RESUMO
The high sedimentation rates and high organic matter contents in the sediments of the Ría de Vigo (NW Spain) promote the development of anoxic conditions, determining the dynamics of elements like Fe and conditioning his speciation and reactivity. Four gravity cores were retrieved in anoxic sediments of the Ría de Vigo in November 2012. In order to understand the behavior of Fe in these complex environments different fractions of reactive iron were analyzed. The decrease in highly reactive iron and sulfide contents with depth showed the relationship between the iron and sulfur cycle in the middle and outer zones of the ría. In the inner zone, the apparition of shallow methane gas may cause the slower decrease of the highly reactive iron contents. In zones without methane, sediment layers enriched in iron -with a reactivity higher than in other sediment samples- were observed. An increase was observed in the dithionite and total reactive iron contents from the inner to the outer zone of the ría, according to the gas depth. Furthermore, a decrease in Fe (III)-bearing minerals contents with depth was observed in the outer and middle zones, but not in the innermost area where the gas is shallow. The high organic matter and sulfide contents, mainly in the inner zone of the ría, indicate that the most of the Fe (II) is FeS. Moreover, the high contents of total reactive iron and pH values (6.86-7.98) could contribute the formation of stable minerals like pyrite along the Ría de Vigo.
Assuntos
Monitoramento Ambiental , Sedimentos Geológicos/química , Ferro/análise , Ferro/química , Sulfetos/química , Metano/análise , Espanha , Enxofre/análiseRESUMO
Treatment for 2 h with 200 microM cadmium chloride, followed by recovery, caused apoptosis and induced heat-shock protein 70 (HSP70) expression in U-937 promonocytic cells. However, pre-incubation with the GSH depleting agent L-buthionine-[S,R]-sulfoximine (BSO, 1 mM for 24 h) caused necrosis instead of apoptosis and failed to induce HSP70 expression. This failure was a consequence of necrosis instead of GSH depletion, since BSO allowed or even potentiated HSP70 induction when used in combination with heat shock (2 h at 42.5 degrees C) or with 50 microM cadmium, which caused apoptosis. The administration of N-acetyl-L-cysteine (NAC) at the beginning of recovery after BSO/200 microM cadmium treatment prevented the execution of necrosis and restored the execution of apoptosis, but did not restore HSP70 induction, indicating that the inhibition by BSO of HSP70 expression is an early regulated event. This contrasted with the capacity of NAC to prevent the alterations caused by BSO/200 microM cadmium in other proteins, namely the suppression of Bax expression and the increase in Bcl-2 and HSP-60 expression. Finally, it was observed that treatment with 200 microM cadmium rapidly increased the HSP70 mRNA level and stimulated heat-shock factor 1 (HSF1) trimerization and binding, and that these effects were prevented by pre-incubation with BSO. Taken together, these results indicate that the stress response is compatible with apoptosis but not with necrosis in cadmium-treated promonocytic cells. The suppression of the stress response is specifically due to the early inhibition of HSF1 activation.
Assuntos
Cloreto de Cádmio/farmacologia , Proteínas de Choque Térmico HSP70/biossíntese , Temperatura Alta , Metionina Sulfoximina/análogos & derivados , Monócitos/efeitos dos fármacos , Acetilcisteína , Apoptose , Chaperonina 60/análise , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Glutationa/deficiência , Proteínas de Choque Térmico HSP70/metabolismo , Fatores de Transcrição de Choque Térmico , Humanos , Necrose , Proteínas Proto-Oncogênicas/análise , Proteínas Proto-Oncogênicas c-bcl-2/análise , RNA Mensageiro/biossíntese , Fatores de Transcrição , Células Tumorais Cultivadas , Proteína X Associada a bcl-2RESUMO
Treatment with 0.2 mM hydrogen peroxide (H(2)O(2)) or with 0.5 mM cisplatin caused caspase-9 and caspase-3 activation and death by apoptosis in U-937 human promonocytic cells. However, treatment with 2 mM H(2)O(2), or incubation with the glutathione suppressor DL-buthionine-(S,R)-sulfoximine (BSO) prior to treatment with cisplatin, suppressed caspase activation and changed the mode of death to necrosis. Treatment with 2 mM H(2)O(2) caused a great decrease in the intracellular ATP level, which was partially prevented by 3-aminobenzamide (3-ABA). Correspondingly, 3-ABA restored the activation of caspases and the execution of apoptosis. By contrast, BSO plus cisplatin did not decrease the ATP levels, and the generation of necrosis by this treatment was not affected by 3-ABA. On the other hand, while all apoptosis-inducing treatments and treatment with 2 mM H(2)O(2) caused Bax translocation from the cytosol to mitochondria as well as cytochrome c release from mitochondria to the cytosol, treatment with BSO plus cisplatin did not. Treatment with cisplatin alone caused Bid cleavage, while BSO plus cisplatin as well as 0.2 and 2 mM H(2)O(2) did not. Bcl-2 overexpression reduced the generation of necrosis by H(2)O(2), but not by BSO plus cisplatin. These results indicate the existence of different apoptosis/necrosis regulatory mechanisms in promonocytic cells subjected to different forms of oxidative stress.
