S.-Y. Weng

AMPK regulates macrophage polarization in adipose tissue inflammation and NASH

Molecular and Translational Medicine, Dept. of Medicine I, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstrase 1,55116 Mainz, GermanyCOMMENTARY ON:Hematopoietic AMPK beta1 reduces mouse adipose tissue mac-rophage inflammation and insulin resistance in obesity. Galic S,Fullerton MD, Schertzer JD, Sikkema S, Marcinko K, Walkley CR,Izon D, Honeyman J, Chen ZP, van Denderen BJ, Kemp BE, Stein-berg GR. J Clin Invest 2011;121(12):4903–15. Copyright 2011.Reprinted with permission of American Society for ClinicalInvestigation.http://www.ncbi.nlm.nih.gov/pubmed/22080866Abstract: Individuals who are obese are frequently insulin resistant,putting them at increased risk of developing type 2 diabetes and itsassociated adverse health conditions. The accumulation in adiposetissue of macrophages in an inflammatory state is a hallmark ofobesity-induced insulin resistance. Here, we reveal a role for AMPKb1 in protecting macrophages from inflammation under high lipidexposure. Genetic deletion of the AMPK b1 subunit in mice (referredto herein as b1( / ) mice) reduced macrophage AMPK activity,acetyl-CoA carboxylase phosphorylation, and mitochondrial content,resulting in reduced rates of fatty acid oxidation. b1( / ) macro-phages displayed increased levels of diacylglycerol and markers ofinflammation, effects that were reproduced in WT macrophages byinhibiting fatty acid oxidation and, conversely, prevented by phar-macological activation of AMPK b1-containing complexes. The effectof AMPK b1 loss in macrophages was tested in vivo by transplanta-tion of bone marrow from WT or b1( / ) mice into WT recipients.When challenged with a high-fat diet, mice that received b1( / )bone marrowdisplayedenhancedadiposetissue macrophage inflam-mation and liver insulin resistance compared with animals thatreceived WT bone marrow. Thus, activation of AMPK b1 and increas-ing fatty acid oxidation in macrophages may represent a new thera-peutic approach for the treatment of insulin resistance. 2011 European Association for the Study of the Liver. Publishedby Elsevier B.V. All rights reserved.Obesity has long been linked to type 2 diabetes (T2D), but theinvolved metabolic dysregulation is incompletely understood.Galic et al. [1] recently reported that adenosine monophosphatekinase (AMPK) b1 plays a hitherto unknown role in modulatingobesity-induced insulin resistance. AMPK is a central regulatorof energy balance. Decreased cellular energy status, as reflectedby accumulation of AMP, activates AMPK which turns on expres-sion of catabolic enzymes that permit ATP production and shutsdown energy consuming biosynthetic pathways. Thus, AMPK isa central regulator of fatty acid, cholesterol, and glucose homeo-stasis through phosphorylation of metabolism-regulatingenzymes including acetyl-CoA carboxylase (ACC), glycogen syn-thase (GS), glucose transporter 4 (GLUT4), HMG-CoA reductase,hormone-sensitive lipase (HSL), and mammalian target of rapa-mycin (mTOR). AMPK is a heterotrimer of a catalytic

Inducible knockdown of procollagen I protects mice from liver fibrosis and leads to dysregulated matrix genes and attenuated inflammation

Organ fibrosis is characterized by a chronic wound-healing response, with excess deposition of extracellular matrix components. Here, collagen type I represents the most abundant scar component and a primary target for antifibrotic therapies. Liver fibrosis can progress to cirrhosis and primary liver cancer, which are the major causes of liver related morbidity and mortality. However, a (pro-)collagen type I specific therapy remains difficult and its therapeutic abrogation may incur unwanted side effects. We therefore designed tetracycline-regulated procollagen alpha1(I) short hairpin (sh)RNA expressing mice that permit a highly efficient inducible knockdown of the procollagen alpha1(I) gene in activated (myo-)fibroblasts, to study the effect of induced procollagen type I deficiency. Transgenic mice were generated using recombinase-mediated integration in embryonic stem cells or zinc-finger nuclease-aided genomic targeting combined with miR30-shRNA technology. Liver fibrosis was induced in transgenic mice by carbon tetrachloride, either without or with doxycycline supplementation. Doxycycline treated mice showed an 80-90% suppression of procollagen alpha1(I) transcription and a 40-50% reduction in hepatic collagen accumulation. Procollagen alpha1(I) knockdown also downregulated procollagens type III, IV and VI and other fibrosis related parameters. Moreover, this was associated with an attenuation of chronic inflammation, suggesting that collagen type I serves not only as major scar component, but also as modulator of other collagens and promoter of chronic inflammation.

