Uroporphyrinogen Decarboxylase Activity Research Articles

Porphyria cutanea tarda induced by tamoxifen

Porphyria cutanea tarda (PCT) results from a decrease in the activity of uroporphyrinogen decarboxylase. In the sporadic form, the decrease in the activity is restricted to the liver and is generally related to alcohol, estrogens, iron overload, hepatitis C infection, and halogenated aromatic hydrocarbons. We describe the development of porphyria cutanea tarda in a 53-year-old woman one year after breast cancer surgery and the initiation of treatment with tamoxifen. No additional drugs were prescribed. After tamoxifen was discontinued, a gradual clinical and laboratorial improvement was noticed suggesting a causative role of the drug. There are many reports discussing tamoxifen side-effects, but there are only three case reports in the literature that describe tamoxifen as a probable trigger of porphyria cutanea tarda. In this report, the potential porphyrinogenicity of tamoxifen and clinical implications are the targets of our discussion.

Porphyrie cutanée tardive chez un enfant greffé de moelle

Porphyria cutanea tarda (PCT) is rare in childhood and association with bone marrow transplant has occasionally been reported. A 13-year-old boy was referred to our department for bullous lesions on sun-exposed areas. His past medical history revealed acute biphenotypic leukaemia with complete remission after allogeneic hematopoietic stem cell transplantation (unrelated donor). Complications of bone marrow transplant comprised anaemia (treated by blood transfusions), primary cytomegalovirus (CMV) infection, pulmonary aspergillosis and acute digestive graft-versus-host disease. The diagnosis of type I sporadic PCT was based on high levels of porphyria and normal erythrocytic uroporphyrinogen decarboxylase activity. The bullous lesions disappeared on bleeding, but the patient subsequently developed sclerodermiform lesions. An association between PCT and bone marrow transplant has been reported previously in two independent cases, of which one involved a child. The causative role of bone marrow transplantation in the development of PCT could be related to several triggering factors: primary CMV infection, hepatotoxic drugs, blood transfusion and possible chronic hepatic graft-versus-host disease. We report the second case in a child of type I PCT associated with bone marrow transplantation. This new case reinforces the hypothesis of a non-random relationship between the two conditions.

Smoking but not homozygosity for CYP1A2 g‐163A allelic variant leads to earlier disease onset in patients with sporadic porphyria cutanea tarda

Porphyria cutanea tarda (PCT) results from decreased activity of hepatic uroporphyrinogen decarboxylase (UROD). Both sporadic and familial forms are characterised by typical cutaneous lesions triggered by genetic/environmental factors. Studies in rodents showed that cytochrome P4501A2 (CYP1A2) plays a central role in the synthesis of a competitive inhibitor of hepatic UROD, but there is little evidence in humans. The impact of smoking and CYP1A2 g-163C > A allelic variant upon first appearance of clinical signs was investigated in 102 patients (80 sporadic-PCT) and 150 healthy donors from Spain. We found an increase in the frequency of CYP1A2 g-163A allele in patients with PCT when compared with controls, although the more inducible A/A genotype had no effect on the onset age. In sporadic-PCT, smoking leads to earlier onset of clinically overt disease in moderate-to-heavy smokers (>or=10 cigarettes/day). In conclusion, this study provides evidence that smoking hastens the onset of cutaneous symptoms in sporadic-PCT patients.

