Survivors of Myocardial Infarction due to “Essential” Atherosclerosis

Currently, the porphyrias are classified in four main groups: congenital porphyria, acute intermittent porphyria, porphyria cutanea tarda hereditaria, and porphyria cutanea tarda symptomatica. The acquired form of porphyria (porphyria cutanea tarda symptomatica) occurs in older males and is nearly always associated with chronic alcoholism and hepatic cirrhosis. The main clinical changes are dermatological, with excessive skin fragility and photosensitivity resulting in erosions and bullae. Biochemically, high levels of uroporphyrin are found in the urine and stools. Treatment to date has been symptomatic and usually unsuccessful.A case of porphyria cutanea tarda symptomatica is presented showing dramatic improvement of both the skin lesions and porphyrin levels in urine and blood following repeated phlebotomy.Possible mechanisms of action of phlebotomy on porphyria cutanea tarda symptomatica are discussed.     

Effect of chloroquine wash-out period of photosensitizers in the skin and selected organs in rats

In the last decade, photodynamic therapy has become an alternative method for the diagnosis and therapy of tumors. In human medicine hematoporphyrin derivatives, sulfonated hydrophilic meso-tetraphenylporphyrin (TPPS4) and an oligomer of hematoporphyrin (Photosan 3), are widely used. Chloroquine is used for the treatment of porphyria cutanea tarda for its power to release porphyrins from the liver tissue. The kinetics of two porphyrin photosensitizers TPPS4 and Photosan 3 in the skin and some organs as well as the effect of chloroquine on the porphyrin excretion and their accumulation in skin and organs of Wistar rats were studied. TPPS4 exhibited maximum fluorescence in skin 48 h after application with decreasing to basal level from the 8th to the 14th day. Maximum fluorescence was reached at 72 hours after Photosan 3 application and it decreased to basal level during 96 hours after application. TPPS4 caused significantly higher fluorescence compared to Photosan 3. Chloroquine after oral administration did not change the fluorescence of skin, but it significantly decreased the TPPS4 concentration in rat organs if chloroquine treatment started 3 days or 2 weeks after TPPS4 application. Chloroquine significantly decreased the serum TPPS4 concentration during the period of 28 days. Fluorescence of skin was significantly higher and lasted longer after application of TPPS4 compared to Photosan 3. Chloroquine after oral administration did not influence the fluorescence of the skin, but it significantly decreased the TPPS4 concentration in rat organs. This effect could be useful in photodynamic therapy for mobilizing exogenous porphyrins from tissues after parenteral photodynamic therapy.     

Porphyria cutanea tarda: clinical and laboratory features.

Eleven patients with porphyria cutanea tarda were studied. Biochemical confirmation of the clinical diagnosis required only determination of the total urine porphyrin concentration in a sample of urine voided on rising in the morning. The patients were divided for convenience of discussion into four groups differing in age, sex and etiologic factors. Of the six patients in whom a liver biopsy was done one was shown to have micronodular cirrhosis. Except for a modest elevation in the serum glutamic oxaloacetic transaminase values when the patients were first seen, no evidence was found for liver disease apart from the presence of porphyria cutanea tarda. One patient recovered solely by abstaining from alcohol consumption. Five patients underwent phlebotomy; their iron stores had been found to be between 2 and 3 g. Decreasing urine porphyrin values correlated well with decreasing serum ferritin values during the course of phlebotomy. Porphyria cutanea tarda, which is due to a deficiency of uroporphyrinogen decarboxylase, is manifested in association with alcohol abuse, estrogen therapy, exposure to chlorinated hydrocarbons or increased tissue iron stores, or a combination of these factors. Although relatively uncommon, this condition raises important and unresolved issues regarding the hepatotoxicity of alcohol, estrogens, chlorinated hydrocarbons and iron.     

High-pressure liquid chromatography of plasma free acid porphyrins

The separation and quantitation of plasma free acid porphyrins by high-pressure liquid chromatography and fluorescence is described. Porphyrins were extracted from plasma in a simple manner with a recovery >90%. They were separated by high-pressure liquid chromatography on a silica gel (10 μm) column, using a gradient of acetone:dilute acetic acid. Resolution of seven free acid porphyrin standards including coproporphyrins I and III, but not uroporphyrins I and III, was achieved in 12 min at picomolar concentrations. Plasma of patients with erythropoietic protoporphyria displayed protoporphyrin. Uroporphyrin was the only porphyrin found in plasma of eight patients with porphyria cutanea tarda. Normal plasma contained small amounts of uroporphyrin and/or traces of protoporphyrin.     

