Effect of Homocysteine on the Expression of Matrix Metalloproteinase-9 and Apoptosis in Trabecular Meshwork Cells

Abstract

Purpose: In retinal endothelial cells, homocysteine (Hcy) activates matrix metalloproteinase (MMP)-9, which results in apoptosis. This study investigated these effects of Hcy in human trabecular meshwork cells (HTMC).Methods: HTMC cultures using 5 mM low or 20 mM high glucose (HG)-containing media were exposed to 100 μM Hcy for 3 days. Cell viability was assessed with the MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay. The MMP-9 and tissue inhibitor of MMP (TIMP)-1 levels were measured by western blotting and the degree of apoptosis was analyzed with flow cytometry using Annexin-propidium iodide double staining.Results: Exposure to Hcy in HG decreased cell viability compared to HG alone (<i>p</i> = 0.036). Compared to HG alone, co-exposure to Hcy with HG decreased the TIMP-1 levels, albeit not significantly (<i>p</i> = 0.094), and did not affect the MMP-9 levels (<i>p</i> = 0.413). In addition, co-exposure to Hcy with HG produced no difference in the degree of apoptosis compared to HG alone (<i>p</i> = 0.437).Conclusions: Unlike in retinal endothelial cells, Hcy did not affect the activities of TIMP-1, MMP-9, or the degrees of apoptosis significantly in HTMC. Thus, the effects Hcy may be limited in HTMC.