Endoplasmic Reticulum Stress of Neutrophils Is Required for Ischemia/Reperfusion-Induced Acute Lung Injury

The role of the C5a-C5aR pathway in iron metabolism and gastric cancer progression

Gastric cancer continues to be a leading global health concern, with current therapeutic approaches requiring significant improvement. While the disruption of iron metabolism in the advancement of gastric cancer has been well-documented, the underlying regulatory mechanisms remain largely unexplored. Additionally, the complement C5a-C5aR pathway has been identified as a crucial factor in gastric cancer development. The impact of the complement system on iron metabolism and its role in gastric cancer progression is an area warranting further investigation. Our research demonstrates that the C5a-C5aR pathway promotes gastric cancer progression by enhancing iron acquisition in tumor cells through two mechanisms. First, it drives macrophage polarization toward the M2 phenotype, which has a strong iron-release capability. Second, it increases the expression of LCN2, a high-affinity iron-binding protein critical for iron export from tumor-associated macrophages, by activating endoplasmic reticulum stress in these cells. Both mechanisms facilitate the transfer of iron from macrophages to cancer cells, thereby promoting tumor cell proliferation. This study aims to elucidate the connection between the complement C5a-C5aR pathway and iron metabolism within the tumor microenvironment. Our data suggest a pivotal role of the C5a-C5aR pathway in tumor iron management, indicating that targeting its regulatory mechanisms may pave the way for future iron-targeted therapeutic approaches in cancer treatment.

Endoplasmic Reticulum Stress in Bronchopulmonary Dysplasia: Contributor or Consequence?

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity. Oxidative stress (OS) and inflammation are the major contributors to BPD. Despite aggressive treatments, BPD prevalence remains unchanged, which underscores the urgent need to explore more potential therapies. The endoplasmic reticulum (ER) plays crucial roles in surfactant and protein synthesis, assisting mitochondrial function, and maintaining metabolic homeostasis. Under OS, disturbed metabolism and protein folding transform the ER structure to refold proteins and help degrade non-essential proteins to resume cell homeostasis. When OS becomes excessive, the endogenous chaperone will leave the three ER stress sensors to allow subsequent changes, including cell death and senescence, impairing the growth potential of organs. The contributing role of ER stress in BPD is confirmed by reproducing the BPD phenotype in rat pups by ER stress inducers. Although chemical chaperones attenuate BPD, ER stress is still associated with cellular senescence. N-acetyl-lysyltyrosylcysteine amide (KYC) is a myeloperoxidase inhibitor that attenuates ER stress and senescence as a systems pharmacology agent. In this review, we describe the role of ER stress in BPD and discuss the therapeutic potentials of chemical chaperones and KYC, highlighting their promising role in future therapeutic interventions.

Exploring immune-related pathogenesis in lung injury: Providing new insights Into ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a significant global burden of morbidity and mortality, with lung injury being the primary cause of death in affected patients. The pathogenesis of lung injury, however, remains a complex issue. In recent years, the role of the immune system in lung injury has attracted extensive attention worldwide. Despite advancements in our understanding of various lung injury subtypes, significant limitations persist in both prevention and treatment. This review investigates the immunopathogenesis of ALI/ARDS, aiming to elucidate the pathological processes of lung injury mediated by dendritic cells (DCs), natural killer (NK) cells, phagocytes, and neutrophils. Furthermore, the article expounds on the critical contributions of gut microbiota, inflammatory pathways, and cytokine storms in the development of ALI/ARDS.

Advances in lung ischemia/reperfusion injury: unraveling the role of innate immunity

BACKGROUND

Lung ischemia/reperfusion injury (LIRI) is a common occurrence in clinical practice and represents a significant complication following pulmonary transplantation and various diseases. At the core of pulmonary ischemia/reperfusion injury lies sterile inflammation, where the innate immune response plays a pivotal role. This review aims to investigate recent advancements in comprehending the role of innate immunity in LIRI.

METHODS

A computer-based online search was performed using the PubMed database and Web of Science database for published articles concerning lung ischemia/reperfusion injury, cell death, damage-associated molecular pattern molecules (DAMPs), innate immune cells, innate immunity, inflammation.

RESULTS

During the process of lung ischemia/reperfusion, cellular injury even death can occur. When cells are injured or undergo cell death, endogenous ligands known as DAMPs are released. These molecules can be recognized and bound by pattern recognition receptors (PRRs), leading to the recruitment and activation of innate immune cells. Subsequently, a cascade of inflammatory responses is triggered, ultimately exacerbating pulmonary injury. These steps are complex and interrelated rather than being in a linear relationship. In recent years, significant progress has been made in understanding the immunological mechanisms of LIRI, involving novel types of cell death, the ability of receptors other than PRRs to recognize DAMPs, and a more detailed mechanism of action of innate immune cells in ischemia/reperfusion injury (IRI), laying the groundwork for the development of novel diagnostic and therapeutic approaches.

CONCLUSIONS

Various immune components of the innate immune system play critical roles in lung injury after ischemia/reperfusion. Preventing cell death and the release of DAMPs, interrupting DAMPs receptor interactions, disrupting intracellular inflammatory signaling pathways, and minimizing immune cell recruitment are essential for lung protection in LIRI.

C5a-C5aR1 induces endoplasmic reticulum stress to accelerate vascular calcification via PERK-eIF2α-ATF4-CREB3L1 pathway

AIMS

Vascular calcification (VC) predicts the morbidity and mortality in cardiovascular diseases. Vascular smooth muscle cells (VSMCs) osteogenic transdifferentiation is the crucial pathological basis for VC. To date, the molecular pathogenesis is still largely unclear. Notably, C5a-C5aR1 contributes to the development of cardiovascular diseases, and its closely related to physiological bone mineralization which is similar to VSMCs osteogenic transdifferentiation. However, the role and underlying mechanisms of C5a-C5aR1 in VC remain unexplored.

METHODS AND RESULTS

A cross-sectional clinical study was utilized to examine the association between C5a and VC. Chronic kidney diseases mice and calcifying VSMCs models were established to investigate the effect of C5a-C5aR1 in VC, evaluated by changes in calcium deposition and osteogenic markers. The cross-sectional study identified that high level of C5a was associated with increased risk of VC. C5a dose-responsively accelerated VSMCs osteogenic transdifferentiation accompanying with increased the expression of C5aR1. Meanwhile, the antagonists of C5aR1, PMX 53, reduced calcium deposition, and osteogenic transdifferentiation both in vivo and in vitro. Mechanistically, C5a-C5aR1 induced endoplasmic reticulum (ER) stress and then activated PERK-eIF2α-ATF4 pathway to accelerated VSMCs osteogenic transdifferentiation. In addition, cAMP-response element-binding protein 3-like 1 (CREB3L1) was a key downstream mediator of PERK-eIF2α-ATF4 pathway which accelerated VSMCs osteogenic transdifferentiation by promoting the expression of COL1α1.

CONCLUSIONS

High level of C5a was associated with increased risk of VC, and it accelerated VC by activating the receptor C5aR1. PERK-eIF2α-ATF4-CREB3L1 pathway of ER stress was activated by C5a-C5aR1, hence promoting VSMCs osteogenic transdifferentiation. Targeting C5 or C5aR1 may be an appealing therapeutic target for VC.

Potential Crosstalk between the PACAP/VIP Neuropeptide System and Endoplasmic Reticulum Stress-Relevance to Multiple Sclerosis Pathophysiology

Multiple sclerosis (MS) is an immune-mediated disorder characterized by focal demyelination and chronic inflammation of the central nervous system (CNS). Although the exact etiology is unclear, mounting evidence indicates that endoplasmic reticulum (ER) stress represents a key event in disease pathogenesis. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related neuropeptides that are abundant in the CNS and are known to exert neuroprotective and immune modulatory roles. Activation of this endogenous neuropeptide system may interfere with ER stress processes to promote glial cell survival and myelin self-repair. However, the potential crosstalk between the PACAP/VIP system and ER stress remains elusive. In this review, we aim to discuss how these peptides ameliorate ER stress in the CNS, with a focus on MS pathology. Our goal is to emphasize the importance of this potential interaction to aid in the identification of novel therapeutic targets for the treatment of MS and other demyelinating disorders.

Neutrophil-Mediated Progression of Mild Cognitive Impairment to Dementia

Cognitive impairment is a serious condition that begins with amnesia and progresses to cognitive decline, behavioral dysfunction, and neuropsychiatric impairment. In the final stage, dysphagia and incontinence occur. There are numerous studies and developed drugs for cognitive dysfunction in neurodegenerative diseases, such as Alzheimer's disease (AD); however, their clinical effectiveness remains equivocal. To date, attempts have been made to overcome cognitive dysfunction and understand and delay the aging processes that lead to degenerative and chronic diseases. Cognitive dysfunction is involved in aging and the disruption of inflammation and innate immunity. Recent reports have indicated that the innate immune system is prevalent in patients with AD, and that peripheral neutrophil markers can predict a decline in executive function in patients with mild cognitive impairment (MCI). Furthermore, altered levels of pro-inflammatory interleukins have been reported in MCI, which have been suggested to play a role in the peripheral immune system during the process from early MCI to dementia. Neutrophils are the first responders of the innate immune system. Neutrophils eliminate harmful cellular debris via phagocytosis, secrete inflammatory factors to activate host defense systems, stimulate cytokine production, kill pathogens, and regulate extracellular proteases and inhibitors. This review investigated and summarized the regulation of neutrophil function during cognitive impairment caused by various degenerative diseases. In addition, this work elucidates the cellular mechanism of neutrophils in cognitive impairment and what is currently known about the effects of activated neutrophils on cognitive decline.

Qishen Yiqi Dripping Pills for Cardiovascular Diseases: Effects and Mechanisms

Qishen Yiqi Dripping Pills (QSYQ) is a compound of Chinese medicine, which has been used to treat coronary heart disease and cardiac dysfunction. Its natural components include astragaloside IV, flavonoids, danshensu, protocatechualdehyde, salvianolic acid B, salvianolic acid A, ginsenosides Rg1, ginsenosides Rb1, and essential oils, etc. It exerts effects of nourishing qi and promoting blood circulation to relieve pain. In this review, the bioactive components of QSYQ and its effects for treating cardiovascular diseases and possible mechanism were summarized, providing references for further study and clinical application of QSYQ.

Tranilast reduces cardiomyocyte injury induced by ischemia‑reperfusion via Nrf2/HO‑1/NF‑κB signaling

Tranilast, a synthetic derivative of a tryptophan metabolite, can be used to treat heart diseases. However, the specific mechanism underlying the effect of tranilast on ischemia-reperfusion (I/R) injury-induced cardiomyocyte apoptosis remains unclear. Therefore, the present study aimed to determine if tranilast could attenuate I/R-induced cardiomyocyte injury. A hypoxia/reoxygenation (H/R) model of H9c2 cardiomyocytes was established to simulate I/R-induced cardiomyocyte injury. The viability, apoptosis, inflammation and oxidative stress in H/R-induced H9c2 cells following treatment with tranilast were evaluated by Cell Counting Kit-8 and TUNEL assay. Commercially available kits were used to detect the levels of inflammatory markers and oxidative stress indicators. In addition, the expression levels of the apoptosis- and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1)/NF-κB signalling pathway-associated proteins were detected by western blotting. The levels of reactive oxygen species were determined using 2',7'-dichlorofluorescin diacetate assay kit. The viability of H9c2 cells was decreased following induction with H/R. However, treatment with tranilast increased viability while decreasing apoptosis, oxidative stress and inflammatory response in H/R-induced H9c2 cells by activating Nrf2/HO-1/NF-κB signalling. Furthermore, treatment with ML-385, an Nrf2 inhibitor, reversed the effects of tranilast on H/R-induced H9c2 cells. In conclusion, the results of the present study suggested that tranilast could attenuate I/R-induced cardiomyocyte injury via the Nrf2/HO-1/NF-κB signalling pathway.

New insight of complement system in the process of vascular calcification

The complement system defences against pathogenic microbes and modulates immune homeostasis by interacting with the innate and adaptive immune systems. Dysregulation, impairment or inadvertent activation of complement system contributes to the pathogenesis of some autoimmune diseases and cardiovascular diseases (CVD). Vascular calcification is the pivotal pathological basis of CVD, and contributes to the high morbidity and mortality of CVD. Increasing evidences indicate that the complement system plays a key role in chronic kidney diseases, atherosclerosis, diabetes mellitus and aging-related diseases, which are closely related with vascular calcification. However, the effect of complement system on vascular calcification is still unclear. In this review, we summarize current evidences about the activation of complement system in vascular calcification. We also describe the complex network of complement system and vascular smooth muscle cells osteogenic transdifferentiation, systemic inflammation, endoplasmic reticulum stress, extracellular matrix remodelling, oxidative stress, apoptosis in vascular calcification. Hence, providing a better understanding of the potential relationship between complement system and vascular calcification, so as to provide a direction for slowing the progression of this burgeoning health concern.

Penehyclidine hydrochloride protects against lipopolysaccharide-induced acute lung injury by promoting the PI3K/Akt pathway

INTRODUCTION

Acute lung injury (ALI) attracted attention among physicians because of its high mortality. We aimed to determine whether the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt) pathway is involved in the protective effects of penehyclidine hydrochloride (PHC) against lipopolysaccharide (LPS)-induced ALI.

METHODS

H&E staining was used to observed pathological changes in the lung tissues. ELISA was used to evaluate the concentration of inflammatory mediators in the bronchoalveolar lavage fluid (BALF). White-light microscopy was performed to observe the TUNEL-positive nuclei. The viability of NR8383 alveolar macrophages was determined by using CCK-8. The levels of MPO, MDA, SOD, and GSH-Px were analyzed using ELISA kits. Western blotting was used to evaluate the ERS-associated protein levels and the phosphorylation of PI3K and Akt.

RESULTS

PHC administration defended against LPS-induced histopathological deterioration and increased pulmonary edema and lung injury scores, while all of these beneficial effects were inhibited by LY. In addition, PHC administration mitigated oxidative stress as indicated by decreases in lung myeloperoxidase (MPO) and malondialdehyde (MDA) concentrations, and increases in glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) concentrations. It also alleviated LPS-induced inflammation. PHC administration attenuated apoptosis-associated protein levels, improved cell viability, and decreased the number of TdT-mediated dUTP Nick-End Labeling (TUNEL)-positive cells. Furthermore, PHC inhibited ERS-associated protein levels. Meanwhile, the protection of PHC against inflammation, oxidative stress, apoptosis, and ERS was inhibited by LY. Moreover, PHC administration increased PI3K and Akt phosphorylation, indicating that the upregulation of the PI3K/Akt pathway, while this pathway was inhibited by LY.

CONCLUSION

PHC significantly activates the PI3K/Akt pathway to ameliorate the extent of damage to pulmonary tissue, inflammation, oxidative stress, apoptosis, and ERS in LPS-induced ALI.

Primary Graft Dysfunction: The Role of Aging in Lung Ischemia-Reperfusion Injury

Transplant centers around the world have been using extended criteria donors to remedy the ongoing demand for lung transplantation. With a rapidly aging population, older donors are increasingly considered. Donor age, at the same time has been linked to higher rates of lung ischemia reperfusion injury (IRI). This process of acute, sterile inflammation occurring upon reperfusion is a key driver of primary graft dysfunction (PGD) leading to inferior short- and long-term survival. Understanding and improving the condition of older lungs is thus critical to optimize outcomes. Notably, ex vivo lung perfusion (EVLP) seems to have the potential of reconditioning ischemic lungs through ex-vivo perfusing and ventilation. Here, we aim to delineate mechanisms driving lung IRI and review both experimental and clinical data on the effects of aging in augmenting the consequences of IRI and PGD in lung transplantation.

Selective inhibition of JNK located on mitochondria protects against mitochondrial dysfunction and cell death caused by endoplasmic reticulum stress in mice with LPS‑induced ALI/ARDS

Few pharmacological interventions are able to improve the mortality rate of acute lung injury and acute respiratory distress syndrome (ALI/ARDS). The aim of this research was to elucidate whether endoplasmic reticulum (ER) stress and c-Jun-N-terminal kinase (JNK)-mitochondria pathways serve important roles in ALI/ARDS and to determine whether the key component Sab is a potential treatment target. The current study investigated the activation of ER stress and the JNK pathway, the content of JNK located on the mitochondria during ER stress and lipopolysaccharide (LPS)-induced ALI/ARDS by western blot analysis. The treatment effects of Tat-Sab_KIM1, a selective inhibitor of JNK located on mitochondria were explored by multiple methods including histopathological evaluation, lung cell apoptosis tested by TUNEL assay, mitochondrial membrane permeability and survival analysis. The results verified that ER stress was enhanced during LPS-induced ALI/ARDS and could induce activation of the JNK pathway and JNK-mitochondrial localization as well as mitochondrial dysfunction and cell death. Tat-Sab_KIM1 alleviated LPS injection-induced lung injury and improved mouse survival rates by specifically inhibiting JNK localization to mitochondria and mito-JNK signal activation without affecting cytosolic/nuclear JNK activation. The protective effect of Tat-Sab_KIM1 against ALI/ARDS was partly caused by inhibition of the excessive activation of mitochondria-mediated apoptosis and autophagy. These results showed the important role of Sab as a treatment target of ALI/ARDS and the potential treatment effect of Tat-Sab_KIM1. In conclusion, abnormal activation of the JNK-mitochondrial pathway could significantly disrupt the normal physiological function of lung cells, resulting in the occurrence of ALI/ARDS and selective inhibit of JNK located on mitochondria by Tat-Sab_KIM1 had a protective effect against the mitochondrial dysfunction and cell death caused by endoplasmic reticulum stress in mice with LPS-induced ALI/ARDS.

Quercetin attenuates sepsis-induced acute lung injury via suppressing oxidative stress-mediated ER stress through activation of SIRT1/AMPK pathways

Endoplasmic reticulum (ER) stress and mitochondrial dysfunction play a pivotal role in the pathological process of sepsis-induced acute lung injury (ALI). Quercetin has been proved to exert anti-inflammation in ALI. This study aimed to explore the protection mechanism of quercetin against sepsis-induced ALI via suppressing ER stress and mitochondrial dysfunction. Cecal ligation and puncture (CLP) mouse model was established to mimic sepsis, and LPS was used to stimulate murine lung epithelial (MLE-12) cells. We observed that quercetin ameliorated pulmonary pathological lesion and oxidative damage in sepsis-induced mice. In LPS-stimulated MLE-12 cells, quercetin could inhibit the level of ER stress as evidenced by decreased mRNA expression of PDI, CHOP, GRP78, ATF6, PERK, IRE1α and improve mitochondrial function, as presented by increased MMP, SOD level and reduced production of ROS, MDA. Meanwhile, transcriptome analysis revealed that quercetin upregulated SIRT1/AMPK mRNA expression. Furthermore, we used siRNA to knockdown SIRT1 in MLE-12 cells, and we found that SIRT1 knockdown could abrogate the quercetin-elicited antioxidation in vitro. Therefore, quercetin could protect against sepsis-induced ALI by suppressing oxidative stress-mediated ER stress and mitochondrial dysfunction via induction of the SIRT1/AMPK pathways.

Endoplasmic reticulum stress in airway hyperresponsiveness

Airway hyperresponsiveness(AHR) is a major clinical phenomenon in lung diseases (asthma, COPD and pulmonary fibrosis) and not only a high-risk factor for perioperative airway spasm leading to hypoxaemia, haemodynamic instability and even "silent lung", but also a potential risk for increased mortality from underlying diseases (e.g. asthma, COPD). Airway reactivity is closely linked to airway inflammation, remodelling and increased mucus secretion, and endoplasmic reticulum stress is an important mechanism for the development of these pathologies. This review, therefore, focuses on the effects of endoplasmic reticulum stress on the immune cells involved in airway hyperreactivity (epithelial cells, dendritic cells, eosinophils and neutrophils) in inflammation and mucus & sputum secretion; and on the differentiation and remodelling of airway smooth muscle cells and epithelial cells. The aim is to clarify the mechanisms associated with endoplasmic reticulum stress in airway hyperresponsiveness and to find new ideas and methods for the prevention of airway hyperresponsiveness in the perioperative period.

Rutaecarpine ameliorates lipopolysaccharide‑induced BEAS‑2B cell injury through inhibition of endoplasmic reticulum stress via activation of the AMPK/SIRT1 signaling pathway

Rutaecarpine (RUT) is an alkaloid isolated from Tetradium ruticarpum, which has been reported to protect against several inflammatory diseases. However, to the best of our knowledge, the role of RUT in acute lung injury (ALI) and the specific molecular mechanism remain unknown. In the present study, an in vitro model of ALI was established in BEAS-2B cells by lipopolysaccharide (LPS) administration. Cell viability following RUT treatment with or without LPS stimulation was evaluated using a Cell Counting Kit-8 assay. The inflammatory response and oxidative stress were detected using ELISA kits and commercially available kits, respectively. TUNEL assay and western blotting were performed to assess cell apoptosis. The expression levels of endoplasmic reticulum (ER) stress-related proteins and AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) signaling pathway-related proteins were measured by western blotting. The results revealed that RUT markedly improved cell viability after LPS treatment in a dose-dependent manner. In addition, RUT inhibited the LPS-induced inflammatory response and oxidative stress in BEAS-2B cells, and suppressed the LPS-induced apoptosis of BEAS-2B cells. Mechanistically, RUT alleviated ER stress by inhibiting the production of CHOP, glucose-regulated protein-78, caspase-12 and activating transcription factor 6. Additionally, western blotting demonstrated that RUT activated the phosphorylation of AMPK and SIRT1, which indicated the involvement of the AMPK/SIRT1 signaling pathway in the protective effect of RUT against LPS-induced lung injury. In conclusion, these results demonstrated that RUT mitigated LPS-induced lung cell injury by inhibiting ER stress via the activation of the AMPK/SIRT1 signaling pathway.

Role of Neutrophils on the Ocular Surface

The ocular surface is a gateway that contacts the outside and receives stimulation from the outside. The corneal innate immune system is composed of many types of cells, including epithelial cells, fibroblasts, natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils, mucin, and lysozyme. Neutrophil infiltration and degranulation occur on the ocular surface. Degranulation, neutrophil extracellular traps formation, called NETosis, and autophagy in neutrophils are involved in the pathogenesis of ocular surface diseases. It is necessary to understand the role of neutrophils on the ocular surface. Furthermore, there is a need for research on therapeutic agents targeting neutrophils and neutrophil extracellular trap formation for ocular surface diseases.

The neutrotime transcriptional signature defines a single continuum of neutrophils across biological compartments

Neutrophils are implicated in multiple homeostatic and pathological processes, but whether functional diversity requires discrete neutrophil subsets is not known. Here, we apply single-cell RNA sequencing to neutrophils from normal and inflamed mouse tissues. Whereas conventional clustering yields multiple alternative organizational structures, diffusion mapping plus RNA velocity discloses a single developmental spectrum, ordered chronologically. Termed here neutrotime, this spectrum extends from immature pre-neutrophils, largely in bone marrow, to mature neutrophils predominantly in blood and spleen. The sharpest increments in neutrotime occur during the transitions from pre-neutrophils to immature neutrophils and from mature marrow neutrophils to those in blood. Human neutrophils exhibit a similar transcriptomic pattern. Neutrophils migrating into inflamed mouse lung, peritoneum and joint maintain the core mature neutrotime signature together with new transcriptional activity that varies with site and stimulus. Together, these data identify a single developmental spectrum as the dominant organizational theme of neutrophil heterogeneity.

Gut-lymph-lung pathway mediates sepsis-induced acute lung injury

This review attempts to unveil the possible mechanisms underlying how gut lymph affects lung and further gives rise to acute respiratory distress syndrome, as well as potential interventional targets under the condition of ischemia-reperfusion injury. We searched electronic databases including PubMed, MEDLINE, Cochrane Central Register of Controlled Trials, Google Scholar, Web of Science, and Embase to identify relevant literatures published up to December 2019. We enrolled the literatures including the Mesh Terms of “gut lymph or intestinal lymph and acute lung injury or acute respiratory distress syndrome.” Gut is considered to be the origin of systemic inflammation and the engine of multiple organ distress syndrome in the field of critical care medicine, whereas gut lymph plays a pivotal role in initiation of ischemia-reperfusion injury-induced acute respiratory distress syndrome. In fact, in the having been established pathologic model of sepsis leading to multiple organ dysfunction named by Gut Lymph theory, a variety of literatures showed the position and role of changes in gut lymph components in the initiation of systemic inflammatory response, which allows us to screen out potential intervention targets to pave the way for future clinic and basic research.

Endoplasmic reticulum stress sensor IRE1α propels neutrophil hyperactivity in lupus

Neutrophils amplify inflammation in lupus through the release of neutrophil extracellular traps (NETs). The endoplasmic reticulum stress sensor inositol-requiring enzyme 1 α (IRE1α) has been implicated as a perpetuator of inflammation in various chronic diseases; however, IRE1α has been little studied in relation to neutrophil function or lupus pathogenesis. Here, we found that neutrophils activated by lupus-derived immune complexes demonstrated markedly increased IRE1α ribonuclease activity. Importantly, in neutrophils isolated from patients with lupus, we also detected heightened IRE1α activity that was correlated with global disease activity. Immune complex-stimulated neutrophils produced both mitochondrial ROS (mitoROS) and the activated form of caspase-2 in an IRE1α-dependent fashion, whereas inhibition of IRE1α mitigated immune complex-mediated NETosis (in both human neutrophils and a mouse model of lupus). Administration of an IRE1α inhibitor to lupus-prone MRL/lpr mice over 8 weeks reduced mitoROS levels in peripheral blood neutrophils, while also restraining plasma cell expansion and autoantibody formation. In summary, these data identify a role for IRE1α in the hyperactivity of lupus neutrophils and show that this pathway is upstream of mitochondrial dysfunction, mitoROS formation, and NETosis. We believe that inhibition of the IRE1α pathway is a novel strategy for neutralizing NETosis in lupus, and potentially other inflammatory conditions.

