Pulmonary inflammation after exposure to LPS and glyphosate
Date
2021-08-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-4443-6079
Type
Thesis
Degree Level
Doctoral
Abstract
Background: Agricultural workers experience chronic respiratory effects due to regular exposure to their work-place environments. The adaptation in respiratory inflammatory response is well recognized in workers after chronic agricultural exposures; however, decline in worker’s lung function continues at a higher rate than any other industry exposed worker. Agricultural work-place environments are complex and include a multitude of molecules. Two of the most common agricultural exposures are endotoxin (lipopolysaccharide, LPS) and glyphosate. LPS is well studied, whereas the lung inflammatory capability of glyphosate is poorly understood. Further, the lung inflammatory effects to combined exposure to LPS and glyphosate have not been studied. We hypothesized that exposure to the combination of LPS and glyphosate would induce additive or synergistic lung inflammatory response as compared to individual exposures. The primary aim was to study the lung inflammation after exposure to glyphosate alone and in a combination to LPS for single and repeated exposures.
Objectives: Utilize a mouse model to: i) characterize lung inflammation after single and repeated exposure to glyphosate; and ii) characterize differences in lung inflammation after exposure to LPS alone and glyphosate alone as compared to a combination of LPS and glyphosate for single and repeated exposure periods.
Methods: Male mice of C57BL/6 strain were intranasally treated with saline, LPS (0.5 µg/ml), glyphosate (1 µg/ml), or a combination of LPS (0.5 µg/ml) and glyphosate (1 µg/ml). Exposures were conducted for one day, or daily for five days, and 10 days, excluding weekends. Bronchoalveolar lavage (BAL) fluid was assessed for cellular and cytokine changes and lungs were processed for histology, mRNA, and protein analysis.
Results: Repeated exposure to glyphosate (five-days and 10-days) showed infiltration of inflammatory cells in lungs with significantly higher neutrophil counts, and eosinophil marker. Increases in IL-4, IL-5 and IL-13 observed after 10-days of glyphosate exposure compared to one-day or five-days exposure. Expression of ICAM-1, VCAM-1 and vWF increased in lungs after glyphosate exposure. Exposure to a combination of LPS and glyphosate synergistically increased lung inflammation markers as compared to individual exposures to glyphosate or LPS. Short-term (five-days) repeated exposure to the combination of LPS and glyphosate resulted in robust accumulation of inflammatory cells in the perivascular, peribronchiolar and alveolar regions of the lungs. The inflammatory changes were characterized such as significantly higher total leukocytes counts comprised predominantly of neutrophils; higher expression of ICAM-1; 70-fold greater expression of TLR-2, higher levels of proinflammatory mediators (TNF-α, KC, IL-6) and myeloperoxidase (MPO); and intense immune-staining of CD45+ B and CD3+ T lymphocytes in the perivascular region of the lungs in comparison to the same length of exposure to LPS alone and glyphosate alone. Longer-term exposure (10-days) to a combination of LPS and glyphosate resulted in generally reduced expression of inflammatory markers; however, accumulation of inflammatory cells including CD45+ B and CD3+ T lymphocytes specifically around the perivascular regions, persisted. Longer-term exposure to the combination of LPS and glyphosate resulted in IL-4 increases that remained higher in comparison to the individual exposure groups. MPO and IL-6, although lower than the five-day levels, remained higher as compared to the other exposure groups.
Conclusions: Repeated exposure to glyphosate at exposure levels relevant for agricultural workers induces lung inflammation. Moreover, repeated exposure to the same dose of glyphosate in combination to LPS induces synergistic effect on lung inflammation as induced by glyphosate alone or LPS alone. Longer-term exposure to the combination of glyphosate and LPS induces reduction in inflammatory response with the persistence in accumulation of inflammatory cells in lungs, suggesting an adaptive immune response. Repeated exposure to the combination of agents in a mouse could be used as an animal model to study chronic inflammatory adaptation response in lungs that may help to explain the respiratory effects caused by complex agricultural exposures.
Description
Keywords
Glyphosate, LPS, Combination, Repeated exposure, Lung inflammation, Synergistic, Adaptation
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Medicine
Program
Health Sciences