Thematic Review Series: Recent Advances in the Treatment of Lysosomal Storage Diseases: Development of targeted therapies for Parkinson’s disease and related synucleinopathies

Therapeutic efforts in neurodegenerative diseases have been very challenging, particularly due to a lack of validated and mechanism-based therapeutic targets and biomarkers. The basic idea underlying the novel therapeutic approaches reviewed here is that by exploring the molecular basis of neurodegeneration in a rare lysosomal disease such as Gaucher’s disease (GD), new molecular targets will be identified for therapeutic development in common synucleinopathies. Accumulation of α-synuclein plays a key role in the pathogenesis of Parkinson’s disease (PD) and other synucleinopathies, suggesting that improved clearance of α-synuclein may be of therapeutic benefit. To achieve this goal, it is important to identify specific mechanisms and targets involved in the clearance of α-synuclein. Recent discovery of clinical, genetic, and pathological linkage between GD and PD offers a unique opportunity to examine lysosomal glucocerebrosidase, an enzyme mutated in GD, for development of targeted therapies in synucleinopathies. While modulation of glucocerebrosidase and glycolipid metabolism offers a viable approach to treating disorders associated with synuclein accumulation, the compounds described to date either lack the ability to penetrate the CNS or have off-target effects that may counteract or limit their capabilities to mediate the desired pharmacological action. However, recent emergence of selective inhibitors of glycosphingolipid biosynthesis and noninhibitory pharmacological chaperones of glycosphingolipid processing enzymes that gain access to the CNS provide a novel approach that may overcome some of the limitations of compounds reported to date. These new strategies may allow for development of targeted treatments for synucleinopathies that affect both children and adults.     

A first assessment of genetic variability in the Eurasian Stone‐curlew Burhinus oedicnemus

The Eurasian Stone‐curlew is a species of conservation concern in Europe. We investigate for the first time the extent of population structure among populations sampled from six geographical areas, representing four subspecies inhabiting the western part of the species' distribution. Neither mitochondrial nor nuclear markers fully supported current subspecies boundaries. However, both markers support significant differentiation of the Canary Island populations from those sampled from the Mediterranean. Further work is needed to establish the taxonomic status of this potentially distinct Macaronesian taxon. More broadly, further genetic research is required to design and implement an effective conservation plan for this species.     

The Tight Junction-Associated Protein Occludin Is Required for a Postbinding Step in Hepatitis C Virus Entry and Infection

The precise mechanisms regulating hepatitis C virus (HCV) entry into hepatic cells remain unknown. However, several cell surface proteins have been identified as entry factors for this virus. Of these molecules, claudin-1, a tight junction (TJ) component, is considered a coreceptor required for HCV entry. Recently, we have demonstrated that HCV envelope glycoproteins (HCVgp) promote structural and functional TJ alterations. Additionally, we have shown that the intracellular interaction between viral E2 glycoprotein and occludin, another TJ-associated protein, could be the cause of the mislocalization of TJ proteins. Herein we demonstrated, by using cell culture-derived HCV particles (HCVcc), that interference of occludin expression markedly reduced HCV infection. Furthermore, our results with HCV pseudotyped particles indicated that occludin, but not other TJ-associated proteins, such as junctional adhesion molecule A or zonula occludens protein 1, was required for HCV entry. Using HCVcc, we demonstrated that occludin did not play an essential role in the initial attachment of HCV to target cells. Surface protein labeling experiments showed that both expression levels and cell surface localization of HCV (co)receptors CD81, scavenger receptor class B type I, and claudin-1 were not affected upon occludin knockdown. In addition, immunofluorescence confocal analysis showed that occludin interference did not affect subcellular distribution of the HCV (co)receptors analyzed. However, HCVgp fusion-associated events were altered after occludin silencing. In summary, we propose that occludin plays an essential role in HCV infection and probably affects late entry events. This observation may provide new insights into HCV infection and related pathogenesis.Hepatitis C virus (HCV) is a small enveloped positive-strand RNA virus that belongs to the Flaviviridae family (20). More than 80% of acute infections become chronic, which eventually progress to cirrhosis and hepatocellular carcinoma (28). HCV infects mainly hepatocytes, but the precise mechanisms of infection are largely unknown (11). The HCV particle consists of a nucleocapsid surrounded by a lipid bilayer in which the two envelope glycoproteins (HCVgp), E1 and E2, are anchored as a heterodimer and play a major role in HCV entry (20). The development of an infectious cell culture model based on the production of infective HCV particles (cell culture-derived HCV particles [HCVcc]) (34) and the generation of HCV pseudotyped retroviral particles (HCVpp) (4) have provided powerful tools to study the HCV cycle. HCV entry is a complex multistep process that requires the presence of several factors. There are multiple pieces of evidence for the involvement of host cell proteins in HCV entry, including glycosaminoglycans, the low-density lipoprotein receptor, scavenger receptor class B type I (SR-BI), and the tetraspanin CD81 (11). Recently, claudin-1, a tight junction (TJ) component, has been identified as a coreceptor required for a late step in HCV entry (13).TJs are major components of cell-cell adhesion complexes and are composed of integral membrane proteins, including occludin and claudins, which associate with actin cytoskeleton-interacting proteins, such as zonula occludens protein 1 (ZO-1) (2). These structures maintain cell polarity, separating apical from basolateral membrane domains, and form a paracellular barrier that allows the selective passage of certain solutes (2). In hepatocytes, TJs seal the bile canaliculi and form the intercellular barrier between bile and blood (12). Recently, we have shown that TJ-associated proteins occludin and claudin-1 disappeared from their normal localization in both HCV-infected and genomic HCV replicon-containing Huh7 cells. Furthermore, TJ function was also altered in these cells (5). In this matter, we have reported an intracellular interaction between E2 and occludin (5). Moreover, it has been reported that claudin-1 and several TJ-associated proteins, such as coxsackievirus and adenovirus receptor (35) and junctional adhesion molecule (JAM) (3), act as virus (co)receptors. Since coxsackievirus entry across epithelial TJs requires occludin (10), we have explored the role of occludin in HCV infection.     

