Research Progress of Endoplasmic Reticulum Stress PERK-eIF2α-AFT4-CHOP Signaling Pathway in Hematological Malignancies / 肿瘤防治研究

The biosynthesis and maturation of proteins are primarily regulated by the endoplasmic reticulum in its physiological state. Thus, the disruption of physiological homeostasis initiates the buildup of unfolded and misfolded proteins in the endoplasmic reticulum, resulting in endoplasmic reticulum stress (ERS) and unfolded protein response (UPR). One of the important pathways by which UPR maintains intracellular homeostasis under ERS is activating protein kinase R-like endoplasmic reticulum kinase (PERK). The activation of the PERK pathway stimulates eukaryotic translation initiation factor 2 subunit-α (eIF2α) phosphorylation and the selective translation of active transcription factor 4 (ATF4), and PERK induces cell apoptosis by directly binding to the promoter of pro-apoptotic transcription factor C/EBP homologous protein (CHOP). This signaling pathway is also one of the important mechanisms by which UPR participates in the regulation of hematological malignancies and immune cells in a tumor microenvironment. This article provides an overview of advancements in research into the PERK-eIF2α-ATF4-CHOP signaling pathway in hematological malignancies and the potential therapeutic benefits of targeting this signaling pathway.

Effects and mechanisms of total flavones of Abelmoschus manihot in attenuating diabetic tubulopathy by targeting endoplasmic reticulum stress-induced cell apoptosis / 中国中药杂志

Renal tubular injury in patients with diabetic kidney disease(DKD) may be accompanied by glomerular and microvascular diseases. It plays a critical role in the progression of renal damage in DKD, and is now known as diabetic tubulopathy(DT). To explore the multi-targeted therapeutic effects and pharmacological mechanisms in vivo of total flavones of Abelmoschus manihot(TFA), an extract from traditional Chinese medicine for treating kidney disease, in attenuating DT, the authors randomly divided all rats into four groups: a normal control group(normal group), a DT model group(model group), a DT model+TFA-treated group(TFA group) and a DT model+rosiglitazone(ROS)-treated group(ROS group). The DT rat model was established based on the DKD rat model by means of integrated measures. After successful modeling, the rats in the four groups were continuously given double-distilled water, TFA suspension, and ROS suspension, respectively by gavage every day. After 6 weeks of treatment, all rats were sacrificed, and the samples of their urine, blood, and kidneys were collected. The effects of TFA and ROS on various indicators related to urine and blood biochemistry, renal tubular injury, renal tubular epithelial cell apoptosis and endoplasmic reticulum stress(ERS), as well as the activation of the protein kinase R-like endoplasmic reticulum kinase(PERK)-eukaryotic translation initiation factor 2α(eIF2α)-activating transcription factor 4(ATF4)-C/EBP homologous protein(CHOP) signaling pathway in the kidney of the DT model rats were investigated. The results indicated that hypertrophy of renal tubular epithelial cells, renal tubular hyperplasia and occlusion, as well as interstitial extracellular matrix and collagen deposition occurred in the DT model rats. Moreover, significant changes were found in the expression degree and the protein expression level of renal tubular injury markers. In addition, there was an abnormal increase in tubular urine proteins. After TFA or ROS treatment, urine protein, the characteristics of renal tubular injury, renal tubular epithelial cell apoptosis and ERS, as well as the activation of the PERK-eIF2α-ATF4-CHOP signaling pathway in the kidney of the DT model rats were improved to varying degrees. Therein, TFA was superior to ROS in affecting the pathological changes in renal tubule/interstitium. In short, with the DT model rats, this study demonstrated that TFA could attenuate DT by multiple targets through inhibiting renal tubular ERS-induced cell apoptosis in vivo, and its effect and mechanism were related to suppressing the activation of the PERK-eIF2α-ATF4-CHOP signaling pathway in the kidney. These findings provided preliminary pharmacological evidence for the application of TFA in the clinical treatment of DT.

