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Hematology. American Society of... Dec 2020The porphyrias are a family of metabolic disorders caused by defects in the activity of one of the enzymes in the heme biosynthetic pathway. Acute intermittent porphyria...
The porphyrias are a family of metabolic disorders caused by defects in the activity of one of the enzymes in the heme biosynthetic pathway. Acute intermittent porphyria (AIP), caused by autosomal dominant mutations in the gene encoding hydroxymethylbilane synthase, can lead to hepatocyte overaccumulation and systemic distribution of the proximal porphyrin precursors, 5-aminolevulinic acid (ALA) and porphobilinogen (PBG). ALA and PBG are toxic to neurons and extrahepatic tissue and cause the neurovisceral clinical manifestations of AIP. Management of AIP includes awareness and avoidance of triggering factors, infusions of hemin for severe acute attacks, and, if indicated for chronic suppressive therapy, maintenance treatment with hemin or givosiran, a small interfering RNA molecule that antagonizes ALA synthase 1 transcripts. Erythropoietic protoporphyria (EPP) is most commonly caused by autosomal recessive mutations in the gene encoding ferrochelatase (FECH), the heme pathway terminal enzyme. FECH deficiency leads to erythrocyte overaccumulation and high plasma levels of lipophilic protoporphyrins that photoactivate in the skin, causing burning pain and erythema. Protoporphyrins excreted in the bile can cause gallstones, cholestasis, fibrosis, and ultimately liver failure. Management of EPP includes skin protection and afamelanotide, an α-melanocyte stimulating hormone analog that increases melanin pigment and reduces photoactivation. Liver transplantation may be necessary for severe EPP-induced liver complications. Because AIP and EPP arise from defects in the heme biosynthetic pathway, hematologists are often consulted to evaluate and manage suspected or proven porphyrias. A working knowledge of these disorders increases our confidence and effectiveness as consultants and medical providers.
Topics: Adult; Disease Management; Female; Heme; Humans; Mutation; Porphyria, Acute Intermittent; Protoporphyria, Erythropoietic; Young Adult
PubMed: 33275677
DOI: 10.1182/hematology.2020000124 -
Molecular Genetics and Metabolism... Dec 2021Regulation of 5-aminolevulinate synthase 1 (ALAS1) for nonerythroid heme is critical for respiration, cell signaling mechanisms and steroid/drug metabolism. ALAS1 is...
Regulation of 5-aminolevulinate synthase 1 (ALAS1) for nonerythroid heme is critical for respiration, cell signaling mechanisms and steroid/drug metabolism. ALAS1 is induced in some genetic disorders but unlike other genes in the heme pathway, a gene variant of associated with inherited disease has not been reported. BALB/c mice carrying a null allele caused by a insert were developed and used to determine the consequences of heme demand of a semi gene copy number. Homozygous disruption of (-/-) was lethal for embryo development post day 6.5 but expression in heterozygotes (+/-) was sufficient for the number of offspring and survival. In both wild type (WT +/+) and +/- mice expression of ALAS1 RNA was greatest in liver and harderian gland and much lower in kidney, lung, heart, brain and spleen. The effects of one WT allele in +/- mice on mRNA levels in liver and harderian gland were less marked compared to brain and other organs that were examined. Many other genes were up-regulated by heterozygosity in liver and brain but to a minimal extent. Hepatic heme oxygenase 1 (HMOX1) mRNA expression was significantly lower in +/- mice but not in brain. No elevated translation of WT allele ALAS1 mRNA was detected in +/- liver as a compensatory mechanism for the disabled allele. Fasting induced ALAS1 mRNA in both WT and +/- mice but only in +/- was this manifest as increased ALAS1 protein. The hepatic protoporphyria-inducing drug 4-ethyl-DDC caused induction of hepatic ALAS1 mRNA and protein levels in both WT and +/- mice but markedly less in the mice with only one intact allele. The findings illustrate the complex response of expression for heme demand but limited evidence that upregulation of a wild type allele can compensate for a null allele.
