The molecular chaperone Hsp70 promotes the proteolytic removal of oxidatively damaged proteins by the proteasome

Physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated in underlying of ischemia/reperfusion injury in different organs

Ischemia-reperfusion (I/R) injury, as a pathological phenomenon, takes place when blood supply to an organ is disrupted and then aggravated during restoration of blood flow. Ischemic preconditioning (IPC) is a potent method for attenuating subsequent events of IR damage in numerous organs. IPC protocol is determined by a brief and sequential time periods of I/R before the main ischemia. MicroRNAs are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review introduces the physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated after I/R insult in different organs such as the liver, kidney, heart, brain, and intestine. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2023. Based on these literature studies, IPC/IR intervention can affect cellular mechanisms including oxidative stress, apoptosis, angiogenesis, and inflammation through up-regulation or down-regulation of multiple microRNAs and their target genes.

The Interactive Effects of the Anti-Sea Lice Pesticide Azamethiphos and Temperature on Oxidative Damage and Antioxidant Responses in the Oyster Ostrea chilensis

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L-1, 15 µg L-1 and 100 µg L-1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.

Systematic identification of 20S proteasome substrates

For years, proteasomal degradation was predominantly attributed to the ubiquitin-26S proteasome pathway. However, it is now evident that the core 20S proteasome can independently target proteins for degradation. With approximately half of the cellular proteasomes comprising free 20S complexes, this degradation mechanism is not rare. Identifying 20S-specific substrates is challenging due to the dual-targeting of some proteins to either 20S or 26S proteasomes and the non-specificity of proteasome inhibitors. Consequently, knowledge of 20S proteasome substrates relies on limited hypothesis-driven studies. To comprehensively explore 20S proteasome substrates, we employed advanced mass spectrometry, along with biochemical and cellular analyses. This systematic approach revealed hundreds of 20S proteasome substrates, including proteins undergoing specific N- or C-terminal cleavage, possibly for regulation. Notably, these substrates were enriched in RNA- and DNA-binding proteins with intrinsically disordered regions, often found in the nucleus and stress granules. Under cellular stress, we observed reduced proteolytic activity in oxidized proteasomes, with oxidized protein substrates exhibiting higher structural disorder compared to unmodified proteins. Overall, our study illuminates the nature of 20S substrates, offering crucial insights into 20S proteasome biology.

Cadmium Highlights Common and Specific Responses of Two Freshwater Sentinel Species, Dreissena polymorpha and Dreissena rostriformis bugensis

Zebra mussel (ZM), Dreissena polymorpha, commonly used as a sentinel species in freshwater biomonitoring, is now in competition for habitat with quagga mussel (QM), Dreissena rostriformis bugensis. This raises the question of the quagga mussel's use in environmental survey. To better characterise QM response to stress compared with ZM, both species were exposed to cadmium (100 µg·L-1), a classic pollutant, for 7 days under controlled conditions. The gill proteomes were analysed using two-dimensional electrophoresis coupled with mass spectrometry. For ZM, 81 out of 88 proteoforms of variable abundance were identified using mass spectrometry, and for QM, 105 out of 134. Interestingly, the proteomic response amplitude varied drastically, with 5.6% of proteoforms of variable abundance (DAPs) in ZM versus 9.4% in QM. QM also exhibited greater cadmium accumulation. Only 12 common DAPs were observed. Several short proteoforms were detected, suggesting proteolysis. Functional analysis is consistent with the pleiotropic effects of the toxic metal ion cadmium, with alterations in sulphur and glutathione metabolisms, cellular calcium signalling, cytoskeletal dynamics, energy production, chaperone activation, and membrane events with numerous proteins involved in trafficking and endocytosis/exocytosis processes. Beyond common responses, the sister species display distinct reactions, with cellular response to stress being the main category involved in ZM as opposed to calcium and cytoskeleton alterations in QM. Moreover, QM exhibited greater evidence of proteolysis and cell death. Overall, these results suggest that QM has a weaker stress response capacity than ZM.

Mitochondrial and Cellular Function in Fibroblasts, Induced Neurons, and Astrocytes Derived from Case Study Patients: Insights into Major Depression as a Mitochondria-Associated Disease

The link between mitochondria and major depressive disorder (MDD) is increasingly evident, underscored both by mitochondria's involvement in many mechanisms identified in depression and the high prevalence of MDD in individuals with mitochondrial disorders. Mitochondrial functions and energy metabolism are increasingly considered to be involved in MDD's pathogenesis. This study focused on cellular and mitochondrial (dys)function in two atypical cases: an antidepressant non-responding MDD patient ("Non-R") and another with an unexplained mitochondrial disorder ("Mito"). Skin biopsies from these patients and controls were used to generate various cell types, including astrocytes and neurons, and cellular and mitochondrial functions were analyzed. Similarities were observed between the Mito patient and a broader MDD cohort, including decreased respiration and mitochondrial function. Conversely, the Non-R patient exhibited increased respiratory rates, mitochondrial calcium, and resting membrane potential. In conclusion, the Non-R patient's data offered a new perspective on MDD, suggesting a detrimental imbalance in mitochondrial and cellular processes, rather than simply reduced functions. Meanwhile, the Mito patient's data revealed the extensive effects of mitochondrial dysfunctions on cellular functions, potentially highlighting new MDD-associated impairments. Together, these case studies enhance our comprehension of MDD.

Development of a cell-free strategy to recover aged skeletal muscle after disuse

Extended periods of bed rest and limb immobilization are required for healing post-injury or disease, yet disuse can result in significant muscle atrophy and decreased quality of life in older adults. Physical rehabilitation is commonly prescribed to recover these deficits, yet accumulation of reactive oxygen species and sustained rates of protein degradation persist during the rehabilitation period that can significantly delay or prevent recovery. Pericytes, considered the primary mesenchymal and vascular stromal cell in skeletal muscle, secrete beneficial factors that maintain baseline muscle mass, yet minimal information exists regarding the pericyte response to disuse and recovery. In the current study, single-cell RNA sequencing and functional assays were performed to demonstrate that pericytes in mouse skeletal muscle lose the capacity to synthesize antioxidants during disuse and recovery. This information was used to guide the design of a strategy in which healthy donor pericytes were stimulated with hydrogen peroxide (H2 O2 ) to produce small extracellular vesicles (sEVs) that effectively restored myofibre size in adult and aged muscle after disuse. Proteomic assessment detected 11 differentially regulated proteins in primed sEVs that may account for recovery of muscle, including proteins associated with extracellular matrix composition and anti-inflammatory and antioxidant processes. This study demonstrates that healthy H2 O2 -primed pericyte-derived sEVs effectively improve skeletal muscle recovery after immobilization, presenting a novel acellular approach to rebuild muscle mass in older adults after a period of disuse. KEY POINTS: Previous studies suggest that prolonged oxidative stress is a barrier to skeletal muscle recovery after a period of immobilization. In this study we demonstrate that muscle-resident perivascular stromal cells (pericytes) become dysfunctional and lack the capacity to mount an antioxidant defence after disuse in mice. Hydrogen peroxide treatment of healthy pericytes in vitro simulates the release of small extracellular vesicles (sEVs) that effectively recover skeletal muscle fibre size and extracellular matrix remodelling in young adult and aged mice after disuse. Pericyte-derived sEVs present a novel acellular strategy to recover skeletal muscle after disuse.

Cadmium cardiotoxicity is associated with oxidative stress and upregulated TLR-4/NF-kB pathway in rats; protective role of agomelatine

Cardiotoxicity is one of the hazardous effects of the exposure to the heavy metal cadmium (Cd). Inflammation and oxidative injury are implicated in the cardiotoxic mechanism of Cd. The melatonin receptor agonist agomelatine (AGM) showed promising effects against oxidative and inflammatory responses. This study evaluated the effect of AGM on Cd-induced cardiotoxicity in rats, pointing to its modulatory effect on TLR-4/NF-kB pathway and HSP70. Rats received AGM for 14 days and a single dose of Cd on day 7 and blood and heart samples were collected for analyses. Cd increased serum CK-MB, AST and LDH and caused cardiac tissue injury. Cardiac malondialdehyde (MDA), nitric oxide (NO) and MPO were elevated and GSH, SOD and GST decreased in Cd-administered rats. AGM ameliorated serum CK-MB, AST and LDH and cardiac MDA, NO and MPO, prevented tissue injury and enhanced antioxidants. AGM downregulated serum CRP and cardiac TLR-4, NF-kB, iNOS, IL-6, TNF-α and COX-2 in Cd-administered rats. HSP70 was upregulated in the heart of Cd-challenged rats treated with AGM. In silico findings revealed the binding affinity of AGM with TLR-4 and NF-kB. In conclusion, AGM protected against Cd cardiotoxicity by preventing myocardial injury and oxidative stress and modulating HSP70 and TLR-4/NF-kB pathway.

