Molecular cloning of the cDNA coding for mouse aldehyde oxidase: tissue distribution and regulation in vivo by testosterone

The cDNA coding for mouse aldehyde oxidase (AO), a molybdoflavoprotein, has been isolated and characterized. The cDNA is 4347 nt long and consists of an open reading frame predicting a polypeptide of 1333 amino acid residues, with 5' and 3' untranslated regions of 13 and 335 nt respectively. The apparent molecular mass of the translation product in vitro derived from the corresponding cRNA is consistent with that of the monomeric subunit of the AO holoenzyme. The cDNA codes for a catalytically active form of AO, as demonstrated by transient transfection experiments conducted in the HC11 mouse mammary epithelial cell line. The deduced primary structure of the AO protein contains consensus sequences for two distinct 2Fe-2S redox centres and a molybdopterin-binding site. The amino acid sequence of the mouse AO has a high degree of similarity with the human and bovine counterparts, and a significant degree of relatedness to AO proteins of plant origin. Northern blot and in situ hybridization analyses demonstrate that hepatocytes, cardiocytes, lung endothelial or epithelial cells and oesophagus epithelial cells express high levels of AO mRNA. In the various tissues and organs considered, the level of AO mRNA expression is not strictly correlated with the amount of the corresponding protein, suggesting that the synthesis of the AO enzyme is under translational or post-translational control. In addition, we observed sex-related regulation of AO protein synthesis. In the liver of male animals, despite similar amounts of AO mRNA, the levels of the AO enzyme and corresponding polypeptide are significantly higher than those in female animals. Treatment of female mice with testosterone increases the amounts of AO mRNA and of the relative translation product to levels similar to those in male animals.

Correlation between prevention of cataract development by disulfiram and fates of selenium in selenite-treated rats

PURPOSE

We found a new pharmacological effect of disulfiram (DSF) against rat pups with cataract induced by selenite injection. The possible reactive mechanism is discussed in this present paper.

METHODS

Wistar male and female rats aged 13 and 30 days, and male rats aged 7 weeks were used this present study. Cataract was induced by injection of selenite (19 micromol/kg, s.c.) to 13-day old rats. The lens opacification was monitored by using the slit lamp equipped with an anterior eye segment analysis system (EAS-1000, Nidek). The selenium contents in rat organs were detected fluorimetrically. Liposomes containing DSF (DSF-liposomes) were prepared by the reverse-phase evaporation method. Rat pups were instilled 5 microl of DSF-liposomes into both eyes 4 times per day. Adult rats were administered with DSF suspensions (100 mg/kg) by nasal cannulation. The changes of plasma concentration of diethyldithiocarbamate (DDC), which was a metabolite of disulfiram, were determined by HPLC method.

RESULTS

Intraocular treatment with DSF-liposomes prevented the onset of cataract development in rat pups injected with sodium selenite. Treatment with DSF also significantly reduced the selenium contents in plasma at 1 h post-treatment and in the eye at 96 h post-treatment. No significant differences of selenium content in liver and kidney were observed in 13-day old rats instilled with DSF-liposomes or DSF free liposomes. Cataract could not be induced in the 30-days-old rats with the same dose of selenite (19 micromol/kg) and the liver, kidney, and especially eye of the older rats had lower levels of selenium than 13-day old rats. Diethyldithiocarbamate (DDC), an active metabolite of DSF, was decreased in the plasma following a subcutaneous injection of sodium selenite. The selenium concentration in the plasma was decreased by the intranasal administration of DSF suspensions.

CONCLUSIONS

Instillation of DSF-liposomes into the eyes of rat pups given a subcutaneous injection of sodium selenite to induce cataracts prevented the formation of cataracts. The mechanism of inhibition may have resulted from a decreased level of selenium in the eyes following the treatment with DSF. On the other hand, as it is known that the cataracts may result from selenite-induced oxidative stress in the lens, DSF and DDC may react as anti-oxidants.

