CDP‐CHOLINE PARTLY RESTORES THE PHOSPHATIDYLCHOLINE LEVELS BY DIFFERENTIALLY AFFECTING SECRETORY PHOSPHOLIPASE A 2 IIA AND CTP‐PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE AFTER STROKE

Abstract

Phosphatidylcholine (PtdCho) is a major membrane phospholipid and its loss is sufficient in itself to induce cell death. PtdCho homeostasis is regulated by a balance between hydrolysis and synthesis. PtdCho is hydrolyzed by phospholipase A2 (PLA2), PtdCho-phospholipase C (PtdCho-PLC) and phospholipase D (PLD). PtdCho synthesis is rate-limited by CTP:phosphocholine cytidylyltransferase (CCT) that makes CDP-choline. The final step of PtdCho synthesis is catalyzed by CDP-choline: 1,2-diacylglycerol choline phosphotransferase (CPT). PtdCho synthesis in the brain is predominantly through the CDP-choline pathway. Transient middle cerebral artery occlusion (tMCAO) significantly increased secretory PLA2 (sPLA2) IIA mRNA and protein levels, PtdCho-PLC activity and PLD2 expression at 1 d reperfusion. CDP-choline treatment significantly attenuated sPLA2 mRNA and protein levels and PtdCho-PLC activity, but did not affect PLD2 expression. tMCAO also resulted in loss of CCT activity and protein that were partially restored by CDP-choline. No changes were observed in the cytosolic PLA2 or calcium-independent PLA2 protein levels after tMCAO. The up-regulation of phospholipases and loss of CCT collectively resulted in the loss of PtdCho and total phospholipids, which were partially restored by CDP-choline. CDP-choline treatment significantly attenuated the infarction volume by 55% ± 5 after stroke. TNF-α and IL-1α/β are up-regulated in the brain after stroke. TNF-α/IL-1 activate phospholipases and down-regulate CCT, thus increasing PtdCho hydrolysis and inhibiting PtdCho synthesis. Our studies integrate CDP-choline effects with cytokine biology and lipid metabolism in stroke. Support: NIH UW VA.