Quercetin binds to calcineurin at a similar region to cyclosporin A and tacrolimus

Tacrolimus, Cytochrome P450, Interactions with Food Variables in Organ Transplant Recipients; A Current and Comprehensive Review

The well-established calcineurin inhibitor, tacrolimus, as an immunosuppressive agent, is widely prescribed after organ transplantation. Cytochrome P450 (CYP 450) isoforms are responsible for the metabolism of many features associated with food parameters like phytochemicals, juices, and fruits. This review article summarizes the findings of previous studies to help predict the efficacy or side effects of tacrolimus in the presence of food variables. From the commencement of databases associated with the topic of interest to 26 October 2024, all relevant articles were searched through PubMed, Scopus, and Web of Science. The suggested therapeutic range for tacrolimus trough concentration (C0 ) was reported as 5-15 ng/ml blood. Tacrolimus interaction with food variables could significantly change C0 after organ transplantation. For example, grapefruit juice could increase tacrolimus C0 due to CYP enzyme inhibition. Toxicity such as nephrotoxicity could result from turmeric and other herbal or food products. By inhibiting tacrolimus-metabolizing enzymes and transporters, a high intake of vegetables could increase the risk of adverse effects. Secondary metabolites of vegetables could lead to toxicity in patients with tacrolimus. Furthermore, grapefruit juice, citrus fruits, turmeric, and pomegranate juice could change clinical pharmacokinetics parameters such as Tmax, Cmax, AUC, and C0 of tacrolimus after organ transplantation. Bioavailability of tacrolimus might be decreased by induction of the CYP450 system and P-gp efflux pump due to cranberry, rooibos tea, and boldo. Increased inhibitory effect on CYP450 system and/or P-gp efflux pump by grapefruit juice, schisandra, berberine, turmeric, pomegranate juice, pomelo, and ginger could increase bioavailability of tacrolimus. A vigilant immunosuppressive strategy accompanied by scheduled therapeutic drug monitoring is recommended before and after transplant surgery.

Involvement of heme oxygenase-1 in suppression of T cell activation by quercetin

AIM

Acute rejection is still a major problem in transplantation and one of the most important causes of late graft loss. Cyclosporine and tacrolimus are widely used for suppression of T cell function to avoid graft rejection, but long-term use of these compounds is associated with serious toxicities. Quercetin, a flavonoid found in fruits and vegetables, has been demonstrated to exhibit cytoprotective effects through the induction of heme oxygenase (HO) -1, an enzyme involved in heme catabolism. We hypothesized that quercetin induces HO-1 in T cells and suppresses T cell function via HO-1. In the present study, we showed that quercetin suppressed the A23187-mediated expression of interleukin (IL) -2 in T cells.

METHODS

Mouse splenocytes, enriched T cells, and EL4 cells, a mouse T cell line, were treated with quercetin, and then stimulated with A23187, a calcium ionophore, concanavalin A, or anti-CD3ε and anti-CD28 antibodies. Cell proliferation, expression of IL-2, calcium mobilization, apoptosis, cell cycle, and phosphorylation of extracellular signal-regulated kinase (ERK) were investigated.

RESULTS

Quercetin induced HO-1, and this induction of HO-1 was implicated in the suppression of IL-2 production. Furthermore, the induction of HO-1 by quercetin suppressed the influx of calcium ions, a known trigger of IL-2 production. Additionally, quercetin suppressed T cell proliferation through promotion of cell cycle arrest via HO-1 induction, but quercetin did not induce apoptosis. To investigate the role of the signal transduction pathway in quercetin's effect on cell proliferation, we evaluated the phosphorylation of ERK in T cells. Quercetin suppressed the A23187-mediated stimulation of ERK, an effect that was mediated through HO-1. These results suggested that HO-1 is involved in the suppressive effects of quercetin on T cell activation and proliferation.

CONCLUSION

Our findings indicate that the quercetin may be a promising candidate for inducing HO-1 in T cells, thereby facilitating immunosuppressive effects.

Mice Fed a High-Cholesterol Diet Supplemented with Quercetin-3-Glucoside Show Attenuated Hyperlipidemia and Hyperinsulinemia Associated with Differential Regulation of PCSK9 and LDLR in their Liver and Pancreas

SCOPE

Hepatic LDL receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9) regulate the clearance of plasma LDL-cholesterol (LDL-C): LDLR promotes it, and PCSK9 opposes it. These proteins also express in pancreatic β cells. Using cultured hepatocytes, we previously showed that the plant flavonoid quercetin-3-glucoside (Q3G) inhibits PCSK9 secretion, stimulated LDLR expression, and enhanced LDL-C uptake. Here, we examine whether Q3G supplementation could reverse the hyperlipidemia and hyperinsulinemia of mice fed a high-cholesterol diet, and how it affects hepatic and pancreatic LDLR and PCSK9 expression.

METHODS AND RESULTS

For 12 weeks, mice are fed a low- (0%) or high- (1%) cholesterol diet (LCD or HCD), supplemented or not with Q3G at 0.05 or 0.1% (w/w). Tissue LDLR and PCSK9 is analyzed by immunoblotting, plasma PCSK9 and insulin by ELISA, and plasma cholesterol and glucose by colorimetry. In LCD-fed mice, Q3G has no effect. In HCD-fed mice, it attenuates the increase in plasma cholesterol and insulin, accentuates the decrease in plasma PCSK9, and increases hepatic and pancreatic LDLR and PCSK9. In cultured pancreatic β cells, however, it stimulates PCSK9 secretion.

CONCLUSION

In mice, dietary Q3G could counter HCD-induced hyperlipidemia and hyperinsulinemia, in part by oppositely modulating hepatic and pancreatic PCSK9 secretion.

Peptides derived from transcription factor EB bind to calcineurin at a similar region as the NFAT-type motif

Calcineurin (CN) is involved in many physiological processes and interacts with multiple substrates. Most of the substrates contain similar motifs recognized by CN. Recent studies revealed a new CN substrate, transcription factor EB (TFEB), which is involved in autophagy. We showed that a 15-mer QSYLENPTSYHLQQS peptide from TFEB (TFEB-YLENP) bound to CN. When the TFEB-YLENP peptide was changed to YLAVP, its affinity for CN increased and it had stronger CN inhibitory activity. Molecular dynamics simulations revealed that the TFEB-YLENP peptide has the same docking sites in CN as the 15-mer DQYLAVPQHPYQWAK motif of the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1-YLAVP). Moreover expression of the NFATc1-YLAVP peptide suppressed the TFEB activation in starved Hela cells. Our studies first identified a CN binding site in TFEB and compared the inhibitory capability of various peptides derived from CN substrates. The data uncovered a diversity in recognition sequences that underlies the CN signaling within the cell. Studies of CN-substrate interactions should lay the groundwork for developing selective CN peptide inhibitors that target CN-substrate interaction in vitro experiments.

Impact of quercetin‑induced changes in drug‑metabolizing enzyme and transporter expression on the pharmacokinetics of cyclosporine in rats

The aim of the present study was to evaluate whether quercetin (Que) modulates the mRNA and protein expression levels of drug-metabolizing enzymes (DMEs) and drug transporters (DTs) in the small intestine and liver, and thus modifies the pharmacokinetic profile of cyclosporine (CsA) in rats. This two-part study evaluated the pharmacokinetic profiles of CsA in the presence or absence of Que (experiment I) and the involvement of DMEs and DTs (experiment II). In experiment I, 24 rats received single-dose CsA (10 mg/kg) on day 1, single-dose Que (25, 50 and 100 mg/kg/day; eight rats in each group) on days 3–8, and concomitant CsA/Que on day 9. In experiment II, the mRNA and protein expression levels of cytochrome P (CYP)3A1, CYP3A2, UDP glucuronosyltransferase family 1 member A complex locus, organic anion-transporting polypeptide (OATP)2B1, OATP1B2, P-glycoprotein, breast cancer resistance protein, and multidrug resistance-associated protein 2 in the small intestine and liver of rats were analyzed following oral administration of Que at 25, 50 and 100 mg/kg in the presence or absence of CsA (10 mg/kg) for seven consecutive days. Co-administration of Que (25,50 and 100 mg/kg) decreased the maximum serum concentration of CsA by 46, 50 and 47% in a dose-independent manner. In addition, the area under the curve to the last measurable concentration and area under the curve to infinite time were decreased, by 21 and 16%, 30 and 33%, and 33 and 34% (P<0.01), respectively. However, the mRNA and protein expression levels of the above-mentioned DMEs and DTs were inhibited by Que in a dose-dependent manner (P<0.01) to a similar extent in the small intestine and liver. It was demonstrated that Que was able to reduce the bioavailability of CsA following multiple concomitant doses in rats. Overlapping modulation of intestinal and hepatic DMEs and DTs, as well as the DME-DT interplay are potential explanations for these observations.

Calcineurin β protects brain after injury by activating the unfolded protein response

The Ca²⁺-dependent phosphatase, calcineurin (CN) is thought to play a detrimental role in damaged neurons; however, its role in astrocytes is unclear. In cultured astrocytes, CNβ expression increased after treatment with a sarco/endoplasmic reticulum Ca²⁺-ATPase inhibitor, thapsigargin, and with oxygen and glucose deprivation, an in vitro model of ischemia. Similarly, CNβ was induced in astrocytes in vivo in two different mouse models of brain injury - photothrombotic stroke and traumatic brain injury (TBI). Immunoprecipitation and chemical activation dimerization methods pointed to physical interaction of CNβ with the unfolded protein response (UPR) sensor, protein kinase RNA-like endoplasmic reticulum kinase (PERK). In accordance, induction of CNβ resulted in oligomerization and activation of PERK. Strikingly, the presence of a phosphatase inhibitor did not interfere with CNβ-mediated activation of PERK, suggesting a hitherto undiscovered non-enzymatic role for CNβ. Importantly, the cytoprotective function of CNβ was PERK-dependent both in vitro and in vivo. Loss of CNβ in vivo resulted in a significant increase in cerebral damage, and correlated with a decrease in astrocyte size, PERK activity and glial fibrillary acidic protein (GFAP) expression. Taken together, these data reveal a critical role for the CNβ-PERK axis in not only prolonging astrocyte cell survival but also in modulating astrogliosis after brain injury.

Quercetin targets the interaction of calcineurin with LxVP-type motifs in immunosuppression

Calcineurin (CN) is a unique calcium/calmodulin (CaM)-activated serine/threonine phosphatase. To perform its diverse biological functions, CN communicates with many substrates and other proteins. In the physiological activation of T cells, CN acts through transcriptional factors belonging to the NFAT family and other transcriptional effectors. The classic immunosuppressive drug cyclosporin A (CsA) can bind to cyclophilin (CyP) and compete with CN for the NFAT LxVP motif. CsA has debilitating side effects, including nephrotoxicity, hypertension and tremor. It is desirable to develop alternative immunosuppressive agents. To this end, we first tested the interactions between CN and the LxVP-type substrates, including endogenous regulators of calcineurin (RCAN1) and NFAT. Interestingly, we found that quercetin, the primary dietary flavonol, can inhibit the activity of CN and significantly disrupt the associations between CN and its LxVP-type substrates. We then validated the inhibitory effects of quercetin on the CN-NFAT interactions in cell-based assays. Further, quercetin also shows dose-dependent suppression of cytokine gene expression in mouse spleen cells. These data raise the possibility that the interactions of CN with its LxVP-type substrates are potential targets for immunosuppressive agents.

The Therapeutic Effects of the Chinese Herbal Medicine, Lang Chuang Fang Granule, on Lupus-Prone MRL/lpr Mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that leads to severe multiorgan damage. Lang Chuang Fang (LCF) is a Chinese herbal medicine that is clinically prescribed for treating SLE. In this study, we examined the therapeutic effects of LCF granule on lupus-prone MRL/lpr mice. Female mice were randomly separated into six groups, and LCF treatment groups received LCF granule at the dosage of 0.97 g/kg/d, 1.95 g/kg/d, and 3.90 g/kg/d, respectively. Here, we found that, compared to the MRL/lpr mice, both the spleen coefficient and thymus coefficient were reduced in the LCF granule-treated mice. There was a marked downregulation in CRP and anti-dsDNA autoantibody and an evident upregulation of CH50 in LCF granule-treated mice. LCF granule treatment also obviously reduced the proteinuria, BUN, and SCr levels in MRL/lpr mice at the dosage of 0.97 g/kg/d, 1.95 g/kg/d, and 3.90 g/kg/d, indicating that LCF granule alleviated the renal injury of MRL/lpr mice. Furthermore, LCF granule decreased p65 NF-κB levels and increased Sirt1 and Nrf2 levels in the kidney tissues of MRL/lpr mice, which might elucidate the beneficial effects of LCF on lupus nephritis. In conclusion, this study demonstrates that LCF granule has therapeutic effects on lupus-prone MRL/lpr mice.

Isogarcinol Extracted from Garcinia mangostana L. Ameliorates Systemic Lupus Erythematosus-like Disease in a Murine Model

Isogarcinol is a new immunosuppressant that we extracted from Garcinia mangostana L. In the present study, we elucidate its beneficial effect in chronic graft-versus-host disease (cGVHD) in mice -- a model for systemic lupus erythematosus (SLE) in human. The oral administration of 60 mg/kg isogarcinol significantly reduced proteinuria, corrected the abnormal serum biochemical indicator, and decreased the amount of serum antibodies and lowered the renal histopathology score. In addition, isogarcinol alleviated the abnormal activation of CD4 T cells and decreased the expression of inflammatory genes and cytokines in the kidneys and peritoneal macrophages. The mechanism of action of isogarcinol is associated with downregulation of CD4 T cells and inflammatory effects. Therefore, we believe that isogarcinol may be a potential therapeutic drug candidate for future treatment of SLE.

Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation

Calcineurin (CN) is a Ca(2+)/calmodulin (CaM) activated serine/threonine phosphatase, and its regulatory region (CNRR) plays a critical role in the coupling of Ca(2+) signals to cellular responses. Ca(2+)/CaM binds to the CNRR, resulting in a conformational change that removes an autoinhibitory domain (CN467-486) from the active site of the phosphatase and activates the enzyme. However, almost the entire regulatory region (CN374-521) is not visible in the electron density maps of reported structures. In this study, we produced separate CN fragments corresponding to the CNRR (CNRR381-521, CN residues 381-521) and determined the binding affinity of CNRR381-521 for Ca(2+)/CaM using isothermal titration calorimetry (ITC). The structural change in CNRR381-521 induced by Ca(2+)/CaM binding was also investigated by Fourier transform infrared spectroscopy (FT-IR). The results indicate that Ca(2+)/CaM binding to CNRR381-521 is an exothermic reaction with a dissociation constant of 2.0×10(-6) M. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.

Carbon nano-onions (multi-layer fullerenes): chemistry and applications

This review focuses on the development of multi-layer fullerenes, known as carbon nano-onions (CNOs). First, it briefly summarizes the most important synthetic pathways for their preparation and their properties and it gives the reader an update over new developments in the recent years. This is followed by a discussion of the published synthetic procedures for CNO functionalization, which are of major importance when elucidating future applications and addressing drawbacks for possible applications, such as poor solubility in common solvents. Finally, it gives an overview over the fields of application, in which CNO materials were successfully implemented.

Immune regulation and anti-inflammatory effects of isogarcinol extracted from Garcinia mangostana L. against collagen-induced arthritis

Isogarcinol is a natural compound that we extracted from Garcinia mangostana L., and we were the first to report that it is a new immunosuppressant. In the present study, we investigated the immune regulation and anti-inflammatory effects of isogarcinol on collagen-induced arthritis (CIA) and explored its potential mechanism in the treatment of rheumatoid arthritis. The oral administration of isogarcinol significantly reduced clinical scores, alleviated cartilage and bone erosion, and reduced the levels of serum inflammatory cytokines in CIA mice. Isogarcinol inhibited xylene-induced mouse ear edema in vivo. In vitro, isogarcinol decreased iNOS and COX-2 mRNA expression and NO content by inhibiting NF-κB expression. Furthermore, isogarcinol decreased the activity of NFAT and inhibited IL-2 expression. The mechanism of action of isogarcinol is associated with down-regulation of both autoimmune and inflammatory reactions.

Isogarcinol is a new immunosuppressant

Calcineurin (CN), a unique protein phosphatase, plays an important role in immune regulation. In this study we used CN as a target enzyme to investigate the immunosuppressive properties of a series of natural compounds from Garcinia mangostana L., and discovered an active compound, isogarcinol. Enzymatic assays showed that isogarcinol inhibited CN in a dose-dependent manner. At concentrations resulting in relatively low cytotoxicity isogarcinol significantly inhibited proliferation of murine spleen T-lymphocytes induced by concanavalin A (ConA) and the mixed lymphocyte reaction (MLR). In addition, it performed much better in acute toxicity tests and via oral administration in mice than cyclosporin A (CsA), with few adverse reactions and low toxicity in experimental animals. Oral administration of isogarcinol in mice resulted in a dose-dependent decrease in delayed type hypersensitivity (DTH) and prolonged graft survival in allogeneic skin transplantation. These findings suggest that isogarcinol could serve as a new oral immunomodulatory drug for preventing transplant rejection, and for long-term medication in autoimmune diseases.