The ER and ageing II: calcium homeostasis

Quercetin Alleviates Scleral Remodeling Through Inhibiting the PERK-EIF2α Axis in Experiment Myopia

Purpose

This study aims to investigate the effect of quercetin (QUE) on scleral remodeling by inhibiting the PERK-EIF2α signaling pathway and to evaluate its potential role in slowing myopia.

Methods

Lens-induced myopia (LIM) guinea pigs were obtained and treated with QUE. After 4 and 6 weeks of treatments, ocular biological measurements were conducted. Hematoxylin and eosin (H&E) staining was used to observe the changes in scleral morphology and thickness, and Masson staining was used to examine scleral collagen fiber arrangement. Quantitative PCR (qPCR) and Western bolt were utilized to detect the mRNA and protein expression of PERK, EIF2α, MMP-2, TIMP-2, and collagen I in the scleral tissues. Calcium ion flow in each group was measured using noninvasive micro-test technology, and reactive oxygen species levels were detected by flow cytometry.

Results

Compared with the LIM group, the ocular measurements showed that the refractive errors and axial length of the eyes were significantly reduced in the LIM + QUE group (P < 0.01). H&E and Masson staining showed that sclera in the LIM + QUE group was thickened, collagen was dense, and the fiber gap was reduced. In the LIM + QUE group, the expression levels of PERK, EIF2α, and MMP-2 were decreased, whereas the expression levels of TIMP-2 and collagen I were increased. Calcium release and reactive oxygen species (ROS) in the LIM + QUE group were decreased.

Conclusions

Quercetin ameliorates scleral remodeling in myopic guinea pigs by inhibiting the PERK-EIF2α signaling pathway, thereby alleviating the progression of myopia. These findings provide new experimental evidence for the potential application of quercetin in myopia prevention and treatment.

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.

Evolution of protein domain repertoires of CALHM6

Calcium (Ca2 +) homeostasis is essential in conducting various cellular processes including nerve transmission, muscular movement, and immune response. Changes in Ca2 + concentration in the cytoplasm are significant in bringing about various immune responses such as pathogen clearance and apoptosis. Various key players are involved in calcium homeostasis such as calcium binders, pumps, and channels. Sequence-based evolutionary information has recently been exploited to predict the biophysical behaviors of proteins, giving critical clues about their functionality. Ion channels are reportedly the first channels developed during evolution. Calcium homeostasis modulator protein 6 (CALHM6) is one such channel. Comprised of a single domain called Ca_hom_mod, CALHM6 is a stable protein interacting with various other proteins in calcium regulation. No previous attempt has been made to trace the exact evolutionary events in the domain of CALHM6, leaving plenty of room for exploring its evolution across a wide range of organisms. The current study aims to answer the questions by employing a computational-based strategy that used profile Hidden Markov Models (HMMs) to scan for the CALHM6 domain, integrated the data with a time-calibrated phylogenetic tree using BEAST and Mesquite, and visualized through iTOL. Around 4,000 domains were identified, and 14,000 domain gain, loss, and duplication events were observed at the end which also included various protein domains other than CALHM6. The data were analyzed concerning CALHM6 evolution as well as the domain gain, loss, and duplication of its interacting partners: Calpain, Vinculin, protein S100-A7, Thioredoxin, Peroxiredoxin, and Calmodulin-like protein 5. Duplication events of CALHM6 near higher eukaryotes showed its increasing complexity in structure and function. This in-silico phylogenetic approach applied to trace the evolution of CALHM6 was an effective approach to get a better understanding of the protein CALHM6.

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

Suberoylanilide hydroxamic acid upregulates reticulophagy receptor expression and promotes cell death in hepatocellular carcinoma cells

BACKGROUND

Hepatocellular carcinoma (HCC) is a common clinical condition with a poor prognosis and few effective treatment options. Potent anticancer agents for treating HCC must be identified. Epigenetics plays an essential role in HCC tumorigenesis. Suberoylanilide hydroxamic acid (SAHA), the most common histone deacetylase inhibitor agent, triggers many forms of cell death in HCC. However, the underlying mechanism of action remains unclear. Family with sequence similarity 134 member B (FAM134B)-induced reticulophagy, a selective autophagic pathway, participates in the decision of cell fate and exhibits anticancer activity. This study focused on the relationship between FAM134B-induced reticulophagy and SAHA-mediated cell death.

AIM

To elucidate potential roles and underlying molecular mechanisms of reticulophagy in SAHA-induced HCC cell death.

METHODS

The viability, apoptosis, cell cycle, migration, and invasion of SAHA-treated Huh7 and MHCC97L cells were measured. Proteins related to the reticulophagy pathway, mitochondria-endoplasmic reticulum (ER) contact sites, intrinsic mitochondrial apoptosis, and histone acetylation were quantified using western blotting. ER and lysosome colocalization, and mitochondrial Ca2+ levels were characterized via confocal microscopy. The level of cell death was evaluated through Hoechst 33342 staining and propidium iodide colocalization. Chromatin immunoprecipitation was used to verify histone H4 lysine-16 acetylation in the FAM134B promoter region.

RESULTS

After SAHA treatment, the proliferation of Huh7 and MHCC97L cells was significantly inhibited, and the migration and invasion abilities were greatly blocked in vitro. This promoted apoptosis and caused G1 phase cells to increase in a concentration-dependent manner. Following treatment with SAHA, ER-phagy was activated, thereby triggering autophagy-mediated cell death of HCC cells in vitro. Western blotting and chromatin immunoprecipitation assays confirmed that SAHA regulated FAM134B expression by enhancing the histone H4 lysine-16 acetylation in the FAM134B promoter region. Further, SAHA disturbed the Ca2+ homeostasis and upregulated the level of autocrine motility factor receptor and proteins related to mitochondria-endoplasmic reticulum contact sites in HCC cells. Additionally, SAHA decreased the mitochondrial membrane potential levels, thereby accelerating the activation of the reticulophagy-mediated mitochondrial apoptosis pathway and promoting HCC cell death in vitro.

CONCLUSION

SAHA stimulates FAM134B-mediated ER-phagy to synergistically enhance the mitochondrial apoptotic pathway, thereby enhancing HCC cell death.

WFDC3 inhibits tumor metastasis by promoting the ERβ-mediated transcriptional repression of TGFBR1 in colorectal cancer

Estrogen plays a protective role in colorectal cancer (CRC) and primarily functions through estrogen receptor β (ERβ). However, clinical strategies for CRC therapy associated with ERβ are still under investigation. Our discoveries identified WFDC3 as a tumor suppressor that facilitates estrogen-induced inhibition of metastasis through the ERβ/TGFBR1 signaling axis. WFDC3 interacts with ERβ and increases its protein stability by inhibiting its proteasome-dependent degradation. WFDC3 represses TGFBR1 expression through ERβ-mediated transcription. Blocking TGFβ signaling with galunisertib, a drug used in clinical trials that targets TGFBR1, impaired the migration of CRC cells induced by WFDC3 depletion. Moreover, there was clinical significance to WFDC3 in CRC, as CRC patients with high WFDC3 expression in tumor cells had favorable prognoses. Therefore, this work suggests that WFDC3 could be an indicator for therapies targeting the estrogen/ERβ pathway in CRC patients.

Hypothermic oxygenated perfusion attenuates DCD liver ischemia-reperfusion injury by activating the JAK2/STAT3/HAX1 pathway to regulate endoplasmic reticulum stress

BACKGROUND

Hepatic ischemia-reperfusion injury (IRI) in donation after cardiac death (DCD) donors is a major determinant of transplantation success. Endoplasmic reticulum (ER) stress plays a key role in hepatic IRI, with potential involvement of the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway and the antiapoptotic protein hematopoietic-lineage substrate-1-associated protein X-1 (HAX1). In this study, we aimed to investigate the effects of hypothermic oxygenated perfusion (HOPE), an organ preservation modality, on ER stress and apoptosis during hepatic IRI in a DCD rat model.

