University of Florida dentistry researcher Jorge Frias-Lopez, Ph.D., and colleagues – including UF College of Dentistry’s Ana Duran-Pinedo, Ph.D. – published an article, The effect of the stress hormone cortisol on the metatranscriptome of the oral microbiome, in npj Biofilms and Microbiomes, a Nature Research journal, on October 18.
Imbalances of the microbiome could lead to a series of different diseases, and one factor that has been shown to lead to an imbalance of the microbiome is exposure to psychological stressors.
Throughout evolution, microorganisms of the human microbiome have developed systems for sensing host-associated signals such as hormones associated with those stressors – like cortisol – enabling them to recognize essential changes in their environment, and thus changing their expression gene profile to fit the needs of the new environment.
The findings of Frias-Lopez’s pilot study show that the stress hormone cortisol directly induces shifts in the gene expression profiles of the oral microbiome that reproduce results found in the profiles of expression of periodontal disease and its progression.
Simply put, cortisol has been found to contribute to periodontal disease and its progression.
“These results show that the oral microbiome is capable of sensing human hormones linked to stress and respond to its presence changing their metabolic activities,” Frias-Lopez said. “The mechanisms by which they accomplish that is still a mystery.”
Frias-Lopez and his team note that most investigations regarding stress hormones and virulence have been carried out with gut-associated bacteria, but that a few studies have connected the significant impact stress hormones have on the growth of periodontal pathogens.
Since cortisol is the primary hormone responsible for stress response, its levels increase in saliva with the severity of periodontal disease. Frias-Lopez and his fellow researchers predicted that the oral microbiome is capable of sensing the changes in the levels of stress hormones and that its response could be associated with the severity of periodontal disease.
The research team used a metatranscriptomic approach to obtain first insights into the metabolic changes induced by cortisol, as well as which members of the oral microbiome respond to the presence of cortisol in the environment.
In their first experiments, they treated samples of dental plaque with cortisol at a concentration found in the saliva of patients with periodontitis – and as a control, used plaque under the same conditions as the treatment samples, but without cortisol added to observe activity of organisms in the oral community. Next they looked at how cortisol influenced the profiles of expression of the oral microbiome to observe a number of different activities.
The results? As a whole, they indicate that the presence of cortisol leads to a response very similar to the one observed during periodontitis.
Next, Frias-Lopez and his team will continue studying the cortisol-periodontal disease relationship by trying to identify the mechanisms by which microbes sense stress.
Frias-Lopez earned his Bachelor of Science degree in biology from University of Barcelona in Spain in 1987, and his Ph.D. in microbiology from Barcelona in 1992, while Duran-Pinedo earned her Bachelor of Science degree in bacteriology from Javeriana University in Colombia in 1994, followed by her Ph.D. in microbiology from University of Barcelona in 2001.