Hypoxia and Reactive Oxygen Species as Modulators of Endoplasmic Reticulum and Golgi Homeostasis

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.

The relationship between hypoxia and Alzheimer's disease: an updated review

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and the most prevalent form of dementia. The main hallmarks for the diagnosis of AD are extracellular amyloid-beta (Aβ) plaque deposition and intracellular accumulation of highly hyperphosphorylated Tau protein as neurofibrillary tangles. The brain consumes more oxygen than any other organs, so it is more easily to be affected by hypoxia. Hypoxia has long been recognized as one of the possible causes of AD and other neurodegenerative diseases, but the exact mechanism has not been clarified. In this review, we will elucidate the connection between hypoxia-inducible factors-1α and AD, including its contribution to AD and its possible protective effects. Additionally, we will discuss the relationship between oxidative stress and AD as evidence show that oxidative stress acts on AD-related pathogenic factors such as mitochondrial dysfunction, Aβ deposition, inflammation, etc. Currently, there is no cure for AD. Given the close association between hypoxia, oxidative stress, and AD, along with current research on the protective effects of antioxidants against AD, we speculate that antioxidants could be a potential therapeutic approach for AD and worth further study.

Exploring the redox potential induced by low-intensity focused ultrasound on tumor masses

Cancer is still a major health problem worldwide despite huge efforts being spent on its biomedical research. Beyond the mainstream therapeutic interventions (i.e., surgery, chemotherapy, immunotherapy and radiotherapy), further significant progresses in anticancer therapy could rely on the development of novel treatment paradigms. To this end, one emerging approach consists in the use of non-thermal low-intensity focused ultrasound (LIFU) for conditioning cancer molecules and/or cancer-targeted compounds, thereby leading to cancer cell death with least side-effects. Cellular redox homeostasis manifested as the generation of reactive oxygen species (ROS) during energy metabolism as well as the antioxidant capacity is interwoven to the composition, size and anatomical location of the tumor masses. The higher content of "oxide free radicals" in cancers makes them vulnerable to disruption of redox homeostasis than in the healthy cells and therefore, one of the best options for preferentially eradicating them is increasing their oxidative stress, excessively. A little is known about the modulation of cellular redox homeostasis by LIFU, and so it will be of great interest and utility to understand the effects of LIFU on the energy metabolism of cancer cells. This review is intended to improve our knowledge on the effect of LIFU on cancer cells with particular reference to its redox metabolism for ultrasound-based therapies. Thereby, it could pave the way for exploring novel methodologies and designing combined anti-cancer therapies, especially, for faster and safer eradication of drug resistant and metastasizing solid tumors.

CYP51-mediated cholesterol biosynthesis is required for the proliferation of CD4+ T cells in Sjogren's syndrome

CYtochrome P450, family 51 (CYP51) is an important enzyme for de novo cholesterol synthesis in mammalian cells. In the present study, we found that the expression of CYP51 positively correlated with CD4+ T cell activation both in vivo and in vitro. The addition of ketoconazole, a pharmacological inhibitor of CYP51, prevented the proliferation and activation of anti-CD3/CD28-expanded mouse CD4+ T cells in a dose-dependent fashion. Liquid chromatography-tandem mass spectrometry indicated an increase in levels of lanosterol in T cells treated with ketoconazole during activation. Ketoconazole-induced blockade of the cholesterol synthesis pathway also caused Sterol regulatory element binding protein 2 (SREBP2) activation in CD4+ T cells. Additionally, ketoconazole treatment elicited an integrated stress response in T cells that up-regulated activating transcription factor 4 (ATF4) and DNA-damage inducible transcript 3 (DDIT3/CHOP) at the translational level. Furthermore, treatment with ketoconazole significantly decreased the amount of CD4+ T cells infiltrating lesions in the submandibular glands of NOD/Ltj mice. In summary, our results suggest that CYP51 plays an essential role in the proliferation and survival of CD4+ T cells, which makes ketoconazole an inhibitor of CD4+ T cell proliferation and of the SS-like autoimmune response through regulating the biosynthesis of cholesterol and inducing the integrated stress response.

Endoplasmic Reticulum Stress in Systemic Lupus Erythematosus and Lupus Nephritis: Potential Therapeutic Target

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Approximately one-third to two-thirds of the patients with SLE progress to lupus nephritis (LN). The pathogenesis of SLE and LN has not yet been fully elucidated, and effective treatment for both conditions is lacking. The endoplasmic reticulum (ER) is the largest intracellular organelle and is a site of protein synthesis, lipid metabolism, and calcium storage. Under stress, the function of ER is disrupted, and the accumulation of unfolded or misfolded proteins occurs in ER, resulting in an ER stress (ERS) response. ERS is involved in the dysfunction of B cells, macrophages, T cells, dendritic cells, neutrophils, and other immune cells, causing immune system disorders, such as SLE. In addition, ERS is also involved in renal resident cell injury and contributes to the progression of LN. The molecular chaperones, autophagy, and proteasome degradation pathways inhibit ERS and restore ER homeostasis to improve the dysfunction of immune cells and renal resident cell injury. This may be a therapeutic strategy for SLE and LN. In this review, we summarize advances in this field.

The Golgi Apparatus: A Voyage through Time, Structure, Function and Implication in Neurodegenerative Disorders

This comprehensive review article dives deep into the Golgi apparatus, an essential organelle in cellular biology. Beginning with its discovery during the 19th century until today's recognition as an important contributor to cell function. We explore its unique organization and structure as well as its roles in protein processing, sorting, and lipid biogenesis, which play key roles in maintaining homeostasis in cellular biology. This article further explores Golgi biogenesis, exploring its intricate processes and dynamics that contribute to its formation and function. One key focus is its role in neurodegenerative diseases like Parkinson's, where changes to the structure or function of the Golgi apparatus may lead to their onset or progression, emphasizing its key importance in neuronal health. At the same time, we examine the intriguing relationship between Golgi stress and endoplasmic reticulum (ER) stress, providing insights into their interplay as two major cellular stress response pathways. Such interdependence provides a greater understanding of cellular reactions to protein misfolding and accumulation, hallmark features of many neurodegenerative diseases. In summary, this review offers an exhaustive examination of the Golgi apparatus, from its historical background to its role in health and disease. Additionally, this examination emphasizes the necessity of further research in this field in order to develop targeted therapeutic approaches for Golgi dysfunction-associated conditions. Furthermore, its exploration is an example of scientific progress while simultaneously offering hope for developing innovative treatments for neurodegenerative disorders.

Vitamin C: From nutrition to oxygen sensing and epigenetics

Vitamin C is unbeatable - at least when it comes to sales. Of all the vitamin preparations, those containing vitamin C sell best. This is surprising because vitamin C deficiency is extremely rare. Nevertheless, there is still controversy about whether the additional intake of vitamin C supplements is essential for our health. In this context, the possible additional benefit is in most cases merely reduced to the known effect as an antioxidant. However, new findings in recent years on the mechanisms of oxygen-sensing and epigenetic control underpin the multifaceted role of vitamin C in a biological context and have therefore renewed interest in it. In the present article, therefore, known facts are linked to these new key data. In addition, available clinical data on vitamin C use of cancer therapy are summarized.

Synergistic mechanism between the endoplasmic reticulum and mitochondria and their crosstalk with other organelles

Organelles are functional areas where eukaryotic cells perform processes necessary for life. Each organelle performs specific functions; however, highly coordinated crosstalk occurs between them. Disorder of organelle networks often occur in various diseases. The endoplasmic reticulum (ER) and mitochondria are crucial organelles in eukaryotic cells as they are the material synthesis and oxidative metabolism centers, respectively. Homeostasis and orchestrated interactions are essential for maintaining the normal activities of cells. However, the mode and mechanism of organelle crosstalk is still a research challenge. Furthermore, the intricate association between organelle dyshomeostasis and the progression of many human diseases remains unclear. This paper systematically summarized the latest research advances in the synergistic mechanism between the endoplasmic reticulum and mitochondria and their crosstalk with other organelles based on recent literature. It also highlights the application potential of organelle homeostasis maintenance as a preventative and treatment strategy for diseases.

The disulfide catalyst QSOX1 maintains the colon mucosal barrier by regulating Golgi glycosyltransferases

Mucus is made of enormous mucin glycoproteins that polymerize by disulfide crosslinking in the Golgi apparatus. QSOX1 is a catalyst of disulfide bond formation localized to the Golgi. Both QSOX1 and mucins are highly expressed in goblet cells of mucosal tissues, leading to the hypothesis that QSOX1 catalyzes disulfide-mediated mucin polymerization. We found that knockout mice lacking QSOX1 had impaired mucus barrier function due to production of defective mucus. However, an investigation on the molecular level revealed normal disulfide-mediated polymerization of mucins and related glycoproteins. Instead, we detected a drastic decrease in sialic acid in the gut mucus glycome of the QSOX1 knockout mice, leading to the discovery that QSOX1 forms regulatory disulfides in Golgi glycosyltransferases. Sialylation defects in the colon are known to cause colitis in humans. Here we show that QSOX1 redox control of sialylation is essential for maintaining mucosal function.

