11 Jan Enzymes Linking Triclosan in Soaps and Toothpastes to IBD Identified

MedicalResearch.com Interview with:

Morgan Walker

Morgan Walker
Ph.D. Candidate, UNC-Chapel Hill Chemistry
Redinbo Laboratory

MedicalResearch.com: What is the background for this study? Where is triclosan commonly found?

Response: Triclosan is a commonly found antibacterial compound present in hand soaps, toothpastes, athletic clothes, and children’s toys. A previous study by the Zhang group (corresponding author on this publication) found that antimicrobial compounds including triclosan increased inflammation (similar to that of inflammatory bowel disease (IBD)) and tumor formation in the colon. These effects were observed only in mice with an intact gut microbiome, not in germ-free mice which lack a gut microbiome, suggesting that the gut microbiome is somehow responsible for the toxicity of triclosan to the gut. Our study investigates how gut bacteria promote triclosan toxicity in the gut 

MedicalResearch.com: What are the main findings?

Response: We identify that a key class of gut microbial enzymes called beta-glucuronidases (GUS) remove a sugar molecule from an inactivated metabolite of triclosan, generating the toxic compound that causes inflammation in the gut. Specifically, two classes of GUS enzymes preferentially catalyze this reaction. After learning which enzymes were responsible for generating the toxic form of triclosan, we used a targeted inhibitor to block this reaction in the gut of mice. Use of this inhibitor relieved inflammation caused by triclosan consumption, demonstrating that these GUS enzymes are indeed responsible for triclosan toxicity. 

MedicalResearch.com: What should readers take away from your report?

Response: First, our study confirmed that triclosan is an irritant to the gut and causes inflammation similar to that of IBD. We then identified key components of the gut microbiome that cause the toxicity of triclosan, and we effectively alleviated inflammation caused by triclosan by using a targeted inhibitor. By identifying the key enzymes and bacteria responsible for triclosan toxicity, we can gain new clues about the causes of IBD.

People with IBD can experience periods of worsened disease known as “flares” after being in remission for a long time, seemingly without reason. Our study suggests that environmental compounds like triclosan that are variably acted upon by the gut microbiome could contribute to these IBD flares.

MedicalResearch.com: What recommendations do you have for future research as a result of this work? 

Response: The majority of our study was conducted using animal models. Future research would examine the effects of triclosan on humans to further confirm our results. Additionally, as we found that two specific classes of gut microbial GUS enzymes preferentially act on triclosan, there may be significant inter-individual variation based on which GUS enzymes each person has in their gut microbiome. Further examination is needed to determine if individuals with specific GUS enzymes are more susceptible to triclosan’s toxic effects.

In 2016, the U.S. Food and Drug Administration (FDA) took steps to regulate the presence of triclosan in over-the-counter hand soaps. However, this action was based primarily on studies showing no additional benefits of triclosan-containing soaps over plain soap, not on the toxicity of triclosan. Despite this act by the FDA, triclosan remains in many consumer products including toothpastes. As we conclude in our study, consumption of triclosan can have adverse gastrointestinal effects. We suggest that the use of triclosan in all consumer products, not just hand soaps, should be re-evaluated.

Disclosures: Matthew Redinbo, co-corresponding author on this study, is a Founder of Symberix, Inc., which is developing microbiome-targeted therapeutics. He is also the recipient of research funding from Merck and Lilly, although those funds were not used in this project. The remaining authors declare no competing interests.

Citation:

Zhang, J., Walker, M.E., Sanidad, K.Z. et al. Microbial enzymes induce colitis by reactivating triclosan in the mouse gastrointestinal tract. Nat Commun 13, 136 (2022). https://doi.org/10.1038/s41467-021-27762-y

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Last Updated on January 11, 2022 by Marie Benz MD FAAD