In Vitro and In Vivo Cardioprotective Effects of Curcumin against Doxorubicin-Induced Cardiotoxicity: A Systematic Review

Objective This study aimed to review the potential chemoprotective effects of curcumin against the doxorubicin-induced cardiotoxicity. Methods According to the PRISMA guideline, a comprehensive systematic search was performed in different electronic databases (Web of Science, PubMed, and Scopus) up to July 2021. One hundred and sixty-four studies were screened in accordance with a predefined set of inclusion and exclusion criteria. Eighteen eligible articles were finally included in the current systematic review. Results According to the in vitro and in vivo findings, it was found that doxorubicin administration leads to decreased cell survival, increased mortality, decreased bodyweight, heart weight, and heart to the bodyweight ratio compared to the control groups. However, curcumin cotreatment demonstrated an opposite pattern in comparison with the doxorubicin-treated groups alone. Other findings showed that doxorubicin significantly induces biochemical changes in the cardiac cells/tissue. Furthermore, the histological changes on the cardiac tissue were observed following doxorubicin treatment. Nevertheless, for most of the cases, these biochemical and histological changes mediated by doxorubicin were reversed near to control groups following curcumin coadministration. Conclusion It can be mentioned that coadministration of curcumin alleviates the doxorubicin-induced cardiotoxicity. Curcumin exerts these cardioprotective effects through different mechanisms of antioxidant, antiapoptosis, and anti-inflammatory. Since the finding presented in this systematic review are based on in vitro and in vivo studies, suggesting the use of curcumin in cancer patients as a cardioprotector agent against cardiotoxicity mediated by doxorubicin requires further clinical studies.


Introduction
For many years, cardiovascular anomalies are considered as the leading cause of death in the worldwide; therefore, cardiotoxicity has become a crucial concern for scientific community [1,2]. Literature supports that severe cardiotoxicity is commonly evident in antitumor treatments [3][4][5][6][7][8]; hence, even if these patients survive from malignant tumor, they end up with heart complications in longer run that lead to compromised life style or death [9]. In this regard, drug-induced cardiotoxicity has withdrawn much attention in past two decades, as it has led to ban on various classes of drugs (such as rosiglitazone, prenylamine, rofecoxib, and levomethadyl acetate) due to their associated severe cardiotoxicity [10][11][12][13]. Nevertheless, there are still some cardiotoxic drugs that are applied by clinicians either other safer alternatives are not available or these drugs outweigh the risk of cardiac deformities. Doxorubicin (adriamycin) is an effective chemotherapy drug which belongs to nonselective class I anthracycline family [14]. is chemotherapeutic agent is widely applied for the treatment of different cancers, such as acute leukemia, lymphomas, lung cancer, testicular cancer, thyroid cancer, ovarian cancer, breast cancer, and so on [15][16][17][18][19]. Major limitation reported for doxorubicin is the associated toxicity on various body organs, particularly the heart [9]. e doxorubicin-induced cardiotoxicity can manifest as aberrant arrhythmias, congestive heart failure, and ventricular dysfunction [20][21][22]. It has been also reported that the doxorubicin-induced cardiomyopathy has poor prognosis and can lead to death in most of the cases [17,23]. Fortunately, the mentioned adverse effects overcome through combination chemotherapy [24,25]. In this regard, coadministration of doxorubicin with other agents having chemoprotective capabilities can diminish the toxicity to normal tissues and enhance the tumoricidal efficacy of doxorubicin at the same time [26,27].
According to the published studies, it can be stated that using the herbal and natural compounds or their derivatives to alleviate the adverse effects induced by radiotherapy/ chemotherapy agents (radio/chemoprotectors) and/or increase the sensitivity of tumoral cells to radiotherapy/chemotherapy agents (radio/chemosensitizers) has attracted much attention over the past several decades [28][29][30][31]. Curcumin is a vibrant yellow spice extracted from rhizome of turmeric (Curcuma longa) that is insoluble in water [32,33]. is natural polyphenol is a main active component of turmeric [34] that has antioxidant [35,36], antiapoptotic [37], anti-inflammatory [38][39][40], hepatoprotective [41,42], analgesic and antiarthritic [43,44], pulmonoprotective [45], lipid-modifying [46,47], immunomodulatory [48,49], and antidiabetic [50,51] actions. Curcumin also has anticancer activity, and it has been assessed in different malignant tumors, including colorectal cancer, prostate cancer, lung cancer, gastric cancer, breast cancer, and so on [52]. Moreover, this herbal agent can be used as an adjuvant in combination with other cancer therapeutic modalities such as radiotherapy and chemotherapy [32,53]. In this regard, curcumin is able to alleviate the radiotherapy/chemotherapy-induced adverse effects (radio/chemoprotectors) and/or increase the sensitivity of cancer cells to radiotherapy/ chemotherapy drugs (radio/chemosensitizers) which exerts the mentioned effects through the antiproliferative, antioxidant, antiapoptotic, and anti-inflammatory activities.
To the best of our knowledge, the present study is the first systematic review on the cardioprotective effects of curcumin, as an adjuvant, against doxorubicin-induced cardiotoxicity. In this regard, we tried to answer the following questions: (a) How does doxorubicin chemotherapy drug lead to cardiac adverse effects? (b) What are the underlying mechanisms of cardiotoxicity induced by doxorubicin? (c) What is the role of curcumin on the doxorubicin-induced cardiotoxicity? (d) What are the cardioprotective mechanisms of curcumin against doxorubicin-induced cardiotoxicity?

