Osteomeles schwerinae Extract and Its Major Compounds Inhibit Methylglyoxal-Induced Apoptosis in Human Retinal Pigment Epithelial Cells

Abstract

The accumulation and formation of advanced glycation end products (AGEs) are related to diabetes and age-related disease. Osteomeles schwerinae C. K. Schneid. (Rosaceae, OSSC) is used traditionally for the treatment of various diseases in Asia. Previous studies have shown that OSSC elicits preventive effects in an in vivo model of diabetes. This study was to evaluate the antiapoptotic effects of dried leaves and twigs of OSSC extract and its major compounds in ARPE-19 cells-spontaneously arising human retinal pigment epithelial cells-under diabetic conditions. To examine the effects of an OSSC extract and its active compounds (acetylvitexin, hyperoside and quercitrin) on apoptosis in methylglyoxal (MG, the active precursor in the formation of AGEs)-treated ARPE-19 cells and the mechanism by which these effects occur, apoptosis was measured using flow cytometry analysis. Protein expression levels of phospho-p53 (p-p53), Bax and Bcl-2 were determined by western blot analyses. The OSSC extract inhibited apoptosis in MG-treated ARPE-19 cells in a dose-dependent manner. The major compounds also reduced the rate of apoptosis. Both the extract and major compounds also inhibited the expression of p-p53 and Bax and increased the levels of Bcl-2 that had been previously reduced by MG treatment. The OSSC extract (0.1 μg/mL) and its major compounds (0.01 μM) attenuated apoptosis in ARPE-19 cells under toxic diabetic conditions by downregulating of expression of p-p53 and Bax. OSSC may serve as an alternative therapy to retard the development of diabetic retinopathy.

Keywords: Osteomeles schwerinae; apoptosis; diabetic retinopathy; human retinal pigment epithelial cells; methylglyoxal.

Figure 1

Effects of the Osteomeles schwerinae C. K. Schneid. (OSSC) extract and its major compounds on the viability of methylglyoxal (MG)-treated cells; (A) proliferation rates. Data are representative of three independent experiments and are expressed as the mean ± S.E.M. (n = 4). *** P < 0.01 vs. control; (B) FACS analysis. *** P < 0.01, ** P < 0.05 vs. control, respectively; (C) proliferation rates after treatment with the OSSC extract (0.1−20 μg/mL) and its major compounds (0.01–1 μM). *** P < 0.001 vs. control; ^### P < 0.001, ^## P < 0.01, ^# P < 0.05 vs. MG, respectively.

Figure 1

Effects of the Osteomeles schwerinae C. K. Schneid. (OSSC) extract and its major compounds on the viability of methylglyoxal (MG)-treated cells; (A) proliferation rates. Data are representative of three independent experiments and are expressed as the mean ± S.E.M. (n = 4). *** P < 0.01 vs. control; (B) FACS analysis. *** P < 0.01, ** P < 0.05 vs. control, respectively; (C) proliferation rates after treatment with the OSSC extract (0.1−20 μg/mL) and its major compounds (0.01–1 μM). *** P < 0.001 vs. control; ^### P < 0.001, ^## P < 0.01, ^# P < 0.05 vs. MG, respectively.

Figure 2

Effects of the OSSC extract and its maker compounds on MG-induced apoptosis. (A) Annexin V and PI staining; (B) percent rate of apoptosis. Data are expressed as the mean ± S.E.M. (n = 3). ** P < 0.01 vs. control; ^### P < 0.001 vs. MG; (C) expression of apoptosis-related proteins (p-p53, Bax and Bcl-2). Actin as the loading control.