Biodiversity and chemodiversity: future perspectives in bioprospecting

Biological diversity and its constituent chemical diversity have served as one of the richest sources of bioprospecting leading to the discovery of some of the most important bioactive molecules for mankind. Despite this excellent record, in the recent past, however, bioprospecting of biological resources has met with little success; there has been a perceptible decline in the discovery of novel bioactive compounds. Several arguments have been proposed to explain the current poor success in bioprospecting. Among them, it has been argued that to bioprospect more biodiversity may not necessarily be productive, considering that chemical and functional diversity might not scale with biological diversity. In this paper, we offer a critique on the current perception of biodiversity and chemodiversity and ask to what extent it is relevant in the context of bioprospecting. First, using simple models, we analyze the relation among biodiversity, chemodiversity and functional redundancies in chemical plans of plants and argue that the biological space for exploration might still be wide open. Second, in the context of future bioprospecting, we argue that brute-force high throughput screening approaches alone are insufficient and cost ineffective in realizing bioprospecting success. Therefore, intelligent or non-random approaches to bioprospecting need to be adopted. We review here few examples of such approaches and show how these could be further developed and used in the future to accelerate the pace of discovery.

The phosphoinositide 3-kinase signaling pathway as a therapeutic target in grade IV brain tumors

Brain tumors comprise a wide variety of neoplasia classified according to their cellular origin and their morphological and histological characteristics. The transformed phenotype of brain tumor cells has been extensively studied in the past years, achieving a significant progress in our understanding of the molecular pathways leading to tumorigenesis. It has been reported that the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway is frequently altered in grade IV brain tumors resulting in uncontrolled cell growth, survival, proliferation, angiogenesis, and migration. This aberrant activation can be explained by oncogenic mutations in key components of the pathway or through abnormalities in its regulation. These alterations include overexpression and mutations of receptor tyrosine kinases (RTKs), mutations and deletions of the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor gene, encoding a lipid kinase that directly antagonized PI3K activity, and alterations in Ras signaling. Due to promising results of preclinical studies investigating the PI3K/AKT pathway in grade IV brain tumors like glioblastoma and medulloblastoma, the components of this pathway have emerged as promising therapeutic targets to treat these malignant brain tumors. Although an arsenal of small molecule inhibitors that target specific components of this signaling pathway is being developed, its successful application in the clinics remains a challenge. In this article we will review the molecular basis of the PI3K/AKT signaling pathway in malignant brain tumors, mainly focusing on glioblastoma and medulloblastoma, and we will further discuss the current status and potential of molecular targeted therapies.

An integrated nano-scale approach to profile miRNAs in limited clinical samples

Profiling miRNA expression in cells that directly contribute to human disease pathogenesis is likely to aid the discovery of novel drug targets and biomarkers. However, tissue heterogeneity and the limited amount of human diseased tissue available for research purposes present fundamental difficulties that often constrain the scope and potential of such studies. We established a flow cytometry-based method for isolating pure populations of pathogenic T cells from bronchial biopsy samples of asthma patients, and optimized a high-throughput nano-scale qRT-PCR method capable of accurately measuring 96 miRNAs in as little as 100 cells. Comparison of circulating and airway T cells from healthy and asthmatic subjects revealed asthma-associated and tissue-specific miRNA expression patterns. These results establish the feasibility and utility of investigating miRNA expression in small populations of cells involved in asthma pathogenesis, and set a precedent for application of our nano-scale approach in other human diseases. The microarray data from this study (Figure 7) has been submitted to the NCBI Gene Expression Omnibus (GEO; http://ncbi.nlm.nih.gov/geo) under accession no. GSE31030.

