Mechanism of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

Effects of Dendrimer-Like Biopolymers on Physical Stability of Amorphous Solid Dispersions and Drug Permeability Across Caco-2 Cell Monolayers

The potential applications of dendrimer-like biopolymers (DLB) as stabilizing excipients for amorphous solid dispersion (ASD) of niclosamide, celecoxib, and resveratrol were evaluated based on (1) the formation and physical stability of the ASD and (2) the permeability and flux of the agents across Caco-2 cell monolayers. The evaluation was made by comparing the performance of prototype phytoglycogen derivatives (DLB1, DLB2, and DLB3) with commonly used polymers such as HPMCAS, PVPVA, and Soluplus®. PXRD was used to confirm the formation of the dispersions and detect crystallinity peaks formed during 2- and 4-week storage at 40°C/75% RH. At concentrations below 2 g/mL, the viability of Caco-2 cells remained above 80% for all DLB samples compared to untreated cells in the MTT assay. Permeability studies revealed a repeating pattern in which an increase in the initial concentration (C₀) was associated with a concomitant decrease in the apparent permeability (P_app) which we theorize is due to differences in drug-polymer interactions. Niclosamide-DLB1 dispersion had the lowest flux due to a significant reduction in P_app. The high increase in the C₀ of celecoxib-DLB2, however, made up for the reduction in the P_app and produced the highest flux values compared to other polymers. Resveratrol-DLB3 had a 5× reduction in P_app, but C₀ increased from 25.8 to 176 μg/mL led to a higher flux compared to the crystalline drug without polymer. Collectively, these results provide a "proof-of-concept" basis to demonstrate that DLB excipients have the ability to increase apparent solubility (Sol_app), most likely due to drug-binding capacity.

Viability Assessment Following Anticancer Treatment Requires Single-Cell Visualization

A subset of cells within solid tumors become highly enlarged and enter a state of dormancy (sustained proliferation arrest) in response to anticancer treatment. Although dormant cancer cells might be scored as “dead” in conventional preclinical assays, they remain viable, secrete growth-promoting factors, and can give rise to progeny with stem cell-like properties. Furthermore, cancer cells exhibiting features of apoptosis (e.g., caspase-3 activation) following genotoxic stress can undergo a reversal process called anastasis and survive. Consistent with these observations, single-cell analysis of adherent cultures (solid tumor-derived cell lines with differing p53 status) has demonstrated that virtually all cells—irrespective of their size and morphology—that remain adherent to the culture dish for a long time (weeks) after treatment with anticancer agents exhibit the ability to metabolize 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl- tetrazolium bromide (MTT). The purpose of this commentary is to briefly review these findings and discuss the significance of single-cell (versus population averaged) observation methods for assessment of cancer cell viability and metabolic activity.

Ambroxol modulates 6-Hydroxydopamine-induced temporal reduction in Glucocerebrosidase (GCase) enzymatic activity and Parkinson's disease symptoms

Reduced glucocerebrosidase (GCase) enzymatic activity is found in sporadic cases of Parkinson's disease making GCase a serious risk factor for PD. GCase gene mutations constitute a major risk factor in early-onset PD but only account for 5-10% cases. Having enough evidence for construct and face validity, 6-OHDA-induced hemiparkinson's model may be useful to assess the GCase-targeting drugs in order to have new leads for treatment of PD. Ambroxol (AMB) is reported to increase GCase activity in different brain-regions. Therefore, we investigated anti-PD like effects of AMB as well as GCase activity in striatal and nigral tissues of rats in hemiparkinson's model. AMB was given a dose of 400 mg/kg per oral twice daily and SEL used as positive control was given in the dose of 10 mg/kg per oral daily from D-4 to D-27 after 6-OHDA administration. 6-OHDA reduced GCase activity in striatal and in a progressive manner in nigral tissues. AMB and SEL attenuated 6-OHDA-induced motor impairments, dopamine (DA) depletion and GCase deficiency. AMB and SEL also ameliorated 6-OHDA-induced mitochondrial dysfunction in terms of MTT reduction, α-synuclein pathology, loss of nigral cells, and intrinsic pathway of apoptosis by modulating cytochrome-C, caspase-9, and caspase-3 expressions. The results suggest that AMB attenuated 6-OHDA-induced GCase deficiency and PD symptoms. Therefore, the regenerative effects of AMB in dopamine toxicity may be due to its effects on GCase activity and mitochondrial function. Results indicate that SEL also has regenerative effect in the 6-OHDA model. Thus, GCase enzymatic activity is likely to be involved in the development of PD symptoms, and 6-OHDA-induced hemiparkinson's model may be used to evaluate compounds targeting GCase activity for management of PD symptoms.

Evaluation of the toxicity effects of silk fibroin on human lymphocytes and monocytes

Silk fibroin nanoparticles (SFNPs) as a natural polymer have been utilized in biomedical applications such as suture, tissue engineering-based scaffolds, and drug delivery carriers. Since there is little data regarding the toxicity effects on different cells and tissues, we aimed to determine the toxicity mechanisms of SFNPs on human lymphocytes and monocytes based on reliable methods. Our results showed that SFNPs (0.5, 1, and 2 mg/mL) induced oxidative stress via increasing reactive oxygen species production, mitochondrial membrane potential (∆Ψ) collapse, which was correlated to cytochrome c release and Adenosine diphosphate (ADP)/Adenosine tri phosphate (ATP) ratio increase as well as lysosomal as another toxicity mechanism, which led to cytosolic release of lysosomal digestive proteases, phosphor lipases, and apoptosis signaling. Taken together, these data suggested that SFNPs toxicity was associated with mutual mitochondrial/lysosomal cross-talk and oxidative stress on human lymphocytes and monocytes with activated apoptosis signaling.

