Ethoxyresorufin and pentoxyresorufin O-dealkylation by hepatic microsomes from female Fischer 344 rats: effects of age and diet

Caloric restriction prevents lead-induced oxidative stress and inflammation in rat liver

The aim of the present study is to investigate the effects of caloric restriction on liver of lead-administered rat. Male Sprague-Dawley rats were randomly divided into two groups: Ad libitum fed group (AL, free access to normal rat chow) and caloric restriction group (CR, fed 65% of AL animals' food intake). After 6 weeks, half of the animals of each group were injected lead acetate and the other half were injected saline. Liver tissue samples were collected at the end of the experiments. Glutathione peroxidase (GPx), superoxide dismutase (SOD), malondialdehyde (MDA), and tumor necrosis factor (TNF-α) were measured in the tissue extracts. Histological studies were also performed. Our results showed that lead administrations (not saline injections) reduced liver SOD and GPx and increased MDA and TNF-α in AL animals, but in the CR animals lead injections did not significantly change the measured parameters. The histological studies supported the biochemical findings. We concluded that 65% CR may prevent lead-induced oxidative stress and inflammation in rat liver.

Effect of dietary n-3 and n-6 oils with and without food restriction on activity of antioxidant enzymes and lipid peroxidation in livers of cyclophosphamide treated autoimmune-prone NZB/W female mice

OBJECTIVE

Cyclophosphamide (CTX), an alkylating agent, is extensively used in the treatment of lupus nephritis, but its administration has been associated with free radical mediated oxidative stress. The present study was designed to investigate the effect of dietary corn oil (CO), fish oil (FO) and food restriction (FR) on the activities of hepatic antioxidant enzymes, fatty acid composition and lipid peroxidation following CTX administration in autoimmune-prone NZB/W female mice.

METHODS

Autoimmune-prone NZB/W female mice were fed either ad libitum (AL) or food restricted (60% of AL intake), semipurified diets containing 5% CO or 5% FO supplemented with equal levels of antioxidants and injected with either phosphate buffered saline (PBS), or CTX (50 mg/kg body weight) every 10 days. Proteinuria was measured biweekly. The treatment was stopped at 10 months and diets were continued until the mice were killed at 12 months. Fatty acid composition, activity of antioxidant enzymes and lipid peroxidation were analyzed in liver homogenates, and anti-DNA antibodies were analyzed in the serum.

RESULTS

Mice in the FO/AL dietary group exhibited significantly higher liver catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities compared to the CO/AL dietary group. CTX significantly decreased SOD and GSH-Px activity in the FO/AL group and CAT and GSH-Px in the CO/AL group. In AL fed mice given CTX, activities of CAT, GSH-Px and GST were significantly higher in mice fed FO diets than in mice fed CO diets. FR increased the activity of enzymes in both the CO and FO diet groups. In FR mice, CTX decreased CAT and GSH-Px activity in both the CO and FO dietary groups, but glutathione S-transferase (GST) only in the CO group. The decrease in SOD activity was not significant in either of the restricted groups. CTX significantly increased generation of thiobarbituric acid reactive substances (TBARS) in both AL groups. FR significantly decreased lipid peroxidation in both the CO and FO groups, with or without CTX. CTX decreased serum anti-DNA antibody levels in both the CO and FO dietary groups. FR also decreased antibody titer in both the CO and FO dietary groups, and it was decreased further with CTX treatment. FO fed animals had higher levels of n-3 fatty acids, whereas CO fed animals had high levels of n-6 fatty acids. CTX significantly increased 20:4 and decreased 18:1 in CO/AL fed animals, whereas it increased 18:1 and decreased 22:6 in FO/AL fed animals.

CONCLUSIONS

Results obtained in the present study suggests that FO and, more significantly, FO combined with FR can have a beneficial effect in hepatic tissues subjected to CTX induced oxidative stress by regulating the activity of antioxidant enzymes. In addition, the study also indicates that n-3 and n-6 dietary lipids are susceptible to lipid peroxidation, particularly in the presence of a prooxidant like CTX, and that FR is beneficial in decreasing lipid peroxidation. The study also suggests that FO and CTX can have additive effects in preventing kidney disease in NZB/W mice.

Influence of propiverine on hepatic microsomal cytochrome p450 enzymes in male rats

The bladder spasmolytics propiverine was shown to induce hepatic cytochrome P450 (P450) and aminopyrine and aniline oxidation in rats. To characterize the type of enzyme induction and its dose dependence, activities of seven hepatic microsomal P450-dependent monooxygenases were measured in 72 male LEW1A albino rats (body weight 236-295 g) after oral treatment with 0.5, 2, 6, and 60 mg/kg of propiverine hydrochloride for 5 days and compared with the effects of 40 mg/kg beta-naphthoflavone, 10 mg/kg phenobarbital, and 20 mg/kg dexamethasone (each group, n = 8). CYP2B expression was measured by Western blotting. Furthermore, the inhibitory potency of propiverine on P450 enzymes was evaluated in competition assays with three most specific monooxygenases. Results show that Propiverine induced several monooxygenases and CYP2B expression dose dependently. The effects were well comparable with a phenobarbital-type inducer with 60 mg/kg being equipotent to 10 mg/kg phenobarbital. Furthermore, propiverine in low concentrations inhibited pentylresorufin O-dealkylase (for CYP2B) in vitro. In conclusion, propiverine is a phenobarbital-type inducer on hepatic P450 enzymes in rats in doses about 100-times above the therapeutic doses in man.

Induction of cytochrome P450 1A1 in rat liver slices by 7-ethoxycoumarin and 4-methyl-7-ethoxycoumarin

7-Ethoxycoumarin (EC) is widely used as a model substrate for monooxygenase function, its O-deethylation representing cytochrome P450 (P450) activity mainly of 1A but also of 2B isoforms. Reports on investigations of its own capacity to induce or suppress P450 activities, however, have not been found in biomedical literature. To avoid the influence of in vivo pharmacokinetics, studies can well be undertaken with liver slice incubation. Therefore in the present investigation precision-cut rat liver slices from male 43-63-day-old male HAN:Wistar outbred rats were incubated at 30 degrees C in carbogen saturated William's Medium E for 24 h. EC was added previously to final concentrations of 10, 25, 50, 75 or 100 microM. After incubation, homogenate was prepared from slices and used for model reactions (7-ethoxyresorufin O-deethylation [EROD] and 7-pentoxyresorufin O-depentylation [PROD]). EROD, indicating activities of 1A isoforms, was enhanced by incubation with EC at 25 and 50 microM to about doublefold but showed control or lower values at 75 and 100 microM. Incubation with beta-naphthoflavone in comparison led to variable increases (3-5-fold of controls). For PROD as an indicator of the phenobarbital inducible P450 isoforms 2B1 and 2B2 no enhancement was found, but a decrease by incubation with 75 and 100 microM EC. To further investigate the correlation between enzyme activity and gene expression after slice incubation, P450 1A1 mRNA content was measured by RT-PCR. Induced gene expression for 1A1 was seen with different EC concentrations to a variable extent, though not as strong as with BNF. Similar incubation with 4-methyl-7-ethoxycoumarin revealed an even stronger induction of EROD activity with maxima at about 10-32 microM, reaching BNF values. In contrast incubation with 7-benzyloxycoumarin had no evident inducing or suppressing effect, neither on EROD nor on PROD activity.