Mitochondrial dysfunction in sepsis: evidence from bacteraemic baboons and endotoxaemic rabbits

Mitochondria, that provide most of the ATP needed for cell work, and that play numerous specific functions in biosyntheses and degradations, as well as contributing to Ca2+ signaling, also play a key role in the pathway to cell death. Impairment of mitochondrial functions caused by mutations of mt-genome, and by acute processes, are responsible for numerous diseases. The involvement of impaired mitochondria in the pathogenesis of sepsis is discussed. By means of the skinned fiber technique and high resolution respirometry, we have detected significantly reduced rates of mitochondrial respiration in heart and skeletal muscle of endotoxaemic rabbits. Mitochondria from heart were more affected than those from skeletal muscle. Decreased respiration rates were accompanied by reduced activities of complex I + III of the respiratory chain. Endotoxin-caused impairment was also detectable at the level of the Langendorff perfused heart, where the coronary vascular resistance was significantly increased. For an investigation of the influence of bacteraemia on the mitochondrial respiratory chain, baboons were made septic by infusion of high and low amounts of E. coli. For complex I + III and II + III, a clear dose-dependent decrease was detectable and in animals which died in septic shock, a further decrease of enzyme activities in comparison to the controls were found. These results are discussed in the light of current knowledge on the role of mitochondria in cell pathology in respect to sepsis. In conclusion, we present evidence that mitochondrial function is disturbed during sepsis. Besides ischaemic and poison-induced disturbances of mitochondrial function, sepsis is a further example of an acute disease where impaired mitochondria have to be taken into account.