Current methodology of MTT assay in bacteria - A review

The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay is a popular tool in estimating the metabolic activity of living cells. The test is based on enzymatic reduction of the lightly colored tetrazolium salt to its formazan of intense purple-blue color, which can be quantified spectrophotometrically. Under properly optimized conditions the obtained absorbance value is directly proportional to the number of living cells. Originally, the MTT assay was devised for use in eukaryotic cells lines and later applied for bacteria and fungi. As the mechanism of MTT reduction was studied in detail mostly considering eukaryotic cells, the lack of information resulted in generating a vast variety of MTT based protocols for bacterial enzymatic activity evaluation. In the presented article the main aspects of the MTT assay applicability in bacterial research were summarized, with special emphasis on sources of inaccuracies and misinterpretation of the test results.

High-Resolution Adhesion Kinetics of EGCG-Exposed Tumor Cells on Biomimetic Interfaces: Comparative Monitoring of Cell Viability Using Label-Free Biosensor and Classic End-Point Assays

A high-throughput label-free resonant waveguide grating biosensor, the Epic BenchTop, was utilized to in situ monitor the adhesion process of cancer cells on Arg-Gly-Asp tripeptide displaying biomimetic polymer surfaces. Using highly adherent human cervical adenocarcinoma (HeLa) cells as a model system, cell adhesion kinetic data with outstanding temporal resolution were obtained. We found that pre-exposing the cells to various concentrations of the main extract of green tea, the (-)-epigallocatechin gallate (EGCG), largely affected the temporal evolution of the adhesion process. For unexposed and low dosed cells, sigmoid shaped spreading kinetics was recorded. Higher dose of EGCG resulted in a complete absence of the sigmoidal character, and displayed adsorption-like kinetics. By using the first derivatives of the kinetic curves, a simple model was developed to quantify the sigmoidal character and the transition from sigmoidal to adsorption-like kinetics. The calculations showed that the transition happened at EGCG concentration of around 60 μg/mL. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide end-point assay, we concluded that EGCG is cytostatic but not cytotoxic. The effect of EGCG was also characterized by flow cytometry. We concluded that, using the introduced label-free methodology, the shape of the cell adhesion kinetic curves can be used to quantify in vitro cell viability in a fast, cost-effective, and highly sensitive manner.

Genetic Variation for Mitochondrial Function in the New Zealand Freshwater Snail Potamopyrgus antipodarum

The proteins responsible for mitochondrial function are encoded by 2 different genomes with distinct inheritance regimes, rendering rigorous inference of genotype-phenotype connections intractable for all but a few model systems. Asexual organisms provide a powerful means to address these challenges because offspring produced without recombination inherit both nuclear and mitochondrial genomes from a single parent. As such, these offspring inherit mitonuclear genotypes that are identical to the mitonuclear genotypes of their parents and siblings but different from those of other asexual lineages. Here, we compared mitochondrial function across distinct asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail model for understanding the evolutionary consequences of asexuality. Our analyses revealed substantial phenotypic variation across asexual lineages at 3 levels of biological organization: mitogenomic, organellar, and organismal. These data demonstrate that different asexual lineages have different mitochondrial function phenotypes, likely reflecting heritable variation (i.e., the raw material for evolution) for mitochondrial function in P. antipodarum. The discovery of this variation combined with the methods developed here sets the stage to use P. antipodarum to study central evolutionary questions involving mitochondrial function, including whether mitochondrial mutation accumulation influences the maintenance of sexual reproduction in natural populations.

Imidazole and beta-carotene photoprotection against photodynamic therapy evaluated by synchrotron infrared microscopy

In order to better understand the role of β-carotene and imidazole on the Photodynamic Therapy (PDT) mechanism, synchrotron infrared microscopy was used to detect the associated intracellular biochemical modifications following the visible light irradiation of HeLa cells incubated with these compounds as typical hydrophobic and hydrophilic singlet oxygen quenchers, respectively. For this purpose, PDT was performed employing the hydrophilic sensitizer 5,10,15,20-Tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate), TMPyP, and the hydrophobic sensitizer 5-(4-Methoxycarboxyphenyl)-10,15,20-triphenyl-21H,23H-porphyrin. The single cell IR spectra of PDT-treated, PDT plus quencher-treated and control HeLa cells were recorded at the SOLEIL Synchrotron Infrared SMIS beamline targeting specifically the cell nucleus. Principal Component Analysis (PCA) was used to assess the IR spectral changes. PCA revealed that there is a frequency shift of the protein Amide I vibrational band for the assays with the TMPyP sensitizer, indicating changes in the protein secondary structures of the PDT-treated cancer cells compared to the controls. In addition, the scores in those cells treated with both quenchers appear to be similar to the controls indicating a photoprotective effect. Comparative experiments carried out with SKMEL-28 and HaCat cells showed non- significant photoprotective effects of β-carotene and imidazole.

Novel Nano-Liposome Formulation for Dry Eyes with Components Similar to the Preocular Tear Film

Dry eye is commonly treated with artificial tears; however, developing artificial tears similar to natural tears is difficult due to the complex nature of tears. We characterized and evaluated a novel artificial tear formulation with components similar to the lipid and aqueous constituents of natural tears. Nano-liposomes, composed in part of phosphatidylcholine, were dispersed in an aqueous solution of bioadhesive sodium hyaluronate. Liposome size, zeta potential, and physicochemical properties of the fresh and stored (4 °C) liposomal formulation were analyzed. In vitro tolerance was tested using human corneal and conjunctival cell lines by exposures of 15 min to 4 h. The tolerance of the liposomal formulation was evaluated in animals (rabbits). The average liposome size was 186.3 ± 7.0 nm, and the zeta potential was negative. The osmolarity of the formulation was 198.6 ± 1.7 mOsm, with a surface tension of 36.5 ± 0.4 mN/m and viscosity of 3.05 ± 0.02 mPa·s. Viability values in the human corneal and conjunctival cell lines were always >80%, even after liposomal formulation storage for 8 weeks. Discomfort and clinical signs after instillation in rabbit eyes were absent. The new formulation, based on phosphatidylcholine-liposomes dispersed in sodium hyaluronate has suitable components and characteristics, including high in vitro cell viability and good in vivo tolerance, to serve as a tear substitute.

