Effect of dihydrotestosterone on mouse embryonic stem cells exposed to H(2)O(2)-induced oxidative stress

Oxidative stresses induced by reactive oxygen species (ROS) have been shown to be involved in several physiological and pathophysiological processes, such as cell proliferation and differentiation. Steroid hormones can protect cells against apoptosis or induce cell proliferation by several mechanisms. Among androgenic hormones, dihydrotestosterone (DHT) is generated by a 5alpha- reduction of testosterone. Unlike testosterone, DHT cannot be aromatized to estradiol, therefore DHT is considered a pure androgenic steroid. This study was conducted to examine the effect of DHT (10(-7) M) on H(2)O(2) (10(-3) M) -induced injuries in mouse embryonic stem (ES) cells. H(2)O(2) induced ROS generation and increased lipid peroxide formation and DNA fragmentation. These effects of H(2)O(2) were inhibited by pretreatment with DHT. H(2)O(2) also increased the phosphorylation of p38 MAPK, SAPK/JNK and nuclear factor kappa B (NF-kappaB), but DHT blocked these effects. Moreover, H(2)O(2) decreased DNA synthesis and the levels of cell cycle regulatory proteins [cyclin D1, cyclin E, cyclin-dependent kinase (CDK) 2, and CDK 4]. These effects of H(2)O(2) were inhibited by pretreatment with DHT. In conclusion, DHT may partially prevent H(2)O(2)-induced cell injury through inhibition of ROS and ROS-induced activation of p38 MAPK, SAPK/JNK and NF-kappaB in mouse ES cells.

Effect of metanil yellow and malachite green on DNA synthesis in N-nitrosodiethylamine induced preneoplastic rat livers.

Metanil yellow (MY) and malachite green (MG) are textile dyes, which, despite the ban occurs unsrupulously as food colouring agents. Accordingly they constitute a serious public health hazard and are of sufficient environmental concern. We have earlier reported that both MY and MG have tumor enhancing effects on the development of hepatic preneoplastic lesions induced by N-nitrosodiethylamine in rats. In order to understand the possible mechanisms by which MY and MG enhance tumor development, in this study we have tested the effects of MY and MG on DNA synthesis and PCNA expression in preneoplastic hepatic lesions during N-nitrosodiethylamine (DEN) induced hepatocarcinogenesis in male Wistar (WR) rats. Rats were administered 200 ppm DEN through drinking water for a period of one month. Administration of DEN for a period of one month showed an upregulation of cell cycle regulatory proteins namely cyclin D1, CDK4, cyclin E and CDK2. Accordingly, in other experiments, the animals were further administered MY and MG for a period of one month following one month DEN treatment. The effects of MY and MG were monitored on the basis of cell proliferation markers--DNA synthesis and PCNA expression both by immunohistochemical and immunoblotting. Following DEN administration, MY, MG and PB showed stimulation of DNA synthesis and increased PCNA expression when compared with either the corresponding controls or only DEN treated animals. In the present study, enhancing effect of MY, MG and PB on the cell proliferation markers during DEN-induced hepatic preneoplasia in rats was observed.

Topoisomerase II poisoning by indazole and imidazole complexes of ruthenium.

Trans-imidazolium (bis imidazole) tetrachloro ruthenate (RuIm) and trans-indazolium (bis indazole) tetrachloro ruthenate (RuInd) are ruthenium coordination complexes, which were first synthesized and exploited for their anticancer activity. These molecules constitute two of the few most effective anticancer ruthenium compounds. The clinical use of these compounds however was hindered due to toxic side effects on the human body. Our present study on topoisomerase II poisoning by these compounds shows that they effectively poison the activity of topoisomerase II by forming a ternary cleavage complex of DNA, drug and topoisomerase II. The thymidine incorporation assays show that the inhibition of cancer cell proliferation correlates with topoisomerase II poisoning. The present study on topoisomerase II poisoning by these two compounds opens a new avenue for renewing further research on these compounds. This is because they could be effective lead candidates for the development of more potent and less toxic ruthenium containing topoisomerase II poisons. Specificity of action on this molecular target may reduce the toxic effects of these ruthenium-containing molecules and thus improve their therapeutic index.

