Cystine
Cystine is two cysteine molecules joined by a disulphide bond, the form in which much of the cysteine outside cells is found. Cells take it in and split it back into cysteine to make glutathione.
Also called L-cystine.
Human cartilage cells grown without cystine in their medium lost glutathione and became more vulnerable to oxidant-driven death (Del Carlo 2003).
A major route in is the xc- transporter, which swaps cystine for glutamate; SLC7A11 is the part that carries cystine. In mouse cartilage cells under inflammatory stress, dihydrolipoic acid lessened the loss of glutathione, GPX4 and SLC7A11 (Chen 2026). Dihydrolipoic acid can also reduce cystine to cysteine outside the cell, so it enters by a different transporter (Han 1997).
Sources
- Carlo MD Jr, Loeser RF. Increased oxidative stress with aging reduces chondrocyte survival: correlation with intracellular glutathione levels. Arthritis Rheum 2003.
- Chen Y, Fang J, Zhou Z et al. Dihydrolipoic acid suppresses ferroptosis in chondrocytes to ameliorate the progression of osteoarthritis by modulating the FOXO1/TXNIP signaling pathway. Free Radic Biol Med 2026.
- Han D, Handelman G, Marcocci L et al. Lipoic acid increases de novo synthesis of cellular glutathione by improving cystine utilization. Biofactors 1997.
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