Induction of 2',5'-oligoadenylate synthetase by retinoic acid in two transformed human cell lines.

2',5'-Oligoadenylate (2-5A) synthetase, which polymerizes adenosine triphosphate into 2-5A, is induced upon treatment of cells with interferon (IFN) and is thought to be involved in its antiviral and anticellular action. We report here that retinoic acid (RA) enhanced the level of this enzyme in two human transformed cell lines, WISH and Namalva. Like IFN, RA induced 2-5A synthetase activity in a time- and dose-dependent manner. Addition of anti IFN-alpha, -IFN-beta, or -IFN-gamma antibodies to the medium concomitantly with RA did not prevent such induction; therefore, the effect of RA is clearly not mediated through the induction and externalization of IFN. Pretreatment of cells with actinomycin D inhibited 2-5A synthetase induction by RA, suggesting that RA increased the transcription of the 2-5A synthetase gene. In WISH cells, the growth of encephalomyocarditis virus was inhibited by RA treatment, which is consistent with the hypothesis that 2-5A synthetase plays an important role in the antiviral action of IFN, at least in encephalomyocarditis virus replication. When the anticellular effects of IFN and RA were compared to their ability to induce 2-5A synthetase activity in four human cell lines, there was no strict correlation between the amplitude of the enzyme activity induced and the extent of the antiproliferative effect. It is concluded that the 2-5A system is probably not the only pathway responsible for the antiproliferative effect of both substances. We further suggest that the induction of 2-5A synthetase by IFN and RA might be connected with at least some of the similarities observed between other biological effects of both compounds.

NF-kappa B activation results in rapid inactivation of JNK in TNF alpha-treated Ewing sarcoma cells: a mechanism for the anti-apoptotic effect of NF-kappa B.

We recently reported that inhibition of NF-kappa B activation as a consequence of the overexpression of a degradation-resistant form of I kappa B alpha [I kappa B alpha(A32/36)] sensitized Ewing sarcoma cells to TNF alpha-induced killing. The c-Jun N-terminal kinases (JNK) have been shown to participate in death signaling triggered by certain stimuli and are activated by TNF alpha. To obtain insight into the mechanism of the anti-apoptotic effect of NF-kappa B, we compared the profiles of JNK activation by TNF alpha in control cells and in cells in which NF-kappa B activation was impaired. We show here that JNK activation was transient in control cells but remained elevated in I kappa B alpha(A32/36)-expressing cells. NF-kappa B repressed specifically the JNK pathway, since the kinetics of activation of the other TNF alpha-activated-MAP kinase p38 were identical in both cells. Prolongation of JNK activation in I kappa B alpha(A32/36)-expressing cells was not inhibited by the broad spectrum caspase inhibitor Z-VAD-FMK and thus was not the consequence of caspase activation. Pretreatment of control cells with the phosphatase inhibitor vanadate greatly prolonged JNK activation by TNF alpha and resulted in induction of apoptosis by this cytokine. Moreover, overexpression of a dominant-negative mutant of JNK1 decreased TNF alpha-induced apoptosis in cells expressing the super repressor of NF-kappa B, indicating that the sustained activation of JNK1 participated in death signaling triggered by TNF alpha. Our results provide evidence that the repression of JNK activation by NF-kappa B participates in the anti-apoptotic effect of this transcription factor in TNF alpha-treated Ewing sarcoma cells.

Induction of p21Waf1/Cip1 by TNFalpha requires NF-kappaB activity and antagonizes apoptosis in Ewing tumor cells.