Methods
In this study, a systematic search was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline [54]. Furthermore, a PICO framework was used to structure the review process [54]. is framework includes participants (P): cardiac cells damaged by doxorubicin (in vitro studies) and/or patients/ animals with cardiac adverse effects induced by doxorubicin (clinical/in vivo studies); intervention (I): patients/animals/ cells treatment with doxorubicin chemotherapeutic drug; comparison (C): patients/animals/cells treated with curcumin and doxorubicin; outcomes (O): there were two critical outcomes: changes induced in the cardiac cells/tissue following doxorubicin treatment compared to control/untreated groups and changes resulted in the cardiac cells/tissue following combined treatment of curcumin and doxorubicin in comparison with doxorubicin treatment alone.

Search Strategy.
We performed a comprehensive systematic search for obtaining all relevant studies on "the role of curcumin on doxorubicin-induced cardiotoxicity" in both medical subject heading (MeSH) or advance in the electronic databases of Scopus, PubMed, and Web of Science up to July 2021 using the keywords of "Doxorubicin" OR "Adriamycin" AND "Curcumin" AND "Heart" OR "Cardiac" OR "Cardiac Toxicity" OR "Cardiac Toxicities" OR "Cardiomyopathy" OR "Arrhythmias" OR "Myocardium" OR "Myocardial" OR "Myocyte" OR "Cardiomyocyte" OR "Cardiopathic" OR "Cardiopathy" OR "Cardiotoxicity" OR "Cardiotoxicities" in title, abstract, or keywords.

Process of Study Selection.
e inclusion criteria considered in this systematic review were full-text scientific studies with English language; our per-defined aim on the role of curcumin on doxorubicin-induced cardiotoxicity (based on the aforementioned keywords); adequate findings; no restriction in publications with clinical, in vivo, or in vitro studies; and no restriction on publication year. Additionally, the exclusion criteria considered for this study were hemodynamic data, not related articles, review papers, case reports, book chapters, letters to the editors, oral presentations, posters, and editorials.

Process of Data Extraction.
Each eligible study was evaluated by two researchers, and the following data were then extracted: author name and year of publication; models (clinical, in vivo or/and in vitro); doxorubicin dosage, protocol of usage, and administration route type; outcomes of doxorubicin on cardiac cells/tissue; curcumin dosage, protocol of usage, and administration route type; and curcumin coadministration outcomes.

Literature Search and Screening.
e study selection process is shown in Figure 1.
One hundred and sixty-four articles were obtained by a comprehensive and systematic search on the electronic databases mentioned above up to July 2021. After removing the duplicated articles (n � 77), the remaining ones (n � 87) were screened in their titles and abstracts. After that, 46 articles were excluded, and remaining ones (n � 41) were qualified for evaluation of their full-texts. Eighteen articles were finally included in this systematic review based on the abovementioned inclusion and exclusion criteria. Table 1 provides a summary of the findings extracted from the eligible articles.

