Alcohol and porphyrin metabolism

Case-based discussion of the acute hepatic porphyrias: Updates on pathogenesis, diagnosis and management

The acute hepatic porphyrias (AHPs) include three autosomal dominant disorders, acute intermittent porphyria, variegate porphyria  and hereditary coproporphyria, and the ultra-rare autosomal recessive 5-aminolevulinic acid dehydratase-deficient porphyria. All four are characterized by episodic acute neurovisceral attacks that can be life-threatening if left untreated. The attacks are precipitated by factors that induce hepatic 5-aminolevulinic acid synthase 1 (ALAS1), resulting in accumulation of the porphyrin precursors, 5-aminolevulinic acid and porphobilinogen, which are believed to cause neurotoxicity. Diagnosis of these rare disorders is often delayed because the symptoms are non-specific with many common aetiologies. However, once clinical suspicion of an AHP is raised, diagnosis can be made by specialized biochemical testing, particularly during attacks. Moderate or severe attacks are treated with intravenous hemin infusions, together with supportive care to relieve pain and other symptoms. Prophylactic treatments are recommended in patients with confirmed recurrent attacks (≥4 attacks in a maximum period of 12 months), the most effective being givosiran, an RNAi therapeutic targeting hepatocyte ALAS1 mRNA. AHP patients with clinically and/or biochemically active disease are at elevated risk for developing long-term complications, including chronic kidney disease, chronic hypertension and hepatocellular carcinoma, thus, surveillance is recommended. Here, using a case-based format, we provide an update on the pathogenesis, diagnosis and treatment of the AHPs based on literature review and clinical experiences.

Athena: Specialty Certificate Examination case for general dermatology

This Athena concerns a 45-year-old man who presented with a 1-year history of recurrent tense fluid-filled lesions over his forearms, hands, feet and face associated with scarring and pigmentary changes. He had a history of regular alcohol intake (> 3 units daily). Lesion biopsy revealed a thick granular deposition of IgG along the basement membrane with thick homogeneous positivity of papillary dermal vessels for various immunoreactants (IgG, IgA, C3, IgM).

Update on the diagnosis and management of the autosomal dominant acute hepatic porphyrias

The autosomal dominant acute hepatic porphyrias (AHPs), acute intermittent porphyria, hereditary coproporphyria (HCP) and variegate porphyria (VP), are low penetrance adult onset disorders caused by partial deficiency of enzymes of haem biosynthesis. All are associated with acute neurovisceral attacks, which are a consequence of the increased hepatic demand for haem triggered by hormones, stress, drugs or systemic infections which leads to upregulation of the pathway and overproduction of haem precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). Acute episodes are characterised by severe abdominal pain, nausea, vomiting, hyponatraemia, hypertension and tachycardia, behavioural disturbance and can progress to include seizures, peripheral motor neuropathy and posterior reversible encephalopathy syndrome if undiagnosed and untreated. VP and HCP may also present with photocutaneous skin lesions either alone or during acute symptoms. Diagnosis involves demonstrating increased excretion of PBG in urine. Treatment focuses on removing or managing triggers, supportive treatment and suppressing the hepatic haem pathway by administering human haemin. Chronic complications include hypertension, chronic kidney disease and hepatocellular carcinoma. A small proportion of symptomatic patients with AHP progress to repeated acute attacks which require preventative therapy. A new RNA interference therapy has recently been licensed and is likely to become the treatment of choice in this situation.

Organ-differential responses to ethanol and kynurenic acid, a component of alcoholic beverages in gene transcription

Excessive alcohol (ethanol) use has long been known to affect human health negatively. However, the underlying molecular basis is incompletely understood. Moreover, consumption of alcohol is often mixed with kynurenic acid (KYNA), an abundant tryptophan metabolite produced during fermentation. The combined effect of ethanol and KYNA on host gene expression has not been investigated. The current study used mice as the model to interrogate the impact of ethanol and/or KYNA on global gene transcription. Adult male mice were administered with 2 g/kg ethanol and/or 0.1 mg/kg KYNA by gavage once a day for a week. Three organs: brain, kidney, and liver were collected and their total RNAs extracted for transcriptome sequencing and quantitative real-time PCR. Gene ontology, Kyoto encyclopedia of genes, and genomes pathway analyses revealed that alcohol affects the three organs differentially. Furthermore, the gene expression profile from alcohol and KYNA co-administration was significantly different from that of alcohol or KYNA administration alone. Strikingly, Indolamine 2,3-dioxygenase 1, a rate-limiting enzyme in tryptophan metabolism, was significantly increased in the brain after a combined exposure of alcohol and KYNA, suggesting that Trp metabolism was skewed towards the kynurenine pathway in the brain. Our systemic analysis provides new insights into the mechanism whereby alcohol and KYNA affects organ functions.

