Paraoxonase and platelet-activating factor acetylhydrolase activities in lipoproteins of beta-thalassemia/hemoglobin E patients.

Background: Iron-induced oxidative stress may be implicated in the alteration of the lipoprotein-associated antioxidant enzymes paraoxonase 1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH), leading to atherosclerosis-related vascular complication in patients with beta-thalassemia hemoglobin E (beta-thal/Hb E).

Methods: Plasma and lipoprotein enzyme activities of PON1 and PAF-AH were studied in 13 mild to moderate and 15 severe cases of beta-thal/Hb E in comparison with 15 normal subjects.

Results: PON1 activity was significantly reduced in association with oxidative stress in the patients. There were significant correlations between high-density lipoprotein (HDL)-PON1 activity and oxidative stress markers, including plasma levels of alpha-tocopherol (r=0.694 p<0.001) and the ratio of cholesteryl linoleate to cholesteryl oleate (CL/CO, r=0.662, p<0.001) in HDL. On the other hand, PAF-AH activity was markedly increased in patients by approximately two-fold and three- to four-fold in plasma and lipoproteins, respectively. Significant correlations of low-density lipoprotein (LDL) and HDL-PAF-AH activity with plasma iron, alpha-tocopherol and the CL/CO ratio were also demonstrated.

Conclusions: We suggest that impairment of PON1 activity may be directly caused by oxidative damage, while increased PAF-AH activity possibly results from oxidative stress-induced inflammatory response in beta-thal/Hb E patients.