September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Regulation of TGFβ1 signaling and TGFβ1-induced matrix synthesis by LOXL1 in trabecular meshwork and Tenon’s capsule fibroblasts cells
Author Affiliations & Notes
  • Panah Liravi
    Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany
  • Matthias Zenkel
    Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany
  • Friedrich E Kruse
    Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany
  • Ursula Schlötzer-Schrehardt
    Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany
  • Footnotes
    Commercial Relationships   Panah Liravi, None; Matthias Zenkel, None; Friedrich Kruse, None; Ursula Schlötzer-Schrehardt, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 4685. doi:
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      Panah Liravi, Matthias Zenkel, Friedrich E Kruse, Ursula Schlötzer-Schrehardt; Regulation of TGFβ1 signaling and TGFβ1-induced matrix synthesis by LOXL1 in trabecular meshwork and Tenon’s capsule fibroblasts cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4685.

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

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Abstract

Purpose : The cross-linking matrix enzyme lysyl oxidase-like 1 (LOXL1) which is a major risk factor for pseudoexfoliation (PEX) syndrome and glaucoma, is expressed in the trabecular meshwork and is regulated by TGFβ isoforms which are elevated in the aqueous humor of glaucoma patients. Here we investigated a potential regulatory effect of LOXL1 on TGFβ1 signalling and TGFβ1 induced matrix synthesis in vitro.

Methods : Expression levels of LOXL1 and TGFβ were analysed in trabecular meshwork specimens of 10 donor eyes with or without PEX syndrome by real-time RT-PCR. To analyse the effect of LOXL1 knockdown or overexpression on TGFβ1 activity, primary human trabecular meshwork cells (hTMC) and Tenon’s capsule fibroblasts (hTCF) were transiently transfected with LOXL1 siRNA or full-length LOXL1 vector construct. Expression of TGFβ signalling factors, extracellular matrix genes was analysed by real-time PCR arrays. Relative levels of phosphorylated targets of canonical Smad and non-canonical MAPK pathways were determined by phospho-antibody arrays and by Western immunoblotting after exposure of cells to TGFβ1 (5 ng/ml) for 6 hours.

Results : In trabecular meshwork specimens of eyes with manifest PEX syndrome, expression levels of LOXL1 were significantly downregulated whereas expression levels of TGFβ1 were significantly upregulated compared to age-matched control eyes. siRNA-mediated knockdown of LOXL1 in hTMC and hTCF increased expression of TGFβ isoforms, TGFβ receptor 1/2, transcription factors Smad 2/3, Smad 7, SP1, AP1 and enhanced TGFβ1-stimulated activation of both canonical and non-canonical MAPK pathways compared to controls. LOXL1 deficiency also upregulated expression levels of extracellular matrix proteins, e.g. collagen, elastin, fibrillin and downregulated expression levels of matrix proteases, e.g. MMP-1, MMP-9, and ADAMTS8. Conversely, overexpression of LOXL1 in hTMC and hTCF attenuated TGFβ expression and signalling together with a concomitant downregulation of expression of matrix proteins.

Conclusions : These findings suggest a negative regulatory feed-back loop between LOXL1 activity and TGFβ signalling which may play an important role in trabecular meshwork tissue homeostasis in health and in glaucoma. The deficiency of LOXL1 characteristic for PEX glaucoma, may contribute to TGFβ1 activation and abnormal matrix deposition in anterior segment tissues.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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