Novel inhibitors of plasminogen activator inhibitor-1: development of new templates from diketopiperazines

(S)-3-(3,4-Dihydroxybenzyl) piperazine-2,5-dione (cyclo-Gly-L-DOPA or CG-Nio-CGLD) peptide loaded in Chitosan Glutamate-Coated Niosomes as anti-Colorectal cancer activity

BACKGROUND

Colorectal cancer (CRC), now the second most prevalent malignant tumor worldwide, is more prevalent in young adults. In recent decades, there has been progress in creating anti-colorectal cancer medications, including cytotoxic compounds.

OBJECTIVES

Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of novel formulations in preventing colorectal cancer.

METHODS

During this study, we assessed a new kind of niosome called cyclo-Gly-L-DOPA (CG-Nio-CGLD) made from chitosan glutamate. We evaluated the anti-colorectal cancer properties of CG-Nio-CGLD utilizing CCK-8, invasion assay, MTT assay, flow cytometry, and cell cycle analysis. The transcription of genes associated with apoptosis was analyzed using quantitative real-time PCR. At the same time, the cytotoxicity of nanomaterials on both cancer and normal cell lines was assessed using MTT assays. Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of newly developed formulations in preventing colorectal cancer.

RESULTS

The Nio-CGLD and CG-Nio-CGLD were spherical mean diameters of 169.12 ± 1.87 and 179.26 ± 2.17 nm, respectively. Entrapment efficiency (EE%) measurements of the Nio-CGLD and CG-Nio-CGLD were 63.12 ± 0.51 and 76.43 ± 0.34%, respectively. In the CG-Nio-CGLD group, the percentages of early, late, necrotic, and viable CL40 cells were 341.93%, 23.27%, 9.32%, and 25.48%. The transcription of the genes PP53, cas3, and cas8 was noticeably higher in the treatment group compared to the control group (P > 0.001). Additionally, the treatment group had lower BCL2 and survivin gene expression levels than the control group (P < 0.01). Additionally, CG-Nio-CGLD formulations demonstrated a biocompatible nanoscale delivery mechanism and displayed little cytotoxicity toward the CCD 841 CoN reference cell line.

CONCLUSION

These findings indicate that chitosan-based noisome encapsulation may enhance the effectiveness of CG-Nio-CGLD formulations in fighting cancer.

Design, Synthesis, and Anticancer Activity of Novel 3,6-Diunsaturated 2,5-Diketopiperazines

Based on the marine natural products piperafizine B, XR334, and our previously reported compound 4m, fourteen novel 3,6-diunsaturated 2,5-diketopiperazine (2,5-DKP) derivatives (1, 2, 4-6, 8-16), together with two known ones (3 and 7), were designed and synthesized as anticancer agents against the A549 and Hela cell lines. The MTT assay results showed that the derivatives 6, 8-12, and 14 had moderate to good anticancer capacities, with IC₅₀ values ranging from 0.7 to 8.9 μM. Among them, compound 11, with naphthalen-1-ylmethylene and 2-methoxybenzylidene functions at the 3 and 6 positions of 2,5-DKP ring, respectively, displayed good inhibitory activities toward both A549 (IC₅₀ = 1.2 μM) and Hela (IC₅₀ = 0.7 μM) cancer cells. It could also induce apoptosis and obviously block cell cycle progression in the G2/M phases in both cells at 1.0 μM. The electron-withdrawing functions might not be favorable for the derivatives with high anticancer activities. Additionally, compared to piperafizine B and XR334, these semi-N-alkylated derivatives have high liposolubilities (>1.0 mg mL^-1). Compound 11 can be further developed, aiming at the discovery of a novel anticancer candidate.

Purification and synergistic antibacterial activity of arginine derived cyclic dipeptides, from Achromobacter sp. associated with a rhabditid entomopathogenic nematode against major clinically relevant biofilm forming wound bacteria

Skin and chronic wound infections caused by various pathogenic bacteria are an increasing and urgent health problem worldwide. In the present investigation ethyl acetate extract of an Achromobacter sp. associated with a Rhabditis entomopathogenic nematode (EPN), displayed promising antibacterial property and was further purified by silica gel column chromatography to get three different cyclic dipeptides (CDPs). Based on the spectral data and Marfey's analyses, the CDPs were identified as cyclo(D-Leu-D-Arg) (1), cyclo(L-Trp-L-Arg) (2), and cyclo(D-Trp-D-Arg) (3), respectively. Three CDPs were active against all the 10 wound associated bacteria tested. The significant antibacterial activity was recorded by CDP 3, and highest activity of 0.5 μg/ml was recorded against Staphylococcus aureus and Pseudomonas aeruginosa. The synergistic antibacterial activities of CDPs and ampicillin were assessed using the checkerboard microdilution method. The results of the current study recorded that the combined effects of CDPs and ampicillin principally recorded synergistic activity. Interestingly, the combination of CDPs and ampicillin also recorded enhanced inhibition of biofilm formation by bacteria. Moreover, CDPs significantly stimulate the production of IL-10 and IL-4 (anti-inflammatory cytokines) by human peripheral blood mononuclear cells. CDPs do not make any significant effect on the production of pro-inflammatory cytokines like TNF-α. The three CDPs have been studied for their effect on intracellular S. aureus in murine macrophages (J774) using 24 h exposure to 0.5X, 1X, and 2X MIC concentrations. Significant decrease in intracellular S. aureus burden was recorded by CDPs. CDPs also recorded no cytotoxicity toward FS normal fibroblast, VERO, and L231 normal lung epithelial cell lines. Antimicrobial activity of the arginine containing CDPs against the wound associated bacteria is reported here for the first. Moreover, this is also the first report on the production of CDPs by Achromobacter sp. Finally, we conclude that the Achromobacter sp. is an incredibly promising source of natural bioactive secondary metabolites especially against wound pathogenic bacteria that may receive significant benefit in the field of human medicine in near future as topical agents.

Small molecules inhibitors of plasminogen activator inhibitor-1 - an overview

PAI-1, a glycoprotein from the serpin family and the main inhibitor of tPA and uPA, plays an essential role in the regulation of intra and extravascular fibrinolysis by inhibiting the formation of plasmin from plasminogen. PAI-1 is also involved in pathological processes such as thromboembolic diseases, atherosclerosis, fibrosis and cancer. The inhibition of PAI-1 activity by small organic molecules has been observed in vitro and with some in vivo models. Based on these findings, PAI-1 appears as a potential therapeutic target for several pathological conditions. Over the past decades, many efforts have therefore been devoted to developing PAI-1 inhibitors. This article provides an overview of the publishing activity on small organic molecules used as PAI-1 inhibitors. The chemical synthesis of the most potent inhibitors as well as their biological and biochemical evaluations is also presented.

The diketopiperazine-fused tetrahydro-β-carboline scaffold as a model peptidomimetic with an unusual α-turn secondary structure

Aiming at restricting the conformational freedom of tryptophan-containing peptide ligands, we designed a THBC (tetrahydro-β-carboline)-DKP (diketopiperazine)-based peptidomimetic scaffold capable of arranging in an unusual α-turn conformation. The synthesis is based on a diastereoselective Pictet–Spengler condensation to give the THBC core, followed by an intramolecular lactamization to complete the tetracyclic THBC-DKP fused ring system. The presence of conformers bearing the intramolecular thirteen-membered hydrogen bond that characterizes the α-turn structure is confirmed by ¹H NMR conformational studies. To the best of our knowledge, this scaffold represents one of the rare examples of a designed constrained α-turn mimic.

Traceless synthesis of diketopiperazine fused tetrahydro-β-carbolines on soluble polymer support

The Pictet-Spengler reaction, using polyethylene glycol immobilized tryptophan ester with a variety of ketones, was achieved by refluxing condition in acidic chloroform. The linear as well as cyclic ketones were employed. All the ketones were reacted within 6-8 h to furnish soluble polymer-supported tetrahydro-β-carboline in good yields. Further expansion at N-terminus of tetrahydro-β-carbolines was achieved through a reaction with chloroacetyl chloride. Finally, the 2,5-diketopiperazine skeleton was constructed over a β-carboline by amination of the resulting N-chloroacetamides and subsequent intramolecular cyclization leading to cleavage of the polymer; constitutes a traceless synthesis of tetracyclic molecular architecture. Significantly, this strategy affords a straightforward and efficient approach for the construction of biological promising molecules with high purity and good yields.

Design, synthesis, and evaluation of orally active inhibitors of plasminogen activator inhibitor-1 (PAI-1) production

A novel series of butadiene-imide 1 (T-686) derivatives having an inhibitory activity against PAI-1 production was synthesized and evaluated their biological activities and DMPK profiles, in which 15k (T-2639) was selected as the best compound based on its strong antithrombotic activity and good bioavailability.

