A Treatment Combined Prussian Blue Nanoparticles With Low-intensity Pulsed Ultrasound Alleviates Cartilage Damage in Knee Osteoarthritis by Initiating PI3K/Akt/mTOR Pathway

Background: Reactive oxidative stress (ROS) related apoptosis in chondrocytes and extracellular matrix (ECM) degradation play crucial roles in the process of osteoarthritis (OA). Prussian blue nanoparticles (PBNPs) are known to scavenge ROS in cellular. Low-intensity pulsed ultrasound (LIPUS) has been used as a non-invasive modality for the is widely used in clinical rehabilitation management of OA. Methods: In this study, we aim to investigate the effects of PBNPs/LIPUS combined treatment on knee osteoarthritis (KOA) and to determine whether phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway mediates this process. Use LPS to process primary cells of knee joint cartilage to establish a cartilage knee arthritis model. After treated with LIPUS and PBNPs, cell viability was rated by CCK-8 and ROS levels were assessed by DCFH-DA. Cell apoptosis was estimated by flow cytometry and TUNEL staining. Articular pathological changes were observed by naked eyes, H&E, and Safranin O staining, then monitored by cartilage lesion grades and Mankin’s score. Protein levels of cleaved caspase-3, Bcl-2, Bax, p-PI3K, PI3K, p-Akt, Akt, p-mTOR, mTOR, IL-1β, MMP3, MMP13, p-JINK, JINK, p-c-Jun, and c-Jun were subjected to western blot. Results: Cellular ROS, apoptosis rate, and TUNEL staining of chondrocytes were fairly decreased in the PBNPs group and the LIPUS group but drastically down-regulated in the PBNPs/LIPUS combination treatment group when compared with the LPS group. Both PBNPs and LIPUS decreased the grades of cartilage lesions and Mankin scores of knee articular cartilage, while combined administration achieved more reduction. Western blot results showed that the cleaved caspase-3, Bax, IL-1β, MMP3 and MMP13 in the PBNPs and LIPUS groups slightly decreased, and Bcl2 increased slightly, while in the combination treatment group, the former was significantly decreased, and Bcl2 was Significantly increased. Conclusion: The PBNPs/LIPUS combination treatment increased protein levels of p-PI3K, p-Akt, and p-mTOR but decreased the protein levels of p-JINK and p-c-Jun, in vitro and vivo. The PBNPs/LIPUS combination treatment reduced cellular ROS, apoptosis, and matrix metalloproteinases (MMPs), as a consequence, alleviated articular cartilage damage in KOA. Moreover, the PBNPs/LIPUS combination treatment suppressed the JINK/c-Jun signal pathway.