Purchase this article with an account.
GD Sharma, JC He, HE P Bazan; Hepatocyte (HGF) and keratinocyte growth factor (KGF) differentially regulate MAP-kinases (Erk1/2, P38 and JNK): evidence of a cross-talk between Erk1/2 and P38 in corneal epithelial cells: . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1634.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: HGF and KGF receptor stimulation induces activation of two main pathways in corneal epithelium: The PI3K-p706SK and the MAP-kinase Erk1/2 pathway (Exp Eye Res, 2001, 73:201 and IOVS, 1998, 39:1329). We investigated the involvement of another set of MAP-kinases, the P38 and JNK, in response to growth factors. We also examined the possible cross-talk between Erk1/2 and P38 and the action of P38 in corneal wound healing. Methods: Primary cultures of rabbit and immortalized human corneal epithelial cells were stimulated with HGF and KGF (20 ng/ml) for different times. In some experiments, 50 µM PD98059 was added 1 hour before stimulation. Activation of p-Erk1/2, p-P38 and p-JNK1/2 was evaluated by Western blotting using phospho-specific antibodies. In organ-culture experiments, rabbit corneas were wounded with 7-mm epithelial debridement. Corneas were treated with the P38 inhibitor SB203580 (20 µM) and with HGF (20 ng/ml) for 24 hours. Areas uncovered by epithelium were measured by image analysis. Immunofluorescence was performed in human cells with specific antibodies. Sheep anti-mouse Ig-FITC was used as secondary antibody, and nuclei were stained with DAPI. Results: HGF and KGF stimulated the phosphorylation of P38, while there was no change in total P38. Activation occurs at 15 minutes and was sustained up to 60 minutes. No activation of JNK1/2 was found. The activation of P38 was weaker than that observed with Erk1/2. Immunofluorescence of HGF- and KGF-stimulated human cells showed p-P38 staining in the perinuclear region and p-Erk1/2 staining in the nuclei. Preincubation of cells with PD98059 and their subsequent stimulation with HGF resulted in a inhibition of p-Erk1/2 and a significant stimulation of p-P38. Immunostaining showed a higher number of cells with p-P38 in the perinuclear region compared to HGF stimulation alone. Similar treatment did not stimulate JNK1/2. In rabbit corneal organ culture inhibition of P38 activation with SB203580 significantly delayed (p<0.05) the wound closure stimulated by HGF. Conclusions: Our results demonstrate that HGF and KGF stimulate the P38 MAP-kinases in corneal epithelial cells. The translocation of p-P38 to the perinuclear area, stimulated by the growth factors, indicated that this kinase may phosphorylate nuclear targets. The existence of differential activation and cross-talk between Erk1/2 and P38 may be significant in modulation of corneal wound healing (Supported by NIH-NE1 EY06635).
This PDF is available to Subscribers Only