title: Loss of FADS2 function severely impairs the use of HeLa cells as an in vitro model for host response studies involving fatty acid effects.
abstract: METHODS
  Established epithelial cell lines equipped with pattern recognition receptors such as the Toll-like receptor (TLR)-2 are common tools for immune response studies on invading pathogens, e.g. the obligate intracellular species of Chlamydia. Moreover, such models are widely used to elucidate fatty acid-mediated immune effects. In several transformed cell lines, however, unusual loss of metabolic functions was described. The cell lines A549 and HeLa are poorly characterized in this respect. Therefore, we comparatively assessed the metabolic capacity of A549 and HeLa prior to proposed application as in vitro model for fatty acid effects on chlamydial infection.
  
  
  RESULTS
  We incubated both cell lines either with substrates (C18:2n-6 or C18:3n-3) or products (C18:3n-6, C18:4n-3) of fatty acid desaturase-2 (FADS2), and analysed the fatty acid profiles after 24 h and 72 h by gas chromatography. Based on these data, we suspected that the complete discontinuation of normal biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFA) in HeLa was due to loss of FADS2 function. Consequently, prostaglandin E2 (PGE2) formation was less inducible by TLR2 stimulation in HeLa, likely as a result of not only insufficient supply of precursors but also weak cyclooxygenase-2 (COX-2) response. In accordance, Chlamydia infection rates were consistently lower in HeLa than in A549. Sequence analysis revealed no alteration within the FADS2 gene in HeLa. The FADS2 expression level, however, was significantly lower and, in contrast to A549, not regulated by C18:2n-6. A549 exhibited regular fatty acid metabolism and enzyme functionality.
  
  
  CONCLUSIONS
  Our data show that HeLa cells considerably differ from A549 at several stages of fatty acid metabolism. The poor metabolic potential of HeLa, mainly concerning FADS2 upstream of COX-2 function, calls into question whether these cells represent a good model to unveil fatty acid or downstream eicosanoid effects in the course of intracellular bacterial infection.
authors.affiliation: Max Rubner-Institut (Federal Research Institute of Nutrition and Food), Department of Physiology and Biochemistry of Nutrition, Karlsruhe, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Jaudszus
authors.affiliation: Institute of Nutrition, Department of Nutritional Physiology, Friedrich Schiller University of Jena, Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Degen
authors.affiliation: Max Rubner-Institut (Federal Research Institute of Nutrition and Food), Department of Physiology and Biochemistry of Nutrition, Karlsruhe, Germany.
authors.forename: Stephan W
authors.initials: SW
authors.lastname: Barth
authors.affiliation: Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Department of Safety and Quality of Milk and Fish Products, Kiel, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Klempt
authors.affiliation: Institute of Nutrition, Department of Nutritional Physiology, Friedrich Schiller University of Jena, Jena, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Schlörmann
authors.affiliation: Max Rubner-Institut (Federal Research Institute of Nutrition and Food), Department of Physiology and Biochemistry of Nutrition, Karlsruhe, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Roth
authors.affiliation: Institute of Nutrition, Department of Nutritional Physiology, Friedrich Schiller University of Jena, Jena, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Rohrer
authors.affiliation: Institute of Animal Science, Physiology & Hygiene Unit, University of Bonn, Bonn, Germany.
authors.forename: Helga
authors.initials: H
authors.lastname: Sauerwein
authors.affiliation: Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Institute of Molecular Pathogenesis, Jena, Germany.
authors.forename: Konrad
authors.initials: K
authors.lastname: Sachse
authors.affiliation: Institute of Nutrition, Department of Nutritional Physiology, Friedrich Schiller University of Jena, Jena, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Jahreis
mesh_terms: D002689:Chlamydia / Q000378:metabolism*; D002690:Chlamydia Infections / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000235:genetics / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000172:deficiency*; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism
chemical_list: D005227:Fatty Acids; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D044943:Fatty Acid Desaturases; C533241:FADS2 protein, human; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D015232:Dinoprostone