δ-Lactones-A New Class of Compounds That Are Toxic to E. coli K12 and R2-R4 Strains.

Lactones are among the well-known organic substances with a specific taste and smell. They are characterized by antibacterial, antiviral, anti-inflammatory, and anti-cancer properties. In recent years, among this group of compounds, new biologically active substances have been searched by modifying the main (leading) structure with new analogs with stronger or different responses that may have a toxic effect on the cells of pathogenic bacteria and constitute an alternative to commonly used antibiotics. A preliminary study of δ-lactone derivatives as new potential candidates for antibacterial drugs was conducted. Particular emphasis was placed on the selection of the structure of lactones with the highest biological activity, especially those with fluorine in their structure as a substituent in terms of action on bacterial lipopolysaccharide (LPS) in the model strains of Escherichia coli K12 (without LPS in its structure) and R2-R4 (LPS of different lengths in its structure). In the presented studies, on the basis of the conducted MIC and MBC tests, it was shown that the antibacterial (toxic) activity of lactones depends on their structure and the length of the bacterial LPS in the membrane of specific strains. Moreover, oxidative damage of bacterial DNA isolated from bacteria after modification with newly synthesized compounds after application of the repair enzyme Fpg glycosylase was analyzed. The analyzed damage values were compared with the modification with appropriate antibiotics: ciprofloxacin, bleomycin, and cloxacillin. The presented research clearly shows that lactone derivatives can be potential candidates as substitutes for drugs, e.g., the analyzed antibiotics. Their chemical and biological activity is related to coumarin derivatives and the corresponding δ-lactone groups in the structure of the substituent. The observed results are of particular importance in the case of increasing bacterial resistance to various drugs and antibiotics, especially in nosocomial infections and neoplasms, and in the era of a microbial pandemic.

1,2-Diarylethanols-A New Class of Compounds That Are Toxic to E. coli K12, R2-R4 Strains.

An initial study of 1,2-diarylethanols derivatives as new potential antibacterial drugs candidates was conducted. Particular emphasis was placed on the selection of the structure of 1,2-diarylethanols with the highest biological activity of lipopolysaccharides (LPS) in the model strains of Escherichia coli K12 (without LPS in its structure) and R2-R4 (with different lengths of LPS in its structure). In the presented studies, based on the conducted minimum inhibitory concentration (MIC) and MBC tests, it was demonstrated that the antibacterial (toxic) effect of 1,2-diarylethanols depends on their structure and the length of LPS bacteria in the membrane of specific strains. Moreover, the oxidative damage of bacterial DNA isolated from bacteria after modification with newly synthesized compounds after application of the repair enzyme Fpg glycosylases was analysed. The analysed damage values were compared with modification with appropriate antibiotics; bacterial DNA after the use of kanamycin, streptomycin, ciprofloxacin, bleomycin and cloxicillin. The presented research clearly shows that 1,2-diarylethanol derivatives can be used as potential candidates for substitutes for new drugs, e.g., the analysed antibiotics. Their chemical and biological activity is related to two aromatic groups and the corresponding chemical groups in the structure of the substituent. The observed results are particularly important in the case of increasing bacterial resistance to various drugs and antibiotics, especially in nosocomial infections and neoplasms, and in the era of pandemics caused by microorganisms.

All That Glitters Is Not Silver-A New Look at Microbiological and Medical Applications of Silver Nanoparticles.

Silver and its nanoparticles (AgNPs) have different faces, providing different applications. In recent years, the number of positive nanosilver applications has increased substantially. It has been proven that AgNPs inhibit the growth and survival of bacteria, including human and animal pathogens, as well as fungi, protozoa and arthropods. Silver nanoparticles are known from their antiviral and anti-cancer properties; however, they are also very popular in medical and pharmaceutical nanoengineering as carriers for precise delivery of therapeutic compounds, in the diagnostics of different diseases and in optics and chemistry, where they act as sensors, conductors and substrates for various syntheses. The activity of AgNPs has not been fully discovered; therefore, we need interdisciplinary research to fulfil this knowledge. New forms of products with silver will certainly find application in the future treatment of many complicated and difficult to treat diseases. There is still a lack of appropriate and precise legal condition regarding the circulation of nanomaterials and the rules governing their safety use. The relatively low toxicity, relative biocompatibility and selectivity of nanoparticle interaction combined with the unusual biological properties allow their use in animal production as well as in bioengineering and medicine. Despite a quite big knowledge on this topic, there is still a need to organize the data on AgNPs in relation to specific microorganisms such as bacteria, viruses or fungi. We decided to put this knowledge together and try to show positive and negative effects on prokaryotic and eukaryotic cells.

