Clinical analysis by proton spin-echo NMR. 2. Oxidation of intracellular glutathione as a consequence of penicillamine therapy in rheumatoid arthritis

Abstract

Spin echo NMR analysis is used to monitor the effect of penicillamine on intact erythrocytes obtained from patients suffering from rheumatoid arthritis during a 12-week period of therapy. The results are compared to the previously reported in vitro effects of the compound (McKay, C. N. N.; et al. Biochim. Biophys. Acta 1986, 888, 30-35). At clinical assessment at week 12, the 20 patients were divided into responder and nonresponder groups. The intracellular glutathione in the responder group is more oxidized (P less than 0.01) than in the nonresponder group. A retrospective analysis of the two patient groups at the initial assessment following the commencement of therapy indicated that in the nonresponder group intracellular glutathione was significantly more reduced (P less than 0.02) than in the responder group. It is postulated that penicillamine stimulates cellular defense against the oxidation of the cell membrane at the expense of cytosolic glutathione. This initial study suggests that spin-echo NMR analysis of erythrocyte glutathione can act as an early indicator of a clinical response to penicillamine therapy.

Alteration of the erythrocyte glutathione redox balance by N‐acetylcysteine, captopril and exogenous glutathione

“…It has been suggested that their beneficial action is due to their ability to scavenge oxygen radicals [20], thus reducing the stress on the cell and resulting in less oxidation of glutathione which is also a radical scavenger. However, in this study it was found that captopril and NAC produced opposite effects on the glutathione pool, with NAC causing a shift to a more reduced state and captopril producing a more oxidised glutathione pool, similar to the effect of penicillamine [3]. Exogenous glutathione, which has previously been reported to stimulate the reduction of intracellular glutathione in a manner similar to NAC [22,23], was found to have no effect on the endogenous glutathione.…”

“…Oxidative stress is a facet of many disease processes such as chronic heart failure [1,2], rheumatoid arthritis [3] and Graves disease [4], and it has recently been implicated in AIDS [5,6]. Chronic heart failure is further complicated by reperfusion injury, where the rapid introduction of oxygen into the ischaemic region generates active oxidants and increases tissue damage [2,7,8].…”

“…The latter measurement is predominantly glutathione (-2 mM). Glutathione is a major naturally occurring antioxidant and hence the redox balance of endogenous glutathione can be used as an index of the stress on the erythrocyte [3,4]. Although glutathione responds to oxidative stress it needs to be supplemented [ 1 l] or stimulated [ 18,191 in chronic conditions.…”

“…Glutathione metabolism can be observed non-invasively in human erythrocytes using 'H spin echo NMR, as this method can measure both the total concentration of glutathione and the ratio of oxidized to reduced glutathione [3,24]. In the spin echo NMR spectrum of the erythrocyte there are 4 resonances assigned to glutathione (see Fig.…”

“…The ratio of the &cysteinyl resonance (g2) to the glutamyl resonance (gJ gives a measure of the glutathione oxidation-reduction status of the cell. If the g& ratio is high the glutathione is predominantly in the reduced form, whereas if the ratio is low the glutathione is mostly present as the disulphide [3,24]. 'H spin echo NMR can therefore be used to differentiate between alterations in glutathione concentration and alterations in redox balance.…”