Liver Mitochondrial Dysfunction Research Articles

Toll-like receptor-3-induced mitochondrial dysfunction in cultured human hepatocytes

Several studies have shown the presence of liver mitochondrial dysfunction during sepsis. TLR3 recognizes viral double-stranded RNA and host endogenous cellular mRNA released from damaged cells. TLR3 ligand amplifies the systemic hyperinflammatory response observed during sepsis and in sepsis RNA escaping from damaged tissues/cells may serve as an endogenous ligand for TLR3 thereby modulating immune responses. This study addressed the hypothesis that TLR3 might regulate mitochondrial function in cultured human hepatocytes. HepG2 cells were exposed to TLR-3 ligand (dsRNA — polyinosine–polycytidylic acid; Poly I:C) and mitochondrial respiration was measured. Poly I:C induced a reduction in maximal mitochondrial respiration of human hepatocytes which was prevented partially by preincubation with cyclosporine A (a mitochondrial permeability transition pore-opening inhibitor). Poly-I:C induced activation of NF-κB, and the mitochondrial dysfunction was accompanied by caspase-8 but not caspase-3 activation and by no major alterations in cellular or mitochondrial ultrastructure.

Peritoneal Inflammation in Pigs is Associated with Early Mitochondrial Dysfunction in Liver and Kidney

The objective of this study was to investigate early effects of peritoneal inflammation on the mitochondrial function in the vital organs, liver and kidney, and their relation to inflammatory and oxidative stress mediators. The study was performed on 14 domestic pigs. Peritoneal inflammation was induced in anesthetized pigs after a midline laparotomy by autologous feces. Fluid resuscitation maintained a MAP above 60 mmHg. Animals were sacrificed 12 h later, and tissue samples were obtained to determine mitochondrial function, mRNA levels of relevant genes [inducible NO synthase (iNOS), inducible HO (HO-1), tumor necrosis factor-alpha (TNF-alpha)], generation of reactive oxygen species (ROS), and HO-1 activity. We found impaired mitochondrial function in both liver and kidney, based on decreased state 3 respiration in the liver and increased states 2 and 4 respiration in the kidney at 12 h. This was accompanied by increased TNF-alpha protein in the blood and up-regulation of TNF-alpha mRNA in the liver. Free iron was elevated in the liver but not in the kidney. In the kidney, mitochondrial ROS production was increased. Nitric oxide levels in blood remained unchanged, corresponding to unchanged levels of iNOS mRNA expression in liver and kidney. Similarly, HO-1 mRNA and heme oxygenase (HO)-activity were unchanged. The inflammatory response in the absence of characteristic septic symptoms was not associated with morphological organ damage at this early time point. Peritoneal inflammation in pigs caused mitochondrial dysfunction in liver and kidney, preceding signs of organ damage. We did not find proof that mitochondrial dysfunction was due to increased levels of either nitric oxide (NO) or products of HO, but it was accompanied by increased levels of oxidative stress markers.

Paralysie faciale périphérique : penser à rechercher un niveau sensitif du tronc et évoquer la maladie de Lyme

Kwashiorkor and marasmus are two clinical syndromes observed in severe acute malnutrition. In this review, we highlighted the differences between these two syndromes by reviewing the data comparing kwashiorkor and marasmus in literature, combined with recent microbiological findings and meta-analysis. Depletion of antioxidants, vitamins and minerals were more severe in kwashiorkor than marasmus. This was consistent with the severe and uncontrolled oxidative stress associated with the depletion of gut anaerobes and the relative proliferation of aerotolerant gut pathogens. This relative proliferation and invasion of gut microbes belonging to the aerotolerant Proteobacteria phylum and pathogens suggested a specific microbial process critical in the pathogenesis of kwashiorkor. Liver mitochondrial and peroxisomal dysfunction could be secondary to toxic microbial compounds produced in the gut such as ethanol, lipopolysaccharides and endotoxins produced by Proteobacteria, particularly Klebsiella pneumoniae, and aflatoxin produced by Aspergillus species. The gut-liver axis alteration is characterized by oedema and a fatty and enlarged liver and was associated with a dramatic depletion of methionine and glutathione, an excessive level of free circulating iron and frequent lethal bacteraemia by enteric pathogens. This was consistent with the fact that antibiotics improved survival only in children with kwashiorkor but not marasmus. The specific pathogenic characteristics of kwashiorkor identified in this review open new avenues to develop more targeted and effective treatments for both marasmus and/or kwashiorkor. Urgent correction of plasma glutathione depletion, alongside supply of specific essential amino acids, particularly methionine and cysteine, early detection of pathogens and an antibiotic more efficient than amoxicillin in supressing gut Proteobacteria including K. pneumoniae, and probiotics to restore the human gut anaerobic mature microbiota could save many more children with kwashiorkor.

