Overproduction Of Protoporphyrin Research Articles

Management of Patients With Erythropoietic Protoporphyria-Related Progressive Liver Disease.

Erythropoietic protoporphyria (EPP) is an inherited metabolic disorder of heme synthesis resulting from overproduction of protoporphyrin IX (PPIX), which can lead to progressive liver disease characterized by recurrent EPP crises and end-stage liver disease. We used the Australian Transplant Registry to identify 5 patients referred for liver transplantation between 2008 and 2017. A total of 4 patients had EPP secondary to ferrochelatase deficiency, and 1 patient had X-linked EPP. No patient had follow-up with a specialist prior to the diagnosis of progressive liver disease. There were 3 patients who underwent orthotopic liver transplantation, whereas 2 died while on the transplant waiting list. Parenteral PPIX-lowering therapy was used in 4 patients and was effective in 3 patients, although 2 of these had rebound porphyria and worsening liver function following a decrease in the intensity of therapy. Early disease recurrence in the allograft following transplantation occurred in 2 patients requiring red cell exchange (RCE) to successfully attain and maintain low PPIX levels, but RCE was associated with hemosiderosis in 1 patient. Allogeneic stem cell transplantation (AlloSCT) was performed in 2 patients. One failed engraftment twice, whereas the second rejected the first graft but achieved full donor chimerism with a second graft and increased immunosuppression. In conclusion, our observations suggest that progressive liver disease needs parenteral PPIX-lowering treatment with the intensity adjusted to achieve a target Erc-PPIX level. Because EPP liver disease is universally recurrent, AlloSCT should be considered in all patients with adequate immunosuppression to facilitate engraftment. RCE appears to be effective for recurrent EPP liver disease but is associated with an increased risk of iron overload.

Anti-Correlation between the Dynamics of the Active Site Loop and C-Terminal Tail in Relation to the Homodimer Asymmetry of the Mouse Erythroid 5-Aminolevulinate Synthase.

Biosynthesis of heme represents a complex process that involves multiple stages controlled by different enzymes. The first of these proteins is a pyridoxal 5′-phosphate (PLP)-dependent homodimeric enzyme, 5-aminolevulinate synthase (ALAS), that catalyzes the rate-limiting step in heme biosynthesis, the condensation of glycine with succinyl-CoA. Genetic mutations in human erythroid-specific ALAS (ALAS2) are associated with two inherited blood disorders, X-linked sideroblastic anemia (XLSA) and X-linked protoporphyria (XLPP). XLSA is caused by diminished ALAS2 activity leading to decreased ALA and heme syntheses and ultimately ineffective erythropoiesis, whereas XLPP results from “gain-of-function” ALAS2 mutations and consequent overproduction of protoporphyrin IX and increase in Zn2+-protoporphyrin levels. All XLPP-linked mutations affect the intrinsically disordered C-terminal tail of ALAS2. Our earlier molecular dynamics (MD) simulation-based analysis showed that the activity of ALAS2 could be regulated by the conformational flexibility of the active site loop whose structural features and dynamics could be changed due to mutations. We also revealed that the dynamic behavior of the two protomers of the ALAS2 dimer differed. However, how the structural dynamics of ALAS2 active site loop and C-terminal tail dynamics are related to each other and contribute to the homodimer asymmetry remained unanswered questions. In this study, we used bioinformatics and computational biology tools to evaluate the role(s) of the C-terminal tail dynamics in the structure and conformational dynamics of the murine ALAS2 homodimer active site loop. To assess the structural correlation between these two regions, we analyzed their structural displacements and determined their degree of correlation. Here, we report that the dynamics of ALAS2 active site loop is anti-correlated with the dynamics of the C-terminal tail and that this anti-correlation can represent a molecular basis for the functional and dynamic asymmetry of the ALAS2 homodimer.

