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Institute of Physiology and Pathophysiology

Research Areas

Hypoxia in the Brain

Our research group investigates the effects of hypoxia in the brain. Tissue hypoxia in the brain is a central problem in a number of disorders such as ischemia, tumors, brain injury, high altitude sickness and epilepsy. The insufficient availability of oxygen to the cells can be caused by reduced supply or increased consumption. Therefore our interest is focused on the neurovascular interplay which also includes glial cells. We study two hypoxia-related processes in particular: 1) the activation of endogenous factors which protect neurons against cell death or which induce their regeneration (neuroprotection and neurogenesis), and 2) the opening of the blood-brain barrier leading to cerebral oedema formation. We utilise various in vivo experimental models (hypoxia chamber, ischemia models), including transgenic animals, and combine these with modern molecular biology techniques. By analysing and characterising this endogenous protective response we hope to find clues for new therapies for human diseases.

1) Neuroprotection and Neurogenesis


Tissue hypoxia is detected via various oxygen sensors (polylhydoxylases, PHD), which activate specific transcription factors (hypoxia-inducible factors, HIF), which, in turn, lead to the induction of neurogenic and neuroprotective factors such as vascular endothelial growth factor (VEGF) or erythropoietin (Epo). It is the aim of our research to understand in detail the underlying mechanisms and to manipulate them in a positive way.




Brain-specific overexpression of VEGF reduces infarct (pale area) size. Infarct size quantification on cresyl violet-stained brain tissue sections revealed a significant 40% reduction in VEGF transgenic mice (VEGF-tg) as compared with non transgenic littermate controls (ntg).

 

from Wang et al.; Brain (2005); 128: 52-63

2) Blood-Brain Barrier


Besides its positive properties (neuroprotection, neurogenesis, angiogenesis) VEGF has one negative effect on the blood-brain barrier (BBB), which complicates its immediate therapeutic use:  VEGF leads to the opening of the BBB and, as a consequence, to the formation of a cerebral oedema. We investigate the molecular mechanisms of this opening by characterising the processes at the endothelial cell-cell contacts (tight junctions) and at the extracellular matrix. It is our goal to reduce oedema formation by intervention without affecting the neuroprotective properties.

 


Hypoxia causes rearrangement and gap formation of the tight junction protein occludin. Mice were exposed for 48 h to 20% (control) or 8% oxygen (hypoxia). Coronal brain sections were
stained immunohistochemically for occludin (green) and CD31 (red), and nuclei were stained with DAPI (blue). Three-dimensional reconstruction after confocal microscopy demonstrates occludin rearrangement and gap formation (arrowheads) after hypoxia, as compared to the continuous, sharp linear staining (arrows) in controls.

 

from Bauer et al.; J Cereb Blood Flow Metab (2010); 30: 837-848.





Recent Publications

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Alterations of distributed neuronal network oscillations during acute pain in freely-moving mice. IBRO Rep. 2020 Dec;9:195-206. doi: 10.1016/j.ibror.2020.08.001. eCollection 2020 Dec. Epub 2020 Aug 11.

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Neuronal gamma oscillations and activity-dependent potassium transients remain regular after depletion of microglia in postnatal cortex tissue. J Neurosci Res. 2020 Oct;98(10):1953-1967. doi: 10.1002/jnr.24689. Epub 2020 Jul 7.

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Synchronicity of excitatory inputs drives hippocampal networks to distinct oscillatory patterns. Hippocampus. 2020 Oct;30(10):1044-1057. doi: 10.1002/hipo.23214. Epub 2020 May 15.

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Processing of hippocampal network activity in the receiver network of the medial entorhinal cortex layer V. J Neurosci. 2020 Sep 25:JN-RM-0586-20. doi: 10.1523/JNEUROSCI.0586-20.2020. Online ahead of print.

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Multifunctional reactive MALDI matrix enabling high-lateral resolution dual polarity MS imaging and lipid C=C position-resolved MS2 imaging. Anal Chem. 2020 Sep 12. doi: 10.1021/acs.analchem.0c03150. Online ahead of print.

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VEGF-D Downregulation in CA1 Pyramidal Neurons Exerts Asymmetric Changes of Dendritic Morphology without Correlated Electrophysiological Alterations. Neuroscience. 2020 Sep 10:S0306-4522(20)30578-9. doi: 10.1016/j.neuroscience.2020.09.012. Online ahead of print.

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Anesthetics and plants: no pain, no brain, and therefore no consciousness. Protoplasma. 2020 Sep 2. doi: 10.1007/s00709-020-01550-9. Online ahead of print.

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Brain energy rescue: an emerging therapeutic concept for neurodegenerative disorders of ageing. Nat Rev Drug Discov. 2020 Sep;19(9):609-633. doi: 10.1038/s41573-020-0072-x. Epub 2020 Jul 24.

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Microglia and lipids: how metabolism controls brain innate immunity. Semin Cell Dev Biol. 2020 Aug 14;S1084-9521(19)30197-1. doi: 10.1016/j.semcdb.2020.08.001. Online ahead of print.

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GM-CSF induces noninflammatory proliferation of microglia and disturbs electrical neuronal network rhythms in situ. J Neuroinflammation. 2020 Aug 11;17(1):235. doi: 10.1186/s12974-020-01903-4.

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Inhibition of cardiac Kv4.3 (Ito) channel isoforms by class I antiarrhythmic drugs lidocaine and mexiletine. Eur J Pharmacol. 2020 Aug 5;880:173159. doi: 10.1016/j.ejphar.2020.173159. Epub 2020 Apr 29.

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Selective inhibition of mitochondrial respiratory complexes controls the transition of microglia into a neurotoxic phenotype in situ. Brain Behav Immun. 2020 Aug;88:802-814. doi: 10.1016/j.bbi.2020.05.052. Epub 2020 May 21.

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Lactate Attenuates Synaptic Transmission and Affects Brain Rhythms Featuring High Energy Expenditure. iScience. 2020 Jul 24;23(7):101316. doi: 10.1016/j.isci.2020.101316. Epub 2020 Jun 27.

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Mild metabolic stress is sufficient to disturb the formation of pyramidal cell ensembles during gamma oscillations. J Cereb Blood Flow Metab. 2019 Dec 16:271678X19892657. doi: 10.1177/0271678X19892657. [Epub ahead of print

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The mitochondrial calcium uniporter is crucial for the generation of fast cortical network rhythms. J Cereb Blood Flow Metab. 2019 Nov 13:271678X19887777. doi: 10.1177/0271678X19887777. [Epub ahead of print]


Institute of
Physiology and Pathophysiology

Heidelberg University

Im Neuenheimer Feld 326

69120 Heidelberg

Germany

Phone:+49 6221 54-4056
Fax:+49 6221 54-6364
E-mail:susanne.bechtel@
physiologie.uni-heidelberg.de