LYSOPHOSPHATIDIC ACID INDUCES NECROSIS AND APOPTOSIS IN HIPPOCAMPAL-NEURONS

A diverse body of evidence indicates a role for the lipid biomediator lysophosphatidic acid (LPA) in the CNS. This study identifies and char acterizes the induction of neuronal death by LPA. Treatment of culture d hippocampal neurons from embryonic rat brains with 50 mu M LPA resul ted in neuronal necrosis, as determined morphologically and by the rel ease of lactate dehydrogenase. A concentration of LPA as low as 10 mu M led to the release of lactate dehydrogenase. In contrast, treatment of neurons with 0.1 or 1.0 mu M LPA resulted in apoptosis, as determin ed by chromatin condensation. In addition, neuronal death induced by 1 mu M LPA was characterized as apoptotic on the basis of terminal dUTP nick end-labeling (TUNEL) staining, externalization of phosphatidylse rine, and protection against chromatin condensation, TUNEL staining, a nd phosphatidylserine externalization by treatment with N-benzyloxycar bonyl-Val-Ala-Asp-fluoromethyl ketone, a broad-spectrum inhibitor of c aspases, i.e., members of the interleukin-1 beta converting enzyme fam ily. Studies with antagonists of ionotropic glutamate receptors did no t indicate;a significant role-for these receptors in apoptosis induced by 1 mu M LPA. LPA (1 mu M) also induced a decrease in mitochondrial membrane potential. Moreover, pretreatment of neurons with cyclosporin A protected against the LPA-induced decrease in mitochondrial membran e potential and neuronal apoptosis. Thus, LPA, at pathophysiological l evels, can induce neuronal apoptosis and could thereby participate in neurodegenerative disorders.