Immunoproteasome-specific subunit PSMB9 induction is required to regulate cellular proteostasis upon mitochondrial dysfunction.

Perturbed cellular protein homeostasis (proteostasis) and mitochondrial dysfunction play an important role in neurodegenerative diseases, however, the interplay between these two phenomena remains unclear. Mitochondrial dysfunction leads to a delay in mitochondrial protein import, causing accumulation of non-imported mitochondrial proteins in the cytosol and challenging proteostasis. Cells respond by increasing proteasome activity and molecular chaperones in yeast and C. elegans. Here, we demonstrate that in human cells mitochondrial dysfunction leads to the upregulation of a chaperone HSPB1 and, interestingly, an immunoproteasome-specific subunit PSMB9. Moreover, PSMB9 expression is dependent on the translation elongation factor EEF1A2. These mechanisms constitute a defense response to preserve cellular proteostasis under mitochondrial stress. Our findings define a mode of proteasomal activation through the change in proteasome composition driven by EEF1A2 and its spatial regulation, and are useful to formulate therapies to prevent neurodegenerative diseases.

The Impact of Ag Nanoparticles and CdTe Quantum Dots on Expression and Function of Receptors Involved in Amyloid-ß Uptake by BV-2 Microglial Cells.

Microglial cells clear the brain of pathogens and harmful debris, including amyloid-ß (Aß) deposits that are formed during Alzheimer's disease (AD). We studied the expression of Msr1, Ager and Cd36 receptors involved in Aß uptake and expression of Cd33 protein, which is considered a risk factor in AD. The effect of silver nanoparticles (AgNPs) and cadmium telluride quantum dots (CdTeQDs) on the expression of the above receptors and Aß uptake by microglial cells was investigated. Absorption of Aß and NPs was confirmed by confocal microscopy. AgNPs, but not CdTeQDs, caused a decrease in Aß accumulation. By using a specific inhibitor-polyinosinic acid-we demonstrated that Aß and AgNPs compete for scavenger receptors. Real-time PCR showed up-regulation of Cd33 and Cd36 gene expression after treatment with CdTeQDs for 24 h. Analysis of the abundance of the receptors on the cell surface revealed that AgNP treatment significantly reduced the presence of Msr1, Cd33, Ager and Cd36 receptors (6 and 24 h), whereas CdTeQDs increased the levels of Msr1 and Cd36 (24 h). To summarize, we showed that AgNP uptake competes with Aß uptake by microglial cells and consequently can impair the removal of the aggregates. In turn, CdTeQD treatment led to the accumulation of proinflammatory Cd36 protein on the cell surface.

Impact of polymorphism of selected genes on the diagnosis of type 2 diabetes in patients with obstructive sleep apnea.

INTRODUCTION Although the coexistence of type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) may be attributed to environmental risk factors common for both diseases, a genetic background should also be considered. Data on the role of genetic factors in the development of T2DM in patients with OSA are lacking. OBJECTIVES The study was aimed to evaluate the prevalence of polymorphisms of selected genes that are known to be associated with diabetes or obesity in patients with OSA and concomitant T2DM and to assess these polymorphisms in the context of OSA severity. PATIENTS AND METHODS Consecutive patients with newly diagnosed OSA confirmed by polysomnography underwent genotyping for the following single nucleotide polymorphisms (SNPs): SREBF1 rs11868035, HIF1A rs11549465, APOA5 rs3135506, TCF7L2 rs7903146, and FTO rs16945088. The frequency of genotypes was compared between patients with and without concomitant T2DM and was analyzed with regard to OSA severity. RESULTS A total of 600 patients with newly diagnosed OSA were enrolled to the study. Of these, 121 patients (20.2%) were diagnosed with T2DM (97 men and 24 women; median age, 58 years; range, 52-64 years). The prevalence of T2DM was significantly lower in APOA5 rs3135506 GG homozygotes than in CG heterozygotes (18.8% vs 33.3%, P = 0.02). APOA5 rs3135506 CG heterozygotes were at higher risk for developing T2DM (adjusted odds ratio, 2.64; 95% confidence interval,1.38-5.04; P = 0.003). No significant differences were found for the genotype distribution of the other investigated SNPs. CONCLUSIONS Our study shows a possible link between the polymorphism of the gene encoding APOA5 and T2DM in patients with OSA.

