Inhibitory and Agonistic Autoantibodies Directed Against the β2-Adrenergic Receptor in Pseudoexfoliation Syndrome and Glaucoma

Pseudoexfoliation syndrome (PEXS) and glaucoma (PEXG) are assumed to be caused by a generalized elastosis leading to the accumulation of PEX material in ocular as well as in extraocular tissues. The exact pathophysiology of PEXS is still elusive. PEXG, the most common type of secondary open-angle glaucoma (OAG), is characterized by large peaks of intraocular pressure (IOP) with a progressive loss of the visual field. Agonistic autoantibodies (agAAbs) against the β2-adrenergic receptor (AR) have been shown to be present in sera of patients with primary and secondary OAG and ocular hypertension and are seemingly linked to IOP. In the present study, we investigated the autoantibodies directed against the β2-AR in sera of patients with PEXS and PEXG. We recruited 15, 10, and 15 patients with PEXG, PEXS, and primary OAG, respectively. Ten healthy individuals served as controls. All patients underwent standard ophthalmological examination with Octopus G1 perimetry. agAAbs prepared from serum samples were analyzed in a rat cardiomyocyte–based bioassay for the presence of agAAbs. We identified the interacting loop of the β2-AR and the immunoglobulin G (IgG) subclasses using synthetic peptides corresponding to the extracellular loops of the receptors and enzyme-linked immunosorbent assay, respectively. None of the controls were β2-agAAb–positive (0.2 ± 0.5 U). No β2-agAAbs (0.2 ± 0.4 U), but inhibitory β2-AAbs were observed in 80% of the patients that partially blocked the drug-induced β2-adrenergic stimulation; 5.8 ± 1.7 U vs. 11.1 ± 0.9 U for clenbuterol in the absence and the presence of sera from patients with PEXS, respectively. Epitope analyses identified the third extracellular loop of the β2-AR as the target of the inhibitory β2-AAbs, being of IgG3 subtype in PEXS patients. In contrast, patients with PEXG showed β2-agAAbs (5.6 ± 0.9 U), but no inhibitory ones. The β2-agAAbs levels of patients with PEXG and primary OAG patients (3.9 ± 2.8 U; p > 0.05) were at a similar level. In two cases of PEXG, the β2-agAAbs exert synergistic effects with clenbuterol. The activity increased from 11.5 ± 0.3 (clenbuterol only) to 16.3 ± 0.9 U. As autoimmune mechanisms were reportedly involved in the pathogenesis of glaucoma, agonistic and inhibitory β2-AAbs seem to be a part of this multifactorial interplay.

Agonistic autoantibodies against ß2-adrenergic receptor influence retinal microcirculation in glaucoma suspects and patients

Purpose Agonistic β2-adrenergic receptor autoantibodies (β2-agAAb) have been observed in sera of patients with ocular hypertension and open-angle glaucoma (OAG). They target the β2-receptors on trabecular meshwork, ciliary body and pericytes (Junemann et al. 2018; Hohberger et al. 2019). In addition to their influence on the intraocular pressure, an association to retinal microcirculation is discussed. This study aimed to investigate foveal avascular zone (FAZ) characteristics by en face OCT angiography (OCT-A) in glaucoma suspects and its relationship to β2-agAAb status in patients with OAG. Material and methods Thirty-four patients (28 OAG, 6 glaucoma suspects) underwent standardized, clinical examination including sensory testing as white-on-white perimetry (Octopus G1, mean defect, MD) and structural measures as retinal nerve fibre layer (RNFL) thickness, neuroretinal rim width (BMO-MRW), retinal ganglion cell layer (RGCL) thickness, and inner nuclear layer (INL) thickness with high-resolution OCT. FAZ characteristics were measured by OCT-A scans of superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). FAZ-R was calculated (area FAZ (SVP)/area FAZ (ICP)). Using cardiomyocyte bioassays we analysed serum samples for the presence of β2-agAAb. Results (I) Total mean FAZ area [mm2]: 0.34±0.16 (SVP), 0.24±0.12 (ICP), and 0.49±0.24 (DCP); mean FAZ-R 1.58±0.94. No correlation was seen for FAZ-R with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (II) ß2-agAAb have been observed in 91% patients and showed no correlation with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (III) FAZ-R correlated significantly with the β2-agAAb-induced increase of the beat rate of cardiomyocyte (p = 0.028). Conclusion FAZ characteristics did not correlate with any glaucoma associated functional and morphometric follow-up parameter in the present cohort. However, level of β2-agAAb showed a significantly correlation with FAZ-ratio. We conclude that β2-agAAb might be a novel biomarker in glaucoma pathogenesis showing association to FAZ-ratio with OCT-A.

Abstract P211: B Cells Contribute To Hypertension And Cytolytic Nk Cell Activation In Response To Placental Ischemia In Pregnancy