Tetrazolium salts and formazan products in Cell Biology: Viability assessment, fluorescence imaging, and labeling perspectives

For many years various tetrazolium salts and their formazan products have been employed in histochemistry and for assessing cell viability. For the latter application, the most widely used are 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), and 5-cyano-2,3-di-(p-tolyl)-tetrazolium chloride (CTC) for viability assays of eukaryotic cells and bacteria, respectively. In these cases, the nicotinamide-adenine-dinucleotide (NAD(P)H) coenzyme and dehydrogenases from metabolically active cells reduce tetrazolium salts to strongly colored and lipophilic formazan products, which are then quantified by absorbance (MTT) or fluorescence (CTC). More recently, certain sulfonated tetrazolium, which give rise to water-soluble formazans, have also proved useful for cytotoxicity assays. We describe several aspects of the application of tetrazolium salts and formazans in biomedical cell biology research, mainly regarding formazan-based colorimetric assays, cellular reduction of MTT, and localization and fluorescence of the MTT formazan in lipidic cell structures. In addition, some pharmacological and labeling perspectives of these compounds are also described.

Oil type and cross-linking influence growth of Aureobasidium melanogenum on vegetable oils as a single carbon source

Aureobasidium melanogenum is the main fungus found in a spontaneously formed biofilm on a oil‐treated wood. This dark colored biofilm functions as a protective coating. To better understand biofilm formation, in this study A. melanogenum was cultured on olive oil and raw linseed oil. Metabolic activity and oil conversion were measured. The results show that A. melanogenum is able to grow on linseed oil and olive oil as a single carbon source. The fungus produces the enzyme lipase to convert the oil into fatty acids and glycerol. Metabolic activity and oil conversion were equal on linseed oil and olive oil. The fungus was not able to grow on severe cross‐linked linseed oil, meaning that the degree of cross‐linking of the oil is important for growth of A. melanogenum. Dark coloring of the colony was seen on linseed oil, which might be a stress response on the presence of autoxidation products in linseed oil. The colony on olive oil showed delayed melanin production indicating an inhibitory effect of olive oil on melanin production.

Reprogramming induced by isoliquiritigenin diminishes melanoma cachexia through mTORC2-AKT-GSK3β signaling

Isoliquiritigenin (ISL), a member of the flavonoids, is known to have anti-tumor activity in vitro and in vivo. The effect of ISL on reprogramming in cancer cells, however, remains elusive. In this study, we investigated the effect of ISL on reprogramming in human melanoma A375 cells. ISL (15 μg/ml) significantly inhibited A375 cell proliferation, anchorage independent cell proliferation and G2/M cell cycle arrest after ISL exposure for 24 h. However, there were no significant changes in apoptosis rate. Terminal differentiation indicators (melanin content, melanogenesis mRNA expression, tyrosinase (TYR) activity) were all up-regulated by ISL treatment. In ISL-treated cells, glucose uptake, lactate levels and mRNA expression levels of GLUT1 and HK2 were significantly decreased, and accompanied by an increase in O2 consumption rate (OCR) and adenosine triphosphate (ATP) deficiency. Protein expression levels of mTORC2-AKT-GSK3β signaling pathway components (mTOR, p-mTOR, RICTOR, p-AKT, p-GSK3β) decreased significantly after ISL treatment. Co-treatment of ISL and the mTOR-specific inhibitor Ku-0063794 had a synergistic effect on the inhibition of proliferation, and increased melanin content and TYR activity. Glucose uptake and lactate levels decreased more significantly than treatment with ISL alone. These findings indicate that ISL induced reprogramming in A375 melanoma cells by activating mTORC2-AKT-GSK3β signaling.

Remotely controlled fusion of selected vesicles and living cells: a key issue review

Remote control over fusion of single cells and vesicles has a great potential in biological and chemical research allowing both transfer of genetic material between cells and transfer of molecular content between vesicles. Membrane fusion is a critical process in biology that facilitates molecular transport and mixing of cellular cytoplasms with potential formation of hybrid cells. Cells precisely regulate internal membrane fusions with the aid of specialized fusion complexes that physically provide the energy necessary for mediating fusion. Physical factors like membrane curvature, tension and temperature, affect biological membrane fusion by lowering the associated energy barrier. This has inspired the development of physical approaches to harness the fusion process at a single cell level by using remotely controlled electromagnetic fields to trigger membrane fusion. Here, we critically review various approaches, based on lasers or electric pulses, to control fusion between individual cells or between individual lipid vesicles and discuss their potential and limitations for present and future applications within biochemistry, biology and soft matter.

2-Methoxyestradiol protects against pressure overload-induced left ventricular hypertrophy

Numerous experimental studies have supported the evidence that 2-methoxyestradiol (2 ME) is a biologically active metabolite that mediates multiple effects on the cardiovascular system, largely independent of the estrogen receptor. 2 ME is a major cytochrome P450 1B1 (CYP1B1) metabolite and has been reported to have vasoprotective and anti-inflammatory actions. However, whether 2 ME would prevent cardiac hypertrophy induced by abdominal aortic constriction (AAC) has not been investigated yet. Therefore, the overall objectives of the present study were to elucidate the potential antihypertrophic effect of 2 ME and explore the mechanism(s) involved. Our results showed that 2 ME significantly inhibited AAC-induced left ventricular hypertrophy using echocardiography. The antihypertrophic effect of 2 ME was associated with a significant inhibition of CYP1B1 and mid-chain hydroxyeicosatetraenoic acids. Based on proteomics data, the protective effect of 2 ME is linked to the induction of antioxidant and anti-inflammatory proteins in addition to the modulation of proteins involved in myocardial energy metabolism. In vitro, 2 ME has shown a direct antihypertrophic effect through mitogen-activated protein kinases- and nuclear factor-κB-dependent mechanisms. The present work shows a strong evidence that 2 ME protects against left ventricular hypertrophy. Our data suggest the potential of repurposing 2 ME as a selective CYP1B1 inhibitor for the treatment of heart failure.

