Biomedical subjects

G Augusti-Tocco

Publications and source records attributed to G Augusti-Tocco.

At least 19 recordsLinked to original sources

PubMed2003

Hepatocyte growth factor stimulates cell motility in cultures of the striatal progenitor cells ST14A.

Hepatocyte growth factor/scatter factor (HGF/SF) is a growth factor with pleiotropic effects on different cell types. It acts as a mitogen and motility factor for many epithelial cells. HGF/SF and its receptor Met are present in the developing and adult mammalian brain and control neuritogenesis of sympathetic and sensory neurons. We report that the striatal progenitor ST14A cells express the Met receptor, which is activated after binding with HGF/SF. The interaction between Met and HGF/SF triggers a signaling cascade that leads to increased levels of c-Jun, c-Fos, and Egr-1 proteins, in agreement with data reported on the signaling events evoked by HGF in other cellular types. We also studied the effects of the exposure of ST14A cells to HGF/SF. By time-lapse photography, we observed that a 24-hr treatment with 50 ng/ml HGF/SF induced modification in cell morphology, with a decrease in cell-cell interactions and increase of cell motility. In contrast, no effect on cell proliferation was observed. To investigate which intracellular pathway is primarily involved we used PD98059 and LY294002, two specific inhibitors of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAP-kinase/ERK-kinase) and phosphoinositide 3-OH kinase (PI3-K), respectively. Cell motility in HGF/SF treated cultures was inhibited by LY294002 but not by PD98059, suggesting that PI3-K plays a key role in mediating the HGF/SF-induced dissociation of ST14A cells. Previous evidence of HGF stimulation of motility in nervous system has been obtained on postmitotic neurons, which have already acquired their specificity. Data reported here of a motogenic response of ST14A cell line, which displays properties of neuronal progenitors, seem of interest because they suggest that HGF could play a role in very early steps of neurogenesis.

Animals↗

PubMed2002

Alternative acetylcholinesterase molecular forms exhibit similar ability to induce neurite outgrowth.

Several groups have reported that acetylcholinesterase (AChE), through a mechanism not involving its catalytic activity, may have a role in fiber elongation. These observations were performed on experimental systems in which acetylcholine synthesis was active. Because neurite outgrowth can be modulated by neurotransmitters, we used the N18TG2 neuroblastoma line, which is defective for neurotransmitter production, to evaluate whether AChE may modulate neurite sprouting in nonenzymatic ways. To avoid the possibility that differences between transfected and mock-transfected clones may be due to the selection procedure, N18TG2 cells were previously subcloned, and the FB5 subclone was used for transfections. We performed transfections of FB5 cells with three distinct constructs encoding for the glycosylphosphoinositol-anchored AChE form, the tetrameric AChE form, and a soluble monomeric AChE form truncated in its C-terminus. A morphometric analysis of retinoic acid-differentiated clones was also undertaken. The results revealed that higher AChE expression following transfection brings about a greater ability of the clones to grow fibers with respect to nontransfected or mock-transfected cells irrespective of the used construct. Having observed no differences between the morphology of the transfected clones, we tested the possibility that the culture substrate can affect the capability of the clones to extend fibers. Also in this case we revealed no differences between the clones cultured on uncoated or collagen-pretreated dishes. These data indicate that alternative AChE molecular forms that differ in their C-teminal region exhibit similar ability to induce fiber outgrowth and suggest that the protein region responsible for this role is located in the invariant portion of the AChE molecule.

Acetylcholinesterase↗

PubMed2002

Muscarinic acetylcholine receptors induce neurite outgrowth and activate the synapsin I gene promoter in neuroblastoma clones.

The possible role of acetylcholine as a modulator of neuronal differentiation has been tested using a neuroblastoma cell line (N18TG2), which does not synthesize any neurotransmitter. Acetylcholine synthesis has been activated in this line by transfection with a construct containing a choline acetyltransferase (ChAT) cDNA; ChAT-positive clones share a higher ability to grow fibers and an activation of synapsin I expression compared to the parental cells. Atropine, a muscarinic antagonist, abolishes the higher ability to grow fibers of ChAT-positive transfected clones, and the cholinergic agonist carbachol induces higher neurite outgrowth in the parental line. In transient transfections of ChAT-positive clones, the expression of a reporter gene under the control of synapsin I promoter is considerably reduced by atropine, while it is not modified by carbachol; in contrast, in the parental cells, which do not synthesize acetylcholine, the reporter gene expression is induced by carbachol and this effect is abolished by atropine. The data presented provide evidence for the existence of a direct modulation of fiber outgrowth and synapsin I expression by muscarinic receptor activation, which may be related to early growth response gene-1 (EGR-1) levels.

