l-Cysteine Efflux in Erythrocytes As A Function of Human Age: Correlation with Reduced Glutathione and Total Anti-Oxidant Potential

Abstract

Thiol compounds such as cysteine (Cys) and reduced glutathione (GSH) play an important role in human aging and age-related diseases. In erythrocytes, GSH is synthesized by glutamic acid, cysteine, and glycine, but the rate of GSH synthesis is determined only by the availability of L-cysteine. Cysteine supplementation has been shown to ameliorate several parameters that are known to degenerate during human aging. We have studied L-cysteine efflux in vitro in human erythrocytes as a function of age by suspending cells in solution containing 10 mM L-cysteine for uptake; later cells were re-suspended in phosphate-buffered saline (PBS)-glucose to allow efflux. Change in the free sulfhydryl (-SH) concentration was then measured to calculate the rate of efflux. The GSH/oxidized glutathione (GSSG) ratio was taken as a control to study the oxidation/reduction state of the erythrocyte. The total anti-oxidant potential of plasma was measured in terms of ferric reducing ability of plasma (FRAP) values. We have shown a significant (p<0.0001) decline in the efflux of L-cysteine in erythrocytes during human aging, and the GSH/GSSG ratio decreases as a function of human age. The decline in L-cysteine efflux during aging correlates with the decrease in GSH and the FRAP value. This finding may help to explain the shift in the redox status and low GSH concentration that might determine the rate of L-cysteine efflux observed in erythrocytes and an important factor in the development of oxidative stress in erythrocytes during aging.

Red blood cells in hemorrhagic shock: a critical role for glutaminolysis in fueling alanine transamination in rats

“…Even though only steadystate metabolism was monitored with respect to this pathway and future glucose tracing experiments may be necessary to further confirm these observations, no significant changes were observed in shock animals with respect to ribose phosphate (and isobaric pentose phosphate compounds) in common to sham animals, whereas significant decreases in pentose phosphate pathway intermediates were noted (eg, 6-phosphogluconate, erythrose phosphate, and sedoheptulose phosphate). Consistently, cysteine accumulation (a marker of RBC aging in vivo 54,55 ) was here observed in hemorrhaged rats.…”

Age-related changes in erythrocyte membrane sulfhydryl groups and β-D-glucuronidase activity

“…Oxidative modification of erythrocyte membrane -SH groups and β-D-glucuronidase activity is very significant in view of the important role of these components in transport, enzyme activity, membrane fluidity and integrity. In fact, the results of this study are in agreement with our previous reports on the transport functions across erythrocyte membranes, which are affected during human aging [24][25][26].…”

Effect of Copper on l-Cysteine/l-Cystine Influx in Normal Human Erythrocytes and Erythrocytes of Wilson’s Disease

“…Erythrocyte Lcysteine influx was measured by the method of Yildiz et al using 10 mM L-cysteine hydrochloride [20]. This concentration of L-cysteine hydrochloride was also used by Rizvi and Maurya [13] and Kumar and Maurya [21]. RBC L-cysteine influx was expressed as lM/gm Hb/Hr.…”