Vitamin D supplementation reduces some AT1-AA-induced downstream targets implicated in preeclampsia including hypertension

Abstract

Autoantibodies to the ANG II type I receptor (AT₁-AA) are associated with preeclampsia (PE). We found that vitamin D supplementation reduced AT₁-AA and blood pressure (MAP) in the RUPP rat model of PE. However, it was undetermined whether the decrease in AT₁-AA was the mechanism whereby vitamin D lowered MAP or if it were through factors downstream of AT₁-AA. Uterine artery resistance index, placental ET-1, and soluble FMS-like tyrosine kinase-1 are increased with AT₁-AA-induced hypertension and are considered markers of PE in pregnant women. Therefore, we hypothesized that vitamin D would reduce PE factors during AT₁-AA-induced hypertension and could lower blood pressure in a model of hypertension during pregnancy without PE features. Either ANG II (50 ng·kg^-1·day) or AT₁-AA (1:40) was infused from gestational day (GD) 12-19. vitamin D₂ (VD2, 270 IU/day) or vitamin D₃ (VD3, 15 IU/day) was administered orally from GD14-GD18. MAP (mmHg) increased in AT₁-AA (121 ± 4) and ANG II (113 ± 1)-infused pregnant rats compared with normal pregnant rats (NP) (101 ± 2) but was lower in AT₁-AA+VD2 (105 ± 2), AT₁-AA+VD3 (109 ± 2), ANG II+VD2 (104 ± 4), and ANG II+VD3 (104 ± 3). VD2 and/or VD3 improved PE features associated with AT₁-AA during pregnancy, while ANG II did not induce such features, supporting the hypothesis that AT₁-AA induces PE features during pregnancy, and these are improved with vitamin D. In this study, we demonstrate that vitamin D improved many factors associated with PE and reduced blood pressure in a hypertensive model without PE features, indicating that vitamin D could be beneficial for various hypertensive disorders of pregnancy.

Keywords: hypertension; inflammation; pregnancy.

Fig. 1.

A: blood pressures were significantly increased in both ANG II- and AT₁-AA-infused rats compared with NP. Neither VD2 nor VD3 treatment affected blood pressure in NP rats. Both VD2 and VD3 significantly reduced blood pressure in ANG II- and AT₁-AA-infused rats. AT₁-AA infusion increased blood pressure above levels observed in ANG II-infused rats (n: NP = 19, NP+VD2 = 6, NP+VD3 = 5, ANG II = 14, ANG II+VD2 = 9, ANG II+VD3 = 7, AT₁-AA = 6, AT₁-AA+VD2 = 8, and AT₁-AA+VD3 = 6). Comparisons by unpaired t-test. B: there were no changes in pup weight in ANG II or AT₁-AA rats compared with NP. Although pup weights were not significantly less in AT₁-AA or ANGII infusion compared to NP, VD3 treatment did improve pup weight of AT₁-AA infused compared to AT₁-AA alone. Comparisons by unpaired t-test and one-way ANOVA. C: placental weights did not differ in ANG II- or AT₁-AA-infused rats compared with NP. VD2 did reduce placental weight in AT₁-AA-infused rats. No other groups treated with VD2 or VD3 had significantly altered placental weight compared with their untreated counterparts (n: NP = 13, NP+VD2 = 5, NP+VD3 = 4, ANG II = 15, ANG II+VD2 = 9, ANG II+VD3 = 7, AT₁-AA = 6, AT₁-AA+VD2 = 7, and AT₁-AA+VD3 = 6). Comparisons by unpaired t-test. D: placental efficiency, defined as placenta:fetal weight ratio, was not changed with ANG II or AT₁-AA infusion compared with NP rats. In addition, neither VD2 nor VD3 affected placenta:fetal weight ratio in either ANG II- or AT₁-AA-infused pregnant rats (n: NP = 13, NP+VD2 = 5, NP+VD3 = 4, ANG II = 15, ANG II+VD2 = 9, ANG II+VD3 = 7, AT₁-AA = 6, AT₁-AA+VD2 = 7, and AT₁-AA+VD3 = 6). Comparisons by unpaired t-test and one-way ANOVA. E: uterine artery resistance index (UARI) increased significantly in AT₁-AA-infused rats compared with NP. Vitamin D treatment in NP rats did not alter UARI. Resistance was significantly decreased in AT₁-AA+VD3 rats but did not dignificantly change in AT₁-AA+VD2 rats (n: NP = 5, NP+VD2 = 4, NP+VD3 = 3, AT₁-AA = 6, AT₁-AA+VD2 = 6, and AT₁-AA+VD3 = 4). Comparisons by unpaired t-test. *P < 0.05 vs. NP, ΦP < 0.05 vs. ANG II-infused, ψP < 0.05 vs. AT₁-AA-infused.