Liver disease and erythropoietic protoporphyria: A concise review

The porphyries are a group of metabolic disorders characterized by deficiencies in the activity of enzymes involved in the biosynthesis of heme. In erythropoietic protoporphyria (EPP), in the majority of cases an autosomal dominant disease, there is a mutation of the gene that encodes ferrochelatase (FECH). FECH deficiency is associated with increased concentrations of protoporphyrin in erythrocytes, plasma, skin and liver. The prevalence of this inherited disorder oscillates between 1:75 000 and 1:200 000. Clinical manifestations of EPP appear in early infancy upon first exposure to the sun. Nevertheless, approximately 5%-20% of patients with EPP develop liver manifestations. Retention of protoporphyrin in the liver is associated with cholestatic phenomena and oxidative stress that predisposes to hepatobiliary disease of varying degrees of severity, such as cholelithiasis, mild parenchymal liver disease, progressive hepatocellular disease with end-stage liver disease and acute liver failure. Liver damage is the major risk in EPP patients, so surveillance and frequent clinical and biochemical liver follow-up is mandatory. The diagnostic approach consists in detecting increased levels of protoporphyrin, decreased activity of FECH and genetic analysis of the FECH gene. A variety of non-surgical therapeutic approaches have been adopted for the management of EPP associated with liver disease, but none of these has been shown to be unequivocally efficacious. Nevertheless, some may have a place in preparing patients for liver transplantation. Liver transplantation does not correct the constitutional deficiency of FECH. Consequently, there is a risk of recurrence of liver disease after liver transplantation as a result of continuing overproduction of protoporphyrin. Some authors recommend that bone marrow transplantation should be considered in liver allograft recipients to prevent recurrence of hepatic disease.

C-Terminal Deletions in the ALAS2 Gene Lead to Gain of Function and Cause X-linked Dominant Protoporphyria without Anemia or Iron Overload

All reported mutations in ALAS2, which encodes the rate-regulating enzyme of erythroid heme biosynthesis, cause X-linked sideroblastic anemia. We describe eight families with ALAS2 deletions, either c.1706-1709 delAGTG (p.E569GfsX24) or c.1699-1700 delAT (p.M567EfsX2), resulting in frameshifts that lead to replacement or deletion of the 19-20 C-terminal residues of the enzyme. Prokaryotic expression studies show that both mutations markedly increase ALAS2 activity. These gain-of-function mutations cause a previously unrecognized form of porphyria, X-linked dominant protoporphyria, characterized biochemically by a high proportion of zinc-protoporphyrin in erythrocytes, in which a mismatch between protoporphyrin production and the heme requirement of differentiating erythroid cells leads to overproduction of protoporphyrin in amounts sufficient to cause photosensitivity and liver disease.

Curative bone marrow transplantation in erythropoietic protoporphyria after reversal of severe cholestasis

We report the case of a middle-age patient presenting with severe progressive protoporphyric cholestasis. To halt further progression of liver disease, medical treatment was given aimed at different mechanisms possibly causing cholestasis in erythropoietic protoporphyria. Within eighty days, liver biochemistry completely normalized and liver histology markedly improved. Bone marrow transplantation was performed to prevent relapse of cholestatic liver disease by correcting the main site of protoporphyrin overproduction. Thirty-three months after cholestatic presentation and ten months after bone marrow transplantation, liver and porphyrin biochemistry remains normal. The patient is in excellent condition and photosensitivity is absent. The theoretical role of each treatment used to successfully reverse cholestasis and the role of bone marrow transplantation in erythropoietic protoporphyria are discussed. Medical treatment can resolve hepatic abnormalities in protoporphyric cholestasis. Bone marrow transplantation achieves phenotypic reversal and may offer protection from future protoporphyric liver disease.

Photosensitivity and acute liver injury in myeloproliferative disorder secondary to late-onset protoporphyria caused by deletion of a ferrochelatase gene in hematopoietic cells

AbstractLate-onset erythropoietic protoporphyria (EPP) is a rare complication of myelodysplastic syndrome (MDS) but has not been described in association with a myeloproliferative disorder (MPD). EPP is normally an inherited disorder characterized by photosensitivity that starts in early childhood and results from overproduction of protoporphyrin secondary to ferrochelatase (FECH) deficiency. Severe liver disease occurs in 1% to 2% of patients. Here we report that severe photosensitivity and cholestatic liver disease in a patient with a myeloproliferative disorder was caused by excess protoporphyrin production from a clone of hematopoietic cells in which one FECH allele had been deleted. Our observations suggest that the usual explanation for the association of late-onset EPP with MPD and MDS is acquired somatic mutation of one FECH allele in bone marrow and show for the first time that the consequent overproduction of protoporphyrin may be severe enough to cause acute liver damage.