A peptide accelerating the conversion of plasminogen activator inhibitor-1 to an inactive latent state

The serpin plasminogen activator inhibitor-1 (PAI-1) is a specific inhibitor of plasminogen activators and a potential therapeutic target in cancer and cardiovascular diseases. Accordingly, formation of a basis for development of specific PAI-1-inactivating agents is of great interest. One possible inactivation mode for PAI-1 is conversion to the inactive, so-called latent state. We have now screened a phage-displayed peptide library with PAI-1 as bait and isolated a 31-residue cysteine-rich peptide that will be referred to as paionin-4. A recombinant protein consisting of paionin-4 fused to domains 1 and 2 of the phage coat protein g3p caused a 2- to 3-fold increase in the rate of spontaneous inactivation of PAI-1. Paionin-4-D1D2 bound PAI-1 with a K(D) in the high nanomolar range. Using several biochemical and biophysical methods, we demonstrate that paionin-4-D1D2-stimulated inactivation consists of an acceleration of conversion to the latent state. As demonstrated by site-directed mutagenesis and competition with other PAI-1 ligands, the binding site for paionin-4 was localized in the loop between alpha-helix D and beta-strand 2A. We also demonstrate that a latency-inducing monoclonal antibody has an overlapping, but not identical binding site, and accelerates latency transition by another mechanism. Our results show that paionin-4 inactivates PAI-1 by a mechanism clearly different from other peptides, small organochemical compounds, or antibodies, whether they cause inactivation by stimulating latency transition or by other mechanisms, and that the loop between alpha-helix D and beta-strand 2A can be a target for PAI-1 inactivation by different types of compounds.

Synthesis and SAR of 2-carboxylic acid indoles as inhibitors of plasminogen activator inhibitor-1

We synthesized and evaluated a novel series of 2-carboxylic acid indole-based inhibitors of plasminogen activator inhibitor-1 (PAI-1). Systematic modification of the N-1 position and the 5-position of the indole scaffold resulted in the identification of several compounds that showed good potency against PAI-1 in the spectrophotometric assay. This potency did not always translate to the antibody assay. Solubility and serum protein binding studies on selected analogs revealed that protein binding might be a factor in the poor correlation between the two assays.

Design and synthesis of oxadiazolidinediones as inhibitors of plasminogen activator inhibitor-1

A novel series of PAI-1 inhibitors containing an oxadiazolidinedione moiety were identified by high through-put screening. Optimization of substituents by parallel synthesis and the iterative design toward understanding structure-activity relationship to improve potency are described.

Synthesis and biological evaluation of piperazine-based derivatives as inhibitors of plasminogen activator inhibitor-1 (PAI-1)

Compound 2 was identified by high throughput screening as a novel PAI-1 inhibitor. Systematic optimization of the A, B, and C segments of 2 resulted in the identification of a more potent compound 39 with good oral bioavailability. The synthesis and SAR data are presented in this report.

XR5967, a novel modulator of plasminogen activator inhibitor-1 activity, suppresses tumor cell invasion and angiogenesis in vitro

Recent reports suggest that elevated levels of plasminogen activator inhibitor (PAI)-1 may contribute to tumor progression. We have recently shown that antibodies to PAI-1 block the invasive and migratory potential of human fibrosarcoma cells and suppress angiogenesis in vitro. Here we report the in vitro evaluation of a low-molecular-weight modulator of PAI-1, XR5967, on invasion, migration and angiogenesis. XR5967, a diketopiperazine, dose-dependently inhibited the activity of human and murine PAI-1, towards urokinase plasminogen activator (uPA), with IC50 values of 800 nM and 8.3 microM, respectively. This was confirmed by SDS-PAGE, revealing that XR5967 inhibited complex formation between PAI-1 and uPA. This suppression may be caused by XR5967 promoting insertion of the reactive center loop within PAI-1. XR5967 dose-dependently inhibited the invasion of human HT1080 fibrosarcoma cells through Matrigel. Their invasion was reduced by 57% (p<0.001) at 5 microM. HT1080 cell migration was inhibited in a similar manner, indicating that PAI-1 may play an additional role in invasion, which is distinct to its role in the regulation of proteolysis. The potential of XR5967 to inhibit the invasion/migration of human endothelial cells was investigated in an in vitro model of angiogenesis. In this model XR5967 reduced tubule formation by 77% at 5 microM (p<0.001), highlighting a crucial role for PAI-1 in angiogenesis. These data stress the importance of a balanced proteolysis in the processes of invasion, migration and angiogenesis. Our results support the clinical findings and indicate that modulation of PAI-1 activity, with low-molecular-weight inhibitor of PAI-1 activity, may be of therapeutic benefit for the treatment of cancer.

Synthesis and biological evaluation of menthol-based derivatives as inhibitors of plasminogen activator inhibitor-1 (PAI-1)

Compound 1 was identified by high throughput screening as a novel PAI-1 inhibitor. Optimization of the B and C-segments of 1 resulted in a series of structurally simplified compounds with improved potency. The synthesis and SAR data of these compounds are presented here.

New fibrinolytic agents: benzothiophene derivatives as inhibitors of the t-PA-PAI-1 complex formation

The synthesis and activity of novel benzothiophene derivatives are described. In the t-Pa-induced fibrin clot lysis assay, several compounds inhibit the formation of the tPa-PAI-1 complex with submicromolar IC(50). This class of compounds potentially represents a new generation of antithrombotic-fibrinolytic agents.