Implication of aquaporins in ischemic stroke. New target?

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1 Implication of aquaporins in ischemic stroke. New target? Balseanu Tudor-Adrian, MD, PhD EXPERIMENTAL RESEARCH CENTER OF NORMAL AND PATHOLOGICAL AGING University of Medicine and Pharmacy of Craiova, Romania April 26 th 2016

Brain edema in ischemic stroke o Formation of cerebral edema is a common pathological denominator in ischemic stroke After www.strokecenter.

2 Brain edema in ischemic stroke o Formation of cerebral edema is a common pathological denominator in ischemic stroke After o The currently accepted non-surgical approach in the treatment of brain edema is represented by parenteral administration of hypertonic solutions

3 Brain edema in ischemic stroke o Cytotoxic edema / Vasogenic edema After Donkin JJ, Current Opinion in Neurology 2010, 23: o No physio-pathologically-oriented treatment yet for cytotoxic edema

Brain edema in ischemic stroke Increased membrane permeability: oionic gradients loss on cell membranes oexcessive release of glutamate oimpaired glutamate reuptake ointracellular Ca 2+

4 Brain edema in ischemic stroke Increased membrane permeability: oionic gradients loss on cell membranes oexcessive release of glutamate oimpaired glutamate reuptake ointracellular Ca 2+ increases ooveractive Ca 2+ - dependent pathways oneuronal excitotoxicity ofree radicals-induced neuronal death After Kahle KT, Physiology (Bethesda) Aug;24: Glutamate-induced neurotoxicity

5 Modulators of brain edema o Aquaporin 4 (AQP4) is the main gateway of water balance in the CNS Papadopoulos MC, Nature Reviews Neuroscience 14, (April 2013)

6 Modulators of brain edema o AQP4-deficient mice with focal ischemic stroke produced by middle cerebral artery occlusion (MCAO) showed significantly decreased cerebral edema and improved neurological outcomes compare to nontransgenic animals Manley GT. Nat Med 2000, 6: o In models of vasogenic brain edema (freeze-injury model and intraparenchymal fluid infusion model), AQP4-deficient mice had increased brain swelling and worse neurological outcomes Papadopoulos MC. FASEB J Aug;18(11):1291-3

7 Modulators of excitotoxicity o Glutamate transporter 1 (GLT-1; EAAT1) drives glutamate uptake into astrocytes After Stobart JL, Front Cell Neurosci Apr 10;7

8 Modulators of excitotoxicity o GLT-1 deficient mice show increased glutamate toxicity in prone conditions Tanaka K. Science 1997, 276: o Overexpression of GLT-1 significantly reduces glutamate overflow and cell death improving the clinical recovery in animal models of ischemic stroke Harvey BK. PLoS One 2011, 6:e22135 o AQP4 and the glutamate transporter-1 glycoprotein (GLT-1) exist in astrocytic membranes as a functional complex, as neuromyelitis optica autoantibodies directed against AQP4 lead to a concomitant loss of GLT-1 transporters Hinson SR. J Exp Med 2008, 205:

9 Aims o To evaluate AQP4 and GLT-1 on human ischemic stroke pathology o Evaluate their relationship with the vascular compartment o Evaluate their relationship with the neuronal compartment

10 Materials and Methods - Tissue collected from 12 patients with recent and old (organized) ischemic strokes; - 4 control patients - Chromogenic IHC - Immunofluorescence - Deconvolution / 3D renderings

11 AQP4/GLT-1 expression patterns in human stroke o AQP4 diffuses in the perilesional cortices

12 AQP4 expression patterns in human stroke o AQP4 is not expressed only on astrocytic end-feets

13 AQP4 expression patterns in human stroke o AQP4 heterogeneous expression in different types of astrocytes

14 AQP4 expression patterns in human stroke o AQP4 expression decreases with increasing distance from the glial scar

15 GLT-1 expression patterns in human stroke o GLT-1 is not present in the close proximity of the scar and in the glia limitans o Except that, GLT-1 and AQP4 seem to colocalize

16 AQP4 / GLT-1 shift to the neuronal compartment?

17 AQP4 / GLT-1 shift to the neuronal compartment? o A way to measure the randomness of distribution between two classes of objects (Neurons/vessels AQP4)? o Distance frequency analysis: The frequency distribution of red signal pixels function of their distances to the closest neighboring green silhouettes (based on an algorithm developed in Image ProPlus AMS software; Media Cybernetics - Marlow, UK)

18 AQP4 / GLT-1 shift to the neuronal compartment? o Example of image processing for distance frequency analysis

19 AQP4 / GLT-1 shift to the neuronal compartment? o AQP4 and GLT-1 aggregate in the closer proximity to the neuronal silhouettes (especially 0-60µm). o Old ischemic lesions show a density increase while this density decreases in recent lesions (edema may be responsible).

