Background & Aims

Fibromyalgia is a chronic disease classified as nociplastic pain that affects 2-3% of the world population1. Patients with fibromyalgia suffer from muscle pain and comorbidities, such as fatigue, anxiety, and depression. Pharmacological therapy for symptom relief consists of pregabalin, duloxetine, or milnacipran use2. However, it has limited efficacy and causes adverse effects3. So, finding new treatments with fewer adverse effects is necessary. The TRPA1 is an exciting target for the potential treatment of several pain disorders4. It has been shown that TRPA1 plays an essential role in nociplastic pain conditions5. For example, the inhibition or the deletion of TRPA1 expressing primary neurons could reduce the periorbital mechanical allodynia in a migraine model 6. Thus, the objective of this study was verify whether TRPA1 is involved in fibromyalgia pain and if the block on TRPA1 reduces the pain and the comorbidities induced in a mice model of fibromyalgia induced by reserpine.

Methods

C57BL/6J male mice (25 g), (IACUC #5070100119/2019), or wild-type (Trpa1+/+) and TRPA1-deficient (Trpa1?/?) mice (25 g), (IACUC #1194/2015PR), were submitted to fibromyalgia model with reserpine (1 mg/kg) subcutaneously (s.c.) or vehicle (0.1% acetic acid solution and 99.9% of 0.9% saline solution) for 3 consecutive days, once a day1,7. In the 4th day after the first reserpine dose, C57BL/6J mice receive TRPA1 antagonist orally (A967079, 30-100 mg/kg, p.o.)8 or vehicle (10% DMSO, 5% tween 80, and 85% saline solution (0.9%). Pregabalin (30 mg/kg, p.o.)9 and duloxetine (30 mg/kg, p.o.)10 were used as reference drugs. The animals were submitted to a mechanical allodynia test, cold allodynia test, Kondiziela inverted screen test, grip test, burrowing behavior, thigmotaxis behavior, and forced swimming test (FST). The results were expressed and analyzed using GraphPad Prism 8.0 software. The P values less than 0.05 (P < 0.05) were considered significant.

Results

Reserpine reduced the mechanical threshold, the muscle strength, the burrowing behavior, and increased the cold allodynia, the thigmotaxis behavior, and the mice’ immobility time, well-characterized fibromyalgia symptoms. A967079, a TRPA1 antagonist, reversed the reserpine-induced pain, fatigue, anxiety, and depressive-like symptoms. Pregabalin reduced reserpine-induced mechanical allodynia and muscle strength loss but did not reverse the cold allodynia or improve the mice’s burrowing behavior. Duloxetine reduced the reserpine-caused thigmotaxis behavior and the immobility time in the forced swimming test. We also used TRPA1 knockout mice to reinforce the TRPA1 involvement in the symptoms caused by the fibromyalgia model. While reserpine caused painful (mechanical and cold allodynia), fatigue (increased test in inverted screen test), anxiety (thigmotaxis), and depressive-like (increased immobility) symptoms in Trpa1+/+ mice, it did not induce this parameter in Trpa1-/- mice.

Conclusions

The current study confirms the involvement of channel TRPA1 on the pain and comorbid symptoms induced by reserpine in a reserpine-induced fibromyalgia model in mice. The TRPA1 antagonist showed improved effects on fibromyalgia symptoms than drugs currently used to treat fibromyalgia. The use of knockout animals reinforces the TRPA1 role in this condition. More studies must be conducted concerning the clinical use of TRAP1 antagonists. However, the inhibition of TRPA1 could be an excellent approach to relieve fibromyalgia symptoms in patients, increasing their quality of life.

References

1.Brum ES, Becker G, Fialho MFP, Oliveira SM. Animal models of fibromyalgia: What is the best choice? Pharmacol Ther. 2022;230:107959. doi:10.1016/j.pharmthera.2021.107959
2.Sarzi-Puttini P, Giorgi V, Marotto D, Atzeni F. Fibromyalgia: an update on clinical characteristics, aetiopathogenesis and treatment. Nat Rev Rheumatol. 2020;16(11):645-660. doi:10.1038/s41584-020-00506-w
3.Macfarlane GJ, Kronisch C, Atzeni F, et al. EULAR recommendations for the management of fibromyalgia. Ann Rheum Dis. 2017;76(12). doi:10.1136/annrheumdis-2017-211587
4.Tonello R, Trevisan G, Luckemeyer D, Castro-Junior CJ, Gomez MV, Ferreira J. Ph?1?, a dual blocker of TRPA1 and Cav2.2, as an adjuvant drug in opioid therapy for postoperative pain. Toxicon. 2020;188(July):80-88. doi:10.1016/j.toxicon.2020.10.007
5.Souza Monteiro de Araujo D, Nassini R, Geppetti P, De Logu F. TRPA1 as a therapeutic target for nociceptive pain. Expert Opin Ther Targets. 2020;24(10):997-1008. doi:10.1080/14728222.2020.1815191
6.Marone IM, De Logu F, Nassini R, et al. TRPA1/NOX in the soma of trigeminal ganglion neurons mediates migraine-related pain of glyceryl trinitrate in mice. BRAIN. 2018;141:2312-2328. doi:10.1093/brain/awy177
7.Nagakura Y, Oe T, Aoki T, Matsuoka N. Biogenic amine depletion causes chronic muscular pain and tactile allodynia accompanied by depression: A putative animal model of fibromyalgia. Pain. 2009;146(1-2):26-33. doi:10.1016/j.pain.2009.05.024
8.Dalenogare DP, Theisen MC, Peres DS, et al. TRPA1 activation mediates nociception behaviors in a mouse model of relapsing-remitting experimental autoimmune encephalomyelitis. Exp Neurol. 2020;328(January):113241. doi:10.1016/j.expneurol.2020.113241
9.Brusco I, Justino AB, Silva CR, et al. Kinins and their B1 and B2 receptors are involved in fibromyalgia-like pain symptoms in mice. Biochem Pharmacol. 2019;168:119-132. doi:10.1016/j.bcp.2019.06.023
10.Xu X, Wei Y, Guo Q, et al. Pharmacological characterization of H05, a novel serotonin and noradrenaline reuptake inhibitor with moderate 5-HT2A antagonist activity for the treatment of depressions. J Pharmacol Exp Ther. 2018;365(3):624-635. doi:10.1124/jpet.118.248351

Presenting Author

Ana Clara Perazzio Assis

Poster Authors

Ana Clara Assis

undergraduate

Federal University of Santa Maria

Lead Author

E-mail

Evelyne Silva Brum

PhD

Federal University of Santa Maria

Lead Author

E-mail

Maria Fialho

Federal University of Santa Maria, Santa Maria, RS, Brazil

Lead Author

E-mail

Daniel Doctor Araújo

PhD

University of Florence

Lead Author

E-mail

Lorenzo Doctor Landini

PhD

University of Florence

Lead Author

E-mail

Matilde Doctor Marini

PhD

University of Florence

Lead Author

E-mail

Mustafa Doctor Titiz

PhD

University of Florence

Lead Author

E-mail

Pierangelo Doctor Geppetti

PhD

University of Florence

Lead Author

E-mail

Romina Nassini

University of Florence

Lead Author

E-mail

Francesco De Logu

Lead Author

E-mail

Sara Marchesan Oliveira

PhD

Federal University of Santa Maria

Lead Author

E-mail

Topics

  • Models: Chronic Pain - Neuropathic