Bothrops moojeni L-amino acid oxidase induces apoptosis and epigenetic modulation on Bcr-Abl+ cells

Resistance to apoptosis in chronic myeloid leukemia (CML) is associated with constitutive tyrosine kinase activity of the Bcr-Abl oncoprotein. The deregulated expression of apoptosis-related genes and alteration in epigenetic machinery may also contribute to apoptosis resistance in CML. Tyrosine kinase inhibitors target the Bcr-Abl oncoprotein and are used in CML treatment. The resistance of CML patients to tyrosine kinase inhibitors has guided the search for new compounds that may induce apoptosis in Bcr-Abl+ leukemic cells and improve the disease treatment. Methods: In the present study, we investigated whether the L-amino acid oxidase isolated from Bothrops moojeni snake venom (BmooLAAO-I) (i) was cytotoxic to Bcr-Abl+ cell lines (HL-60.Bcr-Abl, K562-S, and K562-R), HL-60 (acute promyelocytic leukemia) cells, the non-tumor cell line HEK-293, and peripheral blood mononuclear cells (PBMC); and (ii) affected epigenetic mechanisms, including DNA methylation and microRNAs expression in vitro. Results: BmooLAAO-I induced ROS production, apoptosis, and differential DNA methylation pattern of regulatory apoptosis genes. The toxin upregulated expression of the pro-apoptotic genes BID and FADD and downregulated DFFA expression in leukemic cell lines, as well as increased miR-16 expression - whose major predicted target is the anti-apoptotic gene BCL2 - in Bcr-Abl+ cells. Conclusion: BmooLAAO-I exerts selective antitumor action mediated by H2O2 release and induces apoptosis, and alterations in epigenetic mechanisms. These results support future investigations on the effect of BmooLAAO-I on in vivo models to determine its potential in CML therapy.(AU)

Cytotoxic and pro-apoptotic action of MjTX-I, a phospholipase A2 isolated from Bothrops moojeni snake venom, towards leukemic cells

A leucemia mieloide crônica (LMC) é uma neoplasia mieloproliferativa BCR-ABL1 + marcada por aumento da mieloproliferação e presença de células leucêmicas resistentes à apoptose. A terapia de primeira linha atual para a LMC é a administração de inibidores da tirosina quinase, mesilato de imatinibe, dasatinibe ou nilotinibe. Embora eficaz no tratamento da LMC, alguns pacientes se tornaram resistentes a essa terapia, levando à progressão da doença e à morte. Assim, a descoberta de novos compostos para melhorar a terapia da LMC ainda é um desafio. Aqui, os destinatários se MjTX-I, uma fosfolipase A 2 isolado a partir de Bothrops moojeni de veneno de cobra, afecta a viabilidade de Bcr-Abl de mesilato de imatinib-resistente + linhas celulares. Métodos: Examinamos o efeito citotóxico e pró-apoptótico de MjTX-I em células K562-S e K562-R Bcr-Abl + e na linha de células HEK-293 não tumorais e células mononucleares de sangue periférico, usando o 3- (4, Brometo de 5-dimetiltiazol-2-il) -2,5-difeniltetrazólio e os métodos de solução fluorescente hipotônica, associados à detecção de ativação de caspases 3, 8 e 9 e clivagem de poli (ADP-ribose) polimerase (PARP). Também analisamos o potencial MjTX-I para modular a expressão de genes relacionados à apoptose em células K562-S e K562-R. Resultados: O MjTX-I diminuiu a viabilidade das células K562-S e K562-R em 60 a 65%, sem afetar a viabilidade das células não tumorais, ou seja, exerceu citotoxicidade seletiva para as linhagens celulares Bcr-Abl + . Em linhas de células leucêmicas, a toxina induziu apoptose, caspases 3, 8 e 9 ativadas, PARP clivada, expressão negativa do gene anti-apoptótico BCL-2 e expressão aumentada do gene pró-apoptótico BAD. Conclusão: O efeito antitumoral de MjTX-I está associado ao seu potencial para induzir apoptose e citotoxicidade em linhagens celulares positivas para Bcr-Abl sensíveis e resistentes ao mesilato de imatinibe, indicando que MjTX-I é um candidato promissor a fármaco para atualizar a terapia de LMC.(AU)

l-Amino acid oxidase isolated from calloselasma rhodostoma snake venom induces cytotoxicity and apoptosis in JAK2V617F-positive cell lines

