JAK-STAT Signaling Mediates Gangliosides-induced Inflammatory Responses in Brain Microglial Cells

Abstract

Neuronal cell membranes are particularly rich in gangliosides, which play important roles in brain physiology and pathology. Previously, we reported that gangliosides could act as microglial activators and are thus likely to participate in many neuronal diseases. In the present study we provide evidence that JAK-STAT inflammatory signaling mediates gangliosides-stimulated microglial activation. Both in rat primary microglia and murine BV2 microglial cells, gangliosides stimulated nuclear factor binding to GAS/ISRE elements, which are known to be STAT-binding sites. Consistent with this, gangliosides rapidly activated JAK1 and JAK2 and induced phosphorylation of STAT1 and STAT3. In addition, gangliosides increased transcription of the inflammation-associated genes inducible nitric-oxide synthase, ICAM-1, and MCP-1, which are reported to contain STAT-binding elements in their promoter regions. AG490, a JAK inhibitor, reduced induction of these genes, nuclear factor binding activity, and activation of STAT1 and -3 in gangliosides-treated microglia. AG490 also inhibited gangliosides-induced release of nitric oxide, an inflammation hallmark. Furthermore, AG490 markedly reduced activation of ERK1/2 MAPK, indicating that ERKs act downstream of JAK-STAT signaling during microglial activation. However, AG490 did not affect activation of p38 MAPK. We also report that the sialic acid residues present on gangliosides may be one of the essential components in activation of JAK-STAT signaling. The present study indicates that JAK-STAT signaling is an early event in gangliosides-induced brain inflammatory responses.

Double-stranded RNA-activated protein kinase is required for the LPS-induced activation of STAT1 inflammatory signaling in rat brain glial cells

“…To examine further the role of PKR in activation of STAT1, we tested the effect of 2-AP on phosphorylation of STAT1 by gangliosides, another glial activator (Kim et al, 2002). Rat primary microglia were stimulated with 50 g/ml bovine brain ganglioside mixture (G mix) in the presence or absence of 0.5 mM 2-AP, and Western blot analysis was performed at the indicated times to measure the levels of phosphorylated PKR and STAT1.…”

“…Excessive production of NO, resulting from nitric oxide synthase (NOS) induction in activated glia, is thought to be involved in various pathophysiological conditions (Liu et al, 2002). Since LPS-stimulated microglial activation was accompanied by NO release (Jacobs and Ignarro, 2001) and the transcription of inducible NOS (iNOS) was regulated by STAT inflammatory signaling in microglia (Kim et al, 2002), we investigated whether inhibition of PKR could alter LPS-induced production of NO in glial cells. Rat primary microglia were treated with 100 ng/ml LPS for 48 h in the presence or absence of 2-AP, and the amount of nitrite derived from NO in the media was measured.…”

“…JAK-STAT signaling can specifically mediate the inflammatory pathways activated by various stimulators in the brain, and appropriate regulation of JAK-STAT intensity and duration can protect against inflammation-induced brain injury (O.S. Kim et al, 2002; H.Y. Kim et al, 2003;Park et al, 2003).…”

GM1 induces p38 and microtubule dependent ramification of rat primary microglia in vitro

“…Hakomori, 2000). Furthermore, gangliosides have previously been shown to induce the phagocytosis of microglia (Bocchini et al, 1988) and activate microglia through various signaling pathways (Jou et al, 2006;Kim et al, 2002;Min et al, 2004;Pyo et al, 1999). In the present study, therefore, we investigated whether exogenously added brain gangliosides mixture (Gmix) enhanced microglial ramification and underlying mechanism of how Gmix enhanced microglial ramification.…”

Transcriptomic effects of adenosine 2A receptor deletion in healthy and endotoxemic murine myocardium

“…Effects in non-cardiac tissues involve TLR/CD14-dependent NFκB and MAPK signalling and interferon/cytokine engagement of the JAK-STAT path [34][35][36]. These mechanisms likely participate in heart, with evidence NFκB and IκB kinase promotes cardiac dysfunction in sepsis/endotoxemia [37,38], while JAK-STAT signalling mediates dysfunction and cell death in myocardial ischemia [39,40].…”