LDL dinitrosyl iron complex acts as an iron donor in mouse macrophages.

[Fe(NO)2] - modified nanoparticles of low-density protein (DNICLDL) can serve as conveyors of iron in the form of stable complexes with ApoB100 protein. As reported recently, in human hepatoma cells DNICLDL significantly increased the total iron content, while showing low toxicity. In the present work, we focused on the effects of internalization of DNIC-modified lipoproteins in macrophages, with special regards to cytotoxicity. DNICLDL was administered to a model macrophage cell line, RAW 264.7. Administration of DNICLDL considerably increased total iron content. High increase of iron was accompanied by moderate toxicity. As shown by in vitro plasmid nicking assay, chelation of iron in the form of DNIC strongly reduced the iron-related reactive oxygen species (ROS) -induced DNA damage. In addition, DNICLDL, plausibly due to its NO-donating activity, did not induce inducible nitric oxide synthase (iNOS) expression, as opposed to other forms of low-density protein (LDL).

mitoLUHMES: An Engineered Neuronal Cell Line for the Analysis of the Motility of Mitochondria.

Perturbations in the transport of mitochondria and their quality control in neuronal cells underlie many types of neurological pathologies, whereas systems enabling convenient analysis of mitochondria behavior in cellular models of neurodegenerative diseases are limited. In this study, we present a modified version of lund human mesencephalic cells, mitoLUHMES, expressing GFP and mitochondrially targeted DsRed2 fluorescent proteins, intended for in vitro analysis of mitochondria trafficking by real-time fluorescence microscopy. This cell line can be easily differentiated into neuronal phenotype and allows us to observe movements of single mitochondria in single cells grown in high-density cultures. We quantified the perturbations in mitochondria morphology and dynamics in cells treated with model neurotoxins: carbonyl cyanide m-chlorophenylhydrazone and 6-hydroxydopamine. For the first time we filmed the processes of fission, fusion, pausing, and reversal of mitochondria movement direction in LUHMES cells. We present a detailed analysis of mitochondria length, velocity, and frequency of movement for static, anterograde, and retrograde motile mitochondria. The observed neurotoxin treatment-mediated decreases in morphological and kinetic parameters of mitochondria provide foundation for the future studies exploiting mitoLUHMES as a new model for neurobiology.

Competition between self-inclusion and drug binding explains the pH dependence of the cyclodextrin drug carrier - molecular modelling and electrochemistry studies.

A non-toxic lipoic acid derivative of ß cyclodextrin (ßCDLip) with an electron-rich aromatic linker was studied as a carrier for the drug doxorubicin with the aim of decreasing the toxic side effects of this drug. The modified cyclodextrin strengthened the drug binding and differentiated the complex-forming ability with dependence on pH. The stability constants of the complexes were evaluated by voltammetry and spectrofluorometry. Molecular modelling provided deeper insight into the nature of the ligand structure itself and the drug-ligand interactions, showing the different contributions of the self-inclusion of the ligand substituent at different pH values. As a result, the modes of interaction of ßCDLip with the drug and factors affecting the stabilities of the complex under the pH conditions of healthy and tumour cells could be discovered and explained.

The role of natural polyphenols in cell signaling and cytoprotection against cancer development.

