@article{BittnerBobakFeuchtenbergeretal.2011,
  author    = {Bittner, Stefan and Bobak, Nicole and Feuchtenberger, Martin and Herrmann, Alexander M and G{\"o}bel, Kerstin and Kinne, Raimund W and Hansen, Anker J and Budde, Thomas and Kleinschnitz, Christoph and Frey, Oliver and Tony, Hans-Peter and Wiendl, Heinz and Meuth, Sven G},
  title     = {Expression of K\(_2\)\(_P\)5.1 potassium channels on CD4\(^+\)T lymphocytes correlates with disease activity in rheumatoid arthritis patients},
  series = {Arthritis Research \& Therapy},
  volume    = {13},
  journal   = {Arthritis Research \& Therapy},
  number    = {R21},
  doi       = {10.1186/ar3245},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-139334},
  year      = {2011},
  abstract  = {Introduction CD4+ T cells express K2P5.1 (TWIK-related acid-sensitive potassium channel 2 (TASK2); KCNK5), a member of the two-pore domain potassium channel family, which has been shown to influence T cell effector functions. Recently, it was shown that K2P5.1 is upregulated upon (autoimmune) T cell stimulation. The aim of this study was to correlate expression levels of K2P5.1 on T cells from patients with rheumatoid arthritis (RA) to disease activity in these patients. Methods Expression levels of K2P5.1 were measured by RT-PCR in the peripheral blood of 58 patients with RA and correlated with disease activity parameters (C-reactive protein levels, erythrocyte sedimentation rates, disease activity score (DAS28) scores). Twenty patients undergoing therapy change were followed-up for six months. Additionally, synovial fluid and synovial biopsies were investigated for T lymphocytes expressing K2P5.1. Results K2P5.1 expression levels in CD4+ T cells show a strong correlation to DAS28 scores in RA patients. Similar correlations were found for serological inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein). In addition, K2P5.1 expression levels of synovial fluid-derived T cells are higher compared to peripheral blood T cells. Prospective data in individual patients show a parallel behaviour of K2P5.1 expression to disease activity parameters during a longitudinal follow-up for six months. Conclusions Disease activity in RA patients correlates strongly with K2P5.1 expression levels in CD4+ T lymphocytes in the peripheral blood in cross-sectional as well as in longitudinal observations. Further studies are needed to investigate the exact pathophysiological mechanisms and to evaluate the possible use of K2P5.1 as a potential biomarker for disease activity and differential diagnosis.},
  language  = {en}
}
@article{EhlingGoebBittneretal.2013,
  author    = {Ehling, Petra and G{\"o}b, Eva and Bittner, Stefan and Budde, Thomas and Ludwig, Andreas and Kleinschnitz, Christoph and Meuth, Sven G.},
  title     = {Ischemia-induced cell depolarization: does the hyperpolarization-activated cation channel HCN2 affect the outcome after stroke in mice?},
  series = {Experimental \& Translational Stroke Medicine},
  volume    = {5},
  journal   = {Experimental \& Translational Stroke Medicine},
  number    = {16},
  doi       = {10.1186/2040-7378-5-16},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131887},
  year      = {2013},
  abstract  = {Background Brain ischemia is known to include neuronal cell death and persisting neurological deficits. A lack of oxygen and glucose are considered to be key mediators of ischemic neurodegeneration while the exact mechanisms are yet unclear. In former studies the expression of two different two-pore domain potassium \((K_{2P})\) channels (TASK1, TREK1) were shown to ameliorate neuronal damage due to cerebral ischemia. In neurons, TASK channels carrying hyperpolarizing \(K^+\) leak currents, and the pacemaker channel HCN2, carrying depolarizing \(I_h\), stabilize the membrane potential by a mutual functional interaction. It is assumed that this ionic interplay between TASK and HCN2 channels enhances the resistance of neurons to insults accompanied by extracellular pH shifts. Methods In C57Bl/6 (wildtype, WT), \(hcn2^{+/+}\) and \(hcn2^{-/-}\) mice we used an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of HCN2 in stroke formation. Subsequent analyses comprise behavioural tests and hcn2 gene expression assays. Results After 60 min of tMCAO induction in WT mice, we collected tissue samples at 6, 12, and 24 h after reperfusion. In the infarcted neocortex, hcn2 expression analyses revealed a nominal peak of hcn2 expression 6 h after reperfusion with a tendency towards lower expression levels with longer reperfusion times. Hcn2 gene expression levels in infarcted basal ganglia did not change after 6 h and 12 h. Only at 24 h after reperfusion, hcn2 expression significantly decreases by ~55\%. However, 30 min of tMCAO in hcn2-/- as well as hcn2+/+ littermates induced similar infarct volumes. Behavioural tests for global neurological function (Bederson score) and motor function/coordination (grip test) were performed at day 1 after surgery. Again, we found no differences between the groups. Conclusions Here, we hypothesized that the absence of HCN2, an important functional counter player of TASK channels, affects neuronal survival during stroke-induced tissue damage. However, together with a former study on TASK3 these results implicate that both TASK3 and HCN2 which were supposed to be neuroprotective due to their pH-dependency, do not influence ischemic neurodegeneration during stroke in the tMCAO model.},
  language  = {en}
}
@article{EhlingGoebBittneretal.2013,
  author    = {Ehling, Petra and G{\"o}b, Eva and Bittner, Stefan and Budde, Thomas and Ludwig, Andreas and Kleinschnitz, Christoph and Meuth, Sven G.},
  title     = {Ischemia-induced cell depolarization: does the hyperpolarization-activated cation channel HCN2 affect the outcome after stroke in mice?},
  series = {Experimental \& Translational Stroke Medicine},
  volume    = {5},
  journal   = {Experimental \& Translational Stroke Medicine},
  number    = {16},
  doi       = {10.1186/2040-7378-5-16},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129240},
  year      = {2013},
  abstract  = {Background Brain ischemia is known to include neuronal cell death and persisting neurological deficits. A lack of oxygen and glucose are considered to be key mediators of ischemic neurodegeneration while the exact mechanisms are yet unclear. In former studies the expression of two different two-pore domain potassium \((K_{2P})\) channels (TASK1, TREK1) were shown to ameliorate neuronal damage due to cerebral ischemia. In neurons, TASK channels carrying hyperpolarizing \(K^+\) leak currents, and the pacemaker channel HCN2, carrying depolarizing Ih, stabilize the membrane potential by a mutual functional interaction. It is assumed that this ionic interplay between TASK and HCN2 channels enhances the resistance of neurons to insults accompanied by extracellular pH shifts. Methods In C57Bl/6 (wildtype, WT), \(hcn2^{+/+}\) and \(hcn2^{-/-}\) mice we used an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of HCN2 in stroke formation. Subsequent analyses comprise behavioural tests and hcn2 gene expression assays. Results After 60 min of tMCAO induction in WT mice, we collected tissue samples at 6, 12, and 24 h after reperfusion. In the infarcted neocortex, hcn2 expression analyses revealed a nominal peak of hcn2 expression 6 h after reperfusion with a tendency towards lower expression levels with longer reperfusion times. Hcn2 gene expression levels in infarcted basal ganglia did not change after 6 h and 12 h. Only at 24 h after reperfusion, hcn2 expression significantly decreases by ~55\%. However, 30 min of tMCAO in hcn2-/- as well as hcn2+/+ littermates induced similar infarct volumes. Behavioural tests for global neurological function (Bederson score) and motor function/coordination (grip test) were performed at day 1 after surgery. Again, we found no differences between the groups. Conclusions Here, we hypothesized that the absence of HCN2, an important functional counter player of TASK channels, affects neuronal survival during stroke-induced tissue damage. However, together with a former study on TASK3 these results implicate that both TASK3 and HCN2 which were supposed to be neuroprotective due to their pH-dependency, do not influence ischemic neurodegeneration during stroke in the tMCAO model.},
  language  = {en}
}