Logic of the Temporal Compartmentalization of the Hepatic Metabolic Cycle

The mammalian liver must cope with various metabolic and physiological changes that normally recur every day and result primarily from rest-activity and fasting-feeding cycles. In this article, I present evidence supporting a temporal compartmentalization of rhythmic hepatic metabolic processes into four main clusters: regulation of energy homeostasis, maintenance of information integrity, immune response, and genetic information flow. I further review literatures and discuss how both the circadian and the newly discovered 12-h ultradian clock work together to regulate these four temporally separated processes in mouse liver, which, interestingly, is largely uncoupled from the liver zonation regulation.

What to do with low O2: Redox adaptations in vertebrates native to hypoxic environments

Reactive oxygen species (ROS) are important cellular signalling molecules but sudden changes in redox balance can be deleterious to cells and lethal to the whole organism. ROS production is inherently linked to environmental oxygen availability and many species live in variable oxygen environments that can range in both severity and duration of hypoxic exposure. Given the importance of redox homeostasis to cell and animal viability, it is not surprising that early studies in species adapted to various hypoxic niches have revealed diverse strategies to limit or mitigate deleterious ROS changes. Although research in this area is in its infancy, patterns are beginning to emerge in the suites of adaptations to different hypoxic environments. This review focuses on redox adaptations (i.e., modifications of ROS production and scavenging, and mitigation of oxidative damage) in hypoxia-tolerant vertebrates across a range of hypoxic environments. In general, evidence suggests that animals adapted to chronic lifelong hypoxia are in homeostasis, and do not encounter major oxidative challenges in their homeostatic environment, whereas animals exposed to seasonal chronic anoxia or hypoxia rapidly downregulate redox balance to match a hypometabolic state and employ robust scavenging pathways during seasonal reoxygenation. Conversely, animals adapted to intermittent hypoxia exposure face the greatest degree of ROS imbalance and likely exhibit enhanced ROS-mitigation strategies. Although some progress has been made, research in this field is patchy and further elucidation of mechanisms that are protective against environmental redox challenges is imperative for a more holistic understanding of how animals survive hypoxic environments.

Dance of The Golgi: Understanding Golgi Dynamics in Cancer Metastasis

The Golgi apparatus is at the center of protein processing and trafficking in normal cells. Under pathological conditions, such as in cancer, aberrant Golgi dynamics alter the tumor microenvironment and the immune landscape, which enhances the invasive and metastatic potential of cancer cells. Among these changes in the Golgi in cancer include altered Golgi orientation and morphology that contribute to atypical Golgi function in protein trafficking, post-translational modification, and exocytosis. Golgi-associated gene mutations are ubiquitous across most cancers and are responsible for modifying Golgi function to become pro-metastatic. The pharmacological targeting of the Golgi or its associated genes has been difficult in the clinic; thus, studying the Golgi and its role in cancer is critical to developing novel therapeutic agents that limit cancer progression and metastasis. In this review, we aim to discuss how disrupted Golgi function in cancer cells promotes invasion and metastasis.

ER-stress promotes VHL-independent degradation of hypoxia-inducible factors via FBXW1A/βTrCP

Metabolic adaptation and signal integration in response to hypoxic conditions is mainly regulated by hypoxia-inducible factors (HIFs). At the same time, hypoxia induces ROS formation and activates the unfolded protein response (UPR), indicative of endoplasmic reticulum (ER) stress. However, whether ER stress would affect the hypoxia response remains ill-defined. Here we report that feeding mice a high fat diet causes ER stress and attenuates the response to hypoxia. Mechanistically, ER stress promotes HIF-1α and HIF-2α degradation independent of ROS, Ca²⁺, and the von Hippel-Lindau (VHL) pathway, involving GSK3β and the ubiquitin ligase FBXW1A/βTrCP. Thereby, we reveal a previously unknown function of the GSK3β/HIFα/βTrCP1 axis in ER homeostasis and demonstrate that inhibition of the HIF-1 and HIF-2 response and genetic deficiency of GSK3β affects proliferation, migration, and sensitizes cells for ER stress promoted apoptosis. Vice versa, we show that hypoxia affects the ER stress response mainly through the PERK-arm of the UPR. Overall, we discovered previously unrecognized links between the HIF pathway and the ER stress response and uncovered an essential survival pathway for cells under ER stress.