Emblica officinalisProtects Against Alcohol-Induced Liver Mitochondrial Dysfunction in Rats

The protective effect of Emblica officinalis, a commonly used botanical in many Ayurvedic preparations, was investigated for its effects on liver mitochondria of ethanol-administered rats. Oxidative stress and reactive oxygen species-mediated toxicity are considered two of the key underlying mechanisms responsible for alcohol-induced liver injury and mitochondrial dysfunction. Alcohol-administered rats showed a significant elevation of plasma transaminases (aspartate and alanine aminotransferases), alkaline phosphatase, and gamma-glutamyl transferase compared to control rats. However, activities of hepatic mitochondrial antioxidant enzymes, viz., superoxide dismutase, glutathione peroxidase, and reduced glutathione, were significantly lower. Chronic alcohol feeding also increased lipid peroxide levels, protein carbonyl content, and overproduction of nitric oxide followed by lowered activities of NADH dehydrogenase, succinate dehydrogenase (SDH), and cytochrome c oxidase and content of cytochromes. Administration of E. officinalis fruit extract (EFE) at a dose of 250 mg/kg of body weight/day to alcoholic rats offers protection by simultaneously lowering the carbonyl content and lipid peroxidation and elevating antioxidant enzyme activities, SDH, NADH dehydrogenase, and cytochrome c oxidase activities, and content of cytochromes in hepatic mitochondria. Our data indicate that EFE administration to chronically alcohol-fed rats offers protection against alcohol-induced alterations. The active tannoid principles and nitric oxide scavenging compounds present in EFE may have contributed to the protection observed.

Notice of Retraction: ‘Liver delivery of NO by NCX‐1000 protects against acute liver failure and mitochondrial dysfunction induced by APAP in mice’ (Br J Pharmacol 143; 33–42; 2004)

Notice of Retraction: ‘Liver delivery of NO by NCX‐1000 protects against acute liver failure and mitochondrial dysfunction induced by APAP in mice’ (<i>Br J Pharmacol</i> 143; 33–42; 2004)

Diallyl trisulfide (DATS) effectively attenuated oxidative stress-mediated liver injury and hepatic mitochondrial dysfunction in acute ethanol-exposed mice

The protective effects of diallyl trisulfide (DATS) on acute ethanol-induced liver injury were investigated. Mice were pretreated with DATS (30 mg/kg bw) for 7 d before being exposed to ethanol (4.8 g/kg bw). The biochemical indices (aspartate amino transferase, AST; alanine amino transferase, ALT; triglyceride, TG) were examined to evaluate the protective effects. Mitochondria were isolated for the mitochondrial permeability transition (MPT), membrane potential (Δ Ψ m) and adenosine nucleotide pool assay. The lipid peroxidation (malondialdehyde, MDA), non-enzymatic antioxidant (glutathione, GSH) and enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione reductase, GR; glutathione peroxidase, GSH-Px) were measured both in the liver homogenate and isolated mitochondria. Acute ethanol exposure resulted in the significant increase of the ALT, AST and TG levels and hepatic mitochondria dysfunction shown as MPT, and the decreases of Δ Ψ m, ATP and energy charge (EC). However, DATS pretreatment dramatically attenuated these adverse effects. Beside this, DATS was found to significantly inhibit the increase of the hepatic and mitochondrial MDA levels, which were decreased by 33.3% ( P < 0.01) and 39.0% ( P < 0.01), respectively. In addition, DATS pretreatment markedly suppressed the ethanol-induced decrease of the hepatic GSH level and increased the mitochondrial GSH level. Moreover, the activities of the hepatic antioxidant enzymes (SOD, CAT, and GR) and the mitochondrial antioxidant enzymes (SOD, GR, and GSH-Px) were significantly boosted. Thus, we concluded that DATS dramatically attenuated acute ethanol-induced liver injury and mitochondrial dysfunction. The increase of the hepatic and mitochondrial GSH levels and the elevation of the antioxidant enzymes activities should account for the preventive effects.

