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Article: In Vivo Evidence Suggesting Reciprocal Renal HIF-1 Up-Regulation and STAT3 Activation in Response to Hypoxic and Non-Hypoxic Stimuli.
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ABSTRACT: In vitro studies suggest that combined activation of HIF and STAT3 promotes the hypoxia response. However, their inter-relationship in vivo remains poorly defined. The present study investigates the possible relationship between HIF-1 upregulation and STAT3 activation in the rodent kidney in vivo. HIF-1 and STAT3 activation were analyzed by immunohistochemical staining and Western blot analysis in: i) models of hypoxia-associated kidney injury induced by radiocontrast media or rhabdomyolysis; ii) following activation of STAT3 by IL-6/sIL-6R complex; or iii) following HIF-1α stabilization using hypoxic and non-hypoxic stimuli (mimosine, FG-4497, CO, cobalt chloride), and in targeted von Hippel-Lindau (VHL) KO mice. Western blot analysis and immunostaining revealed marked induction of both transcription factors in all conditions tested, suggesting that in vivo STAT3 can trigger HIF, and also vice-versa. Co-localization of HIF-1α and phosphorylated STAT3 (p-STAT3) was detected in some, but not all renal cell types, suggesting that in some cells, a paracrine mechanism may be responsible for the reciprocal activation of the two transcription factors. Nevertheless, in several cell types, spatial concordance was observed in the majority of conditions tested, suggesting that HIF-1 and STAT3 may act as co-transcription factors. These in vivo studies suggest that in response to renal hypoxic-stress, upregulation of HIF-1 and activation of STAT3, may be both reciprocal and cell type-dependent. © 2013 The Authors Clinical and Experimental Pharmacology and Physiology © 2013 Wiley Publishing Asia Pty Ltd.Clinical and Experimental Pharmacology and Physiology 02/2013; · 1.85 Impact Factor -
Article: Early hepatocyte DNA synthetic response posthepatectomy is modulated by IL-6 trans-signaling and PI3K/AKT activation.
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ABSTRACT: Interleukin-6 (IL-6) is a crucial factor in liver regeneration following partial hepatectomy (PH); however, the role of IL-6 and IL-6 trans-signaling in particular, in hepatocyte mitosis remains controversial. IL-6 trans-signaling relies upon the release of the soluble IL-6R (sIL-6R), which binds IL-6 to form an agonistic IL-6/sIL-6R complex. Herein we have examined the hypothesis that IL-6 trans-signaling plays a crucial and distinct role in liver regeneration following PH. The specific IL-6/sIL-6R antagonist, sgp130Fc, was expressed in mice and analyzed for its effect on hepatocyte mitosis following PH. Alternatively, we examined the effect of the IL-6/sIL-6R super-agonist, Hyper-IL-6, or IL-6 expressed either alone or in combination with hepatocyte growth factor (HGF) on hepatocyte mitosis in the absence of PH. Following PH, the dramatic rise of circulating IL-6 levels is accompanied by a concurrent ∼2-fold increase in circulating sIL-6R levels. Ectopic expression of sgp130Fc reduced hepatocyte mitosis by about 40% at early times following PH, while substantially reducing AKT, but not STAT3, activation. But, ectopic Hyper-IL-6 expression in mice without PH was not mitogenic to hepatocytes in vivo. Rather, Hyper-IL-6, but not IL-6, markedly increased HGF-induced hepatocyte mitosis. This cooperative effect correlated with greater resistance of HIL-6 than IL-6 to HGF-mediated reduction of AKT activation, rather than changes in STAT3 or MAPK signaling, and was completely blocked by PI3K inhibition. Following PH, IL-6/sIL-6R cooperates with growth factors, through a PI3K/AKT-dependent mechanism to promote entry of hepatocytes into the cell cycle.Journal of Hepatology 10/2010; 54(5):922-9. · 9.26 Impact Factor -
Article: IL-6/IL-6R axis plays a critical role in acute kidney injury.
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ABSTRACT: The response to tissue injury involves the coordination of inflammatory and repair processes. IL-6 expression correlates with the onset and severity of acute kidney injury (AKI), but its contribution to pathogenesis remains unclear. This study established a critical role for IL-6 in both the inflammatory response and the resolution of AKI. IL-6-deficient mice were resistant to HgCl2-induced AKI compared with wild-type mice. The accumulation of peritubular neutrophils was lower in IL-6-deficient mice than in wild-type mice, and neutrophil depletion before HgCl2 administration in wild-type mice significantly reduced AKI; these results demonstrate the critical role of IL-6 signaling in the injurious inflammatory process in AKI. Renal IL-6 expression and STAT3 activation in renal tubular epithelial cells significantly increased during the development of injury, suggesting active IL-6 signaling. Although a lack of renal IL-6 receptors (IL-6R) precludes the activation of classical signaling pathways, IL-6 can stimulate target cells together with a soluble form of the IL-6R (sIL-6R) in a process termed trans-signaling. During injury,serum sIL-6R levels increased three-fold, suggesting a possible role for IL-6 trans-signaling in AKI. Stimulation of IL-6 trans-signaling with an IL-6/sIL-6R fusion protein activated STAT3 in renal tubular epithelium and prevented AKI. IL-6/sIL-6R reduced lipid peroxidation after injury, suggesting that its protective effect may be largely mediated through amelioration of oxidative stress. In summary, IL-6 simultaneously promotes an injurious inflammatory response and, through a mechanism of trans-signaling, protects the kidney from further injury.Journal of the American Society of Nephrology 07/2008; 19(6):1106-15. · 9.66 Impact Factor -
Article: JX401, A p38alpha inhibitor containing a 4-benzylpiperidine motif, identified via a novel screening system in yeast.
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ABSTRACT: In vivo screening of compounds for potential pharmacological activity is more advantageous than in vitro screening. In vivo screens eliminate the isolation of compounds that cannot cross biological membranes, are cytotoxic, or are not specific to the target. However, animal-based or even cell-based systems are usually expensive, time-consuming, and laborious. Here we describe the identification of inhibitors of the mitogen-activated protein kinase p38alpha via a high throughput screen using yeast cells. p38alpha is hyperactive in inflammatory diseases, and various indications suggest that its inhibition would reverse inflammation. However, there are currently no p38alpha inhibitors in clinical use. Because the human p38alpha imposes severe growth retardation when expressed in yeast, we screened a library of 40,000 randomly selected small molecules for compounds that would restore a normal growth rate. We identified two compounds; both share a structural motif of 4-benzylpiperidine, and both were shown to be efficient and selective p38alpha inhibitors in vitro. They were also active in mammalian cells, as manifested by their ability to reversibly inhibit myoblast differentiation. Thus, the yeast screen identified efficient and specific p38alpha inhibitors that are capable of crossing biological membranes, are not toxic, and function in mammalian cells. The rapid and cost-efficient high-throughput screening used here could be applied for isolation of inhibitors of various targets.Molecular Pharmacology 11/2006; 70(4):1395-405. · 4.88 Impact Factor -
Article: Tissue microarray-based study of patients with lymph node-positive breast cancer shows tyrosine phosphorylation of signal transducer and activator of transcription 3 (tyrosine705-STAT3) is a marker of good prognosis.
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ABSTRACT: Although lymph node-positive breast cancers are associated with poorer prognosis, individual patients may have different clinical outcomes. Signal transducer and activator of transcription 3 (STAT3) is a point of convergence for numerous oncogenic signalling pathways. The goal of this study was to determine the prognostic value of phosphorylated (tyrosine705)-STAT3 in node-positive breast cancer patients. Immunohistochemical analysis of Phospho- STAT3 was performed on a tissue microarray of breast cancer specimens. The expression pattern of Phospho-STAT3 was correlated with survival outcome, and clinical and pathological parameters. Out of 125 interpretable tumours, positive Phospho- STAT3 nuclear expression was seen in 35 (28%) of tumours. There was no significant relationship between Phospho-STAT3 expression and clinical-pathological parameters including age, hormonal receptor status, grade and tumour size. Interestingly positive tumours had a significantly improved disease-free survival at 5 years (p=0.035). Additionally, positive Phospho-STAT3 nuclear expression was correlated with significantly improved survival at both 5 years (p=0.023) and 10 years (p=0.026). Finally, in multivariate analyses Phospho-STAT3 was found to be an independent prognostic marker of overall survival in node-positive breast cancer patients. These findings support the role of Phospho- STAT3 as an important independent prognostic marker in node-positive breast cancer patients.Clinical and Translational Oncology 03/2012; 14(3):232-6. · 1.33 Impact Factor