Catalpol improves non-alcoholic fatty liver and lipid-lowering mechanism through endoplasmic reticulum stress-mediated PERK-eIF2α signaling pathway / 中华内分泌代谢杂志

Objective:To investigate effect and underlying lipid-lowering mechanisms of catalpol in non-alcoholic fatty liver disease(NAFLD).Methods:In vivo model of NAFLD was established with high-fat diet-fed ICR mice for 8 weeks. Low(50 mg/kg), medium(150 mg/kg), and high(300 mg/kg) doses of catalpol were administered, and the body weight, liver weight, hepatic index, and biochemical parameters of the mice were analyzed. Free fatty acid-induced LO2 in human hepatocytes to establish NAFLD cell model. Quantitative realtime PCR reaction to detect fatty acid synthesis-related gene levels. Western blotting assay was adopted to analyze proteins in the endoplasmic reticulum stress(ERS)-mediated protein kinase RNA-like endoplasmic reticulum kinase(PERK)-eukaryotic translation initiation factor 2α(eIF2α) signaling pathway. Results:Compared with model mice, body weight [(39.43±1.84)g, (34.01±1.83)g, (32.28±1.11)g vs(42.17±1.37)g, all P<0.001], liver weight [(1.03±0.06)g, (0.79±0.05)g, (0.64±0.04)g vs(1.30±0.13)g, P<0.01 or P<0.001], and liver index [(2.60±0.09)%, (2.32±0.09)%, (1.99±0.11)% vs(3.07±0.30)%, P<0.05 or P<0.001] were reduced in low, medium, and high doses of catapol model. Medium and high doses of catalpol diminished total cholesterol, triglyceride, low density lipoprotein-cholesterol, aspartate aminotransferase, and alanine aminotransferase( P<0.01 or P<0.001), increased high density lipoprotein-cholesterol( P<0.01 or P<0.001). In the cell model, elevated levels of both fatty acid synthesis genes and PERK-eIF2α pathway proteins were attenuated by catalase, and this attenuation was reversed by signaling pathway agonists. Conclusion:The Chinese herb catalpol may play a role in improving NALFD by regulating the ERS-mediated PERK-eIF2α signaling pathway.

Aerobic exercise training and in vivo Akt activation counteract cancer cachexia by inducing a hypertrophic Profile through eIF-2α modulation / Treinamento de exercício aeróbico e ativação de Akt in vivo neutralizam a caquexia do câncer induzindo um perfil hipertrófico através da modulação eIF-2α

Cancer cachexia is a multifactorial and devastating syndrome characterized by severe skeletal muscle mass loss and dysfunction. As cachexia still has neither a cure nor an effective treatment, better understanding of skeletal muscle plasticity in the context of cancer is of great importance. Although aerobic exercise training (AET) has been shown as an important complementary therapy for chronic diseases and associated comorbidities, the impact of AET on skeletal muscle mass maintenance during cancer progression has not been well documented yet. Here, we show that previous AET induced a protective mechanism against tumor-induced muscle wasting by modulating the Akt/mTORC1 signaling and eukaryotic initiation factors, specifically eIF2-α. Thereafter, it was determined whether the in vivo Akt activation would induce a hypertrophic profile in cachectic muscles. As observed for the first time, Akt-induced hypertrophy was able and sufficient to either prevent or revert cancer cachexia by modulating both Akt/mTORC1 pathway and the eIF-2α activation, and induced a better muscle functionality. These findings provide evidence that skeletal muscle tissue still preserves hypertrophic potential to be stimulated by either AET or gene therapy to counteract cancer cachexia.

Protective effect of ethyl acetate extract from Bidens bipinnata on hepatocyte damage induced by endoplasmic reticulum stress / 中国中药杂志

