Benzo(a)pyrene induced adverse pregnancy outcomes by affecting the expression of IL-18 and IL-1RN in placenta

Abstract

Aims: Inflammatory cytokines can destroy the immune balance and lead to adverse pregnancy outcomes. Benzo (a) pyrene (BaP) may induce premature delivery through leading inflammatory reaction. We screened out inflammatory factors related to adverse pregnancy outcomes through bioinformatics analysis. Then we verified the correlation between adverse pregnancy outcomes caused by BaP and abnormal expression of those inflammatory factors.

Main methods: The Gene Expression Omnibus (GEO) database was used to analyze by R to screen the inflammatory genes related to adverse pregnancy outcomes. Based on the established BaP exposure animal model, the expression of key cytokines in placenta was detected by immunohistochemistry.

Key findings: According to the data analysis of GEO database, the expression of IL18, IL18BP and IL18R was up-regulated, while the expression of IL1RN was down regulated in the adverse pregnancy outcome group. BaP exposure significantly increased the rate of adverse pregnancy outcome in pregnant golden hamsters, and also significantly interferes with the process of embryonic development. Meanwhile, the expression of IL18, IL18BP and IL18R in placenta was increased, while the expression of IL1RN protein was decreased, consistent with the mRNA expression level gathered by bioinformatics analysis.

Significance: BaP may induce the inflammatory reaction to cause adverse pregnancy outcome by regulating the expression of IL18, IL18BP, IL18R and IL1RN. Our findings provide experimental basis for the prevention of adverse pregnancy outcome caused by BaP.

Keywords: Adverse pregnancy outcome; BaP; Inflammatory cytokines; Uterine-placental interface.

Figure 1

Screened the differentially expressed genes associated with adverse pregnancy outcomes. A. Differential gene expression data have been visualized in volcano plots. The standard thresholds for screening DEGs were set as adjusted P < 0.05, | log2FC | ≥ 1. B. Gene Ontology (GO) enrichment analysis for molecular functions. C GO enrichment analysis for biological processes. D GO enrichment analysis for cellular components. E. Distribution of candidate genes in GO term. F. KEGG pathway enrichment analysis.

Figure 2

Screened the cytokines related spontaneous abortion A. Venn diagrams indicating the overlap of the DEGs and cytokines. B. Protein–protein interaction (PPI) network of candidate target genes was generated using the STRING database. The color of the first cluster is red. C. Top 10 Hubba nodes by MNC algorithm of CytoHubba plug-in of the Cytoscape software. D. Heat map with Spearman correlations between the expressions of Hub genes. Red color indicates positive- and blue color negative correlation.

Figure 3

Effect of BaP on embryonic development of the golden hamster. A. The number of embryos per litter. B. The number of death and survival embryos in the control group, BaP2.5 group and BaP5.0 group. C. The size of embryos in the control group, BaP2.5 group and BaP5.0 group. The minimum diameter, maximum diameter, mean diameter, length and width of embryos were measured by Image Pro Plus. D. Representative images of embryos in the control group, BaP2.5 group and BaP5.0 group. ∗P < 0.05 compared with the control group.

Figure 4

Bap exposures impaired the morphology of the maternal-fetal interface. A. Representative HE staining images of placentas in control group, BaP2.5 group and BaP5.0 group. The trophospongium (TS), chorionic plate (CP), labyrinth zone (L) and decidua basalis (DB) are indicated. B. Quantification of thickness of the trophospongium and labyrinth zone. C. Ratio of the labyrinth zone to the trophospongium. ∗P < 0.05 compared with the control group (n = 5/group). Data is expressed as means ± SEM. Magnification ×40.

Figure 5

BaP increased the expression of IL18 in the placenta of the golden hamster. Representative images of IL18 expression in trophospongium (TS), chorionic plate (CP), and labyrinth zone (L) are shown in the upper panel and integrated optical density (IOD) of those is shown in the lower panel. ∗P < 0.05 compared with the control group (n = 5/group). Magnification ×400.

Figure 6

BaP increased the expression of IL18BP in the placenta of the golden hamster. Representative images of IL18BP expression in trophospongium (TS), chorionic plate (CP), and labyrinth zone (L) are shown in the upper panel and integrated optical density (IOD) of those is shown in the lower panel. ∗P < 0.05 compared with the control group (n = 5/group). Magnification ×400.

Figure 7

BaP increased the expression of IL18R in the placenta of the golden hamster. Representative images of IL18R expression in trophospongium (TS), chorionic plate (CP), and labyrinth zone (L) are shown in the upper panel and integrated optical density (IOD) of those is shown in the lower panel. ∗P < 0.05 compared with the control group (n = 5/group). Magnification ×400.

Figure 8

BaP decreased the expression of IL1RN in the placenta of the golden hamster. Representative images of IL18R expression in trophospongium (TS), chorionic plate (CP), and labyrinth zone (L) are shown in the upper panel and integrated optical density (IOD) of those are shown in the lower panel. ∗P < 0.05 compared with the control group (n = 5/group). Magnification ×400.