Gangliosides Activate Cultured Rat Brain Microglia

Abstract

Microglia, brain resident macrophages, are activated in brain injuries and several neurodegenerative diseases. However, microglial activators that are produced in the brain are not yet defined. In this study, we showed that gangliosides, sialic acid-containing glycosphingolipids, could be a microglial activator. Gangliosides induced production of nitric oxide (NO) and tumor necrosis factor-␣ (TNF-␣) and expression of cyclooxygenase-2 (COX-2). The effect of gangliosides on NO release increased dose-dependently in the range of 10 -100 g/ml; however, the effect decreased at concentrations higher than 200 g/ml.

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

“…In our previous studies with cultured rat primary microglia (Jou et al, 2006;Kim et al, 2002;Pyo et al, 1999), we observed that brain gangliosides mixture (Gmix) induced morphological changes in cultured rat primary microglia which were different from those induced by other agents such as LPS or IFN-γ. Therefore, to further pursue this observation, we plated cultured rat primary microglia onto 35 mm dishes, incubated them with either Gmix (50 μg/ml), LPS (100 ng/ml), or IFN-γ (10 U/ml) for 3 days, and observed morphological changes using phasecontrast microscopy.…”

“…We previously reported that Gmix activates JAK-STAT and MAPK signaling pathways in rat primary microglia (Kim et al, 2002;Pyo et al, 1999). Therefore, to elucidate whether JAK-STAT and MAPK signaling pathways are involved in the ramified morphological changes in GM1-treated rat primary microglia, microglial cells were preincubated with either Jaki (a selective inhibitor of Jak), PD98059 (a selective inhibitor of Erk1/2), SB203580 (a selective inhibitor of p38), or SP600125 (a selective inhibitor of JNK), and were then incubated with GM1 for 3 days.…”

“…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.…”

Interleukin‐13 and ‐4 induce death of activated microglia

“…We next investigated whether IL-13 could induce cell death of microglia that had been treated with other activators, namely ganglioside and thrombin (Pyo et al, 1999;Ryu et al, 2000). In response to the combination of ganglioside mixture (Gmix) and IL-13, 29.4% Ϯ 13.5%, 42.9% Ϯ 6.7%, and 80.0% Ϯ 7.4% of total cells were Etd-1-positive at day 4, 5, and 6, respectively ( Fig.…”

“…Therefore, like LPS, Gmix also induced microglial cell death in the presence of IL-13, but Gmix alone did not induce cell death, even after 6 days. We also compared the effect of GT1b and GM1 on microglial cell death since GT1b is an active component of Gmix that induces microglial activation, while GM1 does not have such activity (Pyo et al, 1999). The data presented in Figure 2B show that at day 5, 54.6% Ϯ 10.4% of cells treated with GT1b and IL-13 were Etd-1-positive, while only 5.2% Ϯ 2.7% of cells treated with GM1 and IL-13 were Etd-1-positive.…”