Heat shock protein (Hsp) 60 elicits a potent proinflammatory response in the innate immune system and has been proposed as a danger signal of stressed or damaged cells to the immune system. Previous studies reported CD14, TLR2, and TLR4 as mediators of signaling but probably not of binding. Although the receptor for Hsp60 was proposed to be saturable and specific on macrophages, it is not well defined. In the current study, we found that lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), as a receptor for Hsp60, could bind and internalize Hsp60 via the C terminus of Hsp60. Yeast two-hybrid assay revealed that the second β-sheet containing the long-loop region of LOX-1 played an important role in this interaction. Furthermore, LOX-1 might be engaged as a common receptor for different Hsp60 species. Bone marrow-derived dendritic cells could cross-present Hsp60-fused OVA Ag on MHC class I molecules via LOX-1. Inhibition of the recognition of Hsp60 by LOX-1 decreases Hsp60-mediated cross-presentation of OVA and specific CTL response and protective tumor immunity in vivo. Taken together, these results demonstrate that LOX-1 functions as a receptor for Hsp60 and is involved in the delivery of Hsp60-fused Ag into the MHC class I presentation pathway.

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific disorder characterised by raised bile acids in foetal-maternal circulation, which threatens perinatal health. During the progression of ICP, the effect of oxidative stress is underscored. Peroxiredoxin-3 (PRDX3) is a mitochondrial antioxidant enzyme that is crucial to balance intracellular oxidative stress. However, the role of PRDX3 in placental trophoblast cells under ICP is not fully understood. We demonstrated that the level of PRDX3 was downregulated in ICP placentas as well as bile acids–treated trophoblast cells and villous explant in vitro. Toxic levels of bile acids and PRDX3 knockdown induced oxidative stress and mitochondrial dysfunction in trophoblast cells. Moreover, silencing of PRDX3 in trophoblast cell line HTR8/SVneo induced growth arrest and cellular senescence via activation of p38-mitogen-activated protein kinase (MAPK) and induction of p21^WAF1/CIP and p16^INK4A. Additionally, enhanced cellular senescence, determined by senescence-associated beta-galactosidase staining, was obviously attenuated by p38-MAPK inhibitor SB203580. Our data determined that exposure to bile acid decreased PRDX3 level in human trophoblasts. PRDX3 protected trophoblast cells against mitochondrial dysfunction and cellular senescence induced by oxidative stress. Our results suggest that decreased PRDX3 by excessive bile acids in trophoblasts plays a critical role in the pathogenesis and progression of ICP.

Fetal growth restriction (FGR) threatens perinatal health and is correlated with increased incidence of fetal original adult diseases. Most cases of FGR were idiopathic, which were supposed to be associated with placental abnormality. Decreased circulating placental growth factor (PGF) was recognized as an indication of placental deficiency in FGR. In this study, the epigenetic regulation of PGF in FGR placentas and the involvement of PGF in modulation of trophoblast activity were investigated. The expression level of PGF in placental tissues was determined by RT-qPCR, immunohistochemistry and ELISA. DNA methylation profile of PGF gene was analyzed by bisulfite sequencing. Trophoblastic cell lines were treated with ZM-306416, an inhibitor of PGF receptor FLT1, to observe the effect of PGF/FLT1 signaling on cell proliferation and migration. We demonstrated that PGF was downregulated in placentas from FGR pregnancies compared with normal controls. The villous expression of PGF was positively correlated with placental and fetal weight. The CpG island inside PGF promoter was hypomethylated without obvious difference in both normal and FGR placentas. However, the higher DNA methylation at another CpG island downstream exon 7 of PGF was demonstrated in FGR placentas. Additionally, we found FLT1 was expressed in trophoblast cells. Inhibition of PGF/FLT1 signaling by a selective inhibitor impaired trophoblast proliferation and migration. In conclusion, our data suggested that the PGF expression was dysregulated, and disrupted PGF/FLT1 signaling in trophoblast might contribute to placenta dysfunction in FGR. Thus, our results support the significant role of PGF in the pathogenesis of FGR.