The Sesquiterpene Lactone Cynaropicrin Manifests Strong Cytotoxicity in Glioblastoma Cells U-87 MG by Induction of Oxidative Stress

Abstract

Cynaropicrin has shown a wide range of pharmacological properties, such as antitumor action. Here, we showed the inhibitory effect of Cyn on human glioblastoma cell U-87 MG growth. According to the IC50 values, Cyn 4, 8 and 10 µM displayed a significant cytotoxicity, as confirmed by the cell count and MTT assay. Furthermore, Cyn completely abolished the ability of U-87 MG to form colonies and induced drastic morphological changes. Interestingly, pretreatment with ROS scavenger N-acetylcysteine 3 mM reversed the cytotoxicity induced by Cyn 25 µM and preserved the cells by morphological changes. Therefore, oxidative stress induction was evaluated at low 8- and high 25-µM concentrations in U-87 MG, as demonstrated by the quantitative and qualitative analysis of ROS. A prolonged increase in ROS generation under Cyn 25 µM exposure was followed by the loss of the mitochondrial membrane potential in treated U-87 MG cells. An acute treatment with Cyn 25 µM induced Cyt c release, as revealed by immunofluorescence staining and the activation of cell death pathways, apoptosis and autophagy. On the other hand, chronic treatment with Cyn 8 µM induced senescence, as revealed by the increase in SA-β-Gal activity. Moreover, at this concentration, Cyn led to ERK dephosphorylation accompanied by a relevant reduction of the NF-κB p65 subunit. Finally, the combined effect of TMZ and Cyn resulted in synergistic cytotoxicity, as evaluated by the Bliss additivity model. The strong cytotoxicity of Cyn was also confirmed on IDH1 mutant U-87 MG cells and patient-derived IDH wild-type glioblastoma cell lines NULU and ZAR. In conclusion, given the high toxicity at minimal concentrations, the high inhibition of tumor cell growth and synergy with the standard drug for glioblastoma TMZ, Cyn could be proposed as a potential adjuvant for the treatment of glioblastoma.

Cynaropicrin disrupts tubulin and c-Myc-related signaling and induces parthanatos-type cell death in multiple myeloma

“…The fact that the expression of Beclin1 and P62, two autophagy markers, did not change after treatment and the combination of cynaropicrin with either bafilomycin A1 or rapamycin did not significantly alter the sensitivity of AMO1 to cynaropicrin refuted this assumption as well. Unexpectedly, our findings were contradictory to previously published research that suggested that cynaropicrin-induced cytotoxicity is associated to either apoptosis or autophagy [ 76 , 80 , 81 ]. In an attempt to decipher the mode of cell death induced by cynaropicrin in more detail, we studied the effect of cynaropicrin on the mitochondrial membrane potential as mitochondria are the cellular powerhouse and important regulators of cell death [ 82 ].…”

A review of natural products and small‐molecule therapeutics acting on central nervous system malignancies: Approaches for drug development, targeting pathways, clinical trials, and challenges

“…Furthermore, in addition to the chemopreventive effects of phytosterols (Salehi et al, 2021), a number of studies have shown that some phytosterols (Qi et al, 2013) and oxidized phytosterols (oxyphytosterols) (Hovenkamp et al, 2008;Koschutnig et al, 2009) are cytotoxic to cancerous and normal cells. β-Sitosterol has shown apoptosis in HAAE-2 (human abdominal aorta endothelial cells), inducing caspase-3 activity in the cells that corresponded the DNA fragmentation analysis in a terminal uridine deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) study (Rubis et al, 2008). On the other hand, since cholesterol metabolism is deregulated in these tumors, potentially toxic cholesterol analogues and phytosterol derivatives, and LXRs (Liver X Receptors) might be beneficial in metabolic treatments to suppress glioblastoma tumorigenicity, which can lead to glioblastoma cell death (Ahmad et al, 2019;Sassi et al, 2021).…”

Sesquiterpene lactones as emerging biomolecules to cease cancer by targeting apoptosis

“…Cynaropicrin exerts this effect on U-87 MG through inducing intracellular ROS generation, reducing MM, and promoting the release of cytochrome C into the cytoplasm of these cancer cells. It also led to the activation of caspase 3 and caspase 9, suggesting the involvement of the mitochondrial pathway of apoptosis in cynaropicrin effects on U-87 MG cells ( Rotondo et al, 2022 ). Liu T. et al (2019) conducted a study to evaluate the effect of cynaropicrin on the Hela human cervical cancer cell line.…”