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Experimental data suggesting that inflammation mediated rat liver mitochondrial dysfunction results from secondary hypoxia rather than from direct effects of inflammatory mediators.

Weidinger A, Dungel P, Perlinger M, Singer K, Ghebes C, Duvigneau JC, Müllebner A, Schäfer U, Redl H, Kozlov AV - Front Physiol (2013)

Bottom Line: To eliminate this interaction, precision cut liver slices (PCLS) were used in this study aiming to dissect the effects of HOX and IM on mitochondrial function, integrity of cellular membrane, and the expression of genes associated with inflammation.Elevated expression of interleukin 6 (IL-6) was found in both models reflecting converging pathways regulating the expression of this gene.Both models caused damage to hepatocytes resulting in the release of alanine aminotransferase (ALT).

View Article: PubMed Central - PubMed

Affiliation: Ludwig Boltzmann Institute for Experimental and Clinical Traumatology Vienna, Austria.

ABSTRACT
Systemic inflammatory response (SIR) comprises both direct effects of inflammatory mediators (IM) and indirect effects, such as secondary circulatory failure which results in tissue hypoxia (HOX). These two key components, SIR and HOX, cause multiple organ failure (MOF). Since HOX and IM occur and interact simultaneously in vivo, it is difficult to clarify their individual pathological impact. To eliminate this interaction, precision cut liver slices (PCLS) were used in this study aiming to dissect the effects of HOX and IM on mitochondrial function, integrity of cellular membrane, and the expression of genes associated with inflammation. HOX was induced by incubating PCLS or rat liver mitochondria at pO2 < 1% followed by reoxygenation (HOX/ROX model). Inflammatory injury was stimulated by incubating PCLS with IM (IM model). We found upregulation of inducible nitric oxide synthase (iNOS) expression only in the IM model, while heme oxygenase 1 (HO-1) expression was upregulated only in the HOX/ROX model. Elevated expression of interleukin 6 (IL-6) was found in both models reflecting converging pathways regulating the expression of this gene. Both models caused damage to hepatocytes resulting in the release of alanine aminotransferase (ALT). The leakage of aspartate aminotransferase (AST) was observed only during the hypoxic phase in the HOX/ROX model. The ROX phase of HOX, but not IM, drastically impaired mitochondrial electron supply via complex I and II. Additional experiments performed with isolated mitochondria showed that free iron, released during HOX, is likely a key prerequisite of mitochondrial dysfunction induced during the ROX phase. Our data suggests that mitochondrial dysfunction, previously observed in in vivo SIR-models, is the result of secondary circulatory failure inducing HOX rather than the result of a direct interaction of IM with liver cells.

No MeSH data available.


Related in: MedlinePlus

Effect of HOX, ROX, and free iron on state 3 mitochondrial respiration rate. The baseline (BL) represents the respiration of freshly isolated mitochondria. Furthermore, mitochondria were incubated either under air (NOX) or under nitrogen (HOX) with 20 μM FeSO4 (Fe) or without (CO) for 15 min. Subsequently, all samples were incubated under air for further 15 min (ROX). A group of samples received 20 μM desferrioxamine B (Df) immediately after onset of hypoxia. Data are expressed as mean ± SEM of at least n = 5. *p < 0.05; **p < 0.01. Abbreviations used: NOX, Normoxia; HOX, Hypoxia; ROX, reoxygenation; BL, Baseline; CO, control, Fe, FeSO4; Df, desferrioxamine B.
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Figure 5: Effect of HOX, ROX, and free iron on state 3 mitochondrial respiration rate. The baseline (BL) represents the respiration of freshly isolated mitochondria. Furthermore, mitochondria were incubated either under air (NOX) or under nitrogen (HOX) with 20 μM FeSO4 (Fe) or without (CO) for 15 min. Subsequently, all samples were incubated under air for further 15 min (ROX). A group of samples received 20 μM desferrioxamine B (Df) immediately after onset of hypoxia. Data are expressed as mean ± SEM of at least n = 5. *p < 0.05; **p < 0.01. Abbreviations used: NOX, Normoxia; HOX, Hypoxia; ROX, reoxygenation; BL, Baseline; CO, control, Fe, FeSO4; Df, desferrioxamine B.

Mentions: To better understand the mechanisms of mitochondrial dysfunction under hypoxic conditions and the impact of free iron, we performed experiments with isolated mitochondria. No decrease of respiratory activity of mitochondria was observed following 15 min of hypoxic conditions (Figure 5). The presence of iron (Fe) in the hypoxic phase did not influence respiratory activity at this time point. However, after 15 min of ROX mitochondrial function was drastically impaired. The addition of iron chelator desferrioxamine B (Df) abolished the difference in respiration rates between samples with and without iron.


