Ultra-Performance Liquid Chromatography (UPLC) Analysis of Heme Biosynthesis Intermediates.

The utilization of ultra-performance liquid chromatography (UPLC) to analyze the various intermediates in the heme biosynthetic pathway is presented. The first product, ALA, was derivatized to a highly fluorescent pyrrolizine; PBG, the second intermediate, was enzymatically converted to uroporphyrinogen, and all the porphyrinogen intermediates were oxidized in acid to form fluorescent porphyrins. Heme was measured as hemin. The stable porphyrin forms of the intermediates, are then resolved and quantified by UPLC. Further details about the various methods are discussed to promote successful UPLC analyses. Method variations that may be preferable in certain situations are also presented.

Novel UROD mutation for porphyria cutanea tarda, type 2: a case report.

Background: Porphyria cutanea tarda (PCT) is usually caused by acquired defects in uroporphyrinogen decarboxylase (UROD) activity in the liver. This more common form of PCT is called type 1 PCT. Major known risk factors for PCT include iron overload, such as occurs due to mutations in HFE, associated with classical hereditary hemochromatosis, chronic hepatitis C infection, heavy alcohol use, tobacco use, and estrogen therapy. In addition, in about 25% of patients with PCT, namely, those with PCT type 2, an inherited partial defect in UROD activity is found. In such persons, this partial defect, which is found in all cells, including hepatocytes, red blood cells, and others, contributes to the development of biochemically and clinically active disease. Case Description: Herein we describe salient features of a man in his eighth decade of life with onset of clinical PCT. Among risk factors were heavy alcohol and tobacco use. Genetic testing revealed a novel mutation in one of his alleles of the UROD gene, namely, c.224 G>C; p. Arg 75 Pro, and enzymatic testing revealed that red blood cell UROD activity was decreased by 50%. This mutation in the UROD gene is predicted to have a major effect on protein structure and function, confirmed by the 50% decrease in activity of the enzyme. Conclusions: The previously undescribed mutation in UROD, found in this man, namely, c.224 G>C; p. Arg 75 Pro is pathogenic.

Cimetidine Does Not Inhibit 5-Aminolevulinic Acid Synthase or Heme Oxygenase Activity: Implications for Treatment of Acute Intermittent Porphyria and Erythropoietic Protoporphyria.

Acute intermittent porphyria (AIP) is characterized by acute neurovisceral attacks that are precipitated by the induction of hepatic 5-aminolevulinic acid synthase 1 (ALAS1). In erythropoietic protoporphyria (EPP), sun exposure leads to skin photosensitivity due to the overproduction of photoreactive porphyrins in bone marrow erythroid cells, where heme synthesis is primarily driven by the ALAS2 isozyme. Cimetidine has been suggested to be effective for the treatment of both AIP and EPP based on limited case reports. It has been proposed that cimetidine acts by inhibiting ALAS activity in liver and bone marrow for AIP and EPP, respectively, while it may also inhibit the hepatic activity of the heme catabolism enzyme, heme oxygenase (HO). Here, we show that cimetidine did not significantly modulate the activity or expression of endogenous ALAS or HO in wildtype mouse livers or bone marrow. Further, cimetidine did not effectively decrease hepatic ALAS activity or expression or plasma concentrations of the putative neurotoxic porphyrin precursors 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), which were all markedly elevated during an induced acute attack in an AIP mouse model. These results show that cimetidine is not an efficacious treatment for acute attacks and suggest that its potential clinical benefit for EPP is not via ALAS inhibition.