PubMed: 34900592
DOI: 10.1016/j.ymgmr.2021.100818 -
Life (Basel, Switzerland) May 2024Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders of heme biosynthesis characterized by severe cutaneous phototoxicity....
BACKGROUND
Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders of heme biosynthesis characterized by severe cutaneous phototoxicity. Afamelanotide, an α-melanocyte-stimulating hormone analogue, is the only approved treatment for protoporphyria and leads to increased light tolerance and improved quality of life (QoL). However, published experience with afamelanotide in the US is limited.
METHODS
Here, we report on all adults who received at least one dose of afamelanotide at the Massachusetts General Hospital Porphyria Center from 2021 to 2022. Changes in the time to phototoxic symptom onset, QoL, and laboratory parameters were assessed before and during treatment with afamelanotide.
RESULTS
A total of 29 patients with protoporphyria were included, 26 of whom (72.2%) received ≥2 afamelanotide implants. Among the patients who received ≥2 implants, the median time to symptom onset following sunlight exposure was 12.5 min (IQR, 5-20) prior to the initiation of afamelanotide and 120 min (IQR, 60-240) after treatment ( < 0.001). Improvements in QoL during afamelanotide treatment were measured using two QoL tools, with good correlation observed between these two instruments. Finally, we found no improvements in the median levels of metal-free erythrocyte protoporphyrin, plasma protoporphyrin, or liver biochemistries during versus prior to the initiation of afamelanotide treatment.
CONCLUSIONS
This study highlights a dramatic clinical benefit of afamelanotide in relation to light tolerance and QoL in protoporphyria, albeit without improvement in protoporphyrin levels or measures of liver function.
PubMed: 38929673
DOI: 10.3390/life14060689 -
Molecular & Cellular Proteomics : MCP Dec 2020Mallory-Denk-bodies (MDBs) are hepatic protein aggregates associated with inflammation both clinically and in MDB-inducing models. Similar protein aggregation in...
Mallory-Denk-bodies (MDBs) are hepatic protein aggregates associated with inflammation both clinically and in MDB-inducing models. Similar protein aggregation in neurodegenerative diseases also triggers inflammation and NF-κB activation. However, the precise mechanism that links protein aggregation to NF-κB-activation and inflammatory response remains unclear. Herein we find that treating primary hepatocytes with MDB-inducing agents (N-methylprotoporphyrin (NMPP), protoporphyrin IX (PPIX), or Zinc-protoporphyrin IX (ZnPP)) elicited an IκBα-loss with consequent NF-κB activation. Four known mechanisms of IκBα-loss the canonical ubiquitin-dependent proteasomal degradation (UPD), autophagic-lysosomal degradation, calpain degradation and translational inhibition, were all probed and excluded. Immunofluorescence analyses of ZnPP-treated cells coupled with 8 M urea/CHAPS-extraction revealed that this IκBα-loss was due to its sequestration along with IκBβ into insoluble aggregates, thereby releasing NF-κB. Through affinity pulldown, proximity biotinylation by antibody recognition, and other proteomic analyses, we verified that NF-κB subunit p65, which stably interacts with IκBα under normal conditions, no longer binds to it upon ZnPP-treatment. Additionally, we identified 10 proteins that interact with IκBα under baseline conditions, aggregate upon ZnPP-treatment, and maintain the interaction with IκBα after ZnPP-treatment, either by cosequestering into insoluble aggregates or through a different mechanism. Of these 10 proteins, the nucleoporins Nup153 and Nup358/RanBP2 were identified through RNA-interference, as mediators of IκBα-nuclear import. The concurrent aggregation of IκBα, NUP153, and RanBP2 upon ZnPP-treatment, synergistically precluded the nuclear entry of IκBα and its consequent binding and termination of NF-κB activation. This novel mechanism may account for the protein aggregate-induced inflammation observed in liver diseases, thus identifying novel targets for therapeutic intervention. Because of inherent commonalities this MDB cell model is a protoporphyric model, making these findings equally relevant to the liver inflammation associated with clinical protoporphyria.
Topics: Active Transport, Cell Nucleus; Animals; Autophagy; Cell Nucleus; HEK293 Cells; HeLa Cells; Hep G2 Cells; Hepatocytes; Humans; I-kappa B Proteins; Inflammation; Liver; Male; Mice, Inbred C57BL; Mice, Knockout; NF-kappa B; Nuclear Pore Complex Proteins; Protein Aggregates; Protein Binding; Protein Multimerization; Protoporphyrins; RNA, Small Interfering; Sequestosome-1 Protein; Solubility
PubMed: 32912968
DOI: 10.1074/mcp.RA120.002316 -
Cell Chemical Biology Aug 2021Erythropoietic protoporphyria (EPP) is a rare disease in which patients experience severe light sensitivity. It is caused by a deficiency of ferrochelatase (FECH), the...
Erythropoietic protoporphyria (EPP) is a rare disease in which patients experience severe light sensitivity. It is caused by a deficiency of ferrochelatase (FECH), the last enzyme in heme biosynthesis (HBS). The lack of FECH causes accumulation of its photoreactive substrate protoporphyrin IX (PPIX) in patients' erythrocytes. Here, we explored an approach for the treatment of EPP by decreasing PPIX synthesis using small-molecule inhibitors directed to factors in the HBS pathway. We generated a FECH-knockout clone from K562 erythroleukemia cells, which accumulates PPIX and undergoes oxidative stress upon light exposure. We used these matched cell lines to screen a set of publicly available inhibitors of factors in the HBS pathway. Inhibitors of the glycine transporters GlyT1 and GlyT2 lowered levels of PPIX and markers of oxidative stress selectively in K562 cells, and in primary erythroid cultures from an EPP patient. Our findings open the door to investigation of glycine transport inhibitors for HBS disorders.
Topics: Cells, Cultured; Erythrocytes; Glycine Plasma Membrane Transport Proteins; Humans; K562 Cells; Molecular Structure; Protoporphyria, Erythropoietic; Protoporphyrins
PubMed: 33756123
DOI: 10.1016/j.chembiol.2021.02.021 -
Clinical Genetics Jan 2016X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity...
X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity and markedly increased erythrocyte protoporphyrin levels. Patients present with severe cutaneous photosensitivity and may develop liver dysfunction. XLP was originally reported as X-linked dominant with 100% penetrance in males and females. We characterized 11 heterozygous females from six unrelated XLP families and show markedly varying phenotypic and biochemical heterogeneity, reflecting the degree of X-chromosomal inactivation of the mutant gene. ALAS2 sequencing identified the specific mutation and confirmed heterozygosity among the females. Clinical history, plasma and erythrocyte protoporphyrin levels were determined. Methylation assays of the androgen receptor and zinc-finger MYM type 3 short tandem repeat polymorphisms estimated each heterozygotes X-chromosomal inactivation pattern. Heterozygotes with equal or increased skewing, favoring expression of the wild-type allele had no clinical symptoms and only slightly increased erythrocyte protoporphyrin concentrations and/or frequency of protoporphyrin-containing peripheral blood fluorocytes. When the wild-type allele was preferentially inactivated, heterozygous females manifested the disease phenotype and had both higher erythrocyte protoporphyrin levels and circulating fluorocytes. These findings confirm that the previous dominant classification of XLP is inappropriate and genetically misleading, as the disorder is more appropriately designated XLP.
