title: mRNA expression of metabolic enzymes in human cornea, corneal cell lines, and hemicornea constructs.
abstract: OBJECTIVE
  Drugs from ophthalmic formulations are mainly absorbed into the eye via the corneal route. However, little is known about drug metabolism during the transcorneal passage. The objective of this study was to determine the mRNA expression of phase I and II isoenzymes in human corneal epithelial tissue, corneal cell lines, and a tissue-engineered cornea equivalent (a hemicornea construct) as in vitro model for drug absorption studies.
  
  
  METHODS
  The reverse transcription polymerase chain reaction was used to profile the mRNA expression of 10 cytochrome P450 enzymes (CYP) and seven phase II enzymes in the three human corneal cell lines and the hemicornea construct. The human corneal epithelial cell line (HCE-T), human corneal keratocyte cell line (HCK-Ca) and human corneal endothelial cell line (HENC) were used. Human liver tissue, human corneal epithelium from donor corneas, and the human colon adenocarcinoma cell line Caco-2 were also investigated.
  
  
  RESULTS
  All the phase I and II mRNAs were expressed in the human liver tissue. The Caco-2 cell line showed an expression pattern similar to the liver tissue, although the signals for CYP1A2 and CYP3A4 were absent. In the case of the donor human corneal epithelium, all the detected phase I mRNAs had lower levels than did the liver tissue. By contrast, the phase II mRNA expression pattern was heterogeneous to the liver tissue. The expression patterns in the three human corneal cell lines were comparable, although the signals for a few phase I enzymes and N-acetyltransferase (NAT2) mRNAs were only detectable in the HCE-T. In the hemicornea construct, all the investigated phase I and II mRNA (except for CYP1A2, CYP2B6, CYP2C19, and NAT2) were expressed.
  
  
  CONCLUSIONS
  Overall, the mRNA expressions of the tested phase I and phase II enzymes in the hemicornea construct and the three corneal cell lines correlated well with the expression patterns of the ex vivo human corneal epithelium.
authors.affiliation: Institut für Pharmazeutische Technologie, Technische Universität Braunschweig, Braunschweig, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kölln
authors.forename: Stephan
authors.initials: S
authors.lastname: Reichl
mesh_terms: D000042:Absorption / Q000235:genetics; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001191:Arylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D018938:Caco-2 Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003315:Cornea / Q000201:enzymology*; D060527:Corneal Keratocytes; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004728:Endothelium, Corneal / Q000201:enzymology / Q000378:metabolism; D004847:Epithelial Cells / Q000201:enzymology; D019573:Epithelium, Corneal / Q000201:enzymology*; D006801:Humans; D008658:Inactivation, Metabolic; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008875:Middle Aged; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D023822:Tissue Engineering / Q000379:methods; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; C504573:CYP1A2 protein, human; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D001191:Arylamine N-Acetyltransferase; C478900:NAT2 protein, human