Statistical analysis of the mean values of the area percentages of the collagen fibers of the negative control group (group I) and the lycopene group (group II) showed nonsignificant differences between them. Area percentage of the collagen fibers in the BPA group (group III) showed significant increase in comparison with groups I, II, and IV and that of group IV (BPA+lycopene) showed significant increase compared with groups I and II and significant decrease compared with group III (Table 2 and Histogram 2). Statistical analysis of the mean values of the area percentage of the positive immune reaction for vimentin of groups I and II showed nonsignificant differences between them. Area percentage of the positive immune reaction for vimentin in the BPA group (group III) showed significant increase compared with groups I, II, and IV, whereas that of group IV (BPA+lycopene) showed significant decrease compared with group III but it still showed significant increase with group I and group II (Table 3 and Histogram 2).
In the current study, examination of the myocardium from the BPA group showed some myocytes with deeply homogenous acidophilic cytoplasm and devoid of nuclei. Focal areas of loss of myofibrils were seen. Similar results had been noticed in patients suffering from diabetic cardiomyopathy . BPA creates favorable conditions for the onset and progression of cardiovascular diseases by indirectly promoting diabetes  or by directly enhancing oxidant enzyme activity .
In the current study, examination of the myocardium from the BPA group showed many distorted mitochondria with heterogenous electron density, many dilated T-tubules in most of the muscle fibers, and marked enfolding of the sarcolemma of some myocytes. Similar degenerative findings were observed in the myocardium exposed to estrogenic contaminants, such as nonylphenol ethoxylates . BPA is similar in structure to 17β-estradiol and is hence considered one of the endocrine disruptors (EDCs) . BPA may activate intracellular signals through either of two pathways: genomic  or nongenomic . In genomic activation, BPA binds to both estrogen receptors α and β . In nongenomic mechanisms, BPA may affect the ion channel function as increasing the activity of Maxi-K channels .
It has been demonstrated that certain EDCs such as estrogenic contaminants are able to degrade the layer-by-layer assembly because of their ability to penetrate into the cell membranes by their lipophilic nature and disrupt phospholipids within the membraneous organelles and in T-tubules [37,42]. Alterations in these membranes lead to defects in calcium transport . Many of the proteins involved in cellular Ca2+ cycling appear to be concentrated at the T-tubule. Changes in T-tubule structure occur during heart failure . Hence, we suggested that destabilization of phospholipids within membranes of the T-tubules and in membranous organelles within myocytes may be one of the potential ways by which BPA exerts its toxicity on the myocardium.
In the current study, disorganized intercalated discs were observed while examining the myocardium from the BPA group. Deformed intercalated discs lead to loss of effective contraction force in most of the affected areas .
In the current study, the nuclei of the myocytes from the BPA group were variable in shape. Some of them were peripherally located. Deeply indented and dark heterochromatic pyknotic nuclei were observed. BPA caused DNA damage through estrogenic activity . Myocyte necrosis and apoptosis have been demonstrated to be linked to elevated proinflammatory cytokine levels, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interferon-γ . During the progression of cardiac hypertrophy to heart failure, the nuclear shape of the myocytes became bizarre with an irregular nuclear envelope . Increased nuclear enfolding could have been due to increased synthesis of the nuclear membrane in excess of that needed to accommodate the increase in volume during cardiac hypertrophy [48,49].
In the current study, examination of the BPA group revealed focal areas of cellular infiltration, as well as fibroblast cells, myofibroblast cells, and inflammatory cells. Extravasated red blood cells, acidophilic material (edema), and congested blood vessels were observed. We suggest that these findings reflect the inflammatory process associated with BPA administration. Similar findings were detected in the hearts taken from rats with diabetes or hyperglycemia . Lang et al.  linked BPA to diabetes. Proinflammatory cytokines such as TNF-α and IL-1β contribute not only to depression of the left ventricular function and cardiomyocyte loss by apoptosis but also to maintaining the balance in extracellular matrix remodeling [46,51]. Proinflammatory cytokines can trigger neurohumoral activation and increase in oxidative stress, leading to activation of p38-MAP kinase and nuclear factor-κB. These induce cardiomyocytolysis and reduce calcium uptake by the sarcoplasmatic reticulum and hence induce negative inotropic effects [52,53].
In the present study, area percentage of the collagen fibers in the myocardium of the BPA group showed significant increase in comparison with the control. Similar findings were detected in the hearts taken from diabetic rats . Lang et al.  linked BPA to diabetes. Collagen accumulation in cases of diabetic cardiomyopathy was due to impaired collagen degradation rather than to overproduction . Hence, cardiac fibrosis could be explained by the indirect effect of hyperglycemia caused by BPA. On the other hand, it was reported that BPA can induce fibroblast hyperplasia in other organs . Fibroblasts may respond to both mechanical loading  and transforming growth factor-β1 stimulation  by a switch to a myofibroblastic phenotype that is accompanied by stimulation of collagen production. Accumulation of collagen in the cardiac interstitium or ‘reactive interstitial fibrosis’ is accompanied by loss of matrix cross-link integrity  and by a change in the ratio of collagens I and III . This may contribute to increased myocardial stiffness with impaired systolic and diastolic functions [57,58].
