The c‐Raf inhibitor GW5074 provides neuroprotection in vitro and in an animal model of neurodegeneration through a MEK‐ERK and Akt‐independent mechanism

• Published in: Journal of neurochemistry Vol. 90; no. 3; pp. 595 - 608
• Main Authors: Chin, Paul C., Liu, Li, Morrison, Bradley E., Siddiq, Ambreena, Ratan, Rajiv R., Bottiglieri, Teodoro, D'Mello, Santosh R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-08-2004; Blackwell
• Subjects: Animals; Biological and medical sciences; B‐Raf; Cell Death - drug effects; Cells, Cultured; cerebellar granule neurons; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Disease Models, Animal; Enzyme Inhibitors - pharmacology; Farnesol - analogs & derivatives; Farnesol - pharmacology; Huntington Disease - chemically induced; Huntington Disease - pathology; Huntington Disease - prevention & control; Huntington's disease; Indoles - pharmacology; Medical sciences; Mitogen-Activated Protein Kinase Kinases - antagonists & inhibitors; Mitogen-Activated Protein Kinase Kinases - metabolism; Mitogen-Activated Protein Kinases - antagonists & inhibitors; Mitogen-Activated Protein Kinases - metabolism; Nervous system (semeiology, syndromes); Nervous system as a whole; neurodegeneration; Neurodegenerative Diseases - chemically induced; Neurodegenerative Diseases - pathology; Neurodegenerative Diseases - prevention & control; Neurology; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; neuroprotection; Neuroprotective Agents - pharmacology; Neurotoxins; Nitro Compounds; Phenols - pharmacology; Propionates; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins - antagonists & inhibitors; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-raf - antagonists & inhibitors; Rats; Rats, Sprague-Dawley; Salicylates - pharmacology; Signal Transduction - drug effects; Cerebellum; Animal model; Neuroprotection; Extracellular signal-regulated protein kinase; Rat; Central nervous system; neurodegeneration; Encephalon; Degenerative disease; Degeneration; B-Raf; Nervous system diseases; Granule neuron; Enzyme; Rodentia; Huntington disease; Huntington's disease; In vitro; Cerebral disorder; Genetic disease; cerebellar granule neurons; Vertebrata; Mammalia; Animal; Central nervous system disease; Inhibitor; Extrapyramidal syndrome
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2004.02530.x

Cerebellar granule neurons undergo apoptosis when switched from a medium containing high potassium (HK) to one that has low potassium (LK). LK‐induced cell death is blocked by GW5074 {5‐Iodo‐3‐[(3,5‐dibromo‐4‐hydroxyphenyl) methylene]‐2‐indolinone}, a synthetic drug that inhibits c‐Raf activity in vitro. GW5074 has no direct effect on the activities of several apoptosis‐associated kinases when assayed in vitro. In contrast to its effect in vitro, treatment of neurons with GW5074 causes c‐Raf activation (when measured in vitro in the absence of the drug) and stimulates the Raf‐MEK‐ERK pathway. Treatment of neurons with GW5074 also leads to an increase in the activity of B‐Raf, which is not inhibited by GW5074 in vitro at concentrations at which the drug exerts its neuroprotective effect. PD98059 and U0126, two distinct inhibitors of MEK, block the activation of ERK by GW5074 but have no effect on its ability to prevent cell death. Overexpression of a dominant‐negative form of Akt does not reduce the efficacy of GW5074, demonstrating an Akt‐independent mechanism of action. Neuroprotection is inhibited by SN‐50, a specific inhibitor of nuclear factor‐kappa B (NF‐κB) and by the Ras inhibitor S‐trans, trans‐farnesylthiosalicylic acid (FTS) implicating NF‐κB and Ras in the neuroprotective signaling pathway activated by GW5074. In addition to preventing LK‐induced apoptosis, treatment with GW5074 protects against the neurotoxic effects of MPP+ and methylmercury in cerebellar granule neurons, and glutathione depletion‐induced oxidative stress in cortical neurons. Furthermore, GW5074 prevents neurodegeneration and improves behavioral outcome in an animal model of Huntington's disease. Given its neuroprotective effect on distinct types of cultured neurons, in response to different neurotoxic stimuli, and in an animal model of neurodegeneration, GW5074 could have therapeutic value against neurodegenerative pathologies in humans.