Bcl-2 proteins regulate ER membrane permeability to luminal proteins during ER stress-induced apoptosis

Explorative case control study on the associations of serum vitamin D3, folic acid and vitamin B12 levels on Kawasaki disease and coronary artery lesions

Background

Kawasaki Disease (KD) is a pediatric vasculitic disorder characterized by systemic small vasculitis, notably coronary arteritis, with unclear pathogenesis. This explorative case-control study investigated the association between folic acid (FA), vitamin D3 (VD3), and vitamin B12 (VB12) levels and the different types of Kawasaki Disease, as well as the incidence of coronary artery lesions (CALs).

Methods

In this explorative case control study, 365 KD children admitted to our hospital from January 1, 2022 to June 30, 2023 were included as the KD group. Simultaneously, 365 healthy children who received physical examination during the same period were included as the control group. The KD group was divided into typical KD group and incomplete KD group (IKD group), CALs group and non-CALS group, and IVIG sensitive group and IVIG resistant group. The children with CALs were divided into small tumor group, medium tumor group and large tumor group. Serum levels of FA, VB12, and VD3 were compared across all groups.

Results

Serum levels of FA and VD3 were significantly decreased in both the KD and CALs groups (p < 0.05), and both factors were identified as independent risk factors for KD and CALs. Similarly, reduced serum VD3 levels were observed in the IKD and IVIG-resistant groups (p < 0.05), with VD3 also being an independent risk factor for both IKD and IVIG resistance. Additionally, lower serum FA levels were noted in the group with large aneurysms (p < 0.05), establishing FA as an independent risk factor for aneurysm size.

Conclusion

Serum levels of folic FA and vitamin VD3 were significantly reduced in children with KD. Furthermore, these reductions were more pronounced in children with IKD and CALs. This pattern suggests that lower FA and VD3 levels may increase the risk of more severe coronary lesions in KD patients. Therefore, monitoring these biomarkers could provide valuable insights for early clinical diagnosis and intervention.

Heparanase interacting BCLAF1 to promote the development and drug resistance of ICC through the PERK/eIF2α pathway

Intrahepatic cholangiocarcinoma (ICC) is a primary epithelial carcinoma known for its aggressive nature, high metastatic potential, frequent recurrence, and poor prognosis. Heparanase (HPSE) is the only known endogenous β-glucuronidase in mammals. In addition to its well-established enzymatic roles, HPSE critically exerts non-catalytic function in tumor biology. This study herein aimed to investigate the non-enzymatic roles of HPSE as well as relevant regulatory mechanisms in ICC. Our results demonstrated that HPSE was highly expressed in ICC and promoted the proliferation of ICC cells, with elevated HPSE levels implicating a poor overall survival of ICC patients. Notably, HPSE interacted with Bcl-2-associated factor 1 (BCLAF1) to upregulate the expression of Bcl-2, which subsequently activated the PERK/eIF2α-mediated endoplasmic reticulum (ER) stress pathway to promote anti-apoptotic effect of ICC. Moreover, our in vivo experiments revealed that concomitant administration of gemcitabine and the Bcl-2 inhibitor navitoclax enhanced the sensitivity of ICC cells with highly expressed HPSE to chemotherapy. In summary, our findings revealed that HPSE promoted the development and drug resistance of ICC via its non-enzymatic function. Bcl-2 may be considered as an effective target with therapeutic potential to overcome ICC chemotherapy resistance induced by HPSE, presenting valuable insights into the development of novel therapeutic strategies against ICC.

Ammonia nitrogen stress damages the intestinal mucosal barrier of yellow catfish (Pelteobagrus fulvidraco) and induces intestinal inflammation

Nitrogen from ammonia is one of the most common pollutants toxics to aquatic species in aquatic environment. The intestinal mucosa is one of the key mucosal defenses of aquatic species, and the accumulation of ammonia nitrogen in water environment will cause irreversible damage to intestinal function. In this study, histology, immunohistochemistry, ultrastructural pathology, enzyme activity analysis and qRT-PCR were performed to reveal the toxic effect of ammonia nitrogen stress on the intestine of Pelteobagrus fulvidraco. According to histological findings, ammonia nitrogen stress caused structural damage to the intestine and reduced the number of mucous cells. Enzyme activity analysis revealed that the activity of bactericidal substances (Lysozyme, alkaline phosphatase, and ACP) had decreased. The ultrastructure revealed sparse and shortened microvilli as well as badly degraded tight junctions. Immunohistochemistry for ZO-1 demonstrated an impaired intestinal mucosal barrier. Furthermore, qRT-PCR revealed that tight junction related genes (ZO-1, Occludin, Claudin-1) were downregulated, while the pore-forming protein Claudin-2 was upregulated. Furthermore, as ammonia nitrogen concentration grew, so did the positive signal of Zap-70 (T/NK cell) and the expression of inflammation-related genes (TNF, IL-1β, IL-8, IL-10). In light of the above findings, we conclude that ammonia nitrogen stress damages intestinal mucosal barrier of Pelteobagrus fulvidraco and induces intestinal inflammation.

High-resolution imaging of presynaptic ER networks in Atlastin mutants

The endoplasmic reticulum (ER) is a continuous organelle that extends to the periphery of neurons and regulates many neuronal functions including neurite outgrowth, neurotransmission, and synaptic plasticity. Mutations in proteins that control ER shape are linked to the neurodegenerative disorder Hereditary Spastic Paraplegia (HSP). However, the ultrastructure and dynamics of the neuronal ER have been under-investigated, particularly at presynaptic terminals. Here we developed new super-resolution and live imaging methods in D. melanogaster larval motor neurons to investigate ER structure at presynaptic terminals from wild-type animals, and in null mutants of the HSP gene Atlastin. Previous studies indicated diffuse localization of an ER lumen marker at Atlastin mutant presynaptic terminals, which was attributed to ER fragmentation. By contrast, we found using an ER membrane marker that the ER in Atlastin mutants formed robust networks. Further, our high-resolution imaging results suggest that overexpression of luminal ER proteins in Atlastin mutants causes their progressive displacement to the cytosol at synapses, perhaps due to proteostatic stress and/or changes in ER membrane integrity. Remarkably, these luminal ER proteins remain correctly localized in cell bodies, axons, and other cell types such as body wall muscles, suggesting that ER tubules at synapses have unique structural and functional characteristics. This displacement phenotype has not been reported in numerous studies of Atlastin in non-neuronal cells, emphasizing the importance of conducting experiments in neurons when investigating the mechanisms leading to upper motor neuron dysfunction in HSP.

Nephroprotective and nephrotoxic effects of Rhubarb and their molecular mechanisms

Rhubarb, in the form of a traditional Chinese medicine, is used in the treatment of chronic kidney disease (CKD). Previous studies have demonstrated that Rhubarb possesses a good nephroprotective effect, which primarily protects the kidneys from fibrosis, oxidation, inflammation, autophagy, and apoptosis. However, studies have shown that the long-term inappropriate use of Rhubarb may cause damage to renal function. Therefore, how to correctly understand and scientifically evaluate the pharmacodynamics and toxicity of Rhubarb with regard to CKD is a scientific question that urgently needs to be answered. In this review, we explain and illustrate how Rhubarb exerts its nephroprotective effect against CKD. We also describe the mechanisms of action that may cause its nephrotoxicity. Valuable and practical clinical guidance is proposed with regard to methods for mitigating the nephrotoxicity of Rhubarb.