Assuntos
Apoptose/efeitos dos fármacos , Glutationa/deficiência , Peróxido de Hidrogênio/farmacologia , Monócitos/efeitos dos fármacos , Necrose , Trifosfato de Adenosina/metabolismo , Benzamidas/farmacologia , Western Blotting , Butionina Sulfoximina/farmacologia , Caspase 3 , Caspase 9 , Caspases/efeitos dos fármacos , Caspases/metabolismo , Cisplatino/farmacologia , Citocromos c/efeitos dos fármacos , Citocromos c/metabolismo , Complexo III da Cadeia de Transporte de Elétrons/efeitos dos fármacos , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Citometria de Fluxo , Humanos , Microscopia de Fluorescência , Monócitos/citologia , Monócitos/metabolismo , Proteínas Proto-Oncogênicas/efeitos dos fármacos , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Transfecção , Células U937 , Proteína X Associada a bcl-2 , Proteína bcl-XRESUMO
The Ría de Vigo (NW Spain) has a high organic matter content and high rates of sedimentation. The microbial degradation of this organic matter has led to shallow gas accumulations of methane, currently distributed all along the ría. These peculiar characteristics favor the development of anoxic conditions that can determine the dynamics of iron and manganese. In order to study the role played by iron and manganese in the processes that take place in anoxic sediments with shallow gas, four gravity cores were retrieved in anoxic sediments of the Ría de Vigo in November 2012. Methane was present in two of them, below 90cm in the inner zone and below 200cm, in the outer zone. Pore water was collected and analyzed for vertical profiles of pH, sulfide, sulfate, iron and manganese concentrations. Sulfate concentrations decreased with depth but never reached the minimum detection limit. High sulfide concentrations were measured in all cores. The highest sulfide concentrations were found in the inner zone with methane and the lowest were in the outer zone without methane. Concentrations of iron and manganese reached maximum values in the upper layers of the sediment, decreasing with depth, except in the outer zone without gas, where iron and manganese concentration increased strongly toward the bottom of the sediment. In areas with shallow gas iron reduction, sulfate reduction and methane production processes coexist, showing that the traditional redox cascade is highly simplified and suggesting that iron may be involved in a cryptic sulfur cycle and in the oxidation of methane.
Assuntos
Monitoramento Ambiental , Sedimentos Geológicos/química , Rios/química , Poluentes Químicos da Água/química , Ferro , Manganês , Metano/análise , Oxirredução , Espanha , Sulfatos , Sulfetos , Enxofre , Poluentes Químicos da Água/análiseRESUMO
Earlier studies have indicated that Jun/AP-1 activity is associated with, and probably required for apoptosis induction by DNA-damaging and stress-inducing agents in human myeloid cells. To investigate this possibility, we examined the capacity of continuous treatments with etoposide (10 microM) and camptothecin (0.4 microM), and pulse treatments with X-rays (20 Gy), heat (2 h at 42.5 C) and cadmium chloride (2 h at 200 microM) followed by recovery, to provoke apoptosis and to simulate c-jun and c-fos expression and AP-1 binding in U-937 human promonocytic cells. All these treatments generated apoptosis with similar efficacy (50-60% apoptotic cells at 6 h of treatment or recovery). However, the capacity to increase c-jun and c-fos mRNA levels and to stimulate AP-1 binding was very different, ranging from more than a twelve-fold increase in the case of cadmium, to almost no increase in the case of heat-shock and etoposide. When the cells were pre-conditioned with a soft heat shock (1 h at 42 degrees C) the cadmium-provoked apoptosis was greatly inhibited, but the stimulation of AP-1 binding was not affected. The administration of cAMP-increasing agents also reduced the etoposide- and cadmium-provoked apoptosis. However, cAMP greatly stimulated c-jun and c-fos expression and AP-1 binding when applied together with etoposide (which itself was ineffective), and potentiated the cadmium-induced AP-1 binding. Conversely, retinoic acid abrogated the cadmium-provoked stimulation of AP-1 binding and transactivation capacity, and greatly inhibited the stimulation of binding caused by camptothecin and X-rays. However, retinoic acid did not inhibit the induction of apoptosis by these agents. These results indicate that Jun/AP-1 activity is not necessarily coupled with apoptosis, nor required for apoptosis induction by DNA-damaging and stress-inducing agents in human promonocytic cells.
