Chromosomal mapping of the mouse A3 adenosine receptor gene, Adora3

Exploring the directionality of 5-substitutions in a new series of 5-alkylaminopyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine as a strategy to design novel human a(3) adenosine receptor antagonists

The structure-activity relationship (SAR) of new 5-alkylaminopyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines as antagonists of the A(3) adenosine receptor (AR) was explored with the principal aim to establish the directionality of 5-substitutions inside the orthosteric binding site of the A(3) AR. All the synthesized compounds showed affinity for the hA(3) AR from nanomolar to subnanomolar range. In particular, the most potent and selective antagonist presents an (S) α-phenylethylamino moiety at the 5 position (26, K(i) hA(3) = 0.3 nM). Using an in silico receptor-driven approach, we have determined the most favorable orientation of the substitutions at the 5 position of the pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (PTP) scaffold, opening the possibility for further derivatizations aimed at directing the N(5) position toward the extracellular environment.

Cordycepin stimulated steroidogenesis in MA-10 mouse Leydig tumor cells through the protein kinase C Pathway

Cordycepin (3'-deoxyadenosine) is an adenosine analogue isolated from Cordyceps sinensis , which is a Chinese herbal medicine known to have many benefits, including adjustment of the physical condition, an anticancer effect, and enhancement of sexual performance. It was previously demonstrated that cordycepin could simultaneously activate steroidogenesis and apoptosis in MA-10 mouse Leydig tumor cells. However, the mechanism remains elusive. Thus, aim of the present study was to investigate the steroidogenic and apoptotic mechanism of cordycepin in MA-10 cells. MA-10 cells were treated with cordycepin at various dosages and time courses plus different protein kinase inhibitors. Steroid production, protein expression, and cell viability were then determined. Results illustrated that cordycepin stimulated MA-10 cell steroidogenesis in dose- and time-dependent relationships. However, cordycepin could not induce steroidogenic acute regulatory (StAR) protein expression. However, cordycepin did activate the phospholipase C/protein kinase C (PLC/PKC), but not PKA and PI3K, pathway to induce MA-10 cell steroidogenesis. Moreover, cordycepin could stimulate the phosphorylation of PKC, extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun N-terminal kinase (c-JNK), but not p38, in MA-10 cells. In addition, cordycepin could activate the PKC pathway to induce MA-10 cell death, and this death effect was not caused by cordycepin-stimulated progesterone from MA-10 cells. In conclusion, cordycepin stimulated intracellular PLC/PKC and MAPK signal transduction pathways to induce steroidogenesis and cell death in MA-10 mouse Leydig tumor cells.

Inhibition of renal Na+-ATPase activity by inosine is mediated by A1 receptor-induced inhibition of the cAMP signaling pathway

We have previously demonstrated that adenosine is deaminated to inosine in the isolated basolateral membrane (BLM) of kidney proximal tubules. This work investigates the possible effect of inosine on proximal tubule Na(+)-ATPase activity. Inosine reduced Na(+)-ATPase activity by 70%. This effect of inosine was completely attenuated by 10(-8) M DPCPX, an A(1) receptor-selective antagonist, but it was not affected by either 10(-8) M DMPX or 10(-7) M MRS1523, A(2) and A(3) receptor-selective antagonists, respectively. The inhibitory effect of inosine was blocked by: (1) 10(-6) M GDPbetaS, a trimeric G protein inhibitor; (2) 1microg/ml pertussis toxin, a Gi protein inhibitor; (3) 10(-6) M forskolin, an adenylyl cyclase activator; (4) 10(-9) M cholera toxin, a Gs protein activator; (5) 10(-6)M cAMP. Our results demonstrate that the inhibitory effect of inosine on the sodium pump is mediated by the A(1) receptor/Gi/cAMP pathway.