RESUMO
Females are born with a finite number of oocyte-containing follicles and ovary damage results in reduced fertility. Cadmium accumulates in the reproductive system, damaging it, and the cigarette smoke is a potential exposure route. Natural therapies are relevant to health benefits and disease prevention. This study verified the effect of cadmium exposure on the ovaries of mice and the blueberry extract as a potential therapy. Blueberry therapy was effective in restoring reactive species levels and δ-aminolevulinate dehydratase activity, and partially improved the viability of cadmium-disrupted follicles. This therapy was not able to restore the 17 ß-hydroxysteroid dehydrogenase activity. Extract HPLC evaluation indicated the presence of quercetin, quercitrin, isoquercetin, and ascorbic acid. Ascorbic acid was the major substance and its concentration was 620.24 µg/mL. Thus, cadmium accumulates in the ovaries of mice after subchronic exposure, inducing cellular damage, and the blueberry extract possesses antioxidant properties that could protect, at least in part, the ovarian tissue from cadmium toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 188-196, 2017.
Assuntos
Mirtilos Azuis (Planta)/química , Intoxicação por Cádmio/tratamento farmacológico , Doenças Ovarianas/induzido quimicamente , Doenças Ovarianas/tratamento farmacológico , Extratos Vegetais/farmacologia , Sintase do Porfobilinogênio/metabolismo , 11-beta-Hidroxiesteroide Desidrogenases/metabolismo , Animais , Intoxicação por Cádmio/patologia , Feminino , Glutationa Peroxidase/metabolismo , Glutationa Sintase/metabolismo , Camundongos , Doenças Ovarianas/patologia , Folículo Ovariano/efeitos dos fármacos , Sintase do Porfobilinogênio/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismoRESUMO
Delta-aminolevulinate dehydratase (δ-ALA-D) enzyme is sensitive to pro-oxidant agents, including molecular oxygen. Here, we tested whether hyperoxygenation after total intravenous (i.v.) anesthesia could interact with the type of anesthesia (dexmedetomidine, continuous infusion; 0.5 µg/kg/h or remifentanil, continuous infusion; 0.3 µg/kg/min) plus propofol using blood δ-ALA-D activity and thiobarbituric acid reactive substances (TBARS) levels as ending points of toxicity. In absence or presence of dithiothreitol (DTT), δ-ALA-D activity was reduced after hyperoxygenation in the group treated with remifentanil and was not modified in dexmedetomidine group. TBARS increased considerably in the blood of both groups of patients after oxygenation. The results obtained here suggest that the hyperoxygenation was associated with a marked increase in TBARS production regardless of the type of anesthesia. δ-ALA-D activity was only inhibited in remifentanil group, which indicates a possible interaction between oxygenation and the type of anesthetic. This is the first demonstration that dexmedetomidine may protect blood δ-ALA-D from oxidation. However, further studies are necessary to establish a possible antioxidant role of dexmedetomidine against hyperoxygenation in human blood.
Assuntos
Antioxidantes/farmacologia , Dexmedetomidina/farmacologia , Inibidores Enzimáticos/sangue , Estresse Oxidativo/efeitos dos fármacos , Oxigênio/sangue , Sintase do Porfobilinogênio/efeitos dos fármacos , Adulto , Anestesia Intravenosa/efeitos adversos , Inibidores Enzimáticos/administração & dosagem , Feminino , Humanos , Hipnóticos e Sedativos/farmacologia , Complicações Intraoperatórias , Pessoa de Meia-Idade , Oxigênio/administração & dosagem , Piperidinas/farmacologia , Sintase do Porfobilinogênio/antagonistas & inibidores , Sintase do Porfobilinogênio/metabolismo , Remifentanil , Substâncias Reativas com Ácido Tiobarbitúrico/análise , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismo , Adulto JovemRESUMO
UNLABELLED: In this study, we investigated the effects of lipoic acid (LA) in the hippocampus oxidative stress caused by pilocarpine-induced seizures in adult rats. Wistar rats were treated with 0.9% saline (i.p., control group), LA (10mg/kg, i.p., LA group), ubiquinone [20mg/kg, i.p., ubiquinone (UQ) group], pilocarpine (400mg/kg, i.p., P400 group), and the association of LA (10mg/kg, i.p.) plus pilocarpine (400mg/kg, i.p.) or UQ (20mg/kg, i.p.) plus pilocarpine (400mg/kg, i.p.), 30min before of administration of P400 (LA plus P400 group and UQ plus P400 group, respectively). After the treatments, all groups were observed for 1h. The enzyme activities (δ-aminolevulinic dehydratase (δ-ALA-D), Mg(2+) -ATPase, and Na(+) , K(+) -ATPase) were measured using spectrophotometric methods, and the results compared to values obtained from saline and pilocarpine-treated animals. Protective effects of LA and UQ were also evaluated on the same parameters. We reported here for the first time that Na(+) , K(+) -ATPase and δ-ALA-D activities inhibition and Mg(2+) -ATPase stimulation in the pilocarpine model are probably attributed to the oxidative stress caused by seizures in the rat hippocampus. The addition of the antioxidants LA and UQ may reverses the previously mentioned Na(+) , K(+) -ATPase and δ-ALA-D inhibitions and Mg(2+) -ATPase stimulation. CONCLUSIONS: The oxidative stress plays an important signaling role in pilocarpine-induced seizures, and antioxidant drugs might be considered as therapeutical tools in this pathology.
