Hydrogen Nanobubbles Inhibit Oxidative Stress and Myocardial Fibrosis to Reverse Chemotherapy-Induced Myocardial Injury

The most severe side effect of chemotherapy is cardiotoxicity, frequently causing myocardial injury characterized by excessive oxidative stress and fibrosis for which effective treatments are lacking. To address this, a hydrogen delivery system, hydrogen nanobubbles (HNBs), was constructed, leveraging hydrogen’s selective antioxidant and antifibrotic properties to counteract doxorubicin (Dox)-induced myocardial injury and explore its mechanism. HNBs were constructed via polymer self-assembly. Nanoparticle tracking analysis indicated a size of 265.1 ± 26 nm. The average hydrogen content of HNBs measured by chemical titration was about 1.9 mg/L. TEM revealed spherical HNBs with a dense outer lipid polymer layer encapsulating hydrogen. CCK-8 assays confirmed over 90% cell viability, demonstrating good biosafety. ROS fluorescence staining and flow cytometry showed that HNBs significantly reduced Dox-induced ROS increases. RT-qPCR revealed the upregulation of antioxidant genes (NRF2, SOD2, and GPX-1). Flow cytometry and JC-1 staining indicated that HNBs mitigated apoptosis and restored mitochondrial membrane potential. TEM displayed reduced mitochondrial damage and intracellular vacuolation. In a Dox-induced cardiomyopathy mouse model, HNBs improved cardiac function, normalized echocardiographic parameters (EF, FS, LVIDs, and LVIDd), and lowered myocardial ROS levels. Ultrasonic enhanced images showed that HNBs have good myocardial differential targeting. In vivo fluorescence imaging of mice showed that HNBs could accumulate in the myocardium in large quantities at 1 h. mRNA-seq and network pharmacology suggested that HNBs inhibit myocardial fibrosis. Masson staining results showed that HNBs could improve Dox-induced myocardial fibrosis. RT-qPCR and Western blotting confirmed the reduced expression of fibrosis markers (ACTA2, COL1, and FN1), preliminarily linking the mechanism to suppression of both PI3K/AKT and TGF-β/SMAD pathways. In summary, HNBs inhibit oxidative stress and myocardial fibrosis, reversing Dox-induced cardiac injury primarily through the dual suppression of the PI3K/AKT and TGF-β/SMAD pathways.