Nili Schoenfeld

The heme biosynthetic pathway in lymphocytes of patients with malignant lymphoproliferative disorders

The metabolism of heme is impaired in lymphocytes of patients with malignant lymphoproliferative disorders (MLPO). Two of the enzymes of the heme biosynthetic pathway, delta-aminolevulinic acid dehydrase (ALAD) (EC 4.2.1.24) and ferrochelatase (FC) (EC 4.99.1.1) are markedly reduced. The activity of porphobilinogen deaminase (PBGD) (EC 4.3.1.8) is increased. The rate-limiting enzyme of heme biosynthesis in the liver, aminolevulinate synthase (ALAS) (EC 2.3.1.37) remains unchanged although the concentration of total heme in the lymphocytes is markedly reduced. This might reflect a lack of negative feedback inhibition by heme on ALAS activity in this system.

Activity of porphobilinogen deaminase in peripheral blood mononuclear cells of patients with metastatic cancer

Porphobilinogen deaminase (PBGD), one of the enzymes in the pathway of heme synthesis, was found to be elevated in peripheral mononuclear cells of 60% of patients with epithelial tumors and metastatic spread, but only in 14% of patients with tumor and no evidence of metastases. The combination of both high lactic dehydrogenase and high PBGD afforded a sensitivity of 40%, but a specificity of 96% in diagnosing metastatic spread.

Erythrocyte uroporphyrinogen synthase activity as a possible diagnostic aid in the diagnosis of lymphoproliferative diseases

Patients with active lymphoproliferative diseases were shown to have high activity of erythrocyte uroporphyrinogen synthetase (URO‐S), the enzyme which converts porphobilinogen to uroporphyrinogen. In a few patients examined the lymphocyte URO‐S was markedly increased. No correlation was found between the high URO‐S activity and the degree of anemia, reticulocytosis, or the presence of hemolysis. Patients with epithelial malignancies and with some common viral diseases had normal erythrocyte URO‐S values. Three patients with nonalcoholic cirrhosis also had high erythrocyte URO‐S activities. The determination of erythrocyte and lymphocyte URO‐S activity may be of aid in the diagnosis of lymphoproliferative diseases. It may also indicate whether remission has been achieved and whether treatment should be continued or reinstituted. These preliminary observations justify the investigation of a larger patient and control material.

The effects of succinylacetone (4,6-dioxoheptanoic acid) on δ-aminolevulinate synthase activity and the content of heme in monolayers of chick embryo liver cells

Succinylacetone was shown to inhibit aminolevulinate dehydratase (5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing), EC 4.2.1.24) to reduce cellular heme and porphyrins and to induce delta-aminolevulinate synthase (succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37) in monolayers of chick embryo liver cells. Marked synergistic effects on delta-aminolevulinate synthase activity were obtained by combining succinylacetone with levulinate and porphyrogenic drugs. The time course of delta-aminolevulinate synthase activity showed a delayed synergistic response.

Alcohol-induced changes in urinary aminolevulinic acid and porphyrins: unrelated to liver disease.

Urinary porphyrins and their metabolites aminolevulinic acid (ALA) and porphobilinogen (PBG) were determined in 15 normal volunteers and in 45 alcoholics, subdivided into three groups according to their liver function tests and histology: alcoholics exhibiting no evidence of hepatocellular damage; alcoholics with fatty liver and impaired function of liver enzymes; and alcoholics with proven liver cirrhosis. The dominant trend observed in those alcoholics devoid of any evidence of liver disease was increased ALA, PBG, and uroporphyrin. Coproporphyrinuria was shared by the patients exhibiting liver damage. The data shown enabled us to differentiate between the direct, primary effect of alcohol on the heme biosynthetic pathway and the secondary indirect effect, which is probably related to liver damage that follows alcohol consumption. Evaluation of the results led to the suggestion that urinary ALA could possibly serve as a marker of alcoholism. The specificity and sensitivity of the test were found to be 87% and 80%, respectively.

