Ameliorative Effect of N-Acetylcysteine Against 5-Fluorouracil-Induced Cardiotoxicity via Targeting TLR4/NF-κB and...

Background and Objectives: 5-Fluorouracil (5-FU) is a widely prescribed and effective chemotherapeutic drug, but its cardiotoxic side effects pose a significant challenge to its use. Identifying a protective agent that does not affect its anticancer efficacy is essential. Our study aimed to investigate the cardioprotective effect of N-acetyl cysteine (NAC) against 5-FU-induced cardiac injury and to elucidate the underlying mechanisms. Materials and Methods: This study included four experimental groups, each with eight rats (n = 8): Group I (control group), Group II (NAC group), Group III (5-FU group), and Group IV (combined group 5-FU+NAC). Cardiac enzymes, oxidative stress, inflammatory, and apoptotic markers were investigated, and cardiac sections from the different groups were histologically examined. Results: Co-treatment of 5-FU with NAC resulted in significantly lower levels of cardiac enzymes (alanine transaminase (ALT) by 62.1%, aspartate transaminase (AST) by 73.6%, lactate dehydrogenase (LDH) by 55.8%, and creatine kinase (CK) by 57.3%) compared to the 5-FU group, along with marked improvements in heart tissue histology. Additionally, NAC enhanced the activity of cardiac antioxidant enzymes (superoxide dismutase (SOD) by 295.6%, catalase (CAT) by 181%, and glutathione peroxidase (GPx) by 320.9%) while decreasing malondialdehyde (MDA) by 51.1%, a marker of membranous lipid peroxidation. This might be due to significant upregulation of the nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway at the gene and protein levels. The combined treatment significantly decreased the gene expression of the toll-like receptor 4 (TLR4)/nuclear factor kappa-light-chain-enhancer of activated B-cell (NF-κB) pathway. Furthermore, it downregulated the protein levels of inflammatory markers, including tumor necrosis factor-alpha (TNF-α) by 29.9%, interleukin-1 beta (IL-1β) by 21.9%, and interleukin-6 (IL-6) by 49.3%. Moreover, it upregulated the antiapoptotic marker B-cell lymphoma 2 (Bcl-2) protein levels by 269% and decreased apoptotic indicators Bcl-2-associated protein x (Bax) by 57.9% and caspase-3 by 30.6% compared to the 5-FU group. Conclusions: This study confirmed that NAC prevented the cardiotoxic effect of 5-FU through its antioxidant, anti-inflammatory, and antiapoptotic properties, suggesting its potential application as an adjuvant therapy in chemotherapy to alleviate 5-FU-induced cardiotoxicity.