Article

Differential Expression of NLRP3 among Hematopoietic Cells

Department of Biochemistry, University of Lausanne, 1066 Epalinges, Switzerland.
The Journal of Immunology (Impact Factor: 5.36). 02/2011; 186(4):2529-34. DOI: 10.4049/jimmunol.1002720
Source: PubMed

ABSTRACT Although the importance of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in health and disease is well appreciated, a precise characterization of NLRP3 expression is yet undetermined. To this purpose, we generated a knock-in mouse in which the Nlrp3 coding sequence was substituted for the GFP (enhanced GFP [egfp]) gene. In this way, the expression of eGFP is driven by the endogenous regulatory elements of the Nlrp3 gene. In this study, we show that eGFP expression indeed mirrors that of NLRP3. Interestingly, splenic neutrophils, macrophages, and, in particular, monocytes and conventional dendritic cells showed robust eGFP fluorescence, whereas lymphoid subsets, eosinophils, and plasmacytoid dendritic cells showed negligible eGFP levels. NLRP3 expression was highly inducible in macrophages, both by MyD88- and Trif-dependent pathways. In vivo, when mice were challenged with diverse inflammatory stimuli, differences in both the number of eGFP-expressing cells and fluorescence intensity were observed in the draining lymph node. Thus, NLRP3 levels at the site of adaptive response initiation are controlled by recruitment of NLRP3-expressing cells and by NLRP3 induction.

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    • "As demonstrated, these key proteins are identified as NLRP3 (for nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) ASC (apoptosis associated speck-like protein containing a CARD), and procaspase-1 (Figure 1). NLRP3 is expressed predominantly in circulating monocytes and tissue macrophages (Guarda et al., 2011). The NLRP3 inflammasome components contain conserved protein domains and interaction of these domains on inflammasome proteins (i.e., homotypic protein–protein interactions ) leads to inflammasome assembly. "
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    • "For example the ability of inflammasomes to influence autoinflammatory pathogenesis in cell types other than macrophages and dendritic cells has not been studied in detail. Multiple immune and organ-specific cell types express NLRs and inflammasomeassociated proteins (Guarda et al., 2011b; Kufer and Sansonetti, 2011). Investigation of their contribution to disease should provide novel insight. "
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    Frontiers in Immunology 10/2012; 3:315. DOI:10.3389/fimmu.2012.00315
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    • "reduction in pro-inflammatory cytokines observed in Nlrp3-deficient mice suggests that additional proteins in the NLR family may contribute to the response to both ozone and hyaluronan. While ASC and caspase1 are ubiquitously expressed in many cell types, Nlrp3 is primarily expressed in myeloid cells (Guarda et al. 2011). NLR proteins expressed in nonmyeloid cells may prove important. "
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    ABSTRACT: Background: The role of the Nlrp3 inflammasome in nonallergic airway hyperresponsiveness (AHR) has not previously been reported. Recent evidence supports both interleukin (IL) 1β and short fragments of hyaluronan (HA) as contributors to the biological response to inhaled ozone. Objective: Because extracellular secretion of IL-1β requires activation of the inflammasome, we investigated the role of the inflammasome proteins ASC, caspase1, and Nlrp3 in the biological response to ozone and HA. Methods: C57BL/6J wild-type mice and mice deficient in ASC, caspase1, or Nlrp3 were exposed to ozone (1 ppm for 3 hr) or HA followed by analysis of airway resistance, cellular inflammation, and total protein and cytokines in bronchoalveolar lavage fluid (BALF). Transcription levels of IL-1β and IL-18 were determined in two populations of lung macrophages. In addition, we examined levels of cleaved caspase1 and cleaved IL-1β as markers of inflammasome activation in isolated alveolar macrophages harvested from BALF from HA-treated mice. Results: We observed that genes of the Nlrp3 inflammasome were required for development of AHR following exposure to either ozone or HA fragments. These genes are partially required for the cellular inflammatory response to ozone. The expression of IL-1β mRNA in alveolar macrophages was up-regulated after either ozone or HA challenge and was not dependent on the Nlrp3 inflammasome. However, soluble levels of IL-1β protein were dependent on the inflammasome after challenge with either ozone or HA. HA challenge resulted in cleavage of macrophage-derived caspase1 and IL-1β, suggesting a role for alveolar macrophages in Nlrp3-dependent AHR. Conclusions: The Nlrp3 inflammasome is required for the development of ozone-induced reactive airways disease.
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