The Ewing family of tumors is characterized by recurrent reciprocal translocations that generate chimeric proteins, either EWS - FLI-1 or EWS - ERG. These proteins are potent transcriptional activators and are responsible for maintaining the oncogenic properties of tumor cells. Since apoptosis appears to be the main mechanism whereby chemotherapy and radiation kill tumor cells, identification of events that can antagonize apoptosis in Ewing tumors is essential for improving their response to conventional therapies. Here, we report that the transcriptional factor NF-kappaB is a survival factor for Ewing tumor-derived cells. In fact, inhibition of NF-kappaB activation as a consequence of the overexpression of a degradation-resistant form of IkappaBalpha, IkappaBalpha (A32/36), sensitized these cells to TNFalpha-induced killing. Although treatment with TNFalpha did not modify the cellular expression of Bcl-2, c-IAP1, c-IAP2, p53 and EWS - FLI-1 proteins, it increased p21Waf1/Cip1 levels. This induction required NF-kappaB activation since it was not observed in the IkappaBalpha (A32/36) expressing cells. Moreover, overexpression of p21Waf1/Cip1 in these IkappaBalpha (A32/36)-expressing cells, in which NF-kappaB and consequently p21Waf1/Cip1 are no longer inducible by TNFalpha, decreased their susceptibility to TNFalpha-induced killing. Our results therefore identify p21Waf1/Cip1 as a mediator of the antiapoptotic effect of TNFalpha-induced NF-kappaB in Ewing tumor cells.

Autonomous rexinoid death signaling is suppressed by converging signaling pathways in immature leukemia cells.

On their own, retinoid X receptor (RXR)-selective ligands (rexinoids) are silent in retinoic acid receptor (RAR)-RXR heterodimers, and no selective rexinoid program has been described as yet in cellular systems. We report here on the rexinoid signaling capacity that triggers apoptosis of immature promyelocytic NB4 cells as a default pathway in the absence of survival factors. Rexinoid-induced apoptosis displays all features of bona fide programmed cell death and is inhibited by RXR, but not RAR antagonists. Several types of survival signals block rexinoid-induced apoptosis. RARalpha agonists switch the cellular response toward differentiation and induce the expression of antiapoptosis factors. Activation of the protein kinase A pathway in the presence of rexinoid agonists induces maturation and blocks immature cell apoptosis. Addition of nonretinoid serum factors also blocks cell death but does not induce cell differentiation. Rexinoid-induced apoptosis is linked to neither the presence nor stability of the promyelocytic leukemia-RARalpha fusion protein and operates also in non-acute promyelocytic leukemia cells. Together our results support a model according to which rexinoids activate in certain leukemia cells a default death pathway onto which several other signaling paradigms converge. This pathway is entirely distinct from that triggered by RAR agonists, which control cell maturation and postmaturation apoptosis.

HIV-1 p17 and IFN-gamma both induce fructose 1,6-bisphosphatase.

The p17 matrix protein of the human immunodeficiency virus type 1 (HIV-1) plays a crucial role in AIDS pathogenesis. It orchestrates viral assembly and directs the preintegration complex to the nucleus of infected cells. Recently, the three-dimensional structure of p17 was shown to resemble that of interferon-gamma (IFN-gamma), suggesting that both proteins might share analogous functions. We demonstrate that in monocytes, p17 shares with IFN-gamma the ability to induce 1alpha-hydroxylase activity and to activate fructose 1,6-bisphosphatase gene expression in the presence of 25-hydroxyvitamin D3. However, p17 does not bind to the IFN-gamma cell membrane receptor and fails to increase expression of IFN-gamma-induced proteins, such as tryptophanyl-tRNA synthetase, Fc gammaRI, and HLA DR or B7/BB1 antigens. Altogether, our results raise the possibility that the structural resemblance between p17 and IFN-gamma causes the selective activation of a common pathway resulting in the production of 1,25-dihydroxyvitamin D3. We also found that unlike IFN-gamma, p17 increases the intracellular ATP content. Since transport of the HIV-1 preintegration complex through the nuclear membrane is an ATP-dependent process, our observation suggests that p17 plays a double role in this active transport, not only by acting as a chaperone molecule but also by recruiting the necessary energy for this process.

1,25-Dihydroxyvitamin D3 and fetal lung maturation: immunogold detection of VDR expression in pneumocytes type II cells and effect on fructose 1,6 bisphosphatase.

