Molecular Mechanisms Underlying the Filtration Bleb-Maintaining Effects of Suberoylanilide Hydroxamic Acid (SAHA)

Suberoylanilide hydroxamic acid (SAHA) has been shown to support the maintenance of experimental filtration blebs in animal models. This study was performed to investigate the molecular mechanisms underlying the bleb-maintaining effects of SAHA in modulating wound healing activities of conjunctival fibroblasts.

Human conjunctival fibroblasts (HConFs) were pretreated with SAHA before treatment with TGF-β2. Microarray-based screening was used to investigate the gene expression profiles. Gene ontology (GO) analysis was conducted to categorize the gene functions. The expression of TGF-β-induced signaling molecules, α-smooth muscle actin, and extracellular matrix (ECM) proteins were evaluated by Western blot analyses. Multiplex immunoassay was performed to evaluate supernatant cytokine concentrations. Tube formation assay was used to evaluate angiogenesis using human umbilical vein endothelial cells.

GO analysis showed that SAHA, in the presence of TGF-β2, induced changes in expression of genes involved in the TGF-β receptor signaling pathway, cell proliferation, extracellular matrix organization, inflammatory responses, and angiogenesis. Subsequent in vitro experiments showed that SAHA partly inhibited the phosphorylation of Smad2, Smad3, and Akt. SAHA pretreatment potently suppressed TGF-β2-driven cell proliferation, myofibroblast differentiation, contraction, ECM production, and angiogenic cytokine expression. The supernatant of HConFs treated with SAHA inhibited tube formation.

SAHA has been shown to suppress angiogenesis and activation of conjunctival fibroblasts partly via inhibition of Smad and non-Smad TGF-β signaling. This in vitro study provides new evidence for the molecular basis of the potential bleb-maintaining effects of SAHA, a novel candidate drug in modulating scar formation after glaucoma filtration surgery.