Restoration of mitochondrial energy-linked reactions following dexamethasone treatment of rats infected with the liver fluke Fasciola hepatica

Effect of Fasciola hepatica proteins on the functioning of rat hepatocytes

Fasciolosis is a hepatic parasitic infection that affects many mammal species and creates a great economic and veterinary problem. Molecular mechanisms of parasite–hepatocyte interactions have not been precisely characterized yet. Therefore, the aim of the study was to investigate alterations in the metabolic activity of rat liver cells exposed to Fasciola hepatica somatic proteins. Hepatocytes were incubated with 0–1 mg/ml of fluke's somatic proteins for various periods of time. Afterward, changes in hepatocytes metabolic activity were determined with MTT and enzyme leakage tests. Hepatocytes' capacity to synthesize albumin was also investigated. It was observed that protein concentration, as well as longevity of their action, influenced metabolic activity of rat liver cells. Diminution of hepatocytes survival rate, an increase in enzyme leakage and altered synthetic capacity after treatment with parasite's proteins were reported. It is concluded that somatic proteins of F. hepatica may play an important role in liver cell damaging.

Oxidative Modifications of Rat Liver Cell Components During Fasciola hepatica Infection

The aim of this paper was to assess the influence of Fasciola hepatica infection on oxidative modifications of rat liver cell components such as proteins and lipids. Wistar rats were infected per os with 30 metacercariae of F. hepatica. Activities and concentrations of liver damage markers were determined in the 4th, 7th, and 10th week postinfection (wpi). A decrease in antioxidant capacity of the host liver, manifested by a decrease in total antioxidant status (TAS), was observed. Diminution of antioxidant abilities resulted in enhanced oxidative modifications of lipids and proteins. F. hepatica infection enhanced lipid peroxidation, which was visible in the statistically significant increase in the level of different lipid peroxidation products such as conjugated dienes (CDs), lipid hydroperoxides (LOOHs), malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). The level of protein modification markers in the rat liver was also significantly changed and the most intensified changes were observed at seventh week postinfection. Concentration of carbonyl groups and dityrosine was significantly increased, whereas the level of tryptophan and sulfhydryl and amino groups was decreased. Changes in the antioxidant abilities of the liver and in the lipid and protein structure of the cell components resulted in destruction of the function of the liver. F. hepatica infection was accompanied by raising serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as markers of liver damage. A significant decrease in lysosomal as well as in the total activity of cathepsin B during fasciolosis was also observed.

Fasciola hepatica: Effects on the antioxidative properties and lipid peroxidation of rat serum

Fasciola hepatica infection is accompanied by increased formation of reactive oxygen species. The aim of this study was to analyze antioxidative properties of rat serum in the course of fasciolosis. Wistar rats were infected per os with 30 metacercariae of F. hepatica. Activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants in serum were determined at 4, 7, and 10 weeks post-infection (wpi). Activity of superoxide dismutase (Cu, Zn-SOD) significantly decreased (by 35% during the migratory phase, by 40 and 23% at 7 and 10 wpi, respectively), while glutathione reductase activity significantly increased (by 62, 65, and 41%, at 4, 7, and 10 wpi, respectively). No significant changes were found in the activity of glutathione peroxidase. Significant decreases in concentrations of reduced glutathione, vitamins C, E, and A were observed, particularly during the migratory phase of fasciolosis (at 4 wpi). These changes were accompanied by enhancement of lipid peroxidation processes as evidenced by increased levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Concentrations of MDA and 4-HNE at 4 wpi increased by 38% and by 59%. MDA increased by 51% at 7 wpi and by 79% at 10 wpi, while 4-HNE increased by 87 and 118%, respectively. The results indicate that fasciolosis is associated with enhanced oxidative reactions and reduced antioxidant defense capability of rat serum.

Antioxidant potential of rat liver in experimental infection with Fasciola hepatica

The aim of this paper is to assess the antioxidant properties of rat liver in the course of acute and chronic fasciolosis. Wistar rats were infected per os with 30 metacercariae of Fasciola hepatica. Liver activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants were determined at 4, 7, and 10 weeks post-infection. Activities of superoxide dismutase (Cu,Zn-SOD), glutathione peroxidase (GSH-Px), and glutathione reductase (GSSG-R) were decreased, catalase (CAT) activity was increased and non-enzymatic antioxidant concentrations (reduced glutathione, vitamins C, E and A) were reduced simultaneously with enhancement of lipid peroxidation processes as evidenced by increased levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Changes in the antioxidant abilities of the liver and in the phospholipid structure of the cell membrane were accompanied by rising activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as markers of liver damage.

Fasciola hepatica infection in sheep: changes in liver metabolism

Several aspects of liver function during infection with Fasciola hepatica were examined in sheep four weeks after infection and compared with the changes observed in infected rats. Previously reported respiratory abnormalities in mitochondria isolated from the left lobe of the liver of infected sheep were characterised further. Evidence is presented that the respiratory lesion is located in the mitochondrial electron transport chain and that the aberrant respiratory behaviour is not associated with an increase in nonesterified fatty acids and the depletion of mitochondrial phospholipids, as is the case in the rat. Microsomal membranes, which have also been shown to be depleted of phospholipids in the fluke-infected rat liver, showed no such changes in the sheep. However, in common with the rat, a substantial loss of cytochrome P450 was recorded in microsomes prepared from the left lobe, and the glycogen content of the left lobe was found to be less than 50 per cent of control values. No change was observed in glucose 6-phosphatase activity. All these changes were localised effects, confined to areas of fluke infiltration.

