Mitochondrial uncoupling protein UCP2 in synergy with calcium-independent phospholipase A2γ protect...
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glucose. Palmitoleate, the monounsaturated counterpart of palmitate, does not affect glucose-stimulated insulin secretion (GSIS) and does not protect against the harmful effects of palmitate. We have shown that palmitate- induced GSIS impairment is linked to attenuation of glucose sensitivity of mitochondrial respiration and dampening of the coupling efficiency of glucose-stimulated oxidative phosphorylation [1]. Since these bioenergetic parameters are affected similarly by uncoupling protein-2 (UCP2) activity [2], we hypothesised that UCP2 mediates palmitate-induced defects in oxidative phosphorylation. To test this hypothesis we are performing a mitochondrial respiratory analysis with UCP2-depleted INS-1E cells subjected to bovine serum albumin (BSA)-conjugated palmitate and palmitoleate, added alone or together. Preliminary data suggest that 70% UCP2 knockdown through RNA interference does not significantly affect the glucolipotoxic effects of palmitate on the mitochondrial respiratory response to glucose and the coupling efficiency of oxidative phosphory- lation. Palmitoleate remains relatively harmless in UCP2-depleted cells and still does not protect against palmitate toxicity. These data suggest that UCP2 does not mediate the palmitate-induced defects in oxidative phosphorylation and, consequently, GSIS. We will show the full analysis of this ongoing bioenergetic study, including effects of UCP2 knockdown on fatty acid exposure at low glucose levels. Moreover, we will evaluate by static and dynamic GSIS experiments if and how UCP2 depletion affects fatty acid effects on insulin secretion. References [1] J. Barlow, C. Affourtit, Novel insights in pancreatic beta cell glucolipotoxicity from real-time functional analysis of mitochon- drial energy metabolism in INS-1E insulinoma cells, Biochem. J. 456 (2013) 417–426. [2] C. Affourtit, M. Jastroch, M. D. Brand, Uncoupling protein-2 attenuates glucose-stimulated insulin secretion in INS-1E insulinoma cells by lowering mitochondrial reactive oxygen species. Free Radic. Biol. Med. 50 (2011) 609–616. doi:10.1016/j.bbabio.2014.05.344 S3.P4 Mitochondrial uncoupling protein UCP2 in synergy with calcium-independent phospholipase A2γ protect INS-1E β-cells against acute palmitate-induced toxicity Martin Jabůrek, Jan Ježek, Andrea Dlasková, Petr Ježek Department of Membrane Transport Biophysics, Institute of Physiology, ASCR, Czech Republic E-mail address: [email protected] Fatty acids are important to the pancreatic β-cell for its normal function, but elevated levels of free fatty acids are associated with an increased production of reactive oxygen species and augmented glucose- stimulated insulin secretion. Mitochondrial uncoupling protein UCP2 plays an antioxidant role in pancreatic β-cells; however, the molecular mechanism is still poorly understood [1]. Our previous studies provided an evidence for antioxidant role of UCP2 in synergy with a redox- activated calcium-independent phospholipase A2γ (iPLA2γ) in isolated murine mitochondria [2]. Here, we tested the hypothesis that UCP2- mediated, iPLA2γ-dependent antioxidant action protects pancreatic β- cells from acute cytotoxic effects of saturated fatty acids. Using the model of INS-1E insulinoma cells, we exposed the cells to various concentra- tions of palmitate and measured the kinetics of insulin secretion and the rate of superoxide production in the mitochondrial matrix. In the absence of palmitate, there were no significant differences in insulin secretion between non-targeting shRNA INS-1E controls (ntgINS-1E), UCP2-silenced and iPLA2γ-silenced cells in the presence or absence of stimulatory glucose. At low concentrations of palmitate (bellow 30 nmol 10–6 cells), insulin secretion was elevated in ntgINS-1E controls, but markedly inhibited in both UCP2-silenced and iPLA2γ-silenced cells. At corresponding concentrations of palmitate, the mitochondrial superox- ide production was attenuated in ntgINS-1E controls, but elevated in UCP2-silenced and iPLA2γ-silenced cells. These results are consistent with the synergic role of UCP2 and iPLA2γ in a feedback downregulation of mild oxidative stress and indicate that UCP2 and iPLA2γ protect β- cells against toxicity associated with acute fatty acid intake. This work has been supported by Grant Agency of the Czech Republic, grant No. P302/10/034, P305/12/1247, and P304/10/P204. References [1] P. Ježek, T. Olejár, K. Smolková, J. Ježek, A. Dlasková, L. Plecitá-Hlavatá, J. Zelenka, T. Špaček, H. Engstová, D. Pajuelo Reguera, M. Jabůrek, Antioxidant and regulatory role of mitochondrial uncoupling