Trophoblast cells inhibit neutrophil extracellular trap formation and enhance apoptosis through vasoactive intestinal peptide-mediated pathways

• Published in: Human reproduction (Oxford) 2017-01, Vol.32 (1), p.55-64
• Main Authors: Calo, Guillermina, Sabbione, Florencia, Vota, Daiana, Paparini, Daniel, Ramhorst, Rosanna, Trevani, Analía, Pérez Leirós, Claudia
• Format: Article
• Language: English
• Subjects: Apoptosis - drug effects; Apoptosis - physiology; Cell Line; Culture Media, Conditioned - pharmacology; Extracellular Traps - drug effects; Extracellular Traps - metabolism; Female; Humans; Neutrophils - drug effects; Neutrophils - metabolism; Phagocytosis - drug effects; Phagocytosis - physiology; Pregnancy; Reactive Oxygen Species - metabolism; Signal Transduction - drug effects; Signal Transduction - physiology; Trophoblasts - drug effects; Trophoblasts - metabolism; Vasoactive Intestinal Peptide - pharmacology
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/dew292

STUDY QUESTION Do human trophoblast cells modulate neutrophil extracellular trap (NET) formation, reactive oxygen species (ROS) synthesis and neutrophil apoptosis through mechanisms involving vasoactive intestinal peptide (VIP)? SUMMARY ANSWER Trophoblast cells inhibited NET formation and ROS synthesis and enhanced neutrophil apoptosis through VIP-mediated pathways in a model of maternal–placental interaction. WHAT IS KNOWN ALREADY Immune homeostasis maintenance at the maternal–placental interface is mostly coordinated by trophoblast cells. Neutrophil activation and NET formation increases in pregnancies complicated by exacerbated pro-inflammatory responses. VIP has anti-inflammatory and immunosuppressant effects and is synthesized by trophoblast cells. STUDY DESIGN, SIZE, DURATION This is a laboratory-based observational study that sampled circulating neutrophils from 50 healthy volunteers to explore their response in vitro to factors derived from human trophoblast cells. PARTICIPANTS/MATERIALS, SETTING, METHODS Peripheral blood neutrophils were isolated from healthy volunteers and tested in vitro with first trimester trophoblast cell line (Swan-71 and HTR8) conditioned media (CM) or with VIP. The effect of VIP and trophoblast CM on NET formation was assessed by co-localization of elastase and DNA by confocal microscopy, DNA release and elastase activity measurement. Neutrophil apoptosis was determined by flow cytometry or fluorescence microscopy. ROS formation was assessed by flow cytometry with a fluorescent probe. VIP silencing was performed by siRNA transfection. For phagocytosis of apoptotic neutrophils, autologous monocytes were sampled, and engulfment and cytokines were assessed by flow cytometry and ELISA. MAIN RESULTS AND THE ROLE OF CHANCE Trophoblast CM and 10 nM VIP promoted neutrophil deactivation by preventing phorbol myristate acetate–induced NET formation and ROS synthesis while they increased neutrophil spontaneous apoptosis and reversed the anti-apoptotic effect of lipopolysaccharide (all P < 0.05 versus control). The effects of trophoblast CM were prevented by a VIP antagonist or when VIP knocked-down trophoblast cells were used (P < 0.05 versus control). Neutrophils driven to apoptosis by trophoblast CM could be rapidly engulfed by monocytes without increasing IL-12 production. LARGE SCALE DATA Not applicable. LIMITATIONS, REASONS FOR CAUTION The mechanisms of neutrophil deactivation by trophoblast VIP are based on the results obtained