Restoration of immune system function is accelerated in immunocompromised mice by the B-cell-tropic isoxazole R-11

Search for immunomodulatory compounds with antiproliferative activity against melanoma

BACKGROUND

Melanoma is a highly aggressive neoplasm with a high degree of malignancy and rapid acquisition of resistance by cancer cells.

METHODS

Biological studies of a series of isoxazole compounds with immunomodulatory properties were preceded by in silico analysis. The assay evaluated the viability of NHDF and A375 cell cultures after the administration of isoxazole compounds after a 24-hour incubation period in the MTT test. Analyzes of ROS and NO scavenging, P-glycoprotein activity, and properties were performed. The levels of Caspase 3 and Caspase 9 were measured using ELISA to assess which pathways induced apoptosis by the tested compounds. On the chip, the synergistic effect of doxorubicin and the most active compound from the MM9 series on cells of the A375 melanoma line was determined.

RESULTS

All tested N'-substituted derivatives of 5-amino-N,3-dimethyl-1,2-oxazole-4-carbohydrazide with immunomodulatory activity show multidirectional antitumor activity on A375 melanoma lines with an affinity for P-glycoprotein, induction of free radical formation and generation of DNA damage leading to the death of cancer cells, as well as formation of complexes with DNA Topoisomerase II. Most of the tested compounds show pro-apoptotic activity. The most active compound in the series induces apoptosis in three distinct pathways and acts synergistically with doxorubicin.

CONCLUSIONS

The most active compound with immunomodulatory properties showed multidirectional antitumor activity against cells of the A375 melanoma line and also had a synergistic pro-apoptotic effect with doxorubicin, which may result in a reduction of this cytostatic dose with increased effectiveness.

New Oxazolo[5,4-d]pyrimidines as Potential Anticancer Agents: Their Design, Synthesis, and In Vitro Biological Activity Research

Cancer is a large group of diseases in which the rapid proliferation of abnormal cells generally leads to metastasis to surrounding tissues or more distant ones through the lymphatic and blood vessels, making it the second leading cause of death worldwide. The main challenge in designing a modern anticancer therapy is to develop selective compounds that exploit specific molecular targets. In this work, novel oxazolo[5,4-d]pyrimidine derivatives were designed, synthesized, and evaluated in vitro for their cytotoxic activity against a panel of four human cancer cell lines (lung carcinoma: A549, breast adenocarcinoma: MCF7, metastatic colon adenocarcinoma: LoVo, primary colon adenocarcinoma: HT29), along with their P-glycoprotein-inhibitory ability and pro-apoptotic activity. These oxazolo[5,4-d]pyrimidine derivatives, which are structurally similar to nucleic purine bases in general, are characterized by the presence of a pharmacologically favorable isoxazole substituent at position 2 and aliphatic amino chains at position 7 of the condensed heterocyclic system. In silico analysis of the obtained compounds identified their potent inhibitory activity towards human vascular endothelial growth factor receptor-2 (VEGFR-2). Molecular docking was performed to assess the binding mode of new derivatives to the VEGFR-2 active site. Then, their physicochemical, pharmacokinetic, and pharmacological properties (i.e., ADME-administration, distribution, metabolism, and excretion) were also predicted to assess their druglikeness. In particular, compound 3g (with a 3-(N,N-dimethylamino)propyl substituent) was found to be the most potent against the HT29 cell line, with a 50% cytotoxic concentration (CC₅₀) of 58.4 µM, exceeding the activity of fluorouracil (CC₅₀ = 381.2 μM) and equaling the activity of cisplatin (CC₅₀ = 47.2 µM), while being less toxic to healthy human cells (such as normal human dermal fibroblasts (NHDFs)) than these reference drugs. The results suggest that compound 3g is a potentially promising candidate for the treatment of primary colorectal cancer.

