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[Metabolism of methylglyoxal and malignant neoplasms].
The present notions on the metabolism of methylglyoxal, an endogenic controller of cellular proliferation, are adduced. The interaction between metabolism of methylglyoxal and that of carbohydrates, proteins and lipids is demonstrated. The metabolic chart has been worked out and enzymes catalyzing methylglyoxal metabolic reactions are determined. The effect of methylglyoxal and its bisguanylhydrazones derivatives on the processes of cellular proliferation control has been examined.
[Application of gene recombination for cell breeding].
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Effect of methylglyoxal on protein thiol and amino groups in isolated rat enterocytes and colonocytes and activity of various brush border enzymes.
The effect of methylglyoxal on protein -SH and -NH2 groups in cytosolic and membranous fractions of epithelial cells lining the gastrointestinal tract of rat was investigated, using isolated villus and crypt cells (enterocytes) and colonocytes. It was found that 11-12% cytosolic protein -SH and 14-17% membrane protein -SH groups were lost when villus and crypt cells were treated with 2 mM methylglyoxal. In colonocytes, the corresponding loss in protein -SH groups was 46 and 30% under the same treatment. Similarly, 27-37% protein -NH2 group in the cytosolic fraction and 18-19% protein -NH2 group in membranous fractions of the enterocytes were lost by 2 mM methylglyoxal treatment. In colonocytes, the loss of protein -NH2 group was 30 and 15% in cytosolic and membranous fractions, respectively, under the same treatment. Effect of methylglyoxal on activity of various brush border enzymes such as alkaline phosphatase, gamma-glutamyl transpeptidase, leucine aminopeptidase, Mg2(+)-ATPase, sucrase and lactase was also studied. Alkaline phosphatase and gamma-glutamyl transpeptidase activities were inhibited to the extent of 30 and 15% respectively. There was no significant change in the activities of other enzymes after treating the brush border vesicles with 2 mM methylglyoxal. These findings show that methylglyoxal can cause loss of protein thiol and amino groups and enzyme activity in mucosal cells of rat gastrointestinal tract and the effect is more pronounced in colonocytes, which are in constant contact with bacterial metabolites.
Biosynthesis and degradation of methylglyoxal in animals.
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Electronic and dielectric properties of protein--methylglyoxal complexes.
Steady-state conduction and dielectric measurements over the frequency range 10(-5) to 10(5) Hz are reported for several proteins that have been complexed with methylglyoxal. Compared with the normal (white) proteins the brown protein--methylglyoxal complexes exhibit a marked increase in electronic conductivity and a pronounced low-frequency dielectric dispersion. The intensity of the brown colour and the electronic activity is directly related to the number of free lysine groups available to react with the methylglyoxal. It is proposed that the methylglyoxal molecules form Schiff bases with the epsilon-amino groups of lysine residues and that these Schiff bases then form a charge-transfer complex with a neighbouring peptide unit. For collagen, in particular, it is found that the electron 'holes' so formed in the polypeptide backbone are capable of long range motion in what can be interpreted as being the valence band of extended electronic states of the protein structure. The protein--methylglyoxal complexes have electronic and dielectric properties similar to those exhibited by the perylene-chloranil charge-transfer complex.
Erythrocyte glyoxalase activity in genetically obese (ob/ob) and streptozotocin diabetic mice.
Hyperglycemia associated with the manifestation of the obese diabetic (ob/ob) syndrome in mice and the short and long term streptozotocin treatment of lean MF1 mice was accompanied by a significant decrease in erythrocyte glyoxalase 1 activity and a marked increase in the concentration of the alpha-oxoaldehyde methylglyoxal. Erythrocyte glyoxalase II activity was modestly but significantly elevated in both obese mice and short term streptozotocin treated MF1 mice but no significant changes in S-D-lactoylglutathione concentration could be detected. Modification of the cells glyoxalase system during hyperglycaemia, especially the enhanced production of methylglyoxal may be a significant biochemical factor in the development of diabetic complications.
[The current concepts of methylglyoxal metabolism in microorganisms].
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Potentiation of cis-dichlorodiammineplatinum (II)-induced cytotoxicity by methylglyoxal.
