Antiproliferative activity of Rhinella marina and Rhaebo guttatus venom extracts from Southern Amazon

Abstract

The venom of amphibians is a fascinating source of active substances. In view of their medical importance and aiming to explore the amazing Brazilian biodiversity, we conducted bioprospecting of antiproliferative activity in extracts of Rhinella marina and Rhaebo guttatus toads occurring in the Southern Amazon of Mato Grosso, Brazil. LC-MS and HPLC analysis of the venom extracts of R. marina revealed four bufadienolides (telocinobufagin, marinobufagin, bufalin and resibufogenin. R. guttatus venom extracts contained only marinobufagin. First, R. marina and R. guttatus venom extracts were evaluated for cytotoxicity against tumor cell lines by the MTT assay. All extracts revealed cytotoxicity, where R. marina extracts were comparable to doxorubicin (IC₅₀ values ranging from 0.01 to 0.23 μg/mL). Only extracts of R. guttatus toad venom caused membrane disruption of human erythrocytes. The extracts were investigated for selective activity by determining their effect on stimulated human peripheral blood mononuclear cells (PBMC) with the Alamar Blue™ assay. The extracts were up to 80-fold more selective against leukemia cells when compared to dividing leukocytes. Aiming to confirm these antiproliferative effects, BrdU incorporation into DNA was measured in HL-60 treated cells with R. marina venom extracts. These extracts decreased BrdU incorporation at both concentrations tested. In summary, nine extracts of R. marina and R. guttatus venom showed pronounced lethal and discriminating effects on tumor lines, especially those from R. marina, highlighting toad parotoid gland secretions as a promising source for novel lead anticancer chemicals.

Characteristics of cathelicidin-Bg, a novel gene expressed in the ear-side gland of Bufo gargarizans

“…In further studies, the mature peptide of cathelicidin-Bg was shown to inhibit the growth of Gram-positive but not Gramnegative bacteria and fungi. In addition, many AMPs showed anti-tumor activity as observed in previous studies (Ohsaki et al, 1992;Lee et al, 2008;Ferreira et al, 2013). In this study, we showed that cathelicidin-Bg could inhibit the proliferation of HEK293 cells but not HepG2 cells; the mechanism(s) involved should be clarified in future studies.…”

Molecular biology of human epidermal receptors, signaling pathways and targeted therapy against cancers: new evidences and old challenges

“…In the 1970s, these classic approaches significantly changed with the introduction of the concept of adjuvant treatment. Intensive use of post-surgical protocols, including the combination of different chemotherapies (with different mechanisms of action) with radiotherapy and, more recently, the combination with monoclonal antibodies, has improved treatment outcomes of some types of cancers (Weinberg, 2008;Ferreira et al, 2013).…”

Cytotoxic and toxicological effects of phthalimide derivatives on tumor and normal murine cells

“…This is an extremely well characterized method that analyzes the ability of living cells to reduce the yellow dye 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to a purple formazan product by a pool of cellular mitochondrial and cytosolic enzymes such as succinate dehydrogenase bound to the inner mitochondrial membrane of mammalian mitochondria. This method revolutionized cellbased drug screening by offering a high-throughput screening colorimetric assay, whereas it simplified sample processing which did not require radioisotope but it is sensitive enough for miniaturization into 96-well plate formats and have been used in the search for NCEs with antiproliferative action (Alley et al 1988, Berridge et al 1996, Gonzalez and Tarloff 2001, Santos et al 2010, Ferreira et al 2013a, Leite et al 2014.…”

“…This technique has been extensively used to assess different cell types in toxicological, environmental, antimicrobial and cytotoxic susceptibility tests. It presents higher sensibility when compared to other cytotoxicity assays, since smaller amount of cells and steps are required converting it into a suitable method to evaluate proliferation in primary cultures of normal and tumor cells from mice, rats and humans (Al-Nasiry et al 2007, Rampersad et al 2012, Schoonen et al 2012, Ferreira et al 2013a). Ascite-bearing female mice between 7 and 9 days postinoculation were sacrificed by cervical dislocation and a suspension of S180 cells was harvested from the intraperitoneal cavity under aseptic conditions.…”

“…In the fight against cancer, search for new chemical entities (NCEs) with chemotherapeutic properties is really worthy and numerous methods have been utilized to acquire compounds, including isolation from plants and animals and the use of synthetic and combinatorial chemistry and molecular modeling (Srivastava et al 2005, Leite et al 2007, Ferreira et al 2013a, b, Ruchelman et al 2013. Phthalimides, a classical protecting group for amines with two carbonyl groups bound to a secondary amine or ammonia, have been extensively exploited to synthesize molecules with multifaceted pharmacological effects, such as anti-inflammatory (Machado et al 2005, Mazzoccoli et al 2012, Leite et a.…”