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.

Role of endoplasmic reticulum stress response in regulation of adipose tissue metabolism / 生理学报

In eukaryotic cells, the endoplasmic reticulum (ER) is the key quality control organelle for cellular protein synthesis and processing. It also serves as an important site for Ca

Glutamine protects intestine against ischemia-reperfusion injury by alleviating endoplasmic reticulum stress induced apoptosis in rats

Abstract Purpose Glutamine, as an essential part of enteral nutrition and parenteral nutrition agent, has been widely recognized to be a kind of important intestinal mucosa protectant in clinical practice and experimental research. However, the mechanisms of its protective effects are still not fully understand. Consequently, this study aimed to explore the potential mechanism of glutamine on ischemia-reperfusion (I/R) injury induced endoplasmic reticulum (ER) stress in intestine. Methods An experimental model of intestinal I/R in rats was established by 1 hour occlusion of the superior mesenteric artery followed by 3 hours of reperfusion. Morphologic changes of intestinal mucosa, apoptosis of epithelial cells, and expression of intestinal Grp78, Gadd153, Caspase-12, ATF4, PERK phosphorylation (P-PERK) and elF2αphosphorylation(P-elF2α) were determined. Results After I/R, the apoptotic index of intestinal mucosa epithelial cells observably increased with notable necrosis of intestinal mucosa, and the expressions of Grp78, Gadd153, Caspase-12, ATF4, P-PERK and P-elF2αall were increased. However, treatment with glutamine could significantly relieve intestinal I/R injury and apoptosis index. Moreover, glutamine could clearly up-regulate the expression of Grp78, restrain P-PERK and P-elF2α, and reduce ATF4, Gadd153 and Caspase-12 expressions. Conclusion Glutamine may be involved in alleviating ER stress induced intestinal mucosa cells apoptosis.

A case report of EIF2AK3-related Wolcott-Rallison syndrome and literature review / 中国当代儿科杂志

The patient was a female infant aged 1 month and 29 days. She was admitted to the hospital due to convulsions for 6 days and increased blood glucose level for 5 days. She had unstable blood glucose levels. The level of glycosylated hemoglobin was too high to measure. Urine glucose was positive (+ - ++++). The levels of fasting C-peptide and insulin were 0.19 ng/mL and 11.68 μIU/mL respectively. High-throughput sequencing of the genetic endocrine disease gene Panel (412 detected genes, including 49 known diabetes-related genes) showed that the EIF2AK3 gene in the infant had two novel compound heterozygous mutations, c.2731_2732delAG and c.2980G>A, both of which were located in the kinase domain. The infant was diagnosed with Wolcott-Rallison syndrome (WRS). As a rare autosomal recessive disease, WRS is characterized by neonatal diabetes, multiple epiphyseal dysphasia and liver disease. Neonatal diabetes is a prerequisite for the diagnosis of WRS. The EIF2AK3 gene is the pathogenic gene of WRS.

Coxsackievirus B3 Infection Triggers Autophagy through 3 Pathways of Endoplasmic Reticulum Stress / 生物医学与环境科学（英文）

OBJECTIVE@#Autophagy is a highly conserved intracellular degradation pathway. Many picornaviruses induce autophagy to benefit viral replication, but an understanding of how autophagy occurs remains incomplete. In this study, we explored whether coxsackievirus B3 (CVB3) infection induced autophagy through endoplasmic reticulum (ER) stress.@*METHODS@#In CVB3-infected HeLa cells, the specific molecules of ER stress and autophagy were detected using Western blotting, reverse transcription polymerase chain reaction (RT-PCR), and confocal microscopy. Then PKR-like ER protein kinase (PERK) inhibitor, inositol-requiring protein-1 (IRE1) inhibitor, or activating transcription factor-6 (ATF6) inhibitor worked on CVB3-infected cells, their effect on autophagy was assessed by Western blotting for detecting microtubule-associated protein light chain 3 (LC3).@*RESULTS@#CVB3 infection induced ER stress, and ER stress sensors PERK/eIF2α, IRE1/XBP1, and ATF6 were activated. CVB3 infection increased the accumulation of green fluorescent protein (GFP)-LC3 punctuation and induced the conversion from LC3-I to phosphatidylethanolamine-conjugated LC3-1 (LC3-II). CVB3 infection still decreased the expression of mammalian target of rapamycin (mTOR) and p-mTOR. Inhibition of PERK, IRE1, or ATF6 significantly decreased the ratio of LC3-II to LC3-I in CVB3-infected HeLa cells.@*CONCLUSION@#CVB3 infection induced autophagy through ER stress in HeLa cells, and PERK, IRE1, and ATF6a pathways participated in the regulation of autophagy. Our data suggested that ER stress may inhibit mTOR signaling pathway to induce autophagy during CVB3 infection.

Long non-coding RNA HOTAIR promotes UVB-induced apoptosis and inflammatory injury by up-regulation of PKR in keratinocytes

Excessive exposure to ultraviolet (UV) rays can cause damage of the skin and may induce cancer, immunosuppression, photoaging, and inflammation. The long non-coding RNA (lncRNA) HOX antisense intergenic RNA (HOTAIR) is involved in multiple human biological processes. However, its role in UVB-induced keratinocyte injury is unclear. This study was performed to investigate the effects of HOTAIR in UVB-induced apoptosis and inflammatory injury in human keratinocytes (HaCaT cells). Quantitative real-time polymerase chain reaction was performed to analyze the expression levels of HOTAIR, PKR, TNF-α, and IL-6. Cell viability was measured using trypan blue exclusion method and cell apoptosis using flow cytometry and western blot. ELISA was used to measure the concentrations of TNF-α and IL-6. Western blot was used to measure the expression of PKR, apoptosis-related proteins, and PI3K/AKT and NF-κB pathway proteins. UVB induced HaCaT cell injury by inhibiting cell viability and promoting cell apoptosis and expressions of IL-6 and TNF-α. UVB also promoted the expression of HOTAIR. HOTAIR suppression increased cell viability and decreased apoptosis and expression of inflammatory factors in UVB-treated cells. HOTAIR also promoted the expression of PKR. Overexpression of HOTAIR decreased cell viability and increased cell apoptosis and expression of inflammatory factors in UVB-treated cells by upregulating PKR. Overexpression of PKR decreased cell viability and promoted cell apoptosis in UVB-treated cells. Overexpression of PKR activated PI3K/AKT and NF-κB pathways. Our findings identified an essential role of HOTAIR in promoting UVB-induced apoptosis and inflammatory injury by up-regulating PKR in keratinocytes.

Homocysteine activates T cells by enhancing endoplasmic reticulum-mitochondria coupling and increasing mitochondrial respiration

Hyperhomocysteinemia (HHcy) accelerates atherosclerosis by increasing proliferation and stimulating cytokine secretion in T cells. However, whether homocysteine (Hcy)-mediated T cell activation is associated with metabolic reprogramming is unclear. Here, our in vivo and in vitro studies showed that Hcy-stimulated splenic T-cell activation in mice was accompanied by increased levels of mitochondrial reactive oxygen species (ROS) and calcium, mitochondrial mass and respiration. Inhibiting mitochondrial ROS production and calcium signals or blocking mitochondrial respiration largely blunted Hcy-induced T-cell interferon γ (IFN-γ) secretion and proliferation. Hcy also enhanced endoplasmic reticulum (ER) stress in T cells, and inhibition of ER stress with 4-phenylbutyric acid blocked Hcy-induced T-cell activation. Mechanistically, Hcy increased ER-mitochondria coupling, and uncoupling ER-mitochondria by the microtubule inhibitor nocodazole attenuated Hcy-stimulated mitochondrial reprogramming, IFN-γ secretion and proliferation in T cells, suggesting that juxtaposition of ER and mitochondria is required for Hcy-promoted mitochondrial function and T-cell activation. In conclusion, Hcy promotes T-cell activation by increasing ER-mitochondria coupling and regulating metabolic reprogramming.

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.

