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Accession IconGSE20715

Transcript analysis in response to ozone in mice deficient in TLR4

Organism Icon Mus musculus
Sample Icon 21 Downloadable Samples
Technology Badge Icon Affymetrix Mouse Expression 430A Array (moe430a)

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Description
We previously identified toll-like receptor 4 (Tlr4) as a candidate gene responsible for ozone (O3)-induced pulmonary hyperpermeability and inflammation. The objective of this study was to determine the mechanism through which TLR4 modulates O3-induced pulmonary responses and to utilize transcriptomics to determine TLR4 effector molecules. C3H/HeJ (HeJ; Tlr4 mutant) and C3H/HeOuJ (OuJ; Tlr4 normal), mice were exposed continuously to 0.3 ppm O3 or filtered air for 6, 24, 48 or 72 hr. Affymetrix Mouse430A_MOE gene arrays were used to analyze lung homogenates from HeJ and OuJ mice followed using a bioinformatic analysis. Inflammation was assessed by bronchoalveolar lavage and molecular analysis by ELISA, immunoblotting, and transcription factor activity. TLR4 signals through both the MYD88-dependent and independent pathways in OuJ mice, which involves MAP kinase activation, NF-kappaB, AP-1, and KC. Microarray analyses identifiedTLR4 responsive genes for strain and time in OuJ versus HeJ mice (p<0.05). One significantly upregulated cluster of genes in OuJ were the heat shock proteins (Hspa1b; Hsp70), Hsp90ab1). Furthermore, O3-induced expression of HSP70 protein was increased in OuJ compared to HeJ mice following 24-48 h O3. Moreover, BAL polymorphonuclear leukocytes (PMN) and total protein were significantly reduced in response to O3 in Hspa1a/Hspa1btm1Dix (Hsp70-/-) compared to Hsp70+/+ mice (p<0.05). TLR4 signaling (MYD88-dependent), ERK1/2, AP-1 activity, and KC protein content were also significantly reduced after O3 exposure in Hsp70-/- compared to Hsp70+/+ mice (p<0.05). These studies suggest that HSP70 is involved in the regulation of O3-induced lung inflammation through the TLR4 pathway and provide evidence that HSP70 is an endogenous in vivo TLR4 ligand.
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