[Show abstract][Hide abstract] ABSTRACT: Objectives Exposure to high altitudes is associated with oxidative cellular damage due to the increased level of reactive oxygen and nitrogen species and altered activity of antioxidant systems. Subjects were submitted to prolonged hypoxia, to evaluate changes in mitochondrial enzyme activities of monocytes and their attenuation by supplementation with antioxidants. Methods Twelve subjects were randomly assigned to receive antioxidant supplements or placebo prior to and during an expedition to Pik Lenin (7145 m). Monocytes were isolated from blood samples to determine the activity of mitochondrial enzymes cytochrome c oxidase and citrate synthase at 490 m (baseline) and at the altitudes of 3550 m, 4590 m, and 5530 m. Results An increase in citrate synthase activity at all altitudes levels was observed. Hypoxia induced an increase in the activity of cytochrome c oxidase only at 4590 m. Neither citrate synthase activity nor cytochrome c oxidase activity differed between the subjects receiving antioxidant supplements and those receiving placebo. Conclusions Hypoxia leads to an increase in citrate synthase activity of monocyte mitochondria as a marker of mitochondrial mass, which is not modified by antioxidant supplementation. The increase in mitochondrial mass may represent a compensatory mechanism to preserve oxidative phosphorylation of monocytes at high altitudes.
Full-text · Article · Apr 2015 · Redox report: communications in free radical research
[Show abstract][Hide abstract] ABSTRACT: Introduction:
Results on mitochondrial dysfunction in sepsis are controversial. We aimed to assess effects of LPS at wide dose and time ranges on hepatocytes and isolated skeletal muscle mitochondria.
Human hepatocellular carcinoma cells (HepG2) were exposed to placebo or LPS (0.1, 1, and 10 μg/mL) for 4, 8, 16, and 24 hours and primary human hepatocytes to 1 μg/mL LPS or placebo (4, 8, and 16 hours). Mitochondria from porcine skeletal muscle samples were exposed to increasing doses of LPS (0.1-100 μg/mg) for 2 and 4 hours. Respiration rates of intact and permeabilized cells and isolated mitochondria were measured by high-resolution respirometry.
In HepG2 cells, LPS reduced mitochondrial membrane potential and cellular ATP content but did not modify basal respiration. Stimulated complex II respiration was reduced time-dependently using 1 μg/mL LPS. In primary human hepatocytes, stimulated mitochondrial complex II respiration was reduced time-dependently using 1 μg/mL LPS. In isolated porcine skeletal muscle mitochondria, stimulated respiration decreased at high doses (50 and 100 μg/mL LPS).
LPS reduced cellular ATP content of HepG2 cells, most likely as a result of the induced decrease in membrane potential. LPS decreased cellular and isolated mitochondrial respiration in a time-dependent, dose-dependent and complex-dependent manner.
[Show abstract][Hide abstract] ABSTRACT: IntroductionSepsis-induced myopathy and critical illness myopathy (CIM) are possible causes of muscle weakness in intensive care patients. They have been attributed to muscle membrane dysfunction. The aim of this study was to investigate membrane properties in the early stage of experimental sepsis by evaluating muscle excitability.Methods
In total, 20 anesthetized and mechanically ventilated pigs were randomized to either faecal peritonitis (n¿=¿10) or to non-septic controls (n¿=¿10). Resuscitation with fluids and vasoactive drugs was started 3 hours after peritonitis induction. Muscle membrane properties were investigated by measuring muscle velocity recovery cycles before induction of peritonitis as well as 6, 18 and 27 hours thereafter. Muscle relative refractory period (MRRP) and early supernormality (ESN) were assessed.ResultsPeritonitis lasting 27 hours was associated with an increase of MRRP by 28% from 2.38¿±¿0.18 ms (mean¿±¿SD) to 3.47¿±¿1.79 ms (P <0.01) and a decrease of ESN by 31% from 9.64¿±¿2.82% to 6.50¿±¿2.64% (P <0.01). ESN reduction was already apparent 6 hours after induction of peritonitis. Values in controls did not show any significant alterations.Conclusions
Muscle membrane abnormalities consistent with membrane depolarization and/or sodium channel inactivation occurred within 6 hours of peritonitis induction. This indicates that changes that have been described in established sepsis-induced myopathy and/or CIM start early in the course of sepsis. Muscle excitability testing facilitates evaluation of the time course of these changes.