Common variants in PERK, JNK, BIP and XBP1 genes are associated with the risk of prediabetes or diabetes-related phenotypes in a Chinese population / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Prediabetes is an early stage of β-cell dysfunction presenting as insulin resistance. Evidences suggest that endoplasmic reticulum (ER) stress is involved in the pathogenesis of type 2 diabetes mellitus and prediabetes. In a Chinese population with prediabetes, we investigated single nucleotide polymorphisms (SNPs) in the genes of PERK, JNK, XBP1, BIP and CHOP which encode molecular proteins involved in ER stress pathways.</p><p><b>METHODS</b>Nine SNPs at the PERK, JNK, XBP1, BIP and CHOP loci were genotyped by mass spectrometry in 1 448 unrelated individuals. By using a 75 g oral glucose tolerance test (OGTT), 828 subjects were diagnosed as prediabetes and 620 subjects aged 55 years and over as normal controls based on WHO diagnostic criteria (1999) for diabetes mellitus.</p><p><b>RESULTS</b>The allele C of SNP rs867529 at PERK locus was a risk factor for prediabetes, with the carriers of C allele genotype at a higher risk of prediabetes compared to non-carriers (OR = 1.279, 95% CI: 1.013-1.614, P = 0.039, after adjustment for age, sex and body mass index (BMI). The SNPs rs6750998 at PERK locus was associated with homeostasis model assessments of insulin resistance (HOMA-IR) (P = 0.019), and rs17037621 with BMI (P = 0.044). The allele G of SNP rs10986663 in BIP gene was associated with a decreased risk of prediabetes (OR = 0.699, 95% CI: 0.539-0.907, P = 0.007). The SNP rs2076431 in JNK gene was associated with fasting plasma glucose levels (P = 0.006) and waist-hip ratios (P = 0.019). The SNP rs2239815 in XBP1 gene was associated with 2-hour plasma glucose levels after 75 g oral glucose load (P = 0.048) in the observed population.</p><p><b>CONCLUSION</b>Common variants at PERK and BIP loci contributed to the risk of prediabetes, and the genetic variations in JNK and XBP1 genes are associated with diabetes-related clinical parameters in this Chinese population.</p>

PKR as a Regulator of Inflammasome Activation

Detection of pathogen by pattern recognition receptors leads to activation of inflammasome which plays a crucial role in immune system. The inflammasome regulates the release of cytokines, such as interleukin (IL)-1beta, IL-18 and high-mobility group box 1 (HMGB1). Double-stranded RNA-dependent protein kinase (PKR) is a critical component of an inflammatory complex. Recently, the critical role of PKR was reported in regulation of multiple inflammasomes.

Regulation of HMGB1 release by inflammasomes

High mobility group box 1 (HMGB1) is an evolutionarily conserved non-histone chromatin-binding protein. During infection or injury, activated immune cells and damaged cells release HMGB1 into the extracellular space, where HMGB1 functions as a proinflammatory mediator and contributes importantly to the pathogenesis of inflammatory diseases. Recent studies reveal that inflammasomes, intracellular protein complexes, critically regulate HMGB1 release from activated immune cells in response to a variety of exogenous and endogenous danger signals. Double stranded RNA dependent kinase (PKR), an intracellular danger-sensing molecule, physically interacts with inflammasome components and is important for inflammasome activation and HMGB1 release. Together, these studies not only unravel novel mechanisms of HMGB1 release during inflammation, but also provide potential therapeutic targets to treat HMGB1-related inflammatory diseases.

Human Leptin Protein Induces Proliferation of A549 Cells via Inhibition of PKR-Like ER Kinase and Activating Transcription Factor-6 Mediated Apoptosis

PURPOSE: To investigate the anti-apoptotic mechanism of leptin in non-small cell lung cancer. MATERIALS AND METHODS: The influences of leptin on apoptosis were investigated, analyzing the mechanism that triggers growth of A549 cells. The effects of leptin on cell proliferation were examined by XTT analysis. Leptin, C/EBP homologous protein (CHOP), phosphorylated-PKR-like ER kinase (p-Perk), inositol requiring proteins-1, spliced X-box transcription factor-1 (XBP1), cleaved activating transcription factor-6 (ATF6), eukaryotic translation initiation factor-2alpha, caspase-12 and CHOP protein were detected in four groups by western blot, and endoplasmic reticulum (ER) stress related mRNA were detected by reverse transcription PCR. RESULTS: The expression of leptin in A549 and leptin transfected cells inhibited cisplatin activated ER stress-associated mRNA transcription and protein activation. Two ER stress unfolded protein response pathways, PERK and ATF6, were involved, and XBP1 and tumor necrosis factor receptor-associated factor 2 (TRAF2) were increased significantly when treated with cisplatin in A549-siRNA against leptin cells. Furthermore, CHOP expression was inhibited upon leptin expression in A549, LPT-PeP and LPT-EX cells. CONCLUSION: Leptin serves as an important factor that promotes the growth of A549 cells through blocking ER stress-mediated pathways. This blocking is triggered by p-Perk and ATF6 via inhibition of CHOP expression.