Homo-oxidized HSPB1 protects H9c2 cells against oxidative stress via activation of KEAP1/NRF2 signaling pathway

Several heat shock proteins are implicated in the endogenous cardioprotective mechanisms, but little is known about the role of heat shock protein beta-1 (HSPB1). This study aims to investigate the oxidation state and role of HSPB1 in cardiomyocytes undergoing oxidative stress and underlying mechanisms. Here, we demonstrate that hydrogen peroxide (H2O2) promotes the homo-oxidation of HSPB1. Cys137 residue of HSPB1 is not only required for it to protect cardiomyocytes against oxidative injury but also modulates its oxidation, phosphorylation at Ser15, and distribution to insoluble cell components after H2O2 treatment. Moreover, Cys137 residue is indispensable for HSPB1 to interact with KEAP1, thus regulating its oxidation and intracellular distribution, subsequently promoting the nuclear translocation of NRF2, and increasing the transcription of GLCM, HMOX1, and TXNRD1. Altogether, these findings provide evidence that Cys137 residue is indispensable for HSPB1 to maintain its redox state and antioxidant activity via activating KEAP1/NRF2 signaling cascade in cardiomyocytes.

The Role of Heat Shock Proteins and Autophagy in Mechanisms Underlying Effects of Sulforaphane on Doxorubicin-Induced Toxicity in HEK293 Cells

Doxorubicin (DOX) is a cytostatic agent belonging to anthracycline group. Important role in mechanism associated with negative effects of DOX plays an oxidative stress. Heat shock proteins (HSPs) are part of mechanisms initiated in response to stressful stimuli and play an important role in cellular responses to oxidative stress through interaction with components of redox signaling. The present work was aimed to study the role of HSPs and autophagy in mechanisms underlying effects of sulforaphane (SFN), a potential activator of Nrf-2, on doxorubicin-induced toxicity in human kidney HEK293 cells. We investigated effects of SFN and DOX on proteins associated with regulation of heat shock response, redox signaling, and autophagy. Results show that SFN significantly reduced cytotoxic effects of DOX. The positive effects of SFN on DOX-induced changes were associated with up-regulation of Nrf-2 and HSP60 protein levels. In the case of another heat shock protein HSP40, SFN increased its levels when was administered alone but not in conditions when cells were exposed to the effects of DOX. Sulforaphane also reversed negative effects of DOX on activities of superoxide dismutases (SODs) and up-regulation of autophagy markers (LC3A/B-II, Atg5, and Atg12). In conclusion, the changes observed in HSP60 are of particular importance in terms of protecting cells from the effects of DOX. Finding that under conditions where SFN reduced cytotoxic effects of DOX were significantly increased protein levels of both Nrf-2 and HSP60 point to the role of HSP60 in mechanisms of redox signaling underlying effects of SFN on DOX-induced toxicity in HEK293 cells. Moreover, data confirmed an important role of autophagy in effects of SFN on DOX-induced toxicity.

Exploration of anti-stress mechanisms in high temperature exposed juvenile golden cuttlefish (Sepia esculenta) based on transcriptome profiling

Sepia esculenta is a cephalopod widely distributed in the Western Pacific Ocean, and there has been growing research interest due to its high economic and nutritional value. The limited anti-stress capacity of larvae renders challenges for their adaptation to high ambient temperatures. Exposure to high temperatures produces intense stress responses, thereby affecting survival, metabolism, immunity, and other life activities. Notably, the molecular mechanisms by which larval cuttlefish cope with high temperatures are not well understood. As such, in the present study, transcriptome sequencing of S. esculenta larvae was performed and 1,927 differentially expressed genes (DEGs) were identified. DEGs were subjected to functional enrichment analyses using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The top 20 terms of biological processes in GO and 20 high-temperature stress-related pathways in KEGG functional enrichment analysis were identified. A protein-protein interaction network was constructed to investigate the interaction between temperature stress-related genes. A total of 30 key genes with a high degree of participation in KEGG signaling pathways or protein-protein interactions were identified and subsequently validated using quantitative RT-PCR. Through a comprehensive analysis of the protein-protein interaction network and KEGG signaling pathway, the functions of three hub genes (HSP90AA1, PSMD6, and PSMA5), which belong to the heat shock protein family and proteasome, were explored. The present results can facilitate further understanding of the mechanism of high temperature resistance in invertebrates and provide a reference for the S. esculenta industry in the context of global warming.

Unfolding the Interactions between Endoplasmic Reticulum Stress and Oxidative Stress

Oxidative stress is caused by an imbalance in cellular redox state due to the accumulation of reactive oxygen species (ROS). While homeostatic levels of ROS are important for cell physiology and signaling, excess ROS can induce a variety of negative effects ranging from damage to biological macromolecules to cell death. Additionally, oxidative stress can disrupt the function of redox-sensitive organelles including the mitochondria and endoplasmic reticulum (ER). In the case of the ER, the accumulation of misfolded proteins can arise due to oxidative stress, leading to the onset of ER stress. To combat ER stress, cells initiate a highly conserved stress response called the unfolded protein response (UPR). While UPR signaling, within the context of resolving ER stress, is well characterised, how UPR mediators respond to and influence oxidative stress is less defined. In this review, we evaluate the interplay between oxidative stress, ER stress and UPR signaling networks. Specifically, we assess how UPR signaling mediators can influence antioxidant responses.

Proteasome Interactome and Its Role in the Mechanisms of Brain Plasticity

Abstract

Proteasomes are highly conserved multienzyme complexes responsible for proteolytic degradation of the short-lived, regulatory, misfolded, and damaged proteins. They play an important role in the processes of brain plasticity, and decrease in their function is accompanied by the development of neurodegenerative pathology. Studies performed in different laboratories both on cultured mammalian and human cells and on preparations of the rat and rabbit brain cortex revealed a large number of proteasome-associated proteins. Since the identified proteins belong to certain metabolic pathways, multiple enrichment of the proteasome fraction with these proteins indicates their important role in proteasome functioning. Extrapolation of the experimental data, obtained on various biological objects, to the human brain suggests that the proteasome-associated proteins account for at least 28% of the human brain proteome. The proteasome interactome of the brain contains a large number of proteins involved in the assembly of these supramolecular complexes, regulation of their functioning, and intracellular localization, which could be changed under different conditions (for example, during oxidative stress) or in different phases of the cell cycle. In the context of molecular functions of the Gene Ontology (GO) Pathways, the proteins of the proteasome interactome mediate cross-talk between components of more than 30 metabolic pathways annotated in terms of GO. The main result of these interactions is binding of adenine and guanine nucleotides, crucial for realization of the nucleotide-dependent functions of the 26S and 20S proteasomes. Since the development of neurodegenerative pathology is often associated with regioselective decrease in the functional activity of proteasomes, a positive therapeutic effect would be obviously provided by the factors increasing proteasomal activity. In any case, pharmacological regulation of the brain proteasomes seems to be realized through the changes in composition and/or activity of the proteins associated with proteasomes (deubiquitinase, PKA, CaMKIIα, etc.).

Handelin Reduces Ultraviolet A-Induced Photoaging by Inhibiting Reactive Oxygen Species Generation and Enhancing Autophagy

Photoaging is mainly caused by the exposure of the skin to ultraviolet (UV) radiation. Among them, damage to human dermal fibroblast (HDF) cells caused by ultraviolet A (UVA) is the main cause of skin aging. Researchers have dedicated to identifying natural compounds from plants to fight against UV radiation-induced photoaging. We previously found that extracts from wild chrysanthemum could prevent acute damage and photoaging induced by UV irradiation. As one of the most abundant ingredients in wild chrysanthemum extract, handelin was hypothesized to have the potential to prevent UVA-induced photoaging of skin fibroblast. In the present study, we report the great potential of handelin in combating UVA-induced photoaging of fibroblasts. We firstly demonstrated that handelin was safe for skin fibroblast as high as a concentration of 0.0125 μM, showing no toxicity on the cells and improved cell viability. Furthermore, handelin can reduce UVA-induced cellular senescence, indicated by a reduced proportion of senescence-associated beta-galactose positive cells and the expression of P21. We then verified that handelin pretreatment markedly attenuated the production of reactive oxygen species (ROS) generation after UVA irradiation. Meanwhile, we found that handelin enhances autophagy after UVA irradiation, and autophagy is involved in the quality control of intracellular proteins after UV-induced damage (partially indirectly via ROS). Therefore, these results suggest that handelin has a very high potential as an effective ingredient against UVA-induced skin aging. Moreover, this provides an important basis for further research on the photoprotective mechanism of handelin.

