Anti-AQP4 autoantibodies promote ATP release from astrocytes and induce mechanical pain in rats

Teruyuki Ishikura,Tatsusada Okuno,Makoto Kinoshita,Susumu Kusunoki,Shohei Beppu,Daisuke Motooka,Toru Koda,Yasuko Sugiyama,Atsushi Kumanogoh,Tomoyuki Sugimoto,Yoshiaki Yasumizu,Mikito Shimizu,Satoru Tada,Hisashi Murata,Katsuichi Miyamoto,Naoyuki Shiraishi,Kazuya Yamashita,Hideki Mochizuki,Daisuke Okuzaki

doi:10.1186/s12974-021-02232-w

Teruyuki Ishikura, Tatsusada Okuno + Show 17 more

Open Access

https://doi.org/10.1186/s12974-021-02232-w

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Abstract

BackgroundIntractable neuropathic pain is a common symptom of neuromyelitis optica spectrum disorder (NMOSD). However, the underlying mechanism of NMOSD pain remains to be elucidated. In this study, we focused on ATP, which is one of the damage-associated molecular patterns, and also a well-recognized molecule involved in peripheral neuropathic pain.MethodsWe assessed the development of pain symptoms by injecting anti-AQP4 recombinant autoantibodies (rAQP4 IgG) into rat spinal cords. We incubated HEK293 cells expressing AQP4 (HEK-AQP4) and rat astrocytes with rAQP4 IgG and assessed the level of ATP in the supernatant. We performed transcriptome analysis of the spinal cords injected with rAQP4 IgG. Pharmacological inhibition was also applied to investigate the involvement of ATP in the development of neuropathic pain in our rat model. The ATP concentration within the cerebrospinal fluid was examined in patients with NMOSD and other neurological diseases.ResultsDevelopment of mechanical allodynia was confirmed in rAQP4 IgG–treated rats. AQP4-Ab–mediated extracellular ATP release from astrocytes was observed in vitro, and pharmacological inhibition of ATP receptor reversed mechanical allodynia in the rAQP4 IgG–treated rats. Furthermore, transcriptome analysis revealed elevation of gene expressions related to several ATP receptors including P2rx4 and IL1B in the spinal cord of rAQP4 IgG–treated rats. In patients, CSF ATP concentration was significantly higher in the acute and remission phase of NMOSD than in multiple sclerosis or other neurological disorders.ConclusionAnti-AQP4 antibody was shown to induce the release of extracellular ATP from astrocytes. The ATP-mediated development of mechanical allodynia was also suggested in rats treated with anti-AQP4 antibody. Our study indicates the pivotal role of ATP in the pain mechanism of NMOSD.

Highlights

Intractable neuropathic pain is a common symptom of neuromyelitis optica spectrum disorder (NMOSD)
Administration of rAQP4 Recombinant monoclonal AQP4 antibody (IgG) to rats induces the development of mechanical pain To determine whether AQP4 antibodies induce pain symptoms in rats, we used recombinant monoclonal AQP4 antibody from NMOSD patient plasmablasts, which was previously established in our laboratory [12]
The results indicated that 1/1000 dose rAQP4 IgG was not enough to induce pain symptoms in our rat model (Fig. 1F)

Summary

Introduction

Intractable neuropathic pain is a common symptom of neuromyelitis optica spectrum disorder (NMOSD). The underlying mechanism of NMOSD pain remains to be elucidated. Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory disease of the central nervous system that presents with optic neuritis or longitudinally extensive myelitis and is associated with various neurological symptoms [1]. 80% of patients with NMOSD experience intractable pain, and their quality of life is severely affected [2]. A few studies reported pain development in a NMOSD animal model [4]. The detailed analysis of the mechanism related to NMOSD pain has not been performed in the past literature [2]. The detailed pathogenesis of NMOSD pain remains to be elucidated

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