Exposures to 2,4-Dichlorophenoxyacetic acid with or without endotoxin upregulate small cell lung cancer pathway

Geetika Kaur,Baljit Singh,R S Sethi,B V Sunil Kumar

doi:10.1186/s12995-021-00304-4

Abstract

BackgroundPesticide 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 without LPS or in combination with endotoxin.MethodsWe exposed Swiss albino mice (N = 48) orally to high (37mg kg-1) and low (18.5 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 (80 μl/animal). Lung samples and broncho-alveolar fluid (BALF) were subjected to Total histological score (THS) and total leucocyte count (TLC) and differential leucocytes count (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 by qRT-PCR and immunohistochemistry.ResultsTotal histological score (THS) along with 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 without or with LPS 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 without 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-κB1, p53, Cdk6 and Apaf1. Immunohistological and quantitative real time PCR (qRT-PCR) analyses also supported the transcriptomic data.ConclusionsTaken 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 provide the insights of the potential damage on lungs caused by 2,4-D and help to better understand the mechanism of this complex relation.

Highlights

Agricultural workers are commonly exposed to pesticides during production, transportation, planning and utilization of pesticides [1]
We report the first data that 2,4-D exposure dysregulates small cell lung cancer (SCLC) pathway with increased protein expression of Itgb1, NF-κB, p53 and Cdk6 and decreased expression of Apaf1
Exposure to high dose of 2,4-D combined with LPS increased total leucocyte count (TLC) compared to LPS alone (Table 1)

Summary

Introduction

Agricultural workers are commonly exposed to pesticides during production, transportation, planning and utilization of pesticides [1]. Since the registration of 2,4-D for use as herbicide in 1940s, its use has grown globally for controlling broad-leaved weeds in a variety of settings such as crops and other vegetation on rangelands, lawns, golf courses, roadways, parks and forests to aquatic settings [3]. It mimics the growth hormone auxin (Indole acetic acid) resulting in uncontrolled and unorganized growth and eventually death of weeds [4]. 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 by qRT-PCR and immunohistochemistry

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Results

Conclusion