Therapeutic drugs modulate ATP-Binding cassette transporter-mediated transport of amyloid beta(1-42) in brain microvascular endothelial cells.

Deposition of amyloid-ß peptide (Aß(1-42)) is a hallmark of Alzheimer's disease. Clearance of Aß(1-42), across the blood-brain barrier (BBB), is mediated by ATP-binding Cassette (ABC) efflux transporters. Many therapeutic drugs inhibit ABC transporters, but little is known of the effect of therapeutic drugs on Aß(1-42) transport across BBB endothelial cells. The effects of selected, widely prescribed, therapeutic drugs on ABCB1, ABCC5 and ABCG2 activities were determined by measuring intracellular levels of calcein, GS-MF, and Hoechst 33342 respectively in primary porcine brain endothelial cells (PBECs). The ability of ABCB1, ABCC5 and ABCG2 to transport Aß(1-42) was determined using fluorescent Aß(1-42). The ability of the ABCB1, ABCC5 and ABCG2 inhibitor telmisartan to modify transcellular Aß(1-42) transport was investigated using PBEC monolayers housed in Transwell® inserts. Treatment of PBECs with ABC transporter inhibitory drugs (indomethacin, olanzapine, chlorpromazine, telmisartan, pantoprazole, quinidine, sulfasalazine and nefazodone) increased Aß(1-42) intracellular accumulation. Inhibition of ABCB1, ABCC5 and ABCG2 by telmisartan increased Aß(1-42) transport in the apical to basal direction and reduced its transport in basal to apical direction in PBEC monolayers. ABCB1, ABCC5 and ABCG2 mediate the efflux transport of Aß(1-42) in BBB endothelial cells. Inhibition of ABC transporters by therapeutic drugs, at plasma concentrations, could decrease Aß(1-42) clearance from brain, across BBB endothelial cells into blood, and potentially influence levels of the Aß(1-42) peptide within the brain.

Effect of amyloid beta on ATP-binding cassette transporter expression and activity in porcine brain microvascular endothelial cells.

BACKGROUND: Deposition of amyloid-ß peptide (Aß(1-42)) within the brain is characteristic of Alzheimer's disease. Little is known of the effects of Aß(1-42) on blood-brain barrier (BBB) ATP-binding Cassette (ABC) efflux transporters which influence BBB permeability. The effects of Aß(1-42) on ABCB1, ABCC5 and ABCG2 activity and expression and pregnane X receptor (PXR) and constitutive androstane receptor (CAR) transcription factors expression were determined in primary porcine brain endothelial cells (PBECs). METHODS: The effect of Aß(1-42) on transporter activity was determined by measurement of intracellular accumulation of the fluorescent probes calcein (ABCB1), GS-MF (ABCC5) and Hoechst 33342 (ABCG2). Expression of transporters and transcription factors was assessed by Western blotting. RESULTS: Treatment of PBECs with Aß(1-42) significantly decreased activity of ABCB1 (Aß(1-42) at 10 µg/ml, 25 µg/ml and 50 µg/ml), ABCC5 (Aß(1-42) at 25 µg/ml and 50 µg/ml) and ABCG2 (Aß(1-42) at 10 µg/ml, 25 µg/ml and 50 µg/ml). Aß(1-42) also significantly decreased expression of ABCB1 (p < 0.05 at 25 µg/ml and 50 µg/ml), ABCG2 (p < 0.05 at 25 µg/ml and p ≤ 0.001 at 50 µg/ml), ABCC5 (p < 0.05 at 25 µg/ml and 50 µg/ml), PXR (p < 0.05 at 10 µg/ml, 25 µg/ml and 50 µg/ml Aß(1-42)) and CAR (p < 0.05 at 25 µg/ml and 50 µg/ml Aß(1-42)). CONCLUSION: Aß(1-42) inhibits multiple ABC transporters and PXR and CAR in PBECs. GENERAL SIGNIFICANCE: Aß(1-42) reduces ABC transporter activity and expression in BBB endothelial cells and has the potential to influence BBB permeability characteristics.

Glucosamine enhances paracetamol bioavailability by reducing its metabolism.

Paracetamol has an extensive first-pass metabolism that highly affects its bioavailability (BA); thus, dose may be repeated several times a day in order to have longer efficacy. However, hepatotoxicity may arise because of paracetamol metabolism. Therefore, this project aimed to increase paracetamol BA in rats by glucosamine (GlcN). At GlcN-paracetamol racemic mixture ratio of 4:1 and paracetamol dose of 10 mg/kg, paracetamol area under the curve (AUC) and maximum concentration (Cmax ) were significantly increased by 99% and 66%, respectively (p < 0.05). Furthermore, paracetamol AUC and Cmax levels were increased by 165% and 88% in rats prefed with GlcN for 2 days (p < 0.001). Moreover, GlcN significantly reduced phase Ι and phase I/ΙΙ metabolic reactions in liver homogenate by 48% and 54%, respectively. Furthermore, GlcN molecule was found to possess a good in silico binding mode into the CYP2E1 active site-forming bidentate hydrogen bonding with the Thr303 side chain. Finally, serum ALT and AST levels of rats-administered high doses of paracetamol were significantly reduced when rats were prefed with GlcN (p < 0.01). In conclusion, GlcN can increase the relative BA of paracetamol through reducing its metabolism. This phenomenon is associated with reduction in hepatocytes injury following ingestion of high doses of paracetamol.