Catechol cytotoxicity in vitro: Induction of glioblastoma cell death by apoptosis

The exposure to benzene is a public health problem. Although the most well-known effect of benzene is hematopoietic toxicity, there is little information about the benzene and its metabolites effects on the central nervous system (CNS). This study examined the toxic effects of 1,2-dihydroxybenzene (catechol), a benzene metabolite, to human glioblastoma GL-15 cells. GL-15 cell cultures were used as a model to provide more information about the toxic effects of aromatic compounds to the CNS. Catechol induced time- and concentration-dependent cytotoxic effects. Morphological changes, such as the retraction of the cytoplasm and chromatin clumping, were seen in cells exposed to 200 μM catechol for 48 hours. In cells exposed to 600 μM catechol for 48 hours, 78.0% of them presented condensed nuclei, and the Comet assay showed DNA damage. The percentage of cells labeled with annexin V (apoptotic cells) was greater in the group exposed to catechol (20.7%) than in control cells (0.4%). Exposure to catechol at concentrations greater than 100 μM enhanced Bax levels, and a decrease in Bcl-2 level was observed after the exposure to 600 μM catechol for 48 hours. Furthermore, catechol depleted reduced glutathione. Hence, catechol induced cell death mainly by apoptosis.

Flavonoid Rutin Alters the Viability and Function of Mitogen-Stimulated Splenocytes and Thymocytes Compared with Non Stimulated Cells

Rutin is a flavonoid obtained from Dimorphandra mollis (Benth.), a medicinal Brazilian plant used as antioxidative, antihemorrhagic, and blood vessel protector. The present study has examined its effects on the viability and function of immune system cells in vitro. Rat spleen and thymus cells were cultured with 10 nM, 1 microM, and 10 microM of the drug in the presence or absence of PWM, LPS, or ConA mitogens. Cellular proliferation was analyzed by H(3)-thymidin uptake and IFN-gamma and IL-10 were measured by ELISA after 48 and 72 hr. Viability was measured by flow cytometry using Annexin V and PI after 24 and 48 hr. The flavonoid rutin inhibited splenocytes and thymocytes proliferation under ConA stimulation observed by an increase on apoptosis levels of thymocytes stimulated with PWM in 24 hr and on splenocytes stimulated with PWM in 48 hr. Function studies showed a decrease on IFN-gamma production by splenocytes and thymocytes stimulated with PWM or ConA. Spleen cells cultured with LPS and rutin showed a decrease on apoptosis after 24 hr and an increase on the IL-10 levels after 48 hr. There was no significant variation on the necrosis rate, viability, and function of cells treated with rutin in the absence of mitogenic stimulus.

Phenotype analysis of lymphocytes of workers with chronic benzene poisoning

Lifetime exposure to benzene is associated to a variety of blood disorders, and except for the risk of cancer, almost nothing is known concerning health impairment in individuals who are no longer exposed. In Brazil, this exposure is one of the serious problems in workplaces, and many workers have been laid off their jobs due to this intoxication, particularly in the State of Bahia, the largest producer of benzene in Latin America, which is the area of this study. From a larger study to describe health effects and genetic polymorphisms among workers with chronic benzene poisoning (CBP), this previous specific investigation analyzes the association between CBP and the pattern of sub-populations of lymphocytes. The study was performed with a CBP group (n=24) and a control group with other occupational diseases (n=24); both were selected at the Workers Health Study Center in the State of Bahia, Brazil. Clinical and epidemiologic variables were collected from medical records and from a detailed questionnaire. The average age was similar in the two groups (51.1 and 50.7, respectively). Analyzing the mean proportions of the sub-populations of lymphocytes, statistically significant differences were found for T cytotoxic cells (TCD8) (27.9; 19.4; p=0.002) and T helper memory cell (CD4CD45RO) (31.2; 37.0; p=0.015), respectively, for the CBP group and control group. These results should be viewed with caution because of the small sample size, but they strengthen a previous impression that workers exposed to benzene have their immune system impaired, even in the long term, which may contribute to some disorders and carcinogenesis process. These workers must be strictly followed up in a medical surveillance program. Although this problem has been known for a long time, this is the first attempt to study these specific effects in Brazil.

Differences in gamma interferon production in vitro predict the pace of the in vivo response to Leishmania amazonensis in healthy volunteers

The initial encounter of Leishmania cells and cells from the immune system is fundamentally important in the outcome of infection and determines disease development or resistance. We evaluated the anti-Leishmania amazonensis response of naive volunteers by using an in vitro priming (IVP) system and comparing the responses following in vivo vaccination against the same parasite. In vitro stimulation allowed us to distinguish two groups of individuals, those who produced small amounts of gamma interferon (IFN-gamma) (n = 16) (low producers) and those who produced large amounts of this cytokine (n = 16) (high producers). IFN-gamma production was proportional to tumor necrosis factor alpha and interleukin 10 (IL-10) levels but did not correlate with IL-5 production. Volunteers who produced small amounts of IFN-gamma in vitro remained low producers 40 days after vaccination, whereas high producers exhibited increased IFN-gamma production. However, 6 months after vaccination, all individuals tested produced similarly high levels of IFN-gamma upon stimulation of their peripheral blood mononuclear cells with Leishmania promastigotes, indicating that low in vitro producers respond slowly in vivo to vaccination. In high IFN-gamma producers there was an increased frequency of activated CD8(+) T cells both in vitro and in vivo compared to the frequency in low producers, and such cells were positive for IFN-gamma as determined by intracellular staining. Such findings suggest that IVP responses can be used to predict the pace of postvaccination responses of test volunteers. Although all vaccinated individuals eventually have a potent anti-Leishmania cell-mediated immunity (CMI) response, a delay in mounting the CMI response may influence resistance against leishmaniasis.