Lung maturation before birth includes type II pneumocyte differentiation with progressive disappearance of glycogen content and onset of surfactant synthesis. We have shown previously that 1,25-(OH)2D3 increases surfactant synthesis and secretion by type II cells and decreases their glycogen content in fetal rat lung explants. Recently, the gene coding fructose 1,6 bisphosphatase (F1,6BP), a regulatory enzyme of gluconeogenesis, has been identified in type II cells and its promoter bears a Vitamin D response element. Present results show:The coexistence of type II cells at different stages of maturation. in rat fetal lung on day 21 of gestation (electron microscopy), and the association between maturation of type II cells and disappearance of their glycogen content. The immunogold labeling of all type II cells when using the 9A7g VDR-antibody, with significantly more abundant gold particles in cells exhibiting an intermediate glycogen content. The expression of F1,6BP mRNA in a human type II cell line (NCI-H441) and the increase of this expression after 18h incubation with 1,25-(OH)2D3 (10(-8)M). These results bring further evidence for a physiological role of 1,25-(OH)2D3 during type II pneumocyte maturation. Activation of F1,6BP may participate to the 1,25-(OH)2D3 action on surfactant synthesis via the gluconeogenesis pathway.

Time to alcohol dependence after abstinence and first drink.

The first relapse into alcohol dependence after abstinence is characterized by sudden immoderate drinking. The time after abstinence to re-establishing dependence has never been compared to the time taken to establish dependence initially. Thirty one subjects who had been dependent on alcohol, had subsequently been abstinent for at least 2 months, and had had a relapse into dependence were interviewed. The median time to first dependence on alcohol was 13 years (Mean (SD) 14.7 (8) years); median time to dependence when relapsing was 7 days, a 700-fold acceleration (p < 0.00003). Only three subjects drank for more than 30 days (range 90-1825 days) before re-establishing dependence; the average was 82 (330) days overall and 9.3 (8.0) days if these subjects were excluded. Times to initial and subsequent dependence were not correlated nor related to the duration of abstinence (median 9, mean 16.9 (22) months). While abstinent the subjects had felt as if they were healed. It should be emphasized to abstinent patients that alcohol dependence has a latent sequel: they are at risk of accelerated dependence after recurrent drinking, which should be regarded as an emergency.

Primary meningococcal polyarthritis.

We report a case of primary meningococcal polyarthritis simulating bacteraemic gonococcal infection. The clinical similarity between extragenital gonococcal and meningococcal infections is well illustrated. If the clinical features of meningococcal and gonococcal infections are usually different, they may sometimes be indistinguishable. Both gonococcal pharyngitis and meningococcal urethritis have been recorded. The onset of acute polyarthritis, fever and skin lesions is typical of gonococcal infection but these clinical features may also indicate infection due to Neisseria meningitidis. In the case we report, the correct diagnosis of meningococcal arthritis was established only after N. meningitidis group C had been identified in synovial fluid from the knee.

[Role of percutaneous endoscopic gastrostomy in amyotrophic lateral sclerosis]. / Place de la gastrostomie endoscopique percutanée dans la sclérose latérale amyotrophique.

Percutaneous endoscopic gastrostomy (PEG) is an enteral nutritional assistance technique using a simple device compatible with conventional feeding and thus enabling the patient to be integrated into his or her social and familial surroundings. This inexpensive device is quickly and easily inserted under local anaesthesia. It causes little morbidity and virtually no mortality and has many advantages for patients with amyotrophic lateral sclerosis (ALS). We report the results of PEG in 28 ALS patients with bulbar involvement. Three of these patients developed minor complications during 6 consecutive months of PEG-assisted nutrition (2 had periostomial infection, 1 had mild haematemesis). There were no major complications, and mortality directly ascribable to PEG was nil. All patients put on weight or had their weight stabilized, and GEP was well accepted in all cases.