BCL-XL Overexpression Protects Pancreatic β-Cells against Cytokine- and Palmitate-Induced Apoptosis

Diabetes is a chronic disease that affects glucose metabolism, either by autoimmune-driven β-cell loss or by the progressive loss of β-cell function, due to continued metabolic stresses. Although both α- and β-cells are exposed to the same stressors, such as proinflammatory cytokines and saturated free fatty acids (e.g., palmitate), only α-cells survive. We previously reported that the abundant expression of BCL-XL, an anti-apoptotic member of the BCL-2 family of proteins, is part of the α-cell defense mechanism against palmitate-induced cell death. Here, we investigated whether BCL-XL overexpression could protect β-cells against the apoptosis induced by proinflammatory and metabolic insults. For this purpose, BCL-XL was overexpressed in two β-cell lines-namely, rat insulinoma-derived INS-1E and human insulin-producing EndoC-βH1 cells-using adenoviral vectors. We observed that the BCL-XL overexpression in INS-1E cells was slightly reduced in intracellular Ca2+ responses and glucose-stimulated insulin secretion, whereas these effects were not observed in the human EndoC-βH1 cells. In INS-1E cells, BCL-XL overexpression partially decreased cytokine- and palmitate-induced β-cell apoptosis (around 40% protection). On the other hand, the overexpression of BCL-XL markedly protected EndoC-βH1 cells against the apoptosis triggered by these insults (>80% protection). Analysis of the expression of endoplasmic reticulum (ER) stress markers suggests that resistance to the cytokine and palmitate conferred by BCL-XL overexpression might be, at least in part, due to the alleviation of ER stress. Altogether, our data indicate that BCL-XL plays a dual role in β-cells, participating both in cellular processes related to β-cell physiology and in fostering survival against pro-apoptotic insults.

Interaction of the Zika virus with the cytoplasmic dynein-1

Zika virus (ZIKV) infection is a major public health threat, making the study of its biology a matter of great importance. By analyzing the viral-host protein interactions, new drug targets may be proposed. In this work, we showed that human cytoplasmic dynein-1 (Dyn) interacts with the envelope protein (E) of ZIKV. Biochemical evidence indicates that the E protein and the dimerization domain of the heavy chain of Dyn binds directly without dynactin or any cargo adaptor. Analysis of this interactions in infected Vero cells by proximity ligation assay suggest that the E-Dyn interaction is dynamic and finely tuned along the replication cycle. Altogether, our results suggest new steps in the replication cycle of the ZIKV for virion transport and indicate a suitable molecular target to modulate infection by ZIKV.

NEK6 Regulates Redox Balance and DNA Damage Response in DU-145 Prostate Cancer Cells

NEK6 is a central kinase in developing castration-resistant prostate cancer (CRPC). However, the pathways regulated by NEK6 in CRPC are still unclear. Cancer cells have high reactive oxygen species (ROS) levels and easily adapt to this circumstance and avoid cell death by increasing antioxidant defenses. We knocked out the NEK6 gene and evaluated the redox state and DNA damage response in DU-145 cells. The knockout of NEK6 decreases the clonogenic capacity, proliferation, cell viability, and mitochondrial activity. Targeting the NEK6 gene increases the level of intracellular ROS; decreases the expression of antioxidant defenses (SOD1, SOD2, and PRDX3); increases JNK phosphorylation, a stress-responsive kinase; and increases DNA damage markers (p-ATM and γH2AX). The exogenous overexpression of NEK6 also increases the expression of these same antioxidant defenses and decreases γH2AX. The depletion of NEK6 also induces cell death by apoptosis and reduces the antiapoptotic Bcl-2 protein. NEK6-lacking cells have more sensitivity to cisplatin. Additionally, NEK6 regulates the nuclear localization of NF-κB2, suggesting NEK6 may regulate NF-κB2 activity. Therefore, NEK6 alters the redox balance, regulates the expression of antioxidant proteins and DNA damage, and its absence induces the death of DU-145 cells. NEK6 inhibition may be a new strategy for CRPC therapy.

Isolation, molecular typing and antimicrobial resistance of Clostridium difficile in dogs and cats in Lanzhou city of Northwest China

Clostridium difficile infection (CDI) in human and animals belonged usually to antibiotic-associated diarrhea, ranging in severity from mild to life-threatening intestinal tract illnesses. This study aimed to isolation and characterization, toxin genes test, molecular typing, and drug sensitivity of Clostridium difficile (C. difficile) which were isolated from clinical diseased dogs and cats. A total of 247 clinical samples were collected from five animal hospitals in Lanzhou City of Northwest China, of which dogs and cats accounted for 74.9% (185/247) and 25.1% (62/247), respectively. We successfully identified 24 C. difficile strains by 16S rRNA and Matrix-Assisted Laser Desorption/Ionization Time of Fight Mass Spectroscopy (MALDI-TOF-MS). 10.3% (19/185) of dogs and 8.1% (5/62) of cats were positive for C. difficile. Among them, 16 strains were toxic and 8 were non-toxic, with a toxic rate of 57.9% (11/19) in dogs and 100% (5/5) in cats. A total of 10 STs and 10 RTs were identified in this study. The percentages of ST42 (RT106) and ST2 (RT014/LW01) among 16 toxic strains were 41.7 and 12.5%, respectively. However, ST3 (RT001), ST1 (RT027), ST133 (LW04), and ST-UN (LW04) had only one strain. ST42 (RT106) was the most common genotype and RT027 strain was first isolated in China from pets. Antimicrobial susceptibility test showed that isolates were extremely sensitive to vancomycin and metronidazole but were resistant to erythromycin and ciprofloxacin. The drug resistant rates to clindamycin, levofloxacin, moxifloxacin and meropenem were 62.5, 20.8, 16.7, and 8.3%, respectively. In conclusion, C. difficile was quietly prevalent in dogs and cats in Lanzhou city with RT106 and RT014 as the main ribotypes. The CDI in pets should be paying more attention and further studies are needed.

Regulatory Role of Sphingosine-1-Phosphate and C16:0 Ceramide, in Immunogenic Cell Death of Colon Cancer Cells Induced by Bak/Bax-Activation

We recently identified the sphingosine kinases (SphK1/2) as key intracellular regulators of immunogenic cell death (ICD) in colorectal cancer (CRC) cells. To better understand the mechanism by which SphK inhibition enhances ICD, we focused on the intracellular signaling pathways leading to cell surface exposure of calreticulin (ectoCRT). Herein, we demonstrate that ABT-263 and AZD-5991, inhibitors of Bcl-2/Bcl-XL and Mcl-1, respectively, induce the production of ectoCRT, indicative of ICD. Inhibition of SphK1 significantly enhanced ABT/AZD-induced ectoCRT production, in a caspase 8-dependent manner. Mechanistically, we demonstrate that ABT/AZD-induced Bak/Bax activation stimulates pro-survival SphK1/sphingosine-1-phosphate (S1P) signaling, which attenuates ectoCRT production. Additionally, we identified a regulatory role for ceramide synthase 6 (CerS6)/C16:0 ceramide in transporting of ectoCRT to the cell surface. Together, these results indicate that the sphingolipid metabolic regulators of the sphingolipid rheostat, S1P and C16:0 ceramide, influence survival/death decisions of CRC cells in response to ICD-inducing chemotherapeutic agents. Importantly, SphK1, which produces S1P, is a stress-responsive pro-survival lipid kinase that suppresses ICD. While ceramide, produced by the inhibition of SphK1 is required for production of the cell surface marker of ICD, ectoCRT. Thus, inhibition of SphK1 represents a means to enhance the therapeutic efficacy of ICD-inducing agents.

Modulation of Ca2+ signaling by antiapoptotic Bcl-2 versus Bcl-xL: From molecular mechanisms to relevance for cancer cell survival

Members of the Bcl-2-protein family are key controllers of apoptotic cell death. The family is divided into antiapoptotic (including Bcl-2 itself, Bcl-xL, Mcl-1, etc.) and proapoptotic members (Bax, Bak, Bim, Bim, Puma, Noxa, Bad, etc.). These proteins are well known for their canonical role in the mitochondria, where they control mitochondrial outer membrane permeabilization and subsequent apoptosis. However, several proteins are recognized as modulators of intracellular Ca²⁺ signals that originate from the endoplasmic reticulum (ER), the major intracellular Ca²⁺-storage organelle. More than 25 years ago, Bcl-2, the founding member of the family, was reported to control apoptosis through Ca²⁺ signaling. Further work elucidated that Bcl-2 directly targets and inhibits inositol 1,4,5-trisphosphate receptors (IP₃Rs), thereby suppressing proapoptotic Ca²⁺ signaling. In addition to Bcl-2, Bcl-xL was also shown to impact cell survival by sensitizing IP₃R function, thereby promoting prosurvival oscillatory Ca²⁺ release. However, new work challenges this model and demonstrates that Bcl-2 and Bcl-xL can both function as inhibitors of IP₃Rs. This suggests that, depending on the cell context, Bcl-xL could support very distinct Ca²⁺ patterns. This not only raises several questions but also opens new possibilities for the treatment of Bcl-xL-dependent cancers. In this review, we will discuss the similarities and divergences between Bcl-2 and Bcl-xL regarding Ca²⁺ homeostasis and IP₃R modulation from both a molecular and a functional point of view, with particular emphasis on cancer cell death resistance mechanisms.

Heat shock protein Grp78/BiP/HspA5 binds directly to TDP-43 and mitigates toxicity associated with disease pathology

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no cure or effective treatment in which TAR DNA Binding Protein of 43 kDa (TDP-43) abnormally accumulates into misfolded protein aggregates in affected neurons. It is widely accepted that protein misfolding and aggregation promotes proteotoxic stress. The molecular chaperones are a primary line of defense against proteotoxic stress, and there has been long-standing interest in understanding the relationship between chaperones and aggregated protein in ALS. Of particular interest are the heat shock protein of 70 kDa (Hsp70) family of chaperones. However, defining which of the 13 human Hsp70 isoforms is critical for ALS has presented many challenges. To gain insight into the specific Hsp70 that modulates TDP-43, we investigated the relationship between TDP-43 and the Hsp70s using proximity-dependent biotin identification (BioID) and discovered several Hsp70 isoforms associated with TDP-43 in the nucleus, raising the possibility of an interaction with native TDP-43. We further found that HspA5 bound specifically to the RNA-binding domain of TDP-43 using recombinantly expressed proteins. Moreover, in a Drosophila strain that mimics ALS upon TDP-43 expression, the mRNA levels of the HspA5 homologue (Hsc70.3) were significantly increased. Similarly we observed upregulation of HspA5 in prefrontal cortex neurons from human ALS patients. Finally, overexpression of HspA5 in Drosophila rescued TDP-43-induced toxicity, suggesting that upregulation of HspA5 may have a compensatory role in ALS pathobiology.

Zinc Accumulation Aggravates Cerebral Ischemia/Reperfusion Injury Through Inducing Endoplasmic Reticulum Stress

Zinc is highly enriched in the central nervous system. Numerous evidences suggest that high concentration of zinc acts as a critical mediator of neuronal death in the ischemic brain, however, the possible mechanisms of neurotoxicity of zinc during cerebral ischemia/reperfusion (I/R) remain elusive. Endoplasmic reticulum (ER) is a storage location of intracellular zinc. ER stress related genes were up-regulated during zinc-induced neuronal death in vascular-type senile dementia. In the present study, we investigated whether intracellular accumulated zinc aggravates I/R injury through ER stress and ER stress-associated apoptosis. Male Sprague-Dawley rats were subjected to 90 min middle cerebral artery occlusion (MCAO) and received either vehicle or zinc chelator TPEN 15 mg/kg. The expression of ER stress related factors glucose-regulated protein 78 (GRP78) and phosphorylated eukaryotic initiation factor 2α (p-eIF2α), ER stress related apoptotic proteins CCAAT-enhancer-binding protein homologous protein (CHOP) and caspase-12, as well as anti-apoptotic factor B-cell lymphoma-2 (Bcl-2) were assessed 24 h after reperfusion. Our results showed that the levels of GRP78 and p-eIF2α, as well as CHOP and caspase-12, were increased in ischemic brain, indicating that cerebral I/R triggers ER stress. Furthermore, GRP78, CHOP and caspase-12 were all colocalized with the zinc-specific dyes NG, suggesting that there is certain relationship between cytosolic labile zinc and ER stress following cerebral ischemia. Chelating zinc with TPEN reversed the expression of GRP78, p-eIF2α in ischemic rats. Moreover, CHOP and NeuN double staining positive cells, as well as caspase-12 and TUNEL double staining positive cells were also decreased after TPEN treatment, indicating that chelating zinc might inhibit ER stress and decreased ER stress associated neuronal apoptosis. In addition, TPEN treatment reversed the downregulated level of Bcl-2, which localized in the ER membrane and involved in the dysfunction of ER, confirming that the anti-apoptosis effects of chelating zinc following I/R are exerted via inhibition of the ER stress. Taken together, this study demonstrated that excessive zinc activates ER stress and zinc induced neuronal cell death is at least partially due to ER stress specific neuronal apoptosis in ischemic penumbra, which may provide an important mechanism of cerebral I/R injury.

HSP70 and HSP90 in Cancer: Cytosolic, Endoplasmic Reticulum and Mitochondrial Chaperones of Tumorigenesis

HSP70 and HSP90 are two powerful chaperone machineries involved in survival and proliferation of tumor cells. Residing in various cellular compartments, HSP70 and HSP90 perform specific functions. Concurrently, HSP70 and HSP90 homologs may also translocate from their primary site under various stress conditions. Herein, we address the current literature on the role of HSP70 and HSP90 chaperone networks in cancer. The goal is to provide a comprehensive review on the functions of cytosolic, mitochondrial and endoplasmic reticulum HSP70 and HSP90 homologs in cancer. Given that high expression of HSP70 and HSP90 enhances tumor development and associates with tumor aggressiveness, further understanding of HSP70 and HSP90 chaperone networks may provide clues for the discoveries of novel anti-cancer therapies.

Inhibition of histone demethylase KDM4 by ML324 induces apoptosis through the unfolded protein response and Bim upregulation in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is an extremely aggressive malignancy that ranks as the sixth-leading cause of cancer-associated death worldwide. Recently, various epigenetic mechanisms including gene methylation were reported to be potential next era HCC therapeutics and biomarkers. Although inhibition of epigenetic enzymes including histone lysine demethylase 4 (KDM4) enhanced cell death in HCC cells, the detailed mechanism of cell death machinery is poorly understood. In this study, we found that ML324, a small molecule KDM4-specific inhibitor, induced the death of HCC cells in a general cell culture system and 3D spheroid culture with increased cleavage of caspase-3. Mechanistically, we identified that unfolded protein responses (UPR) were involved in ML324-induced HCC cell death. Incubation of HCC cells with ML324 upregulated death receptor 5 (DR5) expression through the activation transcription factor 3 (ATF3)-C/EBP homologous protein (CHOP)-dependent pathway. Moreover, we identified BIM protein as a mediator of ML324-induced apoptosis using CRISPR/Cas9 knockout analysis. We showed that the loss of Bim suppressed ML324-induced apoptosis by flow cytometry analysis, colony formation assay, and caspase-3 activation assay. Interestingly, BIM protein expression by ML324 was regulated by ATF3, CHOP, and DR5 which are factors involved in UPR. Specifically, we confirmed the regulating roles of KDM4E in Bim and CHOP expression using a chromatin immune precipitation (ChIP) assay. Physical binding of KDM4E to Bim and CHOP promoters decreased the response to ML324. Our findings suggest that KDM4 inhibition is a potent anti-tumor therapeutic strategy for human HCC, and further studies of UPR-induced apoptosis and the associated epigenetic functional mechanisms may lead to the discovery of novel target for future cancer therapy.