The effect of DL-propranolol on γ-aminolevulinic acid synthetase activity and urinary excretion of porphyrins in allylisopropylacetamide-induced experimental porphyria

Abstract Experimental porphyria was induced in rats by allylisopropylacetamide. DL -Propranolol, a β-adrenergic-receptor blocking agent, significantly reduced the elevated urinary excretion of δ-aminolevulinic acid, porphobilinogen and total porphyrins. DL -Propranolol also partially prevented the increased activity of δ-aminolevulinic acid synthesis in liver homogenates of allylisopropylacetamide-treated rats. It had no effect on the above parameters in normal rats. These findings support the hypothesis that δ-aminolevulinic acid exists in two forms, a constitutive and an inducible one. In order to examine whether the action of the drug was caused by its membrane effect. D -propranolol and quinidine sulphate were used in similar sets of experiments. These drugs had no effect on the abnormal porphyrin metabolism of allylisoprpyl-acetamide-treated rats, indicating that the results obtained with DL -propranolol were not due to its membrane action.

High-performance liquid chromatographic detection of pitfalls in porphobilinogen deaminase determination

Potential pitfalls in the determination of porphobilinogen deaminase activity, as well as ways of eliminating these sources of error and determining the activity accurately, are discussed. In addition to measurement of the accurate activity, the described method (a combination of incubation of homogenate with porphobilinogen and high-performance liquid chromatographic separation) can also be used to detect enzymic defects in the haem biosynthetic pathway, according to the pattern of accumulation of the various porphyrins.

The effect of agents blocking adrenergic β-receptors on incorporation of amino acids into protein in tissue cultures of chick embryo liver cells☆

Abstract The effect of β-receptor blocking agents on [14C] amino acid incorporation into protein in cultures of chick embryo liver cells was studied. DL-Propranolol, a β-blocker with non-specific membrane effects, caused a 40 per cent inhibition of incorporation of [14C] amino acids into protein. The inhibition was concentration dependent and reversible. A similar inhibition was obtained by oxprenolol (Trasicor), which is also a β-receptor blocking agent with non-specific membrane effects, and by the membrane active compounds: D-propranolol, lidocaine and quinidine. Pindolol (Visken), and practolol, which are almost devoid of membrane activity, were ineffective. These data indicate that the inhibitory effect of dl -propranolol and oxprenolol on protein synthesis is caused by their non-specific membrane effects.

Evidence for the interference of aluminum with bacterial porphyrin biosynthesis

Aluminum (0.74 mm) was found to retard bacterial growth, and enhance porphyrin formation and excretion in Arthrobacter aurescens RS-2. Coproporphyrin III was shown to be the main porphyrin excreted by aluminum-exposed A. aurescens RS-2 cultures and by RS-2 cultures grown under anoxic conditions. Synthesis and excretion of porphyrins in A. aurescens RS-2 increased in a dose-dependent manner when the bacteria were exposed to increasing aluminum concentrations. Incubation of A. aurescens RS-2 with δ-aminolevulinic acid (δ-ALA, 1.2 mm) brought about the intense formation and excretion of porphyrins by the cells, in the presence or absence of aluminum. δ-ALA slightly enhanced the toxicity of aluminum towards RS-2 bacteria. Furthermore, the intracellular concentration of heme was reduced by 63.9 ± 8.67% in aluminum-exposed RS-2 bacteria when compared with control cultures. The results are discussed in light of the recent finding concerning aluminum toxicity and porphyrin biosynthesis in microorganisms.

ACUTE NEUROPATHY MIMICKING PORPHYRIA INDUCED BY AMINOLEVULINIC ACID DURING PHOTODYNAMIC THERAPY

An 82‐year‐old man developed severe, acute, predominantly motor polyneuropathy, signs of autonomic involvement, and skin changes following aminolevulinic acid (ALA) administration. The compound was used as a prodrug for photodynamic therapy of Barretts esophagitis. Changes were observed in various parameters of the heme pathway. The case reported represents a rare response to ALA treatment, resembling an acute attack of hepatic porphyria with neurological features. Muscle Nerve, 2005