Um estudo retrospectivo dos achados histopatológicos em 894 casos de megacólon: qual é a relação entre megacólon e o câncer de cólon?

Patients with megaesophagus (ME) have increased prevalence of cancer of the esophagus. In contrast, a higher incidence of colorectal cancer is not observed in patients with megacolon (MC). MC is very common in some regions of Brazil, where it is mainly associated with Chagas disease. We reviewed the pathology records of surgical specimens of all patients submitted for surgical resection of MC in the Hospital das Clínicas of the Faculty of Medicine of Ribeirão Preto (HC-FMRP), from the University of São Paulo. We found that 894 patients were operated from 1952 until 2001 for MC resection. Mucosal ulcers, hyperplasia and chronic inflammation were frequently found, while polyps were uncommon. No patients with MC presented any type of colonic neoplasm. This observation reinforces the hypothesis that MC has a negative association with cancer of the colon. This seems to contradict the traditional concept of carcinogenesis in the colon, since patients with MC presents important chronic constipation that is thought to cause an increase in risk for colon cancer. MC is also associated with other risk factors for cancer of colon, such as hyperplasia, mucosal ulcers and chronic inflammation. In ME these factors lead to a remarkable increase in cancer risk. The study of mucosal cell proliferation in MC may provide new insights and useful information about the role of constipation in colonic carcinogenesis.Pacientes com megaesôfago (ME) possuem incidência aumentada de câncer de esôfago. Em contraste, há poucos relatos na literatura de associação entre megacólon (MC) e câncer de cólon. O MC é muito comum em algumas regiões do Brasil, e na maioria das vezes, está associado à Doença de Chagas. Nós reavaliamos os arquivos de patologia de peças cirúrgicas de todos os pacientes submetidos à ressecção de MC no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HC-FMRP), da Universidade de São Paulo. Encontramos o número de 894 pacientes que foram operados de 1952 até 2001 para a ressecção do MC. Úlceras da mucosa, hiperplasia e inflamação crônica foram frequentemente encontrados, enquanto pólipos foram incomuns. Nenhum paciente com MC apresentou qualquer tipo de neoplasia do cólon. Essa observação reforça a hipótese de que o MC tem uma associação negativa com câncer de cólon. Isso parece contradizer o conceito tradicional de carcinogênese do cólon, uma vez que pacientes com MC apresentam constipação crônica importante, a qual é tida como uma causa que aumenta o risco de câncer de cólon. MC também está associado a outros fatores de risco para o câncer de cólon, como hiperplasia, úlceras da mucosa e inflamação crônica. No megaesôfago (ME), tais fatores aumentam o risco de câncer esofágico. O estudo da proliferação celular da mucosa no MC pode fornecer informações úteis sobre o papel da constipação na carcinogênese colônica

JNK Signaling Confers Tolerance to Oxidative Stress and Extends Lifespan in Drosophila

AbstractChanges in the genetic makeup of an organism can extend lifespan significantly if they promote tolerance to environmental insults and thus prevent the general deterioration of cellular function that is associated with aging. Here, we introduce the Jun N-terminal kinase (JNK) signaling pathway as a genetic determinant of aging in Drosophila melanogaster. Based on expression profiling experiments, we demonstrate that JNK functions at the center of a signal transduction network that coordinates the induction of protective genes in response to oxidative challenge. JNK signaling activity thus alleviates the toxic effects of reactive oxygen species (ROS). In addition, we show that flies with mutations that augment JNK signaling accumulate less oxidative damage and live dramatically longer than wild-type flies. Our work thus identifies the evolutionarily conserved JNK signaling pathway as a major genetic factor in the control of longevity

Изучение ассоциации однонуклеотидных полиморфных замен в генах ферментов антиоксидантной системы с риском развития рака предстательной железы в Сибирском регионе России