To explore the protective effect and mechanism of ethyl acetate extract from Bidens bipinnata on hepatocyte damage induced by endoplasmic reticulum stress. Tunicamycin was used to establish the damage model in L02 cells. Methyl thiazolyl tetrazolium(MTT) colorimetric assay was used to investigate the survival rate of ethyl acetate extract from B. bipinnata in L02 cells injury induced by endoplasmic reticulum stress; the protein expressions of endoplasmic reticulum stress-related molecule glucose regulated protein 78(GRP78), PKR-like ER kinase(PERK), eukaryotic initiation factor-2(eIF2α), activating transcription factor 4(ATF4), C/EBP homologous protein(CHOP), B-cell CLL/lymphoma 2(Bcl-2), Bal-2 associated X apoptosis regulator(Bax) were examined by Wes-tern blot. The expressions of the above proteins were also detected after endoplasmic reticulum stress inhibitor(4-phenyl butyric acid) and CHOP shRNA-mediated knockdowns were added. The expressions of GRP78, PERK, CHOP in L02 cells were observed by immunofluorescence method. The results showed that ethyl acetate extract from B. bipinnata could significantly increase the survival rate of L02 cell injury caused by endoplasmic reticulum stress in a dose and time-dependent manner(P<0.05 or P<0.01). The expression levels of GRP78, PERK, eIF2α, ATF4, CHOP and Bax in the drug treatment groups were significantly down-regulated(P<0.05 or P<0.01), while Bcl-2 was significantly up-regulated(P<0.01). After endoplasmic reticulum stress inhibitor and CHOP shRNA-mediated knockdowns were added, the expression levels of GRP78, PERK, eIF2α, ATF4, CHOP, Bax in the drug treatment groups were significantly down-regulated(P<0.01), whereas Bcl-2 was significantly up-regulated(P<0.01). Immunofluorescence results showed that the expressions of GRP78, PERK, CHOP were consistent with the Western blot method. In conclusion, ethyl acetate extract from B. bipinnata has a significant protective effect on the damage of L02 cells caused by endoplasmic reticulum stress. The mechanism may be related to the inhibition of endoplasmic reticulum stress and the down-regulation of apoptosis in cells through the PERK/eIF2α/ATF4/CHOP signaling pathway.

Effect of endoplasmic reticulum stress on the osteogenic differentiation of periodontal ligament cells under continuous static pressure / 口腔疾病防治

Objective@#To study the effect of continuous static pressure on the endoplasmic reticulum of human periodontal ligament cells (hPDLCs) and the mechanism of osteogenic differentiation.@*Methods@#hPDLCs cultured in vitro were subjected to 1 g/cm 2 of continuous compressive pressure (CCP) by custom-made, round, glass panes for 0, 2, 4, and 6 h, respectively. Alkaline phosphatase staining was used to detect osteogenic differentiation, and real-time quantitative PCR was used to detect the expression of protein kinase receptor-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), and transcription activation factor 4 (ATF-4). The 0 h loading group was the control group.@*Results@#After CCP treatment, the alkaline phosphatase staining of hPDLCs was blue-violet and significantly stronger than that of cells in the control group. The expression levels of PERK and ATF4 in the hPDLCs after CCP treatment were higher than those of cells in the control group (P < 0.05) and increased over time (P < 0.05). The expression of eIF2α was lower in the experimental groups than in the control group (P < 0.05) and decreased over time (P < 0.05).@*Conclusion @#Mechanical stimulation can activate ERS in hPDLCs, leading to enhanced PERK-eIF2α-ATF4 signaling and inducing osteogenic differentiation.

Effect of oxidative stress on periprosthetic osteolysis induced by TCP wear particles in mouse calvaria and its mechanism / 中国应用生理学杂志

OBJECTIVE@#To explore the effect of oxidative stress on periprosthetic osteolysis induced by TCP wear particles in mouse calvaria and its mechanism.@*METHODS@#Thirty-six male ICR mice were randomly divided into three groups (=12):sham group, TCP wear particles (TCP) group and N-acetyl-L-cysteine (NAC) group. Aperiprosthetic osteolysis model in mouse was established by implanting 30 mg of TCP wear particles onto the surface of bilateral parietal bones following removal of the periosteum. On the 2nd day post-operation, NAC (1.0 mg/kg) was locally injected to the calvarium under the periosteum every other day for 2 weeks. Then, all the mice were sacrificed to obtain blood and the calvaria. Periprosthetic osteolysis in the mouse calvaria was observed by tartrate resistant acid phosphatase (TRAP) staining; serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), interleukin-6 (IL-6); total anti-oxidation capacity (T-AOC) and superoxide dismutase (SOD) activity were examined by ELISA and chemical colorimetry, respectively; protein levels of glucose-regulated protein 78 (GRP78), protein kinase R-like ER kinase (PERK), phospho-PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α) and phospho-eIF2α (p-eIF2α) in periprosthetic bone tissue were detected by Western blot.@*RESULTS@#Compared with sham group, serum levels of TNF-α, IL-1β and IL-6, and osteolysis area were increased obviously in TCP group (<0.05), and serum level of T-AOC and SOD activity were decreased significantly in TCP group (<0.05), GRP78 expression, the ratio of p-PERK and PERK, p-eIF2α and eIF2α in the mouse calvaria of TCP group were up-regulated markedly. Compared with TCP group, serum levels of TNF-α, IL-1β and IL-6, and osteolysis area were decreased markedly in NAC group (<0.05), serum level of T-AOC and SOD activity were increased obviously in NAC group (<0.05), and GRP78 expression, the ratio of p-PERK/PERK and p-eIF2α/eIF2α were obviously down-regulated.@*CONCLUSIONS@#Inhibition of oxidative stress can prevent periprosthetic osteolysis induced by TCP wear particles, which may be mediated by inactivation of PERK/eIF2α signaling pathway.

