Elevated intracellular cAMP concentration mediates growth suppression in glioma cells

Abstract

Supressed levels of intracellular cAMP have been associated with malignancy. Thus, elevating cAMP through activation of adenylyl cyclase (AC) or by inhibition of phosphodiesterase (PDE) may be therapeutically beneficial. Here, we demonstrate that elevated cAMP levels suppress growth in C6 cells (a model of glioma) through treatment with forskolin, an AC activator, or a range of small molecule PDE inhibitors with differing selectivity profiles. Forskolin suppressed cell growth in a protein kinase A (PKA)-dependent manner by inducing a G2/M phase cell cycle arrest. In contrast, trequinsin (a non-selective PDE2/3/7 inhibitor), not only inhibited cell growth via PKA, but also stimulated (independent of PKA) caspase-3/-7 and induced an aneuploidy phenotype. Interestingly, a cocktail of individual PDE 2,3,7 inhibitors suppressed cell growth in a manner analogous to forskolin but not trequinsin.Finally, we demonstrate that concomitant targeting of both AC and PDEs synergistically elevated intracellular cAMP levels thereby potentiating their antiproliferative actions.

CGRP, adrenomedullin and adrenomedullin 2 display endogenous GPCR agonist bias in primary human cardiovascular cells

“…Cells were incubated for a further 72 h at 37°C in 5% CO 2 . After 72 h incubation, 5 μl of Cell Counting Kit-8 (CCK-8, Sigma, UK) was added to each well and cells were then incubated for another 2 h at 37°C in 5% CO 2 and in the dark 61 . The absorbance of each well was measured using a Mithras LB940 microplate reader with an excitation of 450 nm.…”

Modulation of Cyclic AMP Levels in Fallopian Tube Cells by Natural and Environmental Estrogens

“…The fact that various PDE inhibitors and cAMP inducers inhibit early embryo development [ 21 , 22 , 23 , 24 , 25 , 26 , 52 ] suggests that abnormal increases in cAMP may be deleterious. Indeed, cAMP has been shown to inhibit growth [ 7 , 8 ]; moreover, FT cells can convert cAMP to adenosine, which may result in activation of cAMP in distant cells, including the early embryo, via A 2B receptors [ 38 ]. Adenosine has been linked to fibrosis in some tissues, and fibrosis in FT is linked to ectopic pregnancy [ 47 , 48 , 49 ].…”

“…Hormonal stimulation rapidly increases cAMP levels within FT cells by approximately five-fold, and this newly generated cAMP has diverse effects on cellular biology. For example, intracellular cAMP regulates cell growth and has been shown to both stimulate as well as inhibit cell growth [ 7 , 8 ]. Specifically, cAMP inhibits cell growth at high concentrations [ 8 ].…”

“…For example, intracellular cAMP regulates cell growth and has been shown to both stimulate as well as inhibit cell growth [ 7 , 8 ]. Specifically, cAMP inhibits cell growth at high concentrations [ 8 ]. cAMP also relaxes smooth muscle cells [ 9 ].…”

“…cAMP regulates steroidogenesis by modulating aromatase activity in the ovary [ 16 ] and actively contributes to the cyclic contractility of the oviduct to facilitate fertilization and early embryo development and transit for implantation [ 17 ]. Apart from influencing muscle tone and motility, cAMP is a potent regulator of growth [ 7 ], and high concentrations of cAMP induce anti-mitogenic actions [ 7 , 8 ]. Within the ovary, cAMP plays a crucial role in oocyte maturation [ 18 , 19 ].…”