Neuroprotective Effects of Memantine

Hippocampal slice cultures Brown et al., Soc. Neurosci 2003 Semi-chronic 3-NP toxicity in organotypic hippocampal cultures Parallel incubation of 3-NP and memantine for 7 or 12 days Cresyl violet staining Homogenization Immunoblot Incubation with synaptic markers Memantine in an In Vitro Model for Neurodegeneration

Semi-chronic 3-NP toxicity in organotypic hippocampal cultures Brown et al., Soc. Neurosci NP for 7 days Control 10 µM1 µM5 µM Memantine Vehicle GluR1 (arbitary units) Neuroprotective Effect of Memantine In Vitro

Semi-chronic 3-NP toxicity in organotypic hippocampal cultures Brown et al., Soc. Neurosci NP for 7 days Vehicle Control 10 µM1 µM5 µM Memantine Synapsin II b (arbitary units) Neuroprotective Effect of Memantine In Vitro

CA1 Control3-NP 14 days3-NP + Memantine DG Semi-chronic 3-NP toxicity in organotypic hippocampal cultures Brown et al., Soc. Neurosci 2003 Neuroprotective Effect of Memantine In Vitro

or Memantine injection 30 min before NMDA Memantine infusion for 2 weeks Unilateral injection of NMDA (7.5 nmol) or 3NP (250 nmol) into the NBM Biochemical assay Choline acetyltransferase in the frontal cortex 2 weeks Wenk et al., Eur J Pharmacol 1995, NeuroReport 1996 Memantine‘s effect on lesions of the nucleus basalis magnocellularis (NBM) Memantine in an Animal Model for Neurodegenerative Dementia

ChAT activity control - lesioned side (nmol ACh/h*mg proteine) Wenk et al., Eur J Pharmacol Memantine (ED 50 = 2.8 mg/kg) MK-801 (ED 50 = mg/kg) Dose (mg/kg) Memantine injection (i.p.) attenuated NMDA-induced lesion of the NBM Protection of Cholinergic Neurons by Memantine

Wenk et al., NeuroReport 1996 Cortical ChAT activity control - lesioned side (nmol ACh/h*mg proteine) * p < 0.01 versus control 3-NP lesion NMDA lesion * * Memantine (20 mg/kg/d) Control Infusion of memantine attenuated damage to NBM neurones induced by injection of NMDA or 3-NP Degeneration of Cholinergic Neurons was Attenuated by Memantine

Memantine infusion (20 mg/kg/day) 7 daysImmunohistochemistry in the hippocampus: neuronal damage GFAP Miguel-Hidalgo et al., Brain Res 2002 Injection of ß-amyloid (1-40) into the hippocampus 2 days Memantine‘s effect on ß-amyloid-induced lesion of the hippocampus Memantine in an Animal Model for Alzheimer´s Disease

Memantine Placebo Extent of ß-amyloid-induced damage in the CA1 region Extent (µm) VehicleMemantine * Miguel-Hidalgo et al., Brain Res 2002 * p < 0.02 versus placebo Protection by Memantine Against A  - Induced Neurodegeneration Vehicle Memantine

Miguel-Hidalgo et al., Brain Res 2002 * p < 0.03 versus vehicle Area (%) Protection by Memantine Against A  - Induced Neurodegeneration Area of GFAP profiles around the injection site Vehicle Memantine * VehicleMemantine

Memantine effect on lipopolysaccharide (LPS)-induced brain insult and inflammation Memantine infusion (s.c. 20 mg/kg/day for 37 days) Infusion of LPS into the basal forebrain (37 days) Willard et al., Exp Brain Res 2000 Biochemical analysis in the frontal cortex: ChAT activity 10 days Effect of Memantine on Inflammation Induced Neurodegeneration

* p < versus control; ** p < 0.05 versus LPS Willard et al., Exp Brain Res 2000 Effect of LPS infusion into the basal forebrain on cortical ChAT activity ** ControlLPSLPS + Memantine * Decline in cortical ChAT activity [%] Memantine Protected Cholinergic Neurons from Damage by Inflammation