METHODS

To investigate whether HOPE could improve IRI in DCD livers, levels of different related proteins were examined by western blotting and quantitative real-time polymerase chain reaction. Further expression analyses, immunohistochemical analyses, immunofluorescence staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and transmission electron microscopy were conducted to analyze the effects of HOPE on ER stress and apoptosis. To clarify the role of the JAK2/STAT3 pathway and HAX1 in this process, AG490 inhibitor, JAX1 plasmid transfection, co-immunoprecipitation (CO-IP), and flow cytometry analyses were conducted.

RESULTS

HOPE reduced liver injury and inflammation while alleviating ER stress and apoptosis in the DCD rat model. Mechanistically, HOPE inhibited unfolded protein responses by activating the JAK2/STAT3 pathway, thus reducing ER stress and apoptosis. Moreover, the activated JAK2/STAT3 pathway upregulated HAX1, promoting the interaction between HAX1 and SERCA2b to maintain ER calcium homeostasis. Upregulated HAX1 also modulated ER stress and apoptosis by inhibiting the inositol-requiring enzyme 1 (IRE1) pathway.

CONCLUSIONS

JAK2/STAT3-mediated upregulation of HAX1 during HOPE alleviates hepatic ER stress and apoptosis, indicating the JAK2/STAT3/HAX1 pathway as a potential target for IRI management during DCD liver transplantation.

A multi-hit hypothesis for an APOE4-dependent pathophysiological state

The APOE gene encoding the Apolipoprotein E protein is the single most significant genetic risk factor for late-onset Alzheimer's disease. The APOE4 genotype confers a significantly increased risk relative to the other two common genotypes APOE3 and APOE2. Intriguingly, APOE4 has been associated with neuropathological and cognitive deficits in the absence of Alzheimer's disease-related amyloid or tau pathology. Here, we review the extensive literature surrounding the impact of APOE genotype on central nervous system dysfunction, focussing on preclinical model systems and comparison of APOE3 and APOE4, given the low global prevalence of APOE2. A multi-hit hypothesis is proposed to explain how APOE4 shifts cerebral physiology towards pathophysiology through interconnected hits. These hits include the following: neurodegeneration, neurovascular dysfunction, neuroinflammation, oxidative stress, endosomal trafficking impairments, lipid and cellular metabolism disruption, impaired calcium homeostasis and altered transcriptional regulation. The hits, individually and in combination, leave the APOE4 brain in a vulnerable state where further cumulative insults will exacerbate degeneration and lead to cognitive deficits in the absence of Alzheimer's disease pathology and also a state in which such pathology may more easily take hold. We conclude that current evidence supports an APOE4 multi-hit hypothesis, which contributes to an APOE4 pathophysiological state. We highlight key areas where further study is required to elucidate the complex interplay between these individual mechanisms and downstream consequences, helping to frame the current landscape of existing APOE-centric literature.

Protective Role of Hepassocin against Hepatic Endoplasmic Reticulum Stress in Mice

Hepassocin (HPS) is a hepatokine that has multiple proposed physiological functions. Some of the biological processes in which it is involved are closely related to endoplasmic reticulum (ER) stress, but the role of HPS in the regulation of ER stress remains unclear. Here, we demonstrated that HPS transcription is induced by the protein kinase RNA-like ER kinase (PERK)/activating transcription factor 4 (ATF4) cascade upon ER stress in hepatocytes. Additionally, fasting/refeeding also induced HPS expression in mice liver. The loss of HPS sensitizes hepatocytes to ER stress-related cytotoxicity in vitro, whereas HPS treatment altered these phenotypes. HPS deficiency exacerbates fasting/refeeding-induced ER stress in vivo. The preliminary administration of HPS ameliorates liver steatosis, cell death, and inflammation in mice injected with tunicamycin (TM). The improvement of HPS can be observed even if HPS protein is injected after TM treatment. Furthermore, the administration of an ER stress inhibitor alleviated steatohepatitis in methionine- and choline-deficient (MCD) diet-fed HPS-deficient mice. These results suggest that HPS protects hepatocytes from physiological and pathological ER stress, and that the inactivation of HPS signaling aggravating ER stress may be a novel mechanism that drives the development of steatohepatitis. The protective mechanism of HPS against ER stress in hepatocytes was associated with the regulation of ER calcium handling, and the suppression of calcium influx release from ER upon stressor treatment. Collectively, our findings indicate that HPS may act in a negative feedback fashion to regulate hepatic ER stress and protect hepatocytes from ER stress-related injury. HPS has the potential to be a candidate drug for the treatment of ER stress-related liver injury.

Induction of Endoplasmic Reticulum Stress by CdhM Mediates Apoptosis of Macrophage During Mycobacterium tuberculosis Infection

The normal operation of the endoplasmic reticulum (ER) is critical for cells and organisms. However, ER stress, caused by imbalanced protein folding, occurs frequently, which perturbs the function of the ER and even results in cell apoptosis eventually. Many insults can induce ER stress; pathogen infection is one of them. Most of the genes involved in ER stress have been reported to be upregulated in Mycobacterium tuberculosis (Mtb) granulomas of humans and mice, implicating that infection with Mtb can induce ER stress. However, little is known about the molecular mechanism of Mtb induction of ER stress. Here, we reveal that Mycobacterium protein CDP-diglyceride hydrolase of Mycobacteriumn (CdhM) could target the ER and cause abnormal ER morphology and cell death. RNA-seq analysis suggests that most of the ER stress-involved genes were modulated by CdhM. Further assessed by biochemical experiments, the transcription and protein levels of ER stress markers BiP and CHOP, as well as the levels of XBP1 splicing and eIF2α phosphorylation, were significantly increased by CdhM, confirming that CdhM could induce ER stress alone or during infection. A single conserved amino acid mutant of CdhM, including L44A, G96A, H150A, and W175A, was incapable of inducing ER stress, which indicates that induction of ER stress by CdhM is specific and functional. Furthermore, CdhM-induced ER stress could also promote apoptosis of macrophages during Mtb infection. Overexpression of CdhM conferred a significant benefit for Mtb replication by releasing Mtb into extracellular during infection of macrophage in vitro, as presented in CFU assays. Overall, our study identified a novel Mtb effector protein CdhM which may promote Mtb dissemination and proliferation by induction of ER stress and apoptosis and provided new insight into the physiological significance of induction of ER stress in tuberculosis (TB) granulomas.

Cold-inducible RNA-binding protein migrates from the nucleus to the cytoplasm under cold stress in normal human bronchial epithelial cells via TRPM8-mediated mechanism

Background

Cold-inducible RNA-binding protein (CIRP or hnRNP A18) is a multifunctional stress-responsive protein. Our previous study demonstrated that cold stress increased CIRP expression and migrated from the nucleus to the cytoplasm in airway epithelial cells. However, the mechanism through which CIRP migrates from the nucleus to the cytoplasm upon cold stress remains unknown.

Methods

The expression of CIRP in the bronchial epithelium was examined using immunofluorescence, real-time polymerase chain reaction (RT-PCR), and Western blotting. The expression of inflammatory factors interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) were detected by ELISA and RT-PCR. Transient receptor potential melastatin 8 (TRPM8) receptor function was characterized by Ca²⁺ imaging.

Results

Cold stress upregulated the expression of CIRP, inflammatory factors and promoted the translocation of CIRP from the nucleus to the cytoplasm in normal human bronchial epithelial (NHBE) cells. Cold stress activated the TRPM8/(Ca²⁺)/PKCα/glycogen synthase kinase 3β (GSK3β) signaling cascade, and that inhibition of this signaling pathway attenuated the migration of CIRP from the nucleus to cytoplasm but did not decrease its overexpression induced by cold stress. Knocked down CIRP expression or blocked CIRP migration between the nucleus and cytoplasm significantly decreased inflammatory factor expression.

