Protein disulfide isomerase suppresses the transcriptional activity of NF-κB

Changes in tissue protein N-glycosylation and associated molecular signature occur in the human Parkinsonian brain in a region-specific manner

Parkinson's disease (PD) associated state of neuroinflammation due to the aggregation of aberrant proteins is widely reported. One type of post-translational modification involved in protein stability is glycosylation. Here, we aimed to characterize the human Parkinsonian nigro-striatal N-glycome, and related transcriptome/proteome, and its correlation with endoplasmic reticulum (ER) stress and unfolded protein response (UPR), providing a comprehensive characterization of the PD molecular signature. Significant changes were seen upon a PD: a 3% increase in sialylation and 5% increase in fucosylation in both regions, and a 2% increase in oligomannosylated N-glycans in the substantia nigra. In the latter, a decrease in the mRNA expression of sialidases and an upregulation in the UPR pathway were also seen. To show the correlation between these, we also describe a small in vitro study where changes in specific glycosylation trait enzymes (inhibition of sialyltransferases) led to impairments in cell mitochondrial activity, changes in glyco-profile, and upregulation in UPR pathways. This complete characterization of the human nigro-striatal N-glycome provides an insight into the glycomic profile of PD through a transversal approach while combining the other PD "omics" pieces, which can potentially assist in the development of glyco-focused therapeutics.

CDDO-Me Abrogates Aberrant Mitochondrial Elongation in Clasmatodendritic Degeneration by Regulating NF-κB-PDI-Mediated S-Nitrosylation of DRP1

Clasmatodendrosis is a kind of astroglial degeneration pattern which facilitates excessive autophagy. Although abnormal mitochondrial elongation is relevant to this astroglial degeneration, the underlying mechanisms of aberrant mitochondrial dynamics are still incompletely understood. Protein disulfide isomerase (PDI) is an oxidoreductase in the endoplasmic reticulum (ER). Since PDI expression is downregulated in clasmatodendritic astrocytes, PDI may be involved in aberrant mitochondrial elongation in clasmatodendritic astrocytes. In the present study, 26% of CA1 astrocytes showed clasmatodendritic degeneration in chronic epilepsy rats. 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; bardoxolone methyl or RTA 402) and SN50 (a nuclear factor-κB (NF-κB) inhibitor) ameliorated the fraction of clasmatodendritic astrocytes to 6.8 and 8.1% in CA1 astrocytes, accompanied by the decreases in lysosomal-associated membrane protein 1 (LAMP1) expression and microtubule-associated protein 1A/1B light-chain 3 (LC3)-II/LC3-I ratio, indicating the reduced autophagy flux. Furthermore, CDDO-Me and SN50 reduced NF-κB S529 fluorescent intensity to 0.6- and 0.57-fold of vehicle-treated animal level, respectively. CDDO-Me and SN50 facilitated mitochondrial fission in CA1 astrocytes, independent of dynamin-related protein 1 (DRP1) S616 phosphorylation. In chronic epilepsy rats, total PDI protein, S-nitrosylated PDI (SNO-PDI), and SNO-DRP1 levels were 0.35-, 0.34- and 0.45-fold of control level, respectively, in the CA1 region and increased CDDO-Me and SN50. Furthermore, PDI knockdown resulted in mitochondrial elongation in intact CA1 astrocytes under physiological condition, while it did not evoke clasmatodendrosis. Therefore, our findings suggest that NF-κB-mediated PDI inhibition may play an important role in clasmatodendrosis via aberrant mitochondrial elongation.

Functions and mechanisms of protein disulfide isomerase family in cancer emergence

The endoplasmic reticulum (ER) is a multi-layered organelle that is essential for the synthesis, folding, and structural maturation of almost one-third of the cellular proteome. It houses several resident proteins for these functions including the 21 members of the protein disulfide isomerase (PDI) family. The signature of proteins belonging to this family is the presence of the thioredoxin domain which mediates the formation, and rearrangement of disulfide bonds of substrate proteins in the ER. This process is crucial not only for the proper folding of ER substrates but also for maintaining a balanced ER proteostasis. The inclusion of new PDI members with a wide variety of structural determinants, size and enzymatic activity has brought additional epitomes of how PDI functions. Notably, some of them do not carry the thioredoxin domain and others have roles outside the ER. This also reflects that PDIs may have specialized functions and their functions are not limited within the ER. Large-scale expression datasets of human clinical samples have identified that the expression of PDI members is elevated in pathophysiological states like cancer. Subsequent functional interrogations using structural, molecular, cellular, and animal models suggest that some PDI members support the survival, progression, and metastasis of several cancer types. Herein, we review recent research advances on PDIs, vis-à-vis their expression, functions, and molecular mechanisms in supporting cancer growth with special emphasis on the anterior gradient (AGR) subfamily. Last, we posit the relevance and therapeutic strategies in targeting the PDIs in cancer.

Roles of Protein Disulfide Isomerase in Breast Cancer

Protein disulfide isomerase (PDI) is the endoplasmic reticulum (ER)'s most abundant and essential enzyme and serves as the primary catalyst for protein folding. Due to its apparent role in supporting the rapid proliferation of cancer cells, the selective blockade of PDI results in apoptosis through sustained activation of UPR pathways. The functions of PDI, especially in cancers, have been extensively studied over a decade, and recent research has explored the use of PDI inhibitors in the treatment of cancers but with focus areas of other cancers, such as brain or ovarian cancer. In this review, we discuss the roles of PDI members in breast cancer and PDI inhibitors used in breast cancer research. Additionally, a few PDI members may be suggested as potential molecular targets for highly metastatic breast cancers, such as TNBC, that require more attention in future research.