Assuntos
Antioxidantes/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Convulsões/tratamento farmacológico , Animais , Antioxidantes/metabolismo , ATPase de Ca(2+) e Mg(2+)/efeitos dos fármacos , ATPase de Ca(2+) e Mg(2+)/metabolismo , Modelos Animais de Doenças , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Pilocarpina/toxicidade , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , ATPase Trocadora de Sódio-Potássio/efeitos dos fármacos , ATPase Trocadora de Sódio-Potássio/metabolismo , Ácido Tióctico/farmacologia , Ubiquinona/farmacologiaRESUMO
In the present study, we investigated the effects of lipoic acid (LA) in the brain oxidative stress caused by pilocarpine-induced seizures in adult rats. Wistar rats were treated with 0.9% saline (i.p., control group), lipoic acid (10 mg/kg, i.p., LA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), and the association of LA (10 mg/kg, i.p.) plus pilocarpine (400 mg/kg, i.p.), 30 min before the administration of LA (LA plus pilocarpine group). After the treatments, all groups were observed for 1 h. The enzyme activities [delta-aminolevulinic dehydratase (delta-ALA-D), glutathione peroxidase (GPx), glutathione reductase (GR), and Na+,K+-ATPase] as well as the glutathione-reduced (GSH) and ascorbic acid (AA) concentrations were measured using spectrophotometric methods, and the results were compared to values obtained from saline and pilocarpine-treated animals. Protective effects of LA were also evaluated on the same parameters. In pilocarpine group, no changes were observed in GPx and GR activities and AA content. Moreover, in the same group, decrease in GSH levels as well as a reduction in delta-ALA-D and Na+,K+-ATPase activities after seizures was observed. In turn, in LA plus pilocarpine group, the appearance of seizures was abolished, and the decreases in delta-ALA-D and Na+,K+-ATPase activities produced by seizures as well as increases in GSH levels and GPx activity were reversed, when compared to the pilocarpine seizing group. The results of the present study demonstrated that preadministration of LA abolished seizure episodes induced by pilocarpine in rat, probably by reducing oxidative stress in rat hippocampus caused by seizures.
Assuntos
Enzimas/efeitos dos fármacos , Glutationa/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Convulsões/tratamento farmacológico , Convulsões/enzimologia , Ácido Tióctico/farmacologia , Animais , Antioxidantes/farmacologia , Antioxidantes/uso terapêutico , Convulsivantes/antagonistas & inibidores , Convulsivantes/toxicidade , Modelos Animais de Doenças , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/fisiologia , Enzimas/metabolismo , Glutationa/metabolismo , Glutationa Peroxidase/efeitos dos fármacos , Glutationa Peroxidase/metabolismo , Masculino , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Estresse Oxidativo/fisiologia , Pilocarpina/antagonistas & inibidores , Pilocarpina/toxicidade , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Convulsões/fisiopatologia , ATPase Trocadora de Sódio-Potássio/efeitos dos fármacos , ATPase Trocadora de Sódio-Potássio/metabolismo , Espectrofotometria/métodos , Ácido Tióctico/uso terapêuticoRESUMO
In this study, we examined the effects of low levels and sub-chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [delta-aminolevulinic acid dehydratase (delta-ALA-D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 microg/kg/day) by gavage; (Group III) received MeHg (100 microg/kg/day). The time of exposure was 90 days. BuChE and ALA-D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA-D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = -0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA-D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long-term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.