Conclusions

These results indicate that cold stress leads to the migration of CIRP from the nucleus to the cytoplasm with alteration of expression, which are involved in the expression of inflammatory factors (IL-1β, IL-6, IL-8 and TNF-α) induced by cold air, through TRPM8/Ca²⁺/PKCα/GSK3β signaling cascade.

The Critical Role of Oxidative Stress in Sarcopenic Obesity

Sarcopenic obesity (SO) is a combination of obesity and sarcopenia that primarily develops in older people. Patients with SO have high fat mass, low muscle mass, low muscle strength, and low physical function. SO relates to metabolic syndrome and an increased risk of morbimortality. The prevalence of SO varies because of lacking consensus criteria regarding its definition and the methodological difficulty in diagnosing sarcopenia and obesity. SO includes systemic alterations such as insulin resistance, increased proinflammatory cytokines, age-associated hormonal changes, and decreased physical activity at pathophysiological levels. Interestingly, these alterations are influenced by oxidative stress, which is a critical factor in altering muscle function and the generation of metabolic dysfunctions. Thus, oxidative stress in SO alters muscle mass, the signaling pathways that control it, satellite cell functions, and mitochondrial and endoplasmic reticulum activities. Considering this background, our objectives in this review are to describe SO as a highly prevalent condition and look at the role of oxidative stress in SO pathophysiology.

Sarcopenia; functional concerns, molecular mechanisms involved, and seafood as a nutritional intervention - review article

The fundamental basis for the human function is provided by skeletal muscle. Advancing age causes selective fiber atrophy, motor unit loss, and hybrid fiber formation resulting in hampered mass and strength, thus referred to as sarcopenia. Influence on the loss of independence of aged adults, contribute toward inclined healthcare costs conveys the injurious impact. The current understating of age-related skeletal muscle changes are addressed in this review, and further discusses mechanisms regulating protein turnover, although they do not completely define the process yet. Moreover, the reduced capacity of muscle regeneration due to impairment of satellite cell activation and proliferation with neuronal, immunological, hormonal factors were brought into the light of attention. Nevertheless, complete understating of sarcopenia requires disentangling it from disuse and disease. Nutritional intervention is considered a potentially preventable factor contributing to sarcopenia. Seafood is a crucial player in the fight against hunger and malnutrition, where it consists of macro and micronutrients. Hence, the review shed light on seafood as a nutritional intrusion in the treatment and prevention of sarcopenia. Understanding multiple factors will provide therapeutic targets in the prevention, treatment, and overcoming adverse effects of sarcopenia.

Aging increases senescence, calcium signaling, and extracellular matrix deposition in human airway smooth muscle

Lung function declines as people age and their lungs become stiffer. With an increasing elderly population, understanding mechanisms that contribute to these structural and functional changes in the aging lung is important. Part of the aging process is characterized by thicker, more fibrotic airways, and senile emphysema caused by changes in lung parenchyma. There is also senescence, which occurs throughout the body with aging. Here, using human airway smooth muscle (ASM) cells from patients in different age groups, we explored senescence pathways and changes in intracellular calcium signaling and extracellular matrix (ECM) deposition to elucidate potential mechanisms by which aging leads to thicker and stiffer lungs. Senescent markers p21, γH2AX, and β-gal, and some senescence-associated secretory proteins (SASP) increased with aging, as shown by staining and biochemical analyses. Agonist-induced intracellular Ca2+ responses, measured using fura-2 loaded cells and fluorescence imaging, increased with age. However, biochemical analysis showed that expression of the following markers decreased with age: M3 muscarinic receptor, TRPC3, Orai1, STIM1, SERCA2, MMP2 and MMP9. In contrast, collagen III, and fibronectin deposition increased with age. These data show that senescence increases in the aging airways that is associated with a stiffer but surprisingly greater intracellular calcium signaling as a marker for contractility. ASM senescence may enhance fibrosis in a feed forward loop promoting remodeling and altered calcium storage and buffering.

CISD2 maintains cellular homeostasis

CDGSH Iron Sulfur Domain 2 (CISD2) is the causative gene for the disease Wolfram syndrome 2 (WFS2; MIM 604928), which is an autosomal recessive disorder showing metabolic and neurodegenerative manifestations. CISD2 protein can be localized on the endoplasmic reticulum (ER), outer mitochondrial membrane (OMM) and mitochondria-associated membrane (MAM). CISD2 plays a crucial role in the regulation of cytosolic Ca²⁺ homeostasis, ER integrity and mitochondrial function. Here we summarize the most updated publications and discuss the central role of CISD2 in maintaining cellular homeostasis. This review mainly focuses on the following topics. Firstly, that CISD2 has been recognized as a prolongevity gene and the level of CISD2 is a key determinant of lifespan and healthspan. In mice, Cisd2 deficiency shortens lifespan and accelerates aging. Conversely, a persistently high level of Cisd2 promotes longevity. Intriguingly, exercise stimulates Cisd2 gene expression and thus, the beneficial effects offered by exercise may be partly related to Cisd2 activation. Secondly, that Cisd2 is down-regulated in a variety of tissues and organs during natural aging. Three potential mechanisms that may mediate the age-dependent decrease of Cisd2, via regulating at different levels of gene expression, are discussed. Thirdly, the relationship between CISD2 and cell survival, as well as the potential mechanisms underlying the cell death control, are discussed. Finally we discuss that, in cancers, CISD2 may functions as a double-edged sword, either suppressing or promoting cancer development. This review highlights the importance of the CISD2 in aging and age-related diseases and identifies the urgent need for the translation of available genetic evidence into pharmaceutic interventions in order to alleviate age-related disorders and extend a healthy lifespan in humans.

Endoplasmic Reticulum Calcium Pumps and Tumor Cell Differentiation

Endoplasmic reticulum (ER) calcium homeostasis plays an essential role in cellular calcium signaling, intra-ER protein chaperoning and maturation, as well as in the interaction of the ER with other organelles. Calcium is accumulated in the ER by sarco/endoplasmic reticulum calcium ATPases (SERCA enzymes) that generate by active, ATP-dependent transport, a several thousand-fold calcium ion concentration gradient between the cytosol (low nanomolar) and the ER lumen (high micromolar). SERCA enzymes are coded by three genes that by alternative splicing give rise to several isoforms, which can display isoform-specific calcium transport characteristics. SERCA expression levels and isoenzyme composition vary according to cell type, and this constitutes a mechanism whereby ER calcium homeostasis is adapted to the signaling and metabolic needs of the cell, depending on its phenotype, its state of activation and differentiation. As reviewed here, in several normal epithelial cell types including bronchial, mammary, gastric, colonic and choroid plexus epithelium, as well as in mature cells of hematopoietic origin such as pumps are simultaneously expressed, whereas in corresponding tumors and leukemias SERCA3 expression is selectively down-regulated. SERCA3 expression is restored during the pharmacologically induced differentiation of various cancer and leukemia cell types. SERCA3 is a useful marker for the study of cell differentiation, and the loss of SERCA3 expression constitutes a previously unrecognized example of the remodeling of calcium homeostasis in tumors.

Cellular Aging Characteristics and Their Association with Age-Related Disorders

Different molecular signaling pathways, biological processes, and intercellular communication mechanisms control longevity and are affected during cellular senescence. Recent data have suggested that organelle communication, as well as genomic and metabolic dysfunctions, contribute to this phenomenon. Oxidative stress plays a critical role by inducing structural modifications to biological molecules while affecting their function and catabolism and eventually contributing to the onset of age-related dysfunctions. In this scenario, proteins are not adequately degraded and accumulate in the cell cytoplasm as toxic aggregates, increasing cell senescence progression. In particular, carbonylation, defined as a chemical reaction that covalently and irreversibly modifies proteins with carbonyl groups, is considered to be a significant indicator of protein oxidative stress and aging. Here, we emphasize the role and dysregulation of the molecular pathways controlling cell metabolism and proteostasis, the complexity of the mechanisms that occur during aging, and their association with various age-related disorders. The last segment of the review details current knowledge on protein carbonylation as a biomarker of cellular senescence in the development of diagnostics and therapeutics for age-related dysfunctions.

