Protective effect of sRAGE on fetal development in pregnant rats with gestational diabetes mellitus

To investigate the protective effect of secretory receptor for advanced glycation endproducts (sRAGE) on the fetal development using rat model of gestational diabetes mellitus (GDM). The model of pregnant rats with intrauterine hyperglycemia was established by intraperitoneal injection of 25 mg/kg streptozotocin (STZ). Rats with established GDM were randomly grouped, and the pregnant rats in the experimental group were subsequently injected with recombinant sRAGE protein (5 mg/kg, in 0.2 mL PBS) at tail vein every 24 h, while the rats in control group were injected with the same dosage of albumin solution. Blood glucose, serum levels of advanced glycation endproducts (AGEs), and levels of RAGE protein in brain and heart tissues of pregnant rats were measured at 3, 13, and 19 days postconception. At 19 days fetuses were delivered by cesarean section, number of fetuses, their weight and placental weights were recorded, and fetal malformations and defects were analyzed visually and pathologically. The expression level of RAGE, NOX2, MCP-1, p65, VCAM-1, and VEGF mRNA in placenta was evaluated by real-time PCR. p65 protein localization was detected by immunohistochemistry in fetal brain and heart tissue sections. We analyzed the correlation between AGEs and RAGE level and the development of fetal rats, and the protective effect of blocking AGEs-RAGE pathway on the fetal development in the rat model of GDM was investigated. (1) The concentration of blood glucose and AGEs in serum of pregnant rats with GDM was significantly higher than in control group (p < 0.05), with strong correlation between blood glucose and levels of AGEs (r = 0.693, p < 0.05). (2) While both the number of fetuses and placental wet weight in pregnant rat model of GDM were similar to control group, pups from GDM group exhibited higher incidence of developmental abnormalities and higher average weight (p < 0.05). sRAGE treatment slightly but not significantly reduced the probability of the fetal developmental defects, as compared to GDM group. (3) p65, a part of the NF-kB heterodimeric complex, was localized to cell nuclei in the fetal tissues of pups delivered by GDM rats, while sRAGE treatment partially restored cytoplasmic localization of p65, similarly to control tissues. Increased incidence of fetal developmental defects observed in offsprings of pregnant rats with GDM had significant correlation with the level of AGEs in serum of pregnant rats and expression levels of RAGE protein in tissues. GDM resulted in upregulation of mRNA expression of several pro-inflammatory and ROS-inducing genes in placental tissues of pregnant rats. Elevated blood glucose, serum AGEs levels, and increased gene expression are attenuated by intravenous sRAGE treatment. sRAGE appears to reduce the activity of NF-κB in fetal tissues, thus potentially having a protective effect on fetal development.