Anti-asthmatic effects of Warburgia ugandensis using BALB/c mouse model for asthma and isolated rabbit trachea

Abstract

Asthma is a chronic respiratory disease characterized by recurrent airway inflammation, hyper-responsiveness and reversible airway obstruction. Warburgia ugandensis is widely used by herbalist due to its therapeutic properties with observational studies showing it can be used in management of asthma. This study through experimental study sought to find out the anti-asthmatic effects of W ugandensis using BALB/c mouse model for asthma and isolated rabbit trachea. Percent protection to developing airway resistance by measure of Pre Convulsion Time (PCT), efficacy in reduction of inflammatory cells count and Nitric Oxide levels in BALF, reduction in bronchiole wall thickness and muscarinic and beta receptor activity were determined. Animals were induced with asthma and challenged with methacholine one hour after final OVA inhalation to determine baseline PCT. Intervention was done with (500mg/kg, 250mg/kg, negative control (NS), positive control (budesonide) then challenged with methacholine 72 hours after final OVA inhalation, PCT taken was compared to the baseline PCT and percent protection calculated. Hemocytometer was used to determine total inflammatory cell count and four- part differential counts of 200 cells per slide performed for differential cell count. NO level was determined using Griess reagent protocol. Bronchiole wall thickness was assessed using image j v1.50i©, Java 1.6.0_20© image analysis open source software. Receptor activity was demonstrated by percent relaxation dose response curves drawn from contraction recordings of isolated rabbit trachea hanged on an organ bath. Pre-convulsion time was not significantly different across all groups before intervention (p>0.05); however, it was significantly higher in 500mg/kg percent inhibition (88.02±1.72b) though not significantly different from positive control percent inhibition (82.03±1.29b). Negative control recorded highest total cell count (619.67±15.50a) most being eosinophils (494.33±12.01) and decreased significantly following interventions p<0.05. NO was highest in negative control (494.33±12.01a) and decreased significantly with interventions, positive control (0.082±0.003d), 250mg/kg (0.114±0.00c) and 500mg/kg (-0.013±0.003d) p<0.05. Bronchiole wall thickness significantly decreased with W. ugandensis 500 mg/kg intervention (0.633±0.292) and was comparable to positive control (0.587±0.439), p<0. 05. W. ugandensis had duo relaxation effects, Beta receptor percent relaxation was 55.74% and anti-muscarinic percent relaxation was 13.6%, P < 0.05. Results attested that W. ugandensis stem bark extract has anti-asthmatic effects though there is need for further validation of anti-asthmatic potent molecules to augment the findings.