Puerariae radix extract suppresses H2O2-induced ARPE-19 cell death and permeability via phosphorylation of p38MAPK and JNK

Puerariae radix (root of Pueraia lobata; Leguminosae) is one of the most important herbs in Korean traditional medicine and has been frequently used for the treatment of diarrhea, diabetes, cardiovascular disease and osteonecrosis. Retinopathy is a major cause of vision loss among middle aged and elderly people. The retinal pigment epithelium (RPE) plays an important role in the maintenance of photoreceptors in the retina, and RPE cells (ARPE-19) are used to investigate the pathology and physiology of retinopathy.

The roots of P. lobata were collected in Kyonggi-do, Korea, in April 2005 and were identified by Professor J.-H. Kim. The major compounds, puerarin, daidzin and daidzein, were isolated from the EtOH extract of Puerariae radix (PR). We evaluated whether the EtOH extract of PR and its major compounds could prevent cell death and decrease the membrane permeability in oxidative stress-induced ARPE-19. PR significantly protected against H2O2-induced cell death, whereas its major compounds did not inhibit H2O2-induced intracellular ROS generation.

The effect of PR on the RPE barrier was conducted by measuring paracellular permeability of dextran in ARPE-19. PR showed significant decrease in the membrane permeability. Paracellular permeability is related with the alteration in tight junction protein expression. PR also attenuated the decrease in the expression of ZO-1 and occludin. ZO-1 expression was altered in response to oxidative damage. To identify the signaling pathway through which PR exhibits its effects in H₂O₂-induced cells, we examined the effects of PR on phosphorylation of ERK, p38MAPK, and JNK. PR significantly suppressed the phosphorylation of pERK, p38 MAPK, and JNK in ARPE-19 cells, indicating that PR significantly suppressed H₂O₂-induced ARPE-19 cell death and permeability via phosphorylation of pERK, p38MAPK and JNK.

Taken together, these results suggest PR to be a potential alternative for preventing the progression of oxidative stress-related retinopathy.