Effect of KIOM-79 against mitochondrial damage induced by streptozotocin in pancreatic beta-cells

Effects of diazoxide on streptozotocin induced β cell damage via HSP70/HSP90/TLR4/AMPK signaling pathways

I investigated the effects of diazoxide, a mitochondrial potassium channel opener, on streptozotocin (STZ) induced pancreatic β cell damage via the HSP70/HSP90/TLR4/AMPK signaling pathways in vitro. I used the pancreatic β cell line, 1.1B4, to create four groups: control, STZ treated, diazoxide treated, STZ + diazoxide treated. The STZ treated cells were exposed to 20 µM STZ for 2 h with or without 100 µM diazoxide for 24 h. Total antioxidant status (TAS), total oxidant status (TOS), cell viability and mitochondrial membrane potential (MMP) were measured. Expression of ATP-sensitive potassium channel (K_ATP) subunits, heat shock protein-70 (HSP70), heat shock protein-90 (HSP90), toll-like receptor 4 (TLR4), AMP-activated protein kinase (AMPK) and some apoptotic proteins were detected using western blotting. Apoptosis was assessed using TUNEL staining. STZ increased TOS and OSI in the pancreatic β cells; however, diazoxide failed to improve oxidative stress. Also, STZ increased tunnel positive cells in the pancreatic β cells. Diazoxide decreased the tunnel positive cells in the STZ treated β cell. STZ decreased MMP; however, diazoxide did not normalize MMP in the STZ induced β cells. Diazoxide increased the HSP70:HSP90 protein expression ratio. STZ decreased expression of AMPK and subunits of K_ATP channel and increased the expression of caspase-3 and TLR4 protein; diazoxide normalized the expression of all proteins studied. K_ATP channel opening by diazoxide protects pancreatic β cells against STZ toxicity via HSP70/HSP90/TLR4/AMPK signaling.

Berberine, an isoquinoline alkaloid, inhibits streptozotocin-induced apoptosis in mouse pancreatic islets through down-regulating Bax/Bcl-2 gene expression ratio

Diabetes may cause apoptosis in pancreatic islets. Berberine is an isoquinoline alkaloid used for its pharmacological functions including anti-inflammation. However, the berberine effect on pancreatic islets is still not clear. This study is aimed at clarifying the protective mechanism in berberine against islet cell apoptosis. This study established in vitro experimental models using streptozotocin (STZ)-treated primary pancreatic islet cells from ICR mice to unravel the protective mechanism of berberine on islets. The Bax/Bcl-2 (pro-/anti-apoptotic) genes expression in the islets was determined using real-time quantitative polymerase chain reaction assay. The results showed that berberine administration at one time or before STZ-stimulation significantly (P<0.05) down-regulated the Bax/Bcl-2 genes expression ratio, compared to those in STZ-treatment alone group. Our results suggest that berberine's anti-apoptotic effect on pancreatic primary islets is through down-regulating the Bax/Bcl-2 genes expression ratio in both concurrent and preventive manners.