NADPH oxidases in ischemic stroke: cellular sources and pharmacological translation

• Applicant: Professor Dr. Christoph Kleinschnitz
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Clinical Neurology; Neurosurgery and Neuroradiology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2010 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 167057491

• Final Report Year: 2018

Final Report Abstract

Ischemic injury represents the most frequent cause of death and disability, and it remains unclear why, of all body organs, the brain is most sensitive to hypoxia. In many tissues, type 4 NADPH oxidase is induced upon ischemia or hypoxia, converting oxygen to reactive oxygen species. Here, we show in mouse models of ischemia in the heart, brain, and hindlimb that only in the brain NADPH oxidase 4 (NOX4) leads to ischemic damage. We explain this distinct cellular distribution pattern through cellspecific knockouts. Endothelial NOX4 breaks down the blood brain barrier, while neuronal NOX4 leads to neuronal autotoxicity. Vascular smooth muscle NOX4, the common denominator of ischemia within all ischemic organs, played no apparent role in our stroke models. The direct neuroprotective potential of pharmacological NOX4 inhibition was confirmed in an ex vivo model, free of vascular and BBB components. Our results demonstrate that the high sensitivity of the brain to ischemic damage is due to an organ-specific role of NOX4 in blood brain barrier endothelial cells and neurons. This mechanism is conserved in at least two rodents and humans, making NOX4 a prime target for a first-in-class mechanism-based, cytoprotective therapy in the unmet high medical need indication of ischemic stroke. NADPH oxidase type 5 (NOX5) is a calcium-activated enzyme, producing reactive oxygen species, which is naturally lacking in rodents. We generated a humanised mouse line which expresses the human Nox5 gene in endothelial cells (NOX5 KI). These transgenic mice developed increased infarct volumes, more blood brain barrier damage and more production of reactive oxygen species. This resulted in a worse functional outcome of the NOX5KI mice after stroke compared to the WT control mice, showing the detrimental role of NOX5 in ischemic stroke.

Publications

• A combined pre-clinical meta-analysis and randomized confirmatory trial approach to improve data validity for therapeutic target validation. Sci Rep. 2015;5:13428
  Kleikers PW, Hooijmans C, Göb E, Langhauser F, Rewell SS, Radermacher K, Ritskes-Hoitinga M, Howells DW, Kleinschnitz C, Schmidt HH
  
• NOS knockout or inhibition but not disrupting PSD-95-NOS interaction protect against ischemic brain damage. J Cereb Blood Flow Metab. 2016;36(9):1508-1512
  Kleinschnitz C, Mencl S, Kleikers PW, Schuhmann MK, G López M, Casas AI, Sürün B, Reif A, Schmidt HH
  
• NOX4 is an early initiator of neuropathic pain. Exp Neurol. 2017;288:94-103
  Geis C, Geuss E, Sommer C, Schmidt HH, Kleinschnitz C
  
• NOX4-dependent neuronal autotoxicity and BBB breakdown explain the superior sensitivity of the brain to ischemic damage. Proc Natl Acad Sci USA. 2017;114(46):12315-12320
  Casas AI, Geuss E, Kleikers PWM, Mencl S, Herrmann AM, Buendia I, Egea J, Meuth SG, Lopez MG, Kleinschnitz C, Schmidt HHHW