Induction of TNF-alpha by LPS in Schwann cell is regulated by MAPK activation signals.
Mitogen-activated protein kinases (MAPKs) are important mediators of cytokine expression and are critically involved in the immune response. The lipopolysaccharide (LPS) of gram-negative bacteria induces the expression of cytokines and proinflammatory genes via the toll-like receptor 4 (TLR4) signaling pathway in diverse cell types. In vivo, Schwann cells (SCs) at the site of injury may also produce tumor necrosis factor-- alpha (TNF-alpha). However, the precise mechanisms of TNF-alpha synthesis are still not clear. The purpose of the present study was to elucidate the underlying molecular mechanisms in the cultured SCs for its ability to activate the MAPKs and TNF-alpha gene, in response to LPS. Using enzyme-linked immunosorbent assay (ELISA), it was confirmed that treatment with LPS stimulated the synthesis of TNF-alpha in a concentration- and time-dependent manner. Intracellular location of TNF-alpha was detected under confocal microscope. Moreover, LPS activated extracellular signal-regulated kinase (ERK1/2), P38 and stress activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and induced their phosphorylation. LPS-elicited SCs TNF-alpha production was also drastically suppressed by PD98059 (ERK inhibitor), SB202190 (P38 inhibitor), or SP600125 (SAPK/JNK inhibitor). Additionally, the expression of CD14 and TLR4 was examined by RT-PCR. It was demonstrated that the expression of CD14, TLR4 was crucial for the SCs responses to LPS. In conclusion, the results provide novel mechanisms for the response of SCs to LPS stimulation, through MAPKs signaling pathways.
Cheng
Chun
C
Key Laboratory for Neuroregeneration of JiangSu Province, Nantong University, 19 Qixiu Road, Nantong 226001 Jiangsu, PR China.
Qin
Yongwei
Y
Shao
Xiaoyi
X
Wang
Haibo
H
Gao
Yongjing
Y
Cheng
Mengling
M
Shen
Aiguo
A
D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; C507781:Myd88 protein, rat; D053594:Myeloid Differentiation Factor 88; D012333:RNA, Messenger; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases