Protective effects of quercetin against oxidative stress induced by bisphenol-A in rat cardiac mitochondria

Research has shown a relationship between the exposures to a chemical agent called bisphenol-A (BPA), which is extensively used in the production of polycarbonate plastics and the incidence of cardiovascular diseases. This association is most likely caused by the BPA's ability to disrupt multiple cardiac mechanisms, including mitochondrial functions. Therefore, this study aimed to explore the ability of quercetin (QUER) to limit the cardiotoxic effect of BPA in the rat's cardiac mitochondria. The experiment was carried out on 32 male Wistar rats, which were randomly assigned to four groups. The negative control group received olive oil; the positive control group received olive oil plus BPA (250 mg/kg); the third group received olive oil, BPA, and QUER (75 mg/kg); and the fourth group received olive oil and QUER, all orally for 14 days. The rats were slaughtered 24 h after the last treatment. The measured parameters included creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) as the biomarkers of cardiotoxicity, triglyceride (TG), total cholesterol (TC), and low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C) as the measures of dyslipidemia, glutathione (GSH) content, catalase activity (CAT), reactive oxygen species (ROS), lipid peroxidation (LPO), and the level of damage to the mitochondrial membranes as the indicators of the impact of QUER on the BPA cardiotoxic effect. Finally, the rats treated with QUER showed better results in terms of serum CK-MB, serum LDH, serum lipid profile, GSH level, CAT activity, mitochondrial membrane potential (ΔΨm), LPO, and ROS. According to the results, QUER could be used as a protective agent against BPA-induced mitochondrial toxicity.

Keywords: Bisphenol-A; Quercetin; Cardiac mitochondria; Cardiotoxicity; Oxidative stress; Rat

Cardiovascular disease (CVD) is a major cause of death worldwide and has become a particularly challenging public health problem in countries with an aging population, where it is more common to encounter a high rate of cardiovascular problems. According to studies, oxidative stress accelerates the progression of atherosclerosis and increase the risk of CVD through various mechanisms (Katakami [29]).

Bisphenol-A is a chemical agent that has been extensively used in the plastics industry for more than 100 years. BPA is commonly used as a monomer in the production of polycarbonate (PC) plastics, epoxy resins, food and beverage cans, water pipes, safety equipment, electronics, laminate flooring, printed thermal paper products, dental sealants, and medical equipment (Quagliariello et al. [46]). It should be mentioned that exposure to BPA can happen through oral use, inhalation, and skin contact. Although BPA-free plastics have become increasingly popular, this chemical agent is still abundantly present in the environment (Bilal et al. [9]).

In addition, biomonitoring studies have shown that 90% of the population is exposed to BPA at any given time. Human epidemiological studies have also confirmed the relationship between high concentration of urinary BPA and the increased incidence of CVD, including hypertension (Aekplakorn et al. [1]), atherosclerosis (Lind and Lind [39]), angina, and myocardial infarction (Lang et al. [35]; Vandenberg et al. [50]). Another research showed that several action mechanisms of BPA include the induced ROS production, reduced activities of enzymatic and non-enzymatic antioxidants, and increased lipid peroxidation (Mohammed et al. [40]). Moreover, the cell damage caused by toxicity-induced oxidative stress can lead to various diseases, including atherosclerosis, coronary artery disease, Alzheimer's, and cancer (Lee et al. [38]). In the case of CVD, excessive oxidative stress is known to be the primary pathologic characteristic observed in this family of conditions (Kojda and Harrison [34]). Furthermore, animal studies have shown that BPA induces oxidative stress in the liver, kidney, brain, and heart by increasing ROS generation, decreasing the activity of enzymatic and non-enzymatic antioxidants, and increasing lipid peroxidation (Gong and Han [19]; Kabuto et al. [28]).

