In this study, we investigated crosstalk between highly purified Toll-like receptor (TLR)2-knock out (TLR2-KO) and wild-type (WT) microglia and astrocytes. Microglia and astrocytes showed a time-dependent pro-inflammatory (tumor necrosis factor, TNF) and anti-inflammatory (Interleukin-10, IL-10) protein release after TLR2 (Pam3CSK4) and TLR9 (CpG oligodeoxynucleotides (ODN)) activation, respectively

The major immune cells of the central nervous systems (CNS) are microglia and astrocytes, subsets of the glial cell population. The crosstalk between glia via soluble signaling molecules plays an indispensable role for neuropathologies, brain development as well as homeostasis. In this study, we investigated crosstalk between highly purified Toll-like receptor (TLR)2-knock out (TLR2-KO) and wild-type (WT) microglia and astrocytes. Microglia and astrocytes showed a time-dependent pro-inflammatory (tumor necrosis factor, TNF) and anti-inflammatory (Interleukin-10, IL-10) protein release after TLR2 (Pam3CSK4) and TLR9 (CpG oligodeoxynucleotides (ODN)) activation, respectively. We further examined the crosstalk of TLR2-KO microglia and astrocytes in the presence of WT supernatants of the respective other glial cell type. Interestingly, we observed a significant TNF release by TLR2-KO astrocytes, which were activated with Pam3CSK4-stimulated WT microglial supernatants, strongly indicating a crosstalk between microglia and astrocytes upon TLR2 activation. Furthermore, transcriptome analysis using RNA-seq revealed a wide range of significant up- and down-regulated genes such as CD300, Tnfrsf9 or lcn2, which might be involved in the molecular conversation between microglia and astrocytes. Finally, co-culturing microglia and astrocytes confirmed the prior results by demonstrating a significant TNF release by WT microglia co-cultured with TLR2-KO astrocytes. Our study suggests a molecular conversation between microglia and astrocytes via signaling molecules in the context of TLR2 activation.