Multiple binding modes of isothiocyanates that inhibit macrophage migration inhibitory factor

Covalent Isothiocyanate Inhibitors of Macrophage Migration Inhibitory Factor as Potential Colorectal Cancer Treatments

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that has roles in innate and adaptive human immune responses, as well as inflammation. MIF exerts its biological activity by binding to the cell surface receptor CD74 as well as intracellular signalling proteins. MIF also possesses keto-enol tautomerase activity. Inhibition of the tautomerase activity has been associated with loss of biological activity of MIF and a potential anticancer target. Isothiocyanates (ITCs) are a class of compounds present in cruciferous vegetables that inhibit the MIF tautomerase activity via covalent modification of the N-terminal proline. A range of substituted ITCs featuring benzyl, phenethyl and phenyl propyl isothiocyanates were designed, synthesised and tested to determine any structure activity relationship for inhibiting MIF. Crystal structures of covalent compounds 8 and 9 in complex with rhMIF revealed key hydrogen bonding and edge-to-face π stacking interactions. Compound 9 and 11 with sub micromolar activity were tested in the NCI60 cancer cell lines panel. Both compounds showed tissue-specific reduced growth in colon and renal cancer cell lines, while one of these showed potent, dose-dependent inhibition of growth against all seven colon cancer cell lines (GI50<2.5 μM) and all eight renal cancer cell lines (GI50<2.2 μM).

The Effects of Interventions with Glucosinolates and Their Metabolites in Cruciferous Vegetables on Inflammatory Bowel Disease: A Review

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract which affects millions of individuals worldwide. Despite advancements in treatment options, there is increasing interest in exploring natural interventions with minimal side effects. Cruciferous vegetables, such as broccoli, cabbage, and radishes, contain bioactive compounds known as glucosinolates (GLSs), which have shown promising effects in alleviating IBD symptoms. This review aims to provide a comprehensive overview of the physiological functions and mechanisms of cruciferous GLSs and their metabolites in the context of IBD. Reviewed studies demonstrated that GLSs attenuated all aspects of IBD, including regulating the intestinal microbiota composition, exerting antioxidant and anti-inflammatory effects, restoring intestinal barrier function, and regulating epigenetic mechanisms. In addition, a few interventions with GLS supplementation in clinical studies were also discussed. However, there are still several challenges and remaining knowledge gaps, including variations in animals' experimental outcomes, the bioavailability of certain compounds, and few clinical trials to validate their effectiveness in human subjects. Addressing these issues will contribute to a better understanding of the therapeutic potential of cruciferous GLSs and their metabolites in the management of IBD.

Nutritional Sources and Anticancer Potential of Phenethyl Isothiocyanate: Molecular Mechanisms and Therapeutic Insights

Phenethyl isothiocyanate (PEITC), a compound derived from cruciferous vegetables, has garnered attention for its anticancer properties. This review synthesizes existing research on PEITC, focusing on its mechanisms of action in combatting cancer. PEITC has been found to be effective against various cancer types, such as breast, prostate, lung, colon, and pancreatic cancers. Its anticancer activities are mediated through several mechanisms, including the induction of apoptosis (programmed cell death), inhibition of cell proliferation, suppression of angiogenesis (formation of new blood vessels that feed tumors), and reduction of metastasis (spread of cancer cells to new areas). PEITC targets crucial cellular signaling pathways involved in cancer progression, notably the Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB), Protein Kinase B (Akt), and Mitogen-Activated Protein Kinase (MAPK) pathways. These findings suggest PEITC's potential as a therapeutic agent against cancer. However, further research is necessary to determine the optimal dosage, understand its bioavailability, and assess potential side effects. This will be crucial for developing PEITC-based treatments that are both effective and safe for clinical use in cancer therapy.

Main group cyanides: from hydrogen cyanide to cyanido-complexes

Homoleptic cyanide compounds exist of almost all main group elements. While the alkali metals and alkaline earth metals form cyanide salts, the cyanides of the lighter main group elements occur mainly as covalent compounds. This review gives an overview of the status quo of main group element cyanides and cyanido complexes. Information about syntheses are included as well as applications, special substance properties, bond lengths, spectroscopic characteristics and computations. Cyanide chemistry is presented mainly from the field of inorganic chemistry, but aspects of chemical biology and astrophysics are also discussed in relation to cyano compounds.

