Identificação de alterações bioquímicas em células epiteliais bronquiais humanas normais expostas a fumarato / Identification of biochemical changes in normal human bronchial epitelial cells exposed to fumarate

A reprogramação metabólica de células do câncer é apontada como uma característica essencial para o desenvolvimento da doença (cancer hallmark). Estudos mostram que mutações na enzima fumarato hidratase levam ao aumento da concentração intra e extracelular de fumarato, o que ocorre paralelamente à indução da transformação maligna. Neste trabalho, a fim de entender se o excesso de fumarato extracelular pode propiciar a transformação de células normais, foram quantificados alguns endpoints relacionados aos efeitos do fumarato e à transformação maligna, além de alterações metabólicas em células imortalizadas de epitélio brônquico humano normal (BEAS-2B) expostas ao fumarato. Uma vez que fumarato nas concentrações de 0,1 a 10 mM ao longo de 144 h não foi citotóxico, foram selecionadas as concentrações de 1 mM, 5 mM e 10 mM para as incubações. Fumarato induziu a formação de colônias em soft-agar após o período de sete dias (168 h) de exposição, o que indica a indução de transformação celular. Fumarato é um oncometabólito que inibe enzimas que dependem de α-cetoglutarato como co-substrato, dentre as quais as enzimas ten eleven translocation (TET) que catalisam a formação de 5-hidroximetilcitosina (5-hmC) a partir de 5-metilcitosina (5-mC), o primeiro passo da sequência de reações que levam à desmetilação do DNA. Os níveis totais de 5-hmC estavam diminuídos no DNA das células expostas. Colônias retiradas do soft-agar (controle, 1, 5 e 10 mM de fumarato) foram cultivadas e, após 90 dias em cultura, as células foram submetidas ao ensaio de invasão e migração em câmara de Boyden (transwell), tendo sido observada maior capacidade de migração/invasão das células anteriormente expostas ao fumarato. Foi observada indução de estresse redox nas células expostas ao fumarato. A partir da quantificação de metabólitos intracelulares por HPLC-ESI-MS/MS e HPLC-ESI-Q-TOF, verificamos que as células BEAS-2B absorveram o fumarato adicionado ao meio de cultura, o qual foi convertido intracelularmente a malato, aspartato, argininosuccinato, citrato, succinato e glutamato. O oncometabólito 2-L-hidroxiglutarato foi detectado em níveis aumentados nas células expostas a fumarato, assim como adenosina, enquanto que NAD+ e NADP+ apareceram diminuídos. As alterações metabólicas na presença de fumarato contribuíram para a manutenção do balanço energético das células, ou mesmo para um saldo positivo de energia. A exposição das células a [13C4]fumarato permitiu a análise do fluxo inicial do fumarato absorvido pelas células. A partir dessa análise verificamos que o fumarato absorvido entra no ciclo de Krebs, gerando malato, que é em grande parte desviado para reações externas ao ciclo, como a geração de aspartato e argininosuccinato. Citrato proveniente das reações de [13C4]fumarato no ciclo de Krebs foi detectado em níveis inferiores aos endógenos. O uso de [13C4]fumarato permitiu a visualização da geração de [13C4]succinato, que tem como possível fonte a atividade reversa da succinato desidrogenase. Verificamos também a geração de [13C3]glutamato. Supõe-se que as alterações metabólicas induzidas pelo fumarato absorvido pelas células BEAS-2B contribuam para a modulação da expressão de genes e da atividade de proteínas que favorecem o processo tumorigênico

