Chinese scientists claim their iron oxide nanoparticle formulation that stabilises the gut microenvironment may provide new possibilities for treating noise-induced hearing loss (NIHL).
They found oral administration of a specific blend can inhibit immune-inflammatory responses in the cochlea, protecting against NIHL and cochlear hair cell loss in mice.
Their study, published in the June 2024 edition of National Science Review, used FDA-approved carboxymethyl cellulose as a coating agent to develop the pH-responsive superparamagnetic iron oxide nanoparticle assembly (SPIOCA).
The research suggested SPIOCA exerted protective effects and could prevent NIHL by regulating composition of the gut microbiota and enhancing sphingolipid metabolism.
Sphingolipids are a class of lipids that play a crucial role in cell signalling and structural stability, and their metabolic pathways are essential for hearing protection.
“Noise exposure often leads to the proliferation of harmful bacteria, disrupting the balance of the gut microbiota,” the scientists said. “Oral administration of SPIOCA not only reduces the proliferation of harmful bacteria but also maintains the number of beneficial bacteria, thereby stabilising the gut microenvironment.
“The stability of the gut microbiota is crucial for suppressing intestinal inflammation and oxidative stress responses. SPIOCA protects the integrity of the gut barrier by inhibiting intestinal inflammation and oxidative stress.
“This process reduces the transport of pro-inflammatory factors into the bloodstream, thereby lowering the risk of systemic inflammatory responses. This protective effect extends to the inner ear, effectively safeguarding auditory function.”
The study also found SPIOCA can increase the abundance of Bacteroides, a beneficial bacterium in the gut that can produce sphingolipids.
“By regulating sphingolipid metabolism in the gut-inner ear axis, SPIOCA further enhances its protective effect on hearing,” the researchers added. “The findings of this study not only provide a new method for hearing protection but also offer new ideas for treating other microbiota dysbiosis-related diseases.”
The researchers were nanomedicine expert, Professor Ning Gu from Nanjing University Medical School, Professor Renjie Chai, Associate Professor Dongfang Liu and doctoral student Zhanhang Guo from Southeast University and Associate Professor Yunhao Wu from Shandong First Medical University.
“This study demonstrates a novel mechanism whereby the gut microbiota influences cochlear inflammation, providing valuable insights into the field of hearing protection. Additionally, it reveals, for the first time, the positive restorative effect of iron oxide nanomaterials on dysbiotic gut microbiota,” they said.
“By targeting the modulation of gut microbiota, SPIOCA has the potential to become an effective nanomedicine for the treatment of NIHL. Nevertheless, further in-depth research is still required to elucidate the mechanisms underlying the impact of SPIOCA on gut microbiota changes.”
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