Gliclazide does not fully prevent 2-deoxy-D-ribose-induced oxidative damage because it does not restore glutathione content in a pancreatic β-cell line

System χc- overexpression prevents 2-deoxy-d-ribose-induced β-cell damage

Pancreatic β-cells are vulnerable to oxidative stress, which promotes β-cell failure in type 2 diabetes. System χ_c- is a sodium-independent, cystine/glutamate antiporter that mediates the exchange of extracellular l-cystine and intracellular l-glutamate. The import of l-cystine through this transporter is the rate-limiting step in the glutathione (GSH) biosynthesis pathway that plays a significant role in antioxidative defense. Previously, we reported that 2-deoxy-d-ribose (dRib) induces oxidative damage through GSH depletion in pancreatic β-cells. In the current study, we elucidated the mechanism underlying the oxidative stress-induced β-cell damage. We measured the intracellular l-[¹⁴C]cystine uptake, GSH content, reactive oxygen species (ROS) levels, cytotoxicity, and apoptosis in rat insulinoma cell line, RINm5F. Treatment of dRib decreased the intracellular l-[¹⁴C]cystine uptake and GSH content and increased the intracellular ROS levels, cytotoxicity, and apoptosis in a time- and dose-dependent manner. Conversely, 2-mercaptoethanol (2-ME), a cystine uptake enhancer, recovered the dRib-induced decrease in l-[¹⁴C]cystine uptake, GSH content, and cell viability in a Na⁺-independent manner. In the case of isolated islets, dRib dose-dependently decreased the intracellular l-[¹⁴C]cystine uptake and cell viability; however, dRib-induced cytotoxicity was completely recovered by adding N-acetyl cysteine (NAC). To confirm that system χ_c- mediates the oxidative stress-induced β-cell damage, we overexpressed xCT (the substrate-specific subunit of system χ_c-) using a lentiviral vector in RINm5F cells. Overexpression of xCT fully recovered the dRib-induced decrease in l-[¹⁴C]cystine uptake and GSH content and prevented the dRib-induced increase in ROS levels, cytotoxicity, and apoptosis. The overexpression of xCT showed a protective effect against dRib-induced oxidative damage in RINm5F cells. Our study showed that dRib depletes intracellular GSH content through inhibition of cystine transport via system χ_c- in β-cells.

Gliclazide

Gliclazide is a second-generation oral hypoglycemic drug used for the treatment of noninsulin-dependent diabetes mellitus. It belongs to the sulfonylurea class that stimulates insulin secretion from pancreatic β-cells by inhibiting ATP-dependent potassium channels. Gliclazide also possesses unique antioxidant properties and other beneficial hemobiological effects. This profile represents a comprehensive description of the physical properties, chemical synthesis, spectroscopic characterization (FTIR, ¹H NMR, ¹³C NMR, UV, and single-crystal X-ray), methods of analysis, pharmacological actions, and pharmacokinetic and pharmacodynamic properties of the title drug.

Intracellular glutathione production, but not protein glycation, underlies the protective effects of captopril against 2-deoxy-D-ribose-induced β-cell damage

Our previous study reported that both oxidative stress and protein glycation were the principal mechanisms underlying 2‑deoxy‑D‑ribose (dRib)‑induced pancreatic β‑cell damage. The aim of the present study was to investigate the effects of captopril on dRib‑induced damage in pancreatic β‑cells, as well as to determine the mechanisms underlying these effects. Treatment with dRib increased the levels of cytotoxicity, apoptosis, and intracellular reactive oxygen species in Syrian hamster insulinoma HIT‑T15 cells; however, pretreatment with captopril significantly inhibited the effects of dRib. The intracellular levels of reduced and oxidized glutathione were depleted following treatment with dRib; however, these levels were restored following HIT‑T15 cell treatment with captopril. In rat islets, dRib stimulation suppressed the mRNA expression levels of insulin, and pancreatic and duodenal homeobox 1, as well as insulin content; however, these effects were dose‑dependently reversed by treatment with captopril. Treatment with buthionine sulfoximine, an inhibitor of intracellular glutathione biosynthesis, inhibited the protective effects of captopril on dRib‑mediated glutathione depletion and cytotoxicity in HIT‑T15 cells. Following incubation with albumin, dRib increased the formation of dicarbonyl and advanced glycation end products. Treatment with captopril did not inhibit the dRib‑induced increase in production of dicarbonyl and advanced glycation end products. In conclusion, treatment with captopril reversed dRib‑induced oxidative damage and suppression of insulin expression in β‑cells. The mechanism underlying the protective effects of captopril may involve increased intracellular glutathione production, rather than protein glycation.