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Cobalt Protoporpyhrin Reduces Caspase-3,-7 Enzyme Activity in Neonatal Porcine Islets, But Does Not Inhibit Cell Death Induced by TNF-α

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Apoptotic phenomena observed in vitro following isolation and following transplantation contribute significantly to islet graft loss. Strategies to reduce apoptosis of islet tissue prior to and posttransplantation may improve graft survival and function and reduce the amount of tissue necessary to achieve insulin independence. The expression of cytoprotective proteins is one such strategy that may prolong islet survival. In this light, heme-oxygenase 1 (HO-1) upregulation has been studied in both allo- and xenotransplantation models. In this study, the effect of HO-1 on apoptosis in neonatal porcine islet-like cell clusters (NPICC) was assessed. In in vitro assessments of NPICC apoptosis, NPICC showed a high sensitivity to apoptotic stimulation using a combination of TNF-α and cycloheximide. Stimulation with TNF-α alone was sufficient to induce reproducible apoptotic responses as demonstrated by caspase-3,-7 activation and subdiploid DNA analysis. Dose-dependent, high-level HO-1 protein expression was achieved following culture of NPICC in medium containing either cobalt protoporphyrin (CoPP) or cobalt mesoporphyrin (CoMP). CoPP treatment resulted in the reduction of caspase-3,-7 enzyme activity following TNF-α stimulation. However, such an effect was not associated with a reduction in the levels of cell death. Indeed, the inhibition of caspase enzyme activity resulted in decreased PARP-1 cleavage, which may lead to heightened levels of necrosis in treated NPICC cultures, possibly explaining the observed commitment of NPICC to the death pathway.

Keywords: Apoptosis; Islet; Metalloporphyrin; Necrosis; Porcine

Document Type: Research Article


Publication date: June 1, 2008

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  • Cell Transplantation publishes original, peer-reviewed research and review articles on the subject of cell transplantation and its application to human diseases. To ensure high-quality contributions from all areas of transplantation, separate section editors and editorial boards have been established. Articles deal with a wide range of topics including physiological, medical, preclinical, tissue engineering, and device-oriented aspects of transplantation of nervous system, endocrine, growth factor-secreting, bone marrow, epithelial, endothelial, and genetically engineered cells, among others. Basic clinical studies and immunological research papers are also featured. To provide complete coverage of this revolutionary field, Cell Transplantation will report on relevant technological advances, and ethical and regulatory considerations of cell transplants. Cell Transplantation is now an Open Access journal starting with volume 18 in 2009, and therefore there will be an inexpensive publication charge, which is dependent on the number of pages, in addition to the charge for color figures. This will allow work to be disseminated to a wider audience and also entitle the corresponding author to a free PDF, as well as prepublication of an unedited version of the manuscript.

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