L-amino acid oxidase from snake venom: Biotransformation and induction of apoptosis in human colon cancer cells

Resistance to 5-fluorouracil: The molecular mechanisms of development in colon cancer cells

Colon cancer is a significant health problem worldwide as it is one of the most common and deadliest cancers. The standard approach for the treatment of colon cancer is 5-fluorouracil (5-FU) based chemotherapy, which is limited by the development of resistance to this drug. Therefore, our study aimed to establish 5-FU resistance in SW-480 and HT-29 colon cancer cells and to precisely determine the molecular mechanisms and biomarkers that contribute to its development, both after short-term exposure and in cells with already developed resistance (SW-480-5FUR and HT-29-5FUR). The expression of various molecules involved in the different mechanisms of resistance development was monitored at the gene (qPCR) and protein (immunocytochemistry) levels. Based on the obtained results, alterations in the 5-FU anabolic pathway, biotransformation, drug efflux, mismatch repair, and apoptosis process together contributed to the development of 5-FU resistance in SW-480 and HT-29 colon cancer cells. In addition, UMPS, ABCC1, ABCC5, and MLH1, as well as the disturbed ratio of pro-apoptotic BAX and anti-apoptotic BCL2, should be taken into consideration as potential targets for the discovery of 5-FU resistance-related biomarkers in colon cancer cells. We suggest that future investigations focus on further validation of these findings by additional in vitro and in vivo testing, which is a limitation of our study.

Emerging anticancer potential and mechanisms of snake venom toxins: A review

Animal-derived venom, like snake venom, has been proven to be valuable natural resources for the drug development. Previously, snake venom was mainly investigated in its pharmacological activities in regulating coagulation, vasodilation, and cardiovascular function, and several marketed cardiovascular drugs were successfully developed from snake venom. In recent years, snake venom fractions have been demonstrated with anticancer properties of inducing apoptotic and autophagic cell death, restraining proliferation, suppressing angiogenesis, inhibiting cell adhesion and migration, improving immunity, and so on. A number of active anticancer enzymes and peptides have been identified from snake venom toxins, such as L-amino acid oxidases (LAAOs), phospholipase A2 (PLA2), metalloproteinases (MPs), three-finger toxins (3FTxs), serine proteinases (SPs), disintegrins, C-type lectin-like proteins (CTLPs), cell-penetrating peptides, cysteine-rich secretory proteins (CRISPs). In this review, we focus on summarizing these snake venom-derived anticancer components on their anticancer activities and underlying mechanisms. We will also discuss their potential to be developed as anticancer drugs in the future.

Snake venom toxins: Potential anticancer therapeutics

Snake venom contains a cocktail of compounds dominated by proteins and peptides, which make up the toxin. The toxin components of snake venom attack several targets in the human body including the neuromuscular system, kidney and blood coagulation system and cause pathologies. As such, the venom toxins can be managed and used for the treatment of these diseases. In this regard, Captopril used in the treatment of cardiovascular diseases was the first animal venom toxin-based drug approved by the US Food and Drug Administration and the European Medicines Agency. Cancers cause morbidity and mortality worldwide. Due to side effects associated with the current cancer treatments including chemotherapy, radiotherapy, immunotherapy, hormonal therapy and surgery, there is a need to improve the efficacy of current treatments and/or develop novel drugs from natural sources including animal toxin-based drugs. There is a long history of earlier and ongoing studies implicating snake venom toxins as potential anticancer therapies. Here, we review the role of crude snake venoms and toxins including phospholipase A2, L-amino acid oxidase, C-type lectin and disintegrin as potential anticancer agents tested in cancer cell lines and animal tumour models in comparison to normal cell lines. Some of the anti-tumour activities of snake venom toxins include induction of cytotoxicity, apoptosis, cell cycle arrest and inhibition of metastasis, angiogenesis and tumour growth. We thus propose the advancement of multidisciplinary approaches to more pre-clinical and clinical studies for enhanced bioavailability and targeted delivery of snake venom toxin-based anticancer drugs.

Biosynthesis and characterization of silver nanoparticles synthesized using extracts of Agrimonia eupatoria L. and in vitro and in vivo studies of potential medicinal applications

This research explores the synthesis, characterization, and biological activities of silver nanoparticles (AgNPs) derived from acetone (AgNPs-acetone) and aqueous (AgNPs-H2O) extracts of Agrimonia eupatoria. The nanoparticles exhibit isometric morphology and uniform size distribution, as elucidated through Transmission Electron Microscopy (TEM) and high-resolution TEM (HRTEM) analyses. The utilization of Scanning Transmission Microscopy (STEM) with High-Angle Annular Dark-Field (HAADF) imaging and energy dispersive spectrometry (EDS) confirms the crystalline nature of AgNPs. Fourier Transform Infrared (FTIR) analysis reveals identical functional groups in the plant extracts and their corresponding AgNPs, suggesting the involvement of phytochemicals in the reduction of silver ions. Spectrophotometric monitoring of the synthesis process, influenced by various parameters, provides insights into the kinetics and optimal conditions for AgNP formation. The antioxidant activities of the plant extracts and synthesized AgNPs are evaluated through DPPH and ABTS methods, highlighting AgNPs-acetone as a potent antioxidant. Third-instar larvae exposed to the extracts have differential effects on DNA damage, with the acetone extract demonstrating antigenotoxic properties. Similarly, biosynthesized AgNPs-acetone displays antigenotoxic effects against EMS-induced DNA damage. The genotoxic effect of water extract and AgNPs-acetone was dose-dependent. Hemolytic potential is assessed on rat erythrocytes, revealing that low concentrations of AgNPs-acetone and AgNPs-H2O had a nontoxic effect on erythrocytes. Cytotoxicity assays demonstrate time-dependent and dose-dependent effects, with AgNPs-acetone exhibiting superior cytotoxicity. Proapoptotic activity is confirmed through apoptosis induction, emphasizing the potential therapeutic applications of AgNPs. The antimicrobial activity of AgNPs reveals concentration-dependent effects. AgNPs-H2O display better antibacterial activity, while antifungal activities are comparable between the two nanoparticle types.

Substituted kynurenic acid derivatives as fluorophore-based probes for D- and L-amino acid oxidase assays and their in vitro application in eels

High levels of D-amino acid oxidase (DAO) are associated with neurological and psychiatric disorders, while L-amino acid oxidase (LAO) exhibits antimicrobial and antitumor properties. The enzymatic conversion of the non-fluorescent kynurenine (KYN) into the endogenous weak fluorescent kynurenic acid (KYNA) by the action of DAO has previously been reported. However, the fluorescence of KYNA can be improved by changing the substituents on the aromatic rings. In this study, we prepared different 6-phenyl-substituted KYNA derivatives and investigated their fluorescence properties. Among them, 2-MePh-KYNA showed the maximum fluorescence quantum yield of 0.881 at 340 nm excitation and 418 nm emission wavelengths. The effects of solvent properties (dielectric constant, pKa, viscosity, and proticity) on the fluorescence intensity (FLI) of the KYNA derivatives were explored. The FLI of 2-MePh-KYNA was significantly large in protic solvents. Subsequently, 2-MePh-D-KYN and 2-MePh-L-KYN were prepared with high enantiopurity (>99.25%) for the enzymatic conversion. 2-MePh-D-KYN exhibited high sensitivity (∼19 times that of a commercial DAO substrate and ∼60 times that of the previously reported MeS-D-KYN) and high selectivity, as it was not cross-reactive towards LAO, while 2-MePh-L-KYN was also converted into 2-MePh-KYNA by LAO. Furthermore, the 2-MePh-D-KYN probe successfully detected DAO in eel liver, kidney, and heparin-anticoagulated plasma in the in vitro study.

Oxidative stress induced by Pollonein-LAAO, a new L-amino acid oxidase from Bothrops moojeni venom, prompts prostate tumor spheroid cell death and impairs the cellular invasion process in vitro

Cancer cells produce abnormal levels of reactive oxygen species (ROS) that contribute to promote their malignant phenotype. In this framework, we hypothesized that the change in ROS concentration above threshold could impair key events of prostate cancer cells (PC-3) progression. Our results demonstrated that Pollonein-LAAO, a new L-amino acid oxidase obtained from Bothrops moojeni venom, was cytotoxic to PC-3 cells in two-dimensional and in tumor spheroid assays. Pollonein-LAAO was able to increase the intracellular ROS generation that culminates in cell death from apoptosis by both intrinsic and extrinsic pathways due to the up-regulation of TP53, BAX, BAD, TNFRSF10B and CASP8. Additionally, Pollonein-LAAO reduced mitochondrial membrane potential and caused G0/G1 phase to delay, due to the up-regulation of CDKN1A and the down-regulation of the expression of CDK2 and E2F. Interestingly, Pollonein-LAAO inhibited critical steps of the cellular invasion process (migration, invasion and adhesion), due to the down-regulation of SNAI1, VIM, MMP2, ITGA2, ITGAV and ITGB3. Furthermore, the Pollonein-LAAO effects were associated with the intracellular ROS production, since the presence of catalase restored the invasiveness of PC-3 cells. In this sense, this study contributes to the potential use of Pollonein-LAAO as ROS-based agent to enhance the current understanding of cancer treatment strategies.

Potential of Orlistat to induce apoptotic and antiangiogenic effects as well as inhibition of fatty acid synthesis in breast cancer cells

Breast cancer as most often women's cancer is the second cause of mortality worldwide. Research interest increased in testing non-standard drugs to suppress breast cancer progression and become significant supplements in anticancer therapy. The anti-obesity drug Orlistat showed significant ability for modulation of cancer cell metabolism via antiproliferative, proapoptotic, antiangiogenic, antimetastatic, and hypolipidemic effects. The anticancer potential of Orlistat was evaluated by cytotoxicity (MTT assay), type of cell death (AO/EB double staining), determination of redox status parameters (superoxide, hydrogen peroxide, lipid peroxidation, reduced glutathione), and total lipid levels with colorimetric methods, as well on angiogenesis-related (VEGF, MMP-9, CXCR4/CXCL12) and fatty acid synthesis-related (ACLY, ACC, FASN) parameters on gene and protein levels (immunocytochemistry and qPCR). Based on obtained results Orlistat induces significant cytotoxic, proapoptotic, and anti-angiogenic effects in MDA-MB-231, MDA-MB-468 and MCF-7 breast cancer cells, without significant cytotoxic effects on normal MRC-5 cells. It decreased total lipid levels and changed redox status parameters and cancer cell metabolism via suppression of genes and proteins involved and fatty acid synthesis. Based on showed, Orlistat may be an important supplement in antiangiogenic therapy against breast cancer with no side effects on normal cells, making it a good candidate for future clinical trials.

Bibliometric Analysis of Literature in Snake Venom-Related Research Worldwide (1933-2022)

Snake envenomation is a severe economic and health concern affecting countries worldwide. Snake venom carries a wide variety of small peptides and proteins with various immunological and pharmacological properties. A few key research areas related to snake venom, including its applications in treating cancer and eradicating antibiotic-resistant bacteria, have been gaining significant attention in recent years. The goal of the current study was to analyze the global profile of literature in snake venom research. This study presents a bibliometric review of snake venom-related research documents indexed in the Scopus database between 1933 and 2022. The overall number of documents published on a global scale was 2999, with an average annual production of 34 documents. Brazil produced the highest number of documents (n = 729), followed by the United States (n = 548), Australia (n = 240), and Costa Rica (n = 235). Since 1963, the number of publications has been steadily increasing globally. At a worldwide level, antivenom, proteomics, and transcriptomics are growing hot issues for research in this field. The current research provides a unique overview of snake venom research at global level from 1933 through 2022, and it may be beneficial in guiding future research.

