Oxidative protein folding in eukaryotes: mechanisms and consequences

To target cellular senescence in diabetic kidney disease: the known and the unknown

Cellular senescence represents a condition of irreversible cell cycle arrest, characterized by heightened senescence-associated beta-galactosidase (SA-β-Gal) activity, senescence-associated secretory phenotype (SASP), and activation of the DNA damage response (DDR). Diabetic kidney disease (DKD) is a significant contributor to end-stage renal disease (ESRD) globally, with ongoing unmet needs in terms of current treatments. The role of senescence in the pathogenesis of DKD has attracted substantial attention with evidence of premature senescence in this condition. The process of cellular senescence in DKD appears to be associated with mitochondrial redox pathways, autophagy, and endoplasmic reticulum (ER) stress. Increasing accumulation of senescent cells in the diabetic kidney not only leads to an impaired capacity for repair of renal injury, but also the secretion of pro-inflammatory and profibrotic cytokines and growth factors causing inflammation and fibrosis. Current treatments for diabetes exhibit varying degrees of renoprotection, potentially via mitigation of senescence in the diabetic kidney. Targeting senescent cell clearance through pharmaceutical interventions could emerge as a promising strategy for preventing and treating DKD. In this paper, we review the current understanding of senescence in DKD and summarize the possible therapeutic interventions relevant to senescence in this field.

Activation of retinoid X receptors protects retinal neurons and pigment epithelial cells from BMAA-induced death

Exposure to the non-protein amino acid cyanotoxin β-N-methylamino-L-alanine (BMAA), released by cyanobacteria found in many water reservoirs has been associated with neurodegenerative diseases. We previously demonstrated that BMAA induced cell death in both retina photoreceptors (PHRs) and amacrine neurons by triggering different molecular pathways, as activation of NMDA receptors and formation of carbamate-adducts was only observed in amacrine cell death. We established that activation of Retinoid X Receptors (RXR) protects retinal cells, including retina pigment epithelial (RPE) cells from oxidative stress-induced apoptosis. We now investigated the mechanisms underlying BMAA toxicity in these cells and those involved in RXR protection. BMAA addition to rat retinal neurons during early development in vitro increased reactive oxygen species (ROS) generation and polyADP ribose polymers (PAR) formation, while pre-treatment with serine (Ser) before BMAA addition decreased PHR death. Notably, RXR activation with the HX630 agonist prevented BMAA-induced death in both neuronal types, reducing ROS generation, preserving mitochondrial potential, and decreasing TUNEL-positive cells and PAR formation. This suggests that BMAA promoted PHR death by substituting Ser in polypeptide chains and by inducing polyADP ribose polymerase activation. BMAA induced cell death in ARPE-19 cells, a human epithelial cell line; RXR activation prevented this death, decreasing ROS generation and caspase 3/7 activity. These findings suggest that RXR activation prevents BMAA harmful effects on retinal neurons and RPE cells, supporting this activation as a broad-spectrum strategy for treating retina degenerations.

Protective Effects of an Octapeptide Identified from Riceberry™ (Oryza sativa) Protein Hydrolysate on Oxidative and Endoplasmic Reticulum (ER) Stress in L929 Cells

Reactive oxygen species (ROS) play a critical role in oxidative stress and cellular damage, underscoring the importance of identifying potent antioxidants. This research focuses on the antioxidant capabilities of Riceberry™-derived peptides and their protective effects against oxidative and endoplasmic reticulum (ER) stress in L929 cells. By simulating human digestion, Riceberry™ protein hydrolysate was generated, from which antioxidant peptides were isolated using OFFGEL electrophoresis and LC-MS/MS. Notably, an octapeptide (VPAGVAHW) from the hydrolysate demonstrated significant antioxidant activity, particularly against oxidative stress induced by iodoacetic acid (IAA) or hydrogen peroxide (H2O2) and ER stress caused by tunicamycin (TM) in L929 cells. This peptide's effectiveness was evident in its dose-dependent ability to enhance cell viability and mitigate stress effects, although its efficiency varied with the stress inducer. Our study suggests that Riceberry™-derived peptides could serve as a promising natural antioxidant with potential benefits for health promotion and applications in the food industry, offering an environmentally friendly alternative to synthetic antioxidants.

Effects of ginsenoside Rh2 on cisplatin-induced nephrotoxicity in renal tubular epithelial cells by inhibiting endoplasmic reticulum stress

Nephrotoxicity remains a major adverse reaction of the anticancer drug cisplatin (CDDP) chemotherapy, which is an important risk factor for chronic renal disease. Ginsenoside Rh2 from Panax ginseng has been shown to protect against CDDP-induced nephrotoxicity in vivo, but its pharmacological effect on renal tubular epithelial cells is not clearly understood. This study examined the molecular mechanisms underlying the nephroprotective effects of Rh2 on CDDP-induced HK-2 cells and acute kidney injury (AKI) mice. As a result of Rh2 treatment, CDDP-induced HK-2 cells showed increased cell viability and reduced lactate dehydrogenase release. Moreover, Rh2 ameliorated CDDP-induced mitochondrial membrane potential, increased antioxidant enzyme activities, and reduced pro-inflammatory cytokine expression to reduce damage. Rh2 inhibited apoptosis and enhanced the antioxidant capacity of HK-2 cells by reducing proteins associated with endoplasmic reticulum (ER) stress, as well as by attenuating tunicamycin-induced ER stress. In addition, treatment of CDDP-induced AKI mice with Rh2 substantially reduced blood urea nitrogen and serum creatinine levels, attenuated histological damage of kidney. Further, Rh2 also improved kidney function by inhibiting ER stress to support in vitro findings. These results consistently demonstrated that Rh2 protects renal tubular epithelial cells from CDDP-induced nephrotoxicity and apoptosis by restoring ER homeostasis, which might suggest a therapeutic potential and providing new insights into AKI alternative therapies.

Implications of endoplasmic reticulum stress and autophagy in aging and cardiovascular diseases

The average lifespan of humans has been increasing, resulting in a rapidly rising percentage of older individuals and high morbidity of aging-associated diseases, especially cardiovascular diseases (CVDs). Diverse intracellular and extracellular factors that interrupt homeostatic functions in the endoplasmic reticulum (ER) induce ER stress. Cells employ a dynamic signaling pathway of unfolded protein response (UPR) to buffer ER stress. Recent studies have demonstrated that ER stress triggers various cellular processes associated with aging and many aging-associated diseases, including CVDs. Autophagy is a conserved process involving lysosomal degradation and recycling of cytoplasmic components, proteins, organelles, and pathogens that invade the cytoplasm. Autophagy is vital for combating the adverse influence of aging on the heart. The present report summarizes recent studies on the mechanism of ER stress and autophagy and their overlap in aging and on CVD pathogenesis in the context of aging. It also discusses possible therapeutic interventions targeting ER stress and autophagy that might delay aging and prevent or treat CVDs.

Stress and the domestic cat: have humans accidentally created an animal mimic of neurodegeneration?

Many neurodegenerative diseases (NDD) appear to share commonality of origin, chronic ER stress. The endoplasmic reticulum (ER) is a dynamic organelle, functioning as a major site of protein synthesis and protein posttranslational modifications, required for proper folding. ER stress can occur because of external stimuli, such as oxidative stress or neuroinflammatory cytokines, creating the ER luminal environment permissive for the accumulation of aggregated and misfolded proteins. Unresolvable ER stress upregulates a highly conserved pathway, the unfolded protein response (UPR). Maladaptive chronic activation of UPR components leads to apoptotic neuronal death. In addition to other factors, physiological responses to stressors are emerging as a significant risk factor in the etiology and pathogenesis of NDD. Owned cats share a common environment with people, being exposed to many of the same stressors as people and additional pressures due to their "quasi" domesticated status. Feline Cognitive Dysfunction Syndrome (fCDS) presents many of the same disease hallmarks as human NDD. The prevalence of fCDS is rapidly increasing as more people welcome cats as companions. Barely recognized 20 years ago, veterinarians and scientists are in infancy stages in understanding what is a very complex disease. This review will describe how cats may represent an unexplored animal mimetic phenotype for human NDD with stressors as potential triggering mechanisms. We will consider how multiple variations of stressful events over the short-life span of a cat could affect neuronal loss or glial dysfunction and ultimately tip the balance towards dementia.

