The First Reciprocal Activities of Chiral Peptide Pharmaceuticals: Thymogen and Thymodepressin, as Examples.

Peptides show high promise in the targeting and intracellular delivery of next-generation biotherapeutics. The main limitation is peptides' susceptibility to proteolysis in biological systems. Numerous strategies have been developed to overcome this challenge by chemically enhancing the resistance to proteolysis. In nature, amino acids, except glycine, are found in L- and D-enantiomers. The change from one form to the other will change the primary structure of polypeptides and proteins and may affect their function and biological activity. Given the inherent chiral nature of biological systems and their high enantiomeric selectivity, there is rising interest in manipulating the chirality of polypeptides to enhance their biomolecular interactions. In this review, we discuss the first examples of up-and-down homeostasis regulation by two enantiomeric drugs: immunostimulant Thymogen (L-Glu-L-Trp) and immunosuppressor Thymodepressin (D-Glu(D-Trp)). This study shows the perspective of exploring chirality to remove the chiral wall between L- and D-biomolecules. The selected clinical result will be discussed.

A novel FK506-loading mesoporous silica nanoparticle homing to lymph nodes for transplant rejection treatment.

Tacrolimus (FK506) is an effective therapeutic for transplant rejection in clinical practice, primarily inhibiting rejection by suppressing the activation and proliferation of allogeneic T cells in the lymph nodes (LNs). However, conventional administration methods face challenges in directly delivering free FK506 to the LNs. In this study, we introduce a novel LN-targeted delivery system based on mesoporous silica nanoparticles (MSNs-FK506-MECA79). These particles were designed to selectively target high endothelial venules in LNs; this was achieved through surface modification with MECA79 antibodies. Their mean size and zeta potential were 201.18 ± 5.98 nm and - 16.12 ± 0.36 mV, respectively. Our findings showed that MSNs-FK506-MECA79 could accumulate in LNs and increase the local concentration of FK506 from 28.02 ± 7.71 ng/g to 123.81 ± 76.76 ng/g compared with the free FK506 treatment group. Subsequently, the therapeutic efficacy of MSNs-FK506-MECA79 was evaluated in a skin transplantation model. The treatment with MSNs-FK506-MECA79 could lead to a decrease in the infiltration of T cells in the grafts, a reduction in the grade of rejection, and a significant prolongation of survival. Consequently, this study presents a promising strategy for the active LN-targeted delivery of FK506 and improving the immunotherapeutic effects on transplant rejection.

Ergosterols with rare peroxide, oxetane ring moiety, and a lactone ring from Aspergillus spectabilis and their immunosuppressive activities.

Ten ergostane-type steroids, including seven undescribed ones named spectasteroids A-G, were obtained from Aspergillus spectabilis. Their structures and absolute configurations were determined based on HRESIMS, NMR, ECD calculations, and single-crystal X-ray diffraction analyses. Structurally, spectasteroid A was a unique example of aromatic ergostane-type steroid that featured a rare peroxide ring moiety; spectasteroid B contained a rare oxetane ring system formed between C-9 and C-14; and spectasteroid C was an unusual 3,4-seco-ergostane steroid with an extra lactone ring between C-3 and C-9. Spectasteroids F and G specifically showed inhibitory effects against concanavalin A-induced T lymphocyte proliferation and lipopolysaccharide-induced B lymphocyte proliferation, with IC50 values ranging from 2.33 to 4.22 µM. Spectasteroid F also showed excellent antimultidrug resistance activity, which remarkable enhanced the inhibitory activity of PTX on the colony formation of SW620/Ad300 cells.

Bibenzyl-Phenylpropane Hybrids with Immunosuppressive Activities from Dendrobium Nobile Lindl.

Fifteen bibenyls and four fluorenones, including five new bibenzyl-phenylpropane hybrids, were isolated from the aerial part of Dendrobium nobile Lindl. Their structures were determined by spectroscopic methods. Bioassay on the LPS-induced proliferations of mouse splenic B lymphocytes, and Con A-induced T lymphocytes showed that compounds 1, 2, and 14 showed excellent immunosuppressive activities with IC50 values of 1.23, 1.01, and 3.87 µM, respectively, while compounds 3-4, 7, 10, 13, and 15 exhibited moderate immunosuppressive activities with IC50 values ranging from 6.89 to 14.2 µM.

Asperustins A-J: Austocystins with Immunosuppressive and Cytotoxic Activities from Aspergillus ustus NRRL 5856.

Ten new (1-10) and nine known (11-19) austocystins, along with four known anthraquinones (20-23), were isolated from the culture of Aspergillus ustus NRRL 5856 by bioactivity-guided fractionation. The structures of the new compounds were elucidated by spectroscopic data analysis, X-ray crystallographic study, the modified Mosher's method, [Rh2(OCOCF3)4]-induced ECD spectral analysis, and comparison of the experimental ECD spectra with those of the similar analogues. Compounds 1-8 represent the first examples of austocystins with a C-4' oxygenated substitution. The absolute configuration of 1″-hydroxy austocystin D (11) was determined by single-crystal X-ray diffraction and consideration of its biosynthetic origin. Compounds 5, 9, and 11 exhibited significant inhibitory effects against the proliferation of ConA-induced T cells with IC50 values of 1.1, 1.0, and 0.93 µM, respectively. Furthermore, these compounds suppressed the expression of IL-6 in a dose-dependent manner. Compounds 10-12 and 14 showed pronounced cytotoxicities against MCF-7 with IC50 values of 3.9, 1.3, 0.46, and 2.3 µM, respectively.

Pharmacological Effects of FTY720 and its Derivatives.

FTY720 is an analog of sphingosine-1-phosphate (S1P) derived from the ascomycete Cordyceps sinensis. As a new immunosuppressant, FTY720 is widely used to treat multiple sclerosis. FTY720 binds to the S1P receptor after phosphorylation, thereby exerting immunosuppressive effects. The nonphosphorylated form of FTY720 can induce cell apoptosis, enhance chemotherapy sensitivity, and inhibit tumor metastasis of multiple tumors by inhibiting SPHK1 (sphingosine kinase 1) and activating PP2A (protein phosphatase 2A) and various cell death pathways. FTY720 can induce neutrophil extracellular traps to neutralize and kill pathogens in vitro, thus exerting anti- infective effects. At present, a series of FTY720 derivatives, which have pharmacological effects such as anti-tumor and alleviating airway hyperresponsiveness, have been developed through structural modification. This article reviews the pharmacological effects of FTY720 and its derivatives.

Generation of Bioactivity-Tailored FK506/FK520 Analogs by CRISPR Editing in Streptomyces tsukubaensis.

For a potential application of FK506 in the treatment of acute kidney failure only the FKBP12 binding capability of the compound is required, while the immunosuppressive activity via calcineurin binding is considered as a likely risk to the patients. The methoxy groups at C13 and C15 are thought to have significant influence on the immunosuppressive activity of the molecule. Consequently, FK506 analogs with different functionalities at C13 and C15 were generated by targeted CRISPR editing of the AT domains in module 7 and 8 of the biosynthetic assembly line in Streptomyces tsukubaensis. In addition, the corresponding FK520 (C21 ethyl derivative of FK506) analogs could be obtained by media adjustments. The compounds were tested for their bioactivity in regards to FKBP12 binding, BMP potentiation and calcineurin sparing. 15-desmethoxy FK506 was superior to the other tested analogs as it did not inhibit calcineurin but retained high potency towards FKBP12 binding and BMP potentiation.

[Advances of the novel immunosuppressant brasilicardin A].

Brasilicardin A (BraA) is a natural diterpene glycoside isolated from the pathogenic actinomycete Nocardia brasiliensis IFM 0406 with highly potent immunosuppressive activity (IC50=0.057 µg/mL). BraA potently inhibits the uptake of amino acids that are substrates for amino acid transport system L of T cells, which is different from the existing clinical immunosuppressants. BraA is more potent in a mouse mixed lymphocyte reaction and less toxic against various human cell lines compared with the known clinical immunosuppressants, such as cyclosporin A, ascomycin and tacrolimus. Therefore, BraA attracted more attention as a new promising immunosuppressant. However, the development of this promising immunosuppressant as drug for medical use is so far hindered because BraA has the unusual and synthetically challenging skeleton and shows the low-yield production in the natural pathogenic producer. This review introduces the molecular structure of BraA, its activity, mechanism of action, chemical synthesis of BraA analogs, heterologous expression of gene cluster, and an application of combining microbial and chemical synthesis for production of BraA, with the aim to facilitate the efficient production of BraA and its analogs.

Immunosuppressive effects of new thiophene-based KV1.3 inhibitors.

