Oxidative modification of HDLs (high-density lipoproteins) by MPO (myeloperoxidase) compromises its anti-atherogenic properties, which may contribute to the development of atherosclerosis. Although it has been established that HOCl (hypochlorous acid) produced by MPO targets apoA-I (apolipoprotein A-I), the major apolipoprotein of HDLs, the role of the other major oxidant generated by MPO, HOSCN (hypothiocyanous acid), in the generation of dysfunctional HDLs has not been examined. In the present study, we characterize the structural and functional modifications of lipid-free apoA-I and rHDL (reconstituted discoidal HDL) containing apoA-I complexed with phospholipid, induced by HOSCN and its decomposition product, OCN- (cyanate). Treatment of apoA-I with HOSCN resulted in the oxidation of tryptophan residues, whereas OCN- induced carbamylation of lysine residues to yield homocitrulline. Tryptophan residues were more readily oxidized on apoA-I contained in rHDLs. Exposure of lipid-free apoA-I to HOSCN and OCN- significantly reduced the extent of cholesterol efflux from cholesterol-loaded macrophages when compared with unmodified apoA-I. In contrast, HOSCN did not affect the anti-inflammatory properties of rHDL. The ability of HOSCN to impair apoA-I-mediated cholesterol efflux may contribute to the development of atherosclerosis, particularly in smokers who have high plasma levels of SCN- (thiocyanate).

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The molecular mechanisms that suppress Th1 immune responses in pregnancy are unknown. We assessed the expression of the Th1 cytokine transcription factor T-bet. We isolated PBMC and T cells from non-pregnant and pregnant women and demonstrated that T-bet is specifically down-regulated in pregnancy under basal and stimulated conditions. Low levels of T-bet protein were detected in the nuclear fraction of unstimulated PBMC from non-pregnant, but not pregnant women. Nuclear levels of T-bet increased in response to PMA/ionomycin in PBMC from non-pregnant, but not pregnant women. T-bet expression was greater in whole cell lysates of stimulated CD3 + T cells from non-pregnant relative to pregnant women. NF-jB is specifically downregulated in T cells in pregnant women, resulting in suppressed expression of Th1 cytokines IL-2, IFN-c and TNF-a. In this study, down-regulation of NF-jB also resulted in diminished expression of T-bet. PMA induces NF-jB translocation, T-bet expression and IL-2, IFN-c and TNF-a production. Conversely, pre-incubation with SN50, and NF-jB oligodeoxyribonucleotide decoys suppressed PMA-induced NF-jB translocation and gene transcription, respectively, resulting in diminished T-bet expression and Th1 cytokine production. Therefore, maintenance of the cytokine environment for pregnancy success is mediated via strict regulation of Th1 immune responses, more specifically through control of NF-jB and T-bet transcription.

Background: Regulated suppression of maternal Th1 immunity is necessary for normal pregnancy since inappropriate Th1 responses results in increased pregnancy loss and complications including intrauterine growth restriction (IUGR). We have shown that suppression of the p65 subunit of NF-κB in maternal T-cells underlies this change in T-cell responses. This study aimed to determine mechanism(s) that control p65 suppression.