Assuntos
Apoptose , Dano ao DNA , Proteínas Proto-Oncogênicas c-jun/genética , Fator de Transcrição AP-1/metabolismo , Cloreto de Cádmio/farmacologia , Camptotecina/farmacologia , Colforsina/metabolismo , Colforsina/farmacologia , AMP Cíclico/metabolismo , Inibidores Enzimáticos/farmacologia , Etoposídeo/farmacologia , Expressão Gênica , Calefação , Humanos , Monócitos , Teofilina/metabolismo , Teofilina/farmacologia , Inibidores da Topoisomerase I , Inibidores da Topoisomerase II , Tretinoína/metabolismo , Tretinoína/farmacologia , Células U937 , DesacopladoresRESUMO
Treatment of U-937 human promonocytic cells with the stress inducers cadmium chloride (2 h at 200 microM), heat (2 h at 42.5 C) or X-rays (20 Gy), followed by recovery, caused death by apoptosis and stimulated caspase-3 activity. In addition, all stress agents caused intracellular oxidation, as measured by peroxide and/or anion superoxide accumulation. However, while pre-incubation with antioxidants (N-acetyl-L-cysteine or butylated hydroxyanisole) inhibited the induction of apoptosis by cadmium and X-rays, it did not affect the induction by heat-shock. Pre-incubation for 24 h with the GSH-depleting agent L-buthionine-[S,R]-sulfoximine (BSO) switched the mode of death from apoptosis to necrosis in cadmium-treated cells. By contrast, BSO only caused minor modifacions in the rate of apoptosis without affecting the mode of death in heat- and X-rays-treated cells. BSO potentiated peroxide accumulation in cells treated with both cadmium and X-rays. However, while the accumulation of peroxides was stable in the case of cadmium, it was transient in the case of X-rays. Moreover, the administration of antioxidants during the recovery period sufficed to prevent necrosis and restore apoptosis in BSO plus cadmium-treated cells. Cadmium and X-rays caused a decrease in intracellular ATP levels, but the decrease was similar in both apoptotic and necrotic cells. Taken together, these results demonstrate that (i) stress inducers cause intracellular oxidation, but oxidation is not a general requirement for apoptosis; and (ii) the duration of the oxidant state seems to be critical in determining the mode of death.
Assuntos
Apoptose/fisiologia , Estresse Oxidativo/fisiologia , Trifosfato de Adenosina/metabolismo , Antimetabólitos/farmacologia , Antioxidantes/farmacologia , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , Butionina Sulfoximina/farmacologia , Cloreto de Cádmio/farmacologia , Caspases/metabolismo , Fluoresceínas , Temperatura Alta , Humanos , Necrose , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Células U937 , Raios XRESUMO
The treatment of U-937 human promonocytic cells with the differentiation inducer sodium butyrate (0.75 mM) transiently increased heat-shock protein 70 (HSP70) mRNA levels between 3 and 6 h, and heat-shock protein 27 (HSP27) mRNA levels between 12 and 24 h, as indicated by northern blot assays. Gel retardation assays indicated that butyrate also stimulated heat-shock factor (HSF) binding activity between 3 and 6 h, suggesting that the activation of HSP70 gene expression was mediated by the heat-shock factor DNA response element (HSE). In addition, the treatment provoked a biphasic alteration of the c-fos mRNA level, consisting of a slight increase between 0.5 and 3 h followed by a greater increase between 12 and 48 h, while it caused a single increase between 12 and 48 h in c-jun mRNA level. The possible involvement of the heat-shock protein genes in the butyrate-induced differentiation of U-937 cells is discussed.
Assuntos
Butiratos/farmacologia , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico/genética , Leucemia Promielocítica Aguda/metabolismo , Sequência de Bases , Ácido Butírico , Diferenciação Celular/efeitos dos fármacos , Proteínas de Ligação a DNA/metabolismo , Genes fos , Genes jun , Fatores de Transcrição de Choque Térmico , Humanos , Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/patologia , Dados de Sequência Molecular , RNA Mensageiro/análise , Fatores de Transcrição , Células Tumorais CultivadasRESUMO
Pulse-treatment of U-937 human promonocytic cells with cadmium chloride followed by recovery caused caspase-9/caspase-3-dependent, caspase-8-independent apoptosis. However, pre-incubation with the glutathione (GSH)-suppressing agent DL-buthionine-(S,R)-sulfoximine (cadmium/BSO), or co-treatment with H2O2 (cadmium/H2O2), switched the mode of death to caspase-independent necrosis. The switch from apoptosis to necrosis did not involve gross alterations in Apaf-1 and pro-caspase-9 expression, nor inhibition of cytochrome c release from mitochondria. However, cadmium/H2O2-induced necrosis involved ATP depletion and was prevented by 3-aminobenzamide, while cadmium/BSO-induced necrosis was ATP independent. Pre-incubation with BSO increased the intracellular cadmium accumulation, while co-treatment with H2O2 did not. Both treatments caused intracellular peroxide over-accumulation and disruption of mitochondrial transmembrane potential (delta psi m). However, while post-treatment with N-acetyl-L-cysteine or butylated hydroxyanisole reduced the cadmium/BSO-mediated necrosis and delta psi m disruption, it did not reduce the effects of cadmium/H2O2. Bcl-2 over-expression, which reduced peroxide accumulation without affecting the intracellular GSH content, attenuated necrosis generation by cadmium/H2O2 but not by cadmium/BSO. By contrast, AIF suppression, which reduced peroxide accumulation and increased the GSH content, attenuated the toxicity of both treatments. These results unravel the existence of two different oxidation-mediated necrotic pathways in cadmium-treated cells, one of them resulting from ATP-dependent apoptosis blockade, and the other involving the concurrence of multiple regulatory factors.
Assuntos
Apoptose/efeitos dos fármacos , Cádmio/farmacologia , Monócitos/efeitos dos fármacos , Estresse Oxidativo , Acetilcisteína/farmacologia , Trifosfato de Adenosina/análise , Trifosfato de Adenosina/metabolismo , Antimetabólitos Antineoplásicos/farmacologia , Benzamidas/farmacologia , Butionina Sulfoximina/farmacologia , Cádmio/análise , Caspase 3 , Caspase 9 , Caspases/metabolismo , Interações Medicamentosas , Glutationa/análise , Glutationa/metabolismo , Humanos , Peróxido de Hidrogênio/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Necrose/induzido quimicamente , Necrose/patologia , Oxidantes/farmacologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Interferente Pequeno/metabolismo , Transfecção , Células U937RESUMO
Treatment of U-937 promonocytic cells with the DNA topoisomerase II inhibitor etoposide rapidly caused death by apoptosis, as determined by changes in chromatin structure, production of DNA breaks, nucleosome-sized DNA degradation, decrease in mitochondrial membrane potential and phosphatidyl serine translocation in the plasma membrane, and at the same time induced intracellular acidification. Both the execution of the apoptotic process and the intracellular acidification were reduced by the addition of forskolin plus theophylline or other cAMP increasing agents. These agents also attenuated the induction of apoptosis by camptothecin, heat-shock, cadmium chloride and X-radiation. Although etoposide slightly increased the production of reactive oxygen intermediates, this increase was not prevented by forskolin plus theophylline, and the addition of antioxidant agents failed to inhibit apoptosis. Etoposide caused a great increase in NF-(kappa)B binding activity, which was not prevented by forskolin plus theophylline, while AP-1 binding was little affected by the topoisomerase inhibitor. The treatments did not significantly alter the levels of Bcl-2 and Bax. By contrast, the expression of c-myc, which was very high in untreated U-937 cells and only partially inhibited by etoposide, was rapidly and almost totally abolished by the cAMP increasing agents. Finally, it was observed that etoposide caused a transient dephosphorylation of retinoblastoma (Rb), which was associated with cleavage of poly(ADP-ribose) polymerase (PARP). Both Rb dephosphorylation and PARP cleavage were inhibited by forskolin plus theophylline. The inhibition of Rb (type I) phosphatase and ICE/CED-3-like protease activities, and the abrogation of c-myc expression, are mechanisms which could explain the anti-apoptotic action of cAMP increasing agents in myeloid cells.
