Autoantibodies against the second extracellular loop of the β1-adrenoceptor induced cardiac insufficiency through up-regulating chemokine CXCL16

Abstract

Objective To screen out the cytokines relating to cardiac insufficiency caused by autoantibodies against the second extracellular loop of the β1-adrenoceptor (β1-AA) using cytokine chip technique, and to analyze the changes in signaling pathways. Methods Blood samples were collected from 67 patients with coronary artery disease (CAD) and 42 healthy subjects. ELISA was performed to detect β1-AA in plasma. BALB/c mice were passively immunized with the monoclonal antibodies against β1-AA (β1-AA mAb). Dynamic changes in mouse cardiac structure and functions were detected by heart ultrasound. Hematoxylin and eosin (HE) and Masson staining were used to observe morphological changes in heart tissues. Cytokine chip technique was used to screen out the cytokines causing myocardial injury. Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis were used to classify the differentially expressed cytokines. Results Patients with CAD showed increased titer and positive rate of β1-AA as compared with healthy subjects (P<0.001). The mouse model of heart injury was induced by β1-AA at the 8th week after immunization. A total of 37 differentially expressed cytokines were found in the model group, of which 11 cytokines were up-regulated and 26 cytokines were down-regulate as compared with those in the mouse control group. The level of CXCL16 was significantly increased in β1-AA-positive mice. GO analysis showed that CXCL16 was mainly involved in life processes including the positive regulation of cell death, migration, locomotion and cellular component movement. KEGG pathway enrichment analysis showed CXCL16 was significantly enriched in the pathway of cytokine-cytokine receptor interaction and chemokine signaling pathway. ELISA showed that compared with β1-AA-negative patients, CXCL16 level was significantly increased in β1-AA-positive patients (P<0.01). A positive correlation was found between β1-AA and CXCL16 (P<0.01, r=0.43). Conclusion CXCL16 may play a critical role in the development of cardiac insufficiency induced by β1-AA. Key words: β1-AA; Cardiac insufficiency; CXCL16