Experimental data suggesting that inflammation mediated rat liver mitochondrial dysfunction results from secondary hypoxia rather than from direct effects of inflammatory mediators.

Weidinger A, Dungel P, Perlinger M, Singer K, Ghebes C, Duvigneau JC, Müllebner A, Schäfer U, Redl H, Kozlov AV - Front Physiol (2013)

Effect of HOX, ROX, and free iron on state 3 mitochondrial respiration rate. The baseline (BL) represents the respiration of freshly isolated mitochondria. Furthermore, mitochondria were incubated either under air (NOX) or under nitrogen (HOX) with 20 μM FeSO4 (Fe) or without (CO) for 15 min. Subsequently, all samples were incubated under air for further 15 min (ROX). A group of samples received 20 μM desferrioxamine B (Df) immediately after onset of hypoxia. Data are expressed as mean ± SEM of at least n = 5. *p < 0.05; **p < 0.01. Abbreviations used: NOX, Normoxia; HOX, Hypoxia; ROX, reoxygenation; BL, Baseline; CO, control, Fe, FeSO4; Df, desferrioxamine B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3675332&req=5

Figure 5: Effect of HOX, ROX, and free iron on state 3 mitochondrial respiration rate. The baseline (BL) represents the respiration of freshly isolated mitochondria. Furthermore, mitochondria were incubated either under air (NOX) or under nitrogen (HOX) with 20 μM FeSO4 (Fe) or without (CO) for 15 min. Subsequently, all samples were incubated under air for further 15 min (ROX). A group of samples received 20 μM desferrioxamine B (Df) immediately after onset of hypoxia. Data are expressed as mean ± SEM of at least n = 5. *p < 0.05; **p < 0.01. Abbreviations used: NOX, Normoxia; HOX, Hypoxia; ROX, reoxygenation; BL, Baseline; CO, control, Fe, FeSO4; Df, desferrioxamine B.
Mentions: To better understand the mechanisms of mitochondrial dysfunction under hypoxic conditions and the impact of free iron, we performed experiments with isolated mitochondria. No decrease of respiratory activity of mitochondria was observed following 15 min of hypoxic conditions (Figure 5). The presence of iron (Fe) in the hypoxic phase did not influence respiratory activity at this time point. However, after 15 min of ROX mitochondrial function was drastically impaired. The addition of iron chelator desferrioxamine B (Df) abolished the difference in respiration rates between samples with and without iron.

Bottom Line: To eliminate this interaction, precision cut liver slices (PCLS) were used in this study aiming to dissect the effects of HOX and IM on mitochondrial function, integrity of cellular membrane, and the expression of genes associated with inflammation.Elevated expression of interleukin 6 (IL-6) was found in both models reflecting converging pathways regulating the expression of this gene.Both models caused damage to hepatocytes resulting in the release of alanine aminotransferase (ALT).

View Article: PubMed Central - PubMed

Affiliation: Ludwig Boltzmann Institute for Experimental and Clinical Traumatology Vienna, Austria.

ABSTRACT
Systemic inflammatory response (SIR) comprises both direct effects of inflammatory mediators (IM) and indirect effects, such as secondary circulatory failure which results in tissue hypoxia (HOX). These two key components, SIR and HOX, cause multiple organ failure (MOF). Since HOX and IM occur and interact simultaneously in vivo, it is difficult to clarify their individual pathological impact. To eliminate this interaction, precision cut liver slices (PCLS) were used in this study aiming to dissect the effects of HOX and IM on mitochondrial function, integrity of cellular membrane, and the expression of genes associated with inflammation. HOX was induced by incubating PCLS or rat liver mitochondria at pO2 < 1% followed by reoxygenation (HOX/ROX model). Inflammatory injury was stimulated by incubating PCLS with IM (IM model). We found upregulation of inducible nitric oxide synthase (iNOS) expression only in the IM model, while heme oxygenase 1 (HO-1) expression was upregulated only in the HOX/ROX model. Elevated expression of interleukin 6 (IL-6) was found in both models reflecting converging pathways regulating the expression of this gene. Both models caused damage to hepatocytes resulting in the release of alanine aminotransferase (ALT). The leakage of aspartate aminotransferase (AST) was observed only during the hypoxic phase in the HOX/ROX model. The ROX phase of HOX, but not IM, drastically impaired mitochondrial electron supply via complex I and II. Additional experiments performed with isolated mitochondria showed that free iron, released during HOX, is likely a key prerequisite of mitochondrial dysfunction induced during the ROX phase. Our data suggests that mitochondrial dysfunction, previously observed in in vivo SIR-models, is the result of secondary circulatory failure inducing HOX rather than the result of a direct interaction of IM with liver cells.

No MeSH data available.


Related in: MedlinePlus