Mitochondrial Antioxidants Alleviate Oxidative and Nitrosative Stress in a Cellular Model of Sepsis

Mitochondrial dysfunction plays a key role in sepsis. We used a sepsis model of human endothelial cells (HUVEC) to study mitochondrial function during normoxic (21% O-2) and hypoxic (1% O-2) conditions. When stimulated with a LPS cocktail, HUVEC displayed an increase of nitric oxide (NO) in normoxic and hipoxic conditions, being higher at 21% O-2. LPS-activation for 24 h at 1% O-2 increased ROS production, which was reversed with the mitochondrial antioxidant Mitoquinone (MQ) and Glutathione Ethyl Ester (GEE). Activated cells displayed diminished mitochondrial O-2 consumption with specific inhibition of Complex I, accompanied by increase in tyrosine nitration and Type II NOS protein expression, effects which were recovered by antioxidants and/or with L-NAME. These parameters varied with O-2 environment, namely inhibition of respiration observed in both O-2 environments at 24 h was very similar, whereas O-2 consumption rate fell earlier in 1% O-2-exposed cells. While no significant differences were detected at earlier time points, at 24 h tyrosine nitration was higher in normoxic vs. hypoxic cells. Mitochondria are heavily implicated in sepsis. Mitochondrial antioxidants provide a mechanistic model for the development of potential therapies.