Suppression of Endoplasmic Reticulum Stress by 4-PBA Protects Against Hyperoxia-Induced Acute Lung Injury via Up-Regulating Claudin-4 Expression

Endoplasmic Reticulum Dysfunction: An Emerging Mechanism of Vitiligo Pathogenesis

The endoplasmic reticulum (ER) is the main site of protein synthesis, transport, and modification. Its abnormal status has now emerged as an established cause of many pathological processes, such as tumors and autoimmune diseases. Recent studies also demonstrated that the defective functions of ER may lead to pigmentary diseases. Vitiligo is a depigmenting ailment skin disorder whose pathogenesis is now found to be associated with ER. However, the detailed mechanism is still unclear. In this review, we try to link the association between ER with its inter- and intra-organellar interactions in vitiligo pathogenesis and focus on the function, mechanism, and clinical potential of ER with vitiligo. Expand ER is found in melanocytes of vitiligo and ER stress (ERS) might be a bridge between oxidative stress and innate and adaptive immunity. Meanwhile, the tight association between ER and mitochondria or melanosomes in organelles levels, as well as genes and cytokines, is the new paradigm in the pathogenesis of vitiligo. This undoubtedly adds a new aspect to the understanding of vitiligo, facilitating the design of targeted therapies for vitiligo.

PBA alleviates cadmium-induced mouse spermatogonia apoptosis by suppressing endoplasmic reticulum stress

OBJECTIVE

Endoplasmic reticulum (ER) stress mediates Cd-caused germ cell apoptosis in testis. The effects of 4-phenylbutyric acid (PBA), a classical chaperone, were investigated on Cd-induced apoptosis in mouse GC-1 spermatogonia cells.

METHODS

The cells were pretreated with PBA before Cd exposure. TUNEL and flow cytometry assays were applied to determine apoptosis. Some key biomarkers of ER stress were analyzed using RT-PCR and western blot.

RESULTS

as expected, the apoptotic cells exposed to Cd apparently increased. The mRNA and protein expression levels of GRP78 and ATF6α, were elevated in the Cd groups. Additional experiments displayed that Cd notably increased IRE1α and JNK phosphorylation, and upregulated XBP-1 mRNA and protein expression. Moreover, p-eIF2α and CHOP expressions were clearly elevated in the Cd groups. Interestingly, PBA almost completely inhibited ER stress and protected spermatogonia against apoptosis induced by Cd.

CONCLUSION

PBA alleviated Cd-induced ER stress and spermatogonia apoptosis, and may have the therapeutic role in Cd-induced male reproductive toxicity.

Phenylbutyric acid inhibits hypoxia-induced trophoblast apoptosis and autophagy in preeclampsia via the PERK/ATF-4/CHOP pathway

Preeclampsia (PE) is a common pregnancy complication with a high mortality rate. Abnormally activated endoplasmic reticulum stress (ERS) is believed to be responsible for the destruction of key placental cells-trophoblasts. Phenylbutyric acid (4-PBA), an ERS inhibitor, is involved in regulating the development of ERS-related diseases. At present, how 4-PBA affects trophoblasts and its mechanisms is still unclear. In this study, PE cell models were established by stimulating HTR-8/SVneo cells with hypoxia. To verify the underlying mechanisms of 4-PBA on PE, CCT020312, an activator of PERK, was also used. The results showed that 4-PBA restored hypoxia-induced trophoblast viability, inhibited HIF-1α protein expression, inflammation, and PERK/ATF-4/CHOP pathway. Hoechst 33342 staining and flow cytometry results confirmed that 4-PBA decreased hypoxia-induced apoptosis in trophoblasts. The results of the JC-1 analysis and apoptosis initiation enzyme activity assay also demonstrated that 4-PBA inhibited apoptosis related to the mitochondrial pathway. Furthermore, by detecting autophagy in trophoblasts, an increased number of autophagic vesicles, damaged mitochondria, enhanced dansylcadaverine fluorescence, enhanced levels of autophagy proteins Beclin-1, LC3II, and decreased p62 were seen in hypoxia-stimulated cells. These changes were reversed by 4-PBA. Furthermore, it was observed that CCT020312 reversed the effects of 4-PBA on the viability, apoptosis, and autophagosome number of hypoxia-induced trophoblasts. In summary, 4-PBA reduces autophagy and apoptosis via the PERK/ATF-4/CHOP pathway and mitochondrial pathway, thereby restoring the viability of hypoxic trophoblasts. These findings provide a solid evidence base for the use of 4-PBA in PE treatment and guide a new direction for improving the outcomes of patients with PE.

Sestrin2 ameliorates diabetic retinopathy by regulating autophagy and ferroptosis

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes. The aim of this study was to explore the effect of Sestrin2 on DR through the regulation of autophagy and ferroptosis levels and its mechanism. In vitro and in vivo DR models were established by high glucose (HG) and streptozotocin (STZ) induction of ARPE-19 human retinal pigment epithelial cells and C57BL/6 mice, respectively. In this study, we demonstrated that after HG treatment, the activity of ARPE-19 cells was decreased, the apoptosis rate was increased, endoplasmic reticulum (ER) stress was activated, autophagy levels were decreased, and ferroptosis levels were increased. Overexpression of Sestrin2 enhanced cell viability, reduced apoptosis and ferroptosis, and enhanced autophagy. However, the effect of overexpression of Sestrin2 was attenuated after the addition of the STAT3 phosphorylation activator Colivelin TFA (C-TFA), the mTOR pathway activator MHY1485 or the autophagy inhibitor 3-methyladenine (3-MA). In addition, the effect of Sestrin2 knockdown on cells was opposite to the effect of overexpression of Sestrin2, while the effect of Sestrin2 knockdown was attenuated after treatment with the ER stress inhibitor 4-phenylbutyric acid (4-PBA). Animal experiments also confirmed the results of cell experiments and attenuated the effects of overexpression of Sestrin2 after injection of the ferroptosis activators erastin or 3-MA. Our study revealed that Sestrin2 inhibits ferroptosis by inhibiting STAT3 phosphorylation and ER stress and promoting autophagy levels, thereby alleviating DR.

Nitric oxide-induced endoplasmic reticulum stress of Schistosoma japonicum inhibits the worm development in rats

Schistosomiasis, caused by Schistosoma spp., is a zoonotic parasitic disease affecting human health. Rattus norvegicus (rats) are a non-permissive host of Schistosoma, in which the worms cannot mature and cause typical egg granuloma. We previously demonstrated that inherent high levels of nitric oxide (NO), produced by inducible NO synthase (iNOS), is a key molecule in blocking the development of S. japonicum in rats. To further explore the mechanism of NO inhibiting S. japonicum development in rats, we performed S-nitrosocysteine proteomics of S. japonicum collected from infected rats and mice. The results suggested that S. japonicum in rats may have undergone endoplasmic reticulum (ER) stress. Interestingly, we found that the ER of S. japonicum in rats showed marked damage, while the ER of the worm in iNOS-/- rats and mice were relatively normal. Moreover, the expression of ER stress markers in S. japonicum from WT rats was significantly increased, compared with S. japonicum from iNOS-/- rats and mice. Using the NO donor sodium nitroprusside in vitro, we demonstrated that NO could induce ER stress in S. japonicum in a dose-dependent manner, and the NO-induced ER stress in S. japonicum could be inhibited by ER stress inhibitor 4-Phenyl butyric acid. We further verified that inhibiting ER stress of S. japonicum in rats promoted parasite development and survival. Furthermore, we demonstrated that NO-induced ER stress of S. japonicum was related to the efflux of Ca2+ from ER and the impairment of mitochondrial function. Collectively, these findings show that high levels of NO in rats could induce ER stress in S. japonicum by promoting the efflux of Ca2+ from ER and damaging the mitochondrial function, which block the worm development. Thus, this study further clarifies the mechanism of anti-schistosome in rats and provides potential strategies for drug development against schistosomiasis and other parasitosis.

