

H9c2 cells were stimulated with hypoxia and then the cells were treated with or without emodin, and/or transfected with miR-26a mimic, pcDNA-survivin and their corresponding negative control (NC). Cell viability and cell apoptosis were detected by Cell Counting kit-8 assay and flow cytometry, respectively. In addition, the expression of apoptotic proteins, Janus kinase 1 (JNK)/signal transducer and activator of transcription 3 (STAT3) pathway factors, and survivin were evaluated by using Western blot analysis. The expression of miR-26a was analyzed by quantitative real time polymerase chain reaction (qRT-PCR). Moreover, the target of miR-26a was verified by using a luciferase report assay.

RESULTS

Hypoxia significantly decreased cell viability and increased cell apoptosis, and the accumulated levels of cleaved caspase-3 and cleaved-caspase-9 were upregulated by hypoxia compared with the control. However, emodin administration led to the opposite result. A further result showed that emodin increased the phosphorylation of JNK/STAT3 pathway-related proteins and the pathway inhibitor AG490 impaired the protective effects of emodin on hypoxia-induced injury. In addition, emodin negatively regulated the miR-26a expression, and overexpression of miR-26a enhanced cell apoptosis and upregulated the expression of cleaved-caspase-3 and cleaved-caspase-9 compared with the NC. Moreover, emodin statistically upregulated the expression of survivin, and overexpression of miR-26a decreased the expression of survivin. The luciferase of miR-26a overexpression was decreased in the wild type of the survivin group.

CONCLUSION

Emodin protects hypoxia-induced cell injury as evidenced by increasing cell viability and decreasing apoptosis through downregulation of miR-26a as well as activation of the JNK/STAT3 pathway.

Myocardial Hypertrophic Remodeling and Impaired Left Ventricular Function in Mice with a Cardiac-Specific Deletion of Janus Kinase 2

The Janus kinase (JAK) system is involved in numerous cell signaling processes and is highly expressed in cardiac tissue. The JAK isoform JAK2 is activated by numerous factors known to influence cardiac function and pathologic conditions. However, although abundant, the role of JAK2 in the regulation or maintenance of cardiac homeostasis remains poorly understood. Using the Cre-loxP system, we generated a cardiac-specific deletion of Jak2 in the mouse to assess the effect on cardiac function with animals followed up for a 4-month period after birth. These animals had marked mortality during this period, although at 4 months mortality in male mice (47%) was substantially higher compared with female mice (30%). Both male and female cardiac Jak2-deleted mice had hypertrophy, dilated cardiomyopathy, and severe left ventricular dysfunction, including a marked reduction in ejection fractions as assessed by serial echocardiography, although the responses in females were somewhat less severe. Defective cardiac function was associated with altered protein levels of sarcoplasmic reticulum calcium-regulatory proteins particularly in hearts from male mice that had depressed levels of SERCA2 and phosphorylated phospholamban. In contrast, SERCA2 was unchanged in hearts of female mice, whereas phosphorylated phospholamban was increased. Our findings suggest that cardiac JAK2 is critical for maintaining normal heart function, and its ablation produces a severe pathologic phenotype composed of myocardial remodeling, heart failure, and pronounced mortality.

Redox regulation of Janus kinase: The elephant in the room

The redox regulation of Janus kinases (JAKs) is a complex subject. Due to other redox-sensitive kinases in the kinome, redox-sensitive phosphatases, and cellular antioxidant systems and reactive oxygen species (ROS) production systems, the net biological outcomes of oxidative stress on JAK-dependent signal transduction vary according to the specific biological system examined. This review begins with a discussion of the biochemical evidence for a cysteine-based redox switch in the catalytic domain of JAKs, proceeds to consider direct and indirect regulatory mechanisms involved in biological experiments, and ends with a discussion of the role(s) of redox regulation of JAKs in various diseases.

Ischemic postconditioning during reperfusion attenuates intestinal injury and mucosal cell apoptosis by inhibiting JAK/STAT signaling activation

The present study attempts to evaluate the role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling in intestinal ischemia/reperfusion (I/R)-induced intestinal injury and whether immediate ischemic postconditioning ameliorates intestinal injury via attenuation of intestinal mucosal apoptosis subsequent to inhibiting JAK/STAT signaling activation. Anesthetized adult male Sprague-Dawley rats were subjected to superior mesenteric artery occlusion consisting of 60 min of ischemia and 2 h of reperfusion; sham laparotomy served as controls. Animals received either subcutaneous administration of JAK2 inhibitor (AG490, 8 mg/kg) or STAT inhibitor (rapamycin, 0.4 mg/kg) 30 min before ischemia. Ischemic postconditioning was performed by three cycles of 30-s reperfusion and 30-s ischemia initiated immediately upon reperfusion. It was found that intestinal I/R resulted in conspicuous intestinal injury evidenced by significant increases in Chiu's score, lactic acid, and diamine oxidase activity, accompanied with increases in plasma levels of 15-F2t-isoprostane, endothelin 1, and thromboxane B2, as well as increase in the intestinal tissue myeloperoxidase activity. Meanwhile, the apoptotic index and cleaved caspase 3, phosphorylated JAK2, phosphorylated STAT1, and phosphorylated STAT3 expression were significantly enhanced versus sham control. Both ischemic postconditioning and pretreatment with AG490 or rapamycin significantly attenuated all the above changes. These results indicate that JAK/STAT pathway activation plays a critical role in I/R-induced intestinal injury, which is associated with increased oxidative stress, neutrophil accumulation, intestinal mucosal apoptosis, and microcirculation disturbance. Ischemic postconditioning mediates attenuation of intestinal I/R injury, and cell apoptosis may be attributable to the JAK/STAT signaling inhibition.

Hypoxia-induced SOCS3 is limiting STAT3 phosphorylation and NF-κB activation in congenital heart disease

Suppressor of cytokine signaling 3 (SOCS3) is a critical attenuator of the JAK-STAT signaling pathway, and it is involved in mediating the intensity and duration of STAT3 activation in the process of myocardial protection. Nuclear factor-κB (NF-κB) has emerged as a decisive transcription factor in cardiac myocyte compensatory responses to stress that enhance survival. However, the expression, activation and regulation of this signaling molecule in response to hypoxic stress have not been elucidated. We investigated 40 infants with cyanotic or acyanotic cardiac defects, as well as H9c2 embryonic rat cardiomyocytes, to examine the effect of hypoxia on the expression or activation of SOCS3, STAT3 and NF-κB in vivo and in vitro. We found an increase in endogenous cardiac SOCS3, p-STAT3 and AC-RelA activation in the myocardium of infants with cyanotic cardiac defects. In hypoxic cultivated H9c2 cells, SOCS3, STAT3 and AC-RelA activity slowly increased and then reached a stable expression. We evaluated the interaction of SOCS3 with STAT3 and NF-κB by transfecting the SOCS3 plasmid to hypoxic cultured H9c2 cells. Forced expression of SOCS3suppressed tyrosine phosphorylation of STAT3 and transcription of the C-myc and interleukin-6 genes. AC-RelA activation was also suppressed by over expression of SOCS3. These findings suggest that the mechanism of a positive transactivation loop that maintains higher levels of NF-κB and p-STAT3 and the negative feedback factor SOCS3, which maintains balanced NF-κB and p-STAT3 activities, is important in the process of myocardial adaptation to chronic hypoxia. SOCS3 is a rapid hypoxia inducible gene and acts to inhibit activation of the cellular signaling pathway in a classical negative feedback loop. Upregulated SOCS3 might play an important role in cardiocytes during chronic hypoxia as SOCS3 regulates cell signaling crosstalking between NF-κB and p-STAT3 under stressful conditions.

Hypoxic preconditioning suppresses group III secreted phospholipase A2-induced apoptosis via JAK2-STAT3 activation in cortical neurons

Our previous studies show that group III secreted phospholipases A(2) (sPLA(2)s III) induces extensive neuronal apoptosis in brain cortical cultures. However, the molecular mechanisms underlying sPLA(2) III-induced neuronal injury/death are still unknown. Also it is not clear whether hypoxic pre-conditioning (HPC) is able to protect neurons from the sPLA(2) III insult. In this report, we demonstrate that sPLA(2) III significantly decreased production of Bcl-xl and the ratio of Bcl-xl/Bax, and increased expression of Bax, cleaved caspase 3, and cleaved alpha-Fodrin in primary neuronal culture. HPC prevented the sPLA(2) III-induced decreases in production of Bcl-xl and the ratio of Bcl-xl/Bax, and increases in expression of Bax, cleaved caspase 3, and alpha-Fodrin. However, the HPC-produced neuronal protection was eliminated or attenuated by AG490, rapamycin, and STAT3 shRNA. Our results suggest that sPLA(2) III-induced neuronal apoptosis is likely because of its alterations in expression and activity of Bcl-xl, Bax, caspase 3, and its target gene fodrin; and that HPC-produced neuroprotection against the sPLA(2) III toxicity is mediated via JAK-STAT signal pathways that regulate the expression of Bcl-xl, Bax, and cleaved caspase 3 in cultured cortical neurons.