Reprogramming human A375 amelanotic melanoma cells by catalase overexpression: Reversion or promotion of malignancy by inducing melanogenesis or metastasis

Advanced melanoma is the most aggressive form of skin cancer. It is highly metastatic and dysfunctional in melanogenesis; two processes that are induced by H₂O₂. This work presents a melanoma cell model with low levels of H₂O₂ induced by catalase overexpression to study differentiation/dedifferentiation processes. Three clones (A7, C10 and G10) of human A375 amelanotic melanoma cells with quite distinct phenotypes were obtained. These clones faced H₂O₂ scavenging by two main strategies. One developed by clone G10 where ROS increased. This resulted in G10 migration and metastasis associated with the increased of cofilin-1 and CAP1. The other strategy was observed in clone A7 and C10, where ROS levels were maintained reversing malignant features. Particularly, C10 was not tumorigenic, while A7 reversed the amelanotic phenotype by increasing melanin content and melanocytic differentiation markers. These clones allowed the study of potential differentiation and migration markers and its association with ROS levels in vitro and in vivo, providing a new melanoma model with different degree of malignancy.

Common fibrillar spines of amyloid-β and human islet amyloid polypeptide revealed by microelectron diffraction and structure-based inhibitors

Amyloid-β (Aβ) and human islet amyloid polypeptide (hIAPP) aggregate to form amyloid fibrils that deposit in tissues and are associated with Alzheimer's disease (AD) and type II diabetes (T2D), respectively. Individuals with T2D have an increased risk of developing AD, and conversely, AD patients have an increased risk of developing T2D. Evidence suggests that this link between AD and T2D might originate from a structural similarity between aggregates of Aβ and hIAPP. Using the cryoEM method microelectron diffraction, we determined the atomic structures of 11-residue segments from both Aβ and hIAPP, termed Aβ(24-34) WT and hIAPP(19-29) S20G, with 64% sequence similarity. We observed a high degree of structural similarity between their backbone atoms (0.96-Å root mean square deviation). Moreover, fibrils of these segments induced amyloid formation through self- and cross-seeding. Furthermore, inhibitors designed for one segment showed cross-efficacy for full-length Aβ and hIAPP and reduced cytotoxicity of both proteins, although by apparently blocking different cytotoxic mechanisms. The similarity of the atomic structures of Aβ(24-34) WT and hIAPP(19-29) S20G offers a molecular model for cross-seeding between Aβ and hIAPP.

The MTT viability assay yields strikingly false-positive viabilities although the cells are killed by some plant extracts

The MTT assay is one of the often used cell viability/cytotoxicity assays. However, when the methanol extracts of plants are used to test their cytotoxic potential, interference may occur, resulting in false-positive viability results. Therefore, in this study, the reliability of the MTT assay was investigated in the case of plant use. The methanol extracts of three different plants (Hypericum adenotrichum, Salvia kronenburgii, and Pelargonium quercetorum) were tested in breast cancer cell lines (MCF-7 and MDA-MB-231) using the MTT assay and the results were compared to the ATP assay, which is a much more sensitive and reliable assay due to its interference-free feature. Additionally, decreased cell density was confirmed with phase-contrast microscopy and fluorescence staining (Hoechst 33342 dye). Although both of the viability/cytotoxicity assays are considered as metabolic assays, viabilities (in %) in the MTT assay were found to be strikingly higher when compared to the results with the ATP assay. Even in the case of total death, the MTT assay still produced artificial/false increases in viability. The morphology-based evaluation of viability/cytotoxicity by phase-contrast microscopy and Hoechst 33342 staining were greatly compatible with the ATP assay results. Overestimated (false) viabilities in the MTT assay suggests a serious interference between the MTT assay itself and the extracts used. Some ingredients of plants may have reducing activity (like the dehydrogenase activity of the cells) that converts the MTT compound into the colored formazan that is the principle of the assay. Therefore, the MTT assay may not be a suitable assay for some plant extracts, urging great caution when plants are used.

Tramadol ameliorates behavioural, biochemical, mitochondrial and histological alterations in ICV-STZ-induced sporadic dementia of Alzheimer's type in rats

Alzheimer disease represents a major public health issue with limited therapeutic interventions. We explored the possibility of therapeutic approach by repurposing of tramadol in a sporadic animal model of Alzheimer's type. Streptozocin (STZ 3 mg/kg; bilaterally) was injected to male SD rats through intracerebroventricular (ICV) route. Drug treatment was started just after streptozocin administration and continued for 3 weeks. The rats were killed on the 21st day following the last behavioral test, and cytoplasmic fractions of the hippocampus and pre-frontal cortex were prepared for the quantification of acetylcholinesterase, oxidative stress parameter, mitochondrial enzymes activity and histological examination. Tramadol (5, 10 and 20 mg/kg, i.p.) was used as a treatment drug, and memantine (10 mg/kg, i.p.) was used as a standard. Tramadol significantly attenuated behavioral, biochemical, mitochondrial and histological alterations at low (5 mg/kg) and intermediate (10 mg/kg) dose, suggesting its neuroprotective potential in ICV-STZ-treated rats. Further, the neuroprotective effect of tramadol (10 mg/kg) was comparable to memantine (10 mg/kg). In conclusion, our results indicate the effectiveness of tramadol in preventing ICV-STZ-induced cognitive impairment as well as mito-oxidative stress. Further, these findings reveal the possibility of MOR agonist as a therapeutic approach for sporadic Alzheimer disease.

Novel liposome-based and in situ gelling artificial tear formulation for dry eye disease treatment

PURPOSE

Artificial tears are widely used in the treatment of dry eye disease, although current formulations do not closely resemble natural tears. The purpose of this study was the design and characterization of a novel in situ gelling artificial tear formulation, containing both lipid and aqueous components, in order to resemble natural tears and replenish the tear film.

METHODS

Liposomes, containing phosphatidylcholine, cholesterol, vitamins A and E, were prepared by the thin-film hydration method. The aqueous phase of the formulation was comprised of gellan gum, hydroxypropyl methylcellulose, levocarnitine, electrolytes (sodium chloride and potassium chloride), trehalose, and borates. The artificial tear was characterized in terms of liposome size, pH, surface tension, and viscosity. In vitro tolerance studies were performed in a human epithelial carcinoma cell line (HeLa) and a murine macrophage cell line (J774). In vivo tolerance was assessed in rabbits.

