Dreschers Stephan, Gille Christian, Haas Martin, Seubert Florence, Platen Christopher, Orlikowsky Thorsten W
Department of Neonatology, University Children's Hospital, Aachen, Germany.
Department of Neonatology, University Children's Hospital, Tuebingen, Germany.
PLoS One. 2017 Aug 9;12(8):e0182415. doi: 10.1371/journal.pone.0182415. eCollection 2017.
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.
与成人细胞（外周血单核细胞，PBMO）相比，由于CD95途径的差异，脐带血单核细胞（CBMO）中的吞噬作用诱导的细胞死亡（PICD）有所减少。这可能会导致促炎反应延长，并出现新生儿败血症中所见的持续炎症后遗症。在这里，我们假设由于TNFR1依赖性内化的差异，CBMO中TNF-α介导的细胞凋亡诱导受损。单核细胞用大肠杆菌绿色荧光蛋白（E. coli-GFP）感染。分析单核细胞表型、吞噬活性、细胞凋亡诱导以及TNF-α/TNF受体（TNFR）表达。在感染过程中，与PBMO相比，CBMO的TNF-α分泌减少至40%（p<0.05）。用αTNF-α抗体中和TNF-α可使PBMO中的凋亡性PICD降低四倍（与大肠杆菌感染相比，p < 0.05）。与PBMO相比，CBMO中的PICD降低了5倍，并且对αTNF-α抗体的反应性较低。CBMO表达的促凋亡TNFR1较少，在给予TNF-α或用大肠杆菌感染后，其内化程度较低。在吞噬能力相似的情况下，CBMO中TNFR1内化减少伴随着caspase-8的激活降低（与PBMO相比，p < 0.05）。PBMO中更强的caspase-8激活导致效应caspase-3的更多激活和细胞凋亡（与PBMO相比，所有p < 0.05）。我们的结果表明，TNFR1内化在介导大肠杆菌感染后单核细胞中的PICD中起关键作用，并且在CBMO中减少。
