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Adipocytes As a New Source of Catecholamine Production

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Adipocytes As a New Source of Catecholamine Production CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector FEBS Letters 585 (2011) 2279–2284 journal homepage: www.FEBSLetters.org Adipocytes as a new source of catecholamine production ⇑ Peter Vargovic a, , Jozef Ukropec b, Marcela Laukova a, Susannah Cleary d, Bernhard Manz c, Karel Pacak d, Richard Kvetnansky a a Laboratory of Stress Research, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlarska 3, 83306 Bratislava, Slovakia b Diabetes and Metabolic Research Laboratory, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlarska 3, 83306 Bratislava, Slovakia c LDN Labor Diagnostika Nord, D-48531 Nordhorn, Germany d Section on Medical Neuroendocrinology, NICHD, NIH, Bethesda, MD, USA article info abstract Article history: Catecholamines are an important regulator of lipolysis in adipose tissue. Here we show that rat adi- Received 2 February 2011 pocytes, isolated from mesenteric adipose tissue, express genes of catecholamine biosynthetic Revised 28 April 2011 enzymes and produce catecholamines de novo. Administration of tyrosine hydroxylase inhibitor, Accepted 1 June 2011 alpha-methyl-p-tyrosine, in vitro significantly reduced concentration of catecholamines in isolated Available online 16 June 2011 adipocytes. We hypothesize that the sympathetic innervation of adipose tissues is not the only Edited by Laszlo Nagy source of catecholamines, since adipocytes also have the capacity to produce both norepinephrine and epinephrine. Ó 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. Keywords: Adipocyte Endogenous catecholamine Catecholamine biosynthetic enzyme Gene expression 1. Introduction catecholamine biosynthesis. PNMT mRNA and immunoreactive protein were found in the adipose tissue in neuron-like cells of Adipose tissue is a specialized organ serving several functions PNMT-overexpressing transgenic mice but not in wild types [10]. (energy [fat] storage, mechanical and heat insulation, endocrine The primary objective of this study was to investigate whether and secretory functions, thermogenesis) with important medical adipocytes express genetic machinery to produce enzymes which implications [1]. Obesity, an increase of adipose tissue mass, is in might enable de novo production of catecholamines within the close relationship to metabolic and cardiovascular diseases. The adipocyte. sympathoadrenal system plays an important role in the regulation of this process as well as in the fine tuning of adipocyte metabo- 2. Materials and methods lism. Catecholamines are considered the major regulators of lipolysis [2] and affect differentiation and proliferation of adipo- 2.1. Animals cytes [3,4]. There are four enzymes essential for biosynthesis of catecholamines: tyrosine hydroxylase (TH), L-aromatic amino acid Male Sprague–Dawley rats, 4 months old (300–350 g, Charles decarboxylase, dopamine-b-hydroxylase (DBH), and phenyletha- River, Suzfeld, Germany) were used in our experiments. The Ethics nolamine N-methyltransferase (PNMT). Catecholamines are Committee of the Institute of Experimental Endocrinology (Slovak synthesized primarily in the chromaffin cells of the adrenal medul- Academy of Sciences, Bratislava, Slovakia) approved all experimen- la and in neuronal cells, but also in the activated immune cells tal procedures with animals used in this study in protocol No. (T- and B-cells, macrophages) [5]. PNMT mRNA has been detected RO-2804/07-221/3. also in embryonic [6] and adult hearts of rat [7]. More detailed characterization led to the identification of intrinsic cardiac adren- 2.2. Separation of adipose tissue cells ergic cells that express PNMT in rodent and human hearts [8].We have also observed that isolated adult rat cardiomyocytes express Mesenteric adipose tissue (200–300 mg) was separated to PNMT mRNA [9]. There are few indications that adipose tissue may adipocytes and stromal–vascular fraction (SVF) as described previ- also contain specific cells that could express enzymes essential for ously [11]. Adipocyte fraction was washed four times by 1.5 ml Medium 199 (Gibco, Invitrogen, USA) containing 0.5% BSA and ⇑ Corresponding author. Fax: +421 25477 4908. 3 mM CaCl2 (medium + BSA + CaCl2) and filtered through 210 lm E-mail address: [email protected] (P. Vargovic). nylon mesh filter (Small Parts, USA). 