Topics: Alleles; Erythrocytes; Female; Genes, X-Linked; Genetic Diseases, X-Linked; Genotype; Humans; Male; Mutation; Nuclear Proteins; Pedigree; Phenotype; Porphyrins; Protoporphyria, Erythropoietic; Protoporphyrins; Receptors, Androgen; X Chromosome Inactivation
PubMed: 25615817
DOI: 10.1111/cge.12562 -
Molecular Genetics and Metabolism Nov 2019Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare photodermatoses, generally presenting in childhood with severe and painful phototoxicity.... (Observational Study)
Observational Study
Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare photodermatoses, generally presenting in childhood with severe and painful phototoxicity. EPP has been reported to negatively affect quality of life (QoL), but there is limited information on the psychosocial issues faced by patients and families. To address this, an online focus group study was conducted to explore the perspective of parents of children with EPP, and young adults and children with EPP. Five focus groups were conducted in a semi-structured format, with moderator-led discussions exploring the impact on QoL. Three focus groups included parents of children with EPP, one with children aged 10-11 years, and another with young adults aged 24-25 years, for a total of 24 participants. Thematic data analysis showed that parents experience guilt for being unable to protect their children and frustration with the current state of knowledge of EPP. Parents also admitted that the disease can lead to stress within family members which is difficult to manage. Young adults expressed embarrassment over having to explain the disease to others. They reported that the teenage years were the most difficult to navigate; however, they learned to adapt to their disease as they grew older. Children expressed that they had limited understanding of their disease and wished they were told what symptoms to expect by physicians earlier in life. Our findings emphasize the significant impact on QoL for these families and a lack of age appropriate information for children with EPP. These findings can help improve counseling and support resources for patients and caregivers.
Topics: Adult; Child; Counseling; Dermatitis, Phototoxic; Family; Female; Focus Groups; Humans; Longitudinal Studies; Male; Middle Aged; Parents; Protoporphyria, Erythropoietic; Qualitative Research; Quality of Life; Social Behavior; Young Adult
PubMed: 30711301
DOI: 10.1016/j.ymgme.2019.01.023 -
International Journal of Environmental... Mar 2023Erythropoietic protoporphyria (EPP) is an ultra-rare inborn error of metabolism characterised by painful phototoxic burn injuries after short exposure times to visible...
Erythropoietic protoporphyria (EPP) is an ultra-rare inborn error of metabolism characterised by painful phototoxic burn injuries after short exposure times to visible light. Patients with EPP are highly adapted to their condition which makes the quantification of their health-related quality of life (QoL) challenging. In the presented patient-initiated feasibility study, we describe a new approach to assess treatment benefits in EPP by measuring QoL with the generic EQ-5D instrument in five patients under long-term (≥two years) treatment with afamelanotide, the first approved therapy for EPP. For the study, we selected patients with EPP who in addition were affected by an involuntary treatment interruption (caused by a temporary reimbursement suspension) because we hypothesized that individuals who had previously unlearned their adaptation are better able to assess their life without treatment than treatment-naïve patients. QoL under treatment was comparable to the age-matched population norm, and retrospective results for a treatment interruption and phototoxic reaction time point were comparable to the QoL of patients with chronic neuropathic pain and acute burn injuries, respectively. The results were accepted by the National Institute for Health and Care Excellence in England for their evaluation of the cost-effectiveness of afamelanotide, i.e., the calculation of quality-adjusted life years.
