Liu, Yaqiong
(2018)
Investigation of ATP-mediated interleukin-1 secretion in human decidua.
MRes thesis, University of Nottingham.
Abstract
Introduction
The maternal immune system plays a significant role in pregnancy maintenance. Infections during pregnancy could stimulate inflammatory responses and lead to adverse pregnancy outcomes. Interleukin-1 (IL-1), a vital pro-inflammatory cytokine, is implicated in pregnancy infection and infection-induced preterm labour. Meanwhile, human decidua, situated between the fetus and myometrium, has been hypothesized as the main source of cytokines in the presence of infection. Moreover, the most studied inflammasome–NLRP3 inflammasome, involved in the canonical IL-1β secretory pathway, has been found participating in normal pregnancy and pregnancy disorders. However, knowledge about how decidua is involved in the immune response is still limited. In this study, we investigated how IL-1β release with stimuli to TLR4 and the purinergic P2X7 receptor in the full-term decidua, especially on the key components of the inflammasome pathway.
Method
Full-term decidua explants, decidual leukocytes, decidual stromal cells and maternal peripheral blood mononuclear cells were isolated. Tissue explants and cells were stimulated with or without the TLR4 agonist-LPS and the P2X7 receptor antagonist-A7 for 4 hours, and the last half hour stimulated with or without P2X7 receptor agonist-BzATP. The secretion of IL-1β and TNF- in culture media were detected by ELISA assay. The pro-IL-1β and NLRP3 inflammasome components proteins including NLRP3, caspase-1 and ASC in tissue lysates and culture media were evaluated by western blotting or ELISA.
Results
The levels of active IL-1β were higher under single stimulation with LPS in both of decidual tissue explants and maternal, and BzATP could significantly increase IL-1β release, while A7 could inhibit this increased effect. Besides, NLRP3, caspase-1, ASC are expressed in human decidual explants, and the expression of pro-caspase-1 increased after treatment with LPS. Also, NLRP3, p20 caspase-1, and ASC can be detected in culture media consistently, even without treatment. For the decidua cell types, decidual leukocytes, instead of stromal cells, can release IL-1β under costimulation with LPS and BzATP. Moreover, TNF- secretion would be triggered with single stimulation with LPS in decidua explants, maternal PBMC, but these secretions were not affected by BzATP nor A7.
Conclusion
This study demonstrated that decidua explants can release IL-1β and TNF- in response to LPS stimulation. Besides, exogenous BzATP could enhance the release of IL-1β, but not TNF-, potentially through P2X7 receptor. Furthermore, the expression of NLRP3 inflammasome components in decidua and the increased level of NLRP3 and caspase-1 after stimulation provided a clue that inflammasome may play a vital role in processing IL-1β in human decidua.
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