Suppressing Endoplasmic Reticulum Stress Alleviates LPS-Induced Acute Lung Injury via Inhibiting Inflammation and Ferroptosis

Acute lung injury (ALI) is a life-threatening clinical disorder with high mortality rate. Ferroptosis is a new type of programmed cell death with lipid peroxidation and iron ion overloading as the main characteristics. Endoplasmic reticulum (ER) stress and ferroptosis play pivotal roles in the pathogenesis of ALI. The study aimed to investigate the underlying relationship between ER stress and ferroptosis in ALI. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated LPS-induced inflammation, and decreased IL-1β, IL-6, and TNF-α levels in BALF and lungs. The increased MDA and decreased GSH induced by LPS were partially reversed by 4-PBA, which also inhibited the expressions of ferroptosis-related protein ACSL4, COX-2, and FTH1. TEM further confirmed the ferroptosis within airway epithelia cells was ameliorated by 4-PBA. Moreover, 4-PBA reduced the production of ROS and lipid ROS in LPS-exposed BEAS-2B cells in a concentration-dependent way. Meanwhile, 4-PBA mitigated LPS-induced cell apoptosis in vivo and in vitro. Mechanistically, the MAPK signaling pathway activated by LPS was downregulated by 4-PBA. Collectively, these findings suggested that 4-PBA protected against ALI by inhibiting inflammation and ferroptosis through downregulating ER stress, thus providing a potential intervention for ALI and revealing the possible interaction between ER stress and ferroptosis in ALI.

Functional characterization of missense variants affecting the extracellular domains of ABCA1 using a fluorescence-based assay

Excess cholesterol originating from nonhepatic tissues is transported within HDL particles to the liver for metabolism and excretion. Cholesterol efflux is initiated by lipid-free or lipid-poor apolipoprotein A1 interacting with the transmembrane protein ABCA1, a key player in cholesterol homeostasis. Defective ABCA1 results in reduced serum levels of HDL cholesterol, deposition of cholesterol in arteries, and an increased risk of early onset CVD. Over 300 genetic variants in ABCA1 have been reported, many of which are associated with reduced HDL cholesterol levels. Only a few of these have been functionally characterized. In this study, we have analyzed 51 previously unclassified missense variants affecting the extracellular domains of ABCA1 using a sensitive, easy, and low-cost fluorescence-based assay. Among these, only 12 variants showed a distinct loss-of-function phenotype, asserting their direct association with severe HDL disorders. These findings emphasize the crucial role of functional characterization of genetic variants in pathogenicity assessment and precision medicine. The functional rescue of ABCA1 loss-of-function variants through proteasomal inhibition or by the use of the chemical chaperone 4-phenylbutyric acid was genotype specific. Genotype-specific responses were also observed for the ability of apolipoprotein A1 to stabilize the different ABCA1 variants. In view of personalized medicine, this could potentially form the basis for novel therapeutic strategies.

Suppression of endoplasmic reticulum stress by 4-PBA enhanced atherosclerotic plaque stability via up-regulating CLOCK expression

Endoplasmic reticulum (ER) stress refers to a condition where the normal functioning of the ER is disrupted due to a variety of cellular stress factors. As a result, there is an accumulation of unfolded and misfolded proteins within the ER. Numerous studies have shown that ER stress can exacerbate inflammatory reactions and contribute to the development of various inflammatory diseases. However, the role of ER stress in the stability of atherosclerotic plaques remains poorly understood. In this study, we aimed to explore the potential impact of a specific ER stress inhibitor known as 4-phenyl butyric acid (4-PBA) on atherosclerosis in mice. The mice were fed a high-fat diet, and treatment with 4-PBA significantly improved the stability of the atherosclerotic plaques. This was evidenced by a reduction in oxidative stress and an increase in circadian locomotor output cycles kaput (CLOCK) protein and mRNA expression within the plaques. Additionally, 4-PBA reduced the expression of ER stress-related proteins and decreased apoptosis in the atherosclerotic plaques. In vitro investigation, we observed the effect of 4-PBA on vascular smooth muscle cells (VSMCs) that were exposed to oxidized low-density lipoprotein (ox-LDL), a significant contributor to the development of atherosclerosis. 4-PBA reduced reactive oxygen species (ROS) production and attenuated apoptosis, GRP78 and CHOP protein expression in ox-LDL-Induced VSMCs via up-regulating CLOCK expression. However, when the short hairpin RNA against CLOCK (sh-CLOCK) was introduced to the VSMCs, the protective effect of 4-PBA was abolished. This suggests that the up-regulation of CLOCK expression is crucial for the beneficial effects of 4-PBA on atherosclerotic plaque stability. This finding suggests that targeting ER stress and modulating CLOCK protein levels might be a promising way to enhance the stability of atherosclerotic plaques.

Asperuloside Promotes Apoptosis of Cervical Cancer Cells through Endoplasmic Reticulum Stress-Mitochondrial Pathway

OBJECTIVE

To investigate the effects of asperuloside on cervical cancer based on endoplasmic reticulum (ER) stress and mitochondrial pathway.

METHODS

Different doses (12.5-800 µg/mL) of asperuloside were used to treat cervical cancer cell lines Hela and CaSki to calculate the half maximal inhibitory concentration (IC50) of asperuloside. The cell proliferation was analyzed by clone formation assay. Cell apoptosis, intracellular reactive oxygen species (ROS) and mitochondrial membrane potential were determined by flow cytometry. The protein expressions of cleaved-caspase-3, Bcl-2, Bax, Cyt-c, cleaved-caspase-4 and glucose-regulated protein 78 (GRP78) were analyzed by Western blot. And the inhibitor of ER stress, 4-phenyl butyric acid (4-PBA) was used to treat cervical cancer cells to further verify the role of ER stress in the apoptosis of cervical cancer cells induced by asperuloside.

RESULTS

Asperuloside of 325, 650, and 1300 µg/mL significantly inhibited the proliferation and promoted apoptosis of Hela and CaSki cells (P<0.01). All doses of asperuloside significantly increased intracellular ROS levels, reduced mitochondrial membrane potential, significantly reduced Bcl-2 protein expression level, and increased Bax, Cyt-c, GRP78 and cleaved-caspase-4 expressions (P<0.01). In addition, 10 mmol/L 4-PBA treatment significantly promoted cell proliferation and reduced apoptosis (P<0.05), and 650 µg/mL asperuloside could reverse 4-PBA-induced increased cell proliferation, decreased apoptosis and cleaved-caspase-3, -4 and GRP78 protein expressions (P<0.05).

CONCLUSION

Our study revealed the role of asperuloside in cervical cancer, suggesting that asperuloside promotes apoptosis of cervical cancer cells through ER stress-mitochondrial pathway.

Connexin 36 Mediated Intercellular Endoplasmic Reticulum Stress Transmission Induces SSTA Resistance in Growth Hormone Pituitary Adenoma

Somatostatin analogues (SSTA) are first-line pharmacological treatment choice for acromegaly, which received satisfying tumor shrinkage and normalization of growth hormone. However, there are still patients unresponsive to SSTA, and the underline mechanism remains unknown. Besides, there is no evidence regarding the role of endoplasmic reticulum stress (ERS) and its transmission in SSTA resistance, which also require investigation. Primary growth hormone adenoma cells and cell lines were treated with SSTA; autophagy double-labeled LC3 (mRFP-GFP) adenovirus transfection, flow cytometry sorting, western blotting, calcium imaging as well as immunofluorescence staining were used to determine ERS and autophagy signal transmission; xenograft and syngeneic tumor in vivo model were exploited to confirm the ERS signal transmission mediated effect. Our results revealed that SSTA induces ERS in pituitary growth hormone (GH) adenoma cells. The ERS signals can be intercellularly transmitted, leading to less responsible to SSTA treatment. Moreover, SSTA stimulates inositol triphosphate (IP3) elevation, mediating ERS intercellular transfer. In addition, connexin 36 tunnels ERS transmission, and its blocker, Quinine, exhibits a synergistic effect with SSTA treating GH adenoma. Our study provided insight into ERS intercellular transmission mediated SSTA resistance, which could be translated into clinical usage to improve SSTA efficiency in GH adenoma treatment.

Quercetin alleviates cadmium-induced BRL-3A cell apoptosis by inhibiting oxidative stress and the PERK/IRE1α/ATF6 signaling pathway

Cadmium (Cd) is a highly toxic environmental pollutant. The liver is an important metabolic organ in the body and is susceptible to Cd toxicity attacks. Quercetin (Que) is a flavonoid compound with pharmacological activities of scavenging free radicals and antioxidant activity. Previous studies have shown that Que can alleviate Cd caused hepatocyte apoptosis in rats, but the specific mechanism remains unclear. To explore the specific mechanism, we established a model of Cd toxicity and Que rescue in BRL-3A cells and used 4-phenylbutyrate (4-PBA), an endoplasmic reticulum stress (ERS) inhibitor, as positive control. Set up a control group, Cd treatment group, Cd and Que co treatment group, Que treatment group, Cd and 4-PBA co treatment group, and 4-PBA treatment group. Cell Counting Kit-8 (CCK-8) method was employed to measure cell viability. Fluorescence staining was applied to observe cell apoptosis. Flow cytometry was performed to detect reactive oxygen species levels. Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot method was adopted to detect the mRNA and protein expression levels of ERS and apoptosis-related genes. The results showed that compared with the control group, the Cd treated group showed a significant decrease in cell viability (P < 0.01), an increase in intracellular ROS levels, and apoptosis. The mRNA and protein expression levels of ERS and apoptosis related factors such as GRP78, IRE1α, XBP1, ATF6, Caspase-12, Caspase-3 and Bax in the cells were significantly increased (P < 0.01), while the mRNA and protein expression levels of Bcl-2 were significantly reduced (P < 0.01). Compared with the Cd treatment group, the Cd and Que co treatment group and the Cd and 4-PBA co treatment group showed a significant increase in cell viability (P < 0.01), a decrease in intracellular ROS levels, a decrease in cell apoptosis, and a significant decrease in the expression levels of ERS and apoptosis related factors mRNA and protein (P < 0.01), as well as a significant increase in Bcl-2 mRNA and protein expression (P < 0.01). We confirmed that Que could alleviate the apoptosis caused by Cd in BRL-3A cells, and the effects of Que were similar to those of ERS inhibitor.

Hypoxic bone marrow mesenchymal stem cell-derived exosomal lncRNA XIST attenuates lipopolysaccharide-induced acute lung injury via the miR-455-3p/Claudin-4 axis

Mesenchymal stem cell-derived exosomes and long non-coding RNAs (lncRNAs) have been identified to play a role in acute lung injury (ALI). In this study, we investigated whether exosomal lncRNAs could regulate ALI and the underlying mechanisms. Bone marrow mesenchymal stem cells (BM-MSCs) were pretreated with hypoxia or normoxia, and exosomes were subsequently extracted from normoxic BM-MSCs (Nor-exos) and hypoxic BM-MSCs (Hypo-exos). A rat model of ALI was established via an airway perfusion of lipopolysaccharide (LPS). Exosomes were administered via the tail vein to evaluate the in vivo effect of exosomes in ALI. LPS-exposed RLE-6TN cells were incubated with exosomes to explore their in vitro effect in ALI. A luciferase reporter assay was used to evaluate the interaction between lncRNA XIST and miR-455-3p, as well as miR-455-3p and Claudin-4. We found that the exosomes attenuated LPS-induced ALI and Hypo-Exos exerted a greater therapeutic effect compared with Nor-exos both in vitro and in vivo. Moreover, an abundance of lncRNA XIST was observed in Hypo-exos compared with Nor-exos. Mechanistically, LncRNA XIST functioned as a miR-455-3p sponge and targeted Claudin-4 in ALI. Our results provide novel insight into the role of exosomal lncRNA XIST for the treatment of ALI. Thus, hypoxic pretreatment may represent an effective method for improving the therapeutic effects of exosomes.

Mannose-doped metal-organic frameworks induce tumor cell pyroptosis via the PERK pathway

BACKGROUND

The implementation of pyroptosis exhibits significant potential as a tactic to enhance tumor immune microenvironments. Previous applications of pyroptosis inducers have encountered various limitations, such as the development of drug resistance, manifestation of toxic side effects, and a deficiency in targeting capabilities. As a result, there is a growing demand for tumor therapeutic molecules that can overcome these obstacles. Therefore, the objective of this study is to develop a multifunctional nanospheres that addresses these challenges by enabling high-precision targeting of tumor cells and inducing effective pyroptosis.

RESULTS

We prepared a mannose-modified MOF called mannose-doped Fe3O4@NH2-MIL-100 (M-FNM). M-FNM could enter CAL27 cells through MR-mediated endocytosis, which caused in a significant increase in the level of intracellular ROS. This increase subsequently triggered ER stress and activated the PERK-eIF2α-ATF4-CHOP signaling pathway. CHOP then mediated the downstream cascade of Caspase-1, inducing pyroptosis. In in vivo experiments, M-FNM demonstrated excellent targeting ability and exhibited anti-tumor effects. Additionally, M-FNM reshaped the immune microenvironment by promoting the infiltration of anti-tumor immune cells, primarily T lymphocytes.

CONCLUSIONS

M-FNM significantly decreased tumor growth. This novel approach to induce pyroptosis in tumor cells using M-FNM may offer new avenues for the development of effective immunotherapies against cancer.