Autoimmunity and HCV infection in porphyria cutanea tarda: a controlled study.

Autoimmunity and high rates of autoantibodies have been implicated in the pathogenesis of porphyria cutanea tarda. These abnormalities could be in part virus-induced, since porphyria cutanea tarda in most geographical regions is highly associated with hepatitis C virus infection. We analyzed the link of autoantibodies, autoimmune hepatitis and systemic lupus erythematosus in 111 patients with porphyria cutanea tarda and sex- and age-matched controls (mean age 58+/-13 years) in Germany, a region with a low prevalence of hepatitis C virus infection. Patients with porphyria cutanea tarda displayed lower rates of anti-nuclear antibodies (16/111, 14% vs 28/111, 25%, p<0,05) and of antibodies against smooth muscle (25/111, 23% vs 48/111, 43%, p<0,01), than controls. The percentage of patients with porphyria cutanea tarda with positive anti-HCV was low but significantly higher than in our controls (9/111, 8% vs 0/111, 0%, respectively), (p<0,05). Two patients with porphyria cutanea tarda (2/111, 2%) fulfilled the criteria for systemic lupus erythematosus and not one of 65 patients was found to have clinical autoimmune hepatitis. In the first controlled study of a large cohort of patients with porphyria cutanea tarda no increased prevalence of selected autoantibodies and autoimmune hepatitis was found. However, a higher prevalence of HCV infection and systemic lupus erythematosus in patients with porphyria cutanea tarda was confirmed.     

Porphyrin biosynthesis from porphobilinogen by duck blood hemolysate

Summary The formation of porphyrins from porphobilinogen by a duck blood hemolysate was examined. The system was found to form mainly protoporphyrin IX and hemin, and accumulated lesser amounts of uroporphyrins, heptacarboxylic porphyrin, and coproporphyrins. By storage at –20° the accumulation of uroporphyrins and heptacarboxylic porphyrin was increased. Both porphyrins were mainly the type III isomers. By addition of dithiothreitol the porphyrin pattern reversed to the original one formed by the fresh hemolysate. Addition of a number of amines also inhibited the decarboxylating system without affecting the original isomer distribution among the porphyrins. Addition of Fe²⁺ (3mm) did not affect the porphyrin pattern or the isomer distribution. Addition of Pb²⁺ (2.5mm) partially inhibited the decarboxylating system, whereas at higher concentrations (4mm) it increased the decarboxylation rate of the heptacarboxylic porphyrin. The obtained results are discussed in relation to porphyrin accumulation in porphyria cutanea tarda and in acquired hepatic porphyrias.Dedicated to professorLuis F. Leloir on the occasion of his 70th birthday.     

Defective human erythrocyte uroporphyrinogen decarboxylase in familial porphyria cutanea tarda: the metabolic lesion or the result of endogenous porphyrinemia?

We have demonstrated that oral charcoal therapy is as effective as therapeutic phlebotomy in reducing porphyrinemia in porphyria cutanea tarda. The effects of immediate and sustained reduction of porphyrinemia on the catalytic properties of partially purified (approximately 200-fold) preparations of red cell uroporphyrinogen decarboxylase of a patient with familial porphyria cutanea tarda were studied. All populations of the patient's red cells exhibited defective enzyme activity, and the apparent Michaelis constants (Km) determined with penta-, hepta-, and octa-carboxylic I porphyrinogen substrates were approximately 3-4 times higher as compared to the normal controls. Mixing experiments (normal and defective enzyme), and preincubation of the normal enzyme with porphyric plasma prior to purification, yielded data supporting the concept that the catalytic defects of red cell uroporphyrinogen decarboxylase in familial porphyria cutanea tarda are independent of interactions between circulating endogenous porphyrins and the enzyme.     

Modified uroporphyrinogen decarboxylase activity in a yeast mutant which mimics porphyria cutanea tarda.

