Targeted disruption of p53 attenuates doxorubicin-induced cardiac toxicity in mice

Trim65 mitigates doxorubicin-induced myocardial injury by reducing ferroptosis

BACKGROUND AND AIMS

The anthracycline chemotherapeutic agent doxorubicin (DOX) is widely used to treat cancer. However, DOX carries a high risk of adverse effects such as cardiovascular events. The aim of this study was to explore the role of Trim65 in DOX-induced cardiotoxicity (DIC) and its underlying mechanisms.

METHODS AND RESULTS

Cellular studies were performed by exposing H9c2 cells (rat cardiomyocytes) to DOX. H9c2 cells were infected with lentivirus encoding negative control (LV-NC) or Trim65 (LV-Trim65). C57BL/6J mice were exposed to adeno-associated virus 9 (AAV9) containing cTnT promoter-encoded Trim65 sequence (AAV-Trim65) or AAV9 negative control sequence (AAV-NC) via tail vein injection. Furthermore, the following analysis were performed: cell viability, intracellular ROS production and lipid peroxidation. Echocardiography was used to measure the heart function of the mice. qPCR and western blotting were used to assess the expression of Trim65, p53, SLC7A11, and GPX4. According to our study, Trim65 expression was significantly downregulated in DIC. Overexpression of Trim65 exhibited considerable protection against to DIC, confirmed by both in vitro and in vivo experiments. In DOX-treated mice, mitochondria deformation was observed in the heart, as well as a high level of lipid peroxidation (signs of ferroptosis) and iron content, which were mitigated by overexpression of Trim65. Mechanistically, our study confirmed that DOX reduced the Trim65-mediated ubiquitination of p53, ultimately inhibiting the degration of p53. We also found that Trim65 mitigated DOX-induced ferroptosis via p53.

CONCLUSION

Collectively, our data demonstrated that Trim65 inhibits ferroptosis by degrading p53, thereby alleviating DIC. Therefore, Trim65 could be a promising target for the treatment of DIC.

A Critical Role for Neutral Sphingomyelinase-2 in Doxorubicin-induced Cardiotoxicity

Although Doxorubicin (Dox) is an effective chemotherapeutic, its clinical utility is limited by a cumulative dose-dependent cardiotoxicity. While mechanisms underlying this cardiotoxicity have been investigated, strategies targeting these pathways have had marginal effects or had potential to interfere with Dox's anti-cancer activity. Sphingolipids (SL) are central to the chemotherapy response in multiple cancers, yet comparatively little is known about their role in non-transformed tissue, and actionable SL targets have not been identified. Here, we identified the SL enzyme neutral sphingomyelinase-2 (nSMase2) as a crucial downstream effector of Dox that is critical for chronic Dox-induced cardiotoxicity. In vitro studies showed that Dox treatment induces nSMase2 mRNA, protein, activity, and Cer accumulation in cardiomyocytes (CM) but not in cardiac fibroblasts. Mechanistically, nSMase2 induction was downstream of Top2B and p53, two previously identified molecular regulators of Dox-induced cardiotoxicity. In vivo studies in a chronic Dox model of cardiotoxicity found that loss of nSMase2 activity-null fro/fro mice were significantly protected from Dox-induced cardiac damage, exhibiting maintained ejection fraction, fractional shortening, and reduced left ventricle mass compared to wild-type littermates. Biologically, nSMase2 was dispensable for Dox-induced cell death but was important for Dox-induced CM senescence both in vitro and in vivo . Microarray analysis identified the dual specificity phosphatase DUSP4 as a downstream target of nSMase2 in vitro in Dox-treated CMs and in vivo in the chronic Dox-treated heart. Taken together, these results establish nSMase2 as a key component of the DNA damage response pathway in CMs and define a critical role for nSMase2 as a SL mediator of Dox-induced cardiotoxicity through effects on CM senescence. In addition to cementing a role for SLs in Dox effects in normal tissue, this study further advances nSMase2 as a target of interest for cardioprotection.

Unveiling the Complexities: Exploring Mechanisms of Anthracyclineinduced Cardiotoxicity

The coexistence of cancer and heart disease, both prominent causes of illness and death, is further exacerbated by the detrimental impact of chemotherapy. Anthracycline-induced cardiotoxicity is an unfortunate side effect of highly effective therapy in treating different types of cancer; it presents a significant challenge for both clinicians and patients due to the considerable risk of cardiotoxicity. Despite significant progress in understanding these mechanisms, challenges persist in identifying effective preventive and therapeutic strategies, rendering it a subject of continued research even after three decades of intensive global investigation. The molecular targets and signaling pathways explored provide insights for developing targeted therapies, emphasizing the need for continued research to bridge the gap between preclinical understanding and clinical applications. This review provides a comprehensive exploration of the intricate mechanisms underlying anthracycline-induced cardiotoxicity, elucidating the interplay of various signaling pathways leading to adverse cellular events, including cardiotoxicity and death. It highlights the extensive involvement of pathways associated with oxidative stress, inflammation, apoptosis, and cellular stress responses, offering insights into potential and unexplored targets for therapeutic intervention in mitigating anthracycline-induced cardiac complications. A comprehensive understanding of the interplay between anthracyclines and these complexes signaling pathways is crucial for developing strategies to prevent or mitigate the associated cardiotoxicity. Further research is needed to outline the specific contributions of these pathways and identify potential therapeutic targets to improve the safety and efficacy of anthracycline-based cancer treatment. Ultimately, advancements in understanding anthracycline-induced cardiotoxicity mechanisms will facilitate the development of more efficacious preventive and treatment approaches, thereby improving outcomes for cancer patients undergoing anthracycline-based chemotherapy.

Evolution of Theories on Doxorubicin-Induced Late Cardiotoxicity-Role of Topoisomerase

Doxorubicin (DOX) has been widely used as a cytotoxic chemotherapeutic. However, DOX has a number of side effects, such as myelotoxicity or gonadotoxicity, the most dangerous of which is cardiotoxicity. Cardiotoxicity can manifest as cardiac arrhythmias, myocarditis, and pericarditis; life-threatening late cardiotoxicity can result in heart failure months or years after the completion of chemotherapy. The development of late cardiomyopathy is not yet fully understood. The most important question is how DOX reprograms the cardiomyocyte, after which DOX is excreted from the body, initially without symptoms. However, clinically overt cardiomyopathy develops over the following months and years. Since the 1980s, DOX-induced disorders in cardiomyocytes have been thought to be related to oxidative stress and dependent on the Fe/reactive oxygen species (ROS) mechanism. That line of evidence was supported by dexrazoxane (DEX) protection, the only Food and Drug Administration (FDA)-approved drug for preventing DOX-induced cardiomyopathy, which complexes iron. Thus, the hypothesis related to Fe/ROS provides a plausible explanation for the induction of the development of late cardiomyopathy via DOX. However, in subsequent studies, DEX was used to identify another important mechanism in DOX-induced cardiomyopathy that is related to topoisomerase 2β (Top2β). Does the Top2β hypothesis explain the mechanisms of the development of DOX-dependent late heart failure? Several of these mechanisms have been identified to date, proving the involvement of Top2β in the regulation of the redox balance, including oxidative stress. Thus, the development of late cardiomyopathy can be explained based on mechanisms related to Top2β. In this review, we highlight free radical theory, iron imbalance, calcium overload, and finally, a theory based on Top2β.

Dysregulated RBM24 phosphorylation impairs APOE translation underlying psychological stress-induced cardiovascular disease

Psychological stress contributes to cardiovascular disease (CVD) and sudden cardiac death, yet its molecular basis remains obscure. RNA binding protein RBM24 plays a critical role in cardiac development, rhythm regulation, and cellular stress. Here, we show that psychological stress activates RBM24 S181 phosphorylation through eIF4E2-GSK3β signaling, which causally links psychological stress to CVD by promoting APOE translation (apolipoprotein E). Using an Rbm24 S181A KI mouse model, we show that impaired S181 phosphorylation leads to cardiac contractile dysfunction, atrial fibrillation, dyslipidemia, reduced muscle strength, behavioral abnormalities, and sudden death under acute and chronic psychological stressors. The impaired S181 phosphorylation of RBM24 inhibits cardiac translation, including APOE translation. Notably, cardiomyocyte-specific expression of APOE rescues cardiac electrophysiological abnormalities and contractile dysfunction, through preventing ROS stress and mitochondrial dysfunction. Moreover, RBM24-S181 phosphorylation acts as a serum marker for chronic stress in human. These results provide a functional link between RBM24 phosphorylation, eIF4E-regulated APOE translation, and psychological-stress-induced CVD.

Mechanistic insights into carvedilol's potential protection against doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is an anthracycline chemotherapy drug widely employed in the treatment of various cancers, known for its potent antineoplastic properties but often associated with dose-dependent cardiotoxicity, limiting its clinical use. This review explores the complex molecular details that determine the heart-protective effectiveness of carvedilol in relation to cardiotoxicity caused by DOX. The harmful effects of DOX on heart cells could include oxidative stress, DNA damage, iron imbalance, disruption of autophagy, calcium imbalance, apoptosis, dysregulation of topoisomerase 2-beta, arrhythmogenicity, and inflammatory responses. This review carefully reveals how carvedilol serves as a strong protective mechanism, strategically reducing each aspect of cardiac damage caused by DOX. Carvedilol's antioxidant capabilities involve neutralizing free radicals and adjusting crucial antioxidant enzymes. It skillfully manages iron balance, controls autophagy, and restores the calcium balance essential for cellular stability. Moreover, the anti-apoptotic effects of carvedilol are outlined through the adjustment of Bcl-2 family proteins and activation of the Akt signaling pathway. The medication also controls topoisomerase 2-beta and reduces the renin-angiotensin-aldosterone system, together offering a thorough defense against cardiotoxicity induced by DOX. These findings not only provide detailed understanding into the molecular mechanisms that coordinate heart protection by carvedilol but also offer considerable potential for the creation of targeted treatment strategies intended to relieve cardiotoxicity caused by chemotherapy.

