The lipid peroxidation product 4-hydroxynonenal potently and selectively inhibits synaptic plasma membrane ecto-ATPase activity, a putative regulator of synaptic ATP and adenosine.
Synaptic plasma membrane (SPM)-bound, extracellular-facing (ecto) ATPases are Mg2+- or Ca2+-activated enzymes that regulate the synaptic levels of the excitatory neurotransmitter ATP and provide ADP for the further ecto-nucleotidase-mediated production of the inhibitory neuromodulator adenosine. The present results show that low concentrations (IC50 = 4 microM) of the lipid peroxidation product 4-hydroxynonenal (HNE) inhibited up to about 80% of the ecto-ATPase activity of SPM purified from rat brain cerebral cortex. In contrast, low concentrations of HNE did not inhibit the activity of the "intracellular"-facing Na+, K+, Mg2+-ATPase. In addition, the inhibition of SPM ecto-ATPase activity by HNE was largely irreversible and pH-dependent. Furthermore, structure-activity studies demonstrate that inhibition was dependent on the presence of the reactive functional groups of HNE. These findings suggest that HNE selectively inhibits SPM ecto-ATPase activity by a mechanism that may involve the covalent modification of functionally-critical nucleophilic amino acids. It is proposed that inhibition of SPM ecto-ATPase activity could contribute to the mechanisms by which lipid peroxidation and HNE formation promote excitotoxicity.
Foley
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TD
Section on Neurochemistry, LCS, DICBR, National Institute on Alcohol Abuse and Alcoholism, NIH, Rockville, MD 20852, USA. timf@niaaa.nih.gov
D000241:Adenosine / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000447:Aldehydes / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D000447:Aldehydes; D004791:Enzyme Inhibitors; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D008274:Magnesium; C027576:4-hydroxy-2-nonenal; D000241:Adenosine; D002118:Calcium