Differential effects of prostaglandins and isoproterenol on cAMP content and Na,K pump activity in rat submandibular acini

Summary The -adrenergic agonist isoproterenol and prostaglandins E₁ and E₂ (but not F₂) increased the cAMP content of rat submandibular acini in vitro, but only isoproterenol enhanced ouabain-sensitive⁸⁶Rb (K) uptake. These findings suggest that cAMP is not involved in the activation of the Na, K pump in salivary cells.     

Regulation of calcitonin release from the 6.23 rat C-cell line by cyclic nucleotide analogues and pharmacological mediators.

Calcitonin release from 6.23 rat medullary thyroid carcinoma C-cells was stimulated by dibutyryl cyclic AMP and inhibited by dibutyryl cyclic GMP in concentration dependent fashion. Histamine, isoproterenol, prostaglandin E2 and Bay K 8644 stimulated calcitonin release, while acetylcholine and serotonin had no significant effect on CT release.     

The effect of cyclic AMP on Na+ and K+ transport systems in mouse macrophages

Summary Exogenous cyclic AMP (cAMP) inhibits the Na⁺, K⁺-cotransport system and stimulates the Na⁺, K⁺-pump and Na⁺, Ca²⁺ exchange in mouse macrophages. These effects are enhanced by inhibition of phosphodiesterase with methylisobutylxanthine (MIX). MIX alone showed little or no effect. A similar response was observed after stimulation of endogenous production of cAMP by isoproterenol.     

The inhibitory effect of paraquat on histamine and isoproterenol induced changes of cyclic nucleotides in rat lung slices.

The incubation of rat lung slices with paraquat ion (10(-4) M) had no effect on cAMP and cGMP levels of the rat lung slices. The preincubation with the same concentration of paraquat inhibited the cAMP elevating effect of histamine (10(-5) M) and isoproterenol (10(-5) M) and reduced the cGMP level to approximately 50% of the level obtained without preincubation with paraquat.     

Absence of endotoxin-fever but not hyperthermia in Brattleboro rats

I.c.v. administration of bacterial endotoxin produced a fever in the Long-Evans rat but not in the Brattleboro rat. Similar administration of arachidonic acid, prostaglandin E2, prostacyclin, dibutyryl cAMP, norepinephrine, morphine and beta-endorphin caused hyperthermia in both Long-Evans and Brattleboro rats. Variable doses of exogenous arginine vasopressin (AVP) when centrally administered with endotoxin caused fever in the Brattleboro rat. It is suggested that AVP may play an important role in the production and release of endogenous pyrogen.     

Human papillomavirus 16 E5 up-regulates the expression of vascular endothelial growth factor through the activation of epidermal growth factor receptor, MEK/ ERK1,2 and PI3K/Akt

The E5 oncoprotein of human papillomavirus (HPV) 16 plays an important role in early cervical carcinogenesis. Vascular endothelial growth factor (VEGF) plays a central role in switching on the angiogenic phenotype during early cervical carcinogenesis. However, the relationship between E5 and VEGF has not previously been examined. To clarify the regulatory role of E5 in VEGF expression, we transferred the E5 gene into various cell types. E5 increased VEGF expression. The addition of epidermal growth factor receptor (EGFR) inhibitor significantly suppressed VEGF expression, demonstrating that E5 stimulates VEGF expression through the activation of EGFR. E5-mediated EGFR activation was accompanied by phosphorylation of Akt and ERK1/2, which are also involved in VEGF expression. Furthermore, the mRNA stability of VEGF was not affected by E5, but VEGF promoter activity could be modulated by inhibitors of the EGFR, MEK-ERK1/2 and PI3K/Akt pathways in E5-expressing cells. Collectively, these novel results suggest that HPV 16 E5 increases VEGF expression by activating EGFR, MEK/ERK1/2 and PI3K/Akt. Received 23 November 2005; received after revision 10 January 2006; accepted 9 February 2006     

The inhibitory effect of paraquat on histamine and isoproterenol induced changes of cyclic nucleotides in rat lung slices

Summary The incubation of rat lung slices with paraquat ion (10^–4 M) had no effect on cAMP and cGMP levels of the rat lung slices. The preincubation with the same concentration of paraquat inhibited the cAMP elevating effect of histamine (10^–5 M) and isoproterenol (10^–5 M) and reduced the cGMP level to approximately 50% of the level obtained without preincubation with paraquat.This work was supported by the Research Grant No. 5 R01 HL 19720-03 from NHLI Department of Health, Education and Welfare, Washington, D.C.     