Alterations in cell viability, reactive oxygen species production, and modulation of gene expression involved in mitogen-activated protein kinase/extracellular regulating kinase signaling pathway by glyphosate and its commercial formulation in hepatocellular carcinoma cells

Glyphosate (N-phosphonomethyl glycine) is a non-selective, organophosphate herbicide widely used in agriculture and forestry. We investigated the possible toxic effects of the glyphosate active compound and its commercial formulation (Roundup Star^®) in the human hepatocellular carcinoma (HepG2) cell line, including their effects on the cytotoxicity, cell proliferation, reactive oxygen species (ROS) levels, and expression of oxidative stress-related genes such as HO-1, Hsp70 Nrf2, L-FABP, and Keap1. MTT and NRU tests indicated that the IC₅₀ values of Roundup Star^® were 219 and 140 μM, respectively, and because glyphosate failed to induce cell death at the studied concentrations, an IC₅₀ value could not be determined for this cell line. Roundup Star at concentrations of 50 and 100 μM significantly increased (39.58% and 52%, respectively) cell proliferation, which 200 μM of glyphosate increased by 35.38%. ROS levels increased by 27.97% and 44.77% for 25 and 100 μM of Roundup Star and 32.74% and 38.63% for 100 and 200 μM of glyphosate exposure. In conclusion, Roundup Star and glyphosate significantly increased expression levels of selected genes related to the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway. This suggests that ROS production and the MAPK/ERK signaling pathway may be key molecular mechanisms in the toxicity of glyphosate in liver cells.

gp130 Activates Mitochondrial Dynamics for Hepatocyte Survival in a Model of Steatohepatitis

Obesity is the main cause of metabolic complications. Fatty liver infiltration is a companion of obesity. NAFLD is associated with impaired energy metabolism with an excess of nutrients. Mitochondrial dynamics are important for the regulation of energy balance, which regulates mitochondrial function, apoptosis, and mitophagy. The aim of this study was to investigate the effect of gp130 on the components of mitochondrial dynamics in a cellular model of steatohepatitis. Addition of IL-6/gp130 contributed to an increase in the percentage of live cells and a decrease in the percentage of dead and apoptotic cells. Addition of IL-6/gp130 increased the expression of NF-kB1 gene and mitochondrial dynamics markers (MFN2 and TFAM) in HepG2 with tBHP/Oleic. Addition of IL-6 or gp130 reduced the expression of cytoprotector genes (HSF1 and HSP70) in HepG2 cell cultures with tBHP/Oleic. Increased mitochondrial dynamics gene activity protected against HepG2 cell death in the steatohepatitis model. Trans-signaling resulted in increased TFAM and MAPLC3B, and decreased DNM1L gene expression in HepG2 with tBHP/Oleic.

Effects of carnosine on the embryonic development and TiO2 nanoparticles-induced oxidative stress on Zebrafish

Oxidative stress is due to an unbalance between pro-oxidants, such as reactive oxygen (ROS) and nitrogen (RNS) species, and antioxidants/antioxidant system. Under physiological conditions these species are involved in different cellular processes such as cellular homeostasis and immune response, while an excessive production of ROS/RNS has been linked to the development of various diseases such as cancer, diabetes, and Alzheimer's disease. In this context, the naturally occurring dipeptide carnosine has shown the ability to scavenge ROS, counteract lipid peroxidation, and inhibit proteins oxidation. Titanium dioxide nanoparticles (TiO₂-NPs) have been widely used to produce cosmetics, in wastewater treatment, in food industry, and in healthcare product. As consequence, these NPs are often released into aquatic environments. The Danio rerio (commonly called zebrafish) embryos exposure to TiO₂-NPs did not affect the hatching rate, but induced oxidative stress. According to this scenario, in the present study, we first investigated the effects of carnosine exposure and of a sub-toxic administration of TiO₂-NPs on the development and survival of zebrafish embryos/larvae measured through the acute embryo toxicity test (FET-Test). Zebrafish larvae represent a useful model to study oxidative stress-linked disorders and to test antioxidant molecules, while carnosine was selected based on its well-known multimodal mechanism of action that includes a strong antioxidant activity. Once the basal effects of carnosine were assessed, we then evaluated its effects on TiO₂-NPs-induced oxidative stress in zebrafish larvae, measured in terms of total ROS production (measured with 2,7-dichlorodihydrofluorescein diacetate probe) and protein expression by immunohistochemistry of two cellular stress markers, 70 kDa-heat shock protein (Hsp70) and metallothioneins (MTs). We demonstrated that carnosine did not alter the phenotypes of both embryos and larvae of zebrafish at different hours post fertilization. Carnosine was instead able to significantly decrease the enhancement of ROS levels in zebrafish larvae exposed to TiO₂-NPs and its antioxidant effect was paralleled by the rescue of the protein expression levels of Hsp70 and MTs. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of pathologies characterized by oxidative stress such as neurodegenerative disorders.

The Proteasome and Ageing

The proteasome is a multi-subunit proteolytic complex that functions to degrade normal proteins for physiological regulation and to eliminate abnormal proteins for cellular protection. Generally, the proteasome targets substrate proteins that are marked by attachment of multiple ubiquitin molecules. In various types of cells in an organism, damage to proteins occurs both from internal sources such as reactive oxygen species and from external ones such as UV radiation from the sun. The proteasome functions to protect the cells by degrading damaged proteins. With ageing, however, the capacity of the proteasome to degrade damaged proteins is reduced as indicated by evidence gathered by many studies. Studies on ageing in muscle, skin, and brain show that with age catalytic activity of the proteasome is decreased and the expression of proteasome subunits is altered. Age-related accumulation of damaged or misfolded proteins causes further reduction of proteasome activity. Abnormal proteins also accumulate as a result of age-related neurodegenerative diseases. Deficits in proteasome activity might be responsible for accumulation of protein aggregates and thus contribute to the pathology. Results from several studies suggest a link between the proteasome and longevity. This chapter reviews the various ways in which the proteasome is associated with the ageing process and examines evidence gathered from investigations on cultured cells, model organisms, and humans.

Oxidative Stress, HSP70/HSP90 and eNOS/iNOS Serum Levels in Professional Divers during Hyperbaric Exposition

Heat shock proteins (HSPs) have protective effects against oxidative stress and decompression sickness. Nitric oxide may reduce bubble formation during decompression and its activity is regulated by HSPs. A simulated dive can cause the HSP response. The aim of this study was to describe the effect of simulated dives on the antioxidant system, HSPs, and nitric oxide synthase response and demonste the relationship between the concentration of HSPs and the intensification of oxidative stress. A total of 20 healthy professional divers took part in training, consisting of simulated dry dives in a hyperbaric chamber and split into experiment I (30 m exposure, 400 kPa) and experiment II (60 m exposure, 700 kPa) over 24 h. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and the concentrations of malondialdehyde (MDA), heat shock protein 70 (HSP70), heat shock protein 90 (HSP90), endothelial (eNOS) and inducible (iNOS) nitric oxide synthase were measured. Increases in the activity of SOD and MDA concentration were demonstrated. The activity of GPx depended on the dive profile. The HSP70 serum level in both experiments was significantly lower after the dives. The mean HSP90 level was significantly higher after the simulated dive at 60 m. A significant relationship between HSP concentration and SOD/GPx activity was demonstrated. eNOS concentration increased after 60 m exposure. No change in iNOS concentration was observed. In conclusions, the simulated dive significantly affected the antioxidant system, heat shock protein expression and nitric oxide synthase; however, the changes depend on the diving conditions. There is a relationship between the expression of HSPs and the intensity of oxidative stress.

HSc70 interactome reveal major role of macroautophagy and minor role of chaperone mediated autophagy in K-Ras G12V cell proliferation and survival

Constitutively active K-Ras oncogene mutation at G12V changes the proteome of cells and activates macroautophagy for cell advantage. Inhibition of macroautophagy impairs K-Ras mediated tumor progression to a limited extent with increase of spontaneous tumors due to poorly understood mechanisms. Here, we show that inhibition of macroautophagy in K-Ras G12V mouse embryonic fibroblasts (MEFs) hyper activates chaperon mediated autophagy (CMA). Quantitative identification of CMA substrates through co-immunoprecipitation of CMA component heat shock cognate 70 (Hsc70) demonstrates a shift of proteins from macroautophagy to CMA mediated degradation. However, macroautophagy impairment show significant inhibition on proliferation and CMA hyper activation provides a basal support to macroautophagy-inhibited MEFs for survival. On the other hand, K-Ras G12V MEFs impaired of CMA reduces number of Hsc70 clients but activated macroautophagy significantly compensated CMA loss. Nonetheless, co-inhibition of CMA and macroautophagy had a synergistic detrimental effect on both proliferation and survival of MEFs expressing K-Ras G12V mutant. Our results point to K-Ras G12V MEFs dependency on macroautophagy and CMA partly compensates its loss for survival but not hyper-proliferation; implicating that targeting both macroautophagy and CMA as a promising therapeutic target in G12V mutation associated K-Ras cancers. SIGNIFICANCE: The present study provides a framework of Hsc70 interacting proteins, which differentially interact with Hsc70 in response to autophagy alterations. The role of proteins accumulation and induced proteo-toxicity could be underlying factor in macroautophagy and CMA co-inhibited K-Ras G12V MEFs phenotype. Our study provides rational for adaptive mechanisms in K-Ras tumors inhibited with different autophagy pathways and also supports targeting both macroautophagy and CMA simultaneously as therapeutic target. At the same time current study will help in characterizing the underlying cellular processes that may play a role in escaping tutor suppressor role CMA and macroautophagy in cancers harboring K-Ras G12V mutation that may be further utilized to identify molecular targets for K-Ras-driven cancers.

Hsp70 in Redox Homeostasis

Cellular redox homeostasis is precisely balanced by generation and elimination of reactive oxygen species (ROS). ROS are not only capable of causing oxidation of proteins, lipids and DNA to damage cells but can also act as signaling molecules to modulate transcription factors and epigenetic pathways that determine cell survival and death. Hsp70 proteins are central hubs for proteostasis and are important factors to ameliorate damage from different kinds of stress including oxidative stress. Hsp70 members often participate in different cellular signaling pathways via their clients and cochaperones. ROS can directly cause oxidative cysteine modifications of Hsp70 members to alter their structure and chaperone activity, resulting in changes in the interactions between Hsp70 and their clients or cochaperones, which can then transfer redox signals to Hsp70-related signaling pathways. On the other hand, ROS also activate some redox-related signaling pathways to indirectly modulate Hsp70 activity and expression. Post-translational modifications including phosphorylation together with elevated Hsp70 expression can expand the capacity of Hsp70 to deal with ROS-damaged proteins and support antioxidant enzymes. Knowledge about the response and role of Hsp70 in redox homeostasis will facilitate our understanding of the cellular knock-on effects of inhibitors targeting Hsp70 and the mechanisms of redox-related diseases and aging.

The innate immune system and fever under redox control: A Narrative Review

ABSTRACT:

In living cells, redox potential is vitally important for normal physiological processes that are closely regulated by antioxidants, free amino acids and proteins that either have reactive oxygen and nitrogen species capture capability or can be compartmentalized. Although hundreds of experiments support the regulatory role of free radicals and their derivatives, several authors continue to claim that these perform only harmful and non-regulatory functions. In this paper we show that countless intracellular and extracellular signal pathways are directly or indirectly linked to regulated redox processes. We also briefly discuss how artificial oxidative stress can have important therapeutic potential and the possible negative effects of popular antioxidant supplements.

The responses of harmful dinoflagellate Karenia mikimotoi to simulated ocean acidification at the transcriptional level

The HAB-forming, toxic dinoflagellate Karenia mikimotoi, previously found to benefit from ocean acidification (OA), was cultivated to investigate its transcriptional response to simulated OA for 30 generations. Batch cultures were grown under two CO₂ concentrations, 450 (control) and 1100 (simulated OA) μatm, and physiological parameters [growth, pigments, catalase (CAT), glutathione reductase (GR), and superoxide dismutase (SOD) activity], as well as transcriptomes (obtained via RNA-seq), were compared. Chlorophyll a (Chl a) and carotenoid (Caro) contents, as well as CAT and GR activities, were significantly increased under OA conditions. Transcriptomic analysis revealed 2,490 differentially expressed unigenes in response to OA, which comprised 1.54% of all unigenes. A total of 1,121 unigenes were upregulated, and 1,369 unigenes were downregulated in OA compared to control conditions. The downregulated expression of bicarbonate transporter and carbonic anhydrase genes was a landmark of OA acclimation. Key genes involved in energy metabolism, e.g., photosynthesis, tricarboxylic acid cycle, oxidative phosphorylation, and nitrogen metabolism, were highly upregulated under OA, contributing to increases in the Chl a (55.05%) and Caro (28.37%). The enhanced antioxidant enzyme activities (i.e. CAT, GR) and upregulated genes (i.e. glutathione peroxidase, ascorbate peroxidase, heat shock protein, 20S proteasome, aldehyde dehydrogenase, and apolipoprotein) benefit cells against the potential lower pH stress condition under OA. In addition, the downregulation of four genes associated with motility suggested that the preserved energy could further boost growth. In conclusion, the present study suggests that K. mikimotoi exhibits efficient gene expression regulation for the utilization of energy and resistance to OA-induced stress. Taken together, K. mikimotoi appeared as a tolerant species in response to OA. Thus, more extensive algal blooms that threaten marine organisms are likely in the future. These findings expand current knowledge on the gene expression of HAB-forming species in response to future OA.

Oxidative distress in aging and age-related diseases: Spatiotemporal dysregulation of protein oxidation and degradation

The concept of oxidative distress had arisen from the assessment of cellular response to high concentrations of reactive species that result from an imbalance between oxidants and antioxidants and cause biomolecular damage. The intracellular distribution and flux of reactive species dramatically change in time and space contributing to the remodeling of the redox landscape and sensitivity of protein residues to oxidants. Here, we hypothesize that compromised spatiotemporal control of generation, conversions, and removal of reactive species underlies protein damage and dysfunction of protein degradation machineries. This leads to the accumulation of oxidatively damaged proteins resulted in an age-dependent decline in the organismal adaptability to oxidative stress. We highlight recent data obtained with the use of various cell cultures, animal models, and patients on irreversible and non-repairable oxidation of key redox-sensitive residues. Multiple reaction products include peptidyl hydroperoxides, alcohols, carbonyls, and carbamoyl moieties as well as Tyr-Tyr, Trp-Tyr, Trp-Trp, Tyr-Cys, His-Lys, His-Arg, and Tyr-Lys cross-links. These lead to protein fragmentation, misfolding, covalent cross-linking, oligomerization, aggregation, and ultimately, causing impaired protein function and turnover. 20S proteasome and autophagy-lysosome pathways are two major types of machinery for the degradation and elimination of oxidatively damaged proteins. Spatiotemporal dysregulation of these pathways under oxidative distress conditions is implicated in aging and age-related disorders such as neurodegenerative and cardiovascular diseases and diabetes. Future investigations in this field allow the discovery of new drugs to target components of dysregulated cell signaling and protein degradation machinery to combat aging and age-related chronic diseases.

Oxidative and salt stresses alter the 26S proteasome holoenzyme and associated protein profiles in Arabidopsis thaliana

BACKGROUND

The 26S proteasome, canonically composed of multi-subunit 19S regulatory (RP) and 20S core (CP) particles, is crucial for cellular proteostasis. Proteasomes are re-modeled, activated, or re-localized and this regulation is critical for plants in response to environmental stresses. The proteasome holoenzyme assembly and dissociation are therefore highly dynamic in vivo. However, the stoichiometric changes of the plant proteasomes and how proteasome associated chaperones vary under common abiotic stresses have not been systematically studied.

RESULTS

Here, we studied the impact of abiotic stresses on proteasome structure, activity, and interacting partners in Arabidopsis thaliana. We analyzed available RNA expression data and observed that expressions of proteasome coding genes varied substantially under stresses; however, the protein levels of a few key subunits did not change significantly within 24 h. Instead, a switch in the predominant proteasome complex, from 26S to 20S, occurs under oxidative or salt stress. Oxidative stress also reduced the cellular ATP content and the association of HSP70-family proteins to the 20S proteasome, but enhanced the activity of cellular free form CP. Salt stress, on the other hand, did not affect cellular ATP level, but caused subtle changes in proteasome subunit composition and impacted bindings of assembly chaperones. Analyses of an array of T-DNA insertional mutant lines highlighted important roles for several putative assembly chaperones in seedling establishment and stress sensitivity. We also observed that knockout of PBAC1, one of the α-ring assembly chaperones, resulted in reduced germination and tearing of the seed coat following sterilization.

CONCLUSIONS

Our study revealed an evolutionarily conserved mechanism of proteasome regulation during oxidative stress, involving dynamic regulation of the holoenzyme formation and associated regulatory proteins, and we also identified a novel role of the PBAC1 proteasome assembly chaperone in seed coat development.

Redox metabolism: ROS as specific molecular regulators of cell signaling and function

Redox reactions are intrinsically linked to energy metabolism. Therefore, redox processes are indispensable for organismal physiology and life itself. The term reactive oxygen species (ROS) describes a set of distinct molecular oxygen derivatives produced during normal aerobic metabolism. Multiple ROS-generating and ROS-eliminating systems actively maintain the intracellular redox state, which serves to mediate redox signaling and regulate cellular functions. ROS, in particular hydrogen peroxide (H₂O₂), are able to reversibly oxidize critical, redox-sensitive cysteine residues on target proteins. These oxidative post-translational modifications (PTMs) can control the biological activity of numerous enzymes and transcription factors (TFs), as well as their cellular localization or interactions with binding partners. In this review, we describe the diverse roles of redox regulation in the context of physiological cellular metabolism and provide insights into the pathophysiology of diseases when redox homeostasis is dysregulated.

The Accumulation and Molecular Effects of Trimethylamine N-Oxide on Metabolic Tissues: It's Not All Bad

Since elevated serum levels of trimethylamine N-oxide (TMAO) were first associated with increased risk of cardiovascular disease (CVD), TMAO research among chronic diseases has grown exponentially. We now know that serum TMAO accumulation begins with dietary choline metabolism across the microbiome-liver-kidney axis, which is typically dysregulated during pathogenesis. While CVD research links TMAO to atherosclerotic mechanisms in vascular tissue, its molecular effects on metabolic tissues are unclear. Here we report the current standing of TMAO research in metabolic disease contexts across relevant tissues including the liver, kidney, brain, adipose, and muscle. Since poor blood glucose management is a hallmark of metabolic diseases, we also explore the variable TMAO effects on insulin resistance and insulin production. Among metabolic tissues, hepatic TMAO research is the most common, whereas its effects on other tissues including the insulin producing pancreatic β-cells are largely unexplored. Studies on diseases including obesity, diabetes, liver diseases, chronic kidney disease, and cognitive diseases reveal that TMAO effects are unique under pathologic conditions compared to healthy controls. We conclude that molecular TMAO effects are highly context-dependent and call for further research to clarify the deleterious and beneficial molecular effects observed in metabolic disease research.

Transcriptomic analysis of the mouse retina after acute and chronic normobaric and hypobaric hypoxia

Oxygen delivery to the retinal pigment epithelium and the outer retina is essential for metabolism, function, and survival of photoreceptors. Chronically reduced oxygen supply leads to retinal pathologies in patients and causes age-dependent retinal degeneration in mice. Hypoxia can result from decreased levels of inspired oxygen (normobaric hypoxia) or reduced barometric pressure (hypobaric hypoxia). Since the response of retinal cells to chronic normobaric or hypobaric hypoxia is mostly unknown, we examined the effect of six hypoxic conditions on the retinal transcriptome and photoreceptor morphology. Mice were exposed to short- and long-term normobaric hypoxia at 400 m or hypobaric hypoxia at 3450 m above sea level. Longitudinal studies over 11 weeks in normobaric hypoxia revealed four classes of genes that adapted differentially to the hypoxic condition. Seventeen genes were specifically regulated in hypobaric hypoxia and may affect the structural integrity of the retina, resulting in the shortening of photoreceptor segment length detected in various hypoxic groups. This study shows that retinal cells have the capacity to adapt to long-term hypoxia and that consequences of hypobaric hypoxia differ from those of normobaric hypoxia. Our datasets can be used as references to validate and compare retinal disease models associated with hypoxia.

An astonishing wealth of new proteasome homologs

Motivation

The proteasome is the main proteolytic machine for targeted protein degradation in archaea and eukaryotes. While some bacteria also possess the proteasome, most of them contain a simpler and more specialized homolog, the heat shock locus V protease. In recent years, three further homologs of the proteasome core subunits have been characterized in prokaryotes: Anbu, BPH and connectase. With the inclusion of these members, the family of proteasome-like proteins now exhibits a range of architectural and functional forms, from the canonical proteasome, a barrel-shaped protease without pronounced intrinsic substrate specificity, to the monomeric connectase, a highly specific protein ligase.

Results

We employed systematic sequence searches to show that we have only seen the tip of the iceberg so far and that beyond the hitherto known proteasome homologs lies a wealth of distantly related, uncharacterized homologs. We describe a total of 22 novel proteasome homologs in bacteria and archaea. Using sequence and structure analysis, we analyze their evolutionary history and assess structural differences that may modulate their function. With this initial description, we aim to stimulate the experimental investigation of these novel proteasome-like family members.

Availability and implementation

The protein sequences in this study are searchable in the MPI Bioinformatics Toolkit (https://toolkit.tuebingen.mpg.de) with ProtBLAST/PSI-BLAST and with HHpred (database ‘proteasome_homologs’). The following data are available at https://data.mendeley.com/datasets/t48yhff7hs/3: (i) sequence alignments for each proteasome-like homolog, (ii) the coordinates for their structural models and (iii) a cluster-map file, which can be navigated interactively in CLANS and gives direct access to all the sequences in this study.

Supplementary information

Supplementary data are available at Bioinformatics online.

Deubiquitinase UCHL1 Maintains Protein Homeostasis through the PSMA7-APEH-Proteasome Axis in High-grade Serous Ovarian Carcinoma

High-grade serous ovarian cancer (HGSOC) is characterized by chromosomal instability, DNA damage, oxidative stress, and high metabolic demand that exacerbate misfolded, unfolded, and damaged protein burden resulting in increased proteotoxicity. However, the underlying mechanisms that maintain protein homeostasis to promote HGSOC growth remain poorly understood. This study reports that the neuronal deubiquitinating enzyme, ubiquitin carboxyl-terminal hydrolase L1 (UCHL1), is overexpressed in HGSOC and maintains protein homeostasis. UCHL1 expression was markedly increased in HGSOC patient tumors and serous tubal intraepithelial carcinoma (HGSOC precursor lesions). High UCHL1 levels correlated with higher tumor grade and poor patient survival. UCHL1 inhibition reduced HGSOC cell proliferation and invasion, as well as significantly decreased the in vivo metastatic growth of ovarian cancer xenografts. Transcriptional profiling of UCHL1-silenced HGSOC cells revealed downregulation of genes implicated with proteasome activity along with upregulation of endoplasmic reticulum stress-induced genes. Reduced expression of proteasome subunit alpha 7 (PSMA7) and acylaminoacyl peptide hydrolase (APEH), upon silencing of UCHL1, resulted in a significant decrease in proteasome activity, impaired protein degradation, and abrogated HGSOC growth. Furthermore, the accumulation of polyubiquitinated proteins in the UCHL1-silenced cells led to attenuation of mTORC1 activity and protein synthesis, and induction of terminal unfolded protein response. Collectively, these results indicate that UCHL1 promotes HGSOC growth by mediating protein homeostasis through the PSMA7-APEH-proteasome axis. IMPLICATIONS: This study identifies the novel links in the proteostasis network to target protein homeostasis in HGSOC and recognizes the potential of inhibiting UCHL1 and APEH to sensitize cancer cells to proteotoxic stress in solid tumors.

Dietary Natural Plant Extracts Can Promote Growth and Modulate Oxidative Status of Senegalese Sole Postlarvae under Standard/Challenge Conditions

Simple Summary

Oxidative stress has a direct impact on the welfare of fish, affecting growth performance and health status. Natural plant extracts present a high antioxidant capacity, due to a diversity and abundant content of polyphenols. Thus, the aim of this work was to identify if plant extracts, such as curcumin, green tea, and grape seeds, can promote oxidative status, and ultimately, enhance the growth and physiological stress response of postlarvae. Our results showed that plant extracts can improve the growth and oxidative status of the fish. Moreover, they may help fish to cope under stressful conditions. Dietary formulations with natural supplements may be a viable strategy to improve fish robustness during early life stages, and can therefore contribute to the development of aquafeeds and promote the sustainability of aquaculture production.

Abstract

Plant extracts are known for their high content and diversity of polyphenols, which can improve fish oxidative status. A growth trial with Senegalese sole postlarvae (45 days after hatching) fed with one of four experimental diets—control (CTRL), and supplemented with curcumin (CC), green tea (GT), and grape seed (GS) extracts—was performed to assess if supplementation could improve growth performance and oxidative status. At the end of the growth trial, postlarvae were submitted to a thermal stress to assess their robustness. Sole growth was improved by CC and GS diets when compared to those fed the CTRL. CC and CTRL postlarvae presented the lowest oxidative damage (lipid peroxidation and protein carbonylation values). Stress-related biomarkers (heat shock protein 70 and glutathione-S-transferase) decreased in CC fish compared to those fed the CTRL diet, which might be due to a direct antioxidant capacity. In contrast, oxidative damage increased in GT and GS sole reared in standard conditions. However, after a thermal stress, GT and GS diets prevented the increase of protein carbonylation content and the decrease of antioxidant glutathione, depending on exposure time. Overall, dietary supplementation with natural extracts modulated oxidative status and stress response after a short/long-term exposure to temperature.

An update in toxicology of ageing

The field of ageing research has been rapidly advancing in recent decades and it had provided insight into the complexity of ageing phenomenon. However, as the organism-environment interaction appears to significantly affect the organismal pace of ageing, the systematic approach for gerontogenic risk assessment of environmental factors has yet to be established. This puts demand on development of effective biomarker of ageing, as a relevant tool to quantify effects of gerontogenic exposures, contingent on multidisciplinary research approach. Here we review the current knowledge regarding the main endogenous gerontogenic pathways involved in acceleration of ageing through environmental exposures. These include inflammatory and oxidative stress-triggered processes, dysregulation of maintenance of cellular anabolism and catabolism and loss of protein homeostasis. The most effective biomarkers showing specificity and relevancy to ageing phenotypes are summarized, as well. The crucial part of this review was dedicated to the comprehensive overview of environmental gerontogens including various types of radiation, certain types of pesticides, heavy metals, drugs and addictive substances, unhealthy dietary patterns, and sedentary life as well as psychosocial stress. The reported effects in vitro and in vivo of both recognized and potential gerontogens are described with respect to the up-to-date knowledge in geroscience. Finally, hormetic and ageing decelerating effects of environmental factors are briefly discussed, as well.

