title: Improved Assay for Quantifying a Redox Form of Angiotensinogen as a Biomarker for Pre-Eclampsia: A Case-Control Study.
abstract: OBJECTIVE
  Angiotensinogen exists in two distinct redox forms in plasma, the oxidized sulfhydryl-bridge form and the reduced, unbridged, free thiol form. The oxidized form of angiotensinogen compared to the free thiol form preferentially interacts with renin resulting in increased generation of angiotensin. The predictive potential of the ratio of free-thiol to oxidized angiotensinogen in the plasma for pre-eclampsia was first suggested by the Read group in ref 10. We propose an improved method for determining the ratio and validate the method in a larger cohort of pregnant women.
  
  
  METHODS
  Plasma samples from 115 individuals with pre-eclampsia and from 55 healthy pregnant control subjects were collected sequentially over a 2 year period. Using two distinct enzyme-linked immunosorbent assays (ELISAs) the plasma levels of total and free thiol angiotensinogen were quantified. The oxidized angiotensinogen plasma level is derived by subtracting the level of free thiol, reduced angiotensinogen from the total angiotensinogen levels in the plasma.
  
  
  RESULTS
  The relative proportion of free thiol angiotensinogen, expressed as a percentage of that observed with an in-house standard, is significantly decreased in pre-eclamptic patients (70.85% ± 29.49%) (mean ± SD) as compared to healthy pregnant controls (92.98 ± 24.93%) (mean ± SD) p ≤ 0.0001. The levels of total angiotensinogen did not differ between the two groups.
  
  
  CONCLUSIONS
  Patients with pre-eclampsia had substantially lower levels of free thiol angiotensinogen compared to healthy pregnant controls, whilst maintaining similar total angiotensinogen levels in the plasma. Hence, elevated levels of plasma oxidized angiotensinogen may be a contributing factor to hypertension in the setting of pre-eclampsia.
authors: Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran.
authors: Soheila
authors: S
authors: Rahgozar
authors: Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran.
authors: Tayebeh
authors: T
authors: Amirian
authors: Department of Infectious Diseases, Immunology and Sexual Health and Department of Medicine, St George Hospital, University of New South Wales, Sydney, Australia.
authors: Miao
authors: M
authors: Qi
authors: Department of Obstetrics and Gynaecology, Shahid Beheshti Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.
authors: Zahra
authors: Z
authors: Shahshahan
authors: Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran.
authors: Mansureh
authors: M
authors: Entezar-E-Ghaem
authors: Department of Obstetrics and Gynaecology, Shahid Beheshti Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.
authors: Hatav
authors: H
authors: Ghasemi Tehrani
authors: Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran.
authors: Mehran
authors: M
authors: Miroliaei
authors: Department of Infectious Diseases, Immunology and Sexual Health and Department of Medicine, St George Hospital, University of New South Wales, Sydney, Australia.
authors: Steven A
authors: SA
authors: Krilis
authors: Department of Infectious Diseases, Immunology and Sexual Health and Department of Medicine, St George Hospital, University of New South Wales, Sydney, Australia.
authors: Bill
authors: B
authors: Giannakopoulos
mesh_terms: D000328:Adult; D000808:Angiotensinogen / Q000097:blood* / Q000737:chemistry*; D001681:Biological Assay / Q000379:methods*; D015415:Biomarkers / Q000097:blood*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011225:Pre-Eclampsia / Q000097:blood / Q000175:diagnosis*; D011247:Pregnancy; D012372:ROC Curve
chemical_list: D015415:Biomarkers; D000808:Angiotensinogen