Interleukin-1β (IL-1β) production is impaired in cord blood monocytes. However, the mechanism underlying this developmental attenuation remains unclear. Here, we analyzed the extent of variability within the Toll-like receptor (TLR)/NLRP3 inflammasome pathways in human neonates. We show that immature low CD14 expressing/CD16 pos monocytes predominate before 33 weeks of gestation, and that these cells lack production of the pro-IL-1β precursor protein upon LPS stimulation. In contrast, high levels of pro-IL-1β are produced within high CD14 expressing monocytes, although these cells are unable to secrete mature IL-1β. The lack of secreted IL-1β in these monocytes parallels a reduction of NLRP3 induction following TLR stimulation resulting in a lack of caspase-1 activity before 29 weeks of gestation, whereas expression of the apoptosisassociated speck-like protein containing a CARD and function of the P2×7 receptor are preserved. Our analyses also reveal a strong inhibitory effect of placental infection on LPS/ATP-induced caspase-1 activity in cord blood monocytes. Lastly, secretion of IL-1β in preterm neonates is restored to adult levels during the neonatal period, indicating rapid maturation of these responses after birth. Collectively, our data highlight important developmental mechanisms regulating IL-1β responses early in gestation, in part due to a downregulation of TLR-mediated NLRP3 expression. Such mechanisms may serve to limit potentially damaging inflammatory responses in a developing fetus.Keywords: Human r Inflammasome r Interleukin-1 beta (IL-1β) r Neonate r Toll-like receptor Additional supporting information may be found in the online version of this article at the publisher's web-site Correspondence: Dr. Pascal M. Lavoie e-mail: plavoie@cw.bc.ca * These authors contributed equally to this work.C 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2015. 45: 238-249 Innate immunity 239 IntroductionNewborns are at high risk of infections, in part due to attenuated innate immune defenses [1]. The cytokine interleukin-1β (IL-1β) is an important inflammatory mediator in response to infections [2]. Mice lacking IL-1β display impaired acute phase and pyrogenic responses [3], and increased susceptibility to pathogens commonly encountered in the neonatal period [4,5]. In contrast, high levels of IL-1β in a fetus can result in autoimmune organ damage [2], as well as lethal metabolic disturbances including severe weight loss and hypoglycemia [6]. Together, these data illustrate the evolutionary importance of a tight regulation of IL-1β in order to avoid inflammation-mediated organ damage, neurological injury [7], or even premature birth in a developing human [2,8].Monocytes are primarily responsible for the production of IL-1β in circulating blood [9,10]. Three subsets predominate in humans: "Classical" monocytes express CD14, but lack expression of the immunoglobulin receptor CD16. These CD14 high /CD16 neg monocytes make up the majority of monocytes in peripheral adult bloo...

BackgroundInflammation and infection are major determinants of disease severity and consequently, the quality of life and outcome for patients with cystic fibrosis (CF). Interleukin-1 beta (IL-1β) is a key inflammatory mediator. Secretion of biologically active IL-1β involves inflammasome-mediated processing. Little is known about the contribution of IL-1β and the inflammasomes in CF inflammatory disease. This study examines inflammasome-mediated IL-1β production in CF bronchial epithelial cell lines and human patients with CF.ResultsBronchial epithelial cell lines were found to produce negligible amounts of basal or stimulated IL-1β compared to hematopoeitic cells and they did not significantly upregulate caspase-1 activity upon inflammasome stimulation. In contrast, peripheral blood mononuclear cells (PBMCs) from both CF and healthy control subjects produced large amounts of IL-1β and strongly upregulated caspase-1 activity upon inflammasome stimulation. PBMCs from CF patients and controls displayed similar levels of caspase-1 activation and IL-1β production when stimulated with inflammasome activators. This IL-1β production was dependent on NF-κB activity and could be enhanced by priming with LPS. Finally, chemical inhibition of CFTR activity in control PBMCs and THP-1 cells did not significantly alter IL-1β or IL-8 production in response to P. aeruginosa.ConclusionHematopoeitic cells appear to be the predominant source of inflammasome-induced pro-inflammatory IL-1β in CF. PBMCs derived from CF subjects display preserved inflammasome activation and IL-1β secretion in response to the major CF pathogen Pseudomonas aeruginosa. However, our data do not support the hypothesis that increased IL-1β production in CF subjects is due to an intrinsic increase in NF-κB activity through loss of CFTR function.

Inflammatory lung disease is the major cause of morbidity and mortality in cystic fibrosis (CF); understanding what produces dysregulated innate immune responses in CF cells will be pivotal in guiding the development of novel anti-inflammatory therapies. To elucidate the molecular mechanisms that mediate exaggerated inflammation in CF following TLR signaling, we profiled global gene expression in immortalized human CF and non-CF airway cells at baseline and after microbial stimulation. Using complementary analysis methods, we observed a signature of increased stress levels in CF cells, specifically characterized by endoplasmic reticulum (ER) stress, the unfolded protein response (UPR), and MAPK signaling. Analysis of ER stress responses revealed an atypical induction of the UPR, characterized by the lack of induction of the PERK–eIF2α pathway in three complementary model systems: immortalized CF airway cells, fresh CF blood cells, and CF lung tissue. This atypical pattern of UPR activation was associated with the hyperinflammatory phenotype in CF cells, as deliberate induction of the PERK–eIF2α pathway with salubrinal attenuated the inflammatory response to both flagellin and Pseudomonas aeruginosa. IL-6 production triggered by ER stress and microbial stimulation were both dependent on p38 MAPK activity, suggesting a molecular link between both signaling events. These data indicate that atypical UPR activation fails to resolve the ER stress in CF and sensitizes the innate immune system to respond more vigorously to microbial challenge. Strategies to restore ER homeostasis and normalize the UPR activation profile may represent a novel therapeutic approach to minimize lung-damaging inflammation in CF.