Full-text · Article · Aug 2014 · Critical care (London, England)
[Show abstract][Hide abstract] ABSTRACT: Acute reduction of portal vein blood flow (Qpv) increases hepatic arterial perfusion (Qha) [the hepatic arterial buffer response (HABR)]. Angiotensin II (AT-II) reduces Qpv but its effect on HABR is not known. We explored interactions of AT-II and enalapril with hepatic blood flow regulation. 20 healthy anesthetized pigs were randomized to receive AT-II (n=8) from 5 to 61 ng/kg/min, enalapril (n=8) from 3 to 24μg/kg/h, or saline (n=4). HABR was assessed by occluding portal vein and expressed as 1) ratio between changes in Qha and Qpv, 2) hepatic arterial conductance (Cha). AT-II infusion increased mean arterial blood pressure from 74 (66-77) mmHg to 116 (109-130) mmHg (median, IQR; p<0.0001),and decreased cardiac output, Qpv, and renal artery flow (-24%, -28% and -45%, respectively).The fraction of cardiac output of Qha, carotid, and femoral flows increased. With enalapril, blood pressure decreased, while cardiac output was maintained with flow redistribution favoring hepatic and renal arteries. In AT-II group, dQha/dQpv increased from 0.06 (0.03, 0.17) to 0.24 (0.13, 0.31) (p=0.002), but Cha during acute portal vein occlusion decreased from 4.3 (1.6, 6.6) to 2.9 (1.2, 3.7) ml/mmHg (p=0.003). Both variables remained unchanged in the enalapril group and in controls. AT-II infusion reduces portal flow in parallel with cardiac output and induces a dose-dependent redistribution of flow favoring brain, hepatic artery and peripheral tissues at the expense of renal perfusion. During HABR, AT-II decreases Cha, but increases Qha compensation, likely as result of increased hepatic arterial perfusion pressure. Enalapril had no effect on HABR.
No preview · Article · Jul 2014 · AJP Gastrointestinal and Liver Physiology
[Show abstract][Hide abstract] ABSTRACT: To compare effects of norepinephrine and angiotensin II in experimental sepsis on hemodynamics, organ function, and mitochondrial respiration.
Randomized, controlled, study.
University experimental laboratory.
Twenty-eight anesthetized, mechanically ventilated pigs.
Sixteen pigs were randomized to receive after 12 hours of fecal peritonitis fluid resuscitation and either norepinephrine (group NE; n = 8) or angiotensin II (group AT-II; n = 8) for 48 hours. A separate group (n = 8), treated with enalapril for 1 week before peritonitis and until study end, received fluids and norepinephrine (group E). The blood pressure dose-response to angiotensin II was evaluated in additional four nonseptic pigs.
Blood pressure target (75-85 mm Hg) was reached in both NE and AT-II, and cardiac output increased similarly (NE: from 64 mL/kg/min [60-79 mL/kg/min] to 139 mL/kg/min [126-157 mL/kg/min]; AT-II from 79 mL/kg/min [65-86 mL/kg/min] to 145 mL/kg/min [126-147 mL/kg/min]; median, interquartile range). Renal plasma flow, prevalence of acute kidney injury, inflammation and coagulation patterns, and mitochondrial respiration did not differ between NE and AT-II. In group E, blood pressure targets were not achieved (mean arterial pressure at study end: NE: 81 mm Hg [76-85 mm Hg]; AT-II: 80 mm Hg [77-84 mm Hg]; E: 53 mm Hg [49-66 mm Hg], p = 0.002, compared to NE), whereas skeletal muscle adenosine triphosphate concentrations were increased. During resuscitation one animal died in groups AT-II and E.
Angiotensin II reversed sepsis-induced hypotension with systemic and regional hemodynamic effects similar to those of norepinephrine. Inhibition of angiotensin-converting enzyme before sepsis worsened the hypotension but enhanced skeletal muscle adenosine triphosphate. Modifying the renin-angiotensin system in sepsis should be further evaluated.