The Trypanosoma brucei cAMP phosphodiesterases TbrPDEB1 and TbrPDEB2: flagellar enzymes that are essential for parasite virulence

Cyclic nucleotide specific phosphodiesterases (PDEs) are pivotal regulators of cellular signaling. They are also important drug targets. Besides catalytic activity and substrate specificity, their subcellular localization and interaction with other cell components are also functionally important. In contrast to the mammalian PDEs, the significance of PDEs in protozoal pathogens remains mostly unknown. The genome of Trypanosoma brucei, the causative agent of human sleeping sickness, codes for five different PDEs. Two of these, TbrPDEB1 and TbrPDEB2, are closely similar, cAMP-specific PDEs containing two GAF-domains in their N-terminal regions. Despite their similarity, these two PDEs exhibit different subcellular localizations. TbrPDEB1 is located in the flagellum, whereas TbrPDEB2 is distributed between flagellum and cytoplasm. RNAi against the two mRNAs revealed that the two enzymes can complement each other but that a simultaneous ablation of both leads to cell death in bloodstream form trypanosomes. RNAi against TbrPDEB1 and TbrPDEB2 also functions in vivo where it completely prevents infection and eliminates ongoing infections. Our data demonstrate that TbrPDEB1 and TbrPDEB2 are essential for virulence, making them valuable potential targets for new PDE-inhibitor based trypanocidal drugs. Furthermore, they are compatible with the notion that the flagellum of T. brucei is an important site of cAMP signaling.--Oberholzer, M., Marti, G., Baresic, M., Kunz, S., Hemphill, A., Seebeck, T. The Trypanosoma brucei cAMP phosphodiesterases TbrPDEB1 and TbrPDEB2: flagellar enzymes that are essential for parasite virulence.

Readjusting the glucocorticoid balance: an opportunity for modulators of 11beta-hydroxysteroid dehydrogenase type 1 activity?

Glucocorticoids play a pivotal role in the regulation of most essential physiological processes, including energy metabolism, maintenance of electrolyte balance and blood pressure, immune-modulation and stress responses, cell proliferation and differentiation, as well as regulation of memory and cognitive functions. There are several levels at which glucocorticoid action can be modulated. On a tissue-specific level, glucocorticoid action is tightly controlled by 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes. The conversion of inactive 11-ketoglucocorticoids (cortisone and 11-dehydrocorticosterone) into active 11beta-hydroxyglucocorticoids (cortisol and corticosterone) is catalyzed by 11beta-HSD1, which is expressed in many tissues and plays an important role in metabolically relevant tissues such as the liver, adipose tissue and skeletal muscles. Chronically elevated local glucocorticoid action as a result of increased 11beta-HSD1 activity rather than elevated systemic glucocorticoid levels has been associated with metabolic syndrome, which is characterized by obesity, insulin resistance, type 2 diabetes and cardiovascular complications. Recent studies indicate that compounds inhibiting 11beta-HSD1 activity ameliorate the adverse effects of excessive glucocorticoid concentrations on metabolic processes, providing promising opportunities for the development of therapeutic interventions. This review addresses recent findings relevant for the development and application of therapeutically useful compounds that modulate 11beta-HSD1 function.

Novel insight into the pathobiology of abdominal aortic aneurysm and potential future treatment concepts

The patient with abdominal aortic aneurysm (AAA) commonly is a nondiabetic, white man with a history of smoking. Moreover, AAA represents a leading cause of death in elderly men in Western countries. The purpose of this manuscript is to review current evidence as to the pathobiology of AAA as well as potential future drug targets to prevent progression of AAA.

