Role of protein kinase C in microglia-induced neurotoxicity in mesencephalic cultures.
Microglial activation selectively kills certain neuron populations in mixed neuronal/glial cultures, which may prove useful for modeling neurodegenerative diseases such as Parkinson's disease. In mesencephalic mixed neuronal/glial cultures, microglial activation by zymosan A killed more dopaminergic neurons, assessed by [3H]dopamine uptake and by counting tyrosine hydroxylase-immunoreactive neuron number, than did microglial activation by lipopolysaccharide (LPS). The additional toxicity of zymosan resulted from microglial protein kinase C (PKC) activation. Both zymosan and PMA, but not LPS, activated PKC in enriched microglial preparations. In the mixed neuronal/glial cultures, activation of PKC by phorbol myristate acetate (PMA) increased LPS-induced nitric oxide (NO; by nitrite measurements), but not zymosan-induced NO production, and increased LPS-induced dopaminergic neurotoxicity, but not zymosan-induced dopaminergic neurotoxicity. Additive effects of PMA and LPS, similar to zymosan effects alone, reflected activation of distinct neurotoxic pathways in the microglia. The NO synthase inhibitor N-nitro-L-arginine methyl ester (NAME) totally blocked the neurotoxicity of LPS, and partially blocked zymosan-induced neurotoxicity; NAME did not block the PKC component of neurotoxicity. In addition to stimulating NO production as effectively as LPS, zymosan also activates microglial PKC and associated non-NO-mediated neurotoxic pathways that may be important in human neurodegenerative diseases. Since the role of NO in human microglia-induced neurotoxicity is controversial, zymosan may prove more useful than LPS as a microglial activator in the rodent mixed neuronal/glial culture model.
McMillian
M K
MK
Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Helsinki, Finland.
Vainio
P J
PJ
Tuominen
R K
RK
D000818:Animals; D002478:Cells, Cultured / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008636:Mesencephalon / Q000187:drug effects*; D017628:Microglia / Q000187:drug effects*; D011493:Protein Kinase C / Q000494:pharmacology*; D051381:Rats; D015054:Zymosan / Q000494:pharmacology*
D008070:Lipopolysaccharides; D015054:Zymosan; D011493:Protein Kinase C