Lack of evidence for a pathogenic role of proteasome-directed autoimmunity in dilated cardiomyopathy
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The proteasome has been identified as a target of the humoral autoimmune response in different inflammatory disease entities including dilated cardiomyopathy (DCM). However, the role of proteasome autoantibodies (ProtAb) remains to be studied. Here, we have isolated human ProtAb by affinity-purification from the IgG fractions obtained from DCM patients, which predominantly detected the outer ring subunits α3 of the 20S proteasome. In an attempt to study the cellular effects potentially exerted by these ProtAb, simultaneous calcium and cell contractility measurements were performed in rat cardiomyocytes revealing no short-term effects upon human ProtAb exposure. Immunofluorescence staining and FACS analysis pointed towards a failure of human ProtAb to bind to the intact cell membrane, whereas human ProtAb detected 20S proteasomes in the cytoplasm and nucleus. The lack of the cell surface interaction of human ProtAb was in agreement with the failure of these autoantibodies to interfere with the cellular viability. Further, we investigated whether the removal of ProtAb by immunoadsorption (IA) resulted in functional improvement in DCM patients. IA was performed in 90 DCM patients (left ventricular ejection fraction ≤45%, ProtAb detection at baseline in 30% of these DCM patients). Improvement of LVEF was not associated with the initial detection and removal of ProtAb in DCM patients. ProtAb were reconstituted to baseline levels as soon as after 3 months post-IA/IgG treatment despite the overall improvement of LVEF in this study group. In conclusion, our data argue against a direct impact of ProtAb in the pathogenesis of DCM.
KeywordsCardiomyopathy Proteasome Immunoadsorption Autoimmunity
This study was supported by the Deutsche Forschungsgemeinschaft SFB/TR 19: TP B3 to AV, UK, PMK; TP C2 to AS and SF; TP Z4 to KK and TP B5 to RK as well as by the Deutsche Forschungsgemeinschaft FE 470/3-1 to EF.
Conflict of interest statement
There are no financial conflicts to declare.
- 4.Buvall L, Bollano E, Chen J, Shultze W, Fu M (2006) Phenotype of early cardiomyopathic changes induced by active immunization of rats with a synthetic peptide corresponding to the second extracellular loop of the human beta(1)-adrenergic receptor. Clin Exp Immunol 143:209–215CrossRefPubMedGoogle Scholar
- 14.Felix SB, Staudt A, Dorffel WV, Stangl V, Merkel K, Pohl M, Docke WD, Morgera S, Neumayer HH, Wernecke KD, Wallukat G, Stangl K, Baumann G (2000) Hemodynamic effects of immunoadsorption and subsequent immunoglobulin substitution in dilated cardiomyopathy—three-month results from a randomized study. J Am Coll Cardiol 35:1590–1598CrossRefPubMedGoogle Scholar
- 16.Fu MLX, Schulze W, Wallukat G, Hjalmarson A, Hoebeke J (1996) A synthetic peptide corresponding to the second extracellular loop of the human M2 acetylcholine receptor induces pharmacological and morphological changes in cardiomyocytes by active immunization after 6 months in rabbits. Clin Immunol Immunopathol 80:203–207CrossRefGoogle Scholar
- 21.Jane-Wit D, Altuntas CZ, Johnson JM, Yong S, Wickley PJ, Clark P, Wang Q, Popovic ZB, Penn MS, Damron DS, Perez DM, Tuohy VK (2007) beta(1)-Adrenergic receptor autoantibodies mediate dilated cardiomyopathy by agonistically inducing cardiomyocyte apoptosis. Circulation 116:399–410CrossRefPubMedGoogle Scholar
- 26.Kordonouri O, Meyer K, Egerer K, Hartmann R, Scheffler S, Burmester SSGR, Kuckelhorn U (2004) Prevalence of 20S proteasome, anti-nuclear and thyroid antibodies in young patients at onset of type 1 diabetes mellitus and the risk of autoimmune thyroiditis. J Pediatr Endocrinol Metab 17:975–981PubMedGoogle Scholar
- 29.Liu JH, Mao WK, Iwai CK, Fukuoka S, Vulapalli R, Huang HL, Wang TC, Sharma VK, Sheu SS, Fu M, Liang CS (2008) Adoptive passive transfer of rabbit beta(1)-adrenoceptor peptide immune cardiomyopathy into the Rag2(−/−) mouse: participation of the ER stress. J Mol Cell Cardiol 44:304–314PubMedGoogle Scholar
- 30.Maron BJ, Towbin JA, Thiene G, Antzelevitch C, Corrado D, Arnett D, Moss AJ, Seidman CE, Young JB (2006) Contemporary definitions and classification of the cardiomyopathies—an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation 113:1807–1816CrossRefPubMedGoogle Scholar
- 31.Matsui S, Fu MLX, Katsuda S, Hayase M, Yamaguchi N, Teraoka K, Kurihara T, Takekoshi N, Murakami E, Hoebeke J, Hjalmarson A (1997) Peptides derived from cardiovascular G-protein-coupled receptors induce morphological cardiomyopathic changes in immunized rabbits. J Mol Cell Cardiol 29:641–655CrossRefPubMedGoogle Scholar
- 32.Matsui S, Larsson L, Hayase M, Katsuda S, Teraoka K, Kurihara T, Murano H, Nishikawa K, Fu M (2006) Specific removal of beta 1-adrenoceptor autoantibodies by immunoabsorption in rabbits with autoimmune cardiomyopathy improved cardiac structure and function. J Mol Cell Cardiol 41:78–85CrossRefPubMedGoogle Scholar
- 40.Staudt A, Böhm M, Knebel F, Staudt Y, Bischoff C, Hummel A, Borges A, Wallukat G, Delbruck M, Baumann G, Felix SB (2002) Potential role of autoantibodies belonging to the immunoglobulin G-3 subclass in cardiac dysfunction among patients suffering from dilated cardiomyopathy. Circulation 106:2448–2453CrossRefPubMedGoogle Scholar
- 45.Szalay G, Meiners S, Voigt A, Lauber J, Spieth C, Speer N, Sauter M, Kuckelkorn U, Zell A, Klingel K, Stangl K, Kandolf R (2006) Ongoing coxsackievirus myocarditis is associated with increased formation and activity of myocardial immunoproteasomes. Am J Pathol 168:1542–1552CrossRefPubMedGoogle Scholar