Collagen I and III mRNA gene expression and cell growth potential of skin fibroblasts in patients with essential hypertension

OBJECTIVES

Despite the claimed disregulation of extracellular matrix synthesis and the increased proliferation rate of different cell types in experimental models of hypertension, very few data are available on collagen synthesis and the proliferation rate of fibroblasts in essential hypertensive patients.

DESIGN

We measured collagen I, collagen III, histone H3 mRNA gene expression, collagen protein concentration and thymidine incorporation in fibroblasts from 17 essential hypertensive patients (EH) and 13 healthy normotensive control subjects (NC).

METHODS

A Northern blot analysis was performed on fibroblasts in culture obtained from skin biopsies. Collagen protein concentration and DNA synthesis were measured by means of incorporation of tritiated proline and tritiated thymidine, respectively.

RESULTS

In cultivated fibroblasts from hypertensives, the expression of collagen III mRNA after addition of fetal calf serum was significantly increased in comparison with that of normotensive-derived cells. After addition of fetal calf serum, collagen protein was statistically increased in cultures from EH patients as compared to NC. In hypertensives, the expression of histone H3 mRNA as well as tritiated thymidine incorporation were both increased as compared to normotensives.

CONCLUSIONS

Our data suggest that cultivated fibroblasts from essential hypertensive patients are characterized by an increased expression of type III collagen mRNA and collagen protein synthesis in response to fetal serum, as compared to normotensive-derived cells. Cells from hypertensives are characterized by an increased rate of proliferation after addition of fetal serum, as ascertained by increased thymidine incorporation and increased histone H3 mRNA gene expression, as compared to normotensive-derived cells. This phenotype could be genetically determined and may have an important role in the pathogenesis of essential hypertension.

NF-kappaB and ERK cooperate to stimulate DNA synthesis by inducing ornithine decarboxylase and nitric oxide synthase in cardiomyocytes treated with TNF and LPS

We previously reported that tumor necrosis factor-alpha (TNF) and lipopolysaccharide (LPS) stimulate DNA synthesis in chick embryo cardiomyocytes (CM) via nitric oxide and polyamine biosynthesis. Here we show an involvement of nuclear factor-kappaB (NF-kappaB) in the induction of nitric oxide synthase (NOS) and ornithine decarboxylase (ODC), the key enzyme in polyamine biosynthesis. In addition NF-kappaB activation appears to favor survival of CM by reducing caspase activation. TNF and LPS also stimulate phosphorylation of extracellular signal-regulated kinase (ERK), which is required for the changes in ODC and caspase activity, but not for NOS induction or NF-kappaB activation. In conclusion, these results indicate that NF-kappaB, in cooperation with ERK, plays a pivotal role in the growth stimulating effects of TNF and LPS, leading to the induction of both ODC and NOS and to the reduction of caspase activity.

The stimulation of inducible nitric-oxide synthase by the prion protein fragment 106--126 in human microglia is tumor necrosis factor-alpha-dependent and involves p38 mitogen-activated protein kinase

A synthetic peptide consisting of amino acid residues 106-126 of the human prion protein (PrP-(106--126)) has been previously demonstrated to be neurotoxic and to induce microglial activation. The present study investigated the expression of the inducible form of the nitric-oxide synthase (NOS-II) in human microglial cells treated with PrP-(106--126). Using reverse transcriptase-polymerase chain reaction, we found that PrP-(106--126) induces NOS-II gene expression after 24 h of treatment and that this effect is accompanied by a peak of nuclear factor kappa B (NF-kappa B) binding at 30 min as evaluated by electrophoretic mobility shift assay. Since our previous data demonstrated tumor necrosis factor-alpha (TNF-alpha) to be a potent inducer of NOS-II in these cells, we analyzed the expression of this cytokine in PrP-(106--126)-treated microglia. PrP-(106--126) caused the release of TNF-alpha as detected by enzyme-linked immunosorbent assay, and a blocking antibody, anti-TNF-alpha, abolished NOS-II induction elicited by this peptide. Moreover, PrP-(106-126) activates p38 mitogen-activated protein kinase, and the inhibition of this pathway determines the ablation of NF-kappa B binding induced by this fragment peptide.