Elucidation of the liver proteome in response to an antioxidant intake in rabbits

Background

Antioxidant intakes are one of the most cherished dietary approaches for the management of oxidative stress-induced liver damages. These antioxidants exist as the bioactive compounds present in plants and other natural sources functioning in varieties of ways from acting as direct scavengers of the free radicals to acting as the modifiers of genes and proteins expressions. Chlorella vulgaris is one of such antioxidants; it is a unicellular microalga and a rich source of polyphenols which has been reported for its capacity of reducing oxidative stress by upregulation of antioxidant genes. However, there are scarce reports on its effect on antioxidant protein expressions and functions in the liver. This situation necessitates untargeted proteomic profiling of the liver due to the antioxidant intakes as carried out in this present study. Sixteen laboratory weaner rabbits of 8 weeks old with initial average bodyweight of 1060 ± 29.42 g were randomly divided into two groups (n = 8 per group); the first group served as control while the second served as the treatment group were used for this study.

Results

After a period of 120 days daily consumption of 500 mg of Chlorella vulgaris biomass per kg bodyweight of the rabbit models, the animals were sacrificed and their livers were harvested followed by protein extraction for the untargeted proteomic profiling using LC-MS/Orbitrap Fusion Tribrid™ peptides quantifier and sequencer. Also, there was an assessment of the oxidative stress biomarkers in the liver and serum of the rabbits. Five-hundred and forty-four (544) proteins were identified out of which 204 were unique to the control, 198 were unique to the treatment group, while 142 were common to both groups of the rabbits. Antioxidant proteins commonly found in both groups were upregulated in the treatment group and were significantly associated with oxidative stress-protective activities. There was a reduction in oxidative stress biomarkers of the supplemented group as indicated by the assessment of the liver malondialdehyde concentrations (p < 0.05), total antioxidant capacities (p < 0.05), and antioxidant enzyme activities (p < 0.05). Similarly, these biomarkers were significantly reduced in the serum of the supplemented rabbits (p < 0.05).

Conclusion

The study concluded that Chlorella vulgaris is an antioxidant agent that could be suitable for reducing liver oxidative stress damage and it is a potential drug candidate for protecting the liver against oxidative stress damages as revealed in the rabbit models.

Effects of dietary inclusion of Radix Bupleuri extract on the growth performance, and ultrastructural changes and apoptosis of lung epithelial cells in broilers exposed to atmospheric ammonia

To explore whether Radix Bupleuri extract (RBE) could protect lung injury of broilers under ammonia (NH3) exposure, 360 one-d-old male broilers were randomly allocated to four groups of six replicates each in a 2 × 2 factorial design with two diets (the basal diet [control; CON] and the basal diet supplemented with RBE [RB]) and two air conditions (normal condition [<2 ppm of NH3; NOR] and NH3 exposure [70 ppm of NH3; NH70]). The RB diet contained 80 mg saikosaponins/kg diet. On day 7, the lung tissues were collected and the lung epithelial cells (LEC) were isolated. Our experimental results showed that the NH3 exposure decreased body weight gain and feed intake irrespective of dietary treatments during days 1 to 7. However, the RBE addition decreased feed consumption to body weight gain ratio in broilers under NH70 conditions. In the LEC of CON-fed broilers under NH70 conditions, Golgi stacks showed the dilation of cisternaes and reduced secretory vesicles, mitochondria enlarged, the inner membrane of mitochondria became obscure, and the cristae of mitochondria ruptured, whereas only a mild enlargement of Golgi cisternaes and the part rupture of mitochondrial cristaes occurred in the LEC of RB-fed broilers under NH70 conditions. The NH3 exposure increased malondialdehyde (MDA) level, but decreased total antioxidant capacity (T-AOC) in the lungs of CON-fed broilers. However, the RBE addition decreased MDA level and increased T-AOC in the lungs of broilers under NH70 conditions. Simultaneously, the NH3 exposure increased apoptotic rate (AR), mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) level in the isolated LEC of CON-fed broilers. The RBE addition decreased AR, MMP, and ROS in the isolated LEC of broilers under NH70 condition. Besides, the NH3 exposure increased mRNA expression of B-cell lymphoma-2 associated X protein (BAX), caspase-3, and tumor necrosis factor α (TNF-α), but increased interferon γ (IFN-γ) mRNA abundance in the lungs of CON-fed broilers. The RBE supplement decreased mRNA levels of BAX, caspase-3, and TNF-α, but increased IFN-γ, interleukin (IL)-4, and IL-17 mRNA levels in the lungs of broilers under NH70 conditions. These results indicated that dietary RBE addition alleviated NH3 exposure-induced intercellular ultrastructural damage via mitochondrial apoptotic pathway, possibly due to RBE-induced increase of antioxidant capacity and immunomodulatory function in the lungs of broilers under NH3 exposure.