Effects of 1,25-(OH)2D3on endoplasmic reticulum stress and ATG12 expression in pulmonary fibrosis / 医学研究生学报

Objective It is not yet clear whether 1,25-(OH)2D3acts on endoplasmic reticulum stress(ERS)and autoph-agy in pulmonary fibrosis(PF).This study aimed to investigate the roles of ERS and autophagy in the development and progression of pulmonary fibrosis in rats and the effects of 1,25-(OH)2D3on the expressions of ERS-related molecules and autophagy-related gene 12 (ATG12). Methods Ninety male SD rats were randomly divided into a control, a PF model and a treatment group of equal number.Bleomycin was injected into the tracheas of the latter two groups of rats to induce PF.On the second day after modeling, the rats of the treatment group were injected intraperitoneally with 1,25-(OH)2D3at 2 μg/kg,those of the PF model group with 1,25-(OH)2D3solvent at 200 μL,and those of the control group with iso-tonic saline at 200 μL,all once 2 days.Then the mRNA expressions of PERK,ATF4 and ATG12 were measured by real-time PCR and the protein expressions of PERK and ATF4 detected by immunohistochemistry. Results At 14, 21 and 28 days after treat-ment,the expression levels of PERK were significantly higher in the PF model group(2.30±0.19, 3.59±0.27, and 4.63±0.19) and treatment group(1.44±0.34,1.92±0.17,and 2.52±0.15)than in the control(1.01±0.23,1.05±0.09,and 1.04±0.08)(P<0.05), and so were the expression levels of ATF4 in the PF models(2.10±0.12, 3.91±0.14, and 6.20±0.28)and treated rats (1.49±0.27,2.52±0.42, and 4.02±0.31)than in the controls(1.04±0.07,1.05±0.08,and 1.03±0.10)(P<0.05).Compared with the control group,the PF model and treatment groups showed markedly increased expression levels of ATG 12 mRNA at 14 days (P<0.05), but decreased at 21 and 28 days(P<0.05).Both the expressions of PERK and ATF4 proteins were remarkably higher in the model and treatment groups than in the control at 14,21 and 28 days(P<0.05), increasing in a time-dependent manner. Conclusion By suppressing the PERK -eIF2α-ATF4 signaling pathway,1,25-(OH)2D3inhibits the development and progression of pulmonary fibrosis.

Role of PERK/eIF2α signaling pathway in systemic damages resulted from fluorosis / 中华地方病学杂志

Fluoride can cause phrenology and non-phrenology damage,but the mechanisms were unclear.It is reported that fluoride can decrease protein synthesis and induce cell apoptosis,leading to extensive systemic damage.Many studies have found that the mechanism is closely associated with endoplasmic reticulum stress.Protein kinase receptor-like ER kinase/Eukaryotic translation initiation factor 2α (PERK/eIF2α) signaling pathway is the first activation pathway when endoplasmic reticulum stress occurs which may play an important role in the pathogenesis of fluorosis.This present paper is focused on the role of PERK/elF2α signaling pathway-related factors in the systemic and organism damages resulted from fluorosis,which may provide new ideas in mechanism and prevention of fluorosis.

Laxative effects of Liriope platyphylla are tightly correlated with suppression of endoplasmic reticulum stress in loperamide-induced constipation of SD rats / 한국실험동물학회지

