Structural studies of the interaction of Crataeva tapia bark protein with heparin and other glycosaminoglycans

Cutaneous Melanoma: An Overview of Physiological and Therapeutic Aspects and Biotechnological Use of Serine Protease Inhibitors

BACKGROUND

Metastatic melanoma stands out as the most lethal form of skin cancer because of its high propensity to spread and its remarkable resistance to treatment methods.

METHODS

In this review article, we address the incidence of melanoma worldwide and its staging phases. We thoroughly investigate the different melanomas and their associated risk factors. In addition, we underscore the principal therapeutic goals and pharmacological methods that are currently used in the treatment of melanoma.

RESULTS

The implementation of targeted therapies has contributed to improving the approach to patients. However, because of the emergence of resistance early in treatment, overall survival and progression-free periods continue to be limited.

CONCLUSIONS

We provide new insights into plant serine protease inhibitor therapeutics, supporting high-throughput drug screening soon, and seeking a complementary approach to explain crucial mechanisms associated with melanoma.

Crataeva nurvala Bark (Capparidaceae) Extract Modulates Oxidative Stress-Related Gene Expression, Restores Antioxidant Enzymes, and Prevents Oxidative Stress in the Kidney and Heart of 2K1C Rats

Objective

Crataeva nurvala is a medicinal plant, which contains a wide range of polyphenolic and bioactive compounds. The aim of the study was to evaluate the renal-protective activity of Crataeva nurvala in two-kidney, one-clip (2K1C) rats.

Methods

In this study, the ethanol extract of Crataeva nurvala bark at a dose of 100 mg/kg was orally used to treat 2K1C rats for four weeks. At the end of the experiment, all rats were sacrificed and tissue samples were collected for further biochemical and histological assessments.

Results

This investigation showed that Crataeva nurvala treatment prevented the kidney dysfunction in 2K1C rats. Uric acid and creatinine concentration and CK-MB activities increased in 2K1C rats which were normalized by Crataeva nurvala. 2K1C rats also showed increased oxidative stress, depicted by the elevated level of MDA, NO, and APOP in plasma and tissues. Oxidative stress parameters declined in 2K1C rats by the treatment of Crataeva nurvala. These results could be attributed to the restoration of antioxidant enzyme activities such as catalase and SOD. Crataeva nurvala extracts also upregulated antioxidant gene expression in the kidneys of 2K1C rats. Moreover, several anti-inflammatory genes were suppressed by Crataeva nurvala treatment in 2K1C rats. Furthermore, fibrosis and collagen deposition in the kidneys were also lowered by the treatment of the Crataeva nurvala extract.

Conclusion

The experimental data suggest that the Crataeva nurvala extract protected renal damage and oxidative stress, probably by restoring antioxidant enzymes activities in 2K1C rats.

Impairment of SK-MEL-28 Development-A Human Melanoma Cell Line-By the Crataeva tapia Bark Lectin and Its Sequence-Derived Peptides

Melanoma is difficult to treat with chemotherapy, prompting the need for new treatments. Protease inhibitors have emerged as promising candidates as tumor cell proteases promote metastasis. Researchers have developed a chimeric form of the Bauhinia bauhinioides kallikrein inhibitor, rBbKIm, which has shown negative effects on prostate tumor cell lines DU145 and PC3. Crataeva tapia bark lectin, CrataBL, targets sulfated oligosaccharides in glycosylated proteins and has also demonstrated deleterious effects on prostate and glioblastoma tumor cells. However, neither rBbKIm nor its derived peptides affected the viability of SK-MEL-28, a melanoma cell line, while CrataBL decreased viability by over 60%. Two peptides, Pep. 26 (Ac-Q-N-S-S-L-K-V-V-P-L-NH2) and Pep. 27 (Ac-L-P-V-V-K-L-S-S-N-Q-NH2), were also tested. Pep. 27 suppressed cell migration and induced apoptosis when combined with vemurafenib, while Pep. 26 inhibited cell migration and reduced nitric oxide and the number of viable cells. Vemurafenib, a chemotherapy drug used to treat melanoma, was found to decrease the release of interleukin 8 and PDGF-AB/BB cytokines and potentiated the effects of proteins and peptides in reducing these cytokines. These findings suggest that protease inhibitors may be effective in blocking melanoma cells and highlight the potential of CrataBL and its derived peptides.

