Dibromoacetonitrile induced autophagy by mediating the PERK signalling pathway and ROS interaction in HT22 cell.

Dibromoacetonitrile (DBAN) is a high-risk haloacetonitrile (HAN) generated as a byproduct of chloramine disinfection in drinking water. DBAN-induced neurotoxicity in mouse hippocampal neuronal cells (HT22) and mammals was observed to be related to reactive oxygen species (ROS). ROS, endoplasmic reticulum stress (ERS) and autophagy play crucial roles in regulating a variety of cellular processes. However, whether ERS and autophagy are associated with HAN-responsive apoptosis remains unclear. This study indicated that DBAN (10 µM, 24 h) activated the ERS protein kinase like endoplasmic reticulum kinase (PERK) signaling pathway. The ERS inhibitor 4-phenylbutyric acid (4-PBA) reversed DBAN-inhibited cell viability and alleviated DBAN-induced apoptosis in HT22 cell, indicating that activation of the ERS PERK pathway mediates DBAN induced cytotoxicity. Moreover, DBAN activated autophagy. The autophagy inhibitor 3-methyladenine(3-MA) reversed DBAN-inhibited cell viability and alleviated DBAN-induced apoptosis in HT22 cell, suggesting that autophagy activation mediates DBAN-induced cell toxicity. Notably, the results showed that 4-PBA inhibited DBAN-activated autophagy, demonstrating that ERS-PERK promotes DBAN-induced cellular autophagy. Pretreatment with antioxidant N-acetylcysteine (NAC) inhibited the increase in ROS production and the activation of ERS, and protected cells from toxicity. Furthermore, 4-PBA pretreatment reduced the increase in ROS production, indicating that the ROS and PERK promote each other and form a positive feedback loop. ROS also promoted DBAN-induced autophagy. In summary, our findings indicate that DBAN induced autophagy by mediating the PERK signalling pathway and ROS interaction, leading to HT22 cell damage. Accordingly, targeting these pathogenic mechanisms may provide a potential target and theoretical basis for preventing and improving HAN-induced neurotoxicity.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway.

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Ufl1 deficiency causes kidney atrophy associated with disruption of endoplasmic reticulum homeostasis.

The UFMylation modification is a novel ubiquitin-like conjugation system, consisting of UBA5 (E1), UFC1 (E2), UFL1 (E3), and the conjugating molecule UFM1. Deficiency in this modification leads to embryonic lethality in mice and diseases in humans. However, the function of UFL1 is poorly characterized. Studies on Ufl1 conditional knockout mice have demonstrated that the deletion of Ufl1 in cardiomyocytes and in intestinal epithelial cells causes heart failure and increases susceptibility to experimentally induced colitis, respectively, suggesting an essential role of UFL1 in the maintenance of the homeostasis in these organs. Yet, its physiological function in other tissues and organs remains completely unknown. In this study, we generate the nephron tubules specific Ufl1 knockout mice and find that the absence of Ufl1 in renal tubular results in kidney atrophy and interstitial fibrosis. In addition, Ufl1 deficiency causes the activation of unfolded protein response and cell apoptosis, which may be responsible for the kidney atrophy and interstitial fibrosis. Collectively, our results have demonstrated the crucial role of UFL1 in regulating kidney function and maintenance of endoplasmic reticulum homeostasis, providing another layer of understanding kidney atrophy.

Dendrobium nobile Lindl alkaloid and metformin ameliorate cognitive dysfunction in senescence-accelerated mice via suppression of endoplasmic reticulum stress.

The senescence-accelerated mouse prone 8 (SAMP8) mice have many pathological features of Alzheimer's disease (AD) with aging. We previously reported that Dendrobium nobile Lindl alkaloid (DNLA) effectively improved cognitive deficits in multiple Alzheimer's disease (AD) models. This study further used SAMP8 mice to study the anti-aging effects of DNLA, focusing on endoplasmic reticulum (ER) stress. DNLA and metformin were orally administered to SAMP8 mice starting at 4-month of age for 6 months. Behavioral tests were performed in 10-month-old SAMP8 mice and age-matched SAMR1 control mice. At the end of experiment, neuron damage was evaluated by histology and transmission electron microscopy. ER stress-related proteins were analyzed with Western-blot. DNLA improved learning and memory impairments, reduced the loss of neurons and Nissl bodies in the hippocampus and cortex. DNLA ameliorated ER dilation and swelling in the hippocampal neurons. DNLA down-regulated the protein kinase RNA-like endoplasmic reticulum kinase (PERK) signaling pathway, decreased calpain 1, GSK-3ß and Cdk5 activities and the Tau hyper-phosphorylation. The effects of DNLA were comparable to metformin. In summary, DNLA was effective in improving cognitive deficits in aged SAMP8 mice, possibly via suppression of ER stress-related PERK signaling pathway, sequential inhibition of calpain 1, GSK-3ß and Cdk5 activities, and eventually reducing the hyper-phosphorylation of Tau.

The active nuclear form of SREBP1 amplifies ER stress and autophagy via regulation of PERK.

Endoplasmic reticulum (ER) stress and autophagy dysfunction contribute to the establishment and progression of diverse pathologies. Proteolytic activation of the transcription factor nSREBP1 is induced under ER stress; however, little is known about how SREBP1 and its nuclear active form nSREBP1 influence autophagy and unfolded protein response (UPR) activation in osteosarcoma cells. Our research focused on the effect of SREBP1/nSREBP1 upon apoptosis and autophagy during ER stress and the molecular mechanisms involved. Here, we showed that nSREBP1 binds to the promoter of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and then regulates ER stress, cell growth, cell apoptosis, and autophagy through the PERK signaling pathway. nSREBP1 increased PERK gene expression and phosphorylation. nSREBP1 was further demonstrated to activate ER stress response through stimulatory effects on PERK signaling. Overexpression of SREBP1 increased its cleavage and release of nSREBP1; therefore, the effect of SREBP1 is achieved through the enhancement of the expression of nSREBP1. Overexpression of SREBP1/nSREBP1 amplifies PERK-associated cell cycle stagnation with G1 phase arresting, S phase reducing, and G2-M phase delaying. LV-SREBP1/nSREBP1 can also bolster PERK's ER stress-associated pro-apoptotic effects. LV-SREBP1/nSREBP1 and LV-PERK can activate autophagy in ER stress response, along with the overexpression of SREBP1/nSREBP1 and PERK. This resulted in amplification of PERK-related changes to cell proliferation and ER stress-mediated apoptosis and autophagy, with the biological effect of nSREBP1 relying on PERK, which makes up one of the three branches of the UPR signaling pathway. This study reveals important roles for SREBP1/nSREBP1 in PERK signaling under ER stress. Furthermore, nSREBP1, the nuclear active form of SREBP1, is able to robustly augment the effects of PERK. Description of the link between PERK and SREBP1/nSREBP1 function offers an improved understanding of the ER stress response and insight into the biological function of SREBP1/nSREBP1.

Effect of nickel sulfate on cell survival rate and related apoptotic proteins in human normal hepatocytes / 中国职业医学

OBJECTIVE: To investigate the effect of nickel sulfate on cell survival rate and apoptosis of normal human liver L02 cells. METHODS: i) L02 cells in logarithmic growth phase were divided into 9 groups, each with 6 wells. L02 cells in each group were treated with 0, 100, 200, 300, 400, 500, 600, 700 and 800 μmol/L nickel sulfate. The survival rate of L02 cells was determined by CCK-8 assay after cells were treated for 0, 6, 12, 24, 48 and 72 hours. The nickel sulfate exposure dose and exposure time for subsequent experiments were selected based on the results of CCK-8 assay. ii) L02 cells in logarithmic growth phase were divided into control group, 100 and 300 μmol/L dose groups, and were exposed to 0, 100 and 300 μmol/L nickel sulfate for 12 hours, respectively. Western blot was used to detect the relative protein expression of B cell lymphoma/leukemia 2(BCL-2), Bcl-2 related protein X(BAX), caspase-3, phosphorylated RNA-dependent protein kinase-like endoplasmic reticulum kinase(p-PERK), phosphorylated eukaryotic translation initiation factor 2α(p-eIF2α), CCAAT/enhancer-binding protein homologous protein(CHOP) and glucose regulatory protein 78(GRP78). RESULTS: i) After treatment with nickel sulfate, the survival rate of cells decreased with the increase of dose and the prolongation of exposure time(all P values were <0.01). According to the half inhibitory concentration of nickel sulfate on L02 cells, the nickel sulfate exposure time in subsequent experiments was selected as 12 hours, and the exposure concentration was 100 and 300 μmol/L. ii) Compared with the control group, the relative expression of BCL-2 protein in L02 cells in the 100 and 300 μmol/L dose groups decreased(all P values were <0.05), while the relative protein expression of BAX, caspase-3 protein and ratio BAX/BCL-2 increased(all P values were <0.05). Compared with 100 μmol/L dose group, the relative expression of BCL-2 protein in L02 cells of 300 μmol/L dose group decreased(P<0.05), while the relative expression of BAX and caspase-3 protein and the ratio of BAX/BCL-2 increased(all P values were <0.05). Compared with the control group, the relative expression levels of p-PERK, p-eIF2α, CHOP and GRP78 protein in L02 cells were increased in 100 and 300 μmol/L dose groups(all P values were P<0.05). Compared with 100 μmol/L dose group, the relative expression levels of p-eIF2α, CHOP and GRP78 protein in 300 μmol/L dose group were increased(all P values were<0.05).CONCLUSION: Nickel sulfate can regulate the expression of apoptosis related proteins and PERK signaling pathway related proteins in L02 cells, aggravate apoptosis of L02 cells and decrease the cell survival rate.

Prosurvival roles mediated by the PERK signaling pathway effectively prevent excessive endoplasmic reticulum stress-induced skeletal muscle loss during high-stress conditions of hibernation.

Stress conditions like hypoxia, ischemia, and ischemia/reperfusion can trigger excessive endoplasmic reticulum stress (ERS), which can lead to cell apoptosis-induced skeletal muscle atrophy in non-hibernators. However, although hibernators experience multiple stress conditions during hibernation, their skeletal muscles appear to be well protected. We hypothesize that hibernators effectively avoid cell apoptosis, at least partially, by controlling ERS level. Here, we focused on the potential occurrence of ERS and how hibernators cope with it during different hibernation states. Results indicated that the protein expression levels of glucose-regulated protein 78 (GRP78), phosphorylated PKR-like ER protein kinase, phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α), and activating transcription factor 4 were significantly increased during hibernation, but primarily recovered in posthibernation. In the torpor-arousal cycle, the expression levels of the above indicators were lower during inter-bout arousal (IBA) than that during late torpor (LT). However, there was no change in C/EBP homologous protein expression and no apoptosis in skeletal muscles during the different hibernation states. In conclusion, the upregulation of p-eIF2α and GRP78 were identified as two crucial mechanisms mediated by the PERK signaling pathway to alleviate elevated ERS. The downregulation of ERS during IBA may be a unique countermeasure for hibernating squirrels to prevent excessive ERS. Thus, these special anti-excessive ERS abilities of ground squirrels contribute to the prevention of skeletal muscle cell apoptosis during hibernation.

The role of PERK and IRE1 signaling pathways in excessive fluoride mediated impairment of lymphocytes in rats' spleen in vivo and in vitro.

Fluoride is capable of inducing immunotoxicity, but its molecular mechanisms remain elusive. This study aimed to explore the roles of Protein kinase receptor-like ER kinase (PERK) and inositol requiring enzyme 1 (IRE1) signaling pathways in excessive fluoride-induced immunotoxicity, focusing on the regulatory roles of these two pathways in cell division and apoptosis. Firstly, we assessed the changes in cell division and apoptosis in rats exposed to 0, 50, or 100 mg/L fluoride, and detected the expression of PERK and IRE1 signaling-related proteins in spleen. Additionally, to validate the role of these two pathways, we evaluated the changes in cell division and apoptosis of primary lymphocytes from rat's spleen to 4 mM fluoride after knockdown of PERK and IRE1 in vitro. In vivo results confirmed that fluoride inhibited cell division, promoted the apoptosis and resulted in histological and ultrastructural abnormalities of rat spleen. In addition, fluoride induced activation of the PERK and IRE1 signalings and the associated apoptosis. Moreover, the in vitro results further verified the findings in vivo that fluoride activated these two signalings in B lymphocytes. Importantly, after knockdown of PERK and IRE1 in lymphocytes, the cell division ability was restored, and apoptosis decreased in fluoride-treated lymphocytes; the results correlated well with the expression of PERK and IRE1 signaling-related proteins, thus confirming the pivotal role of these pathways in immunosuppression by excessive fluoride. This study indicates that the mechanisms underlying the deleterious effects of fluoride on immune system are related to activation of the PERK and IRE1 signaling pathways.

Hydroxycamptothecin Prevents Fibrotic Pathways in Fibroblasts In Vitro.

Peritendinous fibrosis, which leads to impaired tendon function, is a clinical problem worldwide, and it is urgent to explore potential ways to reduce the formation of peritendinous adhesion. Several studies have demonstrated the biological roles of hydroxycamptothecin (HCPT) in inhibiting fibrosis in different tissues. In this study, we investigated whether HCPT could inhibit tendon fibrosis in vitro. Our results revealed that HCPT inhibited transforming growth factor (TGF)-ß1-induced cell viability of human fibroblasts, decreased excessive cell hyperproliferation and promoted fibroblasts apoptosis. In addition, HCPT treatment also inhibited expression of fibrosis genes COL3A1 and α-smooth muscle actin (α-SMA). In terms of mechanism, we pretreated fibroblasts with the endoplasmic reticulum stress (ER) inhibitor salubrinal and RNA-dependent protein kinase-like ER kinase (PERK) short hairpin RNA, these treatments abolished the inhibitory effects of HCPT on fibrosis, thereby suggesting that HCPT's inhibition of TGF-ß1-induced tendon fibrosis might be mediated by the PERK signaling pathway in vitro. In conclusion, our results suggested that HCPT had protective effects on peritendinous tissue fibrosis and might be promising in future clinical applications. © 2019 IUBMB Life, 71(5):653-662, 2019.