Full-text · Article · May 2014 · Critical care medicine
[Show abstract][Hide abstract] ABSTRACT: Background:
Changes in hepatosplanchnic lactate exchange are likely to contribute to hyperlactatemia in sepsis. We hypothesized that septic and cardiogenic shock have different effects on hepatosplanchnic lactate exchange and its contribution to hyperlactatemia.
Materials and methods:
24 anesthetized pigs were randomized to fecal peritonitis (P), cardiac tamponade (CT), and to controls (n = 8 per group). Oxygen transport and lactate exchange were calculated during 24 hours.
While hepatic lactate influx increased in P and in CT, hepatic lactate uptake remained unchanged in P and decreased in CT. Hepatic lactate efflux contributed 20% (P) and 33% (CT), respectively, to whole body venous efflux. Despite maintained hepatic arterial blood flow, hepatic oxygen extraction did not increase in CT.
Whole body venous lactate efflux is of similar magnitude in hyperdynamic sepsis and in cardiogenic shock. Although jejunal mucosal pCO2 gradients are increased, enhanced lactate production from other tissues is more relevant to the increased arterial lactate. Nevertheless, the liver fails to increase hepatic lactate extraction in response to rising hepatic lactate influx, despite maintained hepatic oxygen consumption. In cardiac tamponade, regional, extrasplanchnic lactate production is accompanied by hepatic failure to increase oxygen extraction and net hepatic lactate output, despite maintained hepatic arterial perfusion.
[Show abstract][Hide abstract] ABSTRACT: The circulating, endocrine renin-angiotensin system (RAS) is important to circulatory homeostasis, while ubiquitous tissue and cellular RAS play diverse roles, including metabolic regulation. Indeed, inhibition of RAS is associated with improved cellular oxidative capacity. Recently it has been suggested that an intra-mitochondrial RAS directly impacts on metabolism. Here we sought to rigorously explore this hypothesis. Radiolabelled ligand-binding and unbiased proteomic approaches were applied to purified mitochondrial sub-fractions from rat liver, and the impact of AngII on mitochondrial function assessed. Whilst high-affinity AngII binding sites were found in the mitochondria-associated membrane (MAM) fraction, no RAS components could be detected in purified mitochondria. Moreover, AngII had no effect on the function of isolated mitochondria at physiologically relevant concentrations. We thus found no evidence of endogenous mitochondrial AngII production, and conclude that the effects of AngII on cellular energy metabolism are not mediated through its direct binding to mitochondrial targets.
Full-text · Article · Aug 2013 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: Background:
The relevance of mitochondrial dysfunction as to pathogenesis of multiple organ dysfunction and failure in sepsis is controversial. This focused review evaluates the evidence for impaired mitochondrial function in sepsis.
Review of original studies in experimental sepsis animal models and clinical studies on mitochondrial function in sepsis. In vitro studies solely on cells and tissues were excluded. PubMed was searched for articles published between 1964 and July 2012.
Data from animal experiments (rodents and pigs) and from clinical studies of septic critically ill patients and human volunteers were included. A clear pattern of sepsis-related changes in mitochondrial function is missing in all species. The wide range of sepsis models, length of experiments, presence or absence of fluid resuscitation and methods to measure mitochondrial function may contribute to the contradictory findings. A consistent finding was the high variability of mitochondrial function also in control conditions and between organs.
Mitochondrial function in sepsis is highly variable, organ specific and changes over the course of sepsis. Patients who will die from sepsis may be more affected than survivors. Nevertheless, the current data from mostly young and otherwise healthy animals does not support the view that mitochondrial dysfunction is the general denominator for multiple organ failure in severe sepsis and septic shock. Whether this is true if underlying comorbidities are present, especially in older patients, should be addressed in further studies.
Full-text · Article · Feb 2013 · European Journal of Clinical Investigation
[Show abstract][Hide abstract] ABSTRACT: Introduction
The objective of this study was to evaluate the effects of two different mean arterial blood pressure (MAP) targets on needs for resuscitation, organ dysfunction, mitochondrial respiration and inflammatory response in a long-term model of fecal peritonitis.
