scholarly journals Metabolism of cyclic GMP in peritoneal macrophages of rat and guinea pig.

2003 ◽  
Vol 50 (3) ◽  
pp. 837-847 ◽  
Author(s):  
Marcin Kobiałka ◽  
Hanna Witwicka ◽  
Jakub Siednienko ◽  
Wojciech A Gorczyca
Keyword(s):  
Protein Kinase ◽  
Guinea Pig ◽  
Active Form ◽  
Soluble Guanylyl Cyclase ◽  
Peritoneal Macrophages ◽  
Dependent Protein Kinase ◽  
Cgmp Dependent Protein Kinase ◽  
Cgmp Pathway ◽  
Dependent Protein ◽  
Species Specific

The aim of our studies was to establish which enzymes constitute the "cGMP pathway" in rat and guinea pig peritoneal macrophages (PM). We found that in guinea pig PM synthesis of the nucleotide was significantly enhanced in response to activators of soluble guanylyl cyclase (sGC) and it was only slightly stimulated by specific activators of particulate guanylyl cyclases (pGC). In contrast, rat PM responded strongly to atrial natriuretic peptide (ANP), the activator of pGC type A. The rat cells synthesized about three-fold more cGMP than an equal number of the guinea pig cells. The activity of phosphodiesterases (PDE) hydrolyzing cGMP was apparently regulated by cGMP itself in PM of both species and again it was higher in the rat cells than in those isolated from guinea pig. However, guinea pig PM revealed an activity of Ca(2+)/calmodulin-dependent PDE1, which was absent in the rat cells. Using Western blotting analysis we were unable to detect the presence of cGMP-dependent protein kinase 1 (PKG1) in PM isolated from either species. In summary, our findings indicate that particulate GC-A is the main active form of GC in the rat PM, while in guinea pig macrophages the sGC activity dominates. Since the profiles of the PDE activities in rat and guinea pig PM are also different, we conclude that the mechanisms regulating cGMP metabolism in PM are species-specific. Moreover, our results suggest that targets for cGMP other than PKG1 should be present in PM of both species.

Intrathecally Administered cGMP-dependent Protein Kinase Iα Inhibitor Significantly Reduced the Threshold for Isoflurane Anesthesia

2000 ◽  
Vol 92 (2) ◽  
pp. 493-493 ◽  
Author(s):  
Yuan-Xiang Tao ◽  
Aalya Hassan ◽  
Roger A. Johns
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Protein Kinase ◽  
Guanosine Monophosphate ◽  
Dependent Protein Kinase ◽  
No Donor ◽  
Cgmp Dependent Protein Kinase ◽  
Significant Reversal ◽  
Cgmp Pathway ◽  
Dependent Protein

Background Inhalational anesthetics have been shown to inhibit the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway. Previous studies indicated that inhibition of the NO-cGMP pathway decreased the level of consciousness and augmented anesthesia, analgesia, or sedation. The current study investigated the possible involvement of cGMP-dependent protein kinases (PKGs) as major effectors for the NO-cGMP pathway in the anesthetic state. Methods After initial baseline determination of the minimum alveolar concentration (MAC), a selective cGMP-dependent protein kinase Ialpha inhibitor, Rp-8-p-CPT-cGMPS, or an NO donor, (NOC-12), were injected intrathecally. Ten minutes later, MAC measurement was repeated. The rats also were evaluated for the presence of locomotor dysfunction by intrathecal administration of Rp-8-p-CPT-cGMPS and NOC-12 in conscious rats. Results Rp-8-p-CPT-cGMPS at 25, 50, 100, and 200 microg/10 microl produced a significant decrease from isoflurane control MAC of -4+/-3.1%, 16+/-4.5%, 30+/-5.0%, and 21+/-2.2%, respectively, which was not accompanied by significant changes in either blood pressure or heart rate. In contrast, NOC-12 at 100 microg/10 microl caused an increase from isoflurane control MAC of 23+/-5.8%, which was accompanied by significant decrease in blood pressure but not in heart rate. Rp-8-p-CPT-cGMPS (100 microg/10 microl) produced a significant reversal of isoflurane MAC increase induced by NOC-12 (100 microg/10 microl), which was accompanied by significant reversal of the reduction of blood pressure induced by NOC-12. Locomotor activity was not changed. Conclusions The results indicate that cGMP-dependent protein kinase Ialpha inhibitor not only markedly reduces MAC for isoflurane, but also completely blocks the NO-induced increase in isoflurane MAC, which suggests that cGMP-dependent protein kinase Ialpha may mediate the action for the NO-cGMP pathway in anesthetic mechanisms at the spinal cord level.