A dysfunction of endoplasmic reticulum (ER) stress response can result in various diseases, including cancer, inflammation, diabetes and neurodegenerative disorders. To investigate whether ER stress response can play an essential role in the induction and treatment of chronic constipation, alterations in the key parameters for ER stress were measured in loperamide (Lop) induced constipation Sprague Dawley (SD) rats treated with aqueous extracts of Liriope platyphylla (AEtLP), which has been shown to have a laxative effect. Symptoms of chronic constipation including alteration of stool parameters and the transverse colon's structure were successfully induced by Lop treatment. Laxative effects such as enhancement of stools parameters, recovery of the mucosa thickness, increased muscle thickness and recovery of flat luminal surface were also observed in the Lop+AEtLP treated group. Furthermore, enhancement of eukaryotic initiation factor 2 alpha (eIF2α) phosphorylation and inositol-requiring enzyme 1 beta (IRE1β) expression, key indicators for ER stress, that were observed in the Lop+vehicle treated group were significantly recovered in the Lop+AEtLP treated group, although the phosphorylation level of c-Jun N-terminal protein kinase (JNK) remained constant. Moreover, alterations in the transcription level of the marker genes X-box binding protein 1 (XBP-1) and growth arrest and DNA damage-inducible protein (GADD34) were similar to those of eIF2α and IRE1β. However, their level was slightly or completely recovered after AEtLP treatment. Overall, this study provides the first evidence that ER stress response may be tightly correlated with chronic constipation induced by Lop treatment, as well as the laxative effects of AEtLP.

Role of PERK/eIF2α/CHOP Endoplasmic Reticulum Stress Pathway in Oxidized Low-density Lipoprotein Mediated Induction of Endothelial Apoptosis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>PERK/eIF2α/CHOP is a major signaling pathway mediating endoplasmic reticulum (ER) stress related with atherosclerosis. Oxidized LDL (ox-LDL) also induces endothelial apoptosis and plays a vital role in the initiation and progression of atherosclerosis. The present study was conducted to explore the regulatory effect of ox-LDL on PERK/eIF2α/CHOP signaling pathway in vascular endothelial cells.</p><p><b>METHODS</b>The effects of ox-LDL on PERK and p-eIF2α protein expression of primary human umbilical vein endothelial cells (HUVECs) were investigated by Western blot analysis. PERK gene silencing and selective eIF2α phosphatase inhibitor, salubrinal were used to inhibit the process of ox-LDL induced endothelial cell apoptosis, caspase-3 activity, and CHOP mRNA level.</p><p><b>RESULTS</b>Ox-LDL treatment significantly increased the expression of PERK, PERK-mediated inactivation of eIF2α phosphorylation, and the expression of CHOP, as well as the caspase-3 activity and apoptosis. The effects of ox-LDL were markedly decreased by knocking down PERK with stable transduction of lentiviral shRNA or by selective eIF2α phosphatase inhibitor, salubrinal.</p><p><b>CONCLUSION</b>This study provides the first evidence that ox-LDL induces apoptosis in vascular endothelial cells mediated largely via the PERK/eIF2α/CHOP ER-stress pathway. It adds new insights into the molecular mechanisms underlying the pathogenesis and progression of atherosclerosis.</p>

5-Hydroxymethylfurfural protects against ER stress-induced apoptosis in GalN/TNF-α-injured L02 hepatocytes through regulating the PERK-eIF2α signaling pathway / 中国天然药物

5-Hydroxymethylfurfural (5-HMF), a water-soluble compound extracted from wine-processed Fructus corni, is a novel hepatic protectant for treating acute liver injury. The present study was designed to investigate the protective effect of 5-HMF in human L02 hepatocytes injured by D-galactosamine (GalN) and tumor necrosis factor-α (TNF-α) in vitro and to explore the underlying mechanisms of action. Our results showed that 5-HMF caused significant increase in the viability of L02 cells injured by GalN/TNF-α, in accordance with a dose-dependent decrease in apoptotic cell death confirmed by morphological and flow cytometric analyses. Based on immunofluorescence and Western blot assays, we found that GalN/TNF-α induced ER stress in the cells, as indicated by the disturbance of intracellular Ca(2+) concentration, the activation of protein kinase RNA (PKR)-like ER kinase (PERK), phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α), and expression of ATF4 and CHOP proteins, which was reversed by 5-HMF pre-treatment in a dose-dependent manner. The anti-apoptotic effect of 5-HMF was further evidenced by balancing the expression of Bcl-2 family members. In addition, the knockdown of PERK suppressed the expression of phospho-PERK, phospho-eIF2α, ATF4, and CHOP, resulting in a significant decrease in cell apoptosis after the treatment with GalN/TNF-α. 5-HMF could enhance the effects of PERK knockdown, protecting the cells against the GalN/TNF-α insult. In conclusion, these findings demonstrate that 5-HMF can effectively protect GalN/TNF-α-injured L02 hepatocytes against ER stress-induced apoptosis through the regulation of the PERK-eIF2α signaling pathway, suggesting that it is a possible candidate for liver disease therapy.