Acetylcholine↗

PubMed2002

Impairment of cell cycle progression by aflatoxin B1 in human cell lines.

Aflatoxin B1 is a mycotoxin produced by Aspergillus flavus and Aspergillus parasiticum, which may be present as a food contaminant. It is known to cause acute toxic effects and act as a carcinogenic agent. The carcinogenic action has been related to its ability to form unstable adducts with DNA, which represent possible mutagenic sites. On the other hand, the primary cellular target responsible for its toxic action has not yet been clearly identified. Previous data suggested a possible correlation between cell proliferation and responsiveness to aflatoxin toxicity. These observations led us to investigate the effect of the toxin on cell cycle progression of three human cell lines (HepG2, SK-N-MC and SK-N-SH derived from liver and nervous tissue tumours); they were shown to display different responses to toxin exposure and have different growth kinetics. We performed analysis of the cell cycle, DNA synthesis and expression of p21 and p53 in the presence and absence of the toxin in all cell lines exposed. The results of cell cycle cytofluorometric analysis show significant alterations of cell cycle progression as a result of toxin treatment. In all cell lines exposure to a 24 h toxin treatment causes a dose-dependent accumulation in S phase, however, the ability to recover from impairment to traverse S phase varies in the cell lines under study. SK-N-MC cells appear more prone to resume DNA synthesis when the toxin is removed, while the other two cell lines maintain a significant inhibition of DNA synthesis, as indicated by cytofluorimetry and [(3)H]dTR incorporation. The level of p53 and p21 expression in the three cell lines was examined by western blot analysis and significant differences were detected. The ready resumption of DNA synthesis displayed by SK-N-MC cells could possibly be related to the absence of p53 control of cell cycle progression.

Aflatoxin B1↗

PubMed2001

In vitro and in vivo inhibition of SK-N-MC neuroblastoma growth using cyclic nucleotide phosphodiesterase inhibitors.

The effect of cyclic nucleotide phosphodiesterase (PDE) inhibitors Zaprinast and DC-TA-46 has been tested on SK-N-MC neuroblastoma growth. Antiproliferative activity of the tested drugs was assayed both in vitro and in the xenograft model of nude mice. In clonal density experiments, the IC50 value was 3.3 microM for Zaprinast and 1.9 microM for DC-TA-46, while 7.5 microM BCNU alkylating agent was required to obtain the same effect. SK-N-MC cells xenografted in the nude mouse showed that the administration of Zaprinast and DC-TA-46 caused a significant 50% decrease of the tumour weight. These data demonstrate that PDE inhibitors may be useful for at least reducing tumour growth; they may be of interest for further evaluation as alternative molecules in the design of multiple agent protocols for neuroblastoma treatment.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2000

Modulation of cholinergic marker expression by nerve growth factor in dorsal root ganglia.

The presence of cholinergic markers in sensory ganglia has suggested a possible functional role of acetylcholine both as a cofactor of morphogenesis in embryonic life and in sensory transduction during adult life. Acetylcholine, in fact, is able to excite cutaneous nociceptors and to modulate noxious stimuli. Nerve growth factor (NGF) overexpression induces the survival of nociceptive neurons, the expression of their specific markers, and hyperalgesia. On the other hand, NGF modulate the levels of cholinergic markers in several area of nervous system. Considering these observations, the present work aims to investigate whether NGF is able also to control the expression of cholinergic markers in chick sensory neurons in culture. We selected three developmental stages (E8, E12, and E18) representative of different phases of chick embryo development and performed observations on culture in which NGF was omitted at the plating time, withdrawn after the initial 24 hr of culture or maintained for 48 hr. In the experimental protocol devised, NGF did not significantly affect cell survival. At E12 a 48 hr treatment with NGF causes a significant but limited increase in acetylcholinesterase activity; activity increase was not observed when NGF was removed after 24 hr. No changes in acetylcholinesterase activity were observed at E8 and E18 stages. NGF appears to be more effective in the modulation of choline acetyltransferase activity. At E12, in fact, about a doubling of enzyme activity was measured after 24 or 48 hr of treatment with NGF. A response was also found at E18, when a 50% increase in choline acetyltransferase activity was observed just after 24 hr treatment. The behavior of muscarinic receptors in response to NGF differs compared to the two cholinergic enzymes. At E8 and E12 a profound increase in muscarinic receptor expression was observed. Conversely, at E18 NGF produces a 50% reduction of receptors. Considering these observations and the demonstrated role of muscarinic receptors in the desensitization of nociceptors, the reduction of muscarinic receptors in DRG after NGF treatment is in agreement with the proposed algogenic action of NGF in the skin.