Cyclin D1 is an early target in hepatocyte proliferation induced by thyroid hormone (T3)

The thyroid hormone (T3) affects cell growth, differentiation, and regulates metabolic functions via its interaction with the thyroid hormone nuclear receptors (TRs). The mechanism by which TRs mediate cell growth is unknown. To investigate the mechanisms responsible for the mitogenic effect of T3, we have determined changes in activation of transcription factors, mRNA levels of immediate early genes, and levels of proteins involved in the progression from G1 to S phase of the cell cycle. We show that hepatocyte proliferation induced by a single administration of T3 to Wistar rats occurred in the absence of activation of AP-1, NF-kappa B, and STAT3 or changes in the mRNA levels of the immediate early genes c-fos, c-jun, and c-myc. These genes are considered to be essential for liver regeneration after partial hepatectomy (PH). On the other hand, T3 treatment caused an increase in cyclin D1 mRNA and protein levels that occurred much more rapidly compared to liver regeneration after 2/3 PH. The early increase in cyclin D1 expression was associated with accelerated onset of DNA synthesis, as demonstrated by a 20-fold increase of bromodeoxyuridine-positive hepatocytes at 12 h after T3 treatment and by a 20-fold increase in mitotic activity at 18 h. An early increase of cyclin D1 expression was also observed after treatment with nafenopin, a ligand of a nuclear receptor (peroxisome proliferator-activated receptor alpha) of the same superfamily of steroid/thyroid receptors. T3 treatment also resulted in increased expression of cyclin E, E2F, and p107 and enhanced phosphorylation of pRb, the ultimate substrate in the pathway leading to transition from G1 to S phase. The results demonstrate that cyclin D1 induction is one of the earlier events in hepatocyte proliferation induced by T3 and suggest that this cyclin might be a common target responsible for the mitogenic activity of ligands of nuclear receptors.

Molecular features of primary mediastinal B-cell lymphoma: involvement of p16INK4A, p53 and c-myc

Primary mediastinal B-cell lymphoma (PMBL) shows chromosome 9p anomalies in 50% of cases. Based on reports that p16INK4A gene, located on this chromosomal arm, is frequently altered in aggressive lymphomas, we analysed for alterations of this gene in 27 cases of PMBL, which were part of a series of 32 PMBL cases that have been characterized for alterations in c-myc, p53, N-ras, bcl-1, bcl-2, bcl-6 and for Epstein-Barr virus (EBV) infection. Four cases showed p16INK4A gene anomalies, including three with promoter methylation and one homozygous deletion. Eight PMBLs showed c-myc rearrangements. Three additional cases showed sequence variations in the c-myc P2 promoter, two of which consisted of the same germline variation involving a novel polymorphic XhoI site. Four tumours contained p53 gene mutations and three had clonal EBV infection. One case had a bcl-6 rearrangement. In conclusion, our study shows that p16INK4, c-myc and p53 alterations occur in 15%, 25% and 13% of PMBLs, respectively. EBV monoclonality was found in 9% of cases, whereas no abnormality was detected in bcl-1, bcl-2 and N-ras. Thus, none of the common genetic aberrations seen in other types of non-Hodgkin's lymphomas appears to be stringently involved in the pathogenesis of this unique lymphoma type.

Correlation of poly(ADP-ribose)polymerase and p53 expression levels in high-grade lymphomas

The steady-state levels of mRNA for the poly(ADP-ribose)polymerase (PARP), c-myc, p53, and histone H3 genes were investigated in 31 high-grade B-cell lymphomas by northern blot analysis. The panel included 15 nodal large B-cell lymphomas, nine mediastinal large B-cell lymphomas, and seven sporadic Burkitt's lymphomas. The PARP mRNA level was significantly higher in lymphomas than in control tissues and corresponded with the amount of PARP protein, as assessed by immunoblot analysis in six samples. The level of PARP mRNA was positively correlated with that of p53 mRNA. No correlation was found between the mRNA expression levels of PARP and histone H3, suggesting that PARP expression levels are independent of the proliferation rate of neoplastic cells. In this setting, the strong correlation between PARP and p53 suggests that the high expression of PARP may be associated with ongoing DNA damage in high-grade lymphomas.

Rapid inactivation of NOS-I by lipopolysaccharide plus interferon-gamma-induced tyrosine phosphorylation

Human astrocytoma T67 cells constitutively express a neuronal NO synthase (NOS-I) and, following administration of lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma), an inducible NOS isoform (NOS-II). Previous results indicated that a treatment of T67 cells with the combination of LPS plus IFNgamma, by affecting NOS-I activity, also inhibited NO production in a very short time. Here, we report that under basal conditions, a NOS-I protein of about 150 kDa was weakly and partially tyrosine-phosphorylated, as verified by immunoprecipitation and Western blotting. Furthermore, LPS plus IFNgamma increased the tyrosine phosphorylation of NOS-I, with a concomitant inhibition of its enzyme activity. The same effect was observed in the presence of vanadate, an inhibitor of phosphotyrosine-specific phosphatases. On the contrary, genistein, an inhibitor of protein-tyrosine kinases, reduced tyrosine phosphorylation of NOS-I, enhancing its enzyme activity. Finally, using reverse transcriptase-polymerase chain reaction, we have observed that a suboptimal induction of NOS-II mRNA expression in T67 cells was enhanced by vanadate (or L-NAME) and inhibited by genistein. Because exogenous NO has been found to suppress NOS-II expression, the decrease of NO production that we have obtained from the inactivation of NOS-I by LPS/IFNgamma-induced tyrosine phosphorylation provides the best conditions for NOS-II expression in human astrocytoma T67 cells.

In vivo hepatocyte proliferation is inducible through a TNF and IL-6-independent pathway

Recent studies in mice harboring a targeted disruption of genes encoding TNF receptor 1 (TNFR-1) or Interleukin 6 (IL-6) suggested a critical role for TNF and IL-6 in initiation of liver regeneration after 2/3 partial hepatectomy. However, hepatocyte proliferation can also occur following treatment with agents that do not induce tissue loss (primary mitogens). To determine whether the above cytokines could also be involved in mitogen-induced liver cell proliferation, we studied the hepatocyte proliferative response after treatment with primary mitogens in mice knock-out for TNFR-1 or IL-6. Our results showed no difference in the proliferative response of the liver between the wild type and the knock-out mice following treatment with the mitogens 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP), or the peroxisome proliferator, ciprofibrate, suggesting that TNF or IL-6 may not play a major role in this type of proliferation. Gel shift assay indicated that TCPOBOP-induced hepatocyte proliferation is not associated with activation of STAT3 transcription factor, a major target of IL-6 and other growth factors/cytokines. Our results thus indicate that hepatocyte proliferation can be induced by at least two different pathways; compensatory regeneration being TNF and IL-6-dependent, and mitogen-induced direct hyperplasia which does not require TNF or IL-6.

Liver cell proliferation induced by nafenopin and cyproterone acetate is not associated with increases in activation of transcription factors NF-kappaB and AP-1 or with expression of tumor necrosis factor alpha

Our previous studies have shown a different pattern of immediate early gene and growth factor gene expression between compensatory liver regeneration occurring after cell loss/death and direct hyperplasia induced by primary mitogens. In the present study, modifications in the activation of two transcription factors, NF-kappaB and AP-1; steady-state levels of tumor necrosis factor alpha (TNF-alpha) messenger RNA (mRNA); and induction of the inducible nitric oxide synthase (iNOS) were examined in rat liver during different types of cell proliferation. Compensatory regeneration was induced in male Wistar rats by partial hepatectomy of two thirds (PH) or a necrogenic dose of CCl4 (2 mL/kg), whereas direct hyperplasia was induced by a single administration of the primary mitogens lead nitrate (LN, 100 micromol/kg), cyproterone acetate (CPA, 60 mg/kg), or nafenopin (NAF, 200 mg/kg). Liver regeneration after treatment with CCl4 was associated with an increase in steady-state levels of TNF-alpha mRNA, activation of NF-kappaB and AP-1, and induction of iNOS. A strong and prolonged activation of NF-kappaB but not of AP-1 was observed in LN-induced hyperplasia. LN also induced an increase in hepatic levels of TNF-alpha and iNOS mRNA. On the other hand, direct hyperplasia induced by two other primary mitogens, NAF and CPA, occurred in the complete absence of modifications in the hepatic levels of TNF-alpha mRNA, activation of NF-kappaB and AP-1, or induction of iNOS, although the number of hepatocytes entering S phase 18 to 24 hours after NAF was similar to that seen after PH. These results add further support to the hypothesis that cell proliferation occurring in the absence of cell loss/death may be triggered by unknown signaling pathways different from those responsible for the transition of hepatocytes from G0 to G1 after PH or cell necrosis.

On the presence of DNA polymerase alpha in human lymphocyte nuclei and chromosomes

Experiments were carried out to correlate the cytological localization of DNA polymerase alpha with the presence of its specific mRNA in human lymphocytes studied at different times after phytohaemagglutinin stimulation. Our data indicated that in resting cells it is not possible to detect DNA polymerase alpha protein or mRNA by Northern hybridization. By contrast, in stimulated cells the detection of mRNA specific for DNA polymerase alpha synthesis is possible after 16 h phytohaemagglutin stimulation, whereas immunolocalization is possible after only 4 h stimulation. Observation of cytological preparations from cells stimulated for times long enough to obtain mitoses surprisingly showed an intense immunoreaction in mitotic chromosomes treated with monoclonal antibodies to DNA polymerase alpha.

TPA and cycloheximide modulate the activation of NF-kappa B and the induction and stability of nitric oxide synthase transcript in primary neonatal rat hepatocytes

12-O-Tetradecanoylphorbol 13-acetate (TPA) elicited a transient increase in the transcription of the inducible nitric oxide synthase (iNOS) gene coupled with a shortening of the half-life of its mRNA in primary neonatal rat hepatocytes. These effects of TPA were preceded by a surge in nuclear translocation of the transcription factor NF-kappa B, and followed by a mounting accumulation of NO-2 in the growth medium. Even cycloheximide (CHX) added by itself elicited an early, sustained activation of NF-kappa B followed by an intense induction of iNOS gene expression, irrespective of what degree of protein synthesis inhibition was brought about by the several concentrations tested. When given together, TPA and CHX exerted additive effects on hepatocellular iNOS mRNA levels. These results suggest the likelihood of an ordered sequence of events by which an activated NF-kappa B mediates the induction of iNOS gene expression in TPA- and/or CHX-treated primary hepatocytes.