Structural Determinants of the Specific Activities of an L-Amino Acid Oxidase from Pseudoalteromonas luteoviolacea CPMOR-1 with Broad Substrate Specificity

The Pseudoalteromonas luteoviolacea strain CPMOR-1 expresses a flavin adenine dinucleotide (FAD)-dependent L-amino acid oxidase (LAAO) with broad substrate specificity. Steady-state kinetic analysis of its reactivity towards the 20 proteinogenic amino acids showed some activity to all except proline. The relative specific activity for amino acid substrates was not correlated only with K_m or k_cat values, since the two parameters often varied independently of each other. Variation in K_m was attributed to the differential binding affinity. Variation in k_cat was attributed to differential positioning of the bound substrate relative to FAD that decreased the reaction rate. A structural model of this LAAO was compared with structures of other FAD-dependent LAAOs that have different substrate specificities: an LAAO from snake venom that prefers aromatic amino acid substrates and a fungal LAAO that is specific for lysine. While the amino acid sequences of these LAAOs are not very similar, their overall structures are comparable. The differential activity towards specific amino acids was correlated with specific residues in the active sites of these LAAOs. Residues in the active site that interact with the amino and carboxyl groups attached to the α-carbon of the substrate amino acid are conserved in all of the LAAOs. Residues that interact with the side chains of the amino acid substrates show variation. This provides insight into the structural determinants of the LAAOs that dictate their different substrate preferences. These results are of interest for harnessing these enzymes for possible applications in biotechnology, such as deracemization.

Shedding Lights on Crude Venom from Solitary Foraging Predatory Ant Ectatomma opaciventre: Initial Toxinological Investigation

Some species of primitive predatory ants, despite living in a colony, exercise their hunting collection strategy individually; their venom is painful, paralyzing, digestive, and lethal for their prey, yet the toxins responsible for these effects are poorly known. Ectatomma opaciventre is a previously unrecorded solitary hunting ant from the Brazilian Cerrado. To overcome this hindrance, the present study performed the in vitro enzymatic, biochemical, and biological activities of E. opaciventre to better understand the properties of this venom. Its venom showed several proteins with masses ranging from 1-116 kDa, highlighting the complexity of this venom. Compounds with high enzymatic activity were described, elucidating different enzyme classes present in the venom, with the presence of the first L-amino acid oxidase in Hymenoptera venoms being reported. Its crude venom contributes to a state of blood incoagulability, acting on primary hemostasis, inhibiting collagen-induced platelet aggregation, and operating on the fibrinolysis of loose red clots. Furthermore, the E. opaciventre venom preferentially induced cytotoxic effects on lung cancer cell lines and three different species of Leishmania. These data shed a comprehensive portrait of enzymatic components, biochemical and biological effects in vitro, opening perspectives for bio-pharmacological application of E. opaciventre venom molecules.

The biological activity of Ocimum minimum L. flowers on redox status parameters in HCT-116 colorectal carcinoma cells

Medicinal plants have widely been used as a natural source of remedies for treating several diseases, including colorectal cancer. Ocimum minimum L. is a very important dietary plant used in traditional and modern medicine, due to its health beneficial effect realized by cytotoxic, proapoptotic, antioxidant/prooxidant, antiviral and antimicrobial activity. The biological activity of O. minimum flowers has been evaluated in HCT116 colorectal carcinoma cells through antiproliferative activity by MTT assay, pro-apoptotic activity by AO/EB and concentrations of redox status parameters (O2∙ and lipid peroxidation) by colorimetric methods. The protein expression of iNOS was analyzed by immunocytochemistry, while the antimigratory effect was measured by xCELLigence system. The treatment with O. minimum shows the antiproliferative, proapoptotic, impact on redox status parameters and antimigratory effect on HCT-116 cells. Based on obtained results, the pharmacological effect of O. minimum is evident against HCT-116 colorectal carcinoma cells, suggesting that this plant may be good start material for future anticancer therapy investigation.