Myeloid-Specific Tristetraprolin Deficiency in Mice Results in Extreme Lipopolysaccharide Sensitivity in an Otherwise Minimal Phenotype

Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
The Journal of Immunology (Impact Factor: 4.92). 04/2012; 188(10):5150-9. DOI: 10.4049/jimmunol.1103700
Source: PubMed


Tristetraprolin (TTP) is a mRNA-destabilizing protein that binds to AU-rich elements in labile transcripts, such as the mRNA encoding TNF, and promotes their deadenylation and degradation. TTP-deficient (knockout [KO]) mice exhibit an early-onset, severe inflammatory phenotype, with cachexia, erosive arthritis, left-sided cardiac valvulitis, myeloid hyperplasia, and autoimmunity, which can be prevented by injections of anti-TNF Abs, or interbreeding with TNF receptor-deficient mice. To determine whether the excess TNF that causes the TTP KO phenotype is produced by myeloid cells, we performed myeloid-specific disruption of Zfp36, the gene encoding TTP. We documented the lack of TTP expression in LPS-stimulated bone marrow-derived macrophages from the mice, whereas fibroblasts expressed TTP mRNA and protein normally in response to serum. The mice exhibited a minimal phenotype, characterized by slight slowing of weight gain late in the first year of life, compared with the early-onset, severe weight loss and inflammation seen in the TTP KO mice. Instead, the myeloid-specific TTP KO mice were highly and abnormally susceptible to a low-dose LPS challenge, with rapid development of typical endotoxemia signs and extensive organ damage, and elevations of serum TNF levels to 110-fold greater than control. We conclude that myeloid-specific TTP deficiency does not phenocopy complete TTP deficiency in C57BL/6 mice under normal laboratory conditions, implying contributions from other cell types to the complete phenotype. However, myeloid cell TTP plays a critical role in protecting mice against LPS-induced septic shock, primarily through its posttranscriptional regulation of TNF mRNA stability.

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    • "Murine bone marrow derived macrophages were prepared from bone marrow of 8–10 weeks old mice following the procedure described previously [31], [32]. Briefly, tibias and femurs were collected aseptically from the ttp wild type (+/+) and null (−/−) mice. "
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