https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1538-7836.2004.01063.x

Flow cytometric analysis of intraplatelet VASP phosphorylation for the detection of clopidogrel resistance in patients with ischemic cardiovascular diseases.

An overview of the history of studies of the biological actions of extracellular ATP is presented. The basis of the subdivision of receptors for purines into P1-purinoceptors for adenosine and P2-purinoceptors for ATP and ADP are considered, as well as the recent proposal for subdivision of the ATP receptors into P2X-, P2Y-, P2Z-, and P2T- purinoceptor subtypes. These purinoceptor subtypes are discussed with respect to their transduction mechanisms, their distribution, and their physiological roles, including their roles in cotransmission and neuromodulation.

Overview. Purinergic mechanisms.

Nitric oxide (NO) and angiotensin II (AII) can effect vascular smooth muscle cell (SMC) proliferation. However, the effects of such agents on SMC migration, an equally important phenomenon with regard to vascular pathophysiology, have received little attention. The objectives of the present study were: (a) to determine whether NO inhibits AII-induced migration of vascular SMCs; (b) to investigate the mechanism of the interaction of NO and AII on SMC migration; and (c) to evaluate the AII receptor subtype that mediates AII-induced SMC migration. Migration of rat SMCs was evaluated using a modified Boydens Chamber (transwell inserts with gelatin-coated polycarbonate membranes, 8 microns pore size). AII stimulated SMC migration in a concentration-dependent manner, and this effect was inhibited by sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP). In the presence of L-arginine, but not D-arginine, IL-1 beta, an inducer of inducible NO synthase, also inhibited AII-induced SMC migration, and this effect was prevented by the NO-synthase inhibitor, N-nitro-L-arginine methyl ester. The effects of NO donors on AII-induced SMC migration were mimicked by 8-bromo-cGMP. Also, the antimigratory effects of SNAP were partially inhibited by LY83583 (an inhibitor of soluble guanylyl cyclase) and by KT5823 (an inhibitor of cGMP-dependent protein kinase). Although 8-bromo-cAMP (cAMP) also mimicked the antimigratory effects of NO donors, the antimigratory effects of SNAP were not altered by 2',5'-dideoxyadenosine (an inhibitor of adenyl cyclase) or by (R)-p-adenosine-3',5'-cyclic phosphorothioate (an inhibitor of the cAMP-dependent protein kinase). Low concentrations of the subtype AT1-receptor antagonist CGP 48933, but not the subtype AT2-receptor antagonist CGP 42112, blocked AII-induced SMC migration. These findings indicate that (a) NO inhibits AII-induced migration of vascular SMCs; (b) the antimigratory effect of NO is mediated in part via a cGMP-dependent mechanism; and (c) AII stimulates SMC migration via an AT1 receptor.

/pdf/nitric-oxide-inhibits-angiotensin-ii-induced-migration-of-30vwmwmmct.pdf

Nitric oxide inhibits angiotensin II-induced migration of rat aortic smooth muscle cell. Role of cyclic-nucleotides and angiotensin1 receptors.

The field EPSP recorded in the CA1 region of rat hippocampal slices is potentiated by bath application of the direct adenylate cyclase activator forskolin (Chavez-Noriega and Stevens, 1992a) We have now used the whole-cell patch-clamp technique to analyze the effect of forskolin on evoked synaptic currents and on spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) recorded in rat hippocampal slices in order to determine the relative contributions of pre- and postsynaptic mechanisms to this increased synaptic strength Application of 50 microM forskolin in the presence of 3-isobutyl-1-methylxanthine (IBMX; a phosphodiesterase inhibitor) enhanced the evoked EPSC (eEPSC) peak amplitude to 230 +/- 43% of control (n = 13) No significant change in sEPSC or in mEPSC amplitude was detected after forskolin addition (106 +/- 7%, n = 9), indicating that postsynaptic receptor sensitivity at synaptic junctions is not greatly affected In contrast, a large increase in sEPSC and mEPSC frequency was noted in all cells (299 +/- 81%) Following forskolin application, the amplitude distribution of evoked synaptic currents shifted to larger values, but more significantly, a sharp decrease in failure rate was produced in all cells tested Also, a significant correlation was found between the potentiation produced by forskolin in IBMX on the eEPSC and the ratio of the squared coefficient of variation (CV = SD/mean) Finally, a quantal analysis of four cells was consistent with the hypothesis that transmitter release was increased by forskolin/IBMX with, if anything, a concomitant decrease in quantal size Together, these observations indicate that presynaptic mechanisms significantly contribute to the enhancement produced by this diterpene(ABSTRACT TRUNCATED AT 250 WORDS)

https://www.jneurosci.org/content/jneuro/14/1/310.full.pdf

Increased transmitter release at excitatory synapses produced by direct activation of adenylate cyclase in rat hippocampal slices