RESULTS

Liposomes presented a unimodal distribution with a mean size of 200.1 ± 4.4 nm. The resulting surface tension was 53.4 ± 1.1 mN/m (at 33 °C) and the pH was 7.6 ± 0.1. The viscosity of the formulation presented a mean value of 4.0 ± 0.1 mPa s within the shear rate interval of 200-1000 s^-1 at 33 °C. Cell viability remained higher than 90% in both cell lines. No discomfort or clinical signs were observed in rabbits.

CONCLUSIONS

The liposome-based and in situ gelling artificial tear formulation presented good tolerance and suitable properties for topical ophthalmic administration. It may be beneficial in the treatment of dry eye disease.

Rapid, Acid-Free Synthesis of High-Quality Graphene Quantum Dots for Aggregation Induced Sensing of Metal Ions and Bioimaging

Graphene quantum dots (GQDs) are zero-dimensional materials that exhibit characteristics of both graphene and quantum dots. Herein, we report a rapid, relatively green, one-pot synthesis of size-tunable GQDs from graphene oxide (GO) by a sonochemical method with intermittent microwave heating, keeping the reaction temperature constant at 90 °C. The GQDs were synthesized by oxidative cutting of GO using KMnO₄ as an oxidizing agent within a short span of time (30 min) in an acid-free condition. The synthesized GQDs were of high quality and exhibited good quantum yield (23.8%), high product yield (>75%), and lower cytotoxicity (tested up to 1000 μg/mL). Furthermore, the as-synthesized GQDs were demonstrated as excellent fluorescent probes for bioimaging and label-free sensing of Fe(III) ions, with a detection limit as low as 10 × 10^-6 M.

Toxic effects of phytol and retinol on human glioblastoma cells are associated with modulation of cholesterol and fatty acid biosynthetic pathways

Glioblastoma (GBM) is the most common primary brain tumor. Genetic mutations may reprogram the metabolism of neoplastic cells. Particularly, alterations in cholesterol and fatty acid biosynthetic pathways may favor biomass synthesis and resistance to therapy. Therefore, compounds that interfere with those pathways, such as phytol (PHY) and retinol (RET), may be appropriate for cytotoxic approaches. We tested the effect of PHY or RET on the viability of human GBM cell lines (U87MG, A172 and T98G). Since the compounds showed a dose-dependent cytotoxic effect, additional analyses were performed with IC₅₀ values. Transcriptome analyses of A172 cells treated with PHY IC₅₀ or RET IC₅₀ revealed down-regulated genes involved in cholesterol and/or fatty acid biosynthetic pathways. Thus, we investigated the expression of proteins required for cholesterol and/or fatty acid synthesis after treating all lineages with PHY IC₅₀ or RET IC₅₀ and comparing them with controls. Sterol regulatory element-binding protein 1 (SREBP-1) expression was reduced by PHY in U87 and T98G cells. However, fatty acid synthase (FAS) protein expression, which is regulated by SREBP-1, was down-regulated in all lineages after both treatments. Moreover, farnesyl-diphosphate farnesyltransferase (FDFT1) levels, a protein associated with cholesterol synthesis, were reduced in all lineages by PHY and in U87MG and A172 cells by RET. Our results suggest that SREBP-1, FAS and FDFT1 are potential target(s) for future in vivo approaches against GBM and support the use of inhibitors of their synthesis, including PHY and RET, for such approaches.

Prostaglandin J2 promotes O-GlcNAcylation raising APP processing by α- and β-secretases: relevance to Alzheimer's disease

Regulation of the amyloid precursor protein (APP) processing by α- and β-secretases is of special interest to Alzheimer's disease (AD), as these proteases prevent or mediate amyloid beta formation, respectively. Neuroinflammation is also implicated in AD. Our data demonstrate that the endogenous mediator of inflammation prostaglandin J2 (PGJ2) promotes full-length APP (FL-APP) processing by α- and β-secretases. The decrease in FL-APP was independent of proteasomal, lysosomal, calpain, caspase, and γ-secretase activities. Moreover, PGJ2-treatment promoted cleavage of secreted APP, specifically sAPPα and sAPPβ, generated by α and β-secretase, respectively. Notably, PGJ2-treatment induced caspase-dependent cleavage of sAPPβ. Mechanistically, PGJ2-treatment selectively diminished mature (O- and N-glycosylated) but not immature (N-glycosylated only) FL-APP. PGJ2-treatment also increased the overall levels of protein O-GlcNAcylation, which occurs within the nucleocytoplasmic compartment. It is known that APP undergoes O-GlcNAcylation and that the latter protects proteins from proteasomal degradation. Our results suggest that by increasing protein O-GlcNAcylation levels, PGJ2 renders mature APP less prone to proteasomal degradation, thus shunting APP toward processing by α- and β-secretases.

Near-infrared photothermal/photodynamic therapy with indocyanine green induces apoptosis of hepatocellular carcinoma cells through oxidative stress

Indocyanine green (ICG) is a photothermal agent, photosensitizer, and fluorescence imaging probe which shows specific accumulation in hepatocellular carcinoma (HCC) cells. We recently developed a photodynamic therapy (PDT) using ICG and near-infrared (NIR) laser as a new anti-cancer treatment for HCC. However, the molecular mechanism underlying this effect needs to be elucidated. HuH-7 cells, a well-differentiated human HCC cell line, were transplanted subcutaneously into BALB/c-nu/nu mice for in vivo experiment. ICG was administered 24 h before NIR irradiation. The irradiation was performed at three tumor locations by 823-nm NIR laser on days 1 and 7. The temperature of HuH-7 xenografts increased to 48.5 °C 3 minutes after ICG-NIR irradiation start. Reactive oxygen species (ROS) production was detected after ICG-NIR irradiation both in vitro and in vivo. There was certain anti-tumor effect and ROS production even under cooling conditions. Repeated NIR irradiation increased the cell toxicity of ICG-NIR therapy; the mean tumor volume on day 9 was significantly smaller after ICG-NIR irradiation compared to tumor without irradiation (87 mm3 vs. 1332 mm3; p = 0.01) in HCC mice xenografts model. ICG-NIR therapy induced apoptosis in HCC cells via a photothermal effect and oxidative stress. Repeated ICG-NIR irradiation enhanced the anti-tumor effect.

