Péter Lakatos, Dániel Tóka, Fruzsina Bagaméry, Tamás Tábi, Éva Szökő
Department of Pharmacodynamics, Semmelweis University, Budapest, Hungary
Introduction: D-serine is a co-agonist of glutamatergic NMDA receptor. Hypofunction of NMDA receptors has been studied in several central nervous system diseases, e.g. schizophrenia and bipolar disorder. Decreased level of D-serine may play an important role in the pathophysiological mechanisms. Different transport systems modulate extracellular D-serine concentration, inclusive of sodium dependent ASCT1 and 2, as well as sodium-independent asc1.
Aims: Characterization of D-serine uptake in SH-SY5Y neuroblastoma cell line and comparison to primary astrocytes.
Method: Cells were incubated with different concentrations of D-serine. The intracellular concentration was measured by a capillary electrophoresis – laser induced fluorescence detection method developed in our laboratory. The effect of various amino acids and sodium-free environment on the D-serine uptake was investigated. Data was evaluated by OriginPro 8 SRO v8.0724 software.
Results: Time- and dose dependent D-serine uptake to both cell types was observed. Main transport form was found sodium-dependent since in sodium-free environment about 80% less D-serine uptake was measured. D-serine uptake was concentration dependently inhibited by neutral amino acids, substrates of these transporters. In case of L-alanine and L-threonine a two-step inhibition characteristic was noticed in both cell types. Previously L-glutamine was reported as a preferential inhibitor of ASCT2. However it caused complete inhibition in two steps in SH-SY5Y cells and astrocytes alike similarly to the other examined neutral amino acids. Recent data show that ASCT1 can be selectively inhibited by trans-4-hydroxy-L-proline (t-proline). In both cell types D-serine uptake was moderately inhibited in two steps by t-proline. In its selective concentration range t-proline reduced D-serine transport by about 30%, which supposedly related to ASCT1 transporter.
Conclusion: The characteristic of D-serine uptake was similar in both cell types. Mainly sodium-dependent D-serine transport was observed and at least two transporter systems are considered to be responsible for it.
Doctoral School of Pharmaceutical Sciences
Experimental and Clinical Pharmacology
Supervisor: Éva Szökő