Hepatoerythropoietic Porphyria Misdiagnosed as Child Abuse

Hepatoerythropoietic porphyria (HEP) is a rare autosomal recessive disorder resulting from the markedly deficient, but not absent, activity of the heme biosynthetic enzyme uroporphyrinogen decarboxylase (UROD). The disorder typically manifests during infancy or early childhood with extreme photosensitivity, skin fragility in sun-exposed areas, hypertrichosis, erythrodontia, and pink urine. Three siblings, offspring of parents of Puerto Rican and Dominican descent, had with excessive scarring on the face and dorsal aspect of the forearms, which initially led to the erroneous suspicion of child abuse. Although these lesions were photodistributed, overt photosensitivity had not been observed, with the exception of a single episode of blistering and onycholysis after intense sun exposure in 1 affected child. Mild facial hypertrichosis, chronic anemia, polyarticular arthritis, and developmental delay represented additional findings. Biochemical studies of urine, plasma, and erythrocyte porphyrins from the affected siblings established the diagnosis of HEP. Sequencing of the UROD gene revealed compound heterozygosity for a novel missense mutation, V166A, and a complex deletion/insertion, 645del1053ins10. Our report expands the phenotypic and genotypic spectrum of HEP, highlighting mild cutaneous presentations that can occur without obvious photosensitivity and masquerade as child abuse.

Familial and Sporadic Porphyria Cutanea Tarda

Porphyria cutanea tarda is the most frequent porphyria and occurs in both sporadic and familial forms. We conducted the current study in a series of 152 consecutive patients with porphyria cutanea tarda attending the Porphyria Unit of the Hospital Clinic of Barcelona, Spain, to update the clinical manifestations of the disease and to study the sex differences, the proportion of familial forms, and the role of different risk factors in this population. Patients were classified as familial and sporadic cases according to erythrocyte uroporphyrinogen-decarboxylase activity and uroporphyrinogen-decarboxylase genotyping. In our cohort, skin fragility and blisters on the hands were the most frequent clinical manifestations. Women more frequently had facial hypertrichosis (84.8%; p = 0.004), affected areas other than the hands and face (33.3%; p = 0.008), and pruritus (27.3%; p = 0.041) compared with men. Of our patients, 11.8% did not present the typical clinical onset of the disease, with facial hypertrichosis and hyperpigmentation the more frequent complaints in these cases. Analysis of risk factors showed a high prevalence of hepatitis C virus infection (65.8%) and alcohol abuse (59.9%), both being more frequent in men (p < 0.001). Hepatitis C virus infection was the only risk factor that showed differences between the sporadic and familial forms in the logistic regression model (odds ratio, 0.05; 95% confidence interval, 0.006-0.46). In conclusion, atypical forms of presentation of porphyria cutanea tarda should be considered in order to prevent delayed diagnosis. We note the sustained role of hepatitis C virus infection in the precipitation of sporadic porphyria cutanea tarda. Therefore, in countries with a high prevalence of hepatitis C virus infection, the absence of such infection in a patient with porphyria cutanea tarda may suggest a possible familial case.

Complex Gene−Chemical Interactions: Hepatic Uroporphyria As a Paradigm

Many toxicological disorders, in common with numerous human diseases, are probably the consequence of multigene interactions with a variety of chemical and physiological factors. The importance of genetic factors may not be obvious initially from association studies because of their complexity and variable penetrance. The human disease, porphyria cutanea tarda (PCT), is a skin disease caused by the photosensitizing action of porphyrins arising secondary to the decreased activity of an enzyme of heme biosynthesis, uroporphyrinogen decarboxylase (UROD), in the liver. It is triggered by idiosyncratic hepatic interaction between genetic factors and chemicals such as alcohol, estrogenic drugs, and polyhalogenated aromatics. PCT and its animal models are known collectively as the hepatic uroporphyrias. There is strong evidence for the participation of iron in the pathogenesis of these conditions. Mouse models have been used to explore the relative importance of a variety of agents such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), alcohol, and iron in the development of uroporphyria and to elucidate the mechanism of the depression of hepatic UROD activity. Mutations of the UROD and hemochromatosis (HFE) genes are genetic factors in some PCT patients which can be mimicked in mice heterozygous for the Hfe and Urod null genes. Association studies of uroporphyria induced by TCDD or hexachlorobenzene with DNA markers in mouse intercrosses have shown the participation of other, unknown, genetic factors in addition to the strong influence of the Ahr gene. The pathogenesis of hepatic uroporphyrias exemplifies the complexity of the interactions between chemical and genetic factors that can contribute to the hepatotoxicity of chemicals.