Ascorbic acid: metabolism and functions of a multi-facetted molecule

Ascorbic acid (vitamin C) is the most abundant antioxidant in plants. Its biosynthetic pathway via GDP-D-mannose and L-galactose, which was proposed only recently, is now supported by molecular genetic evidence from Arabidopsis thaliana and transgenic potato plants. Except for the last step (which is located on the inner mitochondrial membrane) the pathway is cytosolic, sharing GDP-sugar intermediates with cell-wall polysaccharide and glycoprotein synthesis. Ascorbate peroxidase is emerging as a key enzyme in the fine control of H(2)O(2) concentration; its expression being controlled by redox signals and H(2)O(2). Convincing evidence of the involvement of ascorbate in cell division and growth is also accumulating. Its role as a cofactor in the synthesis of cell wall hydroxyproline-rich glycoproteins is one mechanism for this function.     

Response to long-term growth hormone therapy in short children with reduced GH bioactivity

BACKGROUND/AIMS: The aim of the present study was to investigate whether short children with normal growth hormone (GH) immunoreactivity, but reduced bioactivity (bioinactive GH) could benefit from rhGH treatment as GH deficient (GHD) patients. Methods: We evaluated 12 pre-pubertal children (8 M, 4 F), with GH deficiency-like phenotype showing normal serum GH peak levels (>10 ng/ml), measured by immunofluorimetric assay (IFMA-GH), in contrast with a reduced GH bioactivity (bio-GH), evaluated using the Nb(2) cells. We also evaluated 15 age-matched GHD pre-pubertal children (11 M, 4 F) with serum GH peak <5 ng/ml. Both groups were treated with rhGH therapy at the dose of 0.23 mg/kg/week s.c. RESULTS: Serum bio-GH/IFMA-GH ratio at peak time for each patient during the provocative test was significantly lower in bioinactive GH than in GHD children (0.29 vs. 2.05, p = 0.00001). Recombinant human GH therapy induced a significant (p < 0.001) increase in growth rate in both groups during the first 2 years. In the third year of treatment, while growth rate in GHD children is maintained, in bioinactive GH patients it decreases remaining, however higher compared to the pre-treatment one. CONCLUSIONS: Short rhGH therapy given to selected bioinactive GH children improve growth rate and might result in greater final adult height.     

