TAK1 inhibition in mouse astrocyte cultures ameliorates cytokine-induced chemokine production and neutrophil migration.

Systemic inflammation can exacerbate symptoms of many neurological diseases. This effect may be facilitated by glial cells of the central nervous system (CNS) that alter their transcriptional responses and up-regulate cytokine and chemokine expression which can, in turn trigger immune surveillance. In this study, we sought to determine the effects of pro-inflammatory cytokine stimulation (TNF, IL-1α, IL-1β) on astrocyte and microglia chemokine secretion. Primary cultures of astrocytes or microglia were stimulated with the recombinant cytokines and the levels of secreted chemokines were semi-quantitatively determined using a chemokine-specific proteome profiler array and densitometry. Pharmacological inhibitors were used to determine the effects of p38 MAPK, JNK, ERK1/2, NFkB, and transforming growth factor beta-associated kinase 1 (TAK1) in controlling chemokine production. Finally, neutrophil migration assays were performed to demonstrate functionality. Our data show that stimulated astrocytes secrete at least eight chemokines as a response to cytokine stimulation. These include those involved in neutrophil chemo-attraction and proved capable of promoting neutrophil migration in vitro. In contrast, microglia up-regulated few chemokines in response to cytokine stimulation and did not promote neutrophil migration. However, microglia readily secreted chemokines following stimulation with the toll-like receptor agonists. Finally, we show that both the production of chemokines and neutrophil migration resulting from cytokine stimulation of astrocytes was dependent on TAK1 signaling. Collectively, this study adds to the understanding of how astrocytes and microglia respond to stimuli and their role in promoting neutrophil migration to the CNS during inflammatory conditions.