The dicarbonyl compound methylglyoxal (MG) potentiated the cell inactivating effect of cis-dichlorodiammine-platinum (II) (cis-DDP) when cultured human NHIK 3025 cells were treated with both drugs in simultaneous combination. While a 2 h treatment with cis-DDP alone resulted in a surviving fraction of 0.024 +/- 0.008, the simultaneous presence of 0.5 mM MG, a non-cytotoxic concentration, reduced the fraction of cells surviving treatment to 0.0009 +/- 0.0001. Although the cell inactivating effect of cis-DDP was potentiated, the amount of cell-associated platinum was not affected by MG. Glyoxal, another dicarbonyl compound, did not affect cis-DDP-induced cytotoxicity in any manner, nor did the aliphatic aldehydes acetaldehyde and propionaldehyde. Cell inactivation induced by MG alone at concentrations above 0.5 mM could be prevented by the simultaneous presence of cysteine or glutathione, indicating that cellular sulfhydryls may be involved in the expression of MG-induced cytotoxicity. Furthermore, MG-induced cell inactivation was increased by a dose-modifying factor of 2.6 when NHIK 3025 cells were first pretreated with buthionine sulfoximine, a glutathione synthesis inhibiting compound. We propose that MG reacts with cellular sulfhydryls which may also be involved in the mediation of cis-DDP cytotoxicity. Reactions between cellular sulfhydryls and MG therefore increase the cytotoxicity of cis-DDP by allowing more platinum to react with cellular targets, not by increasing the amount of platinum entering cells.
A new class of synthetic biological response modifiers: the methylfurylbutyrolactones (Nafocare B).
A new class of synthetic biological response modifiers (BRMs) has been produced by combining a highly electrophilic reactant, 2-methyl-2, 5-dihydrofuran (a cyclic acetal of cis-3-acetyl acrolein), with L-ascorbic acid. The parent class of compounds can be referred to as methylfurylbutyrolactones (MFBL), previously termed Nafocare B. This parent molecule is amorphous, has a molecular weight of 252.7, and the chemical name [3,6] cyclohemiketal of 2-(5-methyl-2-furyl)-3-keto-L-butyrolactone. Two crystalline forms were produced by a reaction of the MFBL parent molecule with either succinic anhydride or succinimide, to create MFBL-SA (Nafocare B2) and MFBL-S (Nafocare B3) dimers, respectively. The structure of these compounds has been confirmed by modern methods of analytical chemistry, including x-ray crystallography. All three forms of the MFBLs showed negligible toxicity in single-dose acute LD-50s in mice. Also, the MFBLs did not demonstrate genotoxic activity at 800 mg/kg in the mouse micronucleus assay. The MFBLs are immunostimulatory in assays involving T- and B-lymphocytes, but not in immunoassays on macrophages derived from resident- or thioglycollate-elicited peritoneal exudate cells (PEC). Spleen cells from mice treated 4 days via the intraperitoneal, intravenous, or the oral routes responded significantly over controls to suboptimal stimulatory concentrations of polyclonal mitogens in the lymphocyte stimulation assay. The MFBLs were not mitogenic, since they did not increase DNA synthesis in resting spleen cells from MFBL-treated mice. Antibody production is also amplified by the MFBLs. Mice immunized with sheep erythrocytes, a T-cell-dependent antigen, and treated with MFBLs had a 200-800% increase in the numbers of antibody-producing splenic lymphocytes detected by the Jerne hemolytic plaque assay. Also, mice immunized with soluble bovine serum albumin (BSA), and treated with a MFBL, demonstrated at least a fourfold increase in IgG-specific antibodies to BSA, when compared with controls. To demonstrate effects of MFBLs on macrophages, we used the Fc receptor (FcR) surface marker and superoxide anion assays. Only at the highest in vitro dose of MFBL (16 micrograms/ml) was a significant increase in erythrocyte antibody rosette formation detected, using resident macrophages isolated from PEC. In the superoxide anion release assay neither resident- nor thioglycollate-elicited PECs, obtained from in vivo-treated mice or macrophages treated in vitro, showed increased production of superoxide anion.(ABSTRACT TRUNCATED AT 400 WORDS)
Aminoacetone oxidase from goat liver. Formation of methylglyoxal from aminoacetone.