Twenty-four anesthetized and mechanically ventilated pigs were randomly assigned (n = 8/group) to a septic control group (septic-CG) without resuscitation until death or one of two groups with resuscitation performed after 12 hours of untreated sepsis for 48 hours, targeting MAP 50-60 mmHg (low-MAP) or 75-85 mmHg (high-MAP).
MAP at the end of resuscitation was 56 ± 13 mmHg (mean ± SD) and 76 ± 17 mmHg respectively, for low-MAP and high-MAP groups. One animal each in high- and low-MAP groups, and all animals in septic-CG died (median survival time: 21.8 hours, inter-quartile range: 16.3-27.5 hours). Norepinephrine was administered to all animals of the high-MAP group (0.38 (0.21-0.56) mcg/kg/min), and to three animals of the low-MAP group (0.00 (0.00-0.25) mcg/kg/min; P = 0.009). The high-MAP group had a more positive fluid balance (3.3 ± 1.0 mL/kg/h vs. 2.3 ± 0.7 mL/kg/h; P = 0.001). Inflammatory markers, skeletal muscle ATP content and hemodynamics other than MAP did not differ between low- and high-MAP groups. The incidence of acute kidney injury (AKI) after 12 hours of untreated sepsis was, respectively for low- and high-MAP groups, 50% (4/8) and 38% (3/8), and in the end of the study 57% (4/7) and 0% (P = 0.026). In septic-CG, maximal isolated skeletal muscle mitochondrial Complex I, State 3 respiration increased from 1357 ± 149 pmol/s/mg to 1822 ± 385 pmol/s/mg, (P = 0.020). In high- and low-MAP groups, permeabilized skeletal muscle fibers Complex IV-state 3 respiration increased during resuscitation (P = 0.003).
The MAP targets during resuscitation did not alter the inflammatory response, nor affected skeletal muscle ATP content and mitochondrial respiration. While targeting a lower MAP was associated with increased incidence of AKI, targeting a higher MAP resulted in increased net positive fluid balance and vasopressor load during resuscitation. The long-term effects of different MAP targets need to be evaluated in further studies.
Full-text · Article · Jan 2013 · Critical care (London, England)
[Show abstract][Hide abstract] ABSTRACT: During sepsis, liver dysfunction is common, and failure of mitochondria to effectively couple oxygen consumption with energy production has been described. In addition to sepsis, pharmacological agents used to treat septic patients may contribute to mitochondrial dysfunction. This study addressed the hypothesis that remifentanil interacts with hepatic mitochondrial oxygen consumption. The human hepatoma cell line HepG2 and their isolated mitochondria were exposed to remifentanil, with or without further exposure to tumor necrosis factor-α (TNF-α). Mitochondrial oxygen consumption was measured by high-resolution respirometry, Caspase-3 protein levels by Western blotting, and cytokine levels by ELISA. Inhibitory κBα (IκBα) phosphorylation, measurement of the cellular ATP content and mitochondrial membrane potential in intact cells were analysed using commercial ELISA kits. Maximal cellular respiration increased after one hour of incubation with remifentanil, and phosphorylation of IκBα occurred, denoting stimulation of nuclear factor κB (NF-κB). The effect on cellular respiration was not present at 2, 4, 8 or 16 hours of incubation. Remifentanil increased the isolated mitochondrial respiratory control ratio of complex-I-dependent respiration without interfering with maximal respiration. Preincubation with the opioid receptor antagonist naloxone prevented a remifentanil-induced increase in cellular respiration. Remifentanil at 10× higher concentrations than therapeutic reduced mitochondrial membrane potential and ATP content without uncoupling oxygen consumption and basal respiration levels. TNF-α exposure reduced respiration of complex-I, -II and -IV, an effect which was prevented by prior remifentanil incubation. Furthermore, prior remifentanil incubation prevented TNF-α-induced IL-6 release of HepG2 cells, and attenuated fragmentation of pro-caspase-3 into cleaved active caspase 3 (an early marker of apoptosis). Our data suggest that remifentanil increases cellular respiration of human hepatocytes and prevents TNF-α-induced mitochondrial dysfunction. The results were not explained by uncoupling of mitochondrial respiration.
