ZFP36 stabilizes RIP1 via degradation of XIAP and cIAP2 thereby promoting ripoptosome assembly

Background

ZFP36 is an mRNA binding protein that exerts anti-tumor activity in glioblastoma by triggering cell death, associated to an increase in the stability of the kinase RIP1.

Methods

We used cell death assays, size exclusion chromatography, Co-Immunoprecipitation, shRNA lentivectors and glioma neural stem cells to determine the effects of ZFP36 on the assembly of a death complex containing RIP1 and on the induction of necroptosis.

Results

Here we demonstrate that ZFP36 promotes the assembly of the death complex called Ripoptosome and induces RIP1-dependent death. This involves the depletion of the ubiquitine ligases cIAP2 and XIAP and leads to the association of RIP1 to caspase-8 and FADD. Moreover, we show that ZFP36 controls RIP1 levels in glioma neural stem cell lines.

Conclusions

We provide a molecular mechanism for the tumor suppressor role of ZFP36, and the first evidence for Ripoptosome assembly following ZFP36 expression. These findings suggest that ZFP36 plays an important role in RIP1-dependent cell death in conditions where IAPs are depleted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1388-5) contains supplementary material, which is available to authorized users.

Is osteopontin involved in cutaneous fibroblast activation? Its hypothetical role in scleroderma pathogenesis

Osteopontin (OPN) is an extracellular matrix protein implicated in bone remodeling, but it presents also pro-inflammatory and pro-fibrotic properties. OPN expression also occurs upon exposure of cells to classical mediators of acute inflammation such as tumor necrosis growth factor alpha (TNF-alpha) and interleukin-1 beta (IL-1beta), as well as fibrogenic cytokines such as transforming growth factor beta (TGF-beta), although a detailed understanding of these regulatory pathways is still unknown. Plasma OPN levels in both limited and diffuse systemic sclerosis patients (lSSc and dSSc) were statistically higher compared to those of control subjects. Immunohistology demonstrated that high TGF-beta levels, alpha smooth muscle actin (alphaSMA) levels and consequently high OPN levels were found in the affected skin of sclerodermic patients (lSSc and dSSc) compared to levels found in healthy skin. In order to better understand how OPN interferes with the fibrotic process, healthy skin fibroblasts were treated for 24 and 48 hours with bleomycin and with endothelin-1 (ET-1) plus TGF-beta in order to induce the fibrogenesis. After 48 hours of stimulation, healthy treated fibroblasts showed statistically increased alphaSMA levels (index of differentiation into myofibroblasts) and simultaneously statistically increased OPN levels compared to healthy untreated ones. This study demonstrates that OPN levels increase simultaneously with the increasing of alphaSMA levels, therefore it is reasonable to hypothesize that OPN interferes in the pathogenesis of Systemic Sclerosis in the early stage of fibroblast differentiation process.

Atheroprotective remodelling of vascular dermatan sulphate proteoglycans in response to hypercholesterolaemia in a rat model

Proteoglycan accumulation within the arterial intima has been implicated in atherosclerosis progression in humans. Nevertheless, hypercholesterolaemia is unable to induce intimal thickening and atheroma plaque development in rats. The study was performed to analyse proteoglycans modifications in rats fed with a high-cholesterol diet to understand whether vascular wall remodelling protects against lesions. Sections obtained from rat aortas showed normal features, in intimal-to-media ratio and lipid accumulation. However, focal endothelial hyperplasia and neo-intima rearrangement were observed in high-cholesterol animals. Besides, hypercholesterolaemia induced an inflammatory microenviroment. We determined the expression of different proteoglycans from aortic cells by Western blot and observed a diminished production of decorin and biglycan in high-cholesterol animals compared with control (P < 0.01 and P < 0.05, respectively). Versican was increased in high-cholesterol animals (P < 0.05), whereas perlecan production showed no differences. No modification of the total content of glycosaminoglycans (GAGs) was found between the two experimental groups. In contrast, the chondroitin sulphate/dermatan sulphate ratio was increased in the high-cholesterol group as compared to the control (0.56 and 0.34, respectively). Structural alterations in the disaccharide composition of galactosaminoglycans were also detected by HPLC, as the ratio of 6-sulphate to 4-sulphate disaccharides was increased in high-cholesterol animals (P < 0.05). Our results suggest that attenuation of decorin and biglycan expression might be an effective strategy to inhibit the first step in atherogenesis, although specific GAG structural modification associated with the development of vascular disease took place. Results emphasize the potential application of therapies based on vascular matrix remodelling to treat atherosclerosis.