The Beneficial Effects of Taurine to Counteract Sarcopenia

Aging is a multifactorial process characterized by several features including low-grade inflammation, increased oxidative stress and reduced regenerative capacity, which ultimately lead to alteration in morpho-functional properties of skeletal muscle, thus promoting sarcopenia. This condition is characterized by a gradual loss of muscle mass due to an unbalance between protein synthesis and degradation, finally conveying in functional decline and disability. The development of specific therapeutic approaches able to block or reverse this condition may represent an invaluable tool for the promotion of a healthy aging among elderly people. It is well established that changes in the quantity and the quality of dietary proteins, as well as the intake of specific amino acids, are able to counteract some of the physiopathological processes related to the progression of the loss of muscle mass and may have beneficial effects in improving the anabolic response of muscle in the elderly. Taurine is a non-essential amino acid expressed in high concentration in several mammalian tissues and particularly in skeletal muscle where it is involved in the modulation of intracellular calcium concentration and ion channel regulation and where it also acts as an antioxidant and anti-inflammatory factor. The aim of this review is to summarize the pleiotropic effects of taurine on specific muscle targets and to discuss its role in regulating signaling pathways involved in the maintenance of muscle homeostasis. We also highlight the potential use of taurine as a therapeutic molecule for the amelioration of skeletal muscle function and performance severely compromised during aging.

Expression profiles and function analysis of microRNAs in postovulatory aging mouse oocytes

In this study, microRNA (miRNA) profiles in postovulatory aging mouse oocytes were analyzed by microarray screening and RT-qPCR. Hierarchical cluster analysis on the microarray data and KEGG pathway enrichment analysis on the mRNAs targeted by differentially expressed (DE) miRNAs between two adjacent egg-ages suggest that while only a mild alteration in miRNA expression occurred from 13 to 18 h, a great change took place from 18 to 24 h post hCG injection. Theoretical exploration on functions of the predicted target genes suggest that KEGG pathways enriched by 13-18 h DE miRNAs are correlated with early events of oocyte aging while pathways most enriched by 18-24 h or 24-30 h DE miRNAs are correlated with the late symptoms of aged oocytes. Experimental verification on functions of the key proteins predicted by the KEGG analysis and injection of miR-98 mimics or inhibitors further confirmed that miRNAs played stimulatory/inhibitory roles in postovulatory oocyte aging. In conclusion, marked changes in miRNA expression are associated with significant alterations in function and morphology of postovulatory aging oocytes.

Alzheimer's disease pathology and the unfolded protein response: prospective pathways and therapeutic targets

Many vital interdependent cellular functions including proteostasis, lipogenesis and Ca homeostasis are executed by the endoplasmic reticulum (ER). Exogenous insults can impair ER performance: this must be rapidly corrected or cell death will ensue. Protective adaptations can boost the functional capacity of the ER and form the basis of the unfolded protein response (UPR). Activated in response to the accumulation of misfolded proteins, the UPR can halt protein translation while increasing protein-handling chaperones and the degradation of erroneous proteins through a conserved three-tier molecular cascade. However, prolonged activation of the UPR can result in the maladaptation of the system, resulting in the activation of inflammatory and apoptotic effectors. Recently, UPR and its involvement in neurodegenerative disease has attracted much interest and numerous potentially 'drugable' points of crosstalk are now emerging. Here, we summarize the functions of the ER and UPR, and highlight evidence for its potential role in the pathogenesis of Alzheimer's disease, before discussing several key targets with therapeutic potential.

Vitamin D deficiency accelerates ageing and age-related diseases: a novel hypothesis

Ageing can occur at different rates, but what controls this variable rate is unknown. Here I have developed a hypothesis that vitamin D may act to control the rate of ageing. The basis of this hypothesis emerged from studyng the various cellular processes that control ageing. These processes such as autophagy, mitochondrial dysfunction, inflammation, oxidative stress, epigenetic changes, DNA disorders and alterations in Ca²⁺ and reactive oxygen species (ROS) signalling are all known to be regulated by vitamin D. The activity of these processes will be enhanced in individuals that are deficient in vitamin D. Not only will this increase the rate of ageing, but it will also increase the probability of developing age-related diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and cardiovascular disease. In individual with normal vitamin D levels, these ageing-related processes will occur at lower rates resulting in a reduced rate of ageing and enhanced protection against these age-related diseases.

Inhibition and conformational change of SERCA3b induced by Bcl-2

An interaction of Bcl-2 with SERCA had been documented in vitro using the SERCA1a isoform isolated from rat skeletal muscle [Dremina, E. S., Sharov, V. S., Kumar, K., Azidi, A., Michaelis, E. K., Schöneich, C. (2004) Biochem. J. 383 (361-370)]. Here, we demonstrate the interaction of Bcl-2 with the SERCA3b isoform both in vitro and in cell culture. In vitro, the interaction of Bcl-2 with SERCA3b was studied using Bcl-2∆21, a truncated form of human Bcl-2, and microsomes isolated from SERCA3b-overexpressing HEK-293 cells. For these experiments, SERCA3b was quantified by a combination of amino acid analysis and Western blotting. We observed that Bcl-2∆21 both inactivates SERCA3b and co-immunoprecipitates with SERCA3b. The incubation with Bcl-2∆21 changes the distribution of SERCA3b during sucrose density gradient centrifugation, likely as the result of Bcl-2∆21-induced conformational change of SERCA3b. When SERCA3b-overexpressing HEK-293 cells were co-transfected with Bcl-2, Bcl-2-dependent SERCA3b inactivation was observed. In these cells, Bcl-2 interaction with SERCA3b was demonstrated by co-immunoprecipitation. Furthermore, overexpression of Bcl-2 reduced fluorescein isothiocyanate (FITC) labeling of SERCA3b. Together, our data provide evidence for the interaction of Bcl-2 with SERCA3b in vitro and in cell culture, and for Bcl-2-dependent conformational and functional changes of SERCA3b.

Amplified RLR signaling activation through an interferon-stimulated gene-endoplasmic reticulum stress-mitochondrial calcium uniporter protein loop

Type I interferon (IFN-I) is critical for a host against viral and bacterial infections via induction of hundreds of interferon-stimulated genes (ISGs), but the mechanism underlying the regulation of IFN-I remains largely unknown. In this study, we first demonstrate that ISG expression is required for optimal IFN-β levels, an effect that is further enhanced by endoplasmic reticulum (ER) stress. Furthermore, we identify mitochondrial calcium uniporter protein (MCU) as a mitochondrial antiviral signaling protein (MAVS)-interacting protein that is important for ER stress induction and amplified MAVS signaling activation. In addition, by performing an ectopic expression assay to screen a library of 117 human ISGs for effects on IFN-β levels, we found that tumor necrosis factor receptor 1 (TNFR1) significantly increases IFN-β levels independent of ER stress. Altogether, our findings suggest that MCU and TNFR1 are involved in the regulation of RIG-I-like receptors (RLR) signaling.

Melatonin ameliorates ER stress-mediated hepatic steatosis through miR-23a in the liver

The endoplasmic reticulum (ER) stress induces hepatic steatosis and inflammation in the liver. Although melatonin ameliorates ER stress-target genes, it remains unknown whether melatonin protects against hepatic steatosis as well as inflammation through regulation of miRNA. MicroRNAs have been identified as pivotal regulators in the field of gene regulation and their dysfunctions are a common feature in a variety of metabolic diseases. Especially, among miRNAs, miR-23a has been shown to regulate ER stress. Herein, we investigated the crucial roles of melatonin in hepatic steatosis and inflammation in vivo. Tunicamycin challenge caused increase of hepatic triglyceride and intracellular calcium levels through activation of ER stress, whereas these phenomena were partially disrupted by melatonin. We also demonstrated that expression of miR-23a stimulated with tunicamycin was rescued by melatonin treatment, resulting in reduced ER stress in primary hepatocytes. Overall, these results suggest a new function of melatonin that is involved in ameliorating ER stress-induced hepatic steatosis and inflammation by attenuating miR-23a. Melatonin may be useful as a pharmacological agent to protect against hepatic metabolic diseases due to its ability to regulate expression of miR-23a.

Identification of tetrahydrocarbazoles as novel multifactorial drug candidates for treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative brain disorder and the most frequent cause of dementia. To date, there are only a few approved drugs for AD, which show little or no effect on disease progression. Impaired intracellular calcium homeostasis is believed to occur early in the cascade of events leading to AD. Here, we examined the possibility of normalizing the disrupted calcium homeostasis in the endoplasmic reticulum (ER) store as an innovative approach for AD drug discovery. High-throughput screening of a small-molecule compound library led to the identification of tetrahydrocarbazoles, a novel multifactorial class of compounds that can normalize the impaired ER calcium homeostasis. We found that the tetrahydrocarbazole lead structure, first, dampens the enhanced calcium release from ER in HEK293 cells expressing familial Alzheimer's disease (FAD)-linked presenilin 1 mutations. Second, the lead structure also improves mitochondrial function, measured by increased mitochondrial membrane potential. Third, the same lead structure also attenuates the production of amyloid-beta (Aβ) peptides by decreasing the cleavage of amyloid precursor protein (APP) by β-secretase, without notably affecting α- and γ-secretase cleavage activities. Considering the beneficial effects of tetrahydrocarbazoles addressing three key pathological aspects of AD, these compounds hold promise for the development of potentially effective AD drug candidates.

Increased skeletal muscle expression of the endoplasmic reticulum chaperone GRP78 in patients with myasthenia gravis

In myasthenia gravis (MG), damage to neuromuscular junctions may induce endoplasmic reticulum (ER) stress in skeletal muscles. In the current study, skeletal muscles obtained from patients with MG exhibited upregulation of glucose-regulated protein 78 (GRP78) mRNA that was activated by ER stress. Furthermore, GRP78 mRNA expression was higher in patients with MG and myositis than in patients with non-myopathy. We also observed a significant positive correlation between GRP78 mRNA expression and GRP78 protein levels and between GRP78 mRNA expression and age of MG onset. Our findings suggest that muscle weakness in MG might be caused by both neuromuscular junction disruption and ER stress.

Ca²⁺-sensor proteins in the autophagic and endocytic traffic

Autophagy and endocytosis are two evolutionarily conserved catabolic processes that comprise vesicle trafficking events for the clearance of the sequestered intracellular and extracellular cargo. Both start differently but end in the same compartment, the lysosome. Mounting evidences from the last years have established the involvement of proteins sensitive to intracellular Ca²⁺ in the control of the early autophagic steps and in the traffic of autophagic, endocytic and lysosomal vesicles. However, this knowledge is based on dispersed outcomes that do not set up a consensus model of the Ca²⁺-dependent control of autophagy and endocytosis. Here, we will provide a critical synopsis of insights from the last decade on the involvement of Ca²⁺-sensor proteins in the activation of autophagy and in fusion events of endocytic vesicles, autophagosomes and lysosomes.

Toxoplasma gondii-skeletal muscle cells interaction increases lipid droplet biogenesis and positively modulates the production of IL-12, IFN-g and PGE2

Background

The interest in the mechanisms involved in Toxoplasma gondii lipid acquisition has steadily increased during the past few decades, but it remains not completely understood. Here, we investigated the biogenesis and the fate of lipid droplets (LD) of skeletal muscle cells (SkMC) during their interaction with T. gondii by confocal and electron microscopy. We also evaluated whether infected SkMC modulates the production of prostaglandin E₂ (PGE₂), cytokines interleukin-12 (IL-12) and interferon-gamma (INF-g), and also the cyclooxygenase-2 (COX-2) gene induction.

Methods

Primary culture of skeletal muscle cells were infected with tachyzoites of T. gondii and analysed by confocal microscopy for observation of LD. Ultrastructural cytochemistry was also used for lipid and sarcoplasmatic reticulum (SR) detection. Dosage of cytokines (IL-12 and INF-g) by ELISA technique and enzyme-linked immunoassay (EIA) for PGE₂ measurement were employed. The COX-2 gene expression analysis was performed by real time reverse transcriptase polymerase chain reaction (qRT-PCR).

Results

We demonstrated that T. gondii infection of SkMC leads to increase in LD number and area in a time course dependent manner. Moreover, the ultrastructural analysis demonstrated that SR and LD are in direct contact with parasitophorous vacuole membrane (PVM), within the vacuolar matrix, around it and interacting directly with the membrane of parasite, indicating that LD are recruited and deliver their content inside the parasitophorous vacuole (PV) in T. gondii-infected SkMC. We also observed a positive modulation of the production of IL-12 and IFN-g, increase of COX-2 mRNA levels in the first hour of T. gondii-SkMC interaction and an increase of prostaglandin E₂ (PGE₂) synthesis from 6 h up to 48 h of infection.

Conclusions

Taken together, the close association between SR and LD with PV could represent a source of lipids as well as other nutrients for the parasite survival, and together with the increased levels of IL-12, INF-g and inflammatory indicators PGE₂ and COX-2 might contribute to the establishment and maintenance of chronic phase of the T. gondii infection in muscle cell.

Expression of genes encoding the calcium signalosome in cellular and transgenic models of Huntington's disease

Huntington's disease (HD) is a hereditary neurodegenerative disease caused by the expansion of a polyglutamine stretch in the huntingtin (HTT) protein and characterized by dysregulated calcium homeostasis. We investigated whether these disturbances are correlated with changes in the mRNA level of the genes that encode proteins involved in calcium homeostasis and signaling (i.e., the calciosome). Using custom-made TaqMan low-density arrays containing probes for 96 genes, we quantified mRNA in the striatum in YAC128 mice, a model of HD, and wildtype mice. HTT mutation caused the increased expression of some components of the calcium signalosome, including calretinin, presenilin 2, and calmyrin 1, and the increased expression of genes indirectly involved in calcium homeostasis, such as huntingtin-associated protein 1 and calcyclin-binding protein. To verify these findings in a different model, we used PC12 cells with an inducible expression of mutated full-length HTT. Using single-cell imaging with Fura-2AM, we found that store-operated Ca²⁺ entry but not endoplasmic reticulum (ER) store content was changed as a result of the expression of mutant HTT. Statistically significant downregulation of the Orai calcium channel subunit 2, calmodulin, and septin 4 was detected in cells that expressed mutated HTT. Our data indicate that the dysregulation of calcium homeostasis correlates with changes in the gene expression of members of the calciosome. These changes, however, differed in the two models of HD used in this study. Our results indicate that each HD model exhibits distinct features that may only partially resemble the human disease.

Endoplasmic reticulum stress in human skeletal muscle: any contribution to sarcopenia?

Skeletal muscle is vital to life as it provides the mechanical power for locomotion, posture and breathing. Beyond these vital functions, skeletal muscle also plays an essential role in the regulation of whole body metabolism, e.g., glucose homeostasis. Although progressive loss of muscle mass with age seems unavoidable, it is critical for older people to keep the highest mass as possible. It is clear that the origin of sarcopenia is multifactorial but, in the present review, it was deliberately chosen to evaluate the likely contribution of one specific cellular stress, namely the endoplasmic reticulum (ER) stress. It is proposed that ER stress can: (1) directly impact muscle mass as one fate of prolonged and unresolved ER stress is cell death and; (2) indirectly create a state of anabolic resistance by inhibiting the mammalian target of rapamycin complex 1 (mTORC1) pathway. With age, many of the key components of the unfolded protein response, such as the chaperones and enzymes, display reduced expression and activity resulting in a dysfunctional ER, accelerating the rate of proteins discarded via the ER-associated degradation. In addition, ER stress can block the mTORC1 pathway which is essential in the response to the anabolic stimulus of nutrients and contractile activity thereby participating to the well-known anabolic resistance state in skeletal muscle during ageing. As exercise increases the expression of several chaperones, it could anticipate or restore the loss of unfolded protein response components with age and thereby reduce the level of ER stress. This hypothesis has not been tested yet but it could be a new mechanism behind the beneficial effects of exercise in the elderly not only for the preservation of muscle mass but also for the regulation of whole body metabolism.

House dust mite-induced calcium signaling instigates epithelial barrier dysfunction and CCL20 production

BACKGROUND

House dust mite (HDM) affects the immunological and physical barrier function of airway epithelium, leading to allergic sensitization, airway remodeling, and eosinophilic inflammation in mouse models, although the mechanisms are still largely unknown.

OBJECTIVE

Given the implications for adenosine triphosphate (ATP)-dependent Ca(2+) signaling in allergic sensitization in mice, we sought to determine the role of intracellular Ca(2+) concentration ([Ca(2+)](i)) in HDM-induced barrier dysfunction and pro-inflammatory activity of bronchial epithelium.

METHODS

We investigated the effect of HDM on accumulation of [Ca(2+)](i) levels, barrier function, and CCL20 release in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) from healthy subjects and asthma patients. Involvement of ATP-dependent activation of purinergic receptors and downstream Ca(2+) influx was studied, using the ATP hydrolyzing agent apyrase, the purinergic receptor agonist PPADS, the calcium chelator BAPTA-AM, and calpain inhibitors.

RESULTS

Asthma PBECs were more susceptible to HDM-induced barrier dysfunction, CCL20 secretion, and Ca(2+) influx than healthy PBECs. Furthermore, we show that the HDM-induced increase in CCL20 in PBECs and 16HBE cells and the HDM-induced barrier dysfunction in 16HBE cells are dependent on [Ca(2+)](i) accumulation. Additionally, we demonstrate that [Ca(2+)](i) accumulation is initiated partly through the activation of purinergic receptors, which contributes to HDM-induced epithelial barrier dysfunction by disruption of cell-cell contacts, but not CCL20 secretion.

CONCLUSION

Our data show for the first time that Ca(2+) signaling plays a crucial role in barrier dysfunction and the pro-inflammatory response of bronchial epithelium upon HDM exposure and may thus have important implications for the development of allergic asthma.

Beclin 1 interactome controls the crosstalk between apoptosis, autophagy and inflammasome activation: impact on the aging process

Autophagy and apoptosis are crucial cellular housekeeping and tissue survival mechanisms. There is emerging evidence of important crosstalk between apoptosis and autophagy which can be linked to inflammasome activation. Beclin 1 is a platform protein which assembles an interactome consisting of diverse proteins which control the initiation of autophagocytosis and distinct phases in endocytosis. Recent studies have demonstrated that the anti-apoptotic Bcl-2 family members can interact with Beclin 1 and inhibit autophagy. Consequently, impaired autophagy can trigger inflammasome activation. Interestingly, the hallmarks of the ageing process include a decline in autophagy, increased resistance to apoptosis and a low-grade inflammatory phenotype. Age-related stresses, e.g. genotoxic, metabolic and environmental insults, enhance the expression of NF-κB-driven anti-apoptotic Bcl-2 proteins which repress the Beclin 1-dependent autophagy. Suppression of autophagocytosis provokes inflammation including NF-κB activation which further potentiates anti-apoptotic defence. In a context-dependent manner, this feedback defence mechanism can enhance the aging process or provoke tumorigenesis or cellular senescence. We will review the role of Beclin 1 interactome in the crosstalk between apoptosis, autophagy and inflammasomes emphasizing that disturbances in Beclin 1-dependent autophagy can have a crucial impact on the aging process.

Molecular mechanisms of garlic-derived allyl sulfides in the inhibition of skin cancer progression

Skin cancer is a serious concern whose incidence is increasing at an alarming rate. Allyl sulfides—i.e., sulfur metabolites in garlic oil—have been demonstrated to have anticancer activity against several cancer types, although the mechanisms underlying these effects remain enigmatic. Our previous study showed that diallyl trisulfide (DATS) is more potent than mono- and disulfides against skin cancer. DATS inhibits cell growth of human melanoma A375 cells and basal cell carcinoma (BCC) cells by increasing the levels of intracellular reactive oxygen species (ROS) and DNA damage and by inducing G2/M arrest, endoplasmic reticulum (ER) stress, and mitochondria-mediated apoptosis, including the caspase-dependent and -independent pathways. This short review focuses on the molecular mechanisms of garlic-derived allyl sulfides on skin cancer prevention.

Aberrant endoplasmic reticulum stress in vascular smooth muscle increases vascular contractility and blood pressure in mice deficient of AMP-activated protein kinase-α2 in vivo

OBJECTIVE

The endoplasmic reticulum (ER) plays a critical role in ensuring proper folding of newly synthesized proteins. Aberrant ER stress is reported to play a causal role in cardiovascular diseases. However, the effects of ER stress on vascular smooth muscle contractility and blood pressure remain unknown. The aim of this study was to investigate whether aberrant ER stress causes abnormal vasoconstriction and consequent high blood pressure in mice.

METHODS AND RESULTS

ER stress markers, vascular smooth muscle contractility, and blood pressure were monitored in mice. Incubation of isolated aortic rings with tunicamycin or MG132, 2 structurally unrelated ER stress inducers, significantly increased both phenylephrine-induced vasoconstriction and the phosphorylation of myosin light chain (Thr18/Ser19), both of which were abrogated by pretreatment with chemical chaperones or 5-Aminoimidazole-4-carboxamide ribonucleotide and metformin, 2 potent activators for the AMP-activated protein kinase. Consistently, administration of tauroursodeoxycholic acid or 4-phenyl butyric acid, 2 structurally unrelated chemical chaperones, in AMP-activated protein kinase-α2 knockout mice lowered blood pressure and abolished abnormal vasoconstrictor response of AMP-activated protein kinase-α2 knockout mice to phenylephrine. Consistently, tunicamycin (0.01 μg/g per day) infusion markedly increased both systolic and diastolic blood pressure, both of which were ablated by coadministration of 4-phenyl butyric acid. Furthermore, 4-phenyl butyric acid or tauroursodeoxycholic acid, which suppressed angiotensin II infusion-induced ER stress markers in vivo, markedly lowered blood pressure in angiotensin II-infused mice in vivo.

CONCLUSIONS

We conclude that ER stress increases vascular smooth muscle contractility resulting in high blood pressure, and AMP-activated protein kinase activation mitigates high blood pressure through the suppression of ER stress in vivo.

Age-associated changes in Ca(2+)-ATPase and oxidative damage in sarcoplasmic reticulum of rat heart

Altered Ca(2+) handling may be responsible for the development of cardiac contractile dysfunctions with advanced age. In the present study, we investigated the roles of oxidative damage to sarcoplasmic reticulum (SR) and expression of Ca(2+)-ATPase (SERCA 2a) and phospholamban in age-associated dysfunction of cardiac SR. SR vesicles were prepared from hearts of 2-, 6-, 15-, and 26-month-old Wistar rats. Although activity of Ca(2+)-ATPase decreased with advancing age, no differences in relative amounts of SERCA 2a and phospholamban protein were observed. On the other hand, significant accumulation of protein oxidative damage occurred with aging. The results of this study suggest that age-related alteration in Ca(2+)-ATPase activity in the rat heart is not a consequence of decreased protein levels of SERCA 2a and phospholamban, but could arise from oxidative modifications of SR proteins. Cellular oxidative damage caused by reactive oxygen species could contribute to age-related alternations in myocardial relaxation.

