title: Natural Compounds as Occult Ototoxins? Ginkgo biloba Flavonoids Moderately Damage Lateral Line Hair Cells.
abstract: Several drugs, including aminoglycosides and platinum-based chemotherapy agents, are well known for their ototoxic properties. However, FDA-approved drugs are not routinely tested for ototoxicity, so their potential to affect hearing often goes unrecognized. This issue is further compounded for natural products, where there is a lack of FDA oversight and the manufacturer is solely responsible for ensuring the safety of their products. Natural products such as herbal supplements are easily accessible and commonly used in the practice of traditional eastern and alternative medicine. Using the zebrafish lateral line, we screened a natural products library to identify potential ototoxins. We found that the flavonoids quercetin and kaempferol, both from the Gingko biloba plant, demonstrated significant ototoxicity, killing up to 30 % of lateral line hair cells. We then examined a third Ginkgo flavonoid, isorhamnetin, and found similar levels of ototoxicity. After flavonoid treatment, surviving hair cells demonstrated reduced uptake of the vital dye FM 1-43FX, suggesting that the health of the remaining hair cells was compromised. We then asked if these flavonoids enter hair cells through the mechanotransduction channel, which is the site of entry for many known ototoxins. High extracellular calcium or the quinoline derivative E6 berbamine significantly protected hair cells from flavonoid damage, implicating the transduction channel as a site of flavonoid uptake. Since known ototoxins activate cellular stress responses, we asked if reactive oxygen species were necessary for flavonoid ototoxicity. Co-treatment with the antioxidant D-methionine significantly protected hair cells from each flavonoid, suggesting that antioxidant therapy could prevent hair cell loss. How these products affect mammalian hair cells is still an open question and will be the target of future experiments. However, this research demonstrates the potential for ototoxic damage caused by unregulated herbal supplements and suggests that further supplement characterization is warranted.
authors.affiliation: College of Arts and Sciences, Washington State University, Vancouver, WA, 98686, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Neveux
authors.affiliation: College of Arts and Sciences, Washington State University, Vancouver, WA, 98686, USA. nickikalani@gmail.com.
authors.forename: Nicole K
authors.initials: NK
authors.lastname: Smith
authors.affiliation: College of Arts and Sciences, Washington State University, Vancouver, WA, 98686, USA.|Camas High School, Camas, WA, 98607, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Roche
authors.affiliation: RTI International, Research Triangle Park, NC, 27709, USA.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Blough
authors.affiliation: RTI International, Research Triangle Park, NC, 27709, USA.
authors.forename: Wimal
authors.initials: W
authors.lastname: Pathmasiri
authors.affiliation: College of Arts and Sciences, Washington State University, Vancouver, WA, 98686, USA. Allison.coffin@wsu.edu.|Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA, 98686, USA. Allison.coffin@wsu.edu.
authors.forename: Allison B
authors.initials: AB
authors.lastname: Coffin
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D020441:Ginkgo biloba; D006198:Hair Cells, Auditory / Q000187:drug effects*; D044949:Kaempferols / Q000633:toxicity*; D010936:Plant Extracts / Q000633:toxicity*; D011794:Quercetin / Q000031:analogs & derivatives / Q000633:toxicity*; D015027:Zebrafish; D000096983:Ginkgo Extract
chemical_list: D044949:Kaempferols; D010936:Plant Extracts; D011794:Quercetin; C047368:3-methylquercetin; C063170:Ginkgo biloba extract; D000096983:Ginkgo Extract; C006552:kaempferol
keywords: Hearing loss; Herbal supplements; Oxidative stress; Zebrafish