Methional derived from 4-methylthio-2-oxobutanoate is a cellular mediator of apoptosis in BAF3 lymphoid cells

Two-photon, red light uncaging of alkyl radicals from organorhodium(III) phthalocyanine complexes

A stepwise two-photon, red light excitation of organorhodium(III) phthalocyanine complexes was found to induce the activation of the axial metal-carbon bond to generate alkyl radicals/aldehydes. The cooperative action of the photouncaging reaction and the photochemical generation of reactive oxygen species were indicated to induce the cell deaths.

Analysis of differential neonatal lethality in cystathionine β-synthase deficient mouse models using metabolic profiling

Cystathionine beta-synthase (CBS) is a key enzyme of the trans-sulfuration pathway that converts homocysteine to cystathionine. Loss of CBS activity due to mutation results in CBS deficiency, an inborn error of metabolism characterized by extreme elevation of plasma total homocysteine (tHcy). C57BL6 mice containing either a homozygous null mutation in the cystathionine β-synthase (Cbs^-/- ) gene or an inactive human CBS protein (Tg-G307S Cbs^-/- ) are born in mendelian numbers, but the vast majority die between 18 and 21 days of age due to liver failure. However, adult Cbs null mice that express a hypomorphic allele of human CBS as a transgene (Tg-I278T Cbs^-/- ) show almost no neonatal lethality despite having serum tHcy levels similar to mice with no CBS activity. Here, we characterize liver and serum metabolites in neonatal Cbs^+/- , Tg-G307S Cbs^-/- , and Tg-I278T Cbs^-/- mice at 6, 10, and 17 days of age to understand this difference. In serum, we observe similar elevations in tHcy in both Tg-G307S Cbs^-/- and Tg-I278T Cbs^-/- compared to control animals, but methionine is much more severely elevated in Tg-G307S Cbs^-/- mice. Large scale metabolomic analysis of liver tissue confirms that both methionine and methionine-sulfoxide are significantly more elevated in Tg-G307S Cbs^-/- animals, along with significant differences in several other metabolites including hexoses, amino acids, other amines, lipids, and carboxylic acids. Our data are consistent with a model that the neonatal lethality observed in CBS-null mice is driven by excess methionine resulting in increased stress on a variety of related pathways including the urea cycle, TCA cycle, gluconeogenesis, and phosphatidylcholine biosynthesis.

Endogenous toxic metabolites and implications in cancer therapy

It is well recognized that many metabolic enzymes play essential roles in cancer cells in producing building blocks such as nucleotides, which are required in greater amounts due to their increased proliferation. On the other hand, the significance of enzymes in preventing the accumulation of their substrates is less recognized. Here, we outline the evidence and underlying mechanisms for how many metabolites normally produced in cells are highly toxic, such as metabolites containing reactive groups (e.g., methylglyoxal, 4-hydroxynonenal, and glutaconyl-CoA), or metabolites that act as competitive analogs against other metabolites (e.g., deoxyuridine triphosphate and l-2-hydroxyglutarate). Thus, if a metabolic pathway contains a toxic intermediate, then we may be able to induce accumulation and poison a cancer cell by targeting the downstream enzyme. Furthermore, this poisoning may be cancer cell selective if this pathway is overactive in a cancer cell relative to a nontransformed cell. We describe this concept as illustrated in selenocysteine metabolism and other pathways and discuss future directions in exploiting toxic metabolites to kill cancer cells.

Urinary metabolomic signatures in reticular oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease. Among all the clinical forms in OLP, reticular type has the highest incidence rate. Previous studies have applied metabolomics to investigate the metabolic changes of oral mucosa and blood samples from reticular OLP patients. Urinary metabolomic signatures is also useful in analyzing the pathological changes of the patients, which was a complement to the previous studies. Through these researches, we may have a more comprehensive understanding of the disease. Metabolic profiles of urinary samples from OLP patients and control subjects were analyzed by liquid chromatography (LC)-mass spectrometry (MS) system. Differentially expressed metabolites were identified via OSI/SMMS software for the pathology analysis. Totally, 30 differentially expressed metabolites were identified. Pathological network showed that these metabolites participated in 8 pathological processes, that is, DNA damage and repair disorder, apoptosis process, inflammatory lesion, oxidative stress injury, carbohydrate metabolism disorder, mood dysfunction, abnormal energy expenditure, and other pathological process. These findings demonstrated that the analysis of human urine metabolome might be conducive to the achievement of the objectives of this study.