IL-4 Receptor Alpha Signaling through Macrophages Differentially Regulates Liver Fibrosis Progression and Reversal

Chronic hepatitis leads to liver fibrosis and cirrhosis. Cirrhosis is a major cause of worldwide morbidity and mortality. Macrophages play a key role in fibrosis progression and reversal. However, the signals that determine fibrogenic vs fibrolytic macrophage function remain ill defined. We studied the role of interleukin-4 receptor α (IL-4Rα), a potential central switch of macrophage polarization, in liver fibrosis progression and reversal. We demonstrate that inflammatory monocyte infiltration and liver fibrogenesis were suppressed in general IL-4Rα−/− as well as in macrophage-specific IL-4Rα−/− (IL-4RαΔLysM) mice. However, with deletion of IL-4RαΔLysM spontaneous fibrosis reversal was retarded. Results were replicated by pharmacological intervention using IL-4Rα-specific antisense oligonucleotides. Retarded resolution was linked to the loss of M2-type resident macrophages, which secreted MMP-12 through IL-4 and IL-13-mediated phospho-STAT6 activation. We conclude that IL-4Rα signaling regulates macrophage functional polarization in a context-dependent manner. Pharmacological targeting of macrophage polarization therefore requires disease stage-specific treatment strategies. Research in Context Alternative (M2-type) macrophage activation through IL-4Rα promotes liver inflammation and fibrosis progression but speeds up fibrosis reversal. This demonstrates context dependent, opposing roles of M2-type macrophages. During reversal IL-4Rα induces fibrolytic MMPs, especially MMP-12, through STAT6. Liver-specific antisense oligonucleotides efficiently block IL-4Rα expression and attenuate fibrosis progression.

Regulatory T cell deficient scurfy mice exhibit a Th2/M2-like inflammatory response in the skin

BACKGROUND Scurfy mice have a functional defect in regulatory T cells (Treg), which leads to lethal multi-organ inflammation. The missing Treg function results in uncontrolled autoimmune cellular and humoral inflammatory responses. We and others have previously shown that during the course of disease scurfy mice develop severe skin inflammation and autoantibodies including anti-nuclear autoantibodies (ANA). OBJECTIVE Autoimmune skin inflammation and ANA are hallmarks for the diagnosis of autoimmune connective tissue diseases; therefore we analyzed scurfy mice for typical signs of these diseases. METHODS Indirect immunofluorescence was used to specify the ANA pattern in scurfy mice. Skin fibrosis was assessed by cutaneous collagen accumulation (Goldeners trichrome staining), collagen crosslinking/disorganization (Sirus red polarimetry) and quantitative PCR for fibrosis-related transcripts. The cellular components of the inflammatory infiltrates in scurfy skin were analyzed by flow cytometry and intracellular cytokine staining. RESULTS The majority of scurfy mice developed ANA with a predominant AC-5 pattern typical for mixed connective tissue disease, especially scleroderma. Scurfy mice showed higher skin collagen content compared to WT controls with a significant tendency in upregulation of TIMP-1. CD3+CD4+ T cells in scurfy skin exhibited a strong Th2 deviation with a significant increase of IL-4, IL-5 and IL-13, and M2-polarized CD11b+MHCII+ macrophages compared to WT mice. CONCLUSION We show that Scurfy mice show a predominant AC-5 ANA pattern typical for mixed connective tissue disease as in scleroderma. The autoimmune inflammation in scurfy skin mainly consists of CD4+ T cells with Th2 differentiation and alternatively-activated (M2) macrophages as it is found in scleroderma with advanced fibrosis.