Combination of betulinic acid and chidamide inhibits acute myeloid leukemia by suppression of the HIF1α pathway and generation of reactive oxygen species

Acute myeloid leukemia (AML) is a heterogeneous disorder of the hematopoietic system with no common genetic “Achilles heel” that can be targeted. Most patients respond well to standard therapy, while a majority relapse, and development of an effective therapy for AML patients is still urgently needed. In this study, we demonstrated that betulinic acid (BA) significantly increased Aryl hydrocarbon receptor (AHR) expression through demethylation on the AHR promoter in AML cells, and the increased AHR expression interacts with and sequesters ARNT, subsequently suppressing hypoxia-inducible factor-1α (HIF1α) pathway. We also found that histone deacetylase inhibitor chidamide (CDM) treatment significantly increased p300 over-acetylation in AML cells with dissociation of p300 with HIF1α, and subsequently suppressed the HIF1α pathway. Further investigation showed that BA/CDM combination additively increased generation of reactive oxygen species (ROS) with DNA damage, apoptosis and mitochondrial dysfunction. Also, BA/CDM combination additively suppressed the HIF1α pathway with decreased VEGF expression. in vivo mice study showed that BA/CDM combination significantly suppressed AML tumor growth, and overexpression of SOD2 and a constitutive HIF1α (HIF1C) completely diminished this effect. We conclude that a BA/CDM combination inhibits AML tumors through ROS over-generation and HIF1α pathway suppression. This is the first time we have shown the potential effect and possible mechanism of BA and CDM on the inhibition of AML tumor growth.

Very Long Chain Fatty Acids Are Functionally Involved in Necroptosis

Necroptosis is a form of regulated cell death that is linked to various human diseases. Distinct membrane-related, thus lipid-dependent, alterations take place during necroptosis. However, little is known about the roles of specific lipids in this process. We used an untargeted LC-MS-based approach to reveal that distinct lipid species are regulated at the molecular level during necroptosis. We found that ceramides and very long chain fatty acids accumulate during this process. Intrigued by the specificity of very long chain fatty acid accumulation, we focused on characterizing their involvement during necroptosis. Biochemical characterizations suggested that activated fatty acid biosynthesis and elongation could be responsible for these accumulations. We further showed that inhibition of fatty acid biosynthesis and depletion of very long chain fatty acids prevented loss of plasma membrane integrity and cell death, strongly suggesting that very long chain fatty acids are functionally involved in necroptosis.

MAO inhibitory activity of bromo-2-phenylbenzofurans: synthesis, in vitro study, and docking calculations

Monoamine oxidase (MAO) is an enzyme responsible for metabolism of monoamine neurotransmitters which play an important role in brain development and function. This enzyme exists in two isoforms, and it has been demonstrated that MAO-B activity, but not MAO-A activity, increases with aging. MAO inhibitors show clinical value because besides the monoamine level regulation they reduce the formation of by-products of the MAO catalytic cycle, which are toxic to the brain. A series of 2-phenylbenzofuran derivatives was designed, synthesized and evaluated against hMAO-A and hMAO-B enzymes. A bromine substituent was introduced in the 2-phenyl ring, whereas position 5 or 7 of the benzofuran moiety was substituted with a methyl group. Most of the tested compounds inhibited preferentially MAO-B in a reversible manner, with IC50 values in the low micro or nanomolar range. The 2-(2'-bromophenyl)-5-methylbenzofuran (5) was the most active compound identified (IC50 = 0.20 μM). In addition, none of the studied compounds showed cytotoxic activity against the human neuroblastoma cell line SH-SY5Y. Molecular docking simulations were used to explain the observed hMAO-B structure-activity relationship for this type of compounds.

Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins

We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.

Purinergic Antagonism Prevents Mitochondrial Dysfunction and Behavioral Deficits Associated with Dopaminergic Toxicity Induced by 6-OHDA in Rats

Purinoceptors are present in neurons, microglia and oligodendrocytes and regulate dopamine (DA) release, striatal-related function and striatal neuronal and DA cells damage. Therefore, purinoceptors may be involved in the pathology of Parkinson's disease (PD) and purinergic antagonism may show neuroprotective effect. The study investigated the role of the non-selective purinergic receptor antagonist pyridoxalphosphate-6-azophenyl-2^', 4^'-disulfonic acid (PPADS) and a selective purinergic receptor P2X7 receptor antagonist Brilliant Blue G (BBG) against 6-OHDA induced dopaminergic neurotoxicity in rats; while adenosine triphosphate (ATP) was used as a P2X receptor agonist. Behavioral parameters like spontaneous motor activity, narrow beam walk, footprint, bar catalepsy, grip strength and rotarod tests were performed to evaluate motor deficits in PD. Striatal DA contents were estimated as neurochemical measures of PD. Mitochondrial studies and oxidative status were assessed to investigate the mechanism of purinergic system antagonists. Involvement of purinergic receptors in apoptosis was assessed by expressing cytochrome-C, caspase-9 and caspase-3. Both the antagonists not only attenuated 6-OHDA induced motor deficits but also protected against 6-OHDA induced DA depletion in the striatum. Oxidative stress, mitochondrial integrity and dysfunction were attenuated by purinergic antagonists. Further, they attenuated mitochondrial-linked apoptosis as observed by a decrease in expression of cytochrome-C, caspase-9 and caspase-3. Therefore, purinoceptor antagonism shows neuroprotective effect in 6-OHDA induced dopamine toxicity through preservation of mitochondrial bioenergetics and anti-apoptotic activities.

