Cross-talk between cAMP and MAPK pathways in HSD11B2 induction by hCG in placental trophoblasts

Abstract

Overexposure of the fetus to glucocorticoids in gestation is detrimental to fetal development. The passage of maternal glucocorticoids into the fetal circulation is governed by 11beta-Hydroxysteroid Dehydrogenase Type 2 (HSD11B2) in the placental syncytiotrophoblasts. Human chorionic gonadotropin (hCG) plays an important role in maintaining placental HSD11B2 expression via activation of the cAMP pathway. In this study, we investigated the relationship between the activation of the cAMP pathway by hCG and subsequent phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) or p38 mitogen-activated protein kinase (MAPK) pathways in the regulation of placental HSD11B2 expression in human placental syncytiotrophoblasts. We found that treatment of the placental syncytiotrophoblasts with either hCG or dibutyl cAMP (dbcAMP) could promote the phosphorylation of p38 and ERK1/2. Inhibition of p38 MAPK with SB203580 not only reduced the basal HSD11B2 mRNA and protein levels but also attenuated HSD11B2 levels induced by either hCG or dbcAMP. By contrast, inhibition of ERK1/2 with PD98059 increased the basal mRNA and protein levels of HSD11B2 and had no effect on HSD11B2 mRNA and protein levels induced by either hCG or dbcAMP. These data suggest that p38 MAPK is involved in both basal and hCG/cAMP-induced expression of HSD11B2, and ERK1/2 may play a role opposite to p38 MAPK at least in the basal expression of HSD11B2 in human placental syncytiotrophoblasts and that there is complicated cross-talk between hCG/cAMP and MAPK cascades in the regulation of placental HSD11B2 expression.

Figure 1. Phosphorylation of p38 MAPK (P-p38) and ERK1/2 induced by dbcAMP (100 µM) and hCG (10 IU/ml) in human placental syncytiotrophoblasts.

Upper panels of each bar graph are the representative blots. The bar graphs are the average data of three experiments. *P<0.05, **P<0.01,***P<0.001 versus 0 min.

Figure 2. (A) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP (100 µM) and hCG (10 IU/ml)-induced HSD11B2 mRNA expression in human placental syncytiotrophoblasts.

*p<0.05, **p<0.01, ***p<0.001 versus control; ## p<0.01 ### p<0.001 versus treatment with db-cAMP and hCG n = 4; (B) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP (db cAMP, 100 µM) and hCG (10 IU/ml)-induced SP1 mRNA expression in human placental syncytiotrophoblasts. *p<0.05, **p<0.01, ***p<0.001 versus control;# p<0.05, ## p<0.01 versus treatment with dbcAMP and hCG (n = 4).

Figure 3. (A) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP (100 µM) and hCG (10 IU/ml)-induced HSD11B2 protein level in human placental syncytiotrophoblasts.

*p<0.05, **p<0.01, ***p<0.001 versus control; ## p<0.01 ### p<0.001 versus treatment with dbcAMP and hCG, n = 4. (B) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP, 100 µM) and hCG (10 IU/ml)-induced SP1 protein level in human placental syncytiotrophoblasts. ***p<0.001 vs control; ### p<0.001 versus treatment with dbcAMP and hCG (n = 4).

Figure 4. (A) Effect of PD98059(ERK1/2 MAPK inhibitor, 50 µM) on the basal and dbcAMP (100 µM) and hCG (10 IU/ml)-induced HSD11B2 mRNA expression in human placental syncytiotrophoblasts.

*p<0.05, **p<0.01, ***p<0.001 versus control (n = 4) (B) Effect of PD98059 (ERK1/2 MAPK inhibitor, 50 µM) on the basal and dbcAMP(100 µM) and hCG (10 IU/ml)-induced SP1 mRNA expression in human placental syncytiotrophoblasts. *p<0.05, **p<0.01, ***p<0.001 versus control (n = 4).

Figure 5. (A) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP (100 µM) and hCG (10 IU/ml)-induced HSD11B2 protein level in human placental syncytiotrophoblasts.

*p<0.05 versus control(n = 4). (B) Effect of SB203580 (p38 MAPK inhibitor, 10 µM) on the basal and dbcAMP (100 µM) and hCG (10 IU/ml)-induced SP1 protein level in human placental syncytiotrophoblasts. ***p<0.001 versus control (n = 4).