Protoporphyrin IX in serum of high-grade glioma patients: A novel target for disease monitoring via liquid biopsy

High-grade gliomas (HGG) carry a dismal prognosis. Diagnosis comprises MRI followed by histopathological evaluation of tissue; no blood biomarker is available. Patients are subjected to serial MRIs and, if unclear, surgery for monitoring of tumor recurrence, which is laborious. MRI provides only limited diagnostic information regarding the differentiation of true tumor progression from therapy-associated side effects. 5-aminolevulinic acid (5-ALA) is routinely used for induction of protoporphyrin IX (PpIX) accumulation in malignant glioma tissue, enabling improved tumor visualization during fluorescence-guided resection (FGR). We investigated whether PpIX can also serve as a serum HGG marker to monitor relapse. Patients (HGG: n = 23 primary, pHGG; n = 5 recurrent, rHGG) undergoing FGR received 5-ALA following standard clinical procedure. The control group of eight healthy volunteers (HCTR) also received 5-ALA. Serum was collected before and repeatedly up to 72 h after drug administration. Significant PpIX accumulation in HGG was observed after 5-ALA administration (ANOVA: p = 0.005, post-hoc: HCTR vs. pHGG p = 0.029, HCTR vs. rHGG p = 0.006). Separation of HCTR from pHGG was possible when maximum serum PpIX levels were reached (CI95% of tMax). ROC analysis of serum PpIX within CI95% of tMax showed successful classification of HCTR and pHGG (AUCROC 0.943, CI95% 0.884-1.000, p < 0.001); the optimal cut-off for diagnosis was 1275 pmol PpIX/ml serum, reaching 87.0% accuracy, 90.5% positive predictive and 84.0% negative predictive value. Baseline PpIX level was similar in patient and control groups. Thus, 5-ALA is required for PpIX induction, which is safe at the standard clinical dosage. PpIX is a new target for liquid biopsy in glioma. More extensive clinical studies are required to characterize its full potential.

Evidence-based consensus guidelines for the diagnosis and management of erythropoietic protoporphyria and X-linked protoporphyria

Erythropoietic protoporphyria and X-linked protoporphyria are rare genetic photodermatoses. Limited expertise with these disorders among physicians leads to diagnostic delays. Here, we present evidence-based consensus guidelines for the diagnosis, monitoring, and management of erythropoietic protoporphyria and X-linked protoporphyria. A systematic literature review was conducted, and reviewed among subcommittees of experts, divided by topic. Consensus on guidelines was reached within each subcommittee and then among all members of the committee. The appropriate biochemical and genetic testing to establish the diagnosis is reviewed in addition to the interpretation of results. Prevention of symptoms, management of acute phototoxicity, and pharmacologic and nonpharmacologic treatment options are discussed. The importance of ongoing monitoring for liver disease, iron deficiency, and vitamin D deficiency is discussed with management guidance. Finally, management of pregnancy and surgery and the safety of other therapies are summarized. We emphasize that these are multisystemic disorders that require longitudinal monitoring. These guidelines provide a structure for evidence-based diagnosis and management for practicing physicians. Early diagnosis and management of these disorders are essential, particularly given the availability of new and emerging therapies.

Mechanistic modelling of enzyme-restoration effects for new recombinant liver-targeted proteins in acute intermittent porphyria

Background and Purpose

Acute intermittent porphyria (AIP) is a rare disease caused by a genetic mutation in the hepatic activity of the porphobilinogen‐deaminase. We aimed to develop a mechanistic model of the enzymatic restoration effects of a novel therapy based on the administration of different formulations of recombinant human‐PBGD (rhPBGD) linked to the ApoAI lipoprotein. This fusion protein circulates in blood, incorporating into HDL and penetrating hepatocytes.

Experimental Approach

Single i.v. dose of different formulations of rhPBGD linked to ApoAI were administered to AIP mice in which a porphyric attack was triggered by i.p. phenobarbital. Data consist on 24 h urine excreted amounts of heme precursors, 5‐aminolevulinic acid (ALA), PBG and total porphyrins that were analysed using non‐linear mixed‐effects analysis.