Protein disulfide isomerase A1‑associated pathways in the development of stratified breast cancer therapies

The oxidoreductase protein disulfide isomerase A1 (PDIA1) functions as a cofactor for many transcription factors including estrogen receptor α (ERα), nuclear factor (NF)-κB, nuclear factor erythroid 2-like 2 (NRF2) and regulates the protein stability of the tumor suppressor p53. Taking this into account we hypothesized that PDIA1, by differentially modulating the gene expression of a diverse subset of genes in the ERα-positive vs. the ERα-negative breast cancer cells, might modify dissimilar pathways in the two types of breast cancer. This hypothesis was investigated using RNA-seq data from PDIA1-silenced MCF-7 (ERα-positive) and MDA-MB-231 (ERα-negative) breast cancer cells treated with either interferon γ (IFN-γ) or etoposide (ETO), and the obtained data were further analyzed using a variety of bioinformatic tools alongside clinical relevance assessment via Kaplan-Meier patient survival curves. The results highlighted the dual role of PDIA1 in suppressing carcinogenesis in the ERα(+) breast cancer patients by negatively regulating the response to reactive oxygen species (ROS) and promoting carcinogenesis by inducing cell cycle progression. In the ERα(−) breast cancer patients, PDIA1 prevented tumor development by modulating NF-κB and p53 activity and cell migration and induced breast cancer progression through control of cytokine signaling and the immune response. The findings reported in this study shed light on the differential pathways regulating carcinogenesis in ERα(+) and ERα(−) breast cancer patients and could help identify therapeutic targets selectively effective in ERα(+) vs. ERα(−) patients.

Identification of amphioxus protein disulfide isomerase as both an enzyme and an immunocompotent factor

Previous studies have shown that protein disulfide isomerase (PDI), a member of the thioredoxin (TRX) superfamily, are broadly associated with immune responses in a variety of animals. However, it remains largely unknown about the direct roles of PDIs during a bacterial infection. In this study, we identified the presence of a single pdi gene in the amphioxus Branchiostoma japonicum, Bjpdi. The deduced protein BjPDI is structurally characterized by the presence of four Trx-like domains in the order of a, b, b' and a' and a short acidic C-terminal tail, that are characteristic of PDIs. We demonstrated that rBjPDI displayed both thiol reductase and disulfide bond isomerase activities, indicating comparability of BjPDI with PDIs in term of enzymatic activities. We also showed that rBjPDI induced bacterial agglutination and exhibited a lectin-like activity capable of binding both bacteria (E. coli and S. aureus) and their signature molecules LPS and LTA. Furthermore, BjPDI could kill S. aureus via inducing membrane depolarization and intracellular ROS production in vitro, and treatment of amphioxus with a blocking anti-PDI antibody in vivo markedly reduced the survival rate of amphioxus following attack by S. aureus. Collectively, our study demonstrates that amphioxus protein disulfide isomerase acts as both an enzyme and an immunocompotent factor, and reports the specific function and mode of action of PDIs in immune responses.

Bacitracin and Rutin Regulate Tissue Factor Production in Inflammatory Monocytes and Acute Myeloid Leukemia Blasts

Simple Summary

Aberrant tissue factor (TF) expression by transformed myeloblasts and inflammatory monocytes contributes to coagulation activation in acute myeloid leukemia (AML). TF procoagulant activity (PCA) is regulated by protein disulfide isomerase (PDI), an oxidoreductase with chaperone activity, but its specific role in AML-associated TF biology is unclear. Here, we provide novel mechanistic insights into this interrelation. We show that bacitracin and rutin, two pan-inhibitors of the PDI family, prevent lipopolysaccharide (LPS)-induced monocyte TF production under inflammatory conditions and constitutive TF expression by THP1 cells and AML blasts, thus exerting promising anticoagulant activity. Downregulation of the TF protein was mainly restricted to its non-coagulant, cryptic pool and was at least partially regulated on the mRNA level in LPS-stimulated monocytes. Collectively, our study indicates a complex role of thiol isomerases in the regulation of myeloid TF PCA, with the most abundant PDI being a promising therapeutic target in the management of AML-associated coagulopathies.

Abstract

Aberrant expression of tissue factor (TF) by transformed myeloblasts and inflammatory monocytes drives coagulation activation in acute myeloid leukemia (AML). Although regulation of TF procoagulant activity (PCA) involves thiol-disulfide exchange reactions, the specific role of protein disulfide isomerase (PDI) and other thiol isomerases in AML-associated TF biology is unclear. THP1 cells and peripheral blood mononuclear cells (PBMCs) from healthy controls or AML patients were analyzed for thiol isomerase-dependent TF production under various experimental conditions. Total cellular and membrane TF antigen, TF PCA and TF mRNA were analyzed by ELISA, flow cytometry, clotting or Xa generation assay and qPCR, respectively. PBMCs and THP1 cells showed significant insulin reductase activity, which was inhibited by bacitracin or rutin. Co-incubation with these thiol isomerase inhibitors prevented LPS-induced TF production by CD14-positive monocytes and constitutive TF expression by THP1 cells and AML blasts. Downregulation of the TF antigen was mainly restricted to the cryptic pool of TF, efficiently preventing phosphatidylserine-dependent TF activation by daunorubicin, and at least partially regulated on the mRNA level in LPS-stimulated monocytes. Our study thus delineates a complex role of thiol isomerases in the regulation of myeloid TF PCA, with PDI being a promising therapeutic target in the management of AML-associated coagulopathies.

Crosstalk between endoplasmic reticulum stress and oxidative stress: Focus on protein disulfide isomerase and endoplasmic reticulum oxidase 1

Cellular stress and inflammation, establishing as disease pathology, have reached great heights in the last few decades. Stress conditions such as hyperglycemia, hyperlipidemia and lipoproteins are known to disturb proteostasis resulting in the accumulation of unfolded or misfolded proteins, alteration in calcium homeostasis culminating in unfolded protein response. Protein disulfide isomerase and endoplasmic reticulum oxidase-1 are the key players in protein folding. The protein folding process assisted by endoplasmic reticulum oxidase-1 results in the production of reactive oxygen species in the lumen of the endoplasmic reticulum. Production of reactive oxygen species beyond the quenching capacity of the antioxidant systems perturbs ER homeostasis. Endoplasmic reticulum stress also induces the production of cytokines leading to inflammatory responses. This has been proven to be the major causative factor for various pathophysiological states compared to other cellular triggers in diseases, which further manifests to increased oxidative stress, mitochondrial dysfunction, and altered inflammatory responses, deleterious to cellular physiology and homeostasis. Numerous studies have drawn correlations between the progression of several diseases in association with endoplasmic reticulum stress, redox protein folding, oxidative stress and inflammatory responses. This review aims to provide an insight into the role of protein disulfide isomerase and endoplasmic reticulum oxidase-1 in endoplasmic reticulum stress, unfolded protein response, mitochondrial dysfunction, and inflammatory responses, which exacerbate the progression of various diseases.