Endogenous sulfur dioxide regulates hippocampal neuron apoptosis in developing epileptic rats and is associated with the PERK signaling pathway.

Epilepsy is among the most common neurological diseases in children. Recurrent seizures can result in hippocampal damage and seriously impair learning and memory functions in children. However, the mechanisms underlying epilepsy-related brain injury are unclear. Neuronal apoptosis is among the most common neuropathological manifestations of brain injury. Endogenous sulfur dioxide (SO2) has been shown to be involved in seizures and related neuron apoptosis. However, the role of endogenous SO2 in epilepsy remains unclear. This study assessed whether endogenous SO2 is involved in epilepsy and its underlying mechanisms. Using a rat epilepsy model induced by an intraperitoneal injection of kainic acid (KA), we found that hippocampal neuron apoptosis was induced in epileptic rats, and the SO2 content and aspartate aminotransferase (AAT) activity in the plasma were increased compared to those in the control group. However, the inhibition of SO2 production by l-aspartate-ß-hydroxamate (HDX) can subvert this response 72h after an epileptic seizure. No difference in apoptosis was observed 7 d after the epileptic seizure in the KA and KA+HDX groups. The protein expression levels of AAT2, glucose-regulated protein 78 (GRP78), pancreatic eIF2 kinase-like ER kinase (PERK) and phospho-PERK (p-PERK) were remarkably elevated in the hippocampi of the epileptic rats, while the HDX treatment was capable of reversing this process 7 d after the epileptic seizure. These results indicate that the inhibition of endogenous SO2 production can alleviate neuronal apoptosis and is associated with the PERK signaling pathway during the initial stages after epileptic seizure, but inhibiting SO2 production only delayed the occurrence of apoptosis and did not prevent neuronal apoptosis in the epileptic rats.

Research progress of PERK signaling pathway under endoplasmic reticulum stress in tumor / 实用肿瘤学杂志

During growth,invasion and metastasis,tumor cells undergo endoplasmic reticulum stress(ERS)under hypoxia,hy-poglycemia and other environmental stresses.In response to ERS,tumor cells induce unfolded protein response(UPR).PERK signa-ling pathway as a key pathway to activate UPR can promote survival,proliferation,invasion and protection of tumor cells by increasing tumor tolerance to adverse microenvironment,inducting angiogenesis,inducing autophagosome formation and activating apoptotic signal molecules.Tumor cells are induced apoptotic and autophagic death when UPR reaches a certain extent.

PERK Signal-Modulated Protein Translation Promotes the Survivability of Dengue 2 Virus-Infected Mosquito Cells and Extends Viral Replication.

Survival of mosquitoes from dengue virus (DENV) infection is a prerequisite of viral transmission to the host. This study aimed to see how mosquito cells can survive the infection during prosperous replication of the virus. In C6/36 cells, global protein translation was shut down after infection by DENV type 2 (DENV2). However, it returned to a normal level when infected cells were treated with an inhibitor of the protein kinase RNA (PKR)-like ER kinase (PERK) signaling pathway. Based on a 7-Methylguanosine 5'-triphosphate (m7GTP) pull-down assay, the eukaryotic translation initiation factor 4F (eIF4F) complex was also identified in DENV2-infected cells. This suggests that most mosquito proteins are synthesized via canonical cap-dependent translation. When the PERK signal pathway was inhibited, both accumulation of reactive oxygen species and changes in the mitochondrial membrane potential increased. This suggested that ER stress response was alleviated through the PERK-mediated shutdown of global proteins in DENV2-infected C6/36 cells. In the meantime, the activities of caspases-9 and -3 and the apoptosis-related cell death rate increased in C6/36 cells with PERK inhibition. This reflected that the PERK-signaling pathway is involved in determining cell survival, presumably by reducing DENV2-induced ER stress. Looking at the PERK downstream target, α-subunit of eukaryotic initiation factor 2 (eIF2α), an increased phosphorylation status was only shown in infected C6/36 cells. This indicated that recruitment of ribosome binding to the mRNA 5'-cap structure could have been impaired in cap-dependent translation. It turned out that shutdown of cellular protein translation resulted in a pro-survival effect on mosquito cells in response to DENV2 infection. As synthesis of viral proteins was not affected by the PERK signal pathway, an alternate mode other than cap-dependent translation may be utilized. This finding provides insights into elucidating how the PERK signal pathway modulates dynamic translation of proteins and helps mosquito cells survive continuous replication of the DENV2. It was ecologically important for virus amplification in mosquitoes and transmission to humans.