Polyamines in rapid growth and cancer

Publisher Summary This chapter presents an overview of PC12 pheochromocytoma cultures in neurobiological research. The PC12 line of rat pheochromocytoma cells promises to be highly useful for studying both chromaffin cells and neurons and, consequently, has been employed in an increasing number of laboratories. PC12 cells propagated in vivo or in culture without nerve-growth factor are readily classifiable as pheochromocytomas by current morphological and chemical criteria. They have no processes and are characterized by numerous secretory granules ranging in diameter up to 350 nm. They also contain total catecholamine stores comparable to those in rat adrenal glands and show intense formaldehyde-induced fluorescence. In addition to catecholamines, PC12 cells contain several other secretory products, some of which have also been reported in human pheochromocytomas. The morphology of the cells and their synthesis, storage, release, and uptake of neurohumoral or neurotransmitter substances can be modulated in a number of ways within the overall chromaffin cell-like phenotype. This chapter reviews the currently known properties of the PC12 line. It also discusses the ways in which it has been and could be exploited to increase the knowledge of neuronal and neurosecretory cells.

PC12 Pheochromocytoma Cultures in Neurobiological Research

Beta-Adrenergic relaxation in bovine coronary arteries is enhanced by inhibition of eicosonoid metabolism and inhibited by its stimulation. We investigated the interaction between eicosonoid metabolism and beta-adrenergic mechanisms by studying the effect of perturbations of eicosonoid metabolism on vascular adenosine 3',5'-monophosphate (cAMP) content and the cAMP-dependent relaxation of isometric force and activation of glycogen phosphorylase. KCl (35 mM) elicited a contraction, activated phosphorylase, and slightly decreased cAMP content. Isoproterenol (10(-7) M) relaxed the KCl contraction, further increased phosphorylase activity, and increased cAMP. Neither indomethacin (5 X 10(-6) M) nor arachidonic acid (3 X 10(-5) M) affected the KCl contraction, but arachidonic acid increased both cAMP and phosphorylase activity and indomethacin decreased cAMP. Indomethacin potentiated the relaxation induced by isoproterenol but inhibited the activation of phosphorylase and had no effect on the isoproterenol-induced increase in cAMP. Arachidonic acid, on the other hand, inhibited the isoproterenol-induced relaxation but potentiated both the increases of phosphorylase activity and cAMP. Thus neither relaxation nor phosphorylase activity was related in a straightforward manner to the total cAMP content. A direct relation between cAMP, relaxation, and phosphorylase can be reconciled with the antiparallel effects of alterations of eicosonoid metabolism observed in this study by a proposed model in which the effects of cAMP are assumed to be functionally compartmentalized.

Eicosonoid metabolism and beta-adrenergic mechanisms in coronary arterial smooth muscle: potential compartmentation of cAMP

https://faculty.washington.edu/scottjdw/pdfs/scott_pharmathera_1991_p123.pdf

Cyclic nucleotide-dependent protein kinases

Four members of a Gardner's syndrome family had rectal and colon polyposis treated with nonsteroid anti-inflammatory drugs. Three of these patients had had subtotal colectomy and ileoproctostomy and the residual polyps arose in the rectal mucosa. The polyps almost completely disappeared when sulindac was administered. Indomethacin therapy over the course of a preceding year was ineffective in one of these patients. One patient (case 4) had diffuse polyposis in an intact colon. After sulindac therapy for a year, only three small mucosal polyps could be identified by air contrast barium enema and colonoscopic examination. These observations confirm those of Pollard and Luckert [1,2] on rats with chemically induced polyposis of the intestinal tract.

Sulindac for polyposis of the colon.

Proposed model of major sequential biochemical events of a trophic response

Both exposure to cold and administration of aminophylline result in rapid increases in cyclic adenosine monophosphate (cyclic AMP) in the adrenal medulla and adrenal cortex. These increases are followed by dramatic increases in ornithine decarboxylase activity is due to new enzyme systhesis. The data suggest that the decarboxylase activity is regulated by an increase in cyclic AMP.

https://science.sciencemag.org/content/sci/187/4177/650.full.pdf

Ornithine decarboxylase activity: control by cyclic nucleotides.

THE role of cyclic AMP in the regulation of cell growth and differentiation has been extensively investigated in many cell types following various growth stimuli1,2. In recent years, peripheral blood lymphocytes treated with antigens3, plant lectins4, lipopolysaccharides5, or periodate oxidation6 have served as a model system for assessing whether cyclic AMP is involved in the regulation of the mitogenic response promoted in these cells by the above classes of agents7,8. There are two conflicting hypotheses, as outlined by Friedman1, concerning the role of cyclic AMP in lymphocyte proliferation. The first hypothesis suggests that the increase in cyclic AMP levels following mitogen stimulation8 and the subsequent increase in 32P incorporated into F1 histones9 and certain cystosol proteins10 implicates cyclic AMP as a positive mediator of mitogenesis in lymphocytes. The other hypothesis reasons that cyclic AMP inhibits proliferation, and this hypothesis is supported primarily by observations from several laboratories that raising the intracellular cyclic AMP level through the use of phosphodiesterase inhibitors11, prostaglandins12, or cyclic AMP analogues11,13–15 effectively inhibits mitogen-stimulated RNA and DNA synthesis. We present here evidence that may help resolve this apparent paradox. Incubation of Ficoll–Hypaque purified human peripheral blood lymphocytes with concanavalin A (conA) leads to the activation of only type I cyclic AMP-dependent protein kinase in these cells even though there are significant amounts of both type I and type II kinase present. But, the addition of dibutyryl cyclic AMP (DBcAMP) to the conA-stimulated lymphocytes at a concentration sufficient to block the synthesis of RNA and DNA results in the activation of both type I and type II cyclic AMP-dependent protein kinase. It therefore seems likely that while the activation of type I protein kinase represents a positive component in the progression of events promoted in a lymphocyte by a mitogenic signal (as it does in other cell types in which a trophic response is evoked), the activation of type II protein kinase (or perhaps types I and II in concert) represents a mechanism by which a negative influence can be imposed on the proliferative process by the generation of abnormally high levels of intracellular cyclic AMP.

Craig V. Byus

Papers

Proposed model of major sequential biochemical events of a trophic response

Ornithine decarboxylase activity: control by cyclic nucleotides.

Type I and type II cyclic AMP-dependent protein kinase as opposite effectors of lymphocyte mitogenesis.

Increase in type I adenosine 3′,5′-monophosphate-dependent protein kinase during isoproterenol-induced cardiac hypertrophy

Effects of methyl xanthine derivatives on cyclic AMP levels and ornithine decarboxylase activity of rat tissues.