Pharmacological Evidence of Eugenia Brasiliensis Leaves in a Reserpine-Induced Fibromyalgia Model: Antinociceptive, Emotional, Anti-Inflammatory, and Neurotrophic Effects

Fibromyalgia (FM) is a painful chronic condition that significantly impacts the quality of life, posing challenges for clinical management. Given the difficulty of understanding the pathophysiology and finding new therapeutics, this study explored the effects of a medicinal plant, E. brasiliensis, in an FM model induced by reserpine in Swiss mice. Animals were treated with saline 0.9% (vehicle), duloxetine 10 mg/kg (positive control), or hydroalcoholic extract of E. brasiliensis leaves 300 mg/kg (HEEb). Nociceptive parameters, as well as locomotion, motor coordination, strength, anxiety, and depressive-like behaviors, were evaluated for 10 days. After that, the brain and blood were collected for further analysis of cytokines (interleukin 1? and interleukin 6), brain-derived neurotrophic factor (BDNF), and the immunocontents of total and phosphorylated Tropomyosin receptor kinase B (TrkB). The results demonstrated that the acute and prolonged treatment with HEEb was able to reduce both mechanical and thermal nociception. It was also possible to observe an increase in the strength, without changing locomotion and motor coordination parameters. Interestingly, treatment with HEEb reduces anxious and depressive-like behaviors. Finally, we observed a reduction in inflammatory cytokines in the hippocampus of animals treated with HEEb, while an increase in BDNF was observed in the prefrontal cortex (PFC). However, no alterations related to total and phosphorylated TrkB receptor expression were found. Our study demonstrated the antinociceptive and emotional effects of HEEb in mice, possibly acting on neuroinflammatory and neurotrophic mechanisms. These data provide initial evidence about the E. brasiliensis potential for treating chronic pain.

Toxicological and pharmacological effects of Eugenia brasiliensis Lam. (Myrtaceae) leaves in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia brasiliensis Lam., popularly known as "grumixama" or "Brazilian cherry", is widely used in folk medicine with astringent, diuretic, energizing, anti-rheumatic, and anti-inflammatory properties.

AIM OF THE STUDY

Despite its traditional use, detailed toxicological studies of Eugenia brasiliensis are few. Thus, in the current study, we evaluate the toxicological effects of hydroalcoholic extract of Eugenia brasiliensis (HEEb) and its antinociceptive and anti-inflammatory activity.

MATERIALS AND METHODS

We used male, and female Swiss mice. Acute toxicity study was performed following the Organization for Economic Cooperation and Development (OECD) guideline 425, and subacute toxicity was assessed following OECD guideline 407. We observed behavioral responses, in addition to hematological, biochemical, and histological evaluations. The antinociceptive and anti-inflammatory activity of HEEb were assessed using the Carrageenan-induced mechanical allodynia and paw edema model. Mechanical allodynia, levels of inflammatory cytokines, and oxidative damage were evaluated.

RESULTS

The treatment with HEEb was not able to generate important toxicological alterations. Moreover, doses of 100 and 300 mg/kg of HEEb were able to reduce mechanical allodynia, paw edema, and inflammatory cytokines (TNF-α, IL-1β, and IL-6), decrease malondialdehyde and increase superoxide dismutase enzyme activity in the paw.

CONCLUSIONS

This study demonstrated that HEEb does not present important toxic effects. Additionally, an important antinociceptive, anti-inflammatory, and antioxidant potential were observed.