The cytoprotective and anticancer action of dietary in-taken natural polyphenols has for long been attributed only to their direct radical scavenging activities. Currently it is well supported that those compounds display a broad spectrum of biological and pharmacological outcomes mediated by their complex metabolism, interaction with gut microbiota as well as direct interactions of their metabolites with key cellular signaling proteins. The beneficial effects of natural polyphenols and their synthetic derivatives are extensively studied in context of cancer prophylaxis and therapy. Herein we focus on cell signaling to explain the beneficial role of polyphenols at the three stages of cancer development: we review the recent proceedings about the impact of polyphenols on the cytoprotective antioxidant response and their proapoptotic action at the premalignant stage, and finally we present data showing how phenolic acids (e.g., caffeic, chlorogenic acids) and flavonols (e.g., quercetin) hamper the development of metastatic cancer.

Formation of glutathionyl dinitrosyl iron complexes protects against iron genotoxicity.

Dinitrosyl iron(i) complexes (DNICs), intracellular NO donors, are important factors in nitric oxide-dependent regulation of cellular metabolism and signal transduction. It has been shown that NO diminishes the toxicity of iron ions and vice versa. To gain insight into the possible role of DNIC in this phenomenon, we examined the effect of GS-DNIC formation on the ability of iron ions to mediate DNA damage, by treatment of the pUC19 plasmid with physiologically relevant concentrations of GS-DNIC. It was shown that GS-DNIC formation protects against the genotoxic effect of iron ions alone and iron ions in the presence of a naturally abundant antioxidant, GSH. This sheds new light on the iron-related protective effect of NO under the circumstances of oxidative stress.

Adaptation of HepG2 cells to silver nanoparticles-induced stress is based on the pro-proliferative and anti-apoptotic changes in gene expression.

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials due to their antibacterial properties. Owing to the recent boost in the usage of AgNPs-containing products, human exposure to AgNPs is increasing, highlighting the need for careful evaluation of AgNPs toxicity in humans. We used two cellular models, hepatic HepG2 and epithelial A549 cell lines, to study the mechanism of AgNPs-induced toxicity at the cellular level. These two cell lines differ significantly in their response to AgNPs treatment. In the case of A549 cells, a minor decrease in viability and increase in the extent of DNA breakage were observed. A markedly different response to AgNPs was observed in HepG2 cells. In short term, a massive induction of DNA breakage was observed, suggesting that the basal activity of antioxidant defence in these cells was not sufficient to effectively protect them from the nanoparticle-induced oxidative stress. After prolonged exposure, the extent of DNA breakage decreased to the level observed in the control cells proving that a successful adaptation to the new conditions had taken place. The cells that were unable to adapt must have died, as revealed by the Neutral Red assay that indicated less than half viable cells after 24-h treatment with 100 µg/ml of 20nm AgNPs. The gene expression analysis revealed that the observed adaptation was underlain by a pro-proliferative, anti-apoptotic signal leading to up-regulation of the genes promoting proliferation and inflammatory response (EGR1, FOS, JUN, HK2, IL4, MMP10, VEGFA, WISP1, CEBPB, IL8, SELPLG), genes coding the anti-apoptotic proteins (BCL2A1, CCL2) and factors involved in the response to stress (HSPB1, GADD45A). Such a selection of highly resistant population of cells should be taken into account in the case of medical applications of nanoparticles since the sustained proliferative signalling and resistance to cell death are hallmarks of cancer, acquired by the cells in the process of carcinogenesis.

Basal PIR expression in HeLa cells is driven by NRF2 via evolutionary conserved antioxidant response element.

Pirin, a product of the PIR gene, is an iron-binding protein acting as a transcriptional coregulator implicated in the regulation of the NF-κB-related transcription via interaction with RelA (p65), as well as BCL3 and NF-κB1 (p50) proteins. Alterations in pirin expression were observed in various tumors and under oxidative stress conditions. The aim of the present work was to analyze the regulation of the transcription of the human PIR gene. Using constructs containing a different sized PIR promoter and the luciferase reporter genes we found that in HeLa cells PIR transcription is mostly dependent on a highly conserved antioxidant response element located 281 bp downstream of the transcription start site. We have proved that the NRF2 transcription factor binds to this element in vivo and drives the basal PIR expression. We hypothesize that regulation of the PIR expression may constitute a mechanism by which NRF2 is able to modulate the activity of NF-κB and possibly other signaling pathways.