Antagonistic effect of selenium on programmed necrosis of testicular Leydig cells caused by cadmium through endoplasmic reticulum stress in chicken

Cadmium (Cd) is a widely distributed environmental contaminant that is highly toxic to animals and humans. However, detailed reports on Cd-induced programmed necrosis have not been seen in chicken testicular Leydig cells. Selenium (Se) is a trace element in the human body that has cytoprotective effects in a variety of pathological damages caused by heavy metals. This study investigated the potential mechanisms of Cd-induced programmed cell necrosis and the antagonistic effect of Se on Cd toxicity. Chicken testis Leydig cells were divided into six groups, namely, control, Se (5 µmol/L Na2SeO3), Cd (20 µmol/L CdCl2), Se + Cd (5 µmol/L Na2SeO3 and 20 µmol/L CdCl2), 4-phenylbutyric acid (4-PBA) + Cd (10 mmol/L 4-phenylbutyric acid and 20 µmol/L CdCl2), and Necrostatin-1 (Nec-1) + Cd (60 µmol/L Necrostatin-1 and 20 µmol/L CdCl2). The results showed that Cd exposure decreased the activity of CAT, GSH-Px, and SOD and the concentration of GSH, and increased the concentration of MDA and the content of ROS. Relative mRNA and protein expression of GRP78, PERK, ATF6, IRE1, CHOP, and JNK increased in the Cd group, and mRNA and protein expression of TNF-α, TNFR1, RIP1, RIP3, MLKL, and PARP1 significantly increased in the Cd group, while Caspase-8 mRNA and protein expression significantly decreased. The abnormal expression of endoplasmic reticulum stress-related proteins was significantly reduced by 4-PBA pretreatment; the increased expression of TNF-α, TNFR1, RIP1, RIP3, MLKL, and PARP1 caused by Cd toxicity was alleviated; and the expression of caspase-8 was upregulated. Conversely, the increased mRNA and protein expression of endoplasmic reticulum stress marker genes (GRP78, ATF6, PERK, IRE1, CHOP, JNK) caused by Cd was not affected after pretreatment with Nec-1. We also found that these Cd-induced changes were significantly attenuated in the Se + Cd group. We clarified that Cd can cause programmed necrosis of chicken testicular Leydig cells through endoplasmic reticulum stress, and Se can antagonize Cd-induced programmed necrosis of chicken testicular Leydig cells.

Chemical Chaperone 4-PBA Mitigates Tumor Necrosis Factor Alpha-Induced Endoplasmic Reticulum Stress in Human Airway Smooth Muscle

Airway inflammation and pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα) underlie the pathophysiology of respiratory diseases, including asthma. Previously, we showed that TNFα activates the inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 spliced (XBP1s) endoplasmic reticulum (ER) stress pathway in human airway smooth muscle (hASM) cells. The ER stress pathway is activated by the accumulation of unfolded proteins in the ER. Accordingly, chemical chaperones such as 4-phenylbutyric acid (4-PBA) may reduce ER stress activation. In the present study, we hypothesized that chemical chaperone 4-PBA mitigates TNFα-induced ER stress in hASM cells. hASM cells were isolated from bronchiolar tissue obtained from five patients with no history of smoking or respiratory diseases. The hASM cells' phenotype was confirmed via the expression of alpha-smooth muscle actin and elongated morphology. hASM cells from the same patient sample were then separated into three 12 h treatment groups: (1) TNFα (20 ng/mL), (2) TNFα + 4-PBA (1 μM, 30 min pretreatment), and (3) untreated control. The expressions of total IRE1α and phosphorylated IRE1α (pIRE1αS724) were determined through Western blotting. The splicing of XBP1 mRNA was analyzed using RT-PCR. We found that TNFα induced an increase in pIRE1αS724 phosphorylation, which was mitigated by treatment with chemical chaperone 4-PBA. We also found that TNFα induced an increase in XBP1s mRNA, which was also mitigated by treatment with chemical chaperone 4-PBA. These results support our hypothesis and indicate that chemical chaperone 4-PBA treatment mitigates TNFα-induced ER stress in hASM cells.

Sivelestat sodium alleviated lipopolysaccharide-induced acute lung injury by improving endoplasmic reticulum stress

Acute lung injury (ALI) is a common inflammatory respiratory disorder characterized by a high incidence and mortality rate. This study aimed to investigate the potential therapeutic effects of the neutrophil elastase inhibitor Sivelestat sodium (SIV) in improving endoplasmic reticulum stress (ERS) while treating lipopolysaccharide (LPS)-induced ALI. An ALI model was established using LPS induction. The effects of SIV on ALI were observed both in vivo and in vitro, along with its impact on ERS. Lung tissue damage was assessed using Hematoxylin-eosin (H&E) staining. Lung edema was measured by the lung wet/dry weight ratio. The expression levels of protein kinase R-like ER kinase (PERK), Phospho-protein kinase R-like ER kinase (p-PERK), activating transcription factor 4 (ATF4), eukaryotic translation initiation factor 2α (EIF2a), phosphorylated α subunit of eukaryotic initiation factor 2α (P-EIF2a), and C/EBP homologous protein (CHOP) were analyzed by Western blotting in vivo and in vitro. The levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in Lung tissue samples supernatants were measured by ELISA. Oxidative stress markers were measured by ELISA. Apoptosis was measured using the TUNEL assay. Apoptosis-associated proteins B-cell lymphoma-2 (Bcl-2)、Bcl2-associated × (Bax)、caspase-3 were evaluated through Western blotting in vivo and in vitro. The expression levels of ERS-related proteins, including p-PERK, ATF4, P-EIF2a, and CHOP, were significantly increased in the LPS-induced ALI model. However, SIV markedly reduced the expression levels of these proteins, suppressing the LPS-induced ERS response. Further investigations revealed that SIV exerted a protective effect on ALI by alleviating lung tissue damage and apoptosis, improving lung function, and reducing inflammation and oxidative stress levels. However, when SIV was co-administered with Tunicamycin (TUN), TUN blocked the beneficial effects of SIV on ERS and reversed the protective effects of SIV on ALI. In conclusion, SIV alleviated lung tissue damage and apoptosis, improving lung function, and reducing inflammation and oxidative stress in LPS-induced ALI by improving ERS.

Endoplasmic reticulum stress and alterations of peroxiredoxins in aged hearts

Aging-related cardiovascular disease is influenced by multiple factors, with oxidative stress being a key contributor. Aging-induced endoplasmic reticulum (ER) stress exacerbates oxidative stress by impairing mitochondrial function. Furthermore, a decline in antioxidants, including peroxiredoxins (PRDXs), augments the oxidative stress during aging. To explore if ER stress leads to PRDX degradation during aging, young adult (3 mo.) and aged (24 mo.) male mice were studied. Treatment with 4-phenylbutyrate (4-PBA) was used to alleviate ER stress in young adult and aged mice. Aged hearts showed elevated oxidative stress levels compared to young hearts. However, treatment with 4-PBA to attenuate ER stress reduced oxidative stress in aged hearts, indicating that ER stress contributes to increased oxidative stress in aging. Moreover, aging resulted in reduced levels of peroxiredoxin 3 (PRDX3) in mitochondria and peroxiredoxin 4 (PRDX4) in myocardium. While 4-PBA treatment improved PRDX3 content in aged hearts, it did not restore PRDX4 content in aged mice. These findings suggest that ER stress not only leads to mitochondrial dysfunction and increased oxidant stress but also impairs a vital antioxidant defense through decreased PRDX3 content. Additionally, the results suggest that PRDX4 may contribute an upstream role in inducing ER stress during aging.

Combination of RUNX1 inhibitor and gemcitabine mitigates chemo-resistance in pancreatic ductal adenocarcinoma by modulating BiP/PERK/eIF2α-axis-mediated endoplasmic reticulum stress

BACKGROUND

Gemcitabine (GEM)-based chemotherapy is the first-line option for pancreatic ductal adenocarcinoma (PDAC). However, the development of drug resistance limits its efficacy, and the specific mechanisms remain largely unknown. RUNX1, a key transcription factor in hematopoiesis, also involved in the malignant progression of PDAC, but was unclear in the chemoresistance of PDAC.

