Background: Systemic inflammation associated with brain death (BD) decreases islet yield and quality, negatively affecting outcomes of human islet transplantation. A recent study from our group showed an increased expression of uncoupling protein-2 (UCP2) in pancreas from rats with BD as compared with controls. UCP2 is located in the mitochondrial inner membrane and regulates production of reactive oxygen species and glucose-stimulated insulin secretion. It has been suggested that UCP2 also plays a role in β cell apoptosis, but these findings remain controversial.
Methods: We have presently performed a case-control study to assess UCP2 expression in pancreas from BD donors (cases) and subjects who underwent pancreatectomy (controls). We next investigated the role of Ucp2 in cytokine-induced apoptosis of rat insulin-producing INS-1E cells.
Results: UCP2 gene expression was higher in pancreas from BD donors compared with controls (1.73 ± 0.93 vs 0.75 ± 0.66; fold change, P < 0.05). Ucp2 knockdown (80% at the protein and messenger RNA levels) reduced by 30% cytokine-induced apoptosis and nitric oxide production in INS-1E cells. This protection was associated with decreased expression of cleaved (activated) caspases 9 and 3, suggesting that Ucp2 knockdown interferes with cytokine triggering of the intrinsic apoptotic pathway. Moreover, both messenger RNA and protein concentrations of the antiapoptotic protein Bcl-2 were increased after Ucp2 knockdown in INS-1E cells.
Conclusions: These data suggest that UCP2 has an apoptotic effect in β cells via regulation of the intrinsic pathway of apoptosis.
Donor brain death (BD) decreases pancreatic islet yield. Uncoupling protein-2 (UCP2) regulates production of reactive oxygen species and insulin secretion. UCP2 mRNA and protein is higher in pancreas from human BD donors compared to controls. Ucp2 knockdown in INS-1E beta-cell line reduced cytokine-induced apoptosis and nitric-oxide production.
1 Endocrine Division, Laboratory of Human Pancreatic Islet Biology, Hospital de Clinicas de Porto Alegre, Porto Alegre, RS, Brazil.
2 Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
3 ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium.
Received 8 January 2016. Revision received 15 April 2016.
Accepted 19 April 2016.
This study was supported by grants from the Conselho Nacional de Desenvolvimento Científico e Tecnólogico (CNPq), Fundação de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundo de Incentivo a Pesquisa e Eventos (FIPE) from Hospital de Clínicas de Porto Alegre to D.C., and by grants from the European Union (projects NAMIT and BetaBat, in the Framework Program 7 of the European Community) and Actions de Recherche Concertée de la Communauté Française (ARC) and the Fonds National de la Recherche Scientifique (FNRS), Belgium to D.L.E. D.C. and C.B.L. are recipients of scholarships from CNPq, and L.A.B. and T.H.R are the recipients of scholarships from CAPES (processes number 99999.003676/2014-05 and CSF 12108-13-8).
The authors declare no conflicts of interest.
L.A.B. designed the study, researched data, and wrote the manuscript. G.B. researched data and contributed to discussion. T.H.R researched data, contributed to discussion and reviewed the manuscript. C.B.L and A.C.B contributed to discussion and reviewed the manuscript. D.C. and D.L.E. designed the study, contributed to the discussion and reviewed the last version of the manuscript. L.A.B., D.L.E, and D.C. are joint guarantors of this work and, as such, had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Correspondence: Daisy Crispim, PhD, Rua Ramiro Barcelos 2350; prédio 12; 4° andar, zip code 90035-003, Porto Alegre, RS, Brazil. (firstname.lastname@example.org).
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