The novel synthetic retinoid 6-[3-adamantyl-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) causes apoptosis in acute promyelocytic leukemia cells through rapid activation of caspases

The synthetic retinoid 6-[3-adamantyl-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437), which was originally developed as an retinoic acid receptor (RAR)-gamma agonist, induces rapid apoptosis in all-trans retinoic acid (ATRA)-sensitive and ATRA-resistant clones of the NB4 cell line, a widely used experimental model of acute promyelocytic leukemia (APL). In addition, the compound is apoptogenic in primary cultures of freshly isolated APL blasts obtained from a newly diagnosed case and an ATRA-resistant relapsed patient. NB4 cells in the S-phase of the cycle are most sensitive to CD437-triggered apoptosis. CD437-dependent apoptosis does not require de novo protein synthesis and activation of RAR-gamma or any of the other nuclear retinoic acid receptors. The process is preceded by rapid activation of a caspase-like enzymatic activity capable of cleaving the fluorogenic DEVD but not the fluorogenic YVAD tetrapeptide. Increased caspase activity correlates with caspase-3 and caspase-7 activation. Inhibition of caspases by z-VAD suppresses the nuclear DNA degradation observed in NB4 cells treated with CD437, as well as the degradation of pro-caspase-3 and pro-caspase-7. CD437-dependent activation of caspases is preceded by release of cytochrome c from the mitochondria into the cytosol of treated cells. Leakage of cytochrome c lays upstream of caspase activation, because the phenomenon is left unaffected by pretreatment of NB4 cells with z-VAD. Treatment of APL cells with CD437 is associated with a caspase-dependent degradation of promyelocytic leukemia-RAR-alpha, which can be completely inhibited by z-VAD.

Isolation and characterization of the gene coding for human cytidine deaminase

The human gene coding for cytidine deaminase (CD), the enzyme which catalyzes the deamination of cytidine and deoxycytidine to uridine and deoxyuridine, was isolated and structurally characterized. CD is a single copy gene with a length of 31 kb and consists of four exons. Exon-intron junctions do not bracket functional domains of the encoded protein as the boundary between exons 2 and 3 interrupts the catalytically important zinc-finger domain, which is well conserved along phylogenesis. 5'-RACE and RNase mapping experiments identify one major and multiple other minor transcription initiation sites, which are present in placenta as well as in the myeloid cell lines, HL-60 and U937. The 5'-flanking region of the gene contains an orientation-dependent functional promoter and is characterized by the presence of several potential sites for the binding of known transcriptional factors.

Cross-talk between retinoic acid and interferons: molecular mechanisms of interaction in acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) and interferons (IFNs) are active anticancer agents. ATRA is capable of inducing complete remission in acute promyelocytic leukemia (APL) patients, whereas IFNalpha is successfully used in the treatment of the stable phase of chronic myeloid leukemia. ATRA and IFNs have shown synergistic interactions in various experimental conditions and represent a potentially useful therapeutic combination in the treatment of various types of leukemias and solid tumors. The molecular basis of these interactions are poorly understood and need to be elucidated. In this review, we summarize a series of recent observations concerning the molecular mechanisms underlying the cross-talk between the intracellular pathways activated by ATRA and IFNs in APL cells. In APL blasts, IFNs regulate the expression of retinoic acid receptors, and ATRA, in turn, modulates the levels and the state of activation of members of the Jak-STAT second messenger pathway. This demonstrates a two-way interaction between ATRA and IFNs, which leads to cross-modulation of genes normally under the control of the retinoid and the cytokine. These data may be relevant in the context of a rational use of the combination between ATRA and IFNs in the clinical management of myeloid leukemias.

