Electrospray ionization mass spectrometry analyses of nuclear membrane phospholipid loss after reperfusion of ischemic myocardium

The role of nuclear membrane phospholipids as targets of phospholipases res ulting in the generation of nuclear signaling messengers has received atten tion. In the present study, we have exploited the utility of electrospray i onization mass spectrometry to determine the phospholipid content of nuclei isolated from perfused hearts. Rat heart nuclei contained choline glycerop hospholipids composed of palmitoyl and stearoyl residues at the sn-1 positi on with oleoyl, linoleoyl, and arachidonoyl residues at the sn-2 position, Diacyl molecular species were the predominant molecular subclass in the cho line glycerophospholipids, with the balance of the molecular species being plasmalogens, In the ethanolamine glycerophospholipid pool from rat heart n uclei approximately 50% of the molecular species were plasmalogens, which w ere enriched with arachidonic acid at the sn-2 position. A 50% loss of myoc ytic nuclear choline and ethanolamine glycerophospholipids was observed in hearts rendered globally ischemic for 15 min followed by 90 min of reperfus ion in comparisons with the content of these phospholipids in control perfu sed hearts. The loss of nuclear choline and ethanolamine glycerophospholipi ds during reperfusion of ischemic myocardium was partially reversed by the calcium-independent phospholipase A(2) (iPLA(2)) inhibitor bromoenol lacton e (BEL), suggesting that the loss of nuclear phospholipids during ischemia/ reperfusion is mediated, in part, by iPLA(2). Western blot analyses of isol ated nuclei from ischemic hearts demonstrated that iPLA(2) is translocated to the nucleus after myocardial ischemia. Taken together, these studies hav e demonstrated that nuclear phospholipid mass decreases least in part, phos pholipoiysis mediated by iPLA(2).