Doxorubicin-induced acute cardiotoxicity is associated with increased oxidative stress, autophagy, and inflammation in a murine model

Drug-induced cardiotoxicity is a life-threatening side effect of doxorubicin (DOX) treatment that impacts patient prognosis and survival. In the majority of cases, the acute clinical form often remains asymptomatic, with few patients presenting rather nonspecific electrocardiographic abnormalities. While chronic toxicity has been more widely studied, the alterations appearing in acute cardiotoxicity are much less investigated. Thus, our in vivo study aimed to evaluate the process of DOX-induced acute myocardial toxicity by investigating oxidative stress and autophagy markers as mechanisms of myocardial toxicity in correlation with echocardiography and electrocardiography findings. Our results show that both autophagy and oxidative homeostasis were disrupted as soon as 7 days after DOX treatment, alterations that occurred even before the significant increase of NT-proBNP, a clinical marker for cardiac suffering. Moreover, we found a large number of alterations in the electrocardiography and echocardiography of treated rats. These findings suggest that DOX-induced myocardial toxicity started early after treatment initiation, possibly marking the initial phase of the unfolding process of cardiac damage. Further studies are required to completely decipher the mechanisms of DOX-induced cardiotoxicity.

Regulation of Transplanted Cell Homing by FGF1 and PDGFB after Doxorubicin Myocardial Injury

There is no effective treatment for the total recovery of myocardial injury caused by an anticancer drug, doxorubicin (Dox). In this study, using a Dox-induced cardiac injury model, we compared the cardioprotective effects of ventricular cells harvested from 11.5-day old embryonic mice (E11.5) with those from E14.5 embryos. Our results indicate that tail-vein-infused E11.5 ventricular cells are more efficient at homing into the injured adult myocardium, and are more angiogenic, than E14.5 ventricular cells. In addition, E11.5 cells were shown to mitigate the cardiomyopathic effects of Dox. In vitro, E11.5 ventricular cells were more migratory than E14.5 cells, and RT-qPCR analysis revealed that they express significantly higher levels of cytokine receptors Fgfr1, Fgfr2, Pdgfra, Pdgfrb and Kit. Remarkably, mRNA levels for Fgf1, Fgf2, Pdgfa and Pdgfb were also found to be elevated in the Dox-injured adult heart, as were the FGF1 and PDGFB protein levels. Addition of exogenous FGF1 or PDGFB was able to enhance E11.5 ventricular cell migration in vitro, and, whereas their neutralizing antibodies decreased cell migration. These results indicate that therapies raising the levels of FGF1 and PDGFB receptors in donor cells and or corresponding ligands in an injured heart could improve the efficacy of cell-based interventions for myocardial repair.

Vildagliptin improves vascular smooth muscle relaxation and decreases cellular senescence in the aorta of doxorubicin-treated rats

INTRODUCTION

Doxorubicin (DOX) is a chemotherapeutic agent used in cancer treatment. Its use is limited by later toxicity to the cardiovascular system (CVS). Cellular senescence has been proposed as one mechanism of DOX toxicity. It has also been suggested that senescence reduction can improve the condition in many pathologies. We hypothesised that vildagliptin treatment can reduce senescence and thus improve the relaxation of vascular smooth muscle (VSM) in the aorta of a rat DOX model.

METHODS

The rats received DOX and were treated with vildagliptin for 6 weeks. Thereafter, the rats were sacrificed, and the aorta prepared for measurements of VSM relaxation and RNA isolation to detect the level of senescence markers. To further prove the antisenescence effect of the main vildagliptin effector glucagon-like peptide 1(GLP-1), VSM cells (VSMCs) were incubated with DOX and treated with GLP-1. Subsequently, senescence was detected by senescence-associated beta-galactosidase (SA-β-gal) and by the presence of senescence markers.

RESULTS

DOX in rats caused diminished relaxation of VSM to sodium nitrate and caused an increase in the senescence mRNA markers p16Ink4a and p27Kip1 and the senescence-associated secretory phenotype (SASP) IL-6 and IL-8. Vildagliptin treatment led to improved relaxation and a reduction in senescence and SASP markers. Furthermore, in VSMCs DOX increased SA-β-gal activity, p16Ink4a, p27Kip1, IL-6 and IL-8, and GLP1 treatment led to a decrease of both senescence and SASP markers.

