Background and purpose: Pregnancy-associated vascular remodeling is essential for both maternal and fetal health. We have previously shown that maternal endothelial cell tetrahydrobiopterin (BH4) deficiency causes poor pregnancy outcomes. Here, we investigated the role and mechanisms of endothelial cell-mediated vasorelaxation function in these outcomes. Experimental approach: The vascular reactivity of mouse aortas and uterine arteries from non-pregnant and pregnant endothelial cell-specific BH4 deficient mice (Gch1fl/flTie2cre mice) was assessed by wire myography. Systolic blood pressure was assessed by tail cuff plethysmography. Key results: Key results: In late pregnancy, systolic blood pressure was significantly higher (~24 mmHg) in Gch1fl/flTie2cre mice compared with wild-type littermates. This was accompanied by enhanced vasoconstriction and reduced endothelial-dependent vasodilation in both aorta and uterine arteries from pregnant Gch1fl/flTie2cre mice. In uterine arteries loss of eNOS-derived vasodilators was partially compensated by upregulation of intermediate and large-conductance Ca2+-activated K+ channels. In rescue experiments, oral BH4 supplementation alone did not rescue vascular dysfunction and pregnancy-induced hypertension in pregnant Gch1fl/flTie2cre mice. However, combination with the fully reduced folate, 5-methyltetrahydrofolate (5-MTHF), restored endothelial cell vasodilator function and blood pressure. Conclusions and implications: We identify a critical requirement for maternal endothelial cell BH4 biosynthesis in endothelial cell vasodilator function in pregnancy. Targeting vascular Gch1 and BH4 biosynthesis with reduced folates may provide a novel therapeutic target for the prevention and treatment of pregnancy-related hypertension.

Bruton’s tyrosine kinase (BTK) is a non-receptor kinase best known for its role in B lymphocyte development that is critical for proliferation, and survival of leukaemia cells in B cell malignancies. However, BTK is expressed in myeloid cells, particularly monocytes and macrophages where its inhibition has been reported to exhibit anti-inflammatory properties. Therefore, we explored the role of BTK on the migration of myeloid cells in vitro and in vivo. Using the zymosan induced peritonitis model of sterile inflammation we demonstrated that acute (1 h prior to zymosan) inhibition of BTK using a wide range of FDA (Ibrutinib and Acalabrutinib) and non-FDA approved inhibitors (ONO-4059, CNX-774, Olumatinib and LFM-A13) reduced neutrophil and monocyte recruitment. XID mice, which have a point mutation in the Btk gene had reduced neutrophil and monocyte recruitment to the peritoneum following zymosan challenge. To better understand the role of BTK in myeloid cell recruitment we investigated both chemotaxis and chemokine production in monocytes and macrophages. Pharmacological or genetic inhibition of BTK signalling substantially reduced human monocyte and murine macrophage chemotaxis to a range of chemoattractants (complement C5a and CCL2). We also demonstrated that inhibition of BTK in tissue resident macrophages significantly decreases chemokine secretion by reducing NF-kB activity and Akt signalling. Our work has identified a new role of BTK in regulating myeloid cell recruitment via two mechanisms, 1) reducing monocyte/macrophages’ ability to undergo chemotaxis, and 2) reducing chemokine secretion, via reduced NF-kB activity in tissue resident macrophages.