Differential regulation of cytokine and receptor transcript expression in human corneal and limbal fibroblasts by epidermal growth factor, transforming growth factor-alpha, platelet-derived growth factor B, and interleukin-1 beta.
OBJECTIVE
To explore further the significance of three patterns of cytokine dialogues that have been characterized between human corneal and limbal epithelial cells and fibroblasts.


METHODS
Northern hybridization of the transcript expression of type I cytokine receptors (EGFR, IL-1R, and PDGFR-beta), type II cytokines (bFGF, LIF, and TGF-beta 1), and type III cytokines (HGF and KGF) by human corneal and limbal fibroblasts was conducted under the modulation of TGF-alpha, PDGF-BB, IL-1 beta, and EGF (type I cytokines). The mechanism of upregulation by IL-1 beta was studied further with respect to proto-oncogene expression and under the treatment of cycloheximide and actinomycin D.


RESULTS
Results showed that EGF upregulated LIF and HGF but downregulated KGF and M-CSF. Unlike EGF, TGF-alpha upregulated additional EGFR, PDGFR-beta, bFGF, and TGF-beta 1, suggesting that although they share the same EGFR, TGF-alpha, which is produced by epithelium, is more effective in activating fibroblasts than EGF, which is present in tears. The upregulation of PDGF-BB was similar to that of TGF-alpha, except that it further stimulated IL-8, supporting their synergistic roles in promoting wound healing. Uniquely, IL-1 beta upregulated KGF expression by limbal fibroblasts more than corneal fibroblasts and IL-8 and M-CSF expression, but it downregulated PDGFR-beta. In IL-1 beta, the upregulation of cytokines and receptors was preceded by the upregulation of c-fos, c-jun, and c-myc, and it was inhibited by actinomycin D. Its upregulation of LIF was superinduced, but the upregulation of bFGF and KGF was inhibited, and that of the rest was not affected by cycloheximide.


CONCLUSIONS
These findings suggest that epithelial cells under stress or injury (producing IL-1) might preferentially activate limbal epithelial stem cells indirectly by fibroblasts and simultaneously might promote inflammation during wound healing.
Li
D Q
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Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, Florida 33101, USA.
Tseng
S C
SC
D000328:Adult; D015152:Blotting, Northern; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D016207:Cytokines / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D015342:DNA Probes; D003609:Dactinomycin / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D016850:Limbus Corneae / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008875:Middle Aged; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism*; D016211:Transforming Growth Factor alpha / Q000494:pharmacology; D015854:Up-Regulation
D016207:Cytokines; D015342:DNA Probes; D007375:Interleukin-1; C000715470:MAS1 protein, human; D010982:Platelet-Derived Growth Factor; D011500:Protein Synthesis Inhibitors; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D016211:Transforming Growth Factor alpha; D003609:Dactinomycin; D004815:Epidermal Growth Factor; D012313:RNA; D003513:Cycloheximide