Engineering of L-amino acid deaminases for the production of α-keto acids from L-amino acids

α-keto acids are organic compounds that contain an acid group and a ketone group. L-amino acid deaminases are enzymes that catalyze the oxidative deamination of amino acids for the formation of their corresponding α-keto acids and ammonia. α-keto acids are synthesized industrially via chemical processes that are costly and use harsh chemicals. The use of the directed evolution technique, followed by the screening and selection of desirable variants, to evolve enzymes has proven to be an effective way to engineer enzymes with improved performance. This review presents recent studies in which the directed evolution technique was used to evolve enzymes, with an emphasis on L-amino acid deaminases for the whole-cell biocatalysts production of α-keto acids from their corresponding L-amino acids. We discuss and highlight recent cases where the engineered L-amino acid deaminases resulted in an improved production yield of phenylpyruvic acid, α-ketoisocaproate, α-ketoisovaleric acid, α-ketoglutaric acid, α-keto-γ-methylthiobutyric acid, and pyruvate.

One-step biosynthesis of α-keto-γ-methylthiobutyric acid from L-methionine by an Escherichia coli whole-cell biocatalyst expressing an engineered L-amino acid deaminase from Proteus vulgaris

α-Keto-γ-methylthiobutyric acid (KMTB), a keto derivative of l-methionine, has great potential for use as an alternative to l-methionine in the poultry industry and as an anti-cancer drug. This study developed an environment friendly process for KMTB production from l-methionine by an Escherichia coli whole-cell biocatalyst expressing an engineered l-amino acid deaminase (l-AAD) from Proteus vulgaris. We first overexpressed the P. vulgarisl-AAD in E. coli BL21 (DE3) and further optimized the whole-cell transformation process. The maximal molar conversion ratio of l-methionine to KMTB was 71.2% (mol/mol) under the optimal conditions (70 g/L l-methionine, 20 g/L whole-cell biocatalyst, 5 mM CaCl₂, 40°C, 50 mM Tris-HCl [pH 8.0]). Then, error-prone polymerase chain reaction was used to construct P. vulgarisl-AAD mutant libraries. Among approximately 10⁴ mutants, two mutants bearing lysine 104 to arginine and alanine 337 to serine substitutions showed 82.2% and 80.8% molar conversion ratios, respectively. Furthermore, the combination of these mutations enhanced the catalytic activity and molar conversion ratio by 1.3-fold and up to 91.4% with a KMTB concentration of 63.6 g/L. Finally, the effect of immobilization on whole-cell transformation was examined, and the immobilized whole-cell biocatalyst with Ca²⁺ alginate increased reusability by 41.3% compared to that of free cell production. Compared with the traditional multi-step chemical synthesis, our one-step biocatalytic production of KMTB has an advantage in terms of environmental pollution and thus has great potential for industrial KMTB production.

Genome instability in Maple Syrup Urine Disease correlates with impaired mitochondrial biogenesis

OBJECTIVE

The mitochondrial branched-chain ketoacid dehydrogenase (BCKD) catalyzes the degradation of branched-chain amino acids (BCAA), which have been shown to induce oxidative stress. Maple Syrup Urine Disease (MSUD) is caused by impaired activity of BCKD, suggesting that oxidative stress and resulting DNA damage could contribute to pathology. We evaluated the potential effect of BCKD deficiency on genome integrity and mitochondrial function as a downstream target.

METHODS

Primary fibroblasts from MSUD patients and controls were either cultivated under normal conditions or exposed to metabolic or oxidative stress. DNA was analyzed for damage and mitochondrial function was evaluated by gene expression analyses, functional assays and immunofluorescent methods.