Assuntos
Antineoplásicos Fitogênicos/farmacologia , AMP Cíclico/biossíntese , Inibidores Enzimáticos/farmacologia , Etoposídeo/farmacologia , Leucemia Promielocítica Aguda/tratamento farmacológico , Inibidores da Topoisomerase II , Apoptose/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Genes myc , Humanos , Leucemia Promielocítica Aguda/patologia , NF-kappa B/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Ligação Proteica , Fator de Transcrição AP-1/metabolismo , Células Tumorais CultivadasRESUMO
Treatment with the DNA topoisomerase inhibitors etoposide, doxorubicin, and camptothecin, and with the alkylating agents cisplatin and melphalan, caused peroxide accumulation and apoptosis in U-937 human promonocytic cells. Preincubation with the reduced glutathione (GSH) synthesis inhibitor l-buthionine-(S,R)-sulfoximine (BSO) always potentiated peroxide accumulation. However, although GSH depletion potentiated the toxicity of cisplatin and melphalan, occasionally switching the mode of death from apoptosis to necrosis, it did not affect the toxicity of the other antitumor drugs. Hypoxia or preincubation with antioxidant agents attenuated death induction, apoptotic and necrotic, by alkylating drugs. The generation of necrosis by cisplatin could not be mimicked by addition of exogenous H(2)O(2) instead of BSO and was not adequately explained by caspase inactivation nor by a selective fall in ATP content. Treatment with cisplatin and melphalan caused a late decrease in mitochondrial transmembrane potential (DeltaPsim), which was much greater during necrosis than during apoptosis. The administration of the antioxidant agents N-acetyl-l-cysteine and butylated hydroxyanisole after pulse treatment with cisplatin or melphalan did not affect apoptosis but attenuated necrosis. Under these conditions, both antioxidants attenuated the necrosis-associated DeltaPsim decrease. These results indicate that oxidation-mediated alterations in mitochondrial function regulate the selection between apoptosis and necrosis in alkylating drug-treated human promonocytic cells.
Assuntos
Antineoplásicos/toxicidade , Apoptose , Glutationa/metabolismo , Monócitos/metabolismo , Necrose , Oxigênio/metabolismo , Trifosfato de Adenosina/metabolismo , Alquilantes/farmacologia , Antimetabólitos Antineoplásicos/farmacologia , Antineoplásicos/farmacologia , Antineoplásicos Alquilantes/farmacologia , Antineoplásicos Fitogênicos/farmacologia , Antioxidantes/farmacologia , Butionina Sulfoximina/farmacologia , Camptotecina/farmacologia , Morte Celular , Cisplatino/farmacologia , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Doxorrubicina/farmacologia , Inibidores Enzimáticos/farmacologia , Etoposídeo/farmacologia , Citometria de Fluxo , Glutationa/antagonistas & inibidores , Humanos , Peróxido de Hidrogênio/farmacologia , Hipóxia , Immunoblotting , Melfalan/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Mitocôndrias/metabolismo , Inibidores da Síntese de Ácido Nucleico/farmacologia , Protetores contra Radiação/farmacologia , Espécies Reativas de Oxigênio , Espectrometria de Fluorescência , Fatores de Tempo , Inibidores da Topoisomerase I , Células U937RESUMO
Infection of HeLa cells with adenovirus-carrying HSF1(+) cDNA, which encodes a mutated form of HSF1 with constitutive transactivation capacity, increased multidrug resistance 1 (MDR1) mRNA level and P-glycoprotein (P-gp) cell surface content and stimulated rhodamine 123 accumulation and vinblastine efflux activity. On the other hand, infection with adenovirus-carrying HSP70 and HSP27 cDNAs did not increase MDR1/P-gp expression. HSF1 regulates MDR1/P-gp expression at the transcriptional level, since HSF1(+) bound the heat-shock consensus elements (HSEs) in the MDR1 gene promoter and also activated the expression of an MDR1 promoter-driven reporter plasmid (pMDR1(-1202)). In addition, heat-shock increased pMDR1(-1202) promoter activity but not the activity of a similar reporter plasmid with point mutations at specific HSEs, and the heat-induced increase was totally inhibited by co-transfection with an expression plasmid carrying HSF1(-), a dominant negative mutant of HSF1. The stress inducers arsenite, butyrate, and etoposide also increased pMDR1(-1202) promoter activity, but the increase was not inhibited (in the case of butyrate) or was only partially inhibited (in the case of arsenite and etoposide) by HSF1(-). These results demonstrate that HSF1 regulates MDR1 expression, and that the HSEs present in the -315 to -285 region mediate the heat-induced activation of the MDR1 promoter. However, other factors may also participate in MDR1 induction by stressing agents.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Proteínas de Ligação a DNA/metabolismo , Resistência a Múltiplos Medicamentos/genética , Regulação da Expressão Gênica , Proteínas de Choque Térmico , Regiões Promotoras Genéticas , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Sequência de Bases , Sítios de Ligação , Proteínas de Ligação a DNA/genética , Genes Reporter , Proteínas de Choque Térmico HSP27 , Proteínas de Choque Térmico HSP70/genética , Células HeLa , Fatores de Transcrição de Choque Térmico , Temperatura Alta , Humanos , Cinética , Chaperonas Moleculares , Proteínas de Neoplasias/genética , Proteínas Recombinantes/metabolismo , Fatores de Tempo , Fatores de Transcrição/metabolismo , Transcrição Gênica , Transfecção , Vimblastina/farmacocinéticaRESUMO
Treatment of U-937 human promonocytic cells with the cAMP increasing agents isoproterenol plus theophylline decreased the basal level of heat-shock protein 70 (HSP70) mRNA. In addition, the cAMP increasing agents attenuated the increase in HSP70 mRNA and protein levels produced by cadmium chloride in U-937 and other human myeloid cell lines, reduced the capacity of cadmium treatment to generate stress-tolerance, and attenuated the cadmium-produced stimulation of heat-shock factor (HSF) binding activity. By contrast, isoproterenol plus theophylline failed to attenuate the stimulation of HSP70 gene expression and HSF binding activity caused by heat-shock. Isoproterenol plus theophylline did not prevent the uptake of cadmium into the cells, and increased to a similar extent the intracellular cAMP levels in cadmium- and heat-treated cells. The cAMP increasing agents reduced the induction by cadmium of the HSP27 stress gene, but failed to attenuate other cadmium-elicited stress reactions such as the inhibition of total protein synthesis. It is concluded that cAMP does not inhibit the stress response as a whole, but it interferes with some step of the pathway by which cadmium specifically stimulates HSF binding activity and as a consequence HSP70 gene expression, in human myeloid cell lines.
Assuntos
Cádmio/farmacologia , Cloretos/farmacologia , AMP Cíclico/metabolismo , Expressão Gênica/efeitos dos fármacos , Proteínas de Choque Térmico HSP70/biossíntese , Isoproterenol/farmacologia , Teofilina/farmacologia , Sequência de Bases , Cádmio/antagonistas & inibidores , Cádmio/metabolismo , Cloreto de Cádmio , Linhagem Celular , Núcleo Celular/metabolismo , Cloretos/antagonistas & inibidores , Temperatura Alta , Humanos , Cinética , Leucemia , Dados de Sequência Molecular , Oligodesoxirribonucleotídeos , RNA Mensageiro/análise , RNA Mensageiro/biossíntese , Células Tumorais Cultivadas , Valina/metabolismoRESUMO
Heat-shock for 2 hours at 42 degrees C, or the administration for 3 hours of 100 or 150 microM cadmium chloride, inhibited the subsequent proliferation activity, induced the expression of functional differentiation markers, and caused an increase in the amount of the stress-responsive HSP70 protein in U-937 human promonocytic cells. In addition, both heat and cadmium produced an increase in the amount of the intermediate filament protein vimentin, as determined by immunoblot and immunofluorescence assays. By contrast, the amounts of actin and beta-tubulin were not significantly altered. The amount of vimentin mRNA was also increased during recovery from stress, indicating that vimentin expression was not exclusively regulated at the protein level. Although cadmium caused an early, transient stimulation of c-jun and c-fos expression and AP-1 binding activity, heat-shock failed to alter both protooncogene expression and transcription factor binding, indicating that the stress-induced vimentin increase was not the result of AP-1-mediated transcriptional activation. Finally, it was observed that the rate of decay of vimentin mRNA upon actinomycin D administration was decreased in heat- and cadmium-pretreated cells in comparison to untreated cells. These results indicate that stress treatments cause an increase in vimentin levels in promonocytic cells, which may be explained at least in part by transcript stabilization.
