title: Selective increase of two ABC drug efflux transporters at the blood-spinal cord barrier suggests induced pharmacoresistance in ALS.
abstract: ATP-binding cassette (ABC) drug efflux transporters in the CNS are predominantly localized to the luminal surface of endothelial cells in capillaries to impede CNS accumulation of xenobiotics. Inflammatory mediators and cellular stressors regulate their activity. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of upper and lower motor neurons characterized by extensive neuroinflammation. Here we tested the hypothesis that disease-driven changes in ABC transporter expression and function occur in ALS. Given the multitude of ABC transporters with their widespread substrate recognition, we began by examining expression levels of several ABC transporters. We found a selective increase in only two transporters: P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) both at mRNA and protein levels, in the SOD1-G93A mouse model of ALS, specifically in disease-affected CNS regions. Detailed analysis revealed a similar disease-driven increase in P-gp and BCRP levels in spinal cord microvessels, indicating that their altered expression occurs at the blood spinal cord barrier. Transport activity of P-gp and BCRP increased with disease progression in spinal cord and cerebral cortex capillaries. Finally, P-gp and BCRP protein expression also increased in spinal cords of ALS patients. Preclinical drug trials in the mouse model of ALS have failed to decisively slow or arrest disease progression; pharmacoresistance imparted by ABC transporters is one possible explanation for these failures. Our observations have large implications for ALS therapeutics in humans and suggest that the obstacle provided by these transporters to drug treatments must be overcome to develop effective ALS pharmacotherapies.
authors.affiliation: Weinberg Unit for ALS Research, Farber Institute for Neuroscience, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Jablonski
authors.forename: Dena A
authors.initials: DA
authors.lastname: Jacob
authors.forename: Christopher
authors.initials: C
authors.lastname: Campos
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Maragakis
authors.forename: Piera
authors.initials: P
authors.lastname: Pasinelli
authors.forename: Davide
authors.initials: D
authors.lastname: Trotti
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism* / Q000473:pathology; D004351:Drug Resistance; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D021381:Protein Transport / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism* / Q000473:pathology
chemical_list: C116614:ABCG2 protein, human; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins