CALCIUM-SENSITIVE CYTOSOLIC PHOSPHOLIPASE A(2) (CPLA(2)) IS EXPRESSED IN HUMAN BRAIN ASTROCYTES

Calcium-sensitive cytosolic phospholipase A(2) (cPLA(2)) is responsible for receptor-mediated liberation of arachidonic acid, and thus plays an important role in the initiation of the inflammatory lipid-mediator cascade generating eicosanoids and platelet-activating factor. In this study we have investigated the cellular distribution of cPLA(2) in brain using a monoclonal antibody raised against cPLA(2) to immunostain tissue sections of human cerebral cortex. We have localized cPLA(2) in astrocytes of the gray matter. Colocalization with glial fibrillary acidic protein (GFAP) confirmed that cPLA(2) is associated predominantly with protoplasmic astrocytes. Astrocytes of the white matter, on the other hand, were not immunoreactive. In experiments using different human astrocytoma cell lines we found that cPLA(2) can be immunochemically localized in UC-11 MG cells, but cannot be detected in U-373 MG cells. This finding is consistent with the observation that cPLA(2) mRNA as well as cPLA(2) enzymatic activity can be readily measured in UC-11 MG astrocytoma cells, yet cannot be detected in U-373 MG cells. Our data suggest that the astrocyte is a primary source of cPLA(2) in the brain and provide further evidence for the importance of this cell type in inflammatory processes in the brain.