Given the role of the cardiac myocytes in generating ATP through aerobic metabolism, they have the highest oxygen uptake (0.1 ml O2/g per minute at basal rates) and the highest density of mitochondria in the entire human body (Hassanpour et al. [22]). In fact, endothelial cells, neutrophils, and myocytes are among the primary sources of ROS generation inside the heart (Tsutsui et al. [49]). Actually, ROS is generated in the mitochondria during the respiratory chain by transferring one electron to molecular oxygen. Under normal physiological conditions, all of the produced ROS can be detoxified by the antioxidant mechanisms of myocytes endogens, but the mitochondria of the damaged cardiac myocytes generate greater amounts of radical O2, which can cause functional and structural damages to the myocardium through the oxidation of proteins, DNA, and membrane phospholipids (Sawyer and Colucci [47]).

Research showed that flavonoids, including anthocyanins, flavonols, flavanols, flavanones, flavones, and isoflavones are the most abundant polyphenols in the human diet. However, one of the most important type of flavonoids is quercetin (QUER) with the chemical composition 3,5,7,3-4-pentahydroxy flavone (Bahadoran et al. [6]). Examples of QUER-rich foods include fruits and vegetables, especially red onion, apple, berry, citrus, tea, nuts, and seeds (Aguirre et al. [2]).

As stated by researchers, the known pharmacological effects of QUER are antioxidant properties, prevention of the platelet aggregation and LDL oxidation, relaxation of the venous smooth muscle, reduction of the serum lipid level and the systolic blood pressure, weight loss in animals, reduction of the plasma insulin and level of inflammatory plasma markers, and anticancer effects (Gnoni et al. [17]; Panchal et al. [41]). In addition, researchers proved the efficacy of QUER in controlling and treating hypertension, heart ischemia, congestive heart failure, atherosclerosis, coagulation disorders, diabetic neuropathy, and ischemia-induced necrosis and lesions of various tissues (Bahadoran et al. [6]; Hubbard et al. [24]). It has also been shown that QUER has stronger antioxidant effects in the presence of high levels of inflammation and oxidative stress (Edremitlioğlu et al. [14]). Moreover, in an animal study, the intravenous administration of QUER at a dose of 100–150 mg/kg body weight in rabbits produced no complication (Aguirre et al. [2]). However, other animal studies have also found no evidence of significant increase in the neoplasm after oral administration of QUER.

According to studies, structural causes of the antioxidant properties of QUER include hydroxyl at position 3 of the C-ring, a double bond between C2 and C3 in the C-ring, a carbonyl group at C4, and its hydroxylation pattern. Moreover, because of the presence of carbonyl at C4 and hydroxyl groups at C5/C3, chelating with iron ions allows the compound to neutralize the free radicals (Babujanarthanam et al. [5]). It was also found that the antioxidant enzymes activity such as superoxide dismutase (SOD), catalase activity (CAT), and glutathione peroxidase (GPx) increase with QUER supplementation (Zhao et al. [53]). Quercetin can also increase the ω-oxidation of fatty acid in the liver, thereby reducing the amount of lipids in circulation. Although QUER reduces the serum level of total fatty acid, it slightly increases some of the polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid and arachidonic acid, which indicates a shift in the plasma fatty acids towards healthier variants (Hoek-van den Hil et al. [23]).

Considering the scarcity of research on the possible efficacy of QUER in protecting cardiac tissues against BPA-induced mitochondrial toxicity, this study investigated the protective effects of QUER against BPA-induced cardiotoxicity on the rats by examining the cardiac biochemical markers, lipid profile, oxidative stress, and mitochondrial membrane potential.

All of the compounds used in the study, including d-mannitol, 2′,7′-dichlorofluorescin diacetate (DCF-DA), thiobarbituric acid (TBA), quercetin, reduced GSH, Coomassie blue G, 2-[4-(2-hydroxyethyl) piperazin-1-yl] ethanesulfonic acid (HEPES), tetraethoxypropane (TEP), sucrose, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), dithiobis-2-nitrobenzoic acid (DTNB), bovine serum albumin (BSA), ethylene glycol-bis (2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA), and rhodamine 123 (Rh 123) were commercially obtained from Sigma Aldrich Chemicals (St. Louis, MO, USA).

