In the podcast “Exosomes in your nose and in your gut” in the series “This Week in Microbiology”, hosts Michael Schmidt, Michele Swanson, and Vincent Racaniello talk primarily about two recent articles (Schmidt et al., 2019). The first article focuses on the immune response in nasal epithelial cells to invading pathogens. Titled “Exosome swarms eliminate airway pathogens and provide passive epithelial immunoprotection through nitric oxide”, the article describes an experiment in which nasal mucosa–derived exosomes demonstrate antimicrobial activity (Nocera et al., 2019). The study demonstrated that upon LPS activation of Toll-like receptor 4 (which occurs naturally when recognizing patterns on pathogens such as Pseudomonas), billions of exosomes flood the nasal passages in humans (Nocera et al., 2019). These exosomes contain nitric oxide, nitric oxide synthase, and antimicrobial peptides that combat pseudomonal bacteria effectively (Nocera et al., 2019). Additionally, after release of these exosomes following LPS stimulation, the exosomes are moved backwards through mucociliary flow into the sinuses. The podcast hosts highlight that this activates the innate immune response of “naïve cells” that have not yet encountered the invading bacteria (Nocera et al., 2019). The podcast hosts also concisely explain how this study shows a combination of the innate and adaptive immune system, and how this is a fascinating method of effectively combating airborne pathogens in the nose.
Next, the podcast takes a different turn as the hosts explain how exosomes can help certain bacteria in the gut protect against inflammation in mice and humans. After describing how exosomes are multi-vesicular cells that carry cargo through budding off of host cells, the hosts look at another microbiology article titled “Plant-Derived Exosomal MicroRNAs Shape the Gut Microbiota” by Teng et al. (2018). This article is focused on exosomes in plant materials and their effect on gut microbiota composition and activity. Although the article is long and extremely detailed, the hosts summarize the key points in the podcast. Ginger exosomes, as well as other plant-derived exosomes such as carrot, garlic, turmeric and grapefruit, are introduced into either mice or humans in trials, and the results on gut microbiota observed (Teng et al., 2019). These exosomes are seen to be incorporated into and change the community composition of the gut microbiome, most likely through microRNAs contained in the exosomes (Teng et al., 2019). The lipid composition of the exosomes also determines their destination, such as the intestine or the gut (Teng et al., 2018). Additionally, ginger exosomes protect against DDS induced colitis in mice, but not in germ-free mice, indicating that these exosomes reduce inflammation through gut microbiota and not through another method (Teng et al., 2018). A proposed mechanism for this in the paper is through IL-2, a cytokine which “tightens” the gut lining so that more interior cells are protected (Schmidt et al., 2019). The ginger exosomes are shown to increase production of this cytokine (Teng et al., 2018). The paper thoroughly goes through many experiments to examine the effect of plant exosomes on gut microbiota, with 25 authors and contributions from several labs. Plant exosomes having a positive effect on gut bacteria is a novel way of vegetables benefiting gut health, and the hosts emphasized how much exciting research can be done with this in mind (Schmidt et al., 2019).
The hosts did a great job at appealing to both more experienced people in the field and new students. The podcast had a good mix of scientific details and explanations as well as more personal background and information on exosomes. Although there was some content obviously geared towards more consistent viewers, such as chatting about the weather, the podcast was helpful for learning about microbes for a relative beginner such as myself. I look forward to learning more about microbes through This Week in Microbiology.
Schmidt, M., Swanson, M., & Racaniello, V. (2019). Exosomes in your nose and in your gut (No. 190). https://www.asm.org/Podcasts/TWiM/Episodes/Exosomes-in-your-nose-and-in-your-gut-TWiM-190
Teng, Y., Ren, Y., Sayed, M., Hu, X., Lei, C., Kumar, A., Hutchins, E., Mu, J., Deng, Z., Luo, C., Sundaram, K., Sriwastva, M. K., Zhang, L., Hsieh, M., Reiman, R., Haribabu, B., Yan, J., Jala, V. R., Miller, D. M., … Zhang, H.-G. (2018). Plant-Derived Exosomal MicroRNAs Shape the Gut Microbiota. Cell Host & Microbe, 24(5), 637-652.e8. https://doi.org/10.1016/j.chom.2018.10.001
Nocera, A. L., Mueller, S. K., Stephan, J. R., Hing, L., Seifert, P., Han, X., Lin, D. T., Amiji, M. M., Libermann, T., & Bleier, B. S. (2019). Exosome swarms eliminate airway pathogens and provide passive epithelial immunoprotection through nitric oxide. Journal of Allergy and Clinical Immunology, 143(4), 1525-1535.e1. https://doi.org/10.1016/j.jaci.2018.08.046