Key Results

The mechanistic model successfully characterized over time the amounts excreted in urine of the three heme precursors for different formulations of rhPBGD and unravelled several mechanisms in the heme pathway, such as the regulation in ALA synthesis by heme. Treatment with rhPBGD formulations restored PBGD activity, increasing up to 51 times the value of the rate of tPOR formation estimated from baseline. Model‐based simulations showed that several formulation prototypes provided efficient protective effects when administered up to 1 week prior to the occurrence of the AIP attack.

Conclusion and Implications

The model developed had excellent performance over a range of doses and formulation type. This mechanistic model warrants use beyond ApoAI‐conjugates and represents a useful tool towards more efficient drug treatments of other enzymopenias as well as for acute intermittent porphyria.

Afterglow Amplification for Fast and Sensitive Detection of Porphyria in Whole Blood

Porphyria is a group of genetic photodermatoses that cause too much porphyrin to accumulate in the blood, skin, and liver, resulting in skin photosensitivity and damage, liver disease, or potential liver failure. Conventional detection methods include high-performance liquid chromatography and fluorescence spectrometry. However, these methods usually require complicated pretreatment and time-consuming processes. Therefore, efficient and fast detection of porphyria is urgently needed. Herein, we develop a molecular afterglow reporter-based sensing scheme for the detection of porphyrins in whole blood. The afterglow reporter can respond to the production of singlet oxygen (¹O₂) of porphyrins after light excitation, and the detection signals can be amplified through adjusting the amount of singlet oxygen and afterglow reporter molecules. Moreover, without the use of a real-time excitation source, afterglow signals can avoid the scattering and autofluorescence interference in biological samples, thereby reducing background noise. More importantly, we prove the applicability of the afterglow reporter in the quantitative detection of porphyrins in whole blood and demonstrate its great clinical potential.

Hepatitis C virus core protein triggers abnormal porphyrin metabolism in human hepatocellular carcinoma cells

Porphyria cutanea tarda (PCT), the most common of the human porphyrias, arises from a deficiency of uroporphyrinogen decarboxylase. Studies have shown a high prevalence of hepatitis C virus (HCV) infection in patients with PCT. While these observations implicate HCV infection as a risk factor for PCT pathogenesis, the mechanism of interaction between the virus and porphyrin metabolism is unknown. This study aimed to assess the effect of HCV core protein on intracellular porphyrin metabolism to elucidate the link between HCV infection and PCT. The accumulation and excretion of porphyrins after treatment with 5-aminolevulinic acid, a porphyrin precursor, were compared between cells stably expressing HCV core protein and controls. Cells expressing HCV core protein had lower amounts of intracellular protoporphyrin IX and heme and had higher amounts of excreted coproporphyrin III, the oxidized form of coproporphyrinogen III, compared with controls. These observations suggest that HCV core protein affects porphyrin metabolism and facilitates the export of excess coproporphyrinogen III and/or coproporphyrin III, possibly via porphyrin transporters. Real-time PCR analysis revealed that the presence of HCV core protein increased the mRNA expression of porphyrin exporters ABCG2 and FLVCR1. Western blot analysis showed a higher expression level of FLVCR1, but not ABCG2, as well as a higher expression level of mature ALAS1, which is the rate-limiting enzyme in the heme synthesis pathway, in HCV core protein-expressing cells compared with controls. The data indicate that HCV core protein induced abnormal intracellular porphyrin metabolism, with an over-excretion of coproporphyrin III. These findings may partially account for the susceptibility of HCV-infected individuals to PCT development.

Determination of porphyrins in oral bacteria by liquid chromatography electrospray ionization tandem mass spectrometry

Biofilms in the oral cavity can be visualized by fluorescence and a common assumption is that the endogenously produced porphyrins in certain bacteria give rise to this fluorescence. Porphyrin content in oral bacteria has been sparingly investigated, and non-selective detection techniques such as utilizing the Soret fluorescence band of porphyrins are often used. In the present study, a quantitative and selective method for the determination of porphyrins in oral bacteria has been developed and validated using high performance liquid chromatography-tandem mass spectrometry. Lysis of bacteria using Tris-EDTA buffer together with ultrasonication showed high microbial killing efficiency ≥99.98 %, and sample clean-up using C₁₈-solid phase extraction resulted in low matrix effects ≤14 % for all analytes. Using this method, the porphyrin content was determined in the two oral pathogens Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as for baker’s yeast, Saccharomyces cerevisiae. Uroporphyrin, 7-carboxylporphyrin, 6-carboxylporphyrin, coproporphyrin, and protoporphyrin IX were identified in the investigated microorganisms, and it was shown that the porphyrin profile differs between the two bacteria, as well as for S. cerevisiae. To our knowledge, this is the first time the porphyrin profile has been determined for the bacterium A. actinomycetemcomitans.

Graphical Abstract

Clinical manifestations and diagnostic challenges in acute porphyrias

The porphyrias are a group of disorders characterized by an enzyme deficiency in the heme biosynthetic pathway. These can be classified into either erythropoietic or hepatic forms depending on the site of the major enzyme deficiency. The diagnosis of acute porphyrias, however, can be very challenging due to overlapping features amongst the various types. Initial suspicion is based on a myriad of clinical manifestations, which then are confirmed by laboratory testing where available. Genetic testing is now also available for the different types of porphyrias, aiding in the definitive diagnosis. Here, we present a challenging case of porphyria in a patient with end-stage renal disease and present the diagnostic challenges associated with the case and the ways forward.

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.

5-Methyltetrahydrofolate can be photodegraded by endogenous photosensitizers

Folate deficiency is linked to serious birth defects, pregnancy complications, male infertility, cardiovascular diseases, and even the evolution of human skin color. Conflicting data exist on whether exposure to sun or artificial UV sources may deplete the levels of blood folate in humans. Blood contains several photosensitizers and proteins, as well as antioxidants, which when exposed to UV radiation and visible light may be involved in the degradation of folate. In this study the photodegradation of 5-methyltetrahydrofolate (5MTHF) in aqueous and deuterious solutions exposed to UVB, UVA, or visible light in the absence or presence of riboflavin, uroporphyrin, and conjugated bilirubin was investigated by absorption spectroscopy. 5MTHF is stable under exposure to visible light and UVA radiation, whereas it is slowly photooxidized under UVB exposure. However, it is rapidly oxidized by UVA or visible radiation in the presence of riboflavin or uroporphyrin, but not in the presence of conjugated bilirubin, which acts in a protective manner. Reactive oxygen species produced in type I and/or type II reactions were involved. This study suggests that 5MTHF in blood can be photodegraded in the presence of the flavins and porphyrins, but protected by bilirubins. This may have health and evolutionary implications.

Photodegradation of 5-methyltetrahydrofolate in the presence of Uroporphyrin

The main form of folate in human plasma is 5-methyltetrahydrofolate (5MTHF). The observation that folate in human serum is photosensitive supports the hypothesis that humans developed dark skin in high ultraviolet fluences areas in order to protect folate in the blood from UV radiation. However, folates alone are quite photostable. Therefore, in this study, we examined for the first time the photodegradation of 5MTHF in the presence of the endogenous photosensitizer uroporphyrin (Uro), which is sometimes present in low concentration in human serum, under UV and near-UV light exposure. We found strong indications that while 5MTHF alone is rather photostable, it is degraded quickly in the presence of Uro. Using deuterium oxide (D(2)O) as an enhancer of the lifetime of singlet oxygen and the singlet oxygen sensor green reagent (SOSG) as a scavenger of singlet oxygen, we have found that the photodegradation most likely proceeds via a type II photosensitization. Our results show that singlet oxygen is likely to be the main intermediate in the photodegradation of 5MTHF mediated by Uro. Our findings may be useful for further studies the evolution of human skin colours.

