Inhibition of Microglial Activation by Amitriptyline and Doxepin in Interferon-beta Pre-Treated Astrocyte-Microglia Co-Culture Model of Inflammation

Depression may occur in patients with multiple sclerosis, especially during interferon-beta (IFN-beta) treatment, and therapy with antidepressants may be necessary. Interactions of IFN-beta with antidepressants concerning glia-mediated inflammation have not yet been studied. Primary rat co-cultures of astrocytes containing 5% (M5, consistent with "physiological" conditions) or 30% (M30, consistent with "pathological, inflammatory" conditions) of microglia were incubated with 10 ng/mL amitriptyline or doxepin for 2 h, or with 2000 U/mL IFN-beta for 22 h. To investigate the effects of antidepressants on IFN-beta treatment, amitriptyline or doxepin was added to IFN-b pre-treated co-cultures. An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was performed to measure the glial cell viability, immunocytochemistry was performed to evaluate the microglial activation state, and ELISA was performed to measure pro-inflammatory TNF-alpha and IL-6 cytokine concentrations. Incubation of inflammatory astrocyte-microglia co-cultures with amitriptyline, doxepin or IFN-beta alone, or co-incubation of IFN-beta pre-treated co-cultures with both antidepressants, significantly reduced the extent of inflammation, with the inhibition of microglial activation. TNF-alpha and IL-6 levels were not affected. Accordingly, the two antidepressants did not interfere with the anti-inflammatory effect of IFN-beta on astrocytes and microglia. Furthermore, no cytotoxic effects on glial cells were observed. This is the first in vitro study offering novel perspectives in IFN-beta treatment and accompanying depression regarding glia.