Histopathological studies of microtubule disassembling agent-induced myocardial lesions in rats

Anti-tumor and cardiotoxic effects of microtubule polymerization inhibitors: The mechanisms and management strategies

Microtubule polymerization inhibitors (MPIs) have long been used as anticancer agents because they inhibit mitosis. Microtubules are thought to play an important role in the migration of tumor cells and the formation of tumor blood vessels, and new MPIs are being developed. Many clinical trials of novel MPIs have been conducted in humans, while some clinical studies in dogs have also been reported. More attempts to apply MPIs not only in humans but also in the veterinary field are expected to be made in the future. Meanwhile, MPIs have a risk of cardiotoxicity. In this paper, we review findings on the pharmacological effects and cardiotoxicity of MPIs, as well as the mechanisms of their cardiotoxicity. Cardiotoxicity of MPIs involves not only the direct effects of MPIs on cardiomyocytes but also their effects on vascular function. For example, hypertension induced by impaired vascular function also contributes to the exacerbation of myocardial damage, and blood pressure control may be useful in reducing cardiotoxicity. By combined administration of MPIs and other anticancer agents, MPI efficacy may be enhanced, thereby potentially allowing to keep MPI dosage low. Measurement of myocardial injury markers in blood and echocardiography may be useful for monitoring cardiotoxicity. In particular, two-dimensional speckle tracking may have high sensitivity for the early detection of MPI-induced cardiac dysfunction. The exploration of the potential of new MPIs while understanding their toxicity and how to deal with them will lead to the further development of cancer chemotherapy.

Pretreatment with tadalafil attenuates cardiotoxicity induced by combretastatin A4 disodium phosphate in rats

Combretastatin A4 disodium phosphate (CA4DP) is a prodrug of combretastatin A4 (CA4), a microtubule-disassembling agent that exhibits antitumor effects by inhibiting tumor cell proliferation and inducing morphological changes and apoptosis in vascular endothelial cells in tumors. However, cardiotoxicity induced by ischemia and hypertension is a severe adverse event. In this study, we focused on the fact that phosphodiesterase (PDE) 5 inhibitors dilate the heart and peripheral blood vessels and aimed to investigate whether co-administration of tadalafil, a PDE5 inhibitor, can attenuate cardiotoxicity without altering the antitumor effect of CA4DP. To investigate cardiotoxicity, CA4DP and/or tadalafil were administered to rats, and blood pressure, echocardiography, histopathology, and cGMP concentration in the myocardium were examined. Administration of CA4DP increased systolic blood pressure, decreased cardiac function, lowered cGMP levels in the myocardium, and led to necrosis of myocardial cells. Co-administration of tadalafil attenuated these CA4DP-induced changes. To investigate the antitumor effect, canine mammary carcinoma cell lines (CHMp-13a) and human umbilical vein endothelial cells were cultured with CA4 and/or tadalafil, and cell proliferation and endothelial vascular tube disruption were examined. CHMp-13a cells were transplanted into nude mice and treated with CA4DP and/or tadalafil. CA4-induced inhibition of cell proliferation and disruption of the endothelial vascular tube were not affected by co-treatment with tadalafil, and the antitumor effects of CA4DP in xenograft mice were not reduced by co-administration of tadalafil. These results revealed that myocardial damage induced by CA4DP was attenuated by co-administration of tadalafil while maintaining antitumor efficacy.

Cardiotoxicity in children with cancer treated with anthracyclines: A position statement on dexrazoxane

Cardiovascular disease is the leading cause of non-malignant morbidity and mortality in childhood cancer survivors (CCSs). Anthracyclines are included in many treatment regimens for paediatric cancer, but unfortunately, these compounds are cardiotoxic. One in 10 CCSs who has received an anthracycline will develop a symptomatic cardiac event over time. Given the crucial need to mitigate anthracycline-related cardiotoxicity (ARC), the authors critically examined published data to identify effective cardioprotective strategies. Based on their expert analysis of contemporary literature data, it was concluded that consideration should be given for routine use of dexrazoxane in children with cancer who are at risk of ARC.

Co-administration of JQ1, a bromodomain-containing protein 4 inhibitor, enhances the antitumor effect of combretastatin A4, a microtubule inhibitor, while attenuating its cardiotoxicity

Combretastatin A4 (CA4) inhibits microtubule polymerization, and clinical trials of the prodrug, CA4 disodium phosphate (CA4DP), as an anti-cancer agent have been conducted. However, CA4DP has not been marketed to date because the margin between the effective dose and the cardiotoxic dose is insufficient. Meanwhile, bromodomain-containing protein 4 (BRD4) has been reported to be required for recovery from mitotic arrests induced by anti-microtubule drugs. BRD4 has also been reported to be involved in the progression of heart failure. Therefore, we hypothesized that the combined use of CA4DP with BRD4 inhibitors can enhance the antitumor effect and attenuate CA4DP-induced cardiotoxicity. In this study, the antitumor effect and cardiotoxicity caused by the co-administration of CA4DP with JQ1, a BRD4 inhibitor, were evaluated. CA4 or JQ1 alone reduced the viability of cultured canine mammary tumor cells (CHMp-13a). Viability was further reduced by co-administration, through the suppression of c-Myc. BRD4 positivity in CHMp-13a cytoplasm showed a significant increase when treated with CA4 alone, while the increase was not significant following co-administration. In CHMp-13a xenograft-transplanted mice, co-administration of CA4DP and JQ1 suppressed tumor growth significantly. In CA4DP-induced cardiac injury model rats, echocardiography showed a CA4DP-induced decrease in cardiac function and histopathology showed cardiomyocyte necrosis. Meanwhile, these cardiac changes tended to be milder following the co-administration of CA4DP and JQ1. These results suggest that CA4DP-JQ1 co-administration enhances the antitumor effect of CA4DP while attenuating its cardiotoxicity and therefore potentially open the doors to the development of a novel cancer chemotherapy with reduced cardiotoxicity risks.

Cardiovascular Toxicity Induced by Chronic Vincristine Treatment

Vincristine is an effective anticancer agent for treating leukemias, lymphomas, and other solid tumors. Vincristine's better-known severe side effects include bone marrow depression, hyponatremia, peripheral neuropathy, and gastrointestinal distress. In recent years, cardiovascular damage also has been described during vincristine treatments. However, the vascular toxicity induced by vincristine is little studied. The aim of the present is to evaluate whether these alterations remain after the suspension of chemotherapy treatment (sequelae) and the possible mechanisms involved in this vascular damage. Adult male Wistar rats were used. The animals were divided into four treatment groups: two groups of saline (0.9% NaCl; saline, sequelae saline) and two groups of vincristine (100 μg/kg; vincristine, sequelae vincristine). Saline or vincristine was administered intraperitoneally in two cycles of 5 days each, leaving a rest period between cycles of 2 days. The final cumulative vincristine dose administered was 1 mg/kg. Sequelae groups correspond to 2 weeks after stopping treatment with the antitumor agent. At the end of the different experimental protocols, cardiac and vascular functions were analyzed. Alterations in the expression of different proteins in the cardiovascular tissues were also investigated. Chronic treatment with vincristine did not produce significant changes in basal cardiac function but provoked significant endothelial dysfunction in the aorta and a significant decrease in the mesenteric contractile function. These cardiovascular functional alterations disappeared 2 weeks after the suspension of chemotherapy treatment. Vincristine treatment caused a significant increase in the expression of tumor necrosis factor-alpha (TNFα), endothelial and inducible nitric oxide synthases (eNOS and iNOS), and connexin 43 in cardiac tissue. In the aorta, the chronic treatment with vincristine caused a slight non-significant increase in TNFα expression, a significant increase in eNOS and iNOS, and a significant decrease in connexin 43. After 2 weeks of vincristine treatment (sequelae group), the expression of TNFα increased and eNOS and iNOS expressions disappeared, but a significant decrease in the expression of connexin 43 was still observed in the aorta. In mesenteric arteries, similar data to those found in the aorta were observed. In conclusion, chronic treatment with vincristine causes functional alterations in the vascular function of both conductance and resistance vessels and changes in the expressions of TNFα, eNOS, iNOS, and connexin 43 in cardiovascular tissues, implicating direct toxicity during its treatment. These functional alterations are transitory and disappear after the suspension of its treatment.

