Effect of chronic ethanol exposure on mouse brain arachidonic acid specific phospholipase A2

The enzyme phospholipase A(2) (PLA(2)), which catalyzes the hydrolysis of an ester bond at the sn-2 position of 1,2-sn-diacylglycerols, has been suggested to play an important role in regulating cellular functions. Although ethanol (EtOH)-induced activation of PLA(2) activity was reported previously by us in mouse brain (Hungund et al., Neurochem Int 25: 321-325, 1994), its subcellular localization and biochemical properties have not been investigated. Therefore, in the present study, we examined the subcellular localization and characterization of EtOH-activated PLA(2) activity in mouse brain. The results indicated that EtOH treatment decreased the specific activity of PLA(2) for the first 48 hr, and then the activity increased and reached a peak level in both cytosol (1.6-fold) and membrane (1.7-fold) fractions at 96 hr of exposure; Specific activity was found to be higher in the membrane fraction than in the cytosol. Using differential density gradient centrifugation, subcellular localization of the membrane-associated PLA(2) revealed that most of the EtOH-activated PLA(2) specific activity was associated with the synaptic membrane (44%) followed by the nuclear membrane (13%). No significant increase in the PLA(2) specific activity of mitochondrial and microsomal membranes was observed. No activity was detected in the myelin membrane. PLA(2) specific activity of membranes from control and EtOH-exposed mouse brain exhibited preference for arachidonic acid over linoleic acid at the sn-2 position of glycero-3-phosphocholine (PC). No detectable PLA(2) specific activity was found when PC containing oleic acid at the sn-2 position was used as a substrate. The present results also indicated that the PLA(2) specific activity of membrane from control and EtOH exposed mouse brain was insensitive to dithiothreitol, strongly stimulated by Ca2+, enhanced by glycerol, and inhibited by the cytosolic PLA(2) (cPLA(2)) inhibitor methyl arachidonyl fluorophosphonate with an IC50 value of 3.33 mu M. In summary, results suggest that the properties of EtOH-activated PLA(2) activity found in mouse brain membrane fraction are similar to those of cPLA(2) found in variety of cells, including mammalian brain. (C) 1998 Elsevier Science Inc.