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* Davis Heart and Lung Research Institute, Division of Pulmonary Allergy Critical Care and Sleep Medicine, Ohio State University, Columbus, OH 43210; and
Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205
Relative to monocytes, human macrophages are deficient in their ability to process and release IL-1β. In an effort to explain this difference, we used a model of IL-1β processing and release that is dependent upon bacterial escape into the cytosol. Fresh human blood monocytes were compared with monocyte-derived macrophages (MDM) for their IL-1β release in response to challenge with Francisella novicida. Although both cell types produced similar levels of IL-1β mRNA and intracellular pro-IL-1β, only monocytes readily released processed mature IL-1β. Baseline mRNA expression profiling of candidate genes revealed a remarkable deficiency in the pyrin gene, MEFV, expression in MDM compared with monocytes. Immunoblots confirmed a corresponding deficit in MDM pyrin protein. To determine whether pyrin levels were responsible for the monocyte/MDM difference in mature IL-1β release, pyrin expression was knocked down by nucleofecting small interfering RNA against pyrin into monocytes or stably transducing small interfering RNA against pyrin into the monocyte cell line, THP-1. Pyrin knockdown was associated with a significant drop in IL-1β release in both cell types. Importantly, M-CSF treatment of MDM restored pyrin levels and IL-1β release. Similarly, the stable expression of pyrin in PMA-stimulated THP-1-derived macrophages induces caspase-1 activation, associated with increased IL-1β release after infection with F. novicida. In summary, intracellular pyrin levels positively regulate MDM IL-1β responsiveness to Francisella challenge.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported by the National Institutes of Health/National Institute of Allergy and Infectious Diseases Regional Center of Excellence for Bio-defense and Emerging Infectious Diseases Research (RCE) Program U54-AI-057153; by National Institutes of Health Grants HL40871 and HL76278; and by Davis Heart and Lung Research Institute intramural grant (to M.A.G.).
2 Address correspondence and reprint requests to Dr. Mikhail A. Gavrilin and Dr. Mark D. Wewers, 201 Davis Heart and Lung Research Institute, Division of Pulmonary Allergy Critical Care and Sleep Medicine, Ohio State University, 473 W. 12th Avenue, Columbus, OH 43210. E-mail addresses: gavrilin.1{at}osu.edu and wewers.2{at}osu.edu
3 Abbreviations used in this paper: PRR, pattern recognition receptor; CARD, caspase recruitment domain; EGFP, enhanced GFP; LDH, lactate dehydrogenase; MDM, monocyte-derived macrophage; MOI, multiplicity of infection; NLR, nucleotide binding and oligomerization domain-like receptor; PAMP, pathogen-associated molecular pattern; PYD, pyrin domain; qPCR, quantitative PCR; RCN, relative copy number; siRNA, small interfering RNA; TDM, THP-derived macrophage; TRIM, tripartite motif.
4 The online version of this article contains supplemental material.
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