Isothiocyanates as Tubulin Polymerization Inhibitors-Synthesis and Structure-Activity Relationship Studies

Among the various substances that interfere with the microtubule formation process, isothiocyanates (ITCs) are the group of compounds for which the binding mode and mechanism of action have not yet been explained. To better understand the structure-activity relationship of tubulin-isothiocyanate interactions, we designed and synthesized a series of sixteen known and novel, structurally diverse ITCs, including amino acid ester-derived isothiocyanates, bis-isothiocyanates, analogs of benzyl isothiocyanate, and phosphorus analogs of sulforaphane. All synthesized compounds and selected natural isothiocyanates (BITC, PEITC, AITC, and SFN) were tested in vitro to evaluate their antiproliferative activity, tubulin polymerization inhibition potential, and influence on cell cycle progression. The antiproliferative activity of most of the newly tested compounds exceeded the action of natural isothiocyanates, with four structures being more potent as tubulin polymerization inhibitors than BITC. As a confirmation of anti-tubulin activity, the correlation between polymerization inhibition and cell cycle arrest in the G2/M phase was observed for the most active compounds. In light of the biological results indicating significant differences in the impact of structurally diverse isothiocyanate on tubulin polymerization, in silico analysis was conducted to analyze the possible mode of isothiocyanate-tubulin binding and to show how it can influence the polymerization reaction.

IgYs: on her majesty's secret service

There has been an increasing interest in using Immunoglobulin Y (IgY) antibodies as an alternative to "classical" antimicrobials. Unlike traditional antibiotics, they can be utilized on a continual basis without leading to the development of resistance. The veterinary IgY antibody market is growing because of the demand for minimal antibiotic use in animal production. IgY antibodies are not as strong as antibiotics for treating infections, but they work well as preventative agents and are natural, nontoxic, and easy to produce. They can be administered orally and are well tolerated, even by young animals. Unlike antibiotics, oral IgY supplements support the microbiome that plays a vital role in maintaining overall health, including immune system function. IgY formulations can be delivered as egg yolk powder and do not require extensive purification. Lipids in IgY supplements improve antibody stability in the digestive tract. Given this, using IgY antibodies as an alternative to antimicrobials has garnered interest. In this review, we will examine their antibacterial potential.

Novel inhibitors of HSV-1 protease effective in vitro and in vivo

Herpes simplex virus type 1 (HSV-1) is a widespread human pathogen known to cause infections of diverse severity, ranging from mild ulceration of mucosal and dermal tissues to life-threatening viral encephalitis. In most cases, standard treatment with acyclovir is sufficient to manage the disease progression. However, the emergence of ACV-resistant strains drives the need for new therapeutics and molecular targets. HSV-1 VP24 is a protease indispensable for the assembly of mature virions and, as such, constitutes an interesting target for the therapy. In this study, we present novel compounds, KI207M and EWDI/39/55BF, that block the activity of VP24 protease and consequently inhibit HSV-1 infection in vitro and in vivo. The inhibitors were shown to prevent the egress of viral capsids from the cell nucleus and suppress the cell-to-cell spread of the infection. They were also proven effective against ACV-resistant HSV-1 strains. Considering their low toxicity and high antiviral potency, the novel VP24 inhibitors could provide an alternative for treating ACV-resistant infections or a drug to be used in combined, highly effective therapy.

The prevalence and role of functional autoantibodies to angiotensin-converting-enzyme-2 in patients with systemic sclerosis

INTRODUCTION

Systemic sclerosis (SSc) is an autoimmune disease caused by the imbalance between the activity of angiotensin II and angiotensin-(1-7). Their balance should be controlled by angiotensin-converting enzyme 2 (ACE2), which degrades angiotensin II into angiotensin-(1-7). Previously, autoantibodies to ACE2 (anti-ACE2) were identified in patients with vasculopathy due to different connective tissue diseases, including SSc, but their frequency in SSc was not further analyzed. The aim of the research was to investigate the prevalence and potential role of those anti-ACE2 antibodies in SSc patients.

MATERIALS AND METHODS

There were enrolled 27 patients with SSc and 23 healthy donors. ELISA assay determined the presence of anti-ACE2 autoantibodies in serum samples. The results were compared to plasma measurements of angiotensin-(1-7) level via commercial ELISA.

