Hydrophilic loop 1 of Presenilin-1 and the APP GxxxG transmembrane motif regulate γ-secretase function in generating Alzheimer-causing Aβ peptides

γ-Secretase is responsible for the proteolysis of amyloid precursor protein (APP) into amyloid-beta (Aβ) peptides, which are centrally implicated in the pathogenesis of Alzheimer’s disease (AD). The biochemical mechanism of how processing by γ-secretase is regulated, especially as regards the interaction between enzyme and substrate, remains largely unknown. Here, mutagenesis reveals that the hydrophilic loop-1 (HL-1) of presenilin-1 (PS1) is critical for both γ-secretase step-wise cleavages (processivity) and its allosteric modulation by heterocyclic γ-modulatory compounds. Systematic mutagenesis of HL-1, including all of its familial AD mutations and additional engineered variants, and quantification of the resultant Aβ products show that HL-1 is necessary for proper sequential γ-secretase processivity. We identify Y106, L113, and Y115 in HL-1 as key targets for heterocyclic γ-secretase modulators (GSMs) to stimulate processing of pathogenic Aβ peptides. Further, we confirm that the GxxxG domain in the APP transmembrane region functions as a critical substrate motif for γ-secretase processivity: a G29A substitution in APP-C99 mimics the beneficial effects of GSMs. Together, these findings provide a molecular basis for the structural regulation of γ-processivity by enzyme and substrate, facilitating the rational design of new GSMs that lower AD-initiating amyloidogenic Aβ peptides

La genetica dell’asma bronchiale.

L’asma bronchiale è una malattia infiammatoria cronica delle vie aeree caratterizzata da ricorrenti episodi di ostruzione reversibile del flusso aereo responsabili delle crisi di respiro sibilante, senso di costrizione toracica, dispnea e tosse stizzosa1. L’atopia, definita come un aumento della sintesi di immunoglobuline E (IgE) in risposta all’esposizione a comuni allergeni, è uno dei il fattore di rischio più importanti per la comparsa di asma 2. Da un punto di vista genetico, l’asma bronchiale è una malattia genetica complessa dovuta all’interazione tra fattori genetici, che conferiscono soprattutto la predisposizione alla comparsa dell’asma, e fattori ambientali, quali allergeni, inquinanti atmosferici ed infezioni che agiscono soprattutto come fattori scatenanti la malattia.In questo capitolo dopo una breve introduzione allo studio delle malattie genetiche complesse, passeremo in rassegna gli studi ed i progressi compiuti nell’identificare i geni potenzialmente coinvolti nella patogenesi dell’asma

Inhibition of spinal oxidative stress by bergamot polyphenolic fraction attenuates the development of morphine induced tolerance and hyperalgesia in mice

Citrus Bergamia Risso, commonly known as Bergamot, is a fruit whose Essential Oil and Bergamot Polyphenolic Fraction have numerous medicinal properties. It is also an excellent antioxidant and in this study, for the first time, its potential effect on morphine induced tolerance in mice has been investigated. Our studies revealed that development of antinociceptive tolerance to repeated doses of morphine in mice is consistently associated with increased formation of superoxide, malondialdehyde and tyrosine-nitrated proteins in the dorsal horn of the spinal cord such as the enzyme glutamine synthase. Nitration of this protein is intimately linked to inactivation of its biological function and resulting increase of glutamate levels in the spinal cord. Administration of Bergamot Polyphenolic Fraction (5-50 mg/kg) attenuated tolerance development. This effect was accompanied by reduction of superoxide and malondialdehyde production, prevention of GS nitration, re-establishment of its activity and of glutamate levels. Our studies confirmed the main role of free radicals during the cascade of events induced by prolonged morphine treatment and the co-administration of natural derivatives antioxidant such as Bergamot Polyphenolic Fraction can be an important therapeutic approach to restore opioids analgesic efficacy

Virulomic Analysis of Multidrug-Resistant Klebsiella pneumoniae Isolates and Experimental Virulence Model Using Danio rerio (Zebrafish)

This study evaluates a possible correlation between multidrug-resistant Klebsiella pneumoniae strains and virulence markers in a Danio rerio (zebrafish) model. Whole-genome sequencing (WGS) was performed on 46 strains from three Brazilian hospitals. All of the isolates were colistin-resistant and harbored blaKPC-2. Ten different sequence types (STs) were found; 63% belonged to CC258, 22% to ST340, and 11% to ST16. The virulence factors most frequently found were type 3 fimbriae, siderophores, capsule regulators, and RND efflux-pumps. Six strains were selected for a time-kill experiment in zebrafish embryos: infection by ST16 was associated with a significantly higher mortality rate when compared to non-ST16 strains (52% vs. 29%, p = 0.002). Among the STs, the distribution of virulence factors did not differ significantly except for ST23, which harbored a greater variety of factors than other STs but was not related to a higher mortality rate in zebrafish. Although several virulence factors are described in K. pneumoniae, our study found ST16 to be the only significant predictor of a virulent phenotype in an animal model. Further research is needed to fully understand the correlation between virulence and sequence types

Bergamot polyphenolic fraction components.

<p>Bergamot polyphenolic fraction components.</p

MDA assay demonstrated increased lipid peroxidation in tolerant mice.

<p>Spinal cord extract from morphine group demonstrated a significant increase in MDA that was reduced by BPF (25 mg/kg) as well as by MnTBAP (10 mg/kg). Results are expressed as mean ± SEM for 15 rats. *P<0.001 vs Naive; †P<0.01 vs morphine.</p

Morphine dose-response curve analysis.

<p>Acute injection of morphine (3 mg/kg), in mice, produced a significant near-maximal antinociceptive response until 60 minutes. Results are expressed as mean ± SEM for 15 mice;*P<0.001 vs morphine 0 mg/kg.</p