This study was conducted on 32 adult male Wistar rats aged 8 to 10 weeks and weight of 180 to 200 g, which were collected from the Laboratory Animal Breeding and Care Center of Jundishapur University of Medical Sciences (Ahvaz, Iran). The rats were kept in polypropylene cages under a controlled temperature (25 ± 2 °C) and 12:12 light/dark cycle with free access to the standard feed and water. All experiments were performed according to the instructions of the Jundishapur University Animal Ethics Committee (Ethical code: IR.AJUMS.REC. 1395.632).

Using our pilot study and the similar works as a basis for estimating the sample size, the sample size was calculated to eight rats per group (Khorsandi et al. [32]). Accordingly, 32 rats were collected and randomly assigned to four groups (n = 8). In groups II and III, one dose of BPA (250 mg/kg) was administered daily for 14 days through intragastric intubation. Group I (negative control) received olive oil, group II (positive control) received olive oil and BPA (250 mg/kg), group III received olive oil and BPA (250 mg/kg) and QUER (75 mg/kg), and finally group IV received olive oil and QUER (75 mg/kg), all for 14 days. Notably, QUER was administered orally. Moreover, BPA and QUER doses were chosen according to our pilot study and similar works (Goloubkova et al. [18]; Khan et al. [30]; Zou et al. [54]).

All rats were weighed on the first and 14th day of the study and were sacrificed 24 h after the last treatment. Then, the heart tissue was weighed, and the result was divided by the body weight on the last day to obtain the relative heart weight in percentages.

According to the research design, mitochondria was isolated by differential centrifugation of the heart tissue according to Aon's method with some modifications (Aon et al. [4]). For this purpose, the removed heart tissue was finely minced and placed in a freshly prepared cold mannitol solution containing 10 mM HEPES-potassium hydroxide, 75 mM sucrose, 0.2% (w/v) BSA, 225 mM d-mannitol, and 1 mM EGTA at pH of 7.4. The minced tissue was homogenized by a glass homogenizer. Then, the broken cell debris and nuclei were centrifuged at 500×g and 4 °C for 15 min. Afterwards, supernatants were centrifuged at 7700×g and 4 °C for 5 min. The upper layer was then removed, and the pellet was washed with mild suspension in the isolation buffer. The resulting compound was centrifuged at 10,000×g and 4 °C for 10 min. Finally, the obtained mitochondrial pellets were placed in a small amount of isolation buffer (for resuspension). Then, the protein concentrations were measured using the biuret method (Gornall et al. [20]).

The mitochondrial ROS was measured using DCF-DA fluorescence probes. In summary, after centrifuging the heart mitochondria suspension, the resulting precipitates were added to a freshly prepared 1.6 μM DCF-DA solution and was incubated at 37 °C after gentle mixing for 10 min. The rate of ROS generation was then measured by a Perkin Elmer LS-50B luminescence fluorescence spectrophotometer (CA, USA) based on the fluorescence measurements at emission and excitation wavelengths of 500 and 520 mm (Crow [12]).

Mitochondrial membrane potential (ΔΨm) was determined based on the mitochondrial absorption of cationic fluorescent dye (Rh 123). Therefore, the mitochondrial suspension (0.5 mg protein/ml) was incubated with 1.5 μM rhodamine 123 solution at 37 °C for 10 min, and the fluorescence intensity at emission and excitation wavelengths of 490 and 535 nm was measured using Elmer LS-50B luminescence fluorescence spectrophotometer (Baracca et al. [7]).

