Constitutive activation of JAK–STAT3 signaling by BRCA1 in human prostate cancer cells

AbstractGerm-line mutations of the breast cancer susceptibility gene 1 (BRCA1) confer a high risk for breast and ovarian cancer in women and prostate cancer in men. The BRCA1 protein contributes to cell proliferation, cell cycle regulation, DNA repair and apoptosis; however, the mechanisms underlying these functions of BRCA1 remain largely unknown. Here, we showed that, in Du-145 human prostate cancer cells, enhanced expression of BRCA1 resulted in constitutive activation of signal transducer and activator transcription factor 3 (STAT3) tyrosine and serine phosphorylation. Moreover, Janus kinase 1 (JAK1) and JAK2, the upstream activators of STAT3, were also activated by BRCA1. Immunoprecipitation assay showed that BRCA1 interacted with JAK1 and JAK2. Blocking STAT3 activation using antisense oligonucleotides significantly inhibited cell proliferation and triggered apoptosis in Du-145 cells with enhanced expression of BRCA1. These findings indicate that BRCA1 interacts with the components of the JAK–STAT signaling cascade and modulates its activation, which may provide a new critical survival signal for the growth of breast, ovarian and prostate cancers in the presence of normal BRCA1

α-Adrenergic inhibition of proliferation in HepG2 cells stably transfected with the α1B-adrenergic receptor through a p42MAP kinase/p21Cip1/WAF1-dependent pathway

AbstractActivation of α1B adrenergic receptors (α1BAR) promotes DNA synthesis in primary cultures of hepatocytes, yet expression of α1BAR in hepatocytes rapidly declines during proliferative events. HepG2 human hepatoma cells, which do not express α1BAR, were stably transfected with a rat α1BAR cDNA (TFG2 cells), in order to study the effects of maintained α1BAR expression on hepatoma cell proliferation. TFG2 cells had a decreased rate of growth compared to mock transfected HepG2 cells as revealed by a decrease in [3H]thymidine incorporation into DNA. Stimulation of α1BAR with phenylephrine caused a further large reduction in TFG2 cell growth, whereas no effect on growth was observed in mock transfected cells. Reduced cell growth correlated with increased percentages of cells found in G0/G1 and G2/M phases of the cell cycle. In TFG2 cells, phenylephrine increased p42MAP kinase activity by 1.5- to 2.0-fold for up to 24 h and increased expression of the cyclin dependent kinase inhibitor protein p21Cip1/WAF1. Treatment of TFG2 cells with the specific MEK1 inhibitor PD98059, or infection with a −/− MEK1 recombinant adenovirus permitted phenylephrine to increase rather than decrease [3H]thymidine incorporation. In addition, inhibition of MAP kinase signaling by PD98059 or MEK1 −/− blunted the ability of phenylephrine to increase p21Cip1/WAF1 expression. In agreement with a role for increased p21Cip1/WAF1 expression in causing growth arrest, infection of TFG2 cells with a recombinant adenovirus to express antisense p21Cip1/WAF1 mRNA blocked the ability of phenylephrine to increase p21Cip1/WAF1 expression and to inhibit DNA synthesis. Antisense p21Cip1/WAF1 permitted phenylephrine to stimulate DNA synthesis in TFG2 cells, and abrogated growth arrest. These results suggest that transformed hepatocytes may turn off the expression of α1BARs in order to prevent the activation of a growth inhibitory pathway. Activation of this inhibitory pathway via α1BAR appears to be p42MAP kinase and p21Cip1/WAF1 dependent