RESULTS

The presence of anti-ACE2 autoantibodies was confirmed in five patients with SSc and two healthy controls. Two of those SSc subjects were anti-Scl70+, another two were double anti-Scl70+ and anti-Ro/SSA+, and anti-PM/Scl antibodies were detected in one patient. Median plasma level of Ang-(1-7) in anti-ACE2 negative patients was 47.4 pg/ml and stayed below the detection level in anti-ACE2 positive subjects. The plasma level of Ang-(1-7) was undetectable in four SSc patients, and three of them were anti-ACE2 positive.

CONCLUSIONS

Anti-ACE2 antibodies appear to be other functional autoantibodies with the potential to dysregulate the balance between Ang II and Ang-(1-7). They are non-specific for SSc and probably result from polyautoimmunity which affect some of SSc patients. Their occurrence in SSc settings may be associated with a severe depletion of plasma Ang-(1-7).

Human proteinase 3 resistance to inhibition extends to alpha-2 macroglobulin

Polymorphonuclear neutrophils contain at least four serine endopeptidases, namely neutrophil elastase (NE), proteinase 3 (PR3), cathepsin G (CatG), and NSP4, which contribute to the regulation of infection and of inflammatory processes. In physiological conditions, endogenous inhibitors including α2-macroglobulin (α2-M), serpins [α1-proteinase inhibitor (α1-PI)], monocyte neutrophil elastase inhibitor (MNEI), α1-antichymotrypsin, and locally produced chelonianins (elafin, SLPI) control excessive proteolytic activity of neutrophilic serine proteinases. In contrast to human NE (hNE), hPR3 is weakly inhibited by α1-PI and MNEI but not by SLPI. α2-M is a large spectrum inhibitor that traps a variety of proteinases in response to cleavage(s) in its bait region. We report here that α2-M was more rapidly processed by hNE than hPR3 or hCatG. This was confirmed by the observation that the association between α2-M and hPR3 is governed by a k_ass in the ≤ 10⁵  m^-1 ·s^-1 range. Since α2-M-trapped proteinases retain peptidase activity, we first predicted the putative cleavage sites within the α2-M bait region (residues 690-728) using kinetic and molecular modeling approaches. We then identified by mass spectrum analysis the cleavage sites of hPR3 in a synthetic peptide spanning the 39-residue bait region of α2-M (39pep-α2-M). Since the 39pep-α2-M peptide and the corresponding bait area in the whole protein do not contain sequences with a high probability of specific cleavage by hPR3 and were indeed only slowly cleaved by hPR3, it can be concluded that α2-M is a poor inhibitor of hPR3. The resistance of hPR3 to inhibition by endogenous inhibitors explains at least in part its role in tissue injury during chronic inflammatory diseases and its well-recognized function of major target autoantigen in granulomatosis with polyangiitis.

Development and Evaluation of an Immunoglobulin Y-Based ELISA for Measuring Prostate Specific Antigen in Human Serum

Background

Measurement of serum prostate specific antigen (PSA) concentrations remains one of the leading methods for diagnosing prostate cancer. We developed and evaluated an immunoglobulin Y (IgY)-based ELISA to measure total PSA (tPSA) concentrations in human serum that could be used as an alternative to commercially available in vitro diagnostic assays that rely on mouse monoclonal IgG.

Methods

A sandwich ELISA based on an anti-PSA IgY antibody was developed. We evaluated the ability of the anti-PSA IgY antibody to detect free and complexed PSA at the same molar ratio. The assay was optimized, and its analytical performance was verified by calculating limit of background (LoB), limit of detection (LoD), and limit of quantification (LoQ). We performed correlation and regression analyses between tPSA concentrations measured by our ELISA and those from commercial assays: Cobas 6000 (Roche Diagnostics, Warszawa, Poland) and PSA total ELISA (IBL International, Hamburg, Germany).

Results

LoB, LoD, and LoQ, were 0.061, 0.083, and 0.100 ng/mL, respectively, and linearity range was 0.100–3.375 ng/mL. tPSA concentrations from our IgY-based ELISA strongly correlated with those from the commercial assays.

