Production of reactive oxygen species in mitochondria of HeLa cells under oxidative stress

Abstract

Mitochondria can be a source of reactive oxygen species (ROS) and a target of oxidative damage during oxidative stress. In this connection, the effect of photodynamic treatment (PDT) with Mitotracker Red (MR) as a mitochondria-targeted photosensitizer has been studied in HeLa cells. It is shown that MR produces both singlet oxygen and superoxide anion upon photoactivation and causes photoinactivation of gramicidin channels in a model system (planar lipid bilayer). Mitochondria-targeted antioxidant (MitoQ) inhibits this effect. In living cells, MR-mediated PDT initiates a delayed ("dark") accumulation of ROS, which is accelerated by inhibitors of the respiratory chain (piericidin, rotenone and myxothiazol) and inhibited by MitoQ and diphenyleneiodonium (an inhibitor of flavin enzymes), indicating that flavin of Complex I is involved in the ROS production. PDT causes necrosis that is prevented by MitoQ. Treatment of the cell with hydrogen peroxide causes accumulation of ROS, and the effects of inhibitors and MitoQ are similar to that described for the PDT model. Apoptosis caused by H2O2 is augmented by the inhibitors of respiration and suppressed by MitoQ. It is concluded that the initial segments of the respiratory chain can be an important source of ROS, which are targeted to mitochondria, determining the fate of the cell subjected to oxidative stress.

The lipid peroxidation product 4-hydroxy-2-nonenal induces tissue factor decryption via ROS generation and the thioredoxin system

“…This could reflect the diffusion of ROS from mitochondria to other compartments or ROS-induced ROS generation. 27,28 To delineate the role of the mitochondrial electron transport chain in HNE-induced ROS generation and TF decryption, cells were pretreated with specific inhibitors of electron transport chain complexes. As shown in Figure 1B, the inhibitors of complex I, II, and IV (ie, rotenone, THF, and sodium azide, respectively) did not inhibit HNE-induced ROS generation.…”

Oxidative Stress Enzymes Are Required for DAF-16-Mediated Immunity Due to Generation of Reactive Oxygen Species byCaenorhabditis elegans

“…Although our model envisions extracellular production of ROS, certain species, such as hydrogen peroxide, can diffuse through membranes and cause intracellular damage. Also, it has recently been shown that extracellular oxidative stress increases ROS production in the mitochondria of HeLa cells (Chernyak et al 2006). However, an alternative explanation for CTL-2's and SOD-3's protective effects is that there is an increase only in intracellular ROS production.…”

Increased Resistance of Complex I Mutants to Phytosphingosine-induced Programmed Cell Death

“…Interestingly, the response of the different mutant strains to H 2 O 2 mirrored their response to PHS in terms of sensitivity. Hydrogen peroxide can cause oxidative stress and cell death since it easily permeates through cellular membranes (55) and it induces the production of more ROS (41). We reasoned that ROS production/removal could be a key factor in PHSinduced cell death and explain why different strains display different responses to the drug.…”