RESULTS

Patient fibroblasts accumulated damage in mitochondrial DNA (mtDNA) and nuclear DNA, with a corresponding reduction in mitochondrial transcription, mtDNA copy number and pyruvate dehydrogenase. We found no evidence of increased level of reactive oxygen species (ROS) in patient fibroblasts under normal conditions, suggesting that the genotoxic effect is ascribed to accumulating metabolites.

CONCLUSIONS

Impaired BCKD activity as in MSUD, results in accumulation of DNA damage and corresponding mitochondrial dysfunction.

A review of methionine dependency and the role of methionine restriction in cancer growth control and life-span extension

Methionine is an essential amino acid with many key roles in mammalian metabolism such as protein synthesis, methylation of DNA and polyamine synthesis. Restriction of methionine may be an important strategy in cancer growth control particularly in cancers that exhibit dependence on methionine for survival and proliferation. Methionine dependence in cancer may be due to one or a combination of deletions, polymorphisms or alterations in expression of genes in the methionine de novo and salvage pathways. Cancer cells with these defects are unable to regenerate methionine via these pathways. Defects in the metabolism of folate may also contribute to the methionine dependence phenotype in cancer. Selective killing of methionine dependent cancer cells in co-culture with normal cells has been demonstrated using culture media deficient in methionine. Several animal studies utilizing a methionine restricted diet have reported inhibition of cancer growth and extension of a healthy life-span. In humans, vegan diets, which can be low in methionine, may prove to be a useful nutritional strategy in cancer growth control. The development of methioninase which depletes circulating levels of methionine may be another useful strategy in limiting cancer growth. The application of nutritional methionine restriction and methioninase in combination with chemotherapeutic regimens is the current focus of clinical studies.

The methionine salvage pathway compound 4-methylthio-2-oxobutanate causes apoptosis independent of down-regulation of ornithine decarboxylase

4-Methylthio-2-oxobutanoic acid (MTOB) is the final compound of the methionine salvage pathway that converts the polyamine byproduct methylthioadenosine to adenine and methionine. Here we find that MTOB inhibits growth of several human cell lines in a dose-dependent manner. Growth inhibition was specific for MTOB as we did not observe any inhibition with other chemically related compounds. MTOB treatment causes apoptosis and reduction of ornithine decarboxylase (ODC) activity but not ODC mRNA. To determine if MTOB exerts its effects primarily via ODC inhibition, we compared the effects of MTOB with the ODC-specific inhibitor difluoromethylornithine (DFMO). We found that MTOB was a more potent inducer of apoptosis than DFMO, lacked activation of caspase 3/7, and was able to induce apoptosis in cells lacking p53. Our results show that MTOB-induced growth inhibition and apoptosis is not simply secondary due to ODC inhibition and implies that MTOB activates apoptosis via other mechanisms.

Synthesis and effects of 3-methylthiopropanoyl thiolesters of lipoic acid, methional metabolite mimics

6S,8S-Bis(3-methylthiopropanoyl) thiolesters of lipoic acid were synthesized with the carboxyl moiety of lipoate modified as methyl or water soluble choline esters. Evaluation on different cell lines in culture showed that they possessed modest antiproliferative activity. However, the 6-fold decrease in IC50 (from 270 to 45 microM) observed with the water soluble 6S,8S-bis(3-methylthiopropenoyl) thiolester dehydro derivative on a human epithelial prostate cancer cell line (DU145) argues in favor of 3-methylthiopropanoyl metabolites as endogenous growth regulatory (apoptogenic) compounds derived from methionine.

Intraperitoneal treatment with dimethylthioampal (DIMATE) combined with surgical debulking is effective for experimental peritoneal carcinomatosis in a rat model

