Magnesium Isoglycyrrhizinate Alleviates Arsenic Trioxide-Induced Cardiotoxicity: Contribution of Nrf2 and TLR4/NF-κB Signaling Pathway

Abstract

Purpose: Magnesium isoglycyrrhizinate (MgIG), a single stereoisomer magnesium salt of glycyrrhizic acid, has beneficial effects on the cardiovascular system through anti-inflammatory, anti-oxidation, and anti-apoptotic actions. However, MgIG has not been shown to provide protection against cardiotoxicity induced by arsenic trioxide (ATO). This study aims to demonstrate the protection of MgIG against ATO-induced cardiac toxicity in mice and to investigate the underlying mechanism.

Methods: A mouse cardiotoxicity model was established by administering 5 mg/kg ATO for 7 days. MgIG used in conjunction with the ATO to assess its cardioprotection.

Results: MgIG administration could significantly reduce reactive oxygen species generation and the changes in tissue morphology. Also, MgIG administration increased the activity of antioxidase, such as superoxide dismutase, catalase, and glutathione peroxidase, and reduced malondialdehyde content and pro-inflammatory cytokine levels. Western blotting showed decreased expression of Bcl-2 associated X protein and Caspase-3, with increased expression of B-cell lymphoma 2. Importantly, MgIG administration increased nuclear factor-erythroid-2-related factor 2 (Nrf2) expression, while the expressions of nuclear factor kappa-B (NF-κB) and toll-like receptor-4 (TLR4) were significantly decreased.

Conclusion: Our data showed that MgIG alleviates ATO-induced cardiotoxicity, which is associated to the anti-inflammation, anti-oxidation, and anti-apoptosis action, potentially through activation of the Nrf2 pathway and suppression of the TLR4/NF-κB pathway.

Keywords: Nrf2; TLR4/NF-κB; arsenic trioxide; cardiotoxicity; magnesium isoglycyrrhizinate.

Figure 1

Chemical structure formula of MgIG.

Figure 2

Effects of MgIG on pathological changes of cardiac tissue as surveyed by H&E staining. Scale bar = 50 µm (H&E, 400 ×). Myocardial tissues are respectively from the CONT group (A), ATO group (B), MgIG alone treatment group (C), H-MgIG group (D), and L-MgIG group (E). The arrows on the myocardial tissue images represent The area of myocardial injury in each group was calculated (F). The arrows on the images of myocardial tissue represent apoptosis (1), inflammatory cell infiltration (2), myocardial necrosis (3), capillary dilatation and congestion (4), and intermyocardial edema (5), respectively. The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^# P < 0.05, ^## P < 0.01 vs the ATO group, n = 6.

Figure 3

Effects of MgIG on the activities of CK (A) and LDH (B). The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^# P < 0.05, ^## P < 0.01 vs the ATO group, n =10.

Figure 4

Effects of MgIG on the levels of SOD (A), MDA (B), GSH-Px (C) and CAT (D). The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^#P < 0.05, ^## P < 0.01 vs the ATO group, n = 10.

Figure 5

Effects of MgIG on the levels of ROS. Fluorescence images of different groups (A), CONT group; (B), ATO group; (C), MgIG alone treated group; (D), H-MgIG group; (E), L-MgIG group) and the ratio graph (F) about ROS are presented. Scale bar = 100 µm (200 ×). The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^## P < 0.01 vs the ATO group, n = 6.

Figure 6

Effects of MgIG on the expressions of IL-1β (A), IL-6 (B) and TNF-α (C). The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^## P < 0.01 vs the ATO group, n = 10.

Figure 7

Effects of MgIG on the expression of Bax, Caspase-3, and Bcl-2 (A). The band intensities of Bax (B), caspase-3 (C), and Bcl-2 (D) were analyzed by normalization to β-actin. The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^#P < 0.05, ^## P < 0.01 vs the ATO group, n = 3.

Figure 8

Effects of MgIG on the expressions of Nrf2, TLR4, and NF-κB (A). The band intensities of Nrf2 (B), NF-κB (C), and TLR4 (D) were analyzed by normalization to β-actin. The values were presented as the mean ± SEM. ** P < 0.01 vs CONT; ^#P < 0.05, ^## P < 0.01 vs the ATO group, n = 3.

Figure 9

The mechanism for protection of MgIG against ATO-treated cardiotoxicity.