According to Zhang et al.'s method, the LPO was determined by measuring the malondialdehyde level (MDA) in the heart tissue (Zhang et al. [52]). In summary, mitochondrial suspension (0.5 mg protein/ml) was incubated with 0.3 ml of 0.2% TBA and 0.25 ml of sulfuric acid (0.05 M) for half an hour. The tubes were then placed in a boiling water bath and finally transferred to an ice bath, where 0.4 ml of butanol was added to each tube. After centrifuging the tubes at 3500×g for 10 min, the absorbance was read by a spectrophotometer (UV-1650 PC, Shimadzu, Japan) at 532 nm. Finally, the total MDA content in each sample was recorded in nmol/mg protein with TEP used as the standard.

The mitochondrial GSH level was determined using Ellman's method (Ellman [15]). Therefore, the heart mitochondrial suspension (0.5 mg protein/ml) was mixed with 0.04% Ellman reagent (DTNB) and placed in 0.1 mol/l phosphate buffer (pH = 7.4) until a yellow color was observed, and then the absorbance was measured by a spectrophotometer (UV-1650 PC, Shimadzu, Japan) at 412 nm. The content of GSH was recorded in μmol/mg protein.

According to the research design, the CAT activity was measured using Claiborne's method in this study (Claiborne [11]). Hence, the mitochondrial suspension from the heart was first mixed with 0.05 mM Tris-HCl and 0.01 mM of H2O2 and incubated for 10 min. Then, ammonium molybdate (4%) was added, and the absorbance change at 410 nm in a 1-minute period was measured based on the rate of H2O2 decomposition. Finally, the CAT-specific activity was recorded in U/mg protein.

Moreover, this study examined a selective group of cardiac function and serum lipid profiles to evaluate the BPA-induced cardiotoxicity and protective effects of QUER. For this evaluation, CK-MB, LDH, TG, TC, HDL, and LDL were measured by spectrophotometry using the assay kit (Pars Azmoon Kit. IRI).

The study presented all data in the form of mean ± SEM for eight animals per group. One-way analysis of variance (ANOVA) was used to compare differences and Fisher's least significant difference (LSD) test or nonparametric Kruskal-Wallis test was used to compare multiple groups. All statistical analyses were performed at a significant level of P < 0.05 using the statistical software Prism 5.0 (San Diego, CA, USA).

As shown in Table 1, BPA and QUER oral administration for 14 days did not significantly change the body weight as well as the absolute and relative heart weight of the rats.

Effects of QUER on the body weight gain, absolute and relative heart weight (mg/kg)

According to Table 2, BPA caused a significant increase in the serum levels of CK-MB and LDH (P < 0.0001). Moreover, the rats in the QUER + BPA–treated group (75 mg/kg) had significantly lower levels of both CK-MB and LDH than those in the BPA group (P < 0.0001).

Effect of treatment with QUER on CK-MB and LDH activities in BPA-induced cardiotoxicity

Data expressed as mean ± SEM (n = 8) *Significantly different from the control group (****P < 0.0001) #Significantly different from the BPA group (####P < 0.0001) applying the one-way ANOVA test

According to Table 3, the BPA group had significantly higher serum TG and LDL-C levels than the control group (P < 0.0001) and a lower TC level (P < 0.001). The QUER + BPA–treated group showed lower serum TG (P < 0.0001) and LDL-C levels (P < 0.01) and higher HDL-C levels than the BPA group (P < 0.05).

Effect of QUER and BPA on serum lipid parameters, in BPA-induced cardiotoxicity

Data expressed as mean ± SEM (n = 8) *Significantly different from the control group (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001) #Significantly different from the BPA group (#P < 0.05, ##P < 0.01, ###P < 0.001, ####P < 0.0001) applying the one-way ANOVA test

In order to determine the relationship between the mitochondrial oxidative stress and BPA-induced cardiotoxicity and the protective effect of QUER, ROS generation was measured by detecting DCFH-DA. The results (Fig. 1) showed a significantly higher ROS generation in the isolated heart mitochondria of the BPA group than in the control group (P < 0.0001). However, mitochondrial ROS generation in the QUER + BPA–treated group was significantly lower than in the BPA group (P < 0.001).

