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Accumulating evidence suggests that liver injury can be induced by the over-expression of β1-adrenergic receptors (β1-ARs). High titers of autoantibodies specific to β1-adrenergic receptors (β1-AA) are detected in the sera of heart failure patients, potentially playing agonist-like roles. However, the role of β1-AA in liver function has not been characterized. In this study, we collect the sera of primary biliary cholangitis (PBC) patients, a condition which easily develops into liver fibrosis, and analyze the relationship between PBC and β1-AA. A passive immunization model is established to assess the effect of β1-AA on the liver. Subsequently, the effect of β1-AA on macrophages is investigated in vitro. Results show that PBC patients have a high titer and ratio of β1-AA, compared to controls. Liver injury and fibrosis are induced by β1-AA. In vitro experiments with ROS probe demonstrate that β1-AA induces macrophages to produce ROS and secrete TNFα. These effects can be partially reversed by metoprolol, a blocker for β1-AR. Results from the transwell and phagocytosis assays show that β1-AA promotes macrophage migration and phagocytosis. FCM tests suggest that β1-AA induces the alteration of M1 rather than M2 markers in macrophages. Finally, the Annexin V/PI assay indicates that macrophage culture supernatants stimulated by β1-AA cause hepatocyte apoptosis. Overall, these results suggest that β1-AA is involved in PBC. The β1-AA-induced activation, phagocytosis and phenotypic modification of macrophages may play an important role in the development of hepatic fibrosis and injury.

Cardiac dysfunction is involved in disorders of energy metabolism. High‐titre autoantibodies against the β1‐adrenoceptor (β1‐AAs) have been reported to exist in patients with cardiac dysfunction; however, the mechanism by which β1‐AAs affect cardiac function is unknown. This study aimed to determine whether β1‐AAs disturb myocardium energy metabolism and cause cardiac dysfunction. β1‐AA monoclonal antibodies (β1‐AAmAbs) were successfully pre‐synthesized by hybridoma clones and used in all experiments. β1‐AAmAbs impaired cardiac function and induced a myocardial metabolic disturbance, as evidenced by decreased left ventricular ejection fraction and fractional shortening. In addition, β1‐AAmAbs decreased the adenosine triphosphate level and increased cardiac energy consumption (rate–pressure product). We further showed that the effects of β1‐AAmAbs on heart tissue might involve the mitochondria and metabolic pathways via the β1‐adrenoceptor based on an immunoprecipitation and mass spectrometry. Additionally, we found that β1‐AAmAbs impaired myocardial mitochondrial structure, decreased the membrane potential, and induced insufficient mitophagy. In conclusion, β1‐AAmAb‐induced cardiac dysfunction is partly due to a disturbance in myocardial energy metabolism. [ABSTRACT FROM AUTHOR]

Preeclamptic women are reported to have inadequate plasma volume expansion coupled with a suppressed secretion of aldosterone; however, the specific mechanism of preeclampsia remains unclear. We demonstrated that the presence of long-term angiotensin II type 1 receptor autoantibody (AT1-AA) reduces aldosterone production by triggering a Ca2+ overload in H295R cells. AT1-AA was discovered in preeclamptic women and reported to activate AT1R, and consequently elevate intracellular Ca2+. We found that AT1-AA significantly prolonged the time of intracellular Ca2+ elevation. Besides promoting aldosterone production as a second messenger, Ca2+ overload shows a cytotoxic effect. Our data reveals that long-term presence of AT1-AA triggered a Ca2+ overload and consequent impairment of aldosterone production, which could be prevented by a PKC inhibitor, Gö 6983, or a calcium channel inhibitor, nifedipine. These findings have clinical significance because AT1R blockers are not recommended for treatment of preeclampsia due to their potential harm to the fetus. Our findings also emphasize a potential clinical benefit of immunoadsorption or neutralization of AT1-AA in preeclamptic women. [ABSTRACT FROM AUTHOR]

Decreased autophagic flux in cardiomyocytes is an important mechanism by which the β 1 -adrenoreceptor (β 1 -AR) autoantibody (β 1 -AA) induces heart failure. A previous study found that β 1 -AA imparts its biological effects via the β 1 -AR/Gs/AC/cAMP/PKA canonical signaling pathway, but PKA inhibition does not completely reverse β 1 -AA-induced reduction in autophagy in myocardial tissues, suggesting that other signaling molecules participate in this process. This study confirmed that Epac1 upregulation is indeed involved β 1 -AA-induced decreased cardiomyocyte autophagy through CE3F4 pretreatment, Epac1 siRNA transfection, western blot and immunofluorescence methods. On this basis, we constructed β 1 -AR and β 2 -AR knockout mice, and used receptor knockout mice, β 1 -AR selective blocker (atenolol), and the β 2 -AR/Gi-biased agonist ICI 118551 to show that β 1 -AA upregulated Epac1 expression through β 1 -AR and β 2 -AR to inhibit autophagy, and biased activation of β 2 -AR/Gi signaling downregulated myocardial Epac1 expression to reverse β 1 -AA-induced myocardial autophagy inhibition. This study aimed to test the hypothesis that Epac1 acts as another effector downstream of cAMP on β 1 -AA-induced reduction in cardiomyocyte autophagy, and β 1 -AA upregulates myocardial Epac1 expression through β 1 -AR and β 2 -AR, and biased activation of the β 2 -AR/Gi signaling pathway can reverse β 1 -AA-induced myocardial autophagy inhibition. This study provides new ideas and therapeutic targets for the prevention and treatment of cardiovascular diseases related to dysregulated autophagy. • Epac1 upregulation participated in β 1 -AA-induced decreased cardiomyocyte autophagy. • β 1 -AA upregulated Epac1 expression through β 1 -AR and β 2 -AR to inhibit autophagy. • Biased activation of β 2 -AR/Gi signal pathway by ICI118551 downregulated myocardial Epac1 expression to improve β 1 -AA-induced autophagy inhibition. [ABSTRACT FROM AUTHOR]

