Methods and compositions for inhibition of axonal degeneration by modulation of the dlk/jnk pathway

Abstract

Methods of reducing Wallerian degeneration are disclosed. These methods comprise inhibiting expression or activity of a mixed lineage kinas such as a dual leucine-zipper-bearing kinase (DLK), inhibiting expression or activity of a molecule acting downstream from DLK, such as a c-Jun N-terminal kinase (JNK), or a combination thereof. Further disclosed are methods of screening candidate compounds for DLK inhibition activity. These methods comprise providing a neuronal culture comprising a plurality of axons; contacting the culture with a candidate compound and with an axon degeneration-triggering agent; and comparing axonal degeneration in the culture to a control culture comprising the axon degeneration-triggering agent but not the candidate compound.

1 . A method of treating or preventing a neuropathy in a mammal, the method comprising administering to a mammal in need thereof, an inhibitor of at least one mixed lineage kinase (MLK) or at least one c-Jun N-terminal kinase (JNK) in an amount effective to inhibit MLK activity and/or MLK expression and/or JNK activity and/or JNK expression in diseased and/or injured neurons and/or supporting cells. 
     
     
         2 . A method according to  claim 1 , wherein the at least one MLK is dual leucine-zipper-bearing kinase (DLK). 
     
     
         3 . A method according to  claim 1 , wherein the at least one JNK is selected from the group consisting of JNK1, JNK2 and JNK3. 
     
     
         4 . A method according to  claim 1 , wherein the neuropathy comprises an axonopathy. 
     
     
         5 . A method according to  claim 4 , wherein the axonopathy comprises Wallerian degeneration. 
     
     
         6 . A method according to  claim 1 , wherein the JNK inhibitor is SP600215. 
     
     
         7 . A method according to  claim 1 , wherein the inhibitor is an siRNA directed against DLK. 
     
     
         8 . A method according to  claim 1 , wherein the inhibitor is an siRNA directed against at least one JNK selected from the group consisting of JNK1, JNK2 and JNK3. 
     
     
         9 . A method according to  claim 1 , wherein the neuropathy is hereditary or congenital or associated with a neurodegenerative disease, a motor neuron disease, a neoplasia, an endocrine disorder, a metabolic disease, a nutritional deficiency, atherosclerosis, an autoimmune disease, a mechanical injury, a chemical injury, a drug-induced injury, a thermal injury, a radiation injury, a nerve compression, a retinal nerve disorder, an optic nerve disorder, a mitochondrial dysfunction, a progressive dementia demyelinating disease, ischemia, stroke, an infectious disease or an inflammatory disease. 
     
     
         10 . A method according to  claim 9 , wherein the neuropathy is induced by a cytotoxic anticancer agent. 
     
     
         11 . A method according to  claim 9 , wherein the optic nerve disorder is selected from the group consisting of glaucoma, retinal ganglion degeneration, optic neuritis, optic degeneration, macular degeneration, ischemic optic neuropathy, traumatic injury to the optic nerve, hereditary optic neuropathy, metabolic optic neuropathy, neuropathy due to a toxic agent, neuropathy caused by an adverse drug reaction and neuropathy caused by a vitamin deficiency. 
     
     
         12 . A method according to  claim 1 , wherein the administering to the mammal comprises intraocular administering. 
     
     
         13 . A method of screening a candidate agent for treating a neuropathy in a mammal, the method comprising:
 contacting a mammalian cell expressing at least one mixed lineage kinase (MLK) with a candidate agent; and   detecting a decrease in MLK activity in the cell.   
     
     
         14 . A method in accordance with  claim 13 , wherein the at least one MLK is dual leucine-zipper-bearing kinase (DLK). 
     
     
         15 . A method in accordance with  claim 13 , wherein the mammalian cell is a neuron. 
     
     
         16 . A method in accordance with  claim 15 , wherein the neuron is a dorsal root ganglion neuron. 
     
     
         17 . A method of screening a candidate agent for treatment of a neuropathy in a mammal, the method comprising:
 contacting at least one mammalian cell expressing at least one mixed lineage kinase (MLK) and at least one c-Jun N-terminal kinase (JNK) with a candidate agent; and   detecting a decrease in activity of the at least one MLK or the at least one JNK activity in the cell.   
     
     
         18 . A method in accordance with  claim 17 , wherein the at least one MLK is dual leucine-zipper-bearing kinase (DLK). 
     
     
         19 . A method in accordance with  claim 17 , wherein the at least one JNK is selected from the group consisting of JNK1, JNK2 and JNK3. 
     
     
         20 . A method in accordance with  claim 17 , wherein the at least one mammalian cell is a mammalian neuron.