AKT Mediates Platelet Activation by Stimulating Nitric Oxide Synthesis and cGMP Elevation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1652-1652
Author(s):  
Aleksandra Stojanovic ◽  
Jasna A. Marjanovic ◽  
Viktor Brokovych ◽  
Randal A. Skidgel ◽  
Nissim Hay ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Protein Kinase ◽  
Platelet Activation ◽  
Critical Role ◽  
Dependent Protein Kinase ◽  
Cgmp Dependent Protein Kinase ◽  
Low Concentrations ◽  
Cgmp Pathway ◽  
Dependent Protein ◽  
Platelet Secretion

Abstract Phosphoinositide 3-kinase (PI3-K) and Akt play important roles in platelet activation. However, the downstream mechanisms for their roles are unclear. We have recently shown that nitric oxide (NO) synthase 3 (NOS3) and cGMP-dependent protein kinase stimulate platelet secretion and aggregation. Here we show that PI3-K-mediated Akt activation plays a critical role in agonist-stimulated platelet NO synthesis and cGMP elevation. Agonist-induced elevation of NO and cGMP was inhibited by Akt inhibitors and reduced in Akt-1 knockout platelets. Akt-1 knockout or Akt inhibitor-treated platelets showed reduced platelet secretion and aggregation in response to low concentrations of agonists, which can be reversed by low concentrations of sodium nitroprusside (SNP) or cGMP analogs. Similarly, PI3-K inhibitors diminished elevation of cGMP and also inhibited platelet secretion and the second-wave platelet aggregation, which was also partially reversed by cGMP analogs and by SNP. These results indicate that the NO-cGMP pathway is an important downstream mechanism mediating PI3-K and Akt signals leading to platelet secretion and aggregation. Conversely, the PI3-K-Akt pathway is a major upstream mechanism responsible for activating the NO-cGMP pathway. Thus, this study delineates a novel platelet activation pathway involving sequential activation of PI3-K, Akt, NOS3, sGC, and cGMP-dependent protein kinase.

scholarly journals The NO/cGMP pathway inhibits Rap1 activation in human platelets via cGMP-dependent protein kinase I

2005 ◽  
Vol 93 (02) ◽  
pp. 319-325 ◽  
Author(s):  
Oliver Danielewski ◽  
Jan Schultess ◽  
Albert Smolenski
Keyword(s):  
Protein Kinase ◽  
Molecular Mechanisms ◽  
Soluble Guanylyl Cyclase ◽  
Human Platelets ◽  
Dependent Protein Kinase ◽  
No Donors ◽  
Cgmp Dependent Protein Kinase ◽  
Cgmp Analog ◽  
Dependent Protein ◽  
Rap1 Activation

SummaryThe NO/cGMP signalling pathway strongly inhibits agonist-induced platelet aggregation. However, the molecular mechanisms involved are not completely defined. We have studied NO/cGMP effects on the activity of Rap1, an abundant guanine-nucleotidebinding protein in platelets. Rap1-GTP levels were reduced by NO-donors and activators of NO-sensitive soluble guanylyl cyclase. Four lines of evidence suggest that NO/cGMP effects are mediated by cGMP-dependent protein kinase (cGKI): (i) Rap1 inhibition correlated with cGKI activity as measured by the phosphorylation state ofVASP, an established substrate of cGKI, (ii) 8-pCPT-cGMP, a membrane permeable cGMP-analog and activator of cGKI, completely blocked Rap1 activation, (iii) Rp- 8pCPT-cGMPS, a cGKI inhibitor, reversed NO effects and (iv) expression of cGKI in cGKI-deficient megakaryocytes inhibited Rap1 activation. NO/cGMP/cGKI effects were independent of the type of stimulus used for Rap1 activation. Thrombin-,ADPand collagen-induced formation of Rap1-GTP in platelets as well as turbulence-induced Rap1 activation in megakaryocytes were inhibited. Furthermore, cGKI inhibited ADP-induced Rap1 activation induced by the G α i -coupled P2Y12 receptor alone, i.e. independently of effects on Ca2+-signalling. From these studies we conclude that NO/cGMP inhibit Rap1 activation in human platelets and that this effect is mediated by cGKI. Since Rap1 controls the function of integrin α IIbβ 3 , we propose that Rap1 inhibition might play a central role in the anti-aggregatory actions of NO/cGMP.

Sign in / Sign up

Export Citation Format

Share Document