Journal Club: Co-administration of gentamycin and ethacrynic acid & macrophage/pericytes in the cochlea

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Today's journal article

Journal Club: Li L, Tan J, Chen D, Luo J, Li P. "Ethacrynic acid regulates gentamicin ototoxicity via the blood-labyrinth barrier." from Hearing Research


Why I picked this article

Today, my journal article is about the effect of gentamycin on the blood-labyrinth barrier. 

Our inner ear organ for hearing, the cochlea, is a very delicate organ. Presumably to protect this organ, the cochlea has a physiological function or property called "blood-labyrinth barrier (BLB)". This is very similar to the blood-brain barrier (BBB) of the brain. Many biomedical researchers are more familiar with BBB in the brain; recent research has pointed a number of pathologies of the brain diseases to be associated with BBB. 

I selected this publication because I am a big believer that a substantial portion of sensorineural hearing loss has underlying vascular pathologies. Isn't it interesting, considering how many brain diseases and retinal diseases arise from vascular pathologies, e.g. stroke, ischaemia, wet glaucoma, diabetic retinopathy, ... just to name a few. And yet, we don't talk no way near as much about vasculatures for sensorineural hearing loss. 

This publication by Li et al (2025) brings attention to BLB of the cochlea, in relation to ototoxic sensorineural hearing loss caused by gentamycin, using a mouse model. 

Some of the research findings 

  • Animal model: C57BL/6J mice, exposed to intravenous injection of gentamycin 100 - 300 mg/kg body weight. 
  • Treatment: time = 0 is the time point for gentamycin treatment. The research group also had groups treated with N-acetyl-L-cysteine (NAC, a powerful antioxidant) or ethacrynic acid (EA, a diuretic used to treat oedema), at t = -6 hours, 0, or +6 hours. 
  • Outcome measures are mostly hair cell loss, but immunohistochemistry is used to visualise marker expressions for endothelial cells (vasculature), pericytes, and macrophages.

What they have noticed, as said in the abstract & text, is that gentamycin induced much more toxicity when administered intravenously compared to peritoneal injection, and this was further substantially enhanced by EA co-administration. 

The research team then reports on the observation that when co-administered with EA, labeling with anti-F4/80 antibody (marker for macrophage) was enhanced near the vasculature) and at the same time, labelling with anti-desmin labelling was more prominent in proximity of BLB (Desmin is expressed in smooth muscle cells and pericytes). 

The authors suggested that this means "EA treatment significantly increases vascular permeability and promotes macrophage activation" and "EA treatment induces a significant increase in pericytes, suggesting compensatory vascular barrier remodelling." 

Part of Figure 7D from Li et al. (2025) - I wonder if capillaries look a bit more dilated? In Figure 7C, capillaries in the EA + GM group appear degenerated already/not label well. 


Haruna's takeaway

This publication is somewhat consistent with the earlier research in the field that demonstrated furosemide can enhance kanamycin toxicity when co-administered. I am not familiar with the mechanism of action for the EA. It seems to be an inhibitor of Na/K/Cl co-transporters. EA is an approved drug under the registered trade name "Edecrin", and apparently, it does not cross the blood-brain barrier according to the FDA (accessed 2025-09-07)  (https://www.accessdata.fda.gov/drugsatfda_docs/label/2005/16092s042,16093s044lbl.pdf) 

The mechanism of observed changes in the upregulation of macrophage marker and pericyte marker by co-administration of EA needs further investigation, but it is really interesting. 

Purely from an animal model perspective, how much effect the drug administration mode has is interesting and important. I also have not used this GS-IB4 fluorescent stain (type of lectin) for endothelial staining myself. I will be quite keen to try this fluorescent dye, as well as desmin and F4/80 antibodies. It looks to be this reagent (https://www.thermofisher.com/order/catalog/product/I21411) or similar?  F4/80 antibody and Desmin antibodies are both from Thermofisher, used at 1:200 and 1:300, respectively. I might try these antibodies to see if they cross-react in animal models we work with (sheep and rats). 


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This is Haruna's 1/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.