Assessing Doxorubicin-Induced Cardiomyopathy by 99mTc-3PRGD2 Scintigraphy Targeting Integrin αvβ3 in a Rat Model

The present study evaluated interstitial alterations in doxorubicin-induced cardiomyopathy using a radiolabeled RGD peptide 99mTc-3PRGD2 specific for integrin αvβ3 that targets myofibroblasts.Cardiomyopathy was induced in 20 Sprague-Dawley rats by intraperitoneal doxorubicin injections (2.5 mg/kg/week) for up to six weeks. 99mTc-3PRGD2 scintigraphy was performed in control rats (n = 6) at baseline and three, six, and nine weeks after first doxorubicin administration (n = 6, 6, and 5 for each time point). For another three rats of 6-week modeling, cold c(RGDyK) was co-injected with 99mTc-3PRGD2 to evaluate specific radiotracer binding. Semi-quantitative parameters were acquired to compare radiotracer uptake among all groups. The biodistribution of 99mTc-3PRGD2 was evaluated by a γ-counter after scintigraphy. Haematoxylin and eosin, and Masson’s staining were used to evaluate myocardial injury and fibrosis, while western blotting and immunofluorescence co-localization were used to analyze integrin αvβ3 expression in the myocardium.The 99mTc-3PRGD2 half-life in the cardiac region (Heartt 1/2) of the 9-week model and heart radioactivity percentage (%Heart20 min, %Heart40 min and %Heart60 min) of the 6 and 9-week models were significantly increased compared to the control. Heart-to-background ratio (HBR20 min, HBR40 min and HBR60 min) increase began in the third week, continued until the sixth week, and was reversed in the ninth week, which paralleled the changing trend of cardiac integrin αvβ3 expression. The myocardial biodistribution of 99mTc-3PRGD2 was significantly correlated with integrin β3 expression.The 99mTc-3PRGD2 scintigraphy allows for non-invasive visualization of interstitial alterations during doxorubicin-induced cardiomyopathy.

Xanthine oxidase inhibition attenuates doxorubicin-induced cardiotoxicity in mice

Background Accumulating evidence suggests that high serum uric acid (UA) is associated with left ventricular (LV) dysfunction. Although xanthine oxidase (XO) activation is a critical regulatory mechanism of the terminal step in ATP and purine degradation, the pathophysiological role of cardiac tissue XO in LV dysfunction remains unclear. Objectives We hypothesized that cardiac XO is activated in doxorubicin-induced LV dysfunction, and XO inhibitors ameliorate LV function by inhibiting cell death signals as well as by modifying cardiac purine metabolism. Methods Either doxorubicin (10 mg/kg) or vehicle was intraperitonially administered in a single injection to ICR mice. Mice were treated with or without oral XO inhibitors (febuxostat 3 mg/kg/day or topiroxostat 5 mg/kg/day) for 8 days starting 24 hours before doxorubicin-injection. The LV function was assessed by echocardiography at day 6 and by ex vivo heart perfusion at day 7. Results Cardiac tissue XO activity measured by a highly sensitive assay with liquid chromatography/mass spectrometry (n=8 each) and cardiac UA content (n=3–6) were significantly increased in doxorubicin-treated mice at day 7 and dramatically reduced by XO inhibitors. Accordingly, XO inhibitors substantially improved LV ejection fraction (n=8 each) and LV developed pressure (n=9 each) that had been impaired by doxorubicin administration. Intriguingly, the expression of GPX4, a negative regulator of ferroptosis, was decreased in doxorubicin-treated hearts but improved by XO inhibitors (n=6 each). Furthermore, metabolome analyses revealed an enhanced purine metabolism in doxorubicin-treated hearts, and XO inhibitors suppressed the serial metabolic reaction of hypoxanthine–xanthine–UA. Conclusions Doxorubicin administration induces cardiac tissue XO activation associated with an impaired LV function. XO inhibition attenuates the doxorubicin-induced cardiotoxicity partly through an anti-ferroptotic effect and the conservation of tissue ATP levels by modulating purine metabolism. The present study suggests that pharmacological XO inhibition represents a potential therapeutic strategy for the treatment of doxorubicin-induced cardiotoxicity. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): This study was supported in part by grants-in-aid for Ministry of Education Culture, Sports, Science and Technology.

S-ADEMETHIONINE EFFECT ON THE ACTIVITY OF FREE RADICAL OXIDATION PROCESSES AND ARGININE/CITRULLINE CYCLE WITH DOXORUBICIN-INDUCED LIVER INJURY

Seeking for effective methods for doxorubicin-induced toxicity prevention is of great clinical importance. The aim of the study is to investigate the effect of S-ademethionine on the activity of free radical oxidation and antioxidant protection and arginine / citrulline cycle, and the relationship between the indicators during the modeled doxorubicin-induced liver injury in rats. Materials and methods. The series of study were performed on 30 white non-linear adult rats, 15 (50%) males, 15 (50%) females, weighing 160-220 g. The experimental animals were divided into 3 groups: I group (n=10) included rats (5 males and 5 females), which during 3 days were intraperitoneally administered with doxorubicin of 5 mg/kg/day to achieve cumulative dose of 15 mg/kg and 0.9% sodium chloride solution 1 ml; ІІ group (n=10) included rats (5 males and 5 females), which for 3 days were administered with doxorubicin in dosage similar to that in group I and S-ademethionine intraperitoneally in a dose of 100 mg/kg/day with a total dose of 300 mg/kg; ІІІ group (n=10) included rats (5 males and 5 females), which were injected intraperitoneally for 3 days with 0.9% sodium chloride 1 ml solution by 2 injections. Thiobarbituric acid reactants, arginine, catalase, arginase and ornithine decarboxylase activity were studied in the liver homogenate. Results. The rats of group I in the course of doxorubicin administration demonstrated the growth of the thiobarbituric acid reactants in 2.57 times (p=0.002) in the liver homogenate that was accompanied by 1.7-fold decreased arginase activity compared to the control group III. An inverse correlation was found between the content of thiobarbituric acid reactants and arginase activity in the liver homogenate of group I rats (r=-0.71; p=0.02). Coadministration of S-ademethionine and doxorubicin administration led to 1.4-fold increase in catalase activity in the liver homogenate of rats compared to the control (p=0.009) that reduced the severity of oxidative stress and prevented changes in the arginine/citrulline cycle. Conclusions: S-ademethionine combined with doxorubicin, reduces the activity of free radical oxidation by potentiating the production of antioxidant protective enzymes that prevent impairments in the arginine / citrulline cycle.