Low-dose radiation induces endoplasmic reticulum stress and activates PERK-CHOP signaling pathway in mouse testicular cells / 中华男科学杂志

<p><b>OBJECTIVE</b>To explore the correlation of low-dose radiation with endoplasmic reticulum stress and the activation of the PERK-CHOP signaling pathway in mouse testicular cells.</p><p><b>METHODS</b>Healthy Kunming mice were randomly assigned to time-effect (0, 3, 6, 12 and 24 h of irradiation at 75 mGy) and dose-effect (12 h of irradiation at 0, 50, 75, 100 and 200 mGy) groups. The contents of H202 and MDA were measured by colorimetry with the agent kits, the expressions of GRP78, PERK and CHOP mRNA detected by quantitative RT-PCR, and the levels of GRP7B, PERK, phosphorylated PERK (pho-PERK) and CHOP proteins determined by Western blotting and image analysis.</p><p><b>RESULTS</b>After whole-body irradiation of the mice with 75 mGy, the content of H2 02 in the testis tissue was increased with time prolongation, while that of MDA decreased slightly at 3 and 6 h and then increased with the lengthening of time, both increased significantly at 12 and 24 h as compared with those at 0 h (P < 0. 05, P < 0. 01). Apart from reduced levels of GRP78 mRNA at 3 and 24 h and GRP78 protein at 6 h after irradiation, significant increases were found in the mRNA expressions of GRP78 at 12 h, PERK at 3,6, 12 and 24 hand CHOP at 12 and 24 h (P < 0.05, P < 0.01), as well as in the protein levels of GRP78 at 12 and 24 h, pho-PERK at 3, 12 and 24 h and CHOP at 3, 6, 12 and 24 h in comparison with those at 0 h (P < 0. 05, P < 0. 01). No obvious regularity was observed in the change of the PERK protein expression. After 12 h of whole-body irradiation, the content of H202 was increased at 50, 75 and 100 mGy, but decreased slightly at 200 mGy, while that of MDA was increased with dose increasing, with significant increases in the content of H2 02 at 75 and 100 mCy and in that of MDA at 75, 100 and 200 mGy as compared with the 0 mGy group. Apart from the reduced levels of GRP78 mRNA at 50 and 200 mCy, significant increases were found in the mRNA expressions of PERK at 75, 100 and 200 mGy and CHOP at 50, 75, 100 and 200 (P c 0. 05, P < 0.01) as well as in the protein levels of GRP78 at 100 and 200 mGy, pho-PERK at 50, 100 and 200 mGy and CHOP at 50, 75, 100 and 200 mCy as compared with those at 0 mGy (P < 0. 05, P < 0. 01). There were differences in the changes of different protein expressions, but no obvious regularity was seen in the change of the PERK protein expression.</p><p><b>CONCLUSION</b>Low-dose radiation can induce endoplasmic reticulum stress in mouse testicular cells, and activate the PERK-CHOP signaling pathway.</p>

Two novel EIF2AK3 mutations in a Chinese boy with Wolcott-Rallison syndrome / 中华儿科杂志