Regulatory effects of ghrelin on endoplasmic reticulum stress, oxidative stress, and autophagy: Therapeutic potential

Ghrelin is a regulatory peptide that is the endogenous ligand of the growth hormone secretagogue 1a (GHS-R1a) which belongs to the G protein-coupled receptor family. Ghrelin and GHS-R1a are widely expressed in the central and peripheral tissues and play therapeutic potential roles in the cytoprotection of many internal organs. Endoplasmic reticulum stress (ERS), oxidative stress, and autophagy dysfunction, which are involved in various diseases. In recent years, accumulating evidence has suggested that ghrelin exerts protective effects by regulating ERS, oxidative stress, and autophagy in diverse diseases. This review article summarizes information about the roles of the ghrelin system on ERS, oxidative stress, and autophagy in multiple diseases. It is suggested that ghrelin positively affects the treatment of diseases and may be considered as a therapeutic drug in many illnesses.

ER Stress Responses: An Emerging Modulator for Innate Immunity

The endoplasmic reticulum (ER) is a critical organelle, storing the majority of calcium and governing protein translation. Thus, it is crucial to keep the homeostasis in all ER components and machineries. The ER stress sensor pathways, including IRE1/sXBP1, PERK/EIf2 and ATF6, orchestrate the major regulatory circuits to ensure ER homeostasis. The embryonic or postnatal lethality that occurs upon genetic depletion of these sensors reveals the essential role of the ER stress pathway in cell biology. In contrast, the impairment or excessive activation of ER stress has been reported to cause or aggravate several diseases such as atherosclerosis, diabetes, NAFDL/NASH, obesity and cancer. Being part of innate immunity, myeloid cells are the first immune cells entering the inflammation site. Upon entry into a metabolically stressed disease environment, activation of ER stress occurs within the myeloid compartment, leading to the modulation of their phenotype and functions. In this review, we discuss causes and consequences of ER stress activation in the myeloid compartment with a special focus on the crosstalk between ER, innate signaling and metabolic environments.

Autophagy-mediated regulation of neutrophils and clinical applications

Autophagy, an adaptive catabolic process, plays a cytoprotective role in enabling cellular homeostasis in the innate and adaptive immune systems. Neutrophils, the most abundant immune cells in circulation, are professional killers that orchestrate a series of events during acute inflammation. The recent literature indicates that autophagy has important roles in regulating neutrophil functions, including differentiation, degranulation, metabolism and neutrophil extracellular trap formation, that dictate neutrophil fate. It is also becoming increasingly clear that autophagy regulation is critical for neutrophils to exert their immunological activity. However, evidence regarding the systematic communication between neutrophils and autophagy is insufficient. Here, we provide an updated overview of the function of autophagy as a regulator of neutrophils and discuss its clinical relevance to provide novel insight into potentially relevant treatment strategies.

Suppression of microRNA‑27a protects against liver ischemia/reperfusion injury by targeting PPARγ and inhibiting endoplasmic reticulum stress

Liver ischemia‑reperfusion (I/R) injury is an important clinical issue related to liver transplantation. Recent studies suggest that microRNAs are implicated in various biological and pathological processes, including liver I/R injury. This study aimed to investigate the role and potential mechanism of miR‑27a during liver I/R injury. A liver I/R model was induced via 60 min of ischemia and reperfusion for 6 h in rats. Cells were transfected with miR‑27a mimics or the miR‑27a inhibitor to examine the effect of miR‑27a on liver I/R. Apoptotic cells were detected by flow cytometry and TUNEL staining. The expression of miR‑27a was measured by real‑time PCR. The expression of peroxisome proliferator‑activated receptor γ (PPARγ); gastrin‑releasing peptide 78 (GRP78) and C/EBP homologous protein (CHOP) were detected by western blot analysis. The results showed that miR‑27a was significantly upregulated during I/R injury in vivo and in vitro. In addition, miR‑27a inhibitors attenuated hypoxia/reoxygenation (H/R)‑induced oxidative stress, endoplasmic reticulum stress (ERS) and apoptosis in AML12 cells. By contrast, miR‑27a mimics promoted hypoxia/reoxygenation‑induced ERS, and apoptosis. Furthermore, PPARγ was identified as a target gene of miR‑27a using bioinformatic analysis and a dual‑luciferase reporter assay. Knockdown of PPARγ significantly abrogated the inhibitory effect of miR‑27a inhibitors on the ERS pathway. Moreover, the miR‑27a antagomir attenuated liver I/R injury in rats, a finding manifested by reduced ALT/AST, hepatocyte apoptosis, oxidative stress and inhibition of the ERS pathway. Taken together, these findings demonstrate that suppression of miR‑27a protects against liver I/R injury by targeting PPARγ and by inhibiting the ERS pathway.

Genipin attenuates mitochondrial-dependent apoptosis, endoplasmic reticulum stress, and inflammation via the PI3K/AKT pathway in acute lung injury

The protective effects of genipin against lipopolysaccharide (LPS)-induced acute lung injury (ALI) have been reported; however, the mechanism is unclear. Genipin performs its pharmacological effects via activation of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In the present study, we aimed to determine whether the PI3K/AKT pathway is involved in the protective effects of genipin against mitochondrial-dependent apoptosis, endoplasmic reticulum stress (ERS), and inflammation in ALI. We constructed in vivo and in vitro models of LPS-induced ALI. PI3K/AKT signaling was inhibited using LY294002. Pretreatment with genipin increased AKT phosphorylation, indicating that PI3K/AKT signaling was upregulated. Genipin pretreatment prevented LPS-induced histopathological deterioration, increased pulmonary edema, and decreased oxygenation index, all of which were inhibited using LY294002. In addition, genipin pretreatment attenuated LPS-mediated mitochondrial apoptosis, as indicated by improved mitochondrial dysfunction, downregulation of BAX (BCL2 associated X, apoptosis regulator), upregulation of BCL2 (BCL2 apoptosis regulator), inhibited the release of cytochrome c, activation of caspase-3, and cell apoptosis. Genipin pretreatment inhibited the LPS-induced upregulation of AF4/FMR2 family member 4 (CHOP), glucose-regulated protein, 78 kDa (GRP78), and X-box binding protein 1 (XBP1) levels, indicating ERS suppression. Moreover, genipin pretreatment alleviated LPS-induced inflammation, indicating by blockade of nuclear factor kappa b (NF-κB) signaling activation and reduced tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 levels in the lung and bronchoalveolar lavage fluid. LY294002 could inhibit these genipin-induced protective effects against apoptosis, ERS, and inflammation. Thus, genipin significantly activates PI3K/AKT signaling to ameliorate mitochondria-dependent apoptosis, ERS, and inflammation in LPS-induced ALI.

Conjugated bile acids attenuate allergen-induced airway inflammation and hyperresponsiveness by inhibiting UPR transducers

Conjugated bile acids (CBAs), such as tauroursodeoxycholic acid (TUDCA), are known to resolve the inflammatory and unfolded protein response (UPR) in inflammatory diseases, such as asthma. Whether CBAs exert their beneficial effects on allergic airway responses via 1 arm or several arms of the UPR, or alternatively through the signaling pathways for conserved bile acid receptor, remains largely unknown. We used a house dust mite-induced (HDM-induced) murine model of asthma to evaluate and compare the effects of 5 CBAs and 1 unconjugated bile acid in attenuating allergen-induced UPR and airway responses. Expression of UPR-associated transcripts was assessed in airway brushings from human patients with asthma and healthy subjects. Here we show that CBAs, such as alanyl β-muricholic acid (AβM) and TUDCA, significantly decreased inflammatory, immune, and cytokine responses; mucus metaplasia; and airway hyperresponsiveness, as compared with other CBAs in a model of allergic airway disease. CBAs predominantly bind to activating transcription factor 6α (ATF6α) compared with the other canonical transducers of the UPR, subsequently decreasing allergen-induced UPR activation and resolving allergic airway disease, without significant activation of the bile acid receptors. TUDCA and AβM also attenuated other HDM-induced ER stress markers in the lungs of allergic mice. Quantitative mRNA analysis of airway epithelial brushings from human subjects demonstrated that several ATF6α-related transcripts were significantly upregulated in patients with asthma compared with healthy subjects. Collectively, these results demonstrate that CBA-based therapy potently inhibits the allergen-induced UPR and allergic airway disease in mice via preferential binding of the canonical transducer of the UPR, ATF6α. These results potentially suggest a novel avenue to treat allergic asthma using select CBAs.

Inhibition of the IRE-1α/XBP-1 pathway prevents chronic GVHD and preserves the GVL effect in mice

Hematopoietic stem cell transplantation (HCT) is a curative procedure for hematological malignancies, but chronic graft-versus-host disease (cGVHD) remains a major complication after allogeneic HCT. Because donor B cells are essential for cGVHD development and B cells are sensitive to endoplasmic reticulum (ER) stress, we hypothesized that the IRE-1α/XBP-1 pathway is required for B-cell activation and function and for the development of cGVHD. To test this hypothesis, we used conditional knock-out mice deficient of XBP-1 specifically in B cells. Recipients transplanted with donor grafts containing XBP-1-deficient B cells displayed reduced cGVHD compared with controls. Reduction of cGVHD correlated with impaired B-cell functions, including reduced production of anti-double-stranded DNA immunoglobulin G antibodies, CD86, Fas, and GL7 surface expression, and impaired T-cell responses, including reduced interferon-γ production and follicular helper T cells. In a bronchiolitis obliterans cGVHD model, recipients of transplants containing XBP-1-deficient B cells demonstrated improved pulmonary function correlated with reduced donor splenic follicular helper T cells and increased B cells compared with those of wild-type control donor grafts. We then tested if XBP-1 blockade via an IRE-1α inhibitor, B-I09, would attenuate cGVHD and preserve the graft-versus-leukemia (GVL) effect. In a cutaneous cGVHD model, we found that prophylactic administration of B-I09 reduced clinical features of cGVHD, which correlated with reductions in donor T-cell and dendritic cell skin infiltrates. Inhibition of the IRE-1α/XBP-1 pathway also preserved the GVL effect against chronic myelogenous leukemia mediated by allogeneic splenocytes. Collectively, the ER stress response mediated by the IRE-1α/XBP-1 axis is required for cGVHD development but dispensable for GVL activity.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Protein Quality Control in the Endoplasmic Reticulum and Cancer

The endoplasmic reticulum (ER) is an essential compartment of the biosynthesis, folding, assembly, and trafficking of secretory and transmembrane proteins, and consequently, eukaryotic cells possess specialized machineries to ensure that the ER enables the proteins to acquire adequate folding and maturation for maintaining protein homeostasis, a process which is termed proteostasis. However, a large variety of physiological and pathological perturbations lead to the accumulation of misfolded proteins in the ER, which is referred to as ER stress. To resolve ER stress and restore proteostasis, cells have evolutionary conserved protein quality-control machineries of the ER, consisting of the unfolded protein response (UPR) of the ER, ER-associated degradation (ERAD), and autophagy. Furthermore, protein quality-control machineries of the ER play pivotal roles in the control of differentiation, progression of cell cycle, inflammation, immunity, and aging. Therefore, severe and non-resolvable ER stress is closely associated with tumor development, aggressiveness, and response to therapies for cancer. In this review, we highlight current knowledge in the molecular understanding and physiological relevance of protein quality control of the ER and discuss new insights into how protein quality control of the ER is implicated in the pathogenesis of cancer, which could contribute to therapeutic intervention in cancer.

Involvement of miR-455 in the protective effect of H2S against chemical hypoxia-induced injury in BEAS-2B cells

The protective effect of hydrogen sulfide (H₂S) against hypoxia-induced injury via anti-apoptosis is well established, but the underlying mechanism remains unclear. The present study aimed to investigate whether miR-455 participated in the H₂S protection of lung epithelial cells against CoCl₂-induced apoptosis by regulating endoplasmic reticulum stress (ERS)-related genes. Human lung epithelial cells BEAS-2B were subjected to hypoxia injury with or without H₂S preconditioning. It was found that hypoxia injury increased apoptosis of BEAS-2B cells, down-regulated the expression of miR-455, and upregulated the expression of calreticulin (Calr). H₂S preconditioning attenuated lung epithelial cells apoptosis, enhanced cell viability, up-regulated the expression of miR-455, as well as down-regulated the expression of Calr following hypoxia injury. In addition, Calr, GRP78, C/EBP homologous protein (CHOP) and Caspase-12 protein was down-regulated by the miR-455 mimic and up-regulated by the miR-455 inhibitor. These results implicate miR-455 regulated H₂S protection of lung epithelial cells against hypoxia-induced apoptosis by stimulating Calr.

IRE1α Implications in Endoplasmic Reticulum Stress-Mediated Development and Pathogenesis of Autoimmune Diseases

Inositol-requiring transmembrane kinase/endoribonuclease 1α (IRE1α) is the most prominent and evolutionarily conserved endoplasmic reticulum (ER) membrane protein. This transduces the signal of misfolded protein accumulation in the ER, named as ER stress, to the nucleus as “unfolded protein response (UPR).” The ER stress-mediated IRE1α signaling pathway arbitrates the yin and yang of cell life. IRE1α has been implicated in several physiological as well as pathological conditions, including immune disorders. Autoimmune diseases are caused by abnormal immune responses that develop due to genetic mutations and several environmental factors, including infections and chemicals. These factors dysregulate the cell immune reactions, such as cytokine secretion, antigen presentation, and autoantigen generation. However, the mechanisms involved, in which these factors induce the onset of autoimmune diseases, are remaining unknown. Considering that these environmental factors also induce the UPR, which is expected to have significant role in secretory cells and immune cells. The role of the major UPR molecule, IRE1α, in causing immune responses is well identified, but its role in inducing autoimmunity and the pathogenesis of autoimmune diseases has not been clearly elucidated. Hence, a better understanding of the role of IRE1α and its regulatory mechanisms in causing autoimmune diseases could help to identify and develop the appropriate therapeutic strategies. In this review, we mainly center the discussion on the molecular mechanisms of IRE1α in the pathophysiology of autoimmune diseases.

Use of cilomilast-loaded phosphatiosomes to suppress neutrophilic inflammation for attenuating acute lung injury: the effect of nanovesicular surface charge

Background

Cilomilast is a phosphodiesterase 4 (PDE4) inhibitor for treating inflammatory lung diseases. This agent has a narrow therapeutic index with significant adverse effects on the nervous system. This study was conducted to entrap cilomilast into PEGylated phosphatidylcholine-rich niosomes (phosphatiosomes) to improve pulmonary delivery via the strong affinity to pulmonary surfactant film. Neutrophils were used as a cell model to test the anti-inflammatory activity of phosphatiosomes. In an in vivo approach, mice were given lipopolysaccharide to produce acute lung injury. The surface charge in phosphatiosomes that influenced the anti-inflammatory potency is discussed in this study.

Results

The average diameter of the phosphatiosomes was about 100 nm. The zeta potential of anionic and cationic nanovesicles was − 35 and 32 mV, respectively. Cilomilast in both its free and nanocapsulated forms inhibited superoxide anion production but not elastase release in activated neutrophils. Cationic phosphatiosomes mitigated calcium mobilization far more effectively than the free drug. In vivo biodistribution evaluated by organ imaging demonstrated a 2-fold ameliorated lung uptake after dye encapsulation into the phosphatiosomes. The lung/brain distribution ratio increased from 3 to 11 after nanocarrier loading. The intravenous nanocarriers deactivated the neutrophils in ALI, resulting in the elimination of hemorrhage and alveolar wall damage. Only cationic phosphatiosomes could significantly suppress IL-1β and TNF-α in the inflamed lung tissue.

Conclusions

These results suggest that phosphatiosomes should further be investigated as a potential nanocarrier for the treatment of pulmonary inflammation.

Unfolded Protein Response of the Endoplasmic Reticulum in Tumor Progression and Immunogenicity

The endoplasmic reticulum (ER) is a pivotal regulator of folding, quality control, trafficking, and targeting of secreted and transmembrane proteins, and accordingly, eukaryotic cells have evolved specialized machinery to ensure that the ER enables these proteins to acquire adequate folding and maturation in the presence of intrinsic and extrinsic insults. This adaptive capacity of the ER to intrinsic and extrinsic perturbations is important for maintaining protein homeostasis, which is termed proteostasis. Failure in adaptation to these perturbations leads to accumulation of misfolded or unassembled proteins in the ER, which is termed ER stress, resulting in the activation of unfolded protein response (UPR) of the ER and the execution of ER-associated degradation (ERAD) to restore homeostasis. Furthermore, both of the two axes play key roles in the control of tumor progression, inflammation, immunity, and aging. Therefore, understanding UPR of the ER and subsequent ERAD will provide new insights into the pathogenesis of many human diseases and contribute to therapeutic intervention in these diseases.

The regulation of pre-metastatic niche formation by neutrophils

Metastasis is a multistep process requiring tumor cell detachment from the primary tumor and migration to target organs through the lymphatic or blood circulatory systems. Specific organs are predisposed to metastases in certain cancers and the formation of supportive metastatic microenvironment determines tumor cell homing. Such an environment is provided by a pre-metastatic niche that is formed through the recruitment of bone marrow-derived myeloid cells, however the mechanisms of its formation are not fully understood. Recent evidence suggests that the primary tumor itself modulates the environment of secondary organs prior to tumor cell dissemination. The contribution of neutrophils to the formation of the pre-metastatic niche is getting growing attention. Obviously, neutrophils can affect the development of metastasis in two contradicting ways, by either stimulation or inhibition of this process, depending on the activation status. Pro-tumor neutrophils actively support metastasis formation by different mechanisms, including the formation of pre-metastatic niche, tumor cell attraction, and the direct support of tumor cell proliferation. Moreover, suppressive neutrophils, which are the granulocytic arm of MDSC, promote tumor progression by dampening anti-tumor T cell immunity. On the other hand, anti-tumor neutrophils can inhibit metastasis formation by the cytotoxicity towards tumor cells in the circulation or at the pre-metastatic site, and even via stimulation of T cell proliferation. Apparently, the regulation of the pro- or anti-tumor neutrophil properties has significant implications on metastatic spread in the host. Here we provide an up to date overview of the different roles neutrophils play in regulating the metastatic processes.

Amelioration of lung ischemia‑reperfusion injury by JNK and p38 small interfering RNAs in rat pulmonary microvascular endothelial cells in an ischemia‑reperfusion injury lung transplantation model

The inhibition of mitogen‑activated protein kinases (MAPKs), including c‑Jun NH2‑terminal protein kinase (JNK), p38 MAPK (p38) and extracellular signal‑regulated protein kinase 1/2 (ERK1/2), have an important effect on lung ischemia‑reperfusion injury (IRI) during lung transplantation (LT). However, the way in which combined MAPK inhibition exerts optimal protective effects on lung IRI remains to be elucidated. Therefore, the present study evaluated the therapeutic efficacy of the inhibition of MAPKs in rat pulmonary microvascular endothelial cells (PMVECs) in an IRI model of LT. The rat PMVECs were transfected with small interfering RNAs (siRNAs) against JNK, p38 or ERK1/2. Cotransfection was performed with siRNAs against JNK and p38 in the J+p group, JNK and ERK1/2 in the J+E group, p38 and ERK1/2 in the p+E group, or all three in the J+p+E group. Non‑targeting (NT) siRNA was used as a control. The PMVECs were then treated to induce IRI, and the levels of inflammation, apoptosis and oxidative stress were detected. Differences between compared groups were determined using Tukey's honest significant difference test. In all groups, silencing of the MAPKs was shown to attenuate inflammation, apoptosis and oxidative stress to differing extents, compared with the NT group. The J+p and J+p+E groups showed lower levels of interleukin (IL)‑1β, IL‑6 and malondialdehyde, a lower percentage of early‑apoptotic cells, and higher superoxide dismutase (SOD) activity, compared with the other groups. No significant differences were observed in the inflammatory response, SOD activity or early apoptosis between the J+p and J+p+E groups. These findings suggested that the dual inhibition of JNK and p38 led to maximal amelioration of lung IRI in the PMVECs of the IRI model of LT, which occurred through anti‑inflammatory, anti‑oxidative and anti‑apoptotic mechanisms.