HSP70-3 Interacts with Phospholipase Dδ and Participates in Heat Stress Defense

Heat shock proteins (HSPs) function as molecular chaperones and are key components responsible for protein folding, assembly, translocation, and degradation under stress conditions. However, little is known about how HSPs stabilize proteins and membranes in response to different hormonal or environmental cues in plants. Here, we combined molecular, biochemical, and genetic approaches to elucidate the involvement of cytosolic HSP70-3 in plant stress responses and the interplay between HSP70-3 and plasma membrane (PM)-localized phospholipase Dδ (PLDδ) in Arabidopsis (Arabidopsis thaliana). Analysis using pull-down, coimmunoprecipitation, and bimolecular fluorescence complementation revealed that HSP70-3 specifically interacted with PLDδ. HSP70-3 bound to microtubules, such that it stabilized cortical microtubules upon heat stress. We also showed that heat shock induced recruitment of HSP70-3 to the PM, where HSP70-3 inhibited PLDδ activity to mediate microtubule reorganization, phospholipid metabolism, and plant thermotolerance, and this process depended on the HSP70-3-PLDδ interaction. Our results suggest a model whereby the interplay between HSP70-3 and PLDδ facilitates the re-establishment of cellular homeostasis during plant responses to external stresses and reveal a regulatory mechanism in regulating membrane lipid metabolism.

Root endophytic fungus Serendipita indica modulates barley leaf blade proteome by increasing the abundance of photosynthetic proteins in response to salinity

AIMS

The present study aimed at analysing the proteome pattern of the leaf blade of barley (Hordeum vulgare L.) in Serendipita indica-colonised plants to decipher the molecular mechanism of S. indica-mediated salt stress. This work is aligned with our previous research on barley leaf sheath to study proteomic pattern variability in leaf blade and sheath of barley plant in response to salinity and S. indica inoculation.

METHODS AND RESULTS

The experiment was conducted using a completely randomised factorial design with four replications and two treatments: salinity (0 and 300 mmol l^-1 NaCl) and fungus (noninoculated and S. indica-inoculated). The leaf blades of the salt-treated S. indica-colonised and noninoculated plants were harvested after 2 weeks of salt treatment for the physiological and proteomic analyses. After exposure to 300 mmol l^-1 NaCl, shoot dry matter production in noninoculated control plants decreased 84% which was about twofold higher than inoculated plants with S. indica. However, the accumulation of sodium in the shoot of S. indica-inoculated plants was significantly lower than the control plants. Analysis of the proteome profile revealed a high number of significantly up-regulated proteins involved in photosynthesis (26 out of 42 identified proteins).

CONCLUSIONS

The results demonstrated how the enhanced plant growth and salt stress resistance induced by S. indica was positively associated with the up-regulation of several proteins involved in photosynthesis and carbohydrate metabolism. In fact, S. indica improved photosynthesis in order to reach the best possible performance of the host plant under salt stress.

SIGNIFICANCE AND IMPACT OF THE STUDY

Current research provides new insight into the mechanism applied by S. indica in reducing the negative impacts of salt stress in barley at physiological and molecular levels.

Andrographolide upregulates protein quality control mechanisms in cell and mouse through upregulation of mTORC1 function

BACKGROUND

Heat shock response (HSR), a component of cellular protein quality control mechanisms, is defective in different neurodegenerative conditions such as Parkinson's disease (PD). Forced upregulation of heat shock factor 1 (HSF1), an HSR master regulator, showed therapeutic promise in PD models. Many of the reported small-molecule HSF1 activators have limited functions. Therefore, identification and understanding the molecular bases of action of new HSF1 activating molecules is necessary.

METHOD

We used a cell-based reporter system to screen Andrographis paniculata leaf extract to isolate andrographolide as an inducer of HSF1 activity. The andrographolide activity was characterized by analyzing its role in different protein quality control mechanisms.

RESULT

We find that besides ameliorating the PD in MPTP-treated mice, andrographolide upregulated different machineries controlled by HSF1 and NRF2 in both cell and mouse brain. Andrographolide achieves these functions through mTORC1 activated via p38 MAPK and ERK pathways. NRF2 activation is reflected in the upregulation of proteasome as well as autophagy pathways. We further show that NRF2 activation is mediated through mTORC1 driven phosphorylation of p62/sequestosome 1. Studies with different cell types suggested that andrographolide-mediated induction of ROS level underlies all these activities in agreement with the upregulation of mTORC1 and NRF2-antioxidant pathway in mice.

CONCLUSION

Andrographolide through upregulating HSF1 activity ameliorates protein aggregation induced cellular toxicity.

GENERAL SIGNIFICANCE

Our results provide a reasonable basis for use of andrographolide in the therapy regimen for the treatment of PD.

Effects and Mechanism of Noninvasive Positive-Pressure Ventilation in a Rat Model of Heart Failure Due to Myocardial Infarction

BACKGROUND Impaired heart function induced by myocardial infarction is a leading cause of chronic heart failure (HF). This study aimed to investigate the effects and mechanism of noninvasive positive-pressure ventilation (NIPPV) in a rat model of HF due to myocardial infarction. MATERIAL AND METHODS To explore the therapeutic effect and mechanism of NIPPV on acute myocardial infarction-induced HF, we established a rat model of HF by ligating the anterior descending branch of the left coronary artery and confirmed by ultrasonic cardiography and brain natriuretic peptide 45 detection. RESULTS The levels of heat-shock protein (HSP)-70 increased and matrix metalloproteinase (MMP)-2, MMP-9, and tumor necrosis factor (TNF)-alpha decreased in the group that received NIPPV treatment compared with the control group. In addition, the histopathologic results showed less severe inflammatory infiltration and a smaller area of myocardial fibrosis in the NIPPV treatment group. CONCLUSIONS In a rat model of HF due to myocardial infarction, NIPPV resulted in increased levels of HSP70 and reduced expression of MMP2, MMP9, and TNF-alpha and reduced myocardial neutrophil infiltration and fibrosis. Taken together, we showed that NIPPV is an effective treatment for HF induced by myocardial infarction by inhibiting the release of inflammatory factors and preventing microvascular embolism.

Lipotoxicity dysregulates the immunoproteasome in podocytes and kidneys in type 2 diabetes

Palmitic acid (PA) leads to lipotoxicity in type 2 diabetes and induces oxidative stress in podocytes. Oxidized cellular proteins are degraded by proteasomes. The role of proteasomes in PA- or oxidative stress-induced podocyte injury and pathogenesis of diabetic nephropathy (DN) is unknown. We investigated the effects of PA on expression of 20S and 26S proteasomes, proteasome activator 28 (PA28) regulators, and the immunoproteasome in cultured podocytes and renal cortical tissues of db/db and db/m mice using Western blot analysis. Glomerular areas and glomerular basement membrane (GBM) widths of db/db and db/m mice were examined using morphometry. Short-term incubation of PA or low levels of H₂O₂ upregulated only the immunoproteasome in cultured podocytes. Long-term exposure of podocytes to PA ultimately downregulated the immunoproteasome as with other proteasomes, whereas oleic acid (OA) or eicosapentaenoic acid (EPA) restored the PA-induced decreased protein levels. In db/db mice, renal cortical immunoproteasome expression with PA28α was significantly decreased compared with db/m mice, and glomerular areas and GBM widths were significantly increased compared with db/m mice. Feeding of an OA-rich olive oil or EPA-rich fish oil protected db/db mice against the reduced renal cortical immunoproteasome expression, glomerular enlargement, and GBM thickening. These results demonstrate that lipotoxicity downregulates the immunoproteasome in podocytes and kidneys in type 2 diabetes and that OA and EPA protected type 2 diabetic mice against decreased renal cortical immunoproteasome expression and the progression of DN. Given this, lipotoxicity-induced podocyte injury with impaired immunoproteasome expression appears to play an important role in the pathogenesis of DN.NEW & NOTEWORTHY In podocytes, PA rapidly induced immunoproteasome expression but ultimately decreased it, while OA and EPA restored the decreased immunoproteasome levels. In the renal cortex of type 2 diabetic mice, immunoproteasome expression was significantly decreased, whereas feeding of OA-rich olive oil or EPA-rich fish oil diets protected them against the reduced immunoproteasome expression and progression of diabetic nephropathy. Thus, lipotoxicity-induced podocyte injury with impaired immunoproteasome expression may be related to the pathogenesis of diabetic nephropathy.

