A brain-penetrant triazolopyrimidine enhances microtubule-stability,reduces axonal dysfunction and decreases tau pathology in a mouse tauopathy model

Background

Alzheimer’s disease (AD) and related tauopathies are neurodegenerative diseases that are characterized by the presence of insoluble inclusions of the protein tau within brain neurons and often glia. Tau is normally found associated with axonal microtubules (MTs) in the brain, and in tauopathies this MT binding is diminished due to tau hyperphosphorylation. As MTs play a critical role in the movement of cellular constituents within neurons via axonal transport, it is likely that the dissociation of tau from MTs alters MT structure and axonal transport, and there is evidence of this in tauopathy mouse models as well as in AD brain. We previously demonstrated that different natural products which stabilize MTs by interacting with β-tubulin at the taxane binding site provide significant benefit in transgenic mouse models of tauopathy. More recently, we have reported on a series of MT-stabilizing triazolopyrimidines (TPDs), which interact with β-tubulin at the vinblastine binding site, that exhibit favorable properties including brain penetration and oral bioavailability. Here, we have examined a prototype TPD example, CNDR-51657, in a secondary prevention study utilizing aged tau transgenic mice.

Methods

9-Month old female PS19 mice with a low amount of existing tau pathology received twice-weekly administration of vehicle, or 3 or 10 mg/kg of CNDR-51657, for 3 months. Mice were examined in the Barnes maze at the end of the dosing period, and brain tissue and optic nerves were examined immunohistochemically or biochemically for changes in MT density, axonal dystrophy, and tau pathology. Mice were also assessed for changes in organ weights and blood cell numbers.

Results

CNDR-51657 caused a significant amelioration of the MT deficit and axonal dystrophy observed in vehicle-treated aged PS19 mice. Moreover, PS19 mice receiving CNDR-51657 had significantly lower tau pathology, with a trend toward improved Barnes maze performance. Importantly, no adverse effects were observed in the compound-treated mice, including no change in white blood cell counts as is often observed in cancer patients receiving high doses of MT-stabilizing drugs.

Conclusions

A brain-penetrant MT-stabilizing TPD can safely correct MT and axonal deficits in an established mouse model of tauopathy, resulting in reduced tau pathology.

     

High Levels of sTNFR p75 and TNFα in Dengue-Infected Patients

Soluble forms of the two molecular species of the cell surface TNF receptors (sTNFR p55 and sTNFR p75) can reduce the activity of TNFα but they may also enhance its function by stabilizing the active TNFα oligomer. Considering the pathophysiological importance of sTNFR p75 for the regulation of the bioavailability of TNFα in the body, we determined the serum levels of sTNFR p75 and TNFα in 45 children and 28 adults with laboratory-confirmed dengue infection by using immunoassays. The serum samples were obtained from day 1 to day 15 after the onset of the disease during the 1989–1990 outbreak of dengue-3 in Tahiti, French Polynesia. The patients were clinically classified as having dengue hemorrhagic fever (DHF) and graded according to the criteria of the World Health Organization (WHO) into four grades from less severe (grade I) to severe (grade IV). The sera of both children and adult patients of all severity grades contained higher levels of sTNFR p75 than the sera of control subjects. Although high levels of TNFα were also detected in children and adults among grade I, II, III and IV patients, we found no correlation between sTNFR p75 and TNFα. We observed in adults a moderate elevation of sTNFR p75 and TNFα in sera compared with that observed in children. The raised levels of immunoreactive sTNFR p75 and TNFα in all clinical groups of dengue-infected patients strongly indicate activation of the TNFα system during dengue infection. The balance between sTNFR p75 and TNFα may be altered in dengue infection. Further investigations are needed to understand the role of sTNFR p75 and TNFα in the pathogenesis of DHF and to improve the management of dengue infection.     

