R. Grätz

The effect of tryptophan plus methionine, 5-azacytidine, and methotrexate on adjuvant arthritis of rat.

Within the wider framework of our studies on the genesis of rheumatoid arthritis we have investigated the two signal processes in arthritis: adenoribosylation of proteins and DNA methylation. Arthritis can be induced when Freunds complete adjuvant is applied to rats. This form of arthritis can then be reduced or even totally suppressed through the application of several different substances. In the present article we have investigated if the effect of two of these substances, 5-azacytidine and methotrexate can be influenced by the application of tryptophan plus methionine. When applied singly, these latter two substances are known to reduce the formation of arthritis. This effect is intensified by a combination of tryptophan plus methionine. Application of tryptophan plus methionine without methotrexate or 5-azacytidine causes an enhanced development of an adjuvant induced arthritis.

Influence of diet free of NAD-precursors on acetaminophen hepatotoxicity in mice

Recently, we demonstrated the hepatoprotective effects of nicotinic acid amide, a selective inhibitor of poly(ADP-ribose) polymerase (PARP; EC 2.4.2.30) on mice suffering from acetaminophen (AAP)-hepatitis, suggesting that the AAP-induced liver injury involves a step which depends on adenoribosylation. The present study investigates the effects of a diet free of precursors of NAD, the substrate on which PARP acts, in female NMRI mice with AAP hepatitis and evaluates the influence of simultaneous ethanol consumption in these animals. Liver injuries were quantified as serum activities of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT). While AAP caused a 117-fold elevation of serum transaminase activities in mice kept on a standard laboratory diet, which was significantly exacerbated by ethanol and inhibited by nicotinic acid amide (NAA), adverse effects were noted in animals fed a diet free of precursors of NAD. In these animals, only minor increases of serum transaminase activities were measured in the presence of AAP, and unlike the exacerbation caused by ethanol in mice on a standard diet, the liver damage was inhibited by 50% by ethanol. A further 64% reduction of hepatitis was observed, when NAA was given to ethanol/AAP-mice. Our results provide evidence that the AAP-induced hepatitis and its exacerbation by ethanol can either be reduced by end-product inhibition of PARP by NAA or by dietary depletion of the enzymes substrate NAD. We see the main application of NAA as for the combinational use in pharmaceutical preparations of acetaminophen in order to avoid hepatic damage in patients treated with this widely used analgesic.

Exacerbation of acetaminophen hepatotoxicity by thalidomide and protection by nicotinic acid amide

1. The effects of racemic thalidomide (D[+]/L[-] alpha-phthalimido-glutarimide) on acetaminophen (AAP)-induced hepatitis were tested in male NMRI mice (n = 133) and quantified as serum activities of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT). 2. A 2.1-fold increase of GOT and a 1.9-fold increase of GPT activities (P < 0.001) were observed in mice treated perorally with 500 mg/kg of AAP plus 150 mg/kg of thalidomide (Thal). In the absence of AAP, Thal did not display any detectable hepatotoxic effects. 3. The Thal-induced exacerbation of AAP hepatotoxicity was completely inhibited by nicotinic acid amide, a selective inhibitor of poly(ADP-ribose) polymerase (PARP) (P < 0.0001), suggesting a possible influence of Thal on the hepatic metabolism of NAD-adenoribosylation. 4. We see the main application of nicotinic acid amide as for the combinational use in pharmaceutical preparations of AAP in order to avoid hepatic damage in patients treated with AAP and Thal.

Influence of D-galactosamine upon the NAD-metabolism in rat liver.

After application of D-galactosamine a hepatitis develops in the rat liver. This can be prevented by different agents, including tryptophan. Yet it has not been possible to give definitive conclusions about the mechanism of galactosamine hepatitis. In this paper we report about the influence of galactosamine on the NAD metabolism. D-galactosamine inhibits the NAD synthesis initiated by nicotinamide in normal and adrenalectomized animals. The NAD synthesis from tryptophan is prevented in normal animals, in adrenalectomized ones however there is an increase of NAD in the presence of D-galactosamine reduces the activity of the ADPR transferase. Inhibitors of the ADPR transferase prevent the galactosamine hepatitis. From the results presented we conclude that the ADPR transferase plays an important role in the development of the galactosamine hepatitis.

The therapeutic effect of a combination of cofpropamine, a caffeine derivative, and cyclophosphamide on the development of adjuvant arthritis of rats and collagen arthritis of mice.

1. Cofpropamine (Cofa), a caffeine derivative that inhibits polyadenoribosylation, enhances the therapeutic effect of cyclophosphamide (CPA) in two animal models of arthritis. 2. The development of adjuvant arthritis of rats is reduced by treatment with 2 x 50 mg/kg IP CPA and 2 x 50 mg/kg IP Cofa. 3. The development of collagen arthritis in mice is prevented by treatment with 12.5 mg/kg IP CPA and 150 mg/kg IP Cofa three times per week.

The Influence of Antagonists of Poly(Adp-Ribose)Polymerase on the Activity Of Antirheumatic Drugs on the Development of Adjuvant Arthritis in Rats and on the Induction of Tyrosine Aminotransferase in the Liver of Rats

Poly-adenoribosylation is a posttranslational modification of chromatin-bound proteins. Recently, there has been increasing evidence that poly-adenoribosylation is involved in the genesis of cancer but also in the genesis of autoimmune diseases such as rheumatoid arthritis. The synthesis of poly(ADP-ribose) by the enzyme poly(ADP-ribose)polymerase depends on the intracellular levels of NAD and this depends on the supply with the precursers tryptophan, nicotinamide, and nicotinic acid. Poly-adenoribosylation is a protective cellular response to DNA damage which leads to a decrease in the NAD content of cells (Kroger et al., 1960). The consequence is a depletion of NAD with a reduced poly(ADP-ribose) accumulation and altered biological responses such as the expression of disease specific genes (Jacobson et al., 1992, Ehrlich, et. al., 1995). The question has been raised whether agents or conditions that influence the NAD-poly(ADP-ribose)metabolism do have an effect on the pathogenesis of diseases such as rheumatoid arthritis. Previously, we reported that a combination of benzamide or a diet without tryptophan and nicotinamide in combination with D-penicillamine leads to an improvement of adjuvant arthritis in rats (Kroger and Ehrlich, 1994). We continued these studies and investigated the effects of the poly(ADP-ri- bose)polymerase antagonists nicotinamide, benzamide, caffeine-derivatives and a diet lacking tryptophan and nicotinamide alone and in combination with the antirheumatic drugs endoxan (cyclophosphamide), D-penicillamine, auranofin, voltaren, and methotrexate on the development of adjuvant arthritis of rats. In another set of experiments we studied the influence of D-penicillamine, benzamide, and cofpropamine (a caffeine-derivative) on the induction of tyrosine aminotransferase in the liver of rats with adjuvant arthritis set on a diet without tryptophan and nicotinamide.

Influence of ethanol upon the introduction of tyrosine aminotransferase in liver, upon the NAD content in liver and brain, and upon the activity of glutamate oxalate aminotransferase and glutamate pyruvate aminotransferase in the serum of rats

The influence of ethanol, tryptophan, nicotinamide and methionine upon the activity of glutamate oxalate aminotransferase and glutamate pyruvate aminotransferase in serum as well as the induction of tyrosine aminotransferase in the liver, and of NAD+ + NADH in liver and brain are described. After oral application of 6 g/kg ethanol, the activities of the examined enzymes and the concentrations of NAD+ + NADH in the brain as well as in the liver did not change over a period of 8 hr. Administration of L-methionine lead--as is the case with DL-tryptophan--to a decrease of the NAD+ + NADH-concentration in the brain. A simultaneous application of nicotinamide, DL-tryptophan, L-methionine of l-methylnicotinamide together with ethanol caused a significant increase of the tyrosine aminotransferase induction in adrenalectomized animals. Ethanol reduced the activity of the ADPR transferase in the nuclei of rat liver cells.

Induction of tyrosine aminotransferase under the influence of D-galactosamine.

The induction of the tyrosine aminotransferase by tyrosine and by tryptophan + methionine is completely inhibited by 375 mg/kg D-galactosamine-HCl. The hydrocortisone induction is reduced in dependence on the amount of D-galactosamine. Tryptophan protects to some extent the influence of low doses of D-galactosamine on the hydrocortisone induction of tyrosine aminotransferase.

Influence of N-methylformamide on the development, the NAD synthesis, and the activity of the ADPR transferase of rat embryos

When N-methylformamide is administered to rats on the 11th day of pregnancy approximately 50% of the fetuses are resorbed and a reduced weight of the developed animals is found in comparison to the controls on the 21th day (delivery by Caesarian section). The toxic effect is increased by using nicotinamide and methionine. If a combination of these substances is employed practically all fetuses are resorbed. Tryptophan, however, has a considerably protective influence. N-Methylformamide has no influence on the NAD-synthesis induced by nicotinamide or tryptophan. It does, however, inhibits the activity of the ADPR transferase.

Short time action of antirheumatic substances on the liver of rat. Protective effect of tryptophan + methionine

1. A large number of drugs, including some antirheumatic substances, cause liver damage. 2. Only a little information is available, so far, on the causes of such damage and their prevention. 3. From studies on a number of antirheumatic drugs as to their effect upon the liver, three categories could be differentiated: (a) large effect (b) low effect (c) no effect. 4. Judging from our results, the liver damage is induced via a disturbance of the NAD-adenoribosylation metabolism.