The isolation of a new mutant Sm1 strain of yeast, Saccharomyces cerevisiae, is described: this strain was partially defective in haem formation and accumulated large amounts of Zn-porphyrins. Genetic analysis showed that the porphyrin accumulation was under the control of a single nuclear recessive mutation. Biochemical analysis showed that the main porphyrins accumulated in the cells were uroporphyrin and heptacarboxyporphyrin, mostly of the isomer-III type. The excreted porphyrins comprised mainly dehydroisocoproporphyrin. Analysis of uroporphyrinogen decarboxylase activity in the cell-free extract revealed a 70-80% decrease of activity in the mutant and showed that the relative rates of the different decarboxylation steps were modified with the mutant enzyme. A 2-3-fold increase in 5-aminolaevulinate synthase activity was measured in the mutant. The biochemical characteristics of the Sm1 mutant are very similar to those described for porphyria cutanea tarda.     

The effects in vivo of mutationally modified uroporphyrinogen decarboxylase in different hem12 mutants of baker''s yeast (Saccharomyces cerevisiae).

Nine new hem12 haploid mutants of baker's yeast (Saccharomyces cerevisiae), totally or partially deficient in uroporphyrinogen decarboxylase activity, were subjected to both genetic and biochemical analysis. The mutations sites studied are situated far apart within the HEM12 gene located on chromosome IV. Uroporphyrinogen decarboxylase activity in the cell-free extracts of the mutants was decreased by 50-100%. This correlated well with the decrease of haem formation and the increased accumulation and excretion of porphyrins observed in vivo. The pattern of porphyrins (uroporphyrin and its decarboxylation products) accumulated in the cells of mutants partially deficient in uroporphyrinogen decarboxylase activity did not differ significantly, although differences in vitro were found in the relative activity of the mutant enzyme at the four decarboxylation steps. The excreted porphyrins comprised mainly dehydroisocoproporphyrin or pentacarboxyporphyrin. In heterozygous hem12-1/HEM12 diploid cells, a 50% decrease in decarboxylase activity led to an increased accumulation of porphyrins as compared with the wild-type HEM12/HEM12 diploid, which points to the semi-dominant character of the hem12-1 mutation. The biochemical phenotypes of both the haploid and the heterozygous diploid resembles closely the situation encountered in porphyria cutanea tarda, the most common human form of porphyria.     

Effects of polychlorinated biphenyl compounds, 2,3,7,8-tetrachlorodibenzo-p-dioxin, phenobarbital and iron on hepatic uroporphyrinogen decarboxylase. Implications for the pathogenesis of porphyria.

Treatment of cultured chick embryo hepatocytes with phenobarbital, polychlorinated biphenyl compounds and 2,3,7,8-tetrachlorodibenzo-p-dioxin resulted in increased delta-aminolaevulinate synthase and decreased uroporphyrinogen decarboxylase activities and porphyrin accumulation; uroporphyrin and heptacarboxyporphyrin predominated. Iron had no effect on these changes. Simultaneous treatment of cultures with dioxin and phenobarbital produced a synergistic response in delta-aminolaevulinate synthase induction, uroporphyrinogen decarboxylase inhibition and porphyrin accumulation. These data suggest that an inhibitor of uroporphyrinogen decarboxylase may be generated in the liver from polychlorinated biphenyl compounds or dioxin by metabolic activation. Additionally these findings bear on the postulated role of these and related chemicals in determining the low levels of uroporphyrinogen decarboxylase activity in porphyria cutanea tarda patients.     

Metabolism of pentacarboxylate porphyrinogens by highly purified human coproporphyrinogen oxidase: further evidence for the existence of an abnormal pathway for heme biosynthesis

