Loss of Multidrug Resistance–Associated Protein 1 Potentiates Chronic Doxorubicin-Induced Cardiac Dysfunction in Mice

Abstract

Doxorubicin (DOX), an effective cancer chemotherapeutic agent, induces dose-dependent cardiotoxicity, in part due to its ability to cause oxidative stress. We investigated the role of multidrug resistance-associated protein 1 (Mrp1/Abcc1) in DOX-induced cardiotoxicity in C57BL wild-type (WT) mice and their Mrp1 null (Mrp1 2/2 ) littermates. Male mice were administered intraperitoneal DOX (3 or 2 mg/kg body weight) or saline twice a week for 3 weeks and examined 2 weeks after the last dose (protocol A total dose: 18 mg/kg) or for 5 weeks, and mice were examined 48 hours and 2 weeks after the last dose (protocol B total dose: 20 mg/kg). Chronic DOX induced body weight loss and hemotoxicity, adverse effects significantly exacerbated in Mrp1 2/2 versus WT mice. In the heart, significantly higher basal levels of glutathione (1.41-fold 6 0.27-fold) and glutathione disulfide (1.35-fold 6 0.16-fold) were detected in Mrp1 2/2 versus WT mice, and there were comparable decreases in the glutathione/glutathione disulfide ratio in WT and Mrp1 2/2 mice after DOX administration. Surprisingly, DOX induced comparable increases in 4-hydroxynonenal glutathione conjugate concentration in hearts from WT and Mrp1 2/2 mice. However, more DOX-induced apoptosis was detected in Mrp1 2/2 versus WT hearts (P , 0.05) (protocol A), and cardiac function, assessed by measurement of fractional shortening and ejection fraction with echocardiography, was significantly decreased by DOX in Mrp1 2/2 versus WT mice (P , 0.05; 95% confidence intervals of 20.0%-24.3% versus 23.7%-29.5% for fractional shortening, and 41.5%-48.4% versus 47.7%-56.7% for ejection fraction; protocol B). Together, these data indicate that Mrp1 protects the mouse heart against chronic DOX-induced cardiotoxicity.

Elevated Glutathione Is Not Sufficient to Protect against Doxorubicin-Induced Nuclear Damage in Heart in Multidrug Resistance–Associated Protein 1 (Mrp1/Abcc1) Null Mice

“…Mice were treated with saline or 2 mg/kg DOX twice a week for 5 weeks, and GSG and GSSG were determined in the hearts 48 hours and 2 weeks after the last treatment. In this chronic treatment model, GSH and the GSH/GSSG ratio were decreased at 48 hours but had recovered by 2 weeks after treatment (Zhang et al, 2015). These data are consistent with a decrease in GSH and GSH/GSSG upon oxidative stress that in turn triggers activation of the antioxidant stress response system to increase GSH synthesis and restore a normal GSH/GSSG ratio.…”

“…Again, these data suggest that complete loss of Mrp1-mediated GS-HNE efflux contributes to its increased retention in Mrp1 2/2 mice. In contrast, after chronic DOX treatment, GS-HNE was somewhat elevated 48 hours after DOX and significantly increased 2 weeks after the last dose of DOX in both WT and Mrp1 2/2 mice (Zhang et al, 2015). These data imply that the early increase in Mrp1 expression is not sufficiently longlasting to sustain low GS-HNE levels in WT mice after 5 weeks of DOX treatment.…”

“…3). Finally, we examined expression of Abcb1 and Abcc4/ Mrp4 protein 2 weeks after chronic DOX treatment and found no changes in their expression between treatments or genotype (Zhang et al, 2015).…”

“…These data imply that the early increase in Mrp1 expression is not sufficiently longlasting to sustain low GS-HNE levels in WT mice after 5 weeks of DOX treatment. Indeed, immunoblots of heart from salineand DOX-treated mice at 48 hours and 2 weeks after chronic DOX treatment showed no differences in expression of Mrp1 (Zhang et al, 2015).…”

“…We also examined the effects of chronic DOX treatment in WT and Mrp1 2/2 mice on GSH homeostasis (Zhang et al, 2015). Mice were treated with saline or 2 mg/kg DOX twice a week for 5 weeks, and GSG and GSSG were determined in the hearts 48 hours and 2 weeks after the last treatment.…”