Protective action of antioxidants on hepatic damage induced by griseofulvin.

Erythropoietic protoporphyria (EPP) is a disease associated with ferrochelatase deficiency and characterized by the accumulation of protoporphyrin IX (PROTO IX) in erythrocytes, liver, and skin. In some cases, a severe hepatic failure and cholestasis were observed. Griseofulvin (Gris) develops an experimental EPP with hepatic manifestations in mice such as PROTO IX accumulation followed by cellular damage as wells as necrotic and inflammatory processes. The antioxidant defense system was also altered. The aim was to evaluate the possible protective effect of different antioxidant compounds: trolox (Tx), ascorbic acid (Asc), the combination Tx and Asc, melatonin (Mel), and the polyphenols: ellagic acid, quercetin, chlorogenic acid, caffeic acid, gallic acid, and ferulic acid on liver damage and oxidative stress markers in a mouse model of EPP. Coadministration of Gris with Tx, Asc, and its combination, or Mel mainly affected heme biosynthetic pathway, resulting in a decrease in ALA-S activity which was increased by Gris, while the tested polyphenols exerted a protective effect on oxidative stress, decreasing lipid peroxidation and the activity of some antioxidant enzymes. In conclusion, antioxidant compounds can only protect partially against the liver damage induced by Gris, reducing oxidative stress or acting on heme regulation.

Hepatic damage and oxidative stress induced by Griseofulvin in mice.

Erythropoietic Protoporphyria (EPP) is a disease associated with ferrochelatase deficiency, which produces accumulation of protoporphyrin IX (PROTO IX) in erythrocytes, liver and skin. In some cases, a severe hepatic failure and cholestasis was observed. Griseofulvin (Gris) develops an experimental EPP with hepatic manifestations in animals. The aim of this work was to further characterize this model studying its effect on different metabolisms in mice Gris feeding (0-2.5%, 7 and 14 days). PROTO IX accumulation in liver, blood and feces, induction of ALA-S activity, and a low rate of Holo/Apo tryptophan pyrrolase activity was produced, indicating a reduction of free heme pool. The progressive liver injury was reflected by the aspect and the enlargement of liver and the induction of hepatic damage. Liver redox balance was altered due to porphyrin high concentrations; as a consequence, the antioxidant defense system was disrupted. Heme oxygenase was also induced, however, at higher concentrations of antifungal, the free heme pool would be so depleted that this enzyme would not be necessary. In conclusion, our model of Protoporphyria produced liver alterations similar to those found in EPP patients.

Sevoflurane: its action on heme metabolism and Phase I drug metabolizing system.

Acute attacks of porphyria are most commonly precipitated by events that decrease heme concentrations. Enzyme inducing-drugs are the most important triggering factors, particularly in relation to anaesthesia. We have reported previously that Enflurane and Isoflurane produced significant heme metabolism alterations, indicating that the use of these anaesthetics in porphyric patients should be avoided. The aim of this work was to evaluate the effect of the anaesthetic Sevoflurane on heme pathway and drug metabolizing Phase I system in mice. To this end, animals received different doses of the anaesthetic (1-2 ml/kg) and were sacrificed at different times (5-60 min). Data revealed important alterations in the enzymes involved in Acute Intermittent Porphyria, such as an induction in hepatic 5-Aminolevulinic acid synthetase activity and a diminished Porphobilinogen deaminase activity in liver and blood 20 minutes after Sevoflurane administration to mice in a dose of 1.5 ml/kg. Heme oxygenase activity was also induced, indicating the onset of oxidative stress. Total CYP levels and CYP2E1 expression were enhanced. As a consequence of these events, heme free pool would be depleted. In conclusion, our results in mice would suggest that Sevoflurane should be used with caution and very careful control in porphyric patients.

Glutamatergic system: another target for the action of porphyrinogenic agents.