Synthesis and structure-activity relationship study of novel 3-heteroarylcoumarins based on pyridazine scaffold as selective MAO-B inhibitors

Compounds of hybrid structure pyridazine-coumarin were discovered as potent, selective and reversible inhibitors of monoamine oxidase B (MAO-B). These compounds were synthesized in good yield following a multistep approach based on Knoevenagel reaction and using as key intermediate pyridazinone 16, which was obtained from maleic anhydride and furan. Compounds 9b and 9d are the most active compounds of these series, with IC₅₀ values in the sub-micromolar range, and lack of cytotoxic effects. Theoretical calculation of ADME properties also suggested a good pharmacokinetic profile for both compounds. Docking simulations provided insights into enzyme inhibitor interactions and allowed us to rationalize the observed structure-activity relationships (SARs).

Paeoniflorin exerts neuroprotective effects against glutamate‑induced PC12 cellular cytotoxicity by inhibiting apoptosis

Paeoniflorin (PF) is an active ingredient of Radix Paeoniae, which is known to exert neuroprotective effects. However, the mechanims behind the neuroprotective effects of PF are not yet fully understood. The apoptosis of neurons plays an important role in the cerebral ischemia-induced cascade response. This study aimed to investigate neuroprotective effects of PF against glutamate‑induced PC12 cellular cytotoxicity and to determine whether these effects are mediated via the inhibition of apoptosis in vitro and the activity of mitochondrial apoptosis-associated proteins in PC12 cells. Exposure of the PC12 cells to glutamate induced cell morphological changes, significantly decreased cell viability and induced apoptosis, with similar results being observed from the Hoechst 33342 staining and Annexin V/PI staining experiments. Glutamate also increased the lactate dehydrogenase release by the PC12 cells. However, treatment with PF prevented these effects. Furthermore, PF inhibited Bax and Bad expression and increased Bcl-2 and Bcl-xL expression; it also decreased the levels of downstream protein (caspase-3 and caspase-9). Collectively, our results indicate that PF protects PC12 cells against glutamate-induced neurotoxicity possibly through the inhibition of the expression of mitochondrial apoptosis-associated proteins.

Hair & skin derived progenitor cells: In search of a candidate cell for regenerative medicine

BACKGROUND & OBJECTIVES

Skin is an established tissue source for cell based therapy. The hair follicle has been introduced later as a tissue source for cell based therapy. The ease of tissue harvest and multipotent nature of the resident stem cells in skin and hair follicle has promoted basic and clinical research in this area. This study was conducted to evaluate skin stem cells (SSCs) and hair follicle stem cells (HFSCs) as candidate cells appropriate for neuronal and melanocyte lineage differentiation.

METHODS

In this study, SSCs and hair follicle stem cells (HFSCs) were expanded in vitro by explant culture method and were compared in terms of proliferative potential and stemness; differentiation potential into melanocytes and neuronal lineage.

RESULTS

SSCs were found to be more proliferative in comparison to HFSCs, however, telomerase activity was more in HFSCs in comparison to SSCs. Capacity to differentiate into two lineages of ectoderm origin (neuronal and melanocyte) was found to be different. HFSCs cells showed more propensities towards melanocyte lineage, whereas SSCs were more inclined towards neuronal lineage.

INTERPRETATION & CONCLUSIONS

The study showed that SSCs had differential advantage over the HFSCs for neuronal cell differentiation, whereas, the HFSCs were better source for melanocytic differentiation.

In vitro study of the proliferation and growth of human fetal osteoblasts on Mg and Si co-substituted tricalcium phosphate ceramics

The objective of this work was to study the feasibility of the solid state sintering, a conventional ceramic processing method, to obtain Mg and Si co-substituted tricalcium phosphate bioceramics and composites containing diopside. A series of new Ca₃ (PO₄ )₂ based ceramics has been prepared from attrition milled mixtures of synthetic Ca₃ (PO₄ )₂ and CaMg(SiO₃ )₂ powders, isostatically pressed and sintered at 1250-1300°C. Materials containing 0, 1, and 5 wt % of CaMg(SiO₃ )₂ were constituted by β + α - Ca₃ (PO₄ )₂ solid solutions while the material containing 60 wt % of CaMg(SiO₃ )₂ was a constituted by β- Ca₃ (PO₄ )₂ and CaMg(SiO₃ )₂ . The biological responses of the developed ceramics were studied in vitro using human fetal osteoblast cultures. Culture times ranged from 1 to 21 days. The new family of materials promotes the adhesion and proliferation of human osteoblasts cultured onto their surface forming a monolayer and showing a normal morphology. The results of the MTT and Alamar Blue assays showed that the soluble components extracted from the Mg/Si- co-substituted Ca₃ (PO₄ )₂ and the Ca₃ (PO₄ )₂ -CaMg(SiO₃ )₂ composite were noncytotoxic. The specimens with diopside exhibited a better in vitro behavior which is attributed to the release of Si and Mg ions to the culture medium, enhancing the activity of cells. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2266-2275, 2017.

Could hypoxia acclimation cause morphological changes and protect against Mn-induced oxidative injuries in silver catfish (Rhamdia quelen) even after reoxygenation?

Exposure to hypoxia has shown beneficial adjustments in different species, including silver catfish (Rhamdia quelen), especially in situations of aquatic contamination with pollutants such as manganese (Mn). Considering that hypoxia is seasonal in the natural aquatic environment, we decided to assess whether these adaptive mechanisms could be maintained when reoxygenation is established. Silver catfish acclimated to moderate hypoxia (∼3 mg L^-1, 41% O₂ saturation) for 10 days and subsequently exposed to Mn (∼8.1 mg L^-1) for additional 10 days displayed lower (47%) Mn accumulation in the gills, and it was maintained (62.6%) after reoxygenation, in comparison to normoxia. Oxidative status in the gills allowed us to observe increased reactive species (RS) generation and protein carbonyl (PC) level together with decreased mitochondrial viability induced by Mn under normoxia. Inversely, while hypoxia per se was beneficial on RS generation and PC level, this acclimation was able to minimize Mn toxicity, as observed by the minor increase of RS generation and the minor reduction of mitochondrial viability, together with decreased PC level. Interestingly, after reoxygenation, part of the protective influences observed during hypoxia against Mn toxicity were maintained, as observed through a lower level of PC and higher mitochondrial viability in relation to the group exposed to Mn under normoxia. Only groups exposed to Mn under hypoxia showed increased activity of both catalase (CAT) and Na⁺/K⁺-ATPase in the gills, but, while CAT activity remained increased after reoxygenation, Na⁺/K⁺-ATPase activity was decreased by Mn, regardless of the oxygen level. Based on these outcomes, it is possible to propose that environment events of moderate hypoxia are able to generate rearrangements in the gills of silver catfish exposed to Mn, whose influence persists after water reoxygenation. These responses may be related to the adaptive development, reducing Mn toxicity to silver catfish. Moderate hypoxia generates rearrangements in the gills of Silver catfish, exerting beneficial and persistent protection against Mn toxicity.