RIP1/RIP3/MLKL-mediated necroptosis contributes to vinblastine-induced myocardial damage

Vinblastine (VBL) has been considered as a first-line anti-tumor drug for many years. However, vinblastine-caused myocardial damage has been continually reported. The underlying molecular mechanism of the myocardial damage remains unknown. Here, we show that vinblastine induces myocardial damage and necroptosis is involved in the vinblastine-induced myocardial damage both in vitro and in vivo. The results of WST-8 and flow cytometry analysis show that vinblastine causes damage to H9c2 cells, and the results of animal experiments show that vinblastine causes myocardial cell damage. The necrosome components, receptor-interacting protein 1 (RIP1) receptor-interacting protein 3 (RIP3), are significantly increased in vinblastine-treated H9c2 cells, primary neonatal rat ventricular myocytes and rat heart tissues. And the downstream substrate of RIP3, mixed lineage kinase domain like protein (MLKL) was also increased. Pre-treatment with necroptosis inhibitors partially inhibits the necrosome components and MLKL levels and alleviates vinblastine-induced myocardial injury both in vitro and in vivo. This study indicates that necroptosis participated in vinblastine-evoked myocardial cell death partially, which would be a potential target for relieving the chemotherapy-related myocardial damage.

Spontaneously occurring cardiovascular lesions in commonly used laboratory animals

The search for new chemical entities which are clinically effective and do not adversely affect the cardiovascular system is an ongoing objective. In vivo studies designed to detect potential drug-induced cardiovascular toxicity typically utilize both rodent and non-rodent species. An important component of such studies includes the microscopic evaluation of tissues for histopathologic changes. A factor which could potentially complicate this type of evaluation relates to the potential for laboratory animals to develop natural or spontaneous pathological cardiovascular lesions. Some types of these naturally occurring alterations are similar to those induced by chemical compounds and thus could confound accurate interpretation. Accurate morphologic analysis becomes contingent upon the ability to distinguish spontaneous cardiovascular changes from actual drug-induced lesions. A summary of some of the more frequently reported spontaneous cardiovascular alterations in commonly-used laboratory animals is presented below. Special emphasis is given to the spectrum of spontaneous background myocardial pathology that might be encountered during preclinical studies conducted to identify potential cardiotoxic actions of anticancer agents.

May a sigma-1 antagonist improve neuropathic signs induced by cisplatin and vincristine in rats?

BACKGROUND

The antineoplastic drugs cisplatin and vincristine induce peripheral neuropathies. The sigma-1 receptor (σ1R) is expressed in areas of pain control, and its blockade with the novel selective antagonist MR-309 has shown efficacy in nociceptive and neuropathic pain models. Our goal was to test whether this compound reduces neuropathic signs provoked by these antitumoural drugs.

METHODS

Rats were treated with cisplatin or vincristine to induce neuropathies. The effects of acute or repeated administration of MR-309 were tested on mechanical and thermal sensitivity, electrophysiological activity of Aδ-primary afferents in the rat skin-saphenous nerve preparation, and gastrointestinal or cardiovascular functions.

RESULTS

Rats treated with antitumourals developed tactile allodynia, while those treated with vincristine also developed mechanical hyperalgesia. These in vivo modifications correlated with electrophysiological hyperactivity (increased spontaneous activity and hyperresponsiveness to innocuous and noxious mechanical stimulation). Animals treated with cisplatin showed gastrointestinal impairment and those receiving vincristine showed cardiovascular toxicity. A single dose of MR-309 strongly reduced both nociceptive behaviour and electrophysiological changes. Moreover, its concomitant administration with the antitumourals blocked the development of neuropathic symptoms, thus restoring mechanical sensitivity, improving the impairment of feeding behaviour and gastrointestinal transit in the cisplatin-treated group along with ameliorating the altered vascular reactivity recorded in rats treated with vincristine.

CONCLUSION

σ1R antagonist, MR-309, reduces sensorial and electrophysiological neuropathic signs in rats treated with cisplatin or vincristine and, in addition, reduces gastrointestinal and cardiovascular side effects.

SIGNIFICANCE

σ1R antagonism could be an interesting and new option to palliate antitumoural neuropathies.

Histopathological and functional changes in a single-dose model of combretastatin A4 disodium phosphate-induced myocardial damage in rats

Cardiotoxicity is a concern in the development of microtubule-disassembling agents (MDAs) as vascular-disrupting agents of tumors. This study investigated cardiotoxicity in rats induced by a single-dose of combretastatin A4 disodium phosphate (CA4DP), an MDA and discussed the use of this rat model in nonclinical studies of MDAs. First, CA4DP (120 mg/kg) was administered to rats intravenously, and cardiac histopathology and blood biomarkers were examined after 0.5, 24, and 72 h. Next, CA4DP (120 mg/kg) was administered to rats intravenously, and the electrocardiography and echocardiography results were analyzed. The results showed that at 0.5 h after dosing, plasma creatine kinase (CK), CK-muscle/brain (CK-MB), and fatty acid binding protein 3 levels increased. At 24 h, lactate dehydrogenase (LDH)-1, CK, and CK-MB levels increased, and multifocal vacuolar degeneration of myocardial cells was observed in the apical inner layer. At 72 h, LDH-1 levels were increased, and multifocal myocardial necrosis was observed in the interventricular septum and inner layer of the apex of left ventricular wall. Furthermore, at 0.5 h, heart rate (HR), ejection fraction (EF), and cardiac output (CO) decreased. At 24 h, CO decreased. Finally, at 72 h, HR, EF, and CO decreased, and depression of the T-wave amplitude was observed. In conclusion, myocardial injury, bradycardia, and depressed cardiac function were induced in rats by a single-dose of CA4DP. The lesion distribution and electrocardiographic features suggested that myocardial injury was induced by ischemia. These findings are similar to MDA-induced cardiotoxicity in humans, and this rat model will prove useful in studies of the cardiotoxicity in humans.

Interest of colchicine in the treatment of acute myocardial infarct responsible for heart failure in a mouse model

BACKGROUND

Inflammation is deeply involved in the pathophysiology of ischemia-reperfusion (I/R) lesions and ventricular remodeling due to an acute myocardial infarction (AMI). Colchicine as a pleiotropic anti-inflammatory molecule may exert cardioprotective effects under acute ischemia. Here, we aimed to evaluate the impact of colchicine on reperfusion injury in a mouse model.

METHOD

Myocardial ischemia/reperfusion (I/R) injury was induced in C57BL/6 male mice, after 45min ligation of the left coronary artery followed by reperfusion. 400μg/kg of colchicine or the vehicle was administrated intraperitoneally (i.p.) 25min before the reperfusion (blinded administration). Mice were sacrificed at 24h after the acute myocardial ischemia (AMI) and the infarct size was determined. Circulating level of troponin and cytokines profile were assessed 4h after the AMI. An echocardiography was performed in a follow-up group mice, 48h and 8weeks after the AMI.

RESULTS

The infarct size was reduced in colchicine treated mice (39.8±3.5% versus 52.9±3.2%, p<0.05). Troponin was significantly lower in the colchicine treated mice (7015.7±1423.7pg/mL, n=5 vs 30,723.7±7959.9pg/mL in the placebo group, n=6; p<0.0001). Fibrosis was decreased in the Colchicine group (24.51±3.13% vs 11.38±2.46%, p=0.03). In the follow-up group mice (n=8), there were no differences between mice treated with placebo (n=9) and mice treated with colchicine (n=9) regarding to cardiac remodeling parameters but outflow approximated by the ITV was higher in the colchicine group.

CONCLUSION

In conclusion, colchicine allowed a significant reduction of infarct size in mice, improves hemodynamic parameters and decrease cardiac fibrosis.

Coronary Spasm after an Injection of Vincristine

Cardiotoxicity, including heart failure, thromboembolic events, and myocardial ischemia, is a concern for cardiologists and oncologists. The most frequently involved drugs are anthracyclines. We report an episode of coronary spasm due to vincristine, a vinca alkaloid, in a 49-year-old man treated for a diffuse undifferentiated carcinoma. The patient suffered recurrent episodes of typical chest pain with ST-elevation in the inferior area. Coronary spasm was confirmed by an angiogram, which showed normal coronary arteries. No recurrence occurred with the medical management. Coronary spasm induced by vincristine is a newly described facet of chemotherapy-related cardiotoxicity.

Combined Effects of Vincristine and Quercetin in Reducing Isoproterenol-Induced Cardiac Necrosis in Rats

Combined effects of vincristine and quercetin in the regulation of isoproterenol (ISO)-induced cardiac necrosis have been evaluated in rats. ISO administration (100 mg/kg, s.c., for two consecutive days) increased the levels of serum creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), glutamate pyruvate transaminase (SGPT) and cardiac troponin (cTnT) as well as cardiac lipid peroxidation products (malondialdehyde and lipid hydroperoxides). However, it reduced the activities of superoxide dismutase (SOD), catalase and the glutathione peroxidase and the level of reduced glutathione. It also increased the heart rate and ST-segment elevation in ECG. Pretreatment of vincristine (25 μg/kg) or quercetin (10 mg/kg) alone for 2 weeks ameliorated these cardiotoxic effects partially. However, treatment of both vincristine and quercetin for a similar period reduced the serum CK-MB, LDH, SGPT and cTnT levels near to normal levels in ISO-treated rats. Concomitantly, the test drugs improved the status of antioxidants and decreased the cardiac lipid peroxidation products. Combined treatment of both the drugs also restored the pathological electrocardiographic patterns and reduced the area of myocardial necrosis. Histopathology of heart in ISO-administered rats that received both vincristine and quercetin showed nearly normal myocardium with very little inflammatory infiltration. In conclusion, the present finding appears to be the first one, suggesting a better protection of cardiac tissues by combined treatment of vincristine and quercetin in isoproterenol-induced cardiac toxicity.

