Apocynin impact on AOPP-mediated TRPA1 activation in RR-EAE neuroinflammation and neuropathic pain

Background & Aims

Relapsing-remitting multiple sclerosis (RRMS) pathology is unclear and causes neuropathic pain in 28% of the patients. Nociception and neuroinflammation are detected in the RR experimental autoimmune encephalomyelitis (RR-EAE) model associated with transient potential receptor ankyrin 1 (TRPA1) activation and NADPH oxidase (Nox) increased activation. Acute apocynin (APO) treatment, an unspecific Nox inhibitor, reduces the neuropathic-like symptoms in a RR-EAE model. Nox induces myeloperoxidase (MPO) activation, leading to advanced oxidative protein products (AOPPs) formation which activates TRPA1 causing pain. However, there is no available TRPA1 antagonist in clinical use for treating MS-related neuropathic pain. Nox inhibitors, tested in phase II clinical trials for diabetic neuropathic pain, inspire our objective. In this study, we evaluate whether 15 days of APO treatment reduces TRPA1-induced neuropathic-like pain and neuroinflammation in RR-EAE mice by modulating AOPP levels.

Methods

We conducted the intracellular calcium in dorsal root ganglion (DRG) neurons from adult C57BL/6 female mice with genetic deletion for TRPA1 (Trpa1?/?) and mice without gene deletion (Trpa1+/+) (protocol#9746010620/1194/2015-PR). Trpa1+/+ mice were immunized with 200 ?g of MOG35–55, 45 ?g of QuilA (subcutaneous), and two doses of 1 ng/?l pertussis toxin (intraperitoneal). APO treatment was initiated 20 days after RR-EAE induction (100 mg/kg oral gavage) daily for 15 days. Tests were assessed 3h post-treatment to avoid acute antinociceptive effects. We measured clinical score, mechanical (von Frey test) and cold allodynia (acetone test), grip test (neuromuscular performance), rotarod (locomotor activity) from days 7 to 35 post-induction and the nest building test (spontaneous pain) on days 34 to 35 day. We measured AOPPs levels, Nox/MPO activity, Mog, Iba-1, Gfap, Olig-1 or Olig-2 by PCR and/or immunofluorescence in the spinal cord.

Results

Administration of AOPPs in DRG cells of Trpa1+/+ mice induced calcium influx, while genetic deletion of TRPA1 prevented it, suggesting that AOPP-induced TRPA1 activation. APO treatment reversed mechanical and cold allodynia, spontaneous nociception, and paw strength after RR-EAE induction without affecting weight or locomotor function. APO treatment also reduced the disease score of RR-EAE-induced mice. AOPP and Nox/MPO activity increased in the spinal cord, and these changes were reversed by APO treatment. Additionally, APO treatment mitigated demyelination, glial activation, and oligodendrocyte dysregulation in the spinal cord.

Conclusions

We demonstrated that AOPP- induces TRPA1 activation in mice DRG. In addition, we observed that AOPPs accumulation is involved in the neuroinflammation and neuropathic-like pain in the RR-EAE model. We have also observed the AOPPs levels reduction after APO repeated treatment may be due to the modulation of MPO/Nox which reduced TRPA1 activation. Furthermore, APO treatment effectively restored myelin and reduced neuroinflammation, resulting in a reduction of the RR-EAE clinical score. These results suggest that compounds targeting the AOPP formation pathway could serve as a potential therapeutic complement for patients with multiple sclerosis.

References

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Presenting Author

Patrícia Rodrigues

Poster Authors

Patrícia Rodrigues

Phd studant

Federal University of Santa Maria

Lead Author

Apocynin impact on AOPP-mediated TRPA1 activation in RR-EAE neuroinflammation and neuropathic pain

Background & Aims

Methods

Results

Conclusions

References

Presenting Author

Patrícia Rodrigues

Poster Authors

Patrícia Rodrigues

Fernanda Viero

Julia Maria Frare

Diulle Spat Peres

Náthaly Andrighetto Ruviaro

Carolina dos Santos Stein

Evelyne Silva Brum

Daniel Doctor Araújo

Matilde Doctor Marini

Lorenzo Doctor Landini

Diéssica Padilha Dalenogare

Francesco De Logu

Pierangelo Geppetti

Romina Nassini

Rafael Noal Moresco

Sara Marchesan de Oliveira

Juliano Ferreira

Guilherme Vargas Bochi

Gabriela Trevisan dos Santos

Topics

IASP 2024 World Congress on Pain