Functional Diversity of Autoantibodies Against Angiotensin II Type 1 Receptor Exists in Patients with Coronary Heart Disease

Background: The autoimmune mechanism in coronary heart disease (CHD) has been concerned recently. It is reported that the second extracellular loop of angiotensin II type 1 receptor (AT1R-ECII) autoantibody (AT1-AA) presents in the serum of CHD patients, but its clinical significance is unclear. The purpose of this study was to identify the diverse functional subclasses of AT1-AA in the patients of CHD. Methods: The AT1-AA levels in sera of 306 CHD patients were detected by ELISA. Then AT1-AA was purified from each patient’s serum (n=127) and their effects on intracellular calcium ([Ca2+]i) of mouse arterial smooth muscle cells (MASMC) was detected to classify the subclasses of AT1-AA from patients. Correlation analysis and logistic regression were used to analyze the clinical significances of different subclasses of AT1-AA in CHD. To further confirm AT1-AA classification, rats were subcutaneously injected with AT1R-ECII peptide. Findings: There were 4 [Ca2+]i change curves indicating different functional subclasses of AT1-AA (H1-, H2-, H3-, and H4-AT1-AA). Correlation analysis showed H1- and H2-AT1-AA levels were positively associated with endogenous and exogenous coagulation, respectively; H3-AT1-AA had no correlation; H4-AT1-AA was negatively correlated with leukocyte number and bile acid. Logistic regression showed H2-AT1-AA had predictive value for severe CHD. Moreover, H1- and H2-AT1-AA exerted cytotoxic effects in vitro, while H4-AT1-AA increased cell viability. 4 similar AT1-AA subclasses were found in AT1-AA-positive rats. Interpretation: This study demonstrates that there are 4 kinds of functional AT1-AA with different clinical significance in CHD patients, suggesting the importance of AT1-AA subclasses distinguishment in cardiovascular disease. Funding Statement: This work is supported by the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education (No. KZ201810025039); the National Natural Science Foundation of China (No. 31771267); the Open Fund from Key Laboratory of Cellular Physiology (Shanxi Medical University), Ministry of Education, China (No. KLMEC/SXMU-201902). Declaration of Interests: The authors have declared that no conflict of interest exists. Ethics Approval Statement: All human studies had been conducted according to Declaration of Helsinki principles and approved by the local Research Ethics Committee (Beijing Anzhen Hospital, Capital Medical University, Beijing, China) (Ethics No.: 2019023X). All patients were identified by number and signed informed consent. All the animal experiments were approved by the Institutional Animal Care and Use Committee and Ethics Committee of Capital Medical University.