Fig. 2.

A: plasma sFlt-1 levels were significantly increased in AT₁-AA-infused rats. sFlt-1 was significantly reduced in AT₁-AA-infused rats treated with either VD2 or VD3. ANG II infusion into pregnant rats did not alter sFlt-1 levels. VD2 did reduce sFlt-1 levels in ANG II-infused rats, but VD3 had no effect. Neither VD2 nor VD3 affected sFlt-1 levels in NP rats (n: NP = 7, NP+VD2 = 3, NP+VD3 = 4, ANG II = 4, ANG II+VD2 = 4, ANG II+VD3 = 4, AT₁-AA = 6, AT₁-AA+VD2 = 6, and AT₁-AA+VD3 = 6). Comparisons by unpaired t-test and one-way ANOVA. B: placental preproendothelin-1 (PPET) was measured by real-time PCR and normalized to NP level. Placental PPET did not change with VD2 or VD3 treatment in NP rats. ANG II did not significantly increase placental PPET expression, and Vitamin D did not have an effect in ANG II-infused rats. AT₁-AA infusion significantly increased placental PPET expression, and both VD2 and VD3 significantly reduced PPET (n: NP = 4, NP+VD2 = 3, NP+VD3 = 3, ANG II = 5, ANG II+VD2 = 5, ANG II+VD3 = 5, AT₁-AA = 4, AT₁-AA+VD2 = 4, and AT₁-AA+VD3 = 4). Comparisons were made by unpaired t-test and one-way ANOVA. C: renal cortex expression of PPET was significantly increased in both ANG II- and AT₁-AA-infused pregnant rats. VD2 modestly decreased renal cortex PPET in ANG II- and AT₁-AA-infused rats; however this did not reach significance. VD3 did not alter PPET in the renal cortices of ANG II- or AT₁-AA-infused pregnant rats. VD2 and VD3 administration to NP rats significantly increased PPET expression in renal cortices (n: NP = 8, NP+VD2 = 5, NP+VD3 = 3, ANG II = 4, ANG II+VD2 = 6, ANG II+VD3 = 5, AT₁-AA = 5, AT₁-AA+VD2 = 4, AT₁-AA+VD3 = 3). Comparisons were made by unpaired t-test. D: 8-isoprostanes were measured in plasma. Isoprostanes did not change with Vitamin D treatment in NP rats. Isoprostanes were significantly increased in AT₁-AA-infused rats and significantly decreased with VD2 and VD3-treated AT₁-AA rats. ANG II rats had significantly increased isoprostanes compared with NP rats; however, neither VD2 nor VD3 affected isoprostane levels in ANG II rats (n: NP = 5, NP+VD2 = 4, NP+VD3 = 4, ANG II = 5, ANGII+VD2 = 5, ANG II+VD3 = 5, AT₁-AA = 5, AT₁-AA+VD2 = 5, and AT₁-AA+VD3 = 5). Comparisons were made by unpaired t-test and one-way ANOVA. *P < 0.05 vs. NP, ΦP < 0.05 vs. ANG II-infused, ψP < 0.05 vs. AT₁-AA-infused.