Loss of FADS2 function severely impairs the use of HeLa cells as an in vitro model for host response studies involving fatty acid effects

PLoS One. 2014 Dec 30;9(12):e115610. doi: 10.1371/journal.pone.0115610. eCollection 2014.

Abstract

Scope: 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.

Methodology/principal findings: 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/significance: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chlamydia / metabolism*
  • Chlamydia Infections / genetics
  • Chlamydia Infections / metabolism*
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism*
  • Dinoprostone / genetics
  • Dinoprostone / metabolism*
  • Fatty Acid Desaturases / deficiency*
  • Fatty Acids / genetics
  • Fatty Acids / metabolism*
  • HeLa Cells
  • Humans
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / metabolism

Substances

  • Fatty Acids
  • TLR2 protein, human
  • Toll-Like Receptor 2
  • Fatty Acid Desaturases
  • FADS2 protein, human
  • Cyclooxygenase 2
  • PTGS2 protein, human
  • Dinoprostone

Grants and funding

This study was financially supported by a grant from the German Research Council DFG Ja 893/5) and a grant provided by the North Rhine-Westphalian Ministry of Environment, Conservation, Agriculture and Consumers Protection (MUNLV) within the Inter-Departmental Center of Sustainable Agriculture (USL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.