Abstract

Background:
Inflammation of the dental pulp is commonly associated with intense nociceptive signaling mediated by interleukin-1β (IL-1β), Substance P, and neurokinin-1 receptors (NK1-R). Natural compounds, such as Rosmarinus officinalis, contain bioactive molecules that may alleviate this response, particularly when expressed in nanoemulsions that enhance tissue penetration.

Aim:
This study explored the modulatory effect of NE-RO on inflammatory and nociceptive markers in an experimental rat model of acute pulpitis.

Methods:
Thirty healthy male Wistar rats were randomly assigned to six treatment groups, including negative and positive controls, three NE-RO treatment concentrations (0.5, 1.0, and 2.0 mg/ml), and an eugenol comparison group, after 1 week of acclimatization under controlled housing conditions. Pulpitis was induced by lipopolysaccharide application to the exposed pulp chamber. After 24 hours of treatment, the first maxillary molars were processed for immunohistochemical assessment of IL-1β, Substance P, and NK1-R. Data were analyzed using analysis of variance or Kruskal–Wallis tests with a 95% confidence level.

Results:
Induction of pulpitis significantly elevated IL-1β, Substance P, and NK1-R expression relative to the untreated control. The administration of 2 mg/ml NE-RO resulted in marked reductions in the levels of Substance P (5.0 ± 0.40) and NK1-R (5.5 ± 0.29) compared with the positive control (p < 0.05), while IL-1β levels showed a downward trend (4.75 ± 0.48; p = 0.08). These outcomes were comparable to those of eugenol treatment.

Conclusion:
Topical application of 2 mg/ml Rosmarinus officinalis nanoemulsion attenuated neuroinflammatory responses in experimental pulpitis, likely through suppression of the IL-1β–Substance P–NK1-R signaling axis. The findings support its potential as a plant-based alternative topical agent for the management of acute pulpitis, pending further safety evaluation.

Key words: Nanoemulsion; IL-1β; Substance P; NK1-R; Acute pulpitis model.