Blockade of Janus kinase-2 signaling ameliorates mouse liver damage due to ischemia and reperfusion

Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling is one of the major pathways for cytokine signal transduction. However, the role of the JAK/STAT pathway in liver ischemia/reperfusion is not clear. This study focuses on Janus kinase-2 (JAK2), which functions upstream of signal transducer and activator of transcription 1 (STAT1) in JAK/STAT, and its role in the mechanism of liver ischemia/reperfusion injury (IRI). Partial warm ischemia was produced in the hepatic lobes of C57BL/6 mice for 90 minutes, and this was followed by 6 hours of reperfusion. Mice were treated with a JAK2 inhibitor (tyrphostin AG490; 40 mg/kg intraperitoneally) or vehicle 60 minutes prior to ischemic insult. JAK2 blockade resulted in a significant reduction of hepatocyte apoptosis and liver injury. Macrophage and neutrophil infiltration, as assessed by immunohistochemistry, was markedly decreased in AG490-treated livers in comparison with controls. The expression of pro-inflammatory cytokines [tumor necrosis factor alpha, interleukin 6 (IL-6), and IL-1beta] and chemokines [chemokine (C-X-C motif) ligand 10 (CXCL-10) and CXCL-2] was also significantly reduced in the AG490-treated group in comparison with controls. AG490-treated livers showed fewer cells positive for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and reduced cleaved caspase-3 protein expression in parallel with increased B-cell lymphoma extra large expression. We employed AG490 (75 mM) in primary bone marrow-derived macrophage (BMM) and hepatoma cell (CRL1830) cultures, which were both stimulated with lipopolysaccharide (LPS; 10 ng/mL). In BMM cultures, AG490 depressed otherwise LPS-induced pro-inflammatory gene expression programs (IL-6, IL-12p40, IL-1beta, CXCL-10, and inducible nitric oxide synthase). In hepatoma cells, AG490 reduced cleaved caspase-3 expression. Moreover, JAK2 blockade inhibited STAT1 and STAT3 phosphorylation. This is the first report documenting that JAK2 signaling is essential in the pathophysiology of liver IRI, as its selective blockage ameliorated the disease process and protected livers from inflammation and apoptosis.

Biological response of osteosarcoma cells to size-controlled nanostructured hydroxyapatite

Osteosarcoma is a primary malignant bone tumor, most prevalent in children and adolescents, and is usually highly aggressive and eventually lethal. Despite multimodal therapies, there is no effective approach to treat this malignant disease. In this study, we observed the biological response of osteosarcoma cells to two kinds of hydroxyapatite nanoparticles (Nano HA), NanoHA-S and NanoHA-L. These nanospheres have the same crystallinity (phase) and morphology, but they differ in size. Cells treated with two kinds of Nano HA were inhibited and mainly led to apoptotic cell death. Caspase-9-dependent intrinsic apoptotic pathway plays a role. It was interesting that the suppression and the apoptosis of osteosarcoma cells was directly related to the size of nanoparticles and that the larger-sized Nano HA exhibited more effectiveness than the smaller one. This in vitro study suggested the potential of size-controlled calcium phosphate nanoparticles for use in therapeutic replacement and reconstruction of bone merits after osteosarcoma extraction.

JAK redux: a second look at the regulation and role of JAKs in the heart

A number of type 1 receptor cytokine family members protect the heart from acute and chronic oxidative stress. This protection involves activation of two intracellular signaling cascades: the reperfusion injury salvage kinase (RISK) pathway, which entails activation of phosphatidylinositol 3-kinase (PI3-kinase) and ERK1/2, and JAK-STAT signaling, which involves activation of transcription factor signal transducer and activator of transcription 3 (STAT3). Obligatory for activation of both RISK and STAT3 by nearly all of these cytokines are the kinases JAK1 and JAK2. Yet surprisingly little is known about how JAK1 and JAK2 are regulated in the heart or how they couple to PI3-kinase activation. Although the JAKs are linked to antioxidative stress programs in the heart, we recently reported that these kinases are inhibited by oxidative stress in cardiac myocytes. In contrast, others have reported that cardiac JAK2 is activated by acute oxidative stress by an undefined process. Here we summarize recent insights into the regulation of JAK1 and JAK2. Besides oxidative stress, inhibitory regulation involves phosphorylation, nitration, and intramolecular restraints. Stimulatory regulation involves phosphorylation and adaptor proteins. The net effect of stress on JAK activity in the heart likely represents the sum of both inhibitory and stimulatory processes, along with their dynamic interaction. Thus the regulation of JAKs in the heart, once touted as the paragon of simplicity, is proving rather complicated indeed, requiring a second look. It is our contention that a better understanding of the regulation of this kinase family that is implicated in cardiac protection could translate into effective therapeutic strategies for preventing myocardial damage or repairing the injured heart.

Enhanced hypertrophy in ob/ob mice due to an impairment in expression of atrial natriuretic peptide

RATIONALE

We investigated the molecular mechanism(s) that play a role in leptin signaling during the development of left ventricular hypertrophy (LVH) due to pressure overload. To this end, ob/ob leptin deficient and C57BL/6J control mice were subjected transverse aortic constriction (TAC).

METHODS

Control sham C57BL/6J and ob/ob mice, along with C57BL/6J and ob/ob leptin deficient mice were subjected transverse aortic constriction (TAC) for 15 days and then evaluated for morphological, physiological, and molecular changes associated with pressure overload hypertrophy.

RESULTS

Evaluation by echocardiography revealed a significant increase in left ventricular mass (LVmass) and wall thickness in ob/ob mice subjected to transverse aortic constriction (TAC) as compared to C57BL/6J. Analysis of the expression of molecular markers of LVH, such as atrial natriuretic peptide (ANP), revealed a blunted increase in the level of ANP in ob/ob mice as compared to C57BL/6J mice. We observed that leptin plays a role in modulating the transcriptional activity of the promoter of the ANP gene. Leptin acts by regulating NFATc4, a member of the nuclear factor activated T cell (NFAT) family of transcription factors in cardiomyocytes. Our in vivo studies revealed that ob/ob mice subjected to TAC failed to activate the NFATc4 in the heart, however, intraperitoneal injection of leptin in ob/ob mice restored the NFATc4 DNA-binding activity and induced expression of the ANP gene.

CONCLUSION

This study establishes the role of leptin as an anti-hypertrophic agent during pressure overload hypertrophy, and suggests that a key molecular event is the leptin mediated activation of NFATc4 that regulates the transcriptional activation of the ANP gene promoter.

Can the protective actions of JAK-STAT in the heart be exploited therapeutically? Parsing the regulation of interleukin-6-type cytokine signaling

Activation of the transcription factor signal transducers and activators of transcription (STAT) 3 is a defining feature of the interleukin (IL)-6 family of cytokines, which include IL-6, leukemia inhibitory factor, and cardiotrophin-1. These cytokines, as well as STAT3 activation, have been shown to be protective for cardiac myocytes and necessary for ischemia preconditioning. However, the mechanisms that regulate IL-6-type cytokine signaling in cardiac myocytes are largely unexplored. We propose that the protective character of IL-6-type cytokine signaling in cardiac myocytes is determined principally by three mechanisms: redox status of the nonreceptor tyrosine kinase Janus kinase 1 (JAK) 1 that activates STAT3, phosphorylation of STAT3 within the transcriptional activation domain on serine 727, and STAT3-mediated induction of suppressor of cytokine signaling (SOCS) 3 that terminates IL-6-type cytokine signaling. Moreover, we hypothesize that hyperactivation of the JAK kinases, particularly JAK2, mismatched STAT3 serine-tyrosine phosphorylation or heightened STAT3 transcriptional activity, and SOCS3 induction may ultimately prove detrimental. Here we summarize recent evidence that supports this hypothesis, as well as additional possible mechanisms of JAK-STAT regulation. Understanding how IL-6-type cytokine signaling is regulated in cardiac myocytes has great significance for exploiting the therapeutic potential of these cytokines and the phenomenon of preconditioning.

Leptin signaling and obesity: cardiovascular consequences

Leptin, among the best known hormone markers for obesity, exerts pleiotropic actions on multiple organ systems. In this review, we summarize major leptin signaling pathways, namely Janus-activated kinase/signal transducers and activators of transcription and mitogen-activated protein kinase, including possible mechanisms of leptin resistance in obesity. The effects of leptin on the cardiovascular system are discussed in detail, including its contributions to hypertension, atherosclerosis, depressed myocardial contractile function, fatty acid metabolism, hypertrophic remodeling, and reduction of ischemic/reperfusion injury. The overall goal is to summarize current understanding of how altered leptin signaling in obesity contributes to obesity-related cardiovascular disease.