METHODS

Comparative analysis was performed to screen GEM-resistance related genes using our single-cell RNA sequencing(scRNA-seq) data and two public RNA-sequencing datasets (GSE223463, GSE183795) for PDAC. The expression of RUNX1 in PDAC tissues was detected by qRT-PCR, immunohistochemistry (IHC) and western blot. The clinical significance of RUNX1 in PDAC was determined by single-or multivariate analysis and survival analysis. We constructed the stably expressing cell lines with shRUNX1 and RUNX1, and successfully established GEM-resistant cell line. The role of RUNX1 in GEM resistance was determined by CCK8 assay, plate colony formation assay and apoptosis analysis in vitro and in vivo. To explore the mechanism, we performed bioinformatic analysis using the scRNA-seq data to screen for the endoplasm reticulum (ER) stress signaling that was indispensable for RUNX1 in GEM resistance. We observed the cell morphology in ER stress by transmission electron microscopy and validated RUNX1 in gemcitabine resistance depended on the BiP/PERK/eIF2α pathway by in vitro and in vivo oncogenic experiments, using ER stress inhibitor(4-PBA) and PERK inhibitor (GSK2606414). The correlation between RUNX1 and BiP expression was assessed using the scRNA-seq data and TCGA dataset, and validated by RT-PCR, immunostaining and western blot. The mechanism of RUNX1 regulation of BiP was confirmed by ChIP-PCR and dual luciferase assay. Finally, the effect of RUNX1 inhibitor on PDAC was conducted in vivo mouse models, including subcutaneous xenograft and patient-derived xenograft (PDX) mouse models.

RESULTS

RUNX1 was aberrant high expressed in PDAC and closely associated with GEM resistance. Silencing of RUNX1 could attenuate resistance in GEM-resistant cell line, and its inhibitor Ro5-3335 displayed an enhanced effect in inhibiting tumor growth, combined with GEM treatment, in PDX mouse models and GEM-resistant xenografts. In detail, forced expression of RUNX1 in PDAC cells suppressed apoptosis induced by GEM exposure, which was reversed by the ER stress inhibitor 4-PBA and PERK phosphorylation inhibitor GSK2606414. RUNX1 modulation of ER stress signaling mediated GEM resistance was supported by the analysis of scRNA-seq data. Consistently, silencing of RUNX1 strongly inhibited the GEM-induced activation of BiP and PERK/eIF2α signaling, one of the major pathways involved in ER stress. It was identified that RUNX1 directly bound to the promoter region of BiP, a primary ER stress sensor, and stimulated BiP expression to enhance the reserve capacity for cell adaptation, which in turn facilitated GEM resistance in PDAC cells.

CONCLUSIONS

This study identifies RUNX1 as a predictive biomarker for response to GEM-based chemotherapy. RUNX1 inhibition may represent an effective strategy for overcoming GEM resistance in PDAC cells.

Depleted uranium induces thyroid damage through activation of ER stress via the thrombospondin 1-PERK pathway

Depleted uranium (DU) can cause damage to the body, but its effects on the thyroid are unclear. The purpose of this study was to investigate the DU-induced thyroid damage and its potential mechanism in order to find new targets for detoxification after DU poisoning. A model of acute exposure to DU was constructed in rats. It was observed that DU accumulated in the thyroid, induced thyroid structure disorder and cell apoptosis, and decreased the serum T4 and FT4 levels. Gene screening showed that thrombospondin 1 (TSP-1) was a sensitive gene of DU, and the expression of TSP-1 decreased with the increase of DU exposure dose and time. TSP-1 knockout mice exposed to DU had more severe thyroid damage and lower serum FT4 and T4 levels than wild-type mice. Inhibiting the expression of TSP-1 in FRTL-5 cells aggravated DU-induced apoptosis, while exogenous TSP-1 protein alleviated the decreased viability in FRTL-5 cells caused by DU. It was suggested that DU may caused thyroid damage by down-regulating TSP-1. It was also found that DU increased the expressions of PERK, CHOP, and Caspase-3, and 4-Phenylbutyric (4-PBA) alleviated the DU-induced FRTL-5 cell viability decline and the decrease levels of rat serum FT4 and T4 caused by DU. After DU exposure, the PERK expression was further up-regulated in TSP-1 knockout mice, and the increased expression of PERK was alleviated in TSP-1 over-expressed cells, as well as the increased expression of CHOP and Caspase-3. Further verification showed that inhibition of PERK expression could reduce the DU-induced increased expression of CHOP and Caspase-3. These findings shed light on the mechanism that DU may activate ER stress via the TSP 1-PERK pathway, thereby leading to thyroid damage, and suggest that TSP-1 may be a potential therapeutic target for DU-induced thyroid damage.

Endoplasmic reticulum homeostasis: a potential target for diabetic nephropathy

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

Ginsenoside Rc from Panax Ginseng Ameliorates Palmitate-Induced UB/OC-2 Cochlear Cell Injury

By 2050, at least 700 million people will require hearing therapy while 2.5 billion are projected to suffer from hearing loss. Sensorineural hearing loss (SNHL) arises from the inability of the inner ear to convert fluid waves into neural electric signals because of injury to cochlear hair cells that has resulted in their death. In addition, systemic chronic inflammation implicated in other pathologies may exacerbate cell death leading to SNHL. Phytochemicals have emerged as a possible solution because of the growing evidence of their anti-inflammatory, antioxidant, and anti-apoptotic properties. Ginseng and its bioactive molecules, ginsenosides, exhibit effects that suppress pro-inflammatory signaling and protect against apoptosis. In the current study, we investigated the effects of ginsenoside Rc (G-Rc) on UB/OC-2 primary murine sensory hair cell survival in response to palmitate-induced injury. G-Rc promoted UB/OC-2 cell survival and cell cycle progression. Additionally, G-Rc enhanced the differentiation of UB/OC-2 cells into functional sensory hair cells and alleviated palmitate-induced inflammation, endoplasmic reticulum stress, and apoptosis. The current study offers novel insights into the effects of G-Rc as a potential adjuvant for SNHL and warrants further studies elucidating the molecular mechanisms.

Advances in cellular senescence in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and fatal interstitial lung disease of unknown cause, with a median survival of 2-3 years. Its pathogenesis is unclear and there is currently no effective treatment for IPF. Approximately two-thirds of patients with IPF are >60 years old, with a mean age of 66 years, suggesting a link between aging and IPF. However, the mechanism by which aging promotes development of PF remains unclear. Senescence of alveolar epithelial cells and lung fibroblasts (LFs) and their senescence-associated secretion phenotype (SASP) may be involved in the occurrence and development of IPF. The present review focus on senescence of LFs and epithelial and stem cells, as well as SASP, the activation of profibrotic signaling pathways and potential treatments for pathogenesis of IPF.

Dihydroartemisinin elicits immunogenic death through ferroptosis-triggered ER stress and DNA damage for lung cancer immunotherapy

BACKGROUND

The immunosuppressive microenvironment of lung cancer serves as an important endogenous contributor to treatment failure. The present study aimed to demonstrate the promotive effect of DHA on immunogenic cell death (ICD) in lung cancer as well as the mechanism.

