title: Expression of degradative enzymes and protease inhibitors in corneas with keratoconus.
abstract: OBJECTIVE
  Keratoconus is characterized by thinning and scarring of the central region of the cornea. Previous research showed that, in corneas obtained from patients with keratoconus, lysosomal enzyme activities are elevated, whereas levels of protease inhibitors such as alpha1-proteinase inhibitor are reduced. This study was undertaken to examine further the expression of a spectrum of proteolytic enzymes and protease inhibitors.
  
  
  METHODS
  Corneal buttons were collected from patients with keratoconus, healthy subjects, and patients with other corneal diseases. Immunohistochemical staining was performed on paraffin sections. Enzymatic assays and western blot analysis were carried out for cathepsins B and G. In addition, an in situ zymography procedure was used to examine the gelatin- and casein-digesting activities in corneas with keratoconus.
  
  
  RESULTS
  An enhanced staining was found with antibodies to cathepsins B and G. Enzymatic assays and western blotting confirmed that the levels of these two enzymes were elevated in corneas with keratoconus. No alteration was noted with any of the matrix metalloproteinase (MMP) family members and other enzymes and inhibitors examined, although in situ zymography did indicate an increase in net gelatin- and casein-digesting activities in corneas with keratoconus. These activities were mostly abolished by inhibitors for serine and cysteine proteinases, but not by those for MMPs and aspartic proteinases.
  
  
  CONCLUSIONS
  Levels of cathepsins B and G are increased in corneas with keratoconus. These enzymes may contribute to the heightened in situ gelatin- and casein-digesting activities, leading to abnormalities in keratoconus.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zhou
authors.forename: S
authors.initials: S
authors.lastname: Sawaguchi
authors.forename: S S
authors.initials: SS
authors.lastname: Twining
authors.forename: J
authors.initials: J
authors.lastname: Sugar
authors.forename: R S
authors.initials: RS
authors.lastname: Feder
authors.forename: B Y
authors.initials: BY
authors.lastname: Yue
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D002648:Child; D002675:Child, Preschool; D003315:Cornea / Q000201:enzymology* / Q000473:pathology; D003316:Corneal Diseases / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007124:Immunoenzyme Techniques; D007640:Keratoconus / Q000201:enzymology* / Q000473:pathology; D008875:Middle Aged; D011480:Protease Inhibitors / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
chemical_list: D011480:Protease Inhibitors; D010450:Endopeptidases; D010959:Tissue Plasminogen Activator