The N-methyl-diethyl-aspartate (NMDA) receptor has been reported to play an important role in several acute and chronic neuropathologic syndromes. 5-aminolevulinic acid (ALA) accumulates in acute porphyrias due to a deficiency in the heme biosynthetic pathway. Considering that glutamate uptake inhibition caused by ALA could be one of the reasons conducing to porphyric neuropathy, it was of interest to evaluate the effect of porphyrinogenic agents on NMDA glutamatergic system. To this end receptor levels and apparent affinity (Kd) were analyzed in mice brain cortex and cerebellum. NMDA levels were diminished after chronic Isoflurane anaesthesia in brain cortex. In cerebellum, a diminution was observed after acute Enflurane and Isoflurane and allylisopropylacetamide, while ethanol administration showed a significant increase. ALA administration diminished NMDA levels only in cerebellum. Affinity constant was only reduced in brain cortex after chronic Isoflurane treatment. In conclusion, glutamatergic system appears to be involved in the action of some of the porphyrinogenic drugs studied mainly in cerebellum. Receptors regulation should therefore be considered an important mechanism in the cellular response to specific drugs, with the aim of designing new therapies and elucidating the mechanisms leading to porphyric neuropathy and acute attack triggering.

Induction of hepatic aminolevulinate acid synthetase activity by isoflurane in a genetic model for erythropoietic protoporphyria.

Erythropoietic Protoporphyria (EPP) is an inherited deficiency of ferrochelatase, the last enzyme of the heme pathway. Under general anaesthesia, some patients develop neurological dysfunction suggesting upregulation in heme biosynthesis similar to that described for acute porphyrias after xenobiotic administration. Our aim has been to evaluate whether Isoflurane induces alterations in the heme pathway in a mouse model for EPP. Administration of Isoflurane (a single dose of 2 ml/kg, i.p) to wild-type (+/+), heterozygous (+/Fechm1Pas) and homozygous (Fechm1Pas/Fechm1Pas) mice, was evaluated by measuring the activity of delta-aminolevulinic acid synthetase (ALA-S) and Porphobilinogen-deaminase (PBG-D) in different tissues, as well as Heme oxygenase (HO), cytochrome P-450, CYP2E1 and glutathione levels in liver. Porphyrin precursors were measured in 24 h-urine samples. Fechm1Pas/Fechm1Pas mice receiving anaesthesia show enhanced ALA-S and CYP2E1 activities in the liver and increased urinary excretion of porphyrin precursors. No alterations were found in either PBG-D or HO activities. Diminished glutathione levels suggest that anaesthesia may produce oxidative stress in these animals. In conclusion, Isoflurane induces ALA-S activity and increased excretion of porphyrin precursors in EPP mice. These findings appear to confirm our previous hypothesis and indicate that Isoflurane may be an unsafe anaesthetic not only for patients with acute porphyrias but also for individuals with non acute porphyrias.

Heme oxygenase, aminolevulinate acid synthetase and the antioxidant system in the brain of mice treated with porphyrinogenic drugs.

Several drugs and stress are involved in the triggering of attacks in acute porphyrias. The central nervous system is extremely sensitive to free radical damage because of a relatively low antioxidant capacity. We have demonstrated that mice brain cholinergic system was altered by the effect of some porphyrinogenic agents. The aim of this work was to investigate how known porphyrinogenic drugs affect delta-Aminolevulinic acid synthetase (ALA-S), which is the response of heme oxygenase (HO) to this challenge and to evaluate if the xenobiotics studied develop stress oxidative in mice brain. HO activity was 50-70% induced after chronic Enflurane and Isoflurane anaesthesia, dietary Griseofulvin and starvation. An increase in mRNA HO expression was caused by chronic anaesthesia and Veronal treatments; instead allylisopropilacetamide (AIA) reduced mRNA expression. ALA-S activity was induced by acute administration of anaesthetics (89%), veronal (240%) and ethanol (80%), while ALA-S mRNA expression augmented by chronic administration of enflurane, AIA and veronal. Stress markers such as superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities and malondialdehyde and reduced glutathione levels showed different responses depending on the xenobiotic assayed. In conclusion, some of the drugs studied produced oxidative stress in brain that was confirmed through HO induction and this could be one of the factors leading to porphyric neuropathy.

