Anti-caspase-3 preconditioning increases proinsulin secretion and deteriorates posttransplant function of isolated human islets

Abstract

Human islet isolation is associated with adverse conditions inducing apoptosis and necrosis. The aim of the present study was to assess whether antiapoptotic preconditioning can improve in vitro and posttransplant function of isolated human islets. A dose-finding study demonstrated that 200 μmol/L of the caspase-3 inhibitor Ac-DEVD-CMK was most efficient to reduce the expression of activated caspase-3 in isolated human islets exposed to severe heat shock. Ac-DEVD-CMK-pretreated or sham-treated islets were transplanted into immunocompetent or immunodeficient diabetic mice and subjected to static glucose incubation to measure insulin and proinsulin secretion. Antiapoptotic pretreatment significantly deteriorated graft function resulting in elevated nonfasting serum glucose when compared to sham-treated islets transplanted into diabetic nude mice (p< 0.01) and into immunocompetent mice (p < 0.05). Ac-DEVD-CMK pretreatment did not significantly change basal and glucose-stimulated insulin release compared to sham-treated human islets but increased the proinsulin release at high glucose concentrations (20 mM) thus reducing the insulin-to-proinsulin ratio in preconditioned islets (p < 0.05). This study demonstrates that the caspase-3 inhibitor Ac-DEVD-CMK interferes with proinsulin conversion in preconditioned islets reducing their potency to cure diabetic mice. The mechanism behind this phenomenon is unclear so far but may be related to the ketone CMK linked to the Ac-DEVD molecule. Further studies are required to identify biocompatible caspase inhibitors suitable for islet preconditioning.

LRH-1 agonism favours an immune-islet dialogue which protects against diabetes mellitus

“…Two days after xenotransplantation, mice were treated with daily injections of BL001 or vehicle for 7 days. At this time point, rejection of the human islets is anticipated 25 , 26 . Consistent with the protective effect of BL001, grafts from BL001-treated mice showed greater numbers of beta cells than the controls (Fig.…”

The EndoC-βH1 cell line is a valid model of human beta cells and applicable for screenings to identify novel drug target candidates

“…The GSIS data obtained in this study were compared to all other studies reporting the amount of insulin secretion and intracellular content in EndoC-βH1 monolayer cultures [4] , [6] , [7] as well as to a range of data from human islets [14] , [15] , [16] , [17] , [18] , [19] ( Table 2 ). To do this comparison, we did three approximations regarding cell numbers in the various assay setups (for details please refer to Supplementary Materials and Methods ).…”

Optimization and Scale-up Isolation and Culture of Neonatal Porcine Islets: Potential for Clinical Application

“…The superior glucose response of NPIs isolated and cultured according to the scalable protocol compared to the standard protocol is likely due to the increased proportion of β-cells and insulin secretory capacity of NPIs isolated using the scalable protocol over the standard protocol. This enhanced function of NPIs isolated with the scalable protocol is potentially due to decreased β-cell apoptosis as a result of the short-term addition of the general CI (4–6,8,24,25). Pretreatment of human (4) or adult porcine (5) islets with caspase 3 inhibitors for 24–48 h by other groups show significant decreases in islet viability and function both in vivo and in vitro.…”