A critical appraisal of ferroptosis in Alzheimer's and Parkinson's disease: new insights into emerging mechanisms and therapeutic targets

Neurodegenerative diseases represent a pressing global health challenge, and the identification of novel mechanisms underlying their pathogenesis is of utmost importance. Ferroptosis, a non-apoptotic form of regulated cell death characterized by iron-dependent lipid peroxidation, has emerged as a pivotal player in the pathogenesis of neurodegenerative diseases. This review delves into the discovery of ferroptosis, the critical players involved, and their intricate role in the underlying mechanisms of neurodegeneration, with an emphasis on Alzheimer's and Parkinson's diseases. We critically appraise unsolved mechanistic links involved in the initiation and propagation of ferroptosis, such as a signaling cascade resulting in the de-repression of lipoxygenase translation and the role played by mitochondrial voltage-dependent anionic channels in iron homeostasis. Particular attention is given to the dual role of heme oxygenase in ferroptosis, which may be linked to the non-specific activity of P450 reductase in the endoplasmic reticulum. Despite the limited knowledge of ferroptosis initiation and progression in neurodegeneration, Nrf2/Bach1 target genes have emerged as crucial defenders in anti-ferroptotic pathways. The activation of Nrf2 and the inhibition of Bach1 can counteract ferroptosis and present a promising avenue for future therapeutic interventions targeting ferroptosis in neurodegenerative diseases.

ER-GUARD: an evolutionarily conserved antioxidant defense system at ER membranes

Oxidative protein folding in the endoplasmic reticulum (ER) is essential for all eukaryotic cells yet generates hydrogen peroxide (H2O2), a reactive oxygen species (ROS). The ER-transmembrane protein that provides reducing equivalents to ER and guards the cytosol for antioxidant defense remains unidentified. Here we combine AlphaFold2-based and functional reporter screens in C. elegans to identify a previously uncharacterized and evolutionarily conserved protein ERGU-1 that fulfills these roles. Deleting C. elegans ERGU-1 causes excessive H2O2 and transcriptional gene up-regulation through SKN-1, homolog of mammalian antioxidant master regulator NRF2. ERGU-1 deficiency also impairs organismal reproduction and behaviors. Both C. elegans and human ERGU-1 proteins localize to ER membranes and form network reticulum structures. We name this system ER-GUARD, Endoplasmic Reticulum Guardian Aegis of Redox Defense. Human and Drosophila homologs of ERGU-1 can rescue C. elegans mutant phenotypes, demonstrating evolutionarily ancient and conserved functions. Together, our results reveal an ER-membrane-specific protein machinery and defense-net system ER-GUARD for peroxide detoxification and suggest a previously unknown but conserved pathway for antioxidant defense in animal cells.

Compensatory Modulation of Seed Storage Protein Synthesis and Alteration of Starch Accumulation by Selective Editing of 13 kDa Prolamin Genes by CRISPR-Cas9 in Rice

Rice prolamins are categorized into three groups by molecular size (10, 13, or 16 kDa), while the 13 kDa prolamins are assigned to four subgroups (Pro13a-I, Pro13a-II, Pro13b-I, and Pro13b-II) based on cysteine residue content. Since lowering prolamin content in rice is essential to minimize indigestion and allergy risks, we generated four knockout lines using CRISPR-Cas9, which selectively reduced the expression of a specific subgroup of the 13 kDa prolamins. These four mutant rice lines also showed the compensatory expression of glutelins and non-targeted prolamins and were accompanied by low grain weight, altered starch content, and atypically-shaped starch granules and protein bodies. Transcriptome analysis identified 746 differentially expressed genes associated with 13 kDa prolamins during development. Correlation analysis revealed negative associations between genes in Pro13a-I and those in Pro13a-II and Pro13b-I/II subgroups. Furthermore, alterations in the transcription levels of 9 ER stress and 17 transcription factor genes were also observed in mutant rice lines with suppressed expression of 13 kDa prolamin. Our results provide profound insight into the functional role of 13 kDa rice prolamins in the regulatory mechanisms underlying rice seed development, suggesting their promising potential application to improve nutritional and immunological value.

Modulating the Unfolded Protein Response with ISRIB Mitigates Cisplatin Ototoxicity

Cisplatin is a commonly used chemotherapy agent with a nearly universal side effect of sensorineural hearing loss. The cellular mechanisms underlying cisplatin ototoxicity are poorly understood. Efforts in drug development to prevent or reverse cisplatin ototoxicity have largely focused on pathways of oxidative stress and apoptosis. An effective treatment for cisplatin ototoxicity, sodium thiosulfate (STS), while beneficial when used in standard risk hepatoblastoma, is associated with reduced survival in disseminated pediatric malignancies, highlighting the need for more specific drugs without potential tumor protective effects. The unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways have been shown to be involved in the pathogenesis of noise-induced hearing loss and cochlear synaptopathy in vivo, and these pathways have been implicated broadly in cisplatin cytotoxicity. This study sought to determine whether the UPR can be targeted to prevent cisplatin ototoxicity. Neonatal cochlear cultures and HEK cells were exposed to cisplatin and UPR-modulating drugs, and UPR marker gene expression and cell death measured. Treatment with ISRIB, a drug that activates eif2B and downregulates the pro-apoptotic PERK/CHOP pathway of the UPR, was tested in an in vivo mouse model of cisplatin ototoxicity and well as a head and neck squamous cell carcinoma (HNSCC) cell-based assay of cisplatin cytotoxicity. Cisplatin exhibited a biphasic, non-linear dose-response of cell death and apoptosis that correlated with different patterns of UPR marker gene expression in HEK cells and cochlear cultures. ISRIB treatment protected against cisplatin-induced hearing loss and hair-cell death, but did not impact the cytotoxic effects of cisplatin on HNSCC cell viability, unlike STS. These findings demonstrate that targeting the pro-apoptotic PERK/CHOP pathway with ISRIB can mitigate cisplatin ototoxicity without reducing anti-cancer cell effects, suggesting that this may be a viable strategy for drug development.

Redox regulation of UPR signalling and mitochondrial ER contact sites

Mitochondria and the endoplasmic reticulum (ER) have a synergistic relationship and are key regulatory hubs in maintaining cell homeostasis. Communication between these organelles is mediated by mitochondria ER contact sites (MERCS), allowing the exchange of material and information, modulating calcium homeostasis, redox signalling, lipid transfer and the regulation of mitochondrial dynamics. MERCS are dynamic structures that allow cells to respond to changes in the intracellular environment under normal homeostatic conditions, while their assembly/disassembly are affected by pathophysiological conditions such as ageing and disease. Disruption of protein folding in the ER lumen can activate the Unfolded Protein Response (UPR), promoting the remodelling of ER membranes and MERCS formation. The UPR stress receptor kinases PERK and IRE1, are located at or close to MERCS. UPR signalling can be adaptive or maladaptive, depending on whether the disruption in protein folding or ER stress is transient or sustained. Adaptive UPR signalling via MERCS can increase mitochondrial calcium import, metabolism and dynamics, while maladaptive UPR signalling can result in excessive calcium import and activation of apoptotic pathways. Targeting UPR signalling and the assembly of MERCS is an attractive therapeutic approach for a range of age-related conditions such as neurodegeneration and sarcopenia. This review highlights the emerging evidence related to the role of redox mediated UPR activation in orchestrating inter-organelle communication between the ER and mitochondria, and ultimately the determination of cell function and fate.

Crosstalk between protein misfolding and endoplasmic reticulum stress during ageing and their role in age-related disorders

Maintaining the proteome is crucial to retaining cell functionality and response to multiple intrinsic and extrinsic stressors. Protein misfolding increased the endoplasmic reticulum (ER) stress and activated the adaptive unfolded protein response (UPR) to restore cell homeostasis. Apoptosis occurs when ER stress is prolonged or the adaptive response fails. In healthy young cells, the ratio of protein folding machinery to quantities of misfolded proteins is balanced under normal circumstances. However, the age-related deterioration of the complex systems for handling protein misfolding is accompanied by ageing-related disruption of protein homeostasis, which results in the build-up of misfolded and aggregated proteins. This ultimately results in decreased cell viability and forms the basis of common age-related diseases called protein misfolding diseases. Proteins or protein fragments convert from their ordinarily soluble forms to insoluble fibrils or plaques in many of these disorders, which build up in various organs such as the liver, brain, or spleen. Alzheimer's, Parkinson's, type II diabetes, and cancer are diseases in this group commonly manifest in later life. Thus, protein misfolding and its prevention by chaperones and different degradation paths are becoming understood from molecular perspectives. Proteodynamics information will likely affect future interventional techniques to combat cellular stress and support healthy ageing by avoiding and treating protein conformational disorders. This review provides an overview of the diverse proteostasis machinery, protein misfolding, and ER stress involvement, which activates the UPR sensors. Here, we will discuss the crosstalk between protein misfolding and ER stress and their role in developing age-related diseases.

