Diadenosine pentaphosphate pentaammonium, an endogenous vasoactive purine dinucleotide isolated from thrombocytes, is one component of the diadenosine polyphosphates (ApnA, n=2-7) family. These compounds are found in secretory vesicles, including those in platelets, chromaffin cells, Torpedo synaptic terminals, and brain synaptosomes[1][2].
The group IVA phospholipase A2 (PLA2), known as calcium-dependent cytosolic PLA2 (cPLA2), selectively releases arachidonic acid (AA) from membrane phospholipids, playing a central role in initiating the synthesis of prostaglandins (PGs) and leukotrienes (LTs). Pyrrophenone inhibits cPLA2α with an IC50 of 4.2 nM in enzyme assays and potently blocks the release of AA and the production of PGE2 and LTC4 in cells (IC50 = 24, 25, and 14 nM, respectively). Its action is reversible and selective, as pyrrophenone inhibits the secretory type IB and IIA PLA2s with more than a hundred-fold less potency. Pyrrophenone has also been shown to inhibit calcium ionophore (A23187)-stimulated AA release from monocytic cells, interleukin-1-induced PGE2 synthesis in mesangial cells, and the production of PGE2, LTs, and platelet-activating factor by human neutrophils, always with maximal inhibition at concentrations below 1 μM.
Varespladib sodium (LY315920 sodium) is a highly potent and selective inhibitor of group IIA secretory phospholipase A2 (sPLA2), with an IC50 of 9 nM. It demonstrates significant inhibitory activity against sPLA2 in serum samples from multiple species, including rat, rabbit, guinea pig, and human, with IC50 values of 8.1 nM, 5.0 nM, 3.2 nM, and 6.2 nM, respectively.
CRA-2059 hydrochloride is a highly specific and selective tryptase inhibitor, with a Ki of 620 pM for recombinant human tryptase-β (rHTβ)[1][2]. Tryptase is a trypsin-like serine protease found as a major protein component in human mast cell secretory granules. CRA-2059 hydrochloride has the potential for inflammatory bowel disease research[1]. [1]. Tremaine WJ, et al. Treatment of mildly to moderately active ulcerative colitis with a tryptase inhibitor (APC 2059): an open-label pilot study. Aliment Pharmacol Ther. 2002;16(3):407-413.[2]. Selwood T, et al. Potent bivalent inhibition of human tryptase-beta by a synthetic inhibitor. Biol Chem. 2003;384(12):1605-1611.