title: Corneal neurotoxicity due to topical benzalkonium chloride.
abstract: OBJECTIVE
  The aim of this study was to determine and characterize the effect of topical application of benzalkonium chloride (BAK) on corneal nerves in vivo and in vitro.
  
  
  METHODS
  Thy1-YFP+ neurofluorescent mouse eyes were treated topically with vehicle or BAK (0.01% or 0.1%). Wide-field stereofluorescence microscopy was performed to sequentially image the treated corneas in vivo every week for 4 weeks, and changes in stromal nerve fiber density (NFD) and aqueous tear production were determined. Whole-mount immunofluorescence staining of corneas was performed with antibodies to axonopathy marker SMI-32. Western immunoblot analyses were performed on trigeminal ganglion and corneal lysates to determine abundance of proteins associated with neurotoxicity and regeneration. Compartmental culture of trigeminal ganglion neurons was performed in Campenot devices to determine whether BAK affects neurite outgrowth.
  
  
  RESULTS
  BAK-treated corneas exhibited significantly reduced NFD and aqueous tear production, and increased inflammatory cell infiltration and fluorescein staining at 1 week (P < 0.05). These changes were most significant after 0.1% BAK treatment. The extent of inflammatory cell infiltration in the cornea showed a significant negative correlation with NFD. Sequential in vivo imaging of corneas showed two forms of BAK-induced neurotoxicity: reversible neurotoxicity characterized by axonopathy and recovery, and irreversible neurotoxicity characterized by nerve degeneration and regeneration. Increased abundance of beta III tubulin in corneal lysates confirmed regeneration. A dose-related significant reduction in neurites occurred after BAK addition to compartmental cultures of dissociated trigeminal ganglion cells. Although both BAK doses (0.0001% and 0.001%) reduced nerve fiber length, the reduction was significantly more with the higher dose (P < 0.001).
  
  
  CONCLUSIONS
  Topical application of BAK to the eye causes corneal neurotoxicity, inflammation, and reduced aqueous tear production.
authors.affiliation: Corneal Neurobiology Laboratory, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA.
authors.forename: Joy
authors.initials: J
authors.lastname: Sarkar
authors.forename: Shweta
authors.initials: S
authors.lastname: Chaudhary
authors.forename: Abed
authors.initials: A
authors.lastname: Namavari
authors.forename: Okan
authors.initials: O
authors.lastname: Ozturk
authors.forename: Jin-Hong
authors.initials: JH
authors.lastname: Chang
authors.forename: Lisette
authors.initials: L
authors.lastname: Yco
authors.forename: Snehal
authors.initials: S
authors.lastname: Sonawane
authors.forename: Vishakha
authors.initials: V
authors.lastname: Khanolkar
authors.forename: Joelle
authors.initials: J
authors.lastname: Hallak
authors.forename: Sandeep
authors.initials: S
authors.lastname: Jain
mesh_terms: D000818:Animals; D001548:Benzalkonium Compounds / Q000008:administration & dosage / Q000633:toxicity*; D015153:Blotting, Western; D002478:Cells, Cultured; D003315:Cornea / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D003316:Corneal Diseases / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D003902:Detergents / Q000008:administration & dosage / Q000633:toxicity; D051379:Mice; D018613:Microscopy, Confocal; D009883:Ophthalmic Solutions; D013666:Tears / Q000187:drug effects / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000187:drug effects* / Q000473:pathology
chemical_list: D001548:Benzalkonium Compounds; D003902:Detergents; D009883:Ophthalmic Solutions