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AMP-activated protein kinase (AMPK) is a metabolic fuel gauge conserved along the evolutionary scale in eukaryotes that senses changes in the intracellular AMP/ATP ratio (1). Recent evidence indicated an important role for AMPK in the therapeutic benefits of metformin (2,3), thiazolidinediones (4) and exercise (5), which form the cornerstones of the clinical management of type 2 diabetes and associated metabolic disorders. In general, activation of AMPK acts to maintain cellular energy stores, switching on catabolic pathways that produce ATP, mostly by enhancing oxidative metabolism and mitochondrial biogenesis, while switching off anabolic pathways that consume ATP (1). This regulation can take place acutely, through the regulation of fast post-translational events, but also by transcriptionally reprogramming the cell to meet energetic needs. Here we demonstrate that AMPK controls the expression of genes involved in energy metabolism in mouse skeletal muscle by acting in coordination with another metabolic sensor, the [NAD.sup.+]-dependent type III deacetylase SIRT1. AMPK enhances SIRT1 activity by increasing cellular [NAD.sup.+] levels, resulting in the deacetylation and modulation of the activity of downstream SIRT1 targets that include the peroxisome proliferator-activated receptor-γ coactivator 1αand the forkhead box O1 (FOXO1) and 03 (FOXO3a) transcription factors. The AMPK-induced SIRT1-mediated deacetylation of these targets explains many of the convergent biological effects of AMPK and SIRT1 on energy metabolism., AMPK is a critical regulator of mitochondrial biogenesis in response to energy deprivation (6). Although the mechanisms by which AMPK modulates mitochondrial gene expression are not entirely elucidated, they seem [...]

Byline: Martijn D. Kruif (1), Lucienne C. Lemaire (2), Ida A. Giebelen (1,3), Joachim Struck (4), Nils G. Morgenthaler (4), Jana Papassotiriou (4), Peter J. Elliott (5,6), Tom Poll (1,3) Keywords: Corticosteroids; Biological markers; Endotoxin; Sepsis Abstract: Objective Sepsis intervention studies need better patient stratification methods, and one way to realize this is the introduction of stable biomarkers. A set of recently developed novel biomarkers, based upon precursor-fragments of short-lived hormones, was previously shown to be increased during sepsis. However, it is not known whether these biomarkers are influenced by sepsis intervention strategies. Therefore we investigated the markers in a model of human endotoxemia intervened by increasing doses of prednisolone. Design and setting Prospective, open-label study in a specialized clinical research unit of a university hospital. Subjects Thirty-two healthy male volunteers. Interventions Subjects received prednisolone orally at doses of 0, 3, 10 or 30a-mg (na-=a-8 per group) at 2a-h before intravenous injection of Escherichia coli lipopolysaccharide (LPS) (4a-ng/kg). Blood samples were drawn during 24a-h after LPS injection. Measurements and results LPS injection caused an increase in levels of midregional pro-adrenomedullin (MR-proADM), midregional pro-atrial natriuretic peptide (MR-proANP), C-terminal pro-arginine--vasopressin (CT-proAVP) and procalcitonin (PCT). Prednisolone caused a dose dependent inhibition of MR-proADM, MR-proANP and CT-proAVP levels. Conclusions These results show that a set of novel, highly stable sepsis biomarkers was increased during human endotoxemia and was dose-dependently inhibited by corticosteroid pre-treatment. Author Affiliation: (1) Center for Experimental and Molecular Medicine, Room G2-132, Academic Medical Center, Meibergdreef 9, 1105, Amsterdam, AZ, The Netherlands (2) Department of Anesthesiology, University Medical Center Utrecht, P.O. Box 85500, 3508, Utrecht, GA, The Netherlands (3) Center for Infection and Immunity Amsterdam, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, Amsterdam, AZ, The Netherlands (4) Research Department, Brahms AG, Neuendorfstrasse 25, 16761, Hennigsdorf/Berlin, Germany (5) CombinatoRx, Inc., 245 st., 16th floor, 02142, Cambridge, MA, USA (6) Sirtris Pharmaceuticals, 790 Memorial Drive, 02139, Cambridge, MA, USA Article History: Registration Date: 22/11/2007 Received Date: 08/06/2007 Accepted Date: 31/10/2007 Online Date: 14/12/2007 Article note: This study was supported by research funding from CombinatoRx, Inc., Cambridge, MA, USA. One of the authors (Peter J. Elliott) was employed by CombinatoRx at the time of study design and completion. Currently, he is employed elsewhere but he is still a stockholder of CombinatoRx. Joachim Struck, Nils G. Morgenthaler and Jana Papassotiriou are employed by Brahms AG, Hennigsdorf, Germany. This article is discussed in the editorial available at: http://dx.doi.org/10.1007/s00134-007-956-9.

Both acute coronary occlusion and reperfusion of an infarct-related artery lead to significant myocardial cell death. Recent evidence has been presented that activation of the transcription factor nuclear factor-[kappa]B (NF-[kappa]B) plays a critical role in reperfusion injury. NF-[kappa]B is usually bound to its inhibitor, I[kappa]B, and classic activation of NF-[kappa]B occurs when the 20S proteasome degrades I[kappa]B that has been phosphorylated and ubiquitinated. In this study, activation of NF-[kappa]B was inhibited by systemic administration of a 20S proteasome inhibitor (PS-519) in a porcine model of myocardial reperfusion injury. The experimental protocol induced myocardial ischemia in the distribution of the left anterior descending coronary artery for 1 h with subsequent reperfusion for 3 h. A single systemic treatment with PS-519 reduced 20S proteasome activity; blocked activation of NF-[kappa]B induced by reperfusion; reduced creatine kinase, creatine kinase-muscle-brain fraction, and troponin I release from the myocardium; preserved regional myocardial function measured by segmental shortening; significantly reduced the size of myocardial infarction; and exhibited no acute toxicity. These data show that myocardial reperfusion injury can be inhibited by using proteasome inhibitors, which likely function through the inhibition of NF-[kappa]B activation. inflammation; myocardial contraction; multienzyme complexes; transcription factors

The transcription factor NF-[Kappa]B activates a number of genes whose protein products are proinflammatory. In quiescent cells, NF-[Kappa]B exists in a latent form and is activated via a signal-dependent proteolytic mechanism in which the inhibitory protein I[Kappa]B is degraded by the ubiquitin-proteasome pathway. Consequently, inhibition of the proteasome suppresses activation of NF-[Kappa]B. This suppression should therefore decrease transcription of many genes encoding proinflammatory proteins and should ultimately have an anti-inflammatory effect. To this end, a series of peptide boronic acid inhibitors of the proteasome, exemplified herein by PS-341, were developed. The proteasome is the large multimeric protease that catalyzes the final proteolytic step of the ubiquitin-proteasome pathway. PS-341, a potent, competitive inhibitor of the proteasome, readily entered cells and inhibited the activation of NF-[Kappa]B and the subsequent transcription of genes that are regulated by NF-[Kappa]B. Significantly, PS-341 displayed similar effects in vivo. Oral administration of PS-341 had anti-inflammatory effects in a model of Streptococcal cell wall-induced polyarthritis and liver inflammation in rats. The attenuation of inflammation in this model was associated with an inhibition of I[Kappa]B[Alpha] degradation and NF-[Kappa]B-dependent gene expression. These experiments clearly demonstrate that the ubiquitin-proteasome pathway and NF-[Kappa]B play important roles in regulating chronic inflammation and that, as predicted, proteasome inhibition has an anti-inflammatory effect.