Background
The
Conclusions
Schisandrin A had an anti-tumor effect, and its mechanism might be related to the inhibition of the PI3K/AKT/mTOR signaling pathway. The schisandrin A microbubbles could promote the intake of schisandrin A in tumor cells after being destroyed at the site of tumor under ultrasound irradiation, thus playing the best anti-tumor effect.
Methods
The Span-PEG microbubbles loaded with schisandrin A were prepared using Span60, NaCl, PEG-1500, and schisandrin A. The loading rate of schisandrin A in Span-PEG composite microbubbles was determined by ultraviolet spectrophotometry method. The Walker-256 cell survival rate of schisandrin A was determined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay. The content of schisandrin A in the cells was determined by high performance liquid chromatography. Ultrasound imaging was used to evaluate the therapeutic effect in situ. Enzyme linked immunosorbent assay (ELISA) was used to measure the content of inflammatory factors in serum. Hematoxylin-eosin (HE) staining was used to observe the pathological changes of experimental animals in each group. Immunohistochemistry was used to detect the expression of hypoxia inducible factor-1α (HIF-1α), vascular endothlial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR-2) in tumor tissues, and western blot was used to detect the protein expression of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway in tumor tissues.
Results
The composite microbubbles were uniform in size, and the particle size distribution was unimodal and stable, which met the requirements of ultrasound contrast agents. The loading rate of schisandrin A in Span-PEG microbubbles was 8.84 ± 0.14%, the encapsulation efficiency was 82.24±1.21%. The IC50 value of schisandrin A was 2.87 μg/mL. The drug + microbubbles + ultrasound (D+M+U) group had the most obvious inhibitory effect on Walker-256 cancer cells, the highest intracellular drug concentration, the largest reduction in tumor volume, the most obvious reduction in serum inflammatory factors, and the most obvious improvement in pathological results. The results of immunohistochemistry showed that HIF-1α, VEGF and VEGFR-2 protein decreased most significantly in D+M+U group (P < 0.01). WB results showed that D+M+U group inhibited the PI3K/AKT/mTOR signaling pathway most significantly (P < 0.01). Conclusions: Schisandrin A had an anti-tumor effect, and its mechanism might be related to the inhibition of the PI3K/AKT/mTOR signaling pathway. The schisandrin A microbubbles could promote the intake of schisandrin A in tumor cells after being destroyed at the site of tumor under ultrasound irradiation, thus playing the best anti-tumor effect.