Substance P Antagonism Prevents Chemotherapy-Induced Cardiotoxicity

Background: Doxorubicin (DOX), used in chemotherapeutic regimens in many cancers, has been known to induce, cardiotoxicity and life-threatening heart failure or acute coronary syndromes in some patients. We determined the role of Substance P (SP), a neuropeptide and its high affinity receptor, NK-1R in chemotherapy associated cardiotoxicity in mice. We determined if NK-1R antagonism will prevent DOX-induced cardiotoxicity in vivo. Methods: C57BL/6 mice (6- week old male) were injected intraperitoneally with DOX (5 mg per kilogram of body weight once a week for 5 weeks) with or without treatment with aprepitant (a NK-1R antagonist, Emend, Merck & Co., Kenilworth, NJ, USA). Five different dosages of aprepitant were administered in the drinking water five days before the first injection of DOX and then continued until the end of the experiment. Each of these 5 doses are as follows; Dose 1 = 0.9 µg/mL, Dose 2 = 1.8 µg/mL, Dose 3 = 3.6 µg/mL, Dose 4 = 7.2 µg/mL, Dose 5 = 14.4 µg/mL. Controls consisted of mice injected with PBS (instead of DOX) with or without aprepitant treatment. The experiment was terminated 5 weeks post-DOX administration and various cardiac functional parameters were determined. Following euthanization, we measured heart weight to body weight ratios and the following in the hearts, of mice treated with and without DOX and aprepitant; (a) levels of SP and NK1R, (b) cardiomyocyte diameter (to determine evidence of cardiomyocyte hypertrophy), (c) Annexin V levels (to determine evidence of cardiac apoptosis), and (d) ratios of reduced glutathione (GSH) to oxidized glutathione (GSSG) (to determine evidence of oxidative stress). Results: We demonstrated that the levels of SP and NK1R were significantly increased respectively by 2.07 fold and 1.86 fold in the hearts of mice treated with versus without DOX. We determined that DOX-induced cardiac dysfunction was significantly attenuated by treatment with aprepitant. Cardiac functional parameters such as fractional shortening (FS), ejection fraction (EF) and stroke volume (SV) were respectively decreased by 27.6%, 21.02% and 21.20% compared to the vehicle treated group (All, p < 0.05, ANOVA). Importantly, compared to treatment with DOX alone, treatment with lower doses of aprepitant in DOX treated mice significantly reduced the effects of DOX on FS, EF and SV to values not significantly different from sham (vehicle treated) mice (All, p < 0.05, ANOVA). The levels of, apoptosis marker (Annexin V), oxidative stress (ratio of GSH with GSSG) and cardiomyocyte hypertrophy were respectively increased by 47.61%, 91.43% and 47.54% in the hearts of mice treated with versus without DOX. Compared to the DOX alone group, treatment with DOX and Dose 1, 2 and 3 of aprepitant significantly decreased the levels of each of these parameters (All p < 0.05, ANOVA). Conclusions: Our studies indicate that the SP/NK1-R system is a key mediator that induces, DOX-induced, cardiac dysfunction, cardiac apoptosis, cardiac oxidative stress and cardiomyocyte hypertrophy. These studies implicate that NK-1R antagonists may serve as a novel therapeutic tool for prevention of chemotherapy induced cardiotoxicity in cancer.

Abstract 14673: Cardiomyocyte Specific Overexpression of Pellino 1 Reverses Sepsis Induced Cardiac Dysfunction in a Murine Model by Reducing Inflammatory Response and Cardiac Cell Death

Introduction: Sepsis remains a significant cause of mortality in the intensive care unit till today. Recent research suggests nearly one in four deaths in people with heart failure is caused by sepsis. Overexpression of mammalian Pellino-1 (Peli1), a E3 ubiquitin ligase, causes inhibition of apoptosis, oxidative stress, and preservation of cardiac function in a myocardial infarction model. Therefore, in the present study, we explored the possibility to overcome sepsis mediated heart failure by overexpressing Peli1 (AMPEL1Tg/+) in a mouse model of severe sepsis. Methods: C57BL/6J (WT) and AMPEL1 Tg/+ mice were divided into Wild-type sham (WTS), Wild-type Cecal Ligation and Puncture (WTCLP), AMPEL1 Tg/+ sham (AMPEL1 Tg/+ S) and AMPEL1 Tg/+ CLP. Cardiac function (LVEF, FS) by two-dimensional echocardiography was assessed pre-procedure, at 6, and 24 hours post-surgery. Serum IL-6 and TNF-alpha (ELISA) at 6 hours and cardiac apoptosis (TUNEL assay) at 24 hours were measured. Results are expressed as mean ± SEM. Results: Analysis of echocardiographic parameters (EF, FS) preoperatively and among the sham groups were similar however there was significant preservation of post-procedure LVEF (%) in the AMPEL1 Tg/+ CLP at the 6 hour (AMPEL1 Tg/+ :52.7 ± 3.71 vs WT:40.7 ±2.46, p=0.013, n=10-11) and 24-hour time point (AMPEL1 Tg/+ :63.1 ± 1.63 vs WT:49.3 ± 4.41, p=0.002, n=9-11) compared to WT. Similar trend was observed in estimation of FS (%) at 6 hours (AMPEL1 Tg/+ :26.3 ± 2.22 vs WT:19.3 ±1.37, p=0.014, n=10-11) and 24 hours (AMPEL1 Tg/+ :32.4 ± 1.89 vs WT:24.4 ± 2.67, p=0.031, n=9-11). A marked decrease in serum IL-6 (AMPEL1 Tg/+ :259.7 ± 18.70 vs WT:483.2 ± 24.01, p<0.0001, n=6, pg/mL) and TNF-alpha (AMPEL1 Tg/+ :86.89 ± 14.36 vs WT:161.8 ± 20, p=0.012, n=6, pg/mL) was observed in the AMPEL1 Tg/+ CLP at 6 hours. The preserved cardiac function in CLP was further supported by a noticeable decrease in cardiac apoptosis (% TUNEL positive cells) at 24 hours in the AMPEL1 Tg/+ CLP group (4.7 ± 0.94 vs 11.7 ± 2.82, p=0.040, n=6,) compared to WTCLP. Conclusions: Thus, Peli1 overexpression is a novel approach that preserved cardiac function, reduced inflammatory markers, and apoptosis following severe sepsis in a murine genetic model.