e Cardioprotective Effects of Curcumin against
Doxorubicin-Induced Cardiotoxicity 3.2.1. Cell Survival and Mortality. According to the in vitro results, it was found that the cardiac cell survival following doxorubicin treatment was significantly lower than the untreated/control group [2,9,[55][56][57]. Furthermore, the doxorubicin-mediated cytotoxicity was dose and time-dependent. It showed a direct relation between the cell death and posttreatment time/chemotherapy dosage [55,56]. In contrast, the findings revealed that cotreatment of curcumin resulted to protect the cardiac cells against doxorubicininduced decrease in cell viability [2,9,57]. However, a number of studies have shown that combined treatment of curcumin and doxorubicin leads to a further reduction in cell viability than doxorubicin-treated groups alone [55,56]. e results of in vivo studies demonstrated that the mortality in doxorubicin-treated rats was significantly more than the untreated/control group [58][59][60]. e use of curcumin significantly decreased doxorubicin-induced mortality [58][59][60]. For instance, Imbaby et al. reported the survival rates of 58.33%, 66.33%, and 91.66% in the animals treated by doxorubicin, doxorubicin plus curcumin 100 mg/ kg, and doxorubicin plus curcumin 200 mg/kg [59].

Changes in Bodyweight and Heart
Weight. Some studies showed that the bodyweight and heart weight and ventricle weight, and volume of animals treated by doxorubicin were less than the control group [58][59][60][61][62][63]. It was also reported that ratio of heart to the bodyweight of mice/rats were reduced following doxorubicin administration than the control group [60,63].
Coadministration of curcumin and doxorubicin to the mice/rats led to increase the bodyweight, heart weight, ventricle weight and volume, and ratio of heart to bodyweight in comparison with the doxorubicin-treated groups alone [58][59][60][61][62][63].
e results of most studies demonstrated that coadministration of curcumin and doxorubicin could alleviate the doxorubicin-induced histological changes [2, 57-62, 68].

Discussion
In the current study, we aimed to review the doxorubicininduced adverse effects on the cardiac cells/tissue. Additionally, the coadministration effects of curcumin on these adverse effects were reviewed. e findings obtained from the effects of doxorubicin treatment alone or in combination with curcumin on the cardiac cells/tissue are given in Table 1. Moreover, some of the important changes on the cardiac cell following doxorubicin administration as well as the effects of curcumin coadministration on these changes are shown in Figure 2. Doxorubicin, a chemotherapeutic drug belonging to the anthracycline group, is highly effective in the treatment of a variety of malignant tumors [71]. e mechanisms of action for doxorubicin cytotoxic effects in cancerous cells include DNA intercalation leading to topoisomerase II disruption as well as generation of ROS resulting in cell membrane and mitochondrial membrane damage [17,72]. Nevertheless, the clinical use of doxorubicin is restricted by the risk of dosedependent cardiotoxicity [62]. A variety of mechanisms for explanation of doxorubicin-induced cardiomyopathy have been proposed, including oxidative stress, inflammation, apoptosis, iron-loading disorders, and calcium dysregulation [73]. It has been suggested that the use of chemoprotective agents (such as curcumin) can mitigate the doxorubicin-induced cardiotoxicity. e antitumoral activity of curcumin has been reported in some cancers [52]. Moreover, this natural phytochemical agent has multiple biological activities including chemosensitizing properties [74,75] and chemoprotection effects [76,77]. Curcumin exerts its chemoprotective effects through its antioxidant, antiapoptotic, anti-inflammatory activities, and so on. In the following subsections, the mechanistic effects of the doxorubicin chemotherapeutic agent on the cardiac cellular pathway and the mechanistic effects of curcumin against the cardiac adverse effects induced by doxorubicin are discussed.