Inorganic mercury effects on biomarker gene expressions of a freshwater amphipod at two temperatures

Mercury (Hg) is a global contaminant resulting of both natural processes and human activities. In aquatic environments, studies conducted on vertebrates highlighted changes of gene expression or activity of antitoxic and oxidative enzymes. However, although Hg is a highly toxic compound in aquatic environments, only a few studies have evaluated the lethal and sublethal effects of inorganic Hg on Gammarus sp. Therefore, this study aimed at evaluating the effects of inorganic Hg (HgCl₂) on the expression of 17 genes involved in crucial biological functions or mechanisms for organisms, namely respiration, osmoregulation, apoptosis, immune and endocrine system, and antioxidative and antitoxic defence systems. The study was performed in males of the freshwater amphipod Gammarus pulex exposed to two environmentally relevant concentrations (50 and 500 ng/L) at two temperature regime fluctuations (16 °C and 20 °C +/-2 °C) for 7 and 21 days. Results showed that G. pulex mortality was dependent on Hg concentration and temperature; the higher the concentration and temperature, the higher the mortality rate. In addition, the Integrated Biomarker Response emphasized that HgCl₂ toxicity was dependent on the concentration, time and temperature of exposure. Overall, antioxidant and antitoxic defences, as well as the endocrine and immune systems, were the biological functions most impacted by Hg exposure (based on the concentration, duration, and temperature tested). Conversely, osmoregulation was the least affected biological function. The results also demonstrated a possible adaptation of G. pulex after 21 days at 500 ng/L, regardless of the exposure temperature. This study allowed us to show that Hg deregulates many crucial biological functions after a short exposure, but that during a long exposure, an adaptation phenomenon could occur, regardless of temperature.

Heat Shock Proteins in Oxidative Stress and Ischemia/Reperfusion Injury and Benefits from Physical Exercises: A Review to the Current Knowledge

Heat shock proteins (HSPs) are molecular chaperones produced in response to oxidative stress (OS). These proteins are involved in the folding of newly synthesized proteins and refolding of damaged or misfolded proteins. Recent studies have been focused on the regulatory role of HSPs in OS and ischemia/reperfusion injury (I/R) where reactive oxygen species (ROS) play a major role. ROS perform many functions, including cell signaling. Unfortunately, they are also the cause of pathological processes leading to various diseases. Biological pathways such as p38 MAPK, HSP70 and Akt/GSK-3β/eNOS, HSP70, JAK2/STAT3 or PI3K/Akt/HSP70, and HSF1/Nrf2-Keap1 are considered in the relationship between HSP and OS. New pathophysiological mechanisms involving ROS are being discovered and described the protein network of HSP interactions. Understanding of the mechanisms involved, e.g., in I/R, is important to the development of treatment methods. HSPs are multifunctional proteins because they closely interact with the antioxidant and the nitric oxide generation systems, such as HSP70/HSP90/NOS. A deficiency or excess of antioxidants modulates the activation of HSF and subsequent HSP biosynthesis. It is well known that HSPs are involved in the regulation of several redox processes and play an important role in protein-protein interactions. The latest research focuses on determining the role of HSPs in OS, their antioxidant activity, and the possibility of using HSPs in the treatment of I/R consequences. Physical exercises are important in patients with cardiovascular diseases, as they affect the expression of HSPs and the development of OS.

The proteasome beta 5 subunit is essential for sexually divergent adaptive homeostatic responses to oxidative stress in D. melanogaster

Our studies center on the physiological phenomenon of adaptive homeostasis in which very low, signaling levels of an oxidant can induce transient expansion of the baseline homeostatic range of protective mechanisms, resulting in transient stress protection. The 20S proteasome is a major element of such inducible defense enzymes against oxidative stress but the relative importance of each of its three proteolytic subunits, β1, β2, and β5, is only poorly understood. We focused the present studies on determining the role of the β5 subunit in adaptation, survival, and lifespan. Decreased expression of the 20S proteasome β5 subunit (with RNAi) blocked the adaptive increase in the catalytic activities of the 20S proteasome response to signaling levels of H₂O₂ in female flies. Similarly, female-specific adaptive increases in survival following H₂O₂ pretreatment and subsequent toxic challenge was blocked. In contrast, direct overexpression of the 20S proteasome β5 subunit enabled an increased 20S proteasome proteolytic response, but prevented further adaptive homeostatic increases through H₂O₂ signaling, indicating there is a maximum 'ceiling' to the adaptive response. Males showed no adaptive change in proteasomal levels or activity whatsoever with H₂O₂ pretreatment and exhibited no significant impact upon the other 2 proteolytic subunits of the proteasome. However, chronic loss of the β5 subunit led to shortened lifespan in both sexes. Our exploration of the importance of the 20S proteasome β5 subunit in adaptive homeostasis highlights the interconnection between signal transduction pathways and regulated gene expression in sexually divergent responses to oxidative stimulation.

Accumulation of polyubiquitinated proteins: A consequence of early inactivation of the 26S proteasome

The proteasomal degradation system is one of the most important protein degradation systems in the cytosol and nucleus. This system is present in two major forms: the ATP-stimulated 26S/30 S proteasome or the ATP-independent 20S core proteasome. While the first recognize ubiquitin-tagged target proteins and degrade them, the 20S proteasome works also independent from ATP, but requires partially unfolded substrates. While the role of the proteasome in the selective removal of oxidized proteins is undoubted, the debate about a selective ubiquitination of oxidized proteins is still ongoing. Here we demonstrate, that under some conditions of oxidative stress an accumulation of oxidized and of K48-ubiquitinated proteins occurs. However, the removal of oxidized proteins seems not to be linked to ubiquitination. In further experiments, we could show that the accumulation of ubiquitinated proteins under certain oxidative stress conditions is rather a result of a different sensitivity of the 26S proteasome and the ubiquitination machinery towards oxidants.

Biochemical characterization of ClpB protein from Mycobacterium tuberculosis and identification of its small-molecule inhibitors

Tuberculosis, caused by pathogenic M. tuberculosis, remains a global health concern among various infectious diseases. Studies show that ClpB, a major disaggregase, protects the pathogen from various stresses encountered in the host environment. In the present study we have performed a detailed biophysical characterization of M. tuberculosis ClpB followed by a high throughput screening to identify small molecule inhibitors. The sedimentation velocity studies reveal that ClpB oligomerization varies with its concentration and presence of nucleotides. Further, using high throughput malachite green-based screening assay, we identified potential novel inhibitors of ClpB ATPase activity. The enzyme kinetics revealed that the lead molecule inhibits ClpB activity in a competitive manner. These drugs were also able to inhibit ATPase activity associated with E. coli ClpB and yeast Hsp104. The identified drugs inhibited the growth of intracellular bacteria in macrophages. Small angle X-ray scattering based modeling shows that ATP, and not its non-hydrolyzable analogs induce large scale conformational rearrangements in ClpB. Remarkably, the identified small molecules inhibited these ATP inducible conformational changes, suggesting that nucleotide induced shape changes are crucial for ClpB activity. The study broadens our understanding of M. tuberculosis chaperone machinery and provides the basis for designing more potent inhibitors against ClpB chaperone.

Proteasomal degradation of glycated proteins depends on substrate unfolding: Preferred degradation of moderately modified myoglobin

The Maillard reaction generates protein modifications which can accumulate during hyperglycemia or aging and may have inflammatory consequences. The proteasome is one of the major intracellular systems involved in the proteolytic degradation of modified proteins but its role in the degradation of glycated proteins is scarcely studied. In this study, chemical and structural changes of glycated myoglobin were analyzed and its degradation by 20S proteasome was studied. Myoglobin was incubated with physiological (5-10 mM), moderate (50-100 mM) and severe levels (300 mM) of glucose or methylglyoxal (MGO, 50 mM). Glycation increased myoglobin's fluorescence and surface hydrophobicity. Severe glycation generated crosslinked proteins as shown by gel electrophoresis. The concentration of advanced glycation endproducts (AGEs) N-ε-carboxymethyl lysine (CML), N-ε-carboxyethyl lysine (CEL), methylglyoxal-derived hydroimidazolone-1 (MG-H1), pentosidine and pyrraline was analyzed after enzymatic hydrolysis followed by UPLC-MS/MS. Higher concentrations of glucose increased all analyzed AGEs and incubation with MGO led to a pronounced increase of CEL and MG-H1. The binding of the heme group to apo-myoglobin was decreased with increasing glycation indicating the loss of tertiary protein structure. Proteasomal degradation of modified myoglobin compared to native myoglobin depends on the degree of glycation: physiological conditions decreased proteasomal degradation whereas moderate glycation increased degradation. Severe glycation again decreased proteolytic cleavage which might be due to crosslinking of protein monomers. The activity of the proteasomal subunit β5 is influenced by the presence of glycated myoglobin. In conclusion, the role of the proteasome in the degradation of glycated proteins is highly dependent on the level of glycation and consequent protein unfolding.