Assuntos
Butirilcolinesterase/efeitos dos fármacos , Compostos de Metilmercúrio/toxicidade , Animais , Biomarcadores/metabolismo , Butirilcolinesterase/sangue , Butirilcolinesterase/metabolismo , Relação Dose-Resposta a Droga , Masculino , Malondialdeído/metabolismo , Compostos de Metilmercúrio/administração & dosagem , Estresse Oxidativo/efeitos dos fármacos , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Fatores de TempoRESUMO
Paracetamol (acetaminophen, PCM) is widely used as an over-the-counter analgesic and antipyretic drug. Intake of a large dose of PCM may result in severe hepatic necrosis. Oxidative stress mediated by oxidative capacities of the PCM metabolite (N-acetyl-p-benzoquinoneimine (NAPQI), is considered as the main cause of hepatotoxicity of PCM. This work therefore seeks to induce liver damage in mice using single dose (25 0mg/kg) of acetaminophen and to evaluate the possible protective effects of administration (100mg/kg) of some medicinal plants (Kigelia africana, Calotropis procera, Hibiscus sabdariffa and Alchornea cordifolia) on PCM-induced liver damage in mice. The alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities were determined in the plasma of mice. Equally, comparative effects of these plants on lipid peroxidation product thiobarbituric reacting substances (TBARS) and some antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), gluthathione peroxidase (GPx), and delta-aminolevulinate dehydratase (delta-ALA-D) activities, were also evaluated in the mouse liver homogenate. Paracetamol caused liver damage as evident by statistically significant (P<0.05) increased in plasma activities of AST and ALT. There were general statistically significant losses in the activities of SOD, GPx, CAT, and delta-ALA-D and an increase in TBARS in the liver of paracetamol-treated group compared with the control group. However, all the tested plants except Calotropis procera were able to counteract these effects. The present results suggest that these plants can act as hepatoprotectives against paracetamol toxicity and that the mechanism by which they do this is by acting as antioxidants.
Assuntos
Acetaminofen/toxicidade , Analgésicos não Narcóticos/toxicidade , Hepatopatias/prevenção & controle , Estresse Oxidativo/efeitos dos fármacos , Fitoterapia , Plantas Medicinais , Alanina Transaminase/sangue , Alanina Transaminase/efeitos dos fármacos , Animais , Aspartato Aminotransferases/sangue , Aspartato Aminotransferases/efeitos dos fármacos , Calotropis/química , Catalase/efeitos dos fármacos , Catalase/metabolismo , Doença Hepática Induzida por Substâncias e Drogas , Euphorbiaceae , Glutationa Peroxidase/efeitos dos fármacos , Glutationa Peroxidase/metabolismo , Hibiscus , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Camundongos , Extratos Vegetais/farmacologia , Folhas de Planta , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Superóxido Dismutase/efeitos dos fármacos , Superóxido Dismutase/metabolismo , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismoRESUMO
Oxidative stress has been suggested to be an important molecular mechanism of toxic effects of lead in the kidney. Thioredoxin reductase-1 is a selenoprotein involved in many cellular redox processes. This study evaluated the effect of acute and chronic exposure intraperitoneally to lead acetate on thioredoxin reductase-1 activity and on other oxidative stress parameters in the rat kidney, as well as on indicators of renal function commonly used to assess lead poisoning. Acute exposure to 25 mg/kg lead acetate increased superoxide dismutase and thioredoxin reductase-1 activity (after 6, 24 and 48 hr), while exposure to 50 mg/kg lead acetate increased catalase activity (after 48 hr) and inhibited delta-aminolevulinate dehydratase activity (after 6, 24 and 48 hr) in the kidney (P < 0.05). Chronic exposure (30 days) to 5 mg/kg lead acetate inhibited delta-aminolevulinate dehydratase and increased glutathione S-transferase, non-protein thiol groups, catalase, thioredoxin reductase-1 and uric acid plasma levels, while exposure to 25 mg/kg lead acetate reduced body weight and delta-aminolevulinate dehydratase, but increased glutathione S-transferase, non-protein thiol groups and uric acid plasma levels (P < 0.05). No changes were observed in thiobarbituric acid reactive substances, glutathione peroxidase, creatinine or inorganic phosphate levels after either acute or chronic exposure. Our results suggest that thioredoxin reductase-1 may be an early indicator of acute exposure to low lead doses.