Corn Husk Phenolics Modulate Hepatic Antioxidant Response in Nile Tilapia (Oreochromis niloticus) Exposed to Hypoxia

The hypoxia conditions in intensive farming systems generate oxidative stress related to oxidative damage and mortality of fish. Corn husk meal (CHM), as a source of antioxidants, might modulate the antioxidant response and prevent the damage elicited by hypoxia. This study evaluated CHM’s ability to modulate a hepatic response in Nile tilapia exposed to hypoxia. A control and a test diet supplemented with 25 g CHM/kg feed were formulated. Ninety Nile tilapias (5.09 ± 0.55 g initial weight) were fed for 36 days to evaluate growth, feed efficiency, and hepatic antioxidant response (CAT, catalase; SOD, superoxide dismutase, and GPx, glutathione peroxidase) in normal oxygen conditions (normoxia). After the feeding trial (36 days), fish were exposed to hypoxia (1.5 ± 0.2 mg/L dissolved oxygen), and the hepatic antioxidant response was determined. There was no significant effect of CHM on growth and feed efficiency. The CAT activity was significantly increased in tilapias exposed to hypoxia and fed the test diet compared to the control group exposed to hypoxia. The SOD and GPx activities were unchanged in tilapias in normoxia and hypoxia conditions. Results suggest that CHM dietary supplementation promotes the antioxidant response in Nile tilapia exposed to hypoxia through CAT modulation.

Effect of endoplasmic reticulum stress-induced apoptosis in the role of periodontitis on vascular calcification in a rat model

The present study aimed to investigate the mechanism(s) through which endoplasmic reticulum stress (ERS)-induced apoptosis, in the role of periodontitis, affects vascular calcification. Rat models of periodontitis, vascular calcification, periodontitis-vascular calcification, and a normal group were established. Cardiovascular tissues were obtained, and hematoxylin-eosin staining was applied to demonstrate the morphological changes in vascular tissues. Immunohistochemical staining was applied to analyze apoptosis in cardiovascular tissues. The expression levels of apoptotic factor cysteinyl aspartate specific proteinase 3 (Caspase-3), ERS-induced apoptotic factors glucose-regulated protein 78 (GRP78), 94 (GRP94), and ERS-induced apoptosis pathways Caspase-12, C/EBP homologous protein (CHOP), and c-Jun N-terminal kinase (JNK) were analyzed and compared. Hematoxylin-eosin staining revealed that the arterial layers in the normal group were structurally intact. The structural damage to the aortic wall gradually aggravated from the periodontitis group to the vascular calcification group to the combined group. The immunohistochemistry results showed Caspase-3, GRP78, GRP94, and ERS-induced apoptosis pathways in the cardiovascular tissues cells in the periodontitis group, vascular calcification group, and combined group. The Caspase-3, GRP78, GRP94, and CHOP expression levels in the combined group were significantly higher than that in the normal group (P < 0.05); however, the Capase-12 and JNK expression levels in the four groups exhibited no significant differences (P > 0.05). Apoptosis induced by ERS is involved in the effect of periodontitis on vascular calcification and might be mainly achieved through the activation of the CHOP transcription pathway.

1,2,4-Triaminobenzene as a Fluorescent Probe for Intracellular pH Imaging and Point-of-Care Ammonia Sensing

As one of the health indicators, intracellular pH plays important roles in many processes of cell functions. Abnormal pH changes would result in the occurrence of inflammation, cancer, and other diseases. Thus, it is of significant importance to develop effective techniques for sensitive detection of pH changes for the clinical diagnosis of various diseases related to cells. In this paper, 1,2,4-triaminobenzene hydrochloride was explored as an organic molecular fluorescent probe for sensitive and selective detection of intracellular pH changes for the first time. Due to the protonation and deprotonation of amino groups of the probe, its fluorescent intensity at 599 nm or the ratio of absorbance at 505 and 442 nm has a good linear relationship with pH values in the range of 5.0-7.0. Benefiting from the excellent physical and chemical properties of 1,2,4-triaminobenzene hydrochloride, the fluorescent probe has good water solubility, low toxicity, high photostability, great reversibility, good cell penetration, fast response speed, and so on. As a proof-of-concept demonstration, the proposed probe is employed for the fluorescence imaging of cells and mouse tissue sections with satisfactory performance in pH differentiation. Additionally, the probe was successfully employed to prepare test strips as a kind of point-of-care testing device to detect ammonia, which showed great potential in practical applications.