Cadmium toxicity and autophagy: a review

Cadmium (Cd) is an important environmental pollutant that poses a threat to human health and represents a critical component of air pollutants, food sources, and cigarette smoke. Cd is a known carcinogen and has toxic effects on the environment and various organs in humans. Heavy metals within an organism are difficult to biodegrade, and those that enter the respiratory tract are difficult to remove. Autophagy is a key mechanism for counteracting extracellular (microorganisms and foreign bodies) or intracellular (damaged organelles and proteins that cannot be degraded by the proteasome) stress and represents a self-protective mechanism for eukaryotes against heavy metal toxicity. Autophagy maintains cellular homeostasis by isolating and gathering information about foreign chemicals associated with other molecular events. However, autophagy may trigger cell death under certain pathological conditions, including cancer. Autophagy dysfunction is one of the main mechanisms underlying Cd-induced cytotoxicity. In this review, the toxic effects of Cd-induced autophagy on different human organ systems were evaluated, with a focus on hepatotoxicity, nephrotoxicity, respiratory toxicity, and neurotoxicity. This review also highlighted the classical molecular pathways of Cd-induced autophagy, including the ROS-dependent signaling pathways, endoplasmic reticulum (ER) stress pathway, Mammalian target of rapamycin (mTOR) pathway, Beclin-1 and Bcl-2 family, and recently identified molecules associated with Cd. Moreover, research directions for Cd toxicity regarding autophagic function were proposed. This review presents the latest theories to comprehensively reveal autophagy behavior in response to Cd toxicity and proposes novel potential autophagy-targeted prevention and treatment strategies for Cd toxicity and Cd-associated diseases in humans.

Triggers, cascades, and endpoints: connecting the dots of coral bleaching mechanisms

The intracellular coral-dinoflagellate symbiosis is the engine that underpins the success of coral reefs, one of the most diverse ecosystems on the planet. However, the breakdown of the symbiosis and the loss of the microalgal symbiont (i.e. coral bleaching) due to environmental changes are resulting in the rapid degradation of coral reefs globally. There is an urgent need to understand the cellular physiology of coral bleaching at the mechanistic level to help develop solutions to mitigate the coral reef crisis. Here, at an unprecedented scope, we present novel models that integrate putative mechanisms of coral bleaching within a common framework according to the triggers (initiators of bleaching, e.g. heat, cold, light stress, hypoxia, hyposalinity), cascades (cellular pathways, e.g. photoinhibition, unfolded protein response, nitric oxide), and endpoints (mechanisms of symbiont loss, e.g. apoptosis, necrosis, exocytosis/vomocytosis). The models are supported by direct evidence from cnidarian systems, and indirectly through comparative evolutionary analyses from non-cnidarian systems. With this approach, new putative mechanisms have been established within and between cascades initiated by different bleaching triggers. In particular, the models provide new insights into the poorly understood connections between bleaching cascades and endpoints and highlight the role of a new mechanism of symbiont loss, i.e. 'symbiolysosomal digestion', which is different from symbiophagy. This review also increases the approachability of bleaching physiology for specialists and non-specialists by mapping the vast landscape of bleaching mechanisms in an atlas of comprehensible and detailed mechanistic models. We then discuss major knowledge gaps and how future research may improve the understanding of the connections between the diverse cascade of cellular pathways and the mechanisms of symbiont loss (endpoints).

ER stress-induced transcriptional response reveals tolerance genes in yeast

Saccharomyces cerevisiae is important for protein secretion studies, yet the complexities of protein synthesis and secretion under endoplasmic reticulum (ER) stress conditions remain not fully understood. ER stress, triggered by alterations in the ER protein folding environment, poses substantial challenges to cells, especially during heterologous protein production. In this study, we used RNA-seq to analyze the transcriptional responses of yeast strains to ER stress induced by reagents such as tunicamycin (Tm) or dithiothreitol (DTT). Our gene expression analysis revealed several crucial genes, such as HMO1 and BIO5, that are involved in ER-stress tolerance. Through metabolic engineering, the best engineered strain R23 with HMO1 overexpression and BIO5 deletion, showed enhanced ER stress tolerance and improved protein folding efficiency, leading to a 2.14-fold increase in α-amylase production under Tm treatment and a 2.04-fold increase in cell density under DTT treatment. Our findings contribute to the understanding of cellular responses to ER stress and provide a basis for further investigations into the mechanisms of ER stress at the cellular level.

Catechins prevent monoclonal antibody fragmentation during production via fed-batch culture of Chinese hamster ovary cells

Chinese hamster ovary (CHO) cells are widely used for the industrial production of therapeutic monoclonal antibodies (mAbs). To meet the increasing market demands, high productivity, and quality are required in cell culture. One of the critical attributes of mAbs, from a safety perspective, is mAb fragmentation. However, methods for preventing mAbs fragmentation in CHO cell culture are limited. In this study, we observed that the antibody fragment content increased with increasing titers in fed-batch cultures for all three cell lines expressing recombinant antibodies. Adding copper sulfate to the culture medium further increased the fragment content, suggesting the involvement of reactive oxygen species (ROS) in the fragmentation process. Though antioxidants may be helpful to scavenge ROS, several antioxidants are reported to decrease the productivity of CHO cells. Among the antioxidants examined, we observed that the addition of catechin or (-)-epigallocatechin gallate to the culture medium prevented fragmentation content by about 20% and increased viable cell density and titer by 30% and 10%, respectively. Thus, the addition of catechins or compounds of equivalent function would be beneficial for manufacturing therapeutic mAbs with a balance between high titers and good quality.

Cold Atmospheric Pressure Plasma-Activated Medium Modulates Cellular Functions of Human Mesenchymal Stem/Stromal Cells In Vitro

Cold atmospheric pressure plasma (CAP) offers a variety of therapeutic possibilities and induces the formation of reactive chemical species associated with oxidative stress. Mesenchymal stem/stromal cells (MSCs) play a central role in tissue regeneration, partly because of their antioxidant properties and ability to migrate into regenerating areas. During the therapeutic application, MSCs are directly exposed to the reactive species of CAP. Therefore, the investigation of CAP-induced effects on MSCs is essential. In this study, we quantified the amount of ROS due to the CAP activation of the culture medium. In addition, cell number, metabolic activity, stress signals, and migration were analyzed after the treatment of MSCs with a CAP-activated medium. CAP-activated media induced a significant increase in ROS but did not cause cytotoxic effects on MSCs when the treatment was singular and short-term (one day). This single treatment led to increased cell migration, an essential process in wound healing. In parallel, there was an increase in various cell stress proteins, indicating an adaptation to oxidative stress. Repeated treatments with the CAP-activated medium impaired the viability of the MSCs. The results shown here provide information on the influence of treatment frequency and intensity, which could be necessary for the therapeutic application of CAP.

Studying the Changes in Physical Functioning and Oxidative Stress-Related Molecules in People Living with HIV after Switching from Triple to Dual Therapy

BACKGROUND

Physical activity could increase the production of oxidative stress biomarkers, affecting the metabolism and excretion of antiretroviral drugs and, consequently, the clinical outcome. Nowadays, people living with HIV (PLWH) are mostly switching from triple to dual therapy, but no data are available in terms of physical functioning and oxidative stress. The aim of this study was to evaluate if some antioxidant biomarkers and physical functioning tests could be different according to triple or dual antiretroviral therapy.

METHODS

PLWH were evaluated at baseline (BL), while treated with three drugs, and six months after the switch to dual therapy. Physical functioning was quantified using validated tools. Mitochondrial and cytosol antioxidant molecules were evaluated through liquid chromatography.

RESULTS

Twenty-five patients were analyzed. A statistically significant difference between triple and dual therapy was found for mitochondrial glutathione, but not for physical tests. Evaluating differences between physically active and inactive individuals, the following statistically significant differences were suggested, considering triple therapy (mitochondrial n-formyl-methionine p = 0.022, triglycerides p = 0.023) and double therapy (mitochondrial glycine p = 0.035, cytosol glutamic acid p = 0.007, cytosol s-adenosylmethionine p = 0.021).

CONCLUSIONS

For the first time, this study suggests possible differences in terms of antioxidant molecules and physical functioning in PLWH switching from triple to dual therapy.

Ultrafast Biomimetic Oxidative Folding of Cysteine-rich Peptides and Microproteins in Organic Solvents

Disulfides in peptides and proteins are essential for maintaining a properly folded structure. Their oxidative folding is invariably performed in an aqueous-buffered solution. However, this process is often slow and can lead to misfolded products. Here, we report a novel concept and strategy that is bio-inspired to mimic protein disulfide isomerase (PDI) by accelerating disulfide exchange rates many thousand-fold. The proposed strategy termed organic oxidative folding is performed under organic solvents to yield correctly folded cysteine-rich microproteins instantaneously without observable misfolded or dead-end products. Compared to conventional aqueous oxidative folding strategies, enormously large rate accelerations up to 113,200-fold were observed. The feasibility and generality of the organic oxidative folding strategy was successfully demonstrated on 15 cysteine-rich microproteins of different hydrophobicity, lengths (14 to 58 residues), and numbers of disulfides (2 to 5 disulfides), producing the native products in a second and in high yield.

Endoplasmic reticular stress as an emerging therapeutic target for chronic pain: a narrative review

Chronic pain is a severely debilitating condition with enormous socioeconomic costs. Current treatment regimens with nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, or opioids have been largely unsatisfactory with uncertain benefits or severe long-term side effects. This is mainly because chronic pain has a multifactorial aetiology. Although conventional pain medications can alleviate pain by keeping several dysfunctional pathways under control, they can mask other underlying pathological causes, ultimately worsening nerve pathologies and pain outcome. Recent preclinical studies have shown that endoplasmic reticulum (ER) stress could be a central hub for triggering multiple molecular cascades involved in the development of chronic pain. Several ER stress inhibitors and unfolded protein response modulators, which have been tested in randomised clinical trials or apprpoved by the US Food and Drug Administration for other chronic diseases, significantly alleviated hyperalgesia in multiple preclinical pain models. Although the role of ER stress in neurodegenerative disorders, metabolic disorders, and cancer has been well established, research on ER stress and chronic pain is still in its infancy. Here, we critically analyse preclinical studies and explore how ER stress can mechanistically act as a central node to drive development and progression of chronic pain. We also discuss therapeutic prospects, benefits, and pitfalls of using ER stress inhibitors and unfolded protein response modulators for managing intractable chronic pain. In the future, targeting ER stress to impact multiple molecular networks might be an attractive therapeutic strategy against chronic pain refractory to steroids, NSAIDs, or opioids. This novel therapeutic strategy could provide solutions for the opioid crisis and public health challenge.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

SEPN1-related myopathy depends on the oxidoreductase ERO1A and is druggable with the chemical chaperone TUDCA

Selenoprotein N (SEPN1) is a protein of the endoplasmic reticulum (ER) whose inherited defects originate SEPN1-related myopathy (SEPN1-RM). Here, we identify an interaction between SEPN1 and the ER-stress-induced oxidoreductase ERO1A. SEPN1 and ERO1A, both enriched in mitochondria-associated membranes (MAMs), are involved in the redox regulation of proteins. ERO1A depletion in SEPN1 knockout cells restores ER redox, re-equilibrates short-range MAMs, and rescues mitochondrial bioenergetics. ERO1A knockout in a mouse background of SEPN1 loss blunts ER stress and improves multiple MAM functions, including Ca2+ levels and bioenergetics, thus reversing diaphragmatic weakness. The treatment of SEPN1 knockout mice with the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) mirrors the results of ERO1A loss. Importantly, muscle biopsies from patients with SEPN1-RM exhibit ERO1A overexpression, and TUDCA-treated SEPN1-RM patient-derived primary myoblasts show improvement in bioenergetics. These findings point to ERO1A as a biomarker and a viable target for intervention and to TUDCA as a pharmacological treatment for SEPN1-RM.

Biological mechanisms and clinical significance of endoplasmic reticulum oxidoreductase 1 alpha (ERO1α) in human cancer

A firm link between endoplasmic reticulum (ER) stress and tumors has been wildly reported. Endoplasmic reticulum oxidoreductase 1 alpha (ERO1α), an ER-resident thiol oxidoreductase, is confirmed to be highly upregulated in various cancer types and associated with a significantly worse prognosis. Of importance, under ER stress, the functional interplay of ERO1α/PDI axis plays a pivotal role to orchestrate proper protein folding and other key processes. Multiple lines of evidence propose ERO1α as an attractive potential target for cancer treatment. However, the unavailability of specific inhibitor for ERO1α, its molecular inter-relatedness with closely related paralog ERO1β and the tightly regulated processes with other members of flavoenzyme family of enzymes, raises several concerns about its clinical translation. Herein, we have provided a detailed description of ERO1α in human cancers and its vulnerability towards the aforementioned concerns. Besides, we have discussed a few key considerations that may improve our understanding about ERO1α in tumors.

Komagataella phaffii Erp41 is a protein disulfide isomerase with unprecedented disulfide bond catalyzing activity when coupled to glutathione

In the methylotrophic yeast Komagataella phaffii, we identified an endoplasmic reticulum-resident protein disulfide isomerase (PDI) family member, Erp41, with a peculiar combination of active site motifs. Like fungal ERp38, it has two thioredoxin-like domains which contain active site motifs (a and a'), followed by an alpha-helical ERp29c C-terminal domain (c domain). However, while the a domain has a typical PDI-like active site motif (CGHC), the a' domain instead has CGYC, a glutaredoxin-like motif which confers to the protein an exceptional affinity for GSH/GSSG. This combination of active site motifs has so far been unreported in PDI-family members. Homology searches revealed ERp41 is present in the genome of some plants, fungal parasites, and a few nonconventional yeasts, among which are Komagataella spp. and Yarrowia lipolytica. These yeasts are both used for the production of secreted recombinant proteins. Here, we analyzed the activity of K. phaffii Erp41. We report that it is nonessential in K. phaffii, and that it can catalyze disulfide bond formation in partnership with the sulfhydryl oxidase Ero1 in vitro with higher turnover rates than the canonical PDI from K. phaffii, Pdi1, but slower activation times. We show how Erp41 has unusually fast glutathione-coupled oxidation activity and relate it to its unusual combination of active sites in its thioredoxin-like domains. We further describe how this determines its unusually efficient catalysis of dithiol oxidation in peptide and protein substrates.

CYB5R3 functions as a tumor suppressor by inducing ER stress-mediated apoptosis in lung cancer cells via the PERK-ATF4 and IRE1α-JNK pathways

Cytochrome b5 reductase 3 (CYB5R3) is involved in various cellular metabolic processes, including fatty acid synthesis and drug metabolism. However, the role of CYB5R3 in cancer development remains poorly understood. Here, we show that CYB5R3 expression is downregulated in human lung cancer cell lines and tissues. Adenoviral overexpression of CYB5R3 suppresses lung cancer cell growth in vitro and in vivo. However, CYB5R3 deficiency promotes tumorigenesis and metastasis in mouse models. Transcriptome analysis revealed that apoptosis- and endoplasmic reticulum (ER) stress-related genes are upregulated in CYB5R3-overexpressing lung cancer cells. Metabolomic analysis revealed that CYB5R3 overexpression increased the production of nicotinamide adenine dinucleotide (NAD+) and oxidized glutathione (GSSG). Ectopic CYB5R3 is mainly localized in the ER, where CYB5R3-dependent ER stress signaling is induced via activation of protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme 1 alpha (IRE1α). Moreover, NAD+ activates poly (ADP-ribose) polymerase16 (PARP16), an ER-resident protein, to promote ADP-ribosylation of PERK and IRE1α and induce ER stress. In addition, CYB5R3 induces the generation of reactive oxygen species and caspase-9-dependent intrinsic cell death. Our findings highlight the importance of CYB5R3 as a tumor suppressor for the development of CYB5R3-based therapeutics for lung cancer.

Paraoxonase-like APMAP maintains endoplasmic reticulum-associated lipid and lipoprotein homeostasis

Oxidative stress perturbs lipid homeostasis and contributes to metabolic diseases. Though ignored compared to mitochondrial oxidation, the endoplasmic reticulum (ER) generates reactive oxygen species requiring antioxidant quality control. Using multi-organismal profiling featuring Drosophila, zebrafish, and mammalian cells, here we characterize the paraoxonase-like APMAP as an ER-localized protein that promotes redox and lipid homeostasis and lipoprotein maturation. APMAP-depleted mammalian cells exhibit defective ER morphology, elevated ER and oxidative stress, lipid droplet accumulation, and perturbed ApoB-lipoprotein homeostasis. Critically, APMAP loss is rescued with chemical antioxidant NAC. Organismal APMAP depletion in Drosophila perturbs fat and lipoprotein homeostasis, and zebrafish display increased vascular ApoB-containing lipoproteins, particles that are atherogenic in mammals. Lipidomics reveals altered polyunsaturated phospholipids and increased ceramides upon APMAP loss, which perturbs ApoB-lipoprotein maturation. These ApoB-associated defects are rescued by inhibiting ceramide synthesis. Collectively, we propose APMAP is an ER-localized antioxidant that promotes lipid and lipoprotein homeostasis.

Regulation of antioxidants in cancer

Scientists in this field often joke, "If you don't have a mechanism, say it's ROS." Seemingly connected to every biological process ever described, reactive oxygen species (ROS) have numerous pleiotropic roles in physiology and disease. In some contexts, ROS act as secondary messengers, controlling a variety of signaling cascades. In other scenarios, they initiate damage to macromolecules. Finally, in their worst form, ROS are deadly to cells and surrounding tissues. A set of molecules with detoxifying abilities, termed antioxidants, is the direct counterpart to ROS. Notably, antioxidants exist in the public domain, touted as a "cure-all" for diseases. Research has disproved many of these claims and, in some cases, shown the opposite. Of all the diseases, cancer stands out in its paradoxical relationship with antioxidants. Although the field has made numerous strides in understanding the roles of antioxidants in cancer, many questions remain.

Mitochondrial dysfunction in neurodegenerative disorders

Recent advances in understanding the role of mitochondrial dysfunction in neurodegenerative diseases have expanded the opportunities for neurotherapeutics targeting mitochondria to alleviate symptoms and slow disease progression. In this review, we offer a historical account of advances in mitochondrial biology and neurodegenerative disease. Additionally, we summarize current knowledge of the normal physiology of mitochondria and the pathogenesis of mitochondrial dysfunction, the role of mitochondrial dysfunction in neurodegenerative disease, current therapeutics and recent therapeutic advances, as well as future directions for neurotherapeutics targeting mitochondrial function. A focus is placed on reactive oxygen species and their role in the disruption of telomeres and their effects on the epigenome. The effects of mitochondrial dysfunction in the etiology and progression of Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease are discussed in depth. Current clinical trials for mitochondria-targeting neurotherapeutics are discussed.

Fingerprint of the oxido-reductase ERO1: A protein disulfide bond producer and supporter of cancer

Endoplasmic reticulum oxidoreductin 1 (ERO1) alpha (ERO1A) is an endoplasmic reticulum (ER)-localized protein disulfide oxidoreductase, involved in the disulfide bond formation of proteins. ERO1's activity in oxidative protein folding is redundant in higher eukaryotes and its loss is well compensated. Although it is dispensable in non-cancer cells, high ERO1 levels are seen with different cancers and predict their malignant phenotype. ERO1 fosters tumor aggressiveness and the response to drug therapy in hypoxic and highly metastatic tumors. It regulates vascular endothelial growth factor (VEGF) levels, oxidative folding and N-glycosylation in hypoxic conditions, boosting tumor fitness and angiogenesis on multiple levels. In addition, ERO1 regulates protein death ligand-1 (PD-L1) on tumors, interfering with the related immune surveillance mechanism, hence acting on the tumors' response to immune check-point inhibitors (ICI). This all points to inhibition of ERO1 as an effective pharmacological tool, selectively targeting tumors while sparing non-cancer cells from cytotoxicity. The critical discussion here closely examines the molecular basis for ERO1's involvement in tumors and ERO1 inhibition strategies for their treatment.

Renoprotective effect of Limonium duriusculum (de Girard) Kuntze via modulation of oxidative stress/ UPR markers and inflammation during cyclosporine-induced nephrotoxicity in rats

Objectives

The present study aimed to explore the mechanisms underlying the potency of the renoprotective effect of the EtOAc fraction of Limonium duriusculum (EALD) (Plumbaginaceae) against cyclosporine A (CsA), in comparison to vitamin E (Vit. E).

Materials and Methods

In the in-vivo experiment, a model of CsA-induced nephrotoxicity was established by dosing male Wistar rats with 25 mg/kg, for 14 days. The protective effect of EALD was investigated through pretreatment of rats with a dose of 200 mg/kg for 14 days, compared to the oral administration of Vit. E at 100 mg/kg. Renal function and markers of oxidative stress were then assessed. Furthermore, a complementary in-vitro study was carried out to evaluate CsA-induced endoplasmic reticulum stress (ERS) and inflammation on cell culture (3T3 cells and MCT cells) using western blot and quantitative RT-PCR..

Results

Pretreatment of rats with EALD significantly attenuated the elevated levels of renal dysfunction markers (BUN, creatinine) and suppressed malondialdehyde (MDA) levels; It also significantly regulated the changes in superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxydase (GPx), and glutathione S-transferase (GST) levels as compared to Vit. E, demonstrating a more effective recovery in renal tissues. Treatment of cells with CsA was linked to the expression of ERS and inflammatory markers activating transcription factor (ATF4), inositol-requiring enzyme 1α (IRE1α), binding immunoglobulin protein (BiP), and monocyte chemoattractant protein-1 (MCP1). In contrast, pretreatment of cells with EALD resulted in a significant decrease in both ERS and inflammatory markers.

Conclusion

These findings indicate the renoprotective potential of L. duriusculum, as it demonstrated the ability to ameliorate CsA-induced renal dysfunction through its distinctive antioxidant properties.

Beyond Glucose: The Dual Assault of Oxidative and ER Stress in Diabetic Disorders

Diabetes mellitus, a prevalent global health concern, is characterized by hyperglycemia. However, recent research reveals a more intricate landscape where oxidative stress and endoplasmic reticulum (ER) stress orchestrate a dual assault, profoundly impacting diabetic disorders. This review elucidates the interplay between these two stress pathways and their collective consequences on diabetes. Oxidative stress emanates from mitochondria, where reactive oxygen species (ROS) production spirals out of control, leading to cellular damage. We explore ROS-mediated signaling pathways, which trigger β-cell dysfunction, insulin resistance, and endothelial dysfunction the quintessential features of diabetes. Simultaneously, ER stress unravels, unveiling how protein folding disturbances activate the unfolded protein response (UPR). We dissect the UPR's dual role, oscillating between cellular adaptation and apoptosis, significantly influencing pancreatic β-cells and peripheral insulin-sensitive tissues. Crucially, this review exposes the synergy between oxidative and ER stress pathways. ROS-induced UPR activation and ER stress-induced oxidative stress create a detrimental feedback loop, exacerbating diabetic complications. Moreover, we spotlight promising therapeutic strategies that target both stress pathways. Antioxidants, molecular chaperones, and novel pharmacological agents offer potential avenues for diabetes management. As the global diabetes burden escalates, comprehending the dual assault of oxidative and ER stress is paramount. This review not only unveils the intricate molecular mechanisms governing diabetic pathophysiology but also advocates a holistic therapeutic approach. By addressing both stress pathways concurrently, we may forge innovative solutions for diabetic disorders, ultimately alleviating the burden of this pervasive health issue.

From reactive species to disease development: Effect of oxidants and antioxidants on the cellular biomarkers

The influence of modern lifestyle, diet, exposure to chemicals such as phytosanitary substances, together with sedentary lifestyles and lack of exercise play an important role in inducing reactive stress (RS) and disease. The imbalance in the production and scavenging of free radicals and the induction of RS (oxidative, nitrosative, and halogenative) plays an essential role in the etiology of various chronic pathologies, such as cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. The implication of free radicals and reactive species injury in metabolic disturbances and the onset of many diseases have been accumulating for several decades, and are now accepted as a major cause of many chronic diseases. Exposure to elevated levels of free radicals can cause molecular structural impact on proteins, lipids, and DNA, as well as functional alteration of enzyme homeostasis, leading to aberrations in gene expression. Endogenous depletion of antioxidant enzymes can be mitigated using exogenous antioxidants. The current interest in the use of exogenous antioxidants as adjunctive agents for the treatment of human diseases allows a better understanding of these diseases, facilitating the development of new therapeutic agents with antioxidant activity to improve the treatment of various diseases. Here we examine the role that RS play in the initiation of disease and in the reactivity of free radicals and RS in organic and inorganic cellular components.

Disturbed hemodynamics and oxidative stress interaction in endothelial dysfunction and AAA progression: Focus on Nrf2 pathway

Hemodynamic shear stress is one of the major factors that are involved in the pathogenesis of many cardiovascular diseases including atherosclerosis and abdominal aortic aneurysm (AAA), through its modulatory effect on the endothelial cell's redox homeostasis and mechanosensitive gene expression. Among important mechanisms, oxidative stress, endoplasmic reticulum stress activation, and the subsequent endothelial dysfunction are attributed to disturbed blood flow and low shear stress in the vascular curvature and bifurcations which are considered atheroprone regions and aneurysm occurrence spots. Many pathways were shown to be involved in AAA progression. Of particular interest from recent findings is, the (Nrf2)/Keap-1 pathway, where Nrf2 is a transcription factor that has antioxidant properties and is strongly associated with several CVDs, yet, the exact mechanism by which Nrf2 alleviates CVDs still to be elucidated. Nrf2 expression is closely affected by shear stress and was shown to participate in AAA. In the current review paper, we discussed the link between disturbed hemodynamics and its effect on Nrf2 as a mechanosensitive gene and its role in the development of endothelial dysfunction which is linked to the progression of AAA.

Endoplasmic Reticulum Stress Promotes the Expression of TNF-α in THP-1 Cells by Mechanisms Involving ROS/CHOP/HIF-1α and MAPK/NF-κB Pathways

Obesity and metabolic syndrome involve chronic low-grade inflammation called metabolic inflammation as well as metabolic derangements from increased endotoxin and free fatty acids. It is debated whether the endoplasmic reticulum (ER) stress in monocytic cells can contribute to amplify metabolic inflammation; if so, by which mechanism(s). To test this, metabolic stress was induced in THP-1 cells and primary human monocytes by treatments with lipopolysaccharide (LPS), palmitic acid (PA), or oleic acid (OA), in the presence or absence of the ER stressor thapsigargin (TG). Gene expression of tumor necrosis factor (TNF)-α and markers of ER/oxidative stress were determined by qRT-PCR, TNF-α protein by ELISA, reactive oxygen species (ROS) by DCFH-DA assay, hypoxia-inducible factor 1-alpha (HIF-1α), p38, extracellular signal-regulated kinase (ERK)-1,2, and nuclear factor kappa B (NF-κB) phosphorylation by immunoblotting, and insulin sensitivity by glucose-uptake assay. Regarding clinical analyses, adipose TNF-α was assessed using qRT-PCR/IHC and plasma TNF-α, high-sensitivity C-reactive protein (hs-CRP), malondialdehyde (MDA), and oxidized low-density lipoprotein (OX-LDL) via ELISA. We found that the cooperative interaction between metabolic and ER stresses promoted TNF-α, ROS, CCAAT-enhancer-binding protein homologous protein (CHOP), activating transcription factor 6 (ATF6), superoxide dismutase 2 (SOD2), and nuclear factor erythroid 2-related factor 2 (NRF2) expression (p ≤ 0.0183),. However, glucose uptake was not impaired. TNF-α amplification was dependent on HIF-1α stabilization and p38 MAPK/p65 NF-κB phosphorylation, while the MAPK/NF-κB pathway inhibitors and antioxidants/ROS scavengers such as curcumin, allopurinol, and apocynin attenuated the TNF-α production (p ≤ 0.05). Individuals with obesity displayed increased adipose TNF-α gene/protein expression as well as elevated plasma levels of TNF-α, CRP, MDA, and OX-LDL (p ≤ 0.05). Our findings support a metabolic-ER stress cooperativity model, favoring inflammation by triggering TNF-α production via the ROS/CHOP/HIF-1α and MAPK/NF-κB dependent mechanisms. This study also highlights the therapeutic potential of antioxidants in inflammatory conditions involving metabolic/ER stresses.

Endoplasmic reticulum stress in Alzheimer's disease: Molecular mechanisms and therapeutic prospects

Alzheimer's disease (AD) is a progressive neurodegenerative condition that leads to memory loss and cognitive impairment over time. It is characterized by protein misfolding as well as prolonged cellular stress, such as perturbing calcium homeostasis and redox management. Numerous investigations have proven that endoplasmic reticulum failure may exhibit exacerbation of AD pathogenesis in AD patients, in-vivo and in-vitro models. The endoplasmic reticulum (ER) participates in a variety of biological functions including folding of protein, quality control, cholesterol production, and maintenance of calcium balance. A diverse range of physiological, pathological and pharmacological substances can interfere with ER activity and thus lead to exaggeration of ER stress. The unfolded protein response (UPR), an intracellular signaling network is stimulated due to ER stress. Three stress sensors found in the endoplasmic reticulum, the PERK, ATF6, and IRE1 transducers detect protein misfolding in the ER and trigger UPR, a complex system to maintain homeostasis. ER stress is linked to many of the major pathological processes that are seen in AD, including presenilin1 and 2 (PS1 and PS2) gene mutation, tau phosphorylation and β-amyloid formation. The role of ER stress and UPR in the pathophysiology of AD implies that they can be employed as potent therapeutic target. This study shows the relationship between ER and AD and how the pathogenesis of AD is influenced by the impact of ER stress. An effective method for the prevention or treatment of AD may involve therapeutic strategies that modify ER stress pathways.

Cellular stress in the pathogenesis of nonalcoholic steatohepatitis and liver fibrosis

The burden of chronic liver disease is rising substantially worldwide. Fibrosis, characterized by excessive deposition of extracellular matrix proteins, is the common pathway leading to cirrhosis, and limited treatment options are available. There is increasing evidence suggesting the role of cellular stress responses contributing to fibrogenesis. This Review provides an overview of studies that analyse the role of cellular stress in different cell types involved in fibrogenesis, including hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells and macrophages.

Anti-inflammatory potential of platinum nanozymes: mechanisms and perspectives

Inflammation is a complex process of the body in response to pathogen infections or dysregulated metabolism, involving the recruitment and activation of immune system components. Repeated dangerous stimuli or uncontrolled immune effector mechanisms can result in tissue injury. Reactive Oxygen Species (ROS) play key roles in physiological cell signaling as well as in the destruction of internalized pathogens. However, aberrant ROS production and release have deleterious effects on the surrounding environment, making ROS regulation a priority to reduce inflammation. Most of the current anti-inflammatory therapies rely on drugs that impair the release of pro-inflammatory mediators. Nevertheless, increasing the enzymatic activity to reduce ROS levels could be an alternative or complementary therapeutic approach to decrease inflammation. Nanozymes are nanomaterials with high catalytic activity that mimic natural enzymes, allowing biochemical reactions to take place. Such functional particles typically show different and regenerable oxidation states or catalytically reactive surfaces offering long-term activity and stability. In this scenario, platinum-based nanozymes (PtNZs) exhibit broad and efficient catalytic functionalities and can reduce inflammation mainly through ROS scavenging, e.g. by catalase and superoxide dismutase reactions. Dose-dependent biocompatibility and immune compatibility of PtNZs have been shown in different cells and tissues, both in vitro and in vivo. Size/shape/surface engineering of the nanozymes could also potentiate their efficacy to act at different sites and/or steps of the inflammation process, such as cytokine removal or specific targeting of activated leukocytes. In the present review, we analyze key inflammation triggering processes and the effects of platinum nanozymes under exemplificative inflammatory conditions. We further discuss potential platinum nanozyme design and improvements to modulate and expand their anti-inflammatory action.

Identification and functional analysis of endoplasmic reticulum oxidoreductase 1 (ERO1) from the green mud crab Scylla paramamosain: The first evidence of ERO1 involved in invertebrate immune response

Endoplasmic reticulum oxidoreductase 1 (ERO1) is an important mediator in regulating disulfide bond formation and maintaining endoplasmic reticulum homeostasis. Its activity is transcriptionally regulated by the unfolded protein response (UPR) in the endoplasmic reticulum, which is known to be essential in immunity. However, whether ERO1 is involved in innate immunity in invertebrates remains unclear. In the present study, two subtypes of ERO1 from Scylla paramamosain were first identified and characterized. Sequence analysis revealed the conserved ERO1 domain and the oxidative capacity assay verified the oxidative capacity of SpERO1 recombinant protein. Moreover, SpERO1s were found to be ubiquitously expressed in all the tested tissues, with the highest expression observed in hemocytes. Two SpERO1s exhibited distinct expression patterns in response to Vibrio alginolyticus and White Spot Syndrome Virus (WSSV). Importantly, the downregulation of the expression of immune factors upon bacterial challenge in SpERO1-silenced crabs was observed. These results provided an initial foundation for further investigations into the role of ERO1 in the innate immunity of invertebrates.

Peroxiredoxins Play an Important Role in the Regulation of Immunity and Aging in Drosophila

Aberrant immune responses and chronic inflammation can impose significant health risks and promote premature aging. Pro-inflammatory responses are largely mediated via reactive oxygen species (ROS) and reduction-oxidation reactions. A pivotal role in maintaining cellular redox homeostasis and the proper control of redox-sensitive signaling belongs to a family of antioxidant and redox-regulating thiol-related peroxidases designated as peroxiredoxins (Prx). Our recent studies in Drosophila have shown that Prxs play a critical role in aging and immunity. We identified two important 'hubs', the endoplasmic reticulum (ER) and mitochondria, where extracellular and intracellular stress signals are transformed into pro-inflammatory responses that are modulated by the activity of the Prxs residing in these cellular organelles. Here, we found that mitochondrial Prx activity in the intestinal epithelium is required to prevent the development of intestinal barrier dysfunction, which can drive systemic inflammation and premature aging. Using a redox-negative mutant, we demonstrated that Prx acts in a redox-dependent manner in regulating the age-related immune response. The hyperactive immune response observed in flies under-expressing mitochondrial Prxs is due to a response to abiotic signals but not to changes in the bacterial content. This hyperactive response, but not reduced lifespan phenotype, can be rescued by the ER-localized Prx.

