Down‐Regulation of the Noradrenaline Transporter by Interferon‐α in Cultured Bovine Adrenal Medullary Cells

Abstract

The aim of this study was to investigate the effect of long‐term treatment with interferon (IFN)‐α on the noradrenaline transporter of bovine adrenal medullary cells. Treatment of cultured adrenal medullary cells with IFN‐α caused a decrease in uptake of [3H]noradrenaline by the cells in time (4–48 h)‐ and concentration (300–1,000 U/ml)‐dependent manners. IFN‐β also inhibited [3H]noradrenaline uptake to a lesser extent than did IFN‐α, whereas IFN‐γ had little effect. An anti‐IFN‐α antibody reduced the effect of IFN‐α on [3H]noradrenaline uptake. Saturation analysis of [3H]noradrenaline uptake showed that the inhibitory effect of IFN‐α was due to a reduction in the maximal uptake velocity (Vmax) values without altering apparent Michaelis constant (Km) values. Incubation of cells with IFN‐α caused a translocation of protein kinase C from the soluble to the particulate fraction in the cells. The effect of IFN‐α on [3H]noradrenaline uptake was diminished in protein kinase C‐down‐regulated cells. Incubation of cells with IFN‐α for 48 h significantly reduced the specific binding of [3H]desipramine to crude plasma membranes isolated from cells. Scatchard analysis of [3H]desipramine binding revealed that IFN‐α decreased the maximal binding (Bmax) values without any change in the dissociation constant (KD) values. These findings suggest that IFN‐α suppresses the function of noradrenaline transporter by reducing the density of the transporter in cell membranes through, at least in part, a protein kinase C pathway.

Norepinephrine transporter density as a causative factor in alterations in MIBG myocardial uptake in NIDDM model rats

“…The density and affinity of NET can be investigated by studying binding of the tritiated antagonist radioligand, desipramine, to cellular membranes [26,28,29]. We therefore estimated [ 3 H]desipramine binding to the anterior and inferior walls of GK rats, compared with that in controls.…”

“…Binding assays were performed as described previously with some modifications [26,28,29]. Briefly, [ 3 H]desipramine binding was determined by incubating aliquots of membrane suspension with [ 3 H]desipramine (0.25~30 nM) in a final volume of 250 µl for 30 min at 25°C.…”

Kinase-dependent Regulation of Monoamine Neurotransmitter Transporters

“…However, the PKA inhibitor H-89, as well as the NOS inhibitors 7-Nitroindazole and L-N G -Nitroarginine methyl ester also blocked these effects, suggesting the involvement multiple pathways in the control of NET activity. PKC may also mediate the inhibitory effects of IFN-a on NET activity (Toyohira et al, 1998). In bovine adrenal medullary cells, IFN-a decreases the V max of NE uptake, and 48-hour treatment of these cells with b-PMA to induce downregulation of PKC leads to a blunting of these effects.…”

Cytokine Interactions with Adrenal Medullary Chromaffin Cells

“…The CNS actions of IFN-a are particularly important because of the often-severe psychiatric side effects (depression and confusion) that accompany its use in antivirus or anti-tumour therapy (O'Brien et al 2004;Dafny and Yang 2005). This has led to considerable interest in IFN-a influence on various catecholaminergic systems including the adrenal medulla (Tachikawa et al 1997;Toyohira et al 1998).…”