A comparison of Listeria monocytogenes serovar 4b isolates of clinical and food origin in Japan by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) patterns of 102 L. monocytogenes serovar 4b isolates from patients and foods examined in Japan were compared with 16 isolates from foodborne listeriosis episodes which occurred in North America or Europe. Using a combination of PFGE patterns with the restriction enzymes SmaI, ApaI, AscI and Sse8387I, 82 clinical isolates from Japan were categorized into 45 PFGE types: the largest group of 17 isolates (20.7%) were of the same PFGE type as cultures from the large foodborne outbreaks which occurred in California (1985) and Switzerland (1983-1987). Twenty cultures from foods on retail sale in Japan were classified into 12 PFGE types: four isolates were of three PFGE types also recognized among isolates of clinical origin from Japan, including the predominant clinical type.

Isolation and characterization of the human aldehyde oxidase gene: conservation of intron/exon boundaries with the xanthine oxidoreductase gene indicates a common origin

Aldehyde oxidase (AO) is a molybdo-flavo enzyme involved in the metabolism of various endogenous and exogenous N-heterocyclic compounds of pharmacological and toxicological importance. The enzyme is the product of a gene which is implicated in the aetio-pathogenesis of familial recessive amyotrophic lateral sclerosis. Here, we report the cloning and structural characterization of the human AO gene. AO is a single copy gene approximately 85 kb long with 35 transcribed exons. The transcription-initiation site and the sequence of the 5'-flanking region, containing several putative regulatory elements, were determined. The 5'-flanking region contains a functional promoter, as assessed by appropriate reporter constructs in transient transfection experiments. Comparison of the AO gene structure shows conservation of the position and type of exon/intron junctions relative to those observed in the gene coding for another molybdo-flavoprotein, i.e. xanthine oxidoreductase (XOR). As the two genes code for proteins with a high level of amino acid identity, our results strongly suggest that the AO and XOR genetic loci arose as the consequence of a duplication event. Southern blot analysis conducted on genomic DNA from various animal species with specific cDNA probes indicates that the AO gene is less conserved than the XOR gene during evolution.

Sequence analysis of the actA gene of Listeria monocytogenes isolated from human

The region encoding proline-rich units of actA genes was amplified from 24 strains of Listeria monocytogenes using polymerase chain reaction (PCR). PCR products of 13 strains showed the expected size of 623 bp, whereas those of 11 strains showed a short size of 518 bp. The shortening of these PCR products resulted from the deletion of one proline-rich unit. These results indicate that ActA proteins are divided into at least two different types which are unrelated to bacterial serotypes.

Molecular mechanisms of retinoid action in acute promyelocytic leukemia (Review)

Acute promyelocytic leukemia (APL) is, at present, the first and only example of leukemia which can be induced into remission with a single cyto-differentiating agent. This is due to the fact that APL is exquisitely sensitive to the differentiating action of all-trans retinoic acid (ATRA). Thus, the APL model offers a unique opportunity to study the cyto-differentiating action of ATRA and synthetic retinoids in a clinically relevant setting. This review article summarizes the work relating to the molecular mechanisms underlying the action of retinoic acid and retinoids in APL cells, and focuses on: a) genes which are expressed and regulated by ATRA; b) synthetic retinoids as cyto-differentiating agents; c) rational combinations between retinoids and cytokines or other cyto-differentiating agents; d) cellular paradigms of retinoic acid resistance. It is our aim to give an updated, about nonexhaustive, account of some of the most recent development regarding the pharmacological action of retinoic acid and its derivatives in APL cells.

Selective localization of mouse aldehyde oxidase mRNA in the choroid plexus and motor neurons

Aldehyde oxidase (AO), a protein involved in the catabolism of catecholamines, is the product of a gene potentially responsible for one of the familial forms of the motor neuron disease, amyotrophic lateral sclerosis (ALS). Here, we report on the cloning of a partial cDNA coding for the mouse enzyme. Using this cDNA as a probe, we demonstrate that the AO transcript is expressed in the epithelial component of the choroid plexus. More importantly, in the gray matter, the mRNA is selectively localized in the large motor neurons of the nuclei of facial, motor trigemini and hypoglossus nerves and in the motor neurons of the anterior horns of the spinal cord. This localization is consistent with a possible role of AO in the pathogenesis of ALS.