A fucan from the brown seaweed Spatoglossum schröederi inhibits Chinese hamster ovary cell adhesion to several extracellular matrix proteins

Fucans, a family of sulfated polysaccharides present in brown seaweed, have several biological activities. Their use as drugs would offer the advantage of no potential risk of contamination with viruses or particles such as prions. A fucan prepared from Spatoglossum schröederi was tested as a possible inhibitor of cell-matrix interactions using wild-type Chinese hamster ovary cells (CHO-K1) and the mutant type deficient in xylosyltransferase (CHO-745). The effect of this polymer on adhesion properties with specific extracellular matrix components was studied using several matrix proteins as substrates for cell attachment. Treatment with the polymer inhibited the adhesion of fibronectin to both CHO-K1 (2 x 10(5))()and CHO-745 (2 x 10(5) and 5 x 10(5)) cells. No effect was detected with laminin, using the two cell types. On the other hand, adhesion to vitronectin was inhibited in CHO-K1 cells and adhesion to type I collagen was inhibited in CHO-745 cells. In spite of this inhibition, the fucan did not affect either cell proliferation or cell cycle. These results demonstrate that this polymer is a new anti-adhesive compound with potential pharmacological applications

Hepatic regeneration after partial hepatectomy in mice infected with Schistosoma mansoni, at the acute and chronic phases of the disease

Outbred male albino mice normal or infected with 30 cercariae of Schistosoma mansoni (LE strain) were submitted to 65 percent hepatectomy during the acute (70 days) and chronic phase (160 days) phases of the disease. A group of the infected animals was treated with 400 mg/kg of oxamniquine during the acute phase before hepatectomy. Non-infected, infected and treated but not hepatectomized animals were kept as controls. Hepatic regeneration was evaluated by incorporation of tritiated thymidine, intraperitoneally injected into non-hepatectomized and hepatectomized animals, 24 hours after surgery. The results showed that removal of 65 percent of the hepatic parenchyma, during the acute phase, led to a statistically significant increase of thymidine incorporation, when compared with the uninfected hepatectomized controls. This phenomenon was not observed at the chronic phase. Treatment with oxamniquine administered during the acute phase led to a decrease in thymidine incorporation rate 160 days after infection (90 days after treatment) and 24 hours after hepatectomy. The data suggest that infection with S. mansoni represents a considerable stimulus for the regenerative capacity of the liver during the acute, but not the chronic phase of disease

1, 25-Dihydroxyvitamin D3 stimulates growth and inhibits calcitonin secretion in a human C cell carcinoma cell line

1,25-Dihydroxyvitamin D3 (1,25D3), calcitonin (CT) and parathyroid hormone are the major calcium-regulating hormones. In addition, 1,25D3 has been reported to be a modulator of cell growth and differentiation in many tissues. recently, a suppressive effect of 1,25D3 on CT secretion and synthesis in C cells was demonstrated in vivo and also in vitro, but there are no data about in effects on thyroid C cell growth. We investigated the effects of [3H]-1,25D3 on basal and stimulated CT secretion and on [3H]-thymidine incorporation, using a human medullary thyroid carcinoma cell line (TT cells). After a 4-day expossure to 1,25D3, TT cells showed a dose-dependent inhibition of basal CT secretion (64 per cento of value for the control group at 100 nM 1,25D3). calcium (3mM) plus K+ (50mM) greatly increased CT secretion in both the control and vitamin D-treated groups. However, in the cells preincubated with 1,25D3 the stimulated CT levels less than observed in controls. A dose-dependent increase in [3H]-thymidine incorporation (200 per cent of the value for the at 100 nM 1,25D3) and in cell number (150 per cent of the value for the control group at 100 nM 1,25D3 after 72h) was observed in the groups treated with 1,25D3. 24,25D3 had no effect on CT secretion or cell growth compared to the control group. These data show that 1,25D3 decreased basal and Ca2+-stimulated CT secretion, a specialized function of these cells, and stimulated their growth. Hence, in contrast to its effects on other cell lines, 1,25D3 appears to induce a dedifferentiation on TT cell

