Insulin Requires A(2b) Adenosine Receptors To Modulate The L-Arginine/Nitric Oxide Signalling In The Human Fetoplacental Vascular Endothelium From Late-Onset Preeclampsia

Late-onset preeclampsia (LOPE) associates with reduced umbilical vein reactivity and endothelial nitric oxide synthase (eNOS) activity but increased human cationic amino acid (hCAT-1)-mediated L-arginine transport involving A(2A) adenosine receptor in the fetoplacental unit. This study addresses the A(2B) adenosine receptor (A(2B)AR)-mediated response to insulin in the fetoplacental vasculature from LOPE. Umbilical veins and HUVECs were obtained from women with normal (n = 37) or LOPE (n = 35) pregnancies. Umbilical vein rings reactivity to insulin was assayed in the absence or presence of adenosine and MRS-1754 (A(2B)AR antagonist) in a wire myograph. HUVECs were exposed to insulin, MRS-1754, BAY60-6583 (A(2B)AR agonist), NECA (general adenosine receptors agonist) or N-G-nitro-L-arginine methyl ester (NOS inhibitor). A(2B)AR, hCAT-1, total and phosphorylated eNOS, Akt and p44/42(mapk) protein abundance were determined by Western blotting. Insulin receptors A (IR-A) and B (IR-B), eNOS and hCAT-1 mRNA were determined by qPCR. Firefly/Renilla luciferase assay was used to determine -1606 bp SLC7A1 (hCAT-1) promoter activity. L-Citrulline content was measured by HPLC, L-[H-3]citrulline formation from L-[H-3]arginine by the Citrulline assay, and intracellular cGMP by radioimmunoassay. LOPE-reduced dilation of vein rings to insulin was restored by MRS-1754. HUVECs from LOPE showed higher A(2B)AR, hCAT-1, and IR-A expression, Akt and p44/42(mapk) activation, and lower NOS activity. MRS-1754 reversed the LOPE effect on A(2B)AR, hCAT-1, Akt, and eNOS inhibitory phosphorylation. Insulin reversed the LOPE effect on A(2B)AR, IR-A and eNOS, but increased hCAT-1-mediated transport. Thus, LOPE alters endothelial function, causing an imbalance in the L-arginine/NO signalling pathway to reduce the umbilical vein dilation to insulin requiring A(2B)AR activation in HUVECs.