Bcl-2 Family of Proteins in the Control of Mitochondrial Calcium Signalling: An Old Chap with New Roles

Bcl-2 family proteins are considered as one of the major regulators of apoptosis. Indeed, this family is known to control the mitochondrial outer membrane permeabilization (MOMP): a central step in the mitochondrial pathway of apoptosis. However, in recent years Bcl-2 family members began to emerge as a new class of intracellular calcium (Ca²⁺) regulators. At mitochondria-ER contacts (MERCs) these proteins are able to interact with major Ca²⁺ transporters, thus controlling mitochondrial Ca²⁺ homeostasis and downstream Ca²⁺ signalling pathways. Beyond the regulation of cell survival, this Bcl-2-dependent control over the mitochondrial Ca²⁺ dynamics has far-reaching consequences on the physiology of the cell. Here, we review how the Bcl-2 family of proteins mechanistically regulate mitochondrial Ca²⁺ homeostasis and how this regulation orchestrates cell death/survival decisions as well as the non-apoptotic process of cell migration.

Death sentence: The tale of a fallen endoplasmic reticulum

Endoplasmic Reticulum (ER) stress signaling is an adaptive mechanism triggered when protein folding demand overcomes the folding capacity of this compartment, thereby leading to the accumulation of improperly folded proteins. This stress signaling pathway is named the Unfolded Protein Response (UPR) and aims at restoring ER homeostasis. However, if this fails, mechanisms orienting cells towards death processes are initiated. Herein, we summarize the most recent findings connecting ER stress and the UPR with identified death mechanisms including apoptosis, necrosis, pyroptosis, ferroptosis, and autophagy. We highlight new avenues that could be investigated and controlled through actionable mechanisms in physiology and pathology.

The Clinical Characteristics of Patients With Nonneutropenic Invasive Pulmonary Aspergillosis

Objective: The goal of this study was to reveal the clinical manifestations of nonneutropenic invasive pulmonary aspergillosis (IPA), which are different from those of neutropenic patients.

Methods: The clinical data of patients with nonneutropenic IPA were collected at the Department of Respiratory and Critical Care Medicine, Jinling Hospital, from February 2009 to November 2019. We analyzed the general conditions, clinical manifestations, imaging findings, and laboratory tests of these IPA patients.

Results: A total of 116 patients with nonneutropenic IPA (31 proven and 85 probable) were included. They had an average age of 59.8 years. The most common underlying disease was chronic obstructive pulmonary disease (COPD, n = 33). The common clinical symptoms included cough (93.1%, n = 108), expectoration (59.5%, n = 69), fever (57.8%, n = 67), hemoptysis (30.2%, n = 35), and dyspnea (40.5%, n = 47). The common CT imaging manifestations included consolidation (47.4%, n = 55), cavities (47.4%, n = 55), air crescent sign (14.7%, n = 17), and nodules (8.6%, n = 10). Multiple lesions (74.1%, n = 86) were more common than single lesions (17.2%, n = 20) and diffuse lesions (8.6%, n = 10). The positive rate of laboratory tests was 88.2% (30/34) for BALF galactomannan (GM), 55.4% (56/101) for serum GM, 45.3% (48/106) for 1,3-β-D-glucan (BDG), 43.3% (46/106) for sputum culture, and 36.4% (20/55) for BALF culture. Patients who had high serum GM level [GM optical density index (ODI) >1] were more likely to have severe respiratory symptoms and higher serum ferritin. Further investigation showed that there was a positive correlation between serum GM level and serum ferritin level.

Conclusion: The clinical symptoms and radiological manifestations of nonneutropenic IPA are diverse and often lead to delayed diagnosis. It is important to become more vigilant of aspergillosis in nonneutropenic patients in order to achieve early diagnosis and treatment and to reduce mortality.

Polygonum multiflorum-Induced Liver Injury: Clinical Characteristics, Risk Factors, Material Basis, Action Mechanism and Current Challenges

Polygonum multiflorum Thunb. (PM), called Heshouwu in China, is a popular Chinese medicine in clinical practice. Several clinical studies have been conducted to evaluate the traditional therapeutic claims and to study the potential therapeutic activity of PM in dyslipidemia and neurodegenerative diseases, highlighting available clinical evidence. In recent years, reports on clinical adverse reactions of Raw Radix P. multiflorum (RPM) and P. multiflorum Praeparata (PMP) have been on the increase, especially with respect to liver injury. Most liver injury cases had been assessed for causality using RUCAM (Roussel Uclaf Causality Assessment Method) in this paper. However, the components of PM responsible for the reported hepatotoxic effects have not yet been identified. Moreover, many of the reports are contradictory, while studies on the mechanism involved in PM-induced liver damage are not comprehensive. This study was aimed at reviewing the status of research on liver injury due to PM, including clinical characteristics, risk factors, material basis research and mechanism of action, with a view to understanding PM-induced hepatotoxicity, and taking reasonable and effective measures to prevent it. In short, quality control is still one of the major safety problems in TCM drug safety concerns. The model of safety monitoring and risk management of PM drugs is not yet developed. Indeed, the characteristics and risk factors associated with PM require both proper understanding and control of the risk by strengthening standardization of clinical applications, basic science research, quality control in manufacturing, active monitoring methodology and enhancement of international communication and cooperation. Measures should also be encouraged and implemented to promote healthy development of the TCM industry.

The Gα-interacting vesicle-associated protein interacts with and promotes cell surface localization of GRP78 during endoplasmic reticulum stress

Cell surface translocation of the chaperone glucose-regulated protein 78 kDa (GRP78) is a key event that promotes cancer cell survival during endoplasmic reticulum (ER) stress. Here, we identify Gα-interacting vesicle-associated protein (GIV) - an enhancer of prosurvival signaling during ER stress - as a binding partner of GRP78. We show that GIV and GRP78 interact in an ER stress-dependent manner through their respective carboxyl terminal domains and that GIV aids in the localization of GRP78 to the plasma membrane. Kaplan-Meier analysis of disease-free survival in cancer patients shows poor prognosis for patients with high expression of both GIV and GRP78, further suggesting a vital role for these two proteins in enhancing cancer cell viability.

Type I interferons and endoplasmic reticulum stress in health and disease

Type I interferons (IFNs) comprise of pro-inflammatory cytokines created, as well as sensed, by all nucleated cells with the main objective of blocking pathogens-driven infections. Owing to this broad range of influence, type I IFNs also exhibit critical functions in many sterile inflammatory diseases and immunopathologies, especially those associated with endoplasmic reticulum (ER) stress-driven signaling pathways. Indeed, over the years accumulating evidence has indicated that the presence of ER stress can influence the production, or sensing of, type I IFNs induced by perturbations like pattern recognition receptor (PRR) agonists, infections (bacterial, viral or parasitic) or autoimmunity. In this article we discuss the link between type I IFNs and ER stress in various diseased contexts. We describe how ER stress regulates type I IFNs production or sensing, or how type I IFNs may induce ER stress, in various circumstances like microbial infections, autoimmunity, diabetes, cancer and other ER stress-related contexts.

Hsp70 molecular chaperones: multifunctional allosteric holding and unfolding machines

The Hsp70 family of chaperones works with its co-chaperones, the nucleotide exchange factors and J-domain proteins, to facilitate a multitude of cellular functions. Central players in protein homeostasis, these jacks-of-many-trades are utilized in a variety of ways because of their ability to bind with selective promiscuity to regions of their client proteins that are exposed when the client is unfolded, either fully or partially, or visits a conformational state that exposes the binding region in a regulated manner. The key to Hsp70 functions is that their substrate binding is transient and allosterically cycles in a nucleotide-dependent fashion between high- and low-affinity states. In the past few years, structural insights into the molecular mechanism of this allosterically regulated binding have emerged and provided deep insight into the deceptively simple Hsp70 molecular machine that is so widely harnessed by nature for diverse cellular functions. In this review, these structural insights are discussed to give a picture of the current understanding of how Hsp70 chaperones work.

Systematic Overview of Aristolochic Acids: Nephrotoxicity, Carcinogenicity, and Underlying Mechanisms

Aristolochic acids (AAs) are a group of toxins commonly present in the plants of genus Aristolochia and Asarum, which are spread all over the world. Since the 1990s, AA-induced nephropathy (AAN) and upper tract urothelial carcinoma (UTUC) have been reported in many countries. The underlying mechanisms of AAN and AA-induced UTUC have been extensively investigated. AA-derived DNA adducts are recognized as specific biomarkers of AA exposure, and a mutational signature predominantly characterized by A→T transversions has been detected in AA-induced UTUC tumor tissues. In addition, various enzymes and organic anion transporters are involved in AA-induced adverse reactions. The progressive lesions and mutational events initiated by AAs are irreversible, and no effective therapeutic regimen for AAN and AA-induced UTUC has been established until now. Because of several warnings on the toxic effects of AAs by the US Food and Drug Administration and the regulatory authorities of some other countries, the sale and use of AA-containing products have been banned or restricted in most countries. However, AA-related adverse events still occur, especially in the Asian and Balkan regions. Therefore, the use of AA-containing herbal remedies and the consumption of food contaminated by AAs still carry high risk. More strict precautions should be taken to protect the public from AA exposure.

Immunogenic Cell Death and Immunotherapy of Multiple Myeloma

Over the past decades, immunotherapy has demonstrated a prominent clinical efficacy in a wide variety of human tumors. For many years, apoptosis has been considered a non-immunogenic or tolerogenic process whereas necrosis or necroptosis has long been acknowledged to play a key role in inflammation and immune-related processes. However, the new concept of “immunogenic cell death” (ICD) has challenged this traditional view and has granted apoptosis with immunogenic abilities. This paradigm shift offers clear implications in designing novel anti-cancer therapeutic approaches. To date, several screening studies have been carried out to discover bona fide ICD inducers and reveal the inherent capacity of a wide variety of drugs to induce cell death-associated exposure of danger signals and to bring about in vivo anti-cancer immune responses. Recent shreds of evidence place ER stress at the core of all the scenarios where ICD occur. Furthermore, ER stress and the unfolded protein response (UPR) have emerged as important targets in different human cancers. Notably, in multiple myeloma (MM), a lethal plasma cell disorder, the elevated production of immunoglobulins leaves these cells heavily reliant on the survival arm of the UPR. For that reason, drugs that disrupt ER homeostasis and engage ER stress-associated cell death, such as proteasome inhibitors, which are currently used for the treatment of MM, as well as novel ER stressors are intended to be promising therapeutic agents in MM. This not only holds true for their capacity to induce cell death, but also to their potential ability to activate the immunogenic arm of the ER stress response, with the ensuing exposure of danger signals. We provide here an overview of the up-to-date knowledge regarding the cell death mechanisms involved in situations of ER stress with a special focus on the connections with the drug-induced ER stress pathways that evoke ICD. We will also discuss how this could assist in optimizing and developing better immunotherapeutic approaches, especially in MM treatment.

The functional role of Bax/Bak in palmitate-induced lipoapoptosis

Induction of programmed cell death, mainly apoptosis (lipoapoptosis) is a major cellular consequence of the lipotoxicity, a harmful effect resulting from the overload of lipids. Both Endoplasmic reticulum (ER) stress and autophagy have been suggested to play important role in the regulation of lipoapoptosis. However, the exact mechanisms underlying lipoapoptosis remain unclear. In the present study, we aimed to investigate the functional role of Bax/Bak in lipoapoptosis using mouse embryonic fibroblasts (MEFs) cell culture model. Results showed that palmitate induced caspase-dependent apoptosis in wild-type Bax/Bak MEF cells, whereas a caspase-independent cell death was induced by palmitate in Bax/Bak knockout MEF cells, suggesting requirement of Bax/Bak in palmitate-induced caspase activation. More importantly, we found that the status of Bax/Bak is a determinant that governs the decision between the pro-survival or pro-death function of autophagy in response to palmitate exposure, and Bax/Bak is required for palmitate-induced activation of endoplasmic reticulum (ER) stress and subsequently ER stress-mediated apoptosis. The findings of the present study provided novel insights into understanding the mechanisms involved in the regulation of palmitate-induced lipoapoptosis.

The tumorigenic role of DSPP and its potential regulation of the unfolded protein response and ER stress in oral cancer cells

Dentin sialophosphoprotein (DSPP) is upregulated in various human cancers, including head and neck squamous cell carcinoma. Cancer cells are commonly found under constant endoplasmic reticulum (ER) stress and exhibit increased levels of misfolded proteins, due to gene mutations and a stressful microenvironment. The present study examined the effects of DSPP silencing on the regulation of ER stress and the unfolded protein response (UPR) in oral cancer cells. A recently established stable DSPP short hairpin (sh)RNA-silenced OSC2 oral cancer cell line was used. The mRNA expression levels of ER stress-associated proteins, including 78 kDa glucose-regulated protein (GRP78), sarcoplasmic/endoplasmic reticulum calcium ATPase 2b (SERCA2b), inositol 1,4,5-trisphosphate receptor (IP3r), protein kinase R-like endoplasmic reticulum kinase (PERK), serine/threonine-protein kinase/endoribonuclease IRE1 (IRE1), activating transcription factor 6 (ATF6) and matrix metalloproteinase 20 (MMP20), were assessed by reverse transcription-quantitative polymerase chain reaction. The expression levels of apoptosis-related [B‑cell lymphoma 2 (Bcl2), Bcl2-associated X protein (Bax) and cytochrome c] and cell proliferation-related [proliferating cell nuclear antigen (PCNA)] proteins were analyzed by western blotting. Cell viability, apoptosis and migration were monitored by MTT assay, Annexin V-fluorescein isothiocyanate flow cytometry and wound-healing assay, respectively. In transiently transfected puromycin‑free OSC2 cells, DSPP silencing markedly downregulated the mRNA expression levels of major ER stress regulators, including GRP78, SERCA2b, PERK, IRE1 and ATF6, as well as MMP20. DSPP silencing also resulted in decreased cell viability and migration, and enhanced apoptosis. Furthermore, PCNA and Bcl2 levels were decreased, whereas Bax and cytochrome c protein levels were increased in DSPP-silenced OSC2 cells. Sustained puromycin treatment partially counteracted the effects of DSPP silencing on the mRNA expression levels of ER stress-related proteins and MMP20, and on the migratory capacity of OSC2 cells. However, following puromycin treatment of DSPP-silenced cells, cell viability was further reduced and apoptosis was enhanced. In conclusion, these data provide evidence to suggest that DSPP may be involved in ER stress mechanisms in oral squamous cell carcinoma, since its downregulation in OSC2 cells led to significant alterations in the levels of major ER stress-associated proteins, and subsequent collapse of the UPR system.