Conclusions

Our IgY-based ELISA is an efficient equivalent to the above commercial assays. The use of IgY as the detecting agent could reduce the risk of false positive results, as well as decrease the overall cost of analysis.

One Step Beyond: Design of Substrates Spanning Primed Positions of Zika Virus NS2B-NS3 Protease

Although the mosquito-borne Zika virus was discovered in the late 1940s of the 20th century, for years it was neglected, as the disease in humans was rare and relatively mild. Viral NS2B-NS3 protease is essential for virus replication, and except for maturation of viral proteins, it also modulates the infection microenvironment to facilitate virus invasion. Here, we report the combinatorial chemistry approach for the synthesis of internally quenched substrates of the Zika virus NS2B-NS3 protease that were optimized in prime positions of the peptide chain. Final substrate ABZ-Val-Lys-Lys-Arg-Ala-Ala-Trp-Tyr(3-NO₂)-NH₂ displays an excellent kinetic parameter (k _cat/K _M reaching nearly 1.26 × 10⁸ M^-1 × s^-1), which is over 10 times greater than previously reported (7.7 × 10⁶ M^-1 × s^-1) substrate. Moreover, it was found to be selective over West Nile virus protease.

Exploiting the S4-S5 Specificity of Human Neutrophil Proteinase 3 to Improve the Potency of Peptidyl Di(chlorophenyl)-phosphonate Ester Inhibitors: A Kinetic and Molecular Modeling Analysis

The neutrophilic serine protease proteinase 3 (PR3) is involved in inflammation and immune response and thus appears as a therapeutic target for a variety of infectious and inflammatory diseases. Here we combined kinetic and molecular docking studies to increase the potency of peptidyl-diphenyl phosphonate PR3 inhibitors. Occupancy of the S1 subsite of PR3 by a nVal residue and of the S4-S5 subsites by a biotinylated Val residue as obtained in biotin-VYDnV^P(O-C₆H₄-4-Cl)₂ enhanced the second-order inhibition constant k_obs/[I] toward PR3 by more than 10 times ( k_obs/[I] = 73000 ± 5000 M^-1 s^-1) as compared to the best phosphonate PR3 inhibitor previously reported. This inhibitor shows no significant inhibitory activity toward human neutrophil elastase and resists proteolytic degradation in sputa from cystic fibrosis patients. It also inhibits macaque PR3 but not the PR3 from rodents and can thus be used for in vivo assays in a primate model of inflammation.

Development of Adenosine Deaminase-Specific IgY Antibodies: Diagnostic and Inhibitory Application

Adenosine deaminase (ADA) is currently used as a diagnostic marker for tuberculous pleuritis. Although ADA has been suggested as a potential marker for several types of cancer, the importance of each of ADA isoforms as well as their levels and enzymatic activities in tumors need to be further investigated. Herein we developed avian immunoglobulin Y highly specific to human ADA via hens immunization with calf adenosine deaminase. The obtained antibodies were used for the development of a sensitive double-egg yolk immunoglobulin (IgY) sandwich ELISA assay with an ADA detection limit of 0.5 ng/ml and a linearity range of up to 10 ng/ml. Specific, affinity-purified IgYs were able to recognize human recombinant ADA and ADA present in human cancer cell lines. In addition, antigen-specific IgY antibodies were able to inhibit catalytic activity of calf ADA with an IC₅₀ value of 47.48 nM. We showed that generated IgY antibodies may be useful for ADA detection, thus acting as a diagnostic agent in immunoenzymatic assays.

Substrate profiling of Zika virus NS2B-NS3 protease

Zika virus (ZIKV), isolated from macaques in Uganda in 1947, was not considered to be a dangerous human pathogen. However, this view has recently changed as ZIKV infections are now associated with serious pathological disorders including microcephaly and Guillain-Barré syndrome. Similar to other viruses in the Flaviviridae family, ZIKV expresses the serine protease NS3 which is responsible for viral protein processing and replication. Herein, we report the expression of an active NS3^pro domain fused with the NS2B cofactor (NS2B_LN NS3^pro ) in a prokaryotic expression system and profile its specificity for synthesized FRET-type substrate libraries. Our findings pave way for screening potential intracellular substrates of NS3 and for developing specific inhibitors of this ZIKV protease.

Method for generation of peptide-specific IgY antibodies directed to Staphylococcus aureus extracellular fibrinogen binding protein epitope

The IgY antibodies offer an attractive alternative to mammalian IgGs in research, diagnosis and medicine. The isolation of immunoglobulin Y from the egg yolks is efficient and economical, causing minimal suffering to animals. Here we present the methodology for the production of IgY antibodies specific to Staphylococcus aureus fibrinogen binding protein (Efb) and its peptidyl epitope (spanning residues 127-140). The Efb is an extracellular, adhesion protein which binds both human fibrinogen and complement C3 protein thus contributing to the high infectious potential of this pathogen. The selected epitope of Efb protein is responsible for the interaction with C3. The immunochemical characterization of both anti-Efb and epitope-specific IgY antibodies revealed their similar avidity, titer, and reactivity profile, although some differences in the hen's immune response to administered antigens is discussed.

PEGylated substrates of NSP4 protease: A tool to study protease specificity

Herein we present the synthesis of a novel type of peptidomimetics composed of repeating diaminopropionic acid residues modified with structurally diverse heterobifunctional polyethylene glycol chains (abbreviated as DAPEG). Based on the developed compounds, a library of fluorogenic substrates was synthesized. Further library deconvolution towards human neutrophil serine protease 4 (NSP4) yielded highly sensitive and selective internally quenched peptidomimetic substrates. In silico analysis of the obtained peptidomimetics revealed the presence of an interaction network with distant subsites located on the enzyme surface.

Adjuvant-dependent immunogenicity of Staphylococcus aureus Efb and Map proteins in chickens

The avian IgY antibodies generated in hens and isolated from egg yolk have gained in popularity as they present an alternative source of antibodies for diagnostic as well as therapeutic applications. One of the advantages of IgY technology are the large amounts of produced antibodies from a single animal combined with their high reactivity representing an attractive alternative for mammalian antibodies. Despite many known protocols for the immunization of chickens, the administration of new antigens often requires additional modification such as antigen dose or use of an adjuvant in order to elicit a significant immune response. We investigated the immunogenicity of three Staphylococcus aureus antigens including two extracellular proteins Map and Efb and one selected Efb105-124 epitope conjugated to KLH that were administered to the animals. Additionally, the immunization protocol included two adjuvant systems: Freund's complete adjuvant and Emulsigen-D. The results demonstrated a high immunostimulatory potency of Freund's complete adjuvant, especially in case of Efb compared to the immune response elicited by Emulsigen-D. However, after immunization with the KLH-Efb105-124 conjugate, the obtained antibodies showed similar reactivity regardless of adjuvant system used with the only exception being their avidity.

Synthesis of novel phosphonic-type activity-based probes for neutrophil serine proteases and their application in spleen lysates of different organisms

Neutrophils are a type of granulocyte important in the "first line of defense" of the innate immune system. Upon activation, they facilitate the destruction of invading microorganisms by the production of superoxide radicals, as well as the release of the enzymatic contents of their lysozymes. These enzymes include specific serine proteases: cathepsin G, neutrophil elastase, proteinase 3, as well as the recently discovered neutrophil serine protease 4 (NSP4). Under normal conditions, the proteolytic activity of neutrophil proteases is tightly regulated by endogenous serpins; however, this mechanism can be subverted during tissue stress, thereby resulting in the uncontrolled activity of serine proteases, which induce chronic inflammation and subsequent pathology. Herein, we describe the development of low-molecular-weight activity-based probes that specifically target the active sites of neutrophil proteases.

Highly sensitive detection of cancer antigen 15-3 using novel avian IgY antibodies

Early detection of cancer development is crucial for successful therapy and for monitoring patient outcome. Various immunodiagnostic methods are able to detect pathological changes in the human body ahead of symptomatic manifestation of the disease. Most immunological examinations are based on the detection of specific tumor markers in body fluids. Of the various cancer-specific proteins used for breast cancer diagnostics, one of the most commonly applied is the cancer antigen 15-3 (CA 15-3). An elevation in its serum level (>25-40 U/ml) usually correlates with tumor malignancy. The CA 15-3 antigen is also used for monitoring patients after surgical treatment and for measuring therapeutic efficacy. Herein, we present the generation of polyclonal IgY antibodies isolated from egg yolks of immunized hens and their application for CA 15-3 detection. The developed sandwich ELISA assay showed a detection limit of 0.028 U/ml, thus demonstrating its potential for clinical applications.