Protein disulfide isomerase A1 regulates breast cancer cell immunorecognition in a manner dependent on redox state

Oxidoreductase protein disulphide isomerases (PDI) are involved in the regulation of a variety of biological processes including the modulation of endoplasmic reticulum (ER) stress, unfolded protein response (UPR), ER-mitochondria communication and the balance between pro-survival and pro-death pathways. In the current study the role of the PDIA1 family member in breast carcinogenesis was investigated by measuring ROS generation, mitochondrial membrane disruption, ATP production and HLA-G protein levels on the surface of the cellular membrane in the presence or absence of PDIA1. The results showed that this enzyme exerted pro-apoptotic effects in estrogen receptor (ERα)-positive breast cancer MCF-7 and pro-survival in triple negative breast cancer (TNBC) MDA-MB-231 cells. ATP generation was upregulated in PDIA1-silenced MCF-7 cells and downregulated in PDIA1-silenced MDA-MB-231 cells in a manner dependent on the cellular redox status. Furthermore, MCF-7 and MDA-MB-231 cells in the presence of PDIA1 expressed higher surface levels of the non-classical human leukocyte antigen (HLA-G) under oxidative stress conditions. Evaluation of the METABRIC datasets showed that low PDIA1 and high HLA-G mRNA expression levels correlated with longer survival in both ERα-positive and ERα-negative stage 2 breast cancer patients. In addition, analysis of the PDIA1 vs. the HLA-G mRNA ratio in the subgroup of the living stage 2 breast cancer patients exhibiting low PDIA1 and high HLA-G mRNA levels revealed that the longer the survival time of the ratio was high PDIA1 and low HLA-G mRNA and occurred predominantly in ERα-positive breast cancer patients whereas in the same subgroup of the ERα-negative breast cancer mainly this ratio was low PDIA1 and high HLA-G mRNA. Taken together these results provide evidence supporting the view that PDIA1 is linked to several hallmarks of breast cancer pathways including the process of antigen processing and presentation and tumor immunorecognition.

The protective effects of vitamin C on apoptosis, DNA damage and proteome of pufferfish (Takifugu obscurus) under low temperature stress

The aim of this study was to investigate the protective effects of vitamin C on apoptosis, DNA damage and proteome of pufferfish under low temperature stress. Six diets were formulated to contain 2.60, 48.90, 95.50, 189.83, 382.40, 779.53mg/kg vitamin C. After 8-week feeding trial, fish were exposed to low temperature challenge. The results showed that pufferfish receiving vitamin C diet exhibited a significant decrease in ROS production (48.9-189.83mg/kg vitamin C diet groups), cytoplasmic free-Ca²⁺ concentration (48.9-779.53mg/kg vitamin C diet groups), apoptotic cell ratio (95.5-779.53mg/kg vitamin C diet groups) and DNA damage (189.83-779.53mg/kg vitamin C diet groups) under low temperature stress in comparison with those of control. We also investigated the alteration in protein expression under low temperature stress by a comparative proteomic analysis. The results demonstrated that 24 protein spots showed significantly differential expression in the cold-stress-treated group compared with those of the control group, and 5 protein spots were successfully identified. Furthermore, comparative proteomic analysis revealed that vitamin C could increase expressed proteins related to energy metabolism, immune responses and cytoskeleton. These findings would be helpful to understand the protective effects of vitamin C against cold stress.

Immunotherapy in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a disorder characterized by the association of arterial or venous thrombosis and/or pregnancy morbidity with the presence of antiphospholipid antibodies (anticardiolipin antibodies, lupus anticoagulant antibodies, and/or anti-β2-glycoprotein I antibodies). Thrombosis is the major manifestation in patients with aPLs, but the spectrum of symptoms and signs associated with aPLs has broadened considerably, and other manifestations, such as thrombocytopenia, non-thrombotic neurological syndromes, psychiatric manifestations, livedo reticularis, skin ulcers, hemolytic anemia, pulmonary hypertension, cardiac valve abnormality, and atherosclerosis, have also been related to the presence of those antibodies. Several studies have contributed to uncovering the basis of antiphospholipid antibody pathogenicity, including the targeted cellular components, affected systems, involved receptors, intracellular pathways used, and the effector molecules that are altered in the process. Therapy for thrombosis traditionally has been based on long-term oral anticoagulation; however, bleeding complications and recurrence despite high-intensity anticoagulation can occur. The currently accepted first-line treatment for obstetric APS (OAPS) is low-dose aspirin plus prophylactic unfractionated or low-molecular-weight heparin (LMWH). However, in approximately 20% of OAPS cases, the final endpoint, i.e. a live birth, cannot be achieved. Based on all the data obtained in different research studies, new potential therapeutic approaches have been proposed, including the use of new oral anticoagulants, statins, hydroxychloroquine, coenzyme Q10, B-cell depletion, platelet and TF inhibitors, peptide therapy or complement inhibition among others. Current best practice in use of these treatments is discussed.

Molecular characterization of two novel molecular chaperones in bacterial-challenged Apostichopus japonicus

Molecular chaperones of 78 kDa glucose-regulated protein (GRP78) and protein disulfide isomerase (PDI) are involved in protein folding and assembly in the endoplasmic reticulum (ER). Increasing evidences also suggest that these two molecules play an important role in immune response. In the present study, we cloned and characterized GRP78 and PDI genes from Apostichopus japonicus by RNA-seq and RACE approaches (designated as AjGRP78 and AjPDI, respectively). The AjGRP78 cDNA was of 2355bp including an open reading frame (ORF) of 2013 bp encoding a protein of 670 amino acids with three heat shock protein 70 (HSP70) family signatures. AjGRP78 contained a 23-amino acid signal peptide at the N-terminus and a HDEL motif at the C-terminus, which supported the location of the protein in the ER. The full length cDNA of AjPDI was of 1893 bp with a 5' untranslated region (UTR) of 153 bp, a 3' UTR of 228 bp and an ORF of 1512 bp encoding a protein of 503 amino acids. A 17-amino acid signal peptide, two thioredoxin domains with two active sites of CGHC, and KDEL retention signal were totally conserved in the deduced amino acid of AjPDI. Phylogenic analysis and multiple alignments have shown that both genes shared remarkably higher degree of structural conservation and sequence identities with other counterparts from invertebrates and vertebrates, further supporting that the two proteins were novel members of molecular chaperone family. Spatial expression analysis revealed that AjGRP78 mRNA transcripts were dominantly expressed in the tentacle, while AjPDI mRNA levels were abundant in the muscle, intestine and respiratory trees. For Vibrio splendidus challenged sea cucumber, the peak expression of AjGRP78 and AjPDI mRNAs in coelomocytes were detected at 24h with 1.73-fold increase and at 6h with 1.83-fold increase compared with the control group, respectively. Similarly, a significant increase in the relative mRNA levels of AjGRP78 and AjPDI was also identified in 1 μg mL(-1) LPS exposed primary cultured coelomocytes. These results collectively suggested that AjGRP78 and AjPDI were ER chaperones of A. japonicus, of which expression is induced upon bacterial infection.

