Cholinergic differentiation of clonal rat pheochromocytoma cells (PC12) induced by factors contained in glioma-conditioned medium: enhancement of high-affinity choline uptake system and reduction of norepinephrine uptake system

Watery diarrhea, hypokalemia and achlorhydria syndrome due to an adrenal pheochromocytoma

Watery diarrhea, hypokalemia and achlorhydria (WDHA) syndrome caused by vasoactive intestinal polypeptide (VIP) -producing tumor only rarely occurs in patients with nonpancreatic disease. A 49-year-old woman was referred for evaluation of a right adrenal tumor incidentally diagnosed by abdominal ultrasound during the investigation of chronic watery diarrhea. Laboratory findings showed hypokalemia and excessive production of VIP and catecholamines. After surgical resection of the tumor, diarrhea subsided and both electrolytes and affected hormone levels normalized. Immunohistochemical examination confirmed a diagnosis of pheochromocytoma, which contained VIP-positive ganglion-like cells. We herein present the clinical and histogenetic implications of this rare clinical entity, with literature review.

Differential and coordinated regulation of expression of norepinephrine transporter in catecholaminergic cells in culture

The norepinephrine transporter (NET) terminates noradrenergic neurotransmission at synapse by high-affinity sodium-dependent reuptake into presynaptic terminals, and thus serves as a marker of differentiation of noradrenergic neurons. In the present study, we studied the regulatory mechanism of the expression of NET-mRNA in cultured neurons from newborn rat superior cervical ganglia (SCG) and in clonal rat pheochromocytoma cells (PC12) SCG neurons in culture expressed a high level of NET-mRNA, which was further increased 2.5-5 fold from day 1 to day 13. Treatment of SCG neurons with the cholinergic differentiation factor (CDF)/leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF), neurokines known to induce the switch from adrenergic to cholinergic phenotype in SCG neurons, led to the suppression of the level of NET-mRNA in a concentration dependent manner, concomitantly with the suppression of mRNA for tyrosine hydroxylase (TH), an adrenergic marker enzyme in cultured SCG neurons. On the other hand, retinoic acid, a compound which is also known to increase the expression of choline acetyltransferase, a cholinergic marker enzyme, and suppress the expression of TH in the cultured SCG neurons and PCI2 cells, rather increased the level of NET-mRNA in these two cell populations. Alterations of the Na(+)-dependent norepinephrine transport activity which paralleled the changes in the NET-mRNA levels were confirmed by the [3H]norepinephrine uptake assay. These results indicate that cell extrinsic factors regulate the expressions of NET and TH genes by a common as well as by distinct mechanisms.

Induction of cholinergic and adrenergic differentiation in N-18 cells by differentiation agents and DNA demethylating agents

Effects of various differentiating agents and DNA demethylating agents on the expression of choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH), marker enzymes for cholinergic and adrenergic differentiation, respectively, were examined in N-18 neuroblastoma cells. Retinoic acid (RA) and a medium conditioned over C6-glioma cells (GCM), which have been shown to enhance the ChAT activity of PC12 cells, NG108-15 cells and fetal rat brain cells, did not induce ChAT activity of N-18 cells. Treatment of the cells with the DNA demethylating agents alone also did not affect ChAT activity. But after pretreatment of the cells with the DNA demethylating agents, ChAT activity of N-18 cells was greatly increased by either RA or GCM. TH activity of N-18 cells was enhanced by forskolin, an activator of adenylate cyclase. The pretreatment of the cells with the DNA demethylating agents greatly enhanced the induction of TH activity by forskolin. Levels of ChAT and TH messenger RNA were altered in accordance with changes in ChAT and TH activities. Possible mechanisms of the actions of the demethylating agents on cholinergic and adrenergic differentiation are discussed.

Differences in neuronal and glial cell phenotypic expression in neuron-glia cocultures: Influence of glia-conditioned media and living glial cell substrata

Neuron-glia cocultures were prepared using, as a source for glial cells, either C6 glia (2B clone) of early (2B23) or late (2B111) passages or advanced passages of glial cells derived from primary cultures prepared from aged mouse cerebral hemispheres (MACH). Six-day-old chick embryo cerebral hemispheres (E6CH) were the source of neuron-enriched cultures. Glutamine synthetase (GS) activity was used as a marker for astrocytes and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) activity was used as a marker for oligodendrocytes. GS activity was markedly enhanced in cocultures of E6CH neurons and 2B23 glioblastic cells, whereas GS activity was reduced in cocultures of E6CH neurons and 2B111 astrocytic glia. In contrast, CNP activity was enhanced in cocultures of C6 glial cells with E6CH neurons. Glial cells from aged mouse brain did not respond to coculturing with E6CH neurons. It appears from these findings that neuronal input enhances the differentiation of glioblastic cells to either astrocytic or oligodendrocytic expression, whereas it decreases the activity of committed astrocytes. In contrast, glial cells from aged mouse brain do not respond to neuronal input. Choline acetyltransferase (ChAT) activity, a marker for cholinergic neurons, was enhanced only when E6CH cultures were grown in conditioned medium (CM) from 2B23 glioblastic cells. In contrast, ChAT activity was markedly diminished when E6CH neurons were cocultured with MACH glial cells but not when grown in CM from MACH glial cells. Thus, humoral factors from immature glial cells appear to enhance cholinergic neuronal phenotypic expression whereas cell-cell membrane contacts with aged glial cells diminish cholinergic phenotypic expression. The findings present supportive evidence that neuron-glia interrelationships are age dependent.

