Abstract
Justicia pectoralis Jacq. (Acanthaceae) has coumarin and umbelliferone as natural constituents. While the hydroalcoholic extract has relaxant properties in guinea-pig trachea, this plant is useful in folk medicine to treat respiratory diseases (J Ethnopharmacol 2000;70:151). Here, we evaluate the protective effects of SEJP against the development of the hyperresponsive phenotype of isolated Wistar rat trachea induced by antigenic challenge with ovalbumin (OVA). The standardized extract was prepared as described in Phytother Res. 2011;25:444. It was analyzed in HPLC and the content of coumarin and umbelliferone was 1.5 and 0.2 mg/ml extract, respectively. Antigen sensitization was achieved by the injection of OVA (10 mg/kg; i.p.) and antigen challenge occurred by inhalation of OVA (5 mg/ml) 14 days after the sensitization procedure. Tracheal rings of OVA-challenged group (OCG) were hyperresponsive showing significantly higher (p < 0.05) values of Emax to contractile stimuli due to acetylcholine (ACh; 10-8 to 10-3 M; Emax 1.0 ± 0.1 g) or KCl (10-3 to 10-1 M; Emax 0.9 ± 0.1 g) compared to their respective saline-challenged rats (SAL; 0.6 ± 0.1 g for ACh and 0.5 ± 0.1 g for KCl). OCG rats treated with SEJP (˜ 150 mg coumarin/kg, p.o.) showed Emax values for ACh or KCl without significant difference compared to SAL (p > 0.05). SEJP treatment also reduced the hyperresponsiveness of thapsigargin-treated trachea submitted to extracellular Ca2+ restoration under Ca2+-free medium (capacitative Ca2+ entry). SEJP also impaired (p < 0.05) the increased levels of TNFα and IL-1β in OCG. SEJP returned to basal levels (p < 0.05) the relative gene expression (by RT-PCR) of TRPC1 and TRPC5 in lung tissue, which were decreased and augmented, respectively, by the antigen challenge. Thus, SEJP has anti-inflammatory actions that prevent the development of tracheal hyperresponsiveness after antigen challenge in rats. Its effects appear to involve modulation in gene expression of TRPC proteins.
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