Synthesis and Biological Activity of New 7-Amino-oxazolo[5,4-d]Pyrimidine Derivatives

The synthesis of a series of novel 7-aminooxazolo[5,4-d]pyrimidines 5, transformations during their synthesis and their physicochemical characteristics have been described. Complete detailed spectral analysis of the intermediates 2-4, the N'-cyanooxazolylacetamidine by-products 7 and final compounds 5 has been carried out using MS, IR, 1D and 2D NMR spectroscopy. Theoretical research was carried out to explain the privileged formation of 7-aminooxazolo[5,4-d]pyrimidines in relation to the possibility of their isomer formation and the related thermodynamic aspects. Additionally, the single-crystal X-ray diffraction analysis for 5h was reported. Ten 7-aminooxazolo[5,4-d]pyrimidines 5 (SCM1-10) were biologically tested in vitro to preliminarily evaluate their immunological, antiviral and anticancer activity. Compounds SCM5 and SCM9 showed the best immunoregulatory profile. The compounds displayed low-toxicity and strongly inhibited phytohemagglutinin A-induced proliferation of human peripheral blood lymphocytes and lipopolysaccharide-induced proliferation of mouse splenocytes. Compound SCM9 caused also a moderate suppression of tumor necrosis factor α (TNF-α) production in a human whole blood culture. Of note, the compounds also inhibited the growth of selected tumor cell lines and inhibited replication of human herpes virus type-1 (HHV-1) virus in A-549 cell line. Molecular investigations showed that the compounds exerted differential changes in expression of signaling proteins in Jurkat and WEHI-231 cell lines. The activity of SCM5 is likely associated with elicitation of cell signaling pathways leading to cell apoptosis. The compounds may be of interest in terms of therapeutic utility as inhibitors of autoimmune disorders, virus replication and antitumor agents.

Isoxazole Derivatives as Regulators of Immune Functions

In this review, we present reports on the immunoregulatory properties of isoxazole derivatives classified into several categories, such as immunosuppressive, anti-inflammatory, immunoregulatory, and immunostimulatory compounds. The compounds were tested in various models using resident cells from rodents and humans, cell lines, and experimental animal disease models corresponding to human clinical situations. Beneficial features of the described isoxazole derivatives include low toxicity and good bioactivity at low doses. In a majority of studies, the activities of investigated compounds were comparable or even higher than registered reference drugs. Whenever possible, a plausible mechanism of action of the investigated compounds and their potential therapeutic utility were proposed. Among the described compounds, particular attention was paid to the class of immune stimulators with a potential application in chemotherapy patients.

Synthesis, Immunosuppressive Properties, and Mechanism of Action of a New Isoxazole Derivative

This work describes the synthesis of a new series of isoxazole derivatives, their immunosuppressive properties, and the mechanism of action of a representative compound. A new series of N′-substituted derivatives of 5-amino-N,3-dimethyl-1,2-oxazole-4-carbohydrazide (MM1⁻MM10) was synthesized in reaction of 5-amino-N,3-dimethyl-1,2-oxazole-4-carbohydrazide with relevant carbonyl compounds. The isoxazole derivatives were tested in several in vitro models using human cells. The compounds inhibited phytohemagglutinin A (PHA)-induced proliferation of peripheral blood mononuclear cells (PBMCs) to various degrees. The toxicity of the compounds with regard to a reference A549 cell line was also differential. 5-amino-N′-(2,4-dihydroxyphenyl)methylidene-N,3-dimethyl-1,2-oxazole-4-carbohydrazide (MM3) compound was selected for further investigation because of its lack of toxicity and because it had the strongest antiproliferative activity. The compound was shown to inhibit lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF α) production in human whole blood cell cultures. In the model of Jurkat cells, MM3 elicited strong increases in the expression of caspases, Fas, and NF-κB1, indicating that a proapoptotic action may account for its immunosuppressive action in the studied models.

