Persistent effects of doxorubicin on cardiac gene expression

During administration of the anthracycline antitumour agents, their cardiot oxicity can progress from cardiac dysfunction. to heart failure. Cardiomyop athy call also develop years after receiving anthracyclines, To determine i f persistent and/or progressive anthracycline effect(s) are referable to an thracycline effects on cardiac gene expression, steady-state mRNA levels we re determined 4 days (n = 8), 4 weeks (n = 7) and 10 weeks (n = 7) after do xorubicin (DOX; 2 mg/kg IV) in a well-characterized rabbit model, Levels of mRNA for alpha-actin, beta-myosin heavy chain and the calcium pump of the sarcoplasmic reticulum (SERCA2a) in the left ventricle (LV) were determined by Northern blot hybridization and expressed relative to an 18S constituti ve marker. The mRNA levels for the high molecular weight subunit (cardiac i soform) of the ryanodine receptor (RyR2), sarcolemmal calcium channel (dihy dropyridine receptor; DHPR), angiotensin-converting enzyme (ACE), angiotens in II receptor (ATR) and atrial naturetic peptide prohormone (ANP) were det ermined by reverse transcription-polymerase chain reaction (RT-PCR) and Sou thern blot analysis, and expressed relative to GAPDH, a constitutive marker . Histopathologic evidence for anthracycline-induced myocardial cell injury was absent (score <1) in all hearts examined except one (score = 1.1; 4 we eks post-DOX), which was considered separately, Relative mRNA levels for P- myosin heavy chain 4 days after DOX increased 1.9-fold compared to the vehi cle-treated group, but by 4 weeks levels had returned to baseline, Relative mRNA levels for DHPR were increased 1.2-fold 4 days after DOX and were per sistently increased 1.9- and 2.2-fold 4 and 10 weeks after DOX, respectivel y. The mRNA levels for ANP were first decreased (4.5-fold) 4 days after DOX . Four weeks after DOX, ANP message levels approached Control in seven out of eight rabbits. The one rabbit with early LV histopathology 4 weeks post- DOX had increased mRNA for DHPR (2.7-fold) and ANP (80-fold). Between 4 and 10 weeks after DOX, mRNA levels for ANP increased similar to 16-fold: evid ence for late progression, In situ hybridization with specific riboprobes l ocalized the persistent increase in DHPR and the progressive increase in AN P to myocytes, Thus, DOX alters steady-state mRNA levels in LV that are ref erable to both persistent and progressive anthracycline effects on myocellu lar gene expression, (C) 1999 Academic Press.