Imipramine and fluoxetine inhibit LPS-induced activation and affect morphology of microglial cells in the rat glial culture.

Background: Recent evidence has suggested that antidepressants evoke neuroprotective and immunomodulatory effects in the brain, partly at least, by inhibiting glia activation. This study has been conducted on the lipopolysaccharide (LPS)-stimulated primary rat mixed glial cell culture in order to better recognize the influence of imipramine (a tricyclic antidepressant) and fluoxetine (a selective serotonin reuptake inhibitor) on the important balance between pro- and anti-inflammatory cytokines produced by the glial cells. Moreover, microscopic observations were made to describe the morphological alterations in the studied cell cultures exposed to the drugs.

Methods: The effect of both antidepressants on TNF-α, IL-1β and IL-10 levels was determined by ELISA. The mRNA levels of mentioned cytokines were evaluated by qRT-PCR assay. Moreover, drug influence on the LPS-stimulated level of NF-κB p65 subunit in nuclear fraction was determined by the colorimetric transcription factor assay.

Results: After LPS-stimulation both drugs decreased concentration of TNF-α and IL-1β in culture medium and expression of TNF-α and IL-1β mRNAs in cellular extracts. They also diminished the LPS-induced nuclear translocation of NF-κB p65 subunit. In contrast, imipramine and fluoxetine induced a few-fold weaker suppressing effect on the levels of IL-10. Parallelly to the inhibition of the LPS-induced inflammatory response, the antidepressants prevented the morphological alterations of cells elicited by LPS. Moreover, in unstimulated cultures imipramine but not fluoxetine caused transformation of microglia cells into cells with neuron-like morphology.

Conclusions: Imipramine and fluoxetine, by modulating glia activation, may exert anti-inflammatory effects in the CNS. It also seems that microglia cells are important target particularly for imipramine.