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Cross Talk Between Autophagy and Apoptosis Contributes to ZnO Nanoparticle-Induced Human Osteosarcoma Cell Death
Guanping He1, Yunlong Ma2, Ye Zhu3
1Department of Orthopedics, Peking University Third Hospital, No. 49, North Garden Street, Haidian District, Beijing, 100191, China.
Abstract:
Killing osteosarcoma cells by zinc oxide nanoparticles (NPs) and its underlying subcellular mechanism are never studied. Here, it is found that the NPs induce cross talk between apoptosis and autophagy, which leads to osteosarcoma cell death. Specifically, the NP uptake promotes autophagy by inducing accumulation of autophagosomes along with impairment of lysosomal functions. The autophagy further causes the uptaken NPs to release zinc ions by promoting their dissolution. These intracellular zinc ions, together with those that are originally released from the extracellular NPs and flowed into the cells, collectively target and damage mitochondria to produce reactive oxygen species (ROS). Then the ROS inhibit cell proliferation by arresting S phase and trigger apoptosis by extrinsic and intrinsic pathways, ultimately leading to cell death. More importantly, suppression of the early stage autophagy restores cell viability by abolishing apoptosis whereas blockade of the late stage autophagy inversely enhances apoptosis. In contrast, inhibition of apoptosis shows a limited ability to restore cell viability but obviously enhance autophagy. Notably, cell viability is strongly ameliorated by the combination of inhibitors for both the late stage autophagy and the apoptosis. These findings provide a mechanistic understanding of the NP-directed autophagy and apoptosis in osteosarcoma cells.
Insights
Zinc oxide nanoparticles (NPs) trigger osteosarcoma cell death by inducing a complex interplay between autophagy and apoptosis. This study elucidates the subcellular mechanisms driving this cell death pathway.
Area of Science:
- Nanomedicine
- Cancer Biology
- Cellular Mechanisms
Background:
- Osteosarcoma remains a significant challenge in pediatric oncology.
- The therapeutic potential of zinc oxide nanoparticles (NPs) in cancer treatment is emerging.
- The precise subcellular mechanisms by which NPs induce cancer cell death are not fully understood.
Purpose of the Study:
- To investigate the mechanism by which zinc oxide nanoparticles (NPs) induce cell death in osteosarcoma.
- To explore the cross talk between autophagy and apoptosis pathways mediated by NP uptake.
- To identify potential therapeutic targets for enhancing NP-mediated cancer cell death.
Main Methods:
- Cell culture of osteosarcoma cells treated with zinc oxide NPs.
- Analysis of autophagosome formation and lysosomal function.
- Measurement of intracellular zinc ion concentration and reactive oxygen species (ROS) production.
- Flow cytometry to assess cell cycle arrest and apoptosis.
- Pharmacological inhibition of autophagy and apoptosis pathways.
Main Results:
- Zinc oxide NPs induced autophagy by accumulating autophagosomes and impairing lysosomal function.
- NP uptake led to intracellular zinc ion release, mitochondrial damage, and ROS production.
- ROS triggered apoptosis via extrinsic and intrinsic pathways, leading to osteosarcoma cell death.
- Early autophagy suppression restored cell viability, while late-stage autophagy blockade enhanced apoptosis.
- Apoptosis inhibition had limited impact on viability but increased autophagy.
Conclusions:
- Zinc oxide NPs induce osteosarcoma cell death through a coordinated mechanism involving autophagy and apoptosis.
- The interplay between autophagy and apoptosis is crucial, with timing influencing cell fate.
- Combined inhibition of late-stage autophagy and apoptosis significantly improves cell viability, suggesting a novel therapeutic strategy.
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