Mcl-1 regulates reactive oxygen species via NOX4 during chemotherapy-induced senescence

Mcl-1, a Bcl-2 family member, is highly expressed in a variety of human cancers and is believed to enhance tumorigenic potential and chemotherapy resistance through the inhibition of apoptosis and senescence. We previously reported that Mcl-1′s regulation of chemotherapy-induced senescence (CIS) is dependent on its ability to prevent reactive oxygen species (ROS) generation. In this report, we demonstrate that Mcl-1-regulated CIS requires not only ROS, but specifically mitochondrial ROS, and that these events are upstream of activation of the DNA damage response, another necessary step toward senescence. Mcl-1′s anti-senescence activity also involves the unique ability to inhibit ROS formation by preventing the upregulation of pro-oxidants. Specifically, we found that NADPH oxidases (NOXs) are regulated by Mcl-1 and that NOX4 expression in particular is a required step for CIS induction that is blocked by Mcl-1. Lastly, we illustrate that by preventing expression of NOX4, Mcl-1 limits its availability in the mitochondria, thereby lowering the production of mitochondrial ROS during CIS. Our studies not only define the essential role of Mcl-1 in chemoresistance, but also for the first time link a key pro-survival Bcl-2 family member with the NOX protein family, both of which have significant ramifications in cancer progression.

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

Glaucoma Pathogenesis and Neurotrophins: Focus on the Molecular and Genetic Basis for Therapeutic Prospects

BACKGROUND

Retinal ganglion cell (RGC) degeneration is a major feature of glaucoma pathology. Neuroprotective approaches that delay or halt the progression of RGC loss are needed to prevent vision loss which can occur even after conventional medical or surgical treatments to lower intraocular pressure.

OBJECTIVE

The aim of this review was to examine the progress in genetics and cellular mechanisms associated with endoplasmic reticulum (ER) stress, RGC dysfunction and cell death pathways in glaucoma.

MATERIALS AND METHODS

Here, we review the involvement of neurotrophins like brain derived neurotrophic factor (BDNF) and its high affinity receptor tropomyosin receptor kinase (TrkB) in glaucoma. The role of ER stress markers in human and animal retinas in health and disease conditions is also discussed. Further, we analysed the literature highlighting genetic linkage in the context of primary open angle glaucoma and suggested mechanistic insights into potential therapeutic options relevant to glaucoma management.

RESULTS

The literature review of the neurobiology underlying neurotrophin pathways, ER stress and gene associations provide critical insights into association of RGCs death in glaucoma. Alteration in signalling pathway is associated with increased risk of misfolded protein aggregation in ER promoting RGC apoptosis. Several genes that are linked with neurotrophin signalling pathways have been reported to be associated with glaucoma pathology.

CONCLUSION

Understanding genetic heterogeneity and involvement of neurotrophin biology in glaucoma could help to understand the complex pathophysiology of glaucoma. Identification of novel molecular targets will be critical for drug development and provide neuroprotection to the RGCs and optic nerve.

N-(3-Oxo-acyl)-homoserine lactone induces apoptosis primarily through a mitochondrial pathway in fibroblasts

N-(3-Oxododecanoyl)-l-homoserine lactone (C12) is produced by Pseudomonas aeruginosa to function as a quorum-sensing molecule for bacteria-bacteria communication. C12 is also known to influence many aspects of human host cell physiology, including induction of cell death. However, the signalling pathway(s) leading to C12-triggered cell death is (are) still not completely known. To clarify cell death signalling induced by C12, we examined mouse embryonic fibroblasts deficient in "initiator" caspases or "effector" caspases. Our data indicate that C12 selectively induces the mitochondria-dependent intrinsic apoptotic pathway by quickly triggering mitochondrial outer membrane permeabilisation. Importantly, the activities of C12 to permeabilise mitochondria are independent of activation of both "initiator" and "effector" caspases. Furthermore, C12 directly induces mitochondrial outer membrane permeabilisation in vitro. Overall, our study suggests a mitochondrial apoptotic signalling pathway triggered by C12, in which C12 or its metabolite(s) acts on mitochondria to permeabilise mitochondria, leading to activation of apoptosis.

BCL-2 family: integrating stress responses at the ER to control cell demise

In the last decade, the endoplasmic reticulum (ER) has emerged as a central organelle regulating the core mitochondrial apoptosis pathway. At the ER membrane, a variety of stress signals are integrated toward determining cell fate, involving a complex cross talk between key homeostatic pathways including the unfolded protein response, autophagy, calcium signaling and mitochondrial bioenergetics. In this context, key regulators of cell death of the BCL-2 and TMBIM/BI-1 family of proteins have relevant functions as stress rheostats mediated by the formation of distinct protein complexes that regulate the switch between adaptive and proapoptotic phases under stress. Here, we overview recent advances on our molecular understanding of how the apoptotic machinery integrates stress signals toward cell fate decisions upstream of the mitochondrial gateway of death.

p53-mediated suppression of BiP triggers BIK-induced apoptosis during prolonged endoplasmic reticulum stress

Physiological and pathological conditions that affect the folding capacity of the endoplasmic reticulum (ER) provoke ER stress and trigger the unfolded protein response (UPR). The UPR aims to either restore the balance between newly synthesized and misfolded proteins or if the damage is severe, to trigger cell death. However, the molecular events underlying the switch between repair and cell death are not well understood. The ER-resident chaperone BiP governs the UPR by sensing misfolded proteins and thereby releasing and activating the three mediators of the UPR: PERK, IRE1 and ATF6. PERK promotes G2 cell cycle arrest and cellular repair by inducing the alternative translated p53 isoform p53ΔN40 (p53/47), which activates 14-3-3σ via suppression of p21^CDKN1A. Here we show that prolonged ER stress promotes apoptosis via a p53-dependent inhibition of BiP expression. This leads to the release of the pro-apoptotic BH3-only BIK from BiP and activation of apoptosis. Suppression of bip mRNA translation is mediated via the specific binding of p53 to the first 346-nt of the bip mRNA and via a p53 trans-suppression domain located within the first seven N-terminal amino acids of p53ΔN40. This work shows how p53 targets BiP to promote apoptosis during severe ER stress and further illustrates how regulation of mRNA translation has a key role in p53-mediated regulation of gene expression during the UPR.

GRP78 at the Centre of the Stage in Cancer and Neuroprotection

The 78-kDa glucose-regulated protein GRP78, also known as BiP and HSP5a, is a multifunctional protein with activities far beyond its well-known role in the unfolded protein response (UPR) which is activated after endoplasmic reticulum (ER) stress in the cells. Most of these newly discovered activities depend on its position within the cell. GRP78 is located mainly in the ER, but it has also been observed in the cytoplasm, the mitochondria, the nucleus, the plasma membrane, and secreted, although it is dedicated mostly to engage endogenous cytoprotective processes. Hence, GRP78 may control either UPR and macroautophagy or may activated phosphatidylinositol 3-kinase (PI3K)/AKT pro-survival pathways. GRP78 influences how tumor cells survive, proliferate, and develop chemoresistance. In neurodegeneration, endogenous mechanisms of neuroprotection are frequently insufficient or dysregulated. Lessons from tumor biology may give us clues about how boosting endogenous neuroprotective mechanisms in age-related neurodegeneration. Herein, the functions of GRP78 are revealed at the center of the stage of apparently opposite sites of the same coin regarding cytoprotection: neurodegeneration and cancer. The goal is to give a comprehensive and critical review that may serve to guide future experiments to identify interventions that will enhance neuroprotection.

