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+)-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.

Calcineurin (Cn) is the target of immunosuppressive drugs used for maintenance therapy of transplant patients. UV radiation is also known to be immunosuppressive and, like the Cn inhibitors, UV has been shown to positively influence various inflammatory skin diseases. Recently, Cn activity has been demonstrated in skin and skin cell cultures. In the present study we have investigated the effects of UV(A-1) irradiation on Cn activity in skin. In total skin we found a significant reduction in Cn activity after exposure to 450 kJ m(-2) of UVA-1 (340-400 nm). In repeated experiments cultures of fibroblasts and keratinocytes also showed dose-dependent and selective reduction in Cn activity after UVA-1 irradiation. UVB irradiation caused a decrease in the Cn activity of one of two fibroblast cultures and was ineffective in keratinocytes. In Jurkat cells and PBMC UVA-1 reduced Cn activity and also the production of cytokines such as interleukin (IL)-2, gamma-interferon, IL-4 and IL-10 that are controlled by the Ca(2+)-Cn pathway. These results indicate that UV(A-1) irradiation may lead to inactivation of Cn in the skin and thus suppress the skin immune system in a similar fashion to the Cn inhibitors.

BACKGROUND The Ca2+-dependent protein phosphatase enzyme calcineurin (Cn) (protein phosphatase 3) is best known for its role as director of the adaptive immune response. One of its principal substrates is the nuclear factor of activated T cells (NFAT), which translocates to the nucleus after dephosphorylation to mediate gene transcription. Drugs targeting Cn (the Cn inhibitors tacrolimus and cyclosporin A) have revolutionized posttransplantation therapy in allograft recipients by considerably reducing rejection rates. CONTENT Owing primarily to intensive study of the side effects of the Cn inhibitors, the unique importance of Cn and Cn/NFAT signaling in the normal physiological processes of many other cell and tissue types is becoming more evident. During the last decade, it has become clear that an extensive and diverse array of clinical conditions can be traced back, at least in part, to a disturbed Cn-signaling axis. Hence, both diagnostics and therapeutic monitoring could benefit from a technique that conveniently reads out Cn/NFAT operative status. SUMMARY This review outlines the current knowledge on the pathologic conditions that have calcineurin as a common denominator and reports on the progress that has been made toward successfully applying Cn and Cn/NFAT activity markers in molecular diagnostics.

Background and Objectives Colloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion-associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP. Materials and Methods Three units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh-frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume-reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product. Results Colloid osmotic pressure varies widely between conventional products (RBCs, 1Á9; PLTs, 7Á5; and FFP, 20Á1 mmHg); however, all are hypooncotic compared with human plasma COP (25Á4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47Á3 mm Hg. The PVL of concentrated products was lower than conventional products. Conclusion Colloid osmotic pressure of conventional products was low. Therefore, third-space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.

Background Knowledge of possible drug-laboratory test interactions (DLTIs) is important for the interpretation of laboratory test results. Test results may be affected by physiological or analytical drug effects. Failure to recognize these interactions may lead to misinterpretation of test results, a delayed or erroneous diagnosis or unnecessary extra tests or therapy, which may harm patients. Content Thousands of interactions have been reported in the literature, but are often fragmentarily described and some papers even reported contradictory findings. How can healthcare professionals become aware of all these possible interactions in their individual patients? DLTI decision support applications could be a good solution. In a literature search, only four relevant studies have been found on DLTI decision support applications in clinical practice. These studies show a potential benefit of automated DLTI messages to physicians for the interpretation of laboratory test results. All physicians reported that part of the DLTI messages were useful. In one study, 74% of physicians even sometimes refrained from further additional examination. Summary and outlook Unrecognized DLTIs potentially cause diagnostic errors in a large number of patients. Therefore, efforts to avoid these errors, for example with a DLTI decision support application, could tremendously improve patient outcome.