PLA, ACTIVITY REGULATES CA2-DEPENDENT CELLULAR PROLIFERATION( STORAGE)

The objective of this study is to determine the role of arachidonic ac id (AA) in cell proliferation by inhibiting AA synthetic enzyme phosph olipase A, (PLA,) and to determine its involvement in the role of the second messenger intracellular calcium (Ca2+). Methods used to determi ne the effects on proliferation of cell cultures of primary meningioma and astrocytoma U373-MG included treatment with micromolar concentrat ions of PLA(2) inhibitors 4-bromophenacylbromide and quinacrine. Effec ts of these drugs on proliferation were further investigated by the ap plication of concentrations that inhibit growth by 50% while antagoniz ing these agents with AA replacement. Free cytosolic Ca2+ was measured with the use of fluorescent dye Fura-a during PLA(2) agonist/antagoni st studies. These Ca2+ measurements were performed in the absence of e xtracellular Ca2+ to identify the contribution of intracellular Ca2+ s ources. PLA, inhibition resulted in decreased growth of cultured astro cytoma and meningioma cells in a dose-dependent manner in the micromol ar range. This inhibitory effect was antagonized by the addition of AA . PLA, inhibition caused an elevation of basal-cytosolic-free [Ca2+] w hile depleting internal Ca2+ stores, These Ca2+ changes were also anta gonized by the addition of Ak In conclusion, these results demonstrate that AA, a PLA(2) enzyme product, is involved in regulating the growt h rate of these cell types. The PLA(2) pathway also regulates the main tenance of the internal Ca2+ stores. Ca2+ is known to be a growth-rela ted intracellular second messenger. These results suggest that the gro wth regulatory functions of AA are mediated by Ca2+-dependent mechanis ms. (C) 1998 Academic Press.