ag-490 and Neurodegenerative-Diseases

Quinolinic acid (QA) striatal lesion in rodents induces neuronal death, astrogliosis and migration of neuroblasts from subventricular zone to damaged striatum. These phenomena occur in some human neurodegenerative illnesses, but the underlying mechanisms are unknown. We investigated the effect of AG490, a Janus-kinase 2 (JAK2) inhibitor, on astrogliosis, neuronal loss and neurogenesis in the striatum of adult mice after unilateral infusion of QA (30 nmol). Animals were given subcutaneous injections of AG490 (10 mg/kg) or vehicle immediately after lesion and then once daily for six days. Brain sections were used for neuronal stereological quantification, immunohistochemical and Western Blotting analyses for GFAP and doublecortin, markers of astrocytes and neuroblasts, respectively. The total area of doublecortin-positive cells (ADPC) and the number of neurons (NN) in the lesioned (L) and contralateral (CL) sides were evaluated. Neurogenesis index (NI=ADPC(L)/ADPC(CL)) and neuronal ratio (NR=NN(L)/NN(CL)) were calculated. After QA administration, blotting for GFAP showed an ipsilateral decrease of 19% in AG490- vs vehicle-treated animals. NR was 25% higher in mice given AG490 vs controls given vehicle. NI showed a decrease of 21% in AG490- vs vehicle-treated mice. Our results indicate that JAK2 inhibition reduces QA lesion and suggest that astrogliosis may impair neuronal survival in this model.

Topics: Animals; Astrocytes; Blotting, Western; Cell Count; Cell Death; Doublecortin Domain Proteins; Enzyme Inhibitors; Glial Fibrillary Acidic Protein; Gliosis; Immunohistochemistry; Janus Kinase 2; Male; Mice; Mice, Inbred C57BL; Microtubule-Associated Proteins; Neostriatum; Neurodegenerative Diseases; Neurons; Neuropeptides; Neuroprotective Agents; Phosphorylation; Quinolinic Acid; Signal Transduction; STAT Transcription Factors; Tyrphostins

Microglia, the resident macrophage of the brain, mediates immune and inflammatory responses in the central nervous system (CNS). Activation of microglia and secretion of inflammatory cytokines associate with the pathogenesis of CNS diseases, including multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease, prion disease, and AIDS dementia. Microbial pathogens, cytokines, chemokines, and costimulatory molecules are potent inducers of microglial activation in the CNS. Signaling through its receptor, IL-3 induces the activation of JAK-STAT and MAP kinase pathways in microglial cells. In this study, we found that in vitro treatment of EOC-20 microglial cells with tyrphostin AG490 blocked IL-3-induced tyrosine phosphorylation of JAK2, STAT5A, and STAT5B signaling proteins. Stable transfection of EOC-20 cells with a dominant negative JAK2 mutant also blocked IL-3-induced tyrosine phosphorylation of JAK2, STAT5A, and STAT5B in microglia. The blockade of JAK2-STAT5 pathway resulted in a decrease in IL-3-induced proliferation and expression of CD40 and major histocompatibility complex class II molecules in microglia. These findings highlight the fact that JAK2-STAT5 signaling pathway plays a critical role in mediating IL-3-induced activation of microglia.

Topics: Animals; CD40 Antigens; Cell Division; Cell Line; DNA-Binding Proteins; Encephalitis; Enzyme Inhibitors; Gliosis; Histocompatibility Antigens Class II; Humans; Interleukin-3; Janus Kinase 2; Mice; Microglia; Milk Proteins; Neurodegenerative Diseases; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Signal Transduction; STAT5 Transcription Factor; Trans-Activators; Transfection; Tumor Suppressor Proteins; Tyrphostins