Ursodesoxycholic acid and heme-arginate are unable to improve hematopoiesis and liver injury in an erythropoietic protoporphyria mouse model

Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis caused by partial ferrochelatase deficiency, resulting in protoporphyrin overproduction which is responsible for painful skin photosensitivity. Chronic liver disease is the most severe complication of EPP, requiring liver transplantation in some patients. Data from a mouse model suggest that cytotoxic bile formation with high concentrations of bile salts and protoporphyrin may cause biliary fibrosis by damaging bile duct epithelium. In humans, cholestasis is a result of intracellular and canalicular precipitation of protoporphyrin. To limit liver damage two strategies may be considered: the first is to reduce protoporphyrin production and the second is to enhance protoporphyrin excretion. Bile salts are known to increase protoporphyrin excretion via the bile, while heme arginate is used to decrease the production of porphyrins in acute attacks of hepatic porphyrias. The Griseofulvin-induced protoporphyria mouse model has been used to study several aspects of human protoporphyria including the effects of bile salts. However, the best EPP animal model is an ethylnitrosourea-induced point mutation with fully recessive transmission, named ferrochelatase deficiency (Fech(m1Pas)). Here we investigate the effect of early ursodesoxycholic acid (UDCA) administration and heme-arginate injections on the ferrochelatase deficient EPP mouse model. In this model UDCA administration and heme-arginate injections do not improve the protoporphyric condition of Fech(m1Pas)/Fech(m1Pas) mice.

Liver transplantation for erythropoietic protoporphyria: report of a case with medium-term follow-up

A case of liver transplantation is described in a 35-year-old male with hepatic failure due to erythropoietic protoporphyria. Data regarding protoporphyrin levels in erythrocytes and faeces, before and after transplantation, seem to indicate that, in this case, protoporphyrin overproduction was, in part, due to liver synthesis. Four years after surgery, the patient is completely free of skin photosensitivity. Liver function tests are normal and there are no significant protoporphyrin deposits in the new liver. However, recurrence of the disease in the long-term cannot be excluded, since erythrocyte protoporphyrin levels have remained elevated after liver transplantation.

Mutations in the iron-sulfur cluster ligands of the human ferrochelatase lead to erythropoietic protoporphyria

Ferrochelatase (FECH; EC 4.99.1.1) catalyzes the terminal step of the heme biosynthetic pathway. Defects in the human FECHgene may lead to erythropoietic protoporphyria (EPP), a rare inherited disorder characterized by diminished FECH activity with protoporphyrin overproduction and subsequent skin photosensitivity and in rare cases liver failure. Inheritance of EPP appeared to be autosomal dominant with possible modulation by low expression of the wild-type FECH allele. Animal FECHs have been demonstrated to be [2Fe-2S] cluster-containing proteins. Although enzymatic activity and stability of the protein appear to be dependent on the presence of the [2Fe-2S] cluster, the physiologic role of the iron-sulfur center remains to be unequivocally established. Three of the 4 [2Fe-2S] cluster-coordinating cysteines (ie, C403, C406, and C411 in the human enzyme) are located within the C-terminal domain. In this study 5 new mutations are identified in patients with EPP. Three of the point mutations, in 3 patients, resulted in FECH variants with 2 of the [2Fe-2S] cluster cysteines substituted with tyrosine, serine, and glycine (ie, C406Y, C406S, and C411G) and with undetectable enzymatic activity. Further, one of the patients exhibited a triple point mutation (T1224→A, C1225→T, and T1231→G) leading to the N408K/P409S/C411G variant. This finding is entirely novel and has not been reported in EPP. The mutations of the codons for 2 of the [2Fe-2S] cluster ligands in patients with EPP supports the importance of the iron-sulfur center for the proper functioning of mammalian FECH and, in at least humans, its absence has a direct clinical impact.

Mutations in the iron-sulfur cluster ligands of the human ferrochelatase lead to erythropoietic protoporphyria

