Scientists identify a readily available herbicide which might lead to IBD

A new study in Nature has identified an environmental chemical agent that might promote gastrointestinal inflammation or inflammatory bowel disease (IBD).

Herbicides with the active ingredient propyzamide, which is the subject of the research, are available in Australia.

The report says propyzamide may boost inflammation in the small and large intestine by disrupting an anti-inflammatory pathway.

Inflammatory bowel disease is a term for two conditions – Crohn’s disease and ulcerative colitis – which are complex chronic inflammatory disorders of the gastrointestinal tract.

Research has shown that there are about 200 genetic loci associated with the disease, but less is known about the specific environmental factors that influence the risk and severity of IBD.

Now, the Nature study has systematically identified environmental chemical agents that promote gastrointestinal inflammation, and specifically identified a common herbicide called propyzamide, that may boost inflammation in the small and large intestine by disrupting an anti-inflammatory pathway. The research was undertaken in animal models.

Senior author Francisco Quintana, a neurology professor at the Centre for Neurologic Diseases at Harvard Medical School’s Brigham and Women’s Hospital in the US, says environmental factors are known to be important in influencing autoimmune and inflammatory disease.

Propyzamide is widely used to control certain grasses and broad-leaf weeds in sports fields, crops and pastures. It’s used in Australia under various brand names.

And research has shown that about 60% of the chemical remains unmetabolised by the plant 50 days after its application.

With a series of cell-culture, zebrafish, and mouse experiments, they were able to show that propyzamide interferes with the aryl hydrocarbon receptor (AHR), a protein that’s involved in immune regulation.

In the study, researchers found that AHR maintains gut homeostasis by suppressing a second, pro-inflammatory pathway that had previously been shown to be genetically linked with IBD.

“Our methodology allowed us to identify a chemical that disrupts one of the body’s natural ‘brakes’ on inflammation,” Quintana says.

The team is now working to target this inflammatory pathway by engineering nanoparticles and probiotics to activate AHR.

“The anti-inflammatory AHR pathway we identified could be strengthened to ameliorate disease, and, further down the road, we could also investigate additional ways to deactivate the pro-inflammatory response,” says Quintana. “As we learn more about the environmental factors that might contribute to disease, we can develop strategies to limit exposures.

A spokesperson for one distributor, FMC referred Cosmos to the Australian Government pesticide and herbicide regulator: “The APVMA is a world class regulator, and all agricultural chemicals subjected to their expert toxicological review and approved for use by them are deemed safe for use in Australia when used according to the approved label. By virtue of their status as registered and approved products, our products are safe to use,” the company said.

October 20: Cosmos has not yet contacted any distributors of propyzamide-based products for comment.

Updated 25/10/22: On October 21 Cosmos contacted two of the distributors, PCT International which sells the product under the Surefire brand, and FMC which sells the product as Propyzamide 500. Neither company has replied.

Updated 26 October: Content from spokesperson for distributor FMC, included in article.