Variegate porphyria induces plasma and neutrophil oxidative stress: effects of dietary supplementation with vitamins E and C

Portuguese Consensus on Acute Porphyrias: Diagnosis, Treatment, Monitoring and Patient Referral

Acute porphyrias are a group of rare genetic metabolic disorders, caused by a defect in one of the enzymes involved in the heme biosynthesis, which results in an abnormally high accumulation of toxic intermediates. Acute porphyrias are characterized by potentially life-threatening attacks and, for some patients, by chronic manifestations that negatively impact daily functioning and quality of life. Clinical manifestations include a nonspecific set of gastrointestinal, neuropsychiatric, and/or cutaneous symptoms. Effective diagnostic methods are widely available, but due to their clinical heterogeneity and non-specificity, many years often elapse from symptom onset to diagnosis of acute porphyrias, delaying the treatment and increasing morbidity. Therefore, increased awareness of acute porphyrias among healthcare professionals is paramount to reducing disease burden. Treatment of acute porphyrias is centered on eliminating the potential precipitants, symptomatic treatment, and suppressing the hepatic heme pathway, through the administration of hemin or givosiran. Moreover, properly monitoring patients with acute porphyrias and their relatives is fundamental to preventing acute attacks, hospitalization, and long-term complications. Considering this, a multidisciplinary panel elaborated a consensus paper, aiming to provide guidance for an efficient and timely diagnosis of acute porphyrias, and evidence-based recommendations for treating and monitoring patients and their families in Portugal. To this end, all authors exhaustively reviewed and discussed the current scientific evidence on acute porphyrias available in the literature, between November 2022 and May 2023.

Spotlight on Givosiran as a Treatment Option for Adults with Acute Hepatic Porphyria: Design, Development, and Place in Therapy

Small interfering ribonucleic acids [siRNAs] are short ribonucleic acid (RNA) fragments cleaved from double-stranded RNA molecules that target and bind to specific sequences on messenger RNA (mRNA), leading to their destruction. Therefore, the siRNA down-regulates the formation of selected mRNAs and their protein products. Givosiran is one such siRNA that uses this mechanism to treat acute hepatic porphyrias. Acute hepatic porphyrias are a group of rare, inherited metabolic disorders, characterized by acute potentially life-threatening attacks as well as chronic symptoms with a negative impact on quality of life. It has four types, each associated with distinct enzyme defects in the heme biosynthesis pathway in the liver. By targeting the expression of hepatic 5-aminolevulinic acid [ALA] synthase-1 [ALAS1], givosiran can down-regulate levels of toxic metabolites, leading to biochemical and clinical improvement. Givosiran selectively targets hepatocytes due to its linkage to N-acetylgalactosamine (GalNac) leading to its selective uptake via asialoglycoprotein receptors (ASGPR). We provide an up-to-date literature review regarding givosiran in the context of a clinical overview of the porphyrias, an overview of siRNAs for therapy of human disorders, the design and development of givosiran, key clinical trial results of givosiran for prevention of acute porphyric attacks, emerging concerns regarding chronic use of givosiran, and the overall management of acute hepatic porphyrias. These insights are important not only for the management of acute hepatic porphyrias but also for the emerging field of siRNAs and their role in novel therapies for various diseases.

Clinical, biochemical, and genetic characterization of acute hepatic porphyrias in a cohort of Argentine patients

BACKGROUND

Acute Hepatic Porphyrias (AHPs) are characterized by an acute neuroabdominal syndrome including both neuropsychiatric symptoms and neurodegenerative changes. Two main hypotheses explain the pathogenesis of nervous system dysfunction: (a) the ROS generation by autooxidation of 5-aminolevulinic acid accumulated in liver and brain; (b) liver heme deficiency and in neural tissues that generate an oxidative status, a component of the neurodegenerative process.

METHODS

We review results obtained from Acute Intermittent Porphyria (AIP) and Variegate Porphyria (VP) families studied at clinical, biochemical, and molecular level at the CIPYP in Argentina. The relationship between the porphyric attack and oxidative stress was also evaluated in AHP patients and controls, to identify a marker of neurological dysfunction.

