Ultrastructural and Echocardiographic Assessment of Chronic Doxorubicin-Induced Cardiotoxicity in Rats

Abstract

Doxorubicin (DOX) is one of the secondary metabolites of Streptomyces peucetius var. caesius. It is a common and effective chemotherapeutic agent used for the treatment of different diseases, including lymphoma, leukemia, breast cancer, and solid tumors. However, this medicine causes cardiotoxic side effects, which limit its clinical application. The present study examined the cardiomyopathy induced by DOX via echocardiography and transmission electron microscopy (TEM). The main objective was to evaluate the capacity of echocardiography and TEM as diagnostic tools for DOX-induced cardiotoxicity. Moreover, the correlation between intracellular and functional changes due to cardiotoxicity was assessed in a rat model. Cardiomyopathy was induced in rats by two cumulative doses of DOX. Group I received DOX 12 [i.e., 12 mg/kg, intraperitoneal (IP)] and group II received DOX 15 (i.e., 15 mg/kg, IP) in six equal doses over two weeks. Group III as the control (Ctrl) group received normal saline as a vehicle. Mortality during the study was only observed in the DOX 15 group. The echocardiographic assessments revealed significant changes in ejection fraction, fractional shortening, and heart rate in the groups which received DOX. In addition, severe cardiac arrhythmia was evident in DOX-treated groups. Remarkable adverse effects, such as moderately degenerated cells and inflated mitochondria were observed in the TEM analysis of rat hearts in the DOX groups. The present study indicated that rat models are suitable for investigating DOX-induced cardiomyopathy, especially at the dose of 12 mg/kg. Furthermore, echocardiography and TEM examinations were found to be valuable methods for the determination of cardiotoxicity in rats due to DOX.

Keywords: Cardiomyopathy; Doxorubicin; Echocardiography; Electron microscopy; Rat heart.

Figure 1

Bodyweight changes in the three groups; Ctrl: control group (normal saline); DOX 12: doxorubicin 12 mg/kg (2 mg/kg/48h, IP); DOX 15: doxorubicin 15 mg/kg (2.5 mg/kg/48h, IP); data are presented as mean ± standard deviation (n=6) (***P<0.001 in comparison with the control).

Figure 2

Echocardiography results from the three groups. A: control group (normal saline); B: doxorubicin (12 mg/kg; 2 mg/kg/48h, IP); C: doxorubicin (15 mg/kg; 2.5 mg/kg/48h, IP); AW: anterior wall; PW: posterior wall of the ventricular septum

Figure 3

Ultrastructure analysis of the three groups by TEM. Section A: control showing normal rat cardiomyocyte structure with typical mitochondria and sarcomere (×10000). Section B: DOX 12 (12 mg/kg; 2 mg/kg/48h, IP) showing changes in the morphology of mitochondria and sarcomere; M: mitochondria; S: sarcomere, and C: cristae; mitochondria with few cristae were detected (×10000). Section C: DOX 15 (15 mg/kg; 2.5 mg/kg/48h, IP) showing remarkable changes in the morphology of mitochondria. M: mitochondria; S: sarcomere, and C: cristae; giant mitochondria with the lowest number of cristae (×10000). D: DOX 12 (12 mg/kg; 2 mg/kg/48h, IP) deforming sarcomeres and inflated mitochondria (×10000)