<p><b>OBJECTIVE</b>Wolcott-Rallison syndrome (WRS) is a rare autosomal recessive disorder characterized by the association of permanent neonatal or early-infancy insulin-dependent diabetes, multiple epiphyseal dysplasia and growth retardation, and other variable multisystem clinical manifestations. Here we describe a Chinese boy affected by WRS. Genetic testing of his EIF2AK3 gene was performed in order to elucidate molecular variations and subsequently to provide credible genetic counseling for prenatal diagnosis in his family.</p><p><b>METHOD</b>Based on analysis of a nine-year-old boy's clinical symptoms associated with biochemical examination and imaging, the diagnosis of WRS was therefore made. Genomic DNAs were extracted from peripheral blood leukocytes from the boy and his parents with their informed consent for genetic studies. All EIF2AK3 exons and intron-exon boundaries were amplified by Touch-down polymerase chain reaction (Touch-down PCR) and sequenced.</p><p><b>RESULT</b>Direct sequencing of PCR products revealed the presence of a heterozygous T insertion (c.1408_1409insT) in exon 8 of the EIF2AK3 gene leading to frameshifting and termination, and another heterozygous T to A exchange (c.1596T > A) in exon 9 of the EIF2AK3 gene resulting in nonsense C532X mutation.</p><p><b>CONCLUSION</b>Combining mutation screening of EIF2AK3 gene with clinical manifestations and effective examination may provide a reliable diagnostic method for patients. In this research, two novel mutations identified in the Chinese boy locate in the catalytic domain of the EIF2AK3 gene, disrupting the ability of autophosphorylation, leading to the truncated proteins that are unable to phosphorylate the natural substrate, which are responsible for the phenotype of Wolcott-Rallison syndrome.</p>

Role of PERK/eIF2a signaling pathway in hepatocyte apoptosis of alcoholic liver injury rats / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate the role of PERK/eIF2alpha signaling pathway in hepatocyte apoptosis of alcoholic liver injury rats.</p><p><b>METHODS</b>Rat models with ethanol-induced liver injury were successfully developed by gastric gavage with ethanol-corn oil mixtures for 12 weeks. At different time points (4, 6, 10, 12 week), liver pathology was dynamically observed. The hepatocyte apoptosis was quantitatively analyzed by Annexin V-FITC/PI double-labeled flow cytometry, the serum total homocysteine (tHCY) level was detected by ELISA and the expressions of eIF2a, p-eIF2a, GRP78/Bip, GRP94, caspase-3 and caspase-12 in liver were examined using Real-time PCR and Western blot.</p><p><b>RESULTS</b>Typical acute liver injury and chronic liver injury were observed at week 4 and week 12 respectively. The hepatocyte apoptosis rates in 6-week model rats significantly increased compared with normal rats (P value less than 0.05), and the degree of hepatocyte apoptosis continued to increase with the modeling time, and the percentages of early and total apoptosis reached 26% and 29% at week 12. From week 6 to week 12, the serum tHCY levels in model rats were obviously higher than in normal rats (P value less than 0.01). Since week 4, eIF2a protein phosphorylation in model rat livers remarkably elevated compared with that in normal rat livers (P value less than 0.01), and at week 12 the peIF2a protein expression in model rat livers increased by 2.81-fold. Since week 4 the expressions of GRP78/Bip, GRP94, caspase-12 and caspase-3 mRNA and protein in model rat livers showed a significant increase as compared to normal rat livers, and at week 12, these gene and protein levels increased 4.70, 12.95, 3.83, 4.05 fold and 3.93, 6.93, 9.88, 3.31 fold, respectively (P value less than 0.01).</p><p><b>CONCLUSION</b>Activation of PERK/eIF2a signaling pathway contributes to the occurrence and development of hepatocyte apoptosis in alcoholic liver injury rats and it might be as a potential target for therapeutic applications in alcoholic liver diseases.</p>

Interaction of Hsp40 with influenza virus M2 protein: implications for PKR signaling pathway

Influenza virus contains three integral membrane proteins: haemagglutinin, neuraminidase, and matrix protein (M1 and M2). Among them, M2 protein functions as an ion channel, important for virus uncoating in endosomes of virus-infected cells and essential for virus replication. In an effort to explore potential new functions of M2 in the virus life cycle, we used yeast two-hybrid system to search for M2-associated cellular proteins. One of the positive clones was identified as human Hsp40/Hdj1, a DnaJ/Hsp40 family protein. Here, we report that both BM2 (M2 of influenza B virus) and A/M2 (M2 of influenza A virus) interacted with Hsp40 in vitro and in vivo. The region of M2-Hsp40 interaction has been mapped to the CTD1 domain of Hsp40. Hsp40 has been reported to be a regulator of PKR signaling pathway by interacting with p58(IPK) that is a cellular inhibitor of PKR. PKR is a crucial component of the host defense response against virus infection. We therefore attempted to understand the relationship among M2, Hsp40 and p58(IPK) by further experimentation. The results demonstrated that both A/M2 and BM2 are able to bind to p58(IPK) in vitro and in vivo and enhance PKR autophosphorylation probably via forming a stable complex with Hsp40 and P58(IPK), and consequently induce cell death. These results suggest that influenza virus M2 protein is involved in p58(IPK) mediated PKR regulation during influenza virus infection, therefore affecting infected-cell life cycle and virus replication.

