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Current
Pharmaceutical Design
ISSN: 1381-6128
OPEN ACCESS PLUS
Contents
Herbal Medicines and Nutraceuticals for Diabetic
Vascular Complications: Mechanisms of Action and Bioactive
Phytochemicals, 2010, 16, 3776-3807
Eshaifol A. Omar, Antony Kam, Ali Alqahtani,
Kong M. Li, Valentina Razmovski-Naumovski, Srinivas Nammi,
Kelvin Chan, Basil D Roufogalis and George Q. Li
[Abstract] [Full
Text Article]
Ligand-Based Peptide Design and Combinatorial Peptide Libraries
to Target G Protein-Coupled Receptors, 2010, 16,
3071-3088
Christian W. Gruber, Markus Muttenthaler and
Michael Freissmuth
[Abstract] [Full
Text Article]
Clinical PET Imaging of Insulinoma and Beta-Cell Hyperplasia,
2010, 16, 1550-1560
S. Kauhanen, M. Seppänen, H. Minn and
P. Nuutila
[Abstract] [Full
Text Article]
Development of Radiotracers for the Determination of the Beta-Cell
Mass In Vivo 2010, 16, 1561-1567
Maarten Brom, Karolina Andraojc, Wim J.G. Oyen,
Otto C. Boerman and Martin Gotthardt
[Abstract] [Full
Text Article]
In Vivo Beta-Cell Imaging with VMAT 2 Ligands - Current
State-of-the-Art and Future Perspectives, 2010, 16,
1568-1581
Rajakrishnan Veluthakal and Paul Harris
[Abstract] [Full
Text Article]
MR Imaging of Pancreatic Islets: Tracking
Isolation, Transplantation and Function, 2010,
16, 1582-1594
L. Leoni and B.B. Roman
[Abstract] [Full
Text Article]
Regeneration of Mammalian Skeletal Muscle: Basic Mechanisms
and Clinical Implications, 2010, 16, 906-914
Stefano Ciciliot and Stefano Schiaffino
[Abstract] [Full
Text Article]
Prediction of MHC-Peptide Binding: A Systematic and Comprehensive
Overview, 2009, 15, 3209-3220
Esther M. Lafuente and Pedro A.
Reche
[Abstract] [Full
Text Article]
Prevention of Atherosclerosis by Interference with the Vascular
Nitric Oxide System, 2009, 15, 3133-3145
Huige Li and Ulrich Förstermann
[Abstract] [Full
Text Article]
Function and Frustration of Multi-Drug ABC Exporter
Protein and Design of Model Proteins for Drug Delivery Using
Protein Hydration Thermodynamics, 2009, 15, 2833-2867
D.W. Urry, K.D. Urry, W. Szaflarski, M.
Nowicki and M. Zabel
[Abstract] [Full
Text Article]
The Effects of Antipsychotics on the Brain: What Have
We Learnt from Structural Imaging of Schizophrenia? –
A Systematic Review, 2009, 15, 2535-2549
R. Smieskova, P. Fusar-Poli, P. Allen, K.
Bendfeldt, R.D. Stieglitz, J. Drewe, E.W. Radue, P.K. McGuire,
A. Riecher-Rössler and S.J. Borgwardt
[Abstract]
[Full
Text Article]
Modulating Proteostasis: Peptidomimetic Inhibitors
and Activators of Protein Folding, 2009, 15, 2488-2507
F. Hatahet and L.W. Ruddock
[Abstract] [Full
Text Article]
III. Angiogenesis: Complexity of Tumor Vasculature
and Microenvironment, 2009, 15, 1854-1867
M. Furuya, Y. Yonemitsu and I.
Aoki
[Abstract] [Full
Text Article]
The Role of the Gut Microbiota in Energy Metabolism
and Metabolic Disease, 2009, 15, 1546-1558
P.D. Cani and N.M. Delzenne
[Abstract] [Full
Text Article]