A Dialysis Case Presentation and Discussion Edited by Roger A. Rodby: Bullous Skin Lesions in a Patient Undergoing Chronic Hemodialysis

Porphyria cutanea tarda (PCT) is a vesiculobullous skin disorder characterized by a defect in heme biosynthesis. Reduced activity of the hepatic enzyme uroporphyrinogen decarboxylase (URO-D) results in accumulation of photosensitive porphyrins; this ultimately leads to the skin fragility and blistering that is characteristic of this disease. The majority of cases of PCT are associated with acquired deficiencies of the enzyme URO-D, secondary to hepatic injury precipitated by medications or infections. Less commonly, PCT has been documented in patients with end-stage renal disease. The pathogenesis of PCT in long-term hemodialysis (HD) has been attributed to many factors, but the following mechanisms have been implicated: (i) decreased hepatic URO-D activity due to suppressive effects of iron and other hepatotoxins and (ii) poor porphyrin clearance by renal replacement therapies. We report a case of PCT that developed in a patient on maintenance HD for 4 years. He had a history of hepatitis C and evidence of iron overload. However, as the patient was anemic, therapeutic phlebotomy was problematic and therefore erythrocyte-stimulating agents were maximized to mobilize iron stores and allow phlebotomy. With this treatment, the patient's skin lesions improved in conjunction with decreasing ferritin levels.

Associations Among Behavior-Related Susceptibility Factors in Porphyria Cutanea Tarda

Porphyria cutanea tarda (PCT) is the most common of the human porphyrias and results from an acquired deficiency of hepatic uroporphyrinogen decarboxylase (UROD). Some susceptibility factors have been identified; we examined associations among multiple factors in a large cohort of patients. Multiple known or suspected susceptibility factors and demographic and clinical features of 143 patients (mean age 52 years, 66% male, 88% Caucasian) with documented PCT (mean onset at 41 +/- 8.8 years) were tabulated; associations were examined by contingency tables, classification and regression tree (CART) analysis, and logistic regression. The most common susceptibility factors for PCT were ethanol use (87%), smoking (81%), chronic hepatitis C virus (HCV) infection (69%), and HFE mutations (53%; 6% C282Y/C282Y and 8% C282Y/H63D). Of those who underwent hepatic biopsy or ultrasound, 56% had evidence of hepatic steatosis. Of those with PCT, 66% of females took estrogen, 8% were diabetic, 13% had human immunodeficiency virus (HIV) infection, and 17% had inherited uroporphyrinogen decarboxylase (UROD) deficiency (determined by low erythrocyte UROD activity). Three or more susceptibility factors were identified in 70% of patients. HCV infection in patients with PCT was significantly associated with other behavior-related factors such as ethanol use (odds ratio [OR], 6.3) and smoking (OR, 11.9). Susceptibility factors for PCT were similar to previous studies; most patients had 3 or more susceptibility factors. Associations between PCT and HCV, ethanol or smoking could be accounted for by a history of multiple substance abuse; other factors are distributed more randomly among patients.

A Pilot Study Investigating the Safety and Efficacy of Injectable Hemin (Panhematin®) in Patients with Low to Intermediate-1 Risk Myelodysplastic Syndrome.