Inflammatory Signaling: Another Drug Target to Improve Glycemic Control in Type 2 Diabetes

Inflammatory Signaling: Another Drug Target to Improve Glycemic Control in Type 2 Diabetes

Antioxidant treatment reverses mitochondrial dysfunction in a sepsis animal model

Evidence from the literature has demonstrated that reactive oxygen species (ROS) play an important role in the development of multiple organ failure and septic shock. In addition, mitochondrial dysfunction has been implicated in the pathogenesis of multiple organ dysfunction syndrome (MODS). The hypothesis of cytopathic hypoxia postulates that impairment in mitochondrial oxidative phosphorylation reduces aerobic adenosine triphosphate (ATP) production and potentially induces MODS. In this work, our aim was to evaluate the effects of antioxidants on oxidative damage and energy metabolism parameters in liver of rats submitted to a cecal ligation puncture (CLP) model of sepsis. We speculate that CLP induces a sequence of events that culminate with liver cells death. We propose that mitochondrial superoxide production induces mitochondrial oxidative damage, leading to mitochondrial dysfunction, swelling and release of cytochrome c. These events occur in early sepsis development, as reported in the present work. Liver cells necrosis only occurs 24 h after CLP, but all other events occur earlier (6–12 h). Moreover, we showed that antioxidants may prevent oxidative damage and mitochondrial dysfunction in liver of rats after CLP. In another set of experiments, we verified that L-NAME administration did not reverse increase of superoxide anion production, TBARS formation, protein carbonylation, mitochondrial swelling, increased serum AST or inhibition on complex IV activity caused by CLP. Considering that this drug inhibits nitric oxide synthase and that no parameter was reversed by its administration, we suggest that all the events reported in this study are not mediated by nitric oxide. In conclusion, although it is difficult to extrapolate our findings to human, it is tempting to speculate that antioxidants may be used in the future in the treatment of this disease.

Nonalcoholic fatty liver disease and mitochondrial dysfunction

Nonalcoholic fatty liver disease (NAFLD) includes hepatic steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. NAFLD is the most common liver disorder in the United States and worldwide. Due to the rapid rise of the metabolic syndrome, the prevalence of NAFLD has recently dramatically increased and will continue to increase. NAFLD has also the potential to progress to hepatocellular carcinoma (HCC) or liver failure. NAFLD is strongly linked to caloric overconsumption, physical inactivity, insulin resistance and genetic factors. Although significant progress in understanding the pathogenesis of NAFLD has been achieved in years, the primary metabolic abnormalities leading to lipid accumulation within hepatocytes has remained poorly understood. Mitochondria are critical metabolic organelles serving as "cellular power plants". Accumulating evidence indicate that hepatic mitochondrial dysfunction is crucial to the pathogenesis of NAFLD. This review is focused on the significant role of mitochondria in the development of NAFLD.