Assuntos
Rim/efeitos dos fármacos , Compostos Organometálicos/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Tiorredoxina Dissulfeto Redutase/efeitos dos fármacos , Animais , Creatinina/sangue , Relação Dose-Resposta a Droga , Rim/enzimologia , Testes de Função Renal , Masculino , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Tiorredoxina Redutase 1 , Tiorredoxina Dissulfeto Redutase/metabolismo , Ácido Úrico/sangueRESUMO
In the present study the potential neurotoxicity of diphenyl diselenide, as measured by the manifestation of seizures in rat pups (postnatal days, PND, 12-14) was evaluated. The results suggest that the latency for the appearance of tonic-clonic seizures, characterized by rearing and falling of rat pups body, was dependent of the dose tested. Diphenyl diselenide at high doses induced seizure episodes in rat pups. The highest dose of diphenyl diselenide (500 mg/kg) increased the levels of lipid peroxidation and catalase activity as well as decreased delta-ALA-D (delta-aminolevulinate dehydratase) and Na(+), K(+) ATPase activity in the brain of rat pups. Our results indicate the possible involvement of free radical oxygen injury in diphenyl diselenide-induced seizures. The data obtained with the dose of 150 mg/kg in the brain of rats that exhibited seizures are: an increase in lipid peroxidation levels; the lack of effect on catalase activity; an inhibition of delta-ALA-D activity, supporting that the enzyme activity is more sensitive than other parameters analyzed as an indicator of oxidative stress. The lowest dose of diphenyl diselenide emphasizes the relationship between the appearance of seizures and the latency for the onset of the first episode. Taken together, this paper could add to our understanding of diphenyl diselenide neurotoxic effect demonstrated by the appearance of seizures which are, at least in part, related to the oxidative stress.
Assuntos
Derivados de Benzeno/toxicidade , Neurotoxinas/toxicidade , Compostos Organosselênicos/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Sintase do Porfobilinogênio/efeitos dos fármacos , Convulsões/induzido quimicamente , ATPase Trocadora de Sódio-Potássio/efeitos dos fármacos , Administração Oral , Fatores Etários , Análise de Variância , Animais , Derivados de Benzeno/administração & dosagem , Relação Dose-Resposta a Droga , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/fisiologia , Neurotoxinas/administração & dosagem , Compostos Organosselênicos/administração & dosagem , Estresse Oxidativo/fisiologia , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Convulsões/metabolismo , Método Simples-Cego , ATPase Trocadora de Sódio-Potássio/metabolismoRESUMO
The aim of the present study was to evaluate pharmacological and toxicological properties of 1-buthyltelurenyl-2-methylthioheptene (compound 1). In vitro, compound 1 at 1 microM was effective in reducing lipid peroxidation induced by Fe/EDTA. Compound 1 presented neither thiol peroxidase nor thiol oxidase activity and did not change delta-ALA-D (delta-aminolevulinate dehydratase) activity (10-400 microM). Calculated LD(50) of compound 1, administered by oral route, was 65.1 micromol/kg. Rats treated with compound 1 did not reveal any motor impairment in the open field. Hepatic, renal and cerebral lipid peroxidation in treated rats did not differ from those in control rats. Conversely, 0.5 micromol/kg of compound 1 decreased lipid peroxidation in spleen. Delta-ALA-D activity in liver and spleen was inhibited in rats treated with the higher dose of compound 1 but no significant differences were detected in renal delta-ALA-D activity. AST (aspartate aminotransferase) and ALT (alanine aminotransferase) activities as well as urea and creatinine levels were increased by high doses of compound 1 (50-75 micromol/kg). Compound 1 induced a significant decrease in plasma triglyceride levels but none of the doses tested changed the cholesterol level. This is a promising compound for more detailed pharmacological studies involving organotellurium compounds.
