Eutirucallin, a RIP-2 type lectin from the latex of Euphorbia tirucalli L. presents proinflammatory properties

Review: Laticifer as a plant defense mechanism

Laticifers have been utilized as paradigms to enhance comprehension of specific facets of plant ecology and evolution. From the beginning of seedling growth, autonomous laticifer networks are formed throughout the plant structure, extending across all tissues and organs. The vast majority of identified products resulting from laticifer chemistry and metabolism are linked to plant defense. The latex, which is the fluid contained within laticifers, is maintained under pressure and has evolved to serve as a defense mechanism against both aggressors and invaders, irrespective of their capabilities or tactics. Remarkably, the latex composition varies among different species. The current goal is to understand the specific functions of various latex components in combating plant enemies. Therefore, the study of latex's chemical composition and proteome plays a critical role in advancing our understanding about plant defense mechanisms. Here, we will discuss some of these aspects.

A Comprehensive Review on Euphorbiaceae lectins: Structural and Biological Perspectives

Euphorbiaceae, also known as the spurge family, is a large group of flowering plants. Despite being tropical natives, they are now widespread. Due to its medicinal and commercial importance, this family of plants attracted a lot of attention in the scientific community. The distinctive characteristic of the family is production of milky latex, which is a rich source of several lectins, the proteins that bind carbohydrates. Although their function is unclear, they are believed to defend plants against damaging phytopathogenic microorganisms, insects, and predatory animals. Additionally, they serve as crucial metabolic regulators under a variety of stressors. Detection, separation, purification, and characterization of lectins from the Euphorbiaceae family - mostly from the latex of plants - began over 40 years ago. This effort produced over 35 original research papers that were published. However, no systematic review that compiles these published data has been presented yet. This review summarizes and describes several procedures and protocols employed for extraction and purification of lectins belonging to this family. Physicochemical properties and biological activities of the lectins, along with their medicinal and pharmacological properties, have also been analyzed. Additionally, using examples of ricin and ricin agglutinin, we have structurally analyzed characteristics of the lectin known as Ribosome Inactivating Protein Type II (RIP-Type II) that belongs to this family. We anticipate that this review article will offer a useful compendium of information on this important family of lectins, show the scientists involved in lectin research the gaps in our knowledge, and offer insights for future research.

Pinellia ternata lectin induces inflammation through TLR4 receptor and mediates PI3K/Akt/mTOR axis to regulate NF-κB signaling pathway

Pinellia ternata, a widely used traditional Chinese medicine, contains a strong mucosal irritant that is connected with Pinellia ternata lectin (PTL) in its tubers. The purpose of this study was to explore the mechanisms by which PTL induces inflammation. We found that in RAW264.7 cells, PTL activated the PI3K/Akt/mTOR and NF-κB pathways, which resulted in the release of proinflammatory cytokines. Flow cytometry and laser confocal microscopy analysis showed that FITC-labeled PTL bound to the macrophages' surface. Based on kinetic analyses and protein-protein docking simulations, PTL was shown to bind toll-like receptor 4 (TLR4).it was demonstrated that PTL binds highly to Toll-like receptor 4 (TLR4). TLR4 knock-down or knockout resulted in a decrease in both cytokine release and PI3K/Akt/mTOR and NF-κB pathway activation in PTL-stimulated macrophages or mice. RNA-seq analysis showed that genes involved in the PI3K/Akt/mTOR signaling pathway were strongly upregulated in response to PTL stimulation, confirming that the PI3K/Akt/mTOR pathway is linked to the inflammatory effect of PTL in RAW264.7 cells. These findings reveal that PTL can mediate inflammation through TLR4 and activating the PI3K/Akt/mTOR to regulate NF-κB signaling pathways.

Recent advances in the use of legume lectins for the diagnosis and treatment of breast cancer

Poor lifestyle choices and genetic predisposition are factors that increase the number of cancer cases, one example being breast cancer, the third most diagnosed type of malignancy. Currently, there is a demand for the development of new strategies to ensure early detection and treatment options that could contribute to the complete remission of breast tumors, which could lead to increased overall survival rates. In this context, the glycans observed at the surface of cancer cells are presented as efficient tumor cell markers. These carbohydrate structures can be recognized by lectins which can act as decoders of the glycocode. The application of plant lectins as tools for diagnosis/treatment of breast cancer encompasses the detection and sorting of glycans found in healthy and malignant cells. Here, we present an overview of the most recent studies in this field, demonstrating the potential of lectins as: mapping agents to detect differentially expressed glycans in breast cancer, as histochemistry/cytochemistry analysis agents, in lectin arrays, immobilized in chromatographic matrices, in drug delivery, and as biosensing agents. In addition, we describe lectins that present antiproliferative effects by themselves and/or in conjunction with other drugs in a synergistic effect.

Roles of a protease from Euphorbia resinifera latex in human anticoagulant and antithrombotic activities

Thromboembolism is a major cause of morbidity and mortality worldwide. Most therapeutic drugs for treating thrombosis can cause hemorrhage and have short half-lives within human blood circulation resulting in a need to discover and develop novel anticoagulants/antithrombotics. EuRP-61 has been isolated from a plant latex (Euphorbia resinifera) and characterized as a serine protease. In this study, EuRP-61 was able to hydrolyze all chains of human fibrin clots. The enzyme may have long term stability in blood circulation as its fibrinogenolytic activity was not affected by human blood circulating inhibitors such as α₂-macroglobulin and antithrombin III. The enzyme may affect the extrinsic, intrinsic or common pathways of the human blood coagulation cascade as evidenced by its prolonged of both prothrombin (PT) and activated partial thromboplastin (APTT) time. Moreover, the enzyme inhibited platelet aggregation via the ADP-receptor pathway. EuRP-61 was not toxic to human red blood cells in the 4 common blood groups (A, B, O and AB) (all Rh⁺) or human peripheral blood mononuclear cells (hPBMCs). The enzyme may protect human peripheral blood cells from aggregation without destroying them. This study provides evidence that EuRP-61 may have potential as an agent for the treatment of thrombosis.

Transcriptional network inference and master regulator analysis of the response to ribosome-inactivating proteins in leukemia cells

Gene-regulatory networks reconstruction has become a very popular approach in applied biology to infer and dissect functional interactions of Transcription Factors (TFs) driving a defined phenotypic state, termed as Master Regulators (MRs). In the present work, cutting-edge bioinformatic methods were applied to re-analyze experimental data on leukemia cells (human myelogenous leukemia cell line THP-1 and acute myeloid leukemia MOLM-13 cells) treated for 6 h with two different Ribosome-Inactivating Proteins (RIPs), namely Shiga toxin type 1 (400 ng/mL) produced by Escherichia coli strains and the plant toxin stenodactylin (60 ng/mL), purified from the caudex of Adenia stenodactyla Harms. This analysis allowed us to identify the common early transcriptional response to 28S rRNA damage based on gene-regulatory network inference and Master Regulator Analysis (MRA). Both toxins induce a common response at 6 h which involves inflammatory mediators triggered by AP-1 family transcriptional factors and ATF3 in leukemia cells. We describe for the first time the involvement of MAFF, KLF2 and KLF6 in regulating RIP-induced apoptotic cell death, while receptor-mediated downstream signaling through ANXA1 and TLR4 is suggested for both toxins.

Consumption of latex from Euphorbia tirucalli L. promotes a reduction of tumor growth and cachexia, and immunomodulation in Walker 256 tumor-bearing rats

ETHNOPHARMACOLOGICAL RELEVANCE

Euphorbia tirucalli L. is an African plant that grows well in Brazil. Individuals diagnosed with cancer frequently consume latex from E. tirucalli, dissolved in drinking water. In vitro studies confirm the antitumor potential of E. tirucalli latex, but in vivo evaluations are scarce.

AIM OF THE STUDY

To evaluate the effect of intake of an aqueous solution of E. tirucalli latex on tumor growth, cachexia, and immune response in Walker 256 tumor-bearing rats.

MATERIALS AND METHODS

Latex from E. tirucalli was collected and analyzed by LC-MS. Sixty male Wistar rats (age, 90 days) were randomly divided into four groups: C, control group (without tumor); W, Walker 256 tumor-bearing group; SW1, W animals but treated with 25 μL latex/mL water; and SW2, W animals but treated with 50 μL latex/mL water. Animals received 1 mL of latex solution once a day by gavage. After 15 d, animals were euthanized, tumor mass was determined, and glucose and triacylglycerol serum levels were measured by using commercial kits. Change in the body weight during tumor development was calculated, and proliferation capacity of tumor cells was assessed by the Alamar Blue assay. Phagocytosis and superoxide anion production by peritoneal macrophages and circulating neutrophils were analyzed by enzymatic and colorimetric assays. Data are analyzed by one-way ANOVA followed by Tukey's post-hoc test, with the significance level set at 5%.

RESULTS

The analysis of the latex revealed the presence of triterpenes. The ingestion of the latex aqueous solution promoted 40% and 60% reduction of the tumor mass in SW1 and SW2 groups, respectively (p < 0.05). The proliferative capacity of tumor cells from SW2 group was 76% lower than that of cells from W group (p < 0.0001). Animals treated with latex gained, on average, 20 g (SW1) and 8 g (SW2) weight. Glucose and triacylglycerol serum levels in SW1 and SW2 animals were similar to those in C group rats. Peritoneal macrophages and blood neutrophils from SW1 and SW2 animals produced 30-40% less superoxide anions than those from W group animals (p < 0.05), but neutrophils from SW2 group showed an increased phagocytic capacity (20%, vs. W group).

CONCLUSIONS

E. tirucalli latex, administered orally for 15 d, efficiently reduced tumor growth and cachexia in Walker 256 tumor-bearing rats. Decreased tumor cell proliferative capacity was one of the mechanisms involved in this effect. Further, the data suggest immunomodulatory properties of E. tirucalli latex. The results agree with folk data on the antitumor effect of latex ingestion, indicating that it may be useful as an adjunct in the treatment of cancer patients. For this, further in vivo studies in animal and human models need to be conducted.

Ribosome-Inactivating Protein α-Momorcharin Derived from Edible Plant Momordica charantia Induces Inflammatory Responses by Activating the NF-kappaB and JNK Pathways

Alpha-momorcharin (α-MMC), a member of the ribosome-inactivating protein (RIP) family, has been found in the seeds of Momordica charantia (bitter melon). α-MMC contributes a number of pharmacological activities; however, its inflammatory properties have not been well studied. Here, we aim to determine the inflammatory responses induced by recombinant α-MMC and identify the underlying mechanisms using cell culture and animal models. Recombinant α-MMC was generated in Rosetta™(DE3)pLysS and purified by the way of nitrilotriacetic acid (NTA) chromatography. Treatment of recombinant α-MMC at 40 μg/mL exerted sub-lethal cytotoxic effect on THP-1 monocytic cells. Transcriptional profiling revealed that various genes coding for cytokines and other proinflammatory proteins were upregulated upon recombinant α-MMC treatment in THP-1 cells, including MCP-1, IL-8, IL-1β, and TNF-α. Recombinant α-MMC was shown to activate IKK/NF-κB and JNK pathways and the α-MMC-induced inflammatory gene expression could be blocked by IKKβ and JNK inhibitors. Furthermore, murine inflammatory models further demonstrated that α-MMC induced inflammatory responses in vivo. We conclude that α-MMC stimulates inflammatory responses in human monocytes by activating of IKK/NF-κB and JNK pathways, raising the possibility that consumption of α-MMC-containing food may lead to inflammatory-related diseases.

The latex of Euphorbia tirucalli inhibits staphyloxanthin production and protects Tenebrio molitor larvae against Staphylococcus aureus infection

The latex of Euphorbia tirucalli L. (LET) has great etnopharmacological relevance for several traditional communities. In this study, the in vitro and in vivo (using Tenebrio molitor larvae) antimicrobial effects of LET were evaluated. LET did not inhibit the growth of S. aureus, however, a reduction on staphyloxanthin production (an important virulence factor of S. aureus) was observed. LET (at 10 μL/kg) was also able to enhance the survival of larvae infected with a lethal dose of S. aureus, an effect associated with reduction in the numbers of haemocytes. Furthermore, haemocytes from LET-treated larvae exhibited dysfunctional lysosome activity. These results indicate the effectiveness of LET as an anti-infective agent which could be useful as source of lead molecules for the development of new therapies against S. aureus-induced infections.

Fruticulosin: A novel type 2 ribosome-inactivating protein from Abrus fruticulosus seeds that exhibits toxic and antileishmanial activity

Plant ribosome-inactivating proteins (RIPs) are a family of toxins that inhibit protein synthesis. In this study, we have isolated a novel type 2 ribosome-inactivating protein (RIP) present in seeds of the Abrus fruticulosus, named of fruticulosin. Fruticulosin, shows characteristics common to other type 2 RIPs, as specificity by galactosides (d-galactose, N-acetyl-d-galactosamine, and d-lactose), mass of approximately 60 kDa and presence of the of disulfide bonds. The N-terminal amino acid sequence (26 residues) of A-chain fruticulosin, determined by Edman degradation, revealed high similarity of the A-chain with those of other type 2 RIPs. The secondary structure of fruticulosin was analysed by circular dichroism, which showed that fruticulosin contains α-helices (22.3%), β-sheets (43.5%), and random coils and corners (34.2%). Furthermore, fruticulosin showed high toxicity in Artemia sp. (3.12 μg/mL), inhibited in vitro protein synthesis by a cell-free system and showed RNA N-glycosidase activity. Fruticulosin presented biological activities such as agglutination and antileishmanial activity on promastigote forms of Leishmania major.

Targeting the Immune System with Plant Lectins to Combat Microbial Infections

The arsenal of drugs available to treat infections caused by eukaryotic and prokaryotic microbes has been declining exponentially due to antimicrobial resistance phenomenon, leading to an urgent need to develop new therapeutic strategies. Host-directed immunotherapy has been reported as an attractive option to treat microbial infections. It consists in the improvement of host defenses by increasing the expression of inflammatory mediators and/or controlling of inflammation-induced tissue injury. Although the in vitro antimicrobial and immunomodulatory activities of lectins have been extensively demonstrated, few studies have evaluated their in vivo effects on experimental models of infections. This review aims to highlight the experimental use of immunomodulatory plant lectins to improve the host immune response against microbial infections. Lectins have been used in vivo both prophylactically and therapeutically resulting in the increased survival of mice under microbial challenge. Other studies successfully demonstrated that lectins could be used in combination with parasite antigens in order to induce a more efficient immunization. Therefore, these plant lectins represent new candidates for management of microbial infections. Furthermore, immunotherapeutic studies have improved our knowledge about the mechanisms involved in host–pathogen interactions, and may also help in the discovery of new drug targets.

Metagenomic alkaline protease from mangrove sediment

Functional screening of metagenomic libraries is an important tool for the discovery of new molecules. The metabolic diversity of microorganisms enables survival in harsh environments and is related to the production of enzymes. In this study, we identified a protease-producing clone from a metagenomic library derived from mangrove sediment. The protease was purified by ammonium sulphate precipitation and gel filtration chromatography, with a yield of 77.27% and a specific activity of 8.57 U μg^-1 . It had a molecular weight of approximately 70 kDa. MS/MS in ESI-Q-TOF revealed nine peptides similar to a peptidase of Bacillus safensis. The aligned partial sequence showed 47.48% identity and 82.74% similarity to the conserved domains of a glutamyl aminopeptidase from the human gut metagenome and 32.12% total coverage. The protease had an optimal pH of 8.5 and optimal activity at 60°C. At pH 9-12, its activity was greater than 80%. It had moderate thermotolerance and thermostability at temperatures of 40 and 50 °C. The K_M and V_max values were estimated to be 0.92 mg ml^-1 , and 13.15 mmol min^-1 for azocasein. Substrate specificity analysis showed that PR4A3 was active on gelatin, blood, egg yolk, and milk. These results support the potential use of PR4A3 in biotechnological applications.

Eutirucallin: A Lectin with Antitumor and Antimicrobial Properties

Eutirucallin is a lectin isolated from the latex of Euphorbia tirucalli, a plant known for its medical properties. The present study explores various characteristics of Eutirucallin including stability, cytotoxicity against tumor cells, antimicrobial and antiparasitic activities. Eutirucallin was stable from 2 to 40 days at 4°C, maintained hemagglutinating activity within a restricted range, and showed optimal activity at pH 7.0–8.0. Eutirucallin presented antiproliferative activity for HeLa, PC3, MDA-MB-231, and MCF-7 tumor cells but was not cytotoxic for non-tumorigenic cells such as macrophages and fibroblasts. Eutirucallin inhibited the Ehrlich ascites carcinoma in vivo and it was also observed that Eutirucallin inhibited 62.5% of Escherichia coli growth. Also, Eutirucallin showed to be effective when tested directly against Toxoplasma gondii infection in vitro. Therefore, this study sheds perspectives for pharmacological applications of Eutirucallin.

