Search

The quality of colonoscopy has been related to a higher risk of interval cancer, and this issue has been addressed extensively in developed countries. The aim of our study was to explore the main quality indicators of colonoscopy in a large emerging country.Consecutive patients referred for colonoscopy in 14 centres were prospectively included between July and October 2014. Before colonoscopy, several clinical and demographic variables were collected. Main quality indicators (i.e. caecal intubation rate, (advanced) adenoma detection rate, rate of adequate cleansing and sedation) were collected. Data were analysed atA total of 8829 (males: 35%; mean age: 57 + 14 years) patients were included, with 11 centres enrolling at least 100 patients. Screening (including non-alarm symptoms) accounted for 59% (5188/8829) of the indications. Sedation and split preparation were used in 26% (2294/8829) and 25% (2187/8829) of the patients. Caecal intubation was achieved in 7616 patients (86%), and it was ≥85% in 8/11 (73%) centres. Adenoma detection rate was 18% (1550/8829), and it was higher than 20% in five (45%) centres, whilst it was lower than 10% in four (33%) centres. At multivariate analysis, age (OR: 1.020, 95% CI: 1.015-1.024), male sex (OR: 1.2, 95% CI: 1.1-1.3), alarm symptoms (OR: 1.8, 95% CI: 1.7-2), split preparation (OR: 1.4, 95% CI: 1.2-1.6), caecal intubation rate (OR: 1.6, 95% CI: 1.3-1.9) and withdrawal time measurement (OR: 1.2, 95% CI: 1.6-2.1) were predictors of a higher adenoma detection rate, while adequate preparation (OR: 3.4: 95% CI: 2.9-3.9) and sedation (OR: 1.3; 95% CI: 1.1-1.6) were the strongest predictors of caecal intubation rate.According to our study, there is a substantial intercentre variability in the main quality indicators. Overall, the caecal intubation rate appears to be acceptable in most centres, whilst the overall level of adenoma detection appears low, with less than half of the centres being higher than 20%. Educational and quality assurance programs, including higher rates of sedation and split regimen of preparation, may be necessary to increase the key quality indicators.

Understanding the developmental steps shaping the formation of the neuromuscular junction (NMJ) connecting motoneurons to skeletal muscle fibers, is critical. Wnt morphogens are key players in the formation of this specialized peripheral synapse. Yet, the individual and collaborative functions of Wnts as well as their downstream pathways remain poorly understood at the NMJ. Here, we demonstrate through Wnt4 and Wnt11 gain of function studies in culture or in mice that Wnts enhance acetylcholine receptor (AChR) clustering and motor axon outgrowth. In contrast, loss of Wnt11 or Wnt-dependent signaling in vivo decreases AChR clustering and motor nerve terminal branching. Both Wnt4 and Wnt11 stimulate AChR clustering and mRNA downstream activation of the β-catenin pathway. Strikingly, Wnt4 and Wnt11 co-immunoprecipitate with Vangl2, a core component of the Planar Cell Polarity (PCP) pathway, which accumulates at embryonic NMJ. Moreover, mice bearing a Vangl2 loss of function mutation (looptail) exhibit a decreased number of AChR clusters and overgrowth of motor axons bypassing AChR clusters. Taken together, our results provide genetic and biochemical evidences that Wnt4 and Wnt11 cooperatively contribute to mammalian NMJ formation through activation of both the canonical and Vangl2-dependent core PCP pathways.

Alexander disease is a fatal neurodegenerative disease caused by mutations in the astrocyte intermediate filament glial fibrillary acidic protein (GFAP). The disease is characterized by elevated levels of GFAP and the formation of protein aggregates, known as Rosenthal fibers, within astrocytes. Lithium has previously been shown to decrease protein aggregates by increasing the autophagy pathway for protein degradation. In addition, lithium has also been reported to decrease activation of the transcription factor STAT3, which is a regulator of GFAP transcription and astrogliogenesis. Here we tested whether lithium treatment would decrease levels of GFAP in a mouse model of Alexander disease. Mice with the Gfap-R236H point mutation were fed lithium food pellets for 4 to 8 weeks. Four weeks of treatment with LiCl at 0.5% in food pellets decreased GFAP protein and transcripts in several brain regions, although with mild side effects and some mortality. Extending the duration of treatment to 8 weeks resulted in higher mortality, and again with a decrease in GFAP in the surviving animals. Indicators of autophagy, such as LC3, were not increased, suggesting that lithium may decrease levels of GFAP through other pathways. Lithium reduced the levels of phosphorylated STAT3, suggesting this as one pathway mediating the effects on GFAP. In conclusion, lithium has the potential to decrease GFAP levels in Alexander disease, but with a narrow therapeutic window separating efficacy and toxicity.

BACKGROUND: Serotonin (5-HT) is well known as widely distributed modulator of developmental processes in both vertebrates and invertebrates. It is also the earliest neurotransmitter to appear during neuronal development. In aquatic invertebrates, which have larvae in their life cycle, 5-HT is involved in regulation of stages transition including larval metamorphosis and settlement. However, molecular and cellular mechanisms underlying developmental transition in aquatic invertebrate species are yet poorly understood. Earlier we demonstrated that in larvae of freshwater molluscs and marine polychaetes, endogenous 5-HT released from the neurons of the apical sensory organ (ASO) in response to external stimuli retarded larval development at premetamorphic stages, and accelerated it at metamorphic stages. Here we used a freshwater snail Helisoma trivolvis to study molecular mechanisms underlying these dual developmental effects of 5-HT. RESULTS: Larval development of H. trivolvis includes transition from premetamorphic to metamorphic stages and shares the main features of metamorphosis with free-swimming aquatic larvae. Three types of 5-HT receptors (5-HT1-, 5-HT4- and 5-HT7-like) are functionally active at premetamorphic (trochophore, veliger) and metamorphic (veliconcha) stages, and expression patterns of these receptors and respective G proteins undergo coordinated changes during development. Stimulation of these receptors modulated cAMP-dependent regulation of cell divisions. Expression of 5-HT4- and 5-HT7-like receptors and their downstream Gs protein was down-regulated during the transition of pre- to metamorphic stage, while expression of 5-HT1 -like receptor and its downstream Gi protein was upregulated. In accordance with relative amount of these receptors, stimulation of 5-HTRs at premetamorphic stages induces developmental retardation, while their stimulation at metamorphic stages induces developmental acceleration. CONCLUSIONS: We present a novel molecular mechanism that underlies stage-specific changes in developmental tempo of H. trivolvis larvae in response to endogenous 5-HT produced by the neurons of the ASO. We suggest that consecutive changes in expression patterns of different receptors and their downstream partners in the course of larval development represent the molecular base of larval transition from premetamorphic (non-competent) to metamorphic (competent) state. peerReviewed

