The effects of a protease inhibitor fraction from tepary bean (Phaseolus acutifolius) on in vitro cell proliferation and cell adhesion of transformed cells

Tepary Bean (Phaseolus acutifolius) Lectins Induce Apoptosis and Cell Arrest in G0/G1 by P53(Ser46) Phosphorylation in Colon Cancer Cells

A Tepary bean lectin fraction (TBLF) has been studied because it exhibits differential cytotoxic and anticancer effects on colon cancer. The present work focuses on the evaluation of the apoptotic mechanism of action on colon cancer cells. Initially, lethal concentrations (LC₅₀) were obtained for the three studied cell lines (HT-29, RKO and SW-480). HT-29 showed the highest LC₅₀, 10 and 100 times higher than that of RKO and SW-480 cells, respectively. Apoptosis was evaluated by flow cytometry, where HT-29 cells showed the highest levels of early and total apoptosis, caspases activity was confirmed and necrosis was discarded. The effect on cell cycle arrest was shown in the G0/G1 phase. Specific apoptosis-related gene expression was determined, where an increase in p53 and a decrease in Bcl-2 were observed. Expression of p53 gene showed the maximum level at 8 h with an important decrease at 12 and 24 h, also the phosphorylated p53(ser46) increased at 8 h. Our results show that TBLF induces apoptosis in colon cancer cells by p-p53(ser46) involvement. Further studies will focus on studying the specific signal transduction pathway.

Virulence of the fish pathogen Aeromonas dhakensis: genes involved, characterization and histopathology of experimentally infected hybrid tilapia

Aeromonas dhakensis (Ad) CAIM 1873 growth was evaluated at different conditions and antibiotic susceptibility. Mortality and histopathological damages in hybrid tilapia Oreochromis niloticus × O. mossambicus, and virulence factors caused by Ad bacterial cells and extracellular products (ECPs) were evaluated, and the whole genome was obtained. Ad grew between 0.0 and 5.5% NaCl at a pH of between 4 and 10 and from 4 to 37°C. The lowest minimum inhibitory concentration was found for enrofloxacin (<5 µg ml-1), and bacteria were resistant to erythromycin, amoxicillin and ampicillin. Ad bacterial cells (1.86 × 105 cells g-1) and ECPs (0.462 µg protein fish-1) were highly virulent to challenged hybrid tilapia and caused over 80% mortality at 24 h. The primary clinical sign caused was haemorrhage, and damage was most marked in the spleen, liver, kidney and brain of fish challenged with bacterial cells. To our knowledge, this is the first report that Ad causes pyknotic and karyorrhectic nuclei of erythrocytes in the internal organs of hybrid tilapia, which was the most striking histopathological observation. The virulence of Ad to hybrid tilapia may be primarily related to the activity of haemolysins (hlyA genes) and cytotoxins (aerolysin aerA), along with the production of siderophores and proteases. We also found β-lactamase, tetracycline and multiple antibiotic resistance genes, as well as adherence, iron acquisition, toxins (aerolysin family, haemolysins) and diverse protease genes.

Effects of Tepary bean (Phaseolus acutifolius) protease inhibitor and semipure lectin fractions on cancer cells

Some natural and synthetic protease inhibitors (PI), such as the Bowman-Birk PI from soybean, have anticancer effects. We previously purified and characterized a Bowman-Birk-type PI from Tepary bean (Phaseolus acutifolius) seeds (TBPI). A semipure protein fraction containing this inhibitor, when tested its in vitro effect on transformed cells, showed a differential cytotoxic effect, as well as an increase in cell attachment to culture dishes. In this article we report that lectins were responsible for the cytotoxic effect previously observed, exhibiting a differential, antiproliferative effect on nontransformed cells and on different lineages of cancer cells. Although the purified TBPI lacked cytotoxicity, it was found to be responsible for the increase in cell adhesion, decreasing culture dishes' extracellular matrix degradation, leading to a decrease of the in vitro cell invasion capacity. This effect coincided with the suppression of Matrix Metalloproteinase-9 activity. These results indicate that Tepary bean seeds contain at least 2 different groups of bioactive proteins with distinct effects on cancer cells.

Mexican medicinal plants used for cancer treatment: pharmacological, phytochemical and ethnobotanical studies

AIM OF THE STUDY

This review provides a summary of Mexican medicinal flora in terms of ethnobotanical, pharmacology, and chemistry of natural products related to anticancer activity.

MATERIALS AND METHODS

Bibliographic investigation was carried out by analyzing recognized books and peer-reviewed papers, consulting worldwide accepted scientific databases from the last five decades. Mexican plants with attributed anti-cancer properties were classified into six groups: (a) plant extracts that have been evaluated for cytotoxic effects, (b) plant extracts that have documented anti-tumoral effects, (c) plants with active compounds tested on cancer cell lines, (d) plants with novel active compounds found only in Mexican species, (e) plants with active compounds that have been assayed on animal models and (f) plants with anti-cancer ethnopharmacological references but without scientific studies.

RESULTS

Three hundred plant species belonging to 90 botanical families used for cancer treatment have been recorded, of which only 181 have been experimentally analyzed. The remaining 119 plant species are in use in empirical treatment of diseases consistent with cancer symptomatology. Only 88 of the plant extracts experimentally studied in in vitro cellular models have demonstrated active cytotoxic effects in at least one cancer cell line, and 14 out of the 88 have also been tested in vivo with the results that one of them demonstrated anti-neoplasic effects. A total of 187 compounds, belonging to 19 types of plant secondary metabolites, have been isolated from 51 plant extracts with active cytotoxic effects, but only 77 of these compounds (41%) have demonstrated cytoxicity. Seventeen of these active principles have not been reported in other plant species. However, only 5 compounds have been evaluated in vivo, and 3 of them could be considered as active.

CONCLUSION

Clearly, this review indicates that it is time to increase the number of experimental studies and to begin to conduct clinical trials with those Mexican plants and its active compounds selected by in vitro and in vivo activities. Also, the mechanisms of action by which plant extracts and their active compounds exert anti-cancer effects remain to be studied.

Characterization of a highly stable trypsin-like proteinase inhibitor from the seeds of Opuntia streptacantha (O. streptacantha Lemaire)

A trypsin inhibitor from Opuntia streptacantha Lemaire (Prickly pear) seeds was purified and characterized. Of several proteases tested, this inhibitor showed specificity to trypsin-like enzymes. The major inhibitor present in these seeds showed distinctive characteristics, most notably a low molecular weight of 4.19 kDa, as determined by MALDI TOF, and an unusually high thermal stability, retaining most of the activity after heating the sample 1h to 120 degrees C with a pressure of 1 kg/cm(2). Its complete amino acid sequence was obtained through mass spectrometry, this establishing presence a blocked N-terminal region. When comparing its sequence in the MEROPS database for peptidases and peptidase inhibitors, it showed 34.48% identity with a serine-proteinase inhibitor from the I15 family.

Influence of added bean flour (Phaseolus vulgaris L.) on some physical and nutritional properties of wheat flour tortillas

Composite flours containing 15%, 25%, or 35% of small red, black, pinto, or navy bean flours (BF) and wheat were made into tortillas. Dough rheology, firmness, cohesiveness, rollability, and some physical properties of tortillas were negatively affected as BF concentration increased regardless of bean cultivar. Nutritionally, all bean tortillas had significantly higher levels of crude protein, total phenols, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS(+)) in vitro antioxidant activity (AA) and antinutritional compounds such as phytic acid (PA) and trypsin inhibitors (TI) than the wheat control. Tortillas to which 35% of small red, pinto and black BF was added had the highest levels of phenols, which were significantly correlated with both DPPH (r=0.99) and ABTS(+) (r=0.99) AA. Compared to raw flours, PA and TI were reduced from 37.37% to 43.78% and from 50% to 66%, respectively, in the tortillas. Overall analysis indicated that tortillas with acceptable texture and improved nutritional profile were produced at 25% substitution.

