Inhibition of cAMP-dependent protein kinase A: a novel cyclo-oxygenase-independent effect of non-steroidal anti-inflammatory drugs in adipocytes.

1. Non-steroidal anti-inflammatory drugs (NSAIDs) [acetylsalicylic acid (ASS), naproxen, nimesulide and piroxicam] decreased adrenaline- or dibutyryl cAMP-stimulated glycerol release in isolated adipocytes. We aimed to determine the mechanism of this NSAIDs action. 2. Non-steroidal anti-inflammatory drugs decreased cAMP-dependent protein kinase A (PKA) activity in rat adipocyte lysates and in a commercial bovine heart PKA holoenzyme. If added before cAMP, NSAIDs impaired PKA activation by the cyclic nucleotide; however, if PKA was first activated by cAMP, NSAIDs were ineffective. NSAIDs were also ineffective against PKA catalytic subunits. 3. Consequently, NSAIDs lowered hormone-sensitive lipase translocation from cytosol to lipid storage droplets in adipocytes lysates, the critical event to promote lipolysis. 4. These results indicate that inhibition of PKA activation explains NSAIDs-induced decrease in adrenaline-stimulated lipolysis. We suggest that reproduction of such inhibition in nociceptive cells might enhance the understanding of the mechanism underlying the analgesic effects of NSAIDs.

Antagonism between the metabolic responses induced by epinephrine and piroxicam on isolated rat hepatocytes.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most employed therapeutic agents. They have a wide spectrum of biological effects, some of which are independent of cyclooxygenase inhibition, such as the alterations on the components of signal transduction systems. In particular, previous data from our laboratory suggested an antagonism between epinephrine and piroxicam, one of the most prescribed NSAIDs. Thus, this study deals with the epinephrine-piroxicam antagonism recorded for metabolic responses in isolated rat hepatocytes. The obtained results show that epinephrine stimulates lactate and ethanol consumption, stimulates glucose release from lactate only, and has no effect on cellular triacylglycerides content. Otherwise, in a dose-dependent basis, piroxicam stimulates lactate and ethanol consumption accompanied by an increase in triacylglycerides content, without changes in glucose release by hepatocytes. Piroxicam blocks the epinephrine-induced stimulation of glucose release from lactate, and epinephrine blocks the piroxicam-mediated increase in triacylglycerides content from lactate or ethanol. In contrast, the effects of epinephrine and piroxicam, promoting the consumption of lactate and ethanol, are not antagonized or added after the simultaneous administration of both compounds. This last result is probably related to the ability of both compounds to stimulate oxygen consumption. On isolated rat liver mitochondria, micromolar doses of piroxicam partially uncouple oxidative phosphorylation, and paradoxically stimulates an ATP-dependent mitochondrial function as citrullinogenesis. These results show for first time, on isolated rat hepatocytes, an antagonism between the metabolic responses of epinephrine and piroxicam, at the concentration found in plasma after its therapeutical administration.

Butylated hydroxytoluene prevents hepatic damage induced by food oil.

A rapid and reproducible model of fatty liver in rats was developed by injecting corn oil (s.c.). In preliminary experiments, the mortality due to acute ethanol intoxication was significantly higher in this model of acutely fattened animals. Lipid peroxidation is a process that involves free radicals and consumes as substrate unsaturated fatty acids, which are present in great amounts in corn oil. Thus, in this work we explored whether the acute loads of corn oil increased hepatic lipid peroxidation. The three markers of cellular oxidative stress measured in fatty livers from rats injected with corn oil were: the production of thiobarbituric acid-reactive substances (TBARS), liver content of triacylglycerides (TAG), and total glutathione (GSH-GSSG). All were significantly modified. We also studied the effect of butylated hydroxytoluene (BHT), a free radical scavenger frequently used in the food industry to prevent lipid oxidation, and found that it prevented the effect of corn oil on TBARS and TAG but enhanced the depletion of GSH-GSSG caused by the acute administration of large loads of corn oil.

Piroxicam modifies the effects of ethanol on isolated rat hepatocytes.