Assuntos
Antioxidantes/farmacologia , Peroxidação de Lipídeos/efeitos dos fármacos , Compostos Organometálicos/farmacologia , Telúrio/farmacologia , Alanina Transaminase/efeitos dos fármacos , Animais , Antioxidantes/toxicidade , Aspartato Aminotransferases/efeitos dos fármacos , Ácido Edético/farmacologia , Ferro/farmacologia , Rim/efeitos dos fármacos , Rim/enzimologia , Dose Letal Mediana , Fígado/efeitos dos fármacos , Fígado/enzimologia , Compostos Organometálicos/toxicidade , Peroxidases/efeitos dos fármacos , Sintase do Porfobilinogênio/efeitos dos fármacos , Ratos , Baço/efeitos dos fármacos , Baço/enzimologia , Telúrio/toxicidade , Triglicerídeos/sangueRESUMO
Heavy metals have received great attention as environmental pollutants mainly because once introduced in the biological cycle they are incorporated in the food chain. Especially the mercury toxicity due to a diversity of effects caused by different chemical species should be emphasized. Heavy metal intoxication has been treated with chelating agents such as 2,3-dimercapto-1-propanol (BAL). However, the efficacy of this treatment is questionable due to the lack of specific effect on the toxic metal. The present study examined the effects of HgCl2 exposure (five doses of 5.0 mg/kg between ages 8 to 12 days) on physiological parameters, on porphobilinogen synthase activity, and on mercury content in liver, kidneys and brain from suckling rats. The effect of BAL (one dose of 12.5-75 mg/kg) applied 24 hr after mercury intoxication on these parameters was also investigated. The results demonstrate that HgCl2 intoxication induced a decrease of corporal weight gain as well as brain weight and an increase in renal weight. The inhibition of porphobilinogen synthase from liver and kidney, is still significant and was not modified by subsequent BAL treatment. However, BAL altered two effects induced by mercury: increase in death percentage and decrease in mercury contents in liver and kidney. The increase of mortality induced by mercury was not promoted by metal redistribution to brain nor by the increase of porphobilinogen synthase inhibition induced by metal. More investigations are necessary to determine if the different effects of BAL on intoxication by metals are possibly related to other tissues and/or if the probable metal-chelating complex formed is more toxic than the metal itself.
Assuntos
Dimercaprol/farmacocinética , Rim/química , Fígado/química , Cloreto de Mercúrio/farmacocinética , Mercúrio/antagonistas & inibidores , Sintase do Porfobilinogênio/farmacocinética , Animais , Animais Recém-Nascidos/fisiologia , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Química Encefálica , Morte , Dimercaprol/administração & dosagem , Dimercaprol/efeitos adversos , Esquema de Medicação , Interações Medicamentosas , Quimioterapia Combinada , Feminino , Injeções Subcutâneas , Rim/efeitos dos fármacos , Rim/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Cloreto de Mercúrio/administração & dosagem , Cloreto de Mercúrio/antagonistas & inibidores , Mercúrio/química , Tamanho do Órgão/efeitos dos fármacos , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Aumento de Peso/efeitos dos fármacosRESUMO
Heavy metals, like cadmium, lead, and mercury, are potential toxic substances. The exposure to these metals can cause renal disturbances and neurological alterations. Young rats are more sensitive to harmful agents than adult animals. Delta-ALA-D enzyme acts as a biomarker of these exposures, since it has high affinity for divalent metals. The purpose of this search was to investigate the sensitivity of delta-ALA-D from suckling rats to cadmium, lead or mercury in vitro. IC(50) for delta-ALA-D activity of brain, kidneys, and liver from rats with ages between 1 and 6, 8 and 13 or 17 and 21 days was determined using metals concentrations that range from 0 to 200 microM for CdCl(2), 0 to 600 microM for HgCl(2) and from 0 to 50 microM for lead acetate. The results demonstrated that the cerebral delta-ALA-D activity is more sensitive to lead acetate than to cadmium and mercury. Delta-ALA-D from hepatic tissue is the most resistant to presence of mercury chloride in assay medium. Lead and cadmium are more toxic to renal enzyme than mercury. To sum up, the sensitivity of delta-ALA-D enzyme of young rats to heavy metals studied depends on the phase of development and tissue.
