Mechanisms Underlying Neuronal Death Induced by Chromogranin A-activated Microglia

doi:10.1074/jbc.M009711200

Mechanisms Underlying Neuronal Death Induced by Chromogranin A-activated Microglia*

From the Unité INSERM U-338 de Biologie de la Communication Cellulaire, Centre de Neurochimie, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France

Abstract

The neurotoxic effects of activated microglia in neurodegenerative diseases are well established. We recently provided evidence that chromogranin A (CGA), a multifunctional protein localized in dystrophic neurites and in senile plaques, induces an activated phenotype and secretion of neurotoxins by rat microglia in culture. In the present study, we focused on the mechanisms underlying neuronal degeneration triggered by CGA-activated microglia. We found that neuronal death exhibits apoptotic features, characterized by the externalization of phosphatidylserine and the fragmentation of DNA. Microglial neurotoxins markedly stimulate the phosphorylation and activity of neuronal p38 mitogen-activated protein kinase and provoke the release of mitochondrial cytochrome c, which precedes apoptosis. Inhibition of p38 kinase with SB 203580 partially protects neurons from death induced by CGA-activated microglia. Furthermore, neurons are also protected by Fas-Fc, which antagonizes the interactions between the death receptor Fas and its ligand FasL and by cell-permeable peptides that inhibit caspases 8 and 3. Thus, CGA triggers the release of microglial neurotoxins that mobilize several death-signaling pathways in neurons. Our results further support the idea that CGA, which is up-regulated in many neuropathologies, represents a potent endogeneous inflammatory factor possibly responsible for neuronal degeneration.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: CNRS UPR-2356, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France. Tel.: 33 88 45 67 15; Fax: 33 88 60 16 64; E-mail: ciesielski-treska@ neurochem.u-strasbg.fr.
↵§ Present address: CNRS UPR-2356 Neurotransmission et Sécrétion Neuroendocrine, Centre de Neurochimie, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France.
Published, JBC Papers in Press, December 21, 2000, DOI 10.1074/jbc.M009711200
Abbreviations:

CGA

chromogranin A

DMEM

Dulbecco's modified Eagle's medium

sFasL

soluble Fas ligand

PI

propidium iodide

PBS

phosphate-buffered saline

MAP2

microtubule-associated protein 2

MAP kinase

mitogen-activated protein kinase

JNK

c-Jun N-terminal kinase

TUNEL

terminal dUTP nick-end labeling

CM

conditioned medium
- Received October 24, 2000.
- Revision received December 19, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.