July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Non-canonical TGFβ-signaling pathways in lens EMT: interplay between EGFR and p38 MAPK
Author Affiliations & Notes
  • Daisy Shu
    Anatomy and Histology, The University of Sydney, Camperdown, New South Wales, Australia
    Ophthalmology, Save Sight Institute, Sydney, New South Wales, Australia
  • Brooke P Mao
    Anatomy and Histology, The University of Sydney, Camperdown, New South Wales, Australia
  • Frank J Lovicu
    Anatomy and Histology, The University of Sydney, Camperdown, New South Wales, Australia
    Ophthalmology, Save Sight Institute, Sydney, New South Wales, Australia
  • Footnotes
    Commercial Relationships   Daisy Shu, None; Brooke Mao, None; Frank Lovicu, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 6445. doi:
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      Daisy Shu, Brooke P Mao, Frank J Lovicu; Non-canonical TGFβ-signaling pathways in lens EMT: interplay between EGFR and p38 MAPK. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6445.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : TGFβ induces lens epithelial cells (LECs) to undergo an epithelial-mesenchymal transition (EMT) resulting in fibrotic forms of cataract, such as anterior subcapsular cataract and posterior capsular opacification. EGFR-signaling is essential for this process. While the canonical TGFβ/Smad signaling pathway plays a key role in mediating lens EMT, MAPK-signaling, such as EGFR-induced ERK1/2 is also involved, but not required for all aspects of the EMT. As other MAPKs, such as the stress-activated p38 pathway is reported to regulate apoptosis and EMT, the present study aimed to explore its role in TGFβ-induced lens EMT, and its relation to EGFR-signaling.

Methods : Lens epithelial explants from 21-day-old Wistar rats were cultured for up to five days with 200 pg/ml TGFβ2 and/or 5 ng/ml EGF, with or without 100 nM PD153035 (EGFR-inhibitor) or 10μM SB203580 (p38-inhibitor). Cell morphology was examined using phase-contrast microscopy. Labeling of β-catenin, α-smooth muscle actin (α-SMA), phospho-p38 and p38 was assessed using immunofluorescence and/or western blotting.

Results : TGFβ induced LECs to transdifferentiate into myofibroblastic cells by day 2, and subsequently undergo apoptosis by day 5 of culture. Treatment of LECs with a combination of TGFβ and EGF resulted in a more pronounced EMT response compared to TGFβ alone. TGFβ induced the phosphorylation of p38 in LECs, with higher levels of phospho-p38 observed in cells treated with TGFβ and EGF. EGF alone did not induce phospho-p38, nor did it induce EMT in our lens explants. Inhibition of EGFR-signaling using PD153035 suppressed TGFβ-induced activation of p38 signaling. Selective inhibition of p38 activity using SB203580 completely blocked the TGFβ-induced EMT response, with retention of the epithelial phenotype (membranous β-catenin labeling), absence of α-SMA-positive stress fibers and no evidence of cell loss due to apoptosis over the five-day culture period.

Conclusions : p38-signaling is essential for TGFβ-induced EMT of LECs and contributes to the more pronounced EMT response observed when co-treating cells with TGFβ and EGF. TGFβ-driven p38 activation appears to involve EGFR-signaling, highlighting the interplay between these non-canonical TGFβ pathways. Targeting p38-signaling may be an effective strategy for the pharmacological treatment of fibrotic cataract.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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