Coumarin Derivatives as New Toxic Compounds to Selected K12, R1-R4 E. coli Strains.

Coumarins are natural compounds that were detected in 80 species of plants. They have numerous applications including the medical, food, tobacco, perfumery, and spirit industries. They show anti-swelling and diastolic effects. However, excess consumption of coumarins may adversely affect our health, because they are easily absorbed from the intestines into the lymph and blood, causing cirrhosis of the liver. Peptidomimetics are molecules whose structure and function are similar to those of peptides. They are an important group of compounds with biological, microbiological, anti-inflammatory, and anti-cancer properties. Therefore, studies on new peptidomimetics, which load the effect of native peptides, whose half-life in the body is much longer due to structural modifications, are extremely important. A preliminary study of coumarin analogues and its derivatives as new potential antimicrobial drugs containing carboxylic acid or ester was performed to determine their basic structure related to their biological features against various types of Gram-stained bacteria by lipopolysaccharide (LPS). We hypothesized that the toxicity (antibacterial activity) of coumarin derivatives is dependent on the of LPS in bacteria and nature and position of the substituent which may be carboxylic acid, hydroxyl groups, or esters. In order to verify this hypothesis, we used K12 (smooth) and R1-R4 (rough) Escherichia coli strains which are characterized by differences in the type of LPS, especially in the O-antigen region, the outermost LPS layer. In our work, we synthesized 17 peptidomimetics containing a coumarin scaffold and checked their influence on K12 and R1-R4 E. coli strains possessing smooth and rough LPS. We also measured the damage of plasmid DNA caused by target compounds. The results of our studies clearly support the conclusion that coumarin peptidomimetics are antagonistic compounds to many of the currently used antibiotics. The high biological activity of the selected coumarin peptidomimetic was associated with identification of the so-called magic methyl groups, which substantially change the biochemical properties of target compounds. Investigating the effects of these compounds is particularly important in the era of increasingly common resistance in bacteria.

Hydrogen Sulfide in Pharmacotherapy, Beyond the Hydrogen Sulfide-Donors.

Hydrogen sulfide (H2S) is one of the important biological mediators involved in physiological and pathological processes in mammals. Recently developed H2S donors show promising effects against several pathological processes in preclinical and early clinical studies. For example, H2S donors have been found to be effective in the prevention of gastrointestinal ulcers during anti-inflammatory treatment. Notably, there are well-established medicines used for the treatment of a variety of diseases, whose chemical structure contains sulfur moieties and may release H2S. Hence, the therapeutic effect of these drugs may be partly the result of the release of H2S occurring during drug metabolism and/or the effect of these drugs on the production of endogenous hydrogen sulfide. In this work, we review data regarding sulfur drugs commonly used in clinical practice that can support the hypothesis about H2S-dependent pharmacotherapeutic effects of these drugs.

Dimeric peroxiredoxins are druggable targets in human Burkitt lymphoma.