Flow cytometry of leucocyte alkaline phosphatase in normal and pathologic leucocytes

Leucocyte alkaline phosphatase (LAP) is an enzyme expressed on the external aspect of the neutrophilic granulocyte plasma membrane, and represents a specific marker for the fully differentiated granulocyte. In this report we characterize 1B12.1, a monoclonal antibody raised against human bone alkaline phosphatase, by its ability to recognize the LAP protein. As assessed by Western blot analysis, following electrophoresis under non-reducing conditions, the antibody specifically reacts with LAP upon forced expression of the protein in simian COS-7 fibroblasts. In addition, the 1B12.1 antibody recognizes partially purified LAP isolated from peripheral blood granulocytes. With this antibody we developed a quantitative flow-cytometry-based method for the determination of LAP. Double fluorescence flow cytometry demonstrated that the LAP protein was present in relatively high amounts in neutrophilic granulocytes, but not in monocytes, natural killer cells, or B and T lymphocytes of normal individuals. The protein was completely absent in granulocytes obtained from chronic myeloid leukaemia and paroxysmal nocturnal haemoglobinuria patients. Higher than normal levels of LAP protein were evident in neutrophilic granulocytes of patients suffering from polycythaemia vera, essential thrombocythaemia and severe aplastic anaemia. However, the highest amounts of LAP protein were present in the granulocytes of normal individuals treated with G-CSF for the isolation of peripheral blood stem cells.

Stat1 is induced and activated by all-trans retinoic acid in acute promyelocytic leukemia cells

Treatment of freshly isolated acute promyelocytic leukemia (APL) cells and the myelogenous leukemia cell lines, NB4, HL-60, and U937, with all-trans retinoic acid (ATRA) results in a remarkable elevation in the amounts of Stat1 alpha and Stat2 proteins. Stat1 alpha protein levels are augmented by ATRA as a consequence of elevated amounts of the corresponding transcripts. The retinoid increases the levels of nuclear complexes that are capable of binding to interferon (IFN)-regulated consensus sequences and contain Stat1 and/or Stat2 proteins, and causes a rapid and long-lasting elevation in Stat1 alpha tyrosine phosphorylation. Transient transfection experiments show that ATRA enhances the transactivating properties of Stat1 alpha observed on an appropriate reporter gene, in the presence of the RAR alpha retinoic acid receptor, but not in the presence of the PML-RAR protein. Treatment of NB4 cells with ATRA is associated with a remarkable upregulation of the two IFN-responsive genes IFN-responsive factor 1 and 2'-5' oligoadenylate synthetase, as well as with an augmentation in the levels of IFN alpha secretion. Our data show that ATRA is capable of modulating the amounts and the state of activation of some of the components of the IFN intracellular signaling pathways. They also suggest that the retinoid can bypass IFN/IFN-receptor interactions and induce the expression of IFN-regulated genes.

Expression of xanthine oxidoreductase in mouse mammary epithelium during pregnancy and lactation: regulation of gene expression by glucocorticoids and prolactin

In the mammary gland of virgin mice, xanthine oxidoreductase (XOR) enzymic activity is barely measurable. a high increase in the levels of the enzyme is observed during the last days of pregnancy and during lactation, and this is parallelled by an elevation in the amounts of the respective protein and transcript. In situ hybridization experiments demonstrate that the XOR mRNA is specifically expressed in the alveolar epithelial cells of the mammary gland. In HC11 cells, a model culture system for normal breast epithelium, the levels of XOR enzymic activity are dose- and time-dependently induced by dexamethasone, and a further synergistic augmentation is observed in the presence of dexamethasone plus prolactin. Increased XOR gene expression is consequent on glucocorticoid receptor activation, as indicated by sensitivity to the specific receptor antagonist RU486. In addition, the phenomenon is likely to involve protein phosphorylation and dephosphorylation events, as suggested by modulation of XOR mRNA by tyrosine kinase and phosphatase inhibitors.