Capillary electrophoresis separation of human milk neutral and acidic oligosaccharides derivatized with 2-aminoacridone

Human milk is a unique fluid in glycobiology due to the presence of many free structurally complex oligosaccharides emerging as important dietary factors during early life and having many biological and protective functions. Methods that allow accurate profiling of oligosaccharide mixtures in this complex biological fluid with quantification of the four known genetically determined groups are welcomed. A high-voltage CE separation and detection at 254 nm of 17 neutral and acidic human milk oligosaccharide (HMO) standard along with lactose derivatized with 2-aminoacridone, using a BGE containing 20% methanol as an organic modifier and borate, able to form on-capillary anionic borate-polyol complexes, is reported. This CE approach was able to separate both neutral HMOs and acidic HMOs, with the sialic acid residue, also in the presence of lactose in high content. This method was applied to the four secretory groups individually extracted by a rapid and simple preparative step. LODs were found ranging from ∼50 to 700 fmol. We were able to measure HMO content also in the presence of excess fluorophore, or interference from proteins, peptides, salts, and other impurities normally present in this complex biological fluid. Overall, CE equipped with a UV detector is a common analytical approach and this simple CE separation offers high resolution and sensitivity for the differentiation of human milk samples related to genetic groups and days of lactation by considering that important changes in HMO content are a reflection of the lactation day.

Selective removal of keratan sulfate in chondroitin sulfate samples by sequential precipitation with ethanol

Keratan sulfate (KS) is present as a contaminant in chondroitin sulfate (CS) mainly extracted from shark cartilage. We report a selective removal procedure of KS in CS samples by means of sequential precipitation with ethanol. Purified shark CS containing approximately 10% to 15% KS was subjected to a precipitation procedure in the presence of increasing percentages of saturated ethanol. In contrast to other solvents, 1.0 volume of ethanol was able to selectively purify CS, with a purity of approximately 100%, from KS. The current selective and simple procedure appears to be a reliable industrial preparation of CS devoid of large amounts of the residual KS.

Aortic valve leaflet glycosaminoglycans composition and modification in severe chronic valve regurgitation

BACKGROUND AND AIM OF THE STUDY

The surgical segments of aortic valve leaflets from patients with severe chronic aortic regurgitation were analyzed (by percentage and structure) for their content of complex polysaccharides and glycosaminoglycans (GAGs), and compared with control segments.

METHODS

The GAG, hyaluronic acid (HA), chondroitin sulfate (CS) and dermatan sulfate (DS) and disaccharide contents were determined in segments (leaflet, root attachment region and belly) of aortic valve leaflets (non-coronary, left coronary and right coronary) using a multi-analytical approach.

RESULTS

The aortic valve leaflets showed the presence of HA and CS/DS, with an overall charge density of -0.51-0.55. The CS/DS polymers showed a 4-sulfated/6-sulfated ratio of -0.70-0.77 in the belly, and -1.60-1.72 in commissure parts (-/+124%). The total amount of GAGs was -1.60-2.40 microg/mg of tissue. A significant increase in sulfated GAGs was observed in all valve parts in patients suffering from severe aortic insufficiency, as well as an increase in the 4-sulfated/6-sulfated ratio in the leaflet belly (-/+102%).

CONCLUSION

It is speculated that differences in 4-sulfated/6-sulfated ratio determined in the belly and leaflet attachment region-commissure parts of the leaflets may correlate with the tensile or compressive loading of normal aortic valve regions. At the same time, it may be assumed that the increase in sulfated GAGs and 4-sulfated/6-sulfated ratio in the leaflet belly of valves taken from patients suffering severe aortic insufficiency was consistent with an altered matrix microstructure capable of influencing the hydration of these pathological tissues, and of conditioning their mechanical weakness.