Aging impairs Ca2+ sensitization pathways in gallbladder smooth muscle

Calcium sensitization is an important physiological process in agonist-induced contraction of smooth muscle. In brief, calcium sensitization is a pathway that leads to smooth muscle contraction independently of changes in [Ca(2+)](i) by mean of inhibition of myosin light chain phosphatase. Aging has negative impacts on gallbladder contractile response due to partial impairment in calcium signaling and alterations in the contractile machinery. However, information regarding aging-induced alterations in calcium sensitization is scanty. We hypothesized that the calcium sensitization system is negatively affected by age. To investigate this, gallbladders were collected from adult (4 months old) and aged (22-24 months old) guinea pigs. To evaluate the contribution of calcium sensitization pathways we assayed the effect of the specific inhibitors Y-27632 and GF109203X on the "in vitro" isometric gallbladder contractions induced by agonist challenges. In addition, expression and phosphorylation (as activation index) of proteins participating in the calcium sensitization pathways were quantified by Western blotting. Aging reduced bethanechol- and cholecystokinin-evoked contractions, an effect associated with a reduction in MLC20 phosphorylation and in the effects of both Y-27632 and GF109203X. In addition, there was a drop in ROCK I, ROCK II, MYPT-1 and PKC expression and in the activation/phosphorylation of MYPT-1, PKC and CPI-17 in response to agonists. Interestingly, melatonin treatment for 4 weeks restored gallbladder contractile responses due to re-establishment of calcium sensitization pathways. These results demonstrate that age-related gallbladder hypocontractility is associated to alterations of calcium sensitization pathways and that melatonin treatment exerts beneficial effects in the recovery of gallbladder contractility.

The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology

Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.

Age and ovariectomy abolish beneficial effects of female sex on rat ventricular myocytes exposed to simulated ischemia and reperfusion

Sex differences in responses to myocardial ischemia have been described, but whether cardiomyocyte function is influenced by sex in the setting of ischemia and reperfusion has not been elucidated. This study compared contractions and intracellular Ca²⁺ in isolated ventricular myocytes exposed to ischemia and reperfusion. Cells were isolated from anesthetized 3-month-old male and female Fischer 344 rats, paced at 4 Hz (37°C), exposed to simulated ischemia (20 mins) and reperfused. Cell shortening (edge detector) and intracellular Ca²⁺ (fura-2) were measured simultaneously. Cell viability was assessed with Trypan blue. Ischemia reduced peak contractions and increased Ca²⁺ levels equally in myocytes from both sexes. However, contraction amplitudes were reduced in reperfusion in male myocytes, while contractions recovered to exceed control levels in females (62.6±5.1 vs. 140.1±15.8%; p<0.05). Only 60% of male myocytes excluded trypan blue dye after ischemia and reperfusion, while all female cardiomyocytes excluded the dye (p<0.05). Parallel experiments were conducted in myocytes from ∼24-month-old female rats or 5–6-month-old rats that had an ovariectomy at 3–4 weeks of age. Beneficial effects of female sex on myocyte viability and contractile dysfunction in reperfusion were abolished in cells from 24-month-old females. Aged female myocytes also exhibited elevated intracellular Ca²⁺ and alternans in ischemia. Cells from ovariectomized rats displayed increased Ca²⁺ transients and spontaneous activity in ischemia compared to sham-operated controls. None of the myocytes from ovariectomized rats were viable after 15 minutes of ischemia, while 75% of sham cells remained viable at end of reperfusion (p<0.05). These findings demonstrate that cardiomyocytes from young adult females are more resistant to ischemia and reperfusion injury than cells from males. Age and OVX abolish these beneficial effects and induce Ca²⁺ dysregulation at the level of the cardiomyocyte. Thus, beneficial effects of estrogen in ischemia and reperfusion are mediated, in part, by effects on cardiomyocytes.

Role of endoplasmic reticulum stress in age-related susceptibility to lung fibrosis

The incidence of idiopathic pulmonary fibrosis (IPF) increases with age. The mechanisms that underlie the age-dependent risk for IPF are unknown. Based on studies that suggest an association of IPF and γherpesvirus infection, we infected young (2-3 mo) and old (≥18 mo) C57BL/6 mice with the murine γherpesvirus 68. Acute murine γherpesvirus 68 infection in aging mice resulted in severe pneumonitis and fibrosis compared with young animals. Progressive clinical deterioration and lung fibrosis in the late chronic phase of infection was observed exclusively in old mice with diminution of tidal volume. Infected aging mice showed higher expression of transforming growth factor-β during the acute phase of infection. In addition, aging, infected mice showed elevation of proinflammatory cytokines and the fibrocyte recruitment chemokine, CXCL12, in bronchoalveolar lavage. Analyses of lytic virus infection and virus reactivation indicate that old mice were able to control chronic infection and elicit antivirus immune responses. However, old, infected mice showed a significant increase in apoptotic responses determined by in situ terminal deoxynucleotidyl transferase dUTP nick end labeling assay, levels of caspase-3, and expression of the proapoptotitc molecule, Bcl-2 interacting mediator. Apoptosis of type II lung epithelial cells in aging lungs was accompanied by up-regulation of endoplasmic reticulum stress marker, binding immunoglobulin protein, and splicing of X-box-binding protein 1. These results indicate that the aging lung is more susceptible to injury and fibrosis associated with endoplasmic reticulum stress, apoptosis of type II lung epithelial cells, and activation of profibrotic pathways.

Cold temperature induces mucin hypersecretion from normal human bronchial epithelial cells in vitro through a transient receptor potential melastatin 8 (TRPM8)-mediated mechanism

BACKGROUND

Cold air stimulus is a major environmental factor that exacerbates chronic inflammatory airway diseases, such as chronic obstructive pulmonary disease (COPD) and asthma. At the molecular level, cold is detected by transient receptor potential melastatin 8 (TRPM8). To date, TRPM8 expression has not been characterized in the airway epithelium of patients with COPD. The role of TRPM8 channels in a series of airway responses induced by cold stimuli and the molecular and biochemical pathways of TRPM8 in regulating cold-induced responses are largely unknown.

OBJECTIVE

We sought to explore the role of TRPM8 in cold air-provoked mucus hypersecretion and the potential signaling pathway involved in this process.

METHODS

The expression of TRPM8 in the bronchial epithelium was examined by means of immunohistochemistry, RT-PCR, and Western blotting. TRPM8 receptor function and hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) were characterized by means of Ca(2+) imaging and spatiotemporal dynamics of phospholipase C (PLC) δ1-pleckstrin homology-green fluorescent protein, respectively. The expression of MUC5AC mRNA and MUC5AC mucin protein was measured by using real-time PCR and ELISA, respectively. Four serine residues in the myristoylated alanine-rich C kinase substrate (MARCKS)-phosphorylation site domain were mutated to identify the function of MARCKS in TRPM8-mediated airway mucus hypersecretion.

RESULTS

TRPM8 protein and mRNA expression were significantly increased in patients with COPD compared with expression seen in healthy subjects. Cold produced robust increases in intracellular Ca(2+) levels and promoted translocation of PLCδ1-pleckstrin homology-green fluorescent protein. Cold increased expression of MUC5AC mRNA and intracellular and secreted MUC5AC protein in a nonsustained way. Phosphorylation site domain-mutant MARCKS cDNA hindered MUC5AC secretion induced by cold.

CONCLUSIONS

These results indicate that the TRPM8 receptor is involved in cold-induced mucus hypersecretion through the Ca(2+)-PLC-PIP2-MARCKS signaling pathway.

