Cai Song1,2, Yih-Shyuan Wu3, Zhi-You Yang4, Allan V Kalueff4,5,6, Yin-Yin Tsao3, Yilong Dong7, Kuan-Pin Su3. 1. Research Institute for Marine Drugs and Nutrition, Food Science and Technology, Guangdong Ocean University, Zhanjiang, China, cai.song@dal.ca. 2. Graduate Institute of Biomedical Sciences, College of Medicine, China Medical University, and Departments of Medical Research, China Medical University Hospital, Taichung, Taiwan, cai.song@dal.ca. 3. Graduate Institute of Biomedical Sciences, College of Medicine, China Medical University, and Departments of Medical Research, China Medical University Hospital, Taichung, Taiwan. 4. Research Institute for Marine Drugs and Nutrition, Food Science and Technology, Guangdong Ocean University, Zhanjiang, China. 5. Institute of Translational Biomedicine, St. Petersburg State University, St. Petersburg, Russian Federation. 6. Ural Federal University, Ekaterinburg, Russian Federation. 7. School of Medicine, Yunnan University, Kunming, China.
Abstract
OBJECTIVE: Both excitotoxicity and neurotrophin deficiency may contribute to the etiology of depression and neurodegeneration. Astrocytes not only regulate glutamate metabolism and clearance, they also produce neurotrophins in the brain. However, the direct interaction between neurons and astrocytes remains unknown. METHODS: This study evaluated the cellular mechanisms by which astrocyte-conditioned medium (ACM) protects prefrontal cortical neurons from glutamate-induced death by measuring cell viability and morphology as well as mRNA and protein expression of brain-derived neurotrophic factor (BDNF), BDNF receptors, glial cell line-derived neurotrophic factor (GDNF), and the proinflammatory cytokine, tumor necrosis factor (TNF)-α. Neurons and astrocytes were purified from the brains of neonatal 1-day-old Sprague-Dawley rats. ACM was harvested after exposing astrocytes to culture medium containing 100 μM glutamate for 48 h. RESULTS: Glutamate insult (100 μM for 6 h) significantly reduced neuronal cell viability and increased the mRNA expression of BDNF. Glutamate (24 h) decreased neuronal viability and the expression of BDNF, but increased mRNA expression of GFAP, p75 neurotrophin receptor (p75NTR), and TNF-α. ACM pretreatment (2 h) reversed glutamate-decreased cell viability and increased BDNF, but reduced the expression of GDNF, P75NTR, and TNF-α at the mRNA level. Western blotting generally confirmed the mRNA expression following 24 glutamate insults. Furthermore, the glutamate-induced decrease in the protein expression of BDNF and full-length TrkB receptor and increase in pro-BDNF, truncated TrkB isoform 1 receptor, p75NTR, GDNF, and TNF-α were significantly attenuated by ACM pretreatment. CONCLUSIONS: The study demonstrates that ACM exerts neuroprotective effects on cell viability, and this effect is most likely mediated through the modulation of neurotrophin and TNF-α expression.
OBJECTIVE: Both excitotoxicity and neurotrophin deficiency may contribute to the etiology of depression and neurodegeneration. Astrocytes not only regulate glutamate metabolism and clearance, they also produce neurotrophins in the brain. However, the direct interaction between neurons and astrocytes remains unknown. METHODS: This study evaluated the cellular mechanisms by which astrocyte-conditioned medium (ACM) protects prefrontal cortical neurons from glutamate-induced death by measuring cell viability and morphology as well as mRNA and protein expression of brain-derived neurotrophic factor (BDNF), BDNF receptors, glial cell line-derived neurotrophic factor (GDNF), and the proinflammatory cytokine, tumor necrosis factor (TNF)-α. Neurons and astrocytes were purified from the brains of neonatal 1-day-old Sprague-Dawley rats. ACM was harvested after exposing astrocytes to culture medium containing 100 μM glutamate for 48 h. RESULTS:Glutamate insult (100 μM for 6 h) significantly reduced neuronal cell viability and increased the mRNA expression of BDNF. Glutamate (24 h) decreased neuronal viability and the expression of BDNF, but increased mRNA expression of GFAP, p75 neurotrophin receptor (p75NTR), and TNF-α. ACM pretreatment (2 h) reversed glutamate-decreased cell viability and increased BDNF, but reduced the expression of GDNF, P75NTR, and TNF-α at the mRNA level. Western blotting generally confirmed the mRNA expression following 24 glutamate insults. Furthermore, the glutamate-induced decrease in the protein expression of BDNF and full-length TrkB receptor and increase in pro-BDNF, truncated TrkB isoform 1 receptor, p75NTR, GDNF, and TNF-α were significantly attenuated by ACM pretreatment. CONCLUSIONS: The study demonstrates that ACM exerts neuroprotective effects on cell viability, and this effect is most likely mediated through the modulation of neurotrophin and TNF-α expression.