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Peroxynitrite inhibits glutamate transporter subtypes
1Center of Neuropharmacology, Institute of Pharmacological Sciences, University of Milan, Italy.
The Journal of Biological Chemistry
|March 15, 1996
Summary
Peroxynitrite (ONOO-) potently inhibits glutamate uptake by transporters. This oxidant, along with hydrogen peroxide (H2O2), affects glutamate transporter function, impacting neuronal signaling.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Glutamate reuptake by neurons and astrocytes is crucial for terminating excitatory signals and preventing excitotoxicity.
- Oxygen radicals and hydrogen peroxide (H2O2) are known inhibitors of this vital process.
Purpose of the Study:
- To investigate the effect of peroxynitrite (ONOO-), a biological oxidant formed from superoxide and nitric oxide, on glutamate uptake.
- To determine the mechanism and characteristics of ONOO- mediated inhibition of glutamate transporters.
Main Methods:
- Purified and recombinant high-affinity glutamate transporters were reconstituted into liposomes.
- The effect of ONOO- and H2O2 on glutamate transport kinetics (Vmax) was measured.
- Sensitivity to ONOO- was assessed in the presence and absence of vitamin E.
Main Results:
- Peroxynitrite (ONOO-) potently inhibited glutamate uptake, reducing Vmax rapidly, dose-dependently, and persistently.
- This inhibition was insensitive to vitamin E, suggesting direct interaction with transporters.
- Hydrogen peroxide (H2O2) also inhibited uptake, but required higher concentrations and longer exposure.
- Three specific rat brain glutamate transporters (GLT1, GLAST, EAAC1) showed identical sensitivity to ONOO-.
Conclusions:
- Glutamate transporters possess conserved sites vulnerable to peroxynitrite (ONOO-) and other oxidants.
- Oxidative stress, particularly from ONOO-, can significantly impair glutamate transport function.
- This finding has implications for understanding neurological conditions associated with oxidative stress.