mRNA expression of the ATP-binding cassette transporter subfamily A (ABCA) in rat and human brain capillary endothelial cells.

The ATP-binding cassette transporter subfamily A (ABCA) consists of the transporters mediating cholesterol release and regulated by cholesterol. As about 25% of total body cholesterol exists in the brain, sterol homeostasis is an important issue as far as central nervous system function is concerned. The purpose of this study was to clarify the mRNA expression of ABCA subtypes at the blood-brain barrier (BBB) using cultured rat and human brain capillary endothelial cells, TR-BBB and hBME cells, respectively. mRNA expression of ABCA1, 2, 3, 4, 5, 6, 7 and 8/9 was detected in TR-BBB cells. In the brain capillary-rich fraction, mRNA expression of ABCA1, 2, 3, 4, 5, 7 and 8/9 was detected. ABCA2 and 5 mRNA were also detected in hBME cells. These results demonstrate, for the first time, that ABCA subtypes are expressed at the rat and/or human BBB. The expression of ABCA subtypes at the BBB is likely to contribute to sterol homeostasis in the central nervous system.