RESUMO
BACKGROUND: Histamine stimulates cell proliferation in some tumor cell lines through the activation of H(1) receptors coupled to phosphoinositide hydrolysis. We therefore set out to study the presence of H(1) receptors in the prostate cancer cell line DU-145 and the effect of their stimulation on cell growth. METHODS: The presence of histamine receptors was studied by radioligand binding. Phosphoinositide hydrolysis was assessed by measuring [(1)H]-inositol phosphate ([(1)H]-IPs) accumulation and changes in the intracellular concentration of free Ca(2+) ([Ca(2+)](i)). Proliferation was assessed by cell counting and by [(1)H]-thymidine incorporation. RESULTS: DU-145 cells express H(1) receptors (110+/-14 fmol/mg of protein) whose stimulation results in [(1)H]-IPs accumulation (602+/-23% of basal, EC(50) 2.2+/-0.4 microM) and calcium mobilization (resting level 96+/-5 nM, Delta[Ca(2+)](i) 517+/-32 nM, EC(50) 6.2+/-0.1 microM). Incubation with histamine (100 microM, 24 hr) resulted in a decrease in both cell number and [(1)H]-thymidine incorporation, blocked by the H(1) antagonist mepyramine (1 microM). CONCLUSIONS: Histamine inhibits the proliferation of DU-145 cells through the activation of H(1) receptors coupled to phosphoinositide hydrolysis.
Assuntos
Adenocarcinoma/patologia , Divisão Celular , Neoplasias da Próstata/patologia , Receptores Histamínicos H1/fisiologia , Cálcio/metabolismo , Sinalização do Cálcio , Humanos , Hidrólise , Masculino , Fosfatidilinositóis/farmacologia , Células Tumorais CultivadasRESUMO
In human astrocytoma U373 MG cells that express histamine H1 receptors (180 +/- 6 fmol/mg protein) but not H2 or H3 receptors, histamine stimulated mitogenesis as assessed by [3H]-thymidine incorporation (173 +/- 2% of basal; EC50, 2.5 +/- 0.4 microM). The effect of 100 microM histamine was fully blocked by the selective H1 antagonist mepyramine (1 microM) and was markedly reduced (93 +/- 4% inhibition) by the phospholipase C inhibitor U73122 (10 microM). The activator of protein kinase C (PKC) phorbol 12-tetradecanoyl-13-acetate (TPA, 100nM) stimulated [3H]-thymidine incorporation (270 +/- 8% of basal), and this response was not additive with that to 100 microM histamine. The incorporation of [3H]-thymidine induced by 100 microM histamine was partially reduced by the PKC inhibitor Ro 31-8220 (57 +/- 7% inhibition at 300 nM) and by the compound PD 098,059 (30 microM, 62 +/- 14% inhibition), an inhibitor of the mitogen-activated kinase (MAPK) kinases MEK1/MEK2. These results show that histamine H1 receptor activation stimulates the proliferation of human astrocytoma U373 MG cells. The action of histamine appears to be partially mediated by PKC stimulation and MAPK activation.