RESUMO
We report the case of a 50-year-old woman who was admitted to the hospital for acute abdominal pain with nephrotic proteinuria, rapidly progressive renal failure, and moderate anemia. Laboratory tests showed mild Bence Jones (λ) proteinuria with negative serum immunofixation and a mild increase in λ free light chains. A bone marrow biopsy and a fat tissue aspirate showed multiple myeloma and amyloidosis. Because of the end-stage renal disease, the patient began regular dialysis treatment and was started on bortezomib 1.3 mg/m2 plus dexamethasone 40 mg on days 1, 4, 8 and 11 of 21-day cycles. Ten days later she complained of a new episode of abdominal pain with jaundice. A CT scan and an MRI scan ruled out all secondary causes of cholangitis including cancer. Acute intrahepatic cholestasis due to amyloid deposition was then hypothesized. After 4 well tolerated cycles of bortezomib and dexamethasone, blood tests showed a complete hematological response with full reversal of cholestasis. After three months, a new episode of abdominal pain occurred and this time the patient was operated on and found to have an intestinal volvulus. Because of the jaundice, a transjugular liver biopsy was performed showing no evidence of amyloid deposits. Two months later the patient died of septic shock. Although no autopsy was performed and the ultimate cause of the cholestasis could not be ascertained, amyloidosis remains the major culprit in this unfortunate case.
Assuntos
Amiloidose/complicações , Amiloidose/diagnóstico , Doença Hepática Induzida por Substâncias e Drogas/diagnóstico , Colestase Intra-Hepática/etiologia , Hepatopatias/diagnóstico , Erros de Diagnóstico , Feminino , Humanos , Pessoa de Meia-Idade , Recidiva , Índice de Gravidade de DoençaRESUMO
We have identified previously a destabilizing adenine- and uracil-rich element (ARE) in the 3'-UTR of bcl-2 mRNA that interacted with ARE-binding proteins to down-regulate bcl-2 gene expression in response to apoptotic stimuli. We have also described three contiguous 2'-O-methyl oligoribonucleotides (ORNs) in both sense and antisense orientation with respect to the bcl-2 ARE that are able to regulate the bcl-2 mRNA half-life and Bcl-2 protein level in two different cell lines. Here we show that treatment of neuronal cell line (SHSY-5Y) with antisense ORNs targeting the bcl-2 ARE (bcl-2 ARE asORNs) prevents bcl-2 down-regulation in response to apoptotic stimuli with glucose/growth factor starvation (Locke medium) or oxygen deprivation and enhances the apoptotic threshold as evaluated by time-lapse videomicroscopy, fluorescence-activated cell sorting analysis, and caspase-3 activation. Additional effects of bcl-2 ARE asORNs included inhibition of cell cycle entry and a marked increase of cellular neurite number and length, a hallmark of neuronal differentiation resulting from bcl-2 up-regulation. The ability of bcl-2 ARE asORNs to enhance the apoptotic threshold and to induce neuronal differentiation implies their potential application as a novel informational tool to protect cells from ischemic damage and to prevent neuronal degeneration.
Assuntos
Adenina/fisiologia , Apoptose/fisiologia , Diferenciação Celular/genética , Neurônios/citologia , Oligorribonucleotídeos/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , RNA Mensageiro/metabolismo , Uracila/metabolismo , Ciclo Celular/fisiologia , Linhagem Celular Tumoral , Marcação de Genes/métodos , Humanos , Neurônios/fisiologia , Oligorribonucleotídeos/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Mensageiro/biossíntese , RNA Mensageiro/genéticaRESUMO
Pulmonary arterial hypertension (PAH) is an important cause of death in systemic sclerosis (SSc), despite the improvement of therapies. An early diagnosis and the use of drugs interfering with the main pathogenic pathways of PAH is pivotal for the improvement of prognosis in primary PAH and PAH secondary to autoimmune rheumatic diseases, mainly SSc. Lately, new specific therapies have been developed targeting prostacyclin, endothelin, and nitric oxide pathways, the major pathogenic pathways leading to endothelial dysfunction in PAH. Epoprostenol improved life expectancy of patients with primary and secondary PAH, but its continuous intravenous administration requires experienced centers. More stable analogues of prostacyclin, administrated by intravenous (iloprost, treprostinil), subcutaneous, inhalatory (treprostinil, iloprost), and oral route (Beraprost) have shown efficacy in PAH. Bosentan, the first oral endothelin receptor antagonist (with affinity for endothelin A and B receptors) improves exercise function and survival in PAH, both primary and secondary to autoimmune rheumatic diseases. This is confirmed also for Sitaxsentan and Ambrisentan, selective A receptor antagonists. Because of its short half-life and systemic side effects, short-term NO inhalation is used only in short-term management of PAH in critically ill adults. Inhibitors of NO degradation, such as sildenafil, a phosphodiesterase (PDE) type 5 inhibitor, improved functional and hemodynamic parameters without significant side effects. Vardenafil and taladafil, longer-acting PDE inhibitors, also have vascular pulmonary selectivity. All these drugs may be used in combination, to maximize their clinical benefit not only in patients unresponsive to single drugs, but also potentially as initial therapy of PAH.
