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Lipopolysaccharide-Induced Matrix Metalloproteinase-9 Expression Associated with Cell Migration in Rat Brain
Chien-Chung Yang1,2, Chih-Chung Lin3, Li-Der Hsiao4
1Department of Traditional Chinese Medicine, Chang Gung Memorial Hospital at Tao-Yuan, Kwei-San, Tao-Yuan 33302, Taiwan.
Abstract:
Neuroinflammation is a landmark of neuroinflammatory and neurodegenerative diseases. Matrix metalloproteinase (MMP)-9, one member of MMPs, has been shown to contribute to the pathology of these brain diseases. Several experimental models have demonstrated that lipopolysaccharide (LPS) exerts a pathological role through Toll-like receptors (TLRs) in neuroinflammation and neurodegeneration. However, the mechanisms underlying LPS-induced MMP-9 expression in rat brain astrocytes (RBA-1) are not completely understood. Here, we applied pharmacological inhibitors and siRNA transfection to assess the levels of MMP-9 protein, mRNA, and promoter activity, as well as protein kinase phosphorylation in RBA-1 cells triggered by LPS. We found that LPS-induced expression of pro-form MMP-9 and cell migration were mediated through TLR4, proto-oncogene tyrosine-protein kinase (c-Src), proline-rich tyrosine kinase 2 (Pyk2), platelet-derived growth factor receptor (PDGFR), phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt), p38 mitogen-activated protein kinase (MAPK), and Jun amino-terminal kinase (JNK)1/2 signaling molecules in RBA-1 cells. In addition, LPS-stimulated binding of c-Jun to the MMP-9 promoter was confirmed by chromatin immunoprecipitation (ChIP) assay, which was blocked by pretreatment with c-Src inhibitor II, PF431396, AG1296, LY294002, Akt inhibitor VIII, p38 MAP kinase inhibitor VIII, SP600125, and tanshinone IIA. These results suggest that in RBA-1 cells, LPS activates a TLR4/c-Src/Pyk2/PDGFR/PI3K/Akt/p38 MAPK and JNK1/2 pathway, which in turn triggers activator protein 1 (AP-1) activation and ultimately induces MMP-9 expression and cell migration.
Insights
Lipopolysaccharide (LPS) triggers matrix metalloproteinase-9 (MMP-9) expression and cell migration in rat brain astrocytes via Toll-like receptor 4 (TLR4) and downstream signaling pathways, impacting neuroinflammation.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Neuroinflammation is a key feature of neurodegenerative diseases.
- Matrix metalloproteinase-9 (MMP-9) plays a role in the pathology of brain diseases.
- Lipopolysaccharide (LPS) can induce neuroinflammation and neurodegeneration via Toll-like receptors (TLRs).
Purpose of the Study:
- To elucidate the mechanisms of LPS-induced MMP-9 expression in rat brain astrocytes (RBA-1) cells.
- To investigate the signaling pathways involved in LPS-stimulated MMP-9 production and cell migration.
Main Methods:
- Pharmacological inhibitors and siRNA transfection were used to assess MMP-9 levels and signaling.
- Chromatin immunoprecipitation (ChIP) assay was employed to study transcription factor binding.
- Protein kinase phosphorylation was analyzed in response to LPS stimulation.
Main Results:
- LPS induced pro-form MMP-9 expression and RBA-1 cell migration.
- The pathway involved Toll-like receptor 4 (TLR4), c-Src, Pyk2, PDGFR, PI3K/Akt, p38 MAPK, and JNK1/2.
- LPS stimulated c-Jun binding to the MMP-9 promoter, which was blocked by pathway inhibitors.
Conclusions:
- LPS activates a TLR4-mediated signaling cascade in RBA-1 cells.
- This cascade involves c-Src, Pyk2, PDGFR, PI3K/Akt, p38 MAPK, and JNK1/2.
- The pathway ultimately leads to activator protein 1 (AP-1) activation, inducing MMP-9 expression and cell migration.