Relevance of cytochrome P450 levels in the actions of enflurane and isoflurane in mice: studies on the haem pathway.

1. The effect of the fluorinated ether anaesthetics enflurane and isoflurane in mice on haem metabolism and regulation in different metabolic states, such as depression and induction of cytochrome P450 produced by allylisopropylacetamide (AIA) and imidazole, respectively, was investigated. 2. Mice previously treated with AIA (350 mg/kg, i.p.) or imidazole (400 mg/kg, i.p.) received a single dose (1 mL/kg, i.p.) of enflurane or isoflurane and were killed 20 min after anaesthetic administration. 3. Induction of delta-aminolevulinic acid synthetase (ALA-S) activity was found, as expected, in animals receiving AIA and also in animals treated with AIA plus anaesthesia, but no change in the activity of either porphobilinogenase (PBGase) or porphobilinogen deaminase (PBG-D) activities was detected in these two groups of animals. An additional increase in haem destruction was observed in the AIA plus isoflurane-treated group. When mice were injected with imidazol alone or in combination with the anaesthetics, ALA-S activity was increased 50-90% in all groups, but again no change in PBGase or PBG-D activity was observed. Haem oxygenase was diminished in mice receiving imidazole and anaesthesia. 4. In conclusion, neither enflurane nor isoflurane caused additional disturbances in haem metabolism to those produced by AIA or imidazole alone.

Griseofulvin-induced hepatopathy due to abnormalities in heme pathway.

1. The effect of long-term griseofulvin (GRIS) topical administration on some indicators of liver damage was examined. 2. Liver porphyrin accumulation was significant; however, no porhyrin crystals were observed under light microscopy. 3. An earlier onset of hepatopathy was established (3-fold) increase of direct bilirubin values after 7 days of treatment; hepatic injury was confirmed by measuring a 6-fold increase of free bilirubin. 4. Enhanced values of alkaline phosphatase and glutamic oxalacetic transaminase (GOT) confirmed the onset of cholestasis. 5. Topical application of GRIS induced measurable hepatopathy. Nevertheless, we cannot discard the possibility that this hepatopathy could also be attributed in part to a direct reaction to xenobiotics.

Effect of chronic anesthesia on the drug-metabolizing enzyme system and heme pathway regulation.

1. The effect of chronic enflurane or isoflurane anesthesia on hepatic heme regulation and the drug-metabolizing system in mice treated or not with phenobarbital (PB) was investigated. 2. delta-Aminolevulinic acid synthetase was induced 50-170% in all cases. Urinary porphyrin precursor excretion was also enhanced, but these values were lower when animals also received PB. 3. Cytochrome (CYT) P-450 levels were enhanced in animals treated with enflurane whether or not they were given PB. 4. Gluthatione-S-transferase activity was induced by enflurane (138%) or isoflurane (174%), and even more in animals receiving PB also. Sulfatase activity was increased more than 60% with anesthetics. Isoflurane produced a 50% increase of beta-glucuronidase activity and a 35% diminution of tryptophan pyrrolase. 5. The association between anesthetics and PB produced diverse effects on the metabolizing enzyme system. 6. Data suggest that both anesthetics, chemically related, could act through two different mechanisms, however, with the same final effect: heme pathway deregulation.

Strain and sex differences in the effect of enflurane and isoflurane on heme metabolism in mice.

1. The influence of strain and sex on the effect of enflurane and isoflurane and administration on heme metabolism was investigated to identify the animal model which could best reproduce the biochemical signs of acute intermittent porphyria. 2. Enflurane produced 35% and 80% increases in ALA-S activity only in CF1 male and female mice, respectively, whereas isoflurane induced 40% enzyme activity in CF1 male. 3. CF1 males showed around 35% decrease in blood PBGase and PBG-deaminase after administration of enflurane, whereas isoflurane provoked a striking inhibition (70%) in males of the C57 strain. 4. Enflurane produced alterations in heme synthesis, which would fit a model of acute porphyria in CF1 male mice. On the other hand, isoflurane would mimic biochemical alterations of this porphyria in C57 males.

