Calcium-activated chloride conductance in a pancreatic adenocarcinoma cell line of ductal origin (HPAF) and in freshly isolated human pancreatic duct cells.
Winpenny JP. Harris A. Hollingsworth MA. Argent BE. Gray MA.
Department of Physiological Sciences, The Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
Using the whole-cell patch-clamp technique, a calcium-activated chloride conductance (CACC) could be elicited in HPAF cells by addition of 1 microM ionomycin to the bath solution (66 +/- 22 pA/pF;Vm + 60 mV) or by addition of 1 microM calcium to the pipette solution (136 +/- 17 pA/pF; Vm + 60 mV). Both conductances had similar biophysical characteristics, including time-dependent inactivation at hyperpolarising potentials and a linear/slightly outwardly rectifying current/voltage (I/V) curve with a reversal potential (Erev) close to the calculated chloride equilibrium potential. The anion permeability sequence obtained from shifts in Erev was I > Br >/= Cl. 4,4'-Diisothiocyanatostilbene disulphonic acid (DIDS, 500 microM) caused a 13% inhibition of the current (Vm + 60 mV) while 100 microM glibenclamide, 30 nM TS-TM-calixarene and 10 microM tamoxifen, all chloride channel blockers, had no marked effects (8%, -6% and -2% inhibition respectively). Niflumic acid (100 microM) caused a voltage-dependent inhibition of the current of 48% and 17% (Vm +/- 60 mV, respectively). In freshly isolated human pancreatic duct cells (PDCs) a CACC was elicited with 1 microM calcium in the pipette solution (260 +/- 62 pA/pF; Vm + 60 mV). The presence of this CACC in human PDCs could provide a possible therapeutic pathway for treatment of pancreatic insufficiency of the human pancreas in cystic fibrosis.
Granulocyte-colony stimulating factor inhibits TNFalpha production in a human hepatoma cell line.
Frede S. Deetjen C. Schobersberger W. Hoffmann G.
Department of Physiology I, University of Bonn, Nussallee 11, D-53115 Bonn, Germany.
The syndrome of cachexia associated with malignant diseases can be in part attributed to the effects of tumour necrosis factor alpha (TNFalpha) which itself is produced by a variety of tumour cells. We have recently reported that the human hepatoma cell line HepG2 expresses the TNFalpha gene and releases biologically active TNFalpha protein after stimulation with interleukin-1beta (IL-1beta). Granulocyte-colony stimulating factor (G-CSF) is a glycoprotein necessary for the proliferation and differentiation of neutrophil progenitor cells in the bone marrow. In addition G-CSF has been reported to exert anti-inflammatory effects. In our study we tested the effect of recombinant human G-CSF (rhG-CSF) on TNFalpha production in HepG2 cells. It could be shown that rhG-CSF (250 U/ml) significantly reduced IL-1beta-induced (300 pg/ml) TNFalpha gene expression after 1-h and 3-h incubation periods (TNFalpha mRNA concentrations were: 8.8+/-2.1 amol/ microg total RNA after a 1-h incubation with IL-1beta versus 3.8+/-1.3 amol/ microg total RNA after a 1-h incubation with IL-1beta + rhG-CSF and 13.8+/-2.2 amol/ microg total RNA after a 3-h incubation with IL-1beta versus 8.8+/-2. 1 amol/ microg total RNA after a 3-h incubation with IL-1beta + rhG-CSF). From these data we conclude that rhG-CSF is a potent inhibitor of cytokine-induced TNFalpha production by tumour cells. Therefore, treatment of patients with malignant diseases with rhG-CSF might represent a useful tool to improve the tumour-associated cachexia.