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Selective alterations in rat cardiac mRNA induced by doxorubicin: possible subcellular mechanisms
Abstract:
Doxorubicin (Adriamycin, ADR) is an effective antineoplastic agent with a major side effect of dilated cardiomyopathy. Previously we showed ADR selectively decreased alpha cardiac (alpha c) actin mRNA in the rat heart when compared to other mRNAs examined in heart and skeletal muscle. The present study determined if this effect was selective for mRNAs within the thin filament, related to inhibitory effects on mitochondrial transcription, and modified by pretreatment with the cardioprotective chelating agent ICRF-187. Adult Sprague-Dawley rats received ADR at 8 mg/kg intraperitoneally (ip) with or without pretreatment with ICRF-187 given at 80 mg/kg ip. After 3 days, rats were killed and myocardial RNA was extracted, electrophoresed, transferred to nitrocellulose, and hybridized with the [32]cDNA probes alpha c actin, troponin C (TnC), BamHI fragment of mouse mitochondria (MM), and glyceraldehyde-3-phosphate dehydrogenase (G3PD). Results showed a major depressive effect of ADR on rat myocardial alpha c actin mRNA. No depression of the other mRNAs examined (TnC, MM, or G3PD) was seen. ICRF-187 did not modify the effect. We conclude that the ADR-induced decrease in alpha c actin mRNA was: (1) selective within the thin filament; (2) not related to inhibitory effects on mitochondrial transcription; and (3) not related to free radical formation. Possible subcellular mechanisms are discussed.
Insights
Doxorubicin (ADR) chemotherapy significantly reduces alpha cardiac actin mRNA in rat hearts. This effect is specific to the thin filament and not altered by the cardioprotective agent ICRF-187.
Area of Science:
- Biochemistry
- Molecular Biology
- Cardiology
Background:
- Doxorubicin (ADR) is a potent antineoplastic drug.
- A major side effect of ADR is dilated cardiomyopathy.
- Previous studies indicated ADR selectively decreases alpha cardiac (alpha c) actin mRNA in rat hearts.
Purpose of the Study:
- To investigate if the ADR-induced decrease in alpha c actin mRNA is selective within the thin filament.
- To determine if this effect relates to inhibitory effects on mitochondrial transcription.
- To assess if pretreatment with the cardioprotective agent ICRF-187 modifies ADR's impact on alpha c actin mRNA levels.
Main Methods:
- Adult Sprague-Dawley rats were administered ADR (8 mg/kg) with or without ICRF-187 (80 mg/kg).
- Myocardial RNA was extracted after 3 days.
- RNA levels for alpha c actin, troponin C (TnC), mitochondrial mRNA (MM), and glyceraldehyde-3-phosphate dehydrogenase (G3PD) were quantified using Northern blot hybridization.
Main Results:
- ADR significantly decreased myocardial alpha c actin mRNA levels.
- No significant depression was observed for TnC, MM, or G3PD mRNA.
- ICRF-187 pretreatment did not alter the ADR-induced reduction in alpha c actin mRNA.
Conclusions:
- The ADR-induced decrease in alpha c actin mRNA is selective within the cardiac thin filament.
- This effect is not linked to inhibition of mitochondrial transcription.
- The mechanism does not appear to involve free radical formation, and subcellular mechanisms are discussed.