AbstractFerrochelatase (FECH; EC 4.99.1.1) catalyzes the terminal step of the heme biosynthetic pathway. Defects in the human FECHgene may lead to erythropoietic protoporphyria (EPP), a rare inherited disorder characterized by diminished FECH activity with protoporphyrin overproduction and subsequent skin photosensitivity and in rare cases liver failure. Inheritance of EPP appeared to be autosomal dominant with possible modulation by low expression of the wild-type FECH allele. Animal FECHs have been demonstrated to be [2Fe-2S] cluster-containing proteins. Although enzymatic activity and stability of the protein appear to be dependent on the presence of the [2Fe-2S] cluster, the physiologic role of the iron-sulfur center remains to be unequivocally established. Three of the 4 [2Fe-2S] cluster-coordinating cysteines (ie, C403, C406, and C411 in the human enzyme) are located within the C-terminal domain. In this study 5 new mutations are identified in patients with EPP. Three of the point mutations, in 3 patients, resulted in FECH variants with 2 of the [2Fe-2S] cluster cysteines substituted with tyrosine, serine, and glycine (ie, C406Y, C406S, and C411G) and with undetectable enzymatic activity. Further, one of the patients exhibited a triple point mutation (T1224→A, C1225→T, and T1231→G) leading to the N408K/P409S/C411G variant. This finding is entirely novel and has not been reported in EPP. The mutations of the codons for 2 of the [2Fe-2S] cluster ligands in patients with EPP supports the importance of the iron-sulfur center for the proper functioning of mammalian FECH and, in at least humans, its absence has a direct clinical impact.

Inheritance in Erythropoietic Protoporphyria: A Common Wild-Type Ferrochelatase Allelic Variant With Low Expression Accounts for Clinical Manifestation

Erythropoietic protoporphyria (EPP) is a rare autosomal dominant disorder of heme biosynthesis characterized by partial decrease in ferrochelatase (FECH; EC 4.99.1.1) activity with protoporphyrin overproduction and consequent painful skin photosensitivity and rarely liver disease. EPP is normally inherited in an autosomal dominant pattern with low clinical penetrance; the many different mutations that have been identified are restricted to one FECH allele, with the other one being free of any mutations. However, clinical manifestations of dominant EPP cannot be simply a matter of FECH haploinsufficiency, because patients have enzyme levels that are lower than the expected 50%. From RNA analysis in one family with dominant EPP, we recently suggested that clinical expression required coinheritance of a normal FECH allele with low expression and a mutant FECH allele. We now show that (1) coinheritance of a FECH gene defect and a wild-type low-expressed allele is generally involved in the clinical expression of EPP; (2) the low-expressed allelic variant was strongly associated with a partial 5' haplotype [-251G IVS1-23T IVS2microsatA9] that may be ancestral and was present in an estimated 10% of a control group of Caucasian origin; and (3) haplotyping allows the absolute risk of developing the disease to be predicted for those inheriting FECH EPP mutations. EPP may thus be considered as an inherited disorder that does not strictly follow recessive or dominant rules. It may represent a model for phenotype modulation by mild variation in expression of the wild-type allele in autosomal dominant diseases.

Protoporphyria.

Human protoporphyria results from mutations in the ferrochelatase gene. Heritable deficiency of ferrochelatase causes overproduction of protoporphyrin IX, principally in the erythron. Photosensitivity is a universal feature of protoporphyria but hepatic clearance of the hydrophobic protoporphyrin molecule with excretion in bile may lead to precipitation within biliary pathways. Thus cholestatic injury and protoporphyrin gallstones occur. Minor hepatic abnormalities are frequent, but at least 30 patients have been reported with a progressive liver disease that requires transplantation. Fulminant hepatic disease appears to be recessively inherited in some pedigrees. Hazards of liver transplantation include tissue photolysis, hemolysis, and an unexplained neurological syndrome, but most of the 15 patients reported after transplantation have survived for several months to > 6 years. Aspects of protoporphyria, its pathogenesis and contemporary therapeutic strategies are considered, with emphasis on hepatic sequelae.

Erythropoietic protoporphyria.

Partial deficiency of the last enzyme of haem biosynthesis, ferrochelatase, leads to a distinct syndrome of photosensitivity caused by overproduction of protoporphyrin by erythropoietic tissue. Erythropoietic protoporphyria has an indeterminate pattern of inheritance and may be complicated by fulminating liver disease. The recent development of simple assays for ferrochelatase activity and cloning of the human ferrochelatase gene promises to shed light on the transmission of this disorder and may allow clinical expression of disease to be predicted. This review surveys the pathological features, genetics and treatment of porphyria.

Liver transplantation for erythropoietic protoporphyria: Report of a new case with subsequent medium-term follow-up

We report a new case of successful liver transplantation in a 36-year-old patient with terminal hepatic failure due to erythropoietic protoporphyria. Data regarding protoporphyrin levels in erythrocytes and feces, before and after transplantation, seem to indicate that in this case protoporphyrin overproduction was in part due to liver synthesis. Four years after surgery, the patient is completely free of skin photosensitivity. His liver function tests are normal; there are no visible protoporphyrin deposits or ultrastructural abnormalities in his new liver. However, recurrence of the disease in the long term cannot be excluded, since erythrocyte protoporphyrin levels remained elevated after liver transplantation.

