PS127. Antidepressant amitriptyline activates matrix metalloproteinase in astroglial cells: involvement in glial cell line-derived neurotrophic factor expression.

Abstract

Background: Glial cells, especially astrocytes have been implicated in the pathophysiology of mood disorder and the efficacy of antidepressants. The tricyclic antidepressant amitriptyline induces a Gα_i/o/matrix metalloproteinase (MMP)/fibroblast growth factor receptor (FGFR)/ERK cascade, which is crucial for glial cell line-derived neurotrophic factor (GDNF) mRNA expression in rat C6 astroglial cells (C6 cells), primary astrocytes. However, the identity of the MMP involved has yet to be identified. The current study identified the mechanism of MMP activation induced by amitriptyline and the MMP subtypes involved.

Methods: C6 cells and primary astrocytes were used in the following experiments. The level of GDNF mRNA was measured by real-time PCR and the activity of MMP-2, -9 was measured by gelatin-zymography.

Results: Matrix metalloproteinase-2, -3 and -9 were expressed in C6 cells. Following amitriptyline treatment, MMP-9 activity in culture medium increased without any change in mRNA levels, whereas no change in MMP-2 activity was observed. A similar response with MMP-9 was observed with different classes of antidepressants, but not with drugs lacking antidepressant activity and monoamines. Amitriptyline-induced ERK activation/GDNF mRNA expression was blocked by MMP-3 and MMP-9 inhibition, but not by MMP-2 inhibition. Treatment with exogenous MMP-3 and MMP-9 increased GDNF mRNA expression. Amitriptyline-induced MMP-9 activation was suppressed with MMP-3 inhibition and exogenous MMP-3-induced GDNF mRNA expression was suppressed by MMP-9 inhibition, indicating that MMP-3 regulates MMP-9 activity. The FGFR-induced ERK/GDNF cascade was not blocked by MMP inhibition, indicating that MMP activation is upstream of FGFR activation. Furthermore, amitriptyline-induced MMP-9 activation is not direct but via intracellular signaling, as Gα_i/o inhibition and Src family tyrosine kinases inhibition blocked amitriptyline-induced MMP-9 activation.

Conclusion: The current results elaborate a potential non-monoamine mediated mechanism of antidepressant action involving MMP activation and intracellular signaling in astrocytes.