br Results br Discussion br
Materials and Methods
Acknowledgment This work was funded by the Collaborative Research Centre (SFB) 807 of the German Research Foundation (DFG) and supported by the state of Hessen (Center for Biomolecular Magnetic Resonance) and the German Research Foundation (DO545/11, SFB 807). We thank Birgit Schäfer for technical assistance. Author Contributions: F.D., R.B.R. and F.B. conceptualized the project. F.D. and R.B.R. conducted experiments. F.D., S.K., V.D. and F.B. wrote the manuscript. Declaration of Interests: The authors declare no competing financial interests. The article is the authors' original work, has not received prior publication and is not under consideration for publication elsewhere.
Introduction Preeclampsia (PE) affects 2–8% of all pregnancies worldwide , and it is a leading factor of maternal mortality, maternal morbidity, fetal growth restriction (FGR), and preterm birth. Although its pathogenesis remains unclear, a number of hallmarks are central. One of these is the development of a pro-inflammatory state ,  including the B-cell production of functionally-active autoantibodies directed against the Angiotensin II, type 1 receptor (AT1-AA) ,  as well as the endothelin-1 ETA receptor (ETA-AA) . In concordance with endothelin 1 , , , these two autoantibodies increase vasoconstriction activation . Animal studies have demonstrated that AT1-AAs are involved in pathways leading to preeclampsia. Thus, administration of human AT1-AA to pregnant mice induces hypertension, proteinuria, and glomerular endotheliosis, the effects of which can be prevented by the AT1 receptor antagonist losartan . Furthermore, the RUPP rat model of preeclampsia, in which placental ischemia is surgically induced, displays increased Conoidin A sale of TNF-a, IL-6 and AT1-AA , . Also the involvement of ETA-AA is rendered probably, as administration of a specific Endothelin 1 receptor A antagonist to RUPP rats and to the rodent sFlt-1 model normalized their blood pressure , . However, we know little about the mechanism leading to the expression of autoantibodies in women with preeclampsia. It has recently been shown that infusion of interleukin 17 leads to hypertension and increases the production of AT1-AA in normal pregnant rats ; also, the infusion of soluble mouse IL-17 receptor C to inhibit IL-17 signaling decreases blood pressure and AT1-AA production in RUPP rats .
Discussion The results from this study show that 100% of patients with pregnancy-induced hypertensive disorders developed autoantibodies against the angiotensin II receptor 1 irrespective of the grade of the disease, and that the antibodies developed during the pregnancy since the antibodies were not present in samples from the first trimester in these patients. It is also evident that development of these antibodies was absolutely related to pregnancy-induced hypertension since none of the controls with normal pregnancy developed AT1 autoantibodies. The percentage of patients with AT1-AA in patients with preeclampsia is similar to the Brazilian population investigated by Velloso et al. . In further comparison to the results shown by Velloso et al. , we found that a group of patients with severe preeclampsia or HELLP developed Endothelin-1 Receptor type A autoantibodies, and that these were not present in the first trimester in these patients. Again, none of the controls included in the study developed ETA-AA. Only one out of fourteen samples from patients with gestational hypertension or moderate preeclampsia expressed ETA-AA, and in this particular patient, severe preeclampsia developed nine days after the blood sample was drawn at a stage of gestational hypertension. The results from the five cases in which we examined multiple samples at different clinical stages of disease development indicate that the expression of Endothelin-1 Receptor type A autoantibodies is closely linked to the development of severe hypertension in pregnancy-induced hypertensive disorders. However, only approximately 44% of patients with severe preeclampsia or HELLP syndrome displayed Endothelin-1 Receptor type A autoantibodies. The pathophysiological effect of ETA-AA in patients with severe preeclampsia is not known, butexperiments with infusion of ETA-AA into pregnant rats are warranted. Compared to the group which was ETA-AA negative, we did not find any difference related to the severity of the disease, other biomarkers, or time of onset for clinical symptoms. We have recently shown that Endothelin 1 alone and together with sFlt-1 is a strong predictor of the development of severe preeclampsia . Whether expression of ET-1 and ETA-AA are timely correlated in these patients remains to be elucidated.