It has been reported that piroxicam prevents the hepatic increase of triacylglycerides and thiobarbituric acid-reactive substances observed after acute ethanol intoxication in rats and also causes a decrease in blood ethanol concentration. The aim of this study was to assess the effect of piroxicam on these 3 metabolic indicators, using isolated rat hepatocytes incubated with ethanol or lactate, supplemented or not with epinephrine. Epinephrine stimulated the consumption of lactate, but not of ethanol. In the isolated hepatocytes, and in a dose-dependent fashion, piroxicam alone raised the consumption of lactate and ethanol, increased the triacylglyceride pool in cells incubated with lactate or ethanol, and decreased the content of thiobarbituric acid-reactive substances in cells incubated with ethanol, but not with lactate. Epinephrine blocked these actions of piroxicam, except the lowering of the content of thiobarbituric acid-reactive substances. Thus, piroxicam helps to control the oxidative stress produced in isolated hepatocytes by ethanol.

Restoration by piroxicam of liver glutathione levels decreased by acute ethanol intoxication.

The effect of piroxicam, a nonsteroidal anti-inflammatory drug, on blood ethanol and on triacylglycerols, malondialdehyde and glutathione levels in liver of fed rats acutely intoxicated with ethanol was studied. As previously reported for fasted rats, piroxicam in fed rats decreases the concentration of ethanol in blood and inhibits the hepatic increase of triacylglycerols and malondialdehyde consequent to ethanol administration. In addition, the hepatic depletion of reduced and reduced plus oxidized glutathione observed 8 and 12h after gavage of ethanol was reversed when piroxicam was administered simultaneously with ethanol. The importance of the finding is discussed in light of the paramount participation of glutathione during the cellular oxidative stress.

Nonsteroidal antiinflammatory drugs lower ethanol-mediated liver increase in lipids and thiobarbituric acid reactive substances.

Four nonsteroidal antiinflammatory drugs--namely, acetylsalicylic acid, naproxen, nimesulide, and dipyrone--were assayed to search their capability in preventing the hepatic increase of triacylglycerols and thiobarbituric acid reactive substances, as an indication of lipid peroxidation, resulting from the acute intoxication of rats with ethanol. The four antiinflammatory compounds inhibited the ethanol-mediated increase in triacylglycerols and thiobarbituric acid reactive substances. Furthermore, each one of these antiinflammatory drugs produced distinctive actions on blood ethanol levels: a temporal diminution with aspirin and naproxen, no changes with nimesulide, and an increase with dipyrone. It is concluded that the nonsteroidal antiinflammatory drugs contributed to controlling hepatic lipid peroxidation, and hence the oxidative stress promoted by ethanol intoxication.

Importancia del polimorfismo en el metabolismo del etanol / Importance of polimorphism in ethanol metabolism

En este trabajo se presenta la influencia de la variabilidad genética sobre el metabolismo el etanol, hecho que puede generalizarse a prácticamente todos los procesos porque, en mayor a menor proporción, existen variaciones genéticas que influyen de manera importante en la respuesta individual a un estímulo dado; sólo que en la respuesta metabólica a la ingestión aguda o crónica de etanol esto es particularmente claro, porque las principales enzimas que participan en su degradación presentan formas polimórficas con actividades diferentes. Factores como la edad, sexo, raza, etc., contribuyen en la obsorción, la distribución y el metabolismo del etanol. la deshidrogenasa alcohólica y el sistema microsomal oxidante del etanol son los principales sistemas de oxidación del etanol a acetaldehído. formas múltiples de la deshidrogenasa alcohólica han sido caracterizadas y permiten explicar la base molecular del polimorfismo enzimático. La siguiente oxidación del acetaldehído a acetato está catalizada por la deshidrogenasa aldehídica, cuyo polimorfismo influye en el control del alcoholismo, saobre todo en poblaciones de origen monogoloide (chinos, japoneses). Resta determinar el papel de un perfil específico de deshidrogenasa aldehídica en el desarrollo de una hepatopatía

Acute ethanol intake produces lipid peroxidation in rat red blood cells membranes.

