The Effect of Filaggrin Mutations on Dermal Penetration of Diisocyanates

Details

• Personal Author:
  Boyer J ; Nylander-French LA
• Description:
  A significant portion of US workers could be at risk for an increase in exposure to industrial chemicals via a heritable defect resulting in a compromised epidermal barrier associated with atopic dermatitis (AD). The epidermis of the skin, the primary barrier to the environment, consists of layers of differentiated keratinocytes that form a cornified structure (stratum corneum, SC). The continuity of the SC is dependent upon an integrated matrix of lipids and structural proteins, including filaggrin (FLG). The importance of filaggrin to epidermal differentiation and barrier function is evident with the strong association between FLG loss of function mutations and the common chronic human skin lesion diseases, ichthyosis vulgaris and atopic dermatitis. Alternatively, AD can also be triggered by inflammatory cytokines that inhibit FLG expression. These skin diseases are characterized by a compromised epidermal barrier and predisposition to asthma. The epidermal barrier is disrupted in both lesional and non-lesional skin placing all skin surfaces at increased risk for exposure-associated toxicity. We hypothesized that partial loss of FLG function in the skin would impair barrier function resulting in increased chemical penetration, dose, and skin toxicity. We have shown that skin exposure to diisocyanates, known skin and respiratory sensitizers, significantly contribute to systemic exposure. Thus, we proposed to test our hypothesis by exposing in vitro three-dimensional human organotypic skin tissues with and without compromised barrier function to diisocyanates. The skin reconstructs were to use primary keratinocytes screened for FLG expression and content level. Initial results with western blots indicated individual differences in FLG expression but expression could not be quantified. Our next experiments indicated differences in FLG protein and in mRNA expression using AD-associated cytokines. Unexpected challenges in available reagents and technical difficulties in screening individual donor keratinocytes for FLG protein expression by western blot prevented further research. Once required reagents become available, more research is warranted on inter-individual variation in FLG expression under constitutive and AD-like conditions to characterize keratinocyte donors for human skin reconstructs. Due to these challenges, we focused on measuring the cytotoxicity of two distinct forms of 1,6-hexamethylene diisocyanate (HDI) in primary cultures in three skin cell types (isogenic keratinocytes, melanocytes, and fibroblasts) from different donors. Comparative cytotoxicity was measured using the monomer and trimer of HDI using cell viability and cytotoxicity assays. We found that the HDI trimer, isocyanurate, was 30 - 200 times more toxic than the HDI monomer, depending upon the skin cell type. Keratinocytes were about half less sensitive to HDI isocyanurate than melanocytes or fibroblasts while melanocytes were about six times more sensitive to HDI monomer than keratinocytes and fibroblasts. We also concluded that the mechanism of cell death was due to necrosis and not apoptosis. The observed difference in toxicity between HDI monomer and HDI isocyanurate as well as the variation in the skin cell type response may have important implications for understanding acute toxic effects of these chemicals and developing regulatory limits for worker safety. [Description provided by NIOSH]
• Subjects:
  Cytotoxins Dermatitis Isocyanates Occupational Health Safety Skin
• Keywords:
  Biological Effects Cytotoxicity Dermal Exposures Diisocyanates Dose Response Exposure Methods Heredity Hexamethylene Diisocyanate Humans Skin Exposure Skin Irritants Skin Lesions Toxic Effects

  More +
• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  North Carolina ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-18
• NIOSHTIC Number:
  nn:20052360
• NTIS Accession Number:
  PB2018-101424
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R21-OH-010550, 2017 Nov; :1-18
• Contact Point Address:
  Leena A. Nylander-French, Ph.D., CIH, Department of Environmental Sciences and Engineering Gillings School of Global Public Health, University of North Carolina at Chapel Hill, CB# 7431 Rosenau Hall, Chapel Hill, NC 27599-7431
• Email:
  leena_french@unc.edu
• CAS Registry Number:
  Hexamethylene diisocyanate (CAS RN 822-06-0)
• Federal Fiscal Year:
  2018
• Performing Organization:
  University of North Carolina Chapel Hill
• Peer Reviewed:
  False
• Start Date:
  20140901
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20170831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:f10e76e7ca44d178a103ef1dbc1073b1e1f9589e06e41607a2f89a4d9fa9098f91f922695a4b6cae88dd5ccccaa15a631be8ed4e551d6c9dff43e121dfeacf00
• Download URL:
  https://stacks.cdc.gov/view/cdc/218701/cdc_218701_DS1.pdf
• File Type:
  [PDF - 818.62 KB ]