The influence of polymorphic substitutions in antioxidant system genes (SNPsrs1050450 in the GPX1 gene, rs1695 and rs1138272 in the GSTP1gene and rs4880 in the MnSOD gene) on the risk of prostate cancer development in men living in the Siberian region of Russia was studied. The relationship between the studied genotypes and clinical parameters (disease stage and PSA level) was analyzed. For this purpose, the incidence of the studied allelic variants was compared between 399 with prostate cancer patients and 344 men with no history of prostate cancer. Genotyping was performed using real-time PCR. No statistically significant association with the risk of developing prostate cancer was found in the studied SNPs (p>0,05). For the GSTP1SNPrs1695, the correlation with disease stage was obtained: The GG genotype occurred more frequently in patients with stage III-IV prostate cancer (OR [C.I.]=2,66 [1,15–6,18], p=0,02). Both studied SNPs of the GSTP1 gene were associated with the level of prostate-specific antigen (PSA) in blood: the GG rs1695 genotype and TT rs1138272 genotype were associated with higher PSA levels (p=1,5×10-3)Изучено влияние ряда полиморфных замен в генах антиоксидантной системы (SNPsrs1050450 гена GPX1, rs1695 и rs1138272 гена GSTP1 и rs4880 гена MnSOD) на риск развития рака предстательной железы у мужчин, проживающих в Сибирском регионе России. Проведен анализ взаимосвязи исследуемых генотипов с клиническими параметрами (стадией заболевания и уровнем ПСА). С этой целью сравнили частоту встречаемости исследуемых аллельных вариантов у 392 пациентов с раком простаты и у 344 мужчин без онкологических заболеваний в анамнезе. Генотипирование выполнялось при помощи ПЦР в режиме реального времени. Ни для одного из исследуемых SNPs не было получено статистически значимой ассоциации с риском развития рака пред- стательной железы (p>0,05). Для SNPrs1695 гена GSTP1 получена корреляция со стадией заболевания: генотип GG статистически значимо чаще встречается у больных раком простаты III–IV стадий (OR[C.I.]=2,66 [1,15–6,18], p=0,02). Оба исследуемых SNPs гена GSTP1 ассоциированы с уровнем простат-специфического антигена (ПСА) в крови: генотип GG rs1695 и генотип TT rs1138272 ассоциированы с более высокими показателями ПСА (p=1,5×10-3)

N-nitrosopiperidina y N-nitrosodibutilamina (II): relevancia en la carcinógenesis química y genotoxicidad

La N-nitrosopiperidina (NPIP) y la N-nitrosodibutilamina (NDBA) han sido clasificadas como posibles carcinógenos en humanos. La NPIP causa tumores en esófago, y también en cavidad nasal, hígado y estómago, mientras que la NDBA es carcinógeno de vejiga urinaria. Ambas N-nitrosaminas son consideradas carcinógenos genotóxicos indirectos puesto que necesitan una bioactivación para generar metabolitos que reaccionen con el DNA. La principal lesión al DNA inducida por las N-nitrosaminas es el daño alquilativo. En el caso de la NDBA, la posición de alquilación es en el O6 de la guanina, formando la O6 butilguanina y la O6-4-hidroxibutilguanina. Sin embargo, esta N-nitrosamina alquila preferentemente proteínas. Por otra parte, la bioactivación de la NPIP genera metabolitos que reaccionan con el N2 de la guanina in vitro, aunque se desconocen sus efectos in vivo. Además, durante la activación metabólica pueden también producirse especies reactivas del oxígeno (EROs) y del nitrógeno (ERNs). Las lesiones oxidativas y nitrativas más comunes son la 8- hidroxideoxiguanosina (8 OHdG) y la 8-nitroguanina, respectivamente, que producen mutaciones y conducen a la carcinogénesis.N-nitrosopiperidine (NPIP) and N-nitrosodibutylamine (NDBA) have been classified as possibly carcinogenic to humans. NPIP causes tumours in oesophagus, and also in nasal cavity, liver and stomach, whereas NDBA is a bladder carcinogen. Both N-nitrosamines are considered indirect genotoxic carcinogens since they need a bioactivation to generate metabolites that react with DNA. The main DNA lesion induced by N nitrosamines is the alkylative damage. In the case of NDBA, the alkylation position is in O6 of guanine, forming O6 butylguanine and O6-4-hydroxybutylguanine. However, this N-nitrosamine alkylates proteins preferably. On the other hand, NPIP bioactivation generates metabolites that react with N2 of guanine in vitro, although its in vivo effects are unknown. Moreover, during metabolic activation reactive oxygen species (ROS) and nitrogen species (RNS) can be also produced. The most common oxidative and nitrative lesions are 8-hydroxydeoxyguanosine (8-OhdG) and 8-nitroguanine, respectively, that produce mutations and lead to carcinogenesis