Acetylcholine↗

PubMed2000

Muscarinic receptors modulate intracellular calcium level in chick sensory neurons.

In the present work we have studied the variation of intracellular calcium levels induced by muscarinic agonists in chick dorsal root ganglia neurons. Muscarinic agonists such as muscarine and oxotremorine cause an increase of intracellular calcium levels in fura-2AM-loaded DRG neurons of E18 chick embryos. This increase was abolished following treatment with 1 microM atropine but not by 1 microM mecamylamine, indicating that the observed intracellular calcium increase, was dependent on muscarinic receptor activation. Stimulation in absence of external calcium or pre-incubation of the DRG cultures with thapsigargin or Mn(2+) demonstrated that [Ca(2+)](i) increase is mainly due to its release from intracellular stores. The use of selective antagonists of muscarinic receptor subtypes also indicated that M(1) and to a lesser extent M(3) receptor subtypes are responsible for the observed intracellular calcium mobilization. Finally pre-treatment of DRG cultures with pertussis toxin showed that the variation of [Ca(2+)](i) levels was dependent on PTX-insensitive G-protein. Moreover muscarinic agonists induce in DRG also the increase of IPs level, suggesting that the variations of intracellular calcium levels may be due at least in part to the activation of the phosphoinositide transduction pathway. In conclusion the reported observations demonstrate the activity of muscarinic receptors in sensory neurons, suggesting a functional role for acetylcholine in sensory transduction.

Animals↗

PubMed2000

Activation of neurospecific gene expression by antennapedia homeobox peptide.

Antennapedia homeobox peptide has been reported to enhance neurite outgrowth and branching. Thus it is of interest to investigate whether antennapedia peptide is capable of modulating the expression of genes related to different events of neuronal development. In this paper we report the enhancement of a 68 KDa neurofilament subunit, choline acetyltransferase and acetylcholinesterase expression in spinal cord neurons, elicited by antennapedia peptide. Modulation of gene expression is different with respect to each gene product analyzed, suggesting a specific action of the peptide on diverse genes controlling different events of neuronal differentiation.

Acetylcholinesterase↗

PubMed2000

Neuronal glycolytic pathway impairment induced by HIV envelope glycoprotein gp120.

Neurological impairment is a common feature of Acquired Immunodeficiency Syndrome (AIDS); functional alterations have been reported both in central and peripheral nervous system and the Human Immunodeficiency Virus (HIV) envelope glycoprotein gp120 has been proposed as a neurotoxin acting through a calcium-dependent mechanism. On the other hand it has been reported that gp120 treatment also induce about a 20% decrease in the cerebral glucose utilization and in the cellular ATP levels. The reported observations were performed on experimental system where also non-neuronal cells where present; in order to evaluate whether a direct interaction between HIV proteins and neuronal cells takes place, we used a neuroblastoma cultures where only neuronal cells are present. We analysed the effects of gp120 on the N18TG2 neuroblastoma clone. Treatments were performed both on growing and confluent cultures. Short time treatment with gp120 of confluent cultures causes a 25% reduction in the level of neuron-specific enolase, resulting in a similar decrease of oxygen consumption. Long time exposure of growing cells also causes a reduction in cell survival. Furthermore, using a membrane-specific fluorescent probe we observed that gp120 produces an increase of membrane trafficking. These observations suggest a direct interaction between the viral envelope protein and neuronal cells, which results in an alteration of glycolytic metabolism. This alteration may be related to the neurologic impairments observed in AIDS patients.

Animals↗

PubMed2000

Modulation of acetylcholinesterase and voltage-gated Na(+) channels in choline acetyltransferase- transfected neuroblastoma clones.

Neurotransmitters appear early in the developing embryo and may play a role in the regulation of neuronal differentiation. To study potential effects of acetylcholine production in neuronal differentiation, we used the FB5 subclone of N18TG2 murine neuroblastoma cells stably transfected with cDNA for choline acetyltransferase. We tested whether the forced acetylcholine production can modify the expression or the cellular localization of different neuronal markers. We studied the activity, localization, and secretion of acetylcholinesterase in view of its possible role in the modulation of the morphogenetic action of acetylcholine and of its proposed role of a regulator of neurite outgrowth. FB5 cells are characterized by a high level of acetylcholinesterase, predominantly released into the culture medium. Acetylcholinesterase secretion into the medium was lower in choline acetyltransferase-transfected clones than in nontransfected and antisense-transfected controls. Moreover, sequential extraction of acetylcholinesterase revealed that detergent-extracted, i.e., membrane-associated, activity was higher in the transfected clones expressing choline acetyltransferase activity than in both control groups. These observations suggest that a shift occurs in the utilization of acetylcholinesterase in choline acetyltransferase-transfected clones from a secretion pathway to a pathway leading to membrane localization. In addition, the choline acetyltransferase-positive clones showed higher densities of voltage-gated Na(+) channels and enhanced high-affinity choline uptake, suggesting the accomplishment of a more advanced differentiated neuronal phenotype. Finally, binding experiments demonstrated the presence of muscarinic acetylcholine receptors in all examined clones. This observation is consistent with the proposed existence of an autocrine loop, which may be important for the enhancement in the expression of neurospecific traits.

Acetylcholinesterase↗

PubMed2000

Acetylcholine synthesis and neuron differentiation.

Development of the nervous system is dependent on the co-operation between cell determination events and the action of epigenetic factors; in addition to well known factors, e.g. growth factors, neurotransmitters have been assigned a role as "morphogens" and modulators of neuronal differentiation in an early developmental phase. The possible role of acetylcholine as a modulator of neuronal differentiation has been considered in two experimental systems. A neuroblastoma cell line, which does not synthesise any neurotransmitter, has been transfected with a choline acetyltransferase construct; activation of acetylcholine synthesis, thus achieved, is followed by a higher expression of neuronal specific traits. The presence in these cells of muscarinic receptors is consistent with the existence of an autocrine loop, which may be responsible for the more advanced differentiation state observed in the transfected cells. Expression of cholinergic markers appears as a common feature of DRG sensory neurons, independently of the neurotransmitter used. Choline acetyltransferase can be detected in DRG at early developmental stages. The distribution of muscarinic receptors in DRG has suggested that activation of acetylcholine synthesis may be related in an early developmental phase to the interaction between neurons and nonneuronal cells and to modulation of cell differentiation. Both systems suggest that acetylcholine may have a role as a modulator of neuronal differentiation.

Acetylcholine↗

PubMed1999

Expression of muscarinic m2 receptor mRNA in dorsal root ganglia of neonatal rat.

The expression of mRNA coding for m2 subtype of muscarinic cholinergic receptors was assessed in dorsal root ganglia (DRG) of 15-day post-natal rats. Northern blot analysis on total RNA using a mixture of two different oligonucleotide probes, indicated the presence of a single prominent band of approximately 6.5 kb in rat DRG; a band of the same size was observed both in brainstem and cortex taken as positive controls. Analysis by RT-PCR of the mRNA coding for a region of the third cytoplasmic loop of m2 receptor showed a single signal both in rat DRG and hippocampus. In situ hybridization was then used to identify the neuronal subpopulations expressing the mRNA for M2. The transcripts were preferentially localized in medium-small neurons of the ganglion as well as in satellite cells surrounding the neuron cell body. Large neurons were usually negative. Finally, competition binding experiments, performed in the presence of [3H]-quinuclidinyl benzilate (QNB) and methoctramine (a selective competitor for M2 receptors), demonstrated the presence of M2 receptor protein (Ki=100 nM), as previously observed in chick DRG. The preferential localization of M2 in medium-small neurons of the ganglion suggests the involvement of this receptor subtype in the transduction of nociceptive stimuli.

Animals↗

PubMed1999

cAMP-dependent induction of PDE5 expression in murine neuroblastoma cell differentiation.

The present study demonstrates, in both hybrid NG108-15 and mouse neuroblastoma N18TG2 cells, the presence and regulation of PDE5 mRNA during cell differentiation. PDE5 cDNA probes in Northern blot analysis recognize a approximately 9 kb transcript in bovine lung as well as in mouse neuroblastoma cells. Hybridization on total RNA extracted from dibutyryl-cAMP-treated NG108-15 cells shows a 5-fold increase of PDE5 9 kb mRNA: such an increase is not observed in N18TG2 although we observed a similar increase in the enzymatic activity of both cell lines. Our data demonstrate that PDE5 gene expression can be regulated by cAMP and suggest the existence of a complex regulatory system for PDE5 activity.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed1999

Aflatoxin B1 is an inhibitor of cyclic nucleotide phosphodiesterase activity.