The goal was to evaluate the efficiency of intraperitoneal administration of dimethylthioampal (DIMATE), a cellular apoptosis inducer, combined, or not, with cytoreductive surgery on rats with peritoneal adenocarcinomatosis. Peritoneal carcinomatosis was induced in rats by intraperitoneal injection of adenocarcinoma cell line DHD/K12/pro B. Intraperitoneal DIMATE was given at 17.3 mg/kg. Rats were randomized into five groups of eight animals, regarding the day of treatment (2 days or 20 days after peritoneal carcinomatosis induction) and the combination with cytoreductive surgery. All rats were killed at 30 days to evaluate carcinomatosis extent (quantitative score) and ascites volume. The quantitative score of carcinomatosis and the ascites volume were significantly reduced in the groups treated with DIMATE at day 2 (P = 0.005 and P < 0.001, respectively) and when DIMATE was used with cytoreductive surgery at day 20 (P = 0.009 and P < 0.001, respectively). Cytoreductive surgery or DIMATE used alone at day 20 had no significant influence. The intraperitoneal DIMATE administration at day 20, when not combined with surgery, had no significant influence on carcinomatosis extent or on ascites volume. Intraperitoneal DIMATE appeared to be an efficient drug in the prevention or treatment of peritoneal carcinomatosis when combined with cytoreductive surgery or when it was given by intraperitoneal route, before the development of macroscopic peritoneal carcinomatosis. It appears to be a promising therapeutic agent to be investigated in a human phase I trial in peritoneal carcinomatosis.

The role of glutamine transaminase K (GTK) in sulfur and alpha-keto acid metabolism in the brain, and in the possible bioactivation of neurotoxicants

Glutamine transaminase K (GTK), which is a freely reversible glutamine (methionine) aromatic amino acid aminotransferase, is present in most mammalian tissues, including brain. Quantitatively, the most important amine donor in vivo is glutamine. The product of glutamine transamination (i.e., alpha-ketoglutaramate; alphaKGM) is rapidly removed by cyclization and/or conversion to alpha-ketoglutarate. Transamination is therefore "pulled" in the direction of glutamine utilization. Major biological roles of GTK are to maintain low levels of phenylpyruvate and to close the methionine salvage pathway. GTK also catalyzes the transamination of cystathionine, lanthionine, and thialysine to the corresponding alpha-keto acids, which cyclize to ketimines. The cyclic ketimines and several metabolites derived therefrom are found in brain. It is not clear whether these compounds have a biological function or are metabolic dead-ends. However, high-affinity binding of lanthionine ketimine (LK) to brain membranes has been reported. Mammalian tissues possess several enzymes capable of catalyzing transamination of kynurenine in vitro. Two of these kynurenine aminotransferases (KATs), namely KAT I and KAT II, are present in brain and have been extensively studied. KAT I and KAT II are identical to GTK and alpha-aminoadipate aminotransferase, respectively. GTK/KAT I is largely cytosolic in kidney, but mostly mitochondrial in brain. The same gene codes for both forms, but alternative splicing dictates whether a 32-amino acid mitochondrial-targeting sequence is present in the expressed protein. The activity of KAT I is altered by a missense mutation (E61G) in the spontaneously hypertensive rat. The symptoms may be due in part to alteration of kynurenine transamination. However, owing to strong competition from other amino acid substrates, the turnover of kynurenine to kynurenate by GTK/KAT I in nervous tissue must be slow unless kynurenine and GTK are sequestered in a compartment distinct from the major amino acid pools. The possibility is discussed that the spontaneous hypertension in rats carrying the GTK/KAT I mutation may be due in part to disruption of glutamine transamination. GTK is one of several pyridoxal 5'-phosphate (PLP)-containing enzymes that can catalyze non-physiological beta-elimination reactions with cysteine S-conjugates containing a good leaving group attached at the sulfur. These elimination reactions may contribute to the bioactivation of certain electrophiles, resulting in toxicity to kidney, liver, brain, and possibly other organs. On the other hand, the beta-lyase reaction catalyzed by GTK may be useful in the conversion of some cysteine S-conjugate prodrugs to active components in vivo. The roles of GTK in (a) brain nitrogen, sulfur, and aromatic amino acid/kynurenine metabolism, (b) brain alpha-keto acid metabolism, (c) bioactivation of certain electrophiles in brain, (d) prodrug targeting, and (e) maintenance of normal blood pressure deserve further study.