Therapeutic targeting of leukocyte trafficking across the blood-brain barrier

The central nervous system (CNS) has long been regarded as an immune privileged organ implying that the immune system avoids the CNS not to disturb its homeostasis, which is critical for proper function of neurons. Meanwhile, it is accepted that immune cells do in fact gain access to the CNS and that immune responses are mounted within this tissue. However, the unique CNS microenvironment strictly controls these immune reactions starting with tightly regulating immune cell entry into the tissue. The endothelial blood-brain barrier (BBB) and the epithelial blood-cerebrospinal fluid (CSF) barrier control immune cell entry into the CNS, which is rare under physiological conditions. During a variety of pathological conditions of the CNS such as viral or bacterial infections, or during inflammatory diseases such as multiple sclerosis (MS), immunocompetent cells readily traverse the BBB and subsequently enter the CNS parenchyma. Most of our current knowledge on the molecular mechanisms involved in immune cell entry into the CNS has been derived from studies performed in experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Thus, a large part of our current knowledge on immune cell entry across the BBBs is based on the results obtained in this animal model. Similarly, knowledge on the benefits and potential risks associated with therapeutic targeting of immune cell recruitment across the BBB in human diseases are mostly derived from such treatment regimen in MS. Other mechanisms of immune cell entry into the CNS might therefore apply under different pathological conditions such as bacterial meningitis or stroke and need to be considered.

Severe structural damage of the seemingly non-diseased infrarenal aortic aneurysm neck

OBJECTIVE: The success of open and endovascular repair of abdominal aortic aneurysms (AAA) is hampered by postoperative dilatation of the anatomical neck of the AAA, which is used for graft attachment. The purpose of this study was to determine whether the macroscopically non-diseased infrarenal aortic neck of AAA is histologically and biochemically altered at the time of operative repair. METHODS: We harvested full-thickness aortic wall samples as longitudinal stripes spanning from AAA neck to aneurysmal sac in 22 consecutive patients undergoing open surgical AAA repair. Control tissue was obtained from five organ donors and five deceased subjects undergoing autopsy without evidence of aneurysmal disease. We assessed aortic media thickness, number of intact elastic lamellar units, media destruction, and neovascularization grade and performed immunohistochemistry for matrix metalloproteinase (MMP)-9 and phosphorylated c-Jun N-terminal kinase (p-JNK). MMP-9 and p-JNK protein expressions were quantified using Western Blots. RESULTS: The median thickness of the aortic media was 1150 mum in control tissue (range, 1000-1300), 510 mum in aortic necks (250-900), and 200 mum in aortic sacs (50-500, P from nonparametric test for trend <.001). The number of intact elastic lamellar units was 33 in controls (range, 33-55), 12 in aortic necks (0-31) and three in aortic sacs (0-10, P < .001). The expression of MMP-9 and p-JNK as assessed by Western Blots (P = .007 and .061, respectively) and zymography (P for trend <.001) were up regulated in both the AAA neck and sac compared with controls. Except for p-JNK expression, differences between tissues were similar after the adjustment for age, gender, and type of sampling. CONCLUSION: The seemingly non-diseased infrarenal AAA neck in patients with AAA undergoing surgical repair shows histological signs of destruction and upregulation of potential drug targets.

Targeting Myc in pediatric malignancies of the central and peripheral nervous system

Myc family genes are often deregulated in embryonal tumors of childhood including medulloblastoma and neuroblastoma and are frequently associated with aggressive, poorly differentiated tumors. The Myc protein is a transcription factor that regulates a variety of cellular processes including cell growth and proliferation, cell cycle progression, differentiation, apoptosis, and cell motility. Potential strategies that either inhibit the proliferation-promoting effect of Myc and/or activate its pro-apoptotic function are presently being explored. In this review, we will give an overview of Myc activation in embryonal tumors and discuss current strategies aimed at targeting Myc for cancer treatment.

