-s. Cardiomyocyte apoptosis in autoimmune cardiomyopathy: mediated via endoplasmic reticulum stress and exaggerated by norepinephrine. Am J Physiol Heart Circ Physiol 293: H1636-H1645, 2007. First published June 1, 2007; doi:10.1152 doi:10. /ajpheart.01377.2006 suggests that the autoimmune cardiomyopathy produced by a peptide corresponding to the sequence of the second extracellular loop of the ␤ 1-adrenergic receptor (␤1-ECII) is mediated via a biologically active anti-␤ 1-ECII antibody, but the mechanism linking the antibody to myocyte apoptosis and cardiac dysfunction has not been well elucidated. Since the ␤ 1-ECII autoantibody is a partial ␤1-agonist, we speculate that the cardiomyopathy is produced by the ␤ 1-receptormediated stimulation of the CaMKII-p38 MAPK-ATF6 signaling pathway and endoplasmic reticulum (ER) stress, and that excess norepinephrine (NE) exaggerates the cardiomyopathy. Rabbits were randomized to receive ␤ 1-ECII immunization, sham immunization, NE pellet, or ␤ 1-ECII immunization plus NE pellet for 6 mo. Heart function was measured by echocardiography and catheterization. Myocyte apoptosis was determined by terminal deoxytransferasemediated dUTP nick-end labeling and caspase-3 activity, whereas CaMKII, MAPK family (JNK, p38, ERK), and ER stress signals (ATF6, GRP78, CHOP, caspase-12) were measured by Western blot, immunohistochemistry, and kinase activity assay. ␤ 1-ECII immunization produced progressive LV dilation, systolic dysfunction, and myocyte apoptosis. These changes were associated with activation of GRP78 and CHOP and increased cleavage of caspase-12, as well as increased CaMKII activity, increased phosphorylation of p38 MAPK, and nucleus translocation of cleaved ATF6. NE pellet produced additive effects. In addition, KN-93 and SB 203580 abolished the induction of ER stress and cell apoptosis produced by the ␤ 1-ECII antibody in cultured neonatal cardiomyocytes. Thus ER stress occurs in autoimmune cardiomyopathy induced by ␤ 1-ECII peptide, and this is enhanced by increased NE and caused by activation of the ␤ 1-adrenergic receptor-coupled CaMKII, p38 MAPK, and ATF6 pathway.cardiomyocytes; signal transduction EVIDENCE HAS ACCUMULATED indicating that autoimmunity plays an important role in viral myocarditis and dilated cardiomyopathy (18). Among the various known anti-heart autoantibodies, an antibody activating the human ␤ 1 -adrenergic receptor (␤ 1 -AR) has been best studied. The autoantibody is not only present in 30 -40% of patients with dilated cardiomyopathy (7,20) but also has been shown to predict increased mortality in the patients (30). The importance of the ␤ 1 -AR antibody in heart failure has been established by direct demonstration of dilated cardiomyopathy in animals immunized with a peptide corresponding to the sequence of the second extracellular loop of the ␤ 1 -AR (␤ 1 -EC II ) (8, 21). In addition, the ␤ 1 -EC II antisera obtained from the experimental animals have been shown to be biologically active (28,29), with a proapoptotic action via activation of the...

. Importance of antioxidant and antiapoptotic effects of ␤-receptor blockers in heart failure therapy. Am J Physiol Heart Circ Physiol 287: H1003-H1012, 2004. First published April 22, 2004 10.1152/ajpheart.00797.2003.-The present study was carried out to determine whether beneficial effects of carvedilol in congestive heart failure (CHF) are mediated via its ␤-adrenergic blocking, antioxidant, and/or ␣-adrenergic blocking action. Rabbits with heart failure induced by rapid cardiac pacing were randomized to receive subcutaneous carvedilol, metoprolol, propranolol plus doxazosin, or placebo pellets for 8 wk and compared with sham-operated rabbits without pacing. We found rapid cardiac pacing produced clinical heart failure, left ventricular dilation, and decline of left ventricular fractional shortening. This was associated with an increase in left ventricular end-diastolic pressure, decrease in left ventricular first derivative of left ventricular pressure, and myocyte hypertrophy. Tissue oxidative stress measured by GSH/GSSG was increased in the heart with increased oxidation product of mitochondrial DNA, 8-oxo-7,8-dihydro-2Ј-deoxyguanosine, increase of Bax, decrease of Bcl-2, and increase of apoptotic myocytes as measured by anti-single-stranded DNA monoclonal antibody. Administration of carvedilol and metoprolol, which had no effect in sham animals, attenuated cardiac ventricular remodeling, cardiac hypertrophy, oxidative stress, and myocyte apoptosis in CHF. In contrast, propranolol plus doxazosin, which has less antioxidant effects, produced smaller effects on left ventricular function and myocyte apoptosis. In all animals, GSH/GSSG correlated significantly with changes of left ventricular end-diastolic dimension (r ϭ Ϫ0.678, P Ͻ 0.0001), fractional shortening (r ϭ 0.706, P Ͻ 0.0001), and apoptotic myocytes (r ϭ Ϫ0.473, P ϭ 0.0001). Thus our findings suggest antioxidant and antiapoptotic actions of carvedilol and metoprolol are important determinants of clinical beneficial effects of ␤-receptors in the treatment of CHF.carvedilol; metoprolol; oxidative stress; myocytes apoptosis; myocyte hypertrophy.RECENT STUDIES HAVE SHOWN that ␤-adrenergic receptor blockers such as carvedilol, metoprolol, and bisoprolol are efficacious in the treatment of congestive heart failure (CHF) (3). These agents not only increase left ventricular systolic function (15, 28, 30) but also reduce cardiac mortality and morbidity in patients with CHF (7,23,(31)(32)(33). However, the extent of improvements produced by these agents varies, with the greatest improvement in mortality with carvedilol (31). In a direct comparison study published recently (33), carvedilol was shown to produce a greater survival benefit in patients with CHF than metoprolol. Whereas the discrepancies among the studies may relate to the difference in patient populations or degree of ␤-receptor blockade, these ␤-adrenergic blockers may have additional properties that contribute to their different clinical benefits. Unlike metoprolol and bisoprolol, which are sel...

