NLRP3 Inflammasome in the Pathogenesis of Miscarriages

Abstract

Despite significant advances in prenatal medicine, spontaneous miscarriage remains one of the most common and serious pregnancy complications, affecting an increasing number of women. Since many aspects of the pathogenesis of spontaneous miscarriage remain unexplained, the aim of this study has been to assess the involvement of the NLRP3 inflammasome as a potential causative factor. The concentrations of NLRP3, IL-1β, IL-18, and cytochrome C in the serum of patients after miscarriage were measured by means of the immunoenzymatic method. In the placental tissue, the expression of NLRP3, IL-1β, IL-18, and Caspase-1 as well as that of the classical apoptosis biomarkers Fas, FasL, Bcl-2, and Ca was evaluated by means of immunohistochemistry techniques. Additionally, in whole blood, the concentrations of elements crucial for pregnancy progression, such as Ca, K, Mg, and Na, were examined by means of the ICP-OES method. Significantly higher concentrations of NLRP3 and IL-18 were demonstrated in the serum of patients with miscarriage as compared to the control group. In the placental tissue samples, a higher expression of IL-1β, IL-18, and Caspase-1 proteins was noted in women who had experienced miscarriage as compared to the control group. At the same time, a significantly lower expression of FasL and Bcl-2 proteins as well as Ca deposits was observed in women after miscarriage as compared to those with a normal pregnancy outcome. Significantly lower concentrations of Ca and K were recorded in the blood of patients with spontaneous miscarriage as compared to pregnant women. The analysis of the results x indicated a greater involvement of the inflammasome in women with spontaneous miscarriage associated with oxidative-antioxidative imbalance than in the case of miscarriage related to NET formation. Our research has provided evidence for the involvement of the inflammasome in the process of spontaneous miscarriage and identifies a new direction for diagnostics that includes NLRP3 as a preventive element in prenatal care, particularly in light of the steadily declining number of pregnancies and the increasing number of reproductive failures.

Keywords: Bcl-2; CYCS; Ca; Caspase-1; Fas; FasL; IL-18; IL-1β; K; Mg; NETosis; NLRP3; Na; apoptosis; inflammasome; miscarriage.

Figure 1

The expression pattern of the studied parameters.

Figure 2

Proposed cause–effect model in women with miscarriage and pregnant women, based on the obtained research results. The course of pregnancy is significantly influenced by many external and internal factors, the negative effect of which may be miscarriage. The most important of them include environmental pollution/heavy metals; exposure to BPA; invasive prenatal diagnostic procedures; paternal genotype; oxidative stress; activity of the immune/endocrine/metabolic system of the mother; maternal age and lifestyle; diet and body weight; and consumption of alcohol/tobacco/psychoactive substances. In addition, the significantly higher levels of NLRP3, IL-18, and IL-1β and lower amounts of Ca²⁺ and K⁺ in women with miscarriage compared to women with a normal pregnancy suggest the participation of these molecules in the processes leading to miscarriage. NLRP3—NLR Family Pyrin Domain Containing 3; IL-18—Interleukin 18; IL-1β—Interleukin 1 Beta; CYC-S—Cytochrome C Somatic; Ca²⁺—calcium ions; Na⁺—sodium ions; K⁺—potassium ions; Mg²⁺—magnesium ions; Casp-1—Caspase 1; p53—tumor protein p53; Fas—Fas receptor; FasL—Fas Ligand Protein; Bcl-2—B-cell lymphoma 2 protein; Ca deposit—calcium deposits; ↑—increase in concentration/expression; ↓—decrease in concentration/expression; =—similar quantities; +—expression; −—no expression.

Figure 3

The abbreviated protocols for the procedures of the performed assays.

Figure 4

The emission signal profiles of the analysed elements in the samples.