Targeting endogenous blood–brain barrier (BBB) transporters such as organic anion transporting polypeptide 1a4 (Oatp1a4) can facilitate drug delivery for treatment of neurological diseases. Advancement of Oatp targeting for optimization of CNS drug delivery requires characterization of sex-specific differences in BBB expression and/or activity of this transporter.
In this study, we investigated sex differences in Oatp1a4 functional expression at the BBB in adult and prepubertal (i.e., 6-week-old) Sprague–Dawley rats. We also performed castration or ovariectomy surgeries to assess the role of gonadal hormones on Oatp1a4 protein expression and transport activity at the BBB. Slco1a4 (i.e., the gene encoding Oatp1a4) mRNA expression and Oatp1a4 protein expression in brain microvessels was determined using quantitative real-time PCR and western blot analysis, respectively. Oatp transport function at the BBB was determined via in situ brain perfusion using [3H]taurocholate and [3H]atorvastatin as probe substrates. Data were expressed as mean ± SD and analyzed via one-way ANOVA followed by the post hoc Bonferroni t-test.
Our results showed increased brain microvascular Slco1a4 mRNA and Oatp1a4 protein expression as well as increased brain uptake of [3H]taurocholate and [3H]atorvastatin in female rats as compared to males. Oatp1a4 expression at the BBB was enhanced in castrated male animals but was not affected by ovariectomy in female animals. In prepubertal rats, no sex-specific differences in brain microvascular Oatp1a4 expression were observed. Brain accumulation of [3H]taurocholate in male rats was increased following castration as compared to controls. In contrast, there was no difference in [3H]taurocholate brain uptake between ovariectomized and control female rats.
These novel data confirm sex-specific differences in BBB Oatp1a4 functional expression, findings that have profound implications for treatment of CNS diseases. Studies are ongoing to fully characterize molecular pathways that regulate sex differences in Oatp1a4 expression and activity.
Thompson BJ, Sanchez-Covarrubias L, Slosky LM, Zhang Y, Laracuente ML, Ronaldson PT. Hypoxia/reoxygenation stress signals an increase in organic anion transporting polypeptide 1a4 (Oatp1a4) at the blood–brain barrier: relevance to CNS drug delivery. J Cereb Blood Flow Metab. 2014;34(4):699–707. PubMedPubMedCentralCrossRef
Abdullahi W, Brzica H, Ibbotson K, Davis TP, Ronaldson PT. Bone morphogenetic protein-9 increases the functional expression of organic anion transporting polypeptide 1a4 at the blood–brain barrier via the activin receptor-like kinase-1 receptor. J Cereb Blood Flow Metab. 2017;37(7):2340–5. PubMedPubMedCentralCrossRef
Liu H, Yu N, Lu S, Ito S, Zhang X, Prasad B, et al. Solute carrier family of the organic anion-transporting polypeptides 1A2-Madin-Darby Canine Kidney II: a promising in vitro system to understand the role of organic anion-transporting polypeptide 1A2 in blood–brain barrier drug penetration. Drug Metab Dispos. 2015;43(7):1008–18. PubMedCrossRef
Alnouti Y, Petrick JS, Klaassen CD. Tissue distribution and ontogeny of organic cation transporters in mice. Drug Metab Dispos. 2006;34(3):477–82. PubMed
Guo GL, Choudhuri S, Klaassen CD. Induction profile of rat organic anion transporting polypeptide 2 (oatp2) by prototypical drug-metabolizing enzyme inducers that activate gene expression through ligand-activated transcription factor pathways. J Pharmacol Exp Ther. 2002;300(1):206–12. PubMedCrossRef
Takasato Y, Rapoport SI, Smith QR. An in situ brain perfusion technique to study cerebrovascular transport in the rat. Am J Physiol. 1984;247(3 Pt 2):H484–93. PubMed
Kamiie J, Ohtsuki S, Iwase R, Ohmine K, Katsukura Y, Yanai K, et al. Quantitative atlas of membrane transporter proteins: development and application of a highly sensitive simultaneous LC/MS/MS method combined with novel in silico peptide selection criteria. Pharm Res. 2008;25(6):1469–83. PubMedCrossRef
Ohtsuki S, Tomi M, Hata T, Nagai Y, Hori S, Mori S, et al. Dominant expression of androgen receptors and their functional regulation of organic anion transporter 3 in rat brain capillary endothelial cells; comparison of gene expression between the blood–brain and –retinal barriers. J Cell Physiol. 2005;204(3):896–900. PubMedCrossRef
- Sex-specific differences in organic anion transporting polypeptide 1a4 (Oatp1a4) functional expression at the blood–brain barrier in Sprague–Dawley rats
Bianca G. Reilly
Patrick T. Ronaldson
- BioMed Central
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