Tacrolimus (FK506)

From Streptomyces tsukubaensis

Tacrolimus (FK506) is a potent and selective inhibitor of T-lymphocyte and the macrolide immunosuppressant [1].

In vitro, Tacrolimus (FK506) has been reported to inhibit the interleukin 2(IL-2) production and the response of mixed lymphocyte culture. In addition, Tacrolimus (FK506) added to the cell cultures has been revealed to inhibit murine or human mixed lymphocyte reactivity and the generation of cytotoxic T cells. Furermor, Tacrolimus (FK506) has also been reported to dose-dependently suppress the production of various cytokines including IL-2, IL-3, IL-4, and γ-interferon, in response to different stimulis. Besides, Tacrolimus has shown its efficacy in the prevention of allograft rejection in animal transplant models. Tacrolimus has been found to be significantly efficient in experimental hepatic allografts, and has hepatotrophic properties [1].

References:
[1] Wallemacq PE1, Reding R. FK506 (tacrolimus), a novel immunosuppressant in organ transplantation: clinical, biomedical, and analytical aspects. Clin Chem. 1993 Nov; 39(11 Pt 1):2219-28.

Renal Deletion of 12 kDa FK506-Binding Protein Attenuates Tacrolimus-Induced Hypertension.[Pubmed:26432904]

J Am Soc Nephrol. 2016 May;27(5):1456-64.

Tacrolimus is a widely used immunosuppressive drug that inhibits the phosphatase calcineurin when bound to the 12 kDa FK506-binding protein (FKBP12). When this binding occurs in T cells, it leads to immunosuppression. Tacrolimus also causes side effects, however, such as hypertension and hyperkalemia. Previously, we reported that tacrolimus stimulates the renal thiazide-sensitive sodium chloride cotransporter (NCC), which is necessary for the development of hypertension. However, it was unclear if tacrolimus-induced hypertension resulted from tacrolimus effects in renal epithelial cells directly or in extrarenal tissues, and whether inhibition of calcineurin was required. To address these questions, we developed a mouse model in which FKBP12 could be deleted along the nephron. FKBP12 disruption alone did not cause phenotypic effects. When treated with tacrolimus, however, BP and the renal abundance of phosphorylated NCC were lower in mice lacking FKBP12 along the nephron than in control mice. Mice lacking FKBP12 along the nephron also maintained a normal relationship between plasma potassium levels and the abundance of phosphorylated NCC with tacrolimus treatment. In cultured cells, tacrolimus inhibited dephosphorylation of NCC. Together, these results suggest that tacrolimus causes hypertension predominantly by inhibiting calcineurin directly in cells expressing NCC, indicating thiazide diuretics may be particularly effective for lowering BP in tacrolimus-treated patients with hypertension.

Influence of Tacrolimus (FK506) on Nerve Regeneration Using Allografts: A Rat Sciatic Nerve Model.[Pubmed:25869987]

J Oral Maxillofac Surg. 2015 Jul;73(7):1438.e1-9.

PURPOSE: FK506 is an immunosuppressant agent used to prevent rejection after organ transplantation. The aim of the present study was to assess effects of Tacrolimus (FK506) on peripheral nerve regeneration using allografts in a rat sciatic nerve model. MATERIALS AND METHODS: Thirty male white Wistar rats were divided randomly into a normal control (NC) group (n = 10), an allograft (ALLO) group (n = 10), and an FK506-treated (ALLO/FK506) group (n = 10). In the NC group, the left sciatic nerve was exposed through a gluteal muscle incision and, after homeostasis, the muscle was sutured. In the ALLO group, the left sciatic nerve was exposed through a gluteal muscle incision and transected proximal to the tibioperoneal bifurcation, where a 10-mm segment was excised. The same procedure was performed in the ALLO/FK506 group. The harvested nerves of the ALLO group served as allografts for the ALLO/FK506 group and vice versa. The NC and ALLO groups received sterile olive oil 300 muL intraperitoneally once a day for 1 week and the ALLO/FK506 group received FK506 300 muL (1 mg/kg) intraperitoneally once a day for 1 week. RESULTS: Behavioral, functional, and biomechanical recovery and gastrocnemius muscle mass showed earlier regeneration of axons in the ALLO/FK506 than in the ALLO group (P < .05). Histomorphometric and immunohistochemical studies also showed earlier regeneration of axons in the ALLO/FK506 than in the ALLO group (P < .05). CONCLUSIONS: Administration of FK506 could accelerate functional recovery of the sciatic nerve after nerve allografting. It could have clinical implications for the surgical management of patients after facial nerve transection.

Association of long-term tacrolimus (FK506) therapy with abnormal megakaryocytosis, bone marrow fibrosis, and dyserythropoiesis.[Pubmed:26273466]

Clin Case Rep. 2015 Jul;3(7):664-8.

Haematopoietic abnormalities associated with tacrolimus are relatively rare with reversible pure red cell aplasia being the most common. We report for the first time, to our best knowledge, tacrolimus therapy associated with bone marrow fibrosis, abnormal megakaryocytosis, and dyserythopoiesis in a 17-year-old male treated with tacrolimus for nephrotic syndrome.

Ascomycin and FK506: pharmacology and therapeutic potential as anticonvulsants and neuroprotectants.[Pubmed:18482098]

CNS Neurosci Ther. 2008 Spring;14(1):36-46.

Ascomycin and FK506 are powerful calcium-dependent serine/threonine protein phosphatase (calcineurin [CaN], protein phosphatase 2B) inhibitors. Their mechanism of action involves the formation of a molecular complex with the intracellular FK506-binding protein-12 (FKBP12), thereby acquiring the ability to interact with CaN and to interfere with the dephosphorylation of various substrates. Pharmacological studies of ascomycin, FK506, and derivatives have mainly been focused on their action as immunosuppressants and therapeutic use in inflammatory skin diseases, both in animal studies and in humans. CaN inhibitors have been also proposed for the treatment of inflammatory and degenerative brain diseases. Preclinical studies suggest, however, that ascomycin and its derivatives exhibit additional pharmacological activities. Ascomycin has been shown to have anticonvulsant activity when perfused into the rat hippocampus via microdialysis probes, and ascomycin derivatives may be useful in preventing ischemic brain damage and neuronal death. Their pharmacological action in the brain may involve CaN-mediated regulation of gamma aminobutyric acid (GABA) and glutamate receptor channels, neuronal cytoskeleton and dendritic spine morphology, as well as of the inflammatory responses in glial cells. FK506 and ascomycin inhibit signaling pathways in astrocytes and change the pattern of cytokine and neurotrophin gene expression. However, brain-specific mechanisms of action other than CaN inhibition cannot be excluded. CaN is a likely potential target molecule in the treatment of central nervous system (CNS) diseases, so that the therapeutic potential of ascomycin, FK506, and nonimmunosuppressant ascomycin derivatives as CNS drugs should be further explored.

Tissue distribution and abundance of human FKBP51, and FK506-binding protein that can mediate calcineurin inhibition.[Pubmed:9125197]

Biochem Biophys Res Commun. 1997 Mar 17;232(2):437-43.

We previously described the isolation of an FK506-binding protein, FKBP51, that is predominantly expressed in murine T cells and is capable of mediating drug-dependent calcineurin inhibition in vitro. In addition, the gene for FKBP51 is induced by glucocorticoids. Screening of a human thymus cDNA library resulted in the identification of the human homologue of FKBP51. Expression of the 3.7 kb mRNA corresponding to FKBP51 is induced by glucocorticoids in the human T cell line, C7TK.4. The 51.2 kDa protein encoded by this gene shares 87% identity to murine FKBP51 and demonstrates a similar IC50 value for the FK506-mediated inhibition of calcineurin phosphatase in vitro. The distribution and abundance of FKBP51 and FKBP12 in seventeen human tissues were compared by Western analysis. Unlike its murine counterpart, the human FKBP51 is abundantly expressed in numerous tissues and in many cases, is in molar excess over FKBP12.

The complex of FK506-binding protein 12 and FK506 inhibits calcineurin phosphatase activity and IgE activation-induced cytokine transcripts, but not exocytosis, in mouse mast cells.[Pubmed:7530743]

J Immunol. 1995 Feb 15;154(4):1846-51.

FK506 and cyclosporin A (CsA) are immunosuppressive agents that inhibit IL-2 production by activated T cells, but only CsA inhibits IgE activation-induced cytokine transcripts in mouse IL-3-dependent, bone marrow-derived mast cells (BMMC). We previously associated the resistance of BMMC to FK506 with a deficiency in the expression of FK506 binding protein (FKBP) 12, a molecule that forms a complex with FK506 capable of inhibiting calcineurin phosphatase activity in vitro. In this report, we establish that FKBP12 mediates FK506 inhibition of both calcineurin phosphatase activity and IgE activation-induced cytokine transcripts in a Kirsten murine sarcoma virus-immortalized mast cell line that is FKBP12 deficient. Overexpression of FKBP12 by transfection enhanced the ability of FK506 to inhibit calcineurin phosphatase activity (IC50 = 2 nM), compared with cells transfected with the expression vector alone (IC50 > 30 nM). The IC50 value for FK506 inhibition of IgE activation-induced transcripts for TNF-alpha decreased from 40 nM in vector control cells to 10 nM in FKBP12 transfectants. Similarly, the IC50 value for inhibition of IL-6 transcripts decreased from > 1000 nM in vector control cells to 35 nM in FKBP12 transfectants. In contrast, activation-elicited release of the secretory granule mediator beta-hexosaminidase was only partially inhibited by FK506 at 1000 nM, regardless of the levels of FKBP12 expressed by the cells. Thus, FKBP12 is the dominant cytosolic protein that mediates FK506 inhibition of TNF-alpha and IL-6 transcripts.

Tacrolimus (FK506), a macrocyclic lactone, binds to FK506 binding protein (FKBP) to form a complex. Tacrolimus inhibits calcineurin phosphatase, which inhibits T-lymphocyte signal transduction and IL-2 transcription. Immunosuppressive properties.

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