Increased O-Linked N-Acetylglucosamine Modification of NF-IeB and Augmented Cytokine Production in the Placentas from Hyperglycemic Rats

Inflammation as a result of NF-kappa B activation may result from the classical (canonical) pathway, with disconnection of the I kappa B inhibitor and subsequent nuclear translocation or, alternatively, by post-translational modifications of modulatory proteins or NF-kappa B subunits (non-canonical pathway). We hypothesized that hyperglycemia-induced increased glycosylation with O-linked N-acetylglucosamine (O-GlcNAc) of NF-kappa B in placental tissue leads to augmented production of pro-inflammatory cytokines, culminating in placental dysfunction and fetal restriction growth. Single injections of streptozotocin (40 mg/kg) or vehicle were used to induce hyperglycemia or normoglycemia, respectively, in female Wistar rats. After 3 days, rats were mated and pregnancy confirmed. Placental tissue was collected at 21 days of pregnancy. Placental expression of p65 subunit was similar between groups. However, nuclear translocation of p65 subunit, showing greater activation of NF-kappa B, was increased in the hyperglycemic group. Reduced expression of I kappa B and increased expression of phosphorylated I kappa B-Ser32 were observed in the placenta from hyperglycemic rats, demonstrating increased classical NF-kappa B activation. Augmented modification of O-GlcNAc-modified proteins was found in the placenta from hyperglycemic rats and p65 subunit was a key O-GlcNAc target, as demonstrated by immunoprecipitation. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) expressions were increased in the placenta from hyperglycemic rats. Furthermore, placental weight was increased, whereas fetal weight was decreased under hyperglycemic conditions. TNF-alpha and IL-6 demonstrated positive correlations with placental weight and negative correlations with fetal weight and placental efficiency. Therefore, under hyperglycemic conditions, a modulatory role of O-GlcNAc in NF-kappa B activity was demonstrated in the placenta, contributing to fetal and placental dysfunction due to inflammatory cytokine exacerbation.