PLD1 promotes reactive oxygen species production in vascular smooth muscle cells and injury-induced neointima formation

Phospholipase D (PLD) generates the signaling lipid phosphatidic acid (PA) and has been known to mediate proliferation signal in vascular smooth muscle cells (VSMCs). However, it remains unclear how PLD contributes to vascular diseases. VSMC proliferation directly contributes to the development and progression of cardiovascular disease, such as atherosclerosis and restenosis after angioplasty. Using the mouse carotid artery ligation model, we find that deletion of Pld1 gene inhibits neointima formation of the injuried blood vessels. PLD1 deficiency reduces the proliferation of VSMCs in both injured artery and primary cultures through the inhibition of ERK1/2 and AKT signals. Immunohistochemical staining of injured artery and flow cytometry analysis of VSMCs shows a reduction of the levels of reactive oxygen species (ROS) in Pld1−/− VSMCs. An increase of intracellular ROS by hydrogen peroxide stimulation restored the reduced activities of ERK and AKT in Pld1−/− VSMCs, whereas a reduction of ROS by N-acetyl-l-cysteine (NAC) scavenger lowered their activity in wild-type VSMCs. These results indicate that PLD1 plays a critical role in neointima, and that PLD1 mediates VSMC proliferation signal through promoting the production of ROS. Therefore, inhibition of PLD1 may be used as a therapeutic approach to suppress neointimal formation in atherosclerosis and restenosis after angioplasty.