Abstract P341: Juvenile Exposure To Doxorubicin Differentially Alters The Cardiac Response To Angiotensin II And Isoproterenol In Adult Mice

Abstract

Hypertension is the most significant risk factor for heart failure in doxorubicin (DOX)-treated childhood cancer survivors. We previously developed a two-hit mouse model of juvenile DOX-induced latent cardiotoxicity that is exacerbated by adult-onset angiotensin II (ANGII)-induced hypertension. Nevertheless, it is still not known how juvenile exposure to DOX would predispose the heart to other cardiovascular pathologic stimuli that do not cause hypertension. The objective of this work was to compare the effects of ANGII to those of isoproterenol (ISO) in adult C57BL6/N mice pre-exposed to DOX as juveniles. Five-week-old male mice were administered a low dose of DOX (4 mg/kg/week) or saline for 3 weeks and then allowed to recover for 5 weeks. Thereafter, mice were either infused with ANGII (1.4 mg/kg/day) or injected with ISO (10 mg/kg/day) for 14 days. Juvenile exposure to DOX abrogated the hypertrophic response to both ANGII and ISO, while it failed to correct ANGII- and ISO-induced upregulation in the hypertrophic markers ANP and BNP. ANGII, but not ISO, worsened cardiac function in DOX-exposed mice as measured by echocardiography. Cardiac fibrosis was also exacerbated by ANGII, but not ISO, in DOX-exposed mice as evident by Masson’s trichrome staining and upregulation of the inflammatory and fibrotic markers, Cox-2, Col1a1, Col3a1 , and galectin-3 . In conclusion, the current work demonstrates that ANGII causes more severe deterioration in cardiac function and adverse cardiac remodeling in DOX-exposed mice when compared to ISO. The comparison between DOX/ANGII and DOX/ISO models is critical to understanding why hypertension is the most significant risk factor for heart failure in DOX-treated childhood cancer survivors and thereby devising effective therapeutic strategies against this significant clinical problem.