Potential Toxic Effect of Bisphenol A on the Cardiac Muscle of Adult Rat and the Possible Protective Effect of Omega-3: A Histological and Immunohistochemical Study

Abstract

Bisphenol A (BPA) is intensely used in the production of polycarbonate plastics and epoxy resins. Recently, BPA has been receiving increased attention due to its link to various health problems that develop after direct or indirect human exposure. Previous studies have shown the harmful effect of high doses of BPA; however, the effect of small doses of BPA on disease development is controversial. The aim of this study was to investigate the effect of a low dose of BPA on the rat myocardium and to explore the outcome of coadministration of Omega-3 fatty acid (FA). Thirty adult male rats were divided equally into control group, BPA-treated group (1.2 mg/kg/day, intraperitoneally for 3 weeks), and BPA and Omega-3-treated group (received BPA as before plus Omega-3 at a daily dose of 300 mg/kg/day orally) for 3 weeks. Exposure to BPA resulted in structural anomalies in the rat myocardium in the form of disarrangement of myofibers, hypertrophy of myocytes, myocardial fibrosis, and dilatation of intramyocardial arterioles. On the other hand, mast cell density and media-to-lumen area ratio were not significantly altered. Interestingly, concomitant administration of Omega-3 FAs with BPA significantly reduced BPA-induced changes and provided a protective effect to the myocardium. In conclusion, exposure to a low dose of BPA could potentially lead to pathological alterations in the myocardium, which could be prevented by administration of Omega-3 FA.

Keywords: Bisphenol A; Omega-3; histopathology; myocardium.

Figure 1

Omega-3 ameliorates cardiotoxic effect of bisphenol A in adult rat myocardium. Photomicrographs of longitudinal sections of the left ventricular myocardium of (a) control group showing branching and anastomosing cardiac muscle fibers with an acidophilic sarcoplasm and centrally located oval vesicular nuclei (arrowhead). While bisphenol A-treated group showing (b) destruction and discontinuation of cardiac muscle fibers (arrow), (c) wide intercellular space (star), congested blood vessels with extravasated red blood cells in between the muscle fibers (arrow) (d) focal areas of pale homogeneous acidophilic sarcoplasm with either absence of nuclei (arrowhead) or presence of deeply stained pyknotic nuclei (arrow) in addition to (e) mononuclear cellular infiltration (white arrow). On the other hand, (f) coadministration of Omega-3 with bisphenol A showed a near normal structure of cardiac muscle fibers with central oval vesicular nuclei. H and E, scale bar = 20 μm

Figure 2

Bisphenol A-induced hyper trophy of cardiomyocyte. Representative micrographs of the transverse sections of the left ventricular myocardium of (a) control group, (b) bisphenol A-treated group showing increased cardiomyocyte cross-sectional area. (c) Concomitant administration of Omega-3 significantly decreased myocytes cross-sectional area compared to bisphenol A-treated group. H and E, dashed area, representative example for cross-sectional area measurement, scale bar = 20 μm. (d) Plot showing quantitative measurements of myocytes cross-sectional area among the experimental groups. Data are presented as mean ± standard error of mean, ***P < 0.0001

Figure 3

Omega-3 attenuated bisphenol A-induced interstitial fibrosis. Representative micrographs of the longitudinal sections of left ventricular myocardium showing (a) few and fine collagen fibers (arrowhead) between the cardiac muscle fibers of control group. (b) Apparent increase in collagen fibers (arrowhead) between the cardiac muscle fibers of bisphenol A-treated group. (c) Apparent decrease in the interstitial collagen fibers (arrowhead) with Omega-3 administration. Picrosirius red staining, scale bar = 20 μm. (d) Graph showing the quantitative analysis of interstitial collagen fibers area percentage of the experimental groups. Data are presented as mean ± standard error of mean ***P < 0.0001

Figure 4

Mast cells density in the myocardium was not altered with bisphenol A. Representative micrographs of the left ventricle of (a) control group, (b) bisphenol A-treated, and (c) bisphenol A and Omega-3-treated groups showing the violet metachromatic staining of mast cells (arrows) against blue background. Toluidine blue, scale bar = 20 μm. (d) Plot showing quantitative measurements of mast cells density (number/mm²) among all groups. Data are presented as mean ± standard error of the mean, ns: Nonsignificant

Figure 5

Bisphenol A exposure resulted in dilatation in the intramyocardial blood vessels. Representative micrographs of the left ventricle of (a) control group, (b) bisphenol A-treated, and (c) bisphenol A and Omega-3-treated groups showing immunoreactivity to anti-alpha-smooth muscle actin (green). Histogram presented quantitative analysis of the (d) total vessel area, (e) lumen area, and (f) media to the lumen ratio of experimental groups. Data are represented as mean ± standard error of mean *P ≤ 0.05. ns; nonsignificant, scale bar = 20 μm