Interferons induce normal and aberrant retinoic-acid receptors type alpha in acute promyelocytic leukemia cells: potentiation of the induction of retinoid-dependent differentiation markers

Treatment of the acute promyelocytic (APL) cell line NB4 with interferon alpha (IFN(alpha)), as well as IFN(beta) and gamma, results in an increased expression of the transcripts coding for retinoic-acid receptor type alpha (RAR(alpha)) and the leukemia-specific retinoic acid receptor PML-RAR. Transcriptional induction of the RAR(alpha) and PML-RAR mRNAs is rapid and it is parallelled by an increase in the corresponding proteins. Up-regulation of RAR(alpha) and PML-RAR gene expression by IFN(alpha) is accompanied by a strong potentiation in the induction of 2 retinoid-dependent granulocytic markers, i.e., granulocyte-colony-stimulating factor receptor mRNA and leukocyte alkaline phosphatase. However, IFN(alpha) does not have any effects on the retinoid-dependent regulation of the myeloid surface markers CD11b and CD33. The IFN-dependent increase in RAR(alpha) levels and the enhancing effect of the cytokine on retinoid-dependent granulocytic markers expression may be a characteristic of PML-RAR positive cells, since the phenomena are not observed in HL-60 promyelocytes. Interferons as well as retinoids inhibit the growth of NB4 cells, although the 2 classes of compounds do not significantly interact in terms of anti-proliferative activity. These results suggest the possible use of combinations between IFNs and retinoic acid in the cyto-differentiating treatment of APL patients.

Effects of 1,25-dihydroxy vitamin D3 on all-trans retinoic acid sensitive and resistant acute promyelocytic leukemia cells

Following challenge of the acute promyelocytic leukemia (APL) cell line, NB4, with 1, 25 dihydroxy vitamin D3 (1, 25 D3), no increase in the expression of the monocytic surface markers, CD11c, CD14 and HLA-DR is observed. By contrast, 1, 25 D3 increases the expression of CD11b, an early myeloid marker and enhances adherence to plastic following priming of the cells with phorbol 12-myristate 13-acetate (PMA). NB4.306 and NB4.007/6, two all-trans retinoic acid-resistant cell lines originated from NB4 promyelocytes and lacking expression of a complete form of PML-RAR, are totally resistant to 1, 25 D3-dependent induction of CD11b. In addition, NB4.306 cells do not show enhanced plastic adherence following treatment with the vitamin D metabolite and PMA. NB4 and NB4.306 express similar amounts of the transcripts coding for the vitamin D3 receptor and the retinoid accessory receptors, RXR alpha and RXR beta, both in basal conditions and upon treatment with 1, 25 D3.

Retinoic acid and methylation cis-regulatory elements control the mouse tissue non-specific alkaline phosphatase gene expression

To understand the mechanisms regulating the tissue non-specific alkaline phosphatase (TNAP) activity during development, we characterized cis-transcriptional regulatory elements. In embryonic cells and tissues, TNAP expression was driven preferentially by the exon 1A (E1A) promoter, one of the two promoters previously defined. Transcriptional activity of E1A promoter was up-regulated by retinoic acid (RA) through a putative RA-responsive element. Transgenic mice analysis with lacZ reporter constructs revealed negative regulatory elements within 8.5 kb of E1A promoter. Promoter sequences of endogenous TNAP in non-expressing tissues and those carried by the 8.5 kb-lacZ transgene were found to be highly methylated. A 1 kb fragment of E1A promoter increased the methylation level of lacZ and promoter sequences. The role of RA and DNA methylation in defining the embryonic expression pattern of TNAP is discussed.

