Study confirms bacteria’s protective role against chronic sinusitis

As in other countries around the world, the prevalence of chronic rhinosinusitis (CRS) has been alarmingly increasing in Japan over the past decade. CRS is an inflammatory disease that lasts for at least 12 weeks and can cause nasal congestion, runny nose, difficulty breathing through the nose, facial pain, and even loss of smell. Unfortunately, treating CRS is complex because the disease manifests itself in many forms. CRS can be divided into eosinophilic (ECRS) or non-eosinophilic (non-ECRS) types. In ECRS, there is an increase in eosinophils, a type of white blood cell that releases inflammatory compounds, in the tissues of the nasal cavity and sinuses.

The increase in the prevalence of CRS is largely driven by environmental factors, which in turn are influenced by lifestyle changes. Among various environmental factors, microorganisms present in the nasal cavities and passages are known to significantly affect our health. However, it is unclear whether the nasal microbiome contributes to the development of ECRS.

To address this knowledge gap, a Japanese research team led by Assistant Professor Masanori Kidoguchi, School of Medical Sciences, University of Fukui, Japan, recently conducted a study of chronic sinusitis in the Japanese population, focusing on the nasal microbiome. Their paper was also co-authored by Professor Shigeharu Fujieda from the University of Fukui and Professor Emiko Noguchi from the University of Tsukuba, and was published in the Journal of Allergy and Clinical Immunology on September 25, 2023. Dr. Kidoguchi commented: “We conducted this study because the pathological function of bacteria and their metabolites in the development of ECRS remains unknown.”

First, the researchers collected nasal swabs from 143 subjects, 65 with ECRS, 45 with non-ECRS, and 33 healthy control subjects. They then compared the microbiome diversity between the CRS and control groups in these samples and found significant differences, suggesting that the nasal microbiome is indeed related to (or affected by) the disease.

More importantly, there were significant differences in microbiome composition between the ECRS and non-ECRS groups. Using chemical and genetic tests, the team found that ECRS patients had lower amounts of F. nucleatum. Furthermore, metagenomic analysis showed that lipopolysaccharide (LPS) synthesis was higher in non-ECRS patients than in ECRS patients.

Based on these results, Dr. Kidoguchi speculated, “It is known that F. nucleatum causes inflammation by producing LPS. Some studies have shown that LPS has different structures and functions depending on the bacterial species. Therefore, we hypothesized that F. nucleatum originates from F. nucleatum Bacterial LPS may be involved in the pathogenesis of ECRS and non-ECRS.”

To test this hypothesis, the team investigated whether LPS isolated from F. nucleatum had an effect on the expression of specific cytokines in human bronchial epithelial cell cultures. Their experiments showed that LPS derived specifically from F. nucleatum inhibited the expression of ALOX15, an enzyme that plays a key role in the development of nasal polyps and eosinophil-associated inflammation.

Taken together, the results of this study suggest that disruption of the nasal microbiota may play a key role in ECRS. This finding could be used to develop more effective strategies to deal with this troublesome situation. Dr. Kidoguchi commented: “The microbiome may strongly influence treatment resistance in chronic sinusitis and may also have an impact on other allergic diseases. Future research will hopefully lead to the development of probiotics and lifestyle changes to prevent refractory Chronic sinusitis.”

Let’s hope that a deeper understanding of these inflammatory conditions will pave the way for therapeutic and preventive strategies to improve the quality of life of ECRS patients.

About Fukui University, Japan

The University of Fukui is a preeminent research institution with strong undergraduate and graduate schools focused on education, medicine and science, engineering, and global and community studies. The university conducts cutting-edge research and strives to develop human resources capable of contributing to society at the local, national and global levels.

Website: https://www.u-fukui.ac.jp/eng/

About Masanori Kidoguchi, Assistant Professor, Fukui University, Japan

Dr. Masanori Kidoguchi is an Assistant Professor in the Department of Otolaryngology, Head and Neck Surgery, University of Fukui. He received his Ph.D. He received his PhD from the University of Fukui in 2020 and has published several research papers with special interests in otolaryngology, immunology, allergy and genomics.

Funding information

This study was funded by the Japan Society for the Promotion of Science (KAKENHI grant numbers 17H04344, 20K22998, 21H03086, and 21K16827), the Health and Labor Science Research Grant Program (grant number H30-Nanchitou (nan)-Ippan- 016), the Japan Medical Research and Development Agency (grant number JP22ek0410077h) and MSD Life Sciences Foundation, Public Interest Foundation (grant number RA-017).