Exercise training attenuates placental ischemia-induced hypertension and angiogenic imbalance in the rat

Abstract

An imbalance between proangiogenic (vascular endothelial growth factor) and antiangiogenic (soluble fms-like tyrosine kinase 1) factors plays an important role in hypertension associated with reduced uteroplacental perfusion (RUPP). Exercise has been shown to stimulate proangiogenic factors, such as vascular endothelial growth factor, in both the pregnant and nonpregnant state; thus, we hypothesized that exercise training would attenuate both angiogenic imbalance and hypertension attributed to RUPP. Four groups of animals were studied, RUPP and normal pregnant controls and normal pregnant and RUPP+exercise training. Exercise training attenuated RUPP-induced hypertension (P<0.05), decreased soluble fms-like tyrosine kinase 1 (P<0.05), increased VEGF (P<0.05), and elevated the soluble fms-like tyrosine kinase 1:vascular endothelial growth factor ratio. The positive effects of exercise on angiogenic balance in the RUPP rats were confirmed by restoration (P<0.05) of the RUPP-induced decrease in endothelial tube formation in human umbilical vascular endothelial cells treated with serum from each of the experimental groups. Placental prolyl hydroxylase 1 was increased (P<0.05) in RUPP+exercise training rats. Decreased trolox equivalent antioxidant capacity in the placenta, amniotic fluid, and kidney of the RUPP rats was reversed by exercise. RUPP-induced increase in renal thiobarbituric acid reactive species was attenuated by exercise. The present data show that exercise training before and during pregnancy attenuates placental ischemia-induced hypertension, angiogenic imbalance, and oxidative stress in the RUPP rat and reveals that increased prolyl hydroxylase 1 is associated with decreased soluble fms-like tyrosine kinase 1, thus revealing several potential pathways for exercise training to mitigate the effects of placental ischemia-induced hypertension. Lastly, the present study demonstrates that exercise training may be a useful approach to attenuate the development of placental ischemia-induced hypertension during pregnancy.

Figure 1. Effects of RUPP and Exercise on Mean Arterial Pressure (MAP)

MAP was increased by RUPP and was attenuated by exercise before and during pregnancy. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 2. Effects of exercise on fetal (panel A), placental (panel B) weight and placental efficiency (Fetal weight/placental weight; panel C)

Fetal and placental weight was decreased in the reduced uterine perfusion pressure (RUPP) compared to normal pregnant (NP) rats. Exercise had no effect on fetal weight in either the RUPP or NP rats. Exercise decreased placental weight in the RUPP rats, but had no effect in the NP rats. Placental efficiency was increased (P<0.05) in the RUPP+Ex group compared to the RUPP group. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 3. Circulating vascular endothelial growth factor (VEGF) and angiogenic balance in late gestation

Circulating VEGF (panel A) was decreased in the reduced uterine perfusion pressure (RUPP) compared to normal pregnant (NP) rats and exercise training increased free VEGF in the RUPP+Ex compared to RUPP and in the NP+Ex compared to NP. Panel B illustrates that the sFlt-1:VEGF ratio was increased in the RUPP compared to NP rats was decreased by exercise training in pregnancy. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 4. Skeletal muscle (gastrocnemius) VEGF expression

VEGF expression expressed relative to β-actin was increased (P<0.05) in the skeletal muscle of the RUPP +Ex rats compared to the NP and RUPP groups. Representative blots are shown below graph. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 5. Placental prolyl hydroxylase 1 (PHD1) expression

PHD1 expression was increased (P<0.05) in placentas of RUPP+Ex compared to the NP+Ex, NP and RUPP groups. Representative blot images for PHD1 and β-actin are below the graph. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 6. Endothelial cell tube formation assay

Endothelial cell tubule formation was decreased with the addition of RUPP serum to the cells when compared to cells treated with serum from NP rats. This effect was not observed when cells were treated with serum from RUPP rats that exercised. No effect was observed due to exercise in the cells treated with serum from NP rats that exercised. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 7. Total antioxidant capacity in placenta, amniotic fluid and kidney, and TBARS (malondialdehyde) in kidney

Placental antioxidant capacity was decreased (P<0.05) in the RUPP group and this was attenuated by exercise in the RUPP rats. Exercise did not augment total antioxidant status of placental tissue in the NP rats. Panel B shows that amniotic fluid antioxidant status was decreased (P<0.05) in RUPP compared to NP and this was reversed by exercise training. Panel C shows renal antioxidant capacity was decreased (P<0.05) in the kidneys from reduced uterine perfusion pressure (RUPP) compared to normal pregnant (NP) and that this was attenuated by exercise in the RUPP group. Exercise alone did not augment total antioxidant status of renal tissue. Panel D shows that renal MDA was increased in the RUPP compared to NP rats and this was abrogated by exercise training. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.

Figure 8. Placental superoxide dismutase 2 (SOD2) expression

SOD2 was increased (P<0.05) in the RUPP+Ex and NP+Ex groups compared to the RUPP rats. Representative blot images for PHD1 and β-actin are below the graph. Data are expressed as mean ± SEM. Statistical significance for comparisons that are different by post-hoc testing are indicated by lines above the bars and * P<0.05.