Elevated S100A9 in preeclampsia induces soluble endoglin and IL-1ß secretion and hypertension via the NLRP3 inflammasome.

OBJECTIVES: Maternal systemic and placental inflammatory responses participate in the pathogenesis of hypertensive disorders of pregnancy including preeclampsia, a pregnancy-specific syndrome, although the role of inflammation remains unclear. The NLRP3 inflammasome has been implicated in the control of sterile inflammation involved in preeclampsia. In the present study, we hypothesized that S100A9, as major alarmin, are associated with the pathogenesis of preeclampsia and induction of a preeclampsia-like phenotype in pregnant mice. METHODS: Plasma were taken from normal pregnant women and preeclampsia patients. Human placental tissues, trophoblast cell line Sw.71 cells, and human umbilical vein endothelial cells (HUVEC) were treated with S100A9 with or without inhibitors associated with NLRP3 inflammasome. Pregnant mice were administered S100A9. RESULTS: S100A9 was elevated in plasma and released from placentas of preeclampsia patients. S100A9 activated the NLRP3 inflammasome, resulting in IL-1ß secretion, by human placental tissues and trophoblasts. In addition, secretion of soluble endoglin, a main contributor to the pathogenesis of preeclampsia, is regulated via S100A9-stimulated NLRP3 inflammasome activation in the human placenta and HUVECs. S100A9 administration significantly elevated maternal blood pressure and neutrophil accumulation within the placentas of pregnant mice, and both were significantly decreased in Nlrp3-knock out pregnant mice. CONCLUSION: The results of this study demonstrated that S100A9 acts as a danger signal to activate the NLRP3 inflammasome in the placenta, associating with hypertension during pregnancy.

Preeclamptic patient-derived circulating cell-free DNA activates the production of inflammatory cytokines via toll-like receptor 9 signalling in the human placenta.

OBJECTIVES: Preeclampsia, a pregnancy-specific syndrome, is associated with maternal systemic and placental inflammatory responses. Cell-free DNA (cfDNA) and cf-foetal DNA (cffDNA) in the blood are elevated in patients with preeclampsia and act as danger signals. Placenta-derived foetal DNA induces inflammatory responses and pregnancy complications in mice. However, whether extracellular DNA from the placenta really causes inflammatory responses remains unclear. Therefore, we investigated the effect of serum cfDNA and placental cffDNA on inflammatory responses using normal pregnant women and preeclampsia patients. METHODS: Sera were taken from normal pregnant women and preeclampsia patients, and human trophoblast cell line Sw.71 cells were treated with serum with or without toll-like receptor 9 (TLR9; a sensor of exogenous DNA) inhibitor and genome elimination reagent. For cffDNA collection, placental tissue from the participants was cultured, and the released cffDNA was administrated to Sw.71 cells. RESULTS: The amount of serum cfDNA was higher in preeclampsia patients than in normal pregnant women. Treatment of preeclampsia serum stimulated inflammatory cytokine secretion, which was inhibited by a genome elimination reagent. Expression levels of TLR9 and amount of cffDNA from the placenta were higher in preeclampsia patients than of normal pregnant women. Preeclampsia-derived cffDNA increased inflammatory cytokine levels compared with normal pregnant derived cffDNA. CONCLUSION: In human trophoblast cells, preeclampsia patient-derived cfDNA increased inflammatory cytokine levels via TLR9. Preeclampsia placenta released more cffDNA, which stimulated inflammatory cytokine. We suggest that elevated circulating cfDNA and cffDNA induces placental inflammatory responses, resulting in accelerated pathological features of preeclampsia.

Advanced glycation end products regulate interleukin-1ß production in human placenta.

Maternal obesity is a major risk factor for pregnancy complications, causing inflammatory cytokine release in the placenta, including interleukin-1ß (IL-1ß), IL-6, and IL-8. Pregnant women with obesity develop accelerated systemic and placental inflammation with elevated circulating advanced glycation end products (AGEs). IL-1ß is a pivotal inflammatory cytokine associated with obesity and pregnancy complications, and its production is regulated by NLR family pyrin domain-containing 3 (NLRP3) inflammasomes. Here, we investigated whether AGEs are involved in the activation of NLRP3 inflammasomes using human placental tissues and placental cell line. In human placental tissue cultures, AGEs significantly increased IL-1ß secretion, as well as IL-1ß and NLRP3 mRNA expression. In human placental cell culture, although AGE treatment did not stimulate IL-1ß secretion, AGEs significantly increased IL-1ß mRNA expression and intracellular IL-1ß production. After pre-incubation with AGEs, nano-silica treatment (well known as an inflammasome activator) increased IL-1ß secretion in placental cells. However, after pre-incubation with lipopolysaccharide to produce pro-IL-1ß, AGE treatment did not affect IL-1ß secretion in placental cells. These findings suggest that AGEs stimulate pro-IL-1ß production within placental cells, but do not activate inflammasomes to stimulate IL-1ß secretion. Furthermore, using pharmacological inhibitors, we demonstrated that AGE-induced inflammatory cytokines are dependent on MAPK/NF-κB/AP-1 signaling and reactive oxygen species production in placental cells. In conclusion, AGEs regulate pro-IL-1ß production and inflammatory responses, resulting in the activation of NLRP3 inflammasomes in human placenta. These results suggest that AGEs, as an endogenous and sterile danger signal, may contribute to chronic placental cytokine production.