Topics: Humans; Protoporphyria, Erythropoietic; Quality of Life; Retrospective Studies; Quality-Adjusted Life Years; Rare Diseases; Feasibility Studies
PubMed: 37047912
DOI: 10.3390/ijerph20075296 -
American Journal of Human Genetics Jul 2016Red blood cell (RBC) traits are important heritable clinical biomarkers and modifiers of disease severity. To identify coding genetic variants associated with these... (Meta-Analysis)
Meta-Analysis
Red blood cell (RBC) traits are important heritable clinical biomarkers and modifiers of disease severity. To identify coding genetic variants associated with these traits, we conducted meta-analyses of seven RBC phenotypes in 130,273 multi-ethnic individuals from studies genotyped on an exome array. After conditional analyses and replication in 27,480 independent individuals, we identified 16 new RBC variants. We found low-frequency missense variants in MAP1A (rs55707100, minor allele frequency [MAF] = 3.3%, p = 2 × 10(-10) for hemoglobin [HGB]) and HNF4A (rs1800961, MAF = 2.4%, p < 3 × 10(-8) for hematocrit [HCT] and HGB). In African Americans, we identified a nonsense variant in CD36 associated with higher RBC distribution width (rs3211938, MAF = 8.7%, p = 7 × 10(-11)) and showed that it is associated with lower CD36 expression and strong allelic imbalance in ex vivo differentiated human erythroblasts. We also identified a rare missense variant in ALAS2 (rs201062903, MAF = 0.2%) associated with lower mean corpuscular volume and mean corpuscular hemoglobin (p < 8 × 10(-9)). Mendelian mutations in ALAS2 are a cause of sideroblastic anemia and erythropoietic protoporphyria. Gene-based testing highlighted three rare missense variants in PKLR, a gene mutated in Mendelian non-spherocytic hemolytic anemia, associated with HGB and HCT (SKAT p < 8 × 10(-7)). These rare, low-frequency, and common RBC variants showed pleiotropy, being also associated with platelet, white blood cell, and lipid traits. Our association results and functional annotation suggest the involvement of new genes in human erythropoiesis. We also confirm that rare and low-frequency variants play a role in the architecture of complex human traits, although their phenotypic effect is generally smaller than originally anticipated.
Topics: Black or African American; Allelic Imbalance; Erythrocyte Indices; Erythrocytes; Erythropoiesis; Exome; Gene Frequency; Genetic Pleiotropy; Genetic Variation; Genotype; Hematocrit; Hemoglobins; Humans; Quantitative Trait Loci
PubMed: 27346685
DOI: 10.1016/j.ajhg.2016.05.007 -
The Journal of Biological Chemistry Sep 2015Hepatic accumulation of protoporphyrin-IX (PP-IX) in erythropoietic protoporphyria (EPP) or X-linked-dominant protoporphyria (XLP) cause liver damage. Hepatocyte nuclear...
Hepatic accumulation of protoporphyrin-IX (PP-IX) in erythropoietic protoporphyria (EPP) or X-linked-dominant protoporphyria (XLP) cause liver damage. Hepatocyte nuclear lamin aggregation is a sensitive marker for PP-IX-mediated liver injury. We tested the hypothesis that extracellular or intracellular protoporphyria cause damage to different subcellular compartments, in a light-triggered manner. Three hepatoma cell lines (HepG2, Hepa-1, and Huh-7) were treated with exogenous PP-IX (mimicking XLP extrahepatic protoporphyria) or with the iron chelator deferoxamine and the porphyrin precursor 5-aminolevulinic acid (ALA) (mimicking intracellular protoporphyrin accumulation in EPP). Exogenous PP-IX accumulated predominantly in the nuclear fraction and caused nuclear shape deformation and cytoplasmic vacuoles containing electron-dense particles, whereas ALA+deferoxamine treatment resulted in higher PP-IX in the cytoplasmic fraction. Protein aggregation in the nuclear and cytoplasmic fractions paralleled PP-IX levels and, in cell culture, the effects were exclusively ambient light-mediated. PP-IX and ALA caused proteasomal inhibition, whereas endoplasmic reticulum protein aggregation was more prominent in ALA-treated cells. The enhanced ALA-related toxicity is likely due to generation of additional porphyrin intermediates including uroporphyrin and coproporphyrin, based on HPLC analysis of cell lysates and the culture medium, as well as cell-free experiments with uroporphyrin/coproporphyrin. Mouse livers from drug-induced porphyria phenocopied the in vitro findings, and mass spectrometry of liver proteins isolated in light/dark conditions showed diminished (as compared with light-harvested) but detectable aggregation under dark-harvested conditions. Therefore, PP-IX leads to endoplasmic reticulum stress and proteasome inhibition in a manner that depends on the source of porphyrin buildup and light exposure. Porphyrin-mediated selective protein aggregation provides a potential mechanism for porphyria-associated tissue injury.
Topics: Animals; Cell Line, Tumor; Female; Humans; Light; Male; Mice; Porphyrins; Subcellular Fractions
PubMed: 26205816
DOI: 10.1074/jbc.M114.636001