Antioxidant Actions.
Normally, free radicals are produced in the cells in which the relevant defense mechanisms protect the cells against them [78,79]. Of note, the free radicals increase in oxidative stress conditions because an imbalance between the free radicals and these defense systems occurs [80,81]. Some studies have reported that the doxorubicin administration increases the ROS level of cardiac cells. e ROS attacks the cell macromolecules and leads to malfunction of the heart tissue [2,56,57,64]. It also showed that upon mitochondrial damage, the generation of free radicals increases in the cells [82]; in this regard, doxorubicin through impairment of mitochondrial function can elevate the generation of free radicals [2,64,83]. Moreover, this chemotherapeutic agent is able to increase : e molecular mechanisms of cardiac adverse effects mediated by doxorubicin. Mostly, doxorubicin induces oxidative stress through mitochondrial dysfunction. is chemotherapy agent increases free radicals via inhibition of GSH and GPx and also elevates LPO markers (MDA and TBARS). Furthermore, doxorubicin increases the apoptosis process through increments in BAX and caspase-1 activities. Moreover, doxorubicin elevates the inflammatory mediators (such as NF-κB, COX-2, TNF-α, INF-c, IL-1β, IL-6, and IL-18) leading to the cell injury. Curcumin, through an opposite pattern (antioxidant, antiapoptotic, and anti-inflammatory activities), alleviates these doxorubicin-induced cardiac adverse effects. ↑, increased by doxorubicin; ↓, decreased by doxorubicin; BAX, Bcl-2-associated X protein; GSH, glutathione; GPx, glutathione peroxidase; IL-1β, interleukin 1 beta; LPO, lipid peroxidation; MDA, malondialdehyde; TBARS, thiobarbituric acid reactive substances; NF-κB, nuclear factor-kappa B; COX-2, cyclooxygenase-2; INF-c, interferon gamma; TGF-β1, transforming growth factor beta 1; and TNF-α, tumor necrosis factor alpha. the LPO level and decrease the GPx and GSH levels in the heart cells which lead to the cell membrane devastation and malfunction [57-60, 65, 66, 68-70]. Hydrogen peroxide (H 2 O 2 ), as a nonradical ROS, produces 2H 2 O via the activity of GPx enzyme and consuming GSH [84]. According to these findings, it can be mentioned that doxorubicin impairs free radical scavenging capacity of intracellular antioxidant enzymes. Furthermore, there is normally a low amount of NO in the cardiac cells [85] in which its level is increased following doxorubicin treatment [59]. It is noteworthy that NO has remarkable roles in cellular signaling during pathological processes [86,87]. It was also found that doxorubicin leads to increase the O − 2 level in cardiac cells [63]. Interaction of NO with O − 2 generates ONOO − that is a potential free radical [88].
It has been shown that curcumin through its antioxidant effects can help scavenging of free radicals generated by some chemotherapeutic agents, resulting to ameliorate toxic effects of chemotherapy [89]. e results represented in the current study revealed that curcumin could decline the doxorubicin-elevated ROS level of cardiac cells [57,64]. However, it was also found that this herbal agent had a synergistic effect on the doxorubicin-generated ROS level in a concentration-dependent manner [56]. Moreover, Jain and Rani [2] reported that curcumin response on the doxorubicin-induced ROS level in cardiomyoblasts was dependent on mode of treatment, as the cells pretreated with curcumin for one day followed by doxorubicin treatment could decrease the doxorubicin-generated ROS level, while it was increased in the cells simultaneously treated with curcumin and doxorubicin [2]. is antioxidant agent could also reduce doxorubicin-induced mitochondria injury, thereby, inhibiting doxorubicin-induced ROS generation [64]. Moreover, the increased levels of NO and O − 2 following doxorubicin treatment were declined by the curcumin cotreatment [59,63]. Furthermore, the combined treatment of curcumin and doxorubicin (compared to doxorubicin treatment alone) could upregulate GSH and GPx expressions [57-60, 65, 66, 68-70] and downregulate MDA, TBARS, 8-OHdG, and 3,3′-dityrosine levels in the cardiac cells [57,58,60,63,65,68,70].
e findings from other studies showed that doxorubicin can trigger cardiac apoptosis via activation of p53, c-Jun N-terminal kinases (JNKs), and p38 mitogenactivated protein kinases (MAPKs) pathways [111].
Although curcumin can induce apoptosis in cancerous cells [112][113][114][115], it is also able to protect normal cells/tissues during cancer chemotherapy through its antiapoptotic effects [76,116]. e data represented in this systematic review showed that combined treatment of curcumin and doxorubicin results to decrease the apoptosis level of cardiac cells in comparison with the doxorubicin-treated groups alone [57,62,64,70]. It was also found that curcumin had a synergistic effect on the doxorubicin-induced apoptosis level in a dose-dependent manner [56]. Additionally, mode of treatment (as pretreatment or concomitant) affected the curcumin response to doxorubicin-induced apoptosis in cardiomyoblasts; in this regard, it was found that the cardiac cells pretreated with curcumin for one day followed by doxorubicin treatment showed a decrease in the apoptosis level induced by doxorubicin, while the apoptosis level was increased in the cells simultaneously treated with curcumin and doxorubicin [2]. e pretreatment of cardiac cells with curcumin followed by doxorubicin prevented loss of MMP and decreased mPTP opening [57]. Furthermore, curcumin combined to doxorubicin could modulate the expression of antiapoptotic (Bcl-2) and proapoptotic (BAX and caspases-1, 2, 3, 8, and 9) mediators in the cardiac cells treated by doxorubicin [2, 55-57, 62, 63, 68].

Anti-Inflammatory Actions.
e chemotherapy treatment can lead to trigger the inflammatory process [117]. e disorder of inflammatory pathways play a vital role in cancer development [118]. It is also responsible for the incidence of various adverse effects following chemotherapy. [32] e use of doxorubicin during cancer chemotherapy can induce heart inflammation [119,120]. Furthermore, oxidative stress induced by doxorubicin can affect LPO and activate lysosomal enzymes which lead to promotion of the inflammation in heart tissue [85]. e doxorubicin-treated cardiac cells showed an increased production of proinflammatory medicators such as ROS, NF-κB, COX-2, TNF-α, INF-c, TGF-β, IL-1β, IL-6, and IL-18 levels [56,63,68,121]. NF-κB, as a proinflammatory transcription factor, has a key role in the activation of TNF-α, IL-1β, IL-1, IL-2, IFNc, COX-2, and iNOS [122][123][124]. ese inflammatory cytokines are able to induce remarkable pathological changes in the form of transmural myocarditis, biventricular fibrosis, and cardiomyopathy [125]. IL-1 is a cytokine well associated to chronic and acute inflammation and other chronic diseases such as cardiomyopathy. It has been also reported that IL-1β, one of the members of the IL-1 family, exacerbates myocardial injures in cancer patients treated with chemotherapy drugs; hence, pharmacological inhibition of IL-1β can be considered as a promising approach for reduction of chemotherapy-induced adverse cardiovascular events [126]. TGF-β is a profibrogenic cytokine that mediates several aspects of the fibrotic process; for instance, it can induce fibroblast proliferation and transformation to myofibroblasts, causing the deposition of collagen and extracellular matrix protein [127,128]. Additionally, TGF-β can modulate cell proliferation, differentiation, apoptosis, and migration [129].
Several studies have reported that curcumin can be suggested as a promising anti-inflammatory agent [40,130]. Curcumin, through its anti-inflammatory activities, can decrease the resistance of cancer cells to chemotherapeutic drugs and also protect the normal cells against chemotherapyinduced side effects [32]. According to the finding obtained from previous studies, it was shown that curcumin cotreatment alleviates the doxorubicin-induced cardiac inflammation. In details, it can be mentioned that combined treatment of curcumin and doxorubicin declines the elevated levels of NF-κB, COX-2, TNF-α, INF-c, IL-1β, IL-6, and IL-18 in the cardiac cells of the doxorubicin-treated animals [56,62,68]. Furthermore, the findings of histological examinations demonstrated that doxorubicin-induced cardiac inflammation is mitigated by curcumin coadministration [2,[57][58][59][60][61][62]68].

Perspective of Future Research
Because of its potent anticancer activities, doxorubicin is widely applied to treat cancer patients; however, irreversible cardiotoxic effects of this chemotherapeutic drug have limited its clinical applications. e published data demonstrated that using the chemoprotective agent of curcumin can alleviate the doxorubicin-induced cardiotoxicity. e researchers have reported several mechanisms for cardioprotective effects of curcumin against doxorubicin-induced cardiotoxicity, including antioxidant, antiapoptosis, anti-inflammatory, and so on. In addition to its chemoprotective, curcumin through chemosensitizer effects can sensitize cancer cells to chemotherapy drugs. e findings obtained for cardioprotective effects of curcumin against doxorubicin-induced cardiotoxicity are based on nonclinical studies (in vitro and in vivo models). erefore, suggesting the use of curcumin in cancer patients as a cardioprotector agent against cardiotoxicity mediated by doxorubicin or other chemotherapeutic drugs requires further clinical studies because sometimes the findings may be different between the in vitro and in vivo models and clinical studies.

Limitations
ere are several limitations which should be addressed: (1) remarkable heterogeneity was encountered perhaps due to various regimens, doses, duration, center settings, and populations enrolled, calling for cautious interpretation of the data, (2) several studies suffer from significant sources of bias, and (3) the effects of doxorubicin treatment alone or in combination with curcumin on the cardiac cells/tissue in many occasions were assessed by very few studies; hence, the evidence to support it is low.

Conclusion
e data presented in this systematic review reveal that the doxorubicin chemotherapeutic agent induces biochemical and histological changes on the cardiac cells/tissue, leading to cardiac adverse effects. It has been also shown that the curcumin cotreatment alleviates the doxorubicin-mediated cardiotoxicity. Mechanically, curcumin exerts its cardioprotective effects through several main mechanisms, such as antioxidant, antiapoptosis, and anti-inflammatory.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Consent
Not applicable.