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Modification of NMDA receptor by in vitro lipid peroxidation in fetal guinea pig brain
1Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia.
Abstract:
The effect of lipid peroxidation on the NMDA receptor and its modulatory sites in fetal guinea pig brain cell membranes was examined. P2 membrane fractions were prepared from the fetal brain tissue and peroxidized in the presence of ferric chloride and ascorbate. [3H]-MK-801-binding studies were performed and Bmax (number of binding sites) and Kd (affinity) values were used as indices of NMDA receptor modification. In lipid-peroxidized membranes the Kd value increased from 6.76 +/- 2.69 in control to 15.12 +/- 7.38 nM (P < 0.01), indicating a decreased affinity of NMDA receptors following lipid peroxidation. However, there was no significant change in Bmax. The glutamate- and glycine-dependent increase in activation was 40% lower in lipid-peroxidized membranes as compared to control. The spermine-dependent activation was also significantly reduced following lipid peroxidation as compared to control suggesting decreased affinity of spermine site. The results of this study indicate that lipid peroxidation modifies recognition, coactivator and spermine sites of NMDA receptor by decreasing its affinity without affecting the number of binding sites. Normal activation of NMDA receptor is important for neuritic growth, synaptogenesis, long-term potentiation and synaptic plasticity. Therefore, we speculate that any clinical condition causing lipid peroxidation of brain cell membranes could jeopardize these maturational processes in the developing brain causing neurological impairment.
Insights
Lipid peroxidation decreases NMDA receptor affinity in fetal guinea pig brains, impacting neuronal development. This damage affects receptor binding and activation, potentially causing neurological impairment.
Area of Science:
- Neuroscience
- Biochemistry
- Developmental Biology
Background:
- Lipid peroxidation is an oxidative process affecting cell membranes.
- The N-methyl-D-aspartate (NMDA) receptor is crucial for synaptic plasticity and brain development.
- Fetal brain development is particularly vulnerable to oxidative stress.
Purpose of the Study:
- To investigate the impact of lipid peroxidation on NMDA receptor function in fetal guinea pig brain membranes.
- To determine how peroxidation affects NMDA receptor binding affinity (Kd) and site density (Bmax).
- To assess the influence of peroxidation on NMDA receptor activation by co-agonists and modulators.
Main Methods:
- Preparation of P2 membrane fractions from fetal guinea pig brains.
- Induction of lipid peroxidation using ferric chloride and ascorbate.
- Measurement of [3H]-MK-801 binding to quantify NMDA receptor affinity and density.
- Assay of glutamate-, glycine-, and spermine-dependent receptor activation.
Main Results:
- Lipid peroxidation significantly decreased NMDA receptor affinity (increased Kd) without altering the number of binding sites (Bmax).
- Glutamate- and glycine-dependent activation of NMDA receptors was reduced by 40% in peroxidized membranes.
- Spermine-dependent activation also showed a significant reduction, suggesting decreased affinity at the spermine modulatory site.
Conclusions:
- Lipid peroxidation impairs NMDA receptor function by reducing affinity at recognition, coactivator, and spermine sites.
- These alterations in NMDA receptor function may disrupt critical maturational processes like neuritic growth and synaptogenesis.
- Clinical conditions causing lipid peroxidation could lead to neurological impairment in the developing brain.