An abnormal series of porphyrin tetracarboxylic acids known as the isocoproporphyrins, are commonly excreted by patients suffering from the disease porphyria cutanea tarda (PCT). These porphyrins appear to arise by bacterial degradation of dehydroisocoproporphyrinogen that is generated by the premature metabolism of the normal pentacarboxylate intermediate (5dab) by coproporphyrinogen oxidase (copro'gen oxidase). This porphyrinogen can be further metabolized by uroporphyrinogen decarboxylase to give harderoporphyrinogen, one of the usual intermediates in heme biosynthesis. Therefore, it is possible that some of the heme formed under abnormal conditions may originate from the 'isocopro-type' porphyrinogen intermediate. In order to investigate the feasibility of alternative pathways for heme biosynthesis, the four type III pentacarboxylate isomeric porphyrinogens were incubated with purified, cloned human copro'gen oxidase at 37 degrees C with various substrate concentrations under initial velocity conditions. Of the four isomers, only 5dab was a substrate for copro'gen oxidase and this gave dehydroisocoproporphyrin. The structure of the related porphyrin tetramethyl ester was confirmed by proton NMR spectroscopy and mass spectrometry. The K(m) value for proto'gen-IX formation from copro'gen, an indicator of molecular recognition, was similar to the K(m) value for monovinyl product formation with 5dab, although copro'gen-III has an approximately twofold higher K(cat) value. Although 5dab is a slightly poorer substrate than copro'gen-III, these results support the hypothesis that an abnormal route for heme biosynthesis is possible in humans suffering from PCT or related syndromes such as hexachlorobenzene poisoning.     

The isolation of a new compound from urine of humans with porphyria cutanea tarda

A method is reported for the isolation of phyriaviolin, a new compound from human porphyria cutanea tarda urine. The substance has been crystallized and some of its properties are described.     

The role of iron in experimental porphyria and porphyria cutanea tarda

Porphyria cutanea tarda (PCT) and experimental porphyria are characterized by a decreased activity of the enzyme uroporphyrinogen decarboxylase, and accumulation of uroporphyrins and heptacarboxylporphyrins in the liver. Iron (Fe) plays an important role in PCT and experimental porphyria. Biochemically and electron microscopically, we examined the relationship between Fe and porphyrins in liver tissue of C57BL/10 mice made porphyric by administration of iron dextran as Imferon^® (IMF), and in liver biopsies of patients with symptomatic PCT. Accumulation of uroporphyrins and heptacarboxylporphyrins, and an increased amount of Fe were observed in livers of mice treated with IMF and in liver biopsies of patients with PCT. In mice treated with IMF, the activity of uroporphyrinogen decarboxylase was decreased. Both in livers of mice treated with IMF and in livers of patients with PCT, needle-like structures, representing uroporphyrin crystals, were observed by electron microscopy. Uroporphyrin crystals and Fe (as ferritin) were observed in the same hepatocyte. Moreover, there was a striking morphological correlation between uroporphyrin crystals and ferritin-Fe, suggesting a role for (ferritin-)Fe in the pathogenesis of porphyria.     

The isolation of a new compound from urine of humans with porphyria cutanea tarda

A method is reported for the isolation of phyriaviolin, a new compound from human porphyria cutanea tarda urine. The substance has been crystallized and some of its properties are described.     

Familial porphyria cutanea tarda: hybridization analysis of the uroporphyrinogen decarboxylase locus

Familial porphyria cutanea tarda (PCT) results from a deficiency of uroporphyrinogen decarboxylase (URO-D) activity. Hybridization analysis of genomic DNA from unrelated normal individuals and PCT pedigree members failed to detect any major deletions, rearrangements or restriction fragment length polymorphisms at the URO-D locus.     

Rat urinary chemiluminescence: effect of ethanol and/or hexachlorobenzene uptake

Hexachlorobenzene (HCB) administration to rats induces porphyria cutanea tarda, characterized by high levels of urinary porphyrins (>40 μg/day) and accumulation of highly carboxylated porphyrins in liver (>15 μg/g of tissue). Ethanol administration, under the conditions employed, was not porphyrinogenic and was able to diminish some of the responses elicited by HCB. Furthermore, ethanol and/or HCB administration leads to organ disturbances that involve oxidative stress. We have measured the changes in urinary chemiluminescence (CL) levels, as part of a systematic evaluation of the metabolic alterations in rats chronically treated with ethanol and/or HCB. The results, that constitute the first set of urinary CL data obtained from an animal model system, indicate that the measurement of the spontaneous urinary CL can constitute a fast, simple and sensitive method to evaluate disturbances associated with oxidative stress. © 1998 John Wiley & Sons, Ltd.     

