Background & Aims

Objective: This study evaluated the antihyperalgesic and antiedematogenic effects of high-intensity laser therapy (HILT) in mice with peripheral inflammation.

Methods

Peripheral inflammation was induced by a 20 ?l right hindlimb intraplantar (i.pl.) injection of Complete Freund’s Adjuvant (CFA – 50% concentration solution dissolved in 0.9% saline and Tween®80). Fifty-six male Swiss mice (35-40 g) received an i.pl. of CFA and underwent behavioral tests, i.e., mechanical hyperalgesia and edema. The evaluation of mechanical hyperalgesia was made according to a previous study and the withdrawal response frequency of 10 manual applications of 3 s each of 0.6 g of von Frey (VFH, Stoelting, Chicago, IL, USA) was recorded. To assess the effects of HILT on CFA-induced persistent inflammatory pain, animals were treated with laser of different energy densities (2, 4, 8, 12, 16 or 20 J/cm2) for five consecutive days after CFA i.pl. injection. Paw edema was measured using a plethysmometer (Insight, Brazil) 4 h after treatment on days 1, 3 and 5 after CFA injection.

Results

CFA paw injection induced mechanical hyperalgesia (MH) in the paw of the mice, which persisted throughout the evaluation period. On day 1, HILT presented a joule–response analgesic effect as the energy densities of 4, 8 and 12 J/cm2 significantly inhibited MH (maximum inhibition (MI): 27,4 (39,5%); 38,9 (29,2%) and 33,5 (33,6%), respectively): with analgesic effect at 0.5 h. Only the 8 J/cm2 dose inhibited MH for up to 3 hours (p=0.0006). On day 5, HILT also presented a joule–response analgesic effect as the energy densities of 4, 8 and 20 J/cm2 significantly inhibited MH (MI: 29,3 (33,5%); 42,4 (18,6%) and 34,1 (25,5%), respectively): with analgesic effect at 0.5 h. Only the 8 J/cm2 dose inhibited MH for up to 2 hours (p=0.0129). Additionally, repeated treatment of HILT (with 4 and 8 J/cm2 – once a day for five days) significantly inhibited MH (p=0.0008). HILT (2, 4, 8, 12, 16 or 20 J/cm2) did not present any antiedematogenic activity.

Conclusions

Together, these results indicate that laser produces antihyperalgesic effect in a Joule-response way. However, although we found a decrease in paw edema in the treated groups, this difference was not statistically significant. Thus, the laser was not effective in inhibiting edema. These data contribute to the understanding of the therapeutic effect of HILT as well as provide additional support for its use in the treatment of painful conditions of inflammatory etiology.

References

Martins, D. F., Turnes, B. L., Cidral-Filho, F. J., Bobinski, F., Rosas, R. F., Danielski, L. G., Petronilho, F., & Santos, A. R. (2016). Light-emitting diode therapy reduces persistent inflammatory pain: Role of interleukin 10 and antioxidant enzymes. Neuroscience, 324, 485–495. https://doi.org/10.1016/j.neuroscience.2016.03.035

Salm, D. C., Horewicz, V. V., Tanaka, F., Ferreira, J. K., de Oliveira, B. H., Maio, J. M. B., Donatello, N. N., Ludtke, D. D., Mazzardo-Martins, L., Dutra, A. R., Mack, J. M., de C H Kunzler, D., Cargnin-Ferreira, E., Salgado, A. S. I., Bittencourt, E. B., Bianco, G., Piovezan, A. P., Bobinski, F., Moré, A. O. O., & Martins, D. F. (2023). Electrical Stimulation of the Auricular Branch Vagus Nerve Using Random and Alternating Frequencies Triggers a Rapid Onset and Pronounced Antihyperalgesia via Peripheral Annexin A1-Formyl Peptide Receptor 2/ALX Pathway in a Mouse Model of Persistent Inflammatory Pain. Molecular neurobiology, 60(5), 2889–2909. https://doi.org/10.1007/s12035-023-03237-7

Presenting Author

Daniel Martins

Poster Authors

Daniel Martins; Ph.D

Ph.D

University of Southern Santa Catarina (UniSul)

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Daniel Martins

UniSul

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Bruna de Oliveira

UniSul

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Aline Raulino Dutra

UniSul

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Neito Antonio Bonotto

UniSul

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Andrew Hewitson

Avant Wellness Systems, Thousand Oaks, CA, USA.

Lead Author

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Francisco José Cidral-Filho

Integrative Wellbeing Institute, Orlando, FL, USA.

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Topics

  • Models: Chronic Pain - Inflammatory