Chronic Exposure to Pesticide Chlorpyrifos Associated with Changes in Intestinal Microbiota

Written by Angeline A. De Leon, Staff Writer. This study demonstrates how the organophosphate Chloropyrifos altered the intestinal microbiota of healthy adults by transiently altering their composition, diversity, and fermentation activity.

Chlorpyrifos (CPF), an organophosphate sold under many brand names, is one of the most widely used pesticides for agricultural and residential purposes. Being inexpensive, CPF is a popular choice for insect and worm control and has been used on crops, animals, and buildings. It also acts as a potent neurotoxic compound with the potential to cause critical cellular changes in an organism’s tissues ¹. Exposure to CPF can involve dermal, respiratory, and oral routes, and residual levels of CPF (below acute toxicity levels) in food are common ², especially in parts of Asia. Evidence from animal studies show that biological processes such as DNA synthesis and cellular reproduction may be disrupted by exposure to CPF at levels below the threshold for toxicity ³. Although few studies have examined the effects of CPF on the gastrointestinal tract, current research has determined that almost 100% of orally administered CPF is absorbed by the small intestine ⁴ and that low doses of pesticide exposure are associated with significant changes in the intestinal epithelium as well as imbalance of intestinal microbiota ⁵. CPF has also been shown to cause greater membrane permeability of intestinal absorptive cells ⁶, increase total cultural bacterial count, and decrease lactic acid bacteria (helpful probiotic strains such as Lactobacillus spp. and bifid bacteria) ⁷. To further understanding regarding the effects of below-threshold doses of CPF on the composition and metabolic response of the human gut microbiota, a study published in the International Journal of Environmental Research and Public Health employed an in vitro Simulator of the Human Intestinal Microbial Ecosystem (SHIME model), examining the effects of CPF on six different areas of the gastrointestinal tract.

The SHIME model involved a series of reactors simulating the stomach, duodenum/jejunum, ileum/caecum, and three segments of the colon (ascending, transverse, and descending). The last three reactors representing the colon were inoculated with a mixture of fecal microbiota from healthy adult volunteers, and 1 mg/day of CPF dissolved in rapeseed oil was administered to the reactors for four weeks. Samples were collected and analyzed using bacterial culture and molecular biology methods at three time points: immediately prior to the first dose of CPF, 15 days after CPF administration, and 30 days after CPF administration.

Analyses indicated that after 30 days of CPF administration, total cultured bacterial count was significantly higher at Day 15 (8.7 +/- 0.13 log CFU/mL, p < 0.001) and Day 30 (9.9 +/- 0.11 log CFU/mL, p < 0.001) for the colon as a whole and at Day 30 for each of the other colon compartments (p < 0.05). Principle Component Analysis (PCA, a technique used to identify degree of similarity between patterns) also revealed a slight change in the diversity of the Bifidobacterium community (important for human gut health) in the transverse and descending colon reactors on Day 30. Finally, researchers reported that in the colon as a whole, production of L-lactate diminished 30 days following CPF exposure (p < 0.01), while D-lactate levels increased significantly (p < 0.05), indicating altered fermentative activity of cultured microbiota.

General findings speak to the capacity of low-dose CPF to induce changes in the composition, diversity, and fermentative activity of human bacterial microbiota. Using an in vitro model of the human gut, researchers demonstrate that chronic exposure to food contaminants such as pesticides can affect metabolic activity and bacterial community count in different segments of the colon, as well as the colon itself as a whole organ. Chronic CPF exposure appears to transiently alter the composition and function of the human intestinal microbiome, a biological ecosystem whose critical role in immune health and general well-being suggests the need to study the initial effects of toxic contaminants at the intestinal level.

Source: Reigned J, Confetti CJ, Bruneau A, et al. Changes in composition and function of human intestinal microbiota exposed to chlorpyrifos in oil as assessed by the SHIME model. Int. J Envion Res and Public Health. 2016; 13(11): 1088. DOI: 10.3390/ijerph13111088.

© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

Click here to read the full text study.

Posted August 16, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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