Peltophorum dubium and soybean Kunitz-type trypsin inhibitors induce human Jurkat cell apoptosis

Plants constitute an important source of compounds which can induce apoptosis in a variety of cells. Previously, we reported the isolation of a trypsin inhibitor from Peltophorum dubium seeds (PDTI). This inhibitor, as well as soybean trypsin inhibitor (SBTI), both belonging to the Kunitz family, have lectin-like properties and trigger rat lymphoma cell apoptosis. In the present study, we demonstrate for the first time that PDTI and SBTI induce human leukemia Jurkat cell death. Induction of apoptosis was confirmed by flow cytometry after propidium iodide labeling of apoptotic nuclei, showing a considerable increase of the sub G(0)/G(1) fraction, with no cell cycle arrest. With the purpose of gaining insight into the signaling pathways involved, we investigated the activation of caspases and the effect of caspase inhibitors, and showed caspases-3 and -8-like activation by PDTI or SBTI-treatment. Consistent with these results, pan caspase inhibitor and caspase-8 inhibitor protected Jurkat cells from apoptosis. However, there was no caspase-9 activation, confirmed by the failure of caspase-9 inhibitor to prevent cell death. No significant release of cytochrome c from mitochondria was detected suggesting that the intrinsic mitochondrial pathway is not predominant in the apoptotic process. On the other hand, recruitment of Fas-associated death domain (FADD) to the cell membrane indicates the involvement of this adaptor protein in PDTI- and SBTI-induced apoptosis in Jurkat cells. Furthermore, human peripheral lymphocytes, either stimulated with phytohemagglutinin or not, are also susceptible to viability decrease induced by these inhibitors.

Purification and primary structure determination of two Bowman-Birk type trypsin isoinhibitors from Cratylia mollis seeds

Two Bowman-Birk type trypsin inhibitors (CmTI(1) and CmTI(2)) were purified from Cratylia mollis seeds by acetone precipitation, ion exchange, gel filtration and reverse-phase chromatography. CmTI(1) and CmTI(2), with 77 and 78 amino acid residues, respectively, were sequenced in their entirety and show a high structural similarity to Bowman-Birk inhibitors from other Leguminosae. The putative reactive sites of CmTI(1) are a lysine residue at position 22 and a tyrosine residue at position 49. Different reactive sites, as identified by their alignment with related inhibitors, were found for CmTI(2): lysine at position 22 and leucine at position 49. The dissociation constant K(i) of the complex with trypsin is 1.4 nM. The apparent molecular mass is 17 kDa without DDT and 11 kDa with reducing agent and heating.

Tannins, trypsin inhibitors and lectin cytotoxicity in tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) beans

This study compared the levels of antinutritional components and cytotoxic effect of extracts, from tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) beans. Antinutritional factors were evaluated by determining their effect on the viability of epithelial cells isolated from rat small intestine. The protein and carbohydrates content were similar in all the genotypes studied (20 and 60%, respectively). Common beans presented higher content of trypsin inhibitors, tannins and lectins than tepary beans. There was not a significant correlation between tannins and cooking time. However, water absorption and cooking time correlated significantly (p < 0.05). Considerable variation was observed in lectin activity (1302-18161 Ul/mg) of extracts from different beans. Tannins, lectins, trypsin inhibitors and fat content differed between bean varieties whereas protein content was similar. The percent cellularity on rat epithelial cells was significantly different among protein extracts from different bean cultivars and ranged between 53.5% and 87.4% (p < 0.05). These results suggest that the incorporation of tepary beans in the diet would not alter the current nutritional contribution of common beans or introduce adverse toxic effects. The agronomic characteristics of tepary beans make them attractive for cultivation. However, the harder to cook phenomenon may be a limiting factor that needs further consideration.