title: Redox status of serum apolipoprotein E and its impact on HDL cholesterol levels.
abstract: BACKGROUND
  Apolipoprotein E (apoE) is closely involved in the pathogenesis of apoE-related diseases, such as Alzheimer's disease and cardiovascular disease. The redox modulation of cysteine-thiols in a protein is involved in various pathophysiological regulations; however, that of apoE has not been studied in detail. Herein, we devised an analytical method to determine the redox status of serum apoE and assessed its relation to serum cholesterol levels and apoE phenotype.
  
  
  METHODS
  The present method was based on a band shift assay, using a photocleavable maleimide-conjugated polyethylene glycol.
  
  
  RESULTS
  The basic characteristics of the present method were found to be satisfactory to determine the redox status of serum apoE quantitatively. Serum apoE was separated into its reduced-form (r-), non-reduced-form (nr-), apoE-AII complex, and homodimer using this method. R-apoE could be detected as a 40-kDa band, whereas nr-apoE remained as monomeric apoE. R-apoE displayed a preference for VLDL; however, the levels showed the correlation with HDL-cholesterol levels (p<0.005). Redox status of serum apoE was significantly different among apoE phenotypes. The quantitative ratios of nr-apoE to total apoE in serum from subjects with apoE4/E3 were higher than in serum from subjects with apoE3/E3 (p<0.0001) and apoE3/E2 (p<0.001).
  
  
  CONCLUSIONS
  The redox status of serum apoE might be related to the synthesis of HDL. The information concerning the redox status of serum apoE provided by the present method may be a potent indicator to evaluate various apoE-related diseases.
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine, University of Tsukuba, Japan; Department of Medical Sciences, Faculty of Medicine, University of Tsukuba, Japan. Electronic address: yamauchi@md.tsukuba.ac.jp.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Yamauchi
authors.affiliation: Department of Medical Sciences, Faculty of Medicine, University of Tsukuba, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Ebihara
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine, University of Tsukuba, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D016633:Apolipoprotein A-II / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D053329:Apolipoprotein E2 / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D053318:Apolipoprotein E3 / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D053327:Apolipoprotein E4 / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D001057:Apolipoproteins E / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D008076:Cholesterol, HDL / Q000097:blood* / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D003958:Diamide / Q000737:chemistry; D019281:Dimerization; D004229:Dithiothreitol / Q000737:chemistry; D024202:Electrophoretic Mobility Shift Assay; D057809:HEK293 Cells; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D008970:Molecular Weight; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011092:Polyethylene Glycols / Q000737:chemistry; D012995:Solubility; D013439:Sulfhydryl Reagents / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D016633:Apolipoprotein A-II; D053329:Apolipoprotein E2; D053318:Apolipoprotein E3; D053327:Apolipoprotein E4; D001057:Apolipoproteins E; D008076:Cholesterol, HDL; D007202:Indicators and Reagents; D013439:Sulfhydryl Reagents; C017018:apo E-apo A-II complex; D003958:Diamide; D011092:Polyethylene Glycols; D003545:Cysteine; D004229:Dithiothreitol
keywords: Alzheimer's disease; ApoE dimer; Band shift assay; Cysteine-thiol; HDL; Oxidation