20 AQP4 and GLT-1 do not shift towards vessels

AQP4 and GLT-1 do not shift towards vessels o AQP4-positive pixels were grouped close around blood vessels (<10µm), without major differences between

21 AQP4 and GLT-1 do not shift towards vessels o AQP4-positive pixels were grouped close around blood vessels (<10µm), without major differences between pathologies. o GLT-1 distribution around blood vessels showed a peak for all studied instances at µm around the vessels, but without differences.

22 Neuron-vessel proximity control study o Neurons-vessels proximity study showed that the data observed are not given to random tissue volume changes.

23 Conclusions o AQP4 loss of cortical laminar expression might be related to failure of water-drainage mechanisms. o AQP4 expression was not restricted to end-feets, suggesting that water buffering towards and from the blood vessels might not be its only function o Our study suggests a dual and simultaneous astrocytic function depending on the relative distance to neurons and blood vessels: a) with increased water and glutamate-buffering capability in the 0-60µm perineuronal space; b) with water buffering capability in the immediate perineuronal space, even higher then around perivascular spaces.

24 Conclusions

25 Conclusions o AQP4 loss of cortical laminar expression might be related to failure of water-drainage mechanisms. o AQP4 expression was not restricted to end-feets, suggesting that water buffering towards and from the blood vessels might not be its only function o Our study suggests a dual and simultaneous astrocyte function depending on the relative distance to neurons and blood vessels: a) with increased water and glutamate-buffering capability in the 0-60µm perineuronal space; b) with water buffering capability in the immediate perineuronal space, even higher then around perivascular spaces.

26 o Are there selective AQP4 inhibitors?

27 A tale of two tails o Are there selective AQP4 inhibitors? o What about GLT-1 activators?

28 A tale of two tails Igarashi H. Neurol Sci. 2011, 32(1):113-6

29 A tale of two tails Igarashi H. Neurol Sci. 2011, 32(1):113-6

30 A tale of two tails Igarashi H. Neurol Sci. 2011, 32(1):113-6 Suzuki Y. J J Neuroimaging Apr;23(2):219-23

31 A tale of two tails Igarashi H. Neurol Sci. 2011, 32(1):113-6 Fukuda M. J Cereb Blood Flow Metab Oct;33

32 A tale of two tails Igarashi H. Neurol Sci. 2011, 32(1):113-6 Igarashi H. Neurol Sci. 2011, 32(1):113-6 Suzuki Y. J J Neuroimaging Apr;23(2):219-23

33 A tale of two tails

34 Our work

35 Our work o Optimizing the MCAO model and treatment Permanent cauterization of the MCA

36 Our work o Optimizing the MCAO model and treatment

37 Our work o Optimizing the MCAO model and treatment Treated Untreated

38 Our work o Optimizing the MCAO model and treatment Treated Untreated

39 Preliminary data o TGN-020 MCAO rats have less hemorrhages at 3 days o In all cases vessel walls seems to be intact at 3 days Laminin Albumin

Preliminary data o TGN-020 is affecting the whole brain Laminin Albumin Vessles/ mm2 Vessles/ mm2 4500 4500 4000 4000 3500 3500 3000 3000 2500 2500 2000 2000

40 Preliminary data o TGN-020 is affecting the whole brain Laminin Albumin Vessles/ mm2 Vessles/ mm Vascular densities Vascular densities Scar Perilesional Contralateral Scar Treatment Perilesional Ctrl Contralateral Treatment Ctrl

41 Preliminary data o o TGN-020 MCAO rats have less perilesional albumin infiltration Treated rats do not form such a dense glial scar Untreated Treated Alb AQP4 GFAP Alb AQP4 GFAP

42 Preliminary data o TGN-020 MCAO have less blunted, activated astrocytes Treated Untreated

43 Preliminary data o Optimizing organ clearing technique

44 The team o Dpt. of Histology and Research Methodology Assoc. prof. dr. Daniel Pirici Pathology o Dpt. of Pathology Immunofluorescence Deconvolution Multispectral imaging Human stroke brain bank Neuropathology Prof. dr. Claudiu Margaritescu Pathoogy Immunohistochemistry General pathology Microscopy o Dpt. of Physiology Assoc. prof. dr. Adrian Balseanu Neurology / Internal Medicine Teach. Assist. Bogdan Catalin Neurology Animal Facility Small animal surgery 2P microscopy o Dpt. of Anatomy Teaching assist. dr. Ionica Pirici Neurology Behavioral testing Human patient data and material

Function of aquaporin in the brain and brain edema

Nagoya Med. J., 199 Function of aquaporin in the brain and brain edema KAZUYA SOBUE Department of Anesthesiology and Medical crisis Management, Nagoya City University Graduate School of Medical Sciences