Abstract Angiotensin II type 1 receptor autoantibodies (AT1-AA) cause endothelial-dependent smooth muscle relaxation disorder. It is well understood that impairment of the NO–cGMP signaling pathway is one of the mechanisms of endothelial-dependent smooth muscle relaxation disorder. However, it is still unclear whether AT1-AA induces endothelial-dependent smooth muscle relaxation disorder via the impairment of the NO–cGMP signaling pathway. In addition, adiponectin exerts vascular endothelial protection through the NO–cGMP signaling pathway. Therefore, the purpose of this investigation was to assess the mechanism of vascular endothelial-dependent smooth muscle relaxation disorder induced by AT1-AA and the role of adiponectin in attenuating this dysregulation. Serum endothelin-1 (ET-1), adiponectin and AT1-AA were detected by enzyme-linked immunosorbent assay. In preeclamptic patients, there was an increased level of AT1-AA, which was positively correlated with ET-1 and negatively correlated with adiponectin, as elevated levels of ET-1 suggested endothelial injury. AT1-AA-positive animal models were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT1R-ECII) for eight weeks. In thoracic aortas of AT1-AA positive rats, ET-1 was elevated, endothelium-dependent vasodilation was decreased. Paradoxically, as the upstream element of the NO-cGMP signaling pathway, NO production was not decreased but increased, and the ratio of p-VASP/VASP, an established biochemical endpoint of NO-cGMP signaling pathway, was reduced. Moreover, the levels of nitrotyrosine and gp91phox which indicate the presence of peroxynitrite (ONOO-) and superoxide anion (O 2 ·−) were increased. Pretreatment with the ONOO- scavenger FeTMPyP or O 2 ·−scavenger Tempol normalized vasorelaxation. Key enzymes responsible for NO synthesis were also assessed. iNOS protein expression was increased, but p-eNOS(Ser1177)/eNOS was reduced. Preincubation with the iNOS inhibitor 1400 W or eNOS agonist nebivolol restored vasorelaxation. Further experiments showed levels of p-AMPKα (Thr172)/AMPKα, which controls iNOS expression and eNOS activity, to have been reduced. Furthermore, levels of the upstream component of AMPK, adiponectin, was reduced in sera of AT1-AA positive rats and supplementation of adiponectin significantly decreased ET-1 contents, improved endothelial-dependent vasodilation, reduced NO production, elevated p-VASP/VASP, inhibited protein expression of nitrotyrosine and gp91phox, reduced iNOS overexpression, and increased eNOS phosphorylation at Ser1177 in the thoracic aorta of AT1-AA positive rats. These results established that impairment NO–cGMP pathway may aggravate the endothelial-dependent smooth muscle relaxation disorder in AT1-AA positive rats and adiponectin improved endothelial-dependent smooth muscle relaxation disorder by enhancing NO–cGMP pathway. This discovery may shed a novel light on clinical treatment of vascular diseases associated with AT1-AA. Graphical abstract Image 1 Highlights • AT1-AA was negatively correlated with adiponectin in sera of pregnant women. • AT1-AA attenuated vasorelaxation was caused by impairment of the NO-cGMP pathway. • Serum adiponectin was decreased in AT1-AA positive rats. • Supplementation of APN improved endothelial dysfunction via the NO-cGMP pathway. [ABSTRACT FROM AUTHOR]

Objectives The incidence of arrhythmia is associated with autoantibodies against the second extracellular loop of β 1 -adrenergic receptor (β 1 -AAbs). The current study was designed to determine the mechanisms by which arrhythmia experimentally might be induced by β 1 -AAbs. Methods Blood samples were collected from patients with varied arrhythmias or coronary heart disease (CHD) and healthy subjects. The titer of β 1 -AAbs was assessed. Passive immunization rat models with β 1 -AAbs were established to determine whether β 1 -AAbs induced arrhythmia. Conventional intracellular microelectrode technique and whole cell patch clamp were employed to record action potential duration (APD), resting potential (RP), L-type calcium current ( I Ca-L ), sodium–calcium exchange current (INCX), transient outward potassium current ( I to ), inward rectifier potassium current ( I k1 ) and delayed rectifier potassium current ( I k ). Results High levels of β 1 -AAbs were found in the sera of heart disease patients, especially in ventricular arrhythmia (VA). Transfusion with β 1 -AAbs could induce arrhythmias in normal rats in vivo. β 1 -AAbs purified from the sera of active immunized rats induced triggered activity (TA), delayed after depolarization (DAD), and prolonged APD in the papillary muscles of rats. β 1 -AAbs prolonged QT interval, increased I Ca-L and decreased I K1 , I to and I Na–Ca in rat ventricular myocytes in vitro. All these effects can be inhibited by β 1 -AR blocker metoprolol. Conclusions These results demonstrate for the first time that β 1 -AAbs could directly induce ventricular arrhythmia by prolonging QT interval. [ABSTRACT FROM AUTHOR]