Assuntos
Cloreto de Cádmio/farmacologia , Proteínas de Choque Térmico HSP70/análise , Vimentina/metabolismo , Actinas/análise , Animais , Diferenciação Celular , Divisão Celular , Resposta ao Choque Térmico , Humanos , Camundongos , Monócitos , Proteínas , Proteínas Proto-Oncogênicas c-fos/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , RNA Mensageiro/análise , Fator de Transcrição AP-1/metabolismo , Tubulina (Proteína)/análise , Células Tumorais Cultivadas , Vimentina/genéticaRESUMO
We have compared the action on U-937 human promonocytic leukemia cells of two DNA topoisomerase II inhibitors, namely the epipodophyllotoxin etoposide and the bisdioxopiperazine ICRF-193. One hour pulse-treatment with 3 microM etoposide caused topoisomerase associated, primary DNA breakage, which was rapidly followed by apoptosis. By contrast, these effects were not observed upon pulse-treatment with 6 microM ICRF-193. However, continuous treatments with subcytotoxic concentrations of etoposide (0.15 microM) and ICRF-193 (0.3 microM) produced several similar effects, namely decreased cell proliferation, accumulation of cells at G2, increase in cell mass, and induction of differentiation. Under these conditions, etoposide produced a biphasic activation of protein kinase C, which consisted in an early transient activation (from hours 1 to 6) of the membrane-bound enzyme followed by a later activation (hour 48) of the total, membrane-bound and cytosolic enzyme. By contrast, ICRF-193 only provoked a late activation (from hours 72 to 96) of the total enzyme. When used at differentiation-inducing concentrations, both topoisomerase inhibitors caused a great stimulation of AP-1 binding activity, with maximum value at hour 12 in etoposide-treated cells and at hour 48 in ICRF-193-treated cells. By contrast, the binding activity of the NF-kappa(B) and EGR-1 transcription factors was little affected. It is concluded that topoisomerase II inhibitors may induce the differentiation of promonocytic cells, independently of their capacity to cause DNA strand breaks. However, there are other effects, such as the early activation of protein kinase C, which are probably derived from the production of primary DNA breakage by some anti-topoisomerase drugs.
Assuntos
Etoposídeo/farmacologia , Proteínas Imediatamente Precoces , Monócitos/citologia , Piperazinas/farmacologia , Inibidores da Topoisomerase II , Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Dano ao DNA , Proteínas de Ligação a DNA/metabolismo , Dicetopiperazinas , Proteína 1 de Resposta de Crescimento Precoce , Ativação Enzimática , Inibidores Enzimáticos/farmacologia , Humanos , Monócitos/efeitos dos fármacos , NF-kappa B/metabolismo , Proteína Quinase C/metabolismo , Fator de Transcrição AP-1/metabolismo , Fatores de Transcrição/metabolismo , Células Tumorais CultivadasRESUMO
The administration of sodium butyrate at 0.75 mM induced the functional differentiation of U-937 human promonocytic leukemia cells with negligible cell mortality. However, the drug rapidly caused cell death with characteristics of apoptosis when used at concentrations of 5 mM and above. In addition, butyrate stimulated the expression of the stress-responsive heat-shock protein 70 (HSP70) gene when applied at both differentiation-inducing and apoptosis-inducing concentrations. The induction of HSP70 by butyrate was inhibited by the simultaneous addition of cAMP-increasing agents (dibutyryl cAMP or the combination of forskolin plus theophylline). However, these agents did not prevent differentiation and only partially reduced apoptosis. Moreover, the DNA topoisomerase II inhibitor etoposide, which provoked U-937 cell differentiation and apoptosis with the same or greater efficiency than butyrate, failed to stimulate HSP70 expression. Finally, it was observed that cAMP-increasing agents also abrogated the induction of HSP70 and reduced the apoptosis caused by cadmium chloride, a typical inducer of the stress response. Taken together, these results indicate that HSP70 expression is not required for differentiation of promonocytic cells, as earlier proposed, and that butyrate probably triggers the stress response in these cells.
