2122-P: System x(c)- Is a Key Molecule in Oxidative Stress-Induced ß-Cell Damage

Pancreatic β-cells are vulnerable to oxidative stress, which is related to β-cell failure in type 2 diabetes. System x(c)- is a sodium-independent cystine/glutamate antiporter that mediates the exchange of extracelluar L-cystine and intracellular L-glutamate. The import of L-cystine through this transporter is the limiting state of intracellular glutathione (GSH) synthesis that has a major role in defends against oxidative stress. Our previous study reported that 2-deoxy-D-ribose (dRib) induces oxidative damage through GSH depletion in pancreatic β-cells. The aim of the present study was to elucidate the mechanism underlying oxidative stress-induced β-cell damage. We measured intracellular L-[14C] cysteine uptake, GSH content and reactive oxygen species (ROS) levels, cytotoxicity and apoptosis in rat insulinoma cell line (RINm5F cells). Stimulation with dRib dose- and time-dependently decreased intracellular L-[14C] cystine uptake and GSH content and increased intracellular ROS levels, cytotoxicity and apoptosis. The addition of 2-mercaptoethanol (2-ME), a cystine uptake enhancer, sodium-independently recovered the dRib-induced decreases in L-[14C] cystine uptake, GSH content and cell viability. To determine clearly whether system x(c)- deficiency mediate the oxidative stress-induced β-cell damage, we overexpressed xCT, the substrate-specific subunit of the system x(c)-, by using a lentiviral vector in RINm5F cells. Overexpression of xCT fully recovered the dRib-induced decreases in L-[14C] cystine uptake and GSH content and prevented the dRib-induced ROS rises, cytotoxicity and apoptosis.

In summary, overexpression of xCT showed protective effects against oxidative damage in RINm5F cells. It suggests that system x(c)- deficiency play a critical role in oxidative stress-induced β-cell damage.