Increased ATP production and P-glycoprotein activity underlie the marked changes in blood-brain barrier transport of drugs in a mouse model of amyotrophic lateral sclerosis.

Abstract

Background and purpose: Patients with amyotrophic lateral sclerosis (ALS) are prescribed many medications for symptomatic relief. However, how potential alterations to the blood-brain barrier (BBB) affect the brain exposure of drugs in ALS remains under-investigated.

Experimental approach: We used high-dimensional proteomic analysis, cellular metabolism, and mitochondrial functional assays to characterise isolated brain microvascular endothelial cells (BMECs) from wildtype and SOD1^G93A transgenic mice, a mouse model of familial ALS, at a late-symptomatic age (P115-120), together with a transcardiac brain perfusion technique to assess BBB function in situ.

Key results: The BBB of the SOD1^G93A transgenic (TG) mice was significantly altered, including a 1.3-fold decrease in apparent brain microvascular volume, and decreased BBB transport of ³H-diazepam (1.4-fold) and ³H-2-deoxy-D-glucose (1.2-fold). BMEC proteomic analysis revealed multiple changes in TG mice including altered transmembrane activity, metabolism, and mitochondrial function, as revealed by gene set enrichment analysis, alongside altered glucose transporter (Glut1) abundance. These proteomic findings supported the identified increase in mitochondrial basal/ATP-linked respiration, mitochondrial action potential, ATP production, and intracellular ATP levels in SOD1^G93A mouse BMECs. The BBB transport of ³H-digoxin, a specific ATP-binding cassette efflux P-glycoprotein (P-gp) substrate, was reduced by 11.0% in SOD1^G93A mice. This was confirmed by a 46.7% reduction in BMEC uptake of ³H-digoxin, an observation that was reversed by resolving the hypermetabolic state of SOD1^G93A BMECs.

Conclusion and implications: These findings open possible therapeutic avenues that could be exploited to overcome P-gp-mediated CNS drug resistance in ALS.