The effect of lovastatin on proliferation of cultured rat mesangial and aortic smooth muscle cells

In order to investigate the anti-proliferative effect of 3-hydroxy-3-methylglutaryl coenzyme. A reductase inhibitor, we evaluated the effects of lovastatin on DNA replication and the proliferation of rat mesangial and aortic smooth muscle cells, both of which were mesenchymal origin cells. Proliferations were determined by measuring [3H]thymidine uptake, and counting the number of cells. Growth-arrested mesangial and aortic smooth muscle cells were exposed to platelet-derived growth factor (PDGF), endothelin (ET) and angiotensin II (Ang II) to stimulate mitogenesis. All agents exhibited dose-dependent stimulation of [3H] thymidine uptake. PDGF was more potent than the others. Ang II increased [3H] thymidine uptake without demonstrable mitogenic activity. Lovastatin inhibited PDGF (10 ng/ml in mesangial cell, 25 ng/ml in smooth muscle cell)-, ET (10(-7)M)- and Ang II (10(-7)M)-induced [3H] thymidine uptake significantly in a dose-dependent manner in both cells. The increase of cell number in response to PDGF and ET treatment were also inhibited at 10 microM of lovastatin. The inhibitory effect of lovastatin was largely overcome in the presence of exogenous mevalonate at 200 microM, with 75.5% restoration from lovastatin-induced inhibition on PDGF-induced [3H] thymidine uptake in mesangial cells (77.8% in aortic smooth muscle cells). However, the addition of cholesterol did not prevent inhibition by lovastatin. In conclusion, lovastatin had an inhibitory effect on mesangial and aortic smooth muscle cell proliferation, and mevalonate was essential for DNA replication in both types of cells. Lovastatin may reduce glomerular and atherosclerotic injury through an anti-proliferative effect on mesangial and vascular smooth muscle cells, in addition to lowering circulating lipids.

Dual regulatory action of prostatic inhibin (10.7 kDa) on DNA synthesis.

Present studies deal with the role of inhibin in proliferation and growth. The effect of inhibin on incorporation of 3H-thymidine in prostatic DNA in vivo as well as by NRK-49F and Balb/c3T3 cell lines in vitro, was investigated. Also studied the immunocytochemical localization of inhibin in normally proliferating and differentiated tissues of human prostate and endometrium. The in vivo studies revealed a suppression of 3H-thymidine uptake both in ventral (33%) and dorsolateral (26%) lobes of rat prostate. Interestingly, the histology of inhibin treated rat prostate manifested amidst the epithelial lining, an appearance of apoptotic bodies which are considered to be indicative of cell death. Further, the immunocytochemical studies for localization of inhibin showed intense staining in the differentiated human prostate and endometrium as compared to the respective proliferative tissues. Is inhibin kept suppressed in these proliferating tissues, because it is antiproliferative? The present in vitro experiments demonstrated that, at low inhibin concentrations, the incorporation of 3H-thymidine is stimulated while at higher doses it is suppressed. Thus, it is clear that prostatic inhibin seems to have a concentration-dependent dual role in the regulation of DNA synthesis.

Functional aspect of a phosphopeptide derived from calf thymus nuclei and DNA.

