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- 2018
Ciliary Neurotrophic Factor Activated Signaling Pathways in Retinal Müller Cells - Ciliary Neurotrophic Factor Activated Signaling Pathways in Retinal Müller Cells - Open Access PubAbstract: Ciliary neurotrophic factor (CNTF) is a well-tested, neuroprotective agent that has been shown to retard photoreceptor degeneration in several animal models of retinitis pigmentosa. The molecular mechanisms underlying CNTF-mediated neuroprotection are currently not understood. CNTF could act directly on photoreceptors or it could act indirectly by stimulating Müller glial cells to produce photoreceptor neuroprotective agents. To better characterize CNTF action on Müller cells, we have studied signaling pathways activated by CNTF using an established retinal Müller cell line, rMC-1. RNA was isolated from CNTF-treated cultures, and suppressor of signal transducer and activator of transcription (SOCS3) and Glial fibrillary acidic protein (GFAP) transcript levels were assessed by quantitative real-time PCR. Immunoblotting was used to examine activation ofmitogen activated protein kinase (ERK1/2/MAPK) and phosphoinositide 3-kinase (PI3-K)/Aktpathways in response to CNTF. Additionally, the level of5' AMP-activated protein kinase (AMPK), an enzyme that plays a key role in cellular energy homeostasis levels, was determined by immunoblotting. CNTF treatment resulted strong upregulation of SOCS3 and GFAP transcripts that were blocked by expression of a dominant-negative STAT3 mutant. CNTF treatment also resulted in transient activation of ERK1/2/MAPK but not PI3K/Akt signaling pathway. There was no change in activation of AMPK. We conclude that CNTF treatment leads to stimulation of JAK-STAT and MAPK signaling pathways but not the PI3K/AKT pathway, associated with cell death, in Müller cells. DOI10.14302/issn.2470-0436.jos-15-739 Ciliary neurotrophic factor (CNTF) is a neuroprotective agent that has been shown to retard rod photoreceptor degeneration in genetic models of retinitis pigmentosa or in animals with light damage, and is currently in clinical trials for Retinitis pigmentosa and Age-related macular degeneration 1. Its mode of action is not established although it has been postulated that CNTF could act indirectly by stimulating Müller glial cells to release factors that protect photoreceptors 1, 2, 3, 4, 5. To characterize growth factors and cytokines induced in Müller cells, we recently carried out microarray analysis of GFP+-Müller cells that had been flow-sorted from eyes injected with CNTF 6. We found that CNTF treatment leads to robust transcriptional activation of several genes in Müller cells in situ. One or more of the gene products such as Endothelin 2 and Transforming growth factor β1, might be responsible for the neuroprotective action of
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