cyclic-gmp and propentofylline

We evaluated the vasorelaxant effect of propentofylline (PPF), a methylxanthine derivative, and its mechanism of action in equine digital veins (EDVs). Cumulative concentration-response curves to PPF (1 nM-300 µM) were recorded in phenylephrine-precontracted EDV rings under different experimental conditions. PPF-induced relaxation was partially inhibited by endothelium removal, but was unaltered by CGS-15943 (an adenosine receptor antagonist; 3 µM). PPF-induced relaxation was partially inhibited in the presence of L-NAME (a nitric oxide (NO) synthase inhibitor; 100 µM), ODQ (an inhibitor of soluble guanylyl cyclase; 30 µM) or Rp-8-Br-PET-cGMP-S (a protein kinase G inhibitor; 3 µM). It was not modified by indomethacin (a non-selective cyclooxygenase (COX) inhibitor; 10 µM), and was slightly potentiated by H-89 (a protein kinase A inhibitor; 2 µM). In endothelium-intact EDVs, PPF-induced relaxation was associated with a 2.4- and 24.1-fold increase in the tissue cGMP and cAMP content respectively. PPF (100 μM) did not shift the concentration-response curve to phenylephrine (1 nM-300 µM) but reduced the maximal effect. To investigate whether PPF can affect cAMP- and cGMP-induced relaxations, relaxation curves to forskolin (an activator of adenylate cyclase) and to sodium nitroprusside (SNP, a NO donor) were recorded in EDV rings pretreated with PPF (100 µM). PPF only slightly potentiated the forskolin-induced relaxation without affecting the SNP-induced relaxation. We demonstrated that PPF-induced relaxation in EDVs is partially endothelium-dependent. The PPF-induced relaxation partially occurred via NO release and both cAMP and cGMP generation, through COX-independent mechanisms but could also result from the inhibition of cAMP-phosphodiesterase activity for the highest concentrations.

Topics: Animals; Colforsin; Cyclic AMP; Cyclic GMP; Endothelium; Forelimb; Horses; In Vitro Techniques; Nitroprusside; Phenylephrine; Receptors, Purinergic P1; Vasoconstriction; Vasodilation; Vasodilator Agents; Veins; Xanthines

The effect of intracellular cyclic guanosine monophosphate (GMP) increase on neuronal damage was tested using a newly developed nitric oxide-related injury model of cultured spinal cord neurons.. Neuronal damage after 24-hour-exposure to sodium nitroprusside (SNP), a nitric oxide (NO) donor, was evaluated by measuring the activity of released lactate dehydrogenase from injured neurons.. Oxygen radical scavengers had a protective effect, indicating that the neuronal damage, elicited by 10 μM SNP, was largely due to peroxynitrite formation. Alternatively, a strong inhibition of the NO-induced damage could also be achieved by an intracellular cyclic GMP increase resulting from the addition of 100 μM 8-bromo-cyclic GMP. Propentofylline (PPF, 1-100 μM), a xanthine derivative and rather selective phosphodiesterase (PDE) inhibitor, enhanced intracellular cyclic GMP elevation induced by SNP exposure. The neuronal damage induced by 10 μM SNP exposure for 24 hours was almost completely blocked in the presence of 1 μM PPF.. These results suggest that NO has an ambiguous action, i.e. toxic by favoring the formation of, but protective by intracellular cyclic GMP elevation which can be reinforced by PDE inhibition. Therefore, PDE inhibitors, such as PPF, may be useful therapeutic drugs to limit oxidative neuronal damage in the central nervous system.

Topics: Analysis of Variance; Animals; Animals, Newborn; Apoptosis; Cells, Cultured; Cyclic GMP; Dose-Response Relationship, Drug; Drug Interactions; In Situ Nick-End Labeling; L-Lactate Dehydrogenase; Neurons; Neuroprotective Agents; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Rats; Rats, Wistar; Spinal Cord; Xanthines

Hyaluronan must be exported from its site of synthesis, the inner side of plasma membrane, to the extracellular matrix. Here, we identified the multidrug-associated protein MRP5 as the principle hyaluronan exporter from fibroblasts. The expression of the MRP5 (ABC-C5) transporter was silenced in fibroblasts using RNA interference, and a dose-dependent inhibition of hyaluronan export was observed. Hyaluronan oligosaccharides introduced into the cytosol competed with the export of endogenously labeled hyaluronan and the MRP5 substrate fluorescein. Because cGMP is a physiological substrate of MRP5, the intracellular concentrations of cGMP were modulated by the drugs 3-isobutyl-1-methylxanthin, propentofyllin, L-NAME, zaprinast, and bromo-cGMP, and the effects on hyaluronan export were analyzed. Increasing the cGMP levels inhibited hyaluronan export and decreasing it afforded higher concentrations of zaprinast to inhibit the export. Thus, cGMP may be a physiological regulator of hyaluronan export at the level of the export MRP5.

Topics: 1-Methyl-3-isobutylxanthine; Biological Transport; Cell Membrane; Cyclic GMP; Cytosol; Fibroblasts; Humans; Hyaluronic Acid; Models, Biological; Multidrug Resistance-Associated Proteins; NG-Nitroarginine Methyl Ester; Purinones; RNA Interference; Xanthines

Apoptotic cell death has been implicated in Alzheimer's disease pathology and amyloid peptide induced neurotoxicity. We investigated the survival promoting effects of Propentofylline in two models of apoptotic cell death, nerve growth factor withdrawal and beta-amyloid mediated cell death in nerve growth factor differentiated rat pheochromocytoma cell lines. The increase in cell death as measured by lactate dehydrogenase release in response to nerve growth factor withdrawal was suppressed by nitric oxide donor S-nitroso-N-acetylpenicillamine (12.5 to 200 microM) and by 8-bromoguanosine-3',5'-cyclic monophosphate (1.25 to 10mM). Both agents decreased cell death mediated by 25 microM beta-amyloid, suggesting that the protective mechanism involves guanosine -3', 5'-cyclic monophosphate. In support of this hypothesis we can show that S-nitroso-N-acetylpenicillamine increases intracellular levels of guanosine -3',5'-cyclic monophosphate in pheochromocytoma cell lines 3 to 8 fold.Propentofylline, a phosphodiesterase inhibitor, has previously demonstrated neuroprotective activity in stroke models and is a potential candidate for therapeutic treatment in neurodegenerative diseases. The present findings support this claim by providing evidence that Propentofylline has protective effects in both nerve growth factor withdrawal and beta-amyloid mediated cell death. Lactate dehydrogenase release was significantly reduced and caspase-3-like activity was attenuated after cotreatment with Propentofylline. Furthermore Propentofylline dose responsively increases intracellular guanosine-3',5'-cyclic monophosphate levels over the same dose range that provided protection. We hypothesized that guanosine-3',5'-cyclic monophosphate is a key mediator of neuroprotection under these conditions.

Topics: 1-Methyl-3-isobutylxanthine; 4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; Amyloid beta-Peptides; Animals; Apoptosis; Caspase 3; Caspases; Cyclic GMP; Dose-Response Relationship, Drug; Nerve Growth Factor; Neurons; Neuroprotective Agents; Nitric Oxide; Nitric Oxide Donors; PC12 Cells; Penicillamine; Peptide Fragments; Phosphodiesterase Inhibitors; Rats; Rolipram; Xanthines