Cholinergic differentiation of clonal rat pheochromocytoma cells (PC12) induced by retinoic acid: increase of choline acetyltransferase activity and decrease of tyrosine hydroxylase activity

The effects of retinoic acid (RA), a naturally occurring metabolite of vitamin A, on the growth, morphology and neurochemical differentiation of the PC12 clone of rat pheochromocytoma cells were investigated. RA added to the medium inhibited the growth of PC12 cells in a dose-dependent manner up to 10 microM without affecting their morphology. In PC12 cells cultured in the presence of 10 microM RA for 8 days, the specific activity of choline acetyltransferase (ChAT) was increased 2-fold, while the specific activity of tyrosine hydroxylase (TH) was decreased 0.5-fold compared with cells cultured in the absence of RA. Specific activities of acetylcholinesterase (AChE), glutamate decarboxylase (GAD) and lactate dehydrogenase (LDH) were not affected by RA. Both the increase of ChAT and the decrease of TH induced by RA exhibited similar time and dose dependencies. RA inhibited the increase of TH activity induced by nerve growth factor (NGF), an adrenergic neuronotrophic factor on PC12 cells. From these observations it was concluded that RA induces a cholinergic neurochemical differentiation of PC12 cells independent of a morphological differentiation.

Possible involvements of intracellular Ca2+ and Ca2+ -dependent protein phosphorylation in cholinergic differentiation of clonal rat pheochromocytoma cells (PC12) induced by glioma-conditioned medium and retinoic acid

It is known that nerve growth factor (NGF) induces neurite outgrowth and elevation of the activity of adrenergic marker enzyme, tyrosine hydroxylase (TH) in clonal rat pheochromocytoma cells (PC12), whereas glioma-conditioned medium (GCM) induces neurite outgrowth and elevation of the activity of cholinergic marker enzyme, choline acetyltransferase (ChAT) in PC12 cells. In the previous study we have shown that retinoic acid (RA) induces specific elevation of ChAT activity and depression of TH activity without morphological differentiation (Matsuoka, I. et al., Brain Res., 502 (1989]. In the present study, we compared the effects of NGF, GCM and RA on the intracellular signalings in PC12 cells in relation to the mechanism of cholinergic differentiation. Addition of NGF, GCM or RA to the culture medium of PC12 cells caused a rapid rise in intracellular Ca2+ concentration [( Ca2+]i) reaching the level of almost 2.5-fold the resting condition within 3-18 h. Thereafter, [Ca2+]i of NGF-treated cells were decreased to the resting level within 12 h. On the other hand, [Ca2+]i of GCM-and RA-treated cells decreased to a level which was 1.8- to 2-fold the resting condition within 24-48 h and stayed at this level for up to 4-7 days. When homogenates of GCM- and RA-treated PC12 cells were incubated with [gamma-32P]ATP, phosphorylation of a protein with molecular mass of 27 kDa (27 K-protein) was specifically enhanced. The phosphorylation of the 27 K-protein was not seen in the homogenate of the NGF-treated cells. The phosphorylation of the 27 K-protein was dependent on Ca2+ and inhibited by inhibitors of Ca2+-dependent protein kinase, H-7 and W-7. Addition of H-7 and W-7 to the culture medium of PC12 cells abolished the elevation of ChAT activity specifically induced by GCM and RA. These observations suggested that the sustained increase of [Ca2+]i and Ca2+-dependent protein phosphorylation are involved in the intracellular signaling mechanism required for the cholinergic differentiation of PC12 cells induced by GCM and RA.

Antigen recognized by monoclonal antibodies to mesencephalic neural crest and to ciliary ganglion neurons is involved in the high affinity choline uptake mechanism in these cells

High-affinity choline uptake mechanisms are among the characteristics of cholinergic neurons such as the ciliary and choroid subpopulations in the ciliary ganglion (Barald and Berg, 1979). We have produced three monoclonal antibodies (Mabs), two of which were made to 8-day embryonic chick ciliary ganglion (CG) neurons (CG-1, CG-4) (Barald, 1982) and one of which was made to cultured mesencephalic neural crest (NC) cells (CG-14) removed from the embryo 31 hr after incubation. We have shown that all three Mabs label a common 75 kD antigen present on the cell surface of both CG neurons and NC cells (Barald, 1988). Here we report that the CG-1 and CG-4 antibodies, used in the same ratios in which they are synergistically cytotoxic for both the CG and NC cells (Barald, 1988), and Mab CG-14 alone, have specific effects on the high-affinity choline uptake mechanism (HACU) of CG neurons and isolated antigen-positive NC cells in the absence of complement. CG-1 and CG-4 in ratios of 8/1 (the same ratios that are used to kill the CG and the NC subpopulation), but neither singly, inhibit the HACU of CG neurons by 40% and that of isolated antigen-positive NC cells by 75%. However, CG-14 alone, at 1 microgram/ml, inhibits the HACU of both CG neurons and isolated NC cells by 95%. None of the antibodies had an effect on numbers of ouabain binding sites (a measure of the Na+/K+ ATPase) or cell surface acetylcholinesterase (AChE) of CG neurons or NC cells isolated by "no-flow" fluorescence cytometry with a Meridian Instruments ACAS470 cytometer. CG or NC cells grown in the presence of the antibodies without complement grow and remain healthy for many weeks. They exhibit no difference in morphology, protein content, lactate dehydrogenase activity (LDH), or division time from untreated sister cultures. Therefore, the antigen recognized by all three Mabs may be involved in a high-affinity choline uptake mechanism, a common characteristic of cholinergic neurons. The Mabs themselves may possibly label some element of the high-affinity transporter or a proximal membrane component. This implies that such a high-affinity uptake mechanism is present in the subpopulation of NC cells at early times in development. If these cells in fact are destined to contribute to the avian CG, these characteristics are present in the subpopulation before the NC cells take on a neuronal morphology.