No abstract

Problem Maternal obesity induces elevated saturated fatty acid palmitate levels in the blood and causes pregnancy complications such as gestational diabetes, preeclampsia, fetal growth abnormalities, and stillbirth. Sestrin2, a highly conserved stress‐inducible protein, is involved in the cellular responses of various stress conditions and homeostatic regulation. However, the effects of Sestrin2 on trophoblast cells have not yet been investigated. Here, we investigated the role of Sestrin2 in palmitate‐induced lipotoxicity and its underlying mechanisms in human first‐trimester trophoblast cells (Sw.71). Method of study Mouse placental tissues were obtained from low‐fat diet‐fed mice (n = 14) and high‐fat diet‐fed mice (n = 14) at gestation day 17.5. Sw.71 cells were treated with palmitate or bovine serum albumin as vehicle controls. The role of Sestrin2 in palmitate‐induced lipotoxicity was examined by immunocytochemistry, immunoblot analysis, quantitative real‐time PCR, and invasion assay. Results Expression of placental Sestrin2 was elevated in high‐fat diet‐fed dams compared to that of low‐fat diet‐fed dams. Prolonged treatment of Sw.71 cells with palmitate‐induced endoplasmic reticulum (ER) stress‐dependent expressions of Sestrin2 protein and mRNA, and the treatment also triggered apoptosis. Knockdown of Sestrin2 increased palmitate‐mediated ER stress, inflammatory signaling, and apoptosis. Furthermore, Sestrin2 suppressed impaired trophoblast invasion caused by palmitate and attenuated palmitate‐induced ER stress and inflammation via AMPK/mTORC1 pathways. Conclusion Our study provides the relationship between Sestrin2, AMPK/mTORC1 pathway, and trophoblast function, suggesting that Sestrin2 may be a novel potential therapeutic target for the prevention of pregnancy complications.

Sestrin2 (Sesn2), a metabolic regulator, accumulates in response to a diverse array of cellular stresses. Sesn2 regulates cellular metabolism by inhibiting the mammalian target of rapamycin complex 1 through the AMP-activated protein kinase (AMPK) signaling pathway. Recently, researchers reported that Sesn2 regulates the differentiation and function of innate immune cells and T cells; however, the role of Sesn2 in B cells is largely unknown. In this study, we investigated the role of Sesn2 in Ig class switching and Ig production in mouse B cells. We observed that mouse B cells express Sesn2 mRNA. Interestingly, the expression of germline ε transcripts (GLTε) was selectively decreased in lipopolysaccharide-stimulated Sesn2 −/− splenocytes. Overexpression of Sesn2 increased GLTε promoter activity in B cells. In addition, AICAR (an activator of AMPK) selectively increased IL-4-induced GLTε expression and surface IgE (sIgE) expression in splenocytes. Furthermore, AICAR selectively enhanced IL-4-induced GLTε expression, sIgE expression, and IgE production by anti-CD40-stimulated B cells. We observed that ovalbumin (OVA)-specific IgE concentration was reduced in OVA-challenged Sesn2 −/− mice. Taken together, these results indicate that Sesn2-AMPK signaling selectively enhances IL-4-induced IgE class switching and IgE production by B cells, suggesting that this could be a therapeutic strategy targeting Sesn2 in IgE-mediated allergic diseases.