Moderate endoplasmic reticulum stress activates a PERK and p38-dependent apoptosis

The endoplasmic reticulum (ER) has the ability to signal organelle dysfunction via a complex signaling network known as the unfolded protein response (UPR). In this work, hamster fibroblast cells exhibiting moderate levels of ER stress were compared to those exhibiting severe ER stress. Inhibition of N-linked glycosylation was accomplished via a temperature-sensitive mutation in the Dad1 subunit of the oligosaccharyltransferase (OST) complex or by direct inhibition with tunicamycin (Tm). Temperature shift (TS) treatment generated weak activation of ER stress signaling when compared to doses of Tm that are typically used in ER stress studies (500-1000 nM). A dose-response analysis of key ER stress signaling mediators, inositol-requiring enzyme 1 (IRE1) and protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), revealed 20-40 nM of Tm to generate activation intensity similar to TS treatment. In parental BHK21 cells, moderate (20-40 nM) and high doses (200-1000 nM) of Tm were compared to identify physiological and signaling-based differences in stress response. Inhibition of ER Ca2+ release via ITPR activity with 2-aminoethoxydiphenyl borate (2-APB) or Xestospongin C (XeC) was sufficient to protect against apoptosis induced by moderate but not higher doses of Tm. Analysis of kinase activation over a range of Tm exposures revealed the p38 stress-activated protein kinase (SAPK) to display increasing activation with Tm dosage. Interestingly, Tm induced the extracellular regulated kinases (Erk1/2) only at moderate doses of Tm. Inhibition of ER transmembrane stress sensors (IRE1, PERK) or cytosolic signaling mediators (p38, Jnk1, Erk1/2) was used to evaluate pathways involved in apoptosis activation during ER stress. Inhibition of either PERK or p38 was sufficient to reduce cell death and apoptosis induced by moderate, but not high, doses of Tm. During ER stress, cells exhibited a rapid decline in anti-apoptotic Mcl-1 and survivin proteins. Inhibition of PERK was sufficient to block this affect. This work reveals moderate doses of ER stress to generate patterns of stress signaling that are distinct from higher doses and that apoptosis activation at moderate levels of stress are dependent upon PERK and p38 signaling. Studies exploring ER stress signaling should recognize that this signaling acts as a rheostat rather than a simple switch, behaving distinctively in a dose-dependent manner.

Endoplasmic Reticulum Stress-induced Hepatocellular Death Pathways Mediate Liver Injury and Fibrosis via Stimulator of Interferon Genes

Fibrosis, driven by inflammation, marks the transition from benign to progressive stages of chronic liver diseases. Although inflammation promotes fibrogenesis, it is not known whether other events, such as hepatocyte death, are required for the development of fibrosis. Interferon regulatory factor 3 (IRF3) regulates hepatocyte apoptosis and production of type I IFNs. In the liver, IRF3 is activated via Toll-like receptor 4 (TLR4) signaling or the endoplasmic reticulum (ER) adapter, stimulator of interferon genes (STING). We hypothesized that IRF3-mediated hepatocyte death is an independent determinant of chemically induced liver fibrogenesis. To test this, we performed acute or chronic CCl₄ administration to WT and IRF3-, Toll/Interleukin-1R (TIR) domain-containing adapter-inducing interferon-β (TRIF)-, TRIF-related adaptor molecule (TRAM)-, and STING-deficient mice. We report that acute CCl₄ administration to WT mice resulted in early ER stress, activation of IRF3, and type I IFNs, followed by hepatocyte apoptosis and liver injury, accompanied by liver fibrosis upon repeated administration of CCl₄ Deficiency of IRF3 or STING prevented hepatocyte death and fibrosis both in acute or chronic CCl₄ In contrast, mice deficient in type I IFN receptors or in TLR4 signaling adaptors, TRAM or TRIF, upstream of IRF3, were not protected from hepatocyte death and/or fibrosis, suggesting that the pro-apoptotic role of IRF3 is independent of TLR signaling in fibrosis. Hepatocyte death is required for liver fibrosis with causal involvement of STING and IRF3. Thus, our results identify that IRF3, by its association with STING in the presence of ER stress, couples hepatocyte apoptosis with liver fibrosis and indicate that innate immune signaling regulates outcomes of liver fibrosis via modulation of hepatocyte death in the liver.

Paraptosis-like cell death in Wistar rat granulosa cells

Follicular atresia, a common process present in all mammals, involves apoptotic and autophagic cell death. However, the participation of paraptosis, a type of caspase-independent cell death, during follicular atresia is unknown. This study found swollen endoplasmic reticulum in the granulosa cells of adult Wistar rats. Calnexin was used as a marker of the endoplasmic reticulum at the ultrastructural and optical levels. The cells with swelling of the endoplasmic reticulum were negative to the TUNEL assay and active caspase-3 immunodetection, indicating that this swelling is not part of any apoptotic or autophagic process. Additionally, immunodetection of the CHOP protein was used as a marker of endoplasmic reticulum stress, and this confirmed the presence of the paraptosis process. These data suggest that paraptosis-like cell death is associated with the death of granulosa cells during follicular atresia in adult Wistar rats.

Tauroursodeoxycholic Acid Attenuates Renal Tubular Injury in a Mouse Model of Type 2 Diabetes

Renal tubular injury is a critical factor in the pathogenesis of diabetic nephropathy (DN). Endoplasmic reticulum (ER) stress is involved in diabetic nephropathy. Tauroursodeoxycholic acid (TUDCA) is an effective inhibitor of ER stress. Here, we investigated the role of TUDCA in the progression of tubular injury in DN. For eight weeks, being treated with TUDCA at 250 mg/kg intraperitoneal injection (i.p.) twice a day, diabetic db/db mice had significantly reduced blood glucose, albuminuria and attenuated renal histopathology. These changes were associated with a significant decreased expression of ER stress markers. At the same time, diabetic db/db mice had more TUNEL-positive nuclei in the renal tubule, which were attenuated by TUDCA treatment, along with decreases in ER stress-associated apoptotic markers in the kidneys. In summary, the effect of TUDCA on tubular injury, in part, is associated with inhibition of ER stress in the kidneys of diabetic db/db mice. TUDCA shows potential as a therapeutic target for the prevention and treatment of DN.

Endoplasmic reticulum stress-induced apoptosis accompanies enhanced expression of multiple inositol polyphosphate phosphatase 1 (Minpp1): a possible role for Minpp1 in cellular stress response

Inositol polyphosphates represent a group of differentially phosphorylated inositol metabolites, many of which are implicated to regulate diverse cellular processes such as calcium mobilization, vesicular trafficking, differentiation, apoptosis, etc. The metabolic network of these compounds is complex and tightly regulated by various kinases and phosphatases present predominantly in the cytosol. Multiple inositol polyphosphate phosphatase 1 (Minpp1) is the only known endoplasmic reticulum (ER) luminal enzyme that hydrolyzes various inositol polyphosphates in vitro as well as in vivo conditions. However, access of the Minpp1 to cytosolic substrates has not yet been demonstrated clearly and hence its physiological function. In this study, we examined a potential role for Minpp1 in ER stress-induced apoptosis. We generated a custom antibody and characterized its specificity to study the expression of Minpp1 protein in multiple mammalian cells under experimentally induced cellular stress conditions. Our results demonstrate a significant increase in the expression of Minpp1 in response to a variety of cellular stress conditions. The protein expression was corroborated with the expression of its mRNA and enzymatic activity. Further, in an attempt to link the role of Minpp1 to apoptotic stress, we studied the effect of Minpp1 expression on apoptosis following silencing of the Minpp1 gene by its specific siRNA. Our results suggest an attenuation of apoptotic parameters following knockdown of Minpp1. Thus, in addition to its known role in inositol polyphosphate metabolism, we have identified a novel role for Minpp1 as a stress-responsive protein. In summary, our results provide, for the first time, a probable link between ER stress-induced apoptosis and Minpp1 expression.

Sequential changes of endoplasmic reticulum stress and apoptosis in myocardial fibrosis of diabetes mellitus-induced rats

The endoplasmic reticulum (ER) is an organelle in which proteins form their appropriate structures. However, several of these proteins become unfolded or misfolded when exposed to stimuli, including hyperglycemia, oxidative stress, ischemia, disturbance of calcium homeostasis and overexpression of abnormal proteins, which activates ER stress and the unfolded protein response (UPR). To date, investigations have demonstrated that ER stress is important in diabetic myocardial fibrosis by inducing cardiac cell apoptosis. Therefore, in the present study, the polymerase chain reaction, western blotting analysis and tissue staining were performed to identify the changes in UPR signaling proteins and apoptotic proteins in diabetic rats at different time points, and to determine whether the myocardial fibrosis is associated with ER-stress-mediated apoptosis using a diabetes mellitus (DM) rat model. It was found that the upregulation of ER stress markers and apoptotic molecules developed over time. It was also demonstrated that anti-apoptotic markers and proapoptotic markers were activated early following model establishment, and then decreased in months 4 and 5. The changes in myocardial fibrosis were found to accelerate in a time-dependent manner with apoptosis in the DM rats.