Endoplasmic reticulum stress/XBP1 promotes airway mucin secretion under the influence of neutrophil elastase

Endoplasmic reticulum (ER) stress is an important reaction of airway epithelial cells in response to various stimuli, and may also be involved in the mucin secretion process. In the present study, the effect of ER stress on neutrophil elastase (NE)-induced mucin (MUC)5AC production in human airway epithelial cells was explored. 16HBE14o-airway epithelial cells were cultured and pre-treated with the reactive oxygen species (ROS) inhibitor, N-acetylcysteine (NAC), or the ER stress chemical inhibitor, 4-phenylbutyric acid (4-PBA), or the cells were transfected with inositol-requiring kinase 1α (IRE1α) small interfering RNA (siRNA) or X-box-binding protein 1 (XBP1) siRNA, respectively, and subsequently incubated with NE. The results obtained revealed that NE increased ROS production in the 16HBE14o-cells, with marked increases in the levels of ER stress-associated proteins, such as glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), phosphorylated protein kinase R-like endoplasmic reticulum kinase (pPERK) and phosphorylated (p)IRE1α. The protein and mRNA levels of spliced XBP1 were also increased, and the level of MUC5AC protein was notably increased. The ROS scavenger NAC and ER stress inhibitor 4-PBA were found to reduce ER stress-associated protein expression and MUC5AC production and secretion. Further analyses revealed that MUC5AC secretion was also attenuated by IRE1α and XBP1 siRNAs, accompanied by a decreased mRNA expression of spliced XBP1. Taken together, these results demonstrate that NE induces ER stress by promoting ROS production in 16HBE14o-airway epithelial cells, leading to increases in MUC5AC protein production and secretion via the IRE1α and XBP1 signaling pathways.

Heme oxygenase-1(HO-1) regulates Golgi stress and attenuates endotoxin-induced acute lung injury through hypoxia inducible factor-1α (HIF-1α)/HO-1 signaling pathway

Sepsis caused acute lung injury (ALI) is a kind of serious disease in critically ill patients with very high morbidity and mortality. Recently, it has been demonstrated that Golgi is involved in the process of oxidative stress. However, whether Golgi stress is associated with oxidative stress in septic induced acute lung injury has not been elucidated. In this research, we found that lipopolysaccharide (LPS) induced oxidative stress, apoptosis, inflammation and Golgi morphology changes in acute lung injury both in vivo and in vitro. The knockout of heme oxygenase-1(HO-1) aggravated oxidative stress, inflammation, apoptosis and reduced the expression of Golgi matrix protein 130 (GM130), mannosidase Ⅱ, Golgi-associated protein golgin A1 (Golgin 97), and increased the expression of Golgi phosphoprotein 3 (GOLPH3), which caused the fragmentation of Golgi. Furtherly, the activation of hypoxia inducible factor-1α (HIF-1α)/HO-1 pathway, attenuates Golgi stress and oxidative stress by increasing the levels of GM130, mannosidase Ⅱ, Golgin 97, and decreasing the expression of GOLPH3 both in vivo and in vitro. Therefore, the activation of HO-1 plays a crucial role in alleviating sepsis-induced acute lung injury by regulating Golgi stress, oxidative stress, which may provide a therapeutic target for the treatment of acute lung injury.

Endoplasmic reticulum stress and unfolded protein response in cardiovascular diseases

Cardiovascular diseases (CVDs), such as ischaemic heart disease, cardiomyopathy, atherosclerosis, hypertension, stroke and heart failure, are among the leading causes of morbidity and mortality worldwide. Although specific CVDs and the associated cardiometabolic abnormalities have distinct pathophysiological and clinical manifestations, they often share common traits, including disruption of proteostasis resulting in accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER). ER proteostasis is governed by the unfolded protein response (UPR), a signalling pathway that adjusts the protein-folding capacity of the cell to sustain the cell's secretory function. When the adaptive UPR fails to preserve ER homeostasis, a maladaptive or terminal UPR is engaged, leading to the disruption of ER integrity and to apoptosis. ER stress functions as a double-edged sword, with long-term ER stress resulting in cellular defects causing disturbed cardiovascular function. In this Review, we discuss the distinct roles of the UPR and ER stress response as both causes and consequences of CVD. We also summarize the latest advances in our understanding of the importance of the UPR and ER stress in the pathogenesis of CVD and discuss potential therapeutic strategies aimed at restoring ER proteostasis in CVDs.

Recombinant Treponema pallidum protein Tp0768 promotes proinflammatory cytokine secretion of macrophages through ER stress and ROS/NF-κB pathway