Lifestyle factors including diet and biochemical biomarkers in acute intermittent porphyria: Results from a case-control study in northern Norway

BACKGROUND

Lifestyle factors, including a low intake of carbohydrates, dieting, alcohol consumption, cigarette smoking and stress are some of the possible triggers of attacks in acute intermittent porphyria (AIP). The influence of lifestyle factors, including energy intake, diet and alcohol consumption on the biochemical disease activity in AIP and biochemical nutritional markers were examined.

METHODS

A case-control study with 50 AIP cases and 50 controls matched for age, sex and place of residence was performed. Dietary intake was registered using a food diary in 46 matched pairs. Symptoms, alcohol intake, stress and other triggering factors of the last AIP attack were recorded on questionnaires. Porphyrin precursors, liver and kidney function markers, vitamins, diabetogenic hormones and other nutritional biomarkers were analyzed by routine methods. The Wilcoxon matched-pairs signed rank test was used to compare the cases vs. controls. The Spearman's rank correlation coefficient was used on the cases.

RESULTS

Increasing total energy intake was negatively correlated with the biochemical disease activity. The intake of carbohydrates was lower than recommended, i.e., 40 and 39% of total energy intake in the AIP cases and controls, respectively. The plasma resistin level was significantly higher (p = .03) in the symptomatic than asymptomatic cases. Plasma insulin was lower in those with high porphobilinogen levels. The intake of sugar and candies were higher in the AIP cases with low U-delta aminolevulinic acid (ALA) levels (p = .04). Attacks were triggered by psychological stress (62%), physical strain (38%), food items (24%) and alcohol (32%) in the 34 symptomatic cases. Alcohol was used regularly by 88% of the cases (3.2 g ethanol/day) and 90% of the controls (6.3 g/day), but the intake was significantly lower in symptomatic than in asymptomatic cases (p = .045).

CONCLUSION

A high intake of energy, sugar and candies and a higher insulin level were associated with a lower biochemical disease activity. The resistin level was higher in the symptomatic than the asymptomatic cases. AIP patients drink alcohol regularly, but the intake was significantly lower in the symptomatic cases.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01617642.

Clinical Guide and Update on Porphyrias

Physicians should be aware of porphyrias, which could be responsible for unexplained gastrointestinal, neurologic, or skin disorders. Despite their relative rarity and complexity, most porphyrias can be easily defined and diagnosed. They are caused by well-characterized enzyme defects in the complex heme biosynthetic pathway and are divided into categories of acute vs non-acute or hepatic vs erythropoietic porphyrias. Acute hepatic porphyrias (acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and aminolevulinic acid dehydratase deficient porphyria) manifest in attacks and are characterized by overproduction of porphyrin precursors, producing often serious abdominal, psychiatric, neurologic, or cardiovascular symptoms. Patients with variegate porphyria and hereditary coproporphyria can present with skin photosensitivity. Diagnosis relies on measurement of increased urinary 5-aminolevulinic acid (in patients with aminolevulinic acid dehydratase deficient porphyria) or increased 5-aminolevulinic acid and porphobilinogen (in patients with other acute porphyrias). Management of attacks requires intensive care, strict avoidance of porphyrinogenic drugs and other precipitating factors, caloric support, and often heme therapy. The non-acute porphyrias are porphyria cutanea tarda, erythropoietic protoporphyria, X-linked protoporphyria, and the rare congenital erythropoietic porphyria. They lead to the accumulation of porphyrins that cause skin photosensitivity and occasionally severe liver damage. Secondary elevated urinary or blood porphyrins can occur in patients without porphyria, for example, in liver diseases, or iron deficiency. Increases in porphyrin precursors and porphyrins are also found in patients with lead intoxication. Patients with porphyria cutanea tarda benefit from iron depletion, hydroxychloroquine therapy, and, if applicable, elimination of the hepatitis C virus. An α-melanocyte-stimulating hormone analogue can reduce sunlight sensitivity in patients with erythropoietic protoporphyria or X-linked protoporphyria. Strategies to address dysregulated or dysfunctional steps within the heme biosynthetic pathway are in development.

Porphyrin-Induced Protein Oxidation and Aggregation as a Mechanism of Porphyria-Associated Cell Injury

Genetic porphyrias comprise eight diseases caused by defects in the heme biosynthetic pathway that lead to accumulation of heme precursors. Consequences of porphyria include photosensitivity, liver damage and increased risk of hepatocellular carcinoma, and neurovisceral involvement, including seizures. Fluorescent porphyrins that include protoporphyrin-IX, uroporphyrin and coproporphyrin, are photo-reactive; they absorb light energy and are excited to high-energy singlet and triplet states. Decay of the porphyrin excited to ground state releases energy and generates singlet oxygen. Porphyrin-induced oxidative stress is thought to be the major mechanism of porphyrin-mediated tissue damage. Although this explains the acute photosensitivity in most porphyrias, light-induced porphyrin-mediated oxidative stress does not account for the effect of porphyrins on internal organs. Recent findings demonstrate the unique role of fluorescent porphyrins in causing subcellular compartment-selective protein aggregation. Porphyrin-mediated protein aggregation associates with nuclear deformation, cytoplasmic vacuole formation and endoplasmic reticulum dilation. Porphyrin-triggered proteotoxicity is compounded by inhibition of the proteasome due to aggregation of some of its subunits. The ensuing disruption in proteostasis also manifests in cell cycle arrest coupled with aggregation of cell proliferation-related proteins, including PCNA, cdk4 and cyclin B1. Porphyrins bind to native proteins and, in presence of light and oxygen, oxidize several amino acids, particularly methionine. Noncovalent interaction of oxidized proteins with porphyrins leads to formation of protein aggregates. In internal organs, particularly the liver, light-independent porphyrin-mediated protein aggregation occurs after secondary triggers of oxidative stress. Thus, porphyrin-induced protein aggregation provides a novel mechanism for external and internal tissue damage in porphyrias that involve fluorescent porphyrin accumulation.

Porphyria: What Is It and Who Should Be Evaluated?

The porphyrias are a group of rare metabolic disorders, inherited or acquired, along the heme biosynthetic pathway, which could manifest with neurovisceral and/or cutaneous symptoms, depending on the defective enzyme. Neurovisceral porphyrias are characterized by acute attacks, in which excessive heme production is induced following exposure to a trigger. An acute attack usually presents with severe abdominal pain, vomiting, and tachycardia. Other symptoms which could appear include hypertension, hyponatremia, peripheral neuropathy, and mild mental symptoms. In severe attacks there could be severe symptoms including seizures and psychosis. If untreated, the attack might become very severe, affecting the peripheral, central, and autonomic nervous system, leading to paralysis, respiratory failure, hyponatremia, coma, and even death. From the biochemical point of view, acute attacks are involved with increased levels of precursors in the heme biosynthetic pathway, up to the deficient step. Of these precursors, aminolevulinic acid (ALA) is considered to be neurotoxic. Treatment is directed to reduce ALA production by reducing the activity of the enzyme aminolevulinate synthase (ALAS)-most effectively by heme therapy. Cutaneous symptoms are a consequence of elevated porphyrins in the blood stream. These porphyrins react to light; therefore sun-exposed areas are affected, producing fragile erosive skin lesions in porphyria cutanea tarda (PCT) or non-scarring stinging and burning symptoms in erythropoietic protoporphyria (EPP). Unlike the most common neurovisceral porphyria, acute intermittent porphyria (AIP), variegate porphyria (VP), and hereditary coproporphyria (HCP) can have cutaneous symptoms as well. Differentiating them from other cutaneous porphyrias is essential for accurate diagnosis, treatment, and patient recommendations.

Update review of the acute porphyrias

Acute porphyrias are rare inherited disorders due to deficiencies of haem synthesis enzymes. To date, all UK cases have been one of the three autosomal dominant forms, although penetrance is low and most gene carriers remain asymptomatic. Clinical presentation is typically with acute neurovisceral attacks characterised by severe abdominal pain, vomiting, tachycardia and hypertension. Severe attacks may be complicated by hyponatraemia, peripheral neuropathy sometimes causing paralysis, seizures and psychiatric features. Attacks are triggered by prescribed drugs, alcohol, hormonal changes, fasting or stress. The diagnosis is made by finding increased porphobilinogen excretion in a light-protected random urine sample. Management includes administration of intravenous human haemin and supportive treatment with non-porphyrinogenic drugs. A few patients develop recurrent attacks, a chronic illness requiring specialist management. Late complications include chronic pain, hepatocellular carcinoma, chronic renal failure and hypertension. In the UK, the National Acute Porphyria Service provides clinical advice and supplies haemin when indicated.

Recent advances in photodynamic diagnosis of gastric cancer using 5-aminolevulinic acid

Photodynamic diagnosis based on 5-aminolevulinic acid-induced protoporphyrin IX has been clinically applied in many fields based upon its evidenced efficacy and adequate safety. In order to establish a personalized medicine approach for treating gastric cancer patients, rapid intraoperative detection of malignant lesions has become important. Feasibility of photodynamic diagnosis using 5-aminolevulinic acid for gastric cancer patients has been investigated, especially for the detection of peritoneal dissemination and lymph node metastasis. This method enables intraoperative real-time fluorescence detection of peritoneal dissemination, exhibiting higher sensitivity than white light observation without histopathological examination. The method also enables detection of metastatic foci within excised lymph nodes, exhibiting a diagnostic accuracy comparable to that of a current molecular diagnostics technique. Although several complicating issues still need to be resolved, such as the effect of tissue autofluorescence and the insufficient depth penetration of excitation light, this simple and rapid method has the potential to become a useful diagnostic tool for gastric cancer, as well as urinary bladder cancer and glioma.