Cardioprotective Effects of Malvidin Against Isoproterenol-Induced Myocardial Infarction in Rats: A Mechanistic Study

Background

Malvidin (alvidin-3-glucoside) is a polyphenol that belongs to the class of natural anthocyanin, which is abundantly found in red wines, colored fruits, and the skin of red grapes. Therefore, the current investigation was intended to evaluate the effect of malvidin against myocardial infarction induced by isoproterenol in the rats.

Material/Methods

The cardioprotective effects was assessed by determining the effect of malvidin on the activities of endogenous antioxidants – catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH) – and on the levels of lipid peroxidation and serum marker enzymes. The serum levels of IL-6 and TNF-α were also determined using an enzyme-linked immunosorbent assay (ELISA) kit.

Result

The present study demonstrated a significant cardioprotective effect of malvidin by restoring the defensive activities of endogenous antioxidants – catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH) – and by reducing the levels of lipid peroxidation and serum marker enzymes lactate dehydrogenase (LD) and creatine kinase (CK). Malvidin significantly ameliorated the histopathological changes and impaired mitochondria in the cardiac necrosis stimulated with isoproterenol. Additionally, the results also demonstrated that nuclear translocation of Nrf-2 and subsequent HO-1 expression might be associated with nuclear factor kappa B (NF-κB) pathway activation.

Conclusions

Our findings suggest that malvidin exerts cardioprotective effects that might be due to possible strong antioxidant and anti-inflammatory activities. Therefore, this study provides the basis for the development of malvidin as a safe and effective treatment of myocardial infarction.

Metabolic changes and inflammation in cultured astrocytes from the 5xFAD mouse model of Alzheimer's disease: Alleviation by pantethine

Astrocytes play critical roles in central nervous system homeostasis and support of neuronal function. A better knowledge of their response may both help understand the pathophysiology of Alzheimer's disease (AD) and implement new therapeutic strategies. We used the 5xFAD transgenic mouse model of AD (Tg thereafter) to generate astrocyte cultures and investigate the impact of the genotype on metabolic changes and astrocytes activation. Metabolomic analysis showed that Tg astrocytes exhibited changes in the glycolytic pathway and tricarboxylic acid (TCA) cycle, compared to wild type (WT) cells. Tg astrocytes displayed also a prominent basal inflammatory status, with accentuated reactivity and increased expression of the inflammatory cytokine interleukin-1 beta (IL-1β). Compensatory mechanisms were activated in Tg astrocytes, including: i) the hexose monophosphate shunt with the consequent production of reducing species; ii) the induction of hypoxia inducible factor-1 alpha (HIF-1α), known to protect against amyloid-β (Aβ) toxicity. Such events were associated with the expression by Tg astrocytes of human isoforms of both amyloid precursor protein (APP) and presenilin-1 (PS1). Similar metabolic and inflammatory changes were induced in WT astrocytes by exogenous Aβ peptide. Pantethine, the vitamin B5 precursor, known to be neuroprotective and anti-inflammatory, alleviated the pathological pattern in Tg astrocytes as well as WT astrocytes treated with Aß. In conclusion, our data enlighten the dual pathogenic/protective role of astrocytes in AD pathology and the potential protective role of pantethine.

Neurotoxic mechanisms by which the USP14 inhibitor IU1 depletes ubiquitinated proteins and Tau in rat cerebral cortical neurons: Relevance to Alzheimer's disease

In Alzheimer's disease proteasome activity is reportedly downregulated, thus increasing it could be therapeutically beneficial. The proteasome-associated deubiquitinase USP14 disassembles polyubiquitin-chains, potentially delaying proteasome-dependent protein degradation. We assessed the protective efficacy of inhibiting or downregulating USP14 in rat and mouse (Usp14^axJ) neuronal cultures treated with prostaglandin J2 (PGJ2). IU1 concentrations (_HIU1>25μM) reported by others to inhibit USP14 and be protective in non-neuronal cells, reduced PGJ2-induced Ub-protein accumulation in neurons. However, _HIU1 alone or with PGJ2 is neurotoxic, induces calpain-dependent Tau cleavage, and decreases E1~Ub thioester levels and 26S proteasome assembly, which are energy-dependent processes. We attribute the two latter _HIU1 effects to ATP-deficits and mitochondrial Complex I inhibition, as shown herein. These _HIU1 effects mimic those of mitochondrial inhibitors in general, thus supporting that ATP-depletion is a major mediator of _HIU1-actions. In contrast, low IU1 concentrations (_LIU1≤25μM) or USP14 knockdown by siRNA in rat cortical cultures or loss of USP14 in cortical cultures from ataxia (Usp14^axJ) mice, failed to prevent PGJ2-induced Ub-protein accumulation. PGJ2 alone induces Ub-protein accumulation and decreases E1~Ub thioester levels. This seemingly paradoxical result may be attributed to PGJ2 inhibiting some deubiquitinases (such as UCH-L1 but not USP14), thus triggering Ub-protein stabilization. Overall, IU1-concentrations that reduce PGJ2-induced accumulation of Ub-proteins are neurotoxic, trigger calpain-mediated Tau cleavage, lower ATP, E1~Ub thioester and E1 protein levels, and reduce proteasome activity. In conclusion, pharmacologically inhibiting (with low or high IU1 concentrations) or genetically down-regulating USP14 fail to enhance proteasomal degradation of Ub-proteins or Tau in neurons.