Enterovirus 71 induces dsRNA/PKR-dependent cytoplasmic redistribution of GRP78/BiP to promote viral replication

GRP78/BiP is an endoplasmic reticulum (ER) chaperone protein with the important function of maintaining ER homeostasis, and the overexpression of GRP78/BiP alleviates ER stress. Our previous studies showed that infection with enterovirus 71 (EV71), a (+)RNA picornavirus, induced GRP78/BiP upregulation; however, ectopic GRP78/BiP overexpression in ER downregulates virus replication and viral particle formation. The fact that a virus infection increases GRP78/BiP expression, which is unfavorable for virus replication, is counterintuitive. In this study, we found that the GRP78/BiP protein level was elevated in the cytoplasm instead of in the ER in EV71-infected cells. Cells transfected with polyinosinic-polycytidylic acid, a synthetic analog of replicative double-stranded RNA (dsRNA), but not with viral proteins, also exhibited upregulation and elevation of GRP78/BiP in the cytosol. Our results further demonstrate that EV71 infections induce the dsRNA/protein kinase R-dependent cytosolic accumulation of GRP78/BiP. The overexpression of a GRP78/BiP mutant lacking a KDEL retention signal failed to inhibit both dithiothreitol-induced eIF2α phosphorylation and viral replication in the context of viral protein synthesis and viral titers. These data revealed that EV71 infection might cause upregulation and aberrant redistribution of GRP78/BiP to the cytosol, thereby facilitating virus replication.

c-Jun N-terminal Kinase-Dependent Endoplasmic Reticulum Stress Pathway is Critically Involved in Arjunic Acid Induced Apoptosis in Non-Small Cell Lung Cancer Cells

Though arjunic acid, a triterpene isolated from Terminalia arjuna, was known to have antioxidant, antiinflammatory, and cytotoxic effects, its underlying antitumor mechanism still remains unclear so far. Thus, in the present study, the molecular antitumor mechanism of arjunic acid was examined in A549 and H460 non-small cell lung cancer (NSCLC) cells. Arjunic acid exerted cytotoxicity by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT) assay and significantly increased sub-G1 population in A549 and H460 cells by cell cycle analysis. Consistently, arjunic acid cleaved poly (ADP-ribose) polymerase (PARP), activated Bax, and phosphorylation of c-Jun N-terminal kinases (JNK), and also attenuated the expression of pro-caspase-3 and Bcl-2 in A549 and H460 cells. Furthermore, arjunic acid upregulated the expression of endoplasmic reticulum (ER) stress proteins such as IRE1 α, ATF4, p-eIF2α, and C/EBP homologous protein (CHOP) in A549 and H460 cells. Conversely, CHOP depletion attenuated the increase of sub-G1 population by arjunic acid, and also JNK inhibitor SP600125 blocked the cytotoxicity and upregulation of IRE1 α and CHOP induced by arjunic acid in A549 and H460 cells. Overall, our findings suggest that arjunic acid induces apoptosis in NSCLC cells via JNK mediated ER stress pathway as a potent chemotherapeutic agent for NSCLC.

Targeting Mitochondria and Reactive Oxygen Species-Driven Pathogenesis in Diabetic Nephropathy

Diabetic kidney disease is one of the major microvascular complications of both type 1 and type 2 diabetes mellitus. Approximately 30% of patients with diabetes experience renal complications. Current clinical therapies can only mitigate the symptoms and delay the progression to end-stage renal disease, but not prevent or reverse it. Oxidative stress is an important player in the pathogenesis of diabetic nephropathy. The activity of reactive oxygen and nitrogen species (ROS/NS), which are by-products of the diabetic milieu, has been found to correlate with pathological changes observed in the diabetic kidney. However, many clinical studies have failed to establish that antioxidant therapy is renoprotective. The discovery that increased ROS/NS activity is linked to mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, cellular senescence, and cell death calls for a refined approach to antioxidant therapy. It is becoming clear that mitochondria play a key role in the generation of ROS/NS and their consequences on the cellular pathways involved in apoptotic cell death in the diabetic kidney. Oxidative stress has also been associated with necrosis via induction of mitochondrial permeability transition. This review highlights the importance of mitochondria in regulating redox balance, modulating cellular responses to oxidative stress, and influencing cell death pathways in diabetic kidney disease. ROS/NS-mediated cellular dysfunction corresponds with progressive disease in the diabetic kidney, and consequently represents an important clinical target. Based on this consideration, this review also examines current therapeutic interventions to prevent ROS/NS-derived injury in the diabetic kidney. These interventions, mainly aimed at reducing or preventing mitochondrial-generated oxidative stress, improving mitochondrial antioxidant defense, and maintaining mitochondrial integrity, may deliver alternative approaches to halt or prevent diabetic kidney disease.

IRE1 prevents endoplasmic reticulum membrane permeabilization and cell death under pathological conditions

The endoplasmic reticulum (ER) has emerged as a critical regulator of cell survival. IRE1 is a transmembrane protein with kinase and RNase activities that is localized to the ER and that promotes resistance to ER stress. We showed a mechanism by which IRE1 conferred protection against ER stress-mediated cell death. IRE1 signaling prevented ER membrane permeabilization mediated by Bax and Bak and cell death in cells experiencing ER stress. Suppression of IRE1 signaling triggered by its kinase activity led to the accumulation of the BH3 domain-containing protein Bnip3, which in turn triggered the oligomerization of Bax and Bak in the ER membrane and ER membrane permeabilization. Consequently, in response to ER stress, cells deficient in IRE1 were susceptible to leakage of ER contents, which was associated with the accumulation of calcium in mitochondria, oxidative stress in the cytosol, and ultimately cell death. Our results reveal a role for IRE1 in preventing a cell death-initializing step that emanates from the ER and provide a potential target for treating diseases characterized by ER stress, including diabetes and Wolfram syndrome.

β-Arrestin2 encourages inflammation-induced epithelial apoptosis through ER stress/PUMA in colitis

β-Arrestins (β-arrs) are regulators and mediators of G protein-coupled receptor signaling, and accumulating evidence suggests that they are functionally involved in inflammation and autoimmune diseases. However, the effect of β-arrs is unclear in inflammatory bowel disease (IBD), and the role of β-arr2 is unknown in ulcerative colitis (UC) and Crohn's disease (CD). The aim of this study is to investigate whether β-arr2 encourages inflammation-induced epithelial apoptosis through endoplasmic reticulum (ER) stress/p53-upregulated modulator of apoptosis (PUMA) in colitis. In the present study, the results showed that β-arr2 was increased in specimens from patients with UC or CD. Furthermore, a β-arr2 deficiency significantly repressed intestinal inflammation, ameliorated colitis, and alleviated mucosal apoptosis in mice. In addition, the targeted deletion of β-arr2 depressed ER stress, inhibited PUMA, and downregulated PUMA-mediated mitochondrial apoptotic signaling in colitis. β-Arr2, an important modulator of G protein-coupled receptor function, binds eIF2α to activate ER stress signaling. Furthermore, the knockdown of PUMA dramatically prevented β-arr2-induced apoptosis via alleviating ER stress in vitro. The results suggest that β-arr2 encourages inflammation-induced epithelial apoptosis through ER stress/PUMA in colitis and that β-arr2 is a potential therapeutic target for colitis.