CONCLUSION

In summary we conclude that vildagliptin can reduce senescence and improve relaxation of vascular smooth muscle in the aorta of DOX-treated rats, and GLP-1 can reduce senescence of DOX-treated VSMCs. These data suggest that incretin-based drugs are promising candidates for patients suffering from late doxorubicin cardiovascular toxicity.

What is considered cardiotoxicity of anthracyclines in animal studies

Anthracyclines are commonly used anticancer drugs with well-known and extensively studied cardiotoxic effects in humans. In the clinical setting guidelines for assessing cardiotoxicity are well-established with important therapeutic implications. Cardiotoxicity in terms of impairment of cardiac function is largely diagnosed by echocardiography and based on objective metrics of cardiac function. Until this day, cardiotoxicity is not an endpoint in the current general toxicology and safety pharmacology preclinical studies, although other classes of drugs apart from anthracyclines, along with everyday chemicals have been shown to manifest cardiotoxic properties. Also, in the relevant literature there are not well-established objective criteria or reference values in order to uniformly characterize cardiotoxic adverse effects in animal models. This in depth review focuses on the evaluation of two important echocardiographic indices, namely ejection fraction and fractional shortening, in the literature concerning anthracycline administration to rats as the reference laboratory animal model. The analysis of the gathered data gives promising results and solid prospects for both, defining anthracycline cardiotoxicity objective values and delineating the guidelines for assessing cardiotoxicity as a separate hazard class in animal preclinical studies for regulatory purposes.

TRPV2 channel-based therapies in the cardiovascular field. Molecular underpinnings of clinically relevant therapies

The transient receptor potential (TRP) ion channel family is composed of twenty-seven channel proteins that are ubiquitously expressed in the human body. The TRPV (vanilloid) subfamily has been a recent target of investigation within the cardiovascular field. TRPV1, which is sensitive to heat as well as vanilloids, is the best characterized TRPV channel and is the namesake for the subfamily that includes six members. Research into the function of TRPV2 has suggested that it plays an important role in cardiovascular function. Over the last twenty years a greater understanding of the differences among the TRPV channels has allowed for more precise experimentation and has opened various translational opportunities. TRPV2 has been found to be a both a mechanosensor and a mediator of calcium handling and has been found to play important roles in healthy and diseased cardiomyocytes. These roles have been translated into clinical studies in patients with muscular dystrophy (both agonism and antagonism) as well as in patients with cardiomyopathy and heart failure with reduced ejection fraction. Its role as a structural protein has also been elucidated, though the clinical significance of this finding has yet to be established. Despite the clinical progress that has been made there is still a need for large, prospective randomized studies with TRPV2 channel agonists and antagonists in order to bring these basic and translational science findings to the bedside.

TRPV2 channel as a possible drug target for the treatment of heart failure

Heart transplantation is currently the only viable option available for the treatment of severe heart failure conditions such as dilated cardiomyopathy. Hence, novel drugs for treating such conditions need to be developed urgently. Recent studies suggest that Ca²⁺ overload is involved in the onset and progression of dilated cardiomyopathy, and thus heart failure. The expression and activation of the Ca²⁺ permeable channel, transient receptor potential vanilloid 2 (TRPV2) channel have been found to play an essential role in sustained intracellular Ca²⁺ concentration increase, leading to heart failure. However, since there have been no TRPV2-specific inhibitors available until recently, the effect of TRPV2 inhibition on the pathology has not been clearly elucidated. Recent reports show that inhibiting TRPV2 activity effectively improves cardiac function, suppressing myocardial fibrosis and ameliorating the prognosis in animal models of cardiomyopathy with heart failure. In addition to that, inflammation is reported to be involved in the development of heart failure. Here, we review the recent findings on TRPV2 in cardiomyocytes and immune cells involved in the development of heart failure and discuss the current progress of drug development for the treatment of heart failure via targeting TRPV2.

Appraising the "entourage effect": Antitumor action of a pure cannabinoid versus a botanical drug preparation in preclinical models of breast cancer

Breast cancer is the second leading cause of death among women. Although early diagnosis and development of new treatments have improved their prognosis, many patients present innate or acquired resistance to current therapies. New therapeutic approaches are therefore warranted for the management of this disease. Extensive preclinical research has demonstrated that cannabinoids, the active ingredients of Cannabis sativa, trigger antitumor responses in different models of cancer. Most of these studies have been conducted with pure compounds, mainly Δ⁹-tetrahydrocannabinol (THC). The cannabis plant, however, produces hundreds of other compounds with their own therapeutic potential and the capability to induce synergic responses when combined, the so-called "entourage effect". Here, we compared the antitumor efficacy of pure THC with that of a botanical drug preparation (BDP). The BDP was more potent than pure THC in producing antitumor responses in cell culture and animal models of ER+/PR+, HER2+ and triple-negative breast cancer. This increased potency was not due to the presence of the 5 most abundant terpenes in the preparation. While pure THC acted by activating cannabinoid CB₂ receptors and generating reactive oxygen species, the BDP modulated different targets and mechanisms of action. The combination of cannabinoids with estrogen receptor- or HER2-targeted therapies (tamoxifen and lapatinib, respectively) or with cisplatin, produced additive antiproliferative responses in cell cultures. Combinations of these treatments in vivo showed no interactions, either positive or negative. Together, our results suggest that standardized cannabis drug preparations, rather than pure cannabinoids, could be considered as part of the therapeutic armamentarium to manage breast cancer.

Anandamide and endocannabinoid system: an attractive therapeutic approach for cardiovascular disease

Cardiovascular disease is currently not adequately managed and has become one of the main causes of morbidity and mortality worldwide. Current therapies are inadequate in terms of preventing its progression. There are several limitations, such as poor oral bioavailability, side effects, low adherence to treatment, and high dosage frequency of formulations due to the short half-life of the active ingredients used, among others. This review aims to highlight the most relevant aspects of the relationship between the cardiovascular system and the endocannabinoid system, with special attention to the possible translational effect of the use of anandamide in cardiovascular health. The deep and detailed knowledge of this interaction, not always beneficial, and that for years has gone unnoticed, is essential for the development of new therapies. We discuss the most recent and representative results obtained in the field of basic research, referring to the aforementioned subject, emphasizing fundamentally the main role of nitric oxide, renal physiology and its deregulation in pathological processes.

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.

Creatine Supplementation and Doxorubicin-Induced Skeletal Muscle Dysfunction: An Ex Vivo Investigation

Supplementing the diet with creatine (Cr) to manage chemotherapy-induced skeletal muscle weakness and fatigue has potential, but little has been done exploring it as an intervention. This study examined the effects of Cr on skeletal muscle dysfunction induced by the chemotherapy drug doxorubicin (Dox). Soleus and extensor digitorum longus (EDL) from male Sprague-Dawley rats maintained in an organ bath were incubated in Krebs-Henseleit (KH) buffer with or without creatine monohydrate (25 mM) for 30 min. Skeletal muscle was then incubated in KH buffer with or without Dox (24 μM) for an additional 30 min. Baths were then refreshed with KH buffer, and a 100-s fatigue protocol was administered. At baseline (0 s time point), no significant differences in force production were observed in the slow, type I soleus, but the Dox-treated soleus fatigued quicker than the non-Dox-treated soleus; however, pretreatment with Cr extended the time to fatigue in the Dox-treated soleus. In the fast, type II EDL, Dox treatment decreased force production at baseline and increased fatigue, and Cr treatment prior to Dox attenuated this dysfunction. Creatine pretreatment mitigated Dox-induced skeletal muscle dysfunction ex vivo suggesting that Cr may play a role in managing Dox-induced skeletal muscle side effects.

Endocannabinoids and the Cardiovascular System in Health and Disease

The endocannabinoid system is widely distributed throughout the cardiovascular system. Endocannabinoids play a minimal role in the regulation of cardiovascular function in normal conditions, but are altered in most cardiovascular disorders. In shock, endocannabinoids released within blood mediate the associated hypotension through CB(1) activation. In hypertension, there is evidence for changes in the expression of CB(1), and CB(1) antagonism reduces blood pressure in obese hypertensive and diabetic patients. The endocannabinoid system is also upregulated in cardiac pathologies. This is likely to be cardioprotective, via CB(2) and CB(1) (lesser extent). In the vasculature, endocannabinoids cause vasorelaxation through activation of multiple target sites, inhibition of calcium channels, activation of potassium channels, NO production and the release of vasoactive substances. Changes in the expression or function of any of these pathways alter the vascular effect of endocannabinoids. Endocannabinoids have positive (CB(2)) and negative effects (CB(1)) on the progression of atherosclerosis. However, any negative effects of CB(1) may not be consequential, as chronic CB(1) antagonism in large scale human trials was not associated with significant reductions in atheroma. In neurovascular disorders such as stroke, endocannabinoids are upregulated and protective, involving activation of CB(1), CB(2), TRPV1 and PPARα. Although most of this evidence is from preclinical studies, it seems likely that cannabinoid-based therapies could be beneficial in a range of cardiovascular disorders.

