Intestinal inflammation and microbiota modulation impact cochlear function: emerging insights in gut-ear axis.

Area of Science:

• Microbiology
• Neuroscience
• Otolaryngology

Background:

• The gut-microbiota-brain axis is established, but the gut-peripheral nervous system connection, specifically to the inner ear, is less understood.
• Intestinal inflammation and gut microbiota alterations may influence neurological and potentially sensory functions.
• Investigating the gut-inner ear connection is crucial for understanding systemic disease impacts on hearing.

Purpose of the Study:

• To investigate the impact of intestinal inflammation on hearing sensitivity.
• To evaluate the effect of modulating gut microbiota via fecal microbiota transplantation (FMT) on cochlear function.
• To explore the molecular and morphological changes in the cochlea associated with gut health.

Main Methods:

• Auditory brainstem responses (ABR) were used to assess hearing sensitivity in mice with DSS-induced colitis or FMT.
• Cochlear tissues were analyzed for inflammation, oxidative stress, and blood-labyrinth barrier integrity.
• Gut microbiota composition and systemic inflammation markers (LPS) were measured.

Main Results:

• Intestinal dysbiosis correlated with cochlear alterations, including increased oxidative stress, inflammation, and compromised blood-labyrinth barrier.
• Macrophage infiltration and immune activation via the MyD88/NF-κB pathway were observed in the cochlea.
• FMT from active ulcerative colitis patients exacerbated cochlear issues, while FMT from remission patients showed a protective effect on hearing.

Conclusions:

• Gut inflammation and dysbiosis negatively affect inner ear pathology and hearing sensitivity.
• Therapeutic modulation of gut microbiota, as shown by FMT, can positively impact auditory function.
• These findings support a gut-microbiota-inner ear axis where gut health influences cochlear integrity and hearing.