15 Regulation of mitochondria by extramitochondrial calcium is impaired in transgenic models of HD Frank N. Gellerich a,* , Zemfira Gizatullina a , Hoa P. Nguyen b , Sonata Trumbeckaite c , Stephan Vielhaber d , Enn Seppet e , Stephan von Hoersten f , Frank Striggow a a KeyNeurotek Pharmaceuticals AG, ZENIT Technology Park, Magdeburg, Germany; b Department of Medical Genetics, University of Tübingen, Tübingen, Germany; c Institute for Biomedical Research, Kaunas University of Medicine, Kaunas, Lithuania; d Department of Neurology II, Otto von Guericke University Magdeburg, Magdeburg, Germany; e Department of Pathophysiology, Centre of Molecular and Clinical Medicine, University of Tartu, Tartu, Estonia; f Section for Experimental Therapy, Franz-Penzoldt-Center, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany Huntington’s disease (HD) is characterized by polyglutamine expansions of huntingtin (htt) but the underlying pathomechanisms have remained unclear. We studied brain mitochondria of transgenic HD rats with 51 glutamine repeats (htt 51Q ), modeling the adult form of HD. Ca 2þ free up to 2 lM activated state 3 respiration of wild type (WT) mitochondria with glutamate/malate or pyruvate/malate as sub- strates. Ca 2þ free above 2 lM inhibited respiration via cyclosporin A (CsA)-dependent permeability transition (PT). Ruthenium red (RR), an inhibitor of the mitochondrial Ca 2þ uniporter, did not affect the Ca 2þ -dependent activation of respiration, but reduced Ca 2þ -induced inhibition. Thus, Ca 2þ -activation was mediated exclusively by extra- mitochondrial Ca 2þ , whereas inhibition was promoted also by intra- mitochondrial Ca 2þ . In contrast, htt 51Q mitochondria showed a deficient state 3 respiration, lower sensitivity to Ca 2þ activation and a higher susceptibility to Ca 2þ -dependent inhibition. Furthermore, htt 51Q mitochondria exhibited a diminished membrane potential sta- bility in response to Ca 2þ , lower capacities and rates of Ca 2þ accumu- lation and a decreased Ca 2þ threshold for PT in substrate-independent but CsA-sensitive manner. Compared to WT, Ca 2þ -induced inhibition of respiration of htt 51Q mitochondria was less sensitive to RR, indicat- ing the involvement of extramitochondrial Ca 2þ . In conclusion, we demonstrate that interactions between htt 51Q and distinct targets as aralar and/or the PT pore may underlie mito- chondrial dysregulation leading to energetic depression, cell death and tissue atrophy in HD. doi:10.1016/j.mito.2009.12.014 16 Mitochondrial damage in acute carbon monoxide poisoning: The effect of oxygen treatment G. Garrabou a,* , J.M. Inoriza b , C. Morén a , M. Nicolàs a , G. Oliu b , Ò. Miró a , M.J. Martı ´ b , F. Cardellach a a Mitochondrial Research Laboratory, Muscle Research Unit, IDIBAPS-University of Barcelona, Internal Medicine Department-Hospital Clı ´ nic of Barcelona and CIBER de Enfermedades Raras (CIBERER), Barcelona, Spain; b Hyperbaric Medicine Unit, Hospital of Palamós, Serveis de Salut Integrats Baix Emporda, Girona, Spain Background: Acute carbon monoxide (CO) poisoning (ACOP) symptoms are attributed to hypoxia due to carboxihemoglobin (COHb). However, CO also inhibits mitochondrial complex IV (mtCIV), responsible of energy supply and oxidative stress produc- tion. Since COHb rapidly decreases after oxygen (normobaric – NBO or hyperbaric – HBO) treatment, mtCIV and oxidative stress could be more sensitive markers of ACOP severity, treatment efficacy and sequel predictive markers. Methods: Fifty-eight ACOP subjects were distributed as: (a) severe (n=33, COHb >20% and/or clinical symptoms), randomly treated with 1 or 2 HBO sessions (SHBO1, n = 20, and SHBO2, n = 13), and (b) moderate (n = 25, COHb:10–20%), randomly treated with NBO (MNBO, n = 11) or 1 HBO session (MHBO, n = 14). Controls (n = 30) were non-smoker blood donors. Clinical manifestations, COHb, mtCIV activity, mitochondrial mass and peripheral blood mononu- clear cells’ lipid