Ghrelin ameliorates acute lung injury induced by oleic acid via inhibition of endoplasmic reticulum stress

AIMS

Acute lung injury (ALI) is associated with excessive mortality and lacks appropriate therapy. Ghrelin is a novel peptide that protects the lung against ALI. This study aimed to investigate whether endoplasmic reticulum stress (ERS) mediates the protective effect of ghrelin on ALI.

MAIN METHODS

We used a rat oleic acid (OA)-induced ALI model. Pulmonary impairment was detected by hematoxylin and eosin (HE) staining, lung mechanics, wet/dry weight ratio, and arterial blood gas analysis. Plasma and lung content of ghrelin was examined by ELISA, and mRNA expression was measured by quantitative real-time PCR. Protein levels were detected by western blot.

KEY FINDINGS

Rats with OA treatment showed significant pulmonary injury, edema, inflammatory cellular infiltration, cytokine release, hypoxia and CO₂ retention as compared with controls. Plasma and pulmonary content of ghrelin was reduced in rats with ALI, and mRNA expression was downregulated. Ghrelin (10nmol/kg) treatment ameliorated the above symptoms, but treatment with the ghrelin antagonists D-Lys³ GHRP-6 (1μmol/kg) and JMV 2959 (6mg/kg) exacerbated the symptoms. ERS induced by OA was prevented by ghrelin and augmented by ghrelin antagonist treatment. The ERS inducer, tunicamycin (Tm) prevented the ameliorative effect of ghrelin on ALI. The decreased ratio of p-Akt and Akt induced by OA was improved by ghrelin treatment, and was further exacerbated by ghrelin antagonists.

SIGNIFICANCE

Ghrelin protects against ALI by inhibiting ERS. These results provide a new target for prevention and therapy of ALI.

Differential protein expression in chicken macrophages and heterophils in vivo following infection with Salmonella Enteritidis

In this study we compared the proteomes of macrophages and heterophils isolated from the spleen 4 days after intravenous infection of chickens with Salmonella Enteritidis. Heterophils were characterized by expression of MMP9, MRP126, LECT2, CATHL1, CATHL2, CATHL3, LYG2, LYZ and RSFR. Macrophages specifically expressed receptor proteins, e.g. MRC1L, LRP1, LGALS1, LRPAP1 and a DMBT1L. Following infection, heterophils decreased ALB and FN1, and released MMP9 to enable their translocation to the site of infection. In addition, the endoplasmic reticulum proteins increased in heterophils which resulted in the release of granular proteins. Since transcription of genes encoding granular proteins did not decrease, these genes remained continuously transcribed and translated even after initial degranulation. Macrophages increased amounts of fatty acid elongation pathway proteins, lysosomal and phagosomal proteins. Macrophages were less responsive to acute infection than heterophils and an increase in proteins like CATHL1, CATHL2, RSFR, LECT2 and GAL1 in the absence of any change in their expression at RNA level could even be explained by capturing these proteins from the external environment into which these could have been released by heterophils.

Tumorigenic and Immunosuppressive Effects of Endoplasmic Reticulum Stress in Cancer

Malignant cells utilize diverse strategies that enable them to thrive under adverse conditions while simultaneously inhibiting the development of anti-tumor immune responses. Hostile microenvironmental conditions within tumor masses, such as nutrient deprivation, oxygen limitation, high metabolic demand, and oxidative stress, disturb the protein-folding capacity of the endoplasmic reticulum (ER), thereby provoking a cellular state of "ER stress." Sustained activation of ER stress sensors endows malignant cells with greater tumorigenic, metastatic, and drug-resistant capacity. Additionally, recent studies have uncovered that ER stress responses further impede the development of protective anti-cancer immunity by manipulating the function of myeloid cells in the tumor microenvironment. Here, we discuss the tumorigenic and immunoregulatory effects of ER stress in cancer, and we explore the concept of targeting ER stress responses to enhance the efficacy of standard chemotherapies and evolving cancer immunotherapies in the clinic.

Unfolding anti-tumor immunity: ER stress responses sculpt tolerogenic myeloid cells in cancer

Established tumors build a stressful and hostile microenvironment that blocks the development of protective innate and adaptive immune responses. Different subsets of immunoregulatory myeloid populations, including dendritic cells, myeloid-derived suppressor cells (MDSCs) and macrophages, accumulate in the stressed tumor milieu and represent a major impediment to the success of various forms of cancer immunotherapy. Specific conditions and factors within tumor masses, including hypoxia, nutrient starvation, low pH, and increased levels of free radicals, provoke a state of “endoplasmic reticulum (ER) stress” in both malignant cells and infiltrating myeloid cells. In order to cope with ER stress, cancer cells and tumor-associated myeloid cells activate an integrated signaling pathway known as the Unfolded Protein Response (UPR), which promotes cell survival and adaptation under adverse environmental conditions. However, the UPR can also induce cell death under unresolved levels of ER stress. Three branches of the UPR have been described, including the activation of the inositol-requiring enzyme 1 (IRE1), the pancreatic ER kinase (PKR)-like ER kinase (PERK), and the activating transcription factor 6 (ATF6). In this minireview, we briefly discuss the role of ER stress and specific UPR mediators in tumor development, growth and metastasis. In addition, we describe how sustained ER stress responses operate as key mediators of chronic inflammation and immune suppression within tumors. Finally, we discuss multiple pharmacological approaches that overcome the immunosuppressive effect of the UPR in tumors, and that could potentially enhance the efficacy of cancer immunotherapies by reprogramming the function of tumor-infiltrating myeloid cells.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.

WITHDRAWN: Decreased level of endogenous ghrelin is involved in the progression of lung injury induced by oleic acid

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Dual role for the unfolded protein response in the ovary: adaption and apoptosis

The endoplasmic reticulum (ER) is the principal organelle responsible for several specific cellular functions including synthesis and folding of secretory or membrane proteins, lipid metabolism, and Ca²⁺ storage. Different physiological as well as pathological stress conditions can, however, perturb ER homeostasis, giving rise to an accumulation of unfolded or misfolded proteins in the ER lumen, a condition termed ER stress. To deal with an increased folding demand, cells activate the unfolded protein response (UPR), which is initially protective but can become detrimental if ER stress is severe and prolonged. Accumulating evidence demonstrates a link between the UPR and ovarian development and function, including follicular growth and maturation, follicular atresia, and corpus luteum biogenesis. Additionally, ER stress and the UPR may also play an important role in the ovary under pathological conditions. Understanding the molecular mechanisms related to the dual role of unfolded protein response in the ovarian physiology and pathology may reveal the pathogenesis of some reproductive endocrine diseases and provide a new guidance to improve the assisted reproductive technology. Here we review the current literature and discuss concepts and progress in understanding the UPR, and we also analyze the role of ER stress and the UPR in the ovary.