Assessment of aflatoxin B1 myocardial toxicity in rats: mitochondrial damage and cellular apoptosis in cardiomyocytes induced by aflatoxin B1

Abstract

Objective The number of deaths from heart disease is increasing worldwide. Aflatoxin B1 (AFB1), a toxin produced by the fungi Aspergillus flavus and Aspergillus parasiticus, is frequently detected in improperly processed/stored human food products. While AFB1 hepatotoxicity and carcinogenic properties have been well addressed, its myocardial toxicity is poorly documented. This study aimed to investigate myocardial toxic activity of AFB1. Methods Ten rats were fed with AFB1 at a dose that did not result in acute toxic reactions for 30 days and 10 vehicle-fed rats served as controls. Transmission electron microscopy was used to assess mitochondrial damage in cardiomyocytes. The terminal deoxynucleotidyl transferase-mediated UTP nick-end labelling assay was performed to detect apoptosis of cardiomyocytes. Western blotting was performed to measure apoptotic proteins (i.e., active caspase-3, Bax, and Bcl-2) in heart tissue. Results AFB1 treatment resulted in mitochondrial membrane disruption and disorganization of cristae, which are indicators of mitochondrial damage. Myocardial cell apoptosis was significantly higher after AFB1 treatment (22.07% ± 3.29%) compared with controls (6.27% ± 2.78%, P < 0.05). AFB1 treatment enhanced expression of active caspase-3, Bax, and Bcl-2 in cardiac tissue. Conclusion Various adverse effects are exerted by AFB1 on the heart, indicating AFB1 myocardial toxicity.

Keywords: Aflatoxin B1; Bcl-2; caspase-3; cell apoptosis; mitochondria; myocardial toxicity.

Figure 1.

HE staining of heart tissue Representative photomicrographs of HE staining of heart tissue from control (panel a) and experimental animals (AFB1-treated, panel b) are shown. Normal arrangement of myocardial fibres was observed in the control and AFB1-treated samples, and no apparent abnormalities were observed after AFB1 treatment (panel b).

Figure 2.

Transmission electron microscopic analysis of mitochondrial structure in myocardial cells Compared with mitochondrial structure in control animals (panel a), AFB1 treatment resulted in damage to mitochondria (panel b), including disruption of the mitochondrial membrane (red arrows) and disorganization of cristae (red arrow heads).

Figure 3.

Promotion of apoptosis of myocardial cells by AFB1 Panels a and b show representative images of a TUNEL assay for apoptotic cells from control and experimental animals, respectively. The percentage of apoptotic cells in AFB1-treated rats was significantly higher than that in control rats (panel c). All nuclei were stained blue by DAPI. Arrows indicate apoptotic cells (brown). *P < 0.05 compared with controls (n = 6).

Figure 4.

Western blotting analysis of active caspase-3, Bax, and Bcl-2 in heart tissue Representative blots for each protein are shown in the top panels. The relative levels of active caspase-3, Bax, and Bcl-2 were significantly higher in AFB1-treated samples than in control samples (bottom panels). Lane 1: control sample; lanes 2 and 3: two independent experimental samples. *P < 0.05 compared with controls (n = 6).