Arginine-Nitric Oxide Metabolites and Cardiac Dysfunction in Patients With Breast Cancer

Abstract

Background: Oxidative/nitrosative stress and endothelial dysfunction are hypothesized to be central to cancer therapeutics-related cardiac dysfunction (CTRCD). However, the relationship between circulating arginine-nitric oxide (NO) metabolites and CTRCD remains unstudied.

Objectives: This study sought to examine the relationship between arginine-NO metabolites and CTRCD in a prospective cohort of 170 breast cancer patients treated with doxorubicin with or without trastuzumab.

Methods: Plasma levels of arginine, citrulline, ornithine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and N-monomethylarginine (MMA) were quantified at baseline, 1 month, and 2 months after doxorubicin initiation. Determinants of baseline biomarker levels were identified using multivariable linear regression, and Cox regression defined the association between baseline levels and 1- or 2-month biomarker changes and CTRCD rate in 139 participants with quantitated echocardiograms at all time points.

Results: Age, hypertension, body mass index, and African-American race were independently associated with ≥1 of baseline citrulline, ADMA, SDMA, and MMA levels. Decreases in arginine and citrulline and increases in ADMA were observed at 1 and 2 months (all p < 0.05). Overall, 32 participants experienced CTRCD over a maximum follow-up of 5.4 years. Hazard ratios for ADMA and MMA at 2 months were 3.33 (95% confidence interval [CI]: 1.12 to 9.96) and 2.70 (95% CI: 1.35 to 5.41), respectively, and 0.78 (95% CI: 0.64 to 0.97) for arginine at 1 month.

Conclusions: In breast cancer patients undergoing doxorubicin therapy, early alterations in arginine-NO metabolite levels occurred, and early biomarker changes were associated with a greater CTRCD rate. Our findings highlight the potential mechanistic and translational relevance of this pathway to CTRCD.

Keywords: arginine metabolism; cardio-oncology; cardiotoxicity; doxorubicin; nitrosative stress; trastuzumab.

Figure 1. Biomarker Protocol According to Treatment Regimen

Participants were treated with either doxorubicin or doxorubicin + trastuzumab. ǂdenotes visits when blood samples were collected. *denotes visits when transthoracic echocardiograms were performed.

Figure 2. Occurrence of Cancer Therapeutics-Related Cardiac Dysfunction (CTRCD) over Time

Kaplan-Meier plot illustrating the overall incidence of CTRCD in the cohort. The number of individuals at risk of CTRCD over time is shown below the plot. By 12.1 months (95% CI 7.8, 25.9), 15% of the cohort experienced CTRCD. The plot is based on the subset of the cohort with quantitated echocardiography at all time points (N = 139).

Figure 3. Cancer Therapy Related Cardiac Dysfunction (CTRCD) by Arginine-NO Metabolite Levels at 2 Months

Kaplan-Meier plots of first CTRCD event for participants below the first quartile (lowest 25%), or above the third quartile (highest 25%), of the biomarker ratio (level at 2 months versus baseline level). Note that this figure is based on the subset of the cohort with quantitated echocardiography available at all time points (N = 139).

Central Illustration. Pathophysiology of NO Production, Arginine Metabolism, and Anthracycline-Induced Cardiotoxicity

L-arginine (substrate) is oxidized by nitric oxide synthase (NOS) to form citrulline and NO. Alternatively, L-arginine can be catabolized by arginase to form ornithine or shunted to the methylation pathway to form N-monomethylarginine (MMA), symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). Both MMA and ADMA inhibit NOS. Anthracycline-induced cardiotoxicity occurs through formation of superoxide radical, a potent cause of oxidative stress, which then interacts with a variety of molecules, including NO, to produce toxic peroxynitrites that lead to further nitrosative stress. Reductions in NO can also lead to anthracycline-induced cardiotoxicity by disrupting the beneficial physiologic effects that NO exerts on normal well-functioning endothelium. Doxorubicin also results in calcium overload and myofibrillar disarray, topoisomerase-IIβ inhibition which may further exacerbate oxidative stress via alterations in the transcriptome; and iron-mediated generation of oxidative stress.