Sources, Extraction and Biomedical Properties of Polysaccharides

In the recent era, bioactive compounds from plants have received great attention because of their vital health-related activities, such as antimicrobial activity, antioxidant activity, anticoagulant activity, anti-diabetic activity, UV protection, antiviral activity, hypoglycemia, etc. Previous studies have already shown that polysaccharides found in plants are not likely to be toxic. Based on these inspirational comments, most research focused on the isolation, identification, and bioactivities of polysaccharides. A large number of biologically active polysaccharides have been isolated with varying structural and biological activities. In this review, a comprehensive summary is provided of the recent developments in the physical and chemical properties as well as biological activities of polysaccharides from a number of important natural sources, such as wheat bran, orange peel, barely, fungi, algae, lichen, etc. This review also focused on biomedical applications of polysaccharides. The contents presented in this review will be useful as a reference for future research as well as for the extraction and application of these bioactive polysaccharides as a therapeutic agent.

A Bifunctional Molecule with Lectin and Protease Inhibitor Activities Isolated from Crataeva tapia Bark Significantly Affects Cocultures of Mesenchymal Stem Cells and Glioblastoma Cells

Currently available drugs for treatment of glioblastoma, the most aggressive brain tumor, remain inefficient, thus a plethora of natural compounds have already been shown to have antimalignant effects. However, these have not been tested for their impact on tumor cells in their microenvironment-simulated cell models, e.g., mesenchymal stem cells in coculture with glioblastoma cell U87 (GB). Mesenchymal stem cells (MSC) chemotactically infiltrate the glioblastoma microenvironment. Our previous studies have shown that bone-marrow derived MSCs impair U87 growth and invasion via paracrine and cell–cell contact-mediated cross-talk. Here, we report on a plant-derived protein, obtained from Crataeva tapia tree Bark Lectin (CrataBL), having protease inhibitory/lectin activities, and demonstrate its effects on glioblastoma cells U87 alone and their cocultures with MSCs. CrataBL inhibited U87 cell invasion and adhesion. Using a simplified model of the stromal microenvironment, i.e., GB/MSC direct cocultures, we demonstrated that CrataBL, when added in increased concentrations, caused cell cycle arrest and decreased cocultured cells’ viability and proliferation, but not invasion. The cocultured cells’ phenotypes were affected by CrataBL via a variety of secreted immunomodulatory cytokines, i.e., G-CSF, GM-CSF, IL-6, IL-8, and VEGF. We hypothesize that CrataBL plays a role by boosting the modulatory effects of MSCs on these glioblastoma cell lines and thus the effects of this and other natural lectins and/or inhibitors would certainly be different in the tumor microenvironment compared to tumor cells alone. We have provided clear evidence that it makes much more sense testing these potential therapeutic adjuvants in cocultures, mimicking heterogeneous tumor–stroma interactions with cancer cells in vivo. As such, CrataBL is suggested as a new candidate to approach adjuvant treatment of this deadly tumor.

The Plant Proteinase Inhibitor CrataBL Plays a Role in Controlling Asthma Response in Mice

Background. CrataBL is a protein isolated from Crataeva tapia bark. It has been shown to exhibit several biological properties, including anti-inflammatory, analgesic, antitumor, and insecticidal activities. There are no studies evaluating the role of CrataBL in experimental asthma models. Aim. To evaluate the effects of CrataBL on lung mechanics, inflammation, remodeling, and oxidative stress activation of mice with allergic pulmonary inflammation. Materials and Methods. BALB/c mice (6-7 weeks old, 25-30g) were divided into four groups: nonsensitized and nontreated mice (C group, n=8); ovalbumin- (OVA-) sensitized and nontreated mice (OVA group, n=8); nonsensitized and CrataBL-treated mice (C+CR group, n=8); OVA-sensitized and CrataBL-treated mice (OVA+CR group, n=8). We evaluated hyperresponsiveness to methacholine, bronchoalveolar lavage fluid (BALF), pulmonary inflammation, extracellular matrix remodeling, and oxidative stress markers. Results. CrataBL treatment in OVA-sensitized mice (OVA+CR group) attenuated the following variables compared to OVA-sensitized mice without treatment (OVA group) (all p<0.05): (1) respiratory system resistance (Rrs) and elastance (Ers) after methacholine challenge; (2) total cells, macrophages, polymorphonuclear cells, and lymphocytes in BALF; (3) eosinophils and volume fraction of collagen and elastic fibers in the airway and alveolar wall according to histopathological and morphometry analysis; (4) IL-4-, IL-5-, IL-13-, IL-17-, IFN-γ-, MMP-9-, TIMP-1-, TGF-β-, iNOS-, and NF-kB-positive cells and volume of 8-iso-PGF2α in airway and alveolar septa according to immunohistochemistry; and (5) IL-4, IL-5, and IFN-γ according to an ELISA. Conclusion. CrataBL contributes to the control of hyperresponsiveness, pulmonary inflammation, extracellular matrix remodeling, and oxidative stress responses in an animal model of chronic allergic pulmonary inflammation.

Binding kinetics of ultrasmall gold nanoparticles with proteins

Synthetic ultrasmall nanoparticles (NPs) can be designed to interact with biologically active proteins in a controlled manner. However, the rational design of NPs requires a clear understanding of their interactions with proteins and the precise molecular mechanisms that lead to association/dissociation in biological media. Although much effort has been devoted to the study of the kinetics mechanism of protein corona formation on large NPs, the nature of NP-protein interactions in the ultrasmall regime is radically different and poorly understood. Using a combination of experimental and computational approaches, we studied the interactions of a model protein, CrataBL, with ultrasmall gold NPs passivated with p-mercaptobenzoic acid (AuMBA) and glutathione (AuGSH). We have identified this system as an ideal in vitro platform to understand the dependence of binding affinity and kinetics on NP surface chemistry. We found that the structural and chemical complexity of the passivating NP layer leads to quite different association kinetics, from slow and reaction-limited (AuGSH) to fast and diffusion-limited (AuMBA). We also found that the otherwise weak and slow AuGSH-protein interactions measured in buffer solution are enhanced in macromolecular crowded solutions. These findings advance our mechanistic understanding of biomimetic NP-protein interactions in the ultrasmall regime and have implications for the design and use of NPs in the crowded conditions common to all biological media.

The 2.8 Å Electron Microscopy Structure of Adeno-Associated Virus-DJ Bound by a Heparinoid Pentasaccharide

Atomic structures of adeno-associated virus (AAV)-DJ, alone and in complex with fondaparinux, have been determined by cryoelectron microscopy at 3 Å resolution. The gene therapy vector, AAV-DJ, is a hybrid of natural serotypes that was previously derived by directed evolution, selecting for hepatocyte entry and resistance to neutralization by human serum. The structure of AAV-DJ differs from that of parental serotypes in two regions where neutralizing antibodies bind, so immune escape appears to have been the primary driver of AAV-DJ's directed evolution. Fondaparinux is an analog of cell surface heparan sulfate to which several AAVs bind during entry. Fondaparinux interacts with viral arginines at a known heparin binding site, without the large conformational changes whose presence was controversial in low-resolution imaging of AAV2-heparin complexes. The glycan density suggests multi-modal binding that could accommodate sequence variation and multivalent binding along a glycan polymer, consistent with a role in attachment, prior to more specific interactions with a receptor protein mediating entry.

Insights into the effects of glycosylation and the monosaccharide-binding activity of the plant lectin CrataBL

CrataBL is a glycoprotein isolated from Crataeva tapia bark, containing two N-glycosylation sites. It has been identified to present lectin activity with some specificity for binding glucose over galactose. However, to date, no information on the effects of glycosylation or CrataBL monosaccharide-binding sites and monosaccharide specificity has been obtained. Thus, molecular docking and molecular dynamics simulations were employed to characterize the glycosylated CrataBL conformation and dynamics in aqueous solutions, as well as the molecular basis for its binding specificity. The obtained results indicate both local and distant conformational stabilization effects of N-linked glycans over CrataBL protein moiety. Regarding its lectin activity, molecular docking calculations were performed in two possible binding sites, identified through sequence-based, structure-based and evolutionary information, using α- and β-anomeric states of the monosaccharides. The obtained poses were further refined through molecular dynamics simulations, suggesting that positively-charged amino acids dictate the binding preference for glucose over galactose in both sites. In addition, a possible preference for β-monosaccharides was proposed. Such data are expected to contribute to a better comprehension of the lectins monosaccharide-binding activities and carbohydrate-binding site structures.

