Lisofylline, a novel antiinflammatory agent, protects pancreatic beta-cells from proinflammatory cytokine damage by promoting mitochondrial metabolism.
Proinflammatory cytokine-mediated pancreatic beta-cell dysfunction is a key pathological event in type I diabetes mellitus. Lisofylline (LSF), an anti-inflammatory agent, has been shown to protect pancreatic islets from IL-1 beta-induced inhibitory effects on insulin release. However, the mechanism of LSF action is not known. Increasing evidence suggests that the mitochondria play an important role in regulating the beta-cell insulin release capacity and the control of cellular viability. To examine the direct effects of LSF on beta-cells, insulin-secreting INS-1 cells were exposed to a combination of recombinant IL-1 beta, TNF alpha, and IFN gamma with or without LSF for 18 h. Basal and glucose-stimulated static insulin release were measured using RIA. INS-1 cell viability was determined using in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling and LIVE/DEAD dual fluorescence labeling. To evaluate INS-1 mitochondrial function, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) metabolism, change in mitochondrial membrane potential, and intracellular ATP levels were assessed. Cytokine addition reduced basal (7.8 +/- 0.30 vs. 10.0 +/- 0.46 ng/ml.h; P < 0.005), glucose-stimulated insulin secretion (11.6 +/- 0.86 vs. 17.4 +/- 1.86 ng/ml.h; P < 0.005), and MTT metabolism in INS-1 cells. Over 40% of the cytokine-treated beta-cells exhibited nuclear DNA breakage, whereas the control cell death rate remained at 1-2%. Simultaneous application of LSF and cytokines to INS-1 cells restored insulin secretion, MTT metabolism, mitochondrial membrane potential, and cell viability to control levels. LSF increased beta-cell MTT metabolism as well as insulin release and glucose responsiveness. In summary, proinflammatory cytokines lead to a reduction of glucose-induced insulin secretion, mitochondrial activity, and viability in INS-1 cells. LSF at concentrations achievable in vivo protected beta-cells from the cytokine effects. The mechanism of LSF-induced protection may be by promoting mitochondrial metabolism.
Chen
Meng
M
Department of Medicine, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
Yang
Zandong
Z
Wu
Runpei
R
Nadler
Jerry L
JL
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000037:antagonists & inhibitors* / Q000633:toxicity; D004249:DNA Damage; D005456:Fluorescent Dyes; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008566:Membranes / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010431:Pentoxifylline / Q000031:analogs & derivatives / Q000494:pharmacology*; D051381:Rats; D013268:Stimulation, Chemical; D013778:Tetrazolium Salts; D013844:Thiazoles
D000894:Anti-Inflammatory Agents, Non-Steroidal; D016207:Cytokines; D005456:Fluorescent Dyes; D007328:Insulin; D013778:Tetrazolium Salts; D013844:Thiazoles; D000255:Adenosine Triphosphate; C022616:thiazolyl blue; C025189:lisofylline; D010431:Pentoxifylline