Molecular docking and experimental validation for the protective effect of betanin against capecitabine-induced myocardial injury: Binding to TLR4 and downregulation of MyD88/NFκB signaling.

Toll-like receptor 4 (TLR4) is a membrane receptor linked to cardiomyocyte injuries. If activated, TLR4 starts a signaling cascade via recruitment of the myeloid differentiation primary response 88 (MyD88) protein, leading to the phosphorylation of nuclear factor-κB (NFκB) and production of pro-inflammatory cytokines, which fuels the initiation of the cardiac injury. Betanin is a beet-betacyanin that ameliorates organ toxicities via mitigating the cytokine amplification. Molecular docking was done to test TLR4 as a plausible target for betanin and a bioinformatic search elucidated any potential relationship between betanin and TLR4 pathways including those implicated in inflammatory responses and cardiotoxicity. Further, an experimental study used male albino mice were divided equally into 3 groups as 1) Vehicle, 2) Capecitabine and 3) Capecitabine + Betanin (100 mg/kg/day) groups. Capecitabine (200 mg/kg) was given 5 times a week for 3 weeks. Frozen heart samples were processed for ELISA assays for MyD88/NFκB proteins. Formalin-fixed heart samples were used for histopathologic staining using the iron-hematoxylin stain. The bioinformatic analysis confirmed the relationship between myocardial injury and TLR4 signaling. Molecular docking indicated the ability of betanin to block the TLR4 receptors. In the mouse study, betanin mitigated the cardiac histopathological finding, reduced the serum level of cardiac enzymes and downregulated the protein level of MyD88/NFκB. This study highlighted that betanin acts as a putative inhibitor for TLR4. Betanin mitigated capecitabine induced myocardial injury and suppressed the TLR4/MyD88/NFκB signaling. Hence, betanin was identified as a candidate for further investigation in mitigating myocardial injury.