Hypomorphic mutation of PGC-1β causes mitochondrial dysfunction and liver insulin resistance

PGC-1beta is a transcriptional coactivator that potently stimulates mitochondrial biogenesis and respiration of cells. Here, we have generated mice lacking exons 3 to 4 of the Pgc-1beta gene (Pgc-1beta(E3,4-/E3,4-) mice). These mice express a mutant protein that has reduced coactivation activity on a subset of transcription factors, including ERRalpha, a major target of PGC-1beta in the induction of mitochondrial gene expression. The mutant mice have reduced expression of OXPHOS genes and mitochondrial dysfunction in liver and skeletal muscle as well as elevated liver triglycerides. Euglycemic-hyperinsulinemic clamp and insulin signaling studies show that PGC-1beta mutant mice have normal skeletal muscle response to insulin but have hepatic insulin resistance. These results demonstrate that PGC-1beta is required for normal expression of OXPHOS genes and mitochondrial function in liver and skeletal muscle. Importantly, these abnormalities do not cause insulin resistance in skeletal muscle but cause substantially reduced insulin action in the liver.

Dehydroepiandrosterone Inhibits Complex I of the Mitochondrial Respiratory Chain and is Neurotoxic In Vitro and In Vivo at High Concentrations

Dehydroepiandrosterone (DHEA) is widely used as a food supplement and considered to be relatively safe. In animal studies, however, additions of high concentrations of DHEA to the diet have led to hepatotoxicity as well as liver mitochondrial dysfunction. This study was therefore designed to find out whether DHEA is able to inhibit the respiratory activity also in neuronal mitochondria and to reveal whether this leads to functional disturbance in the brain. Using different mitochondrial substrates, we show here that DHEA suppresses the mitochondrial respiration in permeabilized neurons (half maximal inhibitory concentration 13 microM) by inhibiting complex I of the mitochondrial electron transport chain. Treatment with DHEA was associated with increased glucose expenditure in intact cultures and led to neuronal death. The latter was most prominent in hypoglycemic conditions. Mice fed with pellet containing 0.6% DHEA for 3 months showed a significant neuronal loss in the cerebral cortex and hippocampus, a slightly decreased dopamine/dihydroxyphenylacetic acid ratio, as well as motor impairment. The main conclusion of the present study is that high concentrations of DHEA inhibit complex I of the mitochondrial respiratory chain and are neurotoxic in vitro and in vivo.

Predominance of released mitochondrial enzymes by partial hepatectomy-induced rat regenerating liver is controlled by hemodynamic changes and not related to mitochondrial damage

Objective. Serum activities of assumed organ-specific enzymes are useful protein markers in the diagnosis of necrotic liver diseases. However, after partial hepatectomy (PH) in rats, remaining hepatocytes proliferate to restore the lost liver mass, even when there is a drastic but selective elevation of serum enzyme activities. The aim of the present study was to elucidate the underlying mechanisms involved in this PH-induced enhancement of enzyme release. Material and methods. Routine spectrophotometric methods were used to measure nine “marker” enzyme activities in sera, in effluents from isolated perfused livers, as well as in the incubation media used for liver slices and isolated cells from either sham-operated or 70%-PH rats. Results. PH induced a drastic increase in serum activities of liver enzymes, predominantly of mitochondrial localization. In the control and 70%-PH groups, liver enzymes were differentially released by varying in vitro flow rate/liver mass ratio, using livers perfused at variable flow rates. This event was reversible and not associated with liver structural or functional alterations, but was dependent on the flow-bearing physical forces and independent of production of extra-hepatic factors. Liver slices and isolated cells were used to identify additional flow-independent enzyme release. The 70%-PH-induced drastic release of specific enzymes (predominantly those from mitochondria) could be mimicked in control livers by changing the hepatic blood flow/mass ratio, and closely resembled urea production by these livers. Conclusions. PH-induced effects were not associated with liver necrosis or mitochondrial dysfunction and evidenced previously unrecognized mechanisms controlling the rate of enzyme release into the bloodstream, which might have clear clinical implications.