Burkitt lymphoma is a fast-growing tumor derived from germinal center B cells. It is mainly treated with aggressive chemotherapy, therefore novel therapeutic approaches are needed due to treatment toxicity and developing resistance. Disturbance of red-ox homeostasis has recently emerged as an efficient antitumor strategy. Peroxiredoxins (PRDXs) are thioredoxin-family antioxidant enzymes that scavenge cellular peroxides and contribute to red-ox homeostasis. PRDXs are robustly expressed in various malignancies and critically involved in cell proliferation, differentiation and apoptosis. To elucidate potential role of PRDXs in lymphoma, we studied their expression level in B cell-derived primary lymphoma cells as well as in cell lines. We found that PRDX1 and PRDX2 are upregulated in tumor B cells as compared with normal counterparts. Concomitant knockdown of PRDX1 and PRDX2 significantly attenuated the growth rate of lymphoma cells. Furthermore, in human Burkitt lymphoma cell lines, we isolated dimeric 2-cysteine peroxiredoxins as targets for SK053, a novel thiol-specific small-molecule peptidomimetic with antitumor activity. We observed that treatment of lymphoma cells with SK053 triggers formation of covalent PRDX dimers, accumulation of intracellular reactive oxygen species, phosphorylation of ERK1/2 and AKT and leads to cell cycle arrest and apoptosis. Based on site-directed mutagenesis and modeling studies, we propose a mechanism of SK053-mediated PRDX crosslinking, involving double thioalkylation of active site cysteine residues. Altogether, our results suggest that peroxiredoxins are novel therapeutic targets in Burkitt lymphoma and provide the basis for new approaches to the treatment of this disease.

TMAO: A small molecule of great expectations.

Trimethylamine N-oxide (TMAO) is a small organic compound whose concentration in blood increases after ingesting dietary l-carnitine and phosphatidylcholine. Recent clinical studies show a positive correlation between elevated plasma levels of TMAO and an increased risk for major adverse cardiovascular events defined as death, myocardial infarction, or stroke. Several experimental studies suggest a possible contribution of TMAO to the etiology of cardiovascular diseases by affecting lipid and hormonal homeostasis. On the other hand, TMAO-rich seafood, which is an important source of protein and vitamins in the Mediterranean diet, has been considered beneficial for the circulatory system. Although in humans TMAO is known mainly as a waste product of choline metabolism, a number of studies suggest an involvement of TMAO in important biological functions in numerous organisms, ranging from bacteria to mammals. For example, cells use TMAO to maintain cell volume under conditions of osmotic and hydrostatic pressure stresses. In this article, we reviewed well-established chemical and biological properties of TMAO and dietary sources of TMAO, as well as looked at the studies suggesting possible involvement of TMAO in the etiology of cardiovascular and other diseases, such as kidney failure, diabetes, and cancer.

SK053 triggers tumor cells apoptosis by oxidative stress-mediated endoplasmic reticulum stress.

Thioredoxins (Trx) together with thioredoxin reductases (TrxR) participate in the maintenance of protein thiol homeostasis and play cytoprotective roles in tumor cells. Therefore, thioredoxin-thioredoxin reductase system is considered to be a promising therapeutic target in cancer treatment. We have previously reported that SK053, a peptidomimetic compound targeting the thioredoxin-thioredoxin reductase system, induces oxidative stress and demonstrates antitumor activity in mice. In this study, we investigated the mechanisms of SK053-mediated tumor cell death. Our results indicate that SK053 induces apoptosis of Raji cells accompanied by the activation of the endoplasmic reticulum (ER) stress and induction of unfolded protein response. Incubation of tumor cells with SK053 induces increase in BiP, CHOP, and spliced XBP-1 levels, which precede induction of apoptosis. CHOP-deficient (CHOP(-/-)) mouse embryonic fibroblasts are more resistant to SK053-induced apoptosis as compared with normal fibroblasts indicating that the apoptosis of tumor cells depends on the expression of this transcription factor. Additionally, the ER-stress-induced apoptosis, caused by SK053, is strongly related with Trx expression levels. Altogether, our results indicate that SK053 induces ER stress-associated apoptosis and reveal a link between thioredoxin inhibition and induction of UPR in tumor cells.

Adenanthin targets proteins involved in the regulation of disulphide bonds.