Endo-PDI is required for TNFα-induced angiogenesis

Protein disulfide isomerase (PDI) and its homologs are oxidoreductases facilitating protein folding in the ER. Endo-PDI (also termed ERp46) is highly expressed in endothelial cells. It belongs to the PDI family but its physiological function is largely unknown. We studied the role of Endo-PDI in endothelial angiogenic responses. Stimulation of human umbilical vein endothelial cells (with TNFα (10ng/ml) increased ERK1/2 phosphorylation. This effect was largely attenuated by Endo-PDI siRNA, whereas JNK and p38 MAP kinase phosphorylation was Endo-PDI independent. Similarly, TNFα-stimulated NF-κB signaling determined by IκBα degradation as well as TNFα-induced ICAM expression was unaffected by Endo-PDI siRNA. The action of Endo-PDI was not mediated by extracellular thiol exchange or cell surface PDI as demonstrated by nonpermeative inhibitors and PDI-neutralizing antibody. Moreover, exogenously added PDI failed to restore ERK1/2 activation after Endo-PDI knockdown. This suggests that Endo-PDI acts intracellularly potentially by maintaining the Ras/Raf/MEK/ERK pathway. Indeed, knockdown of Endo-PDI attenuated Ras activation measured by G-LISA and Raf phosphorylation. ERK activation influences gene expression by the transcriptional factor AP-1, which controls MMP-9 and cathepsin B, two proteases required for angiogenesis. TNFα-stimulated MMP-9 and cathepsin B induction was reduced by silencing of Endo-PDI. Accordingly, inhibition of cathepsin B or Endo-PDI siRNA blocked the TNFα-stimulated angiogenic response in the spheroid outgrowth assays. Moreover ex vivo tube formation and in vivo Matrigel angiogenesis in response to TNFα were attenuated by Endo-PDI siRNA. In conclusion, our study establishes Endo-PDI as a novel, important mediator of AP-1-driven gene expression and endothelial angiogenic function.

Changes in the proteomic profiles of mouse brain after infection with cyst-forming Toxoplasma gondii

Background

Toxoplasma gondii is an opportunistic pathogenic protozoan parasite, which infects approximately one third of the human population worldwide, causing opportunistic zoonotic toxoplasmosis. The predilection of T. gondii for the central nervous system (CNS) causes behavioral disorders and fatal necrotizing encephalitis and thus constitutes a major threat especially to AIDS patients.

Methods

In the present study, we explored the proteomic profiles of brain tissues of the specific pathogen-free (SPF) Kunming mice at 7 d, 14 d and 21 d after infection with cysts of the Toxoplasma gondii Prugniaud (PRU) strain (Genotype II), by two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF tandem mass spectrometry (MS/MS).

Results

A total of 60 differentially expressed protein spots were selected. Fifty-six spots were successfully identified, which corresponded to 45 proteins of the mouse. Functional analysis using a Gene Ontology database showed that these proteins were mainly involved in metabolism, cell structure, signal transduction and immune responses, and will be beneficial for the understanding of molecular mechanisms of T. gondii pathogenesis.

Conclusions

This study identified some mouse brain proteins involved in the response with cyst-forming T. gondii PRU strain. These results provided an insight into the responsive relationship between T. gondii and the host brain tissues, which will shed light on our understanding of the mechanisms of pathogenesis in toxoplasmic encephalitis, and facilitate the discovery of new methods of diagnosis, prevention, control and treatment of toxoplasmic encephalopathy.

Channel catfish (Ictalurus punctatus) protein disulphide isomerase, PDIA6: molecular characterization and expression regulated by bacteria and virus inoculation

Protein disulfide isomerases (PDIs) are thought to aid protein folding and assembly by catalyzing formation and shuffling of cysteine disulfide bonds in the endoplasmic reticulum (ER). Currently, increasing evidence suggests PDIs play an important role in host cell invasion and they are relevant targets for the host immune response. However the roles of specific PDIs in teleosts are little known. Here, we characterized the Protein disulfide isomerase family A, member 6 (PDIA6) from channel catfish, Ictalurus punctatus (named as ccPDIA6). The catfish ccPDIA6 gene was homologous to those of other vertebrate species with 13 exons and 12 introns. The consensus full-length ccPDIA6 cDNA contained an ORF of 1320 bp encoding a putative protein of 439 amino acids. It had a 19 amino acid signal peptide and two active thioredoxin-like domains. Sequence of phylogenic analysis and multiple alignments showed that ccPDIA6 was conserved throughout vertebrate evolution. Southern blot analysis suggested the presence of one copy of the ccPDIA6 gene in the catfish genome. Tissue distribution shows that ccPDIA6 was expressed in all examined tissues at the mRNA level. When using the aquatic zoonotic pathogens such as Edwardsiella tara, Streptococcus iniae, and channel catfish reovirus （CCRV） to challenge channel catfish, ccPDIA6 expression was significant changed in immune-related tissues such as head kidney, intestine, liver and spleen. The results suggested that ccPDIA6 might play an important role in the immunity of channel catfish. This is the first report that the PDI gene may be involved in fish host defense against pathogen infection.

