Abstract
Phagocytosis-induced cell death (PICD) is diminished in cord blood monocytes (CBMO) as compared to cells from adults (PBMO) due to differences in the CD95-pathway. This may support a prolonged pro-inflammatory response with sequels of sustained inflammation as seen in neonatal sepsis. Here we hypothesized that TNF-α mediated induction of apoptosis is impaired in CBMO due to differences in the TNFR1-dependent internalization. Monocytes were infected with Escherichia coli-GFP (E. coli-GFP). Monocyte phenotype, phagocytic activity, induction of apoptosis, and TNF-α/TNF-receptor (TNFR) -expression were analysed. In the course of infection TNF-α-secretion of CBMO was reduced to 40% as compared to PBMO (p<0.05). Neutralization of TNF-α by an αTNF-α antibody reduced apoptotic PICD in PBMO four-fold (p < 0.05 vs. infection with E. coli). PICD in CBMO was reduced 5-fold compared to PBMO and showed less responsiveness to αTNF-α antibody. CBMO expressed less pro-apoptotic TNFR1, which, after administration of TNF-α or infection with E. coli was internalized to a lesser extent. With similar phagocytic capacity, reduced TNFR1 internalization in CBMO was accompanied by lower activation of caspase-8 (p < 0.05 vs. PBMO). Stronger caspase-8 activation in PBMO caused more activation of effector caspase-3 and apoptosis (all p < 0.05 vs. PBMO). Our results demonstrate that TNFR1 internalization is critical in mediating PICD in monocytes after infection with E.coli and is reduced in CBMO.
Highlights
Pre- and postnatal infections are triggers for a variety of diseases later in life, involving different organ systems
CD95L, CD95, cell death promoting factor (FAS-L) and its receptor (FAS); E.coli, Escherichia coli; GFP, green fluorescent protein; LPS, Lipopolysaccharide; MNC, mononuclear cells; MOI, multiplicity of infection; MFI, mean fluorescence index; PAMPs, Pathogen associated molecular patterns; PBMC, peripheral blood mononuclear cells; PBMO, CD14-positive peripheral blood monocytes from adults; PBS, phosphate buffered saline; PBS-T, phosphate buffered saline Triton-X 100 supplemented; phagocytosis-induced cell death (PICD), phagocytosis induced cell death; Propidium iodide (PI), propidium iodide; p.i., post infection; RIP(c), receptor-interacting-protein 1; RT, room temperature; TUNEL, terminal UTPdeoxynucleotidyl-transferase; TNFR1, Tumor necrosis factor-α receptor 1; TNFR2, Tumor necrosis factor-α receptor 2; TRADD, tumornecrosis-factor-receptor-type-1-associatedDEATH-domain-protein; v/v, volume per volume; WBC, whole blood cells
The present study compared the induction of PICD in cord blood monocytes (CBMO) and PBMO utilizing an in-vitro E.coli infection model
Summary
Pre- and postnatal infections are triggers for a variety of diseases later in life, involving different organ systems. The common link between infection and its secondary sequels, organ damage, is inflammation, and typical diseases of the preterm infant, such as bronchopulmonary dysplasia (BPD) [1], necrotising enterocolitis (NEC) [2], retinopathy of prematurity (ROP) [3], periventricular leucomalacia (PVL) [4], and others have been closely tied to pre- or postnatal infection [5]. Inflammatory reactions following infection are mediated by cytokines and effector cells. A phenomenon called phagocytosis-induced cell death (PICD) plays a key role in the orchestration of an antibacterial host response, by provoking effector cell apoptosis and contributing to a controlled termination of inflammation [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
