Expression of HMGB1-TLR4 in Placentas from Preeclamptic Pregnancies and Its Effect on Proliferation and Invasion of HTR-8/SVneo Cells

Abstract

Objectives: Placental inflammation possibly underlies preeclampsia (PE) pathogenesis. This study aimed to investigate the expression of the high mobility box group 1 (HMGB1)-toll-like receptor 4 (TLR4) signalling pathway in preeclamptic placentas and determine whether HMGB1 regulates the biological behaviour of trophoblasts in vitro. Design: Placental biopsies were taken from 30 preeclamptic patients and 30 normotensive controls. In vitro experiments were carried out in HTR-8/SVneo human trophoblast cells. Participants/Materials, Setting, Methods: HMGB1, TLR4, and nuclear factor kappa B (NF-κB) mRNA and protein were quantified to compare their expression in human placentas from preeclamptic and normotensive pregnancies. HTR-8/SVneo cells were stimulated with HMGB1 (50–400 μg/L) for 6–48 h, and proliferation and invasion of HTR-8/SVneo cells were measured via Cell Counting Kit-8 and transwell assays. HTR-8/SVneo cells were also transfected with HMGB1 and TLR4 small interfering RNA (siRNA) to investigate the effect of knocking down these proteins. The mRNA and protein expression of TLR4, NF-κB, and matrix metalloproteinase 9 (MMP-9) were determined using quantitative real-time PCR and Western blotting, respectively. Data were analysed with either a t-test or one-way analysis of variance. Results: The mRNA and protein levels of HMGB1, TLR4, and NF-κB were significantly higher in the placentas from preeclamptic pregnancies than from normal pregnancies (p < 0.05). HMGB1 stimulation (at concentrations up to 200 μg/L) of HTR-8/SVneo cells significantly increased invasion and proliferation over time. However, at an HMGB1 stimulation concentration of 400 μg/L, the invasion and proliferation ability of HTR-8/SVneo cells decreased. Compared to controls, mRNA and protein expression levels of TLR4, NF-κB, and MMP-9 increased (mRNA level fold change: 1.460, 1.921, 1.667; protein level fold change: 1.600, 1.750, 2.047) when stimulated with HMGB1 (p < 0.05) but decreased when HMGB1 was knocked down (p < 0.05). TLR4 siRNA transfection combined with HMGB1 stimulation reduced the mRNA (fold change: 0.451) and protein (fold change: 0.289) expression of TLR4 (p < 0.05), while NF-κB and MMP-9 were unaffected (p > 0.05). Limitations: Only one trophoblast cell line was used in this study, and the findings were not confirmed in animal studies. Conclusions: This study explored the pathogenesis of PE from two aspects: inflammation and trophoblast invasion. The overexpression of HMGB1 in placentas from preeclamptic pregnancies suggests this protein may be involved in PE pathogenesis. In vitro, HMGB1 was found to regulate the proliferation and invasion of HTR-8/SVneo cells by activating the TLR4-NF-κB-MMP-9 pathway. These findings have implications for targeting HMGB1 could be a therapeutic strategy for treating PE. In the future, we will further verify this in vivo and in other trophoblast cell lines, further exploring the molecular interactions of the pathway.