Methylthioadenosine phosphorylase regulates ornithine decarboxylase by production of downstream metabolites

The gene encoding methylthioadenosine phosphorylase (MTAP), the initial enzyme in the methionine salvage pathway, is deleted in a variety of human tumors and acts as a tumor suppressor gene in cell culture (Christopher, S. A., Diegelman, P., Porter, C. W., and Kruger, W. D. (2002) Cancer Res. 62, 6639-6644). Overexpression of the polyamine biosynthetic enzyme ornithine decarboxylase (ODC) is frequently observed in tumors and has been shown to be tumorigenic in vitro and in vivo. In this paper, we demonstrate a novel regulatory pathway in which the methionine salvage pathway products inhibit ODC activity. We show that in Saccharomyces cerevisiae the MEU1 gene encodes MTAP and that Meu1delta cells have an 8-fold increase in ODC activity, resulting in large elevations in polyamine pools. Mutations in putative salvage pathway genes downstream of MTAP also cause elevated ODC activity and elevated polyamines. The addition of the penultimate salvage pathway compound 4-methylthio-2-oxobutanoic acid represses ODC levels in both MTAP-deleted yeast and human tumor cell lines, indicating that 4-methylthio-2-oxobutanoic acid acts as a negative regulator of polyamine biosynthesis. Expression of MTAP in MTAP-deleted MCF-7 breast adenocarcinoma cells results in a significant reduction of ODC activity and reduction in polyamine levels. Taken together, our results show that products of the methionine salvage pathway regulate polyamine biosynthesis and suggest that MTAP deletion may lead to ODC activation in human tumors.

Anaplerotic reactions in tumour proliferation and apoptosis

Our aim in this commentary is to provide evidence that certain oxoacids formed in anaplerotic reactions control cell proliferation/apoptosis. In tumour cells with impaired Krebs cycle enzymes, some anaplerotic reactions do compensate for the deficit in oxoacids. One of these, oxaloacetate, derived from the transamination of asparagine but not of aspartate, is decarboxylated 4-fold more efficiently in polyoma-virus transformed cells than in their non-transformed counterparts. The deamidation of asparagine, in the cell culture medium, to aspartate by asparaginase decreases asparagine transamination and inhibits concomitantly the growth of asparaginase-sensitive lymphoma cells, suggesting a causal relationship between asparagine transamination and growth. Another oxoacid that can provide ATP when metabolised in mitochondria, but by the branched-chain oxoacid dehydrogenase complex (BCOADC), is 2-oxobutanoate. It has two origins: (a) deamination of threonine, and (b) cleavage of cystathionine, a metabolite derived from methionine. 2-Oxobutanoate in the presence of insulin promotes growth in G1/S arrested cells. But methionine also gives rise to another substrate of BCOADC, 4-methylthio-2-oxobutanoate (MTOB), which is synthesised exclusively from methylthioadenosine (MTA) by the action of MTA phosphorylase. In Met-dependent tumour cells with defective MTA phosphorylase, 2-oxobutanoate production would exceed that of MTOB. Further, BCOADC also has 3-fold greater affinity for 2-oxobutanoate than for MTOB; hence, the deficiency in 3-methylthio propionyl CoA, the final product of MTOB decarboxylation, would be exacerbated. Methional, the transient metabolic precursor in 3-methylthio propionyl CoA biosynthesis, is apoptogenic for both normal and bcl(2)-negative transformed cells in culture. Investigations of other causal relationships between the genes/enzymes mediating the homeostasis of anaplerotic oxoacids and cell growth/death may be worthwhile.

Using CTLL-2 and CTLL-2 bcl2 cells to avoid interference by apoptosis in the in vitro micronucleus test