Surface plasmon resonance imaging biosensor for cathepsin G based on a potent inhibitor: development and applications

A specific surface plasmon resonance imaging (SPRI) array biosensor for the determination of the enzymatically active cathepsin G (CatG) has been developed. For this purpose, a specific interaction between an inhibitor immobilized onto a chip surface and CatG in an analyzed solution was used. The MARS-115 CatG peptidyl inhibitor containing the 1-aminoalkylphosphonate diaryl ester moiety at the C terminus and N-succinamide with a free carboxylic function was synthesized and covalently immobilized onto the gold chip surface via the thiol group (cysteamine). Atomic force microscopy was used for the observation of surface changes during the subsequent steps of chip manufacture. Optimal detection conditions were chosen. High specificity of synthesized inhibitor to CatG was proved. The precision, as well as the accuracy, was found to be well suited to enzyme determination. The sensor application for the determination of CatG in white blood cells and saliva was shown for potential diagnosis of leukemia and oral cavity diseases during the early stages of those pathological states.

The molecular basis of urokinase inhibition: from the nonempirical analysis of intermolecular interactions to the prediction of binding affinity

Urokinase-type plasminogen activator (uPA) is a trypsin-like serine protease that plays a crucial role in angiogenesis process. In addition to its physiological role in healthy organisms, angiogenesis is extremely important in cancer growth and metastasis, resulting in numerous attempts to understand its control and to develop new approaches to anticancer therapy. The alpha-aminoalkylphosphonate diphenyl esters are well known as highly efficient serine protease inhibitors. However, their mode of binding has not been verified experimentally in details. For a group of average and potent phosphonic inhibitors of urokinase, flexible docking calculations were performed to gain an insight into the active site interactions responsible for observed enzyme inhibition. The docking results are consistent with the previously suggested mode of inhibitors binding. Subsequently, rigorous ab initio study of binding energy was carried out, followed by its decomposition according to the variation-perturbation procedure to reveal stabilization energy constituents with clear physical meaning. Availability of the experimental inhibitory activities and comparison with theoretical binding energy allows for the validation of theoretical models of inhibition, as well as estimation of the possible potential for binding affinity prediction. Since the docking results accompanied by molecular mechanics optimization suggested that several crucial active site contacts were too short, the optimal distances corresponding to the minimum ab initio interaction energy were also evaluated. Despite the deficiencies of force field-optimized enzyme-inhibitor structures, satisfactory agreement with experimental inhibitory activity was obtained for the electrostatic interaction energy, suggesting its possible application in the binding affinity prediction.

Novel hydroxamic acid-related phosphinates: inhibition of neutral aminopeptidase N (APN)

Here we describe the inhibitory activity toward neutral aminopeptidase of three new families of phosphinate inhibitors related in structure to hydroxamic acids. These compounds, even as racemic mixtures, are good inhibitors of APN and show strong structure activity relationship (SAR) depending on the substituents in P1 and P1' positions.

Expression of aminopeptidase N/CD13 in human ovarian cancers

Aminopeptidase N/CD13 (EC 3.4.11.2) is suggested to play a role in cancer cells invasion, and its activity can be inhibited using specific inhibitors. CD13 inhibitors evoke apoptosis of CD13-positive cancer cells. However, expression of CD13 has not been described in specimens obtained from ovarian carcinomas. Thus, in the present study, the expression of CD13 and its significance was examined in samples of ovarian cancers. The analyses were performed on sections originating from 73 tumor samples (43 from primary laparotomies [PL] and 30 from secondary cytoreductions [SCRs]). Immunohistochemical reactions were performed on paraffin sections of studied tumors, using monoclonal antibodies against CD13. The analysis demonstrated no relationships between the expression of CD13 on one hand and clinical variables and pathologic variables of the patients on the other hand. Expression of CD13 was demonstrated to be significantly more pronounced in samples obtained in PLs as compared to samples from SCRs (P < 0.001). Thus, the data indicate that a potential treatment of ovarian carcinoma with CD13 inhibitors should be performed before chemotherapy or in parallel to first-lapse chemotherapy.