Abstract 526: Organic Anion Transporting Peptide 2B1, a High Affinity Transporter for Atorvastatin, is Expressed in Plasma Membranes of Human Platelets, Indicating a Role in Drug Uptake
Background & Aim: Effects of statins other than low-density lipoprotein lowering effects include reduced platelet aggregation, which requires drug uptake into platelets. Possible candidates for transport proteins mediating intra-platelet accumulation of these drugs include the organic anion transporting peptide 2B1 (OATP2B1, SLCO2B1), an uptake transporter for sulfated steroids and drugs including atorvastatin, as a high affinity substrate.
Methods & Results: We analyzed OATP2B1 expression, localization and function in platelets. The protein was detected by immunoblotting showing a strong signal at 85 kDa. Localization was analysed applying a new immunomagnetic separation method using structure-specific antibodies in combination with magnetic beads. OATP2B1 detection was highest in the plasma membrane fraction. In addition, immunoflourescent co-staining of OATP2B1 and organelle-specific proteins reveal a predominant co-localisation with plasma membrane markers. Functionally, we could demonstrate a significant reduction of uptake of the OATP2B1 substrate estrone sulfate into platelets in presence of atorvastatin (74 ± 14.5 % of control at 100 μM; P < 0.05) suggesting a functional role of OATP2B1. As a consequence of OATP2B1 mediated uptake of atorvastatin, we demonstrated a significant effect of atorvastatin on the store-regulated Ca2+ release in human platelets (37.3 ± 6.7 % of control at 15 μM; p<0.05). This effect was significantly reduced by addition of the OATP2B1 substrate estrone sulfate (10 μM) (from 44.8 ± 14.2 % to 68.6 ± 1.6 % of control at 10 μM atovastatin). Accordingly expression of HMG-CoA reductase, the primary target of statins, was detected in the cytosol of platelets.
Conclusions: The atorvastin transporter OATP2B1 is expressed in the plasma membrane of human platelets affecting platelet aggregation.