Bioenergetic failure of human peripheral blood monocytes in patients with septic shock is mediated by reduced F1Fo adenosine-5'-triphosphate synthase activity.

OBJECTIVE: Increasing evidence points to the role of mitochondrial dysfunction in the pathogenesis of sepsis. Previous data indicate that mitochondrial function is affected in monocytes from septic patients, but the underlying mechanisms and the impact of these changes on the patients' outcome are unknown. We aimed to determine the mechanisms involved in mitochondrial dysfunction in peripheral blood mononuclear cells from patients with septic shock. DESIGN: A cohort of patients with septic shock to study peripheral blood mononuclear cell mitochondrial respiration by high-resolution respirometry analyses and to compare with cells from control subjects. SETTING: Three intensive care units and an academic research laboratory. SUBJECTS: Twenty patients with septic shock and a control group composed of 18 postoperative patients without sepsis or shock. INTERVENTIONS: Ex vivo measurements of mitochondrial oxygen consumption were carried out in digitonin-permeabilized peripheral blood mononuclear cells from 20 patients with septic shock taken during the first 48 hrs after intensive care unit admission as well as in peripheral blood mononuclear cells from control subjects. Clinical parameters such as hospital outcome and sepsis severity were also analyzed and the relationship between these parameters and the oxygen consumption pattern was investigated. MEASUREMENTS AND MAIN RESULTS: We observed a significant reduction in the respiration specifically associated with adenosine-5'-triphosphate synthesis (state 3) compared with the control group (5.60 vs. 9.89 nmol O2/min/10(7) cells, respectively, p < .01). Reduction of state 3 respiration in patients with septic shock was seen with increased prevalence of organ failure (r = -0.46, p = .005). Nonsurviving patients with septic shock presented significantly lower adenosine diphosphate-stimulated respiration when compared with the control group (4.56 vs. 10.27 nmol O2/min/10(7) cells, respectively; p = .004). Finally, the presence of the functional F1Fo adenosine-5'-triphosphate synthase complex (0.51 vs. 1.00 ng oligo/mL/10(6) cells, p = .02), but not the adenine nucleotide translocator, was significantly lower in patients with septic shock compared with control cells. CONCLUSION: Mitochondrial dysfunction is present in immune cells from patients with septic shock and is characterized as a reduced respiration associated to adenosine-5'-triphosphate synthesis. The molecular basis of this phenotype involve a reduction of F1Fo adenosine-5'-triphosphate synthase activity, which may contribute to the energetic failure found in sepsis.

Sepsis induces brain mitochondrial dysfunction.

OBJECTIVE: Mitochondrial dysfunctions have been associated with the pathogenesis of sepsis. A systematic survey of mitochondrial function in brain tissues during sepsis is lacking. In the present work, we investigate brain mitochondrial function in a septic mouse model. DESIGN: Prospective animal study. SETTING: University research laboratory. SUBJECTS: Male Swiss mice, aged 6-8 wks. INTERVENTIONS: Mice were subjected to cecal ligation and perforation (sepsis group) with saline resuscitation or to sham operation (control group). MEASUREMENTS AND MAIN RESULTS: Oxygen consumption was measured polarographically in an oximeter. Brain homogenates from septic animals presented higher oxygen consumption in the absence of adenosine 5'-diphosphate (state 4) compared with control animals. The increase in state 4 respiration in animals in the cecal ligation and perforation group resulted in a drastic decrease in both respiratory control and adenosine 5'-diphosphate/oxygen ratios, indicating a reduction in the oxidative phosphorylation efficiency. Septic animals presented a significant increase in the recovery time of mitochondrial membrane potential on adenosine 5'-diphosphate addition compared with control animals, suggesting a proton leak through the inner mitochondrial membrane. The septic group presented a general reduction in the content of cytochromes. Moreover, the activity of cytochrome c oxidase was specifically and significantly decreased in the brain during sepsis. Hydrogen peroxide generation by brain mitochondria from septic mice did not respond to substrates of electron transport chain or to adenosine 5'-diphosphate, showing that mitochondrial function may be compromised in a critical level in the brain during sepsis. CONCLUSIONS: The mitochondrial dysfunctions demonstrated here indicate that uncoupling of oxidative phosphorylation takes place in the brain of septic mice, compromising tissue bioenergetic efficiency.