Salivary gland enlargement as a test for a new way of permanent isoproterenol application

Summary Low doses of isoproterenol, given permanently by a new application-method, show the same effects on salivary-gland enlargement of rats throughout approx. 6 days than 10fold higher concentrations given by previous workers as single daily injections.We are very much indebted to Mrs K. Stökl and Miss E. Stangl for their valuable technical assistance.     

Selective protection of cells against X-irradiation. Isoproterenol protects only those cells that possess beta-adrenoreceptors

In mixed culture of Chinese hamster fibroblasts, clone 431, and transformed murine L fibroblasts, clone B-82, isoproterenol was found to protect only 431 cells against ionizing radiation. It was shown that 431 cells, in contrast to B-82 cells, possess beta-adrenoreceptors, and the radioprotective effect of isoproterenol can be realized only if this agent interacts with beta-adrenoreceptors coupled with the cAMP system. Since malignization often causes the disappearance of beta-adrenergic and other hormone receptors, the combined culturing and irradiation of the cells studied can be regarded as a model of the growth of malignant cells (B-82) among normal tissue cells (431 cells) under conditions of radiation therapy. A possibility of selective protection against radiation damage of normal tissue cells, with retention of the former radiosensitivity of tumor cells, is discussed.     

Regulation of calcitonin release from the 6.23 rat C-cell line by cyclic nucleotide analogues and pharmacological mediators

Calcitonin release from 6.23 rat medullary thyroid carcinoma C-cells was stimulated by dibutyryl cyclic AMP and inhibited by dibutyryl cyclic GMP in concentration dependent fashion. Histamine, isoproterenol, prostaglandin E₂ and Bay K 8644 stimulated calcitonin release, while acetylcholine and serotonin had no significant effect on CT release.     

Effect of prostaglandins and dibutyryl cyclic AMP on the morphology of cells in primary astroglial cultures and on metabolic enzymes of GABA and glutamate metabolism

Prostaglandins (PGE1) and dibutyryl cyclic AMP (dBc AMP) induce similar morphological changes in astrocytes obtained in primary cultures. PGE1 and dBc AMP increased 2 enzymes of GABA and glutamate metabolism, GABA-T and AAT, but did not modify GDH and GLN-S. Prostaglandins probably affect the cAMP content of glial cells and act in the same way as dBc AMP on glial cell differentiation.     

Expression, isolation and characterization of a mutated human plasminogen kringle 3 with a functional lysine binding site

Each kringle of human plasminogen (HPg) except kringle 3 (K3) exhibits affinity for omega-aminocarboxylic acids. Assuming that the K3 domain contains a preformed but nonfunctional lysine binding site (LBS), Lys311 was altered by site-directed mutagenesis into Asp311 in accordance with the consensus sequence of the LBS. Cys297 involved in the interkringle disulfide bridge was mutated into Ser297 to minimize dimerization and aggregation. The mutated K3 TYQ[K3HPg/C297S/K311D]DS (r-K3mut) was expressed in Escherichia coli, isolated on an Ni2(+)-nitrilotriacetic acid-agarose column, refolded and purified on a lysine Bio-Gel column. Fluorescence titration indicates affinity of r-K3mut for omega-aminocarboxylic acids with the following association constants (Kass, mM-1): 5-aminopentanoic acid: 1.3; 6-aminohexanoic acid: 4.2; 7-aminoheptanoic acid: 0.5; trans-(aminomethyl)cyclohexanecarboxylic acid: 12.7; p-benzylaminesulfonic acid: 11.8. r-K3mut exhibits an affinity similar to native and mutated (R220G, E221D) K2. The results indicate the presence of a preformed but nonfunctional LBS in native K3 of HPg. We were able to demonstrate for the first time that an appropriate mutation in the LBS of a kringle produced a weak but distinct affinity for omega-aminocarboxylic acids.     