Validation of an endothelial roll preparation for Descemet Membrane Endothelial Keratoplasty by a cornea bank using “no touch” dissection technique

Descemet Membrane Endothelial Keratoplasty (DMEK) selectively replaces the damaged posterior part of the cornea. However, the DMEK technique relies on a manually-performed dissection that is time-consuming, requires training and presents a potential risk of endothelial graft damages leading to surgery postponement when performed by surgeons in the operative room. To validate precut corneal tissue preparation for DMEK provided by a cornea bank in order to supply a quality and security precut endothelial tissue. The protocol was a technology transfer from the Netherlands Institute for Innovative Ocular Surgery (NIIOS) to Lyon Cornea Bank, after formation in NIIOS to the DMEK “no touch” dissection technique. The technique has been validated in selected conditions (materials, microscope) and after a learning curve, cornea bank technicians prepared endothelial tissue for DMEK. Endothelial cells densities (ECD) were evaluated before and after preparation, after storage and transport to the surgery room. Microbiological and histological controls have been done. Twenty corneas were manually dissected; 18 without tears. Nineteen endothelial grafts formed a double roll. The ECD loss after cutting was 3.3 % (n = 19). After transportation 7 days later, we found an ECD loss of 25 % (n = 12). Three days after cutting and transportation, we found 2.1 % of ECD loss (n = 7). Histology found an endothelial cells monolayer lying on Descemet membrane. The mean thickness was 12 ± 2.2 µm (n = 4). No microbial contamination was found (n = 19). Endothelial roll stability has been validated at 3 days in our cornea bank. Cornea bank technicians trained can deliver to surgeons an ECD controlled, safety and ready to use endothelial tissue, for DMEK by “no touch” technique, allowing time saving, quality and security for surgeons.     

Fertility depression among cheese‐making Penicillium roqueforti strains suggests degeneration during domestication

Genetic differentiation occurs when gene flow is prevented, due to reproductive barriers or asexuality. Investigating the early barriers to gene flow is important for understanding the process of speciation. Here, we therefore investigated reproductive isolation between different genetic clusters of the fungus Penicillium roqueforti, used for maturing blue cheeses, and also occurring as food spoiler or in silage. We investigated premating and postmating fertility between and within three genetic clusters (two from cheese and one from other substrates), and we observed sexual structures under scanning electron microscopy. All intercluster types of crosses showed some fertility, suggesting that no intersterility has evolved between domesticated and wild populations despite adaptation to different environments and lack of gene flow. However, much lower fertility was found in crosses within the cheese clusters than within the noncheese cluster, suggesting reduced fertility of cheese strains, which may constitute a barrier to gene flow. Such degeneration may be due to bottlenecks during domestication and/or to the exclusive clonal replication of the strains in industry. This study shows that degeneration has occurred rapidly and independently in two lineages of a domesticated species. Altogether, these results inform on the processes and tempo of degeneration and speciation.     

Influence de la lumière et de la mycosporine sur la composition stérolique du Nectria galligena au cours de la morphogenese sexuée

The nature and content of free sterols, analyzed by MIKE spectrometry, were investigated in in vitro cultures submitted to different light regimes with or without the addition of exogenous mycosporin. The sterol composition was related to varying degrees of induced sexual morphogenesis, particularly when mycosporin was added to the nutrient medium.     

Effects of intracellular signals on Na+/K(+)-ATPase pump activity in the frog skin epithelium.