Effects of memantine on quinolinic acid-induced neurodegeneration 15 sec 10 trials/day 5 days T-maze alternation Biochemical analysis Removal of minipumps 3 days Parallel infusion of memantine (s.c. 20 mg/kg/day) and quinolinic acid (i.c.v.) 2 weeks Misztal et al., Eur J Pharmacol 1996 Memantine in an Animal Model for Neurodegenerative Dementia

Infusion of Memantine (20 mg/kg/day) attenuated T-maze learning deficit induced by chronic i.c.v. infusion of quinolinic acid (QA) Day Misztal et al., Eur J Pharmacol 1996 * p < 0.05 versus control and QA + Memantine Control QA QA + Memantine * * * * * Number of errors Attenuation of Quinolinic Acid Induced Memory Loss by Memantine

Memantine (20 mg/kg/day) attenuated the hippocampal cholinergic deficit induced by chronic i.c.v. infusion of quinolinic acid (QA) * p < 0.05 versus quinolinic acid * * ControlQAQA + Memantine Misztal et al., Eur J Pharmacol 1996 [H 3 ]Hemicholinium-3 binding (µmol/mg tissue) Attenuation of Quinolinic Acid Induced Neurodegeneration by Memantine

Summary Neuroprotective effects of memantine were shown, in vivo on Excitotoxic induced neurodegeneration ß-amyloid induced neuronal damage LPS induced inflammation in vitro on Metabolic disturbances due to mitochondrial dysfunction Conclusion: Neuroprotective effects of memantine have been shown under various conditions which are clinically relevant for Alzheimer's disease.

Memantine Inhibits and Reverses the Alzheimer Type Abnormal Hyperphosphorylation of tau and Associated Neurodegeneration Li L., Sengupta A., Haque N., Grundke-Iqbal I. and Iqbal K. FEBS Letters, 2004, 566 (1-3):

Tau Hyperphosphorylation in Alzheimer‘s Disease Alzheimer‘s disease In vitro model Hippocampal culture + okadaic acid (OA) PP-2A activity  CaMKII activity  PKA activity  Hyperphosphorylation of tau Therapeutic approach Hyperphosphorylation of tau Tangle formation Neurodegeneration

Okadaic acid for 24hMemantine or vehicle for 24h Hippocampal slices Analysis Effects of Memantine on Phosphorylation of tau - Methods Assay for phosphatase- or kinase activity Western blots (p-tau) Assay for cell death

Memantine Counteracted OA-induced PP-2A Inhibition PP-2A activity PP-2A activity (% of control) 24 h OA + 24 h vehicle 24 h OA + 24 h Mem 24 h Mem * p < 0.05 versus OA treated tissue nM OA µM Mem *

CaMKII activity PKA activity Memantine Restored CaMKII and PKA Activity Kinase activity ( % of control) * p < 0.05 versus OA treated tissue nM OA µM Mem h OA + 24 h vehicle 24 h OA + 24 h Mem 24 h Mem * * *

Memantine Counteracted OA-induced Cell Death Cell death assay Control 24 h OA + 24 h vehicle 24 h OA + 24 h Mem 24 h Mem LDH release (ratio after / before treatment) nM OA µM Mem * * * p < 0.05 versus OA treated tissue

nM OA µM Mem - -+ Memantine Counteracted CaMKII- induced Phosphorylation of tau [ 125 I] Western blot with Antibody against pS-262 Control 24 h OA + 24 h vehicle 24 h OA + 24 h Mem (10 µM) Phosphorylation of tau pSer262 pSer422

Immunocytochemical staining of pSer nM OA µM Mem nM OA µM Mem -- + Memantine Counteracted OA-induced Phosphorylation of tau

In an in vitro model using okadaic acid memantine was shown to Restore normal PP-2A, CaMKII and PKA activities Prevent cell death Positively influence phosphorylation / dephosphorylation imbalance Conclusion Apart from the symptomatic benefits, memantine might also positively influence pathological changes in AD. Summary