0014-5793/$36.00 Ó 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.febslet.2011.06.001 2280 P. Vargovic et al. / FEBS Letters 585 (2011) 2279–2284 2.3. Catecholamine determination (Corbett Research, Mortlake, Australia) as described previously [13]. For specific PCR amplification TaqMan probes (Applied Bio- All measurements were performed using 2-CAT or 3-CAT systems) were used: Rn00562500_m1 (TH), Rn00565819_m1 Research RIA kits (Labor Diagnostica Nord, Nordhorn, Germany) (DBH), Rn01495588_m1 (PNMT). Standards for absolute quantifi- according to the manufacturer’s protocol. Values were normalized cation of TH, DBH, PNMT were prepared by PCR amplification to protein in homogenate determined by BCA Protein Assay (Ther- (using Taqman probes), purification by gel extraction and subse- 6 mo Scientific, Rockford, IL) modified for samples with high content quent dilution to concentrations 15–15.10 copies/ll using ddH2O of lipids according to Morton and Evans [12]. containing 50 ng/ll of sonicated salmon sperm DNA (Sigma– Aldrich) used as a DNA carrier. Copy numbers of samples were 2.4. In vitro inhibition of catecholamine biosynthesis evaluated using Rotor-Gene Analysis software version 5.0. Adipocytes freshly isolated from 100 mg mesenteric adipose 2.7. Western blot analysis tissue were suspended in 1 ml of medium + BSA + CaCl2 and incu- bated at 37 °C in water bath with constant gentle agitation for Samples of adipocytes isolated from mesenteric adipose tissue 2 h. To inhibit biosynthesis of catecholamines, 0.6 mM alpha- were sonicated in 0.6 ml of 20 mM Tris pH 7.0, 5 mM PMSF (Pefab- methyl-p-tyrosine (AMPT, Research Biochemicals, Natic, MD), the loc SC + Compete, Roche Diagnostic), stored in ice for 1 h and cen- tyrosine hydroxylase inhibitor, was added. Thereafter, adipocytes trifuged for 15 min (16,100g,4°C). Western blotting was were centrifuged at 1000g for 1 min and washed twice with performed as described previously [14]. The following primary medium + BSA + CaCl2. antibodies were used: Monoclonal anti-TH (1:3000; MAB5280, Chemicon International, Temecula, CA) and polyclonal anti-PNMT 2.5. Total RNA isolation (1:200, CA-401 bMTrab, Protos Biotech Corp., NY). Membranes were incubated with corresponding horseradish peroxidase-linked Total RNA was isolated by TRI Reagent (MRC Ltd., USA) accord- secondary antibodies (TH with anti-mouse Ab diluted 1:5000; ing to the manufacturer’s protocol. The purity and concentration of PNMT with anti-rabbit Ab diluted 1:5000). The signals were de- isolated RNA was measured on GeneQuant Pro spectrophotometer tected using Femto Supersignal reagent (Pierce, Rockford, Illinois) (Amersham Biosciences, Buckinghampshire, UK). Reverse tran- and visualized by exposure to Amersham Hyperfilm (Amersham scription was performed in 34 ll of reaction mixture containing Biosciences). 1.5 lg of total RNA, random oligonucleotide pd(N)6 primer and Ready-To-Go You-Prime First-Strand Beads (GE Healthcare-Life 2.8. Immunohistochemistry Sciences, USA) according to the manufacturer’s protocol. Formalin fixed sections of rat mesenteric adipose tissue were 2.6. Absolute quantification of mRNA levels by TaqMan real time RT- deparaffinized and rehydrated by washing twice for 10 min with PCR xylene, followed by 2 Â 2 min washes in 100%, 95% and 70% (v/v) ethanol. Sections were rinsed in water, placed into a warmed Absolute mRNA levels of TH, DBH and PNMT were evaluated by citrate buffer (0.01 M, pH 6.0) for 5 min, followed by immersion quantitative real time PCR on thermocycler Rotor-Gene 2000 in a hot citrate buffer (58 °C), heated in microwave oven, cooled a Norepinephrine Epinephrine 1400 6000 1200 1000 4000 2000 100 50 0 Epinephrine, pg/mg protein 0 Norepinephrine, pg/mg protein BAT MWAT SWAT EWAT RWAT BAT MWAT SWAT EWAT RWAT b TH DBH PNMT 6 6 1.6x10 6 6x10 1.0x10 6 5x106 1.4x10 8.0x105 4x103 3 2 3x10 4.0x10 3 3x10 3 2x10 3 2 2x10 2.0x10 1x103 1x103 0 0.0 0 mRNA, copies/100 ng total RNA mRNA, copies / 100 ng total RNA mRNA, copies /100 ng total RNA AM AM AM BAT BAT WAT BAT MWAT SWAT EWAT RWAT MWATSWATEWATRWAT MWATSWAT E RWAT Fig. 1. (a) Catecholamine concentration (± S.E.M.) in the mesenteric (MWAT), inguinal subcutaneous (SWAT), epididymal (EWAT), retroperitoneal (RWAT) and interscapular brown (BAT) adipose tissue of rat (n = 8). (b) Absolute quantitation of TH, DBH and PNMT mRNA (± S.E.M.) in rat adipose tissues: MWAT, SWAT, EWAT, RWAT, BAT (n = 8) and in the adrenal medulla (AM, n = 4). P. Vargovic et al. / FEBS Letters 585 (2011) 2279–2284 2281 at room temperature (RT), washed with Tris Buffered Saline (TBS) that all five studied adipose tissue depots contain both norepi- for 3 Â 5 min, transferred into methanol solutions containing nephrine and epinephrine. The highest norepinephrine and 0.5% (v/v) H2O2 and washed again in TBS. Pre-blocking procedure epinephrine concentrations were observed in mesenteric WAT (only TH staining) with a 20 lg/ml solution of donkey anti-mouse and in brown fat. Concentration of epinephrine in all adipose IgG (JacksonImmuno Research, USA) for 1 h at RT was followed by depots was approximately
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