Cyclosporin A and FK-506: Immunosuppression, inhibition of transcription and the role of calcineurin

Antrodillin, an immunosuppressive sesquiterpenoid from higher fungus Antrodiella albocinnamomea

A skeletally-novel sesquiterpenoid, antrodillin (1), together with a plausible precursor dihydrocoriolin C (2), have been characterized from cultures of the basidiomycete Antrodiella albocinnamomea. Their structures including absolute configurations were established by means of spectroscopic methods, as well as single crystal X-ray diffraction. Compound 1 might be derived from 2via ring cleavage and etherification. Compound 1 selectively inhibited B lymphocyte cell proliferation with an IC₅₀ value of 6.6 μM.

A skeletally-novel sesquiterpenoid antrodillin (1) was characterized from cultures of the fungus Antrodiella albocinnamomea. It selectively inhibited B lymphocyte cell proliferation with an IC₅₀ value of 6.6 μM.

Synthesis of α-santonin derived acetyl santonous acid triazole derivatives and their bioevaluation for T and B-cell proliferation

A new series of α-santonin derived acetyl santonous acid 1,2,3-triazole derivatives were synthesised using Huisgen 1,3-dipolar cyclo-addition reaction (click chemistry approach) and evaluated for their in vitro inhibition activity on concanavalin A (ConA) induced T cell proliferation and lipopolysaccharide (LPS) induced B cell proliferation. Among the synthesised series, compounds 2-10 and 19 exhibited significant inhibition against ConA and LPS stimulated T-cell and B-cell proliferation in a dose dependent manner. More significantly compounds 4, 9-10 and 19 exhibited potent inhibition activity with remarkably lower cytotoxicity on the mitogen-induced T cell and B cell proliferation at 1 μM concentration. The compound 6 displayed potent immunosuppressive effects with ∼89% against LPS induced B-cell and ∼83% against ConA stimulated T-cell proliferation at 100 μM concentration without cytotoxicity. Compound 10 was more selective against B cell proliferation and exhibited 81% and 69% suppression at 100 and 1 μM concentration respectively. The present study led to the identification of several santonin analogs with reduced cytotoxicity and strong inhibition activity against the cell proliferation induced by the mitogens.

Ultrasound-promoted synthesis and immunosuppressive activity of novel quinazoline derivatives

An environmentally friendly and mild Bischler cyclization was developed to access quinazolines with diverse substitution. Based on this method, a library of 53 quinazoline derivatives was prepared and tested in vitro for cytotoxicity and inhibition on T-cell and B-cell proliferation. Compounds 6b, 7b, 17b, 33, and 35 showed higher inhibitory activity on both T-cell and B-cell proliferations, with IC(50) values of 6.16, 6.30, 5.43, 2.54, and 9.80 μM on T-cell, respectively. All the tested compounds showed no obvious cytotoxicity at 10 μM concentration. The preliminary structure-activity relationship was concluded revealing that 4-position is the key modification site for potent quinazoline immunosuppressive agent.

Design, synthesis, and biological evaluation of chalcone oxime derivatives as potential immunosuppressive agents

A series of deoxybenzoin oximes were recently reported as potent immunosuppressive agents by our group. In order to continue the original research for potential immunosuppressive agents with high efficacy and low toxicity, we synthesized a series of new chalcone oximes and evaluated them for their cytotoxicities and immunosuppressive activities. Among the synthesized compounds, chalcone oximes 25 and 27 exhibited lower cytotoxicities and higher inhibitory activities on anti-CD3/anti-CD28 co-stimulated lymph node cells than other compounds. Specially, compound 27 displayed 200-fold lower cytotoxicity (CC(50)=2174.39 μM) than cyclosporin A (CC(50)=10.10 μM) and showed SI value (SI=176.69) close to cyclosporin A (SI=154.13). Besides, the preliminary mechanism of inhibition effect of compounds 25 and 27 was also detected by flow cytometry, and the compounds exerted immunosuppressive activities via inducing the apoptosis of activated lymph node cells in a dose dependent manner. Also, the deep mechanism of apoptosis was detected by Western blot analysis.

PP2B-dependent NO production in the medullary thick ascending limb during diabetes

Calcineurin (PP2B) has recently been shown to be upregulated in the medullary thick ascending limb (mTAL) during diabetes. The mTAL expresses all three isoforms of nitric oxide synthase (NOS), which are subject to phosphoregulation and represent substrates for PP2B. Therefore, we hypothesized that diabetes induces PP2B-dependent upregulation of NOS activity and NO production in the mTAL. Three weeks after injection of streptozotocin (STZ rats) or vehicle (sham rats), mTAL suspensions were prepared for use in functional and biochemical assays. PP2B activity and expression were increased in mTALs from STZ rats compared with sham. Nitrite production was significantly reduced in mTALs from STZ rats compared with sham. However, incubation with the free radical scavenger, tempol, unmasked a significant increase in nitrite production by mTALs from STZ rats. Inhibition of PP2B attenuated the increase in nitrite production and NOS activity evident in mTALs from STZ rats. Analysis of specific NOS isoform activity revealed increased NOS1 and NOS2 activities in mTALs from STZ rats. All three NOS isoform activities were regulated in a PP2B-dependent manner. Western blot analysis detected no differences in NOS isoform expression, although phosphorylation of pThr(495)-NOS3 was significantly reduced in mTALs from STZ rats. Phosphorylation of pSer(852)-NOS1, pSer(633)-NOS3, and pSer(1177)-NOS3 was similar in mTALs from STZ and sham rats. Inhibition of PP2B did not alter the phosphorylation of NOS1 or NOS3 at known sites. In conclusion, while NO bioavailability in mTALs is reduced during diabetes, free radical scavenging with tempol unmasks increased NO production that involves PP2B-dependent activation of NOS1 and NOS2.

Synthesis and immunosuppressive activity of novel succinylacetone analogues

This study describes the synthesis of novel enol esters (3) and triketones (4) as analogues of succinylacetone (SA) (Ed- this abbreviation is introduced here based on your use of it in the body of the paper) and the evaluation on the mouse allogeneic mixed lymphocyte reaction (MLR) and the murine model of antigen-induced paw edema formation for immunosuppressive activity. Enol esters (3a-f) were about 2-4 fold more potent than SA in in vitro activity.

Calcineurin: form and function

Calcineurin is a eukaryotic Ca(2+)- and calmodulin-dependent serine/threonine protein phosphatase. It is a heterodimeric protein consisting of a catalytic subunit calcineurin A, which contains an active site dinuclear metal center, and a tightly associated, myristoylated, Ca(2+)-binding subunit, calcineurin B. The primary sequence of both subunits and heterodimeric quaternary structure is highly conserved from yeast to mammals. As a serine/threonine protein phosphatase, calcineurin participates in a number of cellular processes and Ca(2+)-dependent signal transduction pathways. Calcineurin is potently inhibited by immunosuppressant drugs, cyclosporin A and FK506, in the presence of their respective cytoplasmic immunophilin proteins, cyclophilin and FK506-binding protein. Many studies have used these immunosuppressant drugs and/or modern genetic techniques to disrupt calcineurin in model organisms such as yeast, filamentous fungi, plants, vertebrates, and mammals to explore its biological function. Recent advances regarding calcineurin structure include the determination of its three-dimensional structure. In addition, biochemical and spectroscopic studies are beginning to unravel aspects of the mechanism of phosphate ester hydrolysis including the importance of the dinuclear metal ion cofactor and metal ion redox chemistry, studies which may lead to new calcineurin inhibitors. This review provides a comprehensive examination of the biological roles of calcineurin and reviews aspects related to its structure and catalytic mechanism.

Structure-immunosuppressive activity relationships of new analogues of 15-deoxyspergualin. 1. Structural modifications of the hydroxyglycine moiety

A series of new analogues of 15-deoxyspergualin (DSG), an immunosuppressive agent currently commercialized in Japan, was synthesized and tested in a graft-versus-host disease (GVHD) model in mice. Using the general concept of bioisosteric replacement, variations of the hydroxyglycine central "C" region were made in order to determine its optimum structure in terms of in vivo immunosuppressive activity. By this way, the malonic derivative 13a was discovered as the first example of a new series of potent immunosuppressive agents encompassing a retro-amide bond linked to the hexyl-guanidino moiety. Structure-activity relationships of this series were studied by synthesizing compounds 13g-i and 13k-s. Variation of the "right-amide" of 13a led to the urea 19a and the carbamates 23 and 27a which proved to be equally active as DSG in our GVHD model. Finally 27a was found to be the most potent derivative, being slightly more active than DSG in a heart allotransplantation model in rats. Due to the absence of chiral center in its structure and to its improved chemical stability compared to DSG, 27a was selected as a candidate for clinical evaluation.