Polysaccharides extracted from Cassia seeds protect against high glucose-induced retinal endothelial cell injury

Introduction: To investigate the protect effect of Polysaccharides extract from cassia seeds (CSPE) on human retinal endothelial cells (HRECs) in hyperglycemia environment.

Methods: The same amount of human retinal endothelial cells (HRECs), respectively, inoculated in vitro were divided into normal group (Con group), hyperglycemia group (H-Glu group), and different concentration of cassia Polysaccharides extract (CSPE) combined with high glucose medium group (CSPE group). HRECs in Con group were cultured routinely. The cell in H-Glu group was treated with high glucose, in which the concentration of glucose in the medium was 30 mM. HRECs in CSPE group were treated with different concentrations of CSPE combined with high glucose. Enhanced cell counting kit-8(CCK8) assay was used to measure the HRECs cell survival rate in different groups. The generation of Reactive Oxygen Species (ROS) in different group was measured by flow cytometry. The real-time quantitative PCR analysis was used for determining intracellular heme oxygenase-1 (HO-1) mRNA levels. Western Blot was applied to test the change of proteins, such as HO-1- and NF-E2-related factor 2 (Nrf2) protein.

Results: The cell survival rate of the H-Glu group was significantly lower than that of the Con group (P < 0.05). When the concentration of CSPE was 100 mg/ml in CSPE group, the HRECs cell survival rate was significantly lower than that of the Con group (P < 0.05), and there was no significant difference with H-Glu group. When the concentration of CSPE in CSPE group was between 50 µg/ml and 1 × 10⁴ µg/ml, the survival rate of HRECs cells showed no significant difference compared with that of H-Glu group and Con group. However, when the concentration of CSPE in CSPE group was between 2.5 and 40 µg/ml, the HRECs cell survival rate was significantly higher than that of H-Glu group (P < 0.05) with a concentration-independent, and there was no significant difference between CSPE group and Con group. The ROS production was lowest in the CSPE group and was lower in Con group than in the H-Glu group. The contents of HO-1 mRNA (P < 0.05), HO-1 and Nrf2 protein were lower in the H-Glu group than in the CSPE and Con group, and there was no significant difference between the CSPE group and H-Glu group.

Conclusions: A certain concentration range of CSPE can increase the expression of the downstream protein HO-1 and negatively regulate the production of ROS by upregulating the expression of Nrf2, thus protecting human retinal endothelial cells from oxidative damage caused by high glucose.