Aflatoxin B1 (AFB1) action on cyclic nucleotide phosphodiesterase (PDE) activity has been tested on tissue extracts of various organs. In the presence of 100 microM AFB1 a significant inhibition of cAMP and cGMP hydrolytic activity is observed in all tested tissue extracts. However, cGMP hydrolytic activity appears more sensitive to AFB1 inhibition than cAMP hydrolytic activity and a considerably higher inhibition is observed in lung and spleen, than in liver, brain, kidney, and heart. When cGMP is used as substrate, the inhibitory response reaches 72% in lung and spleen extracts. We have also tested AFB1 effects on lung and liver PDE activity peaks separated by DEAE-cellulose chromatography. These data confirm the poor sensitivity to the toxin of all PDE activities present in liver, while the lung peak (where PDE V in present) shows a higher sensitivity to AFB1. In order to establish whether PDE V is in fact more sensitive to AFB1, we have used mouse neuroblastoma cells, in which cGMP hydrolytic activity has been shown to be due to PDE V only. In this case, the calculated IC50 is 24 microM and Dixon plot analysis shows a competitive inhibitory effect with a Ki of 16.7 microM. We have also used aflatoxin B2 and M2, and they proved to be much less effective than AFB1: AFB2 inhibits PDE V with an IC50 of 117 microM, while AFM2 does not show any effect. These results provide the first evidence of a competitive inhibition of AFB1 on an enzymatic activity and suggest that an alteration of cellular cyclic nucleotide levels may play a role in the mechanism of aflatoxin action.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Rat dorsal root ganglia express m1-m4 muscarinic receptor proteins.

The distribution of m1-m4 muscarinic acetylcholine receptors was investigated by immunolight and electron microscopy in rat dorsal root ganglia, by using subtype-specific antibodies. The light microscopic observations show that both the intensity and the localisation of immunolabeling of the four muscarinic subtypes are different. The m2 receptor is the most represented; m2 and m4 receptor proteins are principally expressed in the small-medium type neurones, while m1 and m3 receptor proteins are more homogeneously distributed among the neuronal population of the ganglion. On the contrary, there are no relevant differences in the subcellular distribution. Ultrastructural analysis shows that immunolabeling is associated with the Nissl bodies, budding Golgi cisterns, and as far as the m2 receptor is concerned, just beneath the plasmalemma with discrete loci along the neuronal plasma membrane. Unmyelinated nerve fibres are always immunopositive for all muscarinic receptor subtypes, suggesting an active transport for all subtypes. Occasionally perineuronal satellite cells surrounding large neurones are immunopositive for the m2 receptor, while both myelinating and non-myelinating Schwann cells faintly express all muscarinic receptor subtypes. These observations, together with previous data concerning pharmacological and functional characterisation of muscarinic acetylcholine receptors in dorsal root ganglion, suggest that sensory neurones are able to respond to acetylcholine. The presence of m2 and m4 immunoreactivity in the small type neurones and in their fibres involved in nociceptive response, suggest that these receptors may participate in the modulation of transduction of noxious stimuli from the periphery to the spinal cord. m1 and m3 receptors, having a more homogeneously distribution, may be involved in transduction of different kinds of stimuli.

Animals↗

PubMed1998

Neuronal and non-neuronal cell populations of the avian dorsal root ganglia express muscarinic acetylcholine receptors.

