Salidroside inhibits glioma cell migration and proliferation through CYP2E1-neuroglobin-cytochrome c mediated redox axis

Abstract

Glioblastoma (GB) represents one of the most aggressive primary brain tumors characterized by poor prognosis, high relapse and resistance to conventional therapies. Salidroside, a naturally occurring glucoside derived from Rhodiola rosea, has been reported to exhibit pro-apoptotic and anti-proliferative properties across multiple cancer models; however, its mechanistic basis in glioma and its therapeutic potential remain incompletely characterized. Neuroglobin (Ngb) protein expression was analyzed in 101 glioma brain tissue specimens and 5 normal brain tissues by western blot and immunohistochemical staining. In silico analyses of oxidized and reduced state of Ngb with salidroside was performed along with pharmacokinetics and toxicity predictions to computationally evaluate possible binding interactions and drug-like properties. Further, to determine the underlying mechanisms, in vitro assays were performed in U87MG and LN229 human glioblastoma cells treated with salidroside. MTT assay, transwell assay, Annexin V/PI staining, mitochondrial membrane potential (MMP), CYP2E1 activity, intracellular NADPH levels, Fe2+/Fe3+ ratio and markers of oxidative stress including ROS assay and lipid peroxidation were also measured. The mechanism of Ngb aided apoptosis was investigated by protein expression of Ngb, caspase 3 and cytosolic cytochrome c in glioma cells. Ngb expression in glioma tissues samples significantly downregulated with increasing tumour grade as determined by immunoreactivity and western blot analysis. In-silico analyses predicted a possible interaction of salidroside with reduced state of Ngb, In vitro studies suggested significant reduction in cell viability, migration and invasion in both U87MG and LN229 cells on supplementation with salidroside. These effects were accompanied by increased CYP2E1 activity, altered intracellular NADPH levels indicating induction of oxidative stress. Mitochondrial dysfunction, manifested as reduced MMP, elevated lipid peroxidation and increased cytosolic cytochrome c release indicated activation of intrinsic apoptotic pathway. Computational analyses additionally predicted a preferential interaction with the reduced form of Ngb, providing a mechanistic hypothesis warranting experimental validation. Salidroside exerts multi-faceted anti-cancer effects in glioblastoma cells, potentially involving upregulation of Ngb levels in glioma cells, modulation of redox homeostasis, mitochondrial integrity and intrinsic apoptotic signaling.