Destabilization of macrophage migration inhibitory factor by 4-IPP reduces NF-κB/P-TEFb complex-mediated c-Myb transcription to suppress osteosarcoma tumourigenesis

BACKGROUND

As an inflammatory factor and oncogenic driver protein, the pleiotropic cytokine macrophage migration inhibitory factor (MIF) plays a crucial role in the osteosarcoma microenvironment. Although 4-iodo-6-phenylpyrimidine (4-IPP) can inactivate MIF biological functions, its anti-osteosarcoma effect and molecular mechanisms have not been investigated. In this study, we identified the MIF inhibitor 4-IPP as a specific double-effector drug for osteosarcoma with both anti-tumour and anti-osteoclastogenic functions.

METHODS

The anti-cancer effects of 4-IPP were evaluated by wound healing assay, cell cycle analysis, colony formation assay, CCK-8 assay, apoptosis analysis, and Transwell migration/invasion assays. Through the application of a luciferase reporter, chromatin immunoprecipitation assays, and immunofluorescence and coimmunoprecipitation analyses, the transcriptional regulation of the NF-κB/P-TEFb complex on c-Myb- and STUB1-mediated proteasome-dependent MIF protein degradation was confirmed. The effect of 4-IPP on tumour growth and metastasis was assessed using an HOS-derived tail vein metastasis model and subcutaneous and orthotopic xenograft tumour models.

RESULTS

In vitro, 4-IPP significantly reduced the proliferation and metastasis of osteosarcoma cells by suppressing the NF-κB pathway. 4-IPP hindered the binding between MIF and CD74 as well as p65. Moreover, 4-IPP inhibited MIF to interrupt the formation of downstream NF-κB/P-TEFb complexes, leading to the down-regulation of c-Myb transcription. Interestingly, the implementation of 4-IPP can mediate small molecule-induced MIF protein proteasomal degradation via the STUB1 E3 ligand. However, 4-IPP still interrupted MIF-mediated communication between osteosarcoma cells and osteoclasts, thus promoting osteoclastogenesis. Remarkably, 4-IPP strongly reduced HOS-derived xenograft osteosarcoma tumourigenesis and metastasis in an in vivo mouse model.

CONCLUSIONS

Our findings demonstrate that the small molecule 4-IPP targeting the MIF protein exerts an anti-osteosarcoma effect by simultaneously inactivating the biological functions of MIF and promoting its proteasomal degradation. Direct destabilization of the MIF protein with 4-IPP may be a promising therapeutic strategy for treating osteosarcoma.

Chemoinformatic Analysis of Isothiocyanates: Their Impact in Nature and Medicine

Isothiocyanates (ITCs) have a significant impact on food and natural product chemistry. Several dietary components and food chemicals contain the isothiocyanate moiety. In addition, many ITCs interact with macromolecules of biological relevance, making these compounds relevant for potential therapeutic applications and disease prevention. However, there is a lack of systematic analysis of ITCs in chemical and biological databases. Herein, we conducted a comprehensive analysis of ITCs present in public domain databases, including natural products, food chemicals, macromolecular targets of drugs, and the Protein Data Bank. A total of 154 ITCs were found, which can be classified into seven categories: acyclic, cyclic, polycyclic, aromatic, polyaromatic, indolic, and glycosylated. 24 ITCs were reported in 18 vegetable sources, mainly in cruciferous vegetables (Brassica oleracea L.). Calculated properties of pharmaceutical relevance indicated that 11 % of the 154 ITCs would be suitable to be orally absorbed and 48 % permeate the blood-brain-barrier. It was also found that seven molecular targets have been co-crystallized with ITCs and the most frequent is the macrophage migration inhibitory factor. It is expected that this work will contribute to the sub-disciplines of natural products and food informatics.

Targeting Macrophage Migration Inhibitory Factor in Acute Pancreatitis and Pancreatic Cancer

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine implicated in the pathogenesis of inflammation and cancer. It is produced by various cells and circulating MIF has been identified as a biomarker for a range of diseases. Extracellular MIF mainly binds to the cluster of differentiation 74 (CD74)/CD44 to activate downstream signaling pathways. These in turn activate immune responses, enhance inflammation and can promote cancer cell proliferation and invasion. Extracellular MIF also binds to the C-X-C chemokine receptors cooperating with or without CD74 to activate chemokine response. Intracellular MIF is involved in Toll-like receptor and inflammasome-mediated inflammatory response. Pharmacological inhibition of MIF has been shown to hold great promise in treating inflammatory diseases and cancer, including small molecule MIF inhibitors targeting the tautomerase active site of MIF and antibodies that neutralize MIF. In the current review, we discuss the role of MIF signaling pathways in inflammation and cancer and summarize the recent advances of the role of MIF in experimental and clinical exocrine pancreatic diseases. We expect to provide insights into clinical translation of MIF antagonism as a strategy for treating acute pancreatitis and pancreatic cancer.

7-Hydroxycoumarins Are Affinity-Based Fluorescent Probes for Competitive Binding Studies of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a cytokine with key roles in inflammation and cancer, which qualifies it as a potential drug target. Apart from its cytokine activity, MIF also harbors enzyme activity for keto–enol tautomerization. MIF enzymatic activity has been used for identification of MIF binding molecules that also interfere with its biological activity. However, MIF tautomerase activity assays are troubled by irregularities, thus creating a need for alternative methods. In this study, we identified a 7-hydroxycoumarin fluorophore with high affinity for the MIF tautomerase active site (K_i = 18 ± 1 nM) that binds with concomitant quenching of its fluorescence. This property enabled development of a novel competition-based assay format to quantify MIF binding. We also demonstrated that the 7-hydroxycoumarin fluorophore interfered with the MIF–CD74 interaction and inhibited proliferation of A549 cells. Thus, we provide a high-affinity MIF binder as a novel tool to advance MIF-oriented research.

Therapeutic potential of sulfur-containing natural products in inflammatory diseases

Owing to the prevalence of chronic inflammation and its related disorders, there is a demand for novel therapeutic agents capable of preventing or suppressing inflammation. Natural products (NPs) are well established as an important resource for drug development and provide an almost infinite array of molecular entities. Sulfur-containing NPs (i.e., NPs containing one or more sulfur atoms) are abundant throughout nature, from bacteria to animals. The aim of this review was to survey the emerging evidence on role of sulfur-containing NPs, such as glutathione, garlic-derived sulfur compounds, Epipolythiodioxopiperazines (EPTs), Isothiocyanates (ITCs), and Ergothioneine (EGT), in the control of inflammation and to determine the possible underlying mechanisms. A discussion of how hydrogen sulfide (H₂S), an endogenous gaseous signaling molecule, links sulfur-containing NPs and their anti-inflammatory action is also performed. This review may help to further the development of sulfur-based compounds by providing a guide for structure-activity relationship-based modification for use in modern medicinal chemistry. However, as this field is still in its infancy, the review is concluded by an overview of the progression of these promising entities as therapeutic agents.

Using sulfuramidimidoyl fluorides that undergo sulfur(VI) fluoride exchange for inverse drug discovery

Drug candidates that form covalent linkages with their target proteins have been under-explored compared to conventional counterparts that modulate biological function by reversible binding to proteins, in part due to concerns about off-target reactivity. But toxicity linked to off-target reactivity can be minimized by using latent electrophiles that only become activated towards covalent bond formation upon binding a specific protein. Here, we study sulfuramidimidoyl fluorides (SAFs), a class of weak electrophiles that undergo sulfur(VI) fluoride exchange (SuFEx) chemistry. We show that equilibrium binding of a SAF to a protein can allow nucleophilic attack by a specific amino acid side chain leading to conjugate formation. Sixteen small molecules, each bearing a SAF electrophile, were incubated with human cell lysate, and the protein conjugates formed were identified by affinity chromatography–mass spectrometry. This inverse drug discovery approach identified a compound that covalently binds to, and irreversibly inhibits the activity of PARP1, an important anti-cancer target in living cells.

Regulation of MIF Enzymatic Activity by an Allosteric Site at the Central Solvent Channel

In proteins with multiple functions, such as macrophage migration inhibitory factor (MIF), the study of its intramolecular dynamic network can offer a unique opportunity to understand how a single protein is able to carry out several nonoverlapping functions. A dynamic mechanism that controls the MIF-induced activation of CD74 was recently discovered. In this study, the regulation of tautomerase activity was explored. The catalytic base Pro1 is found to form dynamic communications with the same allosteric node that regulates CD74 activation. Signal transmission between the allosteric and catalytic sites take place through intramolecular aromatic interactions and a hydrogen bond network that involves residues and water molecules of the MIF solvent channel. Once thought to be a consequence of trimerization, a regulatory function for the solvent channel is now defined. These results provide mechanistic insights into the regulation of catalytic activity and the role of solvent channel water molecules in MIF catalysis.

