An overview of the immune modulating effects of enzymatic toxins from snake venoms.

Snake venoms are complex mixtures of organic and inorganic compounds, including proteins belonging to the protease (serine and metalloproteinases), oxidase (L-amino acid oxidases), and phospholipase (especially phospholipases A2) enzyme classes. These toxins account for the serious deleterious effects of snake envenomations, such as tissue necrosis, neurotoxicity, and hemorrhage. In addition to their toxic effects, snake venom toxins have served as important tools for investigating the mechanisms underlying envenomation and discovering new pharmacologically active compounds with immunotherapeutic potential. In this sense, the present review discusses the new findings and therapeutic perspectives in the immune modulating potential of enzymatic toxins from snake venoms belonging to the classes metalloproteinase, serine protease, L-amino acid oxidase, and phospholipase A2.

A new l-amino acid oxidase from Bothrops jararacussu snake venom: Isolation, partial characterization, and assessment of pro-apoptotic and antiprotozoal activities.

A new l-amino acid oxidase (LAAO) from Bothrops jararacussu venom (BjussuLAAO-II) was isolated by using a three-step chromatographic procedure based on molecular exclusion, hydrophobicity, and affinity. BjussuLAAO-II is an acidic enzyme with pI=3.9 and molecular mass=60.36kDa that represents 0.3% of the venom proteins and exhibits high enzymatic activity (4884.53U/mg/mim). We determined part of the primary sequence of BjussuLAAO-II by identifying 96 amino acids, from which 34 compose the N-terminal of the enzyme (ADDRNPLEECFRETDYEEFLEIARNGLSDTDNPK). Multiple alignment of the partial BjussuLAAO-II sequence with LAAOs deposited in the NCBI database revealed high similarity (95-97%) with other LAAOs isolated from Bothrops snake venoms. BjussuLAAO-II exerted a strong antiprotozoal effect against Leishmania amazonensis (IC50=4.56µg/mL) and Trypanosoma cruzi (IC50=4.85µg/mL). This toxin also induced cytotoxicity (IC50=1.80µg/mL) and apoptosis in MCF7 cells (a human breast adenocarcinoma cell line) by activating the intrinsic and extrinsic apoptosis pathways, but were not cytotoxic towards MCF10A cells (a non-tumorigenic human breast epithelial cell line). The results reported herein add important knowledge to the field of Toxinology, especially for the development of new therapeutic agents.

CR-LAAO, an L-amino acid oxidase from Calloselasma rhodostoma venom, as a potential tool for developing novel immunotherapeutic strategies against cancer.

L-amino acid oxidases from snake venoms have been described to possess various biological functions. In this study, we investigated the inflammatory responses induced in vivo and in vitro by CR-LAAO, an L-amino acid oxidase isolated from Calloselasma rhodostoma venom, and its antitumor potential. CR-LAAO induced acute inflammatory responses in vivo, with recruitment of neutrophils and release of IL-6, IL-1ß, LTB4 and PGE2. In vitro, IL-6 and IL-1ß production by peritoneal macrophages stimulated with CR-LAAO was dependent of the activation of the Toll-like receptors TLR2 and TLR4. In addition, CR-LAAO promoted apoptosis of HL-60 and HepG2 tumor cells mediated by the release of hydrogen peroxide and activation of immune cells, resulting in oxidative stress and production of IL-6 and IL-1ß that triggered a series of events, such as activation of caspase 8, 9 and 3, and the expression of the pro-apoptotic gene BAX. We also observed that CR-LAAO modulated the cell cycle of these tumor cells, promoting delay in the G0/G1 and S phases. Taken together, our results suggest that CR-LAAO could serve as a potential tool for the development of novel immunotherapeutic strategies against cancer, since this toxin promoted apoptosis of tumor cells and also activated immune cells against them.

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.

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)

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.

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.

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.

L-amino acid oxidase isolated from Bothrops pirajai induces apoptosis in BCR-ABL-positive cells and potentiates imatinib mesylate effect.

Chronic myeloid leukaemia (CML) is a myeloproliferative disorder characterized by the presence of Philadelphia chromosome and by BCR-ABL1, which encodes the BCR-ABL oncoprotein. Although imatinib mesylate (IM) is effective for CML treatment, patients in accelerated and blastic phases of the disease are often refractory to this therapy, and there are also cases of IM resistance in patients in the chronic phase. Therefore, potential new drugs are being investigated to improve the efficiency of the therapy of CML such as snake venoms and their compounds. In this investigation, Bothrops pirajai L-amino acid oxidase (BpirLAAO-I) effect on normal peripheral blood mononuclear cells (PBMC) and on BCR-ABL(+) cell line was assessed to explore its potential against leukaemic cells. MTT viability assay, lymphocyte subsets quantification and cell activation markers expression were performed to evaluate BpirLAAO-I effect on normal PBMC. The effect of BpirLAAO-I on HL-60 and HL-60.BCR-ABL cell lines was assessed by apoptosis detection. BpirLAAO-I was able to induce apoptosis in HL-60 and HL-60.BCR-ABL cell lines in a dose-dependent manner, promoted caspases 3, 8 and 9 activation and enhanced IM effect while not affecting the viability of normal cells. In addition, BpirLAAO-I promoted immune cells activation and lymphocytes subsets changes on normal PBMC. The results indicate that BpirLAAO-I induces apoptosis and potentiates IM effect on BCR-ABL(+) cells.