ABSTRACT
Mitochondria of Saccharomyces cerevisiae lack the respiratory complex I, but contain three rotenone-insensitive NADH dehydrogenases distributed on both the external (Nde1 and Nde2) and internal (Ndi1) surfaces of the inner mitochondrial membrane. These enzymes catalyse the transfer of electrons from NADH to ubiquinone without the translocation of protons across the membrane. Due to the high resolution of the Blue Native PAGE (BN-PAGE) technique combined with digitonin solubilization, several bands with NADH dehydrogenase activity were observed on the gel. The use of specific S. cerevisiae single and double mutants of the external alternative elements (ΔNDE1, ΔNDE2, ΔNDE1/ΔNDE2) showed that the high and low molecular weight complexes contained the Ndi1. Some of the Ndi1 associations took place with complexes III and IV, suggesting the formation of respirasome-like structures. Complex II interacted with other proteins to form a high molecular weight supercomplex with a molecular mass around 600 kDa. We also found that the majority of the Ndi1 was in a dimeric form, which is in agreement with the recently reported three-dimensional structure of the protein.
Subject(s)
Electron Transport Complex I/metabolism , Mitochondria/enzymology , NADH Dehydrogenase/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae/enzymology , Dimerization , Electron Transport , Electron Transport Complex I/chemistry , Electron Transport Complex I/genetics , Mitochondria/genetics , NAD/metabolism , NADH Dehydrogenase/chemistry , NADH Dehydrogenase/genetics , Saccharomyces cerevisiae/chemistry , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/geneticsABSTRACT
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.
Subject(s)
Adipocytes/drug effects , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Adipocytes/enzymology , Animals , Aspirin/pharmacology , Cattle , Cells, Cultured , Cyclic AMP-Dependent Protein Kinases/metabolism , Cyclooxygenase Inhibitors/pharmacology , Male , Myocardium/enzymology , Naproxen/pharmacology , Piroxicam/pharmacology , Prostaglandin-Endoperoxide Synthases , Rats , Rats, Wistar , Sterol Esterase/metabolism , Sulfonamides/pharmacologyABSTRACT
Acute ethanol intoxication increased triacylglycerides (TAG) and thiobarbituric acid reactive substances (TBARS) in liver and promoted the liberation of epinephrine. Four non-steroidal anti-inflammatory drugs (NSAIDs)--aspirin, naproxen, nimesulide and piroxicam--prevented this increase in TAG and TBARS. Because fatty acids provided by adipose tissue contribute substantially to elevated hepatic TAG in ethanol-intoxicated rats, it was thought that the NSAIDs might reduce epinephrine-stimulated lipolysis in these rats. Isolated rat adipocytes were activated with epinephrine in the presence or absence of the NSAIDs. The NSAIDs inhibited epinephrine-stimulated lipolysis. These drugs did not modify the binding of dihydroalprenolol (beta-adrenergic agonist) to their receptors in isolated guinea-pig liver membranes. The NSAIDs, at concentrations 3,000-fold lower than that of cAMP, inhibited stimulated lipolysis by this messenger. In conclusion, aspirin, naproxen, nimesulide and piroxicam reduce the release of fatty acids from adipose tissue to the liver by inhibiting the epinephrine-stimulated lipolysis, and this, in part, explains the protective action of these NSAIDs against hepatic signs of acute ethanol intoxication.
