Specific activation of the glucocorticoid receptor and modulation of signal transduction pathways in human lens epithelial cells.
OBJECTIVE
Prolonged use of glucocorticoids (GCs) can lead to cataract formation. Lens GC responses have been difficult to elucidate. A previous study showed the presence of the glucocorticoid receptor (GR) in immortalized and primary human lens epithelial cells (hLECs) and GC-induced changes in gene expression. This study demonstrates specific GR activation and identifies the biological effect of GC-induced changes in gene expression in hLECs.


METHODS
HLE B-3 (B-3) and primary cultures of hLECs were transfected with pGRE.Luc and treated with or without dexamethasone (Dex), RU-486, spironolactone, or vehicle. mRNA and protein expression were examined by real-time PCR and Western blot analysis, respectively. Cell proliferation and apoptosis were examined by WST-1 and flow cytometry, respectively.


RESULTS
Dex treatment of B-3 and primary cultures demonstrated specific GR, but not mineralocorticoid receptor (MR), activation and phosphorylation. Pathway analysis revealed GC-induced changes in expression of MAPK regulators. Increased expression of GILZ mRNA and MKP-1 mRNA and protein was observed in immortalized and donor hLECs. This corresponded with a decrease in the phosphorylated forms of RAF, ERK, p38, and AKT, but not in JNK. No net change in LEC proliferation or apoptosis was observed with Dex treatment.


CONCLUSIONS
GC treatment of hLECs activates the GR to modulate the expression of MAPK and PI3K/AKT regulators. This is the first demonstration of GC signaling in hLECs. GCs, MAPK, and PI3K/AKT are involved in cell processes implicated in steroid-induced cataractogenesis. The absence of a net change in cell activity with acute steroid treatment is consistent with the possibility that chronic treatment leads to prolonged modulation of these pathways and steroid-induced cataract.
Gupta
Vanita
V
Department of Biochemistry and Molecular Biology, the Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, NJ, USA. vanita.gupta@mssm.edu
Awasthi
Niranjan
N
Wagner
B J
BJ
D017209:Apoptosis; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics; D049109:Cell Proliferation; D003907:Dexamethasone / Q000494:pharmacology*; D054638:Dual Specificity Phosphatase 1; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D007908:Lens, Crystalline / Q000166:cytology*; D015735:Mifepristone / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D013148:Spironolactone / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; C404226:TSC22D3 protein, human; D014157:Transcription Factors; C028697:dexamethasone receptor; D013148:Spironolactone; D015735:Mifepristone; D003907:Dexamethasone; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases