S-Nitrosoglutathione formation at gastric pH is augmented by ascorbic acid and by the antioxidant vitamin complex, Resiston

Abstract

Context. Exogenous nitrogen oxides must made bioavailable to sustain normal physiology because nitric oxide synthase (NOS) deficient mice are viable. In the stomach, S-nitrosoglutathione (GSNO) is formed from ingested nitrite and high levels airway glutathione (GSH) that are cleared and swallowed. However, gastric GSNO may be broken down by nutrients like ascorbic acid (AA) before it is absorbed. Objective. Study the effect of AA on GSNO formation and stability. Materials and methods. GSH and nitrite were reacted with or without 5 mM AA or Resiston (5 mM AA with retinoic acid and α-tocopherol). GSNO was measured by reduction/chemiluminescence and HPLC. AA and reduced thiols were measured colorimetrically. O-nitrosoascorbate and AA were measured by gas chromatography-mass spectrometry (GC-MS). Results. GSNO was formed in saline and gastric samples (pH ~4.5) from physiological levels of GSH and nitrite. Neither AA nor Resiston decreased [GSNO] at pH > 3; rather, they increased [GSNO] (0.12 ± 0.19 μM without AA; 0.42 ± 0.35 μM with AA; and 0.43 ± 0.23 μM with Resiston; n = 4 each; p ≤ 0.05). However, AA compounds decreased [GSNO] at lower pH and with incubation > 1 hr. Mechanistically, AA, but not dehydroascorbate, increased GSNO formation; and the O-nitrosoascorbate intermediate was formed. Conclusion. AA, with or without other antioxidants, did not deplete GSNO formed from physiological levels of GSH and nitrite at pH > 3. In fact, it favored GSNO formation, likely through O-nitrosoascorbate. Gastric GSNO could be a NOS-independent source of bioavailable nitrogen oxides.

Cyclic compression increases F508 Del CFTR expression in ciliated human airway epithelium

“…Subjects were nonsmoking volunteers, 20 -60 yr old, with no pulmonary disease. Assays were performed in the morning after an overnight fast to prevent both 1) gastric nitrite conversion to NO (40,59), possibly compressed from the stomach into the exhaled air by the vest; and 2) an airwayreducing environment that would deplete NOx (40).…”

“…Immunoblot studies of eNOS Ϫ/Ϫ mice. eNOS Ϫ/Ϫ and background (C57Bl6) lungs were isolated as described previously (59). Tissue was homogenized in CFTR lysis buffer [100 mM NaCl, 50 mM NaF, 50 mM Tris•HCl, pH 7.5, 1% NP-40, 0.25% sodium deoxycholate, 1 mM EDTA, 1 mM EGTA, and protease inhibitor cocktail set III (Calbiochem)] and immunoblotted for CFTR as described above.…”

“…3C; Table 1: ALI 2). Second, we used the capacitance-based immunosensor (31,55) coupled with an anti-S-nitrosocysteine (CSNO) antibody (59) to measure the apical S-nitrosothiol signal (sensor placed in fluid from the apex, adjacent to the eNOS localization; Fig. 3B).…”

Optimization of Conditions for the Activation of Xanthine Oxidase and the Formation of Nitric Oxide in Fresh Sheep Milk

“…However ascorbic acid decomposes S-nitrosocysteine [28] and, therefore, we used L-cysteine as the protector against the oxidation of the cofactor in the active center of XO localized in MFGM. Thus, in our experiments L-cysteine was used for double purposes: as the protector of enzyme Mo-co against the oxidation during heat treatment of milk and as a reagent for S-nitrosothiol formation.…”

An Update on Thiol Signaling: S-Nitrosothiols, Hydrogen Sulfide and a Putative Role for Thionitrous Acid

“…Note that the GSNO breakdown product, S-nitroso-L-cysteine (L-CSNO), is increasingly appreciated as a stereoselective signaling molecule. L-CSNO was originally considered an endothelium derived relaxing factor (EDRF) [43][44][45][46]. Lewis, Bates and others observed that the L-isomers of CSNO and related S-nitrosothiols were substantially more active than the D-isomers, though they evolve NO equally [47][48][49].…”