IP(3) Receptors, Mitochondria, and Ca Signaling: Implications for Aging

The tight interplay between endoplasmic-reticulum-(ER-) and mitochondria-mediated Ca(2+) signaling is a key determinant of cellular health and cellular fate through the control of apoptosis and autophagy. Proteins that prevent or promote apoptosis and autophagy can affect intracellular Ca(2+) dynamics and homeostasis through binding and modulation of the intracellular Ca(2+)-release and Ca(2+)-uptake mechanisms. During aging, oxidative stress becomes an additional factor that affects ER and mitochondrial function and thus their role in Ca(2+) signaling. Importantly, mitochondrial dysfunction and sustained mitochondrial damage are likely to underlie part of the aging process. In this paper, we will discuss the different mechanisms that control intracellular Ca(2+) signaling with respect to apoptosis and autophagy and review how these processes are affected during aging through accumulation of reactive oxygen species.

Prion protein misfolding affects calcium homeostasis and sensitizes cells to endoplasmic reticulum stress

Prion-related disorders (PrDs) are fatal neurodegenerative disorders characterized by progressive neuronal impairment as well as the accumulation of an abnormally folded and protease resistant form of the cellular prion protein, termed PrP^RES. Altered endoplasmic reticulum (ER) homeostasis is associated with the occurrence of neurodegeneration in sporadic, infectious and familial forms of PrDs. The ER operates as a major intracellular calcium store, playing a crucial role in pathological events related to neuronal dysfunction and death. Here we investigated the possible impact of PrP misfolding on ER calcium homeostasis in infectious and familial models of PrDs. Neuro2A cells chronically infected with scrapie prions showed decreased ER-calcium content that correlated with a stronger upregulation of UPR-inducible chaperones, and a higher sensitivity to ER stress-induced cell death. Overexpression of the calcium pump SERCA stimulated calcium release and increased the neurotoxicity observed after exposure of cells to brain-derived infectious PrP^RES. Furthermore, expression of PrP mutants that cause hereditary Creutzfeldt-Jakob disease or fatal familial insomnia led to accumulation of PrP^RES and their partial retention at the ER, associated with a drastic decrease of ER calcium content and higher susceptibility to ER stress. Finally, similar results were observed when a transmembrane form of PrP was expressed, which is proposed as a neurotoxic intermediate. Our results suggest that alterations in calcium homeostasis and increased susceptibility to ER stress are common pathological features of both infectious and familial PrD models.

Minimal peroxide exposure of neuronal cells induces multifaceted adaptive responses

Oxidative exposure of cells occurs naturally and may be associated with cellular damage and dysfunction. Protracted low level oxidative exposure can induce accumulated cell disruption, affecting multiple cellular functions. Accumulated oxidative exposure has also been proposed as one of the potential hallmarks of the physiological/pathophysiological aging process. We investigated the multifactorial effects of long-term minimal peroxide exposure upon SH-SY5Y neural cells to understand how they respond to the continued presence of oxidative stressors. We show that minimal protracted oxidative stresses induce complex molecular and physiological alterations in cell functionality. Upon chronic exposure to minimal doses of hydrogen peroxide, SH-SY5Y cells displayed a multifactorial response to the stressor. To fully appreciate the peroxide-mediated cellular effects, we assessed these adaptive effects at the genomic, proteomic and cellular signal processing level. Combined analyses of these multiple levels of investigation revealed a complex cellular adaptive response to the protracted peroxide exposure. This adaptive response involved changes in cytoskeletal structure, energy metabolic shifts towards glycolysis and selective alterations in transmembrane receptor activity. Our analyses of the global responses to chronic stressor exposure, at multiple biological levels, revealed a viable neural phenotype in-part reminiscent of aged or damaged neural tissue. Our paradigm indicates how cellular physiology can subtly change in different contexts and potentially aid the appreciation of stress response adaptations.

Gill transcriptome response to changes in environmental calcium in the green spotted puffer fish

Background

Calcium ion is tightly regulated in body fluids and for euryhaline fish, which are exposed to rapid changes in environmental [Ca²⁺], homeostasis is especially challenging. The gill is the main organ of active calcium uptake and therefore plays a crucial role in the maintenance of calcium ion homeostasis. To study the molecular basis of the short-term responses to changing calcium availability, the whole gill transcriptome obtained by Super Serial Analysis of Gene Expression (SuperSAGE) of the euryhaline teleost green spotted puffer fish, Tetraodon nigroviridis, exposed to water with altered [Ca²⁺] was analysed.

Results

Transfer of T. nigroviridis from 10 ppt water salinity containing 2.9 mM Ca²⁺ to high (10 mM Ca²⁺ ) and low (0.01 mM Ca²⁺) calcium water of similar salinity for 2-12 h resulted in 1,339 differentially expressed SuperSAGE tags (26-bp transcript identifiers) in gills. Of these 869 tags (65%) were mapped to T. nigroviridis cDNAs or genomic DNA and 497 (57%) were assigned to known proteins. Thirteen percent of the genes matched multiple tags indicating alternative RNA transcripts. The main enriched gene ontology groups belong to Ca²⁺ signaling/homeostasis but also muscle contraction, cytoskeleton, energy production/homeostasis and tissue remodeling. K-means clustering identified co-expressed transcripts with distinct patterns in response to water [Ca²⁺] and exposure time.

Conclusions

The generated transcript expression patterns provide a framework of novel water calcium-responsive genes in the gill during the initial response after transfer to different [Ca²⁺]. This molecular response entails initial perception of alterations, activation of signaling networks and effectors and suggests active remodeling of cytoskeletal proteins during the initial acclimation process. Genes related to energy production and energy homeostasis are also up-regulated, probably reflecting the increased energetic needs of the acclimation response. This study is the first genome-wide transcriptome analysis of fish gills and is an important resource for future research on the short-term mechanisms involved in the gill acclimation responses to environmental Ca²⁺ changes and osmoregulation.

ER stress and hormetic regulation of the aging process

An ability to mount a stress resistance under pressure is a major host defence mechanism and has been a fundamental force during evolution. However, the adaptation capacity clearly declines during aging and this loss of stress resistance accelerates the aging process exposing the organism to degenerative diseases. The effect of stress on organisms seems to be a dose-dependent response, i.e. mild stress induces a stress tolerance and extends the lifespan whereas excessive stress accentuates the aging process. This paradox is known as hormesis in aging research. It is essential to distinguish the intensity of cellular stress and thus mount an appropriate host defence. The endoplasmic reticulum (ER) contains three branches of stress transducers, i.e. IRE1, PERK, and ATF6 pathways, all of which recognize stress-related disturbances in the function of ER. These transducers trigger a complex signaling network which activates an unfolded protein response (UPR). Interestingly, ER stress transducers can distinguish the intensity of ER stress and induce a dose-dependent UPR, either adaptive response to stress or apoptotic cell death. The efficiency of the stress recognition system and UPR signaling declines during aging. We will discuss the role of ER stress in hormetic regulation of aging process and longevity.

Allyl sulfides inhibit cell growth of skin cancer cells through induction of DNA damage mediated G2/M arrest and apoptosis

Diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), extracted from crushed garlic by steam-distillation, have been reported to provide the anticancer activity in several cancer types. However, their mechanisms of effects on skin cancer cells remain unclear. Therefore, we used human melanoma A375 cells and basal cell carcinoma cells as the models to elucidate the effects of these three allyl sulfides. Basal cell carcinoma (BCC) is known to be the most prevalent type of skin cancer, and melanoma is the most lethal form. We found that DATS revealed better growth inhibition of A375 and BCC cells than DADS and DAS did. We further demonstrated that DATS increased intracellular reactive oxygen species (ROS) generation, induced cytosolic Ca(2+) mobilization, and decreased mitochondrial membrane potential (DeltaPsim). Western blot results showed the concordance for the expression of molecules involved in G(2)/M arrest and apoptosis observed by cell cycle and cell viability analysis. Moreover, we detected the activation of p53 pathway in response to the oxidative DNA damage. DATS also displayed selective target of growth inhibition between skin cancer cells and normal keratinocyte HaCaT cells. Taken together, these results suggest that DATS is a potential anticancer compound for skin cancer.