Graph: Fig. 1 The effects of QUER on BPA-induced mitochondrial ROS generation. Asterisks indicate a significant difference in comparison with the control (***P < 0.001, ****P < 0.0001). Number signs indicate a significant difference in comparison with BPA (###P < 0.001)

As shown in Fig. 2, Rh 123 was used to investigate the BPA-induced and QUER-induced changes in ΔΨm (known as ΔΨm). Therefore, a significant increase was found in the ΔΨm level in the BPA group compared with the control group (P < 0.001). However, the ΔΨm level in the isolated mitochondria was lower in the QUER + BPA–treated group (P < 0.001).

Graph: Fig. 2 The effects of QUER on mitochondrial membrane damage in BPA-induced cardiotoxicity. Asterisks indicate a significant difference in comparison with the control (***P < 0.001)

According to Fig. 3, the relationship between the mitochondrial MDA and BPA-induced cardiotoxicity was examined by measuring the LPO using TBARS. Thus, it was found that the BPA group had significantly higher LPO in the mitochondria than the control group (P < 0.0001); however, treatment with QUER significantly reduced this parameter (P < 0.01).

Graph: Fig. 3 Effects of cotreatment with QUER on the MDA levels in BPA-induced cardiotoxicity. Asterisks indicate a significant difference in comparison with the control (**P < 0.01, ****P < 0.0001). Number signs indicate a significant difference in comparison with BPA (##P < 0.01)

Since BPA-induced catechol-o-quinone can produce ROS and oxidative stress through redox cycles, the mitochondrial GSH level can be investigated as a measure of antioxidant protection. As shown in Fig. 4, the GSH levels of the isolated heart mitochondria in the BPA group showed a significant decrease compared with the control group (P < 0.0001). However, the QUER treatment prevented this decline in mitochondrial GSH level (P < 0.01). Finally, these findings suggest that QUER can prevent oxidative damages to the heart by increasing the GSH content.

Graph: Fig. 4 Effects of cotreatment with QUER on the GSH levels in BPA-induced cardiotoxicity. Asterisks indicate a significant difference in comparison with the control (*P < 0.05, ****P < 0.0001). Number signs indicate a significant difference in comparison with BPA (##P < 0.01, ####P < 0.0001)

As shown in Fig. 5, CAT activity (as the enzyme eliminating the excess H2O2) was measured in the isolated rat heart mitochondria. This measurement showed significantly lower CAT activity in the BPA group than in the control group (P < 0.001). In contrast, the rats treated with QUER showed significantly higher CAT activity (P < 0.05). Therefore, it can be concluded that QUER could play a critical role in reducing excess H2O2 by improving the activity of this enzyme.

Graph: Fig. 5 Effects of cotreatment with QUER on the CAT activity in BPA-induced cardiotoxicity. Asterisks indicate a significant difference in comparison with the control (***P < 0.001). Number signs indicate a significant difference in comparison with BPA (#P < 0.05)

This study results showed that in Wistar male rats, QUER had ameliorative effects on the BPA-induced cardiotoxicity resulting from oxidative stress and mitochondrial damage by reducing the lipid profiles, inflammation, and free radicals, increasing antioxidant protection and preserving the mitochondrial function.

Moreover, the incidence of CVDs could be attributed to many causes, including genetics, lifestyle, and environmental factors. Among the mentioned factors, environmental pollutants have received limited attention. In fact, BPA, as a chemical pollutant, can have a damaging impact on the endocrines (Barrios-Estrada et al. [8]). It is notable that acute exposure to BPA activates estrogen receptors of the heart tissue, which causes arrhythmias, followed by ischemia, irreversible cell damage, ventricular dysfunction, and ultimately heart failure (Posnack et al. [45]). In addition, chronic exposure to BPA leads to the increased systolic pressure, diastolic pressure, and mean arterial pressure, oxidative stress, and inflammation (Patel et al. [42]).