METHODS

The lewis lung cancer cells (LLC), A549 cells and LLC-bearing mice were applied as the lung cancer model. The apoptosis, ferroptosis assay, western blotting, immunofluorescent staining, qPCR, comet assay, flow cytometry, confocal microscopy, transmission electron microscopy and immunohistochemistry were conducted to analyze the functions and the underlying mechanism.

RESULTS

An increased apoptosis rate and immunogenicity were detected in DHA-treated LLC and tumor grafts. Further findings showed DHA caused lipid peroxide (LPO) accumulation, thereby initiating ferroptosis. DHA stimulated cellular endoplasmic reticulum (ER) stress and DNA damage simultaneously. However, the ER stress and DNA damage induced by DHA could be abolished by ferroptosis inhibitors, whose immunogenicity enhancement was synchronously attenuated. In contrast, the addition of exogenous iron ions further improved the immunogenicity induced by DHA accompanied by enhanced ER stress and DNA damage. The enhanced immunogenicity could be abated by ER stress and DNA damage inhibitors as well. Finally, DHA activated immunocytes and exhibited excellent anti-cancer efficacy in LLC-bearing mice.

CONCLUSIONS

In summary, the current study demonstrates that DHA triggers ferroptosis, facilitating the ICD of lung cancer thereupon. This work reveals for the first time the effect and underlying mechanism by which DHA induces ICD of cancer cells, providing novel insights into the regulation of the immune microenvironment for cancer immunotherapy by Chinese medicine phytopharmaceuticals.

Claudin-4: A New Molecular Target for Epithelial Cancer Therapy

Claudin-4 (CLDN4) is a key component of tight junctions (TJs) in epithelial cells. CLDN4 is overexpressed in many epithelial malignancies and correlates with cancer progression. Changes in CLDN4 expression have been associated with epigenetic factors (such as hypomethylation of promoter DNA), inflammation associated with infection and cytokines, and growth factor signaling. CLDN4 helps to maintain the tumor microenvironment by forming TJs and acts as a barrier to the entry of anticancer drugs into tumors. Decreased expression of CLDN4 is a potential marker of epithelial-mesenchymal transition (EMT), and decreased epithelial differentiation due to reduced CLDN4 activity is involved in EMT induction. Non-TJ CLDN4 also activates integrin beta 1 and YAP to promote proliferation, EMT, and stemness. These roles in cancer have led to investigations of molecular therapies targeting CLDN4 using anti-CLDN4 extracellular domain antibodies, gene knockdown, clostridium perfringens enterotoxin (CPE), and C-terminus domain of CPE (C-CPE), which have demonstrated the experimental efficacy of this approach. CLDN4 is strongly involved in promoting malignant phenotypes in many epithelial cancers and is regarded as a promising molecular therapeutic target.

4-Phenyl-butyric Acid Inhibits Japanese Encephalitis Virus Replication via Inhibiting Endoplasmic Reticulum Stress Response

Japanese encephalitis virus (JEV) infection causes host endoplasmic reticulum stress (ERS) reaction, and then induces cell apoptosis through the UPR pathway, invading the central nervous system and causing an inflammation storm. The endoplasmic reticulum stress inhibitor, 4-phenyl-butyric acid (4-PBA), has an inhibitory effect on the replication of flavivirus. Here, we studied the effect of 4-PBA on JEV infection both in vitro and vivo. The results showed that 4-PBA treatment could significantly decrease the titer of JEV, inhibit the expression of the JEV NS3 protein (in vitro, p < 0.01) and reduce the positive rate of the JEV E protein (in vivo, p < 0.001). Compared to the control group, 4-PBA treatment can restore the weight of JEV-infected mice, decrease the level of IL-1β in serum and alleviate the abnormalities in brain tissue structure. Endoplasmic reticulum stress test found that the expression level of GRP78 was much lower and activation levels of PERK and IRE1 pathways were reduced in the 4-PBA treatment group. Furthermore, 4-PBA inhibited the UPR pathway activated by NS3, NS4b and NS5 RdRp. The above results indicated that 4-PBA could block JEV replication and inhibit ER stress caused by JEV. Interestingly, 4-PBA could reduce the expression of NS5 by inhibiting transcription (p < 0.001), but had no effect on the expression of NS3 and NS4b. This result may indicate that 4-PBA has antiviral activity independent of the UPR pathway. In summary, the effect of 4-PBA on JEV infection is related to the inhibition of ER stress, and it may be a promising drug for the treatment of Japanese encephalitis.

The neuroprotective effects of targeting key factors of neuronal cell death in neurodegenerative diseases: The role of ER stress, oxidative stress, and neuroinflammation

Neuronal loss is one of the striking causes of various central nervous system (CNS) disorders, including major neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and Amyotrophic lateral sclerosis (ALS). Although these diseases have different features and clinical manifestations, they share some common mechanisms of disease pathology. Progressive regional loss of neurons in patients is responsible for motor, memory, and cognitive dysfunctions, leading to disabilities and death. Neuronal cell death in neurodegenerative diseases is linked to various pathways and conditions. Protein misfolding and aggregation, mitochondrial dysfunction, generation of reactive oxygen species (ROS), and activation of the innate immune response are the most critical hallmarks of most common neurodegenerative diseases. Thus, endoplasmic reticulum (ER) stress, oxidative stress, and neuroinflammation are the major pathological factors of neuronal cell death. Even though the exact mechanisms are not fully discovered, the notable role of mentioned factors in neuronal loss is well known. On this basis, researchers have been prompted to investigate the neuroprotective effects of targeting underlying pathways to determine a promising therapeutic approach to disease treatment. This review provides an overview of the role of ER stress, oxidative stress, and neuroinflammation in neuronal cell death, mainly discussing the neuroprotective effects of targeting pathways or molecules involved in these pathological factors.

Chemical Chaperones to Inhibit Endoplasmic Reticulum Stress: Implications in Diseases

The endoplasmic reticulum (ER) is responsible for structural transformation or folding of de novo proteins for transport to the Golgi. When the folding capacity of the ER is exceeded or excessive accumulation of misfolded proteins occurs, the ER enters a stressed condition (ER stress) and unfolded protein responses (UPR) are triggered in order to rescue cells from the stress. Recovery of ER proceeds toward either survival or cell apoptosis. ER stress is implicated in many pathologies, such as diabetes, cardiovascular diseases, inflammatory diseases, neurodegeneration, and lysosomal storage diseases. As a survival or adaptation mechanism, chaperone molecules are upregulated to manage ER stress. Chemical versions of chaperone have been developed in search of drug candidates for ER stress-related diseases. In this review, synthetic or semi-synthetic chemical chaperones are categorized according to potential therapeutic area and listed along with their chemical structure and activity. Although only a few chemical chaperones have been approved as pharmaceutical drugs, a dramatic increase in literatures over the recent decades indicates enormous amount of efforts paid by many researchers. The efforts warrant clearer understanding of ER stress and the related diseases and consequently will offer a promising drug discovery platform with chaperone activity.

A High-Fiber Diet or Dietary Supplementation of Acetate Attenuate Hyperoxia-Induced Acute Lung Injury

A high fiber diet (HFD) and dietary supplementation with acetate have been reported to have beneficial effects in a variety of diseases. We investigated the effects of a HFD and acetate supplementation on the gut microbiota and hyperoxia-induced acute lung injury (HALI) in mice. Mice were fed a control diet, HFD, or acetate supplementation for three weeks, and their gut microbiome composition, lung tissues, and bronchoalveolar lavage fluid (BALF) were examined after exposure to ambient air or hyperoxia. Both the HFD and acetate supplementation modified the gut microbiota community and increased the proportion of acetate-producing bacteria in mice exposed to hyperoxia. The HFD and acetate supplementation also increased the abundance of Bacteroides acidifaciens and reduced gut dysbiosis according to the ratio of Firmicutes to Bacteroidetes. Compared with hyperoxia-exposed mice fed a control diet, both the HFD and acetate supplementation significantly increased the survival time while reducing the severity of pulmonary edema and the concentrations of protein and inflammatory mediators in BALF. Moreover, the HFD and acetate supplementation reduced the production of free radicals, attenuated NF-κB signaling activation, and decreased apoptosis in the lung tissues. Overall, this study indicates that a HFD or acetate supplementation reduces the severity of HALI through alterations in the gut microbiota to exert anti-inflammatory effects.

Oxygen toxicity: cellular mechanisms in normobaric hyperoxia

In clinical settings, oxygen therapy is administered to preterm neonates and to adults with acute and chronic conditions such as COVID-19, pulmonary fibrosis, sepsis, cardiac arrest, carbon monoxide poisoning, and acute heart failure. In non-clinical settings, divers and astronauts may also receive supplemental oxygen. In addition, under current standard cell culture practices, cells are maintained in atmospheric oxygen, which is several times higher than what most cells experience in vivo. In all the above scenarios, the elevated oxygen levels (hyperoxia) can lead to increased production of reactive oxygen species from mitochondria, NADPH oxidases, and other sources. This can cause cell dysfunction or death. Acute hyperoxia injury impairs various cellular functions, manifesting ultimately as physiological deficits. Chronic hyperoxia, particularly in the neonate, can disrupt development, leading to permanent deficiencies. In this review, we discuss the cellular activities and pathways affected by hyperoxia, as well as strategies that have been developed to ameliorate injury.

Acetate, a gut bacterial product, ameliorates ischemia-reperfusion induced acute lung injury in rats

Recent data suggest that short-chain fatty acids (SCFAs), the major fermentation product from gut microbial degradation of dietary fiber, have protective effects against renal ischemia-reperfusion (IR) injury, colitis, and allergic asthma. However, the effect of SCFAs on acute lung injury (ALI) caused by IR is still unclear. In this study, we examine whether SCFAs have protective effects against IR-induced ALI and explore possible protective mechanisms. IR-induced ALI was established by 40 min ischemia followed by 60 min reperfusion in isolated perfused rat lungs. Rats were randomly assigned to one of six groups: control, control + acetate (400 mg/kg), IR, and IR + acetate at one of three dosages (100, 200, 400 mg/kg). Bronchoalveolar lavage fluids (BALF) and lung tissues were obtained and analyzed at the end of the experiment. In vitro, mouse lung epithelial cells (MLE-12) subjected to hypoxia-reoxygenation (HR) were pretreated with acetate (25 mmol/L) and GPR41 or GPR43 siRNA. Acetate decreased lung weight gain, lung weight/body weight ratios, wet/dry weight ratios, pulmonary artery pressure, and protein concentration of the BALF in a dose-dependent manner for IR-induced ALI. Acetate also significantly inhibited the production of TNF-α, IL-6 and CINC-1 in the BALF. Moreover, acetate treatment restored suppressed IκB-α levels and reduced nuclear NF-κB p65 levels in lung tissues. In addition, acetate mitigated IR-induced apoptosis and tight junction disruption in injured lung tissue. In vitro analyses showed that acetate attenuated NF-κB activation and KC/CXCL-1 levels in MLE-12 cells exposed to HR. The protective effects of acetate in vitro were significantly abrogated by GPR41 or GPR43 siRNA. Acetate ameliorates IR-induced acute lung inflammation and its protective mechanism appears to be via the GPR41/43 signaling pathway. Based on our findings, acetate may provide a novel adjuvant therapeutic approach for IR-induced lung injury.

Qingluo Tongbi Formula Alleviates Hepatotoxicity Induced by Tripterygium wilfordii Hook. F. by Regulating Excessive Mitophagy Through the PERK-ATF4 Pathway

Qingluo Tongbi Formula (QTF) is an empirical formula of Chinese medicine master Zhongying Zhou for the treatment of rheumatoid arthritis. Although including Tripterygium wilfordii Hook. F. (TW), it has not shown liver toxicity in clinical application for many years. Our previous studies have shown that QTF can significantly reduce TW-caused hepatotoxicity, but the mechanism is still unclear. This study aimed to explore the important roles of mitophagy and endoplasmic reticulum stress (ERS) and the relationship between them in QTF in alleviating TW-induced hepatotoxicity. In vivo, C57BL/6J female mice were used to build a model of TW-induced liver toxicity; Then mice were randomly divided into control, TW, TW + RG, TW + PN, TW + SA, TW + BM, and QTF groups. After intragastric administration for 7 days, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) in serum were detected; H and E staining, Oil Red O staining, transmission electron microscopy, Western blotting, and RT-qPCR were used to detect the pathological changes in liver tissue, the levels of ERS and mitophagy related proteins and genes, including GRP78, PERK, DRP1, LC3, etc., In vitro, triptolide (TP), catalpol (CAT), and panax notoginseng saponins (PNS), the main active ingredients of QTF, were selected. The mitophagy inhibitor, ERS inhibitor, and PERK inhibitor were used to further study the relationship between TW-induced ERS and mitophagy in HepaRG cells. The results showed that, QTF reduced excessive mitophagy and ERS in TW-induced hepatotoxicity in C57BL/6J mice, and the attenuating effects of RG and PN in QTF were most obvious, and they also significantly restrained the TW-induced ERS and mitophagy by the PERK-ATF4 pathway. Furthermore, PNS was superior to CAT in inhibiting the expression levels of GRP78, PERK, and ATF4, while CAT was superior to PNS in reversing the expression levels of DRP1, P62, and LC3. The combination of CAT and PNS had the best attenuating effect and the most significant regulation on ERS and mitophagy. In conclusion, QTF can alleviate TW-induced hepatotoxicity by differentially downregulating the PERK-ATF4 pathway and excessive mitophagy by different components.

Endoplasmic Reticulum Stress, Oxidative Stress, and Rheumatic Diseases

Background: The endoplasmic reticulum (ER) is a multi-functional organelle responsible for cellular homeostasis, protein synthesis, folding and secretion. It has been increasingly recognized that the loss of ER homeostasis plays a central role in the development of autoimmune inflammatory disorders, such as rheumatic diseases. Purpose/Main contents: Here, we review current knowledge of the contribution of ER stress to the pathogenesis of rheumatic diseases, with a focus on rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We also review the interplay between protein folding and formation of reactive oxygen species (ROS), where ER stress induces oxidative stress (OS), which further aggravates the accumulation of misfolded proteins and oxidation, in a vicious cycle. Intervention studies targeting ER stress and oxidative stress in the context of rheumatic diseases are also reviewed. Conclusions: Loss of ER homeostasis is a significant factor in the pathogeneses of RA and SLE. Targeting ER stress, unfolded protein response (UPR) pathways and oxidative stress in these diseases both in vitro and in animal models have shown promising results and deserve further investigation.