Induction of nitric oxide synthase mRNA expression. Suppression by exogenous nitric oxide

The reactive nitrogen species, nitric oxide (NO), plays an important role in the pathogenesis of neurodegenerative diseases. The suppression of NO production may be fundamental for survival of neurons. Here, we report that pretreatment of human ramified microglial cells with nearly physiological levels of exogenous NO prevents lipopolysaccharide (LPS)/tumor necrosis factor alpha (TNF alpha)-inducible NO synthesis, because by affecting NF-kappa B activation it inhibits inducible Ca(2+)-independent NO synthase isoform (iNOS) mRNA expression. Using reverse transcriptase polymerase chain reaction, we have found that both NO donor sodium nitroprusside (SNP) and authentic NO solution are able to inhibit LPS/TNF alpha-inducible iNOS gene expression; this effect was reversed by reduced hemoglobin, a trapping agent for NO. The early presence of SNP during LPS/TNF alpha induction is essential for inhibition of iNOS mRNA expression. Furthermore, SNP is capable of inhibiting LPS/TNF alpha-inducible nitrite release, as determined by Griess reaction. Finally, using electrophoretic mobility shift assay, we have shown that SNP inhibits LPS/TNF alpha-elicited NF-kappa B activation. This suggests that inhibition of iNOS gene expression by exogenous NO may be ascribed to a decreased NF-kappa B availability.

Protective effect of NO on gastric lesions and inhibition of expression of gastric inducible NOS by flurbiprofen and its nitro-derivative, nitroflurbiprofen

Nitroflurbiprofen (NFP) causes significantly less gastric lesions than flurbiprofen (FP), probably because of its capacity to release nitric oxide (NO) in the stomach. Lipopolysaccharide (LPS), which induces the expression of an inducible type of NO synthase (iNOS) in rat stomach, also reduces gastric mucosal damage elicited by FP. Furthermore, both FP and NFP decrease significantly the amount of mRNA encoding iNOS induced by LPS in the stomach. The inhibitory effect of NFP seems to be due at least in part to its ability to release NO.

Nitric oxide in the liver: physiopathological roles

Many of the known roles of arginine (e.g. in immune function, wound healing, and protection against ammonia intoxication) are mediated by a metabolic pathway synthesising nitric oxide (NO) in the liver. Contrary to some of the current views, liver-produced NO may be basically beneficial, as it exerts both protective actions against tissue injury and cytotoxic effects on invading microorganisms, parasites, or tumor cells. An ongoing equilibrium between NO and other NO-reactive compounds (e.g. O2 and non-heme iron-sulphur-containing moieties) appears to be important in this respect, even under critical conditions. Thus, NO may prevent liver tissue harm from oxidant stress. Only when this putative counterbalance is upset by an uncontrolled, prolonged and/or massive production of NO, liver tissue damage may occur leading to hepatic inflammation or even tumor development. Moreover, the currently available data support the working hypothesis that hepatocytes partake not only to immunoregulatory processes, but even to immune defence mechanisms. Thus, the liver constitutes an excellent model for investigations into the crosstalks regulating the production of NO which take place among not only the various networks operating inside a single hepatic cell, but even the individual types of liver cells.

Differential expression pattern of jun B and c-jun in the rat brain during the 24-h cycle

Data from a previous report [3] demonstrated that the proto-oncogene c-fos mRNA expression undergoes basally a circadian fluctuation in the rat brain. The present study was designed to verify by means of Northern blot hybridization the eventual occurrence of a spontaneous oscillation in the expression of other two proto-oncogenes, jun B and c-jun, during 24 h. Rats were either entrained to a light-dark photoperiod or maintained under constant darkness or light. During the dark period, as well as the subjective night, the jun B mRNA levels in the cerebral cortex and striatum were 4-6 times higher than in the light hours or subjective day. No consistent oscillation was found in the c-jun mRNA expression during 24 h in any of the examined brain regions. These results suggest the possibility of different interactions of the c-fos, jun B and c-jun gene products throughout a 24-h period in discrete brain regions.