The effects of intracellular signals (pHi, Na+i, Ca2+i, and the electrical membrane potential), on Na+ transport mediated by the Na+/K+ pump were investigated in the isolated Rana esculenta frog skin. In particular we focussed on pHi sensitivity since protons act as an intrinsic regulator of transepithelial Na+ transport (JNa) by a simultaneous control of the apical membrane Na+ conductance (gNa) and the basolateral membrane K+ conductance (gK). pHi changes which modify JNa, gNa and gK, do not affect the Na+ transport mediated by the pump as shown by kinetic and electrophysiological studies. In addition, no changes were observed in the number of 3H-ouabain binding sites in acid-loaded epithelia. Our attempts to modify cellular Ca2+ (by using Ca(2+)-free/EGTA Ringer solution or A23187 addition) also failed to produce any significant effects in the Na+ pump turnover rate or the number of 3H-ouabain binding sites. The Na+ pump current was found to be sensitive to the basolateral membrane potential, saturating for very positive (cell) potentials and a reversal potential of -160 mV was calculated from I-V relationships of the pump. Changes in Na+i considerably affected the Na+ pump rate. A saturating relationship was found between pump rate and Nai+ with maximal activation at Nai+ greater than 40 mmol/l; a high dependence of the pump rate and of the number of 3H-ouabain binding sites was observed in the physiological range of Nai+. We conclude that protons (in the physiological pH range) which act directly and simultaneously on the passive transport pathways (gNa and gK), have no direct effect on the Na+/K+ pump rate. After an acid load, the inhibition of JNa is primarily due to the reduction of gNa. This results in a reduction of Nai and the pump turnover rate then becomes dependent on other pathways of Na+ entry such as the basolateral membrane Na+/H+ exchanger.     

Comparison of Color and Body Condition Between Early and Late Breeding King Penguins

Early breeding is associated with greater reproductive success in many species. In king penguins, Aptenodytes patagonicus , laying extends for 6 mo. Early breeders may fledge a single chick at best, but late breeders virtually never fledge a chick. For early and late breeders, we compared colored ornaments known to be important in mate choice: yellow–orange feathers of the breast and auricular areas, and an ultraviolet and yellow–orange beak spot. Our purpose was to discern differences between males and females in this highly sexually monomorphic species, as well as to discern whether colored ornaments are more important for the more successful early breeders (aspects of color were hue, chroma, and brightness). For this, we weighed and measured 130 penguins. Early males had greater reflectance of ultraviolet color from the beak spot than did early females and late breeders of both sexes, and the early males were heavier and in better condition than late breeding males or females. Late breeding females were the yellowest in breast hue, a trait that has been linked to immunocompetence. Within pairs, males and females were significantly correlated in body mass, but only early in the breeding season. We concluded that early in the breeding season when reproductive success was greatest, potential mates were not only more similar in body mass, but also that females may have chosen males that had brighter beak spots and were in better body condition.     

Assessment of the allelochemical activity of Ostreopsis cf. ovata and the ovatoxins towards competitive benthic microalgae

Aquatic Ecology - Recurrent blooms of the toxic dinoflagellate Ostreopsis cf. ovata are frequently reported in the Northwestern Mediterranean Sea. The impact of these proliferations on other...     

The alternative translated MDMXp60 isoform regulates MDM2 activity

Isoforms derived from alternative splicing, mRNA translation initiation or promoter usage extend the functional repertoire of the p53, p63 and p73 genes family and of their regulators MDM2 and MDMX. Here we show cap-independent translation of an N-terminal truncated isoform of hMDMX, hMDMX^p60, which is initiated at the 7th AUG codon downstream of the initiation site for full length hMDMX^FL at position +384. hMDMX^p60 lacks the p53 binding motif but retains the RING domain and interacts with hMDM2 and hMDMX^FL. hMDMX^p60 shows higher affinity for hMDM2, as compared to hMDMX^FL. In vitro data reveal a positive cooperative interaction between hMDMX^p60 and hMDM2 and in cellulo data show that low levels of hMDMX^p60 promote degradation of hMDM2 whereas higher levels stabilize hMDM2 and prevent hMDM2-mediated degradation of hMDMX^FL. These results describe a novel alternatively translated hMDMX isoform that exhibits unique regulatory activity toward hMDM2 autoubiquitination. The data illustrate how the N-terminus of hMDMX regulates its C-terminal RING domain and the hMDM2 activity.