Supplementation with BH4 fails to prevent vascular dysfunction and pregnancy-induced hypertension in Gch1fl/flTie2cre mice, but is rescued by the addition of reduced folate, 5-Methyltetrahydrofolate.
In our previous study, we showed that treatment of pregnantGch1fl/fl Tie2cre mice with BH4 and 5-MTHF was sufficient to restoration BH4 levels and prevented fetal growth restriction and increased blood pressure in late pregnancy (Chuaiphichai et al., 2021; Landmesser et al., 2003; Williams, Vallance, Neild, Spencer & Imms, 1997). Given the results of our current study we hypothesized that BH4 and 5-MTHF supplementation is acting to restored blood pressure and fetal growth via normalization of pregnancy induced vascular remodelling in Gch1fl/fl Tie2cre mice. To address this, we treated Gch1fl/fl Tie2cre and wild-type mice with either oral BH4 or BH4 with 5-MTHF for 3 days prior to mating, and throughout pregnancy.
We found that oral BH4 supplementation alone was not sufficient to prevent progressive hypertension throughout pregnancy or restore vascular function in uterine arteries fromGch1fl/fl Tie2cre mice. With an enhanced contractile response and reduced sensitivity to the endothelial cell dependent dilator acetylcholine still observed in pregnantGch1fl/fl Tie2cre mice compared to their wild type littermates (Figure 5A, B, C and D).
However, the addition of reduced folate, 5-MTHF to BH4 supplementation resulted in a striking normalization of both the constriction responses to U46619 and relaxation responses to ACh, inGch1fl/fl Tie2cre mice, restoring the responses to those observed in wild-type animals. The combination of 5-MTHF to BH4 oral supplementation just prior to conception was sufficient to prevent progressive pregnancy induced hypertension inGch1fl/fl Tie2cre mice with no difference in blood pressure observed between wild type andGch1fl/fl Tie2cre mice from 2.5 days post-conception until the end of the experiment at gestational day 18.5 (Figure 5C and F).