Poly(ADP-ribose) polymerase: early involvement in glutamate-induced neurotoxicity in cultured cerebellar granule cells

Glutamate neurotoxicity is correlated with an increase of cytosolic free Ca2+. In some cell systems, activation of Ca2+ dependent endonucleases or formation of free radicals can damage DNA and activate the chromatin bound enzyme poly(ADP-ribose) polymerase (pADPRP). We have investigated whether pADPRP may be involved in glutamate neurotoxicity in vitro. Cerebellar granule cells at 12 days in culture when treated with a toxic dose of glutamate (100 microM) showed a rapid and transient increase of polyADP-ribose immunoreactivity. Cellular immunostaining was heterogeneous and returned to control levels after washout of glutamate. In the same cell preparations glutamate elicited a marked increase in enzyme protein immunoreactivity which persisted at later times. Non-toxic doses of glutamate did not affect immunostaining. In another set of experiments, pADPRP mRNA was increased 30 min after glutamate. In order to investigate the role of pADPRP in glutamate-mediated neurotoxicity, structurally different inhibitors of pADPRP (3-aminobenzamide, benzamide,3-aminophthalhydrazide) and their inactive analogues (benzoic acid and phthalimide) were tested in this model. Addition of the inhibitors to cultures 60 min before and during the 30 min of glutamate treatment prevented neuronal death by 60-100%, assessed 24 hr later. Glutamate-induced Ca2+ influx was not affected. Inactive analogues failed to afford neuroprotection. These data indicate that not only is pADPRP activated by the early, possibly Ca(2+)-mediated mechanisms initiated by glutamate, but that it might also actively contribute to the subsequent neuronal death.

Different programs of gene expression are associated with different phases of the 24h and sleep-wake cycles

The Fos and Jun proteins are encoded by proto-oncogenes acting as immediate early genes in that they are rapidly induced by different kinds of stimuli in the nervous system. These two proteins bind to DNA regulating gene transcription, and thus determining the specificity of the neuronal response to the applied stimulation. We investigated whether the expression of these genes undergoes a variation during 24h in the absence of exogenous stimulation. Male Wistar adult (200 gr. body weight) rats, kept under a 12h/12h light-dark cycle, were sacrificed every 4h starting at 0700. The expression of c-fos, c-jun and jun B mRNAs was studied in six different brain areas by means of Northern blot hybridization, c-fos expression was also studied with in situ hybridization and immunohistochemistry. In basal conditions c-fos expression displayed a highly significant spontaneous oscillation, with the highest level during the darkness hours and the lowest during the light hours. Parallel levels of jun B expression were found in the cortex and striatum, whereas c-jun mRNA remained constantly high throughout 24 h. The periodicity of c-fos and jun B oscillation persisted also when the animals were exposed for 6 days to constant (24h/24h) light or darkness. Such oscillation could instead be inverted by manipulating the rest-activity cycle, i.e. keeping the animals awake during the light hours and allowing them to sleep during the dark hours. We then verified whether the expression of fos and jun could be correlated with states of wakefulness (W) and sleep (S), monitored with EEG recording under behavioral control.(ABSTRACT TRUNCATED AT 250 WORDS)

c-fos mRNA is spontaneously induced in the rat brain during the activity period of the circadian cycle

The basal expression of the proto-oncogene c-fos was studied by Northern blot analysis in different regions of the rat brain during 24 h. A striking spontaneous oscillation of c-fos mRNA expression was detected in animals kept in basal conditions with a 12 h light/12 h dark cycle. In these animals c-fos mRNA was just detectable during the rest hours (morning through afternoon), and was high during the activity hours (night). The periodicity of this oscillation persisted and became free-running when the animals were exposed for 6 consecutive days to constant light or darkness. It was thus demonstrated that the fluctuation of c-fos expression is circadian and is not created by the light-dark cycle, but the latter exerts a synchronizing effect. The oscillation of c-fos mRNA was modified by manipulations of the rest-activity cycle. In particular, the fluctuation observed in basal conditions was inverted, keeping the animals awake during the rest hours (diurnal) and allowing them to sleep in the activity period (nocturnal). These data indicated a close relationship between the oscillation of c-fos expression and the rest-activity cycle. Finally, electroencephalographic (EEG) monitoring was performed under behavioural control for 3 h before the animals were killed. These experiments confirmed that, irrespective of the time of day, the EEG pattern typical of a state of sleep (including both slow waves and paradoxical sleep) was associated with low or undetectable c-fos levels, whereas the protracted EEG desynchronization corresponding to wakefulness was associated with high c-fos expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in the steady-state levels of c-fos, c-jun and c-myc messenger RNA during mitogen-induced liver growth and compensatory regeneration

The steady-state levels of c-fos, c-jun and c-myc messenger RNA were investigated in rat liver tissue after proliferative stimuli of different nature-namely, compensatory regeneration induced by partial hepatectomy or carbon tetrachloride administration-and direct hyperplasia induced by four different hepatomitogens: lead nitrate, ethylene dibromide, cyproterone acetate and nafenopin. We show here that whereas c-fos and c-jun expression increased soon after partial hepatectomy or carbon tetrachloride administration, an increased expression of c-jun in the absence of c-fos expression occurred during direct hyperplasia induced by lead nitrate and ethylene dibromide. When hyperplasia was induced by cyproterone acetate and nafenopin, the mitogenic response of the liver was not associated with an increased expression of c-jun or c-fos, despite the fact that the timing of the cell cycle was similar to that observed after partial hepatectomy. Finally, when c-myc expression was analyzed, it was found that proliferative conditions associated with an increased expression of this gene were characterized by an increased expression of c-jun. On the contrary, the hyperplasia induced by cyproterone acetate and nafenopin, which is characterized by a lack of increase in the expression of c-fos and c-jun, was also not associated with an increased c-myc expression. Similar results were obtained in these experiments with the mitogen nafenopin, a peroxisome proliferator. In fact, liver hyperplasia induced by this compound was not preceded or accompanied by an increased expression of c-fos and c-myc. This study suggests that depending on the nature of the proliferative stimulus, an increased expression of c-fos, c-jun and c-myc may not be necessary for in vivo induction of liver cell proliferation.