An enzyme which oxidizes aminoacetone to methylglyoxal has been purified from the particulate fraction of goat liver. Polyamines, such as spermidine and spermine, are also good substrates for this enzyme. The pH optimum for aminoacetone oxidation was found to be 8.2. The apparent Km values of the enzyme for aminoacetone and spermidine were 0.009 and 0.095 mM, respectively. The subunit molecular weight of the enzyme was 93,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular weight of the native enzyme was 186,000 by gel filtration. The enzyme is highly sensitive to carbonyl group reagents. The enzyme is not inhibited by monoamine and diamine oxidase inhibitors.
From methylglyoxal to new immunopotentiating ascorbic acid derivatives.
In Szent-Györgyi's search for alpha-dicarbonyl compounds that play an important role in cell regulation, 3-desoxyglucosulose was isolated first from liver but did not prove active. Methylglyoxal came next, however, its toxicity prompted Szent-Györgyi to suggest a combination with ascorbic acid which, indeed led to immunopotentiating enediol acetals although of low stability. Therefore the vinylogue of methylglyoxal, acetylacrolein was coupled with L-ascorbic acid carbanion. This second new reaction, of the aldol-type, led to the stable, potent immunoactive compound, 2-(5-methylfuryl)-3-ketogulonolactone cyclohemiketal that forms a completely surprising H-bond with succinic anhydride and succinimide based on an X-ray study. A third new reaction in which ascorbic acid plays the role of a Michael donor to alpha,beta-unsaturated aldehydes and ketones proved now to be of general validity; it is unexpectedly acid catalyzed and the adducts formed with aliphatic and alicyclic olefin ketones have definite immunopotentiating effect. A brief description of the biological effects of all types of new compounds is outlined.
[Methylglyoxal shunt of glycolysis in animal muscles].
The comparative activity of the methyglyoxalic bypass of the glycolysis has been studied in muscles of vertebrates and invertebrates. An assumption is advanced that the methylglyoxalic bypass is related to the energy exchange, dissociation of catabolism and anabolism of carbohydrates and proteins maintenance of the constant level of asymmetrical entropy in vivo.
[Methylglyoxal: metabolism and biological activity].
The enzymic formation of methylglyoxal from dihydroxyacetone phosphate and aminoacetone (metabolites of carbohydrates and proteins) is considered. Methylglyoxal transformation into lactic and pyruvic acids is related to energy metabolism, catabolism and anabolism dissociation processes in carbohydrates and proteins, and, probably, to maintenance of asymmetrical entropy in vivo on the constant level. Attention is paid to the methylglyoxal inhibition of enzymes, its interaction with glutathione and polyamines affecting the mechanisms regulating protein synthesis and cellular division. The methods for obtaining and quantitative determination of methylglyoxal are described.
[Role of sodium pyrosulfite and L-cysteine hydrochloride in retarding discoloration of ascorbic acid injection].
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[Cloning of metabolic regulators and regulation of cell proliferation].
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Methylglyoxal in beverages and foods: its mutagenicity and carcinogenicity.
Methylglyoxal was found to induce mutations in Salmonella typhimurium strains TA100, TA102 and TA104, gene conversion in Saccharomyces cerevisiae strain D7, and diphtheria toxin resistance mutation in Chinese hamster lung cells. Methylglyoxal was detected in coffee, whiskey, a soft drink, toasted bread and soy sauce. The mutagenicity of methylglyoxal was suppressed by sulfite, cysteine, glutathione and dithiothreitol, and enhanced by hydrogen peroxide. Methylglyoxal induced sarcomas in rats at the site of its subcutaneous injection.
Stimulation of human PMNs in vitro by a succinimide molecular complex of methylfurylbutyrolactone.
The immunopotentiating effects on human neutrophils of a new synthetic immune biological response modifer were studied. The compound is a succinimide crystalline molecular complex of methylfurylbutyrolactone (MFBL). The MFBL succinimide (MFBL-S) derivative was tested for its in vitro effects on polymorphonuclear leukocyte (PMN) functions. At microgram quantities, MFBL-S stimulated a twofold increase in: directed migration of PMNs; adherence to nylon; and uptake of E. coli lipopolysaccharide. The MFBL-S enhanced phagocytosis by PMNs of S. epidermidis and E. coli. Additionally, intracellular killing of S. epidermidis by MFBL-S treated PMNs was significantly increased at all doses studied, whereas killing of E. coli was only significantly different from controls at concentrations of 10 micrograms/ml.