Assuntos
Escleroderma Sistêmico/terapia , Algoritmos , Humanos , Hipertensão Pulmonar/fisiopatologia , Hipertensão Pulmonar/terapia , Artéria Pulmonar/fisiopatologiaRESUMO
Increased evidence suggests an accelerated macrovascular disease in systemic sclerosis (SSc). Brachial artery flow-mediated vasodilation (FMD) and carotid intima-media thickness (IMT) are two indicators of subclinic cardiovascular disease and are frequently used as surrogate measures of subclinic atherosclerosis. The aim of this study was to evaluate macrovascular involvement in SSc. We studied 35 SSc patients (6 males and 29 females; 11 with diffuse and 24 with limited disease) and 20 healthy controls. Brachial artery FMD was assessed by method described by Celermajer in all patients and 13 control subjects. IMT was measured using high-resolution B-mode ultrasonography in patients and controls. Traditional risk factors for atherosclerosis (hypertension, dyslipidemia, and smoke) were also assessed. FMD was significantly impaired (3.41% +/- 4.56% versus 7.66% +/- 4.24%; P < 0.037) and IMT was significantly elevated compared with healthy controls (0.93 +/- 0.29 mm versus 0.77 +/- 0.13 mm; P < 0.005). FMD was not significantly different in SSc with increased IMT compared with those with normal IMT). No correlation was found between risk factors for atherosclerosis and the impairment of FMD or IMT in SSc patients. The impairment of endothelial function and structural changes of large vessels are evident in SSc, but do not seem associated with traditional risk factors for atherosclerosis. Prospective studies including also clinical outcomes are needed to assess the features and significance of macrovacular involvement in SSc.
Assuntos
Artérias Carótidas/patologia , Escleroderma Sistêmico/complicações , Doenças Vasculares/complicações , Vasodilatação/fisiologia , Artéria Braquial/patologia , Artéria Braquial/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Túnica Íntima/patologia , Túnica Média/patologia , Ultrassonografia , Doenças Vasculares/patologia , Doenças Vasculares/fisiopatologiaRESUMO
In systemic sclerosis (SSc), the involvement of the interstitium or vascular system of the lung may lead to pulmonary arterial hypertension (PAH). PAH is often asymptomatic or oligosymptomatic in early SSc and, when it becomes symptomatic, pulmonary vascular system is already damaged. Exercise echocardiography (ex-echo), measuring pulmonary artery pressure (PAP) during exercise and allowing to differentiate physiologic from altered PAP responses, may identify subclinical PAH. Our aims were (a) to evaluate by ex-echo the change of PAP in patients with SSc without lung involvement; and (b) to correlate PAP during exercise (ex-PAP) values to clinical and biohumoral parameters of PAH. Twenty-seven patients with limited SSc (ISSc) without interstitial lung involvement were studied. Patients underwent rest and exercise two-dimensional and Doppler echocardiography by supine cycloergometer. Systolic PAP was calculated using the maximum systolic velocity of the tricuspid regurgitant jet at rest and during exercise values of systolic PAP exceeding 40 mmHg at ex-echo were considered as abnormal, and biohumoral markers potentially related to PAH were assessed. Eighteen of 27 SSc patients presented an ex-PAP > 40 mmHg, while in 9 of 27 patients ex-PAP values remained < 40 mmHg (48.8 +/- 4.5 mmHg versus 36.2 +/- 3.1 mmHg; P < 0.001). Other echocardiographic and ergometric parameters, clinical tests, and biohumoral markers were not different in the two groups. Ex-PAP significantly correlated with D-dimer (P = 0.0125; r2 = 0.2029). Ex-echo identifies a cluster of SSc patients with subclinical PAH that may develop PAH. This group should be followed up and may be considered for specific therapies to prevent disease evolution.