Voltage-gated potassium channel KV1.3 inhibitors have been shown to be effective in preventing T-cell proliferation and activation by affecting intracellular Ca2+ homeostasis. Here, we present the structure-activity relationship, KV1.3 inhibition, and immunosuppressive effects of new thiophene-based KV1.3 inhibitors with nanomolar potency on K+ current in T-lymphocytes and KV1.3 inhibition on Ltk- cells. The new KV1.3 inhibitor trans-18 inhibited KV1.3 -mediated current in phytohemagglutinin (PHA)-activated T-lymphocytes with an IC50 value of 26.1 nM and in mammalian Ltk- cells with an IC50 value of 230 nM. The KV1.3 inhibitor trans-18 also had nanomolar potency against KV1.3 in Xenopus laevis oocytes (IC50 = 136 nM). The novel thiophene-based KV1.3 inhibitors impaired intracellular Ca2+ signaling as well as T-cell activation, proliferation, and colony formation.

Comparative study of cyclosporine A liposomes and emulsions for ophthalmic drug delivery: Process optimization through response surface methodology (RSM) and biocompatibility evaluation.

Herein, cyclosporine A loaded liposomes (CsA-Lips) were fabricated aimed at improving the biocompatibility of the ophthalmic formulation and getting rid of the direct contact of ocular tissues with irritant excipients. Response surface methodology was exploited in order to investigate the influence of miscellaneous factors on the key characteristics of CsA-Lips. Ratio of EPC:CsA, ratio of EPC:Chol, and stirring speed were selected as the independent variables, while size, drug-loading content (DL), and drug-loading content (DL) loss rate were applied as the response variables. In case of the maximal lack-of-fit p-value and minimum sequential p-value, quadratic model was regarded as the fittest model to analyze the data. The correlation of independent variables with response variables was described by three-dimension surface figures. Optimized formulation for CsA-Lips was obtained with ratio of EPC:CsA set as 15, ratio of EPC:Chol set as 2, and stirring speed set as 800 rpm. The particle size of CsA-Lips was 129.2 nm after optimalization while their TEM images exhibited spherical unilamellar vesicles with clearly shell-core structure. CsA released more rapidly from CsA-Lips in comparison with self-made emulsion and Restasis®. Besides, minimum cytotoxicity of CsA-Lips was perceived via both MTT method and LDH method, indicating the excellent compatibility of the ophthalmic formulation. Simultaneously, CsA-Lips showed enhanced nonspecific internalization in the cytoplasm with a time-dose-dependent manner. In conclusion, CsA-Lips could be adhibited as the hopeful ophthalmic drug delivery system clinically for dry eye syndrome (DES).

Novel amides of mycophenolic acid and some heterocyclic derivatives as immunosuppressive agents.

The group of 18 new amide derivatives of mycophenolic acid (MPA) and selected heterocyclic amines was synthesised as potential immunosuppressive agents functioning as inosine-5'-monophosphate dehydrogenase (IMPDH) uncompetitive inhibitors. The synthesis of 14 of them employed uronium-type activating system (TBTU/HOBt/DIPEA) while 4 of them concerned phosphonic acid anhydride method (T3P/Py) facilitating amides to be obtained in moderate to excellent yields without the need of phenolic group protection. Most of optimised protocols did not require complicated reaction work-ups, including chromatographic, solvent-consuming methods. The biological activity assay was performed on the T-Jurkat cell line and peripheral mononuclear blood cells (PBMCs) which are both dedicated for antiproliferative activity determination. Each of designed derivatives was characterised by reduced cytotoxicity and benzoxazole analogue (A2) revealed the most promising activity. Subsequently, an observed structure-activity relationship was discussed.

Antroxazole A, an oxazole-containing chamigrane dimer from the fungus Antrodiella albocinnamomea with immunosuppressive activity.

Antroxazole A (1), a chamigrane type sesquiterpene dimer containing an oxazole moiety, has been characterized from cultures of the fungus Antrodiella albocinnamomea. The structure with absolute configuration was determined by extensive spectroscopic methods and single crystal X-ray diffraction. A plausible biosynthetic pathway for 1 was proposed. Compound 1 exhibits inhibition specifically against the LPS-induced proliferation of B lymphocyte cells with an IC50 value of 16.3 µM.

Resorcylic acid lactones from a Podospora sp. that induce apoptosis in activated T cells through MAPKs/AKT pathway.

Podomycins A-L (1-12), 12 undescribed hypothemycin-type resorcylic acid lactones (RALs), were characterized from Podospora sp. G214, an endophyte harbored in the roots of Sanguisorba officinalis L. Their structures were addressed by spectroscopic data, X-ray crystallography, the modified Mosher's method, together with Mo2(OAc)4- and Rh2(OCOCF3)4-induced electronic circular dichroism (ICD) experiments. Podomycins A-C (1-3) represent the first class of natural RALs with a 13-membered macrolactone ring, while 4-12 are rearranged methoxycarbonyl substituted RALs. Biologically, compounds 2, 6, 8, 10, and 12 displayed immunosuppressive activities against T cell proliferation with IC50 values of 14.5-21.9 µM, and B cell proliferation with IC50 values of 22.3-36.5 µM, respectively. Further mechanism of action research demonstrated that podomycin F (6) distinctly induced apoptosis in activated T cells via MAPKs/AKT pathway.

