Current Medicinal Chemistry - Volume 10, Issue 10, 2003

The classical model of the coagulation cascade is to be replaced by a new, cell based model of coagulation emphasizing the interaction of coagulation proteins with cell surfaces of platelets subendothelial cells and the endothelium. According to current knowledge hemostasis is initiated by the formation of a complex between tissue factor (TF) exposed as a result of a vessel wall injury, and already activated factor (F) VII (FVIIa) normally present in the circulating blood. The TF-FVIIa complexes convert FX into FXa on the TF bearing cell. FXa then activates prothrombin (FII) into thrombin (FIIa). This limited amount of thrombin activates FVIII, FV, FXI and platelets. Thrombin-activated platelets change shape and as a result will expose negatively charged phospholipids, which form the perfect template for full thrombin generation involving FVIIIa and FIXa. Thrombin also converts fibrinogen into fibrin, it activates the fibrin stabilizing FXIII, as well as the thrombin activatable fibrinolysis inhibitor (TAFI). The fibrin structure has been found to be dependent on the amount of thrombin formed and the rate of thrombin generation. Full thrombin generation is necessary for the formation of a tight, stable fibrin hemostatic plug resistant to premature fibrinolysis which is required for full and sustained hemostasis. Since thrombin has such a crucial role in providing hemostasis, any agent that enhances thrombin generation in situations with impaired thrombin formation may be characterized as a ‘general hemostatic agent’ - a term that has been applied to recombinant activated FVII.Recombinant coagulation factor VIIa (rFVIIa; NovoSeven) was originally developed and approved for the treatment of bleeding episodes and the prevention of bleeding during surgery in hemophilia patients with inhibitors and in patients with auto-antibodies against FVIII or FIX (acquired hemophilia). As rFVIIa in pharmacological doses enhances thrombin generation on activated platelets, it has been suggested that rFVIIa may also help to improve hemostasis in other situations involving impaired thrombin generation. This is substantiated by the accumulation of published data indicating that rFVIIa is able to control bleeding in patients with thrombocytopenia or platelet function deficiencies as well as in patients without pre-existing coagulopathies.

In recent years there has been an increasing interest in the use of natural substances, and some questions concerning the safety of synthetic compounds have encouraged more detailed studies of plant resources. Essential oils, odorous and volatile products of plant secondary metabolism, have a wide application in folk medicine, food flavouring and preservation as well as in fragrance industries. The antimicrobial properties of essential oils have been known for many centuries. In recent years (1987-2001), a large number of essential oils and their constituents have been investigated for their antimicrobial properties against some bacteria and fungi in more than 500 reports. This paper reviews the classical methods commonly used for the evaluation of essential oils antibacterial and antifungal activities. The agar diffusion method (paper disc and well) and the dilution method (agar and liquid broth) as well as turbidimetric and impedimetric monitoring of microorganism growth in the presence of tested essential oils are described. Factors influencing the in vitro antimicrobial activity of essential oils and the mechanisms of essential oils action on microorganisms are reported. This paper gives an overview on the susceptibility of human and food-borne bacteria and fungi towards different essential oils and their constituents. Essential oils of spices and herbs (thyme, origanum, mint, cinnamon, salvia and clove) were found to possess the strongest antimicrobial properties among many tested.

Diagnosis and therapy for malignant gliomas represents one of the most challenging problems in clinical oncology. Current treatment of malignant glioma is multimodal, involving surgical resection, radiotherapy and chemotherapy. Even with these combined therapies, patients usually die within 1 to 2 years after onset of symptoms. Clearly, improved strategies for selective delivery of therapeutic agents to gliomas are needed to combat these devastating and usually fatal cancers. This review summarizes current knowledge concerning targetable molecular markers on the surface of glial tumor cells and tumor vasculature. Such markers are altered or up-regulated in gliomas compared to normal tissues, or they might be glioma-restricted. These markers include growth factor receptors, cell-surface adhesion molecules, and membrane-type matrix metalloproteinases. Current approaches that utilize growth factor peptides and peptide / antibodies identified via phage display technology as carrier ligands for targeting malignant gliomas are discussed.