RESULTS

We studied 116 AIP families and 30 VP families, 609 and 132 individuals, respectively. Genotype/phenotype relation was studied. Oxidative stress parameters and plasma homocysteine levels were measured in 20 healthy volunteers, 22 AIP and 12 VP individuals.

CONCLUSION

No significant difference in oxidative stress parameters and homocysteine levels between the analyzed groups were found.

Nutrients and Porphyria: An Intriguing Crosstalk

Porphyria refers to a group of fascinating diseases from a metabolic and nutritional standpoint as it provides an example of how metabolic manipulation can be used for therapeutic purposes. It is characterized by defects in heme synthesis, particularly in the erythrocytes and liver. Specific enzymes involved in heme biosynthesis directly depend on adequate levels of vitamins and minerals in the tissues. Moreover, micronutrients that are required for producing succinyl CoA and other intermediates in the Krebs (TCA) cycle are indirectly necessary for heme metabolism. This review summarizes articles that describe the nutritional status, supplements intake, and dietary practices of patients affected by porphyria, paying special attention to the therapeutic use of nutrients that may help or hinder this group of diseases.

Acute Hepatic Porphyrias: Review and Recent Progress

The acute hepatic porphyrias (AHPs) are a group of four inherited diseases of heme biosynthesis that present with episodic, acute neurovisceral symptoms. The four types are 5-aminolevulinic acid (ALA) dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria. Their diagnoses are often missed or delayed because the clinical symptoms mimic other more common disorders. Recent results indicate that acute intermittent porphyria, the most severe of the more common types of AHP, is more prevalent than previously thought, occurring in about 1 in 1600 Caucasians, but with low clinical penetrance (approximately 2%-3%). Here we provide an updated review of relevant literature and discuss recent and emerging advances in treatment of these disorders. Symptomatic attacks occur primarily in females between 14 and 45 years of age. AHP is diagnosed by finding significantly elevated levels of porphyrin precursors ALA and porphobilinogen in urine. Acute attacks should be treated promptly with intravenous heme therapy to avoid the development of potentially irreversible neurologic sequelae. All patients should be counseled about avoiding potential triggers for acute attacks and monitored regularly for the development of long-term complications. Their first-degree relatives should undergo targeted gene testing. Patients who suffer recurrent acute attacks can be particularly challenging to manage. Approximately 20% of patients with recurrent symptoms develop chronic and ongoing pain and other symptoms. We discuss newer treatment options in development, including small interfering RNA, to down-regulate ALA synthase-1 and/or wild-type messenger RNA of defective genes delivered selectively to hepatocytes for these patients. We expect that the newer treatments will diminish and perhaps obviate the need for liver transplantation as treatment of these inborn metabolic disorders.

Role of Vitamin C in Skin Diseases

Vitamin C (ascorbic acid) plays an important role in maintaining skin health and can promote the differentiation of keratinocytes and decrease melanin synthesis, leading to antioxidant protection against UV-induced photodamage. Normal skin needs high concentrations of vitamin C, which plays many roles in the skin, including the formation of the skin barrier and collagen in the dermis, the ability to counteract skin oxidation, and the modulation of cell signal pathways of cell growth and differentiation. However, vitamin C deficiency can cause or aggravate the occurrence and development of some skin diseases, such as atopic dermatitis (AD) and porphyria cutanea tarda (PCT). Levels of vitamin C in plasma are decreased in AD, and vitamin C deficiency may be one of the factors that contributes to the pathogenesis of PCT. On the other hand, high doses of vitamin C have significantly reduced cancer cell viability, as well as invasiveness, and induced apoptosis in human malignant melanoma. In this review, we will summarize the effects of vitamin C on four skin diseases (porphyria cutanea tarda, atopic dermatitis, malignant melanoma, and herpes zoster and postherpetic neuralgia) and highlight the potential of vitamin C as a therapeutic strategy to treat these diseases, emphasizing the clinical application of vitamin C as an adjuvant for drugs or physical therapy in other skin diseases.

Haem Biosynthesis and Antioxidant Enzymes in Circulating Cells of Acute Intermittent Porphyria Patients

The aims of the present study were to explore the expression pattern of haem biosynthesis enzymes in circulating cells of patients affected by two types of porphyria (acute intermittent, AIP, and variegate porphyria, VP), together with the antioxidant enzyme pattern in AIP in order to identify a possible situation of oxidative stress. Sixteen and twelve patients affected by AIP and VP, respectively, were analysed with the same numbers of healthy matched controls. Erythrocytes, neutrophils and peripheral blood mononuclear cells (PBMCs) were purified from blood, and RNA and proteins were extracted for quantitative real time PCR (qRT-PCR) and Western-blot analysis, respectively. Porhobilinogen deaminase (PBGD) and protoporphyrinogen oxidase (PPOX) gene and protein expression was analysed. Antioxidant enzyme activity and gene expression were additionally determined in blood cells, together with protein carbonyl content in plasma. PBMCs isolated from AIP patients presented low mRNA levels of PBGD when compared to controls, while PBMCs isolated from VP patients presented a decrease in PPOX mRNA. PPOX protein content was higher in AIP patients and lower in VP patients, compared to healthy controls. Regarding antioxidant enzymes, PBMCs and erythrocyte superoxide dismutase (SOD) presented statistically significant higher activity in AIP patients compared to controls, while catalase activity tended to be lower in these patients. No differences were observed regarding antioxidant gene expression in white blood cells. Circulating cells in AIP and VP patients present altered expression of haem biosynthetic enzymes, which could be useful for the differential diagnosis of these two types of porphyria in certain difficult cases. AIP patients present a condition of potential oxidative stress similar to VP patients, evidenced by the post-transcriptional activation of SOD and possible catalase impairment.

Protective action of antioxidants on hepatic damage induced by griseofulvin

Erythropoietic protoporphyria (EPP) is a disease associated with ferrochelatase deficiency and characterized by the accumulation of protoporphyrin IX (PROTO IX) in erythrocytes, liver, and skin. In some cases, a severe hepatic failure and cholestasis were observed. Griseofulvin (Gris) develops an experimental EPP with hepatic manifestations in mice such as PROTO IX accumulation followed by cellular damage as wells as necrotic and inflammatory processes. The antioxidant defense system was also altered. The aim was to evaluate the possible protective effect of different antioxidant compounds: trolox (Tx), ascorbic acid (Asc), the combination Tx and Asc, melatonin (Mel), and the polyphenols: ellagic acid, quercetin, chlorogenic acid, caffeic acid, gallic acid, and ferulic acid on liver damage and oxidative stress markers in a mouse model of EPP. Coadministration of Gris with Tx, Asc, and its combination, or Mel mainly affected heme biosynthetic pathway, resulting in a decrease in ALA-S activity which was increased by Gris, while the tested polyphenols exerted a protective effect on oxidative stress, decreasing lipid peroxidation and the activity of some antioxidant enzymes. In conclusion, antioxidant compounds can only protect partially against the liver damage induced by Gris, reducing oxidative stress or acting on heme regulation.

Antioxidant micronutrient supplementation increases erythrocyte membrane fluidity in adults from a rural Chinese community

The objective of the present study was to investigate age-related differences in erythrocyte membrane fluidity (EMF) and changes in antioxidant capacity following supplementation. A total of seventy-four children were randomly divided into two groups: group A1 was the placebo-controlled group and group A2 was supplemented daily with 600 μg retinol, 1·0 mg β-carotene, 100 mg tocopherol, 300 mg ascorbic acid and 200 μg Se. A total of ninety young people were randomly divided into B1 and B2 groups, and ninety-one elderly subjects were divided into C1 and C2 groups. Groups B1 and C1 were placebo-controlled groups, and groups B2 and C2 were daily supplemented with 900 μg retinol, 1·5 mg β-carotene, 200 mg tocopherol, 500 mg ascorbic acid and 400 μg Se. Results showed that plasma malondialdehyde (MDA) was 5·35 μmol/l in children, which was lower than in young and elderly people. The MDA levels of the young and elderly individuals in the treated groups were significantly lower compared with the control groups, but the supplementation did not alter MDA levels in children. At baseline, there was a lower value of polarisation (ρ) and microviscosity (η) in children, indicating a higher EMF, than in both the young and elderly subjects. After the 2-month trial, the ρ and η values of young and elderly subjects in the treated groups decreased significantly in comparison with the placebo groups, indicating an increase in EMF. In conclusion, there was a background of higher MDA levels and lower EMF in young and elderly people than in children, which could be improved by antioxidant supplementation.