Abstract 654: Paraoxonase 2 Protects Against Endotoxin-Mediated Inflammation
Introduction. Subclinical endotoxemia is an important source of vascular inflammation and constitutes a strong risk factor for the development of atherosclerosis. Paraoxonase 2 (PON2) is a ubiquitously expressed enzyme that has been implicated in inflammatory diseases including atherosclerosis. We have recently shown that PON2 deficiency caused a greater than 2.7 fold increase in diet-induced atherosclerotic lesion in mice. The objective of the present study is to determine the role of PON2 in endotoxin-mediated cytokine production and toxicity using PON2 deficient mice.
Methods and results. PON2 deficient mice were significantly more susceptible to endotoxin (5 mg/kg) mediated toxicity compared to wild-type C57BL/6J mice (n=5, hazard ratio of 3.46; p<0.05). Macrophage from PON2 deficient mice were more sensitive to endotoxin challenge as evident by enhanced intracellular levels of oxidative stress and elevated expression of both TNFα (~200%, p < 0.05) and IL-1β (~150%, p < 0.05) compared to macrophages from control mice. Preincubation of endotoxin (10 ng/mL) with purified mouse PON2 (7 μg/mL) resulted in a significant (55.5%, p<0.05) decrease in endotoxin-mediated TNFα induction in J774 mouse macrophages. In contrast, preincubation with heat-inactivated (100°C for 15 minutes) mouse PON2 did not affect cytokine induction suggesting that PON2 activity is required for endotoxin inactivation.
Conclusion. The absence of PON2 results in an increased inflammatory response both ex vivo and in vivo upon endotoxin challenge. Increased susceptibility of PON2 deficient mice to endotoxin challenge reflects this exacerbated inflammatory response. Our findings suggest that PON2 may play a novel role in mediating neutralization of inflammatory properties of endotoxins.