Related Experiment Videos
Pro- and antioxidative properties of cortical tissue preparations from human brain exhibiting NMDA-receptor
1Institut für Psychiatrie und für Neurochemie, Ludwig-Maximilians-Universität Würzburg.
Abstract:
The effects of cortical tissue preparations (CTP) from human brain on the production of reactive oxygen species (ROS) has been investigated with several biochemical model reactions. As indicators for ROS, fragmentation of the methionine derivatives, alpha-keto-gamma-methylthiobutyric acid (KMB) or 1-amino-cyclopropane-1-carboxylic acid (ACC), yielding ethene have been used. With these systems we have shown that production of OH-radical-type oxidants by the xanthine oxidase (XOD)-system is strongly stimulated by CTP. This activity is due to intrinsic iron ions since ethene formation from KMB is stimulated by EDTA, inhibited by desferrioxamine (Desferal) and also visible with heat-denatured CTP. CTP by themselves have no XOD activity. 3-Hydroxykynurenine (3HK) is another possible substrate for XOD but produces H2O2 without XOD-catalysis, whereas allopurinol is not inhibiting. CTP contain measurable NAD(P)H oxidoreductase activity, producing OH- radical- type oxidants at the expense of NADPH and (to a lesser extent) NADH as electron donors, shown as redox-cycling of 2-methyl-5-hydroxy-1,4-naphthoquinone, plumbagin. Ethene formation from KMB is also driven by both morpholinosydnonimine (SIN) or ONOOH. The reaction driven by SIN is stimulated by CTP and inhibited by catalase, SOD and hemoglobin. Since ethene release from KMB driven by ONOOH is inhibited by CTP the mechanisms driving KMB fragmentation are different for SIN and ONOOH. Furthermore CTP contain approx. 4 U catalase activity per mg protein and very weak peroxidase (POD) activity shown as ACC fragmentation yielding ethene in the presence of both H2O2 and KBr or NaCl. Since ACC binds to CTP and both compounds, ACC and KMB are natural products, present in food (ACC) or synthesized from methionine in vivo (KMB), these compounds may represent protecting agents in systems where reactive oxygen species are formed. One might even speculate that the production of ethene at these membrane receptor sites may have biological functions, since ethene is known to possess anaesthetic activities.
Insights
Human brain tissue preparations (CTP) enhance reactive oxygen species (ROS) production via intrinsic iron ions and NAD(P)H oxidoreductase activity. Natural compounds like ACC and KMB may act as protective agents against ROS, potentially with biological functions.
Area of Science:
- Biochemistry
- Neuroscience
- Oxidative Stress Research
Background:
- Reactive oxygen species (ROS) play a role in various biological processes and diseases.
- Human brain cortical tissue preparations (CTP) are complex biological matrices.
- Understanding the interaction of CTP with ROS-producing systems is crucial.
Purpose of the Study:
- To investigate the effect of human brain CTP on reactive oxygen species (ROS) production.
- To identify the mechanisms by which CTP influence ROS generation.
- To explore the potential role of natural compounds (ACC, KMB) in mitigating ROS effects.
Main Methods:
- Utilized biochemical model reactions with KMB and ACC as ROS indicators, measuring ethene production.
- Investigated the role of intrinsic iron ions in CTP-mediated ROS production using EDTA and desferrioxamine.
- Assessed NAD(P)H oxidoreductase activity in CTP and their interaction with ROS-generating agents (XOD, SIN, ONOOH).
Main Results:
- CTP significantly stimulated OH-radical-type oxidant production by the xanthine oxidase (XOD) system, attributed to intrinsic iron ions.
- CTP possess NAD(P)H oxidoreductase activity, generating OH-radical-type oxidants using NADPH/NADH.
- Ethene formation from KMB was differentially affected by SIN and ONOOH in the presence of CTP, suggesting distinct mechanisms.
Conclusions:
- Human brain CTP contain intrinsic iron and NAD(P)H oxidoreductase activities that contribute to ROS production.
- Natural compounds alpha-keto-gamma-methylthiobutyric acid (KMB) and 1-amino-cyclopropane-1-carboxylic acid (ACC) may act as endogenous protectants against ROS.
- The ethene production observed may have biological significance, potentially related to anesthetic activities.