Tracheal responsiveness to methacholine and ovalbumin; and lung inflammation in guinea pigs exposed to inhaled lead after sensitization

The association between lead exposure and asthma is controversial. The effect of inhaled lead acetate on lung inflammation, tracheal responsiveness and immune components in guinea pigs after sensitization was examined in this study. Five groups of guinea pigs were randomly allocated to control (group C). sensitized (group S), and three test groups exposed to inhaled lead concentrations 0.1, 0.2 and 0.4 M Pb after sensitization (n=6 for each group). The measured variables included tracheal responsiveness to methacholine and ovalbumin (OA); total and differential white blood cells (WBC) counts of lung lavage; serum cytokine levels (IFN-gamma and IL-4); and lead concentration in lung tissue. Tracheal responsiveness to methacholine and OA; total and differential WBC counts; IL-4 and IFN-gamma were significantly increased in sensitized animals compared to control group (p <0.05 to p <0.001). However, the ratio of IFN-gamma/IL-4 were significantly decreased in group S (p <0.05). In addition, all measured parameters in animals exposed to highest lead concentration and most of them in animals exposed to medium lead concentration were significantly higher than group S. except for the IFN-gamma and IFN-gamma/IL-4 ratio, which were significantly decreased (p <0.05 to p < 0.001). The lead concentration in lung tissues of all test animals was significantly higher than that of group C (p <0.001 for all groups). These results showed that lead acetate exposure can cause further increase in tracheal responsiveness to methacholine and OA, total and differential WBC count and IL-4, IFN-gamma and IFN-gamma/IL-4 ratio. Therefore, environmental exposure to lead may aggravate the severity of asthma. (C) 2012 Published by Elsevier Inc.