Macitentan slows down the dermal fibrotic process in systemic sclerosis: in vitro findings

Systemic sclerosis (or scleroderma) is an autoimmune disease characterized by skin and internal organ fibrosis, caused by microvascular dysfunction. The microvascular damage seems to be a consequence of an endothelial autoimmune response, followed by activation of the inflammatory cascade and massive deposition of collagen. Endothelin-1 (ET-1) contributes to the inflammatory and fibrotic processes by increasing the concentration of pro-inflammatory and pro-fibrotic cytokines, and it is considered one of the most relevant mediators of vascular damage in scleroderma. It is indeed found in very high concentration in serum of sclerodermic patients. Moreover, in these pathological conditions there is an increased expression of ET-1 receptors (ETA and ETB), which mediate the detrimental action of ET-1, and often a change of ETA/ETB ratio. The aim of the present study is to evaluate the in vitro effect of macitentan, an orally active tissue-targeting dual endothelin receptor antagonist, and its major metabolite (ACT-132577) on alpha smooth muscle actin (alphaSMA) expression, evaluated on dermal fibroblasts from healthy subjects and on dermal fibroblasts from lesional and non-lesional skin from sclerodermic patients. The combination of macitentan and its major metabolite reduced the levels of &#945;SMA after 48 h in sclerodermic fibroblasts from lesional skin. No relevant changes in &#945;SMA levels were found in fibroblasts from non-lesional skin, whose behavior is similar to that of dermal fibroblasts from healthy patients.

Plasmatic kinetics of dermatan sulfate during enzyme replacement therapy with iduronate-2-sulfatase in a mucopolysaccharidosis II patient

Enzyme replacement therapy (ERT) is the worldwide standard of care for a number of mucopolysaccharidosis (MPS) diseases. We report a kinetic study of plasmatic dermatan sulfate (DS) in a 3-year-old subject affected by a severe form of MPS II during the first 10 months of ERT with Idursulfase. A strong increase in the DS plasmatic concentration was measured immediately after the first enzyme infusion, with a maximum after 3 h, followed by a continuous decrease in the 8-15 days following the beginning of treatment. After this, a constant plasmatic content of DS concentration was observed. Overall, during the 10-month treatment period, ERT reduced the plasmatic concentration of DS up to ~80-85 %, but it was unable to totally remove it from the blood. We can suppose that immediately after the first enzyme administrations, a large amount of abnormal DS is removed from tissues reaching the blood compartment and eliminated via the urine, and thereafter only minimal changes are observed. The persistency of the residual amounts of DS with the actually recommended dosage in our Patient may suggest the opportunity to promote further studies with increased enzyme dosages to completely remove the accumulation of lysosomal DS.

Pharmacological read-through of nonsense ARSB mutations as a potential therapeutic approach for mucopolysaccharidosis VI

Mucopolysaccharidosis type VI (MPS VI) is a severe lysosomal storage disorder without central nervous system involvement caused by arylsulfatase B (ARSB) deficiency. MPS VI is characterized by dysostosis multiplex, corneal clouding, heart valve defects and urinary excretion of glycosaminoglycans (GAGs). The current treatment for MPS VI is enzyme replacement therapy (ERT) which has limited efficacy on bone, joints and heart valve disease, as well as high costs. A potential therapeutic approach for the subgroup of MPS VI patients that carry nonsense mutations is to enhance stop-codon read-through, using small molecules, to restore production of the full-length ARSB protein. In this study we investigated whether two compounds known to induce stop codon read-through, the aminoglycoside gentamicin and PTC124, can promote read-through of four different ARSB nonsense mutations (p.R315X, p.R327X, p.Q456X and p.Q503X) associated with MPS VI and enable the synthesis of full-length functional ARSB protein in patients fibroblast cell lines. Our study demonstrates that PTC124 but not gentamicin, increases the level of ARSB activity in three MPS VI patient fibroblast cell lines. In two of them the levels of ARSB activity obtained were significantly higher than in untreated cells, reaching ≤2.5 % of those detected in wild-type fibroblasts and resulting in significant reduction of lysosomal size. Since even small increases in enzyme activity can dramatically influence the clinical phenotype of MPS VI, our study suggests that pharmacological read-through may be combined with ERT potentially increasing therapeutic efficacy in those patients bearing nonsense ARSB mutations.