Abstract 4859 Authors J. M. Shammo1, K. Shell1, D. Rhoades1, A. Rizman1, K. E. Anderson2, M. Holmay3, I. Miller1, S. Gregory1 Institutions 1Rush University Medical Center, Chicago, IL, 2University of Texas Medical Branch, Galveston, TX, 3Director CNS Medical Liaisons, Lundbeck, Inc. Background Injectable hemin (Panhematin) is an iron-containing metalloporphyrin that is approved for the treatment of acute intermittent porphyria. Preclinical data indicate that hemin administration has the potential to stimulate progenitor cell growth and gamma globin chain synthesis. Clinical trial data from Europe on the use of hemin in myelodysplastic syndrome (MDS) suggest it can result in hematologic improvements in a subset of patients (Volin 1988, Timonen 1992). Objective This was an investigator initiated study aimed at evaluating the safety and efficacy of Panhematin in patients with low or intermediate-1 risk MDS. Response assessments were done at week 8, as defined by the International Working Group. Secondary endpoints included the alterations of ferritin, porphyrin, and hemoglobin F levels from baseline with treatment Patients and Methods Between 6/2007 and 10/2008, 6 patients (median age 73.5, range 64-80, men = 5, women = 1) were treated. All patients had a diagnosis of low or intermediate-1 risk MDS (International Prognostic Scoring (IPSS) score of 0-1), were transfusion-dependent or had hemoglobin values of ' 10 g/dL, had ' 10% blasts in bone marrow and peripheral blood, had platelet counts &gt; 50,000/ microL and absolute neutrophil counts (ANC) &gt; 500/microL. Patients received daily doses of Panhematin® at 3 mg/kg IV on days 1 through 4 of week 1, and weekly on day 1 of weeks 2 through 8. Efficacy and safety assessments, including bone marrow biopsies, were performed on Week 8. Partial and complete responders in any of the three cell lines were allowed to continue treatment for as long as they benefit. Patients who did not demonstrate a response or those whose disease had progressed at Week 8 were withdrawn from the study. Results Five of 6 patients completed 8 weeks of treatment and were evaluable for response assessment. One patient withdrew his consent. One patient received an additional 4 weekly doses after achieving an erythroid response and was later retreated for an additional 16 weeks. All other patients had stable disease and four of them remained transfusion dependent. Only 1 (with RARS) out of 5 evaluable patients met criteria for hematologic response. His baseline hemoglobin (Hb) of 7.3g/dL increased to 8.5g/dL at week 8, and peaked at 8.7g/dL at week 9. His bone marrow biopsy at week 8 revealed a decrease in ringed sideroblasts from 73% to 51%. Once off treatment, this patient's Hb dropped back to a near baseline level of 7.0g/dL. Approximately a year later (after protocol amendment allowed for re-treatment), he was retreated and his Hb again increased to 8.2 g/dL at week 8, peaking at 8.8 g/dL. In two patients with RARS (the responder and another patient), it was noted that the erythrocyte protoporphyrin level was initially elevated and rose even higher at week 8. Similarly, erythrocyte porphobilinogen deaminase (PBGD) and uroporphyrinogen decarboxylase (UROD) activities increased with treatment, especially in the one patient who responded. In that patient, these activities decreased again after treatment ended. The reticulocyte count increased from 0.0294 to 0.0411 × 10 6/mcL only in this patient. There was no correlation observed between response to panhematin and HbF levels. Treatment was well tolerated in all patients and no major toxicities were observed. Conclusions In this small study of hemin treatment of patients with low to Int-1 risk MDS, one patient responded with increases in hemoglobin and in reticulocytes. The increases in reticulocytes and in erythrocyte PBGD and UROD in the responder may indicate an increase in erythropoeisis resulting in a larger proportion of young erythrocytes in peripheral circulation after treatment. Clearly, such observations need validation in larger studies, which may result in better understanding of MDS disease biology. Disclosures Shammo: ovation pharmaceutical: Research Funding. Off Label Use: the use of Panhematin in MDS.