protein UCP2 in pancreatic beta-cells, Physiol. Res. 63 (2014) S73-91. [2] M. Jabůrek, J. Ježek, J. Zelenka, P. Ježek, Antioxidant activity by a synergy of redox-sensitive mitochondrial phospholipase A2 and uncoupling protein-2 in lung and spleen, Int. J. Biochem. Cell. Biol. 45 (2013) 816–825. doi:10.1016/j.bbabio.2014.05.345 S3.P5 Mitochondrial uncoupling protein of endothelial EA.hy926 cells Agnieszka Koziel a , Wieslawa Jarmuszkiewicz b a Adam MIckiewicz University, Department of Bioenergetics, Poland b Adam Mickiewicz University, Faculty of Biology, Department of Bioenergetics, Poland E-mail address: [email protected] We describe the functional characteristics of mitochondrial uncoupling protein (UCP2) in endothelial EA.hy926 cells and isolated mitochondria. We compared the UCP2 function in endothelial cells cultured in medium with either a high (25 mM) or normal (5.5 mM) glucose concentration. We described concentration-dependent effects of free fatty acid, linoleic acid (LA) and purine nucleotide, GTP on endothelial UCP2 activity (i.e., stimulation of respiration and decrease in membrane potential). The UCP2 activity was significantly higher in mitochondria isolated from cells cultured in high glucose concentration. We also observed increased expression level of UCP2 in response to high glucose. Reactive oxygen species (ROS) production was measured in endothelial cells and isolated mitochondria from the control and high glucose cultures. We evaluated ROS production under activation of UCP2 by LA and inhibition by GTP in isolated EA.hy926 mitochondria. In mitochondria from high glucose-treated cells, a much higher LA- induced GTP-inhibited decrease in ROS generation was observed, indicating antioxidative function of UCP2 that was elevated under stress conditions. Moreover, to examine the role of UCP2 in high glucose-induced oxidative stress of endothelial cells, we silenced UCP2 gene expression using UCP2 siRNA (h) in control and high-glucose cells. UCP2 gene silencing led to an increased rate of mitochondrial ROS generation, especially in high glucose-treated endothelial cells. Mito- chondrial and non-mitochondrial ROS generations were greater in high-glucose cells than in normal-glucose cells independent of UCP2 gene silencing. Furthermore, an immunological analysis with antibodies raised against intracellular adhesion molecule-1 (ICAM-1) identified increased inflammation in high-glucose endothelial cells, especially in those with UCP2 silenced. In the present study, we described a functional characteristic and antioxidative role of endothelial UCP2. Our results confirm the implication that UCP2 may serve as a sensor and negative regulator of mitochondrial ROS production in endothelial cells with elevated glucose levels. This work is supported by the European Abstracts e36
Transcript of Mitochondrial uncoupling protein UCP2 in synergy with calcium-independent phospholipase A2γ protect...
glucose. Palmitoleate, themonounsaturated counterpart of palmitate, doesnot affect glucose-stimulated insulin secretion (GSIS) and does not protectagainst the harmful effects of palmitate. We have shown that palmitate-induced GSIS impairment is linked to attenuation of glucose sensitivity ofmitochondrial respiration and dampening of the coupling efficiency ofglucose-stimulatedoxidative phosphorylation [1]. Since these bioenergeticparameters are affected similarly by uncoupling protein-2 (UCP2) activity[2], we hypothesised that UCP2 mediates palmitate-induced defects inoxidative phosphorylation. To test this hypothesis we are performing amitochondrial respiratory analysis with UCP2-depleted INS-1E cellssubjected to bovine serum albumin (BSA)-conjugated palmitate andpalmitoleate, added alone or together. Preliminary data suggest that 70%UCP2 knockdown through RNA interference does not significantly affectthe glucolipotoxic effects of palmitate on the mitochondrial respiratoryresponse to glucose and the coupling efficiency of oxidative phosphory-lation. Palmitoleate remains relativelyharmless inUCP2-depleted cells andstill does not protect against palmitate toxicity. These data suggest thatUCP2 does not mediate the palmitate-induced defects in oxidativephosphorylation and, consequently, GSIS. We will show the full analysisof this ongoing bioenergetic study, including effects of UCP2 knockdownon fatty acid exposure at low glucose levels. Moreover, wewill evaluate bystatic and dynamic GSIS experiments if and how UCP2 depletion affectsfatty acid effects on insulin secretion.
References[1] J. Barlow, C. Affourtit, Novel insights in pancreatic beta cell
glucolipotoxicity from real-time functional analysis of mitochon-drial energy metabolism in INS-1E insulinoma cells, Biochem. J.456 (2013) 417–426.
