Background: Pesticide residues in food and environment along with airborne contaminants such as endotoxins pose health risk. Although herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) has been associated with increased risk of lung cancers such as small cell lung cancer (SCLC) among agricultural workers, there are no data on the SCLC signaling pathway upon 2,4-D exposure alone or in combination with endotoxin.
Methods: We exposed Swiss albino mice (N=48) orally to high (9.58 mg kg -1 ) and low (5.12 mg kg -1 ) dosages of 2,4-D dissolved in corn oil for 90 days followed by E. coli lipopolysaccharide (LPS) or normal saline solution (80µl/animal. Lung samples and broncho-alveolar fluid (BALF) were subjected to Total histological score (THS) and TLC and DLC analyses, respectively. We used microarray and bioinformatics tools for transcriptomic analyses and differentially expressed genes were analyzed to predict the top canonical pathways followed by validation of selected genes qPCR and immunohistochemistry.
Results: Total histological score (THS) along with broncho-alveolar fluid (BALF) analyses showed lung inflammation following long term dietary exposure to high or low doses of 2,4-D individually or in combination with LPS. Microarray analysis revealed exposure to high dose of 2,4-D alone or with endotoxin upregulated 2178 and 2142 and downregulated 1965 and 1719 genes, respectively (p<0.05; minimum cut off 1.5 log fold change). The low dose alone or with LPS upregulated 2133 and 2054 and downregulated 1838 and 1625 genes, respectively. Bioinformatics analysis showed SCLC as topmost dysregulated pathway along with differential expression of Itgb1, NF-kB1, p53, Cdk6 and Apaf1. Immunohistological and qPCR analyses also supported the transcriptomic data.
Conclusions: Taken together, the data show exposures to high and low dose of 2,4-D with/without LPS induced lung inflammation and altered pulmonary transcriptome profile with the involvement of the SCLC pathway. The data from the study provides the insights of the potential damage on lungs caused by 2,4-D and endotoxin interaction and helps to better understand the mechanism of this complex relation.