Withania somnifera extract ameliorates airway inflammation and oxidative stress in ovalbumin-induced bronchial asthma in rats

Airway inflammation in bronchial asthma involves complex cellular and molecular pathways/mechanisms involving the interactions between immunological mediators produced by inflammatory cells. Withania somnifera (WS) is a well-documented medicinal plant with immense potential for treating various disease conditions associated with inflammation and immunity and the present study was designed to investigate the effects of WS aqueous extract on an experimental model of bronchial asthma in rats. Wistar albino rats of either sex (200–220 g) were immunized with intraperitoneal (i.p.) injection of 10 mg ovalbumin (OVA) adsorbed to 1 mg aluminum hydroxide (Al (OH)3) on day 1 and challenged with 1 mg OVA i.p. on day 14. OVA-immunized and challenged rats were treated with doses of WS extract (200 or 400 mg/kg), and the effects of these treatments were assessed on markers of airway inflammation and immunity in blood and bronchoalveolar lavage fluid (BALF). The results showed that treatment with WS extract (x 14 days) attenuated OVA-induced elevations in immunoglobulin E (IgE), interleukin 4 (IL-4), and tumor necrosis factor-alpha (TNF-α) levels, as well as eosinophil count, in blood and BALF. These reductions were more marked with the higher dose of WS extract (400 mg/kg). Further, treatment with WS extract (400 mg/kg) restored OVA-induced reductions in Histone deacetylase 2 (HDAC2) to near control levels, whereas the effect of the lower dose (200 mg/kg) was less marked. In addition, pre-treatment of rats with WS extract (200 or 400 mg/kg) significantly attenuated OVA-induced changes in oxidative/nitrosative stress in blood and BALF, in a dose-dependent manner, with the higher dose effects being more prominent and comparable with dexamethasone (DEX). Our study findings indicate that WS extract effectively attenuated cellular and molecular markers of airway inflammation and oxidative stress and could have potential as a therapeutic agent for the treatment of allergic asthma.