Chemical Aspects of Biological Activity of Isothiocyanates and Indoles, the Products of Glucosinolate Decomposition

There is growing evidence that cancer chemoprevention employing natural, bioactive compounds may halt or at least slow down the different stages of carcinogenesis. A particularly advantageous effect is attributed to derivatives of sulfur-organic phytochemicals, such as glucosinolates (GLs) synthesized mainly in Brassicaceae plant family. GLs are hydrolysed enzymatically to bioactive isothiocyanates (ITC) and indoles, which exhibit strong anti-inflammatory and anti-carcinogenic activity. Highly bioavailable electrophilic ITC are of particular interest, as they can react with nucleophilic groups of important biomolecules to form dithiocarbamates, thiocarbamates and thioureas. These modifications seem responsible for the chemopreventive activity, but also for genotoxicity and mutagenicity. It was documented that ITC can permanently bind to important biomolecules such as glutathione, cytoskeleton proteins, transcription factors NF-κB and Nrf2, thiol-disulfide oxidoreductases, proteasome proteins or heat shock proteins. Furthermore, ITC may also affect epigenetic regulation of gene expression, e.g. by inhibition of histone deacetylases. Some other derivatives of glucosinolates, especially indoles, are able to form covalent bonds with nucleobases in DNA, which may result in genotoxicity and mutagenicity. This article summarizes the current state of knowledge about glucosinolates and their degradation products in terms of possible interactions with reactive groups of cellular molecules.

The Role of Isothiocyanates as Cancer Chemo-Preventive, Chemo-Therapeutic and Anti-Melanoma Agents

Many studies have shown evidence in support of the beneficial effects of phytochemicals in preventing chronic diseases, including cancer. Among such phytochemicals, sulphur-containing compounds (e.g., isothiocyanates (ITCs)) have raised scientific interest by exerting unique chemo-preventive properties against cancer pathogenesis. ITCs are the major biologically active compounds capable of mediating the anticancer effect of cruciferous vegetables. Recently, many studies have shown that a higher intake of cruciferous vegetables is associated with reduced risk of developing various forms of cancers primarily due to a plurality of effects, including (i) metabolic activation and detoxification, (ii) inflammation, (iii) angiogenesis, (iv) metastasis and (v) regulation of the epigenetic machinery. In the context of human malignant melanoma, a number of studies suggest that ITCs can cause cell cycle growth arrest and also induce apoptosis in human malignant melanoma cells. On such basis, ITCs could serve as promising chemo-therapeutic agents that could be used in the clinical setting to potentiate the efficacy of existing therapies.

Nanosecond Dynamics Regulate the MIF-Induced Activity of CD74

Macrophage migration inhibitory factor (MIF) activates CD74, which leads to severe disorders including inflammation, autoimmune diseases and cancer under pathological conditions. Molecular dynamics (MD) simulations up to one microsecond revealed dynamical correlation between a residue located at the opening of one end of the MIF solvent channel, previously thought to be a consequence of homotrimerization, and residues in a distal region responsible for CD74 activation. Experiments verified the allosteric regulatory site and identified a pathway to this site via the MIF β-strands. The reported findings provide fundamental insights on a dynamic mechanism that controls the MIF-induced activation of CD74.

Advances and Insights for Small Molecule Inhibition of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is an upstream regulator of the immune response whose dysregulation is tied to a broad spectrum of inflammatory and proliferative disorders. As its complex signaling pathways and pleiotropic nature have been elucidated, it has become an attractive target for drug discovery. Remarkably, MIF is both a cytokine and an enzyme that functions as a keto-enol tautomerase. Strategies including in silico modeling, virtual screening, high-throughput screening, and screening of anti-inflammatory natural products have led to a large and diverse catalogue of MIF inhibitors as well as some understanding of the structure-activity relationships for compounds binding MIF's tautomerase active site. With possible clinical trials of some MIF inhibitors on the horizon, it is an opportune time to review the literature to seek trends, address inconsistencies, and identify promising new avenues of research.

The Fate of a Hapten - From the Skin to Modification of Macrophage Migration Inhibitory Factor (MIF) in Lymph Nodes

Skin (contact) allergy, the most prevalent form of immunotoxicity in humans, is caused by low molecular weight chemicals (haptens) that penetrate stratum corneum and modify endogenous proteins. The fate of haptens after cutaneous absorption, especially what protein(s) they react with, is largely unknown. In this study the fluorescent hapten tetramethylrhodamine isothiocyanate (TRITC) was used to identify hapten-protein conjugates in the local lymph nodes after topical application, as they play a key role in activation of the adaptive immune system. TRITC interacted with dendritic cells but also with T and B cells in the lymph nodes as shown by flow cytometry. Identification of the most abundant TRITC-modified protein in lymph nodes by tandem mass spectrometry revealed TRITC-modification of the N-terminal proline of macrophage migration inhibitory factor (MIF) – an evolutionary well-conserved protein involved in cell-mediated immunity and inflammation. This is the first time a hapten-modified protein has been identified in lymph nodes after topical administration of the hapten. Most haptens are electrophiles and can therefore modify the N-terminal proline of MIF, which has an unusually reactive amino group under physiological conditions; thus, modification of MIF by haptens may have an immunomodulating role in contact allergy as well as in other immunotoxicity reactions.

