# Antidepressants Target the ST3GAL5–GM3 Lipid Pathway to Suppress Microglial Inflammation

## TL;DR

This study shows that antidepressants reduce microglial inflammation by targeting a lipid pathway involving ST3GAL5 and GM3.

## Contribution

The study identifies the ST3GAL5–GM3 lipid pathway as a novel target for antidepressant action in suppressing microglial inflammation.

## Key findings

- VEN and VOR suppressed NF-κB and STAT3 activation in microglia, effects mirrored by GM3 treatment and ST3GAL5 overexpression.
- Transcriptomic analysis revealed consistent gene expression changes across VEN, VOR, and ST3GAL5OE conditions.
- Downregulated genes were linked to pro-inflammatory pathways, while upregulated genes were associated with synaptic organization.

## Abstract

Major depression (MD) is associated with chronic inflammation and impaired neuroplasticity; however, the cellular mechanisms underlying antidepressant action remain incompletely understood. We performed transcriptomic profiling and functional validation in human microglia treated with venlafaxine (VEN) and vortioxetine (VOR), or with stable ST3GAL5 overexpression (ST3GAL5OE). Differential expression analysis, enrichment studies, and functional assays using NF-κB-RE-NlucP and SIE-NlucP reporter lines were conducted to assess the impact on inflammatory signaling. Microarray analysis identified 41 genes consistently upregulated and 316 consistently downregulated across VEN, VOR, and ST3GAL5OE conditions. Upregulated genes were enriched for synaptic organization, whereas downregulated genes were associated with nitric oxide biosynthesis and pro-inflammatory pathways, including Rap1, MAPK, and PI3K-Akt signaling. Functional assays confirmed that VEN and VOR suppressed cytokine-induced NF-κB and STAT3 activation, effects that were recapitulated by exogenous GM3 treatment and ST3GAL5 overexpression. Chronic exposure to VEN or VOR produced more modest, pathway-specific suppression, supporting convergence on the ST3GAL5–GM3 axis. These findings extend the conventional monoaminergic model of antidepressant action by highlighting the ST3GAL5–GM3 lipid remodeling axis as a novel regulatory pathway that attenuates microglial inflammatory signaling. Although validation in primary microglia and in vivo models is required, our results suggest that this axis could serve as both a therapeutic target and a candidate biomarker for inflammation-associated MD.