Preeclampsia (PE), new onset hypertension during pregnancy, is associated with inflammation and B cells secreting agonistic autoantibodies against the angiotensin II type 1 receptor (AT1-AA). Two recognized subsets of B Cells are B1 and B2 B Cells. B2 B Cells are involved in adaptive immune responses and produce specific antibodies. B1 B Cells produce natural antibodies and are implicated in the pathophysiology of PE through AT1-AA. The Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia recapitulates many characteristics of PE. We have previously shown that either B cell depletion or AT1-AA epitope binding protein (7AA) in RUPP rats improved hypertension. It is currently unknown which B cell subsets make the AT1AA in PE. This information would add to the design of new therapies targeting one B cell type for depletion. Therefore, we hypothesize that B cells and specifically B2 cells cause hypertension and NK cell activation during pregnancy through production of the AT1-AA. To test this hypothesis, total splenic B Cells and B2 cells were isolated from RUPP rats on Gestation Day (GD)19 RUPP and adoptively transferred into NP rats on GD12, blood pressure (MAP), placental and circulating cNKs were measured by flow cytometry on GD19. To test the role of AT1-AA in the hypertension, 7AA was administered to a group of recipient rats on GD14. MAP increased in NP+RUPP B cells to 116 ± 3 mmHg, n=11, and to 112 mmHg ± 2, n=12, in NP+RUPP B2 cells, compared to NP rats(p<0.001). Administration of 7AA attenuated hypertension in response to total RUPP B cells (99 mmHg ± 6, n=5)(p<0.01) and in response to RUPP B2s (98 mmHg ± 4, n=6) (p<0.05). Circulating cNKs were elevated in NP+RUPPBcells (6 ± 2.5, n=5)(p<0.01) and in NP+RUPP B2 cells (4.8 ± 1.6, n=11)(p<0.01) compared to NP (0.275 ± 0.2, n=11). Placental cNKs were elevated in NP+RUPPBcells (2.32 ± 0.73, n=6)(p<0.01) and in NP+RUPP B2 cells (1.01 ± 0.2, n=11)(p<0.01) compared to NP (0.225 ± 0.2, n=11). In conclusion total B Cells and B2 B cells activated in response to placental ischemia cause hypertension via secretion of the AT1-AA and NK cell activation during pregnancy and play an important role in PE.

Immunoadsorption for Treatment of Patients with Suspected Alzheimer Dementia and Agonistic Autoantibodies against Alpha1a-Adrenoceptor—Rationale and Design of the IMAD Pilot Study

Background: agonistic autoantibodies (agAABs) against G protein-coupled receptors (GPCR) have been linked to cardiovascular disease. In dementia patients, GPCR-agAABs against the α1- and ß2-adrenoceptors (α1AR- and ß2AR) were found at a prevalence of 50%. Elimination of agAABs by immunoadsorption (IA) was successfully applied in cardiovascular disease. The IMAD trial (Efficacy of immunoadsorption for treatment of persons with Alzheimer dementia and agonistic autoantibodies against alpha1A-adrenoceptor) investigates whether the removal of α1AR-AABs by a 5-day IA procedure has a positive effect (improvement or non-deterioration) on changes of hemodynamic, cognitive, vascular and metabolic parameters in patients with suspected Alzheimer’s clinical syndrome within a one-year follow-up period. Methods: the IMAD trial is designed as an exploratory monocentric interventional trial corresponding to a proof-of-concept phase-IIa study. If cognition capacity of eligible patients scores 19–26 in the Mini Mental State Examination (MMSE), patients are tested for the presence of agAABs by an enzyme-linked immunosorbent assay (ELISA)-based method, followed by a bioassay-based confirmation test, further screening and treatment with IA and intravenous immunoglobulin G (IgG) replacement. We aim to include 15 patients with IA/IgG and to complete follow-up data from at least 12 patients. The primary outcome parameter of the study is uncorrected mean cerebral perfusion measured in mL/min/100 gr of brain tissue determined by magnetic resonance imaging with arterial spin labeling after 12 months. Conclusion: IMAD is an important pilot study that will analyze whether the removal of α1AR-agAABs by immunoadsorption in α1AR-agAAB-positive patients with suspected Alzheimer’s clinical syndrome may slow the progression of dementia and/or may improve vascular functional parameters.

Angiotensin II Type 1 Receptor Autoantibodies in Primary Aldosteronism

Primary aldosteronism (PA) is the most common form of endocrine hypertension. Agonistic autoantibodies against the angiotensin II type 1 receptor (AT1R-Abs) have been described in transplantation medicine and women with pre-eclampsia and more recently in patients with PA. Any functional role of AT1R-Abs in either of the two main subtypes of PA (aldosterone-producing adenoma or bilateral adrenal hyperplasia) requires clarification. In this review, we discuss the studies performed to date on AT1R-Abs in PA.

Agonistic Autoantibodies, a Risk Factor in Patients with Type 2 Diabetes

In addition to insulin intolerance, patients with type 2 diabetes suffer from hypertension, renal insufficiency, retinopathy, wound healing disorders, coronary heart disease, heart attacks, strokes, and amputations. In addition to metabolic syndrome, many patients have pathological changes in macro- and microcirculation. One of the causes might be agonistic autoantibodies (agAAB), an immunological component. This specialized group of autoantibodies activates the G protein-coupled receptors similar to the way natural agonists do and triggers receptor-specific reactions in the cell (1). The pathological potential of agAAB has been described in numerous publications. The pathological processes triggered by agAAB for the ß-1-adrenoceptors (AR), AT1 AR, and α 1 AR (2,3,4,5) have been particularly well researched. Animal experiments provided valuable insights into the causality of receptor-specific autoantibodies for the development of diseases and disease-relevant symptoms. These autoantibodies can only be removed with specific antagonists at the receptor or by plasmapheresis or immunoadsorption. The agAAB do not respond to immunosuppression as classical autoantibodies do. Patients in whom agAAB was removed by extracorporeal treatment benefited from it. In patients with dilated cardiomyopathy, cardiac output improved (6,7); those with Alzheimer's disease (8) achieved stabilization of cognition. In subjects with Thromboangiitis obliterans (9), further amputations were able to be avoided after removal of the autoantibodies, and in patients with inadequate control of hypertension through pharmacological means, blood pressure was considerably reduced (10). In only a few cases did agAAB reappear. These positive treatment results for various diseases formed the basis for screening diabetics with respect to the prevalence of agonistic autoantibodies.