Progressive accumulation of the amyloid β protein in extracellular plaques is a neuropathological hallmark of Alzheimer disease. Amyloid β is generated during sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretases. In addition to the proteolytic processing by secretases, APP is also metabolized by lysosomal proteases. Here, we show that accumulation of intracellular sphingosine-1-phosphate (S1P) impairs the metabolism of APP. Cells lacking functional S1P-lyase, which degrades intracellular S1P, strongly accumulate full-length APP and its potentially amyloidogenic C-terminal fragments (CTFs) as compared with cells expressing the functional enzyme. By cell biological and biochemical methods, we demonstrate that intracellular inhibition of S1P-lyase impairs the degradation of APP and CTFs in lysosomal compartments and also decreases the activity of γ-secretase. Interestingly, the strong accumulation of APP and CTFs in S1P-lyase-deficient cells was reversed by selective mobilization of Ca(2+) from the endoplasmic reticulum or lysosomes. Intracellular accumulation of S1P also impairs maturation of cathepsin D and degradation of Lamp-2, indicating a general impairment of lysosomal activity. Together, these data demonstrate that S1P-lyase plays a critical role in the regulation of lysosomal activity and the metabolism of APP.

Insulin-degrading enzyme (IDE) is a Zn(2+) metalloprotease with a characteristic inverted catalytic motif. IDE is ubiquitously expressed and degrades peptide substrates including insulin, endorphin, and the amyloid-β peptide. Although IDE is mainly expressed in the cytosol, it can also be found on the cell surface and in secreted form in extracellular fluids. As IDE lacks a characteristic signal sequence that targets the protein to the classical secretory pathway, release of the enzyme involves non-conventional mechanisms. However, functional domains of IDE involved in its secretion remain elusive. By bioinformatical, biochemical, and cell biological methods, we identified a novel amino acid motif ((853)EKPPHY(858)) close to the C terminus of IDE and characterized its function in the non-conventional secretion of the protein. Because of its close homology to an amino acid sequence found in bacterial proteins belonging to the SlyX family, we propose to call it the SlyX motif. Mutagenesis revealed that deletion of this motif strongly decreased the release of IDE, whereas deletion of a potential microbody-targeting signal at the extreme C terminus had little effect on secretion. The combined data indicate that the non-conventional secretion of IDE is regulated by the newly identified SlyX motif.

Rare coding variants in the triggering receptor expressed on myeloid cells‐2 (TREM2) gene have been associated with Alzheimer disease (AD) and homozygous TREM2 loss‐of‐function variants have been reported in families with monogenic frontotemporal‐like dementia with/without bone abnormalities. In a whole‐exome sequencing study of a family with probable AD‐type dementia without pathogenic variants in known autosomal dominant dementia disease genes and negative for the apolipoprotein E (APOE) ε4 allele, we identified an extremely rare TREM2 coding variant, that is, a glycine‐to‐tryptophan substitution at amino acid position 145 (NM_018965.3:c.433G>T/p.[Gly145Trp]). This alteration is found in only 1 of 251,150 control alleles in gnomAD. It was present in both severely affected as well as in another putatively affected and one 61 years old as yet unaffected family member suggesting incomplete penetrance and/or a variable age of onset. Gly145 maps to an intrinsically disordered region (IDR) of TREM2 between the immunoglobulin‐like and transmembrane domain. Subsequent cellular studies showed that the variant led to IDR shortening and structural changes of the mutant protein resulting in an impairment of cellular responses upon receptor activation. Our results, suggest that a p.(Gly145Trp)‐induced structural disturbance and functional impairment of TREM2 may contribute to the pathogenesis of an AD‐like form of dementia.

Background Triggering receptor expressed on myeloid cells-2 (TREM2) exerts important functions in the regulation of monocytes, like dendritic cells, osteoclasts, tissue macrophages, and microglia. Mutations in TREM2 are associated with several diseases, including Nasu-Hakola disease, frontotemporal dementia, and Alzheimer’s disease (AD). TREM2 undergoes sequential proteolytic processing by ectodomain shedding and intramembrane proteolysis. Findings We show that inhibition of γ-secretase-dependent cleavage of the TREM2 C-terminal fragment in cellular membranes interferes with TREM2-dependent signaling and cellular function. Inhibition of γ-secretase decreases membrane-proximal signaling and intracellular Ca2+ response. Decreased signaling alters morphological changes and phagocytic activity of cells upon selective stimulation of TREM2. Conclusions The data demonstrate the importance of γ-secretase-dependent intramembrane processing in TREM2-mediated signaling and, thus, a functional relation of two AD-associated proteins. Electronic supplementary material The online version of this article (doi:10.1186/s12974-016-0479-9) contains supplementary material, which is available to authorized users.