Assuntos
Ecocardiografia Doppler , Teste de Esforço , Hipertensão Pulmonar/diagnóstico , Hipertensão Pulmonar/etiologia , Escleroderma Sistêmico/complicações , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Artéria Pulmonar/patologiaRESUMO
To provide some insight into molecular mechanisms of 5 fluorouracil (5-FU) clinical resistance in colorectal cancer, we hypothesized that different in vitro exposure schedules of human colorectal cancer cell lines mimicking clinical infusion or bolus regimens could lead to differential gene expression. Resistant HCT-8 colon cancer cell lines (HCT-8/FUI/15R and HCT-8/FUB/2R) were selected from parental sensitive HCT-8 cells by long-term and short-term exposure schedules, respectively. Expression levels of the 437 genes evaluated by the Atlas Select cDNA Expression Human Tumor Array were not substantially different between HCT-8/FUB/2R and HCT-8 cell lines except for three genes downregulated in the resistant subline. Several genes were differentially expressed in HCT-8/FUI/15R cells compared to the parental cell line: 43 genes, including three chemoresistance-related genes, were upregulated, and three genes were downregulated. HCT-8/FUB/2R cells were substantially more resistant to 5-FU in comparison to HCT-8/FUI/15R cells after both 4- and 72-h exposures. No substantial differences were observed among resistant and parental cells in sensitivity to SN-38, the active metabolite of irinotecan, and oxaliplatin. Analysis of the mRNA levels of thymidylate synthase, thymidine phosphorylase, and bcl-2 genes evaluated by reverse transcription and real time PCR (RT-PCR) assay showed comparable results in resistant sublines and sensitive parental cells, whereas expression of the dihydropyrimidine dehydrogenase gene was markedly increased in both resistant cell lines compared to parental cells.
Assuntos
Antineoplásicos/farmacologia , Neoplasias do Colo/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos , Fluoruracila/farmacologia , Regulação Neoplásica da Expressão Gênica , Antineoplásicos/administração & dosagem , Camptotecina/análogos & derivados , Camptotecina/farmacologia , Carcinoma/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Di-Hidrouracila Desidrogenase (NADP)/biossíntese , Ensaios de Seleção de Medicamentos Antitumorais , Fluoruracila/administração & dosagem , Humanos , Irinotecano , Análise de Sequência com Séries de Oligonucleotídeos , Poli A/química , RNA Mensageiro/metabolismoRESUMO
Synthetic ribozymes are catalytic RNA molecules designed to inhibit gene expression by cleaving specific mRNA sequences. We investigated the potential of synthetic ribozymes to inhibit bcl-2 expression in apoptosis defective bcl-2 overexpressing tumors. A chemically stabilized hammerhead ribozyme has been targeted to the A+U-rich regulative element of bcl-2 mRNA that is involved in bcl-2 gene switch-off during apoptosis. The design of the ribozyme was based on the results of probing accessibility of the RNA target in cellular extracts with antisense DNA. The ribozyme was lipotransfected to a bcl-2 overexpressing human lymphoma cell line (Raji). The cellular uptake of this ribozyme resulted in a marked reduction of both bcl-2 mRNA and BCL-2 protein levels and dramatically increased cellular death by apoptosis. Our results suggest a potential therapeutic application of such ribozyme for the treatment of bcl-2 overexpressing tumors.
Assuntos
Linfoma de Burkitt/terapia , Proteínas Proto-Oncogênicas c-bcl-2/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-2/genética , RNA Catalítico/metabolismo , Apoptose , Sequência de Bases , Linfoma de Burkitt/genética , Linfoma de Burkitt/metabolismo , Domínio Catalítico , Linhagem Celular Tumoral , Regulação para Baixo , Genes Sintéticos , Humanos , Oligodesoxirribonucleotídeos Antissenso/química , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Catalítico/química , RNA Catalítico/genética , RNA Mensageiro/química , RNA Mensageiro/metabolismo , Sequências Reguladoras de Ácido RibonucleicoRESUMO
A circadian rhythm in serum leptin, measured every 4 h for 24 h, characterizes normal-weight women (N = 14), and women with gynoid (N = 17) or android (N = 26) obesity, peaking around midnight (P < 0.05), but differing by about 3 h between android and gynoid women (P < 0.01). Obesity is associated with a higher MESOR (rhythm-adjusted mean; P < 0.001) and a smaller relative circadian amplitude (P < 0.05). Gynoid obesity is associated with a larger circadian amplitude of cortisol (P < 0.05), whereas android obesity is associated with a larger circadian amplitude and a higher MESOR of insulin (P < 0.05). Understanding putative mechanisms underlying different body fat distribution may lead to improved chronotherapeutic measures.
