Upregulation of the Bcl-2 family of proteins in end stage heart failure

OBJECTIVES To elucidate the pattern of expression of four members of the Bc l-2 family of proteins and to correlate this with terminal deoxynucleotidyl transferase [TdT]-mediated dUTP nick end labelling (TUNEL) and DNA fragmen tation. BACKGROUND Apoptosis has been implicated as a possible mechanism in the dev elopment of heart failure. However, the mechanisms involved remain unclear. METHODS We have studied the expression of four members of the Bcl-2 family that are involved in the regulation of apoptosis and analyzed DNA fragmenta tion as a marker of apoptosis and as a biochemical criterion to distinguish between apoptosis and necrosis in dilated cardiomyopathy (DCM), ischemic h eart disease (IHD) and normal donors. RESULTS Western blot analysis and immunocytochemistry of the proapoptotic a nd antiapoptotic Bcl-2 proteins demonstrated significantly higher levels of all these proteins in the diseased groups compared with normal donors. Add itionally, Bax was significantly higher in the IHD group compared with DCM. Terminal deoxynucleotidyl transferase [TdT]-mediated dUTP nick end labelli ng analysis demonstrated a significantly higher percentage of TUNEL-positiv e cells in the diseased groups compared with the control. Genomic DNA extra ction of ventricular myocardial tissue showed no demonstrable DNA laddering for any of the groups. CONCLUSIONS The significant increases in the levels of the proapoptotic pro teins Bak and Bax and the higher percentage of TUNEL-positive cells in both diseased groups suggests the presence of ongoing apoptosis. However, incre ases in the antiapoptotic proteins, Bcl-2 and Bcl-x(L), suggest a possible concommitant, compensatory antiapoptotic mechanism in patients with heart f ailure. (J Am Coll Cardiol 2000;35:1769-77) (C) 2000 by the American Colleg e of Cardiology.