Novel nitric oxide-donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide (GIT-27NO) induces p53 mediated apoptosis in human A375 melanoma cells.

In this study we evaluated the effects of the new NO donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide (GIT-27NO) on the A375 human melanoma cell line. Treatment with the drug led to concentration-dependent reduction of mitochondrial respiration and number of viable cells in cultures. Decreased cell viability correlated with release and internalization of NO and was neutralized by the extracellular scavenger hemoglobin. GIT-27NO neither influenced cell division nor induced accidental or autophagic cell death. Early signs of apoptosis were observed upon coculture with the drug, and resulting in marked accumulation of hypodiploid cells, suggesting that the induction of apoptosis is one primary mode of action of the compound in A375 cells. GIT-27NO significantly inhibited the expression of the transcription repressor and apoptotic resistant factor YY1 and, in parallel, augmented the presence of total p53. The capacity of GIT-27NO to induce p53-mediated apoptosis along with inhibition of YY1 repressor in A375 melanoma cells indicates that GIT-27NO possesses an important anti-cancer pharmacological profile. The findings suggest the potential therapeutic use of GIT-27NO in the clinical setting.

Antiglioma action of xanthones from Gentiana kochiana: Mechanistic and structure-activity requirements.

The present study identifies xanthones gentiakochianin and gentiacaulein as the active principles responsible for the in vitro antiglioma action of ether and methanolic extracts of the plant Gentiana kochiana. Gentiakochianin and gentiacaulein induced cell cycle arrest in G(2)/M and G(0)/G(1) phases, respectively, in both C6 rat glioma and U251 human glioma cell lines. The more efficient antiproliferative action of gentiakochianin was associated with its ability to induce microtubule stabilization in a cell-free assay. Both the xanthones reduced mitochondrial membrane potential and increased the production of reactive oxygen species in glioma cells, but only the effects of gentiakochianin were pronounced enough to cause caspase activation and subsequent apoptotic cell death. The assessment of structure-activity relationship in a series of structurally related xanthones from G. kochiana and Gentianella austriaca revealed dihydroxylation at positions 7, 8 of the xanthonic nucleus as the key structural feature responsible for the ability of gentiakochianin to induce microtubule-associated G(2)/M cell block and apoptotic cell death in glioma cells.

Synergistic antiglioma action of hyperthermia and nitric oxide.

To explore combined antiglioma effect of nitric oxide (NO) and hyperthermia, the rat C6 and human U251 glioma cells were exposed to NO-releasing agents sodium nitroprusside(SNP), S-nitrosoglutathione or PAPA-NONOate, followed by hyperthermia (1 h, 43 degrees C). While each treatment alone showed only moderate efficiency, a synergistic cytotoxicity of NO donors and hyperthermia was clearly demonstrated by crystal violet and MTT cytotoxicity assays. The flow cytometric analysis with the appropriate reporter fluorochromes confirmed that hyperthermia and SNP cooperated in inducing oxidative stress, mitochondrial depolarization, caspase activation and DNA fragmentation, leading to both necrotic and caspase-dependent apoptotic cell death. The acridine orange staining of intracellular acidic compartments revealed that SNP completely blocked hyperthermia-induced autophagy, while the inhibition of autophagy by 3-methyl adenine mimicked SNP-triggered oxidative stress, caspase activation and cell death in hyperthermia-exposed cells. Therefore, the synergistic cytotoxicity of SNP and hyperthermia could result from NO-mediated suppression of protective autophagic response in glioma cells.