Immunomodulatory role of native and heat denatured agglutinin from Abrus precatorius

The traditional uses, phytochemistry and pharmacology of Abrus precatorius L.: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Abrus precatorius L. (AP) is a folk medicine with a long-term medicinal history worldwide, which is extensively applied to various ailments, such as bronchitis, jaundice, hepatitis, contraception, tumor, abortion, malaria, etc. Meanwhile, its leaves are also served as tea in China, and its roots are employed as a substitute for Glycyrrhiza uralensis or as a raw material for the extraction of glycyrrhizin in India. Thus, AP is considered to be a plant with dual values of medicine and economy as well as its chemical composition and biological activity, which are of growing interest to the scientific community.

AIM OF REVIEW

In the review, the traditional application, botany, chemical constituents, pharmacological activities, and toxicity are comprehensively and systematically summarized.

MATERIALS AND METHODS

An extensive database retrieval was conducted to gather the specific information about AP from 1871 to 2022 using online bibliographic databases Web of Science, PubMed, SciFinder, Google Scholar, CNKI, and Baidu Scholar. The search terms comprise the keywords "Abrus precatorius", "phytochemistry", "pharmacological activity", "toxicity" and "traditional application" as a combination.

RESULTS

To date, AP is traditionally used to treat various diseases, including sore throat, cough, bronchitis, jaundice, hepatitis, abdominal pain, contraception, tumor, abortion, malaria, and so on. More than 166 chemical compounds have been identified from AP, which primarily cover flavonoids, phenolics, terpenoids, steroids, alkaloids, organic acids, esters, proteins, polysaccharides, and so on. A wide range of in vitro and in vivo pharmacological functions of AP have been reported, such as antitumor, antimicrobial, insecticidal, antiprotozoal, antiparasitic, anti-inflammatory, antioxidant, immunomodulatory, antifertility, antidiabetic, other pharmacological activities. The crushed seeds in powder or paste form were comparatively toxic to humans and animals by oral administration. Interestingly, the methanolic extracts were non-toxic to adult Wistar albino rats at various doses (200 and 400 mg/kg) daily.

CONCLUSIONS

The review focuses on the traditional application, botany, phytochemistry, pharmacological activities, and toxicity of AP, which offers a valuable context for researchers on the current research status and a reference for further research and applications of this medicinal plant.

A Case of Poisoning with Abrus precatarius Complicated with Bilateral Basal Ganglia Haemorrhage

Abrus precatarius is a tropical climber, whose seeds contain abrin, which is known to cause toxicity in humans. We report a case of a young girl, who presented with haemorrhagic enterocolitis, bilateral septal vein thrombosis, and basal ganglia haemorrhage leading to seizures and coma, following ingestion of toxic A. precatarius seeds. To the best of our knowledge, this is the first ever case to describe such an intracranial complication of abrin poisoning.

Potential therapeutic applications of phytoconstituents as immunomodulators: Pre-clinical and clinical evidences

Autoimmune and infectious diseases are the major public health issues and have gained great attention in the last few years for the search of new agents with therapeutic benefits on the host immune functions. In recent years, natural products (NPs) have been studied broadly for their multi-targeted activities under pathological conditions. Interestingly, several attempts have been made to outline the immunomodulatory properties of NPs. Research on in-vitro and in-vivo models have shown the immunomodulatory activity of NPs, is due to their antiinflammatory property, induction of phagocytosis and immune cells stimulation activity. Moreover, studies on humans have suggested that phytomedicines reduce inflammation and could provide appropriate benefits either in single form or complex combinations with other agents preventing disease progression, subsequently enhancing the efficacy of treatment to combat multiple malignancies. However, the exact mechanism of immunomodulation is far from clear, warranting more detailed investigations on their effectiveness. Nevertheless, the reduction of inflammatory cascades is considered as a prime protective mechanism in a number of inflammation regulated autoimmune diseases. Altogether, this review will discuss the biological activities of plant-derived secondary metabolites, such as polyphenols, alkaloids, saponins, polysaccharides and so forth, against various diseases and their potential use as an immunomodulatory agent under pathological conditions.

