Preeclampsia usually occurs after week 20 of gestation and features hypertension and an increased peripheral vascular resistance. The mechanisms are unknown (1). Several lines of evidence implicate angiotensin II (Ang II) and its binding site, the AT 1 receptor. Preeclamptic patients manifest exaggerated pressor responses to Ang II. Gant et al. (2) infused Ang II into pregnant patients from week 10 of pregnancy onward and observed that those who later developed sustained hypertension required diminishing amounts of Ang II to obtain a similar pressor response. One possible explanation for this phenomenon might be increased expression of the AT 1 receptor. Baker et al. (3) also performed Ang II infusion experiments in pregnant patients and identified five patients who subsequently developed hypertension after week 20. These women were compared with seven who did not develop hypertension. The platelets of the preeclamptic women exhibited increased calcium signaling and increased binding sites for Ang II. The authors suggested increased stimulus-effect coupling in terms of Ang II responses in preeclamptic patients. We also observed increased cytosolic calcium responses in the platelets of preeclamptic patients in response to Ang II (4). However, circulating levels of Ang II are not increased in preeclampsia (5-7). In an earlier study of patients with essential hypertension, we observed a remarkably high incidence of circulating antibodies that cross-reacted with the α1-adrenoceptor and stimulated its signaling mechanism (8). In the present study, we tested the hypothesis that circulating antibodies to a vascular receptor might be responsible for the hypertension observed in preeclampsia. We employed a bioassay of beating neonatal rat cardiomyocytes, as well as Western blotting and confocal microscopy. We found that immunoglobulin from preeclamptic women contains a factor that binds to, and stimulates, the AT 1 receptor. MethodsCell culture. Isolation and cultivation of neonatal heart cells were performed as described previously (9). Briefly, single cells were dissociated from the minced ventricles of Wistar rats (1-2 days old) with a 0.25% solution of crude trypsin and were cultured as monolayers with a density of 800 cells/mm 2 in Halle SM 20-I medium equilibrated with humidified air. The medium contained 10% heat-inactivated FCS and 2 µmol/l fluorodeoxyuridine (Serva, Heidelberg, Germany) the latter to prevent proliferation of nonmuscle cells. On the third or fourth days, the cells were incubated for 2 h in 2 ml fresh serum-containing medium. Seven to 10 selected cells or synchronously contracting cell clusters per flask were counted for 15 s. This procedure was Immune mechanisms and the renin-angiotensin system are implicated in preeclampsia. We investigated 25 preeclamptic patients and compared them with 12 normotensive pregnant women and 10 pregnant patients with essential hypertension. Antibodies were detected by the chronotropic responses to AT 1 receptor-mediated stimulation of cultured neonatal rat cardio...

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.

Background-We recently described autoantibodies (angiotensin-1 receptor autoantibodies, AT 1 -AA) directed at the AT 1 receptor in the serum of preeclamptic patients, whose placentas are commonly infarcted and express tissue factor (TF). Mechanisms of how AT 1 -AA might contribute to preeclampsia are unknown. We tested the hypothesis that AT 1 -AA cause vascular smooth muscle cells (VSMC) to express TF. Methods and Results-IgG from preeclamptic patients containing AT 1 -AA was purified with anti-human IgG columns.AT 1 -AA were separated from the IgG by ammonium sulfate precipitation. We transfected Chinese hamster ovary cells overexpressing the AT 1 receptor with TF promoter constructs coupled to a luciferase reporter gene. VSMC were obtained from human coronary arteries. Extracellular signal-related kinase activation was detected by an in-gel kinase assay. AP-1 activation was determined by electromobility shift assay. TF was measured by ELISA and detected by immunohistochemistry. Placentas from preeclamptic women stained strongly for TF, whereas control placentas showed far less staining. We proved AT 1 -AA specificity by coimmunoprecipitating the AT 1 receptor with AT 1 -AA but not with nonspecific IgG. Angiotensin (Ang) II and AT 1 -AA both activated extracellular signal-related kinase, AP-1, and the TF promoter transfected VSMC and Chinese hamster ovary cells, but only when the AP-1 binding site was present. We then demonstrated TF expression in VSMC exposed to either Ang II or AT 1 -AA. All these effects were blocked by losartan. Nonspecific IgG or IgG from nonpreeclamptic pregnant women had a negligible effect. Conclusions-We conclude that AT 1 -AA and Ang II both stimulate the AT 1 receptor and initiate a signaling cascade resulting in TF expression. These results show an action of AT 1 -AA on human cells that could contribute to the pathogenesis of preeclampsia.