Autoantibodies targeting G protein-coupled receptors: An evolving history in autoimmunity. Report of the 4th international symposium.

G protein-coupled receptors (GPCR) are involved in various physiological and pathophysiological processes. Functional autoantibodies targeting GPCRs have been associated with multiple disease manifestations in this context. Here we summarize and discuss the relevant findings and concepts presented in the biennial International Meeting on autoantibodies targeting GPCRs (the 4th Symposium), held in Lübeck, Germany, 15-16 September 2022. The symposium focused on the current knowledge of these autoantibodies' role in various diseases, such as cardiovascular, renal, infectious (COVID-19), and autoimmune diseases (e.g., systemic sclerosis and systemic lupus erythematosus). Beyond their association with disease phenotypes, intense research related to the mechanistic action of these autoantibodies on immune regulation and pathogenesis has been developed, underscoring the role of autoantibodies targeting GPCRs on disease outcomes and etiopathogenesis. The observation repeatedly highlighted that autoantibodies targeting GPCRs could also be present in healthy individuals, suggesting that anti-GPCR autoantibodies play a physiologic role in modeling the course of diseases. Since numerous therapies targeting GPCRs have been developed, including small molecules and monoclonal antibodies designed for treating cancer, infections, metabolic disorders, or inflammatory conditions, anti-GPCR autoantibodies themselves can serve as therapeutic targets to reduce patients' morbidity and mortality, representing a new area for the development of novel therapeutic interventions.

Downregulation of Endothelial Plexin A4 Under Inflammatory Conditions Impairs Vascular Integrity.

Objective: Besides hyperlipidemia, inflammation is an important determinant in the initiation and the progression of atherosclerosis. As Neuroimmune Guidance Cues (NGCs) are emerging as regulators of atherosclerosis, we set out to investigate the expression and function of inflammation-regulated NGCs. Methods and results: NGC expression in human monocytes and endothelial cells was assessed using a publicly available RNA dataset. Next, the mRNA levels of expressed NGCs were analyzed in primary human monocytes and endothelial cells after stimulation with IL1ß or TNFα. Upon stimulation a total of 14 and 19 NGCs in monocytes and endothelial cells, respectively, were differentially expressed. Since plexin A4 (PLXNA4) was strongly downregulated in endothelial cells under inflammatory conditions, the role of PLXNA4 in endothelial function was investigated. Knockdown of PLXNA4 in endothelial cells markedly impaired the integrity of the monolayer leading to more elongated cells with an inflammatory phenotype. In addition, these cells showed an increase in actin stress fibers and decreased cell-cell junctions. Functional assays revealed decreased barrier function and capillary network formation of the endothelial cells, while vascular leakage and trans-endothelial migration of monocytes was increased. Conclusion: The current study demonstrates that pro-inflammatory conditions result in differential expression of NGCs in endothelial cells and monocytes, both culprit cell types in atherosclerosis. Specifically, endothelial PLXNA4 is reduced upon inflammation, while PLXNA4 maintains endothelial barrier function thereby preventing vascular leakage of fluids as well as cells. Taken together, PLXNA4 may well have a causal role in atherogenesis that deserves further investigation.

Metabolomic changes in CSF of migraine patients measured with 1H-NMR spectroscopy.

BACKGROUND: Migraine is a common episodic brain disorder. Treatment options and diagnosis are hampered by an incomplete understanding of disease pathophysiology and the lack of objective diagnostic markers. The aim of this study was to identify biochemical differences characteristic for different subtypes of migraine in cerebrospinal fluid (CSF) of migraine patients using an exploratory 1H-NMR-based metabolomics approach. METHODS: CSF was obtained, in between migraine attacks, via lumbar puncture from patients with hemiplegic migraine, migraine with aura, migraine without aura, and healthy controls. Metabolite concentrations were measured by quantitative 1H-NMR spectroscopy. Multivariate data analysis was used to find the optimal set of predictors, generalized linear models (GLM) were used to ascertain the differential significance of individual metabolites. RESULTS: In CSF samples from 18 patients with hemiplegic migraine, 38 with migraine with aura, 27 migraine without aura, and 43 healthy controls, nineteen metabolites were identified and quantified. Hemiplegic migraine patients could be discriminated from healthy controls using supervised multivariate modelling with 2-hydroxybutyrate and 2-hydroxyisovalerate as the most discriminant metabolites. Univariate GLM analysis showed 2-hydroxybutyrate to be lower in hemiplegic migraine compared with healthy controls; no significant differences were observed for other metabolites. It was not possible to discriminate migraine with and without aura from healthy controls based on their metabolic profile. CONCLUSIONS: Using an exploratory 1H-NMR metabolomics analysis we identified metabolites that were able to discriminate hemiplegic migraine patients from healthy controls. The lower levels of 2-hydroxybutyrate found in patients with hemiplegic migraine could indicate a dysregulation of the brain's energy metabolism. An experimental confirmation in vitro or in animal models will be required to confirm or discard this hypothesis. Migraine with and migraine without aura patients did not reveal a metabolic profile different from healthy controls.