peroxidation were analysed before and immediately after-treatment, and 24 h, 1 month and 3 months after it. Results: Before and immediately after-treatment mtCIV was de- creased in ACOP compared to controls (p < 0.001), independently to intoxication severity and COHb. Time-course mtCIV recovery was significant for ACOP on HBO (SHBO1 p < 0.001, SHBO2 p < 0.005 and MHBO p < 0.05), but not in MNBO. Oxidative stress was not increased at baseline, but in severe ACOP, oxygen treatment raised it for 24 h (p < 0.01). All treatments normalised COHb and acute neurological symptoms except in two ACOP patients (both suf- fering late neurological sequels), which clinical manifestations corre- lated low mtCIV activities and increased oxidative stress. Conclusions: Low mtCIV activity and maintained oxidative stress characterise ACOP. In severe ACOP 1 HBO session is effective enough restoring mtCIV activity and more effective than NBO in moderate ACOP. mtCIV could be a good marker of ACOP recovery, treatment efficacy and sequel development, but would not be a useful poison- ing severity marker because is equally inhibited in all ACOP subjects. Clinical implications of these results remain to be established. Grants: This work has been supported by Fondo de Investigaci- ones Sanitarias (FIS 40381/04, PI041239), Fundación para la investi- gación y la Prevención del SIDA en España (FIPSE 36612-06 and 36572-06), Suports a Grups de Recerca de la Generalitat de Catalu- nya (2005/SGR/0300) and CIBER de Enfermedades Raras (CIBERER, an initiative of ISCIII). doi:10.1016/j.mito.2009.12.015 17 Sepsis effects on mitochondria G. Garrabou * , C. Morén, S. Lopez, M. Nicolàs, F. Cardellach, O. Miro, J. Casademont Mitochondrial Research Laboratory, IDIBAPS, University of Barcelona, Hospital Clı ´ nic of Barcelona and CIBER de Enfermedades Raras (CIBERER), Barcelona, Spain Hypothesis: Muscle mitochondrial dysfunction has been associated to severe sepsis. Mitochondrial damage impairs oxygen consumption and energy production independently to tisular oxygenation and per- fusion and could conditionate clinical severity and recovery. Several mechanisms have been proposed to explain associated mitochondrial dysfunction, but specific etiopathogenesis of mitochondrial impair- ment remains to be established. Methods: Mitochondrial status was assessed in mononuclear cells of 18 patients undergoing a sepsis with respect 20 healthy controls. Enzymatic activities of mitochondrial complexes I, III and IV, oxygen consumption, oxidative stress (lipid peroxidation) and initial apop- tosis level (mitochondrial membrane potential) were assessed. Nitric oxide (nitrate and nitrite) amount was measured in plasma of septic patients as well as oxygen consumption of healthy mitochondria incubated with plasma from septic patients or healthy controls. Results: Enzymatic activities of mitochondrial complexes I, III and IV and oxygen consumption were decreased in mononuclear cells of septic patients with respect controls. However oxidative stress dam- age, initial apoptosis level and nitric oxide amount were increased on those subjects. Oxidative capacity of healthy mitochondria incu- bated with plasma of septic patients was found to be decreased com- pared to incubation with plasma of healthy controls. Conclusion: A general mitochondrial dysfunction is present on those patients undergoing a sepsis process together with increased plasma nitric oxide concentrations. Mitochondrial impairment is inducible in healthy mitochondria by incubation with the plasma of septic individuals. Some plasmatic factor as nitric oxide which presents this characteristic dual capacity to induce mitochondrial dysfunction and increase oxidative stress damage must be responsi- ble for the cellular damage present on septic patients. Supported by: FIS 40381/04 and CIBER de Enfermedades Raras (initiative of the ISCIII). doi:10.1016/j.mito.2009.12.016 204 Abstracts / Mitochondrion 10 (2010) 200–242