• Backialakshmi Dharmalingam, Pratibha Singh, Patrick Schramm, Frank Birklein, Manfred Kaps, Katrin Susanne Lips, Gabor Szalay, Franz Blaes, and Marlene Tschernatsch.
• Department of Neurology, Justus Liebig University, Giessen, Germany.
• Pain. 2022 Dec 1; 163 (12): 244624562446-2456.

AbstractComplex regional pain syndrome (CRPS) is an inadequate local response after a limb trauma, which leads to severe pain and autonomic and trophic changes of the affected limb. Autoantibodies directed against human β2 adrenergic and muscarinic M2 receptors (hβ2AR and hM2R) have been described in CRPS patients previously. We analyzed sera from CRPS patients for autoantibodies against hβ2AR, hM2R, and endothelial cells and investigated the functional effects of purified IgG, derived from 13 patients with CRPS, on endothelial cells. Eleven healthy controls, 7 radial fracture patients without CRPS, and 10 patients with peripheral arterial vascular disease served as control subjects. The CRPS-IgG, but not control IgG, bound to the surface of endothelial cells ( P < 0.001) and to hβ2AR and hM2R ( P < 0.05), the latter being reversed by adding β2AR and M2R antagonists. The CRPS-IgG led to an increased cytotoxicity and a reduced proliferation rate of endothelial cells, and by adding specific antagonists, the effect was neutralized. Regarding second messenger pathways, CRPS-IgG induced ERK1/2, p38, and STAT1 phosphorylation, whereas AKT phosphorylation was decreased at the protein level. In addition, increased expression of adhesion molecules (ICAM-1 and VCAM-1) on the mRNA level was induced by CRPS-IgG, thus inducing a pro-inflammatory condition of the endothelial cells. Our results show that patients with CRPS not only develop autoantibodies against hβ2AR and hM2R, but these antibodies also interfere with endothelial cells, inducing functional effects on these in vitro, and thus might contribute to the pathophysiology of CRPS.Copyright © 2022 International Association for the Study of Pain.

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