title: Inhibition of DDAH1, but not DDAH2, results in apoptosis of a human trophoblast cell line in response to TRAIL.
abstract: OBJECTIVE
  Does inhibition of dimethylarginine dimethylaminohydrolase (DDAH) increase the sensitivity of trophoblasts to TRAIL-induced apoptosis?
  
  
  CONCLUSIONS
  Inhibition of DDAH1, but not DDAH2, increases the sensitivity of trophoblasts to TRAIL-induced apoptosis.
  
  
  BACKGROUND
  Successful human pregnancy is dependent on adequate trophoblast invasion and remodelling of the maternal spiral arteries. Increased trophoblast apoptosis is seen in pregnancies complicated by pre-eclampsia. The mechanism underlying this increase is unknown. We have previously shown that nitric oxide (NO) is involved in regulating trophoblast motility and invasion, and have also demonstrated an important role for NO in regulating trophoblast sensitivity to apoptotic stimuli. DDAH is an enzyme that metabolizes asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthesis, previously shown to be elevated in the plasma of pre-eclamptic mothers.
  
  
  METHODS
  This study used the human extravillous trophoblast-derived cell line SGHPL-4 cells. All experiments were performed at least three times.
  
  
  METHODS
  The effect of DDAH on trophoblast apoptosis was examined using siRNA and time-lapse microscopy. Changes in the expression of DDAH were followed by PCR and western blot analysis. Receptor expression was followed by flow cytometry.
  
  
  RESULTS
  Inhibiting the expression of DDAH1, but not DDAH2, resulted in a significant increase in the sensitivity of the EVT cell line SGHPL-4 to tumour necrosis factor related apoptosis inducing ligand (TRAIL) induced apoptosis (P < 0.01). This response could be mimicked by the addition of Asymmetric Dimethylarginine (ADMA), an endogenous inhibitor of NO synthesis and the substrate for both isoforms of DDAH. We further showed that this increased sensitivity to apoptosis is accompanied by a significant increase in the expression of TRAIL receptor 2 (TR2; P < 0.05) but not TRAIL receptor 1 (TR1).
  
  
  CONCLUSIONS
  This study was performed only in vitro using a well characterized trophoblast cell line, SGHPL-4, derived from first trimester extravillous trophoblasts.
  
  
  CONCLUSIONS
  This study provides new insight into the role of the DDAH/ADMA pathway in the regulation of trophoblast function. Both dysregulation of DDAH and the accumulation of ADMA have been associated with the development of pre-eclampsia. This is the first study to implicate the DDAH/ADMA pathway as a mechanism that might underlie the poor trophoblast invasion seen in this common pregnancy disorder.
  
  
  BACKGROUND
  B.A.L. was supported by a grant from Action Medical Research UK (SP4577). A.E.W. was supported by a grant from the Wellcome Trust (091550). There are no competing interests and the authors have no conflict interest to declare.
authors.affiliation: Reproductive and Cardiovascular Research Group, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: B A
authors.initials: BA
authors.lastname: Lumicisi
authors.affiliation: Reproductive and Cardiovascular Research Group, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: J E
authors.initials: JE
authors.lastname: Cartwright
authors.affiliation: Reproductive and Cardiovascular Research Group, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: K
authors.initials: K
authors.lastname: Leslie
authors.affiliation: Reproductive and Cardiovascular Research Group, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: A E
authors.initials: AE
authors.lastname: Wallace
authors.affiliation: Reproductive and Cardiovascular Research Group, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK g.whitley@sgul.ac.uk.
authors.forename: G S
authors.initials: GS
authors.lastname: Whitley
mesh_terms: D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D002460:Cell Line; D006801:Humans; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D000581:Amidohydrolases; C059999:dimethylargininase
keywords: ADMA; DDAH; TRAIL; apoptosis; extravillous trophoblast