The effect of TRAIL molecule on cell viability in in vitro beta cell culture

Imatinib prevents dexamethasone-induced pancreatic β-cell apoptosis via decreased TRAIL and DR5

Prolonged administration of dexamethasone, a potent anti-inflammatory drug, can lead to steroid-induced diabetes. Imatinib, a medication commonly prescribed for chronic myeloid leukemia (CML), has been shown to improve diabetes in CML patients. Our recent study demonstrated that dexamethasone induces pancreatic β-cell apoptosis by upregulating the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptor, death receptor 5 (DR5). We hypothesized that imatinib may protect against dexamethasone-induced pancreatic β-cell apoptosis by reducing the expression of TRAIL and DR5, thereby favorably modulating downstream effectors in apoptotic pathways. We test this hypothesis by assessing the effects of imatinib on dexamethasone-induced apoptosis in rat insulinoma cell line cells. As anticipated, dexamethasone treatment led to increased TRAIL and DR5 expression, as well as an elevation in superoxide production. Conversely, expression of the TRAIL decoy receptor (DcR1) was decreased. Moreover, key effectors in the extrinsic and intrinsic apoptosis pathways, such as B-cell lymphoma 2 (BCL-2) associated X (BAX), nuclear factor kappa B (NF-κb), P73, caspase 8, and caspase 9, were upregulated, while the antiapoptotic protein BCL-2 was downregulated. Interestingly and importantly, imatinib at a concentration of 10 µM reversed the effect of dexamethasone on TRAIL, DR5, DcR1, superoxide production, BAX, BCL-2, NF-κB, P73, caspase 3, caspase 8, and caspase 9. Similar effects of imatinib on dexamethasone-induced TRAIL and DR5 expression were also observed in isolated mouse islets. Taken together, our findings suggest that imatinib protects against dexamethasone-induced pancreatic β-cell apoptosis by reducing TRAIL and DR5 expression and modulating downstream effectors in the extrinsic and intrinsic apoptosis pathways.

Treatment with recombinant tumor necrosis factor-related apoptosis-inducing ligand alleviates the severity of streptozotocin-induced diabetes

OBJECTIVE

To evaluate the potential therapeutic effect of recombinant human tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) treatment in a model of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Recombinant TRAIL was added in vitro to primary human and mouse peripheral blood mononuclear cells (PBMCs) and isolated human islets to evaluate the expression of the immunoregulatory gene SOCS1. Diabetes was induced by five consecutive daily injections of low-concentration (50 mg/kg) streptozotocin (STZ) in C57 black mice (n = 24). A group of these mice (n = 12) was co-injected with recombinant TRAIL (20 microg/day) for 5 days, and the diabetic status (glycemia and body weight) was followed over time. After 6 weeks, circulating levels of insulin, TNF-alpha, and osteoprotegerin (OPG) were measured, and animals were killed to perform the histological analysis of the pancreas.

RESULTS

The in vitro exposure of both PBMCs and human islets to recombinant TRAIL significantly upregulated the expression of SOCS1. With respect to STZ-treated animals, mice co-injected with STZ+TRAIL were characterized by 1) lower levels of hyperglycemia, 2) higher levels of body weight and insulinemia, 3) a partial preservation of pancreatic islets with normal morphology, and 4) a lower expression of both systemic (TNF-alpha and OPG) and pancreatic (vascular cell adhesion molecule [VCAM]-1) inflammatory markers.

CONCLUSIONS

Overall, these data demonstrate that the administration of recombinant TRAIL ameliorates the severity of STZ-induced type 1 diabetes, and this effect was accompanied by the upregulation of SOCS1 expression.