BML-241 fails to display selective antagonism at the sphingosine-1-phosphate receptor, S1P(3).
OBJECTIVE
The thiazolidine carboxylic acid, BML-241, has been proposed as a lead compound in development of selective antagonists at the sphingosine-1-phosphate receptor (S1P3), based on its inhibition of the rise in intracellular calcium concentrations ([Ca2+]i) in HeLa cells overexpressing S1P receptors. We have studied the antagonistic properties of BML-241 for the S1P(3) receptor in more detail.


METHODS
Chinese hamster ovary (CHO) cells stably transfected with the S1P3, S1P2 or alpha(1A)-adrenoceptors were used to investigate the effect of BML-241 on increases in [Ca2+]i mediated via different receptors. CHO-K1 cells were used to study ATP-induced [Ca2+]i elevations. Effects on S1P3 -mediated inhibition of forskolin-induced cAMP accumulation and on binding to alpha(1A)-adrenoceptors were also investigated. In addition, the effect of BML-241 on contractions of rat mesenteric artery induced by phenylephrine was studied in an organ bath.


RESULTS
High concentrations of BML-241 (10 microM) inhibited the rise in [Ca2+]i induced by S1P3 and S1P2 receptor stimulation; lower concentrations were ineffective. This high concentration of BML-241 also inhibited [Ca2+]i increases via P2 (nucleotide) receptor or alpha(1A)-adrenoceptor stimulation. Moreover, BML-241 (10 microM) inhibited alpha(1)-adrenoceptor-mediated contraction of rat mesenteric artery but did not displace [3H]-prazosin from alpha(1A)-adrenoceptors in concentrations up to 100 microM. BML-241 (10 microM) did not affect the S1P3 -mediated decrease of forskolin-induced cAMP accumulation.


CONCLUSIONS
We conclude that BML-241 is a low potency, non-selective inhibitor of increases in [Ca2+]i, rather than a specific antagonist at the S1P3 receptor.
Jongsma
M
M
Department of Pharmacology & Pharmacotherapy, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Hendriks-Balk
M C
MC
Michel
M C
MC
Peters
S L M
SL
Alewijnse
A E
AE
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects; D049349:Receptors, Lysosphingolipid / Q000037:antagonists & inhibitors*; D018048:Receptors, Purinergic P2 / Q000187:drug effects; D053778:Thiazolidines / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
C515031:BML 241; D018340:Receptors, Adrenergic, alpha-1; D049349:Receptors, Lysosphingolipid; D018048:Receptors, Purinergic P2; D053778:Thiazolidines; D000242:Cyclic AMP; D002118:Calcium; D011224:Prazosin