Noninvasive assessment of the risk of tobacco abuse in oral mucosa using fluorescence spectroscopy: a clinical approach

Tobacco abuse and alcoholism cause cancer, emphysema, and heart disease, which contribute to high death rates, globally. Society pays a significant cost for these habits whose first demonstration in many cases is in the oral cavity. Oral cavity disorders are highly curable if a screening procedure is available to diagnose them in the earliest stages. The aim of the study is to identify the severity of tobacco abuse, in oral cavity, as reflected by the emission from endogenous fluorophores and the chromophore hemoglobin. A group who had no tobacco habits and another with a history of tobacco abuse were included in this study. To compare the results with a pathological condition, a group of leukoplakia patients were also included. Emission from porphyrin and the spectral filtering modulation effect of hemoglobin were collected from different sites. Multivariate analysis strengthened the spectral features with a sensitivity of 60% to 100% and a specificity of 76% to 100% for the discrimination. Total hemoglobin and porphyrin levels of habitués and leukoplakia groups were comparable, indicating the alarming situation about the risk of tobacco abuse. Results prove that fluorescence spectroscopy along with multivariate analysis is an effective noninvasive tool for the early diagnosis of pathological changes due to tobacco abuse.

Pellagra and alcoholism: a biochemical perspective

Historical and clinical aspects of pellagra and its relationship to alcoholism are reviewed from a biochemical perspective. Pellagra is caused by deficiency of niacin (nicotinic acid) and/or its tryptophan (Trp) precursor and is compounded by B vitamin deficiencies. Existence on maize or sorghum diets and loss of or failure to isolate niacin from them led to pellagra incidence in India, South Africa, Southern Europe in the 18th century and the USA following the civil war. Pellagra is also induced by drugs inhibiting the conversion of Trp to niacin and by conditions of gastrointestinal dysfunction. Skin photosensitivity in pellagra may be due to decreased synthesis of the Trp metabolite picolinic acid → zinc deficiency → decreased skin levels of the histidine metabolite urocanic acid and possibly also increased levels of the haem precursor 5-aminolaevulinic acid (5-ALA) and photo-reactive porphyrins. Depression in pellagra may be due to a serotonin deficiency caused by decreased Trp availability to the brain. Anxiety and other neurological disturbances may be caused by 5-ALA and the Trp metabolite kynurenic acid. Pellagra symptoms are resolved by niacin, but aggravated mainly by vitamin B6. Alcohol dependence can induce or aggravate pellagra by inducing malnutrition, gastrointestinal disturbances and B vitamin deficiencies, inhibiting the conversion of Trp to niacin and promoting the accumulation of 5-ALA and porphyrins. Alcoholic pellagra encephalopathy should be managed with niacin, other B vitamins and adequate protein nutrition. Future studies should explore the potential role of 5-ALA and also KA in the skin and neurological disturbances in pellagra.

Non-classical congenital adrenal hyperplasia in association with porphyria cutanea tarda: co-incidence or trigger?

We present an interesting case of porphria cutanea tarda with hereditary haemochromatosis and non-classical congenital adrenal hyperplasia in a postmenopausal woman. This unusual combination of conditions does not appear to be reported in the literature. The exact mechanism causing porphyria in this patient is not clear. We consider the possibility that in addition to iron accumulation and excess alcohol, altered steroid milieu may have been a possible trigger for the development of bullous lesions in this patient.

Differential protein expression of kidney tissue in the scallop Patinopecten yessoensis under acute cadmium stress

Morphological and proteomic changes in the kidney of scallops exposed to acute cadmium chloride (CdCl₂) were observed, analyzed and compared with those in the non-exposed control group. Under microscopy the paraffin-embedded sections of the kidney revealed that the microstructure of the tissue had been severely deformed after Cd exposure. Two dimensional electrophoresis, MALDI-TOF mass spectrometry and database searches showed 13 differentially expressed protein spots, of which 11 were up-regulated, while two were down-regulated. Among these proteins, guanylate kinase (GK) and C₂H₂-type zinc finger protein are considered to be tightly connected with Cd toxicity. Further studies using quantitative PCR method validated that the GK mRNA was induced under Cd stress. Other proteins identified which had some relevance to Cd toxicity are also discussed. We suggested that differential proteins such as GK could play a potential role as novel biomarkers for monitoring the level of Cd contamination in seawater.

Subchronic systemic toxicity and bioaccumulation of Fe3O4 nano- and microparticles following repeated intraperitoneal administration to rats

Aqueous suspensions of 10 nm, 50 nm, or 1 μm Fe(3)O(4) particles were injected intraperitoneally (ip) to rats at a dose of 500 mg/kg in 4 mL of sterile deionized water 3 times a week for 5 weeks. Following exposure, functional and biochemical indices and histopathological examinations of spleen and liver tissues of exposed rats were evaluated for signs of toxicity. The iron content of the blood was measured photometrically, and that of the liver and the spleen by atomic adsorption spectroscopy (AAS) and electron paramagnetic resonance (EPR) methods. It was found that, given equal mass doses, Fe(3)O(4) nanoparticles possess considerably higher systemic toxicity than microparticles, but within the nanometric range the relationship between particle size and resorptive toxicity is intricate and nonunique. The latter fact may be attributed to differences in different nanoparticles' toxicokinetics, which are controlled by both more or less substantial direct penetration of nanoparticles through biological barriers and their unequal solubility.

Porphyrias at a glance: diagnosis and treatment

Porphyrias are a group of eight rare inherited metabolic disorders of heme biosynthesis pathway. Porphyrias are still underdiagnosed, although examinations of urine and plasma are first-line tests for detecting excess of porphyrins or heme precursors in suspected patients. Diagnosis, particularly for the acute forms, is essential to avoid precipitating factors and the use of triggering drugs. Mutation screening of family members is recommended to identify presymptomatic carriers and to prevent acute attacks. The therapeutic approach should be appropriate regarding specific forms of porphyria and treatment should be started promptly.

Porphyrias

Hereditary porphyrias are a group of eight metabolic disorders of the haem biosynthesis pathway that are characterised by acute neurovisceral symptoms, skin lesions, or both. Every porphyria is caused by abnormal function of a separate enzymatic step, resulting in a specific accumulation of haem precursors. Seven porphyrias are the result of a partial enzyme deficiency, and a gain of function mechanism has been characterised in a new porphyria. Acute porphyrias present with acute attacks, typically consisting of severe abdominal pain, nausea, constipation, confusion, and seizure, and can be life-threatening. Cutaneous porphyrias present with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe cutaneous photosensitivity and chronic haemolysis or chronic neurological symptoms with or without photosensitivity. Porphyrias are still underdiagnosed, but when they are suspected, and dependent on clinical presentation, simple first-line tests can be used to establish the diagnosis in all symptomatic patients. Diagnosis is essential to enable specific treatments to be started as soon as possible. Screening of families to identify presymptomatic carriers is crucial to decrease risk of overt disease of acute porphyrias through counselling about avoidance of potential precipitants.

A novel mutation in the biliverdin reductase-A gene combined with liver cirrhosis results in hyperbiliverdinaemia (green jaundice)

BACKGROUND

Hyperbiliverdinaemia is a poorly defined clinical sign that has been infrequently reported in cases of liver cirrhosis or liver carcinoma, usually indicating a poor long-term prognosis.

AIMS

To clarify the pathogenesis of hyperbiliverdinaemia in an extended case report.

METHODS

A 64-year-old man with alcoholic cirrhosis was admitted to hospital with severe bleeding from oesophageal varices. Ultrasonography showed ascites, but no dilatation of the biliary tree. The skin, sclerae, plasma, urine and ascites of the patient showed a greenish appearance. Bilirubin levels were normal, and there were no signs of haemolysis. Biliverdin was analysed in plasma and urine with liquid chromatography coupled to mass spectrometry. The seven exonic regions of the biliverdin reductase-A (BVR-A) gene was amplified by polymerase chain reaction and sequenced.

RESULTS

Biliverdin was present in plasma and urine. In nucleotide 52 of exon I of the DNA isolated from the hyperbiliverdinaemic patient, we discovered a novel heterozygous C-->T nonsense mutation converting an arginine (CGA) in position 18 into a stop codon (TGA) (R18Stop) predicted to truncate the protein N-terminally to the active site Tyr97. Two children of the proband were heterozygous for the identical mutation in the BVR-A gene, but had no clinical signs of liver disease and had normal levels of biliverdin. The BVR-A gene mutation was not found in 200 healthy volunteers or nine patients with end-stage liver cirrhosis.

CONCLUSION

Hyperbiliverdinaemia (green jaundice) with green plasma and urine may be caused by a genetic defect in the BVR-A gene in conjunction with decompensated liver cirrhosis.

Urinary porphyrin excretion in children is associated with exposure to organochlorine compounds

BACKGROUND

Hexachlorobenzene (HCB) and other organochlorines induce porphyria cutanea tarda (PCT) in animal studies. Evidence in humans, however, is contradictory. In neonates and adults from a population historically highly exposed to HCB (Flix, Catalonia, Spain), no relation with PCT or with porphyrin excretion was found.

OBJECTIVES

We aimed to analyze the association between urinary porphyrin excretion and exposure to HCB and other organochlorinated compounds in children 4 years of age.

METHODS

Our birth cohort included all newborns from Flix and the five surrounding towns (where no airborne pollution occurred). Among the 68 children with porphyrins we measured in cord blood, 52 children 4 years of age provided blood to measure organochlorine compounds, hair for methylmercury, and urine for porphyrin excretion pattern.

RESULTS

Quantitative porphyrin excretion was within the normal values. However, total porphyrins, coproporphyrin I (CPI), and coproporphyrin III (CPIII) adjusted to creatinine excretion increased with increasing levels of HCB, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (p,p'-DDE), 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT), and polychlorinated biphenyl congener 153 (PCB-153). We found no association with methylmercury. When we fitted multiple pollutant models, p,p'-DDE had the strongest association. We found these associations in children from both Flix and other towns, and they were independent of breast-feeding and of organochlorine and porphyrin levels at birth.

CONCLUSION

HCB at current levels did not induce porphyria or increase uroporphyrins. However, the increase of urinary coproporphyrins suggests an incipient toxic effect of the organochlorines, especially for p,p'-DDE, on the hepatic heme-synthesis pathway that differs from the major effects seen in PCT.

[Acute intermittent porphyria and chronic transaminase elevation]

Acute intermittent porphyria is an autosomal dominant inherited disorder resulting from a deficiency of porphobilinogen deaminase activity, the third enzyme in the heme biosynthesis pathway. This disease is uncommon, although the prevalence is higher in asymptomatic heterozygotic carriers; however, this prevalence is difficult to establish because of the absence of symptoms. Although acute intermittent porphyria is a multisystemic disease, its most common form of presentation is abdominal pain and neurological or mental symptoms, which can sometimes be due to precipitating factors such as reduced energy intake, smoking, alcohol, some drugs, and stress. Diagnosis can be made by testing urinary porphobilinogen levels, with subsequent measurement of enzyme activity and DNA testing. Treatment is based on prevention of porphyria attacks by avoiding precipitating factors and early administration of intravenous glucose or hemin therapy. We present the case of a patient diagnosed with acute intermittent porphyria based on study of chronic mild alanine aminotransferase (ALT) elevation.

[Acute intermittent porphyria. A clinical chameleon: case study of a 40-year-old female patient]

Acute porphyrias are rare, but often misdiagnosed and may take a dramatic clinical course. The combination of various internal, psychiatric and neurological symptoms can mimic different other diseases. We report a 40-year-old female patient who was admitted with a subacute tetraparesis. During the last 2 months the patient was treated several times because of abdominal pain and just before admission to our clinic in a psychiatric hospital because of acute mental changes and hallucinations. The typical combination of abdominal pain, motor neuropathy and psychiatric symptoms confirmed by increased amounts of porphyrins and their precursors, led us to promptly diagnose acute intermittent porphyria. Better knowledge about the pathogenesis has clearly improved the prognosis of acute porphyria. In remission, measurement of enzyme activities or mutation screening can be the only diagnostic verification. A mutation screening for family members should be conducted to identify symptom-free carriers, especially in cases of a positive family history.

Effects of ethanol and diphenyl diselenide exposure on the activity of δ-aminolevulinate dehydratase from mouse liver and brain

Ethanol toxicity is affected by both environmental and inherited features. Since oxidative stress is an important molecular mechanism for ethanol-induced cellular damage, the concomitant exposure to ethanol and pro-oxidative or antioxidant compounds can alter its toxicity. Here, we investigate the effects of exposure to ethanol and/or diphenyl diselenide, an organochalcogen with antioxidant properties, on parameters related to oxidative stress (thiobarbituric acid reactive species-TBARS-and delta-aminolevulinate dehydratase-delta-ALA-D activity) in mouse liver and brain. In addition, the in vitro effects of ethanol and acetaldehyde on the activity of delta-ALA-D from human erythrocytes were also investigated. Both ethanol and diphenyl diselenide decreased hepatic delta-ALA-D activity and DL-dithiothreitol (DTT) reactivated this enzyme only after ethanol-induced inhibition. Moreover, ethanol increased liver TBARS levels, independently of the presence of diphenyl diselenide treatment. Brain delta-ALA-D activity and TBARS levels were not changed by ethanol or diphenyl diselenide exposure. Under in vitro conditions, acetaldehyde was a more potent inhibitor of delta-ALA-D from human erythrocytes when compared to ethanol, demonstrating a dose-dependent effect. This study indicates that (1) hepatic delta-ALA-D is a molecular target for the damaging effect of ethanol under in vivo conditions; (2) diphenyl diselenide and ethanol seem to inhibit delta-ALA-D by different mechanisms; (3) acetaldehyde, a metabolite of ethanol, is probably the main molecule responsible for the inhibitory effects of the parent compound on delta-ALA-D.

