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Bench-to-bedside review: Cytopathic hypoxia.

Fink MP - Crit Care (2002)

Bottom Line: A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome a,a3 by nitric oxide, and irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite.Recently, however, our laboratory has obtained data to suggest that the most important mechanism underlying the development of cytopathic hypoxia is depletion of cellular stores of nicotinamide adenine dinucleotide (NAD+/NADH) as a result of activation of the enzyme, poly(ADP-ribose) polymerase-1.If cytopathic hypoxia is important in the pathophysiology of established sepsis and multiorgan dysfunction syndrome, then efforts in the future will need to focus on pharmacological interventions designed to preserve normal mitochondrial function and energy production in sepsis.

View Article: PubMed Central - PubMed

Affiliation: Department of Critical Care Medicine, Watson Chair in Surgery, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, USA. finkmp@anes.upmc.edu

ABSTRACT
The rate of oxygen consumption by certain tissues is impaired when mice or rats are injected with lipopolysaccharide. A similar change in the rate of oxygen consumption is observed when Caco-2 human enterocyte-like cells are incubated in vitro with cytomix, a cocktail of cytokines containing tumor necrosis factor, IL-1beta, and IFN-gamma. The decrease in the rate of oxygen consumption is not due to a change in oxygen delivery (e.g. on the basis of diminished microvascular perfusion), but rather to an acquired intrinsic defect in cellular respiration, a phenomenon that we have termed 'cytopathic hypoxia'. A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome a,a3 by nitric oxide, and irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite. Recently, however, our laboratory has obtained data to suggest that the most important mechanism underlying the development of cytopathic hypoxia is depletion of cellular stores of nicotinamide adenine dinucleotide (NAD+/NADH) as a result of activation of the enzyme, poly(ADP-ribose) polymerase-1. If cytopathic hypoxia is important in the pathophysiology of established sepsis and multiorgan dysfunction syndrome, then efforts in the future will need to focus on pharmacological interventions designed to preserve normal mitochondrial function and energy production in sepsis.

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Effect of liposomal nicotinamide adenine dinucleotide (NAD+) on O2 consumption by Caco-2 cells growing on microcarrier beads. Control cells growing on microcarrier beads in six-well dishes were incubated for 24 hours under cytokine-free conditions alone (Control), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Cytokine-stimulated cells were incubated for 24 hours with cytomix alone or with free NAD+ (NAD), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Results are means ± SEM (n = 6–8 per condition). Data were analyzed by analysis of variance followed by Duncan's multiple range test. NS, not significant. Reprinted from [61] with permission.
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Figure 7: Effect of liposomal nicotinamide adenine dinucleotide (NAD+) on O2 consumption by Caco-2 cells growing on microcarrier beads. Control cells growing on microcarrier beads in six-well dishes were incubated for 24 hours under cytokine-free conditions alone (Control), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Cytokine-stimulated cells were incubated for 24 hours with cytomix alone or with free NAD+ (NAD), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Results are means ± SEM (n = 6–8 per condition). Data were analyzed by analysis of variance followed by Duncan's multiple range test. NS, not significant. Reprinted from [61] with permission.

Mentions: Khan et al. reasoned that if NAD+/NADH depletion is responsible for the decrease in cellular respiration induced by cytomix, then replenishing cellular levels of this catalytically essential nucleotide should tend to restore normal rates of O2 consumption [61]. NAD+, however, is a bulky and highly charged molecule that would not be expected to diffuse across the cytosolic membrane. Furthermore, extracellular NAD+/NADH is a substrate for a cell-surface enzyme, nicotinamide adenine dinucleotide glycohydrolase, which converts NAD+/NADH into cyclic ADP-ribose [62]. Simply adding NAD+ or NADH to the incubation medium would thus not be expected to have much of an effect on cellular levels of NAD+/NADH. In an effort to circumvent this problem, the investigators incubated cytomix-stimulated Caco-2 cells with NAD+ encapsulated in liposomes. This strategy worked; when cytomix-stimulated Caco-2 cells were coincubated with liposome-encapsulated NAD+, the cellular NAD+/NADH level was increased to about 85% of the control value (Fig. 6). Furthermore, coincubating cytomix-stimulated Caco-2 cells with liposome-encapsulated NAD+ prevented the development of cytopathic hypoxia (Fig. 7).


Bench-to-bedside review: Cytopathic hypoxia.