Inhibition of virus multiplication and alteration of cyclic AMP level in cell cultures by flavonoids

The inhibitory effect of four flavonoid compounds on virus multiplication and their influence on the intracellular cyclic AMP (cAMP) level were studied in cell cultures. Quercetin and quercitrin reduced the yields of Human (alpha) herpesvirus 1 (HSV-1) and Suid (alpha) herpesvirus 1 (pseudorabies virus), but hesperidin and rutin had no effect. Further, quercetin and quercitrin elevated the intracellular level of cAMP, whereas hesperidin and rutin did not alter the cAMP level. Both antiviral activity and cAMP-enhancing effect were dependent on the concentrations of the flavonoids, and these effects turned out to be parallel. This study suggests that a relation exists between the antiviral effect and the cAMP-enhancing activity of flavonoids.     

EP2 receptor stimulation promotes calcium responses in astrocytes via activation of the adenylyl cyclase pathway

Astrocytes are a heterogeneous population of cells that are endowed with a great variety of receptors for neurotransmitters and neuromodulators. Recently prostaglandin E₂ has attracted great interest since it is not only released by astrocytes but also activates receptors coupled to either phospholipase C or adenylyl cyclase. We report that EP₂ receptor stimulation triggers cAMP production but also causes release of Ca²⁺ from intracellular stores. This effect is shared by other receptors similarly coupled to adenylyl cyclase and elicited by direct stimulation of the enzyme or application of cAMP analogues. However, the stimulation of the Ca²⁺ response by cAMP is not mediated by protein kinase A, since a specific antagonist of this kinase had no effect. Such a cross-talk between cAMP and Ca²⁺ was not observed in all astrocytes. It might therefore reflect a specific resource of either a subpopulation or astrocytes in a specific functional state. Received 6 June 2006; received after revision 25 July 2006; accepted 31 August 2006     

Effect of prostaglandins and dibutyryl cyclic AMP on the morphology of cells in primary astroglial cultures and on metabolic enzymes of GABA and glutamate metabolism

Summary Prostaglandins (PGE₁) and dibutyryl cyclic AMP (dBc AMP) induce similar morphological changes in astrocytes obtained in primary cultures. PGE₁ and dBc AMP increased 2 enzymes of GABA and glutamate metabolism, GABA-T and AAT, but did not modify GDH and GLN-S. Prostaglandins probably affect the cAMP content of glial cells and act in the same way as dBc AMP on glial cell differentiation.     

Inhibition of virus multiplication and alteration of cyclic AMP level in cell cultures by flavonoids

Summary The inhibitory effect of four flavonoid compounds on virus multiplication and their influence on the intracellular cyclic AMP (cAMP) level were studied in cell cultures. Quercetin and quercitrin reduced the yields ofHuman (alpha) herpesvirus 1 (HSV-1) andSuid (alpha) herpesvirus 1 (pseudorabies virus), but hesperidin and rutin had no effect. Further, quercetin and quercitrin elevated the intracellular level of cAMP, whereas hesperidin and rutin did not alter the cAMP level. Both antiviral activity and cAMP-enhancing effect were dependent on the concentrations of the flavonoids, and these effects turned out to be parallel.This study suggests that a relation exists between the antiviral effect and the cAMP-enhancing activity of flavonoids.     

Bacteriophage T4 mutants which propagate on E. coli K12 but not on E. coli B

Summary We have isolated and characterized 2 mutants of coliphage T4 which are able to propagate on E. coli K12 but not on E. coli B. We have assigned the mutations to genes 8 and 53, both structural genes. The products of genes 8 and 53 are found in the baseplate.Supported by grant No 3.519.75 from the Fonds national Suisse de la Recherche Scientifique.     

Effect of dibutyryl cyclic AMP and analogs on the rate of contractions of myocytes in culture.

2O, 6N-butyryl, 3', 5'-cyclic monophosphate (dibu cAMP) when added to fetal rat heart cells in culture inhibits myocyte contraction. This inhibition is 100, 84 and 51% complete when the dibu cAMP concentration used is 2, 0.2 and 0.02 mM, respectively. The potency of dibu cAMP derivatives in myocyte contraction inhibition follows the order, dibu cAMP greater than 6N-bu cAMP greater than 2O-bu cAMP = AMP greater than butyrate. The inhibition caused by the first three chemicals is greater than 70%.