Porphyrie cutanée tardive révélée par le voriconazole

Voriconazole is a systemic antifungal drug that can induce phototoxic reactions suggestive of porphyria cutanea tarda (PCT); however, porphyrin levels in urine, blood and stool remain within the normal range. Superficial cheilitis is frequently associated with this clinical picture; it is believed to be related to drug-induced impairment of endogenous retinoid metabolism. We report a case of true PCT associated with cheilitis, both occurring soon after the introduction of voriconazole and partially disappearing after withdrawal of this drug. A 65-year-old man with a past history of excessive alcohol consumption presented with typical features of PCT associated with a mild superficial desquamating cheilitis. Both symptoms had appeared 12 days after initiation of oral voriconazole for a cavitary aspergillosis. Laboratory tests confirmed a sporadic case of PCT. Withdrawal of voriconazole (replaced by itraconazole) resulted in complete disappearance of the cheilitis but incomplete remission of the PCT. Ultimately, the patient was successfully treated by venous puncture. This patient had both voriconazole-induced superficial cheilitis and a true PCT which seemed related to the same drug. The mechanism by which voriconazole may have revealed PCT remains elusive and could possibly have involved decreased uroporphyrinogen decarboxylase activity in the liver or potentiation of the phototoxic effects of porphyrins by the cutaneous toxicity of voriconazole. On presentation of a clinical picture of PCT-like photosensitivity in a patient on voriconazole, laboratory investigations should be performed routinely to rule out true PCT, even in cases of associated cheilitis.

Familial and Sporadic Porphyria Cutanea Tarda: Characterization and Diagnostic Strategies

Porphyria cutanea tarda (PCT) occurs in sporadic (sPCT) and familial (fPCT) forms, which are generally clinically indistinguishable and have traditionally been differentiated by erythrocyte uroporphyrinogen decarboxylase (UROD, EC 4.1.1.37) activity. We used UROD gene sequencing as the reference standard in assessing the diagnostic accuracy of UROD activity, evaluating the mutation spectrum of the UROD gene, determining the frequency and disease attributes of PCT and its subtypes in Norway, and developing diagnostic models that use clinical and laboratory characteristics for differentiating fPCT and sPCT. All consecutive patients with PCT diagnosed within a 6-year period were used for incidence calculations. UROD activity analysis, UROD gene sequencing, analysis of hemochromatosis mutations, and registration of clinical and laboratory data were carried out for 253 patients. Fifty-three percent of the patients had disease-relevant mutations, 74% of which were c.578G>C or c.636+1G>C. The UROD activity at the optimal cutoff had a likelihood ratio (LR) of 9.2 for fPCT, whereas a positive family history had an LR of 19. A logistic regression model indicated that low UROD activity, a high uroporphyrin-heptaporphyrin ratio, a young age at diagnosis, male sex, and low alcohol consumption were predictors of fPCT. The incidence of PCT was 1 in 100 000. Two commonly occurring mutations are responsible for the high frequency of fPCT in Norway. UROD activity has a high diagnostic accuracy for differentiating the 2 PCT types, and a model that takes into account both clinical information and laboratory test results can be used to predict fPCT.

Identification and characterization of novel uroporphyrinogen decarboxylase gene mutations in a large series of porphyria cutanea tarda patients and relatives

Porphyria cutanea tarda (PCT) arises from decreased hepatic activity of uroporphyrinogen decarboxylase (UROD). Both genetic and environmental factors interplay in the precipitation of clinically overt PCT, but these factors may vary between different geographic areas. Decreased activity of UROD in erythrocytes was used to identify patients with UROD mutations among a group of 130 Spanish PCT patients. Nineteen patients (14.6%) were found to harbor a mutation in the UROD gene. Eight mutations were novel: M1I, 5del10, A22V, D79N, F84I, Q116X, T141I and Y182C. Five others were previously described: F46L, V134Q, R142Q, P150L and E218G. The new missense mutations and P150L were expressed in Escherichia coli. D79N and P150L resulted in proteins that were localized to inclusion bodies. The other mutations produced recombinant proteins that were purified and showed reduced activity (range: 2.3-73.2% of wild type). These single amino acid changes were predicted to produce complex structural alterations and/or reduced stability of the enzyme. Screening of relatives of the probands showed that 37.5% of mutation carriers demonstrated increased urinary porphyrins. This study emphasizes the role of UROD mutations as a strong risk factor for PCT even in areas where environmental factors (hepatitis C virus) have been shown to be highly associated with the disease.