Assuntos
Ritmo Circadiano , Leptina/sangue , Obesidade/fisiopatologia , Adulto , Idoso , Feminino , Humanos , Hidrocortisona/sangue , Insulina/sangue , Pessoa de Meia-Idade , Obesidade/classificação , Fatores de TempoRESUMO
Amyloidosis comprises a group of diseases characterized by the extracellular deposition of insoluble fibrillar proteins. This mechanism generates different clinical syndromes depending on the site and extent of organ involvement. Amyloidosis is classified into categories of systemic and localized disease. Systemic amyloidosis is further subdivided into a hereditary familial form (for example, ATTR amyloidosis), a reactive form (AA amyloidosis), dialysis-related (Abeta(2)M) amyloidosis and immunoglobulin light chain (AL) amyloidosis. Treatment can be symptomatic, directed at the affected organ, or can be directed at reducing the production of the abnormal proteins with different strategies. Despite advances in treatment, the prognosis is still poor and depends on the underlying disease as well as the type and degree of dysfunction in involved organs. Early diagnosis is essential because patients with advanced disease are generally unable to undergo intensive therapy. Patients with systemic amyloidosis often present to a rheumatologist not only because the disease can include musculoskeletal and articular symptoms but also because it can be associated with chronic rheumatic diseases. This Review discusses the clinical features of amyloidosis and its rheumatic manifestations. The various types of amyloidosis, as well their prognosis and treatment, are also presented.
Assuntos
Amiloidose/etiologia , Doenças Reumáticas/etiologia , Amiloidose/diagnóstico , Amiloidose/terapia , Humanos , Doenças Reumáticas/diagnóstico , Doenças Reumáticas/terapiaRESUMO
OBJECTIVE: Systemic sclerosis (SSc) impairs endothelium-dependent vasodilatation. Among angiotensin I (Ang I)-derived compounds, vasoconstrictor angiotensin II (Ang II) and vasodilator angiotensin-(1-7) (Ang-(1-7)), cleaved from ACE and neutral endopeptidase (NEP) 24.11, respectively, play an important role in vascular tone regulation. Ang-(1-7) may act independently or by activating other vasodilating molecules, such as nitric oxide (NO) or prostaglandin I2 (PGI2). Our aim was to assess, in patients with SSc, circulating levels of Ang I, Ang II and Ang-(1-7), with their metabolising enzymes ACE and NEP, and levels of NO and PGI2, and to correlate them to the main characteristics of SSc. METHODS: Levels of Ang I, Ang II, Ang-(1-7), NEP, ACE, NO and PGI2 were measured in 32 patients with SSc, who were also assessed for humoral and clinical characteristics, and 55 controls. RESULTS: Plasma Ang I, Ang II and Ang-(1-7) levels were lower in patients with SSc than in controls (p<0.001in all cases). When Ang II and Ang-(1-7) levels were expressed as a function of the available Ang I, lower Ang-(1-7) levels in patients with SSc than in controls were confirmed (p<0.001), while no difference was found for Ang II levels. In patients with SSc, the Ang II/Ang-(1-7) ratio indicated a prevalence of Ang II over Ang-(1-7), while in controls Ang-(1-7) was prevalent (p<0.001). Levels of ACE, NEP, NO and PGI2 were lower in patients with SSc than in controls (p<0.05 in all cases). CONCLUSION: In patients with SSc, prevalence of the vasoconstricting Ang II over the vasodilator Ang-(1-7) suggests a dysfunction of the angiotensin-derived cascade that may contribute to dysregulation of vascular tone.