Mycobacterium tuberculosis NAD+-dependent DNA ligase is selectively inhibited by glycosylamines compared with human DNA ligase I

DNA ligases are important enzymes which catalyze the joining of nicks between adjacent bases of double-stranded DNA. NAD1-dependent DNA ligases (LigA) are essential in bacteria and are absent in humans. They have therefore been identified as novel, validated and attractive drug targets. Using virtual screening against an in-house database of compounds and our recently determined crystal structure of the NAD1 binding domain of the Mycobacterium tuberculosis LigA, we have identified N1, Nn-bis-(5-deoxy-a-D-xylofuranosylated) diamines as a novel class of inhibitors for this enzyme. Assays involving M.tuberculosis LigA, T4 ligase and human DNA ligase I show that these compounds specifically inhibit LigA from M.tuberculosis. In vitro kinetic and inhibition assays demonstrate that the compounds compete with NAD1 for binding and inhibit enzyme activity with IC50 values in the mM range. Docking studies rationalize the observed specificities and show that among several glycofuranosylated diamines, bis xylofuranosylated diamines with aminoalkyl and 1, 3-phenylene carbamoyl spacers mimic the binding modes of NAD1 with the enzyme. Assays involving LigA-deficient bacterial strains show that in vivo inhibition of ligase by the compounds causes the observed antibacterial activities. They also demonstrate that the compounds exhibit in vivo specificity for LigA over ATPdependent ligase. This class of inhibitors holds out the promise of rational development of new anti-tubercular agents.

Mitochondrial Outer Membrane Proteome of Trypanosoma brucei Reveals Novel Factors Required to Maintain Mitochondrial Morphology

Trypanosoma brucei is a unicellular parasite that causes devastating diseases in humans and animals. It diverged from most other eukaryotes very early in evolution and, as a consequence, has an unusual mitochondrial biology. Moreover, mitochondrial functions and morphology are highly regulated throughout the life cycle of the parasite. The outer mitochondrial membrane defines the boundary of the organelle. Its properties are therefore key for understanding how the cytosol and mitochondria communicate and how the organelle is integrated into the metabolism of the whole cell. We have purified the mitochondrial outer membrane of T. brucei and characterized its proteome using label-free quantitative mass spectrometry for protein abundance profiling in combination with statistical analysis. Our results show that the trypanosomal outer membrane proteome consists of 82 proteins, two-thirds of which have never been associated with mitochondria before. 40 proteins share homology with proteins of known functions. The function of 42 proteins, 33 of which are specific to trypanosomatids, remains unknown. 11 proteins are essential for the disease-causing bloodstream form of T. brucei and therefore may be exploited as novel drug targets. A comparison with the outer membrane proteome of yeast defines a set of 17 common proteins that are likely present in the mitochondrial outer membrane of all eukaryotes. Known factors involved in the regulation of mitochondrial morphology are virtually absent in T. brucei. Interestingly, RNAi-mediated ablation of three outer membrane proteins of unknown function resulted in a collapse of the network-like mitochondrion of procyclic cells and for the first time identified factors that control mitochondrial shape in T. brucei.

Subclinical thyroid dysfunction and cardiovascular outcomes among prospective cohort studies

The association between subclinical thyroid dysfunction and cardiovascular outcomes has been recently clarified with the publication of three individual participant data (IPD) analyses from the Thyroid Studies Collaboration. We identified original cohort studies with a systematic review and pooled individual data from over 70'000 participants to obtain a more precise estimate of the risks of cardiovascular outcomes associated with subclinical thyroid dysfunction. Subclinical hypothyroidism and subclinical hyperthyroidism, defined as normal thyroxine (FT4) levels with increased or decreased Thyroid-Stimulating Hormones (TSH or thyrotropin) respectively, are associated with increased risk of cardiovascular outcomes compared to euthyroid state, particularly in those with a more pronounced thyroid dysfunction. Specifically, subclinical hypothyroidism is associated with an increased risk of coronary heart disease (CHD) events, CHD mortality and heart failure (HF) events in individuals with higher TSH levels, particularly in those with TSH levels ≥10.0 mIU/L. Conversely, subclinical hyperthyroidism is associated with an increased risk of total mortality, CHD mortality, HF and atrial fibrillation, particularly in those with suppressed TSH levels <0.10 mIU/L. Pending ongoing randomized controlled trials, these observational findings allow identifying potential TSH thresholds for thyroid medication initiation based on risk of clinical outcomes, although clinical decision based solely on observational data need caution. The impact of thyroid replacement among the elderly with subclinical hypothyroidism is currently studied in a multicenter international randomized controlled trial (Thyroid Hormone Replacement for Subclinical Hypothyroidism Trial, TRUST trial).