The Redox System in C. elegans, a Phylogenetic Approach

Oxidative stress is a toxic state caused by an imbalance between the production and elimination of reactive oxygen species (ROS). ROS cause oxidative damage to cellular components such as proteins, lipids, and nucleic acids. While the role of ROS in cellular damage is frequently all that is noted, ROS are also important in redox signalling. The "Redox Hypothesis" has been proposed to emphasize a dual role of ROS. This hypothesis suggests that the primary effect of changes to the redox state is modified cellular signalling rather than simply oxidative damage. In extreme cases, alteration of redox signalling can contribute to the toxicity of ROS, as well as to ageing and age-related diseases. The nematode species Caenorhabditis elegans provides an excellent model for the study of oxidative stress and redox signalling in animals. We use protein sequences from central redox systems in Homo sapiens, Drosophila melanogaster, and Saccharomyces cerevisiae to query Genbank for homologous proteins in C. elegans. We then use maximum likelihood phylogenetic analysis to compare protein families between C. elegans and the other organisms to facilitate future research into the genetics of redox biology.

Sub-proteomic study on macrophage response to Candida albicans unravels new proteins involved in the host defense against the fungus

In previous proteomic studies on the response of murine macrophages against Candida albicans, many differentially expressed proteins involved in processes like inflammation, cytoskeletal rearrangement, stress response and metabolism were identified. In order to look for proteins important for the macrophage response, but in a lower concentration in the cell, 3 sub-cellular extracts were analyzed: cytosol, organelle/membrane and nucleus enriched fractions from RAW 264.7 macrophages exposed or not to C. albicans SC5314 for 3 h. The samples were studied using DIGE technology, and 17 new differentially expressed proteins were identified. This sub-cellular fractionation permitted the identification of 2 mitochondrion proteins, a membrane receptor, Galectin-3, and some ER related proteins, that are not easily detected in total cell extracts. Besides, the study of different fractions allowed us to detect, not only total increase in Galectin-3 protein amount, but its distinct allocation along the interaction. The identified proteins are involved in the pro-inflammatory and oxidative responses, immune response, unfolded protein response and apoptosis. Some of these processes increase the host response and others could be the effect of C. albicans resistance to phagocytosis. Thus, the sub-proteomic approach has been a very useful tool to identify new proteins involved in macrophage-fungus interaction. This article is part of a Special Issue entitled: Translational Proteomics.

Protein disulfide isomerase-2 of Arabidopsis mediates protein folding and localizes to both the secretory pathway and nucleus, where it interacts with maternal effect embryo arrest factor

Protein disulfide isomerase (PDI) is a thiodisulfide oxidoreductase that catalyzes the formation, reduction and rearrangement of disulfide bonds in proteins of eukaryotes. The classical PDI has a signal peptide, two CXXC-containing thioredoxin catalytic sites (a,a'), two noncatalytic thioredoxin fold domains (b,b'), an acidic domain (c) and a C-terminal endoplasmic reticulum (ER) retention signal. Although PDI resides in the ER where it mediates the folding of nascent polypeptides of the secretory pathway, we recently showed that PDI5 of Arabidopsis thaliana chaperones and inhibits cysteine proteases during trafficking to vacuoles prior to programmed cell death of the endothelium in developing seeds. Here we describe Arabidopsis PDI2, which shares a primary structure similar to that of classical PDI. Recombinant PDI2 is imported into ER-derived microsomes and complements the E. coli protein-folding mutant, dsbA. PDI2 interacted with proteins in both the ER and nucleus, including ER-resident protein folding chaperone, BiP1, and nuclear embryo transcription factor, MEE8. The PDI2-MEE8 interaction was confirmed to occur in vitro and in vivo. Transient expression of PDI2-GFP fusions in mesophyll protoplasts resulted in labeling of the ER, nucleus and vacuole. PDI2 is expressed in multiple tissues, with relatively high expression in seeds and root tips. Immunoelectron microscopy with GFP- and PDI2-specific antisera on transgenic seeds (PDI2-GFP) and wild type roots demonstrated that PDI2 was found in the secretory pathway (ER, Golgi, vacuole, cell wall) and the nuclei. Our results indicate that PDI2 mediates protein folding in the ER and has new functional roles in the nucleus.

Plasma membrane proteomes of differentially matured dendritic cells identified by LC-MS/MS combined with iTRAQ labelling

Dendritic cells (DCs) play a pivotal role in polarising Th lymphocyte subsets but it is unclear what molecular events occur when DCs generate Th2-type responses. Here, we analysed plasma membrane-enriched fractions from immature, pro-Th1 and pro-Th2 DCs and used a combination of iTRAQ labelling and LC–MS/MS to quantify changes in the proteomes. Analysis was performed on triplicate biological samples and changes verified by flow cytometry. MHC class II molecules and CD29 were up-regulated in pro-Th1 DCs whilst CD18 and CD44 were up-regulated in pro-Th2 DCs. One of the most down-regulated molecules in pro-Th1 DCs was YM-1 whilst the greatest decrease in pro-Th2 DCs was NAP-22. Other molecules up-regulated in pro-Th2 DC compared to pro-Th1 DCs included some potentially involved in protein folding during antigen processing (clathrin and Rab-7), whilst other non-membrane proteins such as enzymes/transporters related to cell metabolism (malate dehydrogenase, pyruvate kinase, and ATPase Na⁺/K⁺) were also recorded. This suggests that pro-Th2 DCs are more metabolically active while pro-Th1 DCs have a mature ‘end state’. Overall, although several molecules were preferentially expressed on pro-Th2 DCs, our proteomics data support the view of a ‘limited maturation’ of pro-Th2 DCs compared to pro-Th1 DCs.

Protein disulfide isomerase blocks CEBPA translation and is up-regulated during the unfolded protein response in AML

Deregulation of the myeloid key transcription factor CEBPA is a common event in acute myeloid leukemia (AML). We previously reported that the chaperone calreticulin is activated in subgroups of AML patients and that calreticulin binds to the stem loop region of the CEBPA mRNA, thereby blocking CEBPA translation. In this study, we screened for additional CEBPA mRNA binding proteins and we identified protein disulfide isomerase (PDI), an endoplasmic reticulum (ER) resident protein, to bind to the CEBPA mRNA stem loop region. We found that forced PDI expression in myeloid leukemic cells in fact blocked CEBPA translation, but not transcription, whereas abolishing PDI function restored CEBPA protein. In addition, PDI protein displayed direct physical interaction with calreticulin. Induction of ER stress in leukemic HL60 and U937 cells activated PDI expression, thereby decreasing CEBPA protein levels. Finally, leukemic cells from 25.4% of all AML patients displayed activation of the unfolded protein response as a marker for ER stress, and these patients also expressed significantly higher PDI levels. Our results indicate a novel role of PDI as a member of the ER stress-associated complex mediating blocked CEBPA translation and thereby suppressing myeloid differentiation in AML patients with activated unfolded protein response (UPR).