The present study indicated that administration of BPA and QUER made no significant change in the body weight, and absolute and relative heart weight of the rats. This finding is consistent with other studies, where BPA administration at doses of 0.5, 5, and 50 for 1 month also did not change the weight of the rats (Hassani et al. [21]).

Considering the scarcity of the research on the BPA-induced inflammation in the heart tissue, we also investigated the serum level of LDH and CK-MB, which could be used as suitable biomarkers for inflammation and necrosis in the heart tissue. Therefore, a significant increase was revealed in the serum levels of LDH and CK-MB, indicating that inflammation could possibly be a mechanism for the damage to BPA on the heart tissue (Khodayar et al. [31]).

According to the analyses, it was found that QUER can improve the activity of LDH and CK-MB enzymes. Moreover, QUER had stronger antioxidant effects in the presence of high levels of inflammation and oxidative stress (Gnoni et al. [17]). Nrf2, HO-1, and NF-kB are some of the markers of oxidative stress and inflammation in the heart whose expression could be regulated by QUER supplementation. In addition, in cases where cardiac function is exposed to impairment due to the cell damage induced by inflammation and oxidative stress (Pearson et al. [43]), Nrf2 system can act as a defense against cell damage. However, under normal conditions, Nrf2 is inactive, but it becomes activated after damage and causes the cell nucleus to activate antioxidant agents and reduce cellular stress through HO-1. It is notable that QUER stimulates antioxidant defense by increasing the expression of Nrf2 and HO-1 (Lee and Johnson [37]). It also reduces the expression of NF-kB, which plays a role in the activation of the inflammatory cascade and causes inflammation in the heart (Lawrence [36]). Hence, the anti-inflammatory effects of QUER are well reflected in the reduced serum levels of cardiac enzymes LDH and CK-MB, which are biomarkers of the BPA-induced inflammation.

According to the studies, dyslipidemia is one of the major risk factors for the development of CVD. Research showed that BPA can contribute to the development of dyslipidemia through an antagonistic effect on the nuclear receptor responsible for regulating lipid homeostasis, peroxisome proliferator–activated receptor (PPAR)-α, and blocking the function of this receptor, thus causing metabolic disruptions and higher levels of lipid. The findings of our study showed that BPA increased the level of TG and LDL-C. In another study, where BPA was administered to animals at doses of 0.5, 5, and 50 mg/kg for 30 days, the findings also showed an increased level of TG and free fatty acids (Hassani et al. [21]). Moreover, the present study found that treatment with QUER reduced TG, LDL-C, and increased HDL-C. In addition, QUER could improve the serum lipid profile by altering the expression of the genes associated with lipid metabolism. Furthermore, by reducing the expression of PPAR-α, QUER increases the expression of the liver genes associated with the lipid metabolism and decreases TG levels. It also decreases the expression of glycerol-3-phosphate acyltransferase 1, mitochondrial (Gpam) gene, which plays a critical role in the synthesis of TG and acts as a target gene for sterol regulatory element-binding protein 1 (SREBP-1) in the lipogenesis pathway (Jung et al. [27]). QUER could also lead to the over-regulation of carnitine palmitoyltransferase 1 (CPT-1) protein, which acts as a regulator of beta-oxidation of fatty acid in the mitochondria (Panchal et al. [41]). In another animal study, addition of QUER to diets at a dose of 5 g/kg for 20 weeks reduced the weight and visceral and hepatic fat of the rats (Kobori et al. [33]) by 13% and 27%, respectively, and significantly decreased the serum levels of TG and fatty acids after 12 weeks (Hoek-van den Hil et al. [23]).

