Hyperglycemia down-regulates cGMP-dependent protein kinase I expression in first trimester cytotrophoblast cells

Diabetes in pregnancy is associated with microvascular complications and a higher incidence of preeclampsia. The regulatory signaling pathways involving nitric oxide, cGMP, and cGMP-dependent protein kinase (PKG) have been shown to be down-regulated under diabetic conditions and contribute to the pathogenesis of vascular complications in diabetes. The present study was undertaken to investigate how high glucose concentrations regulate PKG expression in cytotrophoblast cells (CTBs). Human CTBs (Sw. 71) were treated with 45, 135, 225, 495, or 945 mg/dL glucose for 48 h. Some cells were pretreated with a p38 inhibitor (10 μM SB203580) or 10 μM rosiglitazone. After treatment, the cell lysates were subjected to measure the expression of protein kinase G1α (PKG1α), protein kinase G1β (PKG1β), soluble guanylate cyclase 1α (sGC1α), and soluble guanylate cyclase 1 β (sGC1β) by Western blot. Statistical comparisons were performed using analysis of variance with Duncan's post hoc test. The expressions of PKG1α, PKG1β, sGC1α, and sGC1β were significantly down-regulated (p < 0.05) in CTBs treated with >135 mg/dL glucose compared to basal (45 mg/dL). The hyperglycemia-induced down-regulation of cGMP and cGMP-dependent PKG were attenuated by the SB203580 or rosiglitazone pretreatment. Exposure of CTBs to excess glucose down-regulates cGMP and cGMP-dependent PKG, contributing to the development of vascular complications in diabetic mothers during pregnancy. The attenuation of hyperglycemia-induced down-regulation of PKG proteins by SB203580 or rosiglitazone pretreatment further suggests the involvement of stress signaling mechanisms in this process.