Critical amino acids in human DNA polymerases η and κ involved in erroneous incorporation of oxidized nucleotides

Oxidized DNA precursors can cause mutagenesis and carcinogenesis when they are incorporated into the genome. Some human Y-family DNA polymerases (Pols) can effectively incorporate 8-oxo-dGTP, an oxidized form of dGTP, into a position opposite a template dA. This inappropriate G:A pairing may lead to transversions of A to C. To gain insight into the mechanisms underlying erroneous nucleotide incorporation, we changed amino acids in human Polη and Polκ proteins that might modulate their specificity for incorporating 8-oxo-dGTP into DNA. We found that Arg61 in Polη was crucial for erroneous nucleotide incorporation. When Arg61 was substituted with lysine (R61K), the ratio of pairing of dA to 8-oxo-dGTP compared to pairing of dC was reduced from 660:1 (wild-type Polη) to 7 : 1 (R61K). Similarly, Tyr112 in Polκ was crucial for erroneous nucleotide incorporation. When Tyr112 was substituted with alanine (Y112A), the ratio of pairing was reduced from 11: 1 (wild-type Polκ) to almost 1: 1 (Y112A). Interestingly, substitution at the corresponding position in Polη, i.e. Phe18 to alanine, did not alter the specificity. These results suggested that amino acids at distinct positions in the active sites of Polη and Polκ might enhance 8-oxo-dGTP to favor the syn conformation, and thus direct its misincorporation into DNA

Biological Effects of Food Coloring in In Vivo and In Vitro Model Systems

(1) Background: The suitability of certain food colorings is nowadays in discussion because of the effects of these compounds on human health. For this reason, in the present work, the biological effects of six worldwide used food colorings (Riboflavin, Tartrazine, Carminic Acid, Erythrosine, Indigotine, and Brilliant Blue FCF) were analyzed using two model systems. (2) Methods: In vivo toxicity, antitoxicity, and longevity assays using the model organism Drosophila melanogaster and in vitro cytotoxicity, DNA fragmentation, and methylation status assays using HL-60 tumor human cell line were carried out. (3) Results: Our in vivo results showed safe effects in Drosophila for all the food coloring treatments, non-significant protective potential against an oxidative toxin, and different effects on the lifespan of flies. The in vitro results in HL-60 cells, showed that the tested food colorings increased tumor cell growth but did not induce any DNA damage or modifications in the DNA methylation status at their acceptable daily intake (ADI) concentrations. (4) Conclusions: From the in vivo and in vitro studies, these results would support the idea that a high chronic intake of food colorings throughout the entire life is not advisable

Biopatología de los radicales libres

Biopatología de los radicales libres

Chemopreventive effects of curcumin and green tea on B[a]P-induced carcinogenesis in the hamster cheek pouch

The present study was carried out to examine the chemopreventive effects of curcumin and green tea polyphenols on the hamster cheek pouch carcinogenesis model. This model of oral carcinogenesis has been widely used in chemoprevention studies, however, these studies have been limited to the use of DMBA as the carcinogenic agent. We have developed a protocol of carcinogenesis in the hamster cheek pouch using B[a]P, a broadly distributed environmental carcinogen, formed as a by-product of the combustion of organic materials including cigarette smoke. B[a]P- induced tumors in the hamster cheek pouch are primarily endophytic squamous cell carcinomas that closely resemble squamous cell carcinomas of the human oral mucosa. The cheek pouch of male Syrian hamsters were treated topically for eight weeks with 0.6% curcumin, 6.0% curcumin, 2.5% green tea polyphenols, or 5.0% green tea polyphenols, 3 times per week 30 minutes prior to the application of 2.0% B[a]P. The animals were sacrificed 24 hours and 72 hours after the last treatments. Short-term mechanistic markers of malignant progression were used to determine effects of each compound. Cellular proliferation, assessed by bromodeoxyuridine (Brdu) incorporation, p53 protein accumulation, and apoptotic activity were evaluated. The results of the present study demonstrated that 0.6% curcumin and 2.5% green tea polyphenols had strong inhibitory effects on cellular proliferation and p53 protein accumulation. And 6.0% curcumin and 5.0% green tea polyphenols appeared to induce apoptosis. Our data suggest that curcumin and green tea polyphenols may have a plausible chemopreventive effect on oral carcinogenesis in the hamster cheek pouch model

Cell cycle regulation of redoxyendonuclease activity in human neuroblastoma cells.

