A Pharmacokinetic/Pharmacodynamic Approach to Predict Total Prednisolone Concentrations in Human Plasma

Prednisolone and prednisone are two widely used corticosteroids for various inflammatory and immune diseases. Prednisolone is the active form of prednisone in vivo. Total prednisolone in plasma exhibits nonlinear pharmacokinetics mainly due to its nonlinear protein binding. Other factors such as reversible metabolism (or interconversion between prednisolone and prednisone), competitive protein binding from endogenous cortisol, cortisol circadian rhythm, and prednisolone mediated cortisol suppression complicate prednisolone pharmacokinetics. This study was aimed to develop a new approach to describe the nonlinear pharmacokinetics of total prednisolone and predict total prednisolone concentrations in plasma. Based on literature datasets, a linear two-compartment pharmacokinetic model was developed to adequately describe the reversible metabolism between free prednisone and prednisolone. Cortisol and prednisolone protein binding were described via the sum of a Langmuir and linear type binding. The endogenous cortisol circadian rhythm and cortisol suppression during prednisone or prednisolone exposure were described with a previously reported linear release rate pharmacokinetic/pharmacodynamic (PK/PD) model. By combining the pharmacokinetic models for free prednisone and prednisolone, the linear release rate model for cortisol suppression, and competitive protein binding between cortisol and prednisolone, we were able to predict total prednisolone concentrations in plasma. The predicted total prednisolone concentrations in plasma were in good agreement with the literature reported data. Thus, this PK/PD approach shows that the combination of nonlinear protein binding, cortisol circadian rhythm, and cortisol suppression could account for the nonlinearity of total prednisolone. In addition, it also allows a valid prediction of total prednisolone in plasma after either prednisone or prednisolone administration.

Switching from tacrolimus to sirolimus halts the appearance of new sebaceous neoplasms in Muir-Torre syndrome

Little is known about the effects of immunosuppression on patients with hereditary nonpolyposis colorectal cancer (HNPCC). We describe a kidney transplant recipient with unrecognized Muir-Torre syndrome in whom the administration of a tacrolimus-based regimen led to the eruption of multiple sebaceous tumors. The patient was later found to harbor an MSH2 mutation. Switching to a sirolimus-based regimen resulted in arrest of the disease. When the patient was switched back to tacrolimus, new facial lesions rapidly appeared. Switching again to sirolimus resulted again in halting the appearance of new lesions. This finding is in line with the known antiangiogenic activity of sirolimus and reports on the regression of cutaneous Kaposi's sarcoma in kidney transplant recipients switched from another immunosuppressive regimen to sirolimus. Further studies on the potential use of sirolimus for the treatment of de novo tumors in immunosuppressed kidney transplant recipients with HNPCC are warranted.

Aviäre Influenza und das Schwere Akute Respiratorische Syndrom (SARS) - Erfahrungen und Perspektiven

New respiratory viruses associated with pneumonia have in the past few years been detected in humans. The sudden appearance of the severe acute respiratory syndrome (SARS) in 2003 demonstrated that an emerging and highly infectious disease caused by a hitherto unknown virus was able to spread rapidly, but could finally be contained by stringent measures. The avian influenza A-H5N1-virus of high pathogenicity has crossed in multiple instances the species barriers between humans, mammals, and birds posing a serious pandemic threat. The application of the so far learnt and the continued development of preventive strategies, efficient vaccines, and antiviral substances are besides worldwide surveillance decisive to rapidly detect the repeated, enforced, or new appearance of viruses like the SARS-CoV, influenza A-H5N1 virus, or of new viruses, to contain their spread, and to defeat them.

The FunGenES consortium: functional genomics in engineered embryonic stem cells

Although the complete sequence of a mammalian genome defines the information content of each cell, understanding the selective usage of this information during the development of specific cell types is limited. The fundamental questions that remain to be answered includes, which are the gene subsets that define the pluripotential self-renewing state of embryonic stem (ES) cells, partially and terminally differentiated developmental states, and how are transitions between these states regulated (lineage commitment)? The FunGenES consortium has been formed to address this challenge by mapping the gene subsets involved in pluripotent, lineage committed, and selected differentiated cell types using gene expression profiling and functional screens. They create an atlas of mammalian genome participating in early and late developmental processes. To fulfil the aim, mouse ES cells were used as an in vitro developmental model system that is very close to the human as they are pluripotent. They can be differentiated through the three major developmental pathways ecto-, meso-, and endoderm into many committed cell types and can be genetically engineered with relative ease. Knowledge of genetic pathways in mouse ES cell differentiation and development might be translated to human ES cells and the potential development of stem cell-based therapies.

[Guillain-Barrè syndrome and inadequate antidiuretic hormone secretion syndrome]

Several neurologic disorders including Guillain-Barré syndrome (GBS) are associated with hyponatremia. Hyponatremia and its overly fast correction have major implications to the course of the underlying neurologic disease. We report a case of GBS complicated by hyponatremia secondary to the development of inadequate antidiuretic hormone secretion syndrome. Differential diagnosis, pathophysiology, and therapeutic approach of hyponatremia in association with GBS are discussed.

Dietary Small Molecules and Large-Scale Gene Expression Studies: An Experimental Approach for Understanding their Beneficial Effects on the Development of Malignant and Non-Malignant Proliferative Diseases

Epidemiological studies have repeatedly demonstrated a correlation between nutrition, development and the severity of malignant and non-malignant proliferative diseases such as cancer and atherosclerosis. Therefore, the prevention of chronic proliferative diseases through dietary intervention is currently receiving considerable attention. Until now, much of the research is being focused on the cellular and molecular action mechanisms of dietary small molecules explaining their beneficial effects. Dietary chemicals may affect gene expression in several human diseases. However, significant progress has been made and several molecular action mechanisms have been proposed. Alteration of genetical pathways by nutrition, also called "Nutrigenomics", may offer a new approach for understanding the beneficial effects of dietary compounds on the development of severe polygenic diseases, such as cardiovascular disease, diabetes and hypertension. This review focuses on the nutritional genomics of dietary chemicals with a special emphasis on catechins. Catechins belong to the flavonoid family, which are polyphenolic compounds available in foods of plant origin. Several epidemiological studies have reported that consumption of flavonoids, and especially catechins might function as chemopreventive agents against cancer and cardiovascular diseases.