In the current study, examination of the BPA group revealed focal areas of extensive collagen fibers, numerous congested blood vessels, many fibroblasts, myofibroblast cells, inflammatory cells, and degenerated muscle fibers. Similar changes had been detected in chronic myocardial infarction . BPA exposure has been linked to increase in the risk for coronary artery disease . Hence, structural changes in the myocardium of the BPA group could have been due to the occurrence of minute segmental infarction.
In the current work, significant increase in the area percentage of positive immune reaction for vimentin in the BPA group compared with the control was detected. Similar results were previously demonstrated in cases of dilated cardiomyopathy in humans . The same researchers demonstrated a negative correlation between myocardial vimentin content and the actin–myosin sliding rate. This led to reduced myocyte contraction compared with that in normal individuals . Derangements of cytoskeletal proteins such as vimentin contribute to alterations in intracellular signaling, myocyte function, and coupling of myocytes to the extracellular matrix during cardiac hypertrophy and failure [20,21,61]. Moreover, the myocardial cytoskeleton maintains the internal organization of cellular organelles and transmits the mechanical forces within the cells to and from the adjacent cells and extracellular matrix . The alteration in vimentin expression may be caused by changes in intracellular calcium concentrations . In contrast, the study by Rastogi et al.  showed no changes in vimentin expression in the myocardium of dogs with heart failure. The different species used in the previous studies and different methods of vimentin detection could explain this discrepancy in their results.
The present study showed a positive relation between the level of area percentage of positive immune reaction for vimentin and that of collagen. Increase in the area percentage of positive immune reaction for vimentin could be linked to an increase in interstitial heart tissue . Moreover, the same researchers found proliferation of T-tubules associated with overexpression of vimentin in cardiomyopathy. A positive correlation between vimentin-positive cells and fibrosis was detected, indicating an increase in interstitial tissue in this area .
The current study revealed oxidative damage manifested by significant increase in serum MDA, whereas tissue GSH and CAT showed significant decrease in the BPA group compared with control. BPA induces oxidative stress by decreasing antioxidant enzymes and increasing H2O2 and lipid peroxidation in many organs [14,15]. MDA has been considered a biomarker for lipid peroxidation and oxidative stress . Reduced GSH enzyme is increased in cells exposed to oxidative stress as an adaptive process to maintaining cell integrity because of its reducing properties and participation in cell metabolism . Catalase enzyme, which hydrolyzes H2O2, has been found to increase in cardiotoxicity and aims to improve cardiac function . The heart tissue is very sensitive to free radical damage because of its highly oxidative metabolism and because of its fewer antioxidant defenses . Reactive oxygen species are cytotoxic agents that lead to oxidative damage by attacking biomolecules such as membrane lipids and DNA in cells . Hence, oxidative damage could be the cause of the ultrastructural changes seen in the myofibrils of the BPA group.
In the current study, examination of the myocardiums of the rats in group IV, which received BPA along with lycopene, revealed that the myocardium had an almost normal architecture with the exception of many congested blood capillaries and a few distorted myocytes. Biochemical evaluation of group IV showed that serum MDA showed significant decrease, whereas tissue GSH and CAT showed significant increase in comparison with group III. Lycopene is highly lipophilic and hence has the maximum effect on the scavenging function of the reactive oxygen species in cell lipophilic compartments . Lycopene is most likely involved in the scavenging of two of the reactive oxygen species, singlet molecular oxygen (1O2) and peroxyl radicals. Thus, administration of lycopene reduces lipid peroxidation [17,23] and hence protects the membranous organelles of the cardiac cells. Endogenous antioxidative enzymes can also be stimulated by lycopene . Moreover, lycopene upregulates the gene connexin 43, which allows direct intercellular gap junction communication, allowing small molecules and ions to pass between cells .
In the current work, the myocardium from rats of group IV (BPA+lycopene) showed significant decrease in the area percentage of collagen and vimentin compared with group III. No inflammatory cellular infiltration was detected in the myocardium of the same group. Lycopene can partially reduce the extent of pulmonary fibrosis in rats through the suppression of oxidative stress . Moreover, lycopene has been proven to exert anti-inflammatory properties .
Long-term exposure to BPA could induce biochemical and structural changes in rat cardiac muscles. Moreover, these results suggest that generation of reactive oxygen species plays an important role in the mechanisms of BPA toxicity. These deleterious changes could be partially minimized by concomitant treatment with lycopene. We recommended re-examination of the safety profile of BPA. Consumption of naturally occurring lycopene-rich foods is also recommended for prevention of oxidative stress associated with environmental BPA exposure and with heart diseases. However, further studies are needed before the complete effects of lycopene are properly understood.
No conflict of interest to declare.
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