Coordination of iron ions in the form of histidinyl dinitrosyl complexes does not prevent their genotoxicity.

Formation of dinitrosyl iron complexes (DNICs) was observed in a wide spectrum of pathophysiological conditions associated with overproduction of NO. To gain insight into the possible genotoxic effects of DNIC, we examined the interaction of histidinyl dinitrosyl iron complexes (HIS-DNIC) with DNA by means of circular dichroism. Formation of DNIC was monitored by EPR and FT/IR spectroscopy. Vibrational bands for aquated HIS-DNIC are reported. Dichroism results indicate that HIS-DNIC changes the conformation of the DNA in a dose-dependent manner in 10mM phosphate buffer (pH 6). Increase of the buffer pH or ionic strength decreased the effect. Comparison of HIS-DNIC DNA interaction with the effect of hydrated Fe(2+) ion revealed many similarities. The importance of iron ions in HIS-DNIC induced genotoxicity is confirmed by plasmid nicking assay. Treatment of pUC19 plasmid with 1µM HIS-DNIC did not affect the plasmid supercoiling. Higher concentrations of HIS-DNIC induced single strand breaks. The effect was completely abrogated by addition of deferoxamine, a specific strong iron chelator. Our data reveal that formation of HIS-DNIC does not prevent DNA from iron-induced damage and imply that there is no direct interrelationship between iron-NO coordination and their mutual toxicity modulation.

Putative proto-oncogene Pir expression is significantly up-regulated in the spleen and kidney of cytosolic superoxide dismutase-deficient mice.

Iron binding protein pirin was isolated as an interactor of the NFIX transcription factor but it can also form complexes with Bcl3 and NF-κB1(p50). Alterations of pirin expression were observed in various tumors and after exposure to pro-carcinogenic oxidative stressors. The aim of the present work was to study the level of pirin transcription in an in vivo model of oxidative stress, namely, in Sod1-deficient mice. We have found that Sod1(-/-) mice have a significantly elevated level of Pir mRNA in the spleen and kidney but not in the liver, heart, or/and brain. We have also shown that similarly to its human ortholog, the mouse Pir gene transcription level varies significantly between organs. The highest expression was found in the liver and the lowest in the spleen and kidney. Based on literature data, we propose the involvement of Nrf2, AP-1, and NF-κB transcription factors in Pir up-regulation in Sod1(-/-) mice.

Molecular cross-talk between the NRF2/KEAP1 signaling pathway, autophagy, and apoptosis.

Oxidative stress, perturbations in the cellular thiol level and redox balance, affects many cellular functions, including signaling pathways. This, in turn, may cause the induction of autophagy or apoptosis. The NRF2/KEAP1 signaling pathway is the main pathway responsible for cell defense against oxidative stress and maintaining the cellular redox balance at physiological levels. The relation between NRF2/KEAP1 signaling and regulation of apoptosis and autophagy is not well understood. In this hypothesis article we discuss how KEAP1 protein and its direct interactants (such as PGAM5, prothymosin α, FAC1 (BPTF), and p62) provide a molecular foundation for a possible cross-talk between NRF2/KEAP1, apoptosis, and autophagy pathways. We present a hypothesis for how NRF2/KEAP1 may interfere with the cellular apoptosis-regulatory machinery through activation of the ASK1 kinase by a KEAP1 binding partner-PGAM5. Based on very recent experimental evidence, new hypotheses for a cross-talk between NF-κB and the NRF2/KEAP1 pathway in the context of autophagy-related "molecular hub" protein p62 are also presented. The roles of KEAP1 molecular binding partners in apoptosis regulation during carcinogenesis and in neurodegenerative diseases are also discussed.