Hexachlorobenzene Treatment on Hepatic Mitochondrial Function Parameters and Intracellular Coproporphyrinogen Oxidase Location

These studies try to elucidate why isocoproporphyrin appears in hexachlorobenzene-poisoned rats' feces. Chronic exposure of hexachlorobenzene to rats produces an experimental model for human porphyria cutanea tarda. After 8 weeks of treatment, rats showed high porphyrin excreta and 50% inhibition of liver uroporphyrinogen decarboxylase activity. Uroporphyrin plus heptacarboxylic porphyrin exceeded coproporphyrin in urine, whereas in feces, isocoproporphyrin, from abnormal pentacarboxylic porphyrinogen III oxidative decarboxylation by liver coproporphyrinogen oxidase, became the main porphyrin. Trypsin-treated mitochondria showed that the outer and inner membrane permeability barrier was highly conserved after hexachlorobenzene intoxication. In digitonin-treated hexachlorobenzene mitochondria, coproporphyrinogen oxidase was free in the mitochondrial intermembrane space, whereas in normal mitochondria, 30% to 50% remained anchored to the inner membrane. Hexachlorobenzene led to a decrease in respiratory control and ADP/O ratios (uncoupled mitochondria). Albumin restored oxidative phosphorylation, indicating no irreversible inner membrane damage. Normal and hexachlorobenzene mitochondria oscillatory studies exhibited similar damping factor values, showing that hexachlorobenzene had no significant effect on membrane fluidity and elasticity. Mitochondrial uncoupling could explain the free state of the enzyme within the intermembrane space. The free state of the enzyme makes it more flexible and would allow pentacarboxylic porphyrinogen III, whose levels are increased, to compete with coproporphyrinogen III and being transformed into dehydroisocoproporphyrinogen, the liver forerunner of fecal isocoproporphyrin.

Molecular heterogeneity of familial porphyria cutanea tarda in Spain: characterization of 10 novel mutations in the UROD gene

Porphyria cutanea tarda (PCT) results from decreased hepatic uroporphyrinogen decarboxylase (UROD) activity. In the majority of patients, the disease is sporadic (S-PCT or type I) and the enzyme deficiency is limited to the liver. Familial PCT (F-PCT or type II) is observed in 20-30% of patients in whom mutations on one allele of the UROD gene reduce UROD activity by approximately 50% in all tissues. Another variant of PCT (type III) is characterized by family history of the disease although it is biochemically indistinguishable from S-PCT. To investigate the molecular basis of PCT in Spain and to compare enzymatic and molecular analysis for the identification of patients with F-PCT. Erythrocyte UROD activity measurement and mutation analysis of the UROD gene were carried out in a cohort of 61 unrelated Spanish patients with PCT and 50 control individuals. Furthermore, each novel missense mutation identified was characterized by prokaryotic expression studies. Of these 61 patients, 40 (66%) were classified as having S-PCT, 16 (26%) as having F-PCT and five (8%) as having type III PCT. Discordant results between enzymatic and molecular analysis were observed in two patients with F-PCT. In total, 14 distinct mutations were found, including 10 novel mutations: five missense, one nonsense, three deletions and an insertion. Prokaryotic expression of the novel missense mutations demonstrated that each results in decreased enzyme activity or stability. These results confirm the high degree of molecular heterogeneity of F-PCT in Spain and emphasize the usefulness of molecular genetic analysis to distinguish between F-PCT and S-PCT.