Norcantharidin preferentially induces apoptosis in human leukemic Jurkat cells without affecting viability of normal blood mononuclear cells

Norcantharidin (NCTD) is known to have anti-cancer potentials. The aim of this study was to assess the apoptosis-inducing effect of NCTD on human leukemic Jurkat cells. We found that NCTD preferentially inhibited the growth of Jurkat cells in a dose- and time-dependent manner, but not the growth of normal blood mononuclear cells (MNC). Pretreatment with agonistic (CH-11) and antagonistic (ZB4) Fas antibodies on Jurkat cells showed that NCTD-induced apoptosis might not involve Fas-FasL signaling. Flow cytometric assay of Jurkat cells treated with NCTD showed a markedly increased sub-G1 DNA phase and cell cycle arrest at S phase. Western blot analysis of NCTD-treated cells showed increased expressions of cytochrome c, active caspase-9 and -3, and cleavage of poly(ADP-ribose) polymerase (PARP), but the expressions of Bcl-2, Bax and apoptosis-inducing factor were not increased. The transcription factor STAT1 was translocated from cytosol to nucleus. Pancaspase inhibitor z-VAD-FMK not only limited the level of sub-G1 phase, but also prevented the degradation of PARP in NCTD-treated cells. The NCTD-induced cell cycle arrest and apoptosis were mediated through the regulation of ataxia-telangiectasia mutated (ATM), rather than P63 protein. The conditioned medium produced from human MNC (NCTD-MNC-CM) increased the percentage of apoptotic cells and the expression of PARP cleavage in Jurkat cells. Protein array assay of NCTD-MNC-CM showed 32.4- and 6.2-folds increases in TNF-alpha and GM-CSF, respectively, and the expression of MCP-1, GRO, RANTES and IL-10 was decreased. We conclude that NCTD can induce apoptosis in human leukemic Jurkat cells via a caspase-dependent pathway without affecting the viability of normal MNC, and that the apoptosis-inducing effect of NCTD can also be achieved by soluble cytokines produced from peripheral MNC.

Sequential activation of JAKs, STATs and xanthine dehydrogenase/oxidase by hypoxia in lung microvascular endothelial cells

Xanthine dehydrogenase/oxidase (XDH/XO) is associated with various pathological conditions related to the endothelial injury. However, the molecular mechanism underlying the activation of XDH/XO by hypoxia remains largely unknown. In this report, we determined whether the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) signaling pathway is involved in hypoxia-induced activation of XDH/XO in primary cultures of lung microvascular endothelial cells (LMVEC). We found that hypoxia significantly increased interleukin 6 (IL6) production in a time-dependent manner in LMVEC. Hypoxia also markedly augmented phosphorylation/activation of JAKs (JAK1, JAK2 and JAK3) and the JAK downstream effectors STATs (STAT3 and STAT5). Hypoxia-induced activation of STAT3 was blocked by IL6 antibodies, the JAK inhibitor AG490 and the suppressor of cytokine signaling 3 (SOCS3), implying that hypoxia-promoted IL6 secretion activates the JAK/STAT pathway in LMVEC. Phosphorylation and DNA-binding activity of STAT3 were also inhibited by the p38 MAPK inhibitor SB203580 and the phosphatidylinositol 3-kinase inhibitor LY294002, suggesting that multiple signaling pathways involved in STAT activation by hypoxia. Importantly, hypoxia promoted XDH/XO activation in LMVEC, which was markedly reversed by inhibiting the JAK-STAT pathway using IL6 antibodies, AG490 and SOCS3. These data demonstrated that JAKs, STATs and XDH/XO were sequentially activated by hypoxia. These data provide the first evidence indicating that the JAK-STAT pathway is involved in hypoxia-mediated XDH/XO activation in LMVEC.

Survival pathways in hypertrophy and heart failure: the gp130-STAT3 axis

Circulating levels of interleukin (IL)-6 and related cytokines are elevated in patients with congestive heart failure and after myocardial infarction. Serum IL-6 concentrations are related to decreasing functional status of these patients and provide important prognostic information.Moreover, in the failing human heart, multiple components of the IL-6- glycoprotein (gp)130 receptor system are impaired, implicating an important role of this system in cardiac pathophysiology.Experimental studies have shown that the common receptor subunit of IL-6 cytokines is phosphorylated in response to pressure overload and myocardial infarction and that it subsequently activates at least three different downstream signaling pathways, the signal transducers and activators of transcription 1 and 3 (STAT1/3), the Src-homology tyrosine phosphatase 2 (SHP2)-Ras-ERK, and the PI3K-Akt system. Gp130 receptor mediated signaling promotes cardiomyocyte survival, induces hypertrophy, modulates cardiac extracellular matrix and cardiac function. In this regard, the gp130 receptor system and its main downstream mediator STAT3 play a key role in cardioprotection. This review summarizes the current knowledge of IL-6 cytokines, gp130 receptor and STAT3 signaling in the heart exposed to physiological (aging, pregnancy) and pathophysiological stress (ischemia, pressure overload, inflammation and cardiotoxic agents) with a special focus on the potential role of individual IL-6 cytokines.