5-Amino-3-methyl-4-isoxazolecarboxylic acid hydrazide derivatives with in vitro immunomodulatory activities

Isoxazoles are an important class of compounds of potential therapeutic value. The aim of this study was to determine immunotropic effects of 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide derivatives on spontaneous and mitogen-induced lymphocyte proliferation in young and old mice, cytokine production by peritoneal cells as well as possible mechanism of action in a model of Jurkat cells. Three-month-old and 13-month-old BALB/c mice were used as donors of the cells from a thymus, a spleen, mesenteric lymph nodes, and a peritoneal cavity. Spontaneous and concanavalin A or lipopolysaccharide (LPS)-induced cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric method. IL-1β and TNF-α production induced by LPS in macrophage-enriched peritoneal cell cultures was measured by enzyme-linked immunoassay. 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide, 01K (4-phenyl-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide), and 06K (4-(4-chlorophenyl)-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide) exhibited regulatory activity in the proliferation tests. Prevailing stimulatory activity of the hydrazide and inhibitory activity of 01K and 06K was observed. Those effects were connected with different influence of the compounds on signaling proteins expression in Jurkat cells. The regulatory effects of the compounds on IL-1β production were more profound than those on TNF-α. Differences in the compound activity in young versus old mice were mainly restricted to 01K. Immunosuppressive isoxazole leflunomide and a stimulatory RM-11 (1,7-dimethyl-8-oxo-1,2H-isoxazole [5,4-e]triazepine) were applied as reference drugs.

Immunoregulatory effects of 4-(4-chlorophenyl)-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide (06K) in non-immunized and SRBC-immunized mice

OBJECTIVES

Immunoregulatory properties of 06K derivative (4-(4-chlorophenyl)-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide) in mouse in vivo models were investigated.

METHODS

Several in vivo models were used: humoral and cellular immune response, carrageenan inflammatory reaction and determination of lymphocyte subsets in non-immunized mice.

KEY FINDINGS

The compound administered before or after immunization with sheep erythrocytes (sheep red blood cell (SRBC)) elevated the number of plaque-forming cells (PFC), and this effect was stronger at lower doses. Although total haemagglutinin titres to SRBC decreased upon postimmunization treatment, IgG titre increased. In the model of delayed-type hypersensitivity (DTH) to ovalbumin (OVA), the compound, applied intraperitoneally before an eliciting dose of an antigen but not before immunization, inhibited the magnitude of a cutaneous reaction. Further, 06K significantly diminished carrageenan-induced foot pad inflammation when administered 1 h before carrageenan. The compound, administered intraperitoneally to naïve mice, elicited changes in weight, cell number in lymphoid organs and content of lymphocyte subsets, depending on the dose and number of applications. Phenotypic changes included increased turnover of thymocytes, changes in B-cell distribution in spleens and lymph nodes, increased percentage of CD8⁺ cells and regulatory CD4⁺ CD25⁺ Foxp3⁺ T cells.

CONCLUSIONS

Immunoregulatory properties of 06K involve mobilization of lymphopoiesis and generation of regulatory T cells.

Anti-inflammatory properties of an isoxazole derivative - MZO-2

BACKGROUND

A series of new isoxazole derivatives of expected immunosuppressive activities was synthesized. Following in vitro screening in the human cell models, the activity of MZO-2 compound (ethyl N-{4-[(2,4-dimethoxybenzyl)carbamoyl]-3-methylisoxazol-5-yl}acetimidate) in mouse in vivo models was evaluated.

METHODS

In vitro tests included evaluation of: peripheral blood mononuclear cells (PBMC) viability, phytohemagglutinin (PHA)-induced PBMC proliferation and lipopolysaccharide (LPS)-induced tumor necrosis factor α (TNF α) production in whole blood cell cultures. MZO-2 was studied in mice for its effects on: humoral immune response to sheep erythrocytes (SRBC), delayed type hypersensitivity (DTH) to ovalbumin (OVA), contact sensitivity to oxazolone and carrageenan-induced foot pad edema. In addition, the effect of MZO-2 on expression of caspases in Jurkat cells was determined.

RESULTS

The studied compounds exhibited differential, dose-dependent effects to suppress PHA-induced PBMC proliferation and a weak property to suppress LPS-induced production of TNF α. MZO-2 had no effect on the induction phase of the humoral immune response to SRBC in vitro and in vivo, but moderately suppressed the induction phase of DTH to OVA. Its inhibitory effect on carrageenan-induced paw inflammation was potent. Likewise, MZO-2, applied in ointment, was very effective in reducing ear edema and number of lymphocytes in draining lymph nodes of mice sensitized to oxazolone, comparably to tacrolimus, the reference drug. The expression of caspases 3, 8 and 9 in Jurkat cells was inhibited by the compound.

CONCLUSION

MZO-2, applied systemically or locally, may serve as a potential drug for amelioration of inflammatory processes.

Synthesis and biological activity of cyclolinopeptide A analogues modified with γ(3)-bis(homophenylalanine)

Cyclolinopeptide A, naturally occurring immunomodulatory nonapeptide, was modified with S or R-γ(3)-bis(homophenylalanine) in positions 3 or 4, or both 3 and 4. The replacement of one or both Phe residues by γ(3)-hhPhe led to decrease of their conformational flexibility in the analogues in comparison to CLA. All cyclic peptides, except 11, exist as isomers with the cis Pro-Pro peptide bond. Cyclic peptide 11 with single modification S-γ(3)-hhPhe(4) exists as a mixture of two isomers and the major isomer (89%) contains all peptide bonds of the trans geometry. The peptides were subjected to several immunological tests in vitro and in vivo. Linear peptides 1-8, precursors of CLA analogues 9-16, were not toxic against human peripheral blood mononuclear cells (PBMC) but cyclic analogues showed dose-dependent toxicity with exception of peptide 11. Linear peptides did not inhibit mitogen-induced PBMC proliferation whereas cyclic ones inhibited the proliferation in a dose-dependent manner. The actions of linear and cyclic peptides with regard to lipopolysaccharide (LPS) -induced tumour necrosis factor alpha (TNF α) production in whole human blood cultures were differential but particularly suppressive in the case of linear compound 6. Therefore, for in vivo tests compounds 6 and 11 were selected. The compounds showed comparable, suppressive actions in induction and effector phases of delayed type hypersensitivity as well as in the carrageenan-induced foot pad edema in mouse models. In summary, linear peptide 6 and cyclic peptide 11 are attractive as potential immune suppressor drugs.

In vitro immunomodulatory effects of 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide on the cellular immune response

The aim of this study was to determine the immunomodulatory activity of 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide in vitro. This compound was used for the synthesis of a series of 5-amino-3-methyl-4-isoxazolecarboxylic acid semicarbazides and thiosemicarbazides with documented immunotropic activity. The performed measurements assessed the cytotoxic effect of 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide on the murine macrophages (cell line J774E.1) and lymphoblasts (cell line D10.G4.1), the influence of this compound on the proliferation of murine lymphocytes isolated from peripheral lymphatic organs and murine peritoneal macrophages stimulated with mitogens (concanavalin A(ConA), lipopolysaccharide (LPS), phytohemagglutinin A (PHA)). Moreover, the production of tumor necrosis factor (TNF)-α and interleukin (IL)-1β by the murine peritoneal macrophages stimulated with LPS from Escherichia coli was assessed. It was found that 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide displayed no cytotoxic effects in the murine J774E.1 and D10.G4.1 cell lines in a wide range of concentrations (0.5-200 μg/ml). Furthermore, the compound stimulated proliferation of lymphocytes isolated from the spleen and mesenteric lymph nodes when used alone and in combination with mitogens (ConA and PHA). This effect was stronger in the nonstimulated cells, and it followed a dose-response relationship. The same phenomenon was observed for the proliferation of the murine peritoneal macrophages. The investigated hydrazide, at the highest used concentration of 150 μg/ml, increased the LPS-induced production of IL-1β and did not affect the level of TNF-α. These results confirmed the immunomodulatory properties of 5-amino-3-methyl-4-isoxazolecarboxylic acid hydrazide and indicated that this compound could be useful in further research aimed at finding novel functional drugs.