Bacitracin is not a specific inhibitor of protein disulfide isomerase

To successfully dissect molecular pathways in vivo, there is often a need to use specific inhibitors. Bacitracin is very widely used as an inhibitor of protein disulfide isomerase (PDI) in vivo. However, the specificity of action of an inhibitor for a protein-folding catalyst cannot be determined in vivo. Furthermore, in vitro evidence for the specificity of bacitracin for PDI is scarce, and the mechanism of inhibition is unknown. Here, we present in vitro data showing that 1 mM bacitracin has no significant effect on the ability of PDI to introduce or isomerize disulfide bonds in a folding protein or on its ability to act as a chaperone. Where bacitracin has an effect on PDI activity, the effect is relatively minor and appears to be via competition of substrate binding. Whereas 1 mM bacitracin has minimal effects on PDI, it has significant effects on both noncatalyzed protein folding and on other molecular chaperones. These results suggest that the use of bacitracin as a specific inhibitor of PDI in cellular systems requires urgent re-evaluation.

Proteomic analysis in monocytes of antiphospholipid syndrome patients: deregulation of proteins related to the development of thrombosis

OBJECTIVE

Antiphospholipid antibodies (aPL) are closely related to the development of thrombosis, but the exact mechanism(s) leading to thrombotic events remains unknown. In this study, using proteomic techniques, we evaluated changes in protein expression of monocytes from patients with antiphospholipid syndrome (APS) related to the pathophysiology of the syndrome.

METHODS

Fifty-one APS patients were included. They were divided into 2 groups: patients with previous thrombosis, and patients with recurrent spontaneous abortion. As controls, we studied patients with thrombosis but without aPL, and age- and sex-matched healthy subjects.

RESULTS

The proteins that were more significantly altered among monocytes from APS patients with thrombosis (annexin I, annexin II, protein disulfide isomerase, Nedd8, RhoA proteins, and Hsp60) were functionally related to the induction of a procoagulant state as well as to autoimmune-related responses. Proteins reported to be connected to recurrent spontaneous abortion (e.g., fibrinogen and hemoglobin) were also determined to be significantly deregulated in APS patients without thrombosis. In vitro treatment with IgG fractions purified from the plasma of APS patients with thrombosis changed the pattern of protein expression of normal monocytes in the same way that was observed in vivo for monocytes from APS patients with thrombosis.

CONCLUSION

For the first time, proteomic analysis has identified novel proteins that may be involved in the pathogenic mechanisms of APS, thus providing potential new targets for pathogenesis-based therapies for the disease.

Proteomics in antiphospholipid syndrome: a review

The presence of antiphospholipid antibodies (aPL) has been closely related to the development of thrombosis and complications in pregnancy. However, not all patients with aPL will develop those clinical features. The exact pathogenic mechanisms leading to thrombosis and/or pregnancy morbidity are poorly understood. Currently, biomarkers which enable one to predict the prognosis of patients with positive aPL are not readily available. Current advances in genomics and proteomics provide the opportunity to discover novel biomarkers based on changes in concentration levels or post-translational modifications of proteins and peptides. These techniques are now being applied in various areas of medicine with very promising results. This review covers recent studies that have used this approach for a better understanding of the pathogenic mechanisms involved in the development of thrombosis in patients with antiphospholipid syndrome (APS). Although, there are very few qualified biomarkers that have arisen as a result of efforts in proteomics, it is expected that these techniques will deliver biomarkers that might ultimately identify different subgroups of APS patients with various prognoses that might have implications with respect to management and prognosis. Lupus (2010) 19, 385—388.

The metallopeptide antibiotic bacitracin inhibits interleukin-12 αβ and β2 secretion

The metalloantibiotic bacitracin is a known inhibitor of protein disulfide isomerase (PDI). The disulfide-linked interleukin-12 (IL-12) αβ-heterodimer and β2-homodimer forms are crucial mediators of cell-mediated immune responses and inflammatory reactions. Bacitracin was found to potently block secretion of both the αβ- and β2-dimer forms of IL-12, while it did not affect secretion of the β-monomer. This inhibition coincided with a reduction in the intracellular amount of PDI found in complex with the β-chain during intracellular transit. Bacitracin did not affect mRNA levels of the α- and β-chain. Similar to bacitracin, N-acetylcysteine blocked αβ- and β2-secretion as well as PDI-β-chain complex formation. Thus, blocking PDI or shifting the endoplasmic reticulum towards a more reduced status disrupts the oxidative folding pathway or assembly of IL-12 dimer forms. The assembly stage of cytokines in the endoplasmic reticulum may represent a novel target for pharmacological intervention.

Identification of cancer-associated proteins by proteomics and downregulation of β-tropomyosin expression in colorectal adenoma and cancer

Elucidating the molecular mechanism underlying the development of adenoma, the major precursor lesion of colorectal cancer (CRC), would provide a basis for early detection, prevention as well as treatment of CRC. Using the highly sensitive 2-D DIGE method coupled with MS, we identified 24 differentially expressed proteins in adenoma tissues compared with matched normal colonic mucosa and CRC tissues. Fifteen proteins were downregulated and three proteins were upregulated in adenoma tissues when compared with individual-matched normal colonic mucosa. Five proteins were downregulated, while one protein was upregulated in adenoma tissues when compared with matched CRC tissues. A protein, β-tropomyosin (TM-β), recently suggested to be a biomarker of esophageal squamous carcinoma, was downregulated in both adenoma and CRC tissues. Additionally, the reduction in the level of TM-β in adenoma and CRC tissues was further validated by Western blotting (p<0.05) and RT-PCR (p<0.001). Our findings suggest that downregulation of TM-β is involved in the early development of CRC and that differentially expressed proteins might serve as potential biomarkers for detection of CRC.