Fink MP - Crit Care (2002)

Effect of liposomal nicotinamide adenine dinucleotide (NAD+) on O2 consumption by Caco-2 cells growing on microcarrier beads. Control cells growing on microcarrier beads in six-well dishes were incubated for 24 hours under cytokine-free conditions alone (Control), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Cytokine-stimulated cells were incubated for 24 hours with cytomix alone or with free NAD+ (NAD), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Results are means ± SEM (n = 6–8 per condition). Data were analyzed by analysis of variance followed by Duncan's multiple range test. NS, not significant. Reprinted from [61] with permission.
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Related In: Results  -  Collection

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Figure 7: Effect of liposomal nicotinamide adenine dinucleotide (NAD+) on O2 consumption by Caco-2 cells growing on microcarrier beads. Control cells growing on microcarrier beads in six-well dishes were incubated for 24 hours under cytokine-free conditions alone (Control), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Cytokine-stimulated cells were incubated for 24 hours with cytomix alone or with free NAD+ (NAD), with empty liposomes (Lipo), or with NAD+-containing liposomes (LipoNAD). Results are means ± SEM (n = 6–8 per condition). Data were analyzed by analysis of variance followed by Duncan's multiple range test. NS, not significant. Reprinted from [61] with permission.
Mentions: Khan et al. reasoned that if NAD+/NADH depletion is responsible for the decrease in cellular respiration induced by cytomix, then replenishing cellular levels of this catalytically essential nucleotide should tend to restore normal rates of O2 consumption [61]. NAD+, however, is a bulky and highly charged molecule that would not be expected to diffuse across the cytosolic membrane. Furthermore, extracellular NAD+/NADH is a substrate for a cell-surface enzyme, nicotinamide adenine dinucleotide glycohydrolase, which converts NAD+/NADH into cyclic ADP-ribose [62]. Simply adding NAD+ or NADH to the incubation medium would thus not be expected to have much of an effect on cellular levels of NAD+/NADH. In an effort to circumvent this problem, the investigators incubated cytomix-stimulated Caco-2 cells with NAD+ encapsulated in liposomes. This strategy worked; when cytomix-stimulated Caco-2 cells were coincubated with liposome-encapsulated NAD+, the cellular NAD+/NADH level was increased to about 85% of the control value (Fig. 6). Furthermore, coincubating cytomix-stimulated Caco-2 cells with liposome-encapsulated NAD+ prevented the development of cytopathic hypoxia (Fig. 7).

Bottom Line: A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome a,a3 by nitric oxide, and irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite.Recently, however, our laboratory has obtained data to suggest that the most important mechanism underlying the development of cytopathic hypoxia is depletion of cellular stores of nicotinamide adenine dinucleotide (NAD+/NADH) as a result of activation of the enzyme, poly(ADP-ribose) polymerase-1.If cytopathic hypoxia is important in the pathophysiology of established sepsis and multiorgan dysfunction syndrome, then efforts in the future will need to focus on pharmacological interventions designed to preserve normal mitochondrial function and energy production in sepsis.

View Article: PubMed Central - PubMed

Affiliation: Department of Critical Care Medicine, Watson Chair in Surgery, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, USA. finkmp@anes.upmc.edu

ABSTRACT
The rate of oxygen consumption by certain tissues is impaired when mice or rats are injected with lipopolysaccharide. A similar change in the rate of oxygen consumption is observed when Caco-2 human enterocyte-like cells are incubated in vitro with cytomix, a cocktail of cytokines containing tumor necrosis factor, IL-1beta, and IFN-gamma. The decrease in the rate of oxygen consumption is not due to a change in oxygen delivery (e.g. on the basis of diminished microvascular perfusion), but rather to an acquired intrinsic defect in cellular respiration, a phenomenon that we have termed 'cytopathic hypoxia'. A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome a,a3 by nitric oxide, and irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite. Recently, however, our laboratory has obtained data to suggest that the most important mechanism underlying the development of cytopathic hypoxia is depletion of cellular stores of nicotinamide adenine dinucleotide (NAD+/NADH) as a result of activation of the enzyme, poly(ADP-ribose) polymerase-1. If cytopathic hypoxia is important in the pathophysiology of established sepsis and multiorgan dysfunction syndrome, then efforts in the future will need to focus on pharmacological interventions designed to preserve normal mitochondrial function and energy production in sepsis.

Show MeSH
Related in: MedlinePlus