Intrinsic Cellular Defenses against Virus Infection by Antiviral Type I Interferon

Intrinsic cellular defenses are non-specific antiviral activities by recognizing pathogen-associated molecular patterns (PAMPs). Toll-like receptors (TLRs), one of the pathogen recognize receptor (PRR), sense various microbial ligands. Especially, TLR2, TLR3, TLR4, TLR7, TLR8 and TLR9 recognize viral ligands such as glycoprotein, single- or double-stranded RNA and CpG nucleotides. The binding of viral ligands to TLRs transmits its signal to Toll/interleukin-1 receptor (TIR) to activate transcription factors via signal transduction pathway. Through activation of transcription factors, such as interferon regulatory factor-3, 5, and 7 (IRF-3, 5, 7) or nuclear factor-kappaB (NF-kappaB), type I interferons are induced, and antiviral proteins such as myxovirus-resistance protein (Mx) GTPase, RNA-dependent Protein Kinase (PKR), ribonuclease L (RNase L), Oligo-adenylate Synthetase (OAS) and Interferon Stimulated Gene (ISG) are further expressed. These antiviral proteins play an important role of antiviral resistancy against several viral pathogens in infected cells and further activate innate immune responses.

Interferon resistance of hepatitis C virus genotypes 1a/1b: relationship to structural E2 gene quasispecies mutations

Hepatitis C virus [HCV] envelope glycoprotein-2 [E2] inhibits the interferon [IFN]induced, double stranded RNA activated protein kinase [PKR] via PKR eukaryotic initiation factor-2a phosphorylation homology domain [PePHD]. Present study examined the genetic variability of the PePHD in patients receiving interferon therapy. The PePHD region from HCV genotype 1a/1b infected patients receiving IFN was amplified by reverse transcriptase polymerase chain reaction [RT-PCR] and analyzed using bidirectionaly sequencing. The PePHD sequence was different in pretreatment isolates from three months treated patients. It was shown that the major PePHD quasispecies could change after three months IFN therapy and in one patient; the major PePHD quasispecies could change after six months IFN therapy. These mutations were occurred at codons 665, 666 and 667 of followed-up samples and at codons 660, 661, 666 and 670 of randomly treated patients. Some of these mutations were similar to those reported in previous studies. Other mutations were also detected in upstream and downstream regions of PePHD which may have influenced the structure, conformation and configuration of this region and thereby suppressing PePHD inhibitory properties. In conclusion our data suggested that HCV E2 PePHD may play an important role in determining the interferon response among Iranian HCV infected patients

Weak linkage in hepatitis C PePHD: identification of mutation prone point that can lead to failure of antiviral therapy for prevention of hepatocellular carcinoma.

Hepatitis C is an important blood borne infection caused by hepatitis C virus (HCV). Chronic inflammation induced by this viral infection and its role in carcinogenesis are well recognized. The treatment of HCV infection has developed enormously over recent years and is believed to be a good way for stopping of carcinogenesis process. However, mutation of the virus is an important factor that can bring drug resistance. Presently, prediction of protein nanostructure and function is a great challenge in the proteomics and structural genomics era. To identify points which are vulnerable to mutation is a new trend to expand the knowledge at the genomic and proteomic levels Here, the author performed a bioinformatic analysis to determine positions that trend to comply with peptide motifs in the amino acid sequence of HCV protein kinase -eIF2-alpha phosphorylation homology domain (PePHD). To identify weak linkage in HCV PePHD, a new bioinformatic tool, GlobPlot, was used. Positions 2-7, 29-39, 53-57, 90-98, 123-133, 202-227, 324-355, 439-448 were identified as positions resistant to mutation. Some are already known and others are newly discovered. Based on this study, weak linkages in HCV PePHD could be identified and can be good information for expectation of possible new mutations that can lead to failure of HCV therapy. In addition, the results from this study can be good information for further research on the diagnosis for mutants HCV and vaccine development.