Fatty liver in the intensive care unit

Non-alcoholic steatohepatitis is a liver disease characterized by steatosis and steatohepatitis in subjects whose alcohol consumption is negligible. The primary form is associated with insulin resistance whereas secondary non-alcoholic steatohepatitis occurs notably during total parenteral nutrition or in patients in the intensive care unit. This review is mainly focused on recent developments in the understanding of the pathogenesis of this disease. Pathogenesis involves the direct role of fatty acids in liver injury, oxidative stress, cytokines, genetic susceptibility or mitochondrial dysfunction. An increased delivery of free fatty acids to the liver contributes to the first hit, originating liver steatosis. The process may undergo a second hit, characterized by inflammation and hepatocellular degeneration. Mitochondrial dysfunction plays a key role by leading to abnormal generation of reactive oxygen species, which cause lipid peroxidation. The peroxidation products and cytokines favor progression from steatohepatitis to fibrosis. Fatty liver disease may also be encountered in the intensive care unit in patients receiving parenteral nutrition. However, an adapted glucose-lipid ratio as source of non-protein calories prevents the development of fatty liver. Moreover, recent evidence suggests the importance of the type of lipid infused (structured lipid emulsion or fish oils). The acute phase response associated with severe disease can also lead to the development of fatty liver in spite of adequate nutritional support. The pathogenesis of non-alcoholic steatohepatitis is multifactorial, but there is growing evidence that mitochondrial dysfunction always plays a key role. Adapted nutrition may prevent in part fatty liver in the intensive care unit.

Liver delivery of NO by NCX-1000 protects against acute liver failure and mitochondrial dysfunction induced by APAP in mice.

1. NCX-1000, (3alpha, 5beta, 7beta)-3,7-dihydroxycholan-24oic acid[2-methoxy-4-[3-[4-(nitroxy)butoxy]-3-oxo-1-propenyl]phenyl ester, is a nitric oxide (NO)-derivative of ursodeoxyxholic acid (UDCA) that selectively release NO in the liver. 2. Here, we demonstrated that administering mice with 40 micromol kg(-1) NCX-1000, but not UDCA, improves liver histopathology and reduces mortality caused by 330 micromol kg(-1) APAP from 60 to 25% (P<0.01). Administration of NCX-1000, in a therapeutic manner, that is, 2 h after acetaminophen (APAP) intoxication reduced mortality, improved liver histopathology and prevented liver IFN-gamma, TNF-alpha, Fas/Fas ligand and inducible nitric oxide synthase (iNOS) mRNA accumulation caused by APAP. 3. In vitro exposure of primary cultures of mouse hepatocytes to APAP, 6.6 mm, resulted in apoptosis followed by necrosis. Loss of cell viability correlates with early mitochondrial membrane potential (Deltapsi(m)) hyperpolarization followed by depolarization and cytochrome c translocation from mitochondria to cytosol. APAP-induced apoptosis associated with procaspase-3 and -9 cleavage, appearance of truncated Bid and activation of poly(ADP-ribose) polymerase (PARP). 4. Treating primary culture of hepatocytes with 5 microm cyclosporine and 10 microm trifluoperazine for eight resulted in significant reduction of apoptosis induced by APAP suggesting that loss of Deltapsim was mechanistically involved in apoptosis induced by APAP in vitro. 5. NCX-1000, but not UDCA, concentration-dependently (ED(50)=16 microm) protected against Deltapsi(m) depolarization and reduced transition from apoptosis to necrosis caused by 6.6 mm APAP. 6. Treating primary cultures of hepatocytes with the NO-donor DETA-NO, 100 microm, reduced apoptosis induced by APAP and prevented caspase activation. 7. In conclusion, NCX-1000 is effective in protecting against APAP-induced hepatotoxicity when administered in a therapeutic manner. This protection may involve the inhibition of apoptosis and the maintenance of mitochondrial integrity.

Influence of pancreatic enzyme content on experimental acute pancreatitis.

