Sera and organs were collected after 30 days. in plasma by high-density lipoprotein and its major function is usually to prevent oxidation of low-density lipoprotein [15]. In primary APS, PON activity is usually reduced and correlated inversely with aCL titres and directly with the total antioxidant capacity of plasma [16]. Decreased PON activity, with increased oxidative stress and reduction of NO, may be involved in the early phases of APS. To further evaluate the association between aCL antibodies and oxidative stress for 1 h, using 10 kDa molecular weight filters (Ultrafree-MC; Millipore). Only clear and colourless filtrates were tested. The assay NXY-059 (Cerovive) was performed in a standard flat-bottomed 96-well polystyrene microtitre plate, containing 50 always <0.01). Mice positive for murine IgG aalways <0.01) It should be noted that, in the case of superoxide quenching, reduced superoxide quenching is reflected by values of plasma TAC. All other groups had comparable levels. NO and nitrotyrosine NO (sum of nitrate and nitrite) was decreased in the Is usually4 group (human IgG aCL) when compared with the control groups ([25, NXY-059 (Cerovive) 30], its elevation may indicate previous elevated endothelial NO production induced by aCL. In an oxidative environment NO is usually shifted towards peroxynitrite formation, the latter inducing down-regulation of iNOS. If NO was not generated at all, there would not be any measurable peroxynitrite. On the other hand, down-regulation of iNOS expression may follow a period of increased activity, as reported, but not in autoimmune diseases [31]. The expression of iNOS and eNOS is usually controlled by different feedback mechanisms, the most important of which relates to NO itself [32]. Increased local levels of NO down-regulate iNOS by inhibiting the transcriptional factor NXY-059 (Cerovive) NF-in macrophages and endothelial cells [33], causing lowered NO production HNRNPA1L2 [34, 35]. A by-product of lipid peroxidation, 4-hydroxynonenal, inhibits NF-activation and consequent iNOS expression [36], whereas IgG aCL induces NF-in endothelial cells [37]. An alternative explanation would be that in the face of iNOS down-regulation eNOS still provides a source of NO to scavenge superoxide. In conclusion, we replicated in a mouse model our findings from APS patients [16]. Whereas in humans it is difficult to state when these processes begin, in the mouse model they appear as early as 30 days. NXY-059 (Cerovive) For this very reason we could not detect any (micro)thrombosis or vascular damage. A diet enriched in cholesterol would have been necessary to favour the appearance of atherosclerotic changes in this short span of time, but increased oxidation induced by hypercholesterolaemia may have confounded our results and a second hit would have been required to induce thrombosis. Nevertheless, IgG aPL may induce in mice a sequence of decreased PON activity, enhanced peroxynitrite formation and inhibition of iNOS expression. This is the first report to show intimate relationships between oxidative/nitrosative pathways and IgG aPL; these could be explored in more suitable models to test their association with vascular manifestations of APS. ? Key messages This study shows an association between anticardiolipin antibodies, paraoxonase inhibition and a decrease in iNOS expression. These effects induce a pro-oxidant environment, which can explain in Rheumatology part the enhanced atherogenesis and thrombosis found in antiphospholipid syndrome. Footnotes The authors have declared no conflicts of interest..
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