Phosphorothioate-Stimulated
Cellular Uptake of siRNA: A Cell Culture Model for Mechanistic
Studies, 2008, 14, 3666-3673
A. Detzer, M. Overhoff, A. Mescalchin, M.
Rompf and G. Sczakiel
[Abstract] [Full
Text Article]
Peptide-Mediated Cellular Delivery of Oligonucleotide-Based
Therapeutics In Vitro: Quantitative Evaluation of
Overall Efficacy Employing Easy to Handle Reporter Systems,
2008, 14, 3637-3655
S.D. Laufer and T. Restle
[Abstract] [Full
Text Article]
The Use of Growth Factors in Hematopoietic Stem Cell
Transplantation, 2008, 14, 1950-1961
I. Pusic and J.F. DiPersio
[Abstract] [Full
Text Article]
Heme Oxygenase: A Target Gene for Anti-Diabetic and
Obesity, 2008, 14, 412-421
N.G. Abraham, P.L. Tsenovoy, J. McClung and G.S. Drummond
[Abstract] [Full
Text Article]
Apoptosis in the Homeostasis of the Immune System
and in Human Immune Mediated Diseases, 2008,
14, 253-268
A. Giovannetti, M. Pierdominici, A. Di Iorio, R. Cianci,
G. Murdaca, F. Puppo, F. Pandolfi and R. Paganelli
[Abstract] [Full
Text Article]
Chondromodulin-I and Tenomodulin: The Negative Control
of Angiogenesis in Connective Tissue, 2007, 13, 2101-2112
C. Shukunami and Y. Hiraki
[Abstract] [Full
Text Article]
Advances in Asthma and COPD Treatment: Combination
Therapy with Inhaled Corticosteroids and Long-Acting β2-Agonists,
2006, 12, 3261-3279
A. Miller-Larsson and O. Selroos
[Abstract] [Full
Text Article]
Effects of Nucleotides and Nucleotide Analogue Inhibitors
of HIV 1 Reverse Transcriptase in a Ratchet Model of Polymerase
Translocation, 2006, 12, 1867-1877
M. Götte
[Abstract] [Full
Text Article]
Abstracts
[Back to top]
Herbal Medicines and Nutraceuticals for Diabetic Vascular
Complications: Mechanisms of Action and Bioactive Phytochemicals
Eshaifol A. Omar, Antony Kam, Ali Alqahtani,
Kong M. Li, Valentina Razmovski-Naumovski, Srinivas Nammi,
Kelvin Chan, Basil D Roufogalis and George Q. Li
[Full
Text Article]
Diabetes is one of the most prevalent chronic diseases throughout
the world. The majority of its complications arise from vascular-related
inflammation apparently initiated by endothelial cell injury.
One cause of this injury has been attributed to hyperglycaemiainduced
reactive oxygen species. Consequently, current drug developmental
strategy has targeted specific inflammatory and oxidative
stress pathways for the prevention of diabetic vascular complications.
Herbal medicines have traditionally been used for the treatment
of diabetes and its complications. In fact, current pre-clinical
and clinical studies have demonstrated that many of them exhibit
potent anti-inflammatory and anti-oxidative properties, and
have also identified the active phytochemicals responsible
for their activities. The present review summarises the latest
research on the molecular mechanisms of diabetic vascular
complications, and evaluates the level of scientific evidence
for common herbal medicines and their bioactive phytochemicals.
These agents have been shown to be effective through various
mechanisms, particularly the NF-κB
signalling pathways. Overall, herbal medicines and nutraceuticals,
as well as their bioactive components, which exhibit anti-inflammatory
and anti-oxidative properties, provide a promising approach
for the prevention and treatment of diabetic complications.
[Back to top]
Ligand-Based Peptide Design and Combinatorial
Peptide Libraries to Target G Protein-Coupled Receptors
Christian W. Gruber, Markus Muttenthaler and
Michael Freissmuth
[Full
Text Article]
G protein-coupled receptors (GPCRs) are considered to
represent the most promising drug targets; it has been repeatedly
said that a large fraction of the currently marketed drugs
elicit their actions by binding to GPCRs (with cited numbers
varying from 30-50%). Closer scrutiny, however, shows that
only a modest fraction of (~60) GPCRs are, in fact, exploited
as drug targets, only ~20 of which are peptide-binding
receptors. The vast majority of receptors in the humane genome
have not yet been explored as sites of action for drugs. Given
the drugability of this receptor class, it appears that opportunities
for drug discovery abound. In addition, GPCRs provide for
binding sites other than the ligand binding sites (referred
to as the “orthosteric site”). These additional
sites include (i) binding sites for ligands (referred to as
“allosteric ligands”) that modulate the affinity
and efficacy of orthosteric ligands, (ii) the interaction
surface that recruits G proteins and arrestins, (iii) the
interaction sites of additional proteins (GIPs, GPCR interacting
proteins that regulate G protein signaling or give rise to
G protein-independent signals). These sites can also be targeted
by peptides. Combinatorial and natural peptide libraries are
therefore likely to play a major role in identifying new GPCR
ligands at each of these sites. In particular the diverse
natural peptide libraries such as the venom peptides from
marine cone-snails and plant cyclotides have been established
as a rich source of drug leads. High-throughput screening
and combinatorial chemistry approaches allow for progressing
from these starting points to potential drug candidates. This
will be illustrated by focusing on the ligand-based drug design
of oxytocin (OT) and vasopressin (AVP) receptor ligands using
natural peptide leads as starting points.
[Back to top]
Clinical PET Imaging of Insulinoma and Beta-Cell Hyperplasia
S. Kauhanen, M. Seppänen, H. Minn and
P. Nuutila
[Full
Text Article]
Persistent hyperinsulinemic hypoglycemia (PHH) is caused by
solitary benign insulinoma or hyperplasia of pancreatic beta
cells. In infants, PHH is caused by functionally defective
hyperplastic beta cells, which are either diffusely or focally
distributed in the pancreas. In adults, insulinoma is the
most common cause of PHH, but recently, an increasing number
of beta-cell hyperplasias has been reported among adults.
The cause of adult beta-cell hyperplasia is not known. Whether
the increased use of bariatric surgery in the treatment of
severe obesity plays a role here is under investigation. Accurate
localization of disease focus in both insulinoma and focal
beta-cell hyperplasia provides an important support for surgery,
especially as the use of laparoscopic surgery has increased.
Conventional imaging of these challenging pancreatic lesions
has evolved during recent years, but current imaging methods
still lack sufficient sensitivity or are invasive. In most
pancreatic neuroendocrine tumors (NETs), the usefulness of
positron emission tomography (PET) with fluorine-labeled fluorodeoxyglucose
([18F]FDG) for lesion detection
is limited because of the low glucose turnover of these tumors.
Based on the capacity of pancreatic beta cells to take up
and decarboxylate amine precursors, several investigators
have studied patients with pancreatic NETs using aminoacid
precursors, such as [18F]dihydroxyphenylalanine
(DOPA) and [11C]hydroxytryptophan
(5-HTP), in an attempt to increase the sensitivity of PET
scanning. Another characteristic of NETs is the expression
of somatostatin receptors, and thus encouraging studies with
somatostatin receptor imaging with [18Ga]-labeled
somatostatin analogs have emerged as a new interesting imaging
tool for the diagnosis of pancreatic NETs. This article provides
an overview of our experiences and the current literature
on PET imaging in patients with PHH caused by insulinoma or
beta-cell hyperplasia.
[Back to top]
Development of Radiotracers for the Determination
of the Beta-Cell Mass In Vivo
Maarten Brom, Karolina Andraojc, Wim J.G. Oyen,
Otto C. Boerman and Martin Gotthardt
[Full
Text Article]
The changes in beta-cell mass (BCM) during the course of diabetes
are not yet well characterized. A non-invasive method to measure
the BCM in vivo would allow us to study the BCM during
the onset and progression of the diseases caused by beta-cell
dysfunction. PET and SPECT imaging are attractive approaches
to determine the BCM because of their high sensitivity and
the possibility to quantitatively analyze the images. Several
targets and their corresponding radiotracers have been examined
for their ability to determine the BCM including radiolabeled
antibodies, antibody fragments, peptides and small molecules.
Although some of these tracers show promising results, there
is still no reliable method to determine the beta-cell mass
in vivo. In this review, the targets and the corresponding
radiotracers evaluated so far for the determination of the
BCM in vivo in humans will be discussed.
[Back to top]
In Vivo Beta-Cell Imaging with VMAT
2 Ligands - Current State-of-the-Art and Future Perspectives
Rajakrishnan Veluthakal and Paul Harris
[Full
Text Article]
In diabetic disease, blood glucose, HbA1c and insulin
levels qualify as biomarkers reflecting endocrine pancreas
function, but their shortfall in being truly useful predictors
or surrogate endpoints of "abnormal processes or disease"
lies in that alteration in their levels are dependent on a
variety comorbidities and occur too late in the disease process
to be useful sentinels. Non invasive imaging of molecular
targets within the beta cell carry the promise of revealing
quantitative information about β-cell
mass that can, at least theoretically, be used to monitor,
in real-time, the natural history of T1DM progression, assess
novel therapies designed to drive the proliferation and differentiation
of endogenous beta cell progenitors, appraise methods of preserving
mature beta cell mass as well as to track the function and
viability of transplanted cells and tissues. In this article,
we review and deconstruct available information regarding
the methodology of making non invasive measurements of VMAT2
in the pancreas and the validity of these measurements to
estimate beta cell mass in vivo.
[Back to top]
MR Imaging of Pancreatic Islets: Tracking Isolation,
Transplantation and Function
L. Leoni and B.B. Roman
[Full
Text Article]
The increasing global incidence of diabetes and advancements
in clinical pancreatic islet transplantation for the treatment
of Type I diabetes have renewed the interest in understanding
the variations of β-cell
mass and function relative not only to transplant outcome
but also to the onset and progression of diabetes. A deeper
comprehension of the molecular and cellular processes involved
in pancreatic islet inflammation and cytotoxicity is necessary
to further improve efficacy of islet transplantation and to
develop new therapies aimed at preserving beta cell function
in pathological conditions. Available diagnostic methods based
on metabolic response are unsuitable as they lack correlation
to islet mass, viability and function. Great emphasis has
been placed on developing noninvasive imaging technologies
which enable the tracking of both endogenous and transplanted
islet mass and potentially function overtime, the characterization
of changes in islet vasculature and the degree of T-cell infiltration
during insulitis.
Among the more relevant modalities are magnetic resonance,
positron emitted tomography, single photon emission computed
tomography, bioluminescence and fluorescence optical imaging.