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It is crucial to predict drug effectiveness in chronic disease, such as dilated cardiomyopathy (DCM), in which the left ventricular (LV) function might be improved by beta-blocker therapy. As the functional improvement effected by beta-blocker therapy takes more than 2 months, we investigated whether iodine-123 metaiodobenzylguanidine (123I-MIBG) imaging could be used to predict drug effectiveness. We studied 13 patients (11 men and two women; mean age, 43+/-13 years) with DCM and seven normal subjects (six men and one woman; mean age, 48+/-16 years). We obtained myocardial single-photon emission tomography (SPET) images 15 min and 4 h after administration of 123I-MIBG (111 MBq). Studies were performed in the patients with DCM before and 1 and 3 months after the administration of metoprolol and in the normal subjects. We calculated the regional 123I-MIBG washout rate (r-WR) in the SPET image, and the global 123I-MIBG washout rate (g-WR) and heart-mediastinum activity ratio (H/M) using the anterior planar image. We classified patients into those showing a >/=5% increase in LV ejection fraction (LVEF) at 3 months compared with LVEF values before the treatment (group I, n=7) and those showing a <5% increase in LVEF (group II, n=6). In group I, the r-WR values at pretreatment and at 1 month and 3 months of treatment, respectively, were 36%+/-19%, 29%+/-14%* and 25%+/-13%* in the anterior segment, 39%+/-17%, 33%+/- 17%** and 28%+/-17%* in the lateral segment, 36%+/- 16%, 31%+/-14%* and 22%+/-12%** in the septal segment and 40%+/-11%, 37%+/-19% and 31%+/-18%* in the inferior segment; the g-WR was 45%+/-11%, 43%+/-10% and 34%+/-9%*, respectively (* P<0.05, ** P<0.01 vs pretreatment). In group II, there were no significant changes in regional or global parameters during the 3-month period. In normal subjects, the r-WR values in each of the anterior, lateral, septal and inferior segments were significantly lower than those in groups I and II. These values were 18%+/-9%, 18%+/-15%, 20%+/-12% and 21%+/-15%, respectively. This study demonstrated that with regional assessment 123I-MIBG SPET imaging can be used to predict the functional improvement of LVEF at 1 month of beta-blocker therapy in patients with DCM.

Auto-antibodies against the β 1 -adrenoceptors are present in 30−40% of patients with dilated cardiomyopathy. Recently, a synthetic peptide corresponding to a sequence of the second extracellular loop of the human β 1 -adrenoceptor (β 1 -EC II ) has been shown to produce endoplasmic reticulum (ER) stress, myocyte apoptosis and cardiomyopathy in immunized rabbits. To study the direct cardiac effects of anti-β 1 -EC II antibody in intact animals and if they are mediated via β 1 -adrenoceptor stimulation, we administered IgG purified from β 1 -EC II -immunized rabbits to recombination activating gene 2 knock-out (Rag2 −/− ) mice every two weeks with and without metoprolol treatment. Serial echocardiography and cardiac catheterization showed that β 1 -EC II IgG reduced cardiac systolic function after 3 months. This was associated with increase in heart weight, myocyte apoptosis, activation of caspase-3, -9 and -12, and increased ER stress as evidenced by upregulation of GRP78 and CHOP and cleavage of ATF6. The Rag2 −/− mice also exhibited increased phosphorylation of CaMKII and p38 MAPK. Metoprolol administration, which attenuated the phosphorylation of CaMKII and p38 MAPK, reduced the ER stress, caspase activation and cell death. Finally, we employed the small-interfering RNA technology to reduce caspase-12 in cultured rat cardiomyocytes. This reduced not only the increase of cleaved caspase-12 but also of the number of myocyte apoptosis produced by β 1 -EC II IgG. Thus, we conclude that ER stress plays an important role in cell death and cardiac dysfunction in β 1 -EC II IgG cardiomyopathy, and the effects of β 1 -EC II IgG are mediated via the β 1 -adrenergic receptor.