In vitro assays for chromosome aberrations (i.e., in vitro micronucleus and in vitro metaphase analysis tests) frequently produce false-positive or exaggerated-positive results. Our previous work suggested that apoptosis interferes with these tests, producing misleading results. These previous studies were conducted by performing the in vitro micronucleus test in CTLL-2 cells and a CTLL-2 cell derivative stably transfected with the apoptosis inhibitor gene bcl2. In the present study, these previous observations were extended by examining micronucleus induction with a larger number of compounds in both CTLL-2 and CTLL-2 bcl2 cells and measuring apoptosis with annexin V-FITC. Both cell lines were treated with different classes of compounds that were anticipated to be exclusively apoptosis inducers, or compounds known to be clastogens or aneugens, some of which were anticipated to be both genotoxic and apoptotic. We were able to confirm that compounds that are only apoptogenic induced micronuclei in CTLL-2 but not CTLL-2 bcl2 cells, indicating that the positive responses are due to apoptosis in CTLL-2 cells. Some genotoxins (clastogens and aneugens) did not produce apoptosis by the annexin V assay and gave similar responses in CTLL-2 and CTLL-2 bcl2 cells. Finally, higher responses were induced in CTLL-2 cells compared to CTLL-2 bcl2 cells that were treated with aneugens or clastogens that were also apoptosis inducers, suggesting that the greater response in CTLL-2 cells is a consequence of both genotoxicity and apoptosis. Finally, it was demonstrated that just eliminating CTLL-2 cells having three or more micronuclei from scoring was not adequate for correctly evaluating agents that only produce apoptosis. The results indicate that coupling the in vitro micronucleus test in both CTLL-2 and CTLL-2 bcl2 cells with the measurement of apoptosis is able to distinguish the genotoxic effects of a test compound from its apoptotic potential and is able to avoid interference from apoptosis in the in vitro micronucleus test. These observations may provide the basis for a useful genotoxicity assay.

Novel competitive irreversible inhibitors of aldehyde dehydrogenase (ALDH1): restoration of chemosensitivity of L1210 cells overexpressing ALDH1 and induction of apoptosis in BAF(3) cells overexpressing bcl(2)

4-Amino-4-methyl-pent-2-ynthioc acid S-methyl ester (ampal thiolester: ATE) was used as a lead compound to synthesise new amino-substituted derivatives of alpha, beta acetylenic thiolester compounds as inhibitors of aldehyde dehydrogenase 1, (ALDH1). Of these compounds, the dimethyl derivative (DIMATE) was a competitive irreversible inhibitor (K(i) approximately 280 microM) of baker's yeast ALDH1 in vitro showing 80% inhibition at 400 microM when preincubated with the enzyme for 30min, whereas the trimethyl ammonium and the morpholine derivatives showed only 15% inhibition at 600 microM even after 60min preincubation. ATE inhibited ALDH1 activity in ALDH1-transfected L1210 T cells resistant to hydroperoxycyclophosphamide (HCPA) and inhibited growth synergistically in the presence of HCPA. In non-transfected L1210 counterparts ATE did not potentiate growth inhibition by HCPA. DIMATE was a 30-100-fold more effective growth inhibitor than ATE. Endogenous ALDH1 activities of BAF(3) cells over-expressing different levels of bcl(2) (0-100%) were similar (16-20mU/mg protein) and were all inhibited by DIMATE, reaching 20-30% at 4 microM. Up to 4 microM no apoptosis, as measured by DNA-fragmentation was observed, but at 8 and 10 microM DIMATE, DNA-fragmentation increased concomitantly with ALDH1 inhibition. No DNA-fragmentation was observed with ALDH1 irreversible inhibitors devoid of a thiolester group or with thiolesters which were not inhibitors of ALDH1. It was seen only with competitive irreversible inhibitors having the methanethiol and enzyme-inhibitory moieties. The methanethiol putatively released from DIMATE by ALDH1 esterase activity plays a role, albeit undefined, in lowering intramitochondrial glutathione levels which decreased by 47% as DNA-fragmentation increased.

Retinoic acid receptor-independent mechanism of apoptosis of melanoma cells by the retinoid CD437 (AHPN)

Retinoic acid (RA) induces differentiation of S91 melanoma cells through activation of RA receptor (RAR)gamma without affecting cell viability. The novel RARgamma-agonist CD437 (AHPN), however, also induces concomitant apoptosis through an unknown mechanism which was investigated here. By utilizing DNA microarray analysis, five apoptosis-associated, CD437-induced transcripts (CITs) were identified. Interestingly, all CITs are also regulated by p53 in a DNA damage response, and consistent with this interpretation, CD437 was found to cause DNA adduct-formation. However, p53 is not required for CD437-dependent regulation of CITs. Among this set of genes, induction of p21(WAF1/CIP1) is likely to be responsible for early S-phase growth-arrest of CD437-treated cells, whereas ei24 is a critical mediator of CD437-induced apoptosis in S91 cells. These data suggest an RAR-independent mechanism in which CD437 causes DNA adduct-formation, resulting in induction of a p53-independent DNA damage response, and subsequent growth-arrest and apoptosis. CD437-mediated DNA adduct-formation may also explain its apoptotic effects in other cell types.