This review focuses on the most recent advancements in magnetic
resonance imaging (MRI) of pancreatic islets. In-vitro approaches aimed at characterizing the potency of isolated
islets as well as in-vivo advancements in the assessment
of transplanted beta cell mass are presented together with
the significant progress made in the in-vivo imaging
of the endocrine pancreas and islet vasculature and inflammation.
Different experimental approaches are compared via their advantages
and limitations with respect to their clinical implementation.
[Back to top]
Regeneration of Mammalian Skeletal Muscle: Basic Mechanisms
and Clinical Implications
Stefano Ciciliot and Stefano Schiaffino
[Full
Text Article]
Mammalian skeletal muscles can regenerate following injury
and this response is mediated by a specific type of stem cell,
the satellite cell. We review here the three main phases of
muscle regeneration, including i) the initial inflammatory
response and the dual role of macrophages as both scavengers
involved in the phagocytosis of necrotic debris and promoters
of myogenic differentiation, ii) the activation and differentiation
of satellite cells and iii) the growth and remodeling of the
regenerated muscle tissue. Nerve activity is required to support
the growth of regenerated myofibers and the specification
of muscle fiber types, in particular the activation of the
slow gene program. We discuss the regeneration process in
two different settings. Chronic degenerative diseases, such
as muscular dystrophies, are characterized by repeated cycles
of segmental necrosis and regeneration involving scattered
myofibers. In these conditions the regenerative capacity of
satellite cells becomes exhausted with time and fibrosis prevails.
Acute traumatic injuries, such as strain injuries common in
sport medicine, cause the rupture of large myofiber bundles
leading to muscle regeneration and formation of scar tissue
and new myotendinous junctions at the level of the rupture.
Mechanical loading is essential for muscle regeneration, therefore,
following initial immobilization to avoid the risk of reruptures,
early remobilization is required to induce correct growth
and orientation of regenerated myofibers. Finally, we discuss
the causes of age-dependent decline in muscle regeneration
potential and the possibility of boosting regeneration in
aging muscle and in muscular dystrophies.
[Back to top]
Prediction of MHC-Peptide Binding: A Systematic and
Comprehensive Overview
Esther M. Lafuente and Pedro A.
Reche
[Full
Text Article]
T cell immune responses are driven by the recognition
of peptide antigens (T cell epitopes) that are bound to major
histocompatibility complex (MHC) molecules. T cell epitope
immunogenicity is thus contingent on several events, including
appropriate and effective processing of the peptide from its
protein source, stable peptide binding to the MHC molecule,
and recognition of the MHC-bound peptide by the T cell receptor.
Of these three hallmarks, MHC-peptide binding is the most
selective event that determines T cell epitopes. Therefore,
prediction of MHC-peptide binding constitutes the principal
basis for anticipating potential T cell epitopes. The tremendous
relevance of epitope identification in vaccine design and
in the monitoring of T cell responses has spurred the development
of many computational methods for predicting MHC-peptide binding
that improve the efficiency and economics of T cell epitope
identification. In this report, we will systematically examine
the available methods for predicting MHC-peptide binding and
discuss their most relevant advantages and drawbacks.
[Back to top]
Prevention of Atherosclerosis by Interference with
the Vascular Nitric Oxide System
Huige Li and Ulrich Förstermann
[Full
Text Article]
Nitric oxide (NO) produced by endothelial NO synthase (eNOS)
represents an anti-atherosclerotic principle. NO bioavailability
is decreased in atherosclerosis due to increased NO inactivation
by reactive oxygen species and reduced NO synthesis. Various
types of vascular pathophysiology are associated with oxidative
stress, with NADPH oxidases as the major source of reactive
oxygen species. These inactivate NO. Also, oxidative stress
is likely to be the main cause for oxidation of the essential
NOS cofactor, tetrahydrobiopterin (BH4). A lack of BH4 leads
to eNOS uncoupling (i.e., uncoupling of oxygen reduction from
NO synthesis in eNOS). Based on these pathomechanisms, the
therapeutic potential of a number of compounds is discussed
in this review: (1) NO donors; (2) L-arginine; (3) folic acid;
(4) BH4 and its precursor sepiapterin; (5) compounds that
upregulate eNOS and concomitantly maintain eNOS activity (e.g.
midostaurin, betulinic acid, ursolic acid, AVE9488 and AVE3085);
(6) compounds that enhance the de novo synthesis of BH4 by
stimulating expression or activity of GTP cyclohydrolase I;
and (7) 3-hydroxy-3-methylglutarylcoenzyme A inhibitors (statins)
and drugs interrupting the renin-angiotensin-aldosterone system.
Statins, angiotensin II type 1 receptor blockers, angiotensin-converting
enzyme (ACE) inhibitors, the aldosterone antagonist eplerenone
and the renin inhibitor aliskiren enhance NO bioactivity and
reduce atherosclerosis progression through multiple mechanisms.
[Back to top]
Function and Frustration of Multi-Drug ABC Exporter
Protein and Design of Model Proteins for Drug Delivery Using
Protein Hydration Thermodynamics
D.W. Urry, K.D. Urry, W. Szaflarski, M.
Nowicki and M. Zabel
[Full
Text Article]
The mechanism is presented whereby simultaneous hydrolysis
of two molecules of ATP in the ATP-binding cassette (ABC)
exporter protein, Sav 1866, opens a transmembrane channel
to pump drug out of the cell and confers drug resistance,
e.g., gives rise to methicillin resistant Staphylococcus
aureus, MRSA.
The proposed mechanism suggests pharmaceutical design strategies
for overloading the capacity of two molecules of ATP to open
access to the channel for export. Structural homology of Staphylococcus
aureus, Sav 1866, to human P-glyco- protein and MRP2,
suggests a similar mechanism could be relevant to human carcinoma
cells.
The transport mechanism utilizes two thermodynamic quantities
- ΔGHA, the change in
Gibbs free energy for hydrophobic association, and ΔGap,
an apolar-polar repulsive free energy for hydration, derived
from studies on designed elastic-contractile model proteins
(ECMPs). These quantities also allow design of remarkably
biocompatible ECMPs as drug delivery vehicles with remarkable
control of release profiles and of ECMPs that provide the
means of developing pharmaceuticals for blocking multi-drug
resistance.
[Back to top]
The Effects of Antipsychotics on the Brain: What Have
We Learnt from Structural Imaging of Schizophrenia? –
A Systematic Review
R. Smieskova, P. Fusar-Poli, P. Allen, K. Bendfeldt, R.D.
Stieglitz, J. Drewe, E.W. Radue, P.K. McGuire, A. Riecher-Rösslerand
S.J. Borgwardt
[Full
Text Article]
Despite a large number of neuroimaging studies in schizophrenia
reporting subtle brain abnormalities, we do not know to what
extent such abnormalities reflect the effects of antipsychotic
treatment on brain structure. We therefore systematically
reviewed cross-sectional and follow-up structural brain imaging
studies of patients with schizophrenia treated with antipsychotics.
30 magnetic resonance imaging (MRI) studies were identified,
24 of them being longitudinal and six cross-sectional structural
imaging studies. In patients with schizophrenia treated with
antipsychotics, reduced gray matter volume was described,
particularly in the frontal and temporal lobes. Structural
neuroimaging studies indicate that treatment with typical
as well as atypical antipsychotics may affect regional gray
matter (GM) volume. In particular, typical antipsychotics
led to increased gray matter volume of the basal ganglia,
while atypical antipsychotics reversed this effect after switching.
Atypical antipsychotics, however, seem to have no effect on
basal ganglia structure.
[Back to top]
Modulating Proteostasis: Peptidomimetic Inhibitors
and Activators of Protein Folding
F. Hatahet and L.W. Ruddock
[Full
Text Article]
Protein folding in the cell is a complex process with a fine
balance between productive and non-productive folding. To
modulate, either up-regulating or down-regulating, the level
of one specific protein with multiple approaches is possible,
including the modulation of catalysed protein folding, the
use of chemical and pharmacological chaperones, alteration
of natural protein-protein interactions, the regulation of
degradative pathways and manipulation of natural control mechanisms,
such as the heat shock response and the unfolded protein response.
Errors in proteostasis are linked to a wide range of disease
states and many examples exist of the successful manipulation
of proteostasis for the partial or complete elimination of
the disease phenotype, including for many amyloid based diseases
such as Parkinson’s and Alzheimer’s as well as
for ‘loss-of-function’ diseases such as Fabry’s
and Gaucher’s diseases. This review takes an overview
of the different approaches that can be used to alter proteostasis
with an emphasis on peptidomimetic inhibitors and activators
of protein folding. It covers the modulators available, their
mechanisms of action and potential limitations, including
the problems of specificity in altering proteostasis.
[Back to top]
III. Angiogenesis: Complexity of Tumor Vasculature
and Microenvironment
M. Furuya, Y. Yonemitsu and I.
Aoki
[Full
Text Article]
Vascular system plays critical roles in tumor progression
and metastasis. Tumor vessels generally sprout from preexisting
vascular cells. In addition, pluripotent progenitor cells
also participate in tumor neovascularization. The latter populations
include endothelial progenitor cells, hematopoietic stem cells
and mesenchymal stem cells that are stimulated and attracted
into the lesion. Recent studies on tumor microenvironment
have disclosed that BM (bone marrow)-derived progenitor cells
contain unique subpopulations that do not become fully-differentiated
vascular constituents; instead, they show the nature of immature
myeloid or mesenchymal lineage, and they enhance tumor angiogenic
milieu in close contact with tumor vessels. BM-derived cells
also migrate into pre-metastatic niche and stimulate vascular
beds of distant organ for attracting circulating tumor cells.
Currently, several antiangiogenic molecules are under clinical
trials and they are expected to improve overall prognosis.
Humanized monoclonal antibody bevacizumab specifically targeting
VEGF (vascular endothelial growth factor), and several tyrosine
kinase inhibitors targeting VEGF receptors-mediated pathways
are the most widely studied agents in several types of advanced
cancers. It is obvious that VEGF contributes to tumor neovascularization
as a mastermind molecule. On the other hand, the mechanism
has also been elucidated how tumors evade VEGF targeting therapies.
To establish safer and more effective antiangiogenic therapies,
it is important to understand the cross-communication between
tumors and hosts in proinflammatory milieu. In this review,
we discuss features of tumor angiogenic vessels and their
microenvironment. Recent topics on the contribution of BM-derived
cells, complexities of VEGF-targeting approaches, and chemoattractants
that activate tumor vascular beds are summarized.
[Back to top]
The Role of the Gut Microbiota in Energy Metabolism
and Metabolic Disease
P.D. Cani and N.M. Delzenne
[Full
Text Article]
Obesity is now classically characterized by a cluster of several
metabolic disorders, and by a low grade inflammation. The
evidence that the gut microbiota composition can be different
between healthy and or obese and type 2 diabetic patients
has led to the study of this environmental factor as a key
link between the pathophysiology of metabolic diseases and
the gut microbiota. Several mechanisms are proposed linking
events occurring in the colon and the regulation of energy
metabolism, such as i.e. the energy harvest from the diet,
the synthesis of gut peptides involved in energy homeostasis
(GLP-1, PYY…), and the regulation of fat storage. Moreover,
the development of obesity and metabolic disorders following
a high-fat diet may be associated to the innate immune system.
Indeed, high-fat diet feeding triggers the development of
obesity, inflammation, insulin resistance, type 2 diabetes
and atherosclerosis by mechanisms dependent of the LPS and/or
the fatty acids activation of the CD14/TLR4 receptor complex.
Importantly, fat feeding is also associated with the development
of metabolic endotoxemia in human subjects and participates
in the low-grade inflammation, a mechanism associated with
the development of atherogenic markers. Finally, data obtained
in experimental models and human subjects are in favour of
the fact that changing the gut microbiota (with prebiotics
and/or probiotics) may participate in the control of the development
of metabolic diseases associated with obesity. Thus, it would
be useful to find specific strategies for modifying gut microbiota
to impact on the occurrence of metabolic diseases.
[Back to top]
Phosphorothioate-Stimulated Cellular Uptake of siRNA:
A Cell Culture Model for Mechanistic Studies
A. Detzer, M. Overhoff, A. Mescalchin, M.
Rompf and G. Sczakiel
[Full
Text Article]
The phosphorothioate(PS)-stimulated cellular uptake of naked
short interfering RNA (siRNA) into mammalian cells indicates
a promising new mechanistic strategy because it makes use
of a caveosomal, rather than an endosomal pathway, which is
used by the majority of known delivery systems. This PS-stimulated
mode delivers large amounts of siRNA primarily into the perinuclear
space which is related to measurable though moderate target
suppression. The observed limited efficacy seems to be related
to intracellular trapping of siRNA.
Here, we studied the intracellular localisation of siRNA and
Argonaute 2 (Ago2), the major component of the RNA interference
(RNAi) machinery, by density gradient centrifugation and fluorescence
microscopy after PS-stimulated delivery or transfection with
Lipofectamine 2000. The two cell lines ECV-304 and SKRC-35
both take up siRNA in the PS-stimulated mode but only ECV-304
shows RNAi, i.e. siRNA-mediated suppression of lamin A/C expression,
whereas SKRC-35 does not. This lack of RNAi in the latter
cell line seems to be due to a block of an intracellular siRNA
translocation process.
This study provides strong evidence for the view that co-localisation
of siRNA and Ago2 in the vicinity of the rough endoplasmic
reticulum (rER) in ECV-304 cells is related to target inhibition,
whereas density gradient fractionation of cell organelles
shows a lack of co-localisation in SKRC-35 cells in which
RNAi does not occur after the PS-mediated delivery. In summary,
we propose to exploit this dual cell system to identify important
steps of intracellular trafficking of siRNA after PS mediated
delivery that are crucial for its biological activity and
which seem to be of general importance for the understanding
of the intracellular trafficking and release of siRNA.
[Back to top]
Peptide-Mediated Cellular Delivery of Oligonucleotide-Based
Therapeutics In Vitro: Quantitative Evaluation of
Overall Efficacy Employing Easy to Handle Reporter Systems
S.D. Laufer and T. Restle
[Full
Text Article]
Cellular uptake of therapeutic oligonucleotides and subsequent
intracellular trafficking to their target sites represents
the major technical hurdle for the biological effectiveness
of these potential drugs. Accordingly, laboratories worldwide
focus on the development of suitable delivery systems. Among
the different available non-viral systems like cationic polymers,
cationic liposomes and polymeric nanoparticles, cell-penetrating
peptides (CPPs) represent an attractive concept to bypass
the problem of poor membrane permeability of these charged
macromolecules. While uptake per se in most cases
does not represent the main obstacle of nucleic acid delivery
in vitro, it becomes increasingly apparent that intracellular
trafficking is the bottleneck. As a consequence, in order
to optimize a given delivery system, a side-by-side analysis
of nucleic acid cargo internalized and the corresponding biological
effect is required to determine the overall efficacy. In this
review, we will concentrate on peptide-mediated delivery of
siRNAs and steric block oligonucleotides and discuss different
methods for quantitative assessment of the amount of cargo
taken up and how to correlate those numbers with biological
effects by applying easy to handle reporter systems. To illustrate
current limitations of non-viral nucleic acid delivery systems,
we present own data as an example and discuss options of how
to enhance trafficking of molecules entrapped in cellular
compartments.
[Back to top]
The Use of Growth Factors in Hematopoietic Stem Cell
Transplantation
I. Pusic and J.F. DiPersio
[Full
Text Article]
Mobilized, peripheral blood stem cells (PBSC) are increasingly
used for both autologous and allogeneic transplants. Granulocyte-colony-stimulating
factor is the most widely used cytokine for mobilization.
Several different mechanisms of stem cell mobilization have
been proposed including protease-dependent and non-protease-
dependent mechanisms. In autologous transplants, the addition
of chemotherapy to mobilization can enhance the yield of PBSC
collected but with substantial adverse effects, and not necessarily
faster engraftment. In allogeneic transplants, the use of
mobilized PBSC is associated with faster engraftment and donor
chimerism compared to bone marrow. In the majority of studies,
the rate of acute graft-versus-host disease (GVHD) has not
been shown to be significantly higher with PBSC, but the rate
of chronic GVHD appears to be increased. Several different
strategies have been proposed for patients and donors who
fail initial mobilization, including the use of novel agents.
AMD3100 (Plerixafor) works by directly inhibiting the interaction
between stromal cell-derived factor-1 and its receptor CXCR4,
and mobilizes hematopoietic stem cells within hours. It is
being studied alone or in conjunction with growth factors
for PBSC mobilization in both autologous and allogeneic settings.
Although the use of growth factors after PBSC transplantation
results in faster neutrophil engraftment its impact on treatment-related
mortality and survival does not appear significant. Here,
we review the biology and methods of PBSC mobilization, the
effect of growth factors on normal donors and the controversies
of growth factor use in the post-transplant setting. We also
review the data on novel agents for mobilization of stem cells.
[Back to top]
Heme Oxygenase: A Target Gene for Anti-Diabetic and
Obesity
N.G. Abraham, P.L. Tsenovoy, J. McClung and G.S. Drummond
[Full
Text Article]
Heme oxygenase-1 (HO-1) is central to the regulation of oxidative
injury. The role of increased HO-1 expression and Heme oxygenase
(HO) activity in mitigating the detrimental side effect of
diabetes is examined. A review of the mechanism(s) of action
is included. This may lead to the development of pharmacological
and genetic approaches to mitigate the clinical complications
associated with the progression of diabetes and obesity.
[Back to top]
Apoptosis in the Homeostasis of the Immune System
and in Human Immune Mediated Diseases
A. Giovannetti, M. Pierdominici, A. Di Iorio, R. Cianci,
G. Murdaca, F. Puppo, F. Pandolfi and R. Paganelli
[Full
Text Article]
The immune system has evolved sophisticate mechanisms controlling
the development of responses to dangerous antigens while avoiding
unnecessary attacks to innocuous, commensal or self antigens.
The risk of autoimmunity is continuously checked and balanced
against the risk of succumbing to exogenous infectious agents.
It is therefore of paramount importance to understand the
molecular events linking the breakdown of tolerance and the
development of immunodeficiency. Apoptotic mechanisms are
used to regulate the development of thymocytes, the shaping
of T cell repertoire, its selection and the coordinate events
leading to immune responses in the periphery. Moreover, they
are at the heart of the homeostatic controls restoring T cell
numbers and establishing T cell memory. T lymphocytes shift
continuously from survival to death signals to ensure immune
responsiveness without incurring in autoimmune damage. In
this review we shall consider some key facts on the relationship
of lymphopenia to autoreactivity, the mechanisms controlling
positive and negative selection in the thymus, the role of
apoptosis in selected primary immunodeficiency states and
in systemic and organ-specific autoimmunity, with examples
from human diseases and their animal models.
[Back to top]
Chondromodulin-I and Tenomodulin: The Negative Control
of Angiogenesis in Connective Tissue
C. Shukunami and Y. Hiraki
[Full
Text Article]
The negative regulation of angiogenesis may provide a
promising therapeutic target for a number of lifestyle-related
diseases, as the switch to an angiogenic phenotype in many
tissues represents a critical step during the progression
of such disorders. Cartilage is avascular and shows resistance
to vascular invasion from the surrounding well-vascularized
mesenchyme. Using guanidine extracts of fetal bovine cartilage,
we have identified and purified chondromodulin-I (ChM-I) as
an angiogenesis inhibitor. The cDNA sequence of this factor
has revealed that the ChM-I precursor protein is a type II
transmembrane glycoprotein (334 amino acids) and that mature
ChM-I is encoded in the C-terminal region of the precursor.
After cleavage of the ChM-I precursor at its processing site,
mature ChM-I (120 amino acids) is secreted from chondrocytes
into the extracellular matrix. Following on from the identification
of ChM-I as an angiogenesis inhibitor in cartilage, we have
also cloned both mouse and human tenomodulin (TeM), which
share significant homology with ChM-I at their C-termini.
Moreover, exogenous expression experiments in COS cells suggests
that TeM is a type II transmembrane glycoprotein (317 amino
acids). When overexpressed in HUVECs, the C-terminal domain
(116 amino acids) of the TeM protein shows both anti-angiogenic
and anti-tumorigenic activities at equivalent levels to mature
ChM-I. In our present review, we discuss the structure, biological
activities and localization of these anti-angiogenic molecules.
[Back to top]
Advances in Asthma and COPD Treatment: Combination
Therapy with Inhaled Corticosteroids and Long-Acting β2-Agonists
A. Miller-Larsson and O. Selroos
[Full
Text Article]
Asthma treatment guidelines advocate the use of long-acting
β2-agonists
(LABA) in addition to inhaled corticosteroids (ICS) in patients
whose asthma is uncontrolled by ICS alone, thereby addressing
two processes fundamental to asthma: bronchoconstriction and
inflammation. Superior control – including a reduction
in severe exacerbations – of asthma and COPD by ICS/LABA
combination therapy has been demonstrated. Results from clinical
studies suggest additive and potentially synergistic effects
when the two agents are used in combination. No new safety-related
issues have been identified with ICS/LABA compared with the
monocomponents.
The exact mechanisms for the enhanced efficacy of ICS/LABA
combinations are under investigation but likely include drug
interactions at the receptor level and interwoven signalling
pathways, which may result in improved function of β2-adrenoceptors
and steroid receptors. Data from preclinical studies provide
evidence of additive, compensatory, complementary and synergistic
effects of ICS and LABA in the control of inflammation and
airway and lung remodelling. These effects may contribute
to the improved efficacy seen when treating asthma and COPD
with ICS/LABA combinations in clinical studies.
Two ICS/LABA combination products are available: budesonide/formoterol
(Symbicort®)
and salmeterol/fluticasone propionate (Seretide™).
An ICS/LABA combination in a single inhaler represent safe,
effective and convenient treatment options for the management
of patients with asthma and COPD. Clinical results also suggest
that adjustable dosing with budesonide/formoterol provides
better asthma control than fixed dosing. Further elucidation
of the underlying mechanisms responsible for this superior
disease control is needed.
[Back to top]
Effects of Nucleotides and Nucleotide Analogue Inhibitors
of HIV 1 Reverse Transcriptase in a Ratchet Model of Polymerase
Translocation
M. Götte
[Full
Text Article]
A single cycle of nucleotide incorporation by the reverse
transcriptase of the human immunodeficiency virus type 1 (HIV-1
RT) involves the initial binding of an incoming nucleotide,
a conformational change that traps the substrate, the formation
of a new phosphodiester bond, the release of pyrophosphate
(PPi), and ultimately polymerase translocation, which clears
the nucleotide binding site. This article reviews different
mechanistic models for polymerase translocation with emphasis
placed on HIV-1 RT. Structure-function analyses of stalled
complexes of HIV-1 RT provide strong evidence to suggest that
the enzyme can oscillate between pre- and post-translocational
states. Nucleotide hydrolysis is not required for the movement
of the polymerase in a stalled configuration; thermal energy
is sufficient to allow random bidirectional sliding. The next
complementary nucleotide, following the incorporated chain-terminator,
acts like a pawl of a ratchet that traps the enzyme in the
post-translocation state and prevents the reverse movement.
Quantitative footprinting experiments have shown that the
concentration of the templated nucleotide required to shift
the translocational equilibrium forward depends crucially
on the structure of the 3’end of the primer. Changes
in the relative population of pre- and post-translocation
complexes can influence rates of excision of incorporated
NRTIs, which, in turn, affects drug susceptibility. The concept
of a ratchet model of HIV-1 RT translocation and its implications
for drug action and resistance, and the discovery and development
of novel antiviral compounds is discussed.
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