Aqueous Extract of Descuraniae Semen Attenuates Lipopolysaccharide-Induced Inflammation and Apoptosis by Regulating the Proteasomal Degradation and IRE1α-Dependent Unfolded Protein Response in A549 Cells

Background

Lipopolysaccharide (LPS)-induced acute lung injury (ALI) induces endoplasmic reticulum stress, unfolded protein response (UPR), apoptosis, and inflammation. Inositol-requiring enzyme 1 (IRE1)-α is important for adaptive and apoptotic UPR determination during ER stress. The aqueous extract of Descuraniae Semen (AEDS) is reported to be a safe and effective herb for the treatment of pulmonary edema as it shows anti-inflammatory activities.

Methods

We investigated the effects of AEDS on LPS-induced ALI in A549 cells with respect to the regulation of IRE1α-dependent UPR, proteasomal degradation, mitochondrial membrane potential (MtMP), inflammation, and apoptosis.

Results

AEDS attenuated ER stress by regulating the proteasomal degradation. LPS induced ER stress [binding immunoglobulin protein (BiP), phosphorylated IRE1α, sliced X-box binding protein 1 [XBP1s], phosphorylated cJUN NH2-terminal kinase (pJNK), B-cell lymphoma (Bcl)-2-associated X (Bax), Bcl-2], inflammation (nucleus factor-kappa B (NF-κB) p65 nuclear translocation, nucleus NF-κB, pro-inflammatory cytokines] and apoptosis [C/EBP homologous protein (CHOP), cytochrome c, caspase-8, and caspase-6, and TUNEL] were significantly attenuated by AEDS treatment in A549 cells. AEDS prevents LPS-induced decreased expression of MtMP in A549 cells.

Conclusions

AEDS attenuated LPS-induced inflammation and apoptosis by regulating proteasomal degradation, promoting IRE1α-dependent adaptive UPR, and inhibiting IRE1α-dependent apoptotic UPR. Moreover, IRE1α-dependent UPR plays a pivotal role in the mechanisms of LPS-induced ALI. Based on these findings, AEDS is suggested as a potential therapeutic option for treating patients with ALI.

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.

Involvement of endoplasmic reticulum stress and cell death by synthesized Pa-PDT in oral squamous cell carcinoma cells

Background/purpose

Photodynamic therapy (PDT) is a therapeutic alternative for malignant tumors that uses a photosensitizer. This study examined whether synthesized Pheophorbide a (Pa) -PDT induced apoptosis and autophagy involving endoplasmic reticulum (ER) stress in oral squamous cell carcinoma (OSCC) cells.

Materials and methods

Human OSCC cells were treated with Pa-PDT, and cell proliferation was examined by MTT assay. Apoptosis and autophagy were measured using Western blot analysis. ER stress was examined using RT-PCR and Western blot analysis. In vivo murine OSCC animal model were treated with intratumoral (IT) Pa-PDT, and investigated the therapeutic effect.

Results

Pa-PDT significantly inhibited the proliferation of human OSCC cells in a dose-dependent manner. Pa-PDT induced intrinsic apoptotic cell death and also induced autophagy. Pa-PDT induced ER stress which was observed as demonstrated by the up-regulation of the ER stress marker. Inhibition of the ER stress pathway using 4-phenylbutyric acid (PBA) decreased CHOP and induced inhibition of cell deaths. In addition, the inhibition of ER stress enhanced Pa-PDT mediated autophagy. IT Pa-PDT significantly inhibited the tumor growth and induced apoptosis, autophagy and ER stress in vivo OSCC cells transplanted model.

Conclusion

This study showed that synthesized Pa-PDT induced ER stress trigger apoptosis and apoptotic cell death pathways in OSCC cells. The inhibition of ER stress declined Pa-PDT mediated cytotoxicity with an increase of autophagy. These results may provide Pa-PDT exerts anti-tumor effects through ER stress pathway in OSCC cells and may provide a basis for developing Pa-PDT targeting ER stress as a therapy for OSCC.

Osteoblastic Swedish mutant APP expedites brain deficits by inducing endoplasmic reticulum stress-driven senescence

Patients with Alzheimer’s disease (AD) often have osteoporosis or osteopenia. However, their direct link and relationship remain largely unclear. Previous studies have detected osteoporotic deficits in young adult Tg2576 and TgAPP_swe^OCN mice, which express APP_swe (Swedish mutant) ubiquitously and selectively in osteoblast (OB)-lineage cells. This raises the question, whether osteoblastic APP_swe contributes to AD development. Here, we provide evidence that TgAPP_swe^OCN mice also exhibit AD-relevant brain pathologies and behavior phenotypes. Some brain pathologies include age-dependent and regional-selective increases in glial activation and pro-inflammatory cytokines, which are accompanied by behavioral phenotypes such as anxiety, depression, and altered learning and memory. Further cellular studies suggest that APP_swe, but not APP_wt or APP_lon (London mutant), in OB-lineage cells induces endoplasmic reticulum-stress driven senescence, driving systemic and cortex inflammation as well as behavioral changes in 6-month-old TgAPP_swe^OCN mice. These results therefore reveal an unrecognized function of osteoblastic APP_swe to brain axis in AD development.

Jin-Xiu Pan et al. report that an osteoblast-specific expression of Swedish mutant amyloid precursor protein (APPswe) induces ER stress-driven senescence, leading to systemic inflammation and inflammation in the cortex that drives behavioral changes. The results demonstrate a previously unrecognized function of osteoblastic APPswe to brain axis in AD development.

Long non-coding RNA MALAT1 enhances the protective effect of dexmedetomidine on acute lung injury by sponging miR-135a-5p to downregulate the ratio of X-box binding proteins XBP-1S/XBP-1U

Acute lung injury (ALI) is the common and clinically severe complication. Dexmedetomidine (DEX) can protect against lipopolysaccharide (LPS)-induced ALI through anti-apoptosis, anti-inflammatory and immune regulatory actions. It is well documented that major causes of LPS-induced ALI are endoplasmic reticulum stress (ERS) and abnormally elevated CHOP. Moreover, XBP-1 can enhance CHOP expression. XBP-1S can aggravate ERS and XBP-1 U can repress ERS. By querying Starbase, miR-135a-5p interacts with XBP-1 and lncRNA MALAT1 sponges miR-135a-5p. It has been reported that MALAT1 interference markedly promoted the apoptosis of pulmonary microvascular endothelial cells in ALI rats by activating TLR4/NF-κB pathway. miR-135a-5p inhibitor remarkably alleviated LPS-induced A549 cell injury through suppressing cell apoptosis. In the present work, LPS was dripped into the nasal cavity of SD rats to establish the rat model of ALI and LPS was also applied to stimulate BEAS-2B cells to imitate ALI in vitro. Then, the pathology, lung function indexes, levels of inflammatory factors, apoptosis of lung tissues in SD rats and apoptotic level of BEAS-2B cells were measured, so as to confirm whether upregulation of lncRNA MALAT1 was able to suppress ERS, thus enhancing the protective effect of DEX against ALI. Herein, overexpression of lncRNA MALAT1 strengthened the remission effects of DEX on LPS-triggered ALI, severe pulmonary edema, inflammatory response and cell apoptosis of lung tissues in SD rats and reinforced the anti-apoptosis effect of DEX on LPS-stimulated BEAS-2B cells. Mechanically, lncRNA MALAT1 enhanced the protective effect of DEX against ALI by downregulating the ratio of XBP-1S/XBP-1U to repress ERS.