title: Differential effects of hepatocyte growth factor and keratinocyte growth factor on corneal epithelial cell cycle protein expression, cell survival, and growth.
abstract: OBJECTIVE
  Hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) are secreted in the cornea in response to injury. In this study, we investigated the HGF- and KGF-mediated effect on the expression of cell cycle and apoptosis controlling proteins, cell survival, and growth in the corneal epithelium to better understand the possible role of their signaling mechanisms in repairing epithelial injuries.
  
  
  METHODS
  The cell survival capability of HGF and KGF in epithelial primary cultures was evaluated by using a staurosporine-induced apoptosis model. Apoptosis was quantified with image analysis following nuclear staining with Hoechst fluorescent dye and DNA laddering. Western immunoblotting was used to study the effect of growth factors on the expression of cell cycle- and apoptosis-regulating proteins.
  
  
  RESULTS
  HGF and KGF protected cells from apoptosis for a short duration (10 h), but only KGF exhibited cell survival capability and maintained cell growth for a longer period (24 h). The onset of apoptosis was accompanied by a significant increase in cell cycle inhibitor p27(kip). HGF and KGF suppressed p27(kip) levels in the apoptosis environment; however, KGF- but not HGF-dependent downregulation in p27(kip) expression was sustained for a longer duration. Inhibition of phosphatidylinositol 3-kinase/Akt activation blocked HGF- and KGF-mediated control of p27(kip) expression. Further, when compared to HGF, the presence of KGF produced significant downregulation of p53 and poly(adenosine diphosphate-ribose) polymerase, the key proteins involved in apoptosis and blocked the degradation of G1/S cell cycle progression checkpoint protein retinoblastoma. HGF and KGF upregulated the levels of p21(cip), cyclins A, D, and E and cyclin-dependent kinases (CDK2 and CDK4) as well, but the KGF-mediated effect on the expression of these molecules lasted longer.
  
  
  CONCLUSIONS
  Sustained effect of KGF on cell survival and proliferation could be attributed to its ability to inhibit p53, retinoblastoma, caspases, and p27(kip) functions in apoptosis and cell cycle arrest and promote the expression of cell cycle progressing molecules for longer duration. Designing therapeutic strategies targeting cell cycle control through KGF may be beneficial for repairing difficult-to-heal corneal epithelial injuries that require sustained growth and cell survival promoting signals.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, SD ; Department of Internal Medicine, Sanford School of Medicine of University of South Dakota, Sioux Falls, SD.
authors.forename: Gudiseva
authors.initials: G
authors.lastname: Chandrasekher
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, SD.
authors.forename: Swetha
authors.initials: S
authors.lastname: Pothula
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, SD.
authors.forename: Glenn
authors.initials: G
authors.lastname: Maharaj
authors.affiliation: Eye Center and Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, LA.
authors.forename: Haydee E P
authors.initials: HE
authors.lastname: Bazan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019573:Epithelium, Corneal / Q000166:cytology*; D051523:Fibroblast Growth Factor 7 / Q000494:pharmacology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011817:Rabbits; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D018797:Cell Cycle Proteins; D016213:Cyclins; D051523:Fibroblast Growth Factor 7; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019311:Staurosporine