The agonistic autoantibodies to the angiotensin II type 1 receptor in pregnancies complicated by hypertensive disorders

Abstract

Introduction

The etiology and pathogenesis of pregnancy-related hypertensive disorders is complex and multifactorial. The aim of our study is the investigation of the differences in the autoantibodies against angiotensin II type 1 receptor (AT1-AA) titers among pregnant patients with chronic hypertension, gestational hypertension, and preeclampsia compared to the healthy pregnant women.

Patients and methods

We created three study groups (preeclampsia [n = 16], chronic hypertension [n = 13], gestational hypertension [n = 17]) and the control group consisting of 17 healthy pregnant women. Every compared group was matched for mother’s age, parity, prepregnancy BMI, and gestational age at time of recruitment into study. The autoantibodies titer were assessed using commercially available ELISA kit.

Results

We found a statistically higher AT1-AA titer in the group of patients with gestational hypertension (GH) and preeclampsia (PE) compared to healthy normotensive pregnant women (median 9.6 versus 7.8 ng/ml, p = .01 and 10.9 ng/ml versus 7.8 ng/ml, p = .02, respectively). There was no correlation between blood pressure values and AT1-AA titer in any group. We found no correlation in group with preeclampsia between urinary protein excretion and AT1-AA titer (p = .23, R = 0.32).

Conclusions

We assume that pregnancy-related hypertensive disorders might be autoimmune diseases and AT1-AA contribute to the pathophysiology of the disease. Our study may have some therapeutic implications and shows the necessity of new research into the mechanisms involved in the production of AT1-AA. Such investigations might enable to inhibit the formation of these autoantibodies or elaborate another method for AT1-AA removal.

Keywords:

• Pre-eclampsia
• gestational hypertension
• chronic hypertension
• blood pressure determination
• autoantibodies

Disclosure statement

No potential conflict of interest was reported by the authors to disclosure. The manuscript has not been and will not be submitted to any other journal while it is under consideration by the Journal of Maternal-fetal and Neonatal Medicine. Also, there are no prior publications or submissions with any overlapping information. This work was supported by grant from Poznan University of Medical Sciences.

Appendix

Materials and methods in detail

A case-control study was conducted in the Department of Perinatology and Gynecology of Poznan University of Medical Sciences between November 2014 and March 2016. From a total of 69 initially enrolled pregnant women, 63 patients were eligible for the final analyses. All of them (6/69, 8.7%) were excluded due to the development of some diseases, which was defined as exclusion criteria for the participation in the study. Finally, we analyzed the following group of females – pregnant patients with preeclampsia (PE) [n = 16], those with chronic hypertension (CH) [n = 13], and those with gestational hypertension (GH) [n = 17]. The control group consisted of 17 healthy, normotensive pregnant women (C: control group). Each comparison group was matched for mother’s age, parity, prepregnancy BMI, and gestational age at time of recruitment into study and blood collection.

Twenty-four-hour automatic blood pressure monitoring (ABPM) was carried out using the HolCARD CR-07 blood pressure recorder (Aspel; Zabierzów, Poland). Blood pressure readings were taken at regular 30-minute intervals. We used the cuff size appropriate to the patient’s arm circumference, and the visual preview of the blood pressure values was removed in order to eliminate a possible stressor for the pregnant women.

Venous blood was collected from the antecubital vein in a 5-ml vacuum neutral tube. The blood samples were centrifuged and the plasma collected in 1.5-ml Eppendorf tubes and stored at −80 °C until batch processing by commercial Human angiotensin 2 Receptor 1 antibody ELISA kit (MBS739430; MyBioSource) to measure AT1-AA titers. The assay procedure was performed according to the manufacturer’s instructions. Briefly, on the microtiter plate, 50 µl of the standards and serum samples obtained from the patients enrolled in the study were added in duplication. As a blank, 50 µl PBS was used, and then 100 µl conjugate was added. The microtiter plate was incubated 1 h at 37 °C. After incubation, the plate was rinsed five times with a Wash Solution. Subsequently, 100 μl of Substrate was added, incubated 15 min at 37 °C to develop a color reaction. After this time, 50-µl Stop Solution was added. On the basis of a standard curve, constructed on the OD (l = 450 nm) of the calibrators, AT1-AA serum concentration was determined.

Additional information

Funding

The study was founded by the Poznan University of Medical Sciences, Poland [grant 502-14-02218346-50637; granted to ASG].