Upregulation of P-Glycoprotein and Breast Cancer Resistance Protein Activity in Newly Developed in Vitro Rat Blood–Brain Barrier Spheroids Using Advanced Glycation End-Products

The blood–brain barrier (BBB) is a dynamic interface controlling the compound translocation between the blood and the brain, thereby maintaining neural homeostasis. There is cumulative evidence that BBB impairment during diabetes mellitus (DM) takes part in the progression of cognitive dementia. As tight junction proteins and ATP-binding cassette (ABC) transporters regulate substance exchange between the circulating blood and brain, the expression and function of these molecules under DM should be fully clarified. To understand the alteration of ABC transporter function in the BBB under DM, in vitro multicellular rat BBB spheroids consisting of conditionally immortalized rat brain capillary endothelial cells, astrocytes, and pericytes were newly developed. Immunostaining and permeability analysis of paracellular transport markers suggested the construction of tight junctions on the surface of the BBB spheroids. Transport analyses using fluorescence substrates of P-glycoprotein (P-gp), the breast cancer resistance protein (BCRP), and multidrug resistance-associated protein 4 (MRP4) indicate the functional expression of these transporters in the spheroids. After treatment with advanced glycation end-products (AGEs), involved in various signals during DM, the mRNA expression of tight junction molecules and ABC transporters in the BBB spheroids was upregulated. Furthermore, the functional changes in P-gp and BCRP in the BBB spheroids exposed to AGEs were canceled by the inhibitors of the receptor for AGEs (RAGE). These results suggest that AGE-RAGE interaction upregulates P-gp and BCRP function in the BBB.