AM580, a stable benzoic derivative of retinoic acid, has powerful and selective cyto-differentiating effects on acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) is successfully used in the cyto-differentiating treatment of acute promyelocytic leukemia (APL). Paradoxically, APL cells express PML-RAR, an aberrant form of the retinoic acid receptor type alpha (RAR alpha) derived from the leukemia-specific t(15;17) chromosomal translocation. We show here that AM580, a stable retinobenzoic derivative originally synthesized as a RAR alpha agonist, is a powerful inducer of granulocytic maturation in NB4, an APL-derived cell line, and in freshly isolated APL blasts. After treatment of APL cells with AM580 either alone or in combination with granulocyte colony-stimulating factor (G-CSF), the compound induces granulocytic maturation, as assessed by determination of the levels of leukocyte alkaline phosphatase, CD11b, CD33, and G-CSF receptor mRNA, at concentrations that are 10- to 100-fold lower than those of ATRA necessary to produce similar effects. By contrast, AM580 is not effective as ATRA in modulating the expression of these differentiation markers in the HL-60 cell line and in freshly isolated granulocytes obtained from the peripheral blood of chronic myelogenous leukemia patients during the stable phase of the disease. In NB4 cells, two other synthetic nonselective RAR ligands are capable of inducing LAP as much as AM580, whereas RAR beta- or RAR gamma-specific ligands are totally ineffective. These results show that AM580 is more powerful than ATRA in modulating the expression of differentiation antigens only in cells in which PML-RAR is present. Binding experiments, using COS-7 cells transiently transfected with PML-RAR and the normal RAR alpha, show that AM580 has a lower affinity than ATRA for both receptors. However, in the presence of PML-RAR, the synthetic retinoid is a much better transactivator of retinoic acid-responsive element-containing promoters than the natural retinoid, whereas, in the presence of RAR alpha, AM580 and ATRA have similar activity. This may explain the strong cyto-differentiating potential of AM580 in PML-RAR-containing leukemic cells.

Purification, cDNA cloning, and tissue distribution of bovine liver aldehyde oxidase

Aldehyde oxidase was purified to homogeneity from bovine liver and primary structural information obtained by sequencing a series of cleavage peptides permitted the cloning of the corresponding cDNA. The cDNA is 4,630 base pairs long, and it consists of a 102-base pair 5'-untranslated region followed by a 4017-base pair coding region and a 511-base pair 3'-untranslated region. The open reading frame predicts a 1339-amino acid polypeptide with a calculated molecular weight of 147,441, which is consistent with the size of the aldehyde oxidase monomeric subunit. The aldehyde oxidase polypeptide contains consensus sequences for iron-sulfur centers and a molybdopterin binding site. The amino acid sequence deduced from the cDNA shows significant similarity with that of xanthine dehydrogenases from various sources. The primary structure of bovine aldehyde oxidase is remarkably similar (approximately 86%) to that of the translation product of a cDNA recently isolated by Wright et al. (Wright, R. M., Vaitaitis, G. M., Wilson, C. M., Repine, T. B., Terada, L. S., and Repine, J. E. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 10690-10694) and reported to represent human xanthine dehydrogenase. With the help of a monospecific antibody raised against the purified protein and the isolated cDNA, the tissue distribution of the bovine aldehyde oxidase protein and corresponding mRNA was determined. Aldehyde oxidase is expressed at high levels in liver, lung, and spleen, and, at a much lower level, in many other organs.

[Anesthesia for cesarean section in a patient with intracranial A-V malformation]

We presented a case of intracranial vascular malformations associated with pregnancy. A 32 year-old woman who was at 36 weeks of gestation had been experiencing loss of consciousness and convulsions for 3 years. MRI revealed an intracerebral AVM measuring 3.5 x 3.0cm in the left temporal lobe. Cesarean section was carried out under general anesthesia and epidural anesthesia to prevent the rise of blood pressure and intracranial pressure owing to stress of delivery and labor pain. Intermittent injection of nicardipine was quite effective to control the hypertension during anesthesia.