Enhanced arteriogenesis in mice overexpressing erythropoietin

After permanent occlusion of the femoral artery, the survival of ischemic limb tissue depends on collateral artery growth (arteriogenesis). In previous work, we have shown that shear stress triggers arteriogenesis. To test whether increased shear stress results in enhanced arteriogenesis, we compared arteriogenesis in transgenic mice overexpressing erythropoietin (EPO), which possessed increased blood viscosity through the higher hematocrit (thereby providing increased shear stress), with wild-type mice. The right femoral artery was occluded proximal to the origin of the arteria poplitea. Distal blood flow was assessed by laser Doppler imaging, and the growth and remodeling of collateral arteries was examined by light and electron microscopy and morphometry. After occlusion of the femoral artery, EPO mice demonstrated enhanced arteriogenesis: their collateral arteries developed a 1.7-fold diameter and a 2-fold wall thickness compared with wild-type. However, the blood flow recovery in EPO mice was markedly retarded. Structural remodeling and growth of collateral arteries was markedly enhanced in EPO mice, presumably as a result of increased blood viscosity and shear stress.     

An extract from the brown alga Bifurcaria bifurcata induces irreversible arrest of cell proliferation in a non-small-cell bronchopulmonary carcinoma line

In this study, the antiproliferative activity of a crude extract isolated from Bifurcaria bifurcata (Velley) Ross, a common marine brown alga of the Atlantic shores of Europe, was investigated. Its antiproliferative effect on asynchronous cells of a human non-small-cell bronchopulmonary carcinoma line (NSCLC-N6), particularly chemo-resistant, was expected in vitro. Cell growth appeared to be inhibited in the G1 phase of the cell cycle, and kinetic studies in pretreated cells showed that this growth arrest was irreversible. These events are related to a terminal differentiation induction.     

Effects of <Emphasis Type="SmallCaps">l</Emphasis>-Canavanine and ozone on vascular reactivity in septicemic rats

Septicemia leads to oxidative stress with overproduction of reactive-oxygen species (ROS) and consumption of endogenous antioxidant enzymes. We tested a twofold hypothesis: (1) does oxidative stress (OxS) induced by sepsis acting alone or in concert with augmented inflammatory processes contributes to sepsis-related vascular dysfunction, and, (2) whether ozone (O₃) and l-canavanine (CAV) mitigate the negative impact of the aforementioned phenomena. We investigated the relative impact of treatment with CAV and/or O₃ on vascular OxS associated vascular functional changes in septicemic rats. For this study, 60 male Sprague–Dawley rats were used and divided into six experimental groups (n = 10): control group (C), sham-operated (Sham), septicemic rats (S), S rats treated with CAV (100 mg/kg. i.p; S + CAV), S rats treated with O₃ (1.2 mg/kg, i.p.; S + O₃) and S rats treated with both O₃ and CAV (S + O₃ + CAV). After 22 h, the mean arterial blood pressure (MAP), the aortic ring vascular reactivity to phenylephrine, abdominal aortic blood flow (AABF), serum tumor necrosis factor-α (TNF-α) and plasma nitrite/nitrate (NOx) concentration were measured. In addition, hepatic antioxidant enzyme activities sodium dismutase (SOD) and glutathione peroxidase (GSH-Px) were estimated. Septicemia caused significant elevation of serum TNF-α (p < 0.001) and plasma NOx (p < 0.001) and significant (p < 0.001) reduction of AABF (p < 0.001), aortic vascular response to phenylephrine (p < 0.001), MAP (p < 0.001) and hepatic SOD and GSH-Px activity (p < 0.001) compared with the C group, while treatment with O₃ and/or CAV induced significant amelioration of all those increases. Abnormalities were attenuated to a similar extent with treatment with both O₃ and CAV. These results suggested that concomitant administration of O₃ and CAV alleviated the compromised vascular reactivity in septicemic conditions and prevent its progression into septic shock compared with each alone.     

Potential soil reinforcement by biological denitrification

Currently new ground reinforcement techniques are being developed based on microbially induced carbonate precipitation (MICP). Many studies on MICP use microbially catalyzed hydrolysis of urea to produce carbonate. In the presence of dissolved calcium this process leads to precipitation of calcium carbonate crystals, which form bridges between the sand grains and hence increase strength and stiffness. In addition to urea hydrolysis, there are many other microbial processes which can lead to the precipitation of calcium carbonate. In this study the theoretical feasibility of these alternative MICP processes for ground reinforcement is evaluated. Evaluation factors are substrate solubility, CaCO₃ yield, reaction rate and type and amount of side-product. The most suitable candidate as alternative MICP method for sand consolidation turned out to be microbial denitrification of calcium nitrate, using calcium salts of fatty acids as electron donor and carbon source. This process leads to calcium carbonate precipitation, bacterial growth and production of nitrogen gas and some excess carbon dioxide. The feasibility of MICP by denitrification is tested experimentally in liquid batch culture, on agar plate and in sand column experiments. Results of these experiments are presented and discussed.