Betaine ameliorates doxorubicin-induced cardiomyopathy by inhibiting oxidative stress, inflammation, and fibrosis through the modulation of AMPK/Nrf2/TGF-β expression

Doxorubicin (DOX) is a broad-spectrum antibiotic with potent anti-cancer activity. Nevertheless, despite having effective anti-neoplasm activity, its use has been clinically restricted due to its life-threatening side effects, such as cardiotoxicity. It is evident that betaine has anti-oxidant, and anti-inflammatory activity and has several beneficial effects, such as decreasing the amyloid-β generation, reducing obesity, improving steatosis and fibrosis, and activating AMP-activated protein kinase (AMPK). However, whether betaine could mitigate DOX-induced cardiomyopathy is still unexplored. Cardiomyopathy was induced in male Sprague Dawley rats using DOX (4 mg/kg dose with a cumulative dose of 20 mg/kg, i.p.). Further, betaine (200 and 400 mg/kg) was co-treated with DOX through oral gavage for 28 days. After the completion of the study, several biochemical, oxidative stress parameters, histopathology, western blotting, and qRT-PCR were performed. Betaine treatment significantly reduced CK-MB, LDH, SGOT, and triglyceride levels, which are associated with cardiotoxicity. DOX-induced increased oxidative stress was also mitigated by betaine intervention as the SOD, catalase, MDA, and nitrite levels were restored. The histopathological investigation also confirmed the cardioprotective effect of betaine against DOX-induced cardiomyopathy as the tissue injury was reversed. Further, molecular analysis revealed that betaine suppressed the DOX-induced increased expression of phospho-p53, phospho-p38 MAPK, NF-kB p65, and PINK 1 with an upregulation of AMPK and downregulation of Nrf2 expression. Interestingly, qRT-PCR experiments show that betaine treatment alleviates the DOX-induced increase in inflammatory (TNF-α, NLRP3, and IL-6) and fibrosis (TGF-β and Acta2) related gene expression, halting the cardiac injury. Interestingly, betaine also improves the mRNA expression of Nrf2, thus modulating the expression of antioxidant proteins and preventing oxidative damage. Here, we provide the first evidence that betaine treatment prevents DOX-induced cardiomyopathy by inhibiting oxidative stress, inflammation, and fibrosis by regulating AMPK/Nrf2/TGF-β expression. We believe that betaine can be utilized as a potential novel therapeutic strategy for preventing DOX-induced cardiotoxicity.

Betaine ameliorates doxorubicin‐induced cardiomyopathy by inhibiting oxidative stress, inflammation, and fibrosis through the modulation of AMPK/Nrf2/TGF‐β expression

Doxorubicin (DOX) is a broad‐spectrum antibiotic with potent anti‐cancer activity. Nevertheless, despite having effective anti‐neoplasm activity, its use has been clinically restricted due to its life‐threatening side effects, such as cardiotoxicity. It is evident that betaine has anti‐oxidant, and anti‐inflammatory activity and has several beneficial effects, such as decreasing the amyloid‐β generation, reducing obesity, improving steatosis and fibrosis, and activating AMP‐activated protein kinase (AMPK). However, whether betaine could mitigate DOX‐induced cardiomyopathy is still unexplored. Cardiomyopathy was induced in male Sprague Dawley rats using DOX (4 mg/kg dose with a cumulative dose of 20 mg/kg, i.p.). Further, betaine (200 and 400 mg/kg) was co‐treated with DOX through oral gavage for 28 days. After the completion of the study, several biochemical, oxidative stress parameters, histopathology, western blotting, and qRT‐PCR were performed. Betaine treatment significantly reduced CK‐MB, LDH, SGOT, and triglyceride levels, which are associated with cardiotoxicity. DOX‐induced increased oxidative stress was also mitigated by betaine intervention as the SOD, catalase, MDA, and nitrite levels were restored. The histopathological investigation also confirmed the cardioprotective effect of betaine against DOX‐induced cardiomyopathy as the tissue injury was reversed. Further, molecular analysis revealed that betaine suppressed the DOX‐induced increased expression of phospho‐p53, phospho‐p38 MAPK, NF‐kB p65, and PINK 1 with an upregulation of AMPK and downregulation of Nrf2 expression. Interestingly, qRT‐PCR experiments show that betaine treatment alleviates the DOX‐induced increase in inflammatory (TNF‐α, NLRP3, and IL‐6) and fibrosis (TGF‐β and Acta2) related gene expression, halting the cardiac injury. Interestingly, betaine also improves the mRNA expression of Nrf2, thus modulating the expression of antioxidant proteins and preventing oxidative damage. Here, we provide the first evidence that betaine treatment prevents DOX‐induced cardiomyopathy by inhibiting oxidative stress, inflammation, and fibrosis by regulating AMPK/Nrf2/TGF‐β expression. We believe that betaine can be utilized as a potential novel therapeutic strategy for preventing DOX‐induced cardiotoxicity.

FTO ameliorates doxorubicin-induced cardiotoxicity by inhibiting ferroptosis via P53-P21/Nrf2 activation in a HuR-dependent m6A manner

Doxorubicin (DOX)-induced cardiotoxicity seriously limits its clinical applicability, and no therapeutic interventions are available. Ferroptosis, an iron-dependent regulated cell death characterised by lipid peroxidation, plays a pivotal role in DOX-induced cardiotoxicity. N6-methyladenosine (m6A) methylation is the most frequent type of RNA modification and involved in DOX-induced ferroptosis, however, its underlying mechanism remains unclear. P21 was recently found to inhibit ferroptosis by interacting with Nrf2 and is regulated in a P53-dependent or independent manner, such as through m6A modification. In the present study, we investigated the mechanism underlying m6A modification in DOX-induced ferroptosis by focusing on P21. Our results show that fat mass and obesity-associated protein (FTO) down-regulation was associated with DOX-induced cardiotoxicity. FTO over-expression significantly improved cardiac function and cell viability in DOX-treated mouse hearts and H9C2 cells. FTO over-expression significantly inhibited DOX-induced ferroptosis, and the Fer-1 inhibition of ferroptosis significantly reduced DOX-induced cardiotoxicity. P21 was significantly upregulated by FTO and activated Nrf2, playing a crucial role in the anti-ferroptotic effect. FTO upregulated P21/Nrf2 in a P53-dependent manner by mediating the demethylation of P53 or in a P53-independent manner by mediating P21/Nrf2 directly. Human antigen R (HuR) is crucial for FTO-mediated regulation of ferroptosis and P53-P21/Nrf2. Notably, we also found that P21 inhibition in turn inhibited HuR and P53 expression, while HuR inhibition further inhibited FTO expression. RNA immunoprecipitation assay showed that HuR binds to the transcripts of FTO and itself. Collectively, FTO inhibited DOX-induced ferroptosis via P21/Nrf2 activation by mediating the m6A demethylation of P53 or P21/Nrf2 in a HuR-dependent manner and constituted a positive feedback loop with HuR and P53-P21. Our findings provide novel insight into key functional mechanisms associated with DOX-induced cardiotoxicity and elucidate a possible therapeutic approach.

TBC1D15 deficiency protects against doxorubicin cardiotoxicity via inhibiting DNA-PKcs cytosolic retention and DNA damage

Clinical application of doxorubicin (DOX) is heavily hindered by DOX cardiotoxicity. Several theories were postulated for DOX cardiotoxicity including DNA damage and DNA damage response (DDR), although the mechanism(s) involved remains to be elucidated. This study evaluated the potential role of TBC domain family member 15 (TBC1D15) in DOX cardiotoxicity. Tamoxifen-induced cardiac-specific Tbc1d15 knockout (Tbc1d15CKO) or Tbc1d15 knockin (Tbc1d15CKI) male mice were challenged with a single dose of DOX prior to cardiac assessment 1 week or 4 weeks following DOX challenge. Adenoviruses encoding TBC1D15 or containing shRNA targeting Tbc1d15 were used for Tbc1d15 overexpression or knockdown in isolated primary mouse cardiomyocytes. Our results revealed that DOX evoked upregulation of TBC1D15 with compromised myocardial function and overt mortality, the effects of which were ameliorated and accentuated by Tbc1d15 deletion and Tbc1d15 overexpression, respectively. DOX overtly evoked apoptotic cell death, the effect of which was alleviated and exacerbated by Tbc1d15 knockout and overexpression, respectively. Meanwhile, DOX provoked mitochondrial membrane potential collapse, oxidative stress and DNA damage, the effects of which were mitigated and exacerbated by Tbc1d15 knockdown and overexpression, respectively. Further scrutiny revealed that TBC1D15 fostered cytosolic accumulation of the cardinal DDR element DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Liquid chromatography-tandem mass spectrometry and co-immunoprecipitation denoted an interaction between TBC1D15 and DNA-PKcs at the segment 594-624 of TBC1D15. Moreover, overexpression of TBC1D15 mutant (∆594-624, deletion of segment 594-624) failed to elicit accentuation of DOX-induced cytosolic retention of DNA-PKcs, DNA damage and cardiomyocyte apoptosis by TBC1D15 wild type. However, Tbc1d15 deletion ameliorated DOX-induced cardiomyocyte contractile anomalies, apoptosis, mitochondrial anomalies, DNA damage and cytosolic DNA-PKcs accumulation, which were canceled off by DNA-PKcs inhibition or ATM activation. Taken together, our findings denoted a pivotal role for TBC1D15 in DOX-induced DNA damage, mitochondrial injury, and apoptosis possibly through binding with DNA-PKcs and thus gate-keeping its cytosolic retention, a route to accentuation of cardiac contractile dysfunction in DOX-induced cardiotoxicity.

Infiltrating macrophages amplify doxorubicin-induced cardiac damage: role of catecholamines

BACKGROUND

The functional contribution of non-myocyte cardiac cells, such as inflammatory cells, in the setup of heart failure in response to doxorubicin (Dox) is recently becoming of growing interest.

OBJECTIVES

The study aims to evaluate the role of macrophages in cardiac damage elicited by Dox treatment.

METHODS

C57BL/6 mice were treated with one intraperitoneal injection of Dox (20 mg/kg) and followed up for 5 days by cardiac ultrasounds (CUS), histological, and flow cytometry evaluations. We also tested the impact of Dox in macrophage-depleted mice. Rat cardiomyoblasts were directly treated with Dox (D-Dox) or with a conditioned medium from cultured murine macrophages treated with Dox (M-Dox).

RESULTS

In response to Dox, macrophage infiltration preceded cardiac damage. Macrophage depletion prevents Dox-induced damage, suggesting a key role of these cells in promoting cardiotoxicity. To evaluate the crosstalk between macrophages and cardiac cells in response to DOX, we compared the effects of D-Dox and M-Dox in vitro. Cell vitality was lower in cardiomyoblasts and apoptosis was higher in response to M-Dox compared with D-Dox. These events were linked to p53-induced mitochondria morphology, function, and autophagy alterations. We identify a mechanistic role of catecholamines released by Dox-activated macrophages that lead to mitochondrial apoptosis of cardiac cells through β-AR stimulation.

CONCLUSIONS

Our data indicate that crosstalk between macrophages and cardiac cells participates in cardiac damage in response to Dox.

Cardiotoxicity of anti-cancer drugs: cellular mechanisms and clinical implications

Cardio-oncology is an emerging field that seeks to enhance quality of life and longevity of cancer survivors. It is pertinent for clinicians to understand the cellular mechanisms of prescribed therapies, as this contributes to robust understanding of complex treatments and off-target effects, improved communication with patients, and guides long term care with the goal to minimise or prevent cardiovascular complications. Our aim is to review the cellular mechanisms of cardiotoxicity involved in commonly used anti-cancer treatments and identify gaps in literature and strategies to mitigate cardiotoxicity effects and guide future research endeavours.

Overexpressed SIRT6 ameliorates doxorubicin-induced cardiotoxicity and potentiates the therapeutic efficacy through metabolic remodeling

Since the utilization of anthracyclines in cancer therapy, severe cardiotoxicity has become a major obstacle. The major challenge in treating cancer patients with anthracyclines is minimizing cardiotoxicity without compromising antitumor efficacy. Herein, histone deacetylase SIRT6 expression was reduced in plasma of patients treated with anthracyclines-based chemotherapy regimens. Furthermore, overexpression of SIRT6 alleviated doxorubicin-induced cytotoxicity in cardiomyocytes, and potentiated cytotoxicity of doxorubicin in multiple cancer cell lines. Moreover, SIRT6 overexpression ameliorated doxorubicin-induced cardiotoxicity and potentiated antitumor efficacy of doxorubicin in mice, suggesting that SIRT6 overexpression could be an adjunctive therapeutic strategy during doxorubicin treatment. Mechanistically, doxorubicin-impaired mitochondria led to decreased mitochondrial respiration and ATP production. And SIRT6 enhanced mitochondrial biogenesis and mitophagy by deacetylating and inhibiting Sgk1. Thus, SIRT6 overexpression coordinated metabolic remodeling from glycolysis to mitochondrial respiration during doxorubicin treatment, which was more conducive to cardiomyocyte metabolism, thus protecting cardiomyocytes but not cancer cells against doxorubicin-induced energy deficiency. In addition, ellagic acid, a natural compound that activates SIRT6, alleviated doxorubicin-induced cardiotoxicity and enhanced doxorubicin-mediated tumor regression in tumor-bearing mice. These findings provide a preclinical rationale for preventing cardiotoxicity by activating SIRT6 in cancer patients undergoing chemotherapy, but also advancing the understanding of the crucial role of SIRT6 in mitochondrial homeostasis.

High Glucose Activates Prolyl Hydroxylases and Disrupts HIF-α Signaling via the P53/TIGAR Pathway in Cardiomyocyte

The induction of hypoxia tolerance has emerged as a novel therapeutic strategy for the treatment of ischemic diseases. The disruption of hypoxic signaling by hyperglycemia has been shown to contribute to diabetic cardiomyopathy. In this study, we explored the potential molecular mechanisms by which high glucose (HG) impairs hypoxia-inducible factor-α (HIF-α) signaling in cardiomyocytes. The exposure of H9c2 cell lines to HG resulted in time- and concentration-dependent decreases in HIF-1α and HIF-2α expression together with an increase in prolyl hydroxylase-1,2 (PHD1 and PHD2) expression, the main regulators of HIF-α destabilization in the heart. The exposure of H9c2 cells to normal glucose (5.5 mM) and high glucose (15, 30, and 45 mM) led to dose-dependent increases in p53 and TIGAR and a decrease in SIRT3 expression. The pretreatment of H9c2 with p53 siRNA to knockdown p53 attenuated PHD1 and PHD2 expression, thus significantly enhancing HIF-1α and HIF-2α expression in H9c2 cells under HG conditions. Interestingly, pretreatment with p53 siRNA altered H9c2 cell metabolism by reducing oxygen consumption rate and increasing glycolysis. Similarly, pretreatment with TIGAR siRNA blunted HG-induced PHD1 and PHD2 expression. This was accompanied by an increase in HIF-1α and HIF-2α expression with a reduction in oxygen consumption rate in H9c2 cells. Furthermore, pretreatment with adenovirus-SIRT3 (Ad-SIRT3) significantly reduced the HG-induced expression of p53 and PHDs and increased HIF-1α levels in H9c2 cells. Ad-SIRT3 treatment also regulated PHDs-HIF-1α levels in the hearts of diabetic db/db mice. Our study revealed a novel role of the HG-induced disruption of PHDs-HIF-α signaling via upregulating p53 and TIGAR expression. Therefore, the p53/TIGAR signaling pathway may be a novel target for diabetic cardiomyopathy.

Anthracycline-induced cardiotoxicity and cell senescence: new therapeutic option?

Anthracyclines are chemotherapeutic drugs widely used in the frontline of cancer treatment. The therapeutic mechanisms involve the stabilization of topoisomerase IIα, DNA, and the anthracycline molecule in a ternary complex that is recognized as DNA damage. Redox imbalance is another vital source of oxidative DNA damage. Together, these mechanisms lead to cytotoxic effects in neoplastic cells. However, anthracycline treatment can elicit cardiotoxicity and heart failure despite the therapeutic benefits. Topoisomerase IIβ and oxidative damage in cardiac cells have been the most reported pathophysiological mechanisms. Alternatively, cardiac cells can undergo stress-induced senescence when exposed to anthracyclines, a state primarily characterized by cell cycle arrest, organelle dysfunction, and a shift to senescence-associated secretory phenotype (SASP). The SASP can propagate senescence to neighboring cells in an ongoing process that leads to the accumulation of senescent cells, promoting cellular dysfunction and extracellular matrix remodeling. Therefore, the accumulation of senescent cardiac cells is an emerging pathophysiological mechanism associated with anthracycline-induced cardiotoxicity. This paradigm also raises the potential for therapeutic approaches to clear senescent cells in treating anthracycline-induced cardiotoxicity (i,e, senolytic therapies).

Long noncoding RNA NONMMUT015745 inhibits doxorubicin-mediated cardiomyocyte apoptosis by regulating Rab2A-p53 axis

Doxorubicin (DOX) is an efficacious and widely used drug for human malignancy treatment, but its clinical application is limited due to side effects, especially cardiotoxicity. Our present study revealed that DOX could induce apoptosis in cardiomyocytes. Herein, we screened the dysregulated long noncoding RNAs (lncRNAs) in DOX-treated cardiomyocytes. Notably, overexpression of lncRNA NONMMUT015745 (lnc5745) could alleviate DOX-induced cardiomyocyte apoptosis both in vitro and in vivo. Conversely, silencing lnc5745 promotes cardiomyocyte apoptosis. Moreover, Rab2A, a direct target of lnc5745, possesses a protective effect in DOX-induced cardiotoxicity once knocked down. Importantly, we verified that the p53-related apoptotic signalling pathway was responsible for the lnc5745-mediated protective role against DOX-induced cardiomyocyte apoptosis. Mechanistically, Rab2A interacts with p53 and phosphorylated p53 on Ser 33 (p53 (Phospho-Ser 33)), promotes p53 phosphorylation, thereby activating the apoptotic pathway. Taken together, our results suggested that lnc5745 protects against DOX-induced cardiomyocyte apoptosis through suppressing Rab2A expression, modifying p53 phosphorylation, thereby regulating p53-related apoptotic signalling pathway. Our findings establish the functional mode of the lnc5745-Rab2A-p53 axis in DOX-induced cardiotoxicity. The development of new strategies targeting the lnc5745-Rab2A-p53 axis could attenuate DOX-induced cardiotoxicity, which is beneficial to its clinical anti-tumour application.

Mulberrin Confers Protection against Doxorubicin-Induced Cardiotoxicity via Regulating AKT Signaling Pathways in Mice

Doxorubicin (DOX) is an antitumor anthracycline, but its clinical use was largely limited by its cardiac toxicity. DOX-induced oxidative damage and cardiomyocyte loss have been recognized as the potential causative mechanisms of this cardiac toxicity. Growing interests are raised on mulberrin (Mul) for its wide spectrum of biological activities, including antioxidative and anti-inflammatory properties. The aim of this study was to investigate the effect of Mul on DOX-induced heart injury and to clarify the underlying mechanism. Mice were given daily 60 mg/kg of Mul via gavage for 10 days. Mice received an intraperitoneal injection of DOX to mimic the model of DOX-related acute cardiac injury at the seventh day of Mul treatment. Mul-treated mice had an attenuated cardiac injured response and improved cardiac function after DOX injection. DOX-induced oxidative damage, inflammation accumulation, and myocardial apoptosis were largely attenuated by the treatment of Mul. Activated protein kinase B (AKT) activation was essential for the protective effects of Mul against DOX-induced cardiac toxicity, and AKT inactivation abolished Mul-mediated protective effects against DOX cardiotoxicity. In conclusion, Mul treatment attenuated DOX-induced cardiac toxicity via activation of the AKT signaling pathway. Mul might be a promising therapeutic agent against DOX-induced cardiac toxicity.

The Beneficial Role of Physical Exercise on Anthracyclines Induced Cardiotoxicity in Breast Cancer Patients

The increase in breast cancer (BC) survival has determined a growing survivor population that seems to develop several comorbidities and, specifically, treatment-induced cardiovascular disease (CVD), especially those patients treated with anthracyclines. Indeed, it is known that these compounds act through the induction of supraphysiological production of reactive oxygen species (ROS), which appear to be central mediators of numerous direct and indirect cardiac adverse consequences. Evidence suggests that physical exercise (PE) practised before, during or after BC treatments could represent a viable non-pharmacological strategy as it increases heart tolerance against many cardiotoxic agents, and therefore improves several functional, subclinical, and clinical parameters. At molecular level, the cardioprotective effects are mainly associated with an exercise-induced increase of stress response proteins (HSP60 and HSP70) and antioxidant (SOD activity, GSH), as well as a decrease in lipid peroxidation, and pro-apoptotic proteins such as Bax, Bax-to-Bcl-2 ratio. Moreover, this protection can potentially be explained by a preservation of myosin heavy chain (MHC) isoform distribution. Despite this knowledge, it is not clear which type of exercise should be suggested in BC patient undergoing anthracycline treatment. This highlights the lack of special guidelines on how affected patients should be managed more efficiently. This review offers a general framework for the role of anthracyclines in the physio-pathological mechanisms of cardiotoxicity and the potential protective role of PE. Finally, potential exercise-based strategies are discussed on the basis of scientific findings.

Ferroptosis in Cardiovascular Diseases: Current Status, Challenges, and Future Perspectives

Cardiovascular diseases (CVDs) are still a major cause of global mortality and disability, seriously affecting people’s lives. Due to the severity and complexity of these diseases, it is important to find new regulatory mechanisms to treat CVDs. Ferroptosis is a new kind of regulatory cell death currently being investigated. Increasing evidence showed that ferroptosis plays an important role in CVDs, such as in ischemia/reperfusion injury, heart failure, cardiomyopathy, and atherosclerosis. Protecting against CVDs by targeting ferroptosis is a promising approach; therefore, in this review, we summarized the latest regulatory mechanism of ferroptosis and the current studies related to each CVD, followed by critical perspectives on the ferroptotic treatment of CVDs and the future direction of this intriguing biology.

Therapeutic Targets for DOX-Induced Cardiomyopathy: Role of Apoptosis vs. Ferroptosis

Doxorubicin (DOX) is the most widely used anthracycline anticancer agent; however, its cardiotoxicity limits its clinical efficacy. Numerous studies have elucidated the mechanisms underlying DOX-induced cardiotoxicity, wherein apoptosis has been reported as the most common final step leading to cardiomyocyte death. However, in the past two years, the involvement of ferroptosis, a novel programmed cell death, has been proposed. The purpose of this review is to summarize the historical background that led to each form of cell death, focusing on DOX-induced cardiotoxicity and the molecular mechanisms that trigger each form of cell death. Furthermore, based on this understanding, possible therapeutic strategies to prevent DOX cardiotoxicity are outlined. DNA damage, oxidative stress, intracellular signaling, transcription factors, epigenetic regulators, autophagy, and metabolic inflammation are important factors in the molecular mechanisms of DOX-induced cardiomyocyte apoptosis. Conversely, the accumulation of lipid peroxides, iron ion accumulation, and decreased expression of glutathione and glutathione peroxidase 4 are important in ferroptosis. In both cascades, the mitochondria are an important site of DOX cardiotoxicity. The last part of this review focuses on the significance of the disruption of mitochondrial homeostasis in DOX cardiotoxicity.

Cardiotoxicity of Cancer Treatments: Focus on Anthracycline Cardiomyopathy

Significant progress has been made in developing new treatments and refining the use of preexisting ones against cancer. Their successful use and the longer survival of cancer patients have been associated with reports of new cardiotoxicities and the better characterization of the previously known cardiac complications. Immunotherapies with monoclonal antibodies against specific cancer-promoting genes, chimeric antigen receptor T cells, and immune checkpoint inhibitors have been developed to fight cancer cells, but they can also show off-target effects on the heart. Some of these cardiotoxicities are thought to be due to nonspecific immune activation and inflammatory damage. Unlike immunotherapy-associated cardiotoxicities which are relatively new entities, there is extensive literature on anthracycline-induced cardiomyopathy. Here, we provide a brief overview of the cardiotoxicities of immunotherapies for the purpose of distinguishing them from anthracycline cardiomyopathy. This is especially relevant as the expansion of oncological treatments presents greater diagnostic challenges in determining the cause of cardiac dysfunction in cancer survivors with a history of multiple cancer treatments including anthracyclines and immunotherapies administered concurrently or serially over time. We then provide a focused review of the mechanisms proposed to underlie the development of anthracycline cardiomyopathy based on experimental data mostly in mouse models. Insights into its pathogenesis may stimulate the development of new strategies to identify patients who are susceptible to anthracycline cardiomyopathy while permitting low cardiac risk patients to receive optimal treatment for their cancer.

Serine mutations in overexpressed Hsp27 abrogate the protection against doxorubicin-induced p53-dependent cardiac apoptosis in mice

Small heat shock proteins (sHsps) protect the heart from chemotherapeutics-induced heart failure by inhibiting p53-dependent apoptosis. However, mechanism of such protection has not been elucidated yet. Here we test a hypothesis that serine phosphorylation of sHsps is essential to inhibit the doxorubicin-induced and p53-dependent apoptotic pathway. Three transgenic mice (TG) lines with cardiomyocyte-specific overexpression of human heat shock protein 27 (hHsp27), namely, wild-type [myosin heavy chain (MHC)-hHsp27], S82A single mutant [MHC-mut-hHsp27(S82A)], and trimutant [MHC-mut-hHsp27(S15A/S78A/S82A)] were generated. TG mice were treated with Dox (6 mg/kg body wt; once in a week; 4 wk) along with age-matched nontransgenic (non-TG) controls. The Dox-treated MHC-hHsp27 mice showed improved survival and cardiac function (both MRI and echocardiography) in terms of contractility [ejection fraction (%EF)] and left ventricular inner diameter (LVID) compared with the Dox-treated non-TG mice. However, both MHC-mut-hHsp27(S82A) and MHC-mut-hHsp27(S15A/S78A/S82A) mutants overexpressing TG mice did not show such a cardioprotection. Furthermore, transactivation of p53 was found to be attenuated only in Dox-treated MHC-hHsp27 mice-derived cardiomyocytes in vitro, as low p53 was detected in the nuclei, not in mutant hHsp27 overexpressing cardiomyocytes. Similarly, only in MHC-hHsp27 overexpressing cardiomyocytes, low Bax, higher mechanistic target of rapamycin (mTOR) phosphorylation, and low apoptotic poly(ADP-ribose) polymerase-1 (PARP-1) cleavage (89 kDa fragment) were detected. Pharmacological inhibition of p53 was more effective in mutant TG mice compared with MHC-hHsp27 mice. We conclude that phosphorylation of overexpressed Hsp27 at S82 and its association with p53 are essential for the cardioprotective effect of overexpressed Hsp27 against Dox-induced dilated cardiomyopathy. Only phosphorylated Hsp27 protects the heart by inhibiting p53 transactivation.NEW & NOTEWORTHY Requirement of serine phosphorylation in Hsp27 for cardioprotective effect against Dox is tested in various mutants overexpressing mice. Cardioprotective effect was found to be compromised in Hsp27 serine mutants overexpressed mice compared with wild-type overexpressing mice. These results indicate that cancer patients, who carry these mutations, may have higher risk of aggravated cardiomyopathy on treated with cardiotoxic chemotherapeutics such as doxorubicin.

Sirt6 protects cardiomyocytes against doxorubicin-induced cardiotoxicity by inhibiting P53/Fas-dependent cell death and augmenting endogenous antioxidant defense mechanisms

Sirt6, a class III NAD⁺-dependent deacetylase of the sirtuin family, is a highly specific H3 deacetylase and plays important roles in regulating cellular growth and death. The induction of oxidative stress and death is the critical mechanism involved in cardiomyocyte injury and cardiac dysfunction in doxorubicin-induced cardiotoxicity, but the regulatory role of Sirt6 in the fate of DOX-impaired cardiomyocytes is poorly understood. In the present study, we exposed Sirt6 heterozygous (Sirt6^+/-) mice and their littermates as well as cultured neonatal rat cardiomyocytes to DOX, then investigated the role of Sirt6 in mitigating oxidative stress and cardiac injury in the DOX-treated myocardium. Sirt6 partial knockout or silencing worsened cardiac damage, remodeling, and oxidative stress injury in mice or cultured cardiomyocytes with DOX challenge. Cardiomyocytes infected with adenoviral constructs encoding Sirt6 showed reversal of this DOX-induced damage. Intriguingly, Sirt6 reduced oxidative stress injury by upregulating endogenous antioxidant levels, interacted with oxidative stress-stirred p53, and acted as a co-repressor of p53 in nuclei. Sirt6 was recruited by p53 to the promoter regions of the target genes Fas and FasL and further suppressed p53 transcription activity by reducing histone acetylation. Sirt6 inhibited Fas/FasL signaling and attenuated both Fas-FADD-caspase-8 apoptotic and Fas-RIP3 necrotic pathways. These results indicate that Sirt6 protects the heart against DOX-induced cardiotoxicity by upregulating endogenous antioxidants, as well as suppressing oxidative stress and cell death signaling pathways dependent on ROS-stirred p53 transcriptional activation, thus reducing Fas-FasL-mediated apoptosis and necrosis. •Sirt6 is significantly decreased in DOX-insulted mouse hearts and cardiomyocytes. •Sirt6 attenuates DOX-induced cardiac atrophy, dysfunction and oxidative stress. • Sirt6 reduces oxidative stress injury by upregulating endogenous antioxidants. • Sirt6 interacts with p53 as a co-repressor to suppress p53 transcriptional regulation and inhibits Fas-FasL-mediated apoptosis and necrosis downstream of p53.

The Interplay Between Autophagy and Senescence in Anthracycline Cardiotoxicity

PURPOSE OF REVIEW

Doxorubicin (DOXO) is a highly effective chemotherapeutic drug employed for the treatment of a wide spectrum of cancers, spanning from solid tumours to haematopoietic malignancies. However, its clinical use is hampered by severe and dose-dependent cardiac side effects that ultimately lead to heart failure (HF).

RECENT FINDINGS

Mitochondrial dysfunction and oxidative stress are well-established mechanisms of DOXO-induced cardiotoxicity, although recent evidence suggests that deregulation of other biological processes, like autophagy, could be involved. It is increasingly recognized that autophagy deregulation is intimately interconnected with the initiation of detrimental cellular responses, including autosis and senescence, raising the possibility of using autophagy modulators as well as senolytics and senomorphics for preventing DOXO cardiotoxicity. This review aims at providing an overview of the signalling pathways that are common to autophagy and senescence, with a special focus on how the relationship between these two processes is deregulated in response to cardiotoxic treatments. Finally, we will discuss the potential therapeutic utility of drugs modulating autophagy and/or senescence for counteracting DOXO cardiotoxicity.

Molecular mechanisms of anthracycline cardiovascular toxicity

Anthracyclines are effective chemotherapeutic agents, commonly used in the treatment of a variety of hematologic malignancies and solid tumors. However, their use is associated with a significant risk of cardiovascular toxicities and may result in cardiomyopathy and heart failure. Cardiomyocyte toxicity occurs via multiple molecular mechanisms, including topoisomerase II-mediated DNA double-strand breaks and reactive oxygen species (ROS) formation via effects on the mitochondrial electron transport chain, NADPH oxidases (NOXs), and nitric oxide synthases (NOSs). Excess ROS may cause mitochondrial dysfunction, endoplasmic reticulum stress, calcium release, and DNA damage, which may result in cardiomyocyte dysfunction or cell death. These pathophysiologic mechanisms cause tissue-level manifestations, including characteristic histopathologic changes (myocyte vacuolization, myofibrillar loss, and cell death), atrophy and fibrosis, and organ-level manifestations including cardiac contractile dysfunction and vascular dysfunction. In addition, these mechanisms are relevant to current and emerging strategies to diagnose, prevent, and treat anthracycline-induced cardiomyopathy. This review details the established and emerging data regarding the molecular mechanisms of anthracycline-induced cardiovascular toxicity.

Regulated cell death pathways in doxorubicin-induced cardiotoxicity

Doxorubicin is a chemotherapeutic drug used for the treatment of various malignancies; however, patients can experience cardiotoxic effects and this has limited the use of this potent drug. The mechanisms by which doxorubicin kills cardiomyocytes has been elusive and despite extensive research the exact mechanisms remain unknown. This review focuses on recent advances in our understanding of doxorubicin induced regulated cardiomyocyte death pathways including autophagy, ferroptosis, necroptosis, pyroptosis and apoptosis. Understanding the mechanisms by which doxorubicin leads to cardiomyocyte death may help identify novel therapeutic agents and lead to more targeted approaches to cardiotoxicity testing.

Sirtuin 3 Alleviates Diabetic Cardiomyopathy by Regulating TIGAR and Cardiomyocyte Metabolism

Background

Impairment of glycolytic metabolism is suggested to contribute to diabetic cardiomyopathy. In this study, we explored the roles of SIRT3 (Sirtuin 3) on cardiomyocyte glucose metabolism and cardiac function.

Methods and Results

Exposure of H9c2 cardiomyocyte cell lines to high glucose (HG) (30 mmol/L) resulted in a gradual decrease in SIRT3 and 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase isoform 3 (PFKFB3) expression together with increases in p53 acetylation and TP53‐induced glycolysis and apoptosis regulator (TIGAR) expression. Glycolysis was significantly reduced in the cardiomyocyte exposed to HG. Transfection with adenovirus‐SIRT3 significantly increased PFKFB3 expression and reduced HG‐induced p53 acetylation and TIGAR expression. Overexpression of SIRT3 rescued impaired glycolysis and attenuated HG–induced reactive oxygen species formation and apoptosis. Knockdown of TIGAR in cardiomyocytes by using siRNA significantly increased PFKFB3 expression and glycolysis under hyperglycemic conditions. This was accompanied by a significant suppression of HG–induced reactive oxygen species formation and apoptosis. In vivo, overexpression of SIRT3 by an intravenous jugular vein injection of adenovirus‐SIRT3 resulted in a significant reduction of p53 acetylation and TIGAR expression together with upregulation of PFKFB3 expression in the heart of diabetic db/db mice at day 14. Overexpression of SIRT3 further reduced reactive oxygen species formation and blunted microvascular rarefaction in the diabetic db/db mouse hearts. Overexpression of SIRT3 significantly blunted cardiac fibrosis and hypertrophy and improved cardiac function at day 14.

Conclusions

Our study demonstrated that SIRT3 attenuated diabetic cardiomyopathy via regulating p53 acetylation and TIGAR expression. Therefore, SIRT3 may be a novel target for abnormal energy metabolism in diabetes mellitus.

Vagus nerve stimulation optimized cardiomyocyte phenotype, sarcomere organization and energy metabolism in infarcted heart through FoxO3A-VEGF signaling

Vagus nerve stimulation (VNS) restores autonomic balance, suppresses inflammation action and minimizes cardiomyocyte injury. However, little knowledge is known about the VNS’ role in cardiomyocyte phenotype, sarcomere organization, and energy metabolism of infarcted hearts. VNS in vivo and acetylcholine (ACh) in vitro optimized the levels of α/β-MHC and α-Actinin positive sarcomere organization in cardiomyocytes while reducing F-actin assembly of cardiomyocytes. Consistently, ACh improved glucose uptake while decreasing lipid deposition in myocytes, correlating both with the increase of Glut4 and CPT1α and the decrease of PDK4 in infarcted hearts in vivo and myocytes in vitro, attributing to improvement in both glycolysis by VEGF-A and lipid uptake by VEGF-B in response to Ach. This led to increased ATP levels accompanied by the repaired mitochondrial function and the decreased oxygen consumption. Functionally, VNS improved the left ventricular performance. In contrast, ACh-m/nAChR inhibitor or knockdown of VEGF-A/B by shRNA powerfully abrogated these effects mediated by VNS. On mechanism, ACh decreased the levels of nuclear translocation of FoxO3A in myocytes due to phosphorylation of FoxO3A by activating AKT. FoxO3A overexpression or knockdown could reverse the specific effects of ACh on the expression of VEGF-A/B, α/β-MHC, Glut4, and CPT1α, sarcomere organization, glucose uptake and ATP production. Taken together, VNS optimized cardiomyocytes sarcomere organization and energy metabolism to improve heart function of the infarcted heart during the process of delaying and/or blocking the switch from compensated hypertrophy to decompensated heart failure, which were associated with activation of both P13K/AKT-FoxO3A-VEGF-A/B signaling cascade.

Possible Susceptibility Genes for Intervention against Chemotherapy-Induced Cardiotoxicity

Recent therapeutic advances have significantly improved the short- and long-term survival rates in patients with heart disease and cancer. Survival in cancer patients may, however, be accompanied by disadvantages, namely, increased rates of cardiovascular events. Chemotherapy-related cardiac dysfunction is an important side effect of anticancer therapy. While advances in cancer treatment have increased patient survival, treatments are associated with cardiovascular complications, including heart failure (HF), arrhythmias, cardiac ischemia, valve disease, pericarditis, and fibrosis of the pericardium and myocardium. The molecular mechanisms of cardiotoxicity caused by cancer treatment have not yet been elucidated, and they may be both varied and complex. By identifying the functional genetic variations responsible for this toxicity, we may be able to improve our understanding of the potential mechanisms and pathways of treatment, paving the way for the development of new therapies to target these toxicities. Data from studies on genetic defects and pharmacological interventions have suggested that many molecules, primarily those regulating oxidative stress, inflammation, autophagy, apoptosis, and metabolism, contribute to the pathogenesis of cardiotoxicity induced by cancer treatment. Here, we review the progress of genetic research in illuminating the molecular mechanisms of cancer treatment-mediated cardiotoxicity and provide insights for the research and development of new therapies to treat or even prevent cardiotoxicity in patients undergoing cancer treatment. The current evidence is not clear about the role of pharmacogenomic screening of susceptible genes. Further studies need to done in chemotherapy-induced cardiotoxicity.

Cardiomyocyte specific deletion of p53 decreases cell injury during ischemia-reperfusion: Role of Mitochondria

p53 is a tumor suppressor protein with a very low content in the basal condition, but the content rapidly rises during stress conditions including ischemia-reperfusion. An increase in p53 content increases cardiac injury during ischemia-reperfusion. Since mitochondrial damage plays a key role in cardiac injury during ischemia-reperfusion, we asked if genetic ablation of p53 decreases cardiac injury by protecting mitochondria. Isolated, perfused hearts from cardiac specific p53 deletion or wild type underwent 25 min global ischemia at 37 °C and 60 min reperfusion. At the end of reperfusion, hearts were harvested for infarct size measurement. In separate groups, cardiac mitochondria were isolated at 30 min reperfusion. Time control hearts were buffer-perfused without ischemia. Compared to wild type, deletion of p53 improved cardiac functional recovery and decreased infarct size following ischemia-reperfusion. Oxidative phosphorylation was improved in p53 deletion mitochondria following ischemia-reperfusion compared to wild type. The net release of ROS generation from wild type but not in p53 deletion mitochondria was increased following ischemia-reperfusion. Peroxiredoxin 3 (PRDX 3) content was higher in p53 deletion than that in wild type, indicating that p53 deletion increases a key antioxidant. Ischemia-reperfusion led to increased spectrin cleavage (a marker of cytosolic calpain1 activation) in wild type but not in p53 deletion mice. Ischemia-reperfusion increased the truncation of mature AIF (apoptosis inducing factor, an indicator of mitochondrial calpain1 activation) in wild type but not in p53 deletion mice. The loss of cytochrome c from mitochondria was also decreased in p53 deletion following ischemia-reperfusion. Bcl-2 content was decreased in wild type but not in p53 deletion following reperfusion, suggesting that depletion of bcl-2 contributes to permeabilization of the mitochondrial outer membrane. Thus, deletion of p53 decreases cardiac injury by protecting mitochondria through attenuation of oxidative stress and calpain activation during ischemia-reperfusion.

Doxorubicin-induced p53 interferes with mitophagy in cardiac fibroblasts

Anthracyclines are the critical component in a majority of pediatric chemotherapy regimens due to their broad anticancer efficacy. Unfortunately, the vast majority of long-term childhood cancer survivors will develop a chronic health condition caused by their successful treatments and severe cardiac disease is a common life-threatening outcome that is unequivocally linked to previous anthracycline exposure. The intricacies of how anthracyclines such as doxorubicin, damage the heart and initiate a disease process that progresses over multiple decades is not fully understood. One area left largely unstudied is the role of the cardiac fibroblast, a key cell type in cardiac maturation and injury response. In this study, we demonstrate the effect of doxorubicin on cardiac fibroblast function in the presence and absence of the critical DNA damage response protein p53. In wildtype cardiac fibroblasts, doxorubicin-induced damage correlated with decreased proliferation and migration, cell cycle arrest, and a dilated cardiomyopathy gene expression profile. Interestingly, these doxorubicin-induced changes were completely or partially restored in p53-/- cardiac fibroblasts. Moreover, in wildtype cardiac fibroblasts, doxorubicin produced DNA damage and mitochondrial dysfunction, both of which are well-characterized cell stress responses induced by cytotoxic chemotherapy and varied forms of heart injury. A 3-fold increase in p53 (p = 0.004) prevented the completion of mitophagy (p = 0.032) through sequestration of Parkin. Interactions between p53 and Parkin increased in doxorubicin-treated cardiac fibroblasts (p = 0.0003). Finally, Parkin was unable to localize to the mitochondria in wildtype cardiac fibroblasts, but mitochondrial localization was restored in p53-/- cardiac fibroblasts. These findings strongly suggest that cardiac fibroblasts are an important myocardial cell type that merits further study in the context of doxorubicin treatment. A more robust knowledge of the role cardiac fibroblasts play in the development of doxorubicin-induced cardiotoxicity will lead to novel clinical strategies that will improve the quality of life of cancer survivors.

The beneficial effects of reducing NLRP3 inflammasome activation in the cardiotoxicity and the anti-cancer effects of doxorubicin

Doxorubicin (DOX) is a powerful broad-spectrum anti-neoplastic anthracycline antibiotic. However, DOX may cause a dose-dependent cardiotoxicity that can eventually progress to congestive heart failure and death. Numerous molecular mechanisms have been implicated in the cardiotoxic effect of DOX including topoisomerase IIβ and generation of free radicals. However, targeting these pathways appears to be insufficient to mitigate the cardiotoxic effects of DOX and/or ultimately reduces the anti-tumor activity of DOX. Thus, there remains a crucial need to identify novel pharmacological targets that can alleviate the cardiotoxic effects of DOX without reducing its anti-tumor activity. Recent studies have suggested that the Nucleotide-Binding Domain-Like Receptor Protein 3 (NLRP3) inflammasome is implicated in tumor progression and the chemoresistance of cancer cells to DOX. Of interest, reducing NLRP3 inflammasome activity alleviates DOX-induced cardiotoxicity. Therefore, we postulate that strategies that target the NLRP3 inflammasome can help mitigate the cardiotoxic effects of DOX while maintaining and/or even enhancing its anti-cancer activity. Herein, we review the current knowledge about the potential implication of the NLRP3 inflammasome in the anti-cancer and cardiotoxic effects of DOX.

Sirtuin 3, Endothelial Metabolic Reprogramming, and Heart Failure With Preserved Ejection Fraction

The incidences of heart failure with preserved ejection fraction (HFpEF) are increased in aged populations as well as diabetes and hypertension. Coronary microvascular dysfunction has contributed to the development of HFpEF. Endothelial cells (ECs) depend on glycolysis rather than oxidative phosphorylation for generating adenosine triphosphate to maintain vascular homeostasis. Glycolytic metabolism has a critical role in the process of angiogenesis, because ECs rely on the energy produced predominantly from glycolysis for migration and proliferation. Sirtuin 3 (SIRT3) is found predominantly in mitochondria and its expression declines progressively with aging, diabetes, obesity, and hypertension. Emerging evidence indicates that endothelial SIRT3 regulates a metabolic switch between glycolysis and mitochondrial respiration. SIRT3 deficiency in EC resulted in a significant decrease in glycolysis, whereas, it exhibited higher mitochondrial respiration and more prominent production of reactive oxygen species. SIRT3 deficiency also displayed striking increases in acetylation of p53, EC apoptosis, and senescence. Impairment of SIRT3-mediated EC metabolism may lead to a disruption of EC/pericyte/cardiomyocyte communications and coronary microvascular rarefaction, which promotes cardiomyocyte hypoxia, Titin-based cardiomyocyte stiffness, and myocardial fibrosis, thus leading to a diastolic dysfunction and HFpEF. This review summarizes current knowledge of SIRT3 in EC metabolic reprograming, EC/pericyte interactions, coronary microvascular dysfunction, and HFpEF.

Cardiac Damage in Anthracyclines Therapy: Focus on Oxidative Stress and Inflammation

Significance: Despite their serious side effects, anthracyclines (ANTs) are the most prescribed chemotherapeutic drugs because of their strong efficacy in both solid and hematological tumors. A major limitation to ANTs clinical application is the severe cardiotoxicity observed both acutely and chronically. The mechanism underlying cardiac dysfunction under chemotherapy is mainly dependent on the generation of oxidative stress and systemic inflammation, both of which lead to progressive cardiomyopathy and heart failure. Recent Advances: Over the years, the iatrogenic ANTs-induced cardiotoxicity was believed to be simply given by iron metabolism and reactive oxygen species production; however, several experimental data indicate that ANTs may use alternative damaging mechanisms, such as topoisomerase 2β inhibition, inflammation, pyroptosis, immunometabolism, and autophagy. Critical Issues: In this review, we aimed at discussing ANTs-induced cardiac injury from different points of view, updating and focusing on oxidative stress and inflammation, since these pathways are not exclusive or independent from each other but they together importantly contribute to the complexity of ANTs-induced multifactorial cardiotoxicity. Future Directions: A deeper understanding of the mechanistic signaling leading to ANTs side effects could reveal crucial targeting molecules, thus representing strategic knowledge to promote better therapeutic efficacy and lower cardiotoxicity during clinical application.

Loss of Cardiac Ferritin H Facilitates Cardiomyopathy via Slc7a11-Mediated Ferroptosis

RATIONALE

Maintaining iron homeostasis is essential for proper cardiac function. Both iron deficiency and iron overload are associated with cardiomyopathy and heart failure via complex mechanisms. Although ferritin plays a central role in iron metabolism by storing excess cellular iron, the molecular function of ferritin in cardiomyocytes remains unknown.

OBJECTIVE

To characterize the functional role of Fth (ferritin H) in mediating cardiac iron homeostasis and heart disease.

METHODS AND RESULTS

Mice expressing a conditional Fth knockout allele were crossed with 2 distinct Cre recombinase-expressing mouse lines, resulting in offspring that lack Fth expression specifically in myocytes (MCK-Cre) or cardiomyocytes (Myh6-Cre). Mice lacking Fth in cardiomyocytes had decreased cardiac iron levels and increased oxidative stress, resulting in mild cardiac injury upon aging. However, feeding these mice a high-iron diet caused severe cardiac injury and hypertrophic cardiomyopathy, with molecular features typical of ferroptosis, including reduced glutathione (GSH) levels and increased lipid peroxidation. Ferrostatin-1, a specific inhibitor of ferroptosis, rescued this phenotype, supporting the notion that ferroptosis plays a pathophysiological role in the heart. Finally, we found that Fth-deficient cardiomyocytes have reduced expression of the ferroptosis regulator Slc7a11, and overexpressing Slc7a11 selectively in cardiomyocytes increased GSH levels and prevented cardiac ferroptosis.

CONCLUSIONS

Our findings provide compelling evidence that ferritin plays a major role in protecting against cardiac ferroptosis and subsequent heart failure, thereby providing a possible new therapeutic target for patients at risk of developing cardiomyopathy.

Mitochondrial Determinants of Doxorubicin-Induced Cardiomyopathy

Anthracycline-based chemotherapy can result in the development of a cumulative and progressively developing cardiomyopathy. Doxorubicin is one of the most highly prescribed anthracyclines in the United States due to its broad spectrum of therapeutic efficacy. Interference with different mitochondrial processes is chief among the molecular and cellular determinants of doxorubicin cardiotoxicity, contributing to the development of cardiomyopathy. The present review provides the basis for the involvement of mitochondrial toxicity in the different functional hallmarks of anthracycline toxicity. Our objective is to understand the molecular determinants of a progressive deterioration of functional integrity of mitochondria that establishes a historic record of past drug treatments (mitochondrial memory) and renders the cancer patient susceptible to subsequent regimens of drug therapy. We focus on the involvement of doxorubicin-induced mitochondrial oxidative stress, disruption of mitochondrial oxidative phosphorylation, and permeability transition, contributing to altered metabolic and redox circuits in cardiac cells, ultimately culminating in disturbances of autophagy/mitophagy fluxes and increased apoptosis. We also suggest some possible pharmacological and nonpharmacological interventions that can reduce mitochondrial damage. Understanding the key role of mitochondria in doxorubicin-induced cardiomyopathy is essential to reduce the barriers that so dramatically limit the clinical success of this essential anticancer chemotherapy.

Regulation of cell death in the cardiovascular system

The adult heart is a post-mitotic terminally differentiated organ; therefore, beyond development, cardiomyocyte cell death is maladaptive. Heart disease is the leading cause of death in the world and aberrant cardiomyocyte cell death is the underlying problem for most cardiovascular-related diseases and fatalities. In this chapter, we will discuss the different cell death mechanisms that engage during normal cardiac development, aging, and disease states. The most abundant loss of cardiomyocytes occurs during a myocardial infarction, when the blood supply to the heart is obstructed, and the affected myocardium succumbs to cell death. Originally, this form of cell death was considered to be unregulated; however, research from the last half a century clearly demonstrates that this form of cell death is multifaceted and employees various degrees of regulation. We will explore all of the cell death pathways that have been implicated in this disease state and the potential interplay between them. Beyond myocardial infarction, we also explore the role and mechanisms of cardiomyocyte cell death in heart failure, myocarditis, and chemotherapeutic-induced cardiotoxicity. Inhibition of cardiomyocyte cell death has extensive therapeutic potential that will increase the longevity and health of the human heart.

p53 prevents doxorubicin cardiotoxicity independently of its prototypical tumor suppressor activities

Doxorubicin is a widely used chemotherapeutic agent that causes dose-dependent cardiotoxicity in a subset of treated patients, but the genetic determinants of this susceptibility are poorly understood. Here, we report that a noncanonical tumor suppressor activity of p53 prevents cardiac dysfunction in a mouse model induced by doxorubicin administered in divided low doses as in the clinics. While relatively preserved in wild-type (p53 ^+/+ ) state, mice deficient in p53 (p53 ^-/- ) developed left ventricular (LV) systolic dysfunction after doxorubicin treatment. This functional decline in p53 ^-/- mice was associated with decreases in cardiac oxidative metabolism, mitochondrial mass, and mitochondrial genomic DNA (mtDNA) homeostasis. Notably, mice with homozygous knockin of the p53 R172H (p53 ^172H/H ) mutation, which like p53 ^-/- state lacks the prototypical tumor suppressor activities of p53 such as apoptosis but retains its mitochondrial biogenesis capacity, showed preservation of LV function and mitochondria after doxorubicin treatment. In contrast to p53-null state, wild-type and mutant p53 displayed distinct mechanisms of transactivating mitochondrial transcription factor A (TFAM) and p53-inducible ribonucleotide reductase 2 (p53R2), which are involved in mtDNA transcription and maintenance. Importantly, supplementing mice with a precursor of NAD⁺ prevented the mtDNA depletion and cardiac dysfunction. These findings suggest that loss of mtDNA contributes to cardiomyopathy pathogenesis induced by doxorubicin administered on a schedule simulating that in the clinics. Given a similar mtDNA protection role of p53 in doxorubicin-treated human induced pluripotent stem cell (iPSC)-derived cardiomyocytes, the mitochondrial markers associated with cardiomyopathy development observed in blood and skeletal muscle cells may have prognostic utility.

Translationally controlled tumor protein (TCTP) plays a pivotal role in cardiomyocyte survival through a Bnip3-dependent mechanism

Prevention of cardiomyocyte death is an important therapeutic strategy for heart failure. In this study, we focused on translationally controlled tumor protein (TCTP), a highly conserved protein that is expressed ubiquitously in mammalian tissues, including heart. TCTP plays pivotal roles in survival of certain cell types, but its function in cardiomyocytes has not been examined. We aimed to clarify the role of TCTP in cardiomyocyte survival and the underlying mechanism. Here, we demonstrated that downregulation of TCTP with siRNA induced cell death of cardiomyocytes with apoptotic and autophagic features, accompanied with mitochondrial permeability transition pore (mPTP) opening. TCTP loss did not induce cell death of cardiac fibroblasts. Bcl-2/adenovirus E1B 19-kDa interacting protein 3 (Bnip3) was found to mediate the TCTP-loss-induced cardiomyocyte death. In exploring the clinical significance of the TCTP expression in the heart, we found that DOX treatment markedly downregulated the protein expression of TCTP in cultured cardiomyocytes and in mouse heart tissue. Exogenous rescue of TCTP expression attenuated DOX-induced cardiomyocyte death. In mice, cardiomyocyte-specific overexpression of TCTP resulted in decreased susceptibility to DOX-induced cardiac dysfunction, accompanied with attenuated induction of Bnip3. Dihydroartemisinin, a pharmacological TCTP inhibitor, induced development of heart failure and cardiomyocyte death in control mice, but not in mice with cardiomyocyte-specific TCTP overexpression. Our findings revealed TCTP has a pivotal role in cardiomyocyte survival, at least in part through a Bnip3-dependent mechanism. TCTP could be considered as a candidate therapeutic target to prevent DOX-induced heart failure.

Acylated ghrelin prevents doxorubicin-induced cardiac intrinsic cell death and fibrosis in rats by restoring IL-6/JAK2/STAT3 signaling pathway and inhibition of STAT1

This study investigated if JAK/STAT signaling pathway mediates doxorubicin (DOX)-induced cell death and fibrosis in left ventricles (LVs) of rats and examined if acylated ghrelin affords protection by modulating this pathway. Male rats (120 ± 5 g) were divided into 6 groups (10 rats each) as follows: control; control + AG (10 ng/kg, s.c.); DOX (an accumulative dose 15 mg/kg, i.p.); DOX + AG, DOX + AG + AG490, a JAK2 inhibitor (5 mg/kg, i.p.); and DOX + AG + [D-Lys3]-GHRP-6; an AG receptor antagonist (3.75 mg/kg, i.p.). All treatments were carried out for 35 days. In rats' LVs, DOX significantly impaired the systolic and diastolic functions, enhanced levels of ROS and MDA, reduced levels of GSH and Bcl-2, and increased mRNA and protein levels of collagen I/III and TGF-β and cleaved caspase-3. In addition, although DOX did not affect JAK1 or JAK2 activity, it significantly increased protein levels of IL-6, decreased STAT3 and p-STAT3 (Tyr701&Ser727), and increased STAT1 and p-STAT1 (Tyr701&Ser727) levels, with a concomitant decrease in ERK1/2 activity and an increase in P38 activity. However, without affecting IL-6 and JAK1/2, AG reversed all of the observed alterations with a significant increase in the levels and activities of JAK2. Similar effects of AG were also seen in control rats. Interestingly, all the beneficial effects afforded by AG were abolished by AG490 and AG + [D-Lys3]-GHRP-6. In conclusion, DOX-induced cardiac toxicity involves stimulation of IL-6, P38, and STAT1 signaling levels whereas the protective effect afforded by AG involves the activation of ERK1/2 and JAK2/STAT3 and inhibition of STAT1.

Angiogenic Endothelial Cell Signaling in Cardiac Hypertrophy and Heart Failure

Endothelial cells are, by number, one of the most abundant cell types in the heart and active players in cardiac physiology and pathology. Coronary angiogenesis plays a vital role in maintaining cardiac vascularization and perfusion during physiological and pathological hypertrophy. On the other hand, a reduction in cardiac capillary density with subsequent tissue hypoxia, cell death and interstitial fibrosis contributes to the development of contractile dysfunction and heart failure, as suggested by clinical as well as experimental evidence. Although the molecular causes underlying the inadequate (with respect to the increased oxygen and energy demands of the hypertrophied cardiomyocyte) cardiac vascularization developing during pathological hypertrophy are incompletely understood. Research efforts over the past years have discovered interesting mediators and potential candidates involved in this process. In this review article, we will focus on the vascular changes occurring during cardiac hypertrophy and the transition toward heart failure both in human disease and preclinical models. We will summarize recent findings in transgenic mice and experimental models of cardiac hypertrophy on factors expressed and released from cardiomyocytes, pericytes and inflammatory cells involved in the paracrine (dys)regulation of cardiac angiogenesis. Moreover, we will discuss major signaling events of critical angiogenic ligands in endothelial cells and their possible disturbance by hypoxia or oxidative stress. In this regard, we will particularly highlight findings on negative regulators of angiogenesis, including protein tyrosine phosphatase-1B and tumor suppressor p53, and how they link signaling involved in cell growth and metabolic control to cardiac angiogenesis. Besides endothelial cell death, phenotypic conversion and acquisition of myofibroblast-like characteristics may also contribute to the development of cardiac fibrosis, the structural correlate of cardiac dysfunction. Factors secreted by (dysfunctional) endothelial cells and their effects on cardiomyocytes including hypertrophy, contractility and fibrosis, close the vicious circle of reciprocal cell-cell interactions within the heart during pathological hypertrophy remodeling.

β-Caryophyllene, a natural bicyclic sesquiterpene attenuates doxorubicin-induced chronic cardiotoxicity via activation of myocardial cannabinoid type-2 (CB2) receptors in rats

The cannabinoid type 2 receptor (CB₂) has recently emerged as an important therapeutic target for cancer as well as cardiovascular diseases. The CB₂ receptor downregulation has been reported in solid tumors and cardiovascular diseases, therefore the CB₂ receptor activation has been considered as a viable strategy for chemotherapy as well as cardioprotection. Doxorubicin (DOX) is an important drug that continues to be the mainstay of chemotherapy in solid tumors, leukemia, and lymphoma. However, the use of DOX is often limited due to its lethal cardiotoxicity. Considering the role of CB₂ receptors in cardiovascular diseases and cancer, the activation of CB₂ receptors may protect against DOX-induced chronic cardiotoxicity in rats. In the present study, we investigated the cardioprotective effect of a selective CB₂ receptor agonist; β-Caryophyllene (BCP), a natural bicyclic sesquiterpene, against DOX-induced chronic cardiotoxicity in rats. AM630, a CB₂ receptor antagonist was administered as a pharmacological challenge prior to BCP treatment to demonstrate CB₂ receptor mediated cardioprotective mechanism of BCP. DOX (2.5 mg/kg) was injected intraperitoneally once a week for five weeks to induce chronic cardiotoxicity in rats. BCP was also injected into rats six days a week for a total duration of five weeks. DOX induced a significant decline in cardiac function and oxidative stress evidenced by the depletion of antioxidant enzymes, glutathione, and increased lipid peroxidation. DOX also triggered activation of nuclear factor kappa B (NF-κB) and increased the levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) and expression of the inflammatory mediators (iNOS and COX-2) in the heart. Furthermore, DOX also upregulated the expression of pro-apoptotic markers such as Bax, p53, cleaved PARP, active caspase-3 and downregulated anti-apoptotic marker Bcl-2 in the myocardium. BCP treatment exerted significant cardioprotective effect by salvaging the heart tissues, improving cardiac function, mitigating oxidative stress, inflammation, and apoptosis. The histological and ultrastructural studies also appear in line with our findings of biochemical and molecular parameters. The CB₂ receptor-mediated cardioprotective mechanism was further confirmed by the abrogation of the beneficial effects of BCP with prior administration of the CB₂ receptor antagonist; AM630. Our study revealed the novel mechanism of BCP in cardioprotection against DOX-induced chronic cardiotoxicity by the activation of CB₂ receptors.

Tissue-specific regulation of p53 by PKM2 is redox dependent and provides a therapeutic target for anthracycline-induced cardiotoxicity

Chemotherapy-induced cardiotoxicity (CIC) is a common clinical problem that compromises effective anticancer therapies. Many chemotherapeutics (including anthracyclines, such as doxorubicin) induce the proapoptotic transcription factor p53 in the tumor and nonspecifically in the heart, promoting heart failure. Although inhibition of p53 shows benefit in preclinical heart failure models, it would not be an attractive adjuvant therapy for CIC, because it would prevent tumor regression. A p53-targeting therapy that would decrease chemotherapy-induced apoptosis in the myocardium and, at the same time, enhance apoptosis in the tumor would be ideal. Here, we propose that differences in oxygen tension between the myocardium and the tumor could provide a platform for redox-dependent tissue-specific therapies. We show by coimmunoprecipitation and mass spectrometry that the redox-regulated pyruvate kinase muscle 2 (PKM2) directly binds with p53 and that the redox status of cysteine-423 of tetrameric (but not monomeric) PKM2 is critical for the differential regulation of p53 transcriptional activity. Tetrameric PKM2 suppresses p53 transcriptional activity and apoptosis in a high oxidation state but enhances them in a low oxidation one. We show that the oxidation state (along with cysteine-423 oxidation) is higher in the heart compared to the tumor of the same animal. Treatment with TEPP-46 (a compound that stabilizes tetrameric PKM2) suppressed doxorubicin-induced cardiomyocyte apoptosis, preventing cardiac dysfunction, but enhanced cancer cell apoptosis and tumor regression in the same animals in lung cancer models. Thus, our work suggests that redox-dependent differences in common proteins expressed in the myocardium and tumor can be exploited therapeutically for tissue selectivity in CIC.

PTEN inhibitor VO-OHpic attenuates inflammatory M1 macrophages and cardiac remodeling in doxorubicin-induced cardiomyopathy

Doxorubicin (Doxo) is an effective agent commonly used in cancer therapeutics. Unfortunately, Doxo treatment can stimulate cardiomyopathy and subsequent heart failure, limiting the use of this drug. The role of phosphatase and tensin homolog (PTEN) in apoptosis has been documented in Doxo-induced cardiomyopathy (DIC) and heart failure models. However, whether direct inhibition of PTEN attenuates apoptosis, cardiac remodeling, and inflammatory M1 macrophages in the DIC model remains elusive. Therefore, the present study was designed to understand the effects of VO-OHpic (VO), a potent inhibitor of PTEN, in reducing apoptosis and cardiac remodeling. At day 56, echocardiography was performed, which showed that VO treatment significantly ( P < 0.05) improved heart function. Immunohistochemistry, TUNEL, and histological staining were used to determine apoptosis, proinflammatory M1 macrophages, anti-inflammatory M2 macrophages, and cardiac remodeling. Our data show a significant increase in apoptosis, hypertrophy, fibrosis, and proinflammatory M1 macrophages with Doxo treatment, whereas VO treatment significantly reduced apoptosis, adverse cardiac remodeling, and proinflammatory M1 macrophages significantly ( P < 0.05) compared with the Doxo-treated group. Western blot analysis confirmed the reduction of phosphorylated PTEN and increase in phosphorylated AKT protein expression in the Doxo + VO-treated group. Moreover, VO administration increased anti-inflammatory M2 macrophages. Collectively, our data suggest that VO treatment attenuates apoptosis and adverse cardiac remodeling, a process that is mediated through the PTEN/AKT pathway, resulting in improved heart function in DIC. NEW & NOTEWORTHY Doxorubicin-induced cardiomyopathy (DIC) is still a major issue in patients with cancer. These novel findings on the phosphatase and tensin homolog inhibitor VO-OHpic in DIC is the first report, as per the best of our knowledge, that VO-OHpic significantly decreases apoptosis, fibrosis, hypertrophy, adverse cardiac remodeling, and proinflammatory M1 macrophages and increases anti-inflammatory M2 macrophages along with significantly improved cardiac function. VO-OHpic could be a future therapeutic agent for patients with DIC.

The involvement of Nox4 in fine particulate matter exposure-induced cardiac injury in mice

Epidemiological studies have confirmed that ambient fine particulate matter (PM_2.5) exposure is associated with cardiovascular disease (CVD). However, the underlying mechanisms in PM_2.5 exposure-induced heart injury are largely unknown. It has been acknowledged that NADPH oxidase (Nox) 4 plays a critical role in CVD development. To investigate the acute effects of PM_2.5 on the mouse heart and the role of Nox4 in PM_2.5 exposure-induced cardiac injury, C57BL/6J mice were instilled with saline or 1.5, 3.0, 6.0 mg/kg BW PM_2.5 suspension for two weeks (five days per week). The levels of malondialdehyde (MDA), super oxide dismutase (SOD), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β in heart supernatants were determined using related kits. The expression of Nox4, p67^phox, p47^phox and p22^phox in heart tissue was evaluated by immunofluorescence staining or Western blotting, respectively. Protein levels of p53, Bax, Bcl-2 and Caspase-3 in the heart were examined using immunohistochemical staining and Western blotting. TUNEL assay was used to measure myocardial apoptosis. PM_2.5 exposure leads to obvious cardiac injury. PM_2.5 exposure increases MDA level and iNOS activity, and decreases activity of SOD in heart supernatants of mice. High levels of TNF-α and IL-1β in heart supernatants of mice with PM_2.5 instillation were determined. Nox4 and Nox-associated subunits such as p67^phox, p47^phox and p22^phox expression levels were increased in heart tissue of mice after PM_2.5 exposure. Additionally, PM_2.5 exposure causes myocardial apoptosis in the mouse heart. This study suggested that Nox4 is involved in PM_2.5 exposure-induced cardiac injury in mice.

Rat Model of Cardiotoxic Drug-Induced Cardiomyopathy

Cardiotoxicity from cancer drugs remains a clinical problem. To find reliable markers of cardiotoxicity, animal models were proposed and potential new diagnostic markers have been actively investigated using these models. Here we describe our protocols, using male Sprague-Dawley rats, for inducing cardiomyopathy by single injection of high-dose doxorubicin (5-10 mg/kg) or multiple injections (2-4 times) of low-dose doxorubicin (2.5 mg/kg) with combined single injection of trastuzumab (10 mg/kg). The cardiotoxicity is evaluated by imaging modalities (echocardiography and nuclear imaging), serum troponin levels, and histopathological analyses.