Cannabinoid receptors in GtoPdb v.2023.1

Cannabinoid receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Cannabinoid Receptors [119]) are activated by endogenous ligands that include N-arachidonoylethanolamine (anandamide), N-homo-γ-linolenoylethanolamine, N-docosatetra-7,10,13,16-enoylethanolamine and 2-arachidonoylglycerol. Potency determinations of endogenous agonists at these receptors are complicated by the possibility of differential susceptibility of endogenous ligands to enzymatic conversion [5].There are currently three licenced cannabinoid medicines each of which contains a compound that can activate CB1 and CB2 receptors [111]. Two of these medicines were developed to suppress nausea and vomiting produced by chemotherapy. These are nabilone (Cesamet®), a synthetic CB1/CB2 receptor agonist, and synthetic Δ9-tetrahydrocannabinol (Marinol®; dronabinol), which can also be used as an appetite stimulant. The third medicine, Sativex®, contains mainly Δ9-tetrahydrocannabinol and cannabidiol, both extracted from cannabis, and is used to treat multiple sclerosis and cancer pain

The Orexigenic Effect of Ghrelin Is Mediated through Central Activation of the Endogenous Cannabinoid System

INTRODUCTION Ghrelin and cannabinoids stimulate appetite, this effect possibly being mediated by the activation of hypothalamic AMP-activated protein kinase (AMPK), a key enzyme in appetite and metabolism regulation. The cannabinoid receptor type 1 (CB1) antagonist rimonabant can block the orexigenic effect of ghrelin. In this study, we have elucidated the mechanism of the putative ghrelin-cannabinoid interaction. METHODS The effects of ghrelin and CB1 antagonist rimonabant in wild-type mice, and the effect of ghrelin in CB1-knockout animals, were studied on food intake, hypothalamic AMPK activity and endogenous cannabinoid content. In patch-clamp electrophysiology experiments the effect of ghrelin was assessed on the synaptic inputs in parvocellular neurons of the hypothalamic paraventricular nucleus, with or without the pre-administration of a CB1 antagonist or of cannabinoid synthesis inhibitors. RESULTS AND CONCLUSIONS Ghrelin did not induce an orexigenic effect in CB1-knockout mice. Correspondingly, both the genetic lack of CB1 and the pharmacological blockade of CB1 inhibited the effect of ghrelin on AMPK activity. Ghrelin increased the endocannabinoid content of the hypothalamus in wild-type mice and this effect was abolished by rimonabant pre-treatment, while no effect was observed in CB1-KO animals. Electrophysiology studies showed that ghrelin can inhibit the excitatory inputs on the parvocellular neurons of the paraventricular nucleus, and that this effect is abolished by administration of a CB1 antagonist or an inhibitor of the DAG lipase, the enzyme responsible for 2-AG synthesis. The effect is also lost in the presence of BAPTA, an intracellular calcium chelator, which inhibits endocannabinoid synthesis in the recorded parvocellular neuron and therefore blocks the retrograde signaling exerted by endocannabinoids. In summary, an intact cannabinoid signaling pathway is necessary for the stimulatory effects of ghrelin on AMPK activity and food intake, and for the inhibitory effect of ghrelin on paraventricular neurons

Hepatitis C Virus Induces the Cannabinoid Receptor 1

BACKGROUND: Activation of hepatic CB(1) receptors (CB(1)) is associated with steatosis and fibrosis in experimental forms of liver disease. However, CB(1) expression has not been assessed in patients with chronic hepatitis C (CHC), a disease associated with insulin resistance, steatosis and metabolic disturbance. We aimed to determine the importance and explore the associations of CB(1) expression in CHC. METHODS: CB(1) receptor mRNA was measured by real time quantitative PCR on extracted liver tissue from 88 patients with CHC (genotypes 1 and 3), 12 controls and 10 patients with chronic hepatitis B (CHB). The Huh7/JFH1 Hepatitis C virus (HCV) cell culture model was used to validate results. PRINCIPAL FINDINGS: CB(1) was expressed in all patients with CHC and levels were 6-fold higher than in controls (P<0.001). CB(1) expression increased with fibrosis stage, with cirrhotics having up to a 2 fold up-regulation compared to those with low fibrosis stage (p<0.05). Even in mild CHC with no steatosis (F0-1), CB(1) levels remained substantially greater than in controls (p<0.001) and in those with mild CHB (F0-1; p<0.001). Huh7 cells infected with JFH-1 HCV showed an 8-fold upregulation of CB(1), and CB(1) expression directly correlated with the percentage of cells infected over time, suggesting that CB(1) is an HCV inducible gene. While HCV structural proteins appear essential for CB(1) induction, there was no core genotype specific difference in CB(1) expression. CB(1) significantly increased with steatosis grade, primarily driven by patients with genotype 3 CHC. In genotype 3 patients, CB(1) correlated with SREBP-1c and its downstream target FASN (SREBP-1c; R=0.37, FASN; R=0.39, p<0.05 for both). CONCLUSIONS/SIGNIFICANCE: CB(1) is up-regulated in CHC and is associated with increased steatosis in genotype 3. It is induced by the hepatitis C virus