Enterococcus faecalis rnjB is required for pilin gene expression and biofilm formation.

Pili in Gram-positive bacteria play a major role in the colonization of host tissue and in the development of biofilms. They are promising candidates for vaccines or drug targets since they are highly immunogenic and share common structural and functional features among various Gram-positive pathogens. Numerous publications have helped build a detailed understanding of pilus surface assembly, yet regulation of pilin gene expression has not been well defined. Utilizing a monoclonal antibody developed against the Enterococcus faecalis major pilus protein EbpC, we identified mutants from a transposon (Tn) insertion library which lack surface-exposed Ebp pili. In addition to insertions in the ebp regulon, an insertion in ef1184 (dapA) significantly reduced levels of EbpC. Analysis of in-frame dapA deletion mutants and mutants with the downstream gene rnjB deleted further demonstrated that rnjB was responsible for the deficiency of EbpC. Sequence analysis revealed that rnjB encodes a putative RNase J2. Subsequent quantitative real-time PCR (qRT-PCR) and Northern blotting demonstrated that the ebpABC mRNA transcript level was significantly decreased in the rnjB deletion mutant. In addition, using a reporter gene assay, we confirmed that rnjB affects the expression of the ebpABC operon. Functionally, the rnjB deletion mutant was attenuated in its ability to produce biofilm, similar to that of an ebpABC deletion mutant which lacks Ebp pili. Together, these results demonstrate the involvement of rnjB in E. faecalis pilin gene expression and provide insight into a novel mechanism of regulation of pilus production in Gram-positive pathogens.

Effects of exercise on anxiety and depression disorders: Review of meta-analyses and neurobiological mechanisms

Anxiety and depression are the most frequently diagnosed psychological diseases showing a high co-morbidity. They have a severe impact on the lives of the persons concerned. Many meta-analytical studies suggested a positive anxiolytic and depression reducing effect of exercise programs. The aim of the present article is to synthesize metaanalyses on the effects of exercise on anxiety and depression and to describe average effect sizes. For this purpose 37 meta-analyses were included reporting 50 effect sizes for anxiety scores of 42,264 participants and depression scores of 48,207 persons. The average documented anxiolytic effect of exercise in these reviews was small, 0.34. In contrast, the effect of exercise on depression was significantly higher and at a moderate level, 0.56. Data of randomized controlled trials suggest higher sizes for the effect of exercise on anxiety and depression leading to increases up to moderate and large effects, respectively. Additionally, exercise seems to be more beneficial for patients compared to participants within a nonclinical, normal range of psychological disease. Especially for the effect of exercise on anxiety, more high quality meta-analyses of randomized controlled trials are needed. Finally, possible neurobiological explanations are suggested for the positive effect of exercise on psychological disorders like anxiety and depression.

Effects of physical and psychological stressors on adolescents’ cortisol levels and self-perceived stress in school

Both, psychosocial stress and exercise in the past have been used as stressors to elevate saliva cortisol and change state anxiety levels. In the present study, high-school students at the age of 14 were randomly assigned to three experimental groups: (1) an exercise group (n = 18), that was running 15 minutes at a medium intensity level of 65-75% HRmax, (2) a psychosocial stress group (n = 19), and (3) a control group (n = 18). The psychosocial stress was induced to the students by completing a standardized intelligence test under the assumption that their IQ scores would be made public in class. Results display that only psychosocial stress but not exercise was able to significantly increase cortisol levels but decreased cognitive state anxiety in adolescents. The psychosocial stress protocol applied here is proposed for use in future stress studies with children or adolescents in group settings, e.g., in school.