Autoantibodies against α1- and β1/2-adrenergic receptors were significantly higher in POTS patients versus controls, with 11 of 17 POTS patients possessing β1AR-activating autoantibodies.
Case-Control (n=35)
Do autoantibodies against α1-adrenergic and β1/2-adrenergic receptors play a pathophysiological role in postural tachycardia syndrome?
The study demonstrates a strong relationship between adrenergic autoantibodies and POTS, suggesting an autoimmune etiology involving allosteric modulation of adrenergic receptors.
AIMS: Postural tachycardia syndrome (POTS), a common and debilitating cardiovascular disorder, is characterized by an exaggerated heart rate increase during orthostasis and a wide spectrum of adrenergic-related symptoms. To determine the aetiology of POTS, we examined a possible pathophysiological role for autoantibodies against α1-adrenergic (α1AR) and β1/2-adrenergic receptors (β1/2AR). METHODS AND RESULTS: Immunoglobulin G (IgG) derived from 17 POTS patients, 7 with recurrent vasovagal syncope (VVS), and 11 normal controls was analysed for its ability to modulate activity and ligand responsiveness of α1AR and β1/2AR in transfected cells and to alter contractility of isolated rat cremaster arterioles in vitro. Immunoglobulin G activation of α1AR and β1/2AR was significantly higher in POTS compared with VVS and controls in cell-based assays. Eight, 11, and 12 of the 17 POTS patients possessed autoantibodies that activated α1AR, β1AR and β2AR, respectively. Pharmacological blockade suppressed IgG-induced activation of α1AR and β1/2AR. Eight of 17 POTS IgG decreased the α1AR responsiveness to phenylephrine and 13 of 17 POTS IgG increased the β1AR responsiveness to isoproterenol irrespective of their ability to directly activate their receptors. Postural tachycardia syndrome IgG contracted rat cremaster arterioles, which was reversed by α1AR blockade. The upright heart rate correlated with IgG-mediated β1AR and α1AR activity but not with β2AR activity. CONCLUSION: These data confirm a strong relationship between adrenergic autoantibodies and POTS. They support the concept that allosteric-mediated shifts in the α1AR and β1AR responsiveness are important in the pathophysiology of postural tachycardia.
Fedorowski et al. (Tue,) conducted a case-control in Postural tachycardia syndrome (POTS) (n=35). IgG autoantibodies against α1-adrenergic and β1/2-adrenergic receptors vs. IgG from patients with recurrent vasovagal syncope and normal controls was evaluated on IgG-mediated activation and ligand responsiveness of α1AR and β1/2AR. Autoantibodies against α1- and β1/2-adrenergic receptors were significantly higher in POTS patients versus controls, with 11 of 17 POTS patients possessing β1AR-activating autoantibodies.
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