Assuntos
Angiotensina II/sangue , Angiotensina I/sangue , Fragmentos de Peptídeos/sangue , Escleroderma Sistêmico/sangue , Anti-Hipertensivos/sangue , Epoprostenol/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neprilisina/sangue , Óxido Nítrico/sangue , Peptidil Dipeptidase A/sangue , Vasoconstritores/sangueRESUMO
Chronic sarcoidosis (CS) is often unresponsive to usual treatments. Melatonin, an immunoregulatory drug, was employed in CS patients in whom usual treatments were ineffective or induced severe side effects. Melatonin was given for 2 yr (20 mg/day in the first year, 10 mg/day in the second year) to 18 CS patients. Pulmonary function tests, chest X rays, pulmonary computed tomography, Ga(67) scintigraphy and angiotensin-converting enzyme (ACE) were assayed at baseline and in the follow-up. Normalization of ACE, improvement of pulmonary parameters and resolution of skin involvement were found in the patients given melatonin. After 24 months of melatonin therapy, hylar adenopathy completely resolved in eight patients and parenchymal lesions were markedly improved in all patients; in the five patients with reduced diffusion capacity of the lung for carbon monoxide, the values normalized after 6 months of therapy and remained stable until month 24. After 24 months, Ga(67) pulmonary and extra-pulmonary uptake was totally normalized in seven patients and, at month 12 months, ACE was normalized in six patients in which the values were high at the baseline. Skin lesions, present in three patients, completely disappeared at month 24 months. No side effects were experienced and no disease relapse was observed during melatonin treatment. Melatonin may be an effective and safe therapy for CS when other treatments fail or cause side effects.
Assuntos
Imunossupressores/uso terapêutico , Melatonina/uso terapêutico , Sarcoidose Pulmonar/tratamento farmacológico , Sarcoidose/tratamento farmacológico , Dermatopatias/tratamento farmacológico , Corticosteroides/uso terapêutico , Adulto , Ecocardiografia Doppler , Eletrocardiografia , Feminino , Humanos , Imunossupressores/administração & dosagem , Masculino , Melatonina/administração & dosagem , Melatonina/efeitos adversos , Pessoa de Meia-Idade , Peptidil Dipeptidase A/sangue , Projetos Piloto , Testes de Função Respiratória , Sarcoidose/patologia , Sarcoidose Pulmonar/patologia , Pele/efeitos dos fármacos , Pele/patologia , Dermatopatias/patologiaRESUMO
Oligodeoxyribonucleotides (ODNs) are currently employed to switch-off genes selectively routinely in the laboratory practice. The drawback of ODN application is that they have been often reported to elicit non-antisense effects by different mechanisms. Recently, it has been shown that double-stranded DNA oligonucleotides (30-mers) with protruding ends activate p53 in a cell-free system. In a previous work, we described that simple addition to the culture medium of heterogeneous DNA combined with cationic lipids culminated in inhibition of mitosis and induction of apoptosis. Here, we report that the same effects are achieved by lipotransfecting cultured cells with phosphorodiester ODNs (30-mers). Such effects of ODN were mediated by a non-antisense mechanism that required the wild-type form of the p53 oncosuppressor protein and was dependent on ODN concentration. Mitosis inhibition and apoptosis induction appeared to be determined by the 3' and 5' free ends of ODNs, which activated p53 independently from their sequence. Most probably, this mechanism is analogous to that evoked by genotoxic agent-induced DNA damage or by lipotransfecting cells with heterogeneous DNA.
Assuntos
Apoptose/efeitos dos fármacos , Mitose/efeitos dos fármacos , Oligodesoxirribonucleotídeos/farmacologia , Compostos Organofosforados/química , Proteína Supressora de Tumor p53/fisiologia , Animais , Apoptose/fisiologia , Sequência de Bases , Linhagem Celular , Sistema Livre de Células , Ésteres , Ácidos Graxos Monoinsaturados , Mitose/fisiologia , Oligodesoxirribonucleotídeos/química , Compostos de Amônio Quaternário , Ratos , TransfecçãoRESUMO
We previously identified a conserved A + U-rich element (ARE) in the 3'-untranslated region of bcl-2 mRNA. We have also recently demonstrated that the bcl-2 ARE interacts with a number of ARE-binding proteins (AUBPs) whose pattern changes during apoptosis in association with bcl-2 mRNA half-life reduction. Here we show that the AUBP AUF1 binds in vitro to bcl-2 mRNA. The results obtained in a yeast RNA three-hybrid system have demonstrated that the 1-257-amino acid portion of p37 AUF1 (conserved in all isoforms), containing the two RNA recognition motifs, also binds to the bcl-2 ARE in vivo. UVC irradiation-induced apoptosis results in an increase of AUF1. Inhibition of apoptosis by a general caspase inhibitor reduces this increase by 2-3-fold. These results indicate involvement of AUF1 in the ARE/AUBP-mediated modulation of bcl-2 mRNA decay during apoptosis.
