Dietary lectins can stimulate pancreatic growth in the rat

Differential Apoptotic and Mitogenic Effects of Lectins in Zebrafish

Plant lectins represent a major group of anti-nutritional factors that can be toxic to human and animals. However, the mechanisms by which lectins regulate cell fates are not well-understood. In the present study, the cellular and molecular impacts of three common lectins, agglutinins from wheat germ [wheat germ agglutinin (WGA)], soybean [soybean agglutinin (SBA)], and peanut [peanut agglutinin (PNA)] were examined in zebrafish embryo and liver cells. WGA and SBA were found to induce cell apoptosis both in vitro and in vivo, while PNA stimulated cell proliferation. WGA and SBA reduced levels of B cell lymphoma-2 (Bcl-2), phosphorylation of Bcl-2-associated death promoter (Bad), cyclin-dependent kinase 4 (Cdk4), and phosphorylation of the retinoblastoma (Rb). WGA and SBA also inhibited the activities of cell survival pathways including protein kinase B (Akt), extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), and target of rapamycin (Tor). Furthermore, WGA and SBA shifted the cellular metabolism characterized by reduced expression of glucose-6-phosphate dehydrogenase (g6pd) and increased expression of glutamine synthetase (glul) and glutamate dehydrogenase (glud). However, PNA showed the opposite effects toward these molecular markers compared to those of WGA and SBA. Therefore, our results revealed some plant lectins (WGA and SBA) were toxic while the other (PNA) was mitogenic. Further characterization of the distinct functions of individual lectins should be valuable for both nutrition and other potential applications.

Prognostic value, localization and correlation of PD-1/PD-L1, CD8 and FOXP3 with the desmoplastic stroma in pancreatic ductal adenocarcinoma

We examined the prognostic value of programmed cell death-1 (PD-1) and its ligand (PD-L1) together with CD8+ tumor-infiltrating lymphocytes (TILs) and FOXP3+ Tregs in resectable pancreatic ductal adenocarcinoma (PDAC) samples treated with adjuvant chemotherapy. Whole-mount FFPE tissue sections from 145 pancreatectomies were immunohistochemically stained for PD-1, PD-L1, CD8 and FOXP3. Their expression was correlated with clinicopathological characteristics, and overall survival (OS), progression-free survival (PFS), local progression-free survival (LPFS) and distant metastases free-survival (DMFS), in the context of stroma density (haematoxylin-eosin) and activity (alpha-smooth muscle actin) and in regard to intratumoral lymphoid aggregates. The median OS was 21 months after a mean follow-up of 20 months (range, 2-69 months). In multivariate analysis, high PD-1+ TILs expression was associated with better OS (p = 0.049), LPFS (p = 0.017) and DMFS (p = 0.021). Similar findings were observed for CD8+ TILs, whereas FOXP3 and PD-L1 lacked prognostic significance. Although TIL distribution was heterogeneous, tumors of high stroma density had higher infiltration of CD8+ TILs than loose density stroma and vice versa (p < 0.001), whereas no correlation was found with stromal activity. Sixty (41.4%) tumors contained lymphoid aggregates and the presence of PD-1+ TILs was associated with better OS (p = 0.030), LPFS (p = 0.025) and DMFS (p = 0.033), whereas CD8+ TILs only correlated with superior LPFS (p = 0.039). PD-1+ and CD8+ TILs constitute independent prognostic markers in patients with PDAC treated with adjuvant chemotherapy. Our study provides important insight on the role of PD-1/PD-L1 in the context of desmoplastic stroma and could help guide future immunotherapies in PDAC.

Effects of intragastrically-administered Tepary bean lectins on digestive and immune organs: Preclinical evaluation

Previous work showed that Tepary bean (Phaseolus acutifolius) lectins exhibit differential cytotoxic effects on cancer cell lines by apoptosis induction. In vivo studies using a Tepary bean lectin fraction (TBLF, 50 mg/kg of body weight) after colon cancer induction in rats showed that TBLF inhibited early precancerous lesions without systemic toxicity however, loss of body weight gain and activation of immune cells were observed. In order to know more about the possible adverse effects, we evaluated the administration of TBLF on digestive and immune organs. Sprague Dawley rats were administered TBLF for six weeks and allowed to recover for two weeks. Immune activation was observed through an increased lymphocyte-granulocyte ratio, an increased number of lymphoid follicles in intestinal Peyer's patches and a slight expansion of the splenic white pulp. Atrophy was observed in small intestine villi and crypt foci of the colon without normalization after the recovery period. Pancreas histopathology showed hypertrophy after the six-week administration period, particularly vacuolation and trabecular widening; but after the two-week recovery period atrophy was observed, suggesting a partial compensatory type process. Our results show that TBLF activates the immune system and affects digestive organs through direct interaction with intestinal epithelium, and indirectly by producing pancreatic hyperfunction. Further work will focus in longer recuperation periods after TBLF treatment.

Quantification of epithelial cell proliferation, cell dynamics, and cell kinetics in vivo

The measurement of cell proliferation in vivo is usually carried out by the examination of static measures. These comprise the mitotic index or labeling indices using incorporation of DNA synthesis markers such as bromodeoxyuridine or tritiated thymidine, or intrinsic markers, such as Ki67 and proliferative cell nuclear antigen (PCNA). But static measures only provide a 'snapshot' of cell proliferation. Rate measures, including double labeling methods and the metaphase arrest method, can actually measure cell production rates but they are far less utilized at present. Transit times and migration rates can also be measured using pulse and chase labeling or by following the transit of labeled cells through the tissue. Simple indices of cell division can easily be confounded by concomitant changes in the compartment size and many alleged markers of proliferation have serious shortcomings, as the markers may be involved in multiple aspects of cell regulation. The complexities of studying proliferation in vivo are illustrated here with a focus on the gastrointestinal tract. Some of these methods can help elucidate the role of the stem cells and their relationship to label retaining cells. WIREs Dev Biol 2017, 6:e274. doi: 10.1002/wdev.274 For further resources related to this article, please visit the WIREs website.

Dietary proteins and angiogenesis

Both defective and persistent angiogenesis are linked to pathological situations in the adult. Compounds able to modulate angiogenesis have a potential value for the treatment of such pathologies. Several small molecules present in the diet have been shown to have modulatory effects on angiogenesis. This review presents the current state of knowledge on the potential modulatory roles of dietary proteins on angiogenesis. There is currently limited available information on the topic. Milk contains at least three proteins for which modulatory effects on angiogenesis have been previously demonstrated. On the other hand, there is some scarce information on the potential of dietary lectins, edible plant proteins and high protein diets to modulate angiogenesis.

Lectin from Crataeva tapia Bark Improves Tissue Damages and Plasma Hyperglycemia in Alloxan-Induced Diabetic Mice

Crataeva tapia is a plant popularly used for diabetes treatment, in Brazil. Progressive decline in renal and hepatic functions has been described in patients with diabetes mellitus, and mortality rate is increased in patients with chronic liver and renal disease. This study aimed to evaluate whether Crataeva tapia bark lectin (CrataBL) improves hyperglycemia and renal and hepatic damage in diabetic mice. CrataBL was purified by ion exchange chromatography on CM-cellulose, and intraperitoneal administration of CrataBL to alloxan-induced diabetic mice at dose of 10 mg/Kg/day and 20 mg/Kg/day for 10 days significantly reduced serum glucose levels by 14.9% and 55.9%, respectively. Serum urea, creatinine, aspartate aminotransferase, and alanine aminotransferase were also significantly reduced after treatment with both doses of CrataBL. Furthermore, histological analysis of liver, kidney, and pancreas revealed an improvement in the tissue morphology upon treatment with CrataBL. The results suggest that CrataBL has a beneficial hypoglycemic activity and improves the renal and hepatic complications of diabetes. Therefore, this lectin may be a promising agent for the treatment of diabetes, and this might be the basis for its use in the folk medicine as an alternative treatment to manage diabetes-related complications such as hyperglycemia and tissue damage.

