Inhibition of AMP-Activated Protein Kinase Protects Pancreatic β-Cells From Cytokine-Mediated Apoptosis and CD8+ T-Cell–Induced Cytotoxicity

Abstract

Objective Apoptotic destruction of insulin-producing pancreatic β-cells is involved in the aetiology of both type 1 and type 2 diabetes. AMP-activated protein kinase (AMPK) is a sensor of cellular energy charge whose sustained activation has recently been implicated in pancreatic β-cell apoptosis and in islet cell death post-transplantation. Here, we examine the importance of β-cell AMPK in cytokine-induced apoptosis and in the cytotoxic action of CD8+ T cells. Research Design and Methods Clonal MIN6 β-cells or CD1 mouse pancreatic islets were infected with recombinant adenoviruses encoding enhanced green fluorescent protein (eGFP/Null), constitutively-active AMPK (AMPK CA), or dominant-negative AMPK (AMPK DN) and exposed or not to tumour necrosis factor-α (TNF-α) interleukin-1β (IL-1β) and interferon-γ (IFN-γ). Apoptosis was detected by monitoring the cleavage of caspase-3 and DNA fragmentation. The cytotoxic effect of CD8+ purified T cells was examined against pancreatic islets from NOD mice infected with either Null or the AMPK DN-expressing adenoviruses. Results Exposure to cytokines, or expression of AMPK CA, induced apoptosis in clonal MIN6 β-cells and CD1 mouse pancreatic islets. By contrast, over-expression of AMPK DN protected against the proapoptotic effect of these agents, in part by preventing decreases in cellular ATP, and lowered the cytotoxic effect of CD8+ T cells towards NOD mouse islets. Conclusions Inhibition of AMPK activity enhances islet survival in the face of assault by either cytokines or T cells. AMPK may therefore represent an interesting therapeutic target to suppress immune mediated β-cell destruction, and may increase the efficacy of islet allografts in Type 1 diabetes.

Endurance Training Activates Pancreatic Islets Amp-Activated Kinase-Uncoupling Protein 2 Pathway and Reduces Insulin Secretion

“…According to this proposal, treatment with AICAR prevented hyperinsulinemia and preserved b-cell mass in fat Zucker rats (Pold et al 2005). In contrast, it was also demonstrated that AICAR activation of AMPK in isolated b-cells increased apoptosis (Kefas et al 2003), whereas AMPK inhibition protected b-cell toxicity and apoptosis (Riboulet-Chavey et al 2008). Based on our data and on the aforementioned evidence, one can assume that overall exercise-induced AMPK activation would protect b-cells by counteracting elevated blood nutrient glucolipotoxicity-induced damage as well as by reducing GIIS-associated stress, rather than enhancing intrinsic b-cell survival pathways.…”

Connexin36 contributes to INS-1E cells survival through modulation of cytokine-induced oxidative stress, ER stress and AMPK activity

“…15 Cytokines are also known to stimulate AMPK activity in b-cells, 26 but the mechanisms underlying this activation remained unclear. Here we show that AMPK activation requires the production of NO, and can be achieved with thapsigargin but not with tunicamycin, suggesting that the depletion of ER Ca 2 þ and the subsequent increase in cytosolic Ca 2 þ concentration, rather than the ER stress per se, trigger the activation of the kinase.…”

AMP-activated Protein Kinase Mediates Apoptosis in Response to Bioenergetic Stress through Activation of the Pro-apoptotic Bcl-2 Homology Domain-3-only Protein BMF

“…Although AMPK activation may initially promote cell survival by enhancing ATP generation, this study demonstrates that prolonged AMPK activation during DN-HNF1A induction or pharmacological activation of AMPK with AICAR induces INS-1 cell apoptosis. Indeed, previous studies have demonstrated that prolonged activation of AMPK results in beta cell apoptosis in insulinoma cells (23) and in isolated islets (35). Moreover, transplantation of islets expressing a constitutively active form of AMPK to streptozotocin-induced diabetic mice resulted in a reduced level of beta cell survival compared with control syngeneic islets, whereas those expressing a dominant- negative form of AMPK improved graft efficiency (34).…”