Phosphopeptides (PPs) isolated from highly purified calf thymus DNA (N-DNA) and extracted from calf thymus nuclei were fractionated, and the effect of one PP fraction on DNA replication has been examined. In the absence of inhibitors, the increasing PP concentration caused a linear decrease of 3H-thymidine uptake in L5178Y cells. If PP fraction was mildly hydrolysed with 1NHCl, the decrease in uptake was much steeper. The studies in which the inhibitors were used revealed that by the addition of the unhydrolysed PP fraction the inhibition of 3H-thymidine uptake by alpha-amanitin could be completely overcome, and that the inhibition by puromycin was reduced to 65-77% of the control. With puromycin, there was a gradual decrease of 3H-thymidine uptake with PP concentration above 3 mg/ml. The PPs gave an increase in incorporation of 3H-thymidine even after removal of alpha-amanitin and puromycin; thus, it is suggested that there is no direct interaction of either inhibitor with PP in the cell. Data on the utilization of 3H-cytidine for the synthesise of new DNA suggest that PP fraction might cause an acceleration of DNA replication.

Primary dapsone resistance as assessed by uptake of labelled thymidine by the macrophage resident Mycobacterium leprae.

12 untreated lepromatous leprosy patients were screened for primary dapsone resistance by the uptake of labelled thymidine by macrophage resident M. leprae. There were found to harbour primary dapsone resistant strains of M. leprae and another three partially resistant strains to the drug. This rapid, simple and reliable method should be used routinely to screen leprosy patients, for drug resistance.

Evaluacion de la producion de interleuquina 1 por celulas adherentes en pacientes con diabetes tipo II / Production of interleukin 1 by adherent cells in patients with Diabetes Mellitus type II

Se evaluó la actividad comitogénica de la interleuquina 1 producida en cultivos de células adherentes mononucleares de pacientes con diabetes mellitus (DM) tipo II o insulino no dependente. Dicha actividad fue medida por la incorporación de timidina en cultivos de timocitos de ratones (C3H/Hej, en presencia de fitohemaglutinina (PHA). Se observó que los sobrenadantes de los cultivos de células adherentes de los pacientes con DM tipo II no produjeron efecto sinergista con la PHA, obteniéndose niveles de linfoproliferación semejantes a los obtenidos en ausencia de dicha lectina. Esta falta de efecto comitogénico (p < 0,001) con respecto a la respuesta obtenida con la interleuquina 1 de sujetos normales más PHA, podría deberse a la liberación de algún/os factor/es solubles que podieron interferir con los receptores glicosilados para mitógenos o con los procesos de activación celular

Antagonistic effect of insulin and cortisol on stimulated lymphocytes

En este trabajo se demuestra que la insulina 10*-9M produce en linfocitos humanos circulantes estimulados por distintas dosis de fitohemaglutinina (PHA) un incremento en la incorporación de timidina*-3H. El efecto máximo de 95% se obtuvo a las menores dosis de PHA, mientras que disminuyó a medida que la concentración del mitógeno aumentaba y desapareció cuando PHA alcanzó la respuesta máxima. Se estudió, además, la acción conjunta del cortisol y la insulina, en concentraciones fisiológicas, sobre linfocitos humanos circulantes estimulados con dos dosis de PHA. Con dosis bajas del mitógeno (1micronl) el cortisol 10*-6M disminuyó la incorporación de timida *-3H a 15%, fenómeno que no pudo ser normalizado por la insulina 10*-10M ni 10*-8M. En cambio, las mismas dosis de insulina antagonizaron la acción inhibitoria del cortisol 10*-8M, concentración que llevó a 53% la incorporación de timidina *-3H por las células. Cuando las células se estimularon con 5 microns de PHA (dosis máxima) la insulina 10*-10M y 10*-8M antagonizó parcialmente la inhibición producida por cortisol 5x10*-8M y 10*-7M, pero no la de cortisol 10*-6M. Estos resultados sugieren que la insulina incrementa la síntesis de DNA en linfocitos estimulados solamente cuando en el medio de cucltivo existen concentraciones mitogénicas subóptimas y que la inhibición de las síntesis de DNA producida por el cortisol puede ser revertida por la insulina, siempre que el efecto inhibitorio sea menor de 50%