Transplant recipients generally require lifelong treatment with immunosuppressive medication to prevent rejection of the graft by their immune system. Inhibitors of the enzyme calcineurin,... Show moreTransplant recipients generally require lifelong treatment with immunosuppressive medication to prevent rejection of the graft by their immune system. Inhibitors of the enzyme calcineurin, including cyclosporin A and tacrolimus, constitute a very potent class of immunosuppressants that has revolutionized transplant medicine. However, their reputation has been showing cracks due to the severe side-effects associated with long-term use of these drugs, including an explosively increased risk of developing skin cancer. The pathophysiological mechanism of this phenomenon is not known, although a number of hypotheses have been put forward. In this dissertation, we show that oxidative stress, mainly derived from exposure to UVA radiation, may locally augment the effects of the calcineurin inhibitors; we propose that overly strong suppression of calcineurin activity may result in malignancy formation due to disruption of tumor-suppressive signaling pathways or disturbed immunosurveillance in skin. Show less
Musson, R.E.A.; Mullenders, L.H.F.; Smit, N.P.M. 2012
Calcineurin is a Ca2+-dependent serine/threonine phosphatase and the target of the immunosuppressive drugs cyclosporin and tacrolimus, which are used in transplant recipients to prevent rejection.... Show moreCalcineurin is a Ca2+-dependent serine/threonine phosphatase and the target of the immunosuppressive drugs cyclosporin and tacrolimus, which are used in transplant recipients to prevent rejection. Unfortunately, the therapeutic use of this drugs is complicated by a high incidence of skin malignancy, which has set off a number of studies into the role of calcineurin signaling in skin, particularly with respect to cell cycle control and DNA repair. Both UVA1 radiation and arsenic species are known to promote skin cancer development via production of reactive oxygen species. In light of the well-documented sensitivity of calcineurin to oxidative stress, we examined and compared the effects of UVA1 and arsenite on calcineurin signaling. In this paper, we show that physiologically relevant doses of UVA1 radiation and low micromolar concentrations of arsenite strongly inhibit calcineurin phosphatase activity in Jurkat and skin cells and decrease NFAT nuclear translocation in Jurkat cells. The effects on calcineurin signaling could be partly prevented by inhibition of NADPH oxidase in Jurkat cells or increased dismutation of superoxide in Jurkat and skin cells. In addition, both UVA1 and arsenite decreased NF-κB activity, although at lower concentrations, arsenite enhanced NF-κB activity. These data indicate that UVA1 and arsenite affect a signal transduction route of growingly acknowledged importance in skin and that calcineurin may serve as a potential link between ROS exposure and impaired tumor suppression. Highlights► Calcineurin inhibition has been linked to impaired DNA repair and skin carcinogenesis. ► UVA inhibits calcineurin signaling through oxidative damage. ► Low micromolar doses of arsenite suppress calcineurin signaling. ► Effects of arsenite on calcineurin are mediated by superoxide. Show less
Calcineurin (protein phosphatase 3, Cn) is best known for its central position in Ca(2+)-dependent T-cell signaling. Interest in calcineurin has, however, conserved its momentum as new Ca(2+)... Show moreCalcineurin (protein phosphatase 3, Cn) is best known for its central position in Ca(2+)-dependent T-cell signaling. Interest in calcineurin has, however, conserved its momentum as new Ca(2+)-dependent pathways have been steadily surfacing in several other cell types, such as brain, heart, skin cells and beta pancreatic cells, and Cn appears to serve as a central controller of stress, immune response, and cellular proliferation and differentiation. Calcineurin is the principal target of the immunosuppressive drugs cyclosporin A (CsA) and tacrolimus (TRL). Therapy based on these immunosuppressants has markedly reduced the incidence of transplant rejection in allograft recipients. In addition, these drugs have proven very useful for patients suffering from chronic inflammatory skin conditions. Unfortunately, their application is somewhat limited by a broad spectrum of toxic side-effects, affecting several organ systems. This calls for enhancements in the design of this class of immunosuppressants. An intricate constellation of regulatory systems allows for precise modulation and adaptation of calcineurin activity in vivo. The last few years have been very fruitful in elucidating several long-standing issues regarding the binding patterns of substrates and inhibitors to Cn. This new knowledge may enable more precise manipulation of the Ca(2+)-calcineurin pathway in the near future, preferably targeted towards one specific substrate or cell system. In this review, we will discuss the factors and mechanisms underlying calcineurin activity regulation and their exploitation in recent approaches towards better immunosuppressants. Show less
Over the last decades, restoration of renal function by renal allograft transplantation has evolved into the preferred treatment option for patients with end stage renal disease. The introduction... Show moreOver the last decades, restoration of renal function by renal allograft transplantation has evolved into the preferred treatment option for patients with end stage renal disease. The introduction of the calcineurin inhibitors (CNI) cyclosporine and tacrolimus have significantly contributed to this success. Adverse drug effects, together with the large inter-individual variation in pharmacokinetics of both drugs necessitates therapeutic drug monitoring (TDM). Nowadays, TDM is routinely performed by drug concentration measurement in blood. Unfortunately, the incidence of acute allograft rejection episodes is still 10-20% within first year after transplantation. A strategy to improve clinical immunesuppresion early after transplantation is improved monitoring. Next to advanced pharmacokinetic monitoring, such as estimated AUC monitoring, the development of pharmacodynamic markers could theoretically contribute to improve CNI therapy. Pharmacodynamic monitoring strategies, however, are still in an experimental phase and have not proven clinical benefit yet. They carry the theoretical advantage of monitoring the true effectiveness of immunosuppressive therapy. This led us to investigate pharmacodynamic monitoring as potential tool to guide drug dosing. We choose calcineurin activity as pharmacodynamic marker for monitoring and in this thesis, the analytical aspects, fundamental characteristics and insights in clinical usefulness of calcineurin activity measurement as a pharmacodynamic marker for CNI were investigated. Show less
With the use of combinatorial phage display, solid phase peptide synthesis and a multidiscipline of molecular and cellular assays in vascular biology, the research described in this thesis has... Show moreWith the use of combinatorial phage display, solid phase peptide synthesis and a multidiscipline of molecular and cellular assays in vascular biology, the research described in this thesis has resulted in the identification of two novel peptides targeting to SR-AI and CD40 respectively which hold promise as targeted contrast agents for the diagnosis of atherosclerosis symptom. In addition, a peptide named VIVIT and its derivatives had been discovered and synthesized which constitute a more selective and less toxic drug candidate than currently used immunosuppressant cyclosporine A or FK506, leading to new generation immunosuppressants and therapeutics for autoimmune diseases such as rheumatoid arthritis or allograft transplantation and cardiovascular disorders including atherosclerosis, restenosis and cardiac hypertrophy. Show less