The distribution of muscarinic acetylcholine receptors was investigated by immuno-light and electron microscopy in the chick dorsal root ganglion during embryonic development (E12 and E18) and after hatching. The monoclonal antibody we used recognizes the acetylcholine binding site shared by all five muscarinic acetylcholine receptor subtypes. At E12, light microscopy reveals several immunopositive neurons with variable degrees of immunolabeling, heterogeneously distributed throughout the ganglion. Later in development and after hatching, the intensity of immunolabeling seems to decrease and the immunopositive neurons, of the small-medium-sized type, are located mostly in the medio-dorsal region of the ganglion. Under the electron microscope, the immunoreaction is associated with the Nissl bodies, budding Golgi cisterns and, especially at E12, with discrete loci along the neuronal plasma membrane. Unmyelinated nerve fibers, in both central and peripheral branches, are also immunopositive, suggesting that muscarinic acetylcholine receptors are transported towards the spinal cord and the periphery, respectively. A large number of perineuronal satellite cells and both myelinating and unmyelinating Schwann cells are intensely labeled. These observations, combined with previous data on the pharmacological and functional characterization of muscarinic acetylcholine receptors in the avian dorsal root ganglion, suggest that both sensory neurons and non-neuronal cells are able to respond to acetylcholine stimuli. Since muscarinic acetylcholine receptor-immunoreactivity is restricted to the small-medium-sized neurons and their unmyelinated fibers, of the nociceptive type, we suggest that these receptors are involved in modulating the transduction of noxious stimuli from the periphery.

Animals↗

PubMed1997

Calmodulin-dependent cyclic nucleotide phosphodiesterase in adult and developing chick spinal cord.

We investigated the level and characteristics of "low Km" 3'-5' cyclic nucleotide phosphodiesterase (PDE) activity in adult and embryo chick spinal cord. The DEAE cellulose chromatography elution profile of Triton X-100 extracts showed a single peak of calmodulin-dependent cAMP/cGMP PDE activity. After two additional purification steps, this activity showed a five-fold activation by calmodulin (Ka = 1.5 nM) for cGMP hydrolysis, and a linear kinetic behaviour with a Km of 1.3 microM. Conversely, the activity showed a biphasic behaviour for cAMP hydrolysis, with Km values of 3.1 and 18.5 microM. The enzyme showed a Stokes radius of 4.5 nm. Western blot analysis of the purified enzyme revealed two immunoreactive bands with molecular mass of 59 and 65 kDa, respectively. Immunohistochemical staining showed motoneuron decoration both on cell soma and fibres. The developmental pattern of Ca2+-calmodulin-dependent PDE expression in spinal cord was also studied; the hydrolytic activity for both substrates has been found to increase constantly from E5 to post-hatching stages, when it appears 5.6-fold higher as compared to the early embryo levels. Furthermore, in cultured spinal cord neurons from E8 embryos, muscle extract has been shown to induce a two-fold increase of Ca2+-calmodulin-dependent cGMP activity. In conclusion, the studies reported here present three relevant findings: (1) the presence in adult and embryo chick spinal cord of PDE activities with characteristics similar to those of the mammalian PDE I enzyme; (2) its localization in the ventral horn motoneurons; (3) its regulated expression during embryogenesis that is possibly related to soluble epigenetic factors produced by the target cells.

Animals↗

PubMed1997

Induction of cyclic AMP and cyclic GMP 3':5'-cyclic nucleotide phosphodiesterase activities in neuroblastoma lines under differentiating conditions.

It is now widely accepted that cyclic nucleotide phosphodiesterases (PDEs) play fundamental roles in signal transduction pathways; they show a remarkable molecular complexity, different tissue distribution and complex regulatory mechanisms. Here we report PDE isoforms expression in two dibutyryl cyclic AMP differentiated murine cell lines: the hybrid neuroblastoma-glioma 108CC15 and the parental neuroblastoma N18TG2. They differ in the ability to establish functional synapses, a feature present only in the former. Ionic exchange chromatography elution profiles of N18TG2 and 108CC15 undifferentiated cell extracts show two main peaks of activity. The first one hydrolyzes cyclic GMP and is specifically inhibited by Zaprinast, thus representing a member of the PDE5 family. The second peak hydrolyzes cyclic AMP and is significantly inhibited by rolipram, as all the PDE4 family members. The induction of differentiation by dibutyryl cyclic AMP in both clonal lines results in an increase of PDE activities only after 3 hr of treatment, suggesting that protein neosynthesis is involved. Interestingly in both clones, besides the increase in cyclic AMP hydrolyzing specific activity (3.1-fold in 108CC15 and 2.5-fold in N18TG2), we also observed an increase in cyclic GMP hydrolyzing activity (1.7-fold in 108CC15 and 4.3-fold in N18TG2). While the induction of PDE4, previously reported also in other cellular systems, could be considered as a feedback response to the higher cyclic AMP levels, this is not true for the isoform that hydrolyzes cyclic GMP. These data suggest that the induction of PDE isoforms in neuroblastoma cells could be related to the activation of neuronal differentiative pathway.

3',5'-Cyclic-AMP Phosphodiesterases↗