Adenanthin has been recently shown to inhibit the enzymatic activities of peroxiredoxins (Prdx) I and II through its functional α,ß-unsaturated ketone group serving as a Michael acceptor. A similar group is found in SK053, a compound recently developed by our group to target the thioredoxin-thioredoxin reductase (Trx-TrxR) system. This work provides evidence that next to Prdx I and II adenanthin targets additional proteins including thioredoxin-thioredoxin reductase system as well as protein disulfide isomerase (PDI) that contain a characteristic structural motif, referred to as a thioredoxin fold. Adenanthin inhibits the activity of Trx-TR system and PDI in vitro in the insulin reduction assay and decreases the activity of Trx in cultured cells. Moreover, we identified Trx-1 as an adenanthin binding protein in cells incubated with biotinylated adenanthin as an affinity probe. The results of our studies indicate that adenanthin is a mechanism-selective, rather than an enzyme-specific inhibitor of enzymes containing readily accessible, nucleophilic cysteines. This observation might be of importance in considering potential therapeutic applications of adenanthin to include a range of diseases, where aberrant activity of Prdx, Trx-TrxR and PDI is involved in their pathogenesis.

Synthesis of novel, peptidic kinase inhibitors with cytostatic/cytotoxic activity.

The utility of a novel, chemoenzymatic procedure for the stereocontrolled synthesis of small peptides is presented in the preparation and structure optimisation of dipeptides with cytostatic/cytotoxic activity. The method uses Passerini multicomponent reaction for the preparation of racemic scaffold which is then enantioselectively hydrolysed by hydrolytic enzymes. Products of these transformations are further functionalised towards title compounds. Both activity and selectivity towards tumor cells is optimised. Final compound is shown to be an inhibitor of the protein kinase signaling pathway.

Model studies on the first enzyme-catalyzed Ugi reaction.

Multicomponent reactions are powerful tools for organic chemistry, and among them, the Ugi reaction provides remarkable improvement in many fields of organic chemistry such us combinatorial chemistry, medicinal chemistry, and peptide chemistry. A new, enzyme-catalyzed example of the Ugi three-component reaction is presented. The studies include the selection of an enzyme as well as determination of the scope and limitations of the newly described reaction. The presented method combines the enzyme promiscuity and multicomponent reaction advantages in the first one-pot formation of dipeptide 1.

Studies toward novel peptidomimetic inhibitors of thioredoxin-thioredoxin reductase system.

Thioredoxins (Trx) are ubiquitous multifunctional low-molecular weight proteins that together with thioredoxin reductases (TrxR) participate in the maintenance of protein thiol homeostasis in NADPH-dependent reactions. An increasing number of data reveal that the Trx-TrxR system is an attractive target for anticancer therapies. In this work, we have elaborated a new and simple synthetic approach employing Ugi reaction to synthesize several new inhibitors of this system. The influence of various electrophilic fragments of this new class of compounds on the inhibition of the Trx-TrxR system was evaluated. As a result, a new compound 19a (SK053), which inhibits the activity of the Trx-TrxR system and exhibits antitumor activity, was obtained. Biologic analyses revealed that 19a inhibits induction of NF-κB and AP-1 and decreases H(2)O(2) scavenging capacity in tumor cells. Altogether, we show that 19a is a novel potential antitumor peptidomimetic inhibitor that can be used as a starting compound for further optimization.

Studies of the synthesis of all stereoisomers of MG-132 proteasome inhibitors in the tumor targeting approach.

MG-132 is a tripeptide aldehyde (Z-l-leu-l-leu-l-leu-H, 2) proteasome inhibitor that exerts antitumor activity and enhances cytostatic/cytotoxic effects of chemo- and radiotherapy. Because of a troublesome synthesis of tripeptides with a non-natural configuration and modified side chains of amino acids, only two stereoisomers of MG-132 have been reported. Here, we propose a new approach to the synthesis of tripeptide aldehydes based on the Ugi reaction. Chiral, enantiomerically stable 2-isocyano-4-methylpentyl acetates were used as substrates for Ugi reaction resulting in a formation of tripeptide skeletons. Further functionalization of the obtained products led to a synthesis of tripeptide aldehydes. All stereoisomers of MG-132 were synthesized and studied as potential inhibitors of chymotrypsin-like, trypsin-like, and peptidylglutamyl peptide hydrolyzing activities of proteasome. These studies demonstrated the influence of absolute configuration of chiral aldehydes on the cytostatic/cytotoxic effects of the synthesized compounds and revealed that only (S,R,S)-(-)-2 stereoisomer is a more potent proteasome inhibitor than MG-132.