Redoxyendonuclease activity was detected in extracts of human neuroblastoma cells using a base-release assay specific for thymine glycol in DNA. The level of redoxyendonuclease activity was more than 2-fold higher in dividing cells compared to quiescent cells, suggesting that quiescent cells may have a reduced capacity to repair oxidative DNA base damages. Cells were synchronized by serum deprivation and then stimulated to enter the cell cycle by the addition of serum to determine enzyme activity at different stages of the cell cycle. The redoxyendonuclease activity was regulated in a biphasic manner with a peak in early G1 and a peak in S phase. This suggests that at specific times during the cell cycle actively growing cells may be more resistant to oxidative DNA damage due to increased repair capacity. The repair capacity of neuroblastoma cells was quantified as the decrease in enzyme-sensitive sites determined by alkaline sucrose density gradient centrifugation following treatment with the oxidant osmium tetroxide. Actively dividing cells repaired the oxidative damage in approximately 24 hours, while the quiescent cells failed to excise the damaged sites and subsequently died. These results indicate that non-dividing cells do not effectively repair oxidative DNA damage, as compared to the dividing cells. Similarly, quiescent cells, treated with osmium tetroxide and fed a serum-enriched media, failed to re-enter the cell cycle and did not repair the oxidative damage. The data indicate that non-dividing cells, such as neurons, do not have the capacity to repair excess oxidative damage and may suffer the biological consequences of DNA damage accumulation, including cellular death, mutagenesis or carcinogenesis. When synchronized cells were damaged with osmium tetroxide, there were differential DNA repair rates, depending on the stage of the cell cycle. These DNA repair rates coordinated with the redoxyendonuclease activity profile. The results of the studies described contribute to a further understanding of the DNA repair pathways which are interlinked with complex processes of cell cycle regulation

Produits d'oxydation de l'ADN : influence de la vitamine C et suroxydation de la cytosine

Les travaux effectués lors de ce doctorat ont porté principalement sur la formation des dommages d'oxydation de la cytosine. Celle-ci a été étudiée par deux approches distinctes: Tout d'abord, la formation de dommages d'oxydation à l'ADN en milieu cellulaire en présence d'une concentration élevée en vitamine C en condition de stress (H2O2) a été abordée. Nous avons ainsi observé un effet pro-oxydant de la vitamine C résultant en une amplification de la formation des dommages dans l'ADN tel que la 5-hydroxy-2'-désoxycytidine (5OHdCyd) et la 8-oxo-7,8-dihydro-2'-deoxyguanosine (8oxodGuo). Un changement du ratio de la formation de ces produits en faveur de la 5OHdCyd par rapport à celui obtenu par une réaction de Fenton in vitro a par ailleurs été mis en évidence. L'autre partie de ces travaux a porté sur la suroxydation de produits déjà oxydés de la 2'-désoxycytidine. En effet, ces derniers tel que la 5-hydroxy-2'-désoxyuridine (5OHdUrd) et la 5OHdCyd, ayant des potentiels d'oxydation très faibles, peuvent être sujets à une deuxième oxydation aboutissant à la formation d'autres produits. Nous avons ainsi mis en évidence sur des nucléosides une nouvelle voie de formation de dommages en solution aqueuse aérée impliquant les dérivés nucléosidiques de l'acide isodialurique, l'acide dialurique et la 5-hydroxyhydantoïne (5OHdHyd). Nous avons également caractérisé une nouvelle lésion, le dérivé nucléosidique de la 4-hydroxy-isohydantoïne (4-OHisodHyd), issue d'un réarrangement cétolique de la 5-OHdHyd. L'effet de hautes concentrations en vitamine C en condition de stress et cette suroxydation des bases de l'ADN sont importants car ils peuvent modifier la distribution des produits d'oxydation dans l'ADN cellulaire et jouer un rôle au niveau de la mutagénèse ou de la toxicité, ce qui peut entraîner de lourdes conséquences pour la cellule