Cytotoxic effects of Argentinean plant extracts on tumour and normal cell lines.

In the search for possible new anti-cancer agents, we investigated the effects of 75 aqueous and methanol extracts from 41 Argentinean plant species. The effect in cell growth was evaluated in the LM2 mammary adenocarcinoma cells. In a second stage, the highly active selected extracts were assayed in 3 other tumour cell lines: melanoma B16, bladder MB49 and lung A549; and 3 normal cell lines: mammary Hb4a and keratinocytes PAM212 and HaCat. Eight methanol extracts were found to be highly cytotoxic: Collaea argentina leaf, Iochroma australe leaf, Ipomoea bonariensis flower, Jacaranda mimosifolia flower, Solanum amygdalifolium flower, Solanum chacoense leaf, Solanum sisymbriifolium flower and Solanum verbascifolium flower. However, extract inhibition on cell growth was highly dependent on cell type. In general, except for the highly resistant cell lines, the inhibitory concentrations 50% were in the range of 10-150 µg/ml The eight extracts highly inhibited cell growth in a concentration-dependent manner, and in general the methanol extracts were always more active than the aqueous. Murine cells appear to be more sensitive than human cells to the cytotoxic action of the plant extracts. The human melanoma B16 line was the most resistant to four of the extracts. In terms of selectivity, S. verbascifolium was the species which showed most selectivity for tumour cells. Overall, this is one of the first studies focusing on southern South American native plants and their biological effects. Since some species of 5 genera analyzed have been reported to possess different degrees of alkaloid content, we examined microtubule structures after extract treatments. The eight extracts induced destabilization, condensation and aggregation of microtubules in LM2 cells, although no depolarization, typical of Vinca alkaloids damage was observed. In a near future, antitumour activity of purified fractions of the extracts administered at non-toxic doses will be assayed in transplantable murine tumour models.

The pesticide malathion induces alterations in actin cytoskeleton and in cell adhesion of cultured breast carcinoma cells.

We have studied the effects of the organophosphorous pesticide malathion on cell viability, actin cytoskeleton, cell adhesion complex E-cadherin/beta-catenin, and Rho and Rac1 GTPases from the human mammary carcinoma cell line MCF-7. Malathion induced cell lethality, determined by the MTT assay, depending on the treatment conditions. Cells incubated with low concentrations of malathion, 16-32 microg/ml, showed high survival rates (>95%) at any evaluated time (1-5 days), whereas complete cell lethality was found using 512 microg/ml and 5 days of treatment. Deep morphological changes were induced with high doses of 64 and 128 microg/ml, and long incubation time (5 days); cells showed perinuclear vacuoles, rounding, shrinkage, and a gradual loss of adhesion. These changes were related to a decrease in the expression of the adhesion molecules, E-cadherin and beta-catenin, and to the distribution and reactivity of actin microfilaments to TRITC-phalloidin. Disruption of microfilaments, accompanied by the collapse of actin to perinuclear region, were characteristic of cells with loss of adhesion. At lower concentrations, some cells presented deformations on the plasma membrane as lamellipodia-like structures, which were particularly evident from 32 to 128 microg/ml. Conversely, we observed an increase in the expression of Rho and Rac1 GTPases, modulators of actin cytoskeleton and cell adhesion.

Organophosphorous pesticides in breast cancer progression.

Environmental substances may be involved in the etiology of breast cancers. Many studies have found an association between cancer in humans and exposure to agricultural pesticides. Organophosphorous pesticides have been used to control mosquito plagues. Parathion and malathion, organophosphorous pesticides are cholinesterase inhibitors responsible for the hydrolysis of body choline esters, including acetylcholine at cholinergic synapses. Their primary target of action in insects is the nervous system whereby they inhibit the enzyme acetylcholinesterase at synaptic junction. Atropine is a parasympatholytic alkaloid used as an antidote to acetylcholinesterase inhibitors. We have established an experimental breast cancer model, where epithelial cells in the rat mammary gland underwent a stepwise transformation into malignant cells by exposure to pesticides (Cabello et al, 2001). The aim of this work was to examine whether pesticides were able to induce progression of malignant transformation of a human breast epithelial cell line, MCF7. These results showed that parathion and malathion increased PCNA and induced mutant p53 protein expression of MCF7 cells in comparison to controls and atropine inhibited such action. These results indicated that organophosphorous pesticides can induce more changes in this malignant breast cell line, inducing another step in the progression of the transformation process and atropine on the other hand inhibited the effect of such substances.

Citoquimica de la union de colorantes y fluorocromos con DNA y cromatina. / Cytochemistry of the binding of dyes and flurochromes with DNA and chromatin

El estudio de la interaccion entre colorantes y fluorocromos basicos y acidos nucleicos ha llegado a adquirir una gran importancia en la biologia molecular actual, asi como indudables repercusiones sobre las ciencias biomedicas. El analisis citoquimico de la tincion y/o fluorescencia de la cromatina por colorantes y fluorocromos derivados del xanteno, azina, tiazina, isoquinolina, bezotiazol y ftalocianina, permite obtener indicaciones sobre especificidades y mecanismos de union con el DNA, asi como correlacionar los resultados microscopicos con las caracteristicas fisicoquimicas de los colorantes y de su interaccion con acidos nucleicos

Citoquimica de la union de colorantes y fluorocromos con DNA y cromatina. / Cytochemistry of the binding of dyes and flurochromes with DNA and chromatin

El estudio de la interaccion entre colorantes y fluorocromos basicos y acidos nucleicos ha llegado a adquirir una gran importancia en la biologia molecular actual, asi como indudables repercusiones sobre las ciencias biomedicas. El analisis citoquimico de la tincion y/o fluorescencia de la cromatina por colorantes y fluorocromos derivados del xanteno, azina, tiazina, isoquinolina, bezotiazol y ftalocianina, permite obtener indicaciones sobre especificidades y mecanismos de union con el DNA, asi como correlacionar los resultados microscopicos con las caracteristicas fisicoquimicas de los colorantes y de su interaccion con acidos nucleicos