Assuntos
Apoptose/efeitos dos fármacos , Butiratos/farmacologia , Proteínas de Choque Térmico HSP70/genética , Antagonistas dos Receptores Histamínicos/farmacologia , Linfoma Difuso de Grandes Células B , Antineoplásicos Fitogênicos/farmacologia , Apoptose/fisiologia , Bucladesina/farmacologia , Ácido Butírico , Cloreto de Cádmio/farmacologia , Carcinógenos/farmacologia , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Colforsina/farmacologia , AMP Cíclico/metabolismo , Etoposídeo/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Inibidores de Fosfodiesterase/farmacologia , Estresse Fisiológico/metabolismo , Teofilina/farmacologia , Inibidores da Topoisomerase II , Células Tumorais Cultivadas/citologia , Células Tumorais Cultivadas/efeitos dos fármacos , Células Tumorais Cultivadas/enzimologiaRESUMO
The presence of antibodies in rheumatoid arthritis (RA) patients to antigens on the synoviocyte surface has recently been reported (Scand. J. Immunol. 27, 295, 1988). Here we have further characterized these antigens and found that they are exogenous proteins acquired from the bovine serum used in the culture medium. By immunoprecipitation and ELISA studies, we have identified bovine albumin and transferrin as the antigens recognized by the RA antibodies. These specificities were found not only in the sera but also in the synovial fluid from RA patients. A comparative study with a large panel of RA sera did not show a correlation in the antibody specificities for bovine albumin, bovine transferrin, or the 65-kDa heat shock protein from Mycobacterium bovis. Similar experiments using rabbit and monkey sera as well as human synovial fluid and serum as a source of antigen did not reveal any reactivity with a highly positive RA serum. By sequence alignment, a high degree of homology between residues 142-156 from bovine albumin and residues 65-78 from human pro-collagen alpha 1 (I) was found. The capacity of the synoviocytes to bind exogenous antigens and the presence of antibodies to bovine proteins, normally present in the diet, suggest a role for these type A synoviocytes as well as a possible involvement of food antigens in the pathogenesis of RA.
Assuntos
Antígenos/imunologia , Artrite Reumatoide/imunologia , Soroalbumina Bovina/imunologia , Membrana Sinovial/imunologia , Transferrina/imunologia , Animais , Artrite Reumatoide/etiologia , Bovinos , Dieta , Epitopos/análise , Proteínas de Choque Térmico/imunologia , HumanosRESUMO
Pulse treatment of U-937 promonocytic cells with cadmium chloride (2 h at 200 microM) provoked apoptosis and induced a rapid phosphorylation of p38 mitogen-activated protein kinase (p38(MAPK)) as well as a late phosphorylation of extracellular signal-regulated protein kinases (ERK1/2). However, although the p38(MAPK)-specific inhibitor SB203580 attenuated apoptosis, the process was not affected by the ERK-specific inhibitor PD98059. The attenuation of the cadmium-provoked apoptosis by SB203580 was a highly specific effect. In fact, the kinase inhibitor did not prevent the generation of apoptosis by heat shock and camptothecin, nor the generation of necrosis by cadmium treatment of glutathione-depleted cells, nor the cadmium-provoked activation of the stress response. The generation of apoptosis was preceded by intracellular H(2)O(2) accumulation and was accompanied by the disruption of mitochondrial transmembrane potential, both of which were inhibited by SB203580. On the other hand, the antioxidant agent butylated hydroxyanisole-inhibited apoptosis but did not prevent p38(MAPK) phosphorylation. In a similar manner, p38(MAPK) phosphorylation was not affected by the caspase inhibitors Z-VAD and DEVD-CHO, which nevertheless prevented apoptosis. These results indicate that p38(MAPK) activation is an early and specific regulatory event for the cadmium-provoked apoptosis in promonocytic cells.