A simple and rapid fluorimetric method for simultaneous determination of protoporphyrin IX and zinc protoporphyrin IX in whole blood

Derivative variable-angle synchronous fluorescence (DVASF) spectrometry improves the spectral resolution and selectivity of the fluorescence method. The feasibility of DVASF spectrometry for the simultaneous determination of protoporphyrin IX (PP) and zinc protoporphyrin IX (ZnPP) was investigated. PP and ZnPP were distinguished from each other simultaneously and rapidly by the DVASF method. The spectra were resolved well, and the two components were determined in a single scan, avoiding the spectral compensation factor for PP and chromatographic separation. The linear range of the calibration curve for PP was from 0.190 to 152 nmol/L and for ZnPP was from 0.383 to 230 nmol/L. The detection limits of PP and ZnPP were 0.098 nmol/L and 0.088 nmol/L, respectively. The within-run imprecision (RSD, n = 5) for PP was 4.1%, and for ZnPP was 4.2%. Mean recoveries (SD) of PP and ZnPP added to a blood sample were 86.4 (7.3)% and 72.9 (6.6)%, respectively. This method should be a potential tool in the rapid routine screening of large quantities of samples.

A case of haemodialysis-associated pseudoporphyria successfully treated with oral N-acetylcysteine

We report a 33-year-old woman with haemodialysis-associated pseudoporphyria successfully responding to treatment with oral N-acetylcysteine. We briefly review the current literature on bullous skin disorders in end-stage renal disease, and compare and contrast the pathogenesis of pseudoporphyria and porphyria cutanea tarda in this context. We also discuss the antioxidant properties and clinical applications of N-acetylcysteine, including the treatment of haemodialysis-associated pseudoporphyria.

[Porphyria cutanea tarda in a dialyzed female patient]

Dermatological disorders are a frequent finding in patients with renal insufficiency. Porphyria cutanea tarda, pseudoporphyria, phototoxicity or concurrent bullous diseases may cause the appearance of lesions with liquid content in patients in dialysis. We describe the case of a female patient in dialysis who developed bullous lesions. The clinical and laboratory findings were initially compatible with the suspicion of pseudoporphyria, but the finding of some frankly elevated levels of porphyrins in serum, urine and feces confirmed the diagnosis of porphyria cutanea tarda. Porphyria cutanea tarda and pseudoporphyria present with common clinical manifestations. However, the levels of porphyrins in plasma, urine and feces in pseudoporphyria are normal or slightly elevated.

Hereditary coproporphyria: comparison of molecular and biochemical investigations in a large family

Hereditary coproporphyria (HCP) is the least common of the three autosomal dominant acute porphyrias. To compare the sensitivity of metabolite measurements for the identification of asymptomatic HCP, we carried out a molecular and biochemical investigation of a large family in which HCP is caused by a previously unreported frameshift mutation (c.119delA). Thirteen of 19 asymptomatic family members, aged 10-72 years, were shown by mutational analysis to have HCP. The faecal coproporphyrin isomer III:I ratio was increased in all of these 13 family members; faecal total porphyrin concentration and urinary porphyrin excretion were increased in 11 and 8 of them, respectively. Plasma porphyrin concentrations were marginally increased in three individuals and plasma fluorescence emission scanning showed a porphyrin peak at 618 nm in two of these. Our results add to the evidence that an increased faecal porphyrin coproporphyrin III:I ratio is a highly sensitive test for the detection of clinically latent HCP in individuals over the age of 10 years; its sensitivity below this age remains uncertain. They also show that plasma fluorescence emission scanning is not useful for the investigation of families with HCP.

The porphyrias, appropriate test selection

BACKGROUND

Clinical and biochemical diagnosis of the porphyrias is a difficult task and is currently based upon review of the clinical features and measurement of the various porphyrin metabolites in body fluids.

MATERIALS

Different techniques are available for the diagnosis of the porphyrias and the identification of the eventual defect(s), ranging from simple biochemical measurement of aminolevulinic acid (ALA) and porphobilinogen (PBG) through enzymatic assays to the investigation of genetic abnormalities.

RESULTS

Except for erythrocyte porphobilinogen deaminase, the use of porphyrin enzyme measurement is beyond the scope of most laboratories. Genetic studies are progressing apace in all the porphyrias and are rapidly becoming the 'gold standard' for difficult diagnoses, but actually, these techniques are confined to highly specialized research laboratories.

CONCLUSION

At present time, most clinical chemists must rely on the measurement of porphyrin metabolites for diagnosis and a proposed algorithm for this purpose is presented.

Biochemical differentiation of the porphyrias

OBJECTIVES

To differentiate the porphyrias by clinical and biochemical methods.

DESIGN AND METHODS

We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.