In response to danger signals, macrophages rapidly produce many inflammatory cytokines that trigger the cascade release of inflammatory mediators, leading to tissue damage, which is an important cause of clinical manifestations of syphilis at all stages. However, we still know very little about the specific mechanism of this process. Tp0768 is an infection-stage-dependent antigen that plays an important role in the infection of Treponema pallidum. In this study, we demonstrated that Tp0768 stimulation of macrophages can cause IL-1β, IL-6, and IL-8 mRNA expression levels to increase in a dose- and time-dependent manner. Further research showed that Tp0768 activated ER stress and the ROS/NF-κB pathway in macrophages. Inhibition of ER stress and the ROS/NF-κB pathway inhibited the expression of IL-1β, IL-6, and IL-8 induced by Tp0768. In addition, pretreatment with a PERK pathway inhibitor significantly reduced the expression of the NF-κB and JNK pathways, while also downregulating the expression of IL-1β, IL-6, and IL-8. Tp0768 stimulation can activate IRE1α/XBP-1 signaling and participate in the induction of inflammatory cytokines through the JNK pathway. These findings indicate that Tp0768 promotes the secretion of proinflammatory cytokines IL-1β, IL-6, and IL-8 by macrophages through ER stress and the ROS/NF-κB pathway, which are also involved in the activation of the NF-κB and JNK pathways that are induced by the PERK pathway and activation of IRE1α/XBP-1 signaling. KEY POINTS: • This study found for the first time that the recombinant Treponema pallidum protein Tp0768 promotes the production of IL-1β, IL-6, and IL-8 by macrophages through ER stress. • Recombinant Treponema pallidum protein Tp0768 regulates the ROS/NF-κB pathway through ER stress. • ER stress-related pathway PERK induces the expression of IL-1β, IL-6, and IL-8 by activating the NF-κB pathway and the JNK pathway. • IRE1α can induce the splicing of XBP-1mRNA and activate the JNK pathway.

Endoplasmic reticulum Ca2+ release causes Rieske iron-sulfur protein-mediated mitochondrial ROS generation in pulmonary artery smooth muscle cells

Mitochondrial reactive oxygen species (ROS) cause Ca²⁺ release from the endoplasmic reticulum (ER) via ryanodine receptors (RyRs) in pulmonary artery smooth muscle cells (PASMCs), playing an essential role in hypoxic pulmonary vasoconstriction (HPV). Here we tested a novel hypothesis that hypoxia-induced RyR-mediated Ca²⁺ release may, in turn, promote mitochondrial ROS generation contributing to hypoxic cellular responses in PASMCs. Our data reveal that application of caffeine to elevate intracellular Ca²⁺ concentration ([Ca²⁺]_i) by activating RyRs results in a significant increase in ROS production in cytosol and mitochondria of PASMCs. Norepinephrine to increase [Ca²⁺]_i due to the opening of inositol 1,4,5-triphosphate receptors (IP3Rs) produces similar effects. Exogenous Ca²⁺ significantly increases mitochondrial-derived ROS generation as well. Ru360 also inhibits the hypoxic ROS production. The RyR antagonist tetracaine or RyR2 gene knockout (KO) suppresses hypoxia-induced responses as well. Inhibition of mitochondrial Ca²⁺ uptake with Ru360 eliminates N- and Ca²⁺-induced responses. RISP KD abolishes the hypoxia-induced ROS production in mitochondria of PASMCs. Rieske iron–sulfur protein (RISP) gene knockdown (KD) blocks caffeine- or NE-induced ROS production. Taken together, these findings have further demonstrated that ER Ca²⁺ release causes mitochondrial Ca²⁺ uptake and RISP-mediated ROS production; this novel local ER/mitochondrion communication-elicited, Ca²⁺-mediated, RISP-dependent ROS production may play a significant role in hypoxic cellular responses in PASMCs.

RNA-Seq analysis of European sea bass (Dicentrarchus labrax L.) infected with nodavirus reveals powerful modulation of the stress response

Nodavirus, or nervous necrosis virus (NNV), is the causative agent of viral encephalopathy and retinopathy (VER), a severe disease affecting numerous fish species worldwide. European sea bass, a cultured species of great economic importance, is highly susceptible to the disease. To better understand the response of this organism to NNV, we conducted RNA-Seq analysis of the brain and head kidney from experimentally infected and uninfected sea bass juveniles at 24 and 72 hours post-infection (hpi). Contrary to what was expected, we observed modest modulation of immune-related genes in the brain, the target organ of this virus, and some of these genes were even downregulated. However, genes involved in the stress response showed extremely high modulation. Accordingly, the genes encoding the enzymes implicated in the synthesis of cortisol were almost the only overexpressed genes in the head kidney at 24 hpi. This stress response was attenuated after 72 h in both tissues, and a progressive immune response against the virus was mounted. Moreover, experiments were conducted to determine how stress activation could impact NNV replication. Our results show the complex interplay between viral activity, the stress reaction and the immune response.

