Protective effects of nicotinamide mononucleotide on radiation-related cardiac injury

Abstract

Abstract Background Radiation therapy for cancer treatment can cause damage to the heart. There are numerous possible mechanisms related to radiation-related cardiac dysfunction, among which increased oxidative stress is an important factor. However, the detailed mechanisms remain unclear and effective treatments on radiation-related cardiac dysfunction are still lacking. Nicotinamide mononucleotide (NMN), the most direct precursor of nicotinamide adenine dinucleotide (NAD+), can effectively reduce reactive oxygen species (ROS) production and thus could be a candidate to alleviate radiation-induced damage. However, the protective effects and the underlying mechanisms of NMN on radiation-related cardiac injury remain to be elucidated. Therefore, this study was designed to identify the mechanisms of radiation-related cardiac injury and investigate the protective actions of NMN. Methods Wild-type c57 mice were divided into radiation exposure (7.2Gy radiation) and non-exposure groups. Wild-type C57BL6/J mice supplied with NMN for 12 months before radiation. Echocardiography to detect mice cardiac function. Epicardial electrical mapping technique to detect electrical conduction in the heart. Non-targeted metabolomics was used to detect cardiac different metabolites. In parallel, we observed the effect of radiation on survival and mitochondrial function (ROS production and ATP content) of H9C2 cells with or without NMN. Results In the radiation exposure group, echocardiography showed that the left ventricular ejection fraction (LVEF) and fractional shortening (FS) were reduced, whilst epicardial mapping demonstrated slowed conduction velocity and change in the direction of propagation. Non-targeted metabolomics showed the different metabolites between the radiation group and the control group were mainly in nucleotide and amino acid metabolism. Metabolic pathway enrichment analysis showed that different metabolites were implicated in the metabolism of pyrimidine, folate, arginine and proline, and tryptophan. Mice with NMN before radiation showed reduced mechanical and electrical dysfunction, with non-targeted metabolomic results showed NMN rescued the radiation-induced down-regulation of 1-(4-aminobutyl)urea, 4-aminobenzoic acid, 3-hydroxyanthranilic acid, which ultimately exerted cardioprotective effects. We also found that radiation can reduce the survival, increase ROS production, and reduce ATP content of H9C2 cells in vitro, and these harmful effects can be partially reversed by NMN. Conclusion The mechanical and electrical dysfunction caused by radiation were associated with altered nucleotide and amino acid metabolism in the myocardium, and these harmful effects could be partially mitigated by NMN supplement.