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

Calcium-sensitive cytosolic phospholipase A(2) (cPLA(2)) is responsibl e for receptor-mediated liberation of arachidonic acid, and thus plays an important role in the initiation of the inflammatory lipid-mediato r cascade generating eicosanoids and platelet-activating factor. In th is study we have investigated the cellular distribution of cPLA(2) in brain using a monoclonal antibody raised against cPLA(2) to immunostai n 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 predominan tly with protoplasmic astrocytes. Astrocytes of the white matter, on t he other hand, were not immunoreactive. In experiments using different human astrocytoma cell lines we found that cPLA(2) can be immunochemi cally 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) mR NA 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. Ou r data suggest that the astrocyte is a primary source of cPLA(2) in th e brain and provide further evidence for the importance of this cell t ype in inflammatory processes in the brain.