Lysophosphatidylcholine (LysoPC) is a phospholipid found in abundance in oxidised LDL. Studies have shown that LysoPC can inhibit endothelium-dependent relaxation in isolated vessels from human and animal models. To date human studies have been limited to larger vessels such as the umbilical artery, hence the aim of this study was to determine the effect of LysoPC on acetylcholine-induced relaxation (ACh, 0.1-10 000 nM) in human small resistance arteries.
Human subcutaneous arteries were collected from three patients (2 females, 1 male, ages 64 ± 13 years, mean ± S.E.M.) undergoing elective surgery. All subjects gave written, informed consent to the study which was approved by the Local Medical Research Ethics Committee. Isolated arteries (160.2 ± 6.8 µm) were mounted on a wire myograph, where changes in tension were recorded. The vasorelaxation to ACh was assessed in pre-contracted arteries (noradrenaline, 2-4 µM) before and after incubation with LysoPC (20 µM, 40 min).
Prior to LysoPC treatment all vessels relaxed to ACh in a concentration-dependent manner (EC50 18.7 ± 9.4 nM, maximum relaxation 82.9 ± 1.7 % of the maximum noradrenaline response). After treatment with LysoPC, the relaxation to ACh was again concentration dependent, but the maximum relaxation was reduced in all cases from 82.9 ± 1.7 to 38.0 ± 7.4 % (P < 0.05, Student’s paired t test).
These results clearly show that LysoPC inhibits acetylcholine-induced vasodilatation in human small resistance arteries, suggesting that this phospholipid is causing endothelial dysfunction.