Therapy of porphyria cutanea tarda

Porphyria cutanea tarda (PCT) is the most common type of porphyria. There is an association of PCT with haemochromatosis, diabetes mellitus and hepatitis C infection. The basis of treatment of PCT consists of three elements: avoidance of triggering factors, iron depletion and porphyrin elimination. Alcohol and certain systemic medical drugs, such as oestrogens (or tuberculostatics), should be considered as triggering factors, and as far as possible, avoided. Other triggering factors, such as chronic haemodialysis in renal insufficiency, need a different approach. The hallmark in iron depletion is phlebotomy. Porphyrin elimination is achieved using low-dose chloroquin therapy. The treatment is safe and effective but has its limits in cases with haemochromatosis (HFE) gene mutations. Here iron depletion needs additional phlebotomy. In patients with chronic haemodialysis-associated PCT, chloroquine is ineffective. Erythropoietin, desferroxamine and small-volume phlebotomy have been employed to control the disease. Childhood PCT is very rare. No controlled studies are available, but published experience suggests that body weight-adapted chloroquine therapy or small volume phlebotomy might be useful.

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

BACKGROUND

Inherited and environmental factors are implicated in the expression of porphyria cutanea tarda (PCT); the contribution of each factor depends on the population.

OBJECTIVE

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.

RESULTS

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.

CONCLUSIONS

PCT is multifactorial. Therefore, knowledge of all risk factors in each patient is important for the management of the disease.

Export of a heterologous cytochrome P450 (CYP105D1) in Escherichia coli is associated with periplasmic accumulation of uroporphyrin

This report suggests an important physiological role of a CYP in the accumulation of uroporphyrin I arising from catalytic oxidative conversion of uroporphyrinogen I to uroporphyrin I in the periplasm of Escherichia coli cultured in the presence of 5-aminolevulinic acid. A structurally competent Streptomyces griseus CYP105D1 was expressed as an engineered, exportable form in aerobically grown E. coli. Its progressive induction in the presence of 5-aminolevulinic acid-supplemented medium was accompanied by an accumulation of a greater than 100-fold higher amount of uroporphyrin I in the periplasm relative to cells lacking CYP105D1. Expression of a cytoplasm-resident engineered CYP105D1 at a comparative level to the secreted form was far less effective in promoting porphyrin accumulation in the periplasm. Expression at a 10-fold molar excess over the exported CYP105D1 of another periplasmically exported hemoprotein, the globular core of cytochrome b5, did not substitute the role of the periplasmically localized CYP105D1 in promoting porphyrin production. This, therefore, eliminated the possibility that uroporphyrin accumulation is merely a result of increased hemoprotein synthesis. Moreover, in the strain that secreted CYP105D1, uroporphyrin production was considerably reduced by azole-based P450 inhibitors. Production of both holo-CYP105D1 and uroporphyrin was dependent upon 5-aminolevulinic acid, except that at higher concentrations this resulted in a decrease in uroporphyrin. This study suggests that the exported CYP105D1 oxidatively catalyzes periplasmic conversion of uroporphyrinogen I to uroporphyrin I in E. coli. The findings have significant implications in the ontogenesis of human uroporphyria-related diseases.

The decrease in uroporphyrinogen decarboxylase activity induced by ethanol predisposes rats to the development of porphyria and accelerates xenobiotic-triggered porphyria, regardless of hepatic damage

We evaluated the porphyrinogenic ability of ethanol (20% in drinking water) per se, its effect on the development of sporadic porphyria cutanea tarda induced by hexachlorobenzene in female Wistar rats (170-190 g, N = 8/group), and the relationship with hepatic damage. Twenty-five percent of the animals receiving ethanol increased up to 14-, 25-, and 4.5-fold the urinary excretion of delta-aminolevulinate, porphobilinogen, and porphyrins, respectively. Ethanol exacerbated the precursor excretions elicited by hexachlorobenzene. Hepatic porphyrin levels increased by hexachlorobenzene treatment, while this parameter only increased (up to 90-fold) in some of the animals that received ethanol alone. Ethanol reduced the activities of uroporphyrinogen decarboxylase, delta-aminolevulinate dehydrase and ferrochelatase. In the ethanol group, many of the animals showed a 30% decrease in uroporphyrinogen activity; in the ethanol + hexachlorobenzene group, this decrease occurred before the one caused by hexachlorobenzene alone. Ethanol exacerbated the effects of hexachlorobenzene, among others, on the rate-limiting enzyme delta-aminolevulinate synthetase. The plasma activities of enzymes that are markers of hepatic damage were similar in all drug-treated groups. These results indicate that 1) ethanol exacerbates the biochemical manifestation of sporadic hexachlorobenzene-induced porphyria cutanea tarda; 2) ethanol per se affects several enzymatic and excretion parameters of the heme metabolic pathway; 3) since not all the animals were affected to the same extent, ethanol seems to be a porphyrinogenic agent only when there is a predisposition, and 4) hepatic damage showed no correlation with the development of porphyria cutanea tarda.

Human hereditary hepatic porphyrias

The human hereditary hepatic porphyrias are diseases due to marked deficiencies of enzymes in the heme biosynthetic pathway. Porphyrias can be classified as either hepatic or erythroid, depending on the major production site of porphyrins or their precursors. The pathogenesis of inherited hepatic porphyrias has now been defined at the molecular level. Some gene carriers are vulnerable to a range of exogenous and endogenous factors, which may trigger neuropsychiatric and/or cutaneous symptoms. Early diagnosis is of prime importance since it makes way for counselling. In this article we present an overview of recent advances on hepatic porphyrias: 5-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria (AIP), porphyria cutanea tarda (PCT), hereditary coproporphyria (HC), and variegate porphyria (VP).

Self-rated psychosocial consequences and quality of life in the acute porphyrias

A battery of self-report psychosocial measures was mailed to 116 patients who had been referred for clinical management (clinic attenders) or laboratory diagnosis (non-clinic attenders) to the London Supraregional Assay Service Centre for Porphyria over the past decade and who tested positive for porphyria. Usable replies were received from 81 (70%) patients. Our interest focused on the prevalence of psychosocial symptoms in acute porphyrias and the perceived effects of porphyria on quality of life and patient experience. Research questions examined included (i), lifestyle factors; (ii) life events; (iii) mental health; (iv) general health; and (v) perceptions of illness of patients receiving specialist clinical management compared to respondents referred for diagnostic investigations, between patients with latent or manifest symptomology and between patients with different types of porphyria. Patients with porphyria have an impaired quality of life, particularly manifest cases, compared to controls and to diabetic patients. Depression, and particularly anxiety, is more common than in the general population or general medical outpatient attenders. Quality oflife is lower in acute intermittent porphyria (AIP) than in other forms of porphyria and a significant number of patients had major life event consequences, e.g. failure to secure, or loss of, employment, limitation of family size. Patients attending a clinic providing specialist porphyria advice, management and counselling received some perceived lifestyle benefits.

Pseudoporphyria: a clinical and biochemical study of 20 patients

OBJECTIVE

To describe the clinical and laboratory findings in patients with pseudoporphyria.

PATIENTS AND METHODS

This retrospective review identified 261 patients with either porphyrin metabolism abnormalities or pseudoporphyria who were seen at the Mayo Clinic in Rochester, Minn, between 1992 and 1996. All patients with documented porphyria cutanea tarda (PCT), noncutaneous porphyrias, or variegate porphyria were excluded.

RESULTS

Twenty patients had active cutaneous lesions resembling PCT with no diagnostic laboratory abnormalities. The major presenting clinical features were blistering in 19 patients (95%), scarring in 14 (70%), photosensitivity in 13 (65%), skin fragility in 13 (65%), and milia in 8 (40%). Histologically, of 17 patients tested, 12 (71%) had classic findings of subepidermal separation with festooning of dermal papillae. None of the 11 patients tested had hepatitis B or C. In all 20 patients, porphyrin profiles were nondiagnostic. Of 16 patients for whom follow-up was available, 11 reported persistent symptoms for a mean of 2.5 years after evaluation. Five patients were free of symptoms 1 week to 6 months after discontinuation of the presumed offending agent.

CONCLUSION

Pseudoporphyria mimics the cutaneous symptoms of PCT in the setting of normal or near-normal porphyrin levels in the serum, urine, or stool. Despite efforts to discontinue an offending medication, symptoms may persist indefinitely.

The roles of iron in health and disease

Iron is vital for almost all living organisms by participating in a wide variety of metabolic processes, including oxygen transport, DNA synthesis, and electron transport. However, iron concentrations in body tissues must be tightly regulated because excessive iron leads to tissue damage, as a result of formation of free radicals. Disorders of iron metabolism are among the most common diseases of humans and encompass a broad spectrum of diseases with diverse clinical manifestations, ranging from anemia to iron overload and, possibly, to neurodegenerative diseases. The molecular understanding of iron regulation in the body is critical in identifying the underlying causes for each disease and in providing proper diagnosis and treatments. Recent advances in genetics, molecular biology and biochemistry of iron metabolism have assisted in elucidating the molecular mechanisms of iron homeostasis. The coordinate control of iron uptake and storage is tightly regulated by the feedback system of iron responsive element-containing gene products and iron regulatory proteins that modulate the expression levels of the genes involved in iron metabolism. Recent identification and characterization of the hemochromatosis protein HFE, the iron importer Nramp2, the iron exporter ferroportin1, and the second transferrin-binding and -transport protein transferrin receptor 2, have demonstrated their important roles in maintaining body's iron homeostasis. Functional studies of these gene products have expanded our knowledge at the molecular level about the pathways of iron metabolism and have provided valuable insight into the defects of iron metabolism disorders. In addition, a variety of animal models have implemented the identification of many genetic defects that lead to abnormal iron homeostasis and have provided crucial clinical information about the pathophysiology of iron disorders. In this review, we discuss the latest progress in studies of iron metabolism and our current understanding of the molecular mechanisms of iron absorption, transport, utilization, and storage. Finally, we will discuss the clinical presentations of iron metabolism disorders, including secondary iron disorders that are either associated with or the result of abnormal iron accumulation.