Adenoviral overexpression of interleukin-1 receptor antagonist protein increases β-cell replication in rat pancreatic islets

Abstract

The naturally occurring inhibitor of interleukin-1 (IL-1) action, interleukin-1 receptor antagonist protein (IRAP), binds to the type 1 IL-1 receptor but does not initiate IL-1 signal transduction. In this study, we have determined the effects of IL-1b and IRAP overexpression on adult b-cell replication and viability. IL-1b reduced dramatically b-cell replication in adult rat islets both at 5.5 mM (control: 0.2970.04%; IL-1b: 0.0270.02%, Po0.05) and 22.2 mM glucose (control: 0.8470.2%; IL-1b: 0.0570.05%, Po0.05). This effect was completely prevented in islets overexpressing IRAP after adenoviral gene transfer at 5.5 mM (Ad-IL-1Ra+IL-1b: 0.8470.1%, Po0.05) and 22.2 mM glucose (Ad-IL-1Ra+IL-1b: 1.2270.2%, Po0.05). Moreover, overexpression of IRAP increased glucose-stimulated b-cell replication in the absence of IL-1b exposure (Ad-IL-1Ra: 1.5970.5%, Po0.05). b-Cell death (TUNEL technique) was increased in IL-1b-exposed islets but not in Ad-IL-1Ra-infected islets (control: 0.8270.2%; control+IL-1b: 1.7770.2; IRAP: 0.6170.2%; IRAP+IL-1b: 0.8670.1%, Po0.05). Comparable results were obtained by flow cytometry. To determine the effect of IRAP overexpression on b-cell replication in vivo, Ad-IL-1Ra-transduced islets were transplanted into streptozotocin diabetic rats. b-Cell replication was significantly increased in IRAP-overexpressing islet grafts (0.9870.3%, Po0.05) compared to normal pancreas (0.3570.02%), but not in control islet grafts (0.5070.1%). This study shows that in addition to the effects of IL-1b on bcell viability, this cytokine exerts a deleterious action on b-cell replication, which can be prevented by IRAP overexpression, and provides support for the potential use of IRAP as a therapeutic tool. Gene Therapy (2005) 12, 120-128.

Adenoviral overproduction of interleukin-1 receptor antagonist increases beta cell replication and mass in syngeneically transplanted islets, and improves metabolic outcome

“…The well-known deleterious effects of IL-1β on beta cells include the impairment of beta cell function and the induction of beta cell death [16,17]. In addition, IL-1β suppresses beta cell replication in adult rat islets in vitro [15]. Therefore, the beneficial effects that we found in beta cell replication and mass in IL1RN-overproducing transplanted islets are in agreement with the expected results of blockade of the deleterious actions of IL-1β.…”

“…In addition, non-specific inflammation at the grafted site, involving the expression of pro-inflammatory cytokines, is considered to play a role in early graft failure [4,5,12,13]. We have identified increased production of IL-1β in syngeneically transplanted islet grafts, thereby confirming the presence of an inflammatory process in early islet transplantation even in most favourable conditions for islet survival [14,15]. Considering the well established cytotoxicity of IL-1β [16,17], we have hypothesised that IL-1β contributes to the damage of islet cells occurring in the initial days after transplantation.…”

“…We recently reported that IL1RN overproduction protected cultured islets from IL-1β-induced reduction in beta cell replication, and also found increased beta cell replication in a small number of islet grafts overproducing IL1RN [15]. These results lead us to hypothesise that IL1RN could block the non-specific inflammation mediated by IL-1β and the ensuing beta cell damage and death in recently transplanted islets.…”

“…Groups of 200 islets were infected with Ad-Il1rn or Ad encoding for green fluorescent protein (GFP; Ad-GFP) at a plaque-forming unit of 6.25×10 6 as previously described [15]. After infection, islets were incubated overnight in non-tissue culture treated plastic ware at 37°C in serumcontaining medium at 11.1 mmol/l of glucose.…”

“…At 24 h after infection, islets were dispersed into single cells and analysed by flow cytometry, as previously described [15]. IL1RN production was determined by immunohistochemistry in islets before and after transplantation.…”