The metabolic reprogramming of cancer cells is identified as an essential feature for the development of the disease (a cancer hallmark). Studies show that mutations in the enzyme fumarate hydratase lead to increased intra- and extracellular fumarate concentration, which occurs in parallel with the induction of malignant transformation. In this work, in order to understand if excess extracellular fumarate can lead to the transformation of normal cells, some endpoints related to the effects of fumarate and malignant transformation were quantified, as well as metabolic alterations in the immortalized normal human bronchial epithelial cell line BEAS-2B exposed to fumarate. Since fumarate at concentrations from 0.1 to 10 mM over 144 h was not cytotoxic, the concentrations of 1 mM, 5 mM and 10 mM were selected for incubations. Fumarate induced colony formation in soft agar after the seven day (168 h) exposure period, which indicates the induction of cell transformation. Fumarate is an oncometabolite that inhibits α-ketoglutarate-dependent enzymes, among which are ten eleven translocation (TET) enzymes that catalyze the formation of 5-hydroxymethylcytosine (5-hmC) from 5-methylcytosine (5-mC), the first step in the sequence of reactions leading to DNA demethylation. Total 5-hmC levels were decreased in the DNA of exposed cells. Colonies removed from the soft-agar (control, 1, 5 and 10 mM fumarate) were cultured and after 90 days in culture the cells were subjected to the Boyden chamber (transwell) invasion and migration assay, and a greater capacity for migration/invasion of cells previously exposed to fumarate was observed. Redox stress induction was observed in cells exposed to fumarate. From the quantification of intracellular metabolites by HPLC-ESI-MS/MS and HPLC-ESI-Q-TOF, we found that BEAS-2B cells absorbed the fumarate added to the culture medium, which was intracellularly converted to malate, aspartate, argininosuccinate, citrate, succinate and glutamate. The oncometabolite 2-L-hydroxyglutarate was detected at increased levels in cells exposed to fumarate, as well as adenosine, while NAD+ and NADP+ appeared decreased. Metabolic changes in the presence of fumarate contributed to the maintenance of the energy balance of the cells, or even to a positive energy balance. Exposure of cells to [13C4]fumarate allowed the analysis of the initial flow of the fumarate absorbed by the cells. From this analysis we found that the absorbed fumarate entered the Krebs cycle, generating malate, which was largely diverted to reactions outside the cycle, such as the generation of aspartate and argininosuccinate. Citrate from the reactions of [13C4]fumarate in the Krebs cycle was detected at levels lower than endogenous. The use of [13C4]fumarate allowed the detection of [13C4]succinate, which has as its possible source the reverse activity of succinate dehydrogenase. We also observed the generation of [13C3]glutamate. The metabolic changes induced by the absorbed fumarate are supposed to contribute to the modulation of gene expression and protein activity that favor the tumorigenic process

Effect of folic acid in a modified experimental model of anorectal malformations adriamycin-induced in rats

PURPOSE: To determine the effect of a single dose of adriamycin (ADR) to induce anorectal malformations (ARMs) and determine the effect of folic acid (FA) in this model. METHODS: Ten female Wistar rats were divided randomly in two groups. Group A - ADR; Group B - FA+ADR. Dams from group B received daily, since two weeks before the pregnancy to the end of pregnancy, FA (50mg/kg) by gavage. Dams from both groups received ADR (6mk/kg) by intraperitoneal injection on gestational day (GD) 8. Their fetuses were harvested by cesarean section on GD21 and were examined looking for ARMs. The thickness of anal stratified squamous epithelium (ASSE) and intestinal epithelium (IE) were analyzed. p≤0.05*. RESULTS: 81 fetuses were harvested. The number of fetuses; number of ARMs; mean (∆%) (± SD) were determined to be, respectively: ADR - 41[29;65%(±37%)] versus FA+ADR - 40[04;16%(±36%)] (p=0.05). AMRs were significantly lower in FA+ADR group than in ADR group (p=0.05). The thickness (µm) of ASSE (± SD) and IE (± SD) were measured, respectively: ADR - [25.98(±0.74) and 19.48(±1.68)] versus FA+ADR - [24.74(±0.91) and 24.80(±0.81)] (p<0.005). The thickness of IE was significantly enlarged when FA was given (p<0.005). CONCLUSIONS: Single dose of adriamycin on D8 was able to induce anorectal malformations. Folic acid reduces the number and enlarged the IE of ARMs ADR-induced.

Keratinization and its disorders

Keratins are a diverse group of structural proteins that form the intermediate filament network responsible for maintaining the structural integrity of keratinocytes. In humans, there are around 30 keratin families divided into two groups, namely, acidic and basic keratins, which are arranged in pairs. They are expressed in a highly specific pattern related to the epithelial type and stage of cellular differentiation. A total of 54 functional genes exist which codes for these keratin families. The expression of specific keratin genes is regulated by the differentiation of epithelial cells within the stratifying squamous epithelium. Mutations in most of these genes are now associated with specific tissue fragility disorders which may manifest both in skin and mucosa depending on the expression pattern. The keratins and keratin-associated proteins are useful as differentiation markers because their expression is both region specific and differentiation specific. Antibodies to keratin are considered as important tissue differentiation markers and therefore are an integral aid in diagnostic pathology. The present review discusses the structure of keratin, the various types of keratin and their distribution and the disorders associated with keratinization with special emphasis on the disorders of the oral cavity. A brief note on the clinical significance of keratin is also mentioned

Bilateral mucous cell containing dentigerous cyst of madibular third molars: report of an unusual case

A 38-year-old Caucasian male with bilateral dentigerous cysts of the mandibular third molars is reported as follows. The cyst cavities were lined with a nonkeratinized squamous epithelium. Mucous cells were seen in some areas of the cyst walls