Author Of 1 Presentation
P0746 - Purinergic inhibitors protect astrocytes from aquaporin-4 antibody-mediated complement-dependent death (ID 1699)
Abstract
Background
Neuromyelitis optica (NMO) is an autoimmune disease of the CNS characterized by the presence of autoantibodies against the water channel aquaporin 4 (AQP4), which in the CNS is almost exclusively expressed in astrocytes. AQP4-antibody (AQP4-IgG) mediated astrocyte death is the key event in the pathology of NMO. Upon binding, astrocytes undergo a complement-dependent necrosis. Subsequent pathology shows devastating tissue damage including demyelination and axonal loss. Purinergic receptors are known to be upregulated in neuroinflammation and to contribute to neuronal-glial interaction. Indeed, purinergic antagonists, such as Suramin, have been used for the treatment of immune-mediated inflammatory diseases, showing cell-protective effects in complement-mediated cell injury. However, the mechanisms behind their anti-inflammatory properties are not well understood and their effects in NMO are completely unknown.
Objectives
The goal of this study was to investigate effects of purinergic inhibitors in AQP4-IgG mediated pathology in vitro and in vivo
Methods
Here, we tested purinergic inhibitors in vitro, using AQP4- and MOG-transfected cell lines, and in vivo in an NMO mouse model using two-photon microscopy.
Results
The application of Suramin, PPADS and NF449 in vivo prevented AQP4-IgG-mediated complement-dependent astrocyte death. In vitro, purinergic antagonists inhibited the binding AQP4-IgG or MOG-IgG to AQP4 and MOG- transfected cells in a dose dependent manner. Indeed, HPLC based fractionation of IgG molecules on gel filtration column revealed that these inhibitors lead to a subtle unfolding of antibodies, changing their conformational properties. Moreover, this change in antibody geometry impairs the complement binding to the antibody, thus disrupting complement cascade activation.
Conclusions
Our studies demonstrate that purinergic antagonists mainly mediate their inhibitory activity in our antibody mediated NMO model by inhibiting binding and complement activation. This mechanism is of relevance for the use of purinergic inhibitors in cell culture and in vivo models but also for possible application in humans.