Potential of the Lectin/Inhibitor Isolated from Crataeva tapia Bark (CrataBL) for Controlling Callosobruchus maculatus Larva Development

Callosobruchus maculatus is an important predator of cowpeas. Due to infestation during storage, this insect affects the quality of seed and crop yield. This study aimed to investigate the effects of CrataBL, a multifunction protein isolated from Crataeva tapia bark, on C. maculatus larva development. The protein, which is stable even in extreme pH conditions, showed toxic activity, reducing the larval mass 45 and 70% at concentrations of 0.25 and 1.0% (w/w), respectively. Acting as an inhibitor, CrataBL decreased by 39% the activity of cysteine proteinases from larval gut. Conversely, the activity of serine proteinases was increased about 8-fold. The toxic properties of CrataBL may also be attributed to its capacity of binding to glycoproteins or glycosaminoglycans. Such binding interferes with larval metabolism, because CrataBL-FITC was found in the fat body, Malpighian tubules, and feces of larvae. These results demonstrate the potential of this protein for controlling larva development.

CrataBL, a lectin and Factor Xa inhibitor, plays a role in blood coagulation and impairs thrombus formation

Arterial thrombosis is an important complication of diabetes and cancer, being an important target for therapeutic intervention. Crataeva tapia bark lectin (CrataBL) has been previously shown to have hypoglycemiant effect and also to induce cancer cell apoptosis. It also showed inhibitory activity against Factor Xa (Kiapp=8.6 μm). In the present study, we evaluated the anti-thrombotic properties of CrataBL in arterial thrombosis model. CrataBL prolongs the activated partial thromboplastin time on human and mouse plasma, and it impairs the heparin-induced potentiation of antithrombin III and heparin-induced platelet activation in the presence of low-dose ADP. It is likely that the dense track of positive charge on CrataBL surface competes with the heparin ability to bind to antithrombin III and to stimulate platelets. In the photochemically induced thrombosis model in mice, in the groups treated with 1.25, 5.0, or 10 mg/kg CrataBL, prior to the thrombus induction, the time of total artery occlusion was prolonged by 33.38%, 65%, and 66.11%, respectively, relative to the time of the control group. In contrast to heparin, the bleeding time in CrataBL-treated mice was no longer than in the control. In conclusion, CrataBL was effective in blocking coagulation and arterial thrombus formation, without increasing bleeding time.

Characterization of interactions between heparin/glycosaminoglycan and adeno-associated virus

Adeno-associated virus (AAV) is a key candidate in the development of gene therapy. In this work, we used surface plasmon resonance spectroscopy to study the interaction between AAV and heparin and other glycosaminoglycans (GAGs). Surface plasmon resonance results revealed that heparin binds to AAV with an extremely high affinity. Solution competition studies showed that binding of AAV to heparin is chain length-dependent. AAV prefers to bind full chain heparin. All sulfo groups (especially N-sulfo and 6-O-sulfo groups) on heparin are important for the AAV-heparin interaction. Higher levels of sulfo group substitution in GAGs enhance their binding affinities. Atomic force microscopy was also performed to image AAV-2 in a complex with heparin.

Crystal Structure of Crataeva tapia Bark Protein (CrataBL) and Its Effect in Human Prostate Cancer Cell Lines

A protein isolated from the bark of Crataeva tapia (CrataBL) is both a Kunitz-type plant protease inhibitor and a lectin. We have determined the amino acid sequence and three-dimensional structure of CrataBL, as well as characterized its selected biochemical and biological properties. We found two different isoforms of CrataBL isolated from the original source, differing in positions 31 (Pro/Leu); 92 (Ser/Leu); 93 (Ile/Thr); 95 (Arg/Gly) and 97 (Leu/Ser). CrataBL showed relatively weak inhibitory activity against trypsin (K_iapp = 43 µM) and was more potent against Factor Xa (K_iapp = 8.6 µM), but was not active against a number of other proteases. We have confirmed that CrataBL contains two glycosylation sites and forms a dimer at high concentration. The high-resolution crystal structures of two different crystal forms of isoform II verified the β-trefoil fold of CrataBL and have shown the presence of dimers consisting of two almost identical molecules making extensive contacts (∼645 Ų). The structure differs from those of the most closely related proteins by the lack of the N-terminal β-hairpin. In experiments aimed at investigating the biological properties of CrataBL, we have shown that addition of 40 µM of the protein for 48 h caused maximum growth inhibition in MTT assay (47% of DU145 cells and 43% of PC3 cells). The apoptosis of DU145 and PC3 cell lines was confirmed by flow cytometry using Annexin V/FITC and propidium iodide staining. Treatment with CrataBL resulted in the release of mitochondrial cytochrome c and in the activation of caspase-3 in DU145 and PC3 cells.