Chemistry and biochemistry of 4-hydroxynonenal, malonaldehyde and related aldehydes.

Three models of free radical-induced cell injury.

Glutathione depleting agents and lipid peroxidation

Lipid peroxidation in tumour cells.

The formation, reactivity and toxicity of aldehydes originating from lipid peroxidation of cellular membranes are reviewed. Very reactive aldehydes, namely 4-hydroxyalkenals, were first shown to be formed in autoxidizing chemical systems. It was subsequently shown that 4-hydroxyalkenals are formed in biological conditions, i.e. during lipid peroxidation of liver microsomes incubated in the NADPH-Fe systems. Our studies carried out in collaboration with Hermann Esterbauer which led to the identification of 4-hydroxynonenal (4-HNE) are reported. 4-HNE was the most cytotoxic aldehyde and was then assumed as a model molecule of oxidative stress. Many other aldehydes (alkanals, alk-2-enals and dicarbonyl compounds) were then identified in peroxidizing liver microsomes or hepatocytes. The in vivo formation of aldehydes in liver of animals intoxicated with agents that promote lipid peroxidation was shown in further studies. In a first study, evidence was forwarded for aldehydes (very likely alkenals) bound to liver microsomal proteins of CCl4 or BrCCl3-intoxicated rats. In a second study, 4-HNE and a number of other aldehydes (alkanals and alkenals) were identified in the free (non-protein bound) form in liver extracts from bromobenzene or allyl alcohol-poisoned mice. The detection of free 4-HNE in the liver of CCl(4) or BrCC1(3)-poisoned animals was obtained with the use of an electrochemical detector, which greatly increased the sensitivity of the HPLC method. Furthermore, membrane phospholipids bearing carbonyl groups were demonstrated in both in vitro (incubation of microsomes with NADPH-Fe) and in vivo (CC1(4) or BrCCl(3) intoxication) conditions. Finally, the results concerned with the histochemical detection of lipid peroxidation are reported. The methods used were based on the detection of lipid peroxidation-derived carbonyls. Very good results were obtained with the use of fluorescent reagents for carbonyls, in particular with 3-hydroxy-2-naphtoic acid hydrazide (NAH) and analysis with confocal scanning fluorescence microscopy with image video analysis. The significance of formation of toxic aldehydes in biological membranes is discussed.

Lipid peroxidation and biogenic aldehydes : from the identification of 4-hydroxynonenal to further achievements in biopathology

4-Hydroxy-2,3-trans-pentenal (HPE) hemmt stark den oxydativen Tricarbonsaurecyclus, die Glykolyse und den Einbau radioaktiver Precursor inDNS, RNS, Proteine und Lipide von Ascites-Tumorzellen, aber nicht die Decarboxylierung von Glucose uber den Pentosephosphatcyclus. Die genannten Hemmungen unterbleiben bei Gegenwart vonGSH im Inkubationsmedium, auch kann die Hemmung von Glykolyse und Sauerstoffaufnahme in aldehydbehandelten Zellen durch Zugabe vonCySH aufgehoben werden. Ahnlich wird der Stoffwechsel in Zellen aus normalem Gewebe (Milz, Thymus, Dunndarm) gehemmt, es ist aber hier die erforderliche Dosis anHPE 4mal so hoch. Noch hohere Konzentrationen anHPE (1 mMol/l) fuhren zur Zellzerstorung (Stalagmose). Die Doppelbindung desHPE reagiert lebhaft mit den SH-Gruppen vonGSH undCySH unter Ausbildung einer kovalenten valenten Bindung. In ahnlicher Weise hemmtHPE auch die Aktivitat kristallisierter Glycerinaldehyd-3-phosphat-dehydrogenase; diese Hemmung kann durch hohe Konzentrationen vonCySH aufgehoben werden. Funf andere kristallisierte SH-Enzyme werden dagegen nicht nennenswert beeinflust. Es hat aber den Anschein, dasHPE den Zellstoffwechsel hauptsachlich durch seine Einwirkung auf die entsprechenden SH-Enzyme und/oder SH-Cofaktoren (CoA, Liponsaure,GSH) hemmt. Die verhaltnismasige Widerstandsfahigkeit des Stoffwechsels normaler Zellen mag auf einen hoheren Gehalt an niedermolekularen SH-Verbindungen zuruckzufuhren sein, die einen besseren Schutz der funktionellen SH-Gruppen der Enzyme gewahrleisten.

I. J. Bickis

Papers

Wirkungen von Hydroxypentenal auf den Stoffwechsel von Krebs-und Normalzellen