2-Methyl 2-butanol suppresses human retinoblastoma cells through cell cycle arrest and autophagy

2-Methyl-2-butanol (MBT) is a chemical compound from the group of alcohols more specifically pentanols, which has shown an excellent anti-cancer activity in our previous study. However, its mechanism of action remains unclear. The present study was designed to investigate the anti-cancer effect of MBT on human retinoblastoma cells. The results showed that the use of MBT leads to HXO-RB44 cell death but is cytotoxic to normal cells at higher concentrations. It showed a dose- as well as a time-dependent inhibition of HXO-RB44 cells. P27 is a cell cycle inhibitory protein, which plays an important role in cell cycle regulation whereas cyclin-B1 is a regulatory protein involved in mitosis. MBT increased the cell cycle arrest in a dose-dependent manner by augmenting p27 and reducing cyclin B1 expression. Moreover, it also accelerated apoptosis, increased light chain-3 (LC-3) conversion in a dose-dependent manner, and helped to debulk cancerous cells. LC3 is a soluble protein, which helps to engulf cytoplasmic components, including cytosolic proteins and organelles during autophagy from autophagosomes. In order to verify the effect of MBT, bafilomycin A1, an autophagy inhibitor, was used to block the MTB-induced apoptosis and necrosis. Additionally, a specific Akt agonist, SC-79, reversed the MBT-induced cell cycle arrest and autophagy. Thus, from the present study, it was concluded that MBT induced cell cycle arrest, apoptosis and autophagy through the PI3K/Akt pathway in HXO-RB44 cells.

Apoptotic activity of isoespintanol derivatives in human polymorphonuclear cells / Actividad apoptótica de derivados semisintéticos del isopentanol en células polimorfonucleares humanas

Background: Inflammation is a complex physiopathologic response to different stimuli. Recently, some pharmacological strategies have been proposed that could be used for resolution of inflammation by enhancing apoptosis of inflammatory cells. Objectives: To study in vitro apoptotic activity of isoespintanol [ISO] and of two semi-synthetic derivatives, bromide isoespintanol [BrI] and demethylated isoespintanol [DMI], in human polymorphonuclear (PMN) cells. Methods: PMN were exposed to the different concentrations of ISO, BrI and DMI for 30 min in phosphate-buffered saline pH 7.4 containing 1 mg/mL glucose, 0.4 mM Mg2+, and 1.20 mM Ca2+. Viability was assessed by dimethylthiazol diphenyl tetrazolium bromide (MTT). To distinguish between the two modes of cell death, apoptosis and necrosis, we examined differences in morphological and biochemical changes of cells stained with annexin V- FITC (An) and/or propidium iodide (PI) using two different assays based on flow cytometry Results: The MTT assay revealed the ability of cells to reduce MTT salt to formazan. In the presence of BrI and DMI a significant concentration-dependent decrease of cell viability was observed. The annexin V- FITC binding assay showed a high proportion of apoptotic cells for those treated with BrI (An+/ PI- : 62.3 ± 8.2% vs. 2.1 ± 0.5% of control, P<0.05). The population of PMN treated with DMI produced the highest percentage (An+/IP+: 43.4 ± 5.2 % vs. 0.4 ± 0.3 % of control, P<0.05) of necrotic cells. Apoptotic nuclei were analyzed by PI staining. The cell population in the sub G0/G1 region represents cells with hypodiploidal DNA, an indicator of apoptosis. When cells were incubated with 50 and 100 µM of BrI, the cell population in the sub G0/G1 region increased, suggesting a dose-dependent increase in the population of apoptotic cells. The presence of the pan-inhibitor of caspases (Z-VAD-fmk) showed a significant reduction in cell population in the sub G0/G1 region, indicating less degradation of DNA. Conclusions: Bromide isoespintanol [BrI] induces an apoptotic process in PMN, mediated ­at least in part­ by activation of caspases, although this compound may probably act through other caspase-independent mechanisms as well.

Antecedentes: La inflamación es una respuesta fisiopatológica compleja generada por diferentes estímulos. Recientemente, se han propuesto nuevas estrategias farmacológicas que podrían ser utilizadas para conducir a la resolución de la inflamación mediante el aumento de la apoptosis de células inflamatorias. Objetivo: Estudiar la actividad apoptótica in vitro del isopentanol [ISO] y dos derivados semisintéticos ­bromuro de isoespintanol [BrI] e isoespintanol desmetilado [DMI] ­ en células polimorfonucleares humanas (PMN). Métodos: Las PMN fueron expuestas a diferentes concentraciones de los compuestos durante 30 min en una disolución salina tamponada con fosfato (pH 7,4). La viabilidad celular se evaluó utilizando el ensayo de 3-[4,5-dimetil-tiazol-2-il]-2,5-difenil tetrazolio (MTT). Para distinguir entre los dos modos de muerte celular, la apoptosis y la necrosis, se examinaron las diferencias en los cambios morfológicos y bioquímicos de las células teñidas con anexina V (An) y/o yoduro de propidio (PI) usando dos técnicas de citometría de flujo. Resultados: Mediante el ensayo con MTT, se demostró que los compuestos BrI y DMI disminuyeron significativamente y de manera concentración-dependiente la viabilidad celular. El ensayo de unión con la anexina V-FITC mostró una alta proporción de células apoptóticas en las células tratadas con BrI (An+/PI- : 62,3 ± 8,2% versus 2,1 ± 0,5% del control, P<0,05). El análisis de núcleos apoptóticos se llevó a cabo a través de tinción con PI. La población de células en la región sub G0/G1 representa células con ADN hipodiploidal, que es un indicador de apoptosis. Cuando las células se incubaron con BrI, la población de células en la región sub G0/G1 aumentó, confirmando su mecanismo citotóxico. En presencia de un inhibidor de caspasas (Z-VAD-FMK), se observó una reducción significativa en la población celular en la región sub G0/G1, indicando una menor degradación del ADN. Conclusiones: El bromuro de isoespintanol [BrI], induce un proceso apoptótico en PMN que está mediado ­al menos en parte­ por la activación de las caspasas, aunque este compuesto probablemente podría actuar también a través de otros mecanismos independientes de las caspasas.