Transcriptome and proteome analyses provide insight into laticifer's defense of Euphorbia tirucalli against pests

The cytoplasm of laticifers, which are plant cells specialized for rubber production and defense against microbes and herbivores, is a latex. Although laticifers share common functions, the protein constituents of latexes are highly variable among plant species and even among organs. In this study, transcriptomic and proteomic analyses of Euphorbia tirucalli's (Euphorbiaceae) latex were conducted to determine the molecular basis of the laticifer's functions in this plant. The hybrid de novo assembly of Illumina mRNA-seq and expressed sequence tags obtained by Sanger's sequencing revealed 26,447 unigenes. A unigene similar to Arabidopsis embryo-specific protein 3 (AT5G62200), which is a PLAT domain-containing protein, and rubber elongation factor showed the highest expression levels. The proteome analysis, studied by liquid chromatography-mass spectrometry with the de novo assembled unigenes as the database, revealed 161 proteins in the latex, 107 of which were not detected in the stem. A gene ontology analysis indicated that the laticifer's proteome was enriched with proteins related to proteolysis, phosphatase, defense against various environmental stresses and lipid metabolisms. D-mannose-binding lectin, ricin (which lacked the N-terminal conserved ribosome-inactivating protein domain), chitinase and peroxidase were highly accumulated, as confirmed by two-dimensional polyacrylamide gel electrophoresis. Thus, the lectins and chitinase may be the major defensive proteins against pests, and the other defense-related proteins and transcripts detected in latex may work in coordination with them. Highly expressing unigenes with unknown functions are candidate novel defense- or rubber production-related genes.

Euphorbia tirucalli modulates gene expression in larynx squamous cell carcinoma

BACKGROUND

Some plants had been used in the treatment of cancer and one of these has attracted scientific interest, the Euphorbia tirucalli (E. tirucalli), used in the treatment of asthma, ulcers, warts has active components with activities scientifically proven as antimutagenic, anti-inflammatory and anticancer.

METHODS

We evaluate the influence of the antitumoral fraction of the E. tirucalli latex in the larynx squamous cell carcinoma (Hep-2), on the morphology, cell proliferation and gene expression. The Hep-2 cells were cultivated in complete medium (MEM 10 %) and treated with E. tirucalli latex for 1, 3, 5 and 7 days. After statistically analyzing the proliferation of the tested cells, the cells were cultivated again for RNA extraction and the Rapid Subtractive Hybridization (RaSH) technique was used to identify genes with altered expression. The genes found using the RaSH technique were analyzed by Gene Ontology (GO) using Ingenuity Systems.

RESULTS

The five genes found to have differential expression were validated by real-time quantitative PCR. Though treatment with E. tirucalli latex did not change the cell morphology in comparison to control samples, but the cell growth was significantly decreased. The RaSH showed change in the expression of some genes, including ANXA1, TCEA1, NGFRAP1, ITPR1 and CD55, which are associated with inflammatory response, transcriptional regulation, apoptosis, calcium ion transport regulation and complement system, respectively. The E. tirucalli latex treatment down-regulated ITPR1 and up-regulated ANXA1 and CD55 genes, and was validated by real-time quantitative PCR.

CONCLUSIONS

The data indicate the involvement of E. tirucalli latex in the altered expression of genes involved in tumorigenic processes, which could potentially be applied as a therapeutic indicator of larynx cancer.

Riproximin: A type II ribosome inactivating protein with anti-neoplastic potential induces IL24/MDA-7 and GADD genes in colorectal cancer cell lines

Riproximin (Rpx) is a type II ribosome inactivating protein, which was extracted and purified from the seeds of Ximenia americana. Previous studies demonstrated cytotoxicity of Rpx against a variety of cell lines originating from solid and non-solid cancers. In this study, we investigated the mechanistic aspects of Rpx in selected human and rat colorectal cancer (CRC) cell lines. Cytotoxic levels of Rpx were determined by MTT assay, while cytostatic and apoptotic effects were investigated by flow cytometry and nuclear staining procedures. Effects of Rpx exposure on colony formation/migration of CRC cells and expressional modulations in anticancer/stress-related genes were also studied. Rpx showed significant and comparable levels of cytotoxicity in CRC cells as determined by inhibitory concentration (IC) values. Similar inhibitory effects were found for clonogenicity, while more pronounced inhibition of migration was observed in response to Rpx exposure. Profound arrest in S phases of the cell cycle was noted especially in primary CRC cells. Apoptotic effects were more prominent in rat CRC cells as indicated by Annexin V-FITC assay and Hoechst 33342 nuclear staining. Rpx exposure induced significantly increased levels of the IL24/MDA-7, a well characterized anticancer gene, in all CRC cells. In addition, following Rpx treatment, high expression levels of growth arrest and DNA damage (GADD family) genes were also observed. Increased expression of two additional GADD genes (34 and 153) only in rat CRC cells (CC531) conferred higher sensitivity towards Rpx and subsequent anti-proliferative/apoptotic effects as compared to human CRC cells (SW480 and SW620). The present investigation indicates the anticancer potential of Rpx in CRC and favor further evaluation of this natural compound as therapeutic agent.