Abstract
Purpose :
Increased intraocular pressure (IOP) in high-tension primary open-angle glaucoma (POAG) patients causes the degeneration of the optic nerve and leads to loss of vision. The increase in IOP is mainly due to increased resistance to aqueous humor outflow through the trabecular meshwork (TM) tissue caused by fibrosis [excess deposition of extracellular matrix (ECM)] in the TM tissue. An increase in the levels of active transforming growth factor-β (TGF-β) in the aqueous humor of high-tension POAG patients is implicated in the fibrosis of the TM. In a breakthrough we found that TGF-β induced fibrosis by phosphorylating phosphatase and tensin homolog (PTEN), thereby rendering PTEN inactive in TM cells. We also found that inhibiting PI3-kinase signaling prevents the inhibition of PTEN activity by TGF-β (Tellios et al., 2017). Given the importance of PI3-kinase in cellular biology, pan-inhibition of PI3-kinase could have toxic side effects. Thus, we hypothesize that identifying the specific PI3-kinase p110 catalytic unit isoform(s) that regulate PTEN activity will lead to a more efficient and less toxic treatment to attenuate fibrosis of the TM tissue.
Methods :
Human TM cells in low serum medium will be pre-treated with a p110 isoform (α, β, γ, δ) specific inhibitor for 30 min before treatment with active TGF-β2. Protein will be extracted at 24 h and the effect of inhibition of a specific p110 isoform on the expression and phosphorylation of AKT and PTEN and the expression of fibrotic marker collagen I will be determined by Western blot.
Results :
Our preliminary data show that AS605240, a p110γ specific inhibitor, prevented TGF-β-induced collagen expression and PTEN phosphorylation in TM cells at 24 h. TGX-221, a p110β inhibitor also had a similar effect. However, inhibition of p110α did not prevent the TGF-β-induced increase in collagen expression or PTEN phosphorylation.
Conclusions :
Only certain PI3-kinase isoforms regulate PTEN activity and collagen expression in TM cells. We believe our study on the effect of inhibition of specific PI3-kinase isoforms will lead to viable combination therapies with current glaucoma drugs to attenuate fibrosis in the TM of high-tension POAG patients.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.