title: Sex-related resistance to myocardial ischemia-reperfusion injury is associated with high constitutive ARC expression.
abstract: The female sex has been associated with improved myocardial salvage after ischemia and reperfusion (I/R). Estrogen, specifically 17beta-estradiol, has been demonstrated to mediate this phenomenon by limiting cardiomyocyte apoptosis. We sought to quantitatively assess the effect of sex, ovarian hormone loss, and I/R on myocardial Bax, Bcl-2, and apoptosis repressor with caspase recruitment domain (ARC) expression. Male (n = 48), female (n = 26), and oophorectomized female (n = 20) rabbits underwent 30 min of regional ischemia and 3 h of reperfusion. The myocardial area at risk and infarct size were determined using a double-staining technique and planimetry. In situ oligo ligation was used to assess apoptotic cell death. Western blot analysis was used to determine proapoptotic (Bax) and antiapoptotic (Bcl-2 and ARC) protein levels in all three ischemic groups and, additionally, in three nonischemic groups. Infarct size (43.7 +/- 3.2%) and apoptotic cell death (0.51 +/- 0.10%) were significantly attenuated in females compared with males (56.4 +/- 1.6%, P < 0.01, and 4.29 +/- 0.95%, P < 0.01) and oophorectomized females (55.7 +/- 3.4%, P < 0.05, and 4.36 +/- 0.51%, P < 0.01). Females expressed significantly higher baseline ARC levels (3.62 +/- 0.29) compared with males (1.78 +/- 0.18, P < 0.01) and oophorectomized females (1.08 +/- 0.26, P < 0.01). Males expressed a significantly higher baseline Bax-to-Bcl-2 ratio (4.32 +/- 0.99) compared with females (0.65 +/- 0.13, P < 0.01) and oophorectomized females (0.42 +/- 0.10, P < 0.01). I/R significantly reduced Bax-to-Bcl-2 ratios in males. In all other groups, ARC levels and Bax-to-Bcl-2 ratios did not significantly change. These results support the conclusion that in females, endogenous estrogen limits I/R-induced cardiomyocyte apoptosis by producing a baseline antiapoptotic profile, which is associated with estrogen-dependent high constitutive myocardial ARC expression.
authors.affiliation: Gorman Cardiovascular Research Group, Glenolden Research Laboratory, University of Pennsylvania, 500 S. Ridgeway Ave., Glenolden, PA 19036, USA.
authors.forename: Wobbe
authors.initials: W
authors.lastname: Bouma
authors.forename: Mio
authors.initials: M
authors.lastname: Noma
authors.forename: Shinya
authors.initials: S
authors.lastname: Kanemoto
authors.forename: Muneaki
authors.initials: M
authors.lastname: Matsubara
authors.forename: Bradley G
authors.initials: BG
authors.lastname: Leshnower
authors.forename: Robin
authors.initials: R
authors.lastname: Hinmon
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Gorman
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gorman
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001784:Blood Gas Analysis; D015153:Blotting, Western; D001831:Body Temperature / Q000502:physiology; D053468:CARD Signaling Adaptor Proteins / Q000096:biosynthesis* / Q000235:genetics*; D002469:Cell Separation; D004562:Electrocardiography; D004958:Estradiol / Q000097:blood; D004967:Estrogens / Q000502:physiology; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D008297:Male; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000000981:diagnostic imaging / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000502:physiology; D010052:Ovariectomy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D011817:Rabbits; D012727:Sex Characteristics; D014463:Ultrasonography; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis
chemical_list: D053468:CARD Signaling Adaptor Proteins; D004967:Estrogens; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D004958:Estradiol