Assuntos
Genes bcl-2 , Ribonucleoproteínas Nucleares Heterogêneas Grupo D , RNA Mensageiro/genética , Proteínas de Ligação a RNA/metabolismo , Transcrição Gênica , Apoptose/fisiologia , Sequência de Bases , Sítios de Ligação , Sequência Conservada , Regulação da Expressão Gênica , Ribonucleoproteína Nuclear Heterogênea D0 , Humanos , Células Jurkat , Cinética , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo , RNA Mensageiro/química , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , TransfecçãoRESUMO
The permeability transition pore (PTP) is a mitochondrial channel whose opening causes the mitochondrial membrane potential (deltapsi) collapse that leads to apoptosis. Some ubiquinone analogues have been demonstrated previously to modulate the PTP open-closed transition in isolated mitochondria and thought to act through a common PTP-binding site rather than through oxidation-reduction reactions. We have demonstrated recently both in vitro and in vivo that the ubiquitous free radical scavenger and respiratory chain coenzyme Q10 (CoQ10) prevents keratocyte apoptosis induced by excimer laser irradiation more efficiently than other antioxidants. On this basis, we hypothesized that the antiapoptotic property of CoQ10 could be independent of its free radical scavenging ability and related to direct inhibition of PTP opening. In this study, we have verified this hypothesis by evaluating the antiapoptotic effects of CoQ10 in response to apoptotic stimuli, serum starvation, antimycin A, and ceramide, which do not generate free radicals, in comparison to control, free radical-generating UVC irradiation. As hypothesized, CoQ10 dramatically reduced apoptotic cell death, attenuated ATP decrease, and hindered DNA fragmentation elicited by all apoptotic stimuli. This was accompanied by inhibition of mitochondrial depolarization, cytochrome c release, and caspase 9 activation. Because these events are consequent to mitochondrial PTP opening, we suggest that the antiapoptotic activity of CoQ10 could be related to its ability to prevent this phenomenon.
Assuntos
Apoptose , Sequestradores de Radicais Livres , Mitocôndrias/metabolismo , Oxirredução , Ubiquinona/análogos & derivados , Ubiquinona/fisiologia , Trifosfato de Adenosina/metabolismo , Animais , Antimicina A/farmacologia , Western Blotting , Caspase 9 , Caspases/metabolismo , Sobrevivência Celular , Ceramidas/metabolismo , Ceramidas/farmacologia , Coenzimas , Meios de Cultura Livres de Soro/farmacologia , DNA/metabolismo , Dano ao DNA , Fragmentação do DNA , Sequestradores de Radicais Livres/metabolismo , Queratinócitos/patologia , Potenciais da Membrana , Microscopia de Fluorescência , Modelos Químicos , Coelhos , Espécies Reativas de Oxigênio , Superóxido Dismutase/metabolismo , Fatores de Tempo , Ubiquinona/metabolismo , Raios UltravioletaRESUMO
Hypoxic and chemical hypoxia (antimycin A) commits cultured rat fibroblasts (Rat-1) towards apoptosis, necrosis or an intermediate form of cell death (aponecrosis) depending on the degree of hypoxia. Aponecrosis also occurs in vivo. Here, we demonstrate that c-myc and bcl-2, two proto-oncogenes known to lower or to enhance, respectively, the apoptotic threshold, also affect the type of cell death: apoptosis shifts to aponecrosis and aponecrosis to necrosis, depending on c-myc or bcl-2 expression and the antimycin A concentration (100-400 microM). In cells with basal gene expression, apoptosis shifts to aponecrosis/necrosis at 300 microM antimycin A (middle hypoxia). Overexpression of c-myc markedly increases cumulative cell death in response to antimycin A and lowers the antimycin A concentration required to shift apoptosis to aponecrosis/necrosis from 300 microM to 100 microM (low hypoxia). Overexpression of bcl-2 elicits the opposite effect, decreasing cumulative cell death in response to antimycin A and raising the drug concentration required to shift apoptosis to aponecrosis/necrosis to 400 microM (high hypoxia). The passage from one to the other form of cell death involves various aponecrotic features with observed intermediate aspects between apoptosis and necrosis, a progressive increase in necrotic features being correlated with an increase in antimycin A concentration. The mechanism underlying the various effects of c-myc and bcl-2 on cell-death type has been related to the ability of these genes to counteract, to various extents, the ATP decrease occurring in response to different degrees of chemical hypoxia.