The salt stimulation property of serum paraoxonase (PON1) could be a valuable factor in evaluating the enzyme status in ischemic stroke: the role of activity-determined PON1 192Q/R phenotypes.

Variability in the activity and function of serum paraoxonase (PON1) as an antioxidant enzyme involved in vascular disease has been observed. In this study, we investigated the enzyme activity parameters, based on the 192Q/R polymorphism, using the salt stimulation property of PON1 as an important although neglected property. In total, 172 participants, including 90 control subjects and 82 patients with ischemic stroke were enrolled. Paraoxonase activity (para), arylesterase activity (aryl) and salt-stimulated paraoxonase activity (para-Na) were measured by spectrophotometric assays. The distribution of the 192Q/R phenotypes was determined using the dual substrate method. We observed that the para-percent (percentage stimulation of paraoxonase activity by NaCl) was significantly lower in the patients than in the controls, in both the QR+RR group (p=0.01) and QQ phenotypes (p=0.001). More than the other parameters, para-percent and para-degree (para-Na-para) are affected by ischemic stroke (p<0.001). In R-containing phenotypes, significant correlations were observed between both aryl and para, with age (r=-0.364, p=0.016; and r=-0.333, p=0.029, respectively). The salt stimulation properties of PON1 activity, particularly the parameters para-percent and para-degree, could be considered more important than the prevalent activities of the enzyme, and could be better applied for the assessment of PON1 status in ischemic stroke rather than the common enzyme activities.