Structure-Based Design of Dual-Acting Compounds Targeting Adenosine A2A Receptor and Histone Deacetylase as Novel Tumor Immunotherapeutic Agents.

Adenosine is an immunosuppressive factor in the tumor microenvironment mainly through activation of the A2A adenosine receptor (A2AR), which is a mechanism hijacked by tumors to escape immune surveillance. Small-molecule A2AR antagonists are being evaluated in clinical trials as immunotherapeutic agents, but their efficacy is limited as standalone therapies. To enhance the antitumor effects of A2AR antagonists, dual-acting compounds incorporating A2AR antagonism and histone deacetylase (HDAC) inhibitory actions were designed and synthesized, based on co-crystal structures of A2AR. Compound 24e (IHCH-3064) exhibited potent binding to A2AR (Ki = 2.2 nM) and selective inhibition of HDAC1 (IC50 = 80.2 nM), with good antiproliferative activity against tumor cell lines in vitro. Intraperitoneal administration of 24e (60 mg/kg, bid) inhibited mouse MC38 tumor growth with a tumor growth inhibition rate of 95.3%. These results showed that dual-acting compounds targeting A2AR and HDAC are potentially immunotherapeutic agents that are worth further exploring.

Could ß-Lactam Antibiotics Block Humoral Immunity?

It has been reported that treatment with ß-lactam antibiotics induces leukopenia and candidemia, worsens the clinical response to anticancer immunotherapy and decreases immune response to vaccination. ß-lactamases can cleave ß-lactam antibiotics by blocking their activity. Two distincts superfamilies of ß-lactamases are described, the serine ß-lactamases and the zinc ion dependent metallo-ß-lactamases. In human, 18 metallo-ß-lactamases encoding genes (hMBLs) have been identified. While the physiological role of most of them remains unknown, it is well established that the SNM1A, B and C proteins are involved in DNA repair. The SNM1C/Artemis protein is precisely associated in the V(D)J segments rearrangement, that leads to immunoglobulin (Ig) and T-cell receptor variable regions, which have a crucial role in the immune response. Thus in humans, SNM1C/Artemis mutation is associated with severe combined immunodeficiency characterized by hypogammaglobulinemia deficient cellular immunity and opportunistic infections. While catalytic site of hMBLs and especially that of the SNM1 family is highly conserved, in vitro studies showed that some ß-lactam antibiotics, and precisely third generation of cephalosporin and ampicillin, inhibit the metallo-ß-lactamase proteins SNM1A & B and the SNM1C/Artemis protein complex. By analogy, the question arises as to whether ß-lactam antibiotics can block the SNM1C/Artemis protein in humans inducing transient immunodeficiency. We reviewed here the literature data supporting this hypothesis based on in silico, in vitro and in vivo evidences. Understanding the impact of ß-lactam antibiotics on the immune cell will offer new therapeutic clues and new clinical approaches in oncology, immunology, and infectious diseases.

An Immunomodulatory Peptide Dendrimer Inspired from Glatiramer Acetate.

Glatiramer acetate (GA) is a random polypeptide drug used to treat multiple sclerosis (MS), a chronic autoimmune disease. With the aim of identifying a precisely defined alternative to GA, we synthesized a library of peptide dendrimers with an amino acid composition similar to GA. We then challenged the dendrimers to trigger the release of the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1Ra) from human monocytes, which is one of the effects of GA on immune cells. Several of the largest dendrimers tested were as active as GA. Detailed profiling of the best hit showed that this dendrimer induces the differentiation of monocytes towards an M2 (anti-inflammatory) state as GA does, however with a distinct immune marker profile. Our peptide dendrimer might serve as starting point to develop a well-defined immunomodulatory analog of GA.

Discovery of Benzocyclic Sulfone Derivatives as Potent CXCR2 Antagonists for Cancer Immunotherapy.

