TUMOR NECROSIS FACTOR α (TNFα) INDUCES CONSTRICTION IN MOUSE UTERINE ARTERIES WHEN NITRIC OXIDE (NO) IS INHIBITED
Introduction: Preeclampsia is characterized by maternal endothelial dysfunction involving reduced NO-dependent dilation. Sphingosine-1-phosphate (S1P), a bioactive lipid produced by sphingosine kinase1 (Sphk1) induces dilation and/or constriction depending on cell type and receptors. TNFα is increased in preeclampsia and activates Sphk1. We previously showed that co-infusion of TNFα with LNAME (NOS inhibitor), but not TNFα alone, inside uterine arteries from pregnant mice induces constriction. It is unknown if these effects are Sphk1-dependent or will occur when drugs are added outside the arteries. Hypothesis: Bath addition of TNFα to bind vascular smooth muscle cells (VSMC) of intact arteries when NOS activity is blocked will induce constriction levels similar to infused drugs. Constriction will be mediated through S1P and will be increased in arteries from pregnant mice.
Methods: Pressure myography measured vascular tone of uterine arteries from pregnant and non-pregnant mice. TNFα (10ng/ml) was added to the bath (VSMC stimulation) or infused intraluminally (endothelium stimulation) with or without LNAME, 100µM and/or PF543 (Sphk1 inhibitor, 1µM).
Results: Addition of TNFα alone or with LNAME or PF543 to the bath did not change vascular tone in arteries from pregnant or non-pregnant above that of inhibitors alone. Addition of TNF⍺ with PF543 and LNAME combined induced greater constriction than inhibitors alone in arteries from P (22.15±9.17% vs 10.31±5.75, n=2) but not NP mice.
Conclusion: When NOS activity was blocked, TNFα mediated different responses when infused or added to the bath but only in arteries from pregnant mice. Our initial results showing that TNFα-induced Sphk1 activity in VSMC may generate NO-independent dilation in arteries from pregnant mice are intriguing. Whether S1P generated by the endothelium in infusion experiments could mediate constriction remains to be tested. These results demonstrate that normal NOS function is essential to regulate vascular tone when circulating TNF⍺ levels are elevated, particularly in pregnancy.