[2] C. Affourtit,M. Jastroch,M. D. Brand, Uncoupling protein-2 attenuatesglucose-stimulated insulin secretion in INS-1E insulinoma cells bylowering mitochondrial reactive oxygen species. Free Radic. Biol.Med. 50 (2011) 609–616.
doi:10.1016/j.bbabio.2014.05.344
S3.P4
Mitochondrial uncoupling protein UCP2 in synergy withcalcium-independent phospholipase A2γ protect INS-1Eβ-cells against acute palmitate-induced toxicityMartin Jabůrek, Jan Ježek, Andrea Dlasková, Petr JežekDepartment of Membrane Transport Biophysics, Institute of Physiology,ASCR, Czech RepublicE-mail address: [email protected]
Fatty acids are important to the pancreatic β-cell for its normalfunction, but elevated levels of free fatty acids are associated with anincreased production of reactive oxygen species and augmented glucose-stimulated insulin secretion. Mitochondrial uncoupling protein UCP2plays an antioxidant role in pancreatic β-cells; however, the molecularmechanism is still poorly understood [1]. Our previous studies providedan evidence for antioxidant role of UCP2 in synergy with a redox-activated calcium-independent phospholipase A2γ (iPLA2γ) in isolatedmurine mitochondria [2]. Here, we tested the hypothesis that UCP2-mediated, iPLA2γ-dependent antioxidant action protects pancreatic β-cells fromacute cytotoxic effects of saturated fatty acids. Using themodelof INS-1E insulinoma cells, we exposed the cells to various concentra-tions of palmitate andmeasured the kinetics of insulin secretion and therate of superoxide production in the mitochondrial matrix. In theabsence of palmitate, there were no significant differences in insulinsecretion between non-targeting shRNA INS-1E controls (ntgINS-1E),UCP2-silenced and iPLA2γ-silenced cells in the presence or absence ofstimulatory glucose. At low concentrations of palmitate (bellow 30 nmol
10–6 cells), insulin secretion was elevated in ntgINS-1E controls, butmarkedly inhibited in both UCP2-silenced and iPLA2γ-silenced cells. Atcorresponding concentrations of palmitate, the mitochondrial superox-ide production was attenuated in ntgINS-1E controls, but elevated inUCP2-silenced and iPLA2γ-silenced cells. These results are consistentwith the synergic role of UCP2 and iPLA2γ in a feedback downregulationof mild oxidative stress and indicate that UCP2 and iPLA2γ protect β-cells against toxicity associated with acute fatty acid intake. This workhas been supported by Grant Agency of the Czech Republic, grant No.P302/10/034, P305/12/1247, and P304/10/P204.
References[1] P. Ježek, T. Olejár, K. Smolková, J. Ježek, A. Dlasková, L. Plecitá-Hlavatá,
J. Zelenka, T. Špaček, H. Engstová, D. Pajuelo Reguera, M. Jabůrek,Antioxidant and regulatory role of mitochondrial uncoupling proteinUCP2 in pancreatic beta-cells, Physiol. Res. 63 (2014) S73-91.
[2] M. Jabůrek, J. Ježek, J. Zelenka, P. Ježek, Antioxidant activity by asynergy of redox-sensitive mitochondrial phospholipase A2 anduncoupling protein-2 in lung and spleen, Int. J. Biochem. Cell. Biol.45 (2013) 816–825.
doi:10.1016/j.bbabio.2014.05.345
S3.P5
Mitochondrial uncoupling protein of endothelial EA.hy926 cellsAgnieszka Koziela, Wieslawa JarmuszkiewiczbaAdam MIckiewicz University, Department of Bioenergetics, PolandbAdam Mickiewicz University, Faculty of Biology, Department ofBioenergetics, PolandE-mail address: [email protected]
We describe the functional characteristics of mitochondrialuncoupling protein (UCP2) in endothelial EA.hy926 cells and isolatedmitochondria. We compared the UCP2 function in endothelial cellscultured in medium with either a high (25 mM) or normal (5.5 mM)glucose concentration. We described concentration-dependent effectsof free fatty acid, linoleic acid (LA) and purine nucleotide, GTP onendothelial UCP2 activity (i.e., stimulation of respiration anddecrease inmembrane potential). The UCP2 activity was significantly higher inmitochondria isolated fromcells cultured in high glucose concentration.We also observed increased expression level of UCP2 in response tohigh glucose. Reactive oxygen species (ROS) production was measuredin endothelial cells and isolatedmitochondria from the control and highglucose cultures. We evaluated ROS production under activation ofUCP2 by LA and inhibition by GTP in isolated EA.hy926mitochondria. Inmitochondria from high glucose-treated cells, a much higher LA-induced GTP-inhibited decrease in ROS generation was observed,indicating antioxidative function of UCP2 that was elevated understress conditions. Moreover, to examine the role of UCP2 in highglucose-induced oxidative stress of endothelial cells, we silenced UCP2gene expression using UCP2 siRNA (h) in control and high-glucose cells.UCP2 gene silencing led to an increased rate of mitochondrial ROSgeneration, especially in high glucose-treated endothelial cells. Mito-chondrial and non-mitochondrial ROS generations were greater inhigh-glucose cells than in normal-glucose cells independent of UCP2gene silencing. Furthermore, an immunological analysiswith antibodiesraised against intracellular adhesion molecule-1 (ICAM-1) identifiedincreased inflammation in high-glucose endothelial cells, especially inthose with UCP2 silenced. In the present study, we described afunctional characteristic and antioxidative role of endothelial UCP2.Our results confirm the implication that UCP2may serve as a sensor andnegative regulator of mitochondrial ROS production in endothelial cellswith elevated glucose levels. This work is supported by the European
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