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Introduction: Isoprostanes are the products of free radical oxidation of arachidonic acid bound to phospholipids. Their hydrolysis from phospholipids is thought to be catalysed by phospholipases such as the secretory phospholipase A2 (sPLA2) and the platelet activating factor acetylhydrolase (PAF-AH), also known as lipoprotein-associated phospholipase A2. Therefore, our objective was to investigate the association between sPLA2 and PAF-AH activity and the urinary excretion of 8-iso-prostaglandin F2α (8-iso-PGF2α). Methods: We conducted a case-control study with 12 healthy controls and 24 hypercholesterolemic patients naïve to lipid-lowering therapy that were randomised to atorvastatin 40mg or placebo for 6 weeks. The 8-iso-PGF2α urinary excretion, PAF-AH and sPLA2 activities were measured at baseline and at endpoint. The healthy controls served as reference for baseline measurements. Urinary excretion of 8-iso-PGF2α was measured by gas chromatography-tandem mass spectrometry. PAF-AH and sPLA2 activity were measured by means of two commercially available enzyme activity assays. Results: 8-iso-PGF2α urinary excretion, PAF-AH and sPLA2 activity were similar in the three groups at baseline. No association could be observed between PAF-AH or sPLA2 activity and 8-iso-PGF2α at baseline. At endpoint, atorvastatin treatment decreased total cholesterol (mean 182.17, standard deviation [31.52] vs. 319.75 [60.77] mg/dL at baseline, P=0.002), low-density lipoprotein (102.75 [31.47] vs. 230.50 [54.13] mg/dL, P=0.002) and triglycerides (86.50 [32.53] vs. 151.83 [70.23] mg/dL, P=0.003) but had no significant effect on high-density lipoprotein (62.25 [11.79] vs. 59.17 [11.57] mg/dL, P=0.099). PAF-AH activity was significantly lowered in the atorvastatin group (10.85 [2.60] vs. 16.12 [2.79] nmol/min/mL, P=0.002) compared to the placebo group (17.33 [1.52] vs. 16.65 [2.01] nmol/min/mL, P=0.155), while 8-iso-PGF2α urinary excretion levels were unchanged in both the treated (291.10 [108.33] vs. 257.31 [101.76] pmol/mmol creatinine at baseline, P=0.071) and placebo groups (278.76 [99.83], vs. 238.73 [110.44] pmol/mmol creatinine, P=0.071) as well as sPLA2 activity (4.45 [0.83] vs. 4.12 [1.14] nmol/min/mL, P=0.398 and 5.25 [2.06] vs. 4.35 [0.61] nmol/min/mL, P=0.158 respectively). Conclusion: Our results exclude a role of PAF-AH in the liberation of 8-iso-PGF2a from phospholipids. The major enzyme involved in the liberation of 8-iso-PGF2a remains to be determined.
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J. Vasc. Biol. 42, Sup:2 (2005) pp121-122