Active transmembrane drug transport in microgravity: a validation study using an ABC transporter model

F1000Res. 2014 Aug 21:3:201. doi: 10.12688/f1000research.4909.1. eCollection 2014.

Abstract

Microgravity has been shown to influence the expression of ABC (ATP-Binding Cassette) transporters in bacteria, fungi and mammals, but also to modify the activity of certain cellular components with structural and functional similarities to ABC transporters. Changes in activity of ABC transporters could lead to important metabolic disorders and undesired pharmacological effects during spaceflights. However, no current means exist to study the functionality of these transporters in microgravity. To this end, a Vesicular Transport Assay (®) (Solvo Biotechnology, Hungary) was adapted to evaluate multi-drug resistance-associated protein 2 (MRP2) trans-membrane estradiol-17-β-glucuronide (E17βG) transport activity, when activated by adenosine-tri-phosphate (ATP) during parabolic flights. Simple diffusion, ATP-independent transport and benzbromarone inhibition were also evaluated. A high accuracy engineering system was designed to perform, monitor and synchronize all procedures. Samples were analysed using a validated high sensitivity drug detection protocol. Experiments were performed in microgravity during parabolic flights, and compared to 1g on ground results using identical equipment and procedures in all cases. Our results revealed that sufficient equipment accuracy and analytical sensitivity were reached to detect transport activity in both gravitational conditions. Additionally, transport activity levels of on ground samples were within commercial transport standards, proving the validity of the methods and equipment used. MRP2 net transport activity was significantly reduced in microgravity, so was signal detected in simple diffusion samples. Ultra-structural changes induced by gravitational stress upon vesicle membranes or transporters could explain the current results, although alternative explanations are possible. Further research is needed to provide a conclusive answer in this regard. Nevertheless, the present validated technology opens new and interesting research lines in biology and human physiology with the potential for significant benefits for both space and terrestrial medicine.

Grants and funding

Schneider Electric (Private entity), granted to Felip Fenollosa - Fundació CIM. Solvo Biotechnology (Private entity), granted to Felip Fenollosa - Fundació CIM. Fundació CIM (Public entity), granted to Felip Fenollosa - Fundació CIM. Institut Municipal d’Investigació Mèdica de Barcelona (IMIM) (Public entity), granted to Rafael de la Torre – IMIM. Lloveras (Private entity), granted to Felip Fenollosa - Fundació CIM. Tecnisample (Private entity), granted to Felip Fenollosa - Fundació CIM. Caixa d’Enginyers (Private entity) granted to Felip Fenollosa - Fundació CIM. Sinerges (Private entity), granted to Felip Fenollosa - Fundació CIM. Col•legi d’Enginyers Tècnics Industrials de Barcelona (Public entity), granted to Felip Fenollosa - Fundació CIM. Interempresas (Private entity), granted to Felip Fenollosa - Fundació CIM. Laboratorio para la Investigación en Espacio y Microgravedad (LEEM) (Public entity), granted to The ABCtr TEAM (SV, EC, AR, AG). Universitat Politècnica de Catalunya (UPC) (Public entity). Grant number: N/A. Granted to: Felip Fenollosa - Fundació CIM. Universitat Autònoma de Barcelona (UAB) (Public entity), granted to Rafael de la Torre – IMIM. European Space Agency via the Education Office and the “Fly your thesis” initiative, Grant number: 9140, granted to The ABCtr TEAM (SV, EC, AR, AG).