In this new study, researchers investigated a plant used in traditional Chinese medicine and its anti-cancer effects in non-small cell lung cancer (NSCLC).
Traditional Chinese medicine has long been explored for its potential in treating various diseases, including cancer. Lithospermum erythrorhizon, or purple gromwell, is a mysterious plant native to East Asia, and its dried root is often referred to as Zicao. Acetylshikonin, a compound derived from Zicao, has shown promise in exhibiting a variety of anti-cancer properties. While the effects of acetylshikonin on lung cancer are not yet fully understood, recent research has shed light on its potential as a therapeutic agent.
In a new study, researchers Shih-Sen Lin, Tsung-Ming Chang, Augusta I-Chin Wei, Chiang-Wen Lee, Zih-Chan Lin, Yao-Chang Chiang, Miao-Ching Chi, and Ju-Fang Liu from Shin Kong Wu Ho-Su Memorial Hospital, Chang Gung Memorial Hospital, Chang Gung University of Science and Technology, Ming Chi University of Technology, Taipei Medical University, and China Medical University aimed to explore the mechanisms underlying acetylshikonin-induced cell death in non-small cell lung cancer (NSCLC). On December 19, 2023, their research paper was published in Aging’s Volume 15, Issue 24, entitled, “Acetylshikonin induces necroptosis via the RIPK1/RIPK3-dependent pathway in lung cancer.”
“This study explored the mechanisms underlying acetylshikonin-induced cell death in non-small cell lung cancer (NSCLC).”
Acetylshikonin and Cell Viability Reduction
In this study, researchers investigated the effects of acetylshikonin on the viability of NSCLC cells. The researchers treated H1299 and A549 cells with varying concentrations of acetylshikonin and assessed cell viability using a cell counting kit-8 (CCK-8) assay. The results showed that acetylshikonin significantly reduced cell viability in a dose-dependent manner. The IC50 values for H1299 and A549 cells were determined to be 2.34 μM and 3.26 μM, respectively. These findings suggest that acetylshikonin has the potential to effectively reduce the viability of lung cancer cells without causing significant damage to normal cells.
Cell Death Induction by Acetylshikonin
To further investigate the effects of acetylshikonin on NSCLC cells, the team examined the morphological changes associated with cell death. They observed that acetylshikonin treatment led to chromatin condensation, cell shrinkage, and the formation of cell debris, indicating cell death. Additionally, Annexin V/propidium iodide (PI) staining demonstrated an increase in the population of cells positive for Annexin V and PI, suggesting the induction of both apoptotic and necrotic cell death. Further analysis revealed that acetylshikonin increased membrane permeability, as evidenced by the uptake of PI by the cells. These findings indicate that acetylshikonin promotes cell death in NSCLC cells, potentially through necrotic pathways.
Acetylshikonin and Cell Cycle Arrest
In addition to its effects on cell viability and cell death, acetylshikonin was found to induce cell cycle arrest in NSCLC cells. The researchers examined the cell cycle progression of H1299 and A549 cells treated with acetylshikonin. Flow cytometry analysis revealed an increase in the proportion of cells in the subG1 and G2/M phases, indicating DNA fragmentation and cell cycle arrest in the G2/M phase. Western blot analysis further confirmed these findings by showing a decrease in the expression of cell cycle regulatory proteins, CDK1 and cyclin B1, in acetylshikonin-treated cells. These results suggest that acetylshikonin exerts its anti-cancer effects by inducing cell cycle arrest, thereby inhibiting cancer cell proliferation.
Oxidative Stress and Mitochondrial Dysfunction
The team also investigated the involvement of oxidative stress and mitochondrial dysfunction in acetylshikonin-induced cell death. Acetylshikonin treatment was found to increase intracellular reactive oxygen species (ROS) levels in NSCLC cells. This increase in ROS was associated with a decrease in mitochondrial membrane potential (MMP), indicating mitochondrial dysfunction. These findings suggest that acetylshikonin induces oxidative stress and disrupts mitochondrial function in NSCLC cells, potentially contributing to cell death.
Lipid Peroxidation and GPX4 Expression
The researchers explored the role of lipid peroxidation and the expression of glutathione peroxidase 4 (GPX4) in acetylshikonin-induced cell death. They observed that acetylshikonin treatment caused lipid peroxidation, as evidenced by the quenching of red fluorescence in BODIPY™ 581/591 C11-stained cells. This lipid peroxidation was associated with a decrease in GPX4 expression. GPX4 is an enzyme involved in maintaining cellular homeostasis and protecting against oxidative stress. The downregulation of GPX4 in NSCLC cells treated with acetylshikonin suggests a potential mechanism for inducing cell death.
Necroptosis Pathway Activation by Acetylshikonin
The team further investigated the mechanism by which acetylshikonin induces cell death in NSCLC cells. They found that acetylshikonin promoted the phosphorylation of receptor-interacting serine/threonine-protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like kinase (MLKL). These proteins are key players in the necroptosis signaling pathway. Immunofluorescence staining showed an increase in MLKL phosphorylation in acetylshikonin-treated cells, while Western blot analysis confirmed the activation of RIPK1, RIPK3, and MLKL. Importantly, pretreatment with RIPK1 inhibitors reversed the phosphorylation of MLKL and significantly attenuated cell death induced by acetylshikonin, suggesting that the activation of the RIPK1/RIPK3/MLKL cascade is involved in the necroptotic cell death pathway triggered by acetylshikonin.
In conclusion, acetylshikonin exhibits promising anti-cancer effects in NSCLC cells. It reduces cell viability, induces cell death, and promotes cell cycle arrest in the G2/M phase. Acetylshikonin also increases membrane permeability and activates the necroptosis signaling pathway through the phosphorylation of RIPK1, RIPK3, and MLKL. Furthermore, acetylshikonin induces oxidative stress, disrupts mitochondrial function, and promotes lipid peroxidation. These findings suggest that acetylshikonin holds potential as a therapeutic agent for the treatment of lung cancer. Further research is warranted to explore the clinical applications of acetylshikonin and its potential synergistic effects with existing lung cancer therapies.
“We determined that even low doses of acetylshikonin reduced the viability of lung cancer cells without significantly affecting normal cells. When used to treat lung cancer, acetylshikonin was shown to promote cell death and arrest cell cycle progression in the G2/M phase.”
Click here to read the full research paper published in Aging.
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