Importance of T-cell-dependent inflammatory reactions in the decline of microsomal cytochrome P450 concentration in the livers of rats infected with Fasciola hepatica

The concentration of cytochrome P450, measured spectrophotometrically in microsomal preparations from the livers of rats infected with 30 metacercariae of Fasciola hepatica, declined by approximately 50% at 3 weeks post-infection. Treatment of infected rats with the anti-inflammatory agent dexamethasone (2 mg/kg at 48 h intervals for 8 days prior to assay) abolished the decline in P450 content. Assay of P450 in infected congenitally athymic (nude) rats showed normal levels. These results demonstrate that the T-cell-dependent inflammatory response in the liver of the host is a necessary factor in the development of the decline in hepatic P450, which is known to compromise the metabolism of certain drugs in infected hosts.

Dexamethasone inhibits inorganic phosphate stimulated Ca(2+)-dependent damage of isolated rat liver and renal cortex mitochondria

The prevention of Ca(2+)-induced permeabilization of rat liver and kidney cortex mitochondria by dexamethasone, a common anti-inflammatory glucocorticoid, was the subject of this study. A non-specific release of matrix Ca2+ and membrane depolarization was observed in respiring mitochondrial suspensions subjected to a 30 nmol Ca2+/mg protein load in the presence of 2 mM inorganic phosphate (Pi), or 20 nmol Ca2+/mg protein with 1 mM Pi, for liver and renal cortex mitochondria (RCM), respectively. Additions of dexamethasone prior to Ca2+ in mitochondrial suspensions from liver or kidney cortex (80 and 200 microM final concentrations, respectively) led to 75-80% protection from these permeabilization-associated alterations of functional integrity. In conclusion, dexamethasone appears to show great promise in blocking the opening of a Ca(2+)-dependent 'non-specific pore' in the inner membranes of mitochondria from various sources.

A study of hepatic mitochondrial respiration and microsomal cytochrome P450 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 P450 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 P450 content. Preparations from infected CBA mice showed similar changes to Balb/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 P450 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.

Aberrant mitochondrial respiration in the livers of rats infected with Fasciola hepatica: the role of elevated non-esterified fatty acids and altered phospholipid composition

The non-esterified fatty acid (NEFA) content and phospholipid composition of mitochondria isolated from the livers of Wistar rats infected with Fasciola hepatica were examined in relation to the aberrant mitochondrial respiration previously reported [Rule, Behm, and Bygrave (1989) Biochem. J. 260, 517-523]. At 2 weeks post-infection, elevated NEFA levels were associated with uncoupling of mitochondrial respiration that was reversible in vitro by the addition of BSA. State IV respiration rates showed a strong correlation with NEFA content. At 3 weeks post-infection, NEFA content had increased further and uncoupled mitochondria no longer showed any response to BSA. 31P-NMR analyses of cholate extracts of mitochondria from infected livers at 3 weeks post-infection revealed a marked loss of several major phospholipid species with a concomitant increase in catabolic products, particularly glycerophosphocholine and glycerophosphoethanolamine. Similar changes were observed in microsomal extracts. The NEFA content and phospholipid composition of mitochondria isolated from infected, athymic nude rats were not significantly different from uninfected, athymic rats. These findings suggest that uncoupling of liver mitochondria during infection with F. hepatica is the result of phospholipase activation mediated by the immune system of the host.

Characterization of the oligomycin-sensitivity properties of the F1F0-ATPase in mitochondria from rats infected with the liver fluke Fasciola hepatica

The F1F0-ATPase activity of liver mitochondria isolated from rats infected with Fasciola hepatica at 3 and 4 weeks post-infection showed a marked loss of sensitivity to oligomycin and to N,N'-dicyclohexylcarbodiimide. A loss of sensitivity to diethylstilbestrol was also demonstrated at 4 weeks post-infection. Recovery was apparent in most cases by 6 weeks post-infection. No significant difference in latent ATPase activity was observed between mitochondria from control and infected livers at any stage of the infection. The mitochondria from infected livers were therefore considered to have a full complement of the F1 moiety of the F1F0-ATPase complex. Purification of the mitochondrial ATPase from 4-week infected livers resulted in a very low yield of an oligomycin-insensitive complex. This was due to a failure to enrich specific activity during purification. The evidence presented indicates that infection with Fasciola hepatica gives rise to alterations in the function of the host liver mitochondrial ATPase, namely loss of inhibitor sensitivity and apparent structural alterations of the ATPase complex.

Implications for the involvement of the immune system in parasite-associated cancers

Biological factors can be carcinogenic risk factors in humans and in animals. Numerous theories have been developed to explain the causal link between biologically-associated disease and the ensuing neoplasia. In this paper we discuss the merits of one of these theories, the possible association between the mammalian inflammatory response and cancer.