[Show abstract][Hide abstract] ABSTRACT: : Early treatment in sepsis may improve outcome. The aim of this study was to evaluate how the delay in starting resuscitation influences the severity of sepsis and the treatment needed to achieve hemodynamic stability.
: Prospective, randomized, controlled experimental study.
: Experimental laboratory in a university hospital.
: Thirty-two anesthetized and mechanically ventilated pigs.
: Pigs were randomly assigned (n = 8 per group) to a nonseptic control group or one of three groups in which fecal peritonitis (peritoneal instillation of 2 g/kg autologous feces) was induced, and a 48-hr period of protocolized resuscitation started 6 (ΔT-6 hrs), 12 (ΔT-12 hrs), or 24 (ΔT-24 hrs) hrs later. The aim of this study was to evaluate the impact of delays in resuscitation on disease severity, need for resuscitation, and the development of sepsis-associated organ and mitochondrial dysfunction.
: Any delay in starting resuscitation was associated with progressive signs of hypovolemia and increased plasma levels of interleukin-6 and tumor necrosis factor-α prior to resuscitation. Delaying resuscitation increased cumulative net fluid balances (2.1 ± 0.5 mL/kg/hr, 2.8 ± 0.7 mL/kg/hr, and 3.2 ± 1.5 mL/kg/hr, respectively, for groups ΔT-6 hrs, ΔT-12 hrs, and ΔT-24 hrs; p < .01) and norepinephrine requirements during the 48-hr resuscitation protocol (0.02 ± 0.04 μg/kg/min, 0.06 ± 0.09 μg/kg/min, and 0.13 ± 0.15 µg/kg/min; p = .059), decreased maximal brain mitochondrial complex II respiration (p = .048), and tended to increase mortality (p = .08). Muscle tissue adenosine triphosphate decreased in all groups (p < .01), with lowest values at the end in groups ΔT-12 hrs and ΔT-24 hrs.
: Increasing the delay between sepsis initiation and resuscitation increases disease severity, need for resuscitation, and sepsis-associated brain mitochondrial dysfunction. Our results support the concept of a critical window of opportunity in sepsis resuscitation.
Full-text · Article · Aug 2012 · Critical care medicine
[Show abstract][Hide abstract] ABSTRACT: The relevance of tissue oxygenation in the pathogenesis of organ dysfunction during sepsis is controversial. We compared oxygen transport, lactate metabolism, and mitochondrial function in pigs with septic shock, cardiogenic shock, or hypoxic hypoxia.
Thirty-two anaesthetized, ventilated pigs were randomized to faecal peritonitis (P), cardiac tamponade (CT), hypoxic hypoxia (HH) or controls. Systemic and regional blood flows, lactate, mitochondrial respiration, and tissue hypoxia-inducible factor 1 alpha (HIF-1α) were measured for 24 h.
Mortality was 50% in each intervention group. While systemic oxygen consumption (VO(2) ) was maintained in all groups, hepatic VO(2) tended to decrease in CT [0.84 (0.5-1.3) vs. 0.42 (0.06-0.8)/ml/min/kg; P = 0.06]. In P, fractional hepatic, celiac trunk, and portal vein blood flows, and especially renal blood flow [by 46 (14-91)%; P = 0.001] decreased. In CT, renal blood flow [by 50.4 (23-81)%; P = 0.004] and in HH, superior mesenteric blood flow decreased [by 38.9 (16-100)%, P = 0.009]. Hepatic lactate influx increased > 100% in P and HH, and > 200% in CT (all P < 0.02). Hepatic lactate uptake remained unchanged in P and HH and converted to release in CT. Mitochondrial respiration remained normal. Muscle adenosine triphosphate (ATP) concentrations decreased in P (5.9 ± 1.4 μmol/g wt vs. 2.8 ± 2.7 μmol/g wt, P = 0.04). HIF-1α expression was not detectable in any group.
We conclude that despite shock and renal hypoperfusion, tissue hypoxia is not a major pathophysiological issue in early and established faecal peritonitis. The reasons for reduced skeletal muscle tissue ATP levels in the presence of well-preserved in-vitro muscle mitochondrial respiration should be further investigated.
Full-text · Article · May 2012 · Acta Anaesthesiologica Scandinavica