BACKGROUND: Myeloproliferative neoplasms are Philadelphia chromosome-negative diseases characterized by hyperproliferation of mature myeloid cells, associated or not with the Janus kinase 2 tyrosine kinase mutation, JAK2V617F. As there is no curative therapy, researchers have been investigating new drugs to treat myeloproliferative neoplasms, including l-amino acid oxidase from Calloselasma rhodostoma snake venom (CR-LAAO), which is a toxin capable of eliciting apoptosis in several tumor cell lines. OBJECTIVE: To evaluate the effects of l-amino acid oxidase from C. rhodostoma snake venom in the apoptotic machinery of JAK2-mutated cell lines. METHODS: The HEL 92.1.7 and SET-2 cell lines were cultured with l-amino acid oxidase and catalase for 12 h at 37 °C in 5% carbon dioxide. The cell viability was assessed by the multi-table tournament method, the level of apoptosis was measured by flow cytometry, and the expression of cysteine-dependent aspartate-specific proteases and cleaved Poly(ADP-ribose) polymerase were analyzed by Western blotting. RESULTS: l-Amino acid oxidase from C. rhodostoma snake venom was cytotoxic to HEL 92.1.7 and SET-2 cells (50% inhibitory concentration = 0.15 µg/mL and 1.5 µg/mL, respectively) and induced apoptosis in a concentration-dependent manner. Cell treatment with catalase mitigated the l-amino acid oxidase toxicity, indicating that hydrogen peroxide is a key component of its cytotoxic effect.The activated caspases 3 and 8 expression and cleaved PARP in HEL 92.1.7 and SET-2 cells confirmed the apoptosis activation by CR-LAAO. CONCLUSIONS: l-Amino acid oxidase from C. rhodostoma snake venom is a potential antineoplastic agent against HEL 92.1.7 and SET-2 JAK2V617F-positive cells as it activates the extrinsic apoptosis pathway.

Bothrops snake venoms and their isolated toxins, an L-amino acid oxidase and a serine protease, modulate human complement system pathways

Background Activation of the complement system plays an important role in the regulation of immune and inflammatory reactions, and contributes to inflammatory responses triggered by envenomation provoked byBothrops snakes. The present study aimed to assess whether Bothrops jararacussuand Bothrops pirajai crude venoms and their isolated toxins, namely serine protease (BjussuSP-I) and L-amino acid oxidase (BpirLAAO-I), modulate human complement system pathways.Methods Lyophilized venom and toxin samples solubilized in phosphate buffered saline were diluted in appropriate buffers to evaluate their hemolytic activity on the alternative and classical pathways of the complement system. Venom- and toxin-treated normal human serum was added to the erythrocyte suspension, and the kinetic of hemolysis was measured spectrophotometrically at 700 nm. The kinetic 96-well microassay format was used for this purpose. We determined the t ½values (time required to lyse 50 % of target erythrocytes), which were employed to calculate the percentage of inhibition of the hemolytic activity promoted by each sample concentration. To confirm complement system activation, complement-dependent human neutrophil migration was examined using the Boyden chamber model.Results At the highest concentration tested (120 g/mL), B. jararacussu and B. pirajai crude venoms inhibited the hemolytic activity of the classical pathway (65.3 % and 72.4 %, respectively) more strongly than they suppressed the hemolytic activity of the alternative pathway (14.2 and 13.6 %, respectively). BjussuSP-I (20 g/mL) did not affect the hemolytic activity of the classical pathway, but slightly decreased the hemolytic activity of the alternative pathway (13.4 %). BpirLAAO-I (50 g/mL) inhibited 24.3 and 12.4 % of the hemolytic activity of the classical and alternative pathways, respectively. Normal human serum treated with B. jararacussu and B. pirajai crude venoms induced human neutrophil migration at a level similar to that induced by zymosan-activated normal human serum.Conclusion Together, the results of the kinetics of hemolysis and the neutrophil chemotaxis assay suggest that pre-activation of the complement system byB. jararacussu and B. pirajai crude venoms consumes complement components and generates the chemotactic factors C3a and C5a. The kinetic microassay described herein is useful to assess the effect of venoms and toxins on the hemolytic activity of the complement system.

Immunomodulatory activity of Tityus serrulatus scorpion venom on human T lymphocytes

Background Tityus serrulatus scorpion venom (TsV) contains toxins that act on K + and Na + channels and account for the venoms toxic effects. TsV can activate murine peritoneal macrophages, but its effects on human lymphocytes have been poorly investigated. Considering that lymphocytes may play an important role in envenomation, we assessed whether TsV affects the expression of phenotypic (CD3, CD4, and CD8) and activation (CD69, CD25, and HLA-DR) markers, cell proliferation, and cytokine production in peripheral blood mononuclear cells. Methods Cytotoxicity of TsV was evaluated via the MTT assay. Cell proliferation, expression of phenotypic and activation markers, and release of cytokines were assessed using flow cytometry, after treatment with non-cytotoxic concentrations of TsV. The combined use of carboxyfluorescein diacetate succinimidyl ester and monoclonal antibodies against phenotypic and activation markers enabled us to simultaneously assess cell proliferation extent and cell activation status, and to discriminate among cell subpopulations. Results TsV at concentrations of 25 to 100 g/mL were not cytotoxic towards peripheral blood mononuclear cells. TsV did not induce significant changes in lymphocyte subpopulations or in the expression of activation markers on CD4 + and CD8 + T cells. TsV inhibited the phytohemagglutinin-stimulated lymphocyte proliferation, particularly in the CD8 + CD25 + T lymphocyte subset. TsV alone, at 50 and 100 g/mL, did not induce peripheral blood mononuclear cell proliferation, but elicited the production and release of IL-6, a proinflammatory cytokine that plays an important role in innate and adaptive immune responses. Conclusions TsV is a potential source of molecules with immunomodulatory action on human T lymphocytes.

Bothrops snake venoms and their isolated toxins, an L-amino acid oxidase and a serine protease, modulate human complement system pathways

Background Activation of the complement system plays an important role in the regulation of immune and inflammatory reactions, and contributes to inflammatory responses triggered by envenomation provoked byBothrops snakes. The present study aimed to assess whether Bothrops jararacussuand Bothrops pirajai crude venoms and their isolated toxins, namely serine protease (BjussuSP-I) and L-amino acid oxidase (BpirLAAO-I), modulate human complement system pathways.Methods Lyophilized venom and toxin samples solubilized in phosphate buffered saline were diluted in appropriate buffers to evaluate their hemolytic activity on the alternative and classical pathways of the complement system. Venom- and toxin-treated normal human serum was added to the erythrocyte suspension, and the kinetic of hemolysis was measured spectrophotometrically at 700 nm. The kinetic 96-well microassay format was used for this purpose. We determined the t ½values (time required to lyse 50 % of target erythrocytes), which were employed to calculate the percentage of inhibition of the hemolytic activity promoted by each sample concentration. To confirm complement system activation, complement-dependent human neutrophil migration was examined using the Boyden chamber model.Results At the highest concentration tested (120 μg/mL), B. jararacussu and B. pirajai crude venoms inhibited the hemolytic activity of the classical pathway (65.3 % and 72.4 %, respectively) more strongly than they suppressed the hemolytic activity of the alternative pathway (14.2 and 13.6 %, respectively). BjussuSP-I (20 μg/mL) did not affect the hemolytic activity of the classical pathway, but slightly decreased the hemolytic activity of the alternative pathway (13.4 %). BpirLAAO-I (50 μg/mL) inhibited 24.3 and 12.4 % of the hemolytic activity of the classical and alternative pathways, respectively. Normal human serum treated with B. jararacussu and B. pirajai crude venoms induced human neutrophil migration at a level similar to that induced by zymosan-activated normal human serum.Conclusion Together, the results of the kinetics of hemolysis and the neutrophil chemotaxis assay suggest that pre-activation of the complement system byB. jararacussu and B. pirajai crude venoms consumes complement components and generates the chemotactic factors C3a and C5a. The kinetic microassay described herein is useful to assess the effect of venoms and toxins on the hemolytic activity of the complement system.(AU)