Studies of the relationship between cell proliferation and cell death. II. Early gene expression during concanavalin A-induced proliferation or dexamethasone-induced apoptosis of rat thymocytes

Several data in the literature suggest that an intriguing relationship exists between cell proliferation and cell death. Accordingly, we studied the early expression of different genes in the same cells, i.e. rat thymocytes, undergoing cell proliferation upon stimulation with Concanavalin A or cell death following dexamethasone treatment. We showed that an early accumulation of c-fos, c-jun and c-myc mRNA occurred in both phenomena but with different kinetics. It can be speculated that the early induction of nuclear oncogenes is necessary to allow the later induction of other genes probably regulated at the transcriptional level by the AP-1 complex and/or by Myc protein. The accumulation of the transcript for another gene, i.e. poly(ADP-ribose)polymerase, an enzyme responsible for posttranslational modifications of several nuclear proteins, could instead be related to chromatin modifications occurring in both processes.

Involvement of DNA polymerase beta in proliferation of rat liver induced by lead nitrate or partial hepatectomy

We have studied the expression pattern of DNA polymerase beta in two different models of in vivo cell proliferation. Both mRNA levels and enzyme activity of DNA polymerase beta markedly increased before and/or during DNA synthesis in proliferating hepatocytes in mitogen-treated and partially hepatectomized rats. The time-courses of the expression of the gene coding for DNA polymerase beta were significantly different in the two cell systems. A 5-fold increase in DNA polymerase beta mRNA was observed 8 h after lead nitrate administration, i.e. well before the onset of DNA synthesis. In the regenerative liver cells a 3-fold increase in the amount of mRNA was observed 24-48 h after partial hepatectomy, the event being coincident with extensive DNA synthesis. In both systems, the increase of mRNA levels was always paralleled by an increase in enzyme activity, suggesting that DNA polymerase beta activity may be regulated at a pre-translational level.

The exposure of carcinogen-initiated primary neonatal rat hepatocytes to tumor promoters modulates both the transcripts and the enzymatic activity of nuclear poly(ADP-ribose) polymerase

Four tumor promoters, i.e. PB, TPA, NAF, and DDT, added singly to a calcium-deprived synthetic medium, elicited early and late mitogenic effects and concurrent surges of nuclear poly(ADP-ribose) polymerase (pADPRP) activity in primary neonatal rat hepatocytes mutagenized with an intra-uterine dose of DMN. These actions were fully abated by the pADPRP inhibitor 3-MBA. Conversely, EGF only acted as a full mitogen when medium's calcium was at physiological levels, and its effects could not be blocked by 3-MBA. The same tumor promoters, but not EGF, also evoked a swift and lingering amplification of pADPRP transcripts in DMN-initiated hepatocytes kept in low-calcium medium. Hence, a coordinated modulation of both pADPRP transcripts and activity by xenobiotics is likely to be involved in the clonal expansion of early preneoplastic hepatocytes.

Increase of poly(ADP-ribose) polymerase mRNA levels during TPA-induced differentiation of human lymphocytes

The non-mitogenic stimulation of human peripheral blood mononuclear cells (PBMC) with low concentrations of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) caused a progressive increase in the percent fraction of the cells that were positive for the early activating antigen CD69. At the same time, it caused a progressive increase in the steady-state levels of poly(ADP-ribose) polymerase (pADPRP) transcripts. A further increase in TPA concentration, while inducing the maximal expression of the levels of CD69 activating surface antigen, both in the presence or in the absence of proliferative activity, did not evoke any additional hightening of pADPRP mRNA levels. Time course of PBMC stimulation with a non-mitogenic dose of TPA showed an early increase in the accumulation of pADPRP mRNA, which changed at 8-16 h, and remained high for several days thereafter. On the basis of these data, we suggest that the increase in pADPRP mRNA may be associated with the commitment of human lymphocytes from a quiescent (G0) to an activated (G1) state.

