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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: 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).

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

(A,B) Accumulation of free iron in liver sections under hypoxia. The sections were treated with nitrite solution and frozen for EPR analysis either immediately after preparation (control) or after incubation for 1 h at 37°C under nitrogen (1 h hypoxia). The difference in free iron concentration between control and 1 h hypoxia was approx. 20 nmol/g tissue (A). The amplitudes (Fe) of the g = 2.03 peak were measured in the EPR spectra (B) of control liver sections (dotted line) and after 1 h hypoxia (full line) to determine the concentration of nitrosyl iron complexes. Data are expressed as mean ± SEM of n = 3. *p < 0.05.
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Figure 4: (A,B) Accumulation of free iron in liver sections under hypoxia. The sections were treated with nitrite solution and frozen for EPR analysis either immediately after preparation (control) or after incubation for 1 h at 37°C under nitrogen (1 h hypoxia). The difference in free iron concentration between control and 1 h hypoxia was approx. 20 nmol/g tissue (A). The amplitudes (Fe) of the g = 2.03 peak were measured in the EPR spectra (B) of control liver sections (dotted line) and after 1 h hypoxia (full line) to determine the concentration of nitrosyl iron complexes. Data are expressed as mean ± SEM of n = 3. *p < 0.05.

Mentions: Since iron is known to induce mitochondrial dysfunction, we determined whether or not free iron levels are increased during 1 h of hypoxia. One hour of hypoxia in liver sections resulted in an increase in intracellular free iron levels by approx. 20 nmol/g tissue (Figure 4). In the following experiments we tested the effect of 20 nmol/ml ferrous ion concentration on mitochondrial function.


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)

(A,B) Accumulation of free iron in liver sections under hypoxia. The sections were treated with nitrite solution and frozen for EPR analysis either immediately after preparation (control) or after incubation for 1 h at 37°C under nitrogen (1 h hypoxia). The difference in free iron concentration between control and 1 h hypoxia was approx. 20 nmol/g tissue (A). The amplitudes (Fe) of the g = 2.03 peak were measured in the EPR spectra (B) of control liver sections (dotted line) and after 1 h hypoxia (full line) to determine the concentration of nitrosyl iron complexes. Data are expressed as mean ± SEM of n = 3. *p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: (A,B) Accumulation of free iron in liver sections under hypoxia. The sections were treated with nitrite solution and frozen for EPR analysis either immediately after preparation (control) or after incubation for 1 h at 37°C under nitrogen (1 h hypoxia). The difference in free iron concentration between control and 1 h hypoxia was approx. 20 nmol/g tissue (A). The amplitudes (Fe) of the g = 2.03 peak were measured in the EPR spectra (B) of control liver sections (dotted line) and after 1 h hypoxia (full line) to determine the concentration of nitrosyl iron complexes. Data are expressed as mean ± SEM of n = 3. *p < 0.05.
Mentions: Since iron is known to induce mitochondrial dysfunction, we determined whether or not free iron levels are increased during 1 h of hypoxia. One hour of hypoxia in liver sections resulted in an increase in intracellular free iron levels by approx. 20 nmol/g tissue (Figure 4). In the following experiments we tested the effect of 20 nmol/ml ferrous ion concentration on mitochondrial function.

Bottom Line: 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).

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