Role of ERK1/2 activation and nNOS uncoupling on endothelial dysfunction induced by lysophosphatidylcholine

Abstract

Background and aimsLysophosphatidylcholine (LPC) – a main component of oxidized LDL - is involved in endothelial dysfunction that precedes atherosclerosis, with an increased superoxide anions and a reduced NO production via endothelial NO synthase (eNOS) uncoupling. However, there is no evidence about the mechanisms involved in neuronal NOS (nNOS) uncoupling. Extracellular signal-regulated kinase (ERK) is related to the control of NO production and inflammatory gene transcription activation in atherosclerosis. Our aim was to investigate the role of nNOS/ERK1/2 pathway on endothelial dysfunction induced by LPC, in mouse aorta and human endothelial cells. MethodsThoracic aorta from wild type mice was used to perform vascular reactivity studies in the presence or absence of LPC. Human endothelial cells were used to investigate the effect of LPC on expression of nNOS and his products NO and H2O2. ResultsLPC reduced acetylcholine (ACh)-induced vasodilation in mouse aorta (EmaxCT/LPC = ∼95 ± 2/62 ± 3%, p = 0.0004) and increased phenylephrine-induced vasoconstriction (EmaxCT/LPC = ∼4 ± 0,1/6 ± 0,1 mN/mm, p = 0.0002), with a reduction in NO (fluorescence intensityCT/LPC = 91 ± 3/62±2 × 103, p = 0.0002) and H2O2 (fluorescence intensityCT/LPC = ∼16 ± 0,8/10 ± 0,7 × 103, p = 0.0041) production evocated by ACh. An inhibition of nNOS by TRIM (EmaxCT/CT+TRIM = ∼93 ± 1/43 ± 3%, p = 0,0048; EmaxLPC/LPC+TRIM = ∼62 ± 3/65 ± 3%) or H2O2 degradation by catalase (EmaxCT/CT+cat = ∼93 ± 1/46 ± 2%, p < 0,001; EmaxLPC/LPC+cat = ∼62,8 ± 3,2/60,5 ± 4,7%) reduced the relaxation in the control but not in LPC group. PD98059, an ERK1/2 inhibitor, abolished the increase in vasoconstriction in LPC-treated vessels (EmaxLPC/LPC+PD = ∼6 ± 0,1/3 ± 0,1 mN/mm, p = 0.0001). LPC also reduced the dimer/monomer proportion and increased nNOSser852 phosphorylation. ConclusionsLPC induced nNOS uncoupling and nNOSSer852 phosphorylation, reduced NO and H2O2 production and improved superoxide production by modulating ERK1/2 activity in human and murine endothelial cells.