Enhancement of Rubella Virus Infection in Immortalized Human First-Trimester Trophoblasts Under Low-Glucose Stress Conditions

Oxidative Stress Enhances Rubella Virus Infection in Immortalized Human First-Trimester Trophoblasts

Rubella infection (RuV) during early pregnancy is a known cause of congenital rubella syndrome (CRS). However, the mechanisms by which the virus crosses the placenta and infects the fetus are not fully understood. It has been known that various kinds of cell stresses can occur during the placenta formation. Previously, we demonstrated that low-glucose-induced endoplasmic reticulum stress could drastically enhance RuV infection in immortalized human first-trimester trophoblast cells. In this study, we investigated the roles of oxidative stress in RuV infection in these cells. Oxidative stress was induced in Swan.71 cells by culturing them in medium containing hydrogen peroxide (H2O2) in various concentrations and durations (50 µM or 100 µM for 24 h, or 150 µM for 1 h). RuV infection with a clinical strain was performed 24 h post-treatment, and capsid proteins were visualized at 24 and 48 h post-infection (hpi) using flow cytometry (FCM) and fluorescence microscopy (IF), respectively. The findings demonstrated that oxidative stress significantly enhanced RuV infection, as evidenced by FCM analysis, showing a twofold increase in infection rate, and confirmed by IF assay. Additionally, significantly increased intracellular viral replication was observed at 3 dpi. These findings suggest that oxidative stress during early pregnancy may promote the maternal-to-fetal transmission of rubella, contributing to the development of CRS.

Research Progress of Risk Factors Associated with Gestational Diabetes Mellitus

Gestational Diabetes Mellitus (GDM) is a common endocrine condition associated with adverse pregnancy outcomes. In recent years, a growing number of risk factors associated with gestational diabetes mellitus have been defined. GDM poses a serious threat to maternal health. The etiology is complex and multifactorial and can be divided into inherent and modifiable factors. The inherent factors have been described in other literature, while the modifiable factors are mainly the risk of lifestyle habits. In this study, we performed a narrative review of the progress of risk factors associated with gestational diabetes mellitus.

Roles of TGF-β1 in Viral Infection during Pregnancy: Research Update and Perspectives

Transforming growth factor-beta 1 (TGF-β1) is a pleiotropic growth factor playing various roles in the human body including cell growth and development. More functions of TGF-β1 have been discovered, especially its roles in viral infection. TGF-β1 is abundant at the maternal-fetal interface during pregnancy and plays an important function in immune tolerance, an essential key factor for pregnancy success. It plays some critical roles in viral infection in pregnancy, such as its effects on the infection and replication of human cytomegalovirus in syncytiotrophoblasts. Interestingly, its role in the enhancement of Zika virus (ZIKV) infection and replication in first-trimester trophoblasts has recently been reported. The above up-to-date findings have opened one of the promising approaches to studying the mechanisms of viral infection during pregnancy with links to corresponding congenital syndromes. In this article, we review our current and recent advances in understanding the roles of TGF-β1 in viral infection. Our discussion focuses on viral infection during pregnancy, especially in the first trimester. We highlight the mutual roles of viral infection and TGF-β1 in specific contexts and possible functions of the Smad pathway in viral infection, with a special note on ZIKV infection. In addition, we discuss promising approaches to performing further studies on this topic.

TGF-β1 Promotes Zika Virus Infection in Immortalized Human First-Trimester Trophoblasts via the Smad Pathway

The Zika virus (ZIKV) is well known for causing congenital Zika syndrome if the infection occurs during pregnancy; however, the mechanism by which the virus infects and crosses the placenta barrier has not been completely understood. In pregnancy, TGF-β1 is abundant at the maternal–fetal interface. TGF-β1 has been reported to enhance rubella virus binding and infection in human lung epithelial cells. Therefore, in this study, we investigate the role of TGF-β1 in ZIKV infection in the immortalized human first-trimester trophoblasts, i.e., Swan.71. The cells were treated with TGF-β1 (10 ng/mL) for two days before being inoculated with the virus (American strain PRVABC59) at a multiplicity of infection of five. The results showed an enhancement of ZIKV infection, as demonstrated by the immunofluorescent assay and flow cytometry analysis. Such enhanced infection effects were abolished using SB431542 or SB525334, inhibitors of the TGF-β/Smad signaling pathway. An approximately 2-fold increase in the virus binding to the studied trophoblasts was found. In the presence of the Smad inhibitors, virus replication was significantly suppressed. An enhancement in Tyro3 and AXL (receptors for ZIKV) expression induced by TGF-β1 was also noted. The results suggest that TGF-β1 promotes the virus infection via the Smad pathway. Further studies should be carried out to clarify the underlying mechanisms of these findings.