Glutathione S-transferases: Unexpected roles in astrocyte activation and astrocyte-microglia communication during brain inflammation

Astrocytes and microglia play critical roles in brain inflammation, but their mutual regulation is not fully understood. Here we report unexpected roles for glutathione S-transferases (GSTs), particularly GSTM1, in astrocyte activation and astrocyte-mediated enhancement of microglia activation during brain inflammation. We found that astrocyte-specific silencing of GSTM1 expression in the prefrontal cortex (PFC) attenuated microglia activation in brain inflammation induced by systemic injection of lipopolysaccharides (LPS). Gstm1 silencing in astrocytes also attenuated LPS-induced TNF-α production by microglia in co-culture. In astrocytes, GSTM1 was required for the activation of nuclear factor-κB (NF-κB) and c-Jun N-terminal kinases (JNK) and the production of pro-inflammatory mediators previously implicated in microglia activation, such as granulocyte-macrophage colony-stimulating factor (GM-CSF/CSF2) and chemokine (C-C motif) ligand 2 (CCL2). Similar results were also obtained with GSTT2 both in vitro and in vivo. Thus, our study identified a critical role for GSTs in priming astrocytes and enhancing microglia activation during brain inflammation.