Atorvastatin modifies the protein profile of circulating human monocytes after an acute coronary syndrome

Aggressive treatment with high-dose atorvastatin reduces more effectively the incidence of cardiovascular events than moderate statin therapy. The mechanism of this benefit has not been fully elucidated. In order to know the potential effects of statin treatment on the protein expression of circulating monocytes in acute coronary syndrome (ACS) patients, a proteomic analysis of these cells was carried out by 2-DE and MS. Twenty-five patients with non-ST-elevation acute coronary syndrome (NSTEACS) were randomized, the fourth day after admission, to receive ATV 80 mg/dL (n = 14) or conventional treatment (CT) (n = 11), for two months. Blood was withdrawn at the end of the treatment, and monocytes were extracted for proteomic analysis and their protein expression patterns determined. Age, sex, total cholesterol, LDL, HDL, triglycerides, body mass index, presence of hypertension, diabetes, and smoking status were not significantly different between the two groups of patients. The expression of 20 proteins was modified by intensive ATV. Among the most relevant results stand out the normalization by intensive ATV treatment of the expression of proteins that modulate inflammation and thrombosis such as protein disulfide isomerase ER60 (PDI), Annexin I, and prohibitin, or that have other protective effects as HSP-70. Thus, this approach shed light at the molecular level of the beneficial mechanisms of anti-atherothrombotic drugs.

Protein disulfide isomerase overexpression in vascular smooth muscle cells induces spontaneous preemptive NADPH oxidase activation and Nox1 mRNA expression: effects of nitrosothiol exposure

Mechanisms regulating NADPH oxidase remain open and include the redox chaperone protein disulfide isomerase (PDI). Here, we further investigated PDI effects on vascular NADPH oxidase. VSMC transfected with wild-type PDI (wt-PDI) or PDI mutated in all four redox cysteines (mut-PDI) enhanced (2.5-fold) basal cellular ROS production and membrane NADPH oxidase activity, with 3-fold increase in Nox1, but not Nox4 mRNA. However, further ROS production, NADPH oxidase activity and Nox1 mRNA increase triggered by angiotensin-II (AngII) were totally lost with PDI overexpression, suggesting preemptive Nox1 activation in such cells. PDI overexpression increased Nox4 mRNA after AngII stimulus, although without parallel ROS increase. We also show that Nox inhibition by the nitric oxide donor GSNO is independent of PDI. PDI silencing decreased specifically Nox1 mRNA and protein, confirming that PDI may regulate Nox1 at transcriptional level in VSMC. Such data further strengthen the role of PDI as novel NADPH oxidase regulator.

Proteomic Analysis of Endothelial Cell Autoantigens Recognized by Anti-Dengue Virus Nonstructural Protein 1 Antibodies

We previously showed the occurrence of autoimmune responses in dengue virus (DV) infection, which has potential implications for the pathogenesis of dengue hemorrhagic syndrome. In the present study, we have used a proteomic analysis to identify several candidate proteins on HMEC-1 endothelial cells recognized by anti-DV nonstructural protein 1 (NS1) antibodies. The target proteins, including ATP synthase β chain, protein disulfide isomerase, vimentin, and heat shock protein 60, co-localize with anti-NS1 binding sites on nonfixed HMEC-1 cells using immunohistochemical double staining and confocal microscopy. The cross-reactivity of anti-target protein antibodies with HMEC-1 cells was inhibited by NS1 protein pre-absorption. Furthermore, a cross-reactive epitope on NS1 amino acid residues 311–330 (P311–330) was predicted using homologous sequence alignment. The reactivity of dengue hemorrhagic patient sera with HMEC-1 cells was blocked by synthetic peptide P311–330 pre-absorption. Taken together, our results identify putative targets on endothelial cells recognized by anti-DV NS1 antibodies, where NS1 P311–330 possesses the shared epitope.

Downregulation of protein disulfide isomerase in sepsis and its role in tumor necrosis factor-alpha release

Introduction

Protein disulfide isomerase (PDI) is an important factor for the protein modification step in the post-translational event. PDI plays an essential role in cell survival under various stress conditions. It has been reported that PDI can serve as a negative regulator of nuclear factor-kappa-B (NF-κB) and that it can inhibit lipopolysaccharide (LPS)-induced proinflammatory cytokine production in macrophages. Thus, PDI may be an intracellular anti-inflammatory molecule. Although we have previously shown that Kupffer cell-derived proinflammatory cytokines cause liver injury in sepsis, the effect of sepsis on PDI expression as well as the effect of PDI inhibition on cytokine production have not been investigated. We therefore hypothesized that sepsis downregulates PDI expression and that the inhibition of PDI promotes proinflammatory cytokine production.

Method

Adult male rats were subjected to sepsis by cecal ligation and puncture (CLP) or endotoxemia (continuous infusion of 1 μg/kg body weight LPS by an osmotic pump) for 20 hours. Hepatic tissues were collected and PDI gene expression was determined. In additional experiments, cells from a macrophage-like cell line, RAW 264.7, were treated with 100 ng/mL LPS for 4 hours and protein expressions were measured. RAW 264.7 cells were also treated with bacitracin, a specific PDI inhibitor, for 24 hours, and tumor necrosis factor-alpha (TNF-α) gene and protein expression as well as its release in the cell supernatant were determined. To further confirm the beneficial effect of PDI in sepsis, RAW 264.7 cells were transfected with PDI short interfering RNA (siRNA) and PDI gene expression and TNF-α release were measured by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

Results

PDI gene expression was significantly decreased by 28% and 69% at 20 hours after CLP or LPS infusion, respectively. LPS also decreased PDI protein expression by 33% in RAW 264.7 cells. Incubation of RAW 264.7 cells with bacitracin significantly increased TNF-α gene expression and TNF-α release as well as its cellular levels in a dose-dependent manner. Transfection of RAW 264.7 cells with PDI siRNA produced an average 36.8% inhibition of the PDI gene expression. This downregulation was correlated with a 3.19-fold increase in TNF-α release into the cell supernatant.

Conclusion

Taken together, these results suggest that downregulation of PDI by sepsis significantly increases proinflammatory cytokine production. Thus, prevention of PDI downregulation in sepsis may be a novel approach to attenuate hyperinflammation and to reduce tissue injury under such conditions.

Proteomic profiling reveals that Th2-inducing dendritic cells stimulated with helminth antigens have a 'limited maturation' phenotype

Dendritic cells (DCs) are important in the initiation of primary immune responses against pathogens. To aid understanding of how DCs guide T helper (Th)2-type responses, we employed 2-DE in association with MS/MS to identify proteins which characterise pro-Th2 DCs (matured with zero-to-three hours released proteins (0-3hRP), released by Schistosoma mansoni cercariae) versus pro-Th1 DCs (matured with lipopolysaccharide, LPS) and immature DCs. Software analysis of average 2-DE gels (three replicates per DC type) showed many similarities in the pattern of spots between the three groups of DCs but also marked changes. The major and significant changes in protein expression mainly affected cytoskeletal proteins. Other differences included chaperone proteins and enzymes involved in protein folding, S100 calcium-binding proteins, peroxiredoxin 1, superoxide dismutase 1, several annexins and arginase 1. Our study demonstrates that pro-Th2 DCs matured with 0-3hRP exhibit a proteome that is intermediate between that of immature DCs and pro-Th1 DCs. Finally, the differential regulation of protein spots identified by MALDI-MS/MS as having cytoskeletal and morphological functions was confirmed by contrast, confocal and scanning electron microscopy examination of DCs. Together, our results support the view that Th2 differentiation results from a 'limited maturation' of DCs.

Neospora caninum: functional inhibition of protein disulfide isomerase by the broad-spectrum anti-parasitic drug nitazoxanide and other thiazolides

Nitazoxanide (NTZ) and several NTZ-derivatives (thiazolides) have been shown to exhibit considerable anti-Neospora caninum tachyzoite activity in vitro. We coupled tizoxanide (TIZ), the deacetylated metabolite, to epoxy-agarose-resin and performed affinity chromatography with N. caninum tachyzoite extracts. Two main protein bands of 52 and 43kDa were isolated. The 52kDa protein was readily recognized by antibodies directed against NcPDI, and mass spectrometry confirmed its identity. Poly-histidine-tagged NcPDI-cDNA was expressed in Escherichia coli and recombinant NcPDI (recNcPDI) was purified by Co2+-affinity chromatography. By applying an enzyme assay based on the measurement of insulin crosslinking activity, recNcPDI exhibited properties reminiscent for PDIs, and its activity was impaired upon the addition of classical PDI inhibitors such as bacitracin (1-2mM), para-chloromercuribenzoic acid (0.1-1mM) and tocinoic acid (0.1-1mM). RecNcPDI-mediated insulin crosslinking was inhibited by NTZ (5-100 microM) in a dose-dependent manner. In addition, the enzymatic activity of recNcPDI was inhibited by those thiazolides that also affected parasite proliferation. Thus, thiazolides readily interfere with NcPDI, and possibly also with PDIs from other microorganisms susceptible to thiazolides.

Circulating human monocytes in the acute coronary syndrome express a characteristic proteomic profile

We examined the proteome of circulating monocytes of patients with acute coronary syndrome at different times in comparison to that of patients with stable coronary artery disease. On admission, the expression of 18 spot proteins was altered, 10 of which were totally absent. This pattern changed progressively, and at 6 months, there were no differences with the monocyte proteome of stable patients.

Proteomic Analysis of the Resistance to Aplidin in Human Cancer Cells

Aplidin (plitidepsin) is an antitumoral agent that induces apoptosis via Rac1-JNK activation. A proteomic approach using 2D-DIGE technology found 52 cytosolic and 39 membrane proteins differentially expressed in wild-type and Aplidin-resistant HeLa cells, of which 39 and 27 were identified by MALDI-TOF mass spectrometry and database interrogation. A number of proteins involved in apoptosis pathways were found to be deregulated. Alterations in Rab geranylgeranyltransferase, protein disulfide isomerase (PDI), cystathionine gamma-lyase, ezrin, and cyclophilin A (CypA) were confirmed by immunoblotting. Moreover, the role of PDI and CypA in Aplidin resistance was functionally confirmed by using the inhibitor bacitracin and overexpression, respectively. These deregulated proteins are candidates to mediate, at least partially, Aplidin action and might provide a route to the cells to escape the induction of apoptosis by this drug.

The Nonantibiotic Anti-Inflammatory Effect of Antimicrobial Growth Promoters, the Real Mode of Action? A Hypothesis

Societal concern and government regulations increasingly press for restricting the use of antibiotics as antimicrobial growth promoters (AGP). The search for alternatives is on, hampered by a lack of knowledge about the exact mechanism of AGP. Feed additives, such as AGP and alternatives, interact with the intestine. In the intestine, feed components, microbiota, and the mucosa interact in a very complex and dynamic way. Various mechanisms for AGP have been proposed, invariably based on the direct antibiotic influence on the microbial composition of the intestines. In the literature on antibiotics, however, the direct effects of antibiotics on host cells, in particular inflammatory cells, have been described. It is curious that this has never been considered in the literature on AGP. Presently, a case is being made that AGP most likely work as growth permitters by inhibiting the production and excretion of catabolic mediators by intestinal inflammatory cells. Concomitant or subsequent changes in microflora are most likely the consequence of an altered condition of the intestinal wall. This common, basic mechanism potentially offers an excellent explanation for the highly reproducible effects of AGP, as opposed to those obtained by alternatives aimed at microflora management. Therefore, the search for alternatives could be aimed at nonantibiotic compounds with an effect on the inflammatory system similar to that of AGP.

Atorvastatin modulates the profile of proteins released by human atherosclerotic plaques

The mechanisms by which hydroxymethylglutaryl CoenzymeA reductase inhibitors (statins) reduce atherosclerotic cardiovascular morbidity and mortality remain poorly understood. Statins have been shown to modulate the levels of different inflammatory proteins both in carotid atherosclerotic plaques and in the blood of patients with atherosclerosis. In this work, we hypothesize that statins could also modulate the levels of the proteins secreted by cultured atherosclerotic plaques. Thus, the secretomes obtained from complicated atherosclerotic plaques incubated in the presence/absence of atorvastatin (10 micromol/l, 24 h) were analysed and compared by two-dimensional electrophoresis, considering the fibrous adjacent areas as controls. In total, 54 proteins (83 protein isoforms) were identified by Mass Spectrometry (MS): 24 proteins were increased and 20 proteins decreased in atheroma plaque supernatants compared to controls. Some of these proteins, like Cathepsin D, could play a significant role in plaque instability, becoming a potential target for therapeutical treatment. Interestingly, 66% of the proteins differentially released by atherosclerotic plaques reverted to control values after administration of atorvastatin, among them, Cathepsin D. Moreover, plaques obtained from patients who received atorvastatin treatment prior to carotid endarterectomy showed decreased Cathepsin D