Fetuses from preeclamptic mothers show reduced hepatic erythropoiesis

The fetal liver is the main hematopoietic organ during intrauterine life. Morphometrical studies were performed on liver sections to detect changes occurring with intrauterine growth retardation and preeclampsia. Compared with the controls (n = 10), fetuses from preeclamptic mothers showed a severe reduction of erythroid cells by 60% on average (n = 18). Closer examination revealed that the erythroid cells at early stages of differentiation were more affected (80% reduction) than at later stages (55%). Seven out of 18 fetuses from preeclamptic mothers did not show growth retardation but exhibited severely reduced hepatic erythropoiesis. We suggest that the prime factor for impaired red blood cell production is preeclampsia itself rather than intrauterine growth retardation. Regulation of erythropoiesis in utero might depend on the interaction of many hematopoietic growth factors, and preeclampsia might alter the balance. To test this notion, we quantitated erythropoietin in fetal blood and various cytokines in the amniotic fluid. An elevation of erythropoietin and interleukin (IL)-3 levels was seen in babies born under the conditions of preeclampsia, whereas the concentrations of granulocyte/macrophage-colony-stimulating factor (CSF), granulocyte-CSF, and IL-1 beta were reduced, and the levels of IL-6 and IL-8 remained constant. With preeclampsia, a discrepancy between elevation of erythrocyte numbers in peripheral blood and depression of hematopoiesis at the main production site, the fetal liver, is seen. Concomitantly, there is elevation of some but reduction of other hematopoietic cytokines. We envision that during the course of preeclampsia quantitation of hematopoietic growth factors might allow to predict the deterioration of in utero life conditions.

Altered methional homoeostasis is associated with decreased apoptosis in BAF3 bcl2 murine lymphoid cells

Methional is a potent inducer of apoptosis in an interleukin 3-dependent murine lymphoid cell line BAF3 b0 when it is added to the culture medium. In these cells transfected with the bcl2 gene, BAF3 bcl2, the apoptotic-inducing activity of methional is dramatically reduced. The addition of disulfiram (an inhibitor of aldehyde dehydrogenase) in order to reduce methional oxidation brought about an increase in apoptosis in BAF3 b0 but not in BAF3 bcl2 cells. In contrast, the addition of quercetin (an inhibitor of aldehyde reductase) in an attempt to diminish methional reduction increased apoptosis in both BAF3 b0 and BAF3 bcl2 cells. The extent of DNA fragmentation in BAF3 bcl2 cells approached that in BAF3 b0 cells in the presence of quercetin and exogenous methional, suggesting a defect in methional biosynthesis in BAF3 bcl2 cells. Direct evidence for this was obtained by measuring labelled methional in cells incubated with the sodium, salt of [U-14C]4-methylthio-2-oxobutanoic acid (MTOB), the precursor of methional. The 80% decrease in labelled methional in BAF3 bcl2 compared with BAF3 b0 cells was accompanied by a concomitant rise in the transamination of [14C]MTOB to [14C]methionine in BAF3 bcl2 cells. Inhibition of the transaminase, however, by a synthetic transition-state-type compound, pyridoxal-L-methionine ethyl ester, induced apoptosis in BAF3 b0 but not in BAF3 bcl2 cells, confirming that the defect in BAF3 bcl2 cells was not in the transaminase itself but rather in the oxidative decarboxylation step MTOB --> methional. In addition, no evidence was obtained for the synthesis of [14C]malondialdehyde from [14C]methional in BAF3 bcl2 cells. As these cells show no deficiency in their content of reactive oxygen species compared with that of BAF3 b0 cells, they may possess some other defect in the beta-hydroxylase enzyme system itself.