Regulation of poly(ADP-ribose) polymerase gene expression in mitogen-stimulated human peripheral blood mononuclear cells

The level of mRNA for poly(ADP-ribose) polymerase in human PBMC increased 8 h after addition of PHA, reaching its maximum (9-fold over the basal level) 3-4 days after the stimulation and decreasing thereafter. mRNA maximum slightly preceded in time the maximal value of DNA synthesis. The half-life of poly(ADP-ribose) polymerase mRNA, which is 1.2 h in quiescent PBMC, increased up to 3.4 h in stimulated PBMC. This PHA-induced stabilization of the mRNA for poly(ADP-ribose) polymerase could account for the accumulation of the transcript in mitogen-treated PBMC.

Induction of DNA polymerase beta during proliferation of mitogen-stimulated human lymphocytes

On induction of proliferation of human peripheral blood mononuclear cells by phytohemagglutinin treatment, DNA polymerase beta activity increases markedly before and during DNA replication. The increase of enzymatic activity seems to be well correlated with the increase of DNA polymerase beta mRNA, which is induced by enhanced expression of the DNA polymerase beta gene. These data suggest that DNA polymerase beta is involved in DNA repair, which is linked to replicative DNA synthesis, or directly in replicative DNA synthesis in normal proliferating cells.

Differential expression of poly(ADP-ribose) polymerase and DNA polymerase beta in rat tissues

The activities of two DNA repair-related enzymes, poly(ADP-ribose) polymerase and DNA polymerase beta, and their mRNA levels were measured in 17 tissues of Wistar rats. A large variety in enzyme activity values could be detected in the tissues examined; the highest levels of activity for both enzymes were found in the testis. A good correlation between poly(ADP-ribose) polymerase activity and the level of the transcript of the gene coding for the enzyme was observed in many tissues. A less satisfactory correlation could be evidenced for DNA polymerase beta. The almost parallel amounts of the mRNAs for poly(ADP-ribose) polymerase and DNA polymerase beta in the tissues examined suggest a possible coexpression of the genes coding for these enzymes. Additional studies have been carried out in testis and liver by immunohistochemical techniques and by in situ hybridization analyses. While in the testis the spermatocytes were shown to contain both enzymes and their transcripts, in other types of cells this could not be observed. In the liver mRNAs and enzymes were only found in 20% of the hepatocytes. This may in part explain both the low levels of the mRNAs and the modest activities of the two enzymes in that tissue.

Activation of human monocyte-derived macrophages by interferon gamma is accompanied by increase of poly(ADP-ribose) polymerase activity

We have investigated poly(ADP-ribosyl)ation processes in human monocyte-derived macrophages and the effect of the activating cytokine, interferon gamma (IFN-gamma) on these processes. IFN-gamma was shown to increase the activity of poly(ADP-ribose) polymerase in human macrophages. A 2-3-fold enhancement of poly(ADP-ribose) polymerase activity was observed after 3-4 h of incubation with IFN-gamma, whose effects were dose-dependent and maximal at 20-50 U/ml. Staining with anti-poly(ADP-ribose) antibodies and purification of ADP-ribosylated nuclear proteins by affinity chromatography over boronate agarose showed that enhancement of poly(ADP-ribose) polymerase activity by IFN-gamma was accompanied by accumulation of poly(ADP-ribose) polymers in nuclear proteins. The effects of IFN-gamma on poly(ADP-ribose) polymerase activity were not due to an enhanced accumulation of the message for the enzyme, indicating that the activation of the enzyme activity was due to post-transcriptional modifications. IFN-gamma was shown to induce DNA strand breaks in human macrophages. This phenomenon followed the same time-course and was evident with the same doses of IFN-gamma that increased poly(ADP-ribose) polymerase activity. Since poly(ADP-ribose) polymerase is known to require DNA nicks for its activity, the capability of IFN-gamma to induce DNA strand breaks can explain its effects on poly(ADP-ribosyl)ation processes.

Changes in activity and mRNA levels of poly(ADP-ribose) polymerase during rat liver regeneration

ADP-ribosylation of nuclear proteins, catalysed by the enzyme poly(ADP-ribose) polymerase, is involved in the regulation of different cellular processes of DNA metabolism. To further clarify the role of the enzyme during proliferating activity of mammalian cells, we have studied the control of gene expression in regenerating rat liver. The changes in activity and mRNA levels were analysed during the early and late phases of the compensatory model. When enzyme activity was measured in isolated liver nuclei obtained at different times after hepatectomy, two different phases were observed: an early wave occurring before the onset of DNA synthesis, and a second one, starting several hours after the onset of DNA synthesis and returning to control values at later times. The evaluation of the enzymatic level in nuclear extracts and by activity gel analysis showed a more gradual increase starting 1 day after hepatectomy, in concomitance with the peak of DNA synthesis. By using a specific murine cDNA probe, a significant enhancement of mRNA levels for poly(ADP-ribose) polymerase was observed during liver regeneration, slightly preceding the onset of DNA synthesis. The results obtained show that changes in poly(ADP-ribose) polymerase activity, during liver regeneration, are associated both to early events preceding the increase in DNA synthesis and to later phases of the cell proliferation process.

