Styrene Induced Alterations in Biomarkers of Exposure and Effects in the Cochlea: Mechanisms of Hearing Loss

Details

• Personal Author:
  Chen G ; Chi L ; Henderson D ; Kostyniak PJ
• Description:
  It is known that styrene is ototoxic and causes cochlear damage starting from the middle turn. However, the cellular mechanism underlying styrene ototoxicity is still unclear. In this study, rats were exposed to styrene by gavage at different doses once a day for varying periods. Styrene levels in the cochlear tissues, styrene-induced permanent hearing loss, cochlear disruptions, and cell death pathways were determined. Styrene concentration in the cochlea varied along with the basilar membrane with the lowest level in the basal turn being consistent with the lowest styrene-induced threshold shift and hair cell loss in this region. After 3 weeks of exposure (5 days per week), a dose-dependent permanent hearing loss and a hair cell loss, especially in the midfrequency region, were observed. The styrene exposure at a dose of 200 mg/kg, which induced a blood level of 6.0 +/- 1.0 µg/g, caused an average of 4.4 +/- 0.5% OHC (outer hair cell) loss and 2-5 dB threshold shift in the cochlear region of 20-70% from the apex. A significant OHC loss was not observed until 7 days of exposure at a dose of 800 mg/ kg. Deiters cells appeared to be the most vulnerable target of styrene. When condensed nuclei were observed in Deiters cells after a few days of styrene exposure (800 mg/kg), other cells were still intact. Apoptotic cell death appeared to be the main cell death pathway in the cochlea after styrene exposure. In the styrene-induced apoptotic OHCs, histochemical staining detected activated caspases-9 and 8, indicating that both mitochondrial-dependent pathway and death receptor-dependent pathway were involved in the styrene-induced cell death. [Description provided by NIOSH]
• Subjects:
  Biomarkers Environmental Monitoring Hearing Loss Occupational Health Safety Styrene
• Keywords:
  Auditory-system Cell-damage Dose-response Exposure-assessment Exposure-levels Hearing-loss Organic-chemicals Ototoxicity Styrenes
• ISSN:
  1096-6080
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  New York ; OSHA Region 2
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  167-177
• Volume:
  98
• Issue:
  1
• NIOSHTIC Number:
  nn:20032118
• Citation:
  Toxicol Sci 2007 Jul; 98(1):167-177
• Contact Point Address:
  Guang-Di Chen, Center for Hearing and Deafness, SUNY at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo, NY 14214
• Email:
  gchen@buffalo.edu
• CAS Registry Number:
  Styrene (CAS RN 100-42-5)
• Federal Fiscal Year:
  2007
• Performing Organization:
  State University of New York at Buffalo
• Peer Reviewed:
  True
• Start Date:
  20050501
• Source Full Name:
  Toxicological Sciences
• End Date:
  20090430
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:8e97e619bf991cec95f383a25830d73f9901698c9ec026c00cf8692ea0f40a0f559c5d85a2fbea3b3df7a367aec2bf110fdfcf0a9ee0134e7895408f8edd0669
• Download URL:
  https://stacks.cdc.gov/view/cdc/186169/cdc_186169_DS1.pdf
• File Type:
  [PDF - 1.08 MB ]