Transcriptional effects of anti-inflammatory or anti-depressant drugs on primary human macrophages inflammatory response

The direct communication between our central nervous and inflammatory signalling systems is a well-recognised, yet poorly understood relationship. To increase our understanding of this relationship, we examined the metabolism of serotonin and its precursor tryptophan in macrophages under inflammatory settings. Both are involved in inflammatory signalling and known to play a major role in mood regulation. Tryptophan depletion by macrophages during inflammation can consequently result in a reduction of serotonin systemically and has been suggested to cause depression. Increased understanding of this system could help overcome the problem of treatment resistant depressed patients. To this end, we treated primary human monocyte derived macrophages with a range of anti-depressant/anti-inflammatory drugs and analysed their transcriptional profile under various inflammatory conditions. In addition to the classic endotoxic driver of inflammation, LPS, we also used IFN which is a constitutive cytokine shown to directly induce depression when administered in high doses. The anti-depressant drugs were not found to have any significant effects on macrophage inflammatory signalling. However, the anti-inflammatories drugs were found to alter components of the serotonin/tryptophan metabolism pathways. This study increases our understanding of the intricacies of immune/mood cross-talk and offers into developing anti-inflammatories as co-treatment for depression.

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Regan T, Gill AC, Clohisey SM, Barnett MW, Pariante CM, Harrison NA, MRC Immunopsychiatry Consortium., Hume DA, Bullmore ET, Freeman TC