Epigenetic repression by SAHA leads to cardio-protection in anthracycline-induced long-term cardiotoxicity

Background Cancer therapy-induced cardiotoxicity, particularly from the topoisomerase 2 (Top2b) inhibitor Doxorubicin (DOX), can lead to heart failure even years after treatment. Cardiomyocyte-specific Top2b deletion protect against DOX-induced cardiomyopathy, but the underlying mechanisms remain unclear. ChIP-Seq in neonatal rat cardiomyocytes revealed a high overlap between DOX-induced Top2b-binding sites and those of the transcription factor MEF2. Purpose Given the central role of MEF2 in pathological cardiac remodeling, we hypothesized that targeting the HDAC4-mediated MEF2 suppression via the FDA-approved HDAC inhibitor SAHA could mitigate DOX-induced cardiotoxicity. Methods Mice were treated with DOX (3 mg/kg) via eight injections over a period of two weeks, with or without SAHA (12.5 mg/kg) or TMP195 (15 mg/kg). To evaluate long-term effects, analyses were performed nine weeks post the last injection. Cardiac function was assessed by echocardiography and gene expression was measured using qPCR. Conditional cardiomyocyte-specific HDAC4 knockout mice were treated similarly. Statistical analysis was performed using ANOVA (Bonferroni) test, with p<0.05 considered significant. Results Mice treated with DOX showed reduced left ventricular ejection fraction (LVEF), but co-treatment with SAHA prevented this reduction (Control 50.3 ± 3.1%, n=12 vs. DOX: 43.0 ± 3.4%; vs. DOX+SAHA: 50.6 ± 7.4%, p>0.05). Additionally, DOX-induced upregulation of pathological genes, such as myh7, was attenuated by SAHA. In contrast, inhibiting HDAC4 pharmacologically by using the selective HDAC class II inhibitor TMP195 did not improve DOX-induced cardiac dysfunction (Control 49.1 ± 7.8%, n=12 vs. DOX 40.8 ± 4.8%, n=10, p<0.05; vs. DOX+TMP195 37.1 ± 6.2%, n=6, p<0.05), and MEF2 target gene myh7 was not reversed. Cardiomyocyte-specific HDAC4 knockout mice exhibited impaired cardiac function after DOX and DOX+SAHA treatment (Control 51.7±5.4 %, n=5, vs. DOX 34.9±5.4 %, n=4, p<0.05; vs. DOX+SAHA 37.9±3.9 %, n=4, p<0.05) indicating HDAC4 to be required in SAHA mediated cardio-protection. Conclusion These findings suggest that HDAC4-mediated inhibition of MEF2 by SAHA may protect against DOX-induced cardiotoxicity.