Comprehensive analysis of ferroptosis-related genes in immune infiltration and prognosis in multiple myeloma

Background: One particular type of cellular death that is known as ferroptosis is caused by the excessive lipid peroxidation. It is a regulated form of cell death that can affect the response of the tumor cells. Currently, it is not known if the presence of this condition can affect the prognosis of patients with multiple myeloma (MM). Methods: In this study, we studied the expression differences and prognostic value of ferroptosis-related genes (FRGs) in MM, and established a ferroptosis risk scoring model. In order to improve the prediction accuracy and clinical applicability, a nomogram was also established. Through gene enrichment analysis, pathways closely related to high-risk groups were identified. We then explored the differences in risk stratification in drug sensitivity and immune patterns, and evaluated their value in prognostic prediction and treatment response. Lastly, we gathered MM cell lines and samples from patients to confirm the expression of marker FRGs using quantitative real-time PCR (qRT-PCR). Results: The ability to predict the survival of MM patients is a challenging issue. Through the use of a risk model derived from ferroptosis, we were able to develop a more accurate prediction of the disease's prognosis. They were then validated by a statistical analysis, which showed that the model is an independent factor in the prognosis of MM. Patients of high ferroptosis risk scores had a much worse chance of survival than those in the low-risk groups. The calibration and power of the nomogram were also strong. We noted that the link between the ferroptosis risk score and the clinical treatment was suggested by the FRG's significant correlation with the immune checkpoint genes and the medication sensitivity. We validated the predictive model using qRT-PCR. Conclusion: We demonstrated the association between FRGs and MM, and developed a new risk model for prognosis in MM patients. Our study sheds light on the potential clinical relevance of ferroptosis in MM and highlights its potential as a therapeutic target for patients with this disease.

Reducing oxidative protein folding alleviates senescence by minimizing ER-to-nucleus H2 O2 release

Oxidative protein folding occurs in the endoplasmic reticulum (ER) to generate disulfide bonds, and the by-product is hydrogen peroxide (H2 O2 ). However, the relationship between oxidative protein folding and senescence remains uncharacterized. Here, we find that the protein disulfide isomerase (PDI), a key oxidoreductase that catalyzes oxidative protein folding, accumulated in aged human mesenchymal stem cells (hMSCs) and deletion of PDI alleviated hMSCs senescence. Mechanistically, knocking out PDI slows the rate of oxidative protein folding and decreases the leakage of ER-derived H2 O2 into the nucleus, thereby decreasing the expression of SERPINE1, which was identified as a key driver of cell senescence. Furthermore, we show that depletion of PDI alleviated senescence in various cell models of aging. Our findings reveal a previously unrecognized role of oxidative protein folding in promoting cell aging, providing a potential target for aging and aging-related disease intervention.

Role of the ER-induced UPR pathway, apoptosis, and autophagy in colorectal cancer

When large amounts of misfolded or unfolded proteins accumulate in the endoplasmic reticulum (ER) in response to stress, a process called unfolded protein response (UPR) is activated. The disruption of this process leads to many diseases including diabetes, neurodegenerative diseases, and many cancers. In the process of UPR in response to stress and unfolded proteins, specific signaling pathways are induced in the endoplasmic reticulum and subsequently transmitted to the nucleus and cytoplasm, causing homeostasis and restoring the cell's normal condition with reducing protein translation and synthesis. The UPR response followed by stress enhancement balances cell survival with death, therefore in this condition cells decide either to survive or have the path of apoptosis ahead. However, in some cases, this balance is disturbed and the UPR pathway is chronically activated or not activated and the cell conditions lead to cancer. This study aimed to briefly investigate the association between ER stress, UPR, apoptosis, and autophagy in colorectal cancer (CRC). Moreover, in current study, we will try to demonstrate canonical ways and methods for the treatment of CRC cells with attenuated ER stress.

SIRT6 deficiency in endothelial cells exacerbates oxidative stress by enhancing HIF1α accumulation and H3K9 acetylation at the Ero1α promoter

BACKGROUND

SIRT6, an important NAD+ -dependent protein, protects endothelial cells from inflammatory and oxidative stress injuries. However, the role of SIRT6 in cardiac microvascular endothelial cells (CMECs) under ischemia-reperfusion injury (IRI) remains unclear.

METHODS

The HUVECs model of oxygen-glucose deprivation/reperfusion (OGD/R) was established to simulate the endothelial IRI in vitro. Endoplasmic reticulum oxidase 1 alpha (Ero1α) mRNA and protein levels in SIRT6-overexpressing or SIRT6-knockdown cells were measured by qPCR and Western blotting. The levels of H2 O2 and mitochondrial reactive oxygen species (ROS) were detected to evaluate the status of oxidative stress. The effects of SIRT6 deficiency and Ero1α knockdown on cellular endoplasmic reticulum stress (ERS), inflammation, apoptosis and barrier function were detected by a series of molecular biological experiments and functional experiments in vitro. Chromatin immunoprecipitation, Western blotting, qPCR, and site-specific mutation experiments were used to examine the underlying molecular mechanisms. Furthermore, endothelial cell-specific Sirt6 knockout (ecSirt6-/- ) mice were subjected to cardiac ischemia-reperfusion surgery to investigate the effects of SIRT6 in CMECs in vivo.

RESULTS

The expression of Ero1α was significantly upregulated in SIRT6-knockdown endothelial cells, and high Ero1α expression correlated with the accumulation of H2 O2 and mitochondrial ROS. In addition, SIRT6 deficiency increased ERS, inflammation, apoptosis and endothelial permeability, and these effects could be significantly attenuated by Ero1α knockdown. The deacetylase catalytic activity of SIRT6 was important in regulating Ero1α expression and these biological processes. Mechanistically, SIRT6 inhibited the enrichment of HIF1α and p300 at the Ero1α promoter through deacetylating H3K9, thereby antagonizing HIF1α/p300-mediated Ero1α expression. Compared with SIRT6-wild-type (SIRT6-WT) cells, cells expressing the SIRT6-H133Y-mutant and SIRT6-R65A-mutant exhibited increased Ero1α expression. Furthermore, ecSirt6-/- mice subjected to ischemia-reperfusion surgery exhibited increased Ero1α expression and ERS in CMECs and worsened injuries to microvascular barrier function and cardiac function.

CONCLUSIONS

Our results revealed an epigenetic mechanism associated with SIRT6 and Ero1α expression and highlighted the therapeutic potential of targeting the SIRT6-HIF1α/p300-Ero1α axis.

Time-Course and Tissue-Specific Molecular Responses to Acute Thermal Stress in Japanese Mantis Shrimp Oratosquilla oratoria

Current understanding of adaptability to high temperatures is increasingly important as extreme weather events that can trigger immediate physiological stress in organisms have occurred more frequently. Here, we tracked transcriptomic responses of gills, hepatopancreas, and muscle to acute thermal exposure at 30 °C for 0.5, 6, and 12 h in an economically important crustacean, Oratosquilla oratoria, to gain a preliminary understanding of the tissue-specific and dynamic physiological regulation process under acute heat stress. The unique physiological responses of muscle, hepatopancreas, and gills to acute thermal stress were associated with protein degradation, lipid transport, and energy metabolism in O. oratoria, respectively. Functional enrichment analysis of differentially expressed transcripts and heat-responsive gene clusters revealed a biphasic protective responsiveness of O. oratoria developed from the early responses of signal transduction, immunity, and cytoskeleton reorganization to the responses dominated by protein turnover and energy metabolism at the mid-late stages under acute heat stress. Noteworthy, trend analysis revealed a consistently upregulated expression pattern of high molecular weight heat shock protein (HSP) family members (HSP60, HSP70, and HSP90) during the entire thermal exposure process, highlighting their importance for maintaining heat resistance in O. oratoria. Documenting the whole process of transcriptional responses at fine temporal resolution will contribute to a far-reaching comprehension of plastic responses to acute heat stress in crustaceans, which is critical in the context of a changing climate.