In brief, one of the important causes of heart damage is mitochondrial dysfunction, which can endanger the cellular life in various ways such as reduction of ATP synthesis, increase in the ATP hydrolysis, ROS and LPO generation, and release of the pro-apoptotic proteins (Akar et al. [3]). In fact, by causing dysfunction in the mitochondria hemostasis, BPA generates oxidative stress and accelerates the production of ROS, particularly, superoxide anions in the heart (Huc et al. [25]), which lead to the oxidation of membrane phospholipids, proteins, and DNA, thereby resulting in pathological conditions such as atherosclerosis, ischemic reperfusion, ventricular hypertrophy, and hypertension. However, administration of BPA in our study increased cardiac ΔΨm, but treatment with QUER reduced the damage to the mitochondrial membrane and decreased ΔΨm. Moreover, our investigation of the BPA-induced oxidative stress through MDA measurements based on ROS and LPO levels indicated that BPA increased ROS and LPO. This suggested that BPA caused oxidative stress and LPO in the heart by creating superoxide anions, but treatment with QUER limited this effect. In addition, CAT could protect tissues against hyperactive hydroxyl radicals by decomposing their hydrogen peroxide (Chance et al. [10]). It also acted as an antioxidant enzyme controlling the BPA-induced overproduction of hydrogen peroxide in the heart by converting it into hydrogen oxide. Of course, the significant decrease observed in the activity of this enzyme in this study could be caused by exposure to BPA and its deactivation as a result of elevated ROS generation in mitochondria and microsomes (Pigeolet et al. [44]). In contrast, the QUER + BPA–treated group showed significantly higher CAT activity. In fact, GSH, as the most important non-enzymatic antioxidant, is the first line of defense against ROS, and it was demonstrated that tissues' depletion of GSH led to oxidative stress and consequently tissue damage (Sies [48]). In this study, GSH levels in the BPA group were lower than in the control group, which was probably due to the consumption of GSH for the sweeping of radical hydroxyls (Ezz et al. [16]).

Overall, the observed beneficial effects of QUER could be attributed to its antioxidant property and ability to limit the oxidative stress. In this study, the use of QUER inhibited the generation of ROS and LPO, and the BPA-induced decrease in the antioxidant activity of CAT and GSH. Therefore, this effect could be attributed to LPO inhibition caused by the structural properties of QUER, including the presence of hydroxyl group at C3 (Das and Ratty [13]) and carbonyl group at C4 (Husain et al. [26]), chelating of iron by carbonyl carbonate group (Yuting et al. [51]), and neutralization of radicals. Figure 6 depicts the possible mechanism of action for QUER. In this regard, Edremitlioglu et al. examined the protective effects of QUER against damage to the liver, kidneys, brain, heart, and aorta in diabetes, and reported that QUER indeed played a protective role by reducing oxidative stress, reducing the MDA level and increasing the activity of SOD, CAT, and GPx. Thus, our results confirmed their report regarding the antioxidant and free radical neutralization effects of QUER (Edremitlioğlu et al. [14]).

Graph: Fig. 6 Action mechanism of QUER

In general, the results of this study showed that BPA caused cardiac mitochondrial toxicity by inducing oxidative stress, but QUER could reduce damages to the heart by improving lipid profile, reducing inflammation, neutralizing ROS, protecting the mitochondrial membrane, reducing LPO, and increasing GSH levels through the increased CAT activity. These results suggested that QUER could be utilized as a protective agent against BPA-induced cardiovascular damage.

This work was supported by Deputy of Research of Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. Grant No. NRC-9511.

MM, MAD, and SA designed the study. MAD and SA conducted experiments. ARV and MS analyzed and interpreted the data. ARV drafted the manuscript. MM and MAD revised the manuscript. MM and MAD supervised the study. All authors read and approved the manuscript.

he study was performed according to the instructions of the Jundishapur University animal ethics committee (Ethical code: IR.AJUMS.REC. 1395.632).

The authors declare that they have no conflict of interest.

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