Ciliary neurotrophic factor activates spinal cord astrocytes, stimulating their production and release of fibroblast growth factor-2, to increase motor neuron survival.
At focal CNS injury sites, several cytokines accumulate, including ciliary neurotrophic factor (CNTF) and interleukin-1beta (IL-1beta). Additionally, the CNTF alpha receptor is induced on astrocytes, establishing an autocrine/paracrine loop. How astrocyte function is altered as a result of CNTF stimulation remains incompletely characterized. Here, we demonstrate that direct injection of CNTF into the spinal cord increases GFAP expression and astroglial size and that primary cultures of spinal cord astrocytes treated with CNTF, IL-1beta, or leukemia inhibitory factor exhibit nuclear hypertrophy comparable to that observed in vivo. Using a coculture bioassay, we further demonstrate that CNTF treatment of astrocytes increases their ability to support ChAT(+) ventral spinal cord neurons (presumably motor neurons) more than twofold compared with untreated astrocytes. Also, the complexity of neurites was significantly increased in neurons cultured with CNTF-treated astrocytes compared with untreated astrocytes. RT-PCR analysis demonstrated that CNTF increased levels of FGF-2 and nerve growth factor (NGF) mRNA and that IL-1beta increased NGF and hepatocyte growth factor mRNA levels. Furthermore, both CNTF and IL-1beta stimulated the release of FGF-2 from cultured spinal cord astrocytes. These findings demonstrate that cytokine-activated astrocytes better support CNS neuron survival via the production of neurotrophic molecules. We also show that CNTF synergizes with FGF-2, but not epidermal growth factor, to promote DNA synthesis in spinal cord astrocyte cultures. The significance of these findings is discussed by presenting a new model depicting the sequential activation of astrocytes by cytokines and growth factors in the context of CNS injury and repair.
Albrecht
Phillip J
PJ
Department of Neuroscience and Anatomy, Milton S. Hershey College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033, USA.
Dahl
John P
JP
Stoltzfus
Olivia K
OK
Levenson
Robert
R
Levison
Steven W
SW
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D020934:Ciliary Neurotrophic Factor / Q000494:pharmacology*; D018920:Coculture Techniques; D004247:DNA / Q000096:biosynthesis; D004357:Drug Synergism; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis* / Q000235:genetics; D006131:Growth Inhibitors / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000494:pharmacology; D008297:Male; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects*; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism; D016501:Neurites / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D020934:Ciliary Neurotrophic Factor; D006131:Growth Inhibitors; D007375:Interleukin-1; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2; D004247:DNA