dibutyryl-cyclic-gmp and zaprinast

The role of 3',5'-cyclic guanosine monophosphate (cGMP) in the activation of mitogen-activated protein kinases (MAPKs) was investigated in rat pinealocytes. Treatment with dibutyryl cGMP (DBcGMP) dose-dependently increased the phosphorylation of both p44 and p42 isoforms of MAPK. This effect of DBcGMP was abolished by PD98059 (a MAPK kinase inhibitor), H7 (a nonspecific protein kinase inhibitor), and KT5823 [a selective cGMP-dependent protein kinase (PKG) inhibitor]. Elevation of cellular cGMP content by treatment with norepinephrine, zaprinast (a cGMP phosphodiesterase inhibitor), or nitroprusside was effective in activating MAPK. Natriuretic peptides that were effective in elevating cGMP levels in this tissue were also effective in activating MAPK. Our results indicate that, in this neuroendocrine tissue, the cGMP/PKG signaling pathway is an important mechanism used by hormones and neurotransmitters in activating MAPK.

Topics: Alkaloids; Animals; Atrial Natriuretic Factor; Calcium-Calmodulin-Dependent Protein Kinases; Carbazoles; Cells, Cultured; Cyclic GMP; Dibutyryl Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Flavonoids; Indoles; Isoquinolines; Male; Naphthalenes; Natriuretic Peptide, C-Type; Neurosecretory Systems; Nitroprusside; Phosphodiesterase Inhibitors; Phosphorylation; Pineal Gland; Protein Kinase C; Purinones; Rats; Rats, Sprague-Dawley; Sulfhydryl Reagents; Sulfonamides; Thionucleotides

High concentrations of nitric oxide (NO) inhibit bone resorption by mature osteoclasts. We examined the effects of low NO concentrations on osteoclast formation in mouse bone marrow cultures. The NO releasers sodium nitroprusside (SNP) and S-nitroso-N-acetyl-DL-penicillamine inhibited the formation of multinucleated cells expressing tartrate-resistant acid phosphatase (a marker for osteoclasts) when administered during the last 3 days of 6-day cultures (differentiation stage) but not during the first 3 days (proliferation stage). SNP (1 microM) completely inhibited pit formation on dentine wafers when added to cultures during osteoclast formation, but 100 microM SNP was required to inhibit pitting by mature osteoclasts. Conversely, the NO synthase inhibitors aminoguanidine and nitro-L-arginine methyl ester both increased osteoclast formation. Inhibition of osteoclast formation by NO likely was guanosine 3',5'-cyclic monophosphate (cGMP) dependent, as SNP increased cGMP in marrow cultures, and 1 mM 8-bromo-cGMP or dibutyryl-cGMP reduced osteoclast formation when administered during the differentiation stage. The cGMP-specific type V phosphodiesterase inhibitor, zaprinast (M & B 22948) also inhibited osteoclast formation (half-maximal inhibitory constant, 100 microM) only when added during the differentiation stage. We conclude that the differentiation stage of osteoclast formation is inhibited by increases in cGMP levels elicited by NO.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Bone Marrow Cells; Bone Resorption; Bucladesine; Calcitriol; Cells, Cultured; Cyclic GMP; Dentin; Dibutyryl Cyclic GMP; Guanidines; In Vitro Techniques; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroprusside; Osteoclasts; Penicillamine; Purinones; S-Nitroso-N-Acetylpenicillamine; Whales

The effects of the nonselective phosphodiesterase (PDE)-inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the selective PDE inhibitors SKF 94120 (type III), rolipram (type IV), zardaverine (type III/IV), and zaprinast (type V) on inherent tone in human airways were investigated. Substantial relaxation was achieved by IBMX [concentration eliciting 50% of maximum response (EC50): 2.9 microM, n = 14] and SKF 94120 (EC50: 1.4 microM, n = 15); rolipram and zaprinast were almost ineffective. Zardaverine (EC50: 0.31 microM, n = 8), and the combination of SKF 94120 and rolipram (1 microM; EC50: 0.41 microM) were effective relaxants. Biochemical studies revealed the presence of PDE isozymes I, III, IV, and V in the cytosolic and particulate phase of airway homogenates, whereas PDE II was present only in the cytosol. Partial inhibition of total PDE adenosine 3',5'-cyclic monophosphate-hydrolyzing activity was achieved with rolipram and a selective type III inhibitor, whereas there was almost complete inhibition of total PDE activity with either zardaverine or the combination of type III and IV inhibitors. We conclude that all five PDE isozyme families are present in crude preparations of human peripheral airways. Inherent tone in this tissue is most effectively relaxed through selective type III/IV PDE inhibitors.

Topics: 1-Methyl-3-isobutylxanthine; 2',3'-Cyclic-Nucleotide Phosphodiesterases; Adult; Aged; Bucladesine; Colforsin; Dibutyryl Cyclic GMP; Dose-Response Relationship, Drug; Female; Forced Expiratory Volume; Humans; In Vitro Techniques; Isoenzymes; Lung; Lung Neoplasms; Male; Middle Aged; Muscle Relaxation; Muscle Tonus; Muscle, Smooth; Nitroprusside; Purinones; Pyrazines; Pyridazines; Pyrrolidinones; Rolipram; Vital Capacity

The present experiments were designed to analyze the ability of somatostatin to modulate the proliferation of cultured rat mesangial cells. In the absence of fetal calf serum, somatostatin stimulated cell proliferation in a dose-dependent manner. In contrast, in proliferating cells, somatostatin inhibited cell proliferation, also in a dose-dependent fashion. Zaprinast, a rather specific cyclic GMP phosphodiesterase blocker, inhibited the somatostatin-dependent proliferation in the absence of growth factors. However, it potentiated the inhibitory effect on proliferating cells. These results support a dual role for somatostatin in the regulation of mesangial cell proliferation. The inhibitory effect of the peptide may be mediated by cyclic GMP.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blood; Cattle; Cell Division; Cells, Cultured; Culture Media, Serum-Free; Dibutyryl Cyclic GMP; Dose-Response Relationship, Drug; Glomerular Mesangium; Kinetics; Purinones; Rats; Rats, Wistar; Somatostatin