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Sinha, Sanchari and Koul, N and Dixit, D and Sharma, V and Sen, E (2011) IGF-1 induced HIF-1α-TLR9 cross talk regulates inflammatory responses in glioma. Cellular Signalling, 23. pp. 1869-1875.

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IGF-1 induced HIF-1α-TLR9 cross talk regulates inflammatory responses in glioma.pdf
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Abstract

The insulin-like growth factor (IGF-1) induces hypoxia inducible factor (HIF-1α) regulated genes in glioblastoma multiforme (GBM). As HIF-1α links inflammatory and oncogenic pathways in GBM, we investigated whether IGF-1 affects HIF-1α to regulate inflammatory response in glioma cells under normoxia. IGF-1 induced Ras and Calmodulin-dependent kinase II (CaMKII) regulated HIF-1α transcriptional activity in glioma cells. Increase in HIF-1α was concurrent with decreased Toll-like receptor (TLR9) and CXCR4 expression and elevated suppressor of cytokine signaling (SOCS3) levels. Interestingly, while synthetic CpG containing oligodeoxynucleotide TLR9 agonist (CpG DNA) decreased IGF-1 mediated increase in HIF-1α activity, siRNA mediated knockdown of HIF-1α decreased TLR9 levels. This suggested that IGF-1 induced HIF-1α-TLR9 axis is regulated by both positive and negative feedback loops. Importantly, TLR9 agonist reversed the effect of IGF-1 on CXCR4 and SOCS3 expression. While knockdown of HIF-1α abrogated IGF-1 mediated increase in SOCS3 it elevated IGF-1 induced decrease in CXCR4 levels. Thus HIF-1α positively and negatively regulates SOCS3 and CXCR4 expression respectively, in glioma cells. Though TLR9 agonist had no additive effect on IGF-1 mediated increase in pro-inflammatory cytokines IL-1β, IL-6 and IL-8, treatment with TLR9 agonist alone elevated expression of these pro-inflammatory cytokines. Our studies indicate that a complex HIF-1α-TLR9 cross-talk sustains a self-regulating cycle of inflammatory response through intrinsic negative and positive feedback mechanisms

Item Type: Article
Subjects: Neurodegenerative Disorders
Neuro-Oncological Disorders
Neurocognitive Processes
Neuronal Development and Regeneration
Informatics and Imaging
Genetics and Molecular Biology
Depositing User: Dr. D.D. Lal
Date Deposited: 09 May 2018 03:42
Last Modified: 18 May 2018 11:13
URI: http://nbrc.sciencecentral.in/id/eprint/333

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