Hypoxia inducible factor-1 (HIF-1) is a master regulator under conditions of decreased oxygen availability. As a hypoxia inducible transcription factor HIF-1 is a heterodimer composed of the helix-loop-helix-Per-Arnt-Sim (bHLH-PAS) proteins HIF- 1α and the aryl hydrocarbon nuclear translocator (ARNT) also known as HIF-1β. The HIF-1 transcriptional system senses decreased oxygen availability and transmits this signal into patho-physiological responses such as angiogenesis, erythropoiesis, vasomotor control, an altered energy metabolism, as well as cell survival decisions. Among recent advances are the discoveries that reactive nitrogen species (RNS), oxygen species (ROS), cytokines, and growth factors participate in stability regulation of HIF-1α and HIF-1 transactivation during normoxia. Here we summarize current knowledge and existing concepts that help to understand how NO affects protein accumulation of HIF-1α. Considering the fundamental role of radicals, especially NO, as signaling molecules makes HIF-1α an attractive target under conditions of NO formation that may be attributed to both, physiology and pathology. Although initial observations showed that NO inhibits hypoxia-induced HIF-1α stabilization and HIF-1 transcriptional activation, later studies indicated that exposure of various cells to chemically diverse NO donors or conditions of endogenous NO formation under normoxic conditions induced HIF-1α accumulation, HIF-1-DNA binding, and activation of downstream target gene expression. These contrasting situations evoked by NO provide insights into basic chemical reactions, biochemical signal transduction pathways with broad implications for medicine.

Transgenic technology, especially the use of homologous recombination to disrupt specific genes to produce knockout mice, has added considerably to the understanding of dopamine (DA) neuron develop, survival and function. The current review summarizes results from knockout mice with the target disruption of genes involved in the development of DA neurons (engrailed 1 and 2, lmx1b, and Nurr1), in maintaining DA neurotransmission (tyrosine hydroxylase, vesicular monoamine transporter, DA transporter, DA D2 and D3 receptors) and important for DA neuron survival (α-synuclein, glia cell line-derived neurotrophic factor and superoxide dismutase). As alterations in DA neurotransmission have been implicated in a number of human neuropathologies including Parkinson's disease, schizophrenia and attention deficit / hyperactivity disorder, understanding how specific genes are involved in the function of DA neurons and the compensatory changes that result from loss or reduction in gene expression could provide important insight for the treatment of these diseases.

Aberrant proteolytical processing of the amyloid precursor protein (APP) gives rise to β-amyloid peptides, which form deposits characteristic for the brains of Alzheimer's disease patients. From in vitro studies, protein kinase C (PKC) is known for almost 20 years to be involved the secretory pathway of APP processing, resulting in the reduced generation of β-amyloid peptides. However, the toxicity of activators of PKC, such as phorbol esters, has prevented to test the hypothesis of an inverse regulation of secretory APP processing and β-amyloid generation in vivo. Here we present an animal model which allows to reveal the function of PKC in the proteolytical processing of APP in vivo.Studies by Johnstone and Coyle from the early 1980s have shown that treatment of pregnant rats with methylazoxymethanol acetate (MAM) results in the induction of neocortical microencephalopathy of the offsprings. Later on, the constitutive overactivation of PKC isoforms was described in affected brain structures of these animals. This led to the idea to study the APP processing under conditions of overactivated PKC in the brains of such animals in vivo. However, in mice and rats one can follow the generation of secretory APP products but the detection of rodent β-amyloid peptides is delicate.Therefore, we adapted the MAM model to guinea pigs, which have a human β-amyloid sequence, and investigated the relation between secretory APP processing and β-amyloid generation in vivo. In the brains of microencephalic guinea pigs we observed increased levels of secretory APP fragments but no change in the concentration of β-amyloid peptides. Our results indicate that both pathways of APP processing are differentially controlled under these experimental conditions in vivo.