Pharmacological Activation Gi/o Protein Increases Glial Cell Line-Derived Neurotrophic Factor Production through Fibroblast Growth Factor Receptor and Extracellular Signal-Regulated Kinase Pathway in Primary Cultured Rat Cortical Astrocytes

Abstract

A significant reduction of glial cell line-derived neurotrophic factor (GDNF) has been identified in the pathophysiology of neurodegenerative and neuropsychiatric disorders. Thus, clarification of the mechanism of GDNF production, and modulating brain GDNF levels could be a novel therapeutic approach. A previous study demonstrated that antidepressant amitriptyline-induced GDNF production was significantly inhibited by pertussis toxin (PTX), a Gi/o protein inhibitor in astrocytes, the main source of GDNF in the brain. However, it is not known whether direct activation of Gi/o protein might induce GDNF expression, and what mechanisms might be involved after Gi/o protein activation. The current study investigated Gi/o proteininitiated GDNF production in rat cortical astrocytes using activators that directly activate Gi/o protein, mastoparan and compound48/80. Treatment of astrocytes with either mastoparan or compound48/80 increased GDNF mRNA expression at 3 and 6 h, and GDNF protein release at 24 h. Treatment of astrocyte with either mastoparan or compound48/80 increased brain-derived neurotrophic factor (BDNF) mRNA expression as well as GDNF. Mastoparan and compound48/80-induced GDNF mRNA expression were significantly inhibited by not only PTX, but also fibroblast growth factor receptor (FGFR) inhibitors, and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor. In fact, both FGFR substrate2α (FRS2α) and ERK phosphorylation were increased by treatment with either mastoparan or compound48/80, and these were significantly blocked by PTX. Thus, direct, receptor-independent Gi/o protein activation increases GDNF production through FGFR/ERK signaling pathway. The current results indicate a critical role of Gi/o signaling in the regulation of GDNF expression in astrocytes.Key words astrocyte; Gi/o protein; glial cell line-derived neurotrophic factor; brain-derived neurotrophic factor; neurodegenerative disorder; neuropsychiatric disorder Glial cell line-derived neurotrophic factor (GDNF) was originally identified in conditioned medium of a glial cell line as an index of viability of midbrain tyrosine hydroxylasepositive dopaminergic neurons.

Lysophosphatidic acid induces thrombospondin‐1 production in primary cultured rat cortical astrocytes

“…Potential cytotoxicity of LPA in astrocyte was evaluated by the tetrazolium salt 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide (MTT; Sigma‐Aldrich Co., ) assay as described previously (Hisaoka‐Nakashima et al., 2017). Cell viability was not affected by concentrations of LPA as determined by the MTT assay (Figure S3).…”