Immunomodulatory activity of Tityus serrulatus scorpion venom on human T lymphocytes

Background Tityus serrulatus scorpion venom (TsV) contains toxins that act on K + and Na + channels and account for the venom's toxic effects. TsV can activate murine peritoneal macrophages, but its effects on human lymphocytes have been poorly investigated. Considering that lymphocytes may play an important role in envenomation, we assessed whether TsV affects the expression of phenotypic (CD3, CD4, and CD8) and activation (CD69, CD25, and HLA-DR) markers, cell proliferation, and cytokine production in peripheral blood mononuclear cells. Methods Cytotoxicity of TsV was evaluated via the MTT assay. Cell proliferation, expression of phenotypic and activation markers, and release of cytokines were assessed using flow cytometry, after treatment with non-cytotoxic concentrations of TsV. The combined use of carboxyfluorescein diacetate succinimidyl ester and monoclonal antibodies against phenotypic and activation markers enabled us to simultaneously assess cell proliferation extent and cell activation status, and to discriminate among cell subpopulations. Results TsV at concentrations of 25 to 100 μg/mL were not cytotoxic towards peripheral blood mononuclear cells. TsV did not induce significant changes in lymphocyte subpopulations or in the expression of activation markers on CD4 + and CD8 + T cells. TsV inhibited the phytohemagglutinin-stimulated lymphocyte proliferation, particularly in the CD8 + CD25 + T lymphocyte subset. TsV alone, at 50 and 100 μg/mL, did not induce peripheral blood mononuclear cell proliferation, but elicited the production and release of IL-6, a proinflammatory cytokine that plays an important role in innate and adaptive immune responses. Conclusions TsV is a potential source of molecules with immunomodulatory action on human T lymphocytes.(AU)

Snake venom L-amino acid oxidases: an overview on their antitumor effects

The L-amino acid oxidases (LAAOs) constitute a major component of snake venoms and have been widely studied due to their widespread presence and various effects, such as apoptosis induction, cytotoxicity, induction and/or inhibition of platelet aggregation, hemorrhage, hemolysis, edema, as well as antimicrobial, antiparasitic and anti-HIV activities. The isolated and characterized snake venom LAAOs have become important research targets due to their potential biotechnological applications in pursuit for new drugs of interest in the scientific and medical fields. The current study discusses the antitumor effects of snake venom LAAOs described in the literature to date, highlighting the mechanisms of apoptosis induction proposed for this class of proteins.

Snake venom L-amino acid oxidases: an overview on their antitumor effects

The L-amino acid oxidases (LAAOs) constitute a major component of snake venoms and have been widely studied due to their widespread presence and various effects, such as apoptosis induction, cytotoxicity, induction and/or inhibition of platelet aggregation, hemorrhage, hemolysis, edema, as well as antimicrobial, antiparasitic and anti-HIV activities. The isolated and characterized snake venom LAAOs have become important research targets due to their potential biotechnological applications in pursuit for new drugs of interest in the scientific and medical fields. The current study discusses the antitumor effects of snake venom LAAOs described in the literature to date, highlighting the mechanisms of apoptosis induction proposed for this class of proteins.