Oxidized protein aggregates: Formation and biological effects

The study of protein aggregates has a long history. While in the first decades until the 80ies of the 20th century only the observation of the presence of such aggregates was reported, later the biochemistry of the formation and the biological effects of theses aggregates were described. This review focusses on the complexity of the biological effects of protein aggregates and its potential role in the aging process.

Low steady-state oxidative stress inhibits adipogenesis by altering mitochondrial dynamics and decreasing cellular respiration

Adipogenesis is a fundamental process of white adipose tissue function, supporting lipid storage and release, while avoiding its spillover and ectopic accumulation in tissues and organs. During aging adipogenesis is impaired and among other factors, oxidative stress contributes to this process. Adipogenesis requires functional and dynamic mitochondria; however, this organelle itself becomes dysfunctional during aging and accounts for most of reactive oxygen species (ROS) production. Here, we evaluated whether oxidative stress impairs adipogenesis through functional impairment of mitodynamics by utilizing hyperoxia as a continuous source of oxidative stress while maintaining cellular viability. This negatively impacted mitochondrial function, including respiration and dynamics and ultimately blocked adipogenesis. Interestingly, this state was reversible by using the antidiabetic drug, Rosiglitazone, which reduced oxidative stress, restored mitochondrial dynamics and respiration and augmented adipogenesis. Moreover, in vitro results were in agreement with in vivo models of oxidative stress and aging, in which mice depleted of the superoxide dismutase enzyme 1 (SOD1) and old wild-type C57BL/6JRj mice demonstrated the same trend of adipogenic potential. Importantly, in humans the results follow the same pattern, showing a downregulation of adipogenic markers during aging. Since the levels of oxidative stress and peripheral insulin resistance increase with age, while adipogenesis decreases during aging, our model helps to understand a possible way to overcome physiologically low, steady stress conditions and restore adipogenesis, avoiding accumulation of deleterious hypertrophic adipocytes in favor of beneficial hyperplasia.

HSP70 Inhibition Leads to the Activation of Proteasomal System under Mild Hyperthermia Conditions in Young and Senescent Fibroblasts

Aging has been characterized with the accumulation of oxidized proteins, as a consequence of progressive decline in proteostasis capacity. Among others, proteasomal system is an efficient protein turnover complex to avoid aggregation of oxidized proteins. Heat shock protein 70 (HSP70) is another critical player that is involved in some key processes including the correct folding of misfolded proteins and targeting aggregated proteins to the proteasome for rapid degradation. The aim of this study was to determine the role of proteasomal system and heat shock proteins to maintain proteome balance during replicative senescence in mild hyperthermia conditions. Our results demonstrated that HSP40/70 machinery is induced by mild hyperthermia conditions independent from senescence conditions. Since HSP70 is largely responsible for the rapidly inducible cell protection following hyperthermia, the activation of “heat shock response” resulted in the elevation of HSP40/70 expressions as well as the proteasome activity. Interestingly, when HSP70 expression was inhibited, increased proteasomal activation was shown to be responsive to mild hyperthermia. Since HSP70 is involved in various stress-related pathways such as oxidative and endoplasmic reticulum stress, depletion of HSP70 expression may induce proteasomal degradation to maintain proteome balance of the cell. Thus, our data suggests that in mild heat stress conditions, molecular chaperone HSP70 plays an important role to avoid protein oxidation and aggregation; however, activities of proteasomal system are induced when HSP70 expression is depleted.

Measuring redox effects on the activities of intracellular proteases such as the 20S Proteasome and the Immuno-Proteasome with fluorogenic peptides

Proteolytic enzymes are often strongly affected by redox reactions, free radicals, oxidation, or oxidative stress. The 20S Proteasome and the Immuno-Proteasome are examples of major intracellular proteases whose concentration, transcription, translation, and proteolytic activity are all subject to redox regulation. Proteasomes are essential in maintaining overall protein homeostasis (or proteostasis), and their dysregulation results in detrimental phenotypes associated with various pathologies, including several common age-related diseases. Many studies have used Western blots to assess redox changes in Proteasome protein levels or RT-PCR to study RNA transcript levels, but actual measurements of proteolytic activity are far less common. Since each intact protein substrate exhibits a different proteolytic profile when incubated with proteasome or Immuno-Proteasome [± activators such as 19S or 11S (also called PA28)] and these proteolytic profiles are drastically altered if the protein substrate is denatured, for example by oxidation, heat, acetylation, or methylation. In an attempt to standardize proteasomal activity measurements small fluorogenic protein/peptide substrates were developed to test the three proteolytically active sites of the Proteasome and Immuno-Proteasome: trypsin-like, chymotrypsin-like, and caspase-like activities. Despite extensive use of fluorogenic peptide substrates to measure proteasome activity, there is an absence of a standardized set of best practices. In this study we analyze different parameters, such as sample concentration, AMC conjugated substrate concentration, duration of assay, and frequency of measurements, and examine how they impact the determination of Proteasome and Immuno-Proteasome activities using fluorogenic peptide substrates.

Effects of exercise preconditioning and HSP72 on diaphragm muscle function during mechanical ventilation

BACKGROUND

Mechanical ventilation (MV) is a life-saving measure for patients in respiratory failure. However, prolonged MV results in significant diaphragm atrophy and contractile dysfunction, a condition referred to as ventilator-induced diaphragm dysfunction (VIDD). While there are currently no clinically approved countermeasures to prevent VIDD, increased expression of heat shock protein 72 (HSP72) has been demonstrated to attenuate inactivity-induced muscle wasting. HSP72 elicits cytoprotection via inhibition of NF-κB and FoxO transcriptional activity, which contribute to VIDD. In addition, exercise-induced prevention of VIDD is characterized by an increase in the concentration of HSP72 in the diaphragm. Therefore, we tested the hypothesis that increased HSP72 expression is required for the exercise-induced prevention of VIDD. We also determined whether increasing the abundance of HSP72 in the diaphragm, independent of exercise, is sufficient to prevent VIDD.

METHODS

Cause and effect was determined by inhibiting the endurance exercise-induced increase in HSP72 in the diaphragm of exercise trained animals exposed to prolonged MV via administration of an antisense oligonucleotide targeting HSP72. Additional experiments were performed to determine if increasing HSP72 in the diaphragm via genetic (rAAV-HSP72) or pharmacological (BGP-15) overexpression is sufficient to prevent VIDD.

RESULTS

Our results demonstrate that the exercise-induced increase in HSP72 protein abundance is required for the protective effects of exercise against VIDD. Moreover, both rAAV-HSP72 and BGP-15-induced overexpression of HSP72 were sufficient to prevent VIDD. In addition, modification of HSP72 in the diaphragm is inversely related to the expression of NF-κB and FoxO target genes.

CONCLUSIONS

HSP72 overexpression in the diaphragm is an effective intervention to prevent MV-induced oxidative stress and the transcriptional activity of NF-κB and FoxO. Therefore, overexpression of HSP72 in the diaphragm is a potential therapeutic target to protect against VIDD.

Protein carbonylation in human bronchial epithelial cells exposed to cigarette smoke extract

Cigarette smoke is a well-established exogenous risk factor containing toxic reactive molecules able to induce oxidative stress, which in turn contributes to smoking-related diseases, including cardiovascular, pulmonary, and oral cavity diseases. We investigated the effects of cigarette smoke extract on human bronchial epithelial cells. Cells were exposed to various concentrations (2.5-5-10-20%) of cigarette smoke extract for 1, 3, and 24 h. Carbonylation was assessed by 2,4-dinitrophenylhydrazine using both immunocytochemical and Western immunoblotting assays. Cigarette smoke induced increasing protein carbonylation in a concentration-dependent manner. The main carbonylated proteins were identified by means of two-dimensional electrophoresis coupled to MALDI-TOF mass spectrometry analysis and database search (redox proteomics). We demonstrated that exposure of bronchial cells to cigarette smoke extract induces carbonylation of a large number of proteins distributed throughout the cell. Proteins undergoing carbonylation are involved in primary metabolic processes, such as protein and lipid metabolism and metabolite and energy production as well as in fundamental cellular processes, such as cell cycle and chromosome segregation, thus confirming that reactive carbonyl species contained in cigarette smoke markedly alter cell homeostasis and functions.

Regulation of Proteasome Activity by (Post-)transcriptional Mechanisms

Intracellular protein synthesis, folding, and degradation are tightly controlled processes to ensure proper protein homeostasis. The proteasome is responsible for the degradation of the majority of intracellular proteins, which are often targeted for degradation via polyubiquitination. However, the degradation rate of proteins is also affected by the capacity of proteasomes to recognize and degrade these substrate proteins. This capacity is regulated by a variety of proteasome modulations including (1) changes in complex composition, (2) post-translational modifications, and (3) altered transcription of proteasomal subunits and activators. Various diseases are linked to proteasome modulation and altered proteasome function. A better understanding of these modulations may offer new perspectives for therapeutic intervention. Here we present an overview of these three proteasome modulating mechanisms to give better insight into the diversity of proteasomes.