Some studies demonstrate the crucial role of proteases in the pathogenesis of acute pancreatitis (AP). Systemic release of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) has been demonstrated in AP, yet the mechanism of activation remains unclear. Furthermore, it is not known if the amount of pancreatic enzyme in the pancreas determines the production of proinflammatory cytokines. To determine whether there is a link between the pancreatic enzyme content and the production of cytokines and consequently the systemic lesions observed in AP. Forty-seven animals were divided into three groups: group I had a high pancreatic enzyme level (with and without AP), group II had a low pancreatic enzyme level (cerulein infusion: 0.133 microg x kg(-1) x h(-1)) (with and without AP), and group III were the controls. AP was induced by injection of 5% sodium taurocholate into the pancreatic duct. To evaluate the pancreatic enzyme contents before AP, trypsinogen and amylase analysis was carried out on pancreatic tissue collected after the animals were killed. Two hours after induction of AP, concentrations of pancreatic enzymes and trypsinogen activation peptide (TAP) in serum, ascitic fluid, and pancreatic tissue were determined. The ascitic fluid was assayed for TNF-alpha and the serum was assayed for IL-6 with ELISA kits. Systemic lesions were sought on the basis of hepatic mitochondrial respiratory function measured polarographically. The administration of physiological doses of cerulein diminishes the pancreatic enzyme and TAP levels, the production of proinflammatory cytokines, and the liver mitochondrial dysfunction observed in AP, suggesting that the pancreatic enzyme content is an important factor in the severity of AP.

ONO-5046, an elastase inhibitor, attenuates liver mitochondrial dysfunction after endotoxin.

To investigate the effect of ONO-5046, an elastase inhibitor, on liver mitochondrial dysfunction after endotoxin administration. Prospective, randomized, controlled animal study. Research laboratory. Male Hartley guinea pigs. Endotoxin shock was induced by intravenous infusion of Escherichia coli lipopolysaccharide endotoxin (50 mg/kg). Six guinea pigs were treated with endotoxin and saline. Twenty-four guinea pigs received 5, 10, and 30 mg/kg/hr of ONO-5046 after endotoxin administration. Six guinea pigs received only saline. We measured oxygen uptake in state 3 (substrate and adenosine 5'-diphosphate [ADP]) and state 4 (excess substrate, no ADP), as well as the respiratory control ratio (state 3/state 4), adenosine 5'-diphosphate/oxygen ratio (ADP/O), and arterial ketone body ratio. ONO-5046 was dose dependently effective in liver mitochondrial oxidative phosphorylation, such as oxygen uptake in stage 4, respiratory control ratio, adenosine triphosphate synthesis, ADP/O, and arterial ketone body ratio when ONO-5046 was started 30 mins after endotoxin. The administration of 30 mg/kg/hr of ONO-5046 improved mean blood pressure, which had decreased after endotoxin. ONO-5046 attenuates the endotoxin-induced liver mitochondrial dysfunctions that may be related to increased liver blood flow.

The role of desferrioxamine chelatable iron in rat liver mitochondrial dysfunction in chronic dietary iron overload

Lipid peroxidation and organelle dysfunction are important factors in hepatic iron toxicity. The form of the intracellular iron responsible for these abnormalities is still unknown. In order to investigate the iron species inducing cell injury, the level of chelatable iron in the liver mitochondria isolated from rats fed a 2.5% carbonyl iron diet for 12 weeks was measured by EPR spectroscopy. The presence of lipid peroxidation products and the energy transducing capacility of the mitochondrial inner membrane was evaluated in parallel. The total iron concentration in the liver mitochondria from iron fed rats progressively increased up to 6 weeks, almost reaching a steady-state. By contrast the level of chelatable iron in mitochondrial fraction transiently increased at about 3–6 weeks of treatment. The induction of lipid peroxidation and a large decrease of ATP occurred at the same time. The enhancement of the energy dissipating calcium cycling was in parallel revealed by studying the mitochondria membrane potential. These results gave experimental evidence to the proposal that the chelatable iron level plays a critical role in initiating organelle dysfunction, at least in this experimental model.