Assuntos
Cádmio/toxicidade , Chumbo/toxicidade , Mercúrio/toxicidade , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/farmacologia , Fatores Etários , Animais , Biomarcadores/análise , Encéfalo/efeitos dos fármacos , Encéfalo/enzimologia , Feminino , Rim/efeitos dos fármacos , Rim/enzimologia , Fígado/efeitos dos fármacos , Fígado/enzimologia , Masculino , Sintase do Porfobilinogênio/análise , Ratos , Ratos Wistar/crescimento & desenvolvimentoRESUMO
The short- and long-term pro-oxidant effect of protoporphyrin IX (PROTO) administration to mice was studied in liver. A peak of liver porphyrin accumulation was found 2 h after the injection of PROTO (3.5 mg/kg, i.p.); then the amount of porphyrins diminished due to biliar excretion. After several doses of PROTO (1 dose every 24 h up to 5 doses) a sustained enhancement of liver porphyrins was observed. The activity of delta-aminolevulinic acid synthetase was induced 70-90% over the control values 4 h after the first injection of PROTO and stayed at these high levels throughout the period of the assay. Administration of PROTO induced rapid liver damage, involving lipid peroxidation. Hepatic GSH content was increased 2h after the first injection of PROTO, but then decreased below the control values which were maintained after several doses of porphyrin. After a single dose of PROTO, Cu-Zn superoxide dismutase (SOD) was rapidly induced, suggesting that superoxide radicals had been generated. Increased levels of hydrogen peroxide coming from the reaction catalyzed by SOD and lipid peroxides as a consequence of membrane peroxidation, induced the activity of catalase and glutathione peroxidase (GPx), while decreased GSH levels induced glutathione reductase (GRed) activity. However after 5 doses of PROTO, the activity of SOD was reduced reaching control values. GPx and catalase activities slowly went down, while GRed continued increasing as long as the levels of GSH were kept very low. TBARS values, although lower than those observed after a single dose of PROTO, remained above control values; Glutathione S-transferase activity was instead greatly diminished, indicating sustained liver damage. Our findings would indicate that accumulation of PROTO in liver induces oxidative stress, leading to rapid increase in the activity of the antioxidant enzymes to avoid or revert liver damage. However, constant accumulation of porphyrins provokes a liver damage so severe that the antioxidant system is compromised.
Assuntos
Fígado/metabolismo , Estresse Oxidativo , Protoporfirinas/metabolismo , 5-Aminolevulinato Sintetase/efeitos dos fármacos , 5-Aminolevulinato Sintetase/metabolismo , Animais , Antioxidantes/metabolismo , Catalase/efeitos dos fármacos , Catalase/metabolismo , Glutationa/metabolismo , Glutationa Peroxidase/efeitos dos fármacos , Glutationa Peroxidase/metabolismo , Glutationa Redutase/efeitos dos fármacos , Glutationa Redutase/metabolismo , Heme/metabolismo , Fígado/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos , Oxidantes/metabolismo , Oxidantes/farmacologia , Sintase do Porfobilinogênio/efeitos dos fármacos , Sintase do Porfobilinogênio/metabolismo , Porfirinas/sangue , Protoporfirinas/farmacologia , Superóxido Dismutase/efeitos dos fármacos , Superóxido Dismutase/metabolismoRESUMO
In all the cutaneous porphyrias, alterations in the heme pathway lead to an excessive production and accumulation of porphyrins. Absorption of light energy by circulating porphyrins induces reactive oxygen species generation, which provoke enzyme inactivation and protein structure changes. Protein structure alterations induced by porphyrins with different physico-chemical properties on delta-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) were examined. The action of uroporphyrin (URO), a highly hydrophilic porphyrin, and protoporphyrin (PROTO), most hydrophobic, was tested. ALA-D and PBG-D were partially purified from bovine liver and exposed to URO or PROTO, both in the dark and under UV light. All experiments were performed in solution after removing the porphyrins. Treatment with 10 microM URO I or 10 microM PROTO IX reduced the activity of ALA-D and PBG-D. This effect increased with increasing time of exposure to porphyrins. Solubility of the enzymes in buffer containing 3 M KCl decreased with increasing time of porphyrin treatment; this may be because of exposure of hydrophobic residues that are normally shielded in the native protein structure. Tryptic digestion of ALA-D and PBG-D exposed to URO I or PROTO IX resulted in an increase of protein degradation products, indicating an enhanced susceptibility to proteolysis. Fluorescence emission of several enzymes aminoacids was greatly modified. The structural changes described were observed when the enzymes were exposed to porphyrins both in the dark or under UV light. However, they were more noticeable with UV light. These results suggest that porphyrins per se can act directly on protein structure and that this action may be enhanced by UV irradiation.