Upon activation, brain microglial cells release proinflammatory mediators, such as TNFalpha, which may play an important role in eliciting neuroinflammatory processes causing brain damage. As cannabinoids have been reported to exert anti-inflammatory and neuroprotective actions in the brain, we here examined the effect of both synthetic and endogenous cannabinoids on TNFalpha release elicited by bacterial endotoxin lypopolysaccharide (LPS) in cultured microglia. Exposure of primary cultures of rat cortical microglial cells to LPS significantly stimulated TNFalpha mRNA expression and release. The endogenous cannabinoids anandamide and 2-arachidonylglycerol (2-AG), as well as the synthetic cannabinoids (+)WIN 55,212-2, CP 55,940, and HU210, inhibited in a concentration-dependent manner (1-10 microM) the LPS-induced TNFalpha release. Unlike the high-affinity cannabinoid receptor agonist (+)WIN 55,212-2, the low-affinity stereoisomer (-)WIN 55,212-2 did not exert any significant inhibition on TNFalpha release. Given this stereoselectivity, the ability of (+)WIN 55,212-2 to inhibit LPS-induced TNFalpha release from microglia is most likely receptor-mediated. By RT-PCR we found that the two G(i/o) protein-coupled cannabinoid receptors (type 1 and 2) are both expressed in microglial cultures. However, selective antagonists of type 1 (SR141716A and AM251) and type 2 (SR144528) cannabinoid receptors did not affect the effect of (+)WIN 55,212-2. Consistent with this finding is the observation that the ablative effect of (+)WIN 55,212-2 on LPS-evoked release of TNFalpha was not sensitive to the G(i/o) protein inactivator pertussis toxin. In addition, the cAMP elevating agents dibutyryl cAMP and forskolin both abolished LPS-induced TNFalpha release, thus rendering unlikely the possibility that (+)WIN 55,212-2 could ablate TNFalpha release through the inhibition of adenylate cyclase via the G(i)-coupled cannabinoid receptors type 1 and 2. In summary, our data indicate that both synthetic and endogenous cannabinoids inhibit LPS-induced release of TNFalpha from microglial cells. By showing that such effect does not appear to be mediated by either CB receptor type 1 or 2, we provide evidence suggestive of the existence of yet unidentified cannabinoid receptor(s) in brain microglia.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/glia.10177

Cannabinoids ablate release of TNFalpha in rat microglial cells stimulated with lypopolysaccharide.

Whereas adenosine itself exerted independent stimulatory and inhibitory effects on the adenylate cyclase activity of a platelet particulate fraction at low and high concentrations respectively, 2-substituted and N6-monosubstituted adenosines had stimulatory but greatly decreased inhibitory effects. Deoxyadenosines, on the other hand, had enhanced inhibitory but no stimulatory effects. The most potent inhibitors found were, in order of increasing activity, 9-(tetrahydro-2-furyl)adenine (SQ 22536), 2',5'-dideoxyadenosine and 2'-deoxyadenosine 3'-monophosphate. Kinetic studies on prostaglandin E1-activated adenylate cyclase showed that the inhibition caused by either 2',5'-dideoxyadenosine or compound SQ 22536 was non-competitive with MgATP and that the former compound, at least, showed negative co-operativity; 50% inhibition was observed with 4 micron-2',5'-dideoxyadenosine or 13 micron-SQ 22536. These two compounds also inhibited both the basal and prostaglandin E1-activated adenylate cyclase activities of intact platelets, when these were measured as the increases in cyclic [3H]AMP in platelets that had been labelled with [3H]adenine and were then incubated briefly with papaverine or papaverine and prostaglandin E1. Both compounds, but particularly 2',5'-dideoxyadenosine, markedly decreased the inhibition by prostaglandin E1 of platelet aggregation induced by ADP or [arginine]vasopressin as well as the associated increases in platelet cyclic AMP, so providing further evidence that the effects of prostaglandin E1 on platelet aggregation are mediated by cyclic AMP. 2'-Deoxyadenosine 3'-monophosphate did not affect the inhibition of aggregation by prostaglandin E1, suggesting that the site of action of deoxyadenosine derivatives on adenylate cyclase is intracellular. Neither 2',5'-dideoxyadenosine nor compound SQ 22536 alone induced platelet aggregation. Moreover, neither compound potentiated platelet aggregation or the platelet release reaction when suboptimal concentrations of ADP, [arginine]vasopressin, collagen or arachidonate were added to heparinized or citrated platelet-rich plasma in the absence of prostaglandin E1. These results show that cyclic AMP plays no significant role in the responses of platelets to aggregating agents in the absence of compounds that increase the platelet cyclic AMP concentration above the resting value.

/pdf/inhibition-of-adenylate-cyclase-by-adenosine-analogues-in-1ttj7ephhu.pdf

Inhibition of adenylate cyclase by adenosine analogues in preparations of broken and intact human platelets. Evidence for the unidirectional control of platelet function by cyclic AMP.

/pdf/role-of-cyclic-amp-in-platelet-function-evidence-from-1cp95b1uvp.pdf

M. M. L. Davidson

Papers

Inhibition of adenylate cyclase by adenosine analogues in preparations of broken and intact human platelets. Evidence for the unidirectional control of platelet function by cyclic AMP.

Role of Cyclic Amp in Platelet Function : Evidence from Inhibition of Adenylate Cyclase in Intact Platelets by Adenosine Analogues