Given their role in female reproduction, the effects of progesterone on arginine and related amino acids, polyamines and NF-κB p65 activation were studied across the menstrual cycle. Arginine, ornithine and citrulline as well as putrescine, spermidine, spermine, and N-acetyl-putrescine were determined in plasma, NF-κB p65 activation in peripheral blood mononuclear cells and progesterone in serum of 28 women at early (T1) and late follicular (T2) and mid (T3) and late (T4) luteal phase. Arginine and related amino acids declined from T1 and T2 to T3 and T4, while progesterone increased. At T3, arginine, ornithine, and citrulline were inversely related with progesterone. Changes (ΔT3-T2) in arginine, ornithine, and citrulline were inversely related with changes (ΔT3-T2) in progesterone. Ornithine and citrulline were positively related with arginine, as were changes (ΔT3-T2) in ornithine and citrulline with changes (ΔT3-T2) in arginine. At T2, NF-κB p65 activation was positively related with arginine. Polyamines did not change and were not related to progesterone. All results described were significant at P < 0.001. This study for the first time provides data, at the plasma and PBMC level, supporting a proposed regulatory node of arginine and related amino acids, progesterone and NF-κB p65 at luteal phase of the menstrual cycle, aimed at successful preparation of pregnancy.

Oxidized phospholipids (OxPLs) are increasingly recognized as biologically active lipids involved in various pathologies. Both exposure to pathogenic factors and the efficacy of protective mechanisms are critical to disease development. In this study, we characterized an immunoassay that quantified the total capacity of the plasma to degrade or mask OxPLs, thereby preventing their interaction with cells and soluble proteins. OxLDL-coated plates were first incubated with human blood plasma or a control vehicle, followed by an ELISA using a monoclonal antibody specific to oxidized phosphatidylethanolamine. Pretreatment with the diluted blood plasma markedly inhibited mAb binding. The masking assay was optimized by evaluating the buffer composition, the compatibility with various anticoagulants, potential interfering compounds, the kinetic parameters, pre-analytical stability, statistical robustness, and intra- and inter-individual variability. We propose that this masking assay provides a simple immunological approach to assessing protective mechanisms against lipid peroxidation products. Establishing this robust and reproducible method is essential for conducting clinical association studies that explore masking activity as a potential biomarker of the predisposition to a broad range of lipid-peroxidation-related diseases.