KMID : 0358520090210030259
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Korean Journal of Occupational and Environmental Medicine 2009 Volume.21 No. 3 p.259 ~ p.266
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Induction of Inducible Nitric Oxide Synthase Expression by Manganese in C6 Glioma Cells
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Yu Gyeong-Im
Chung In-Sung Lee Mi-Young Shin Dong-Hoon Lee Dong-Hyul
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Abstract
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Objective: It is well established that manganese neurotoxicity is associated with clinical symptoms similar to those of idiopathic Parkinson¡¯s disease. Recent research has shown that the exposure to manganese(MnCl2) leads to induction of iNOS in BV2 microglial cells via iNOS transcriptional up-regulation and activation of both MAPKs and PI3K/Akt signaling pathways. Here, we further investigated the effect and the action mechanism of MnCl2 on iNOS expression in C6 glioma cells.
Methods: Western blot analyses demonstrated that treatment with MnCl2 at 250 ¥ìM was sufficient to induce iNOS at both the protein and mRNA levels in C6 cells.
Results: These studies demonstrated that the induction of iNOS protein and mRNA was visible after 4 h- and 2 h-treatment with MnCl2, respectively. MnCl2 treatment led to strong phosphorylation of JNKs and ERKs, members of MAP kinases (MAPKs), and Akt, a PI3-kinase (PI3K) downstream effector, in C6 cells. MnCl2 treatment had no effect on I¥êB-¥áin C6 cells. Notably, pretreatment with LY294002 (a PI3K inhibitor), which inhibited phosphorylation of Akt by MnCl2, caused strong suppression of MnCl2-induced iNOS protein and mRNA expression in C6 cells. Moreover, pretreatment with SP600125 (an inhibitor of JNKs) and PD98050 (an inhibitor of ERKs), which respectively interfered with MnCl2-mediated phosphorylation of JNKs and ERKs, led to the partial suppression of MnCl2-induced iNOS protein. Interestingly, pretreatment with LY294002 inhibited phosphorylation of not only Akt, but also ERKs and JNKs, in response to MnCl2. Moreover, there was an effective suppression of MnCl2-mediated phosphorylation of AKT by SP600125.
Conclusion: These results collectively suggest that MnCl2 induces iNOS expression in C6 glioma cells via activation of PI3K/Akt and JNK-ERK MAPK signaling proteins, whose activations seem to be mutually interconnected in response to MnCl2.
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KEYWORD
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Manganese, Inducible nitric oxide synthase, C6 glioma cells
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