Liver Transplantation for Protoporphyria: Evidence for the Predominant Role of the Erythropoietic Tissue in Protoporphyrin Overproduction

Protoporphyria is an inherited disorder of heme biosynthesis characterized by an overproduction of protoporphyrin in the erythropoietic and hepatic tissues, the relative contribution of which in the metabolic disorder has not been directly quantitated. Excess protoporphyrin is eliminated solely by the liver into the bile and feces. We describe the case of a patient with protoporphyria complicated by severe cirrhosis in whom liver transplantation was performed and resulted in almost complete disappearance of skin photosensitivity manifestations and reduction in the level of protoporphyrin in erythrocytes. However, the level of protoporphyrin in feces was not markedly different before and after liver transplantation, which suggests that overproduction of protoporphyrin was unchanged. These findings are consistent with the view that the diseased liver and ensuing low hepatic clearance of protoporphyrin contributed to accumulation of protoporphyrin in the body and that, at least in this patient, the role of the hepatic tissue in the overproduction of protoporphyrin was small in comparison with that of the erythropoietic tissue.

Liver transplantation in protoporphyria. Direct evidence for the minor role of the liver in protoporphyrin overproduction

Liver transplantation in protoporphyria. Direct evidence for the minor role of the liver in protoporphyrin overproduction

The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles.

N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.

Growth cycle-dependent overproduction and accumulation of protoporphyrin IX in Tetrahymena: effect of heavy metals.

Cells of the ciliate Tetrahymena pyriformis GL overproduce and accumulate massive quantities of the heme intermediate, protoporphyrin IX. Protoporphyrin is localized intracellularly in discrete membranous compartments. The amount of porphyrin stored in the cell changes dramatically as cells progress through the growth cycle. Porphyrin overproduction is stimulated by delta-aminolevulinic acid, but only during the mid-stationary phase. Overproduction of protoporphyrin IX apparently results from an increase, late in the growth cycle, of activities subsequent to delta-aminolevulinic acid synthetase. Feedback inhibition in the pathway by accumulated protoporphyrin IX does not occur. The presence of Co2+ completely inhibits accumulation of protoporphyrin IX in a manner reversed by delta-aminolevulinic acid. Sn4+ stimulates protoporphyrin IX accumulation in the culture.

The origin of the increased protoporphyrin in erythrocytes of mice with experimentally induced porphyria.

Abstract Although the administration of 3,5-dicarbethoxy-1, 4-dihydrocollidine (DDC) and griseofulvin increased the circulating erythrocyte and plasma protoporphyrin concentration in mice, activities of δ-aminolevulinic acid (ALA) synthetase, heme synthetase in the spleen, and formation of porphyrins from ALA in erythrocytes were unchanged. After an intraperitoneal injection of protoporphyrin, protoporphyrin concentration in the circulating erythrocytes increased. The overproduction of protoporphyrin in the liver induced by the porphyria-inducing chemicals caused a rise in the concentration of plasma protoporphyrin, which was apparently taken up by the red blood cells of mice, resulting in an increased erythrocyte protoporphyrin concentration.

Erythrocyte Fluorescence in Relatives of Patients With Erythropoietic Protoporphyria

IN 1953, Kosenow and Treibs¹described a new inborn error of porphyrin metabolism which Magnus et al²later termed erythropoietic protoporphyria (EPP). Porter provided evidence that EPP was due to overproduction of protoporphyrin IX in the bone marrow.³Erythrocyte and fecal protoporphyrins and, at times, coproporphyrins are increased, but urinary porphyrins are normal in affected individuals.¹Erythrocytes^1,4,5and their precursors^6,7have been observed to fluoresce in some cases but not in others.⁸A dominant form of inheritance has been suggested by several authors.^6,9-12Asymptomatic relatives with "latent" EPP have been previously identified by slightly increased red blood cell (RBC) protoporphyrin concentrations.^6,13,14We now report increased numbers of red-fluorescing erythrocytes with<i>normal</i>RBC protoporphyrin concentrations in four asymptomatic relatives of two patients with EPP. In addition, a sibling of one of the patients was found to have elevated RBC protoporphyrin levels and