Stress-induced phosphorylation of caveolin-1 and p38, and down-regulation of EGFr and ERK by the dietary lectin jacalin in two human carcinoma cell lines

We have examined the A431 (human epidermoid carcinoma) and HT29 (human colorectal carcinoma) cellular responses evoked by lectins of dietary origin, Jacalin of Artocarpus integrifolia (native jacalin; nJacalin), peanut agglutinin (PNA) of Arachis hypogea, and recombinant single-chain jacalin (rJacalin), which has the same protein backbone but approximately 100-fold less affinity for carbohydrates than nJacalin. All three lectins (nJacalin, rJacalin, and PNA) are cycotoxic inhibitors of proliferation of A431 cells. However, cells recover once jacalin but not PNA have been removed from the growth medium. Treatment of nJacalin results in morphologically visible cell rounding while retaining the membrane integrity when treated at 40 microg ml(-1), but treatment with PNA did not induce such changes. The observed cell rounding was found to be due to stress as the phosphorylation of caveolin-1 (at tyr14), p38 but not c-Jun N-terminal kinase were up-regulated, while PNA did not up-regulate the phosphorylation of the same. Jacalin also down-regulated the phosphorylation of the epidermal growth factor receptor and extracellular signal regulated kinase in contrast to PNA, which failed to down-regulate the same. Confocal microscopic studies reveal that jacalin is not internalized, unlike the lectin of Agaricus bisporous. Analysis of the proteins that bind to an nJacalin-sepharose column revealed the binding of six to eight proteins, and significant among them is a protein at approximately 110 kDa, which appears to be oxygen-regulated protein 150 (ORP150) (endoplasmic reticulum chaperone) as identified by its isoelectric point, two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometric analysis. This 110-kDa band is detectable with anti-Hsp70 antibody because ORP150 has homology with Hsp70. Confocal microscopic studies reveal the presence of Hsp70-like proteins on the surface of A431 cells as revealed by immunostaining with anti-Hsp70 antibody. Moreover, overexpression of ORP150 in A431 cells has resulted in a dramatic protection of A431 cells against jacalin-induced toxicity, confirming that the jacalin-induced cytotoxicity is mediated through ORP150, and impairment of ORP150 functions with the help of jacalin makes the cells more susceptible to death due to stress. Our studies suggest that the cellular responses, as a consequence of lectin binding, may not be exclusively mediated by carbohydrate binding property alone, but other factors such as protein-protein interactions may also contribute to the observed cellular responses.

Fermented mushroom milk-supplemented dietary fibre prevents the onset of obesity and hypertriglyceridaemia in Otsuka Long-Evans Tokushima fatty rats

AIM

Fermented milk product containing edible mushroom water extracts (mushroom yogurt; MY) has been reported to have glycaemic control and triglyceride-lowering effects in streptozotocin (STZ)-induced diabetic rats and Zucker diabetic fatty (ZDF) rats. Here, we investigated how MY-supplemented dietary fibre (10 and 20%, v/w) influences the onset of obesity and hypertriglyceridaemia in Otsuka Long-Evans Tokushima fatty (OLETF) rats.

METHODS

The OLETF rats were fed a powdered chow diet supplemented with MY at the levels of 10 (v/w) and 20% for 6 weeks from 10 weeks of age, but the OLETF control rats were not supplemented. Their weight, fat distribution and lipid profile have been determined.

RESULTS

The body weights in MY-fed rats were reduced compared with the control rats. The perirenal fat was decreased in both MY groups, but the visceral and epididymal fats reduced only in the MY 20% group. The concentrations of serum triglyceride and non-esterified fatty acid in MY-fed rats were decreased in a dose-dependent manner. However, the levels of other serum lipid profiles [total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol] were comparable among all rats.

CONCLUSION

Anti-obesity and triglyceride lowering by MY-supplemented dietary fibre in OLETF rats might have resulted from the synergistic effect of components in the fermented mushroom-milk product.

