Nitric oxide and the etiology of chronic fatigue syndrome: Giving credit where credit is due

Mechanistic studies on the reaction between cob(II)alamin and peroxynitrite: evidence for a dual role for cob(II)alamin as a scavenger of peroxynitrous acid and nitrogen dioxide

Peroxynitrite/peroxynitrous acid (ONOO(-)/ONOOH; pK(a(ONOOH)) =6.8) is implicated in multiple chronic inflammatory and neurodegenerative diseases. Both mammalian B(12)-dependent enzymes are inactivated under oxidative stress conditions. We report studies on the kinetics of the reaction between peroxynitrite/peroxynitrous acid and a major intracellular vitamin B(12) form, cob(II)alamin (Cbl(II)), using stopped-flow spectroscopy. The pH dependence of the reaction is consistent with peroxynitrous acid reacting directly with Cbl(II) to give cob(III)alamin (Cbl(III)) and (.)NO(2) , followed by a subsequent rapid reaction between (.)NO(2) and a second molecule of Cbl(II) to primarily form nitrocobalamin. In support of this mechanism, a Cbl(II)/ONOO(H) stoichiometry of 2:1 is observed at pH 7.35 and 12.0. The final major Cbl(III) product observed (nitrocobalamin or hydroxycobalamin) depends on the solution pH. Analysis of the reaction products in the presence of tyrosine-a well-established (.)NO(2) scavenger-reveals that Cbl(II) reacts with (.)NO(2) at least an order of magnitude faster than tyrosine itself. Given that protein-bound Cbl is accessible to small molecules, it is likely that enzyme-bound and free intracellular Cbl(II) molecules are rapidly oxidized to inactive Cbl(III) upon exposure to peroxynitrite or (.)NO(2).

Will vitamin D supplementation ameliorate diseases characterized by chronic inflammation and fatigue?

Chronic NF-κB activation has been supposed as a key event in chronic fatigue syndrome (CFS) and many other better-defined pro-inflammatory diseases. Knowledge about the impact of deficiency vitamin D on chronic NF-κB activation could open a new disease approach. Whereas NF-κB activation leads at first to a pro-inflammatory immune response, later on a vitamin D-dependent anti-inflammatory response ensues. Binding of the active vitamin D metabolite 1,25(OH)(2)D(3) to vitamin D receptor (VDR) yields a transcription factor which represses NF-κB activation, and additionally modulates and down-regulates adaptive, but enhances innate immune responses, and improves redox balance, thus counterbalancing inflammation on multiple levels. However, this built-in late counterbalance against inflammation works only when stores of calcium and 25(OH)D(3) are abundant. Therefore a connection between lowered vitamin D-metabolism and persistent NF-κB activation, augmented nitrosative-oxidative stress, redox imbalance, chronic inflammation, and concomitant fatigue can be postulated. In order to confirm this hypothesis, randomized controlled clinical studies about the clinical effects of supplementation of calcium and vitamin D(3) would be necessary in diseases characterized by persistent NF-κB activation and chronic inflammation and fatigue.