A porphomethene inhibitor of uroporphyrinogen decarboxylase causes porphyria cutanea tarda

Porphyria cutanea tarda (PCT), the most common form of porphyria in humans, is due to reduced activity of uroporphyrinogen decarboxylase (URO-D) in the liver. Previous studies have demonstrated that protein levels of URO-D do not change when catalytic activity is reduced, suggesting that an inhibitor of URO-D is generated in hepatocytes. Here, we describe the identification and characterization of an inhibitor of URO-D in liver cytosolic extracts from two murine models of PCT: wild-type mice treated with iron, delta-aminolevulinic acid, and polychlorinated biphenyls; and mice with one null allele of Uro-d and two null alleles of the hemochromatosis gene (Uro-d(+/-), Hfe(-/-)) that develop PCT with no treatments. In both models, we identified an inhibitor of recombinant human URO-D (rhURO-D). The inhibitor was characterized by solid-phase extraction, chromatography, UV-visible spectroscopy, and mass spectroscopy and proved to be uroporphomethene, a compound in which one bridge carbon in the uroporphyrinogen macrocycle is oxidized. We synthesized uroporphomethene by photooxidation of enzymatically generated uroporphyrinogen I or III. Both uroporphomethenes inhibited rhURO-D, but the III isomer porphomethene was a more potent inhibitor. Finally, we detected an inhibitor of rhURO-D in cytosolic extracts of liver biopsy samples of patients with PCT. These studies define the mechanism underlying clinical expression of the PCT phenotype, namely oxidation of uroporphyrinogen to uroporphomethene, a competitive inhibitor of URO-D. The oxidation reaction is iron-dependent.

Two novel uroporphyrinogen decarboxylase (URO-D) mutations causing hepatoerythropoietic porphyria (HEP)

Hepatoerythropoietic porphyria (HEP) is a rare form of porphyria in humans. The disorder is caused by homozygosity or compound heterozygosity for mutations of the uroporphyrinogen decarboxylase (URO-D) gene. Subnormal URO-D activity results in accumulation of uroporphyrin in the liver, which ultimately mediates the photosensitivity that clinically characterizes HEP. Two previously undescribed URO-D mutations found in a 2-year-old Caucasian boy with HEP, a maternal nonsense mutation (Gln71Stop), and a paternal missense mutation (Gly168Arg) are reported here. Recombinant Gly168Arg URO-D retained 65% of wild-type URO-D activity and studies in Epstein-Barr Virus (EBV)-transformed lymphoblasts indicated that protein levels are reduced, suggesting that the mutant protein might be subjected to accelerated turnover. The crystal structure of Gly168Arg was determined both as the apo-enzyme and with the reaction product bound. These studies revealed little distortion of the active site, but a loop containing residues 167-172 was displaced, possibly indicating small changes in the catalytic geometry or in substrate binding or increased accessibility to a cellular proteolytic pathway. A second pregnancy occurred in this family, and in utero genotyping revealed a fetus heterozygous for the maternal nonsense mutation (URO-D genotype WT/Gln71Stop). A healthy infant was born with no clinical evidence of porphyria.

Toxicity of hexachlorobenzene and its transference from microalgae ( Chlorella kessleri) to crabs ( Chasmagnathus granulatus)

The aim of this work was to study the transference of hexachlorobenzene from a green alga ( Chlorella kessleri) to an estuary crab ( Chasmagnathus granulatus), and to analyze the toxic effects that the xenobiotic has on the latter. The effect of hexachlorobenzene uptake was evaluated measuring oxidative stress, Uroporphyrinogen decarboxylase activity and morphometric parameter alteration, and also performing a histological analysis of crab hepatopancreas. Results demonstrated that hexachlorobenzene enters the alga, is accumulated in it, and then transferred into the crab, causing a decrease in Uroporphyrinogen decarboxylase activity in both organisms. The high malondialdehyde levels detected in crab hepatopancreas after the toxic treatment suggested the existence of hexachlorobenzene-induced lipid peroxidation. Antioxidant defenses such as superoxide dismutase activity and reduced glutathione content fell below normal values on the fourth week of treatment. At the same time, the hepatosomatic index, used as a morphometric parameter, reduced 20% with respect to the control. The histological analysis revealed epithelium disorganization in hepatopancreas tubules, confirming the existence of structural damage caused by hexachlorobenzene.

Attenuation of polychlorinated biphenyl induced uroporphyria by iron deprivation

A toxic sequel to polyhalogenated aromatic hydrocarbon exposure in humans is the development of porphyria cutanea tarda. In a mouse model (experimental uroporphyria) utilizing an environmentally relevant polychlorinated biphenyl (PCB) mixture, we show that the toxicity can be markedly influenced by nutritional status. In mice made susceptible to uroporphyria through a targeted deletion of one allele of uroporphyrinogen decarboxylase ( Uro-D+/− ), an iron deficient diet prevented the development of the uroporphyria and the changes in associated parameters normally seen within three weeks following a single exposure to Aroclor 1254. Iron deprivation also completely prevented PCB-induced uroporphyria in mice wild-type at the Uro-D locus ( Uro-D+/+), a model that requires δ-aminolevulinic acid administration for the development of uroporphyria. In Uro-D+/− mice consuming δ-aminolevulinic acid, PCB exposure produced a severe uroporphyria that was attenuated, not prevented, by iron deficiency. This attenuation moderated hepatic uroporphyrin and uroporphyrinogen decarboxylase inhibitor levels, but not the depression of cytosolic uroporphyrinogen decarboxylase activity.

The role of inherited and acquired factors in the development of porphyria cutanea tarda in the Argentinean population

Inherited and environmental factors are implicated in the expression of porphyria cutanea tarda (PCT); the contribution of each factor depends on the population. To provide a review of PCT cases diagnosed in Argentina over 24 years and evaluate the role of different precipitating factors in its pathogenesis. Methods Plasma and urinary porphyrin levels and erythrocyte uroporphyrinogen decarboxylase (URO-D) activity were determined. Potential precipitating factors were identified in each patient. Additional tests for hepatitis C virus (HCV) and hemochromatosis gene mutations were carried out. Several factors (mainly alcohol abuse in men and estrogen ingestion in women), alone or combined were identified in our patients. Prevalence of HCV infection was 35.2%. Inherited URO-D deficiency occurs in 25.0% of cases. H63D was the most common hemochromatosis gene mutation. High incidence of PCT associated with HIV infection was found. PCT is multifactorial. Therefore, knowledge of all risk factors in each patient is important for the management of the disease.

Genetic factors influence ethanol-induced uroporphyria in Hfe (—/—) mice

Two major risk factors for porphyria cutanea tarda (PCT) are alcohol consumption and homozygosity for the C282Y mutation in the hereditary hemochromatosis gene (HFE). We recently described an animal model for alcohol-induced uroporphyria, using Hfe(-/-) mice. In the present study we show that this effect is dependent on genetic background and ethanol dose. In the 129S6/SvEvTac (129) strain, treatment with 15% ethanol in the drinking water for 6.5 months produced an accumulation of hepatic uroporphyrin (URO) 4-fold higher than that observed with 10% ethanol, a 90% decrease in uroporphyrinogen decarboxylase activity (UROD), and further increased the activities of hepatic 5-aminolevulinate synthase (ALAS) and CYP1A2. Hepatic nonheme iron (NHFe) and hepatocyte iron staining were not further increased by 15% compared to 10% ethanol. Treatment of C57BL/6 Hfe(-/-) mice with 15% ethanol for 6.5 months did not increase hepatic URO. Although NHFe was increased by ethanol, the resulting level was only half that of ethanol-treated 129 Hfe(-/-) mice. ALAS induction was similar in both Hfe(-/-) strains. In wild-type 129 mice treated with ethanol for 6 to 7 months, administration of iron dextran increased hepatic URO accumulation and decreased UROD activity. In conclusion, this study demonstrates a strong effect of genetic background on ethanol-induced uroporphyria, which is probably due to a greater effect of ethanol on iron metabolism in the susceptible strain. (Hepatology 2004;40:942-950).