Lectins, Interconnecting Proteins with Biotechnological/Pharmacological and Therapeutic Applications

Lectins are proteins extensively used in biomedical applications with property to recognize carbohydrates through carbohydrate-binding sites, which identify glycans attached to cell surfaces, glycoconjugates, or free sugars, detecting abnormal cells and biomarkers related to diseases. These lectin abilities promoted interesting results in experimental treatments of immunological diseases, wounds, and cancer. Lectins obtained from virus, microorganisms, algae, animals, and plants were reported as modulators and tool markers in vivo and in vitro; these molecules also play a role in the induction of mitosis and immune responses, contributing for resolution of infections and inflammations. Lectins revealed healing effect through induction of reepithelialization and cicatrization of wounds. Some lectins have been efficient agents against virus, fungi, bacteria, and helminths at low concentrations. Lectin-mediated bioadhesion has been an interesting characteristic for development of drug delivery systems. Lectin histochemistry and lectin-based biosensors are useful to detect transformed tissues and biomarkers related to disease occurrence; antitumor lectins reported are promising for cancer therapy. Here, we address lectins from distinct sources with some biological effect and biotechnological potential in the diagnosis and therapeutic of diseases, highlighting many advances in this growing field.

Abrus agglutinin is a potent anti-proliferative and anti-angiogenic agent in human breast cancer

Abrus agglutinin (AGG), a plant lectin isolated from the seeds of Abrus precatorius, has documented antitumor and immunostimulatory effects in murine models. To examine possible antitumor activity against breast cancer, we established human breast tumor xenografts in athymic nude mice and intraperitoneally administered AGG. AGG inhibited tumor growth and angiogenesis as confirmed by monitoring the expression of Ki-67 and CD-31, respectively. In addition, TUNEL positive cells increased in breast tumors treated with AGG suggesting that AGG mediates anti-tumorigenic activity through induction of apoptosis and inhibition of angiogenesis. On a molecular level, AGG caused extrinsic apoptosis through ROS generation that was AKT-dependent in breast cancer cells, without affecting primary mammary epithelial cells, suggesting potential cancer specificity of this natural compound. In addition, using HUVECs, AGG inhibited expression of the pro-angiogenic factor IGFBP-2 in an AKT-dependent manner, reducing angiogenic phenotypes both in vitro and in vivo. Overall, the present results establish that AGG promotes both apoptosis and anti-angiogenic activities in human breast tumor cells, which might be exploited for treatment of breast and other cancers.

Review on Medicinal Uses, Pharmacological, Phytochemistry and Immunomodulatory Activity of Plants

Since ancient times, plants have been an exemplary source of medicine. Researchers have discovered some important compounds from plants. The present work constitutes a review of the medicinal plants whose immunomodulant activity has been proven. We performed PUBMED, EMBASE, Google scholar searches for research papers of medicinal plants having immunomodulant activity. Medicinal plants used by traditional physicians or reported as having immunomodulant activity include Acacia concocinna, Camellia sinensis, Lawsonia inermis Linn, Piper longum Linn, Gelidium amansii, Petroselinum crispum, Plantago major and Allium sativum. Immunomodulant activities of some of these medicinal plants have been investigated. The medicinal plants documented have immunomodulant activity and should be further investigated via clinical trial.

Abrus agglutinin suppresses human hepatocellular carcinoma in vitro and in vivo by inducing caspase-mediated cell death

AIM

Abrus agglutinin (AGG) from the seeds of Indian medicinal plant Abrus precatorius belongs to the class II ribosome inactivating protein family. In this study we investigated the anticancer effects of AGG against human hepatocellular carcinoma in vitro and in vivo.

METHODS

Cell proliferation, DNA fragmentation, Annexin V binding, immunocytofluorescence, Western blotting, caspase activity assays and luciferase assays were performed to evaluate AGG in human liver cancer cells HepG2. Immunohistochemical staining and TUNEL expression were studied in tumor samples of HepG2-xenografted nude mice.

RESULTS

AGG induced apoptosis in HepG2 cells in a dose- and time-dependent manner. AGG-treated HepG2 cells demonstrated an increase in caspase 3/7, 8 and 9 activities and a sharp decrease in the Bcl-2/Bax ratio, indicating activation of a caspase cascade. Co-treatment of HepG2 cells with AGG and a caspase inhibitor or treatment of AGG in Bax knockout HepG2 cells decreased the caspase 3/7 activity in comparison to HepG2 cells exposed only to AGG. Moreover, AGG decreased the expression of Hsp90 and suppressed Akt phosphorylation and NF-κB expression in HepG2 cells. Finally, AGG treatment significantly reduced tumor growth in nude mice bearing HepG2 xenografts, increased TUNEL expression and decreased CD-31 and Ki-67 expression compared to levels observed in the untreated control mice bearing HepG2 cells.

CONCLUSION

AGG inhibits the growth and progression of HepG2 cells by inducing caspase-mediated cell death. The agglutinin could be an alternative natural remedy for the treatment of human hepatocellular carcinomas.

Rachycentron canadum (cobia) lectin promoted mitogenic response in mice BALB/c splenocytes

The mitogenic lectins are invaluable tools to study the biochemical changes associated with lymphocyte activation and proliferation of various immune cells. Rachycentron canadum lectin (RcaL) was detected and purified from serum of cobia fish. The aim of this study was to evaluate the proliferative response and cytokine production in splenocytes of mice in vitro stimulated with RcaL lectin; Canavalia ensiformis lectin (Con A) was used as positive control. A high proliferation index was induced by RcaL in relation to control cells. Furthermore, RcaL induced higher IL-2 and IL-6 production in relation to control. The cell viability was 90% in splenocytes treated with RcaL lectin, but RcaL promoted significant late apoptosis after 24 and 48 h in relation to control. RcaL induced proliferative responses suggesting that this lectin can be used as a mitogenic agent in immunostimulatory assays.

Involvement of prohibitin upregulation in abrin-triggered apoptosis

Abrin (ABR), a protein purified from the seeds of Abrus precatorius, induces apoptosis in various types of cancer cells. However, the detailed mechanism remains largely uncharacterized. By using a cDNA microarray platform, we determined that prohibitin (PHB), a tumor suppressor protein, is significantly upregulated in ABR-triggered apoptosis. ABR-induced upregulation of PHB is mediated by the stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) pathway, as demonstrated by chemical inhibitors. In addition, ABR significantly induced the expression of Bax as well as the activation of caspase-3 and poly(ADP-ribose) polymerase (PARP) in Jurkat T cells, whereas the reduction of PHB by specific RNA interference delayed ABR-triggered apoptosis through the proapoptotic genes examined. Moreover, our results also indicated that nuclear translocation of the PHB-p53 complex may play a role in the transcription of Bax. Collectively, our data show that PHB plays a role in ABR-induced apoptosis, which may be helpful for the development of diagnostic or therapeutic agents.

Anticryptococcal cytotoxicity of murine nonadherent cells is perforin and nonperforin mediated

The encapsulated fungal pathogen Cryptococcus neoformans is a significant agent of life-threatening infections, particularly in people with suppressed cell-mediated immunity. The cellular cytotoxicity against C. neoformans infection is mainly mediated by NK and T cells, but effector mechanisms are not well understood. The objective of this study was (i) to determine whether prior exposure to the cryptococcal antigens enhances anticryptococcal activity of cytotoxic cells in mice and (ii) the contribution of perforin- and nonperforin-mediated cytotoxicity of NK and T cells in growth inhibition of C. neoformans. Our data showed that in vitro exposure of nonadherent (NA) spleen mononuclear cells from nonimmunized mice to heat-killed C. neoformans strain Cap67 unencapsulated mutant of B3501 (Ag1) or its supernatant (Ag2) demonstrated higher anticryptococcal activity. This effector mechanism can be enhanced further after immunization with either Ag1 or Ag2. There is a synergistic effect of immunization and in vitro incubation of the NA cells with the same antigens. Concanamycin A (CMA) and strontium chloride (SrCl2) inhibition assays were performed to clarify the contribution of perforin- and nonperforin-mediated anticryptococcal cytotoxicity of NA cells in these events. Treatment with these inhibitors demonstrated that anticryptococcal cytotoxicity of nonprimed NA cells was primarily perforin mediated. Anticryptococcal activity of the NA cells obtained from immunized mice after in vitro incubation with cryptococcal antigens was both perforin and nonperforin mediated. Taken together these data demonstrate that in mice a nonperforin-mediated pathway of anticryptococcal cytotoxicity can be induced by immunization. Further research is needed to examine their potential role for human vaccines strategies and/or therapies.

In vitro immunostimulatory properties of Abrus lectins derived peptides in tumor bearing mice

In vitro immunostimulatory effect of Abrus lectins derived peptide fractions (AGP and ABP) was investigated in DL bearing mice. Both AGP and ABP were found to activate splenocytes and induced production of cytokines like IL-2, IFN-gamma and TNF-alpha indicating a Th1 type of immune response. Analysis of in vitro treated splenocytes by flow cytometry revealed an increase in percentage of T and B cell with high expression of activation markers (CD25(+) and CD71(+)). At the same time, expression of co-stimulatory markers was significantly high compared to tumor control. The tumor associated macrophages were able to stimulate NO production, IL-1 secretion, increased phagocytosis and decreased expression of mannose receptor. It was also observed that NK cell was activated by AGP and ABP. These results suggest that both AGP and ABP act as immunostimulants in vitro in DL bearing mice.

CEL-I, an N-acetylgalactosamine (GalNAc)-specific C-type lectin, induces nitric oxide production in RAW264.7 mouse macrophage cell line

We found that CEL-I, a GalNAc-specific C-type lectin isolated from the marine invertebrate Holothuroidea (Cucumaria echinata), induces inducible nitric oxide synthase (iNOS) expression and NO production in RAW264.7 cells. The NO production was inhibited by an iNOS inhibitor, L-NAME, but was not by a lipopolysaccharide (LPS) inhibitor, polymyxin B. In the presence of 0.1-M GalNAc, increased NO production by CEL-I-treated RAW264.7 cells was observed rather than the inhibition. Bovine serum albumin (BSA) significantly inhibited the CEL-I-induced NO production as well as the binding of FITC-labelled CEL-I on RAW264.7 cells. Three MAP kinase inhibitors (specific to extra-cellular regulated kinase, c-jun NH(2)-terminal kinase and p38 MAP kinase) inhibited CEL-I-induced NO production with different extents. Heat-treatment of CEL-I resulted in a decreased activity of CEL-I depending on the temperature. These results suggest that CEL-I induces NO production in RAW264.7 cells through the protein-cell interaction rather than the binding to the specific carbohydrate chains on the cell surface.

A Bowman-Birk trypsin inhibitor with antiproliferative activity from Hokkaido large black soybeans

A trypsin inhibitor, with an N-terminal sequence highly homologous to those of 8-kDa Bowman-Birk trypsin inhibitors, was isolated from the seeds of Hokkaido large black soybeans. The trypsin inhibitor was unadsorbed on SP-Sepharose but adsorbed on DEAE-cellulose and Mono Q. It inhibited proliferation in breast cancer (MCF-7) cells and hepatoma (Hep G2) cells with an IC50 of 35 and 140 microM, respectively. The trypsin inhibitory activity of the inhibitor was completely preserved after exposure to temperatures up to 100 degrees C for 30 min and to the pH range 2-13 for the same duration. The trypsin inhibitor inhibited HIV-1 reverse transcriptase with an IC50 of 38 microM, but was devoid of antifungal activity toward Fusarium oxysporum and Mycosphaerella arachidicola.

Immunomodulatory and anti-tumor activities of native and heat denatured Abrus agglutinin

Abrus agglutinin (AAG), a hetero tetrameric gal beta (1-3) NAc gal specific lectin, is isolated from seeds of Abrus precatorius. In our previous studies we found that the protein could act as an immunomodulator and immunoadjuvant in native (NA) and heat denatured (HDA) conditions. An anticancer effect of the lectin is reported, but its mode of action is not clearly known. In the present study, the anti-tumor activity of AAG (NA, HDA) has been evaluated in a murine Dalton's lymphoma (DL) ascites tumorogenic model. We found that treatment with both NA and HDA were able to decrease the tumor cell number in vivo and significantly increased median survival time. In vitro studies showed that AAG (NA, HDA) treatment of Dalton's lymphoma ascites cells (DLAC) resulted in growth inhibition at the concentration of 1 microg/ml and above. Whereas, AAG (NA, HDA) at much lower concentrations (approximately 1 ng/ml) can stimulate peritoneal macrophage and spleen derived NK cells in vitro demonstrating cytotoxicity against DLAC. Cell cycle analysis showed an increased number of cells in Sub-G0/G1 phase for in vitro and in vivo treatments. In summary, AAG (NA, HDA) at non-toxic concentration was able to elicit anti-tumor effects in DL bearing mice by stimulating the innate immune system and Th1 type immunomodulation.

Acute demyelinating encephalitis after jequirity pea ingestion (Abrus precatorius)

INTRODUCTION

Castor and jequirity beans are uncommon causes of poisoning. The more common but less severe castor poisoning is well described, but jequirity bean (Abrus Precatorius) poisoning is rare. The toxicity is attributed to toxalbumins (ricin and abrin) that act by inhibiting protein synthesis. Their use as agents of biological warfare, mechanisms of action, and clinical features of poisoning are summarized.

CASE REPORT

A 30-year-old previously healthy female presented with bloody diarrhea and deep coma following ingestion of 3-4 seeds of a plant called 'ratti.' Investigations, including an MRI brain scan, showed evidence of acute demyelinating encephalitis. The patient died three days later due to progressive central nervous system depression.

DISCUSSION

This is a previously unreported manifestation of jequirity bean poisoning. Demyelination is immune-mediated, and Abrus is a well-known immuno-modulator and stimulator. A possible immunological pathogenic mechanism is hypothesized.