Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure.

In vivo animal study using larval zebrafish to evaluate the protective effects of Dihexa against aminoglycoside-induced hair cell loss.

“To evaluate Dihexa as a potential hair cell protectant, we used the larval zebrafish lateral line, which possesses hair cells that are homologous to mammalian inner ear hair cells and show similar responses to toxins.”

Larval zebrafish (Danio rerio), specifically 5 or 6 days post-fertilization, including transgenic Brn3c:mGFP lines.

“Embryos were raised until 5 or 6 days post-fertilization (dpf) prior to experimentation because larvae younger than 5 dpf exhibit some resistance to aminoglycoside ototoxicity”

Between 5 and 11 animals per treatment group, depending on the specific experiment.

“N = 7–11 animals per treatment, error bars represent ± s.e.m.”

Acute exposures of 30 minutes to 6 hours, with assessments performed immediately or after a 45-minute recovery period.

“Fish were then co-treated with Dihexa or DMSO and neomycin (30 min), acute gentamicin (30 min), chronic gentamicin (6 h), or cisplatin (4 h).”

Dihexa at 1 μM confers significant protection against acute aminoglycoside (neomycin and gentamicin) toxicity but does not protect against chronic gentamicin or cisplatin exposure.

“We found that a Dihexa concentration of 1 μM confers optimal protection from acute treatment with either ototoxin.”

Dihexa does not inhibit the uptake of aminoglycosides into hair cells, suggesting its protective mechanism is intracellular rather than blocking entry.

“Pretreatment with Dihexa does not affect the amount of fluorescently tagged gentamicin that enters hair cells, indicating that Dihexa’s protection is likely mediated by intracellular events and not by inhibiting aminoglycoside entry.”

The protective effect of Dihexa is mediated by the HGF/c-Met signaling pathway, as it is attenuated by the HGF antagonist 6-AH and inhibitors of downstream targets Akt, TOR, and MEK.

“Dihexa-mediated protection is attenuated by co-treatment with the HGF antagonist 6-AH, further evidence that HGF activation is a component of the observed protection.”

The study was conducted in zebrafish larvae, and the authors note that future work is needed to address efficacy in mammalian models.

“Future work will address the efficacy of Dihexa as a hair cell protect in mammalian models and against additional aminoglycosides.”