New Insights into the Anti-Inflammatory and Antioxidant Properties of Nitrated Phospholipids

Nitro-fatty acids (NO₂ -FA) have been widely studied with regard to their identification, structural characterization, and biological actions. NO₂ -FA could also be present endogenously esterified to phospholipids (PL), and NO₂ -PL were already detected in cardiac mitochondria from diabetic rats and cardiomyoblasts subjected to starvation. However, the biological actions of NO₂ -PL have been overlooked. In this study, we evaluate the antioxidant and anti-inflammatory potential of the nitrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) formed in vitro by incubation with NO₂ BF₄ , in a well-recognized mimetic model of nitroxidative stress. Nitrated POPC showed anti-radical ability to reduce both 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^• ) (IC₂₀ = 225 ± 4 μg/mL; Trolox equivalent (TE) = 86 ± 6 μmol Trolox/g lipid) and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radical cation (ABTS^•+ ) (IC₅₀ = 124 ± 2 μg/mL; TE = 152 ± 9 μmol Trolox/g lipid). Also, higher lag times were achieved in oxygen radical absorbance capacity (ORAC) assay for nitrated POPC, indicating a faster reaction with oxygen-derived radicals (TE = 1.03 ± 0.22 and TE = 1.30 ± 0.16 mmol Trolox/g lipid for nonmodified and nitrated POPC, respectively). Nitrated POPC showed the ability to inhibit lipid oxidation induced by the hydroxyl radical generated under Fenton reaction conditions, monitored by electrospray ionization (ESI) mass spectrometry (MS) using phosphatidylcholine (PtdCho) liposomes as a model of cell membrane. Nitrated POPC showed anti-inflammatory potential, as assessed by the inhibition of inducible nitric oxide synthase (iNOS) expression in RAW 264.7 macrophages activated by the Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) in a well-described in vitro model of inflammation. Altogether, this study provides new clues regarding the antioxidant and anti-inflammatory potential of nitrated POPC, which should be explored in depth.