A study of hepatic mitochondrial respiration and microsomal cytochrome P 450 content in mice infected with the liver fluke Fasciola hepatica

Previous studies of the effects of infection of Wistar rats with the common liver fluke, Fasciola hepatica, on liver bioenergetic and drug metabolism have demonstrated a loss of respiratory control in isolated mitochondria and reduced microsomal cytochrome P 450 content, respectively, from 2 weeks post-infection throughout the acute phase of the infection. In the present study male Balb c mice infected with F. hepatica showed a loss of respiratory control in isolated liver mitochondria only at 4 weeks post-infection. A similar time course was demonstrated for a reduction in hepatic microsomal cytochrome P 450 content. Preparations from infected CBA mice showed similar changes to Babl c mice but mitochondrial respiration in preparations from infected Swiss outbred mice was normal. A host difference between strains of mice and between mice and rats is therefore evident in the timing and extent of liver mitochondrial dysfunction and in the timing of the decrease in the cytochrome P 450 content of hepatic microsomes. This difference between hosts may be related to the reported differences in cellular inflammatory responses to the migrating juvenile flukes in the livers of rats and mice.

Dysfunction of mouse liver mitochondria induced by 2,2'-azobis-(2-amidinopropane) dihydrochloride, a radical initiator, in vitro and in vivo.

Mouse liver mitochondria were uncoupled in a time dependent by intraperitoneal injection of a radical initiator, 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH) (100 mg/kg). State 3 respiration, ADP/O ratio and respiratory control ratio (RCR) were decreased 30 min after injection but there was no effect on state 4 respiration. Lipid peroxidation was increased and oxidative phosphorylation was uncoupled at one hr after drug injection but gradually recovered to normal levels after 14 hr in vivo. State 3 respiration, RCR and ADP/O ratio but not state 4 respiration of isolated mouse mitochondria were inhibited by short term incubation with AAPH in vitro. This inhibitory action was concentration dependent (ID50 = 5 mM) but was not prevented by alpha-tocopherol. AAPH had no effect on electron transport or the membrane potential of these isolated mitochondria. However, mitochondria were uncoupled via lipid peroxidation and swelling by long term incubation with AAPH. These inhibitory effects of AAPH were reduced by its spontaneous degradation not only in vitro but also in vivo. Thus AAPH induces mitochondrial dysfunction by direct action in the early period of treatment and free radicals produced from AAPH mediate mitochondrial swelling via lipid peroxidation in the late period. From these findings, it is concluded that mitochondrial phosphorylation plays an important role in the pathogenesis of liver injury induced by AAPH and that radicals generated by AAPH might be a source of liver injury and mitochondrial dysfunction in vivo.

Effects of Prostaglandin E1on the Recovery of Ischemia-Induced Liver Mitochondrial Dysfunction in Rats with Cirrhosis

Interruption of hepatic blood supply for 60 min deteriorated liver mitochondrial respiratory functional indices--that is, respiratory control index (RCI) and the rate of oxygen consumption in state-III respiration (ST III O2). Recovery of ischemia-induced decreases in these functional indices in a saline-administered cirrhotic liver group was retarded compared with that in a normal liver group, and significantly low RCI and ST III O2 persisted 15 min after reperfusion. Prostaglandin E1 (PGE1) did not improve ischemia-induced decreases in RCI and ST III O2 but accelerated the recovery of mitochondrial respiratory function after reperfusion. Adenosine triphosphate (ATP) levels were markedly decreased during ischemia, and retardation of ATP recovery was also observed in rats with cirrhosis. PGE1 improved the recovery of ATP level in rats with cirrhosis. Liver blood flow in the cirrhotic liver was significantly lower than that of the normal liver. PGE1 enhanced liver blood flow. These results indicate that retardation of the recovery of RCI and ST III O2 in the cirrhotic liver might be based on the decrease in tissue blood flow and that agents increasing tissue blood flow might contribute to the acceleration of the recovery of mitochondrial respiratory function.