Haem biosynthesis and human porphyria cutanea tarda: effects of alcohol intake

The review describes the structural and biochemical properties of the haem biosynthetic enzyme, uroporphyrinogen decarboxylase (UROD), which sequentially catalyzes the removal of the four carboxyl groups from the acetate side chains of octacarboxylic uroporphyrinogen to form coproporphyrinogen, and the possible biochemical mechanism of the genesis of porphyria cutanea tarda (PCT). The disease is caused when the activity of UROD is significantly reduced. PCT is a multifactorial disease where both inherent and environmental factors such as alcohol, estrogens, halogenated aromatic hydrocarbons and viral infection (mainly hepatitis C) are involved in biochemical and clinical expression. In PCT, hepatic iron plays a key role. Alcohol intake could induce mobilization of iron from protein-bound ferritin. PCT should be managed by avoidance of these toxins and removal of iron by vigorous phlebotomy. Such iron-reduction therapy would provide additional benefit for hepatitis C patients by interferon therapy.     

Red blood cell rhodanese: its possible role in modulating delta-aminolaevulinate synthetase activity in mammals

The optimum conditions for measuring rhodanese activity in human erythrocytes were established. The mean control values for males (112 nmol SCN/30 min/mg protein) and females (127 nmol SCN/30 min/mg protein) were determined. Rhodanese activity was measured in different porphyric patients. The activity was diminished in porphyria cutanea tarda (PCT), acute intermittent porphyria (AIP), variegate porphyria (VP) and lead intoxication (Pb), remaining normal in erythropoietic protoporphyria (EPP). delta-Aminolaevulinate synthetase (ALA-S) activity was increased in PCT, AIP, VP and Pb showing no changes in EPP. It is suggested that a similar scheme, to that proposed for the control of ALA-S in Rhodopseudomonas spheroides and soybean callus, is also operating in animals.     

A mouse model for South African (R59W) variegate porphyria: construction and initial characterization.

Variegate porphyria is inherited as an autosomal dominant disease with variable penetrance. It is characterized clinically by photocutaneous sensitivity and acute neurovisceral attacks, and biochemically by abnormal porphyrin excretion in the urine and feces. While the world-wide incidence of variegate porphyria is relatively low, in South Africa it is one of the most common genetic diseases in humans. Due to the large number of patients with variegate porphyria in South Africa, and the fact that variegate porphyria is representative of both the so-called "acute" and the "photocutaneous" porphyrias, it would be valuable to have an animal model in which to study the disease. In this study we have produced a mouse model of "South African" variegate porphyria with the R59W mutation in C57/BL6 mice via targeted gene replacement. Hepatic protoporphyrinogen oxidase activity was reduced by approximately 50% in mice heterozygous for the mutation. Urine and fecal samples from these mice, in the absence of exogenous inducers of hepatic haem synthesis, contain elevated concentrations of porphyrins and porphyrin precursors in a pattern similar to that found in human variegate porphyric subjects. Bypassing the rate-limiting step in haem biosynthesis by feeding 5-aminolevulinic acid to these mice, results in an accentuated porphyrin excretory pattern characteristic of the variegate porphyric phenotype and urinary porphobilinogen is increased significantly. This initial characterization of these mice suggest that they are a good model for variegate porphyria at the biochemical level.     

Porphyria cutanea tarda: comparison of cases precipitated by alcohol and estrogens.

A group of seven patients with porphyria cutanea tarda (PCT) precipitated by excessive alcohol consumption (A) was compared with a group of nine patients with PCT precipitated by estrogen therapy (B). Comparison was based on clinical signs, biochemical and morphologic evidence of liver disease, results of serum iron studies and response to therapy. Group A patients were men of mean age 57 years; group B patients were women of mean age 39 years who had been taking estrogen orally, either for contraception (in combination with progesterone) or as replacement therapy. Clinical signs were essentially the same in the two groups. Some patients in both groups had biochemical and morphologic evidence of liver disease. Group A patients had elevated values for serum iron and total iron-binding capacity, whereas patients in group B had normal or low values. Cessation of estrogen therapy of less than a year''s duration brought about a spontaneous clinical and biochemical remission in group B patients. Otherwise, phlebotomy seemed to be the therapy of choice in both groups.