The effect of acute ethanol intake on lipid peroxidation (LP) and proteins in red blood cells (RBC) was explored. The amount of malondialdehyde (MDA; an indicator of LP) was elevated transiently when the maximal ethanol level in whole blood was observed. In contrast, erythrocyte membrane proteins were not affected. In in vitro experiments both ethanol and acetaldehyde did not alter the MDA levels. These results indicate that the metabolism of ethanol or acetaldehyde beyond the RBCs is required in order to detect LP on these cells.

Biochemical ethanol effects affected by a non-steroidal anti-inflammatory drug.

The non-steroidal anti-inflammatory drug, piroxicam, prevents the hepatic increase of triacylglycerols and malondialdehyde resulting from the acute intoxication of rats with ethanol. In addition, in the intoxicated rats, piroxicam consistently produces a decrease in the levels of blood ethanol in comparison with control animals. It is suggested that the anti-inflammatory compound stimulates ethanol oxidation.

Importance of age upon the increase in HDL2-cholesterol in the alcoholic.

An inverse relationship has been found between high density lipoprotein cholesterol (HDL-C) and the incidence of coronary disease. A controversy exists in the international literature as to which sub-fraction, HDL2-C or DHL-C, rises after ethanol ingestion. This paper studies a comparison of the levels of circulating cholesterol, HDL-C, HDL2-C and HDL3-C in two groups: a control group of 44 healthy subjects who had no ethanol in over a year, and a second one made up off 40 chronic alcoholics, who consumed between 80 and 160 gr. of ethanol per day. The alcoholic population showed lower levels of cholesterol and higher levels of HDL-C, HDL2-C and HDL3-C. When compared with the control group, the increase was in alcoholics 58% for HDL2-C and 29% for HDL3-C. An analysis of the different age groups shows an increase of 110% in HDL2-C, in alcoholics between ages 31 and 40, as compared with their control group. An increase of 81% occurred between ages 51 and 60, but rarely rose 20% between ages 21 and 30, as well as between 51 and 60. The maximum rise of HDL3-C in drinkers, related to their control group, was 38% during the fourth decade of life. The conclusion is that the HDL2-C subfraction rises in chronic alcoholics, and the changes in other HDL-C subfractions are more useful when they are placed at the different individual's decades of age, than when taken from complete population samples.

"Hormone-like" effect of adenosine and inosine on gluconeogenesis from lactate in isolated hepatocytes.

In isolated rat hepatocytes adenosine and inosine showed a dose-dependent increase in the rate of glucose synthesis from lactate with a Ka of 7.5 x 10(-8) and 9 x 10(-8) M, respectively. Absence of this action was recorded with: IMP, xanthosine, adenine, hypoxanthine, and uric acid. A reciprocal inhibition of individual gluconeogenic stimulation was found in cells incubated with glucagon or epinephrine and adenosine, but not with inosine. 5'-(N-ethyl) carboxamido adenosine was more potent than adenosine, whereas N6-(L-2-phenylisopropyl)-adenosine antagonized the stimulation of gluconeogenesis by adenosine. Neither of the analogs used modified the stimulatory role of inosine on the studied pathway. Adenosine and inosine may be involved in the short term regulation of gluconeogenesis.

Effects of moderate chronic ethanol consumption on rat liver mitochondrial functions.

The biochemical consequences of moderate chronic ethanol ingestion has been scarcely investigated in spite of the fact that most of the human population drinks ethanol on a moderate basis. This paper describes some metabolic effects produced by moderate ethanol consumption. The substitution of drinking water in rats for a 10% ethanol solution during 4 weeks resulted in: a) a decrease of blood urea and citrulline synthesis in liver mitochondria; b) a slight inhibition in state 3 and state 4 respiration either with glutamate-malate as substrates or succinate as substrate; c) no change in ADP/O ratio with succinate but slight increase with glutamate-malate; d) a reduction of the cytochrome oxidase activity and cytochromes a+a3 content; e) a 42% increase in the succinate dehydrogenase activity and a small but constant increase in the Vmax (no change in the Km) of the adenine nucleotide translocase activity in liver mitochondria. These results show that even moderate, but continuous ethanol ingestion, produces metabolic responses that must be carefully evaluated to define health risk in larger human groups.