Increasing evidence shows that the CXC chemokine receptor 2 (CXCR2) signaling pathway is essentially implicated in the recruitment of myeloid-derived suppressor cells (MDSCs) to the tumor microenvironment and leads to MDSC-mediated immune suppression. Therefore, CXCR2 has recently emerged as a promising drug target for cancer immunotherapy. In this paper, benzocyclic sulfone derivatives were designed as potent CXCR2 antagonists. Structure-activity relationship studies resulted in two lead compounds 9b and 11h, which demonstrated double-digit nanomolar potencies against CXCR2 and significantly inhibited neutrophil infiltration into the air pouch in an in vivo setting. More importantly, 9b and 11h dose-dependently inhibited the tumor growth through oral administration in the Pan02 mouse model. Further cytometry and immunohistochemical analyses revealed that 9b and 11h could reduce the infiltration of neutrophils and MDSCs and enhance the infiltration of CD3+ T lymphocytes into the Pan02 tumor tissues, shedding light on their mechanisms of action in cancer immunotherapy.

Structurally diverse biflavonoids from the fruits of Citrus medica L. var. sarcodactylis Swingle and their hypolipidemic and immunosuppressive activities.

The fruit of Citrus medica L. var. sarcodactylis Swingle is not only used as a traditional medicinal plant, but also served as a delicious food. Six new (3'→7″)-biflavonoids (1-6), and twelve known biflavonoid derivatives (7-18) were isolated and characterized from the fruits of C. medica L. var. sarcodactylis Swingle for the first time. Their structures were determined by extensive and comprehensive analyzing NMR, HR-ESI-MS, UV, and IR spectral data coupled with the data described in the literature. Compounds (1-18) were evaluated for their hypolipidemic activities with Orlistat as the positive control, and assayed for their immunosuppressive activities with Dexamethasone as the positive control, respectively. Among them, compounds (1-3) exhibited moderate inhibition of pancreatic lipase activity by inhibiting 68.56 ± 1.40%, 56.18 ± 1.57%, 53.51 ± 1.59% of pancreatic lipase activities at the concentration of 100 µM, respectively. Compounds (4-6) and 8 showed potent immunosuppressive activities with the IC50 values from 16.83 ± 1.32 to 50.90 ± 1.79 µM. The plausible biogenetic pathway and preliminary structure activity relationship of the selected compounds were scientifically summarized and discussed in this study.

Calcium Phosphate-Reinforced Metal-Organic Frameworks Regulate Adenosine-Mediated Immunosuppression.

Long-term accumulation of adenosine (Ado) in tumor tissues helps to establish the immunosuppressive tumor microenvironment and to promote tumor development. Regulation of Ado metabolism is particularly pivotal for blocking Ado-mediated immunosuppression. The activity of adenosine kinase (ADK) for catalyzing the phosphorylation of Ado plays an essential role in regulating Ado metabolism. Specifically, accumulated Ado in the tumor microenvironment occupies the active site of ADK, inhibiting the phosphorylation of Ado. Phosphate can protect ADK from inactivation and restore the activity of ADK. Herein, calcium phosphate-reinforced iron-based metal-organic frameworks (CaP@Fe-MOFs) are designed to reduce Ado accumulation and to inhibit Ado-mediated immunosuppressive response in the tumor microenvironment. CaP@Fe-MOFs are found to regulate the Ado metabolism by promoting ADK-mediated phosphorylation and relieving the hypoxic tumor microenvironment. Moreover, CaP@Fe-MOFs can enhance the antitumor immune response via Ado regulation, including the increase of T lymphocytes and dendritic cells and the decrease of regulatory T lymphocytes. Finally, CaP@Fe-MOFs are used for cancer treatment in mice, alleviating the Ado-mediated immunosuppressive response and achieving tumor suppression. This study may offer a general strategy for blocking the Ado-mediated immunosuppression in the tumor microenvironment and further for enhancing the immunotherapy efficacy in vivo.

Identification of the Primary Structure of Selenium-Containing Polysaccharides Selectively Inhibiting T-Cell Proliferation.

We previously described the biosynthesis, isolation, and immunosuppressive activity of the selenium-containing polysaccharide fraction isolated from the mycelial culture of Lentinula edodes. Structural studies have shown that the fraction was a protein-containing mixture of high molar mass polysaccharides α- and ß-glucans. However, which of the components of the complex fraction is responsible for the immunosuppressive activity non-typical for polysaccharides of fungal origin has not been explained. In the current study, we defined four-polysaccharide components of the Se-containing polysaccharide fraction determined their primary structure and examined the effect on T- and B-cell proliferation. The isolated Se-polysaccharides, α-1,4-glucan (Mw 2.25 × 106 g/mol), unbranched ß-1,6-d-glucan, unbranched ß-1,3-d-glucan and ß-1,3-branched ß-1,6-d-glucan (Mw 1.10 × 105 g/mol), are not typical as components of the cell wall of L. edodes. All are biologically active, but the inhibitory effect of the isolated polysaccharides on lymphocyte proliferation was weaker, though more selective than that of the crude fraction.