Combretastatin A4 disodium phosphate-induced myocardial injury

Histopathological and electrocardiographic features of myocardial lesions induced by combretastatin A4 disodium phosphate (CA4DP) were evaluated, and the relation between myocardial lesions and vascular changes and the direct toxic effect of CA4DP on cardiomyocytes were discussed. We induced myocardial lesions by administration of CA4DP to rats and evaluated myocardial damage by histopathologic examination and electrocardiography. We evaluated blood pressure (BP) of CA4DP-treated rats and effects of CA4DP on cellular impedance-based contractility of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). The results revealed multifocal myocardial necrosis with a predilection for the interventricular septum and subendocardial regions of the apex of the left ventricular wall, injury of capillaries, morphological change of the ST junction, and QT interval prolongation. The histopathological profile of myocardial lesions suggested that CA4DP induced a lack of myocardial blood flow. CA4DP increased the diastolic BP and showed direct effects on hiPS-CMs. These results suggest that CA4DP induces dysfunction of small arteries and capillaries and has direct toxicity in cardiomyocytes. Therefore, it is thought that CA4DP induced capillary and myocardial injury due to collapse of the microcirculation in the myocardium. Moreover, the direct toxic effect of CA4DP on cardiomyocytes induced myocardial lesions in a coordinated manner.

The causes of drug-induced muscle toxicity

PURPOSE OF REVIEW

Clinically identified myopathies are frequently a consequence of medication toxicities. However, recognizing drug-induced myopathies is sometimes difficult. Developing a greater understanding of the underlying mechanisms of drug-induced muscle toxicity will promote enhanced awareness and recognition, and improved management of these syndromes.

RECENT FINDINGS

The adverse impact of certain drugs on muscle metabolism, muscle cell atrophy, and myocyte apoptosis is increasingly clear. Glucocorticoids impair glucose handling and directly promote protein catabolism. Statins impair mitochondrial function and alter intracellular signaling proteins, which can lead to myocyte apoptosis. Alternatively, statins can induce an autoimmune necrotizing myositis. Several medications impair autophagy, thus limiting access to the needed glycogen stores.

SUMMARY

This review provides an overview of the main underlying mechanisms of drug-induced myopathies. These myopathies will most often be related to a drug's ability to alter metabolism and protein balance, induce necrosis, or impair autophagy.

Cardiotoxic changes of colchicine intoxication in rats: electrocardiographic, histopathological and blood chemical analysis

The microtubule inhibitor colchicine is cardiotoxic and is suggested to impair impulse formation and conduction. However, little is known about the electrocardiographic (ECG) changes induced by colchicine in experimental animals and the detailed pathogenesis of its cardiotoxicity. Therefore, we analyzed cardiotoxicity in colchicine-treated rats using electrocardiographic, histopathological and blood-chemistry approaches. A telemetry device for transmitting ECG data was implanted into male Crl:CD(SD) rats, and ECG tracings were obtained. At 6 weeks of age, 1.25 mg/kg colchicine was injected intravenously once daily for 2 consecutive days, and ECG waveforms and heart rate variability were analyzed. Furthermore, 1.25 mg/kg colchicine or vehicle was injected for 1 or 2 consecutive days in other rats at 6 weeks of age. One day after the final dosing, heart and blood samples were taken for histopathological and bloodchemical examination. ECG analysis revealed a prolonged RR interval, QRS duration, PR interval and QT interval. Heart rate variability analysis showed an increase in high frequency (HF) components as an index of parasympathetic nervous activity. In blood chemical examinations, colchicine induced high levels of parameters of cardiac injury and low levels and/or variations in Ca, inorganic phosphorus, potassium and chloride. Histopathologically, colchicine-treated rats showed eosinophilic granular degeneration and cytoplasmic vacuolation of ventricular myocardial cells but no remarkable change in the atrioventricular node. Not only blood chemical and histopathological changes but also ECG changes were induced in colchicine-treated rats, which indicated a decrease in myocardium excitability and conductivity, and these changes might be related to increased parasympathetic nervous activity and low blood Ca levels.