Alterations in fluorinated ether anesthetics effects on heme metabolism following chronic ethanol consumption.

1. The effect of enflurane or isoflurane anesthesia (1 ml/kg, i.p.) in animals chronically treated with ethanol (30%, v/v, in drinking water during a week) on heme metabolism and its regulation was investigated. 2. In those animals previously intoxicated with ethanol that received isoflurane, ALA-S activity was increased (control values: 0.071 +/- 0.022 nmol/mg, n = 10; treated animals: 0.110 +/- 0.034 nmol/mg, n = 8) and blood PBGase and deaminase were strikingly diminished (control values, n = 10: PBGase: 0.101 +/- 0.015 nmol/mg, deaminase: 0.242 +/- 0.075 nmol/mg; treated animals, n = 6: PBGase: 0.063 +/- 0.013 nmol/mg; deaminase: 0.145 +/- 0.045 nmol/mg). 3. The time-response study showed that liver ALA-S is enhanced at shorter times of anesthesia with isoflurane and that blood PBGase and deaminase appeared inhibited later in animals previously treated with ethanol. 4. Results reproduce some biochemical alterations known to occur in acute intermittent porphyria.

Effect of multiple doses of volatile anesthetics on heme enzymes.

1. The effect of the administration of several doses of Enflurane and Isoflurane (2 ml/kg, i.p., daily) on heme metabolism and glucose levels was studied. 2. Liver and kidney delta-Aminolevulinic acid synthetase (ALA-S) activities were 85% (P < 0.01) induced after the third dose of Enflurane, instead induction of this enzyme was only detected, in animals receiving one dose of Isoflurane. 3. Blood Porphobilinogenase and deaminase (50%, P < 0.01) inhibition was produced only when animals received a single dose of the anesthetics. 5. ALA-S induction observed after the third dose of anesthetics could be a consequence of long lasting depletion in heme synthesis produced by blocking at uroporphyrinogen level.

Administration of the anesthetic isoflurane to mice: a model for acute intermittent porphyria?

The effects of isoflurane, a commonly used volatile anesthetic, on the activity of some haem enzymes in liver, kidney, and blood, and glucose content in liver and blood were studied. Mice were injected with different doses of the drug (0.5-6 mL/kg) and killed at varying intervals after injection (5-240 min). Within this dose range, optimal effects on alteration of haem metabolism were obtained at 2 mL/kg. The time-response profile for each enzyme was different. Blood porphobilinogenase (PBGase) and deaminase showed lower activities 20 min after anesthesia. This diminution coupled with the induction of delta-aminolevulinate synthetase activity observed soon after anesthesia (5 min) would fit well with the expected biochemical changes occurring in acute intermittent porphyria, indicating that this may be a suitable animal model for this disease.

Porphyrinogenic properties of the anesthetic enflurane.

1. The effect of enflurane, a volatile anesthetic, on heme metabolism was studied. Different doses (0.5-6.0 ml/kg) of this anesthetic were administered i.p. to mice and animals sacrificed at different times after administration (5-240 min). 2. The dose of 2 ml/kg was chosen as the optimum anesthetic dose producing more alterations in the heme pathway. 3. ALA-S was significantly induced at earlier times of anesthesia. 4. Blood PBGase and deaminase was greatly reduced. 5. This diminution coupled with ALA-S induction are in accordance with the known biochemical changes occurring in acute intermittent porphyria and include enflurane in the list of porphyrinogenic drugs, the use of which is not recommended for the management of anesthesia in porphyric patients.

The effect of griseofulvin on the heme pathway--II. An exhaustive analysis during short and long-term challenge.

1. A clear biphasic response of the enzyme activities as a function of intoxication time due to the topical cutaneous griseofulvin treatment was observed. 2. The initial acute induction of ALA-S activity would be due to depletion of free heme in the regulatory pool caused by cytochrome P 450 destruction. 3. The second induction peak, would be due to less heme formation, secondary to the ferrochelatase inhibition, as expected for the erythropoietic protoporphyria model. 4. The biphasic response of hepatic ALA-D and PBGase activities would be related to ALA-S activity changes and the subsequent augmented available substrates. 5. Endogenous liver porphyrin distribution in cytosolic, mitochondrial and nuclear fractions was investigated. 6. The in vitro biosynthesis of porphyrins confirmed both the biphasic model and the hepatic porphyrins subcellular distribution. 7. Two mechanisms to explain the action of griseofulvin at shorter and longer times of intoxication are proposed.

In vitro effect of cyanide, thiosulphate and S-adenosyl-L-methionine on the activity of rhodanese and other enzymes.

1. Some in vitro studies were performed to elucidate the action of S-adenosyl-L-methionine (SAM) and thiosulphate on liver rhodanese, delta-amino-levulinic acid dehydratase (Al A-D) and cytochrome oxidase affected by cyanide in the experimental conditions. 2. SAM was unable to interact with the sulfur substituted rhodanese complex suggesting that SAM would blockade the thiosulphate binding sites on rhodanese. 3. Cyanide and thiosulphate inhibited ALA-D activity when both compounds were present in the incubation or the preincubation mixture. Cyanide binding on the enzyme was irreversible. 4. Cyanide inhibited cytochrome oxidase activity and the reversible nature of the binding was demonstrated by gel filtration. 5. SAM had no effect on either ALA-D or cytochrome oxidase activities.

The effect of cyanide intoxication on hepatic rhodanese kinetics.

1. Results of studies on the kinetics of hepatic rhodanese and the effects of S-adenosyl-L-methionine (SAM) on these kinetic parameters in cyanide-treated and non-treated mice are reported here. 2. The enzyme exhibited typical Michaelis-Menten behaviour with cyanide inhibition at concentrations higher than 50 mM. Km values of 4.74 and 0.85 mM were obtained for thiosulphate and cyanide, respectively, in control mice. 3. These results stress the biological importance of the rhodanese reaction for cyanide detoxification. 4. Km values were not significantly modified when the animals were intoxicated with a lethal (20 mg/kg) or a non-lethal (4 mg/kg) dose of cyanide. 5. SAM treatment either in control or in cyanide-poisoned animals doubled the Km's for cyanide.

An experimental assessment of cyanide challenge dose-response, time-course and recovery of indicative toxicity parameters.

1. Several sub-lethal doses of cyanide were assayed with the aim of obtaining significant differences in the parameters studied. A dose of 4 mg/kg s.c. was selected. 2. Present studies were carried out to determine the time dependence of the effects produced by s.c. administration of a single dose of potassium cyanide as well as the recovery time of some of the toxicity indicative parameters. 3. It was found that cyanide effects continued for at least 3 days; after the parameters had recovered normal values.

Cyanide intoxication--III. On the analogous and different effects provoked by non-lethal and lethal challenged doses.

1. The effect of acute cyanide administration to mice in a lethal and a non-lethal dose and the anti-cyanide effect of S-adenosyl-L-methionine (SAM) and thiosulphate were investigated. 2. The poisoning action was determined by measuring cytochrome oxidase, rhodanese and delta-aminolevulinic acid dehydratase (ALA-D) activity. 3. The toxic metabolizing degree was investigated by measuring plasma and urine thiocyanate levels. 4. The state of the sulfane sulfur pool was investigated by determining cyanide labile-sulfur levels. 5. These results support the belief that rhodanese plays a fundamental role in the detoxification process only when high levels of cyanide are administered.

Cyanide intoxication. II. The effects of systematic cyanide challenge on indicative toxicity parameters.

1. Present studies were carried out to establish the action of cyanide maintained at a high level during a period as long as desired. 2. One of the earliest effects of cyanide seems to be the inhibition of hepatic rhodanese. These changes do not seem to occur in the blood. 3. Available cyanide labile-sulfur was always altered, unless cyanide tissue levels could not be detected. 4. The inhibitory action of cyanide on enzymatic reaction involving Schiff base intermediates was also corroborated through its effect on delta-aminolevulinate acid dehydratase activity. 5. S-Adenosyl-L-methionine was not able to modify the toxic cyanide action.