All-trans retinoic acid and cyclic adenosine monophosphate cooperate in the expression of leukocyte alkaline phosphatase in acute promyelocytic leukemia cells

Treatment of acute promyelocytic leukemia (APL) blasts with cyclic adenosine monophosphate (cAMP) analogs, in combination with all-trans retinoic acid (ATRA), results in the upregulation of the expression of leukocyte alkaline phosphatase (LAP), a marker for the differentiation of the granulocyte. The synergistic interaction between the cyclic nucleotide analogs and the retinoid is not unique to APL cells, as it is observed also in the peripheral granulocytes of chronic myelogenous leukemia (CML) patients. The molecular mechanisms underlying LAP induction were studied in NB4, an immortalized APL cell line. Induction of LAP enzymatic activity is dependent on the time of exposure and on the concentrations of dibutyryl-cAMP or 8-bromo-cAMP and ATRA, two factors that influence the kinetics of appearance of detectable levels of the enzyme. Augmentation of LAP levels by ATRA and cAMP is the result of both transcriptional and early posttranscriptional events and requires de novo protein synthesis. LAP induction correlates with augmentation in the levels of the type I catalytic subunit of cAMP-dependent protein kinase transcript and with granulocytic differentiation. The transcriptional component of the process leading to increased LAP gene expression was reproduced in its main features by transient transfection experiments performed in COS-7 cells using the normal retinoic acid receptor type alpha (RAR-alpha) or the APL-specific aberrant form (PML-RAR) and the upstream promoter of the liver/bone/kidney (L/B/K)-type alkaline phosphatase gene. The promoter is upregulated by treatment with ATRA, and this upregulation is further increased by cAMP analogs.

Effects of dexamethasone on pro-inflammatory cytokine expression, cell growth and maturation during granulocytic differentiation of acute promyelocytic leukemia cells

In basal conditions, NB4 and HL-60, two acute promyelocytic leukemia cell lines, express high levels of tumor necrosis factor (TNF-alpha) mRNA, whereas they do not synthesize appreciable amounts of the transcripts coding for interleukin-1 beta (IL-1 beta) or interleukin-8 (IL-8). Upon granulocytic differentiation with all-trans retinoic acid (ATRA) or the combination of ATRA and granulocyte-colony-stimulating factor (G-CSF), significant amounts of IL-1 beta and IL-8 mRNAs accumulated in both cell types. These changes in mRNA levels were parallelled by the increased secretion of the two cytokines. Dexamethasone (DEX) had no effect on the induction of IL-1 beta mRNA, while it enhanced the G-CSF-, ATRA- and (ATRA+G-CSF) dependent secretion of the cytokine. In combination with ATRA and G-CSF, the corticosteroid increased the expression of leukocyte alkaline phosphatase, a late marker of granulocytic differentiation.

Tyrosine kinases but not cAMP-dependent protein kinase mediate the induction of leukocyte alkaline phosphatase by granulocyte-colony-stimulating factor and retinoic acid in acute promyelocytic leukemia cells

Leukocyte alkaline phosphatase (LAP) is synergistically induced by the combination of all-trans retinoic acid (ATRA) and granulocyte-colony-stimulating factor (G-CSF) in acute promyelocytic leukemia (APL) cells (Gianni' M. et al., Blood 83: 1909-1921, 1994). The role of cAMP and tyrosine kinases in the induction of LAP was investigated. In the APL cell line NB4, adenosine-3': 5'-monophosphothioate, cyclic, Rp isomer, a reversible inhibitor of cAMP-dependent protein kinase (PKA), has no effect on the induction of LAP enzymatic activity and mRNA triggered by ATRA+G-CSF, in conditions where this compound completely blocks the upregulation of LAP transcript caused by the combination of the PKA agonist, dibutyryl-cAMP (db-cAMP), and ATRA. Challenge of NB4 cells with G-CSF, dbcAMP and ATRA causes a much higher induction of LAP relative to that observed in the presence of ATRA+G-CSF or ATRA+dbcAMP. Treatment of NB4 with ATRA and G-CSF results in increases in the tyrosine phosphorylation of several proteins. In the presence of the cytokine and the retinoid, tyrosine kinase inhibitors decrease LAP enzymatic activity and mRNA.