Differential effects of Bcl-2 and caspases on mitochondrial permeabilization during endogenous or exogenous reactive oxygen species-induced cell death

Abstract

In this study, we have compared several features of cell death triggered by classical inducers of apoptotic pathways (etoposide and tumour necrosis factor (TNF)-α) versus exogenous reactive oxygen species (ROS; hydrogen peroxide (H₂O₂), tert-butyl hydroperoxide (t-BHP)) or a ROS generator (paraquat). Our aim was to characterize relationships that exist between ROS, mitochondrial perturbations, Bcl-2 and caspases, depending on source and identity of ROS. First, we have found that these five inducers trigger oxidative stress, mitochondrial membrane permeabilization (MMP), cytochrome c (cyt c) release from mitochondria and cell death. In each case, cell death could be inhibited by several antioxidants, showing that it is primarily ROS dependent. Second, we have highlighted that during etoposide or TNF-α treatments, intracellular ROS level, MMP and cell death are all regulated by caspases and Bcl-2, with caspases acting early in the process. Third, we have demonstrated that H₂O₂-induced cell death shares many of these characteristics with etoposide and TNF-α, whereas t-BHP induces both caspase-dependent and caspase-independent cell death. Surprisingly, paraquat-induced cell death, which harbours some characteristics of apoptosis such as cyt c release and caspase-3 activation, is not modulated by Bcl-2 and caspase inhibitors, suggesting that paraquat also triggers non-apoptotic cell death signals. On the one hand, these results show that endogenous or exogenous ROS can trigger multiple cell death pathways with Bcl-2 and caspases acting differentially. On the other hand, they suggest that H₂O₂ could be an important mediator of etoposide and TNF-α-dependent cell death since these inducers trigger similar phenotypes.

Protective effect of geranylgeranylacetone against hydrogen peroxide-induced oxidative stress in human neuroblastoma cells

“…These results suggest that GGA might also act on the intrinsic pathway by regulating apoptotic proteins. In addition, ROS production is induced by TNF-α signaling [18] and suppressed by Bcl-2 [19]. In our study, GGA decreased H 2 O 2 -induced ROS generation, suggesting that GGA can perform a protective role in H 2 O 2 -treated SH-SY5Y cells via both extrinsic and intrinsic pathways of apoptosis.…”

Esculetin Neutralises Cytotoxicity oft-BHP but Not of H2O2on Human Leukaemia NB4 Cells

“…Their antioxidant properties with the ability to inhibit lipid peroxidation and to act as ROS scavengers [13, 14] seem to be related to the position and number of hydroxyl groups. Thus esculetin (6,7-dihydroxycoumarin) shows higher antioxidant activity than other coumarins [14].…”

“…Both oxidants, t -BHP and H 2 O 2 , increased ROS in NB4 cells via different mechanisms. t -BHP is a short chain analogue of lipid hydroperoxides, similar to peroxidised fatty acids whereas H 2 O 2 is also generated under oxidative stress conditions modulating fundamental intracellular processes [13]. Therefore, the objective of the current study was to analyze the effect of esculetin acting simultaneously with such oxidants and to observe the early events in the mechanism of esculetin-induced apoptosis.…”

Investigação da atividade apoptótica na abertura luminal dos ductos das glândulas salivares: análise comparativa entre modelo animal e humano

“…intracelular. Além do fator de necrose tumoral, diversas moléculas são capazes de induzir a ativação dessa mesma via, como espécies reativas de oxigênio e peróxido de hidrogênio, porém cada ligante desencadeia eventos moleculares diferentes (Rincheval et al, 2012). Desse modo, a partir do reconhecimento de um ligante específico, ocorre a formação de um complexo de sinalização de morte (deathinducing signaling complex) formado pelos domínios de morte FADD ou MORT-1 e/ou TRADD com outros componentes.…”

“…Atua principalmente através de alterações mitocondriais estimuladas por sinais de estresse intracelular como danos no DNA, hipóxia, ativação de oncogenes e deprivação de fatores de crescimento. A mitocôndria é a organela de ação central dessa via, por meio de modificações estruturais e funcionais, agindo através da liberação de diversas moléculas pró-apoptóticas presentes em seu interior para o citoplasma e por isso é também denominada via mitocondrial (Elmore, 2007;Tait;Rincheval et al, 2012). Além disso, a indução do colapso do potencial de membrana mitocondrial interna e a transição da sua permeabilidade, importantes para a ruptura da organela, também levam à perda da hemostasia celular, ocasionando a interrupção da síntese de ATP e o aumento de espécies reativas de oxigênio (EROS -induzem a ativação de caspases -9 e -3).…”