Synthesis of stable isotope-labeled nasturlexins and potential precursors to probe biosynthetic pathways of cruciferous phytoalexins

The syntheses of perdeuterated phytoalexins nasturlexins A and C, and putative biosynthetic precursors, including phenylethyl isothiocyanates and phenylethyl dithiocarbamates, using commercially available [2,3,4,5,6-D₅ ]phenylalanine, [2,3,4,5,6-D₅ ]nitrobenzene, and [2,3,4,5,6-D₅ ]benzaldehyde are described. In addition, application of an efficient deuterium-hydrogen exchange transformation to nonlabeled starting materials allowed access to new deuterated compounds, including 3-hydroxyphenylethyl glucosinolate.

Post-translational regulation of macrophage migration inhibitory factor: Basis for functional fine-tuning

Macrophage migration inhibitory factor (MIF) is a chemokine-like protein and an important mediator in the inflammatory response. Unlike most other pro-inflammatory cytokines, a number of cell types constitutively express MIF and secretion occurs from preformed stores. MIF is an evolutionarily conserved protein that shows a remarkable functional diversity, including specific binding to surface CD74 and chemokine receptors and the presence of two intrinsic tautomerase and oxidoreductase activities. Several studies have shown that MIF is subject to post-translational modification, particularly redox-dependent modification of the catalytic proline and cysteine residues. In this review, we summarize and discuss MIF post-translational modifications and their effects on the biological properties of this protein. We propose that the redox-sensitive residues in MIF will be modified at sites of inflammation and that this will add further depth to the functional diversity of this intriguing cytokine.

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MIF is a pro-inflammatory cytokine with tautomerase and oxidoreductase activity.

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MIF is susceptible to post-translational modifications, including redox modification.

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Oxidants and electrophiles generated at inflammatory sites can modify MIF.

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The biological consequences of redox modification need detailed characterization.

Brassica-Derived Plant Bioactives as Modulators of Chemopreventive and Inflammatory Signaling Pathways

A high consumption of vegetables belonging to the Brassicaceae family has been related to a lower incidence of chronic diseases including different kinds of cancer. These beneficial effects of, e.g., broccoli, cabbage or rocket (arugula) intake have been mainly dedicated to the sulfur-containing glucosinolates (GLSs)-secondary plant compounds nearly exclusively present in Brassicaceae-and in particular to their bioactive breakdown products including isothiocyanates (ITCs). Overall, the current literature indicate that selected Brassica-derived ITCs exhibit health-promoting effects in vitro, as well as in laboratory mice in vivo. Some studies suggest anti-carcinogenic and anti-inflammatory properties for ITCs which may be communicated through an activation of the redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) that controls the expression of antioxidant and phase II enzymes. Furthermore, it has been shown that ITCs are able to significantly ameliorate a severe inflammatory phenotype in colitic mice in vivo. As there are studies available suggesting an epigenetic mode of action for Brassica-derived phytochemicals, the conduction of further studies would be recommendable to investigate if the beneficial effects of these compounds also persist during an irregular consumption pattern.

Prevention and treatment of cancers by immune modulating nutrients

Epidemiological and laboratory data support the protective effects of bioactive nutrients in our diets for various diseases. Along with various factors, such as genetic history, alcohol, smoking, exercise, and dietary choices play a vital role in affecting an individual's immune responses toward a transforming cell, by either preventing or accelerating a neoplastic transformation. Ample evidence suggests that dietary nutrients control the inflammatory and protumorigenic responses in immune cells. Immunoprevention is usually associated with the modulation of immune responses that help in resolving the inflammation, thus improving clinical outcome. Various metabolic pathway-related nutrients, including glutamine, arginine, vitamins, minerals, and long-chain fatty acids, are important components of immunonutrient mixes. Epidemiological studies related to these substances have reported different results, with no or minimal effects. However, several studies suggest that these nutrients may have immune-modulating effects that may lower cancer risk. Preclinical studies submit that most of these components may provide beneficial effects. The present review discusses the available data, the immune-modulating functions of these nutrients, and how these substances could be used to study immune modulation in a neoplastic environment. Further research will help to determine whether the mechanistic signaling pathways in immune cells altered by nutrients can be exploited for cancer prevention and treatment.