Ribosomal protein mutations and cell competition: autonomous and nonautonomous effects on a stress response

Ribosomal proteins (Rps) are essential for viability. Genetic mutations affecting Rp genes were first discovered in Drosophila, where they represent a major class of haploinsufficient mutations. One mutant copy gives rise to the dominant "Minute" phenotype, characterized by slow growth and small, thin bristles. Wild-type (WT) and Minute cells compete in mosaics, that is, Rp+/- are preferentially lost when their neighbors are of the wild-type genotype. Many features of Rp gene haploinsufficiency (i.e. Rp+/- phenotypes) are mediated by a transcriptional program. In Drosophila, reduced translation and slow growth are under the control of Xrp1, a bZip-domain transcription factor induced in Rp mutant cells that leads ultimately to the phosphorylation of eIF2α and consequently inhibition of most translation. Rp mutant phenotypes are also mediated transcriptionally in yeast and in mammals. In mammals, the Impaired Ribosome Biogenesis Checkpoint activates p53. Recent findings link Rp mutant phenotypes to other cellular stresses, including the DNA damage response and endoplasmic reticulum stress. We suggest that cell competition results from nonautonomous inputs to stress responses, bringing decisions between adaptive and apoptotic outcomes under the influence of nearby cells. In Drosophila, cell competition eliminates aneuploid cells in which loss of chromosome leads to Rp gene haploinsufficiency. The effects of Rp gene mutations on the whole organism, in Minute flies or in humans with Diamond-Blackfan Anemia, may be inevitable consequences of pathways that are useful in eliminating individual cells from mosaics. Alternatively, apparently deleterious whole organism phenotypes might be adaptive, preventing even more detrimental outcomes. In mammals, for example, p53 activation appears to suppress oncogenic effects of Rp gene haploinsufficiency.

Full-Length Transcriptome Sequencing Reveals the Molecular Mechanism of Metasequoia glyptostroboides Seed Responding to Aging

Metasequoia glyptostroboides, Hu and W. C. Cheng, as the only surviving relict species of the Taxodiaceae Metasequoia genus, is a critically endangered and protected species in China. There is a risk of extinction due to the low vigor of M. glyptostroboides seeds, and the physiological mechanism of seed aging in M. glyptostroboides is not yet clear. In order to investigate the physiological and molecular mechanisms underlying the aging process of M. glyptostroboides seeds, we analyzed the antioxidant system and transcriptome at 0, 2, 4, 6, and 8 days after artificial accelerated aging treatment at 40 °C and 100% relative humidity. It was found that the germination percentage of fresh dried M. glyptostroboides seeds was 54 ± 5.29%, and significantly declined to 9.33 ± 1.88% after 6 days of aging, and then gradually decreased until the seed died on day 8. Superoxide dismutase (SOD) activity, ascorbic acid (AsA), glutathione (GSH) content and superoxide anion (O₂^·-) content and production rate significantly decreased, while malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content and glutathione peroxidase (GPX) and catalase (CAT) activity gradually increased during the aging process. A total of 42,189 unigenes were identified in the whole transcriptome, and 40,446 (95.86%) unigenes were annotated in at least one protein database. A total of 15,376 differentially expressed genes (DEGs) were obtained; KEGG enrichment analysis results revealed that seed aging may be mainly involved in the protein-processing pathways in endoplasmic reticulum, oxidative phosphorylation, and ascorbate and aldarate metabolism. Weighted gene co-expression network analysis (WGCNA) revealed that the dark magenta, orange, and medium purple modules were highly correlated with physiological indicators such as SOD, CAT, and GSH and further identified 40 hub genes such as Rboh, ACO, HSF, and CML as playing important roles in the antioxidant network of M. glyptostroboides seeds. These findings provide a broader perspective for studying the regulatory mechanism of seed aging and a large number of potential target genes for the breeding of other endangered gymnosperms.

The role of glutathione in periplasmic redox homeostasis and oxidative protein folding in Escherichia coli

The thiol redox balance in the periplasm of E. coli depends on the DsbA/B pair for oxidative power and the DsbC/D system as its complement for isomerization of non-native disulfides. While the standard redox potentials of those systems are known, the in vivo "steady state" redox potential imposed onto protein thiol disulfide pairs in the periplasm remains unknown. Here, we used genetically encoded redox probes (roGFP2 and roGFP-iL), targeted to the periplasm, to directly probe the thiol redox homeostasis in this compartment. These probes contain two cysteine residues that are virtually completely reduced in the cytoplasm, but once exported into the periplasm, can form a disulfide bond, a process that can be monitored by fluorescence spectroscopy. Even in the absence of DsbA, roGFP2, exported to the periplasm, was almost fully oxidized, suggesting the presence of an alternative system for the introduction of disulfide bonds into exported proteins. However, the absence of DsbA shifted the steady state periplasmic thiol-redox potential from -228 mV to a more reducing -243 mV and the capacity to re-oxidize periplasmic roGFP2 after a reductive pulse was significantly decreased. Re-oxidation in a DsbA strain could be fully restored by exogenous oxidized glutathione (GSSG), while reduced GSH accelerated re-oxidation of roGFP2 in the WT. In line, a strain devoid of endogenous glutathione showed a more reducing periplasm, and was significantly worse in oxidatively folding PhoA, a native periplasmic protein and substrate of the oxidative folding machinery. PhoA oxidative folding could be enhanced by the addition of exogenous GSSG in the WT and fully restored in a ΔdsbA mutant. Taken together this suggests the presence of an auxiliary, glutathione-dependent thiol-oxidation system in the bacterial periplasm.

Endoplasmic reticulum homeostasis: a potential target for diabetic nephropathy

The endoplasmic reticulum (ER) is the most vigorous organelle in intracellular metabolism and is involved in physiological processes such as protein and lipid synthesis and calcium ion transport. Recently, the abnormal function of the ER has also been reported to be involved in the progression of kidney disease, especially in diabetic nephropathy (DN). Here, we reviewed the function of the ER and summarized the regulation of homeostasis through the UPR and ER-phagy. Then, we also reviewed the role of abnormal ER homeostasis in residential renal cells in DN. Finally, some ER stress activators and inhibitors were also summarized, and the possibility of maintaining ER homeostasis as a potential therapeutic target for DN was discussed.

Overexpression of genes by stress-responsive promoters increases protein secretion in Saccharomyces cerevisiae

Recombinant proteins produced by cell factories are now widely used in various fields. Many efforts have been made to improve the secretion capacity of cell factories to meet the increasing demand for recombinant proteins. Recombinant protein production usually causes cell stress in the endoplasmic reticulum (ER). The overexpression of key genes possibly removes limitations in protein secretion. However, inappropriate gene expression may have negative effects. There is a need for dynamic control of genes adapted to cellular status. In this study, we constructed and characterized synthetic promoters that were inducible under ER stress conditions in Saccharomyces cerevisiae. The unfolded protein response element UPRE2, responding to stress with a wide dynamic range, was assembled with various promoter core regions, resulting in UPR-responsive promoters. Synthetic responsive promoters regulated gene expression by responding to stress level, which reflected the cellular status. The engineered strain using synthetic responsive promoters P_{4UPRE2 - TDH3} and P_{4UPRE2 - TEF1} for co-expression of ERO1 and SLY1 had 95% higher α-amylase production compared with the strain using the native promoters P_TDH3 and P_TEF1. This work showed that UPR-responsive promoters were useful in the metabolic engineering of yeast strains for tuning genes to support efficient protein production.

Mitochondria-associated endoplasmic reticulum membranes (MAMs) and their role in glaucomatous retinal ganglion cell degeneration-a mini review

Glaucoma is a leading cause of blindness worldwide, commonly associated with elevated intraocular pressure (IOP), leading to degeneration of the optic nerve and death of retinal ganglion cells, the output neurons in the eye. In recent years, many studies have implicated mitochondrial dysfunction as a crucial player in glaucomatous neurodegeneration. Mitochondrial function has been an increasingly researched topic in glaucoma, given its vital role in bioenergetics and propagation of action potentials. One of the most metabolically active tissues in the body characterized by high oxygen consumption is the retina, particularly the retinal ganglion cells (RGCs). RGCs, which have long axons that extend from the eyes to the brain, rely heavily on the energy generated by oxidative phosphorylation for signal transduction, rendering them more vulnerable to oxidative damage. In various glaucoma models, mitochondrial dysfunction and stress from protein aggregates in the endoplasmic reticulum (ER) have been observed in the RGCs. However, it has been shown that the two organelles are connected through a network called mitochondria-associated ER membranes (MAMs); hence this crosstalk in a pathophysiological condition such as glaucoma should be evaluated. Here, we review the current literature suggestive of mitochondrial and ER stress related to glaucoma, indicating potential cross-signaling and the potential roles of MAMs.