Regulation of poly(ADP-ribose) polymerase mRNA levels during compensatory and mitogen-induced growth of rat liver

Poly(ADP-ribose) polymerase mRNA levels were studied in hepatic regeneration following partial hepatectomy, and in hyperplasia induced by the mitogen lead nitrate. A significant increase in the level of poly(ADP-ribose) polymerase mRNA was found 8 h after partial hepatectomy when no detectable increase of DNA synthesis could be observed; the level of poly(ADP-ribose) polymerase transcripts increased up to six-fold within 1-2 days. A similar increase of the level of poly(ADP-ribose) polymerase mRNA was found 24 h after treatment with lead nitrate. A twofold increase in poly(ADP-ribose) polymerase activity was observed 2 days after (a) partial hepatectomy and (b) lead nitrate treatment. From these results an important role of poly(ADP-ribose) polymerase in cell proliferation could be suggested.

Induction of poly(ADP-ribose) polymerase gene expression in lectin-stimulated human T lymphocytes is dependent on protein synthesis

The poly(ADP-ribose) polymerase mRNA level in quiescent T lymphocytes was low, but was significantly higher than that in B lymphocytes or monocytes. When T lymphocytes were stimulated with phytohemagglutinin, a prompt increase in the mRNA level was observed from 4 hours after stimulation. The level of poly(ADP-ribose) polymerase mRNA reached a maximum in the late G1 phase about 1-2 days after lectin stimulation, and then decreased gradually returning to the basal level 10 days after lectin stimulation. Cycloheximide abrogated increase in poly(ADP-ribose) polymerase gene expression suggesting that a newly synthesized protein(s) was involved in poly(ADP-ribose) polymerase gene induction in lectin-stimulated T lymphocytes.

Effects of lead on red blood cell membrane proteins

The effects of lead on red blood cell (RBC) membrane proteins were studied in two groups of workers with different lead exposure levels: Group I (6 subjects employed in a battery plant) with a mean blood lead of 40.1 (SD = 3.7) micrograms/100 ml; Group II (5 workers employed in different industries) with a mean blood lead of 60.6 (SD = 8.0) micrograms/100 ml, compared with a control group with mean blood lead of 15.6 (SD = 9.3) micrograms/100 ml. The analysis of RBC membrane polypeptides was carried out by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and by using a densitometer for percentage measurement of the bands corresponding to protein fractions. The results show a very significant decrease in Band 3 (anion channel) and 4.1 in more exposed workers (Group II) only. The effects of lead on RBC membrane proteins seem to be evident at blood-lead levels higher (greater than 50 micrograms/100 ml) than those previously reported in literature. These results confirm the effects of lead on membrane proteins, even if the exact mechanism, particularly the influence of proteolysis and the meaning of the interference, still needs to be investigated thoroughly.

Analysis of the methylation pattern of c-Ha-ras oncogene in human prostatic cancer

To determine the methylation pattern of c-Ha-ras oncogene in prostatic tissue and to identify possible changes of methylation associated with cancer, high molecular weight DNA was extracted from 7 normal and 6 carcinomatous human prostates. Analysis of the samples was performed by cleaving DNA with the restriction endonucleases Msp I, Hpa II and Cfo I, and by Southern hybridizing the DNA digests with the 32P-labelled c-Ha-ras (pT24-C3) probe. Several discrete fragments were obtained with Hpa II and Cfo I digestion while the Msp I pattern showed fewer and smaller bands. Therefore, c-Ha-ras appears to be partially methylated. While a considerable polymorphism of the sequence 5'-CCGG-3' was observed at several Msp I sites in all cases, no significant differences could be evidenced in the methylation patterns of normal and neoplastic prostatic DNA samples extracted and purified from each patient.

Mediastinal large-cell lymphoma with sclerosis. Genotypic analysis establishes its B nature

The Southern blot hybridization technique has been applied to study the configuration of immunoglobulin and T-cell receptor genes in 6 cases of the so called mediastinal large cell lymphoma with sclerosis. This lymphoma has been recently recognized as a separate entity among non-Hodgkin lymphomas mainly affecting young adult patients. The B-cell origin of this neoplasm was suggested by means of immunohistochemical analysis. However, the immunophenotypical B-cell related markers used do not always exhibit lineage fidelity. The Southern blot analysis demonstrated the presence of unique heavy and k-light chain immunoglobulin gene rearrangements, establishing genotypically their B-cell origin.

[Salivary levels of immunoglobulin and dental caries in children]

IgG, IgA, IgM and lysozyme levels were determined in whole unstimulated saliva from ten children aged seven-nine years. IgA levels were significantly higher (p less than 0.05) in caries-susceptible subjects when compared with the caries-free ones. High levels of IgG seemed to correlate with a high DMF score. No correlation was found between lysozyme levels and DMF score.