Sjoevall 2010 Crit Care

Sjoevall F, Morota S, Hansson Magnus J, Friberg H, Gnaiger E, Elmer E (2010) Temporal increase of platelet mitochondrial respiration is negatively associated with clinical outcome in patients with sepsis. Crit Care 14:R214.

» PMID: 21106065 Open Access

Sjoevall F, Morota S, Hansson Magnus J, Friberg H, Gnaiger Erich, Elmer E (2010) Crit Care

Abstract: Introduction Mitochondrial dysfunction has been suggested as a contributing factor to the pathogenesis of sepsis-induced multiple organ failure. Also, restoration of mitochondrial function, known as mitochondrial biogenesis, has been implicated as a key factor for the recovery of organ function in patients with sepsis. Here we investigated temporal changes in platelet mitochondrial respiratory function in patients with sepsis during the first week after disease onset.

Methods Platelets were isolated from blood samples taken from 18 patients with severe sepsis or septic shock within 48 hours of their admission to the intensive care unit. Subsequent samples were taken on day 3 to 4 and day 6 to 7. Eighteen healthy blood donors served as controls. Platelet mitochondrial function was analyzed by high-resolution respirometry. Endogenous respiration of viable, intact platelets suspended in their own plasma or PBS glucose was determined. Further, in order to investigate the role of different dehydrogenases and respiratory complexes as well as to evaluate maximal respiratory activity of the mitochondria, platelets were permeabilized and stimulated with complex-specific substrates and inhibitors.

Results Platelets suspended in their own septic plasma exhibited increased basal non-phosphorylating respiration (state 4) compared to controls and to platelets suspended in PBS glucose. In parallel, there was a substantial increase in respiratory capacity of the Electron transfer-pathway from day 1 to 2 to day 6 to 7 as well as compared to controls in both intact and permeabilized platelets oxidizing Complex I and/or II-linked substrates. No inhibition of respiratory complexes was detected in septic patients compared to controls. Non-survivors, at 90 days, had a more elevated respiratory capacity at day 6 to 7 as compared to survivors. Cytochrome c increased over the time interval studied but no change in mitochondrial DNA was detected.

Conclusions The results indicate the presence of a soluble plasma factor in the initial stage of sepsis inducing uncoupling of platelet mitochondria without inhibition of the Electron transfer-pathway. The mitochondrial uncoupling was paralleled by a gradual and substantial increase in respiratory capacity. This may reflect a compensatory response to severe sepsis or septic shock, that was most pronounced in non-survivors, likely correlating to the severity of the septic insult. • Keywords: Sepsis

• O2k-Network Lab: SE Lund Elmer E, AT Innsbruck Gnaiger E

Coupling control and the Q-junction

Mitochondrial coupling control states are measured without simultaneous change of a selected pathway control state, i.e. coupling control is separated from pathway control. Biochemical coupling efficiencies (E-L coupling efficiencies) and P-L coupling efficiencies are, therefore, studied at a defined pathway control state that must not change between measurement of LEAK respiration L, OXPHOS capacity P, and electron transfer capacity E.

A physiologically relevant pathway control state for partial reconstitution of TCA cycle function is obtained by supply of NADH-linked substrates (e.g. pyruvate&malate PM; N-pathway) in combination with succinate (S; S-pathway), supporting convergent electron transfer through Complexes I and II into the Q-junction (NS-pathway). OXPHOS- and ET-capacities are higher in the combined NS-pathway than in the separate N- or S-pathway (Gnaiger 2020). Is the NS-pathway control state appropriate for the analysis of coupling control?

Partial additivity in OXPHOS capacity NS_P or ET capacity NS_E implies that there is competition between the N- and S-pathway, when the NS-pathway capacity is less than the arithmetic sum of the constituent pathway capacities. In mitochondria with lower OXPHOS than ET capacity (P<E; when the phosphorylation system is limiting), the competition in NS_E is increasingly pronounced in NS_P, and when respiration is further reduced by complete inhibition of the phosphorylation system (e.g. by oligomycin), competition between the N- and S-pathways is maximal in LEAK respiration. Different levels of competition imply that the ratio of the effective N- and S-pathway in the NS-pathway state may shift to the extent that the dominant pathway may fully outcompete the other in the LEAK state. Convergent electron input into the Q-junction in NS_E, therefore, may shift to single electron input through either the dominant N- or S-pathway in NS_L, which then would effectively correspond to either N_L or S_L. This has deep implications on LEAK respiration, since the N-pathway has three coupling sites (H⁺ pumps: CI, CIII, CIV) with a correspondingly higher H⁺/O₂ ratio compared to the S-pathway with two coupling sites (H⁺ pumps: CIII, CIV). A higher rate of the proton leak is implied when measuring the same rate of LEAK respiration in N_L than when observing an identical oxygen consumption rate in S_L.

When inhibiting O₂ consumption by oligomycin in the NS-pathway state, the relative contribution of the N- and S-pathways to LEAK respiration is not known. By subsequent uncoupler titrations, the relative contribution of these pathways is likely to change, thus obtaining an undefined combination of pathway control and coupling control. In conclusion, the NS-pathway state is not appropriate for studying coupling control. Coupling control is best studied in the separate N- or S-pathway (Gnaiger et al 2000; 2015).

Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002
Gnaiger E, Boushel R, Søndergaard H, Munch-Andersen T, Damsgaard R, Hagen C, Díez-Sánchez C, Ara I, Wright-Paradis C, Schrauwen P, Hesselink M, Calbet JAL, Christiansen M, Helge JW, Saltin B (2015) Mitochondrial coupling and capacity of oxidative phosphorylation in skeletal muscle of Inuit and caucasians in the arctic winter. https://doi.org/10.1111/sms.12612
Gnaiger E, Méndez G, Hand SC (2000) High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc Natl Acad Sci U S A 97:11080-5. https://doi.org/10.1073/pnas.97.20.11080

Cited by

50 articles in PubMed (2021-12-27) https://pubmed.ncbi.nlm.nih.gov/21106065/

O2k-Publications

Labels: MiParea: Respiration, mt-Biogenesis;mt-density, mt-Medicine, Patients Pathology: Sepsis

Organism: Human Tissue;cell: Blood cells, Platelet Preparation: Permeabilized cells, Intact cells Enzyme: Marker enzyme

Coupling state: LEAK, ROUTINE, OXPHOS, ET Pathway: N, S, NS, ROX HRR: Oxygraph-2k, TIP2k

JP, SE, MitoEAGLE blood cells data, MitoFit 2021 PLT