Human milk glycosaminoglycans: the state of the art and future perspectives

Recently, a complete characterization and detailed evaluation of the glycosaminoglycans of human milk were performed. The total glycosaminoglycans content in milk from healthy mothers having delivered term or preterm newborns showed a constant pattern which was essentially composed of two main polysaccharides: chondroitin sulfate (60-70%) and heparin (30-40%). Moreover, considerable variations of glycosaminoglycans concentration were found during the first month of lactation, the highest values being present in colostrum compared to mature milk. Metabolism and potential biological functions of human milk glycosaminoglycans are hypothesized and future studies are encouraged.

Electrophoresis for the analysis of heparin purity and quality

The adulteration of raw heparin with oversulfated chondroitin sulfate (OSCS) in 2007-2008 produced a global crisis resulting in extensive revisions to the pharmacopeia monographs and prompting the FDA to recommend the development of additional methods for the analysis of heparin purity. As a consequence, a wide variety of innovative analytical approaches have been developed for the quality assurance and purity of unfractionated and low-molecular-weight heparins. This review discusses recent developments in electrophoresis techniques available for the sensitive separation, detection, and partial structural characterization of heparin contaminants. In particular, this review summarizes recent publications on heparin quality and related impurity analysis using electrophoretic separations such as capillary electrophoresis (CE) of intact polysaccharides and hexosamines derived from their acidic hydrolysis, and polyacrylamide gel electrophoresis (PAGE) for the separation of heparin samples without and in the presence of its relatively specific depolymerization process with nitrous acid treatment.

On-line high-performance liquid chromatography-fluorescence detection-electrospray ionization-mass spectrometry profiling of human milk oligosaccharides derivatized with 2-aminoacridone

A high-resolution normal-phase high-performance liquid chromatography-fluorescence detection-electrospray ionization-mass spectrometry separation and structural characterization of the main oligosaccharides along with lactose from human milk samples is described. A total of 22 commercially available oligosaccharides were fluorotagged with 2-aminoacridone and separated on an amide column and identified on the basis of their retention times and mass spectra. Derivatized species having mass lower than approximately 800 to 900 exhibited mainly [M-H](-1) anions, oligomers with mass up to approximately 1000 to 1100 were represented by both [M-H](-1) and [M-2H](-2) anions, and oligomers greater than approximately 1200 to 1300 were characterized by a charge state of -3. Furthermore, the retention times were directly related to the glycans' molecular mass. Human milk samples from the four groups of donors (Se±/Le±) were analyzed for their composition and amount of free oligosaccharides after rapid and simple prepurification and derivatization steps also in the presence of lactose in high content. This analytical approach enabled us to perform the determination of species not detected by traditional techniques, such as sialic acid, as well as of species present in low content easily mistaken with other peaks. Finally, labeled human milk oligosaccharides were analyzed without any interference from excess fluorophore or interference from proteins, peptides, salts, and other impurities normally present in this complex biological fluid.

Glycosaminoglycan content in term and preterm milk during the first month of lactation

BACKGROUND

In a recent study, we performed a complete structural characterization of glycosaminoglycans (GAGs) in human mature milk. However, no data are available on the total content of GAGs in human milk from healthy mothers having delivered term or preterm newborns.

OBJECTIVES

In this study, we evaluated the total content of GAGs in pooled milk from healthy mothers having delivered term or preterm newborns during the first month of lactation.

METHODS

Highly specific and sensitive analytical approaches were used to quantify human milk total GAGs.

RESULTS

Highest GAG values are present at day 4 (9.3 and 3.8 g/l in preterm and term milk, respectively), followed by a progressive decrease up to day 30 (4.3 and 0.4 g/l). The more remarkable differences are related to the first phases of lactation in which a strong decrease in GAGs was observed between days 4 and 10 (about -73% in term and -50% in preterm newborns).

CONCLUSIONS

During the first month of lactation, the absolute amount of polysaccharides was constantly and significantly higher in preterm than in term milk, with a similar behavior in the decrease. These data further indicate that human milk GAGs may have an active role in protecting newborns during the first phases of lactation.