Tannins, trypsin inhibitors and lectin cytotoxicity in tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) beans

This study compared the levels of antinutritional components and cytotoxic effect of extracts, from tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) beans. Antinutritional factors were evaluated by determining their effect on the viability of epithelial cells isolated from rat small intestine. The protein and carbohydrates content were similar in all the genotypes studied (20 and 60%, respectively). Common beans presented higher content of trypsin inhibitors, tannins and lectins than tepary beans. There was not a significant correlation between tannins and cooking time. However, water absorption and cooking time correlated significantly (p < 0.05). Considerable variation was observed in lectin activity (1302-18161 Ul/mg) of extracts from different beans. Tannins, lectins, trypsin inhibitors and fat content differed between bean varieties whereas protein content was similar. The percent cellularity on rat epithelial cells was significantly different among protein extracts from different bean cultivars and ranged between 53.5% and 87.4% (p < 0.05). These results suggest that the incorporation of tepary beans in the diet would not alter the current nutritional contribution of common beans or introduce adverse toxic effects. The agronomic characteristics of tepary beans make them attractive for cultivation. However, the harder to cook phenomenon may be a limiting factor that needs further consideration.

Lectins as Bioactive Plant Proteins: A Potential in Cancer Treatment

Plant lectins, a unique group of proteins and glycoproteins with potent biological activity, occur in foods like wheat, corn, tomato, peanut, kidney bean, banana, pea, lentil, soybean, mushroom, rice, and potato. Thus, dietary intakes by humans can be significant. Many lectins resist digestion, survive gut passage, and bind to gastrointestinal cells and/or enter the circulation intact, maintaining full biological activity. Several lectins have been found to possess anticancer properties in vitro, in vivo, and in human case studies; they are used as therapeutic agents, preferentially binding to cancer cell membranes or their receptors, causing cytotoxicity, apoptosis, and inhibition of tumor growth. These compounds can become internalized into cells, causing cancer cell agglutination and/or aggregation. Ingestion of lectins also sequesters the available body pool of polyamines, thereby thwarting cancer cell growth. They also affect the immune system by altering the production of various interleukins, or by activating certain protein kinases. Lectins can bind to ribosomes and inhibit protein synthesis. They also modify the cell cycle by inducing non-apoptotic G1-phase accumulation mechanisms, G2/M phase cell cycle arrest and apoptosis, and can activate the caspase cascade. Lectins can also downregulate telomerase activity and inhibit angiogenesis. Although lectins seem to have great potential as anticancer agents, further research is still needed and should include a genomic and proteomic approach.

Detection of water soluble lectin and antioxidant component from Moringa oleifera seeds

Seed flour from Moringa oleifera is widely used as a natural coagulant for water treatment in developing countries. Extracts obtained by water soaking of M. oleifera intact seeds were investigated for the presence of lectin, trypsin inhibitor, tannin as well as antioxidant activity. A water soluble M. oleifera lectin (WSMoL) detected was mainly active with rabbit cells at pH 4.5; heat treatment, pH 7.0, fructose and porcine thyroglobulin abolished HA of WSMoL. Trypsin inhibitor or tannins were not detected; the antioxidant component (WSMoAC) reduced 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) was slower than catechin and was thermostable. The extracts showed a primary glycopolypeptide band of Mw 20,000; the main native acidic protein showed hemagglutinating activity. WSMoL may be involved in seed coagulant properties.

Antinutritional properties of plant lectins

Lectins are carbohydrate binding (glyco)proteins which are ubiquitous in nature. In plants, they are distributed in various families and hence ingested daily in appreciable amounts by both humans and animals. One of the most nutritionally important features of plant lectins is their ability to survive digestion by the gastrointestinal tract of consumers. This allows the lectins to bind to membrane glycosyl groups of the cells lining the digestive tract. As a result of this interaction a series of harmful local and systemic reactions are triggered placing this class of molecules as antinutritive and/or toxic substances. Locally, they can affect the turnover and loss of gut epithelial cells, damage the luminal membranes of the epithelium, interfere with nutrient digestion and absorption, stimulate shifts in the bacterial flora and modulate the immune state of the digestive tract. Systemically, they can disrupt lipid, carbohydrate and protein metabolism, promote enlargement and/or atrophy of key internal organs and tissues and alter the hormonal and immunological status. At high intakes, lectins can seriously threaten the growth and health of consuming animals. They are also detrimental to numerous insect pests of crop plants although less is presently known about their insecticidal mechanisms of action. This current review surveys the recent knowledge on the antinutritional/toxic effects of plant lectins on higher animals and insects.