Stimulation of cell invasion by the Golgi Ion Channel GAAP/TMBIM4 via an H2O2-Dependent Mechanism

The mechanisms by which the Golgi apparatus (GA) impacts on cell invasion are poorly understood. The human Golgi Anti-Apoptotic Protein (hGAAP, also known as TMBIM4) is a highly conserved Golgi cation channel that modulates intracellular Ca²⁺ fluxes. Human GAAP is expressed in all human tissues, is essential for cell viability and provides resistance against a range of apoptotic stresses. Furthermore, hGAAP enhances adhesion and cell migration by increasing the turnover of focal adhesions due to activation of store-operated Ca²⁺ entry. Here, we describe a GA-derived mechanism that controls cell invasion. The overexpression of hGAAP stimulates 3-dimensional proteolytic cell invasion by a mechanism that is dependent on the accumulation of intracellular hydrogen peroxide_, which might be produced by the hGAAP-dependent stimulation of mitochondrial respiration. These findings provide new insight into the complex mechanisms by which Ca²⁺ and reactive oxygen species signaling contribute to cell invasion and to the role of the GA in these processes.

Radical Stress Is More Cytotoxic in the Nucleus than in Other Organelles

Cells are exposed to reactive oxygen species (ROS) as a by-product of mitochondrial metabolism, especially under hypoxia. ROS are also enzymatically generated at the plasma membrane during inflammation. Radicals cause cellular damage leading to cell death, as they react indiscriminately with surrounding lipids, proteins, and nucleotides. However, ROS are also important for many physiological processes, including signaling, pathogen killing and chemotaxis. The sensitivity of cells to ROS therefore likely depends on the subcellular location of ROS production, but how this affects cell viability is poorly understood. As ROS generation consumes oxygen, and hypoxia-mediated signaling upregulates expression of antioxidant transcription factor Nrf2, it is difficult to discern hypoxic from radical stress. In this study, we developed an optogenetic toolbox for organelle-specific generation of ROS using the photosensitizer protein SuperNova which produces superoxide anion upon excitation with 590 nm light. We fused SuperNova to organelle specific localization signals to induce ROS with high precision. Selective ROS production did not affect cell viability in most organelles except for the nucleus. SuperNova is a promising tool to induce locally targeted ROS production, opening up new possibilities to investigate processes and organelles that are affected by localized ROS production.

CYT997(Lexibulin) induces apoptosis and autophagy through the activation of mutually reinforced ER stress and ROS in osteosarcoma

Background

Osteosarcoma (OS) is a common malignant cancer in children and adolescents and has a cure rate that has not improved in the last two decades. CYT997 (lexibulin) is a novel potent microtubule-targeting agent with various anticancer activities, such as proliferation inhibition, vascular disruption, and cell cycle arrest and apoptosis induction, in multiple cancers. However, the direct cytotoxic mechanisms of CYT997 have not yet been fully characterized.

Methods

We evaluated apoptosis and autophagy in human osteosarcomas after treatment with CYT997 and investigated the underlying mechanisms. To explore relationships, we used the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC), PERK inhibitor GSK2606414, ERO1 inhibitor EN460 and mitochondrial targeted protection peptide elamipretide. BALB/c-nu mice were inoculated with 143B tumor cells to investigate the in vivo effect of CYT997.

Results

We explored the efficacy and mechanism of CYT997 in osteosarcoma (OS) in vitro and in vivo and demonstrated that CYT997 potently suppresses cell viability and induces apoptosis and autophagy. CYT997 triggered production of ROS and exerted lethal effects via endoplasmic reticulum (ER) stress in OS cells. NAC attenuated these effects. The PERK inhibitor GSK2606414, which can block the ER stress pathway, reduced ROS production and enhanced cell viability. Moreover, activation of ERO1 in the ER stress pathway was responsible for inducing ROS production. ROS produced by the mitochondrial pathway also aggravate ER stress. Protection of mitochondria can reduce apoptosis and autophagy. Finally, CYT997 prominently reduced tumor growth in vivo.

Conclusions

This study suggests that CYT997 induces apoptosis and autophagy in OS cells by triggering mutually enhanced ER stress and ROS and may thus be a promising agent against OS.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1047-9) contains supplementary material, which is available to authorized users.

Cellular Redox Compartments

Although initially considered as harmful, reactive oxygen species (ROS) are now also recognized as important signaling molecules affecting various cellular processes. For example, they contribute to the response to hormones, growth factors, or hypoxia, and defense reactions against mechanical or chemical stress. Therefore, different ROS-generating, ROS-utilizing, and ROS-degrading systems in different intracellular compartments play an important role. On the one hand, this leads to a functional specialization wherein proteins, which participate in a specific ROS-regulated pathway in one compartment, may have another ROS-unrelated specific function in another compartment. On the other hand, this also adds a layer of protection by keeping unwanted side reactions to a minimum. Accordingly, the intracellular communication between different cellular compartments is an important mechanism to achieve proper responses and adaptations at the cellular level.