AT ₁ Receptor Agonistic Antibodies From Preeclamptic Patients Stimulate NADPH Oxidase

Abstract

Background-We recently identified agonistic autoantibodies directed against the angiotensin AT1 receptor (AT 1 -AA) in the plasma of preeclamptic women. To elucidate their role further, we studied the effects of AT 1 -AA on reactive oxygen species (ROS), NADPH oxidase expression, and nuclear factor-B (NF-B) activation. Methods and Results-We investigated human vascular smooth muscle cells (VSMC) and trophoblasts, as well as placentas. AT 1 -AA were isolated from sera of preeclamptic women. Angiotensin II (Ang II) and AT 1 -AA increased ROS production and the NADPH oxidase components, p22, p47, and p67 phox in Western blotting. We next tested if AT 1 -AA lead to NF-B activation in VSMC and trophoblasts. AT 1 -AA activated NF-B. Inhibitor-B␣ (I-B␣) expression was reduced in response to AT 1 -AA. AT1 receptor blockade with losartan, diphenylene iodonium, tiron, and antisense against p22 phox all reduced ROS production and NF-B activation. VSMC from p47phoxϪ/Ϫ mice showed markedly reduced ROS generation and NF-B activation in response to Ang II and AT1-AA. The p22, p47, and p67 phox expression in placentas from preeclamptic patients was increased, compared with normal placentas. Furthermore, NF-B was activated and I-B␣ reduced in placentas from preeclamptic women. Conclusions-NADPH oxidase is potentially an important source of ROS that may upregulate NF-B in preeclampsia. We suggest that AT 1 -AA through activation of NADPH oxidase could contribute to ROS production and inflammatory responses in preeclampsia.

New Aspects in the Pathophysiology of Preeclampsia

“…Indeed, AT-1AA functioned in a Western blot at least as well as currently available commercial antibodies to the AT-1 receptor. Dechend et al (68,69) confirmed these findings by relying on co-immunoprecipitation studies. They could not find evidence for calcium signaling or smooth muscle cell contraction resulting from the autoantibodies.…”

Contractility of Placental Vascular Smooth Muscle Cells in Response to Stimuli Produced by the Placenta: Roles of ACE vs. Non-ACE and AT1 vs. AT2 in Placental Vessel Cells

“…AT1 is constitutively expressed in placental VSMCs as shown in the Western blot data. AT1 plays important roles in angiogenic, inflammatory and oxidative stress responses in the placental vasculature [30][31][32][33]. A recent study by Herse et al showed that AT1 receptor mRNA expression was 10-fold higher in the placenta than in the decidua tissues in both normal and preeclamptic pregnancies, but no difference was noticed for AT1 mRNA expression between normal and preeclamptic placental tissues [34].…”

Agonistic AT1 Receptor Autoantibody Increases in Serum of Patients with Refractory Hypertension and Improves Ca2+ Mobilization in Cultured Rat Vascular Smooth Muscle Cells

“…According to present data, AT 1 -AAs were suggested to have similar effects. Dechend et al reported that AT 1 -AAs induced signaling in vascular cells including AP-1 and NF-κB activation (10,11). Both of these nuclear factors participate in inflammation (23,24).…”

“…AT 1 -AAs induced signaling in vascular cells and trophoblasts including activator protein-1 (AP-1) and nuclear factorkappa B (NF-κB) (10,11), and activated calcineurin-NFAT (nuclear factor of activated T cells) through increased intracellular Ca 2+ mobilization in Chinese hamster ovary cells transferred with the rat AT 1A receptor (12). However, there were limited data related to the role of AT 1 -AAs in pathogenesis of hypertension.…”