RESUMO
Cognitive impairment refers to the abnormality of the hippocampus， cortex and other parts of the brain， which is manifested by the decline of cognitive abilities such as learning， memory and attention. With the increase in people's work pressure and bad living habits， the incidence of cognitive impairment is getting higher and higher， which seriously affects people's normal life. However， there are adverse reactions such as gastrointestinal reactions and extrapyramidal reactions in Western drug treatment for cognitive impairment. Therefore， the development of a drug with relatively minimal adverse reactions is of great significance. Traditional Chinese medicine （TCM） has the characteristics of "multi-component， multi-pathway and multi-target"， and the incidence of adverse reactions is relatively low. Studies have shown that the pathogenesis of cognitive impairment is closely related to oxidative stress， inflammation， apoptosis， autophagy and other processes of neurons in the cerebral cortex and hippocampus. Phosphatidylinositol 3-kinase （PI3K）-protein kinase B （Akt） signal pathway plays an important role in the transmission of intracellular and intracellular signals， and in the regulation of cellular inflammation， apoptosis， autophagy， etc. TCM monomers， TCM extracts， and TCM compounds exert anti-inflammatory， antioxidant， anti-apoptotic and autophagy regulation effects by regulating the PI3K/Akt signaling pathway to improve cognitive impairment. This review first summarized the composition and regulatory process of the PI3K/Akt signaling pathway， and then discussed the research progress on the improvement of cognitive impairment through the improvement of oxidative stress， inflammation， apoptosis and autophagy of neurons. Finally， the recent research status of the regulation of this signaling pathway by TCM extracts， TCM monomers and TCM compounds to improve cognitive impairment was summarized. This study provides a theoretical basis for the future study of new TCM related to cognitive impairment.
RESUMO
OBJECTIVES@#Hypoxia can alter the oral bioavailability of drugs, including various substrates (drugs) of P-glycoprotein (P-gp), suggesting that hypoxia may affect the function of P-gp in intestinal epithelial cells. Currently, Caco-2 monolayer model is the classic model for studying the function of intestinal epithelial P-gp. This study combines the Caco-2 monolayer model with hypoxia to investigate the effects of hypoxia on the expression and function of P-gp in Caco-2 cells, which helps to elucidate the mechanism of changes in drug transport on intestinal epithelial cells in high-altitude hypoxia environment.@*METHODS@#Normally cultured Caco-2 cells were cultured in 1% oxygen concentration for 24, 48, and 72 h, respectively. After the extraction of the membrane proteins, the levels of P-gp were measured by Western blotting. The hypoxia time, with the most significant change of P-gp expression, was selected as the subsequent study condition. After culturing Caco-2 cells in transwell cells for 21 days and establishing a Caco-2 monolayer model, they were divided into a normoxic control group and a hypoxic group. The normoxic control group was continuously cultured in normal condition for 72 h, while the hypoxic group was incubated for 72 h in 1% oxygen concentration. The integrity and polarability of Caco-2 cells monolayer were evaluated by transepithelial electrical resistance (TEER), apparent permeability (Papp) of lucifer yellow, the activity of alkaline phosphatase (AKP), and microvilli morphology and tight junction structure under transmission electron microscope. Then, the Papp of rhodamine 123 (Rh123), a kind of P-gp specific substrate, was detected and the efflux rate was calculated. The Caco-2 cell monolayer, culturing at plastic flasks, was incubated for 72 h in 1% oxygen concentration, the expression level of P-gp was detected.@*RESULTS@#P-gp was decreased in Caco-2 cells with 1% oxygen concentration, especially the duration of 72 h (P<0.01). In hypoxic group, the TEER of monolayer was more than 400 Ω·cm2, the Papp of lucifer yellow was less than 5×10-7 cm/s, and the ratio of AKP activity between apical side and basal side was greater than 3. The establishment of Caco-2 monolayer model was successful, and hypoxia treatment did not affect the integrity and polarization state of the model. Compared with the normoxic control group, the efflux rate of Rh123 was significantly reduced in Caco-2 cell monolayer of the hypoxic group (P<0.01). Hypoxia reduced the expression of P-gp in Caco-2 cell monolayer (P<0.01).@*CONCLUSIONS@#Hypoxia inhibits P-gp function in Caco-2 cells, which may be related to the decreased P-gp level.