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ONO NT-126 is a potent and selective thromboxane A2 antagonist in human astrocytoma cells
1Department of Pharmacology, Fukushima Medical College, Japan.
Abstract:
Stimulation of thromboxane A2 (TXA2) receptors in human astrocytoma cells (1321N1) results in activation of phospholipase C via a pertussis toxin-insensitive G-protein. In the present study, the potency of a new TXA2 receptor antagonist, ONO NT-126, was examined with regard to receptor binding and phosphoinositide hydrolysis in human astrocytoma cells and was compared to that of the other known TXA2 antagonists. [3H]SQ29548 binding to membranes was inhibited by ONO NT-126 and the other TXA2 antagonists with Ki values (nM) of 0.09, 2.18, 8.35 and 25.9 for ONO NT-126, S-145, SQ29548 and ONO3708, respectively. STA2 and U46619, TXA2 receptor agonists, also inhibited [3H]SQ29548 binding with Ki (nM) of 25.1 and 233.5, respectively. STA2 and U46619 stimulated phosphoinositide hydrolysis in a concentration-dependent manner with EC50 values of 43.6 nM for STA2 and 1.2 microM for U46619, respectively. STA2 (1 microM)-induced phosphoinositide hydrolysis was also inhibited by TXA2 antagonists. The Ki values of TXA2 antagonists for the inhibition of phosphoinositide hydrolysis (nM) were 0.10 for ONO NT-126, 3.31 for S-145, 8.31 for SQ29548 and 19.49 for ONO3708 all of which were similar to those for receptor binding. The results indicate that ONO NT-126 is a potent and selective antagonist of TXA2 receptors in human astrocytoma cells.
Insights
A new thromboxane A2 (TXA2) receptor antagonist, ONO NT-126, shows high potency and selectivity. This compound effectively inhibits TXA2 receptor binding and downstream signaling in human astrocytoma cells.
Area of Science:
- Pharmacology
- Cell Biology
- Biochemistry
Background:
- Thromboxane A2 (TXA2) receptors in human astrocytoma cells activate phospholipase C via a G-protein.
- Understanding TXA2 receptor signaling is crucial for potential therapeutic interventions.
Purpose of the Study:
- To evaluate the potency and selectivity of the novel TXA2 receptor antagonist, ONO NT-126.
- To compare ONO NT-126 with existing TXA2 antagonists in human astrocytoma cells.
Main Methods:
- Radioligand binding assays using [3H]SQ29548 to determine antagonist Ki values.
- Measurement of phosphoinositide hydrolysis stimulated by TXA2 receptor agonists (STA2, U46619).
- Assessing the inhibitory effects of ONO NT-126 and other antagonists on agonist-induced signaling.
Main Results:
- ONO NT-126 demonstrated a high affinity for the TXA2 receptor with a Ki of 0.09 nM.
- ONO NT-126 potently inhibited STA2-induced phosphoinositide hydrolysis (Ki = 0.10 nM), comparable to its receptor binding affinity.
- The antagonist's potency in binding assays and functional assays was superior to other tested TXA2 antagonists.
Conclusions:
- ONO NT-126 is a highly potent and selective antagonist of thromboxane A2 receptors in human astrocytoma cells.
- The findings support ONO NT-126's potential as a therapeutic agent targeting TXA2 receptor-mediated pathways.