A study of the toxic effect of oxidized sunflower oil containing 4-hydroperoxy-2-nonenal and 4-hydroxy-2-nonenal on cortical TrkA receptor expression in rats

Abstract

Sunflower oil at a specific oxidation stage (when several oxygenated α,β-unsaturated aldehydes are generated, mainly 4-hydroperoxy-trans-2-alkenals and 4-hydroxy-trans-2-alkenals), caused at 70°C with aeration for 7 days, was administered intraperitoneally to rats. This oil was studied by means of solid phase micro-extraction followed by gas chromatography/mass spectrometry (SPME-GC/MS) and by proton nuclear magnetic resonance (1H-NMR). Oxidized sunflower oil (3 ml/kg/day) was administered to male Sprague–Dawley rats for 21 days. The control group was administered non-oxidized sunflower oil in the same volume and for the same duration as the experimental group. A significant decrease in the number of neural cells positively immunostained for TrkA receptor was detected in the frontal cortex of the experimental group, with respect to controls, suggesting both neuronal damage as well as a deficit in neuronal survival signalling at this level. This could lead to apoptosis of cholinergic neurons, which play a key role in memory and attention function. These results indicate that toxic substances present in the oxidized sunflower oil, among them 4-hydroxy-trans-2-nonenal (HNE) and 4-hydroperoxy-trans-2-nonenal (HPNE), could disrupt survival signalling of frontal cortex cholinergic neurons, which could lead to apoptosis and neurodegenerative diseases. In the case of humans, this fact reinforces the necessity of avoiding the re-utilization of oxidized sunflower oil, in order to contribute to long-term neurodegenerative diseases prevention.