Transformation of adrenergic receptors in the myocardium.

The present series of experiments provided evidence that the generally accepted distinction between alpha- and beta-adrenergic receptors is not immutable. In frog hearts and rat atria 3H-phenoxybenzamine (3H- POB) blocked inotropic responses to catecholamines only at temperatures below l7°C and potentiated responses ab ove 23°C, and considerably more radioactivity was bound to the myocardium at lower temperatures. The converse was true for l4C-propranolol, and the potency of alpha- and beta-adrenergic agonists was shown to parallel the effectiveness of the blocking agents. Alkylation of alpha-adrenergic receptors by POB at l4°c prevented the appearance of beta-adrenergic receptors when the temperature was subsequently raised ta 24°C. Phentolamine prevented block by 3H-POB and considerably reduced its binding to the myocardium at low but not at high temperatures. After exposure to unlabelled POB in the presence of phentolamine at low temperature and thorough washing, exposure to 3H-POB produced a "positive label" of the adrenergic receptors, which was localized in a 20,000 g ("mitochondrial") and in a "soluble protein" fraction. Pretreatment of rats with 6-hydroxydopamine, but not with reserpine, prevented the appearance of alpha-adrenergic receptor characteristics in left atria at low temperatures; this indicated that adrenergic innervation, but probably not stores of neurotransmitter, is necessary to allow transformation of the receptors. It is suggested that alpha- and beta-adrenergic receptors may be different allosteric conformations of the same molecule.L'ensemble des expériences présenté ici fournit l'évidence que la distinction entre les récepteurs adrénergiques alpha et beta n'est pas absolue. Sur le coeur isolé de grenouille et sur l'oreillette du rat, 3H-phenoxybenzamine (3H-POB) n'inhibe l'effet inotropique des catécholamines qu'aux températures au-dessous de l7°C et augmente ces mêmes effets au-dessus de 23°C; en même temps, plus de radioactivité est retenu par le myocarde aux basses températures. Par contre, la puissance bloquante du l4C-propranolol et sa rétention par le myocarde sont diminuées par une baisse de température. De plus, l'effet des agonistes adrénergiques allait de parallèle avec l'effet des bloqueurs. L'alkylation des récepteurs adrénergiques a par 3H-POB à l4°C empêche l'apparition des récepteurs a lorsque la température est subséquemment élevée. La phentolamine, un bloqueur compétitif des récepteurs a, fait obstacle à l'inhibition par le 3H-POB et réduit considérablement sa captation par le myocarde aux basses températures. A basse température, après traitment préalable au POB en présence de phentolamine, on a réussi à marquer sélectivement les récepteurs adrénergiques a par l'exposition des coeurs à 3H-POB. Et de plus, on a localisé dans les fractions "mitochondriale" et "protéines solubles" la radioactivité associée à ces mêmes récepteurs. Le traitment préalable des rats avec 6-hydroxydopamine empêche l'apparition des récepteurs a dans l'oreillette gauche aux basses températures; par contre, le réserpine ne produit aucun effet similaire, ce qui indiquerait que l'innervation adrénergique, mais pas la présence du neurotransmetteur, serait nécéssaire pour la transformation des récepteurs adrénergiques dans le myocarde. Il est suggéré que les récepteurs adrénergiques alpha et beta représentent, probablement, des conformations allostériques d'une seule molécule

Adrenoceptors And Catecholamine Action

v.335 hal;23 c