Exercise mitigates cardiac doxorubicin accumulation and preserves function in the rat

PURPOSE

Doxorubicin (DOX) is an effective antineoplastic agent with well-characterized cardiotoxic effects. Although exercise has been shown to protect against DOX cardiotoxicity, a clear and concise mechanism to explain its cardioprotective effects is lacking. The purpose of this study was to determine if exercise training reduces cardiac DOX accumulation, thereby providing a possible mechanism to explain the cardioprotective effects of exercise against DOX toxicity.

METHODS

Sprague-Dawley rats were randomly assigned to 1 of 3 primary experimental groups: sedentary (n = 77), wheel running (n = 65), or treadmill (n = 65). Animals in wheel running and treadmill groups completed 10 weeks of exercise before DOX treatment. DOX was administered 24 hours after the last training session as a bolus intraperitoneal injection at 10 mg/kg. Subgroups of rats from each primary group were killed at 1, 3, 5, 7, and 9 days after DOX exposure to assess cardiac function and DOX accumulation.

RESULTS

Ten weeks of exercise preconditioning reduced myocardial DOX accumulation, and this reduction in accumulation was associated with preserved cardiac function.

CONCLUSIONS

These data suggest that the cardioprotective effects of exercise against DOX-induced injury may be due, in part, to a reduction in myocardial DOX accumulation.

Tissue retention of doxorubicin and its effects on cardiac, smooth, and skeletal muscle function

Cancer-related fatigue is a pervasive syndrome experienced by a majority of cancer patients undergoing treatment, and muscular dysfunction may be a key component in the development and progression of this syndrome. Doxorubicin (DOX) is a commonly used antineoplastic agent used in the treatment of many cancers. The purpose of this study was to determine the effect of DOX exposure on the function of cardiac, skeletal, and smooth muscle tissues and examine the role accumulation of DOX may play in this process. In these studies, rats were treated with DOX and measurements of cardiac, skeletal, and smooth muscle function were assessed 1, 3, and 5 days after exposure. All muscular tissues showed significant and severe dysfunction, yet there was heterogeneity both in the time course of dysfunction and in the accumulation of DOX. Cardiac and skeletal muscle exhibited a time-dependent progressive decline in function during the 5 days following DOX treatment. In contrast, vascular function showed a decline in function that could be characterized as rapid onset and was sustained for the duration of the 5-day observation period. DOX accumulation was greatest in cardiac tissue, yet all muscular tissues showed a similar degree of dysfunction. Our data suggest that in muscular tissues both DOX-dependent and DOX-independent mechanisms may be involved with the muscular dysfunction observed following DOX treatment. Furthermore, this study highlights the fact that dysfunction of skeletal and smooth muscle may be an underappreciated aspect of DOX toxicity and may be a key component of cancer-related fatigue in these patients.

Exercise training mitigates anthracycline-induced chronic cardiotoxicity in a juvenile rat model

BACKGROUND

Childhood cancer survivors are at greater risk of cardiovascular complications once they reach adulthood. Anthracyclines may be a major contributor to these delayed-onset complications, yet their use continues because of favorable clinical outcomes. Exercise has been shown to protect against anthracycline cardiotoxicity, yet it is unclear whether exercise can protect against delayed-onset cardiotoxicity when treatment is initiated in childhood. The aim of the present study was to determine if exercise training provides cardioprotection in a juvenile rat model of delayed-onset anthracycline cardiotoxicity.

PROCEDURE

At 25 days of age, male Sprague-Dawley rat pups were subjected to a treatment regimen with the anthracycline doxorubicin (DOX). Pups received DOX at 2 mg/kg on 7 consecutive days (cumulative dose 14 mg/kg) or saline as a control. At the time DOX treatment began, pups remained sedentary or were allowed to voluntarily exercise. Ten weeks after the initiation of exercise, cardiac function was assessed both in vivo and ex vivo.

RESULTS

DOX treatment stunted normal growth and significantly impaired cardiac function. While voluntary exercise did not offset changes in the growth curve, it did provide significant cardioprotection against DOX-induced cardiotoxicity.

CONCLUSIONS

Exercise training, initiated at the time treatment begins, can protect against delayed-onset anthracycline-induced cardiotoxicity in adult rats that were treated with anthracyclines as juveniles.

Mice lacking functional TRPV1 are protected from pressure overload cardiac hypertrophy

TRPV1 (transient receptor potential cation channel, subfamily V, member 1) is best studied in peripheral sensory neurons as a pain receptor; however TRPV1 is expressed in numerous tissues and cell types including those of the cardiovascular system. TRPV1 expression is upregulated in the hypertrophic heart, and the channel is positioned to receive stimulatory signals in the hypertrophic heart. We hypothesized that TRPV1 has a role in regulating cardiac hypertrophy. Using transverse aortic constriction to model pressure overload cardiac hypertrophy we show that mice lacking functional TRPV1, compared to wild type, have improved heart function, and reduced hypertrophic, fibrotic and apoptotic markers. This suggests that TRPV1 plays a role in the progression of cardiac hypertrophy, and presents a possible therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Exercise preconditioning provides long-term protection against early chronic doxorubicin cardiotoxicity

Acute doxorubicin (DOX) cardiotoxicity can be attenuated by exercise preconditioning, but little is known of whether this cardioprotection continues beyond 10 days post-DOX administration. The purpose of this study was to determine the effects of exercise preconditioning on early chronic DOX-induced cardiotoxicity. Male rats were randomly assigned to sedentary, treadmill, or wheel running groups. Treadmill and wheel running animals participated in a progressive treadmill training protocol or voluntary wheel running, respectively, for 10 weeks. Following the intervention, animals were further randomized to receive either DOX (sedentary + DOX, treadmill + DOX, wheel running + DOX) or saline (sedentary + saline, treadmill + saline, wheel running + saline). All animals then remained sedentary for 4 weeks. A 22% reduction in fractional shortening was observed in left ventricles from previously sedentary animals receiving DOX when compared with sedentary + saline. This degree of decline was not observed in treadmill + DOX and wheel running + DOX. Sedentary + DOX possessed significantly depressed mitral and aortic valve blood flow velocities when compared with sedentary + saline, but these decrements were not observed in treadmill + DOX and wheel running + DOX. Ex vivo analysis revealed that left ventricular developed pressure and maximal rate of pressure development were significantly lower in sedentary + DOX when compared to sedentary + saline. Treadmill and wheel running prior to DOX treatment protected against these decrements. Exercise cardioprotection was associated with preserved myosin heavy chain but not sarcoendoplasmic reticulum Ca(2+) ATPase 2a expression. In conclusion, 10 weeks of prior exercise protected against early chronic DOX cardiotoxicity suggesting that training status may be a determining factor in the degree of late-onset cardiotoxicity experienced by cancer patients undergoing treatment with DOX.

The vanilloid receptor TRPV1: role in cardiovascular and gastrointestinal protection

It has been shown that the transient receptor potential channel vanilloid type 1 (TRPV1) is able to sense a vast range of stimuli and exerts multiple functions under physiological or pathophysiological conditions. TRPV1 not only plays a fundamental role in pain signaling but also involves in many other physiological or pathophysiological functions including the beneficial effects on cardiovascular and gastrointestinal function. It has been found that TRPV1 could be activated by endogenous ligands such as anandamide, N-arachidonoyl dopamine and N-oleoyldopamine or by exogenous agonists such as capsaicin and rutaecarpine. Since capsaicin-sensitive sensory nerves (rich in TRPV1) are densely distributed in the cardiovascular and gastrointestinal system, activation of TRPV1 either by endogenous ligands or by exogenous agonists has been repeatedly reported to exert hypotensive effects or protective effects against cardiac or gastrointestinal injury through stimulating the synthesis and release of multiple neurotransmitters such as calcitonin gene-related peptide and substance P. Therefore, TRPV1 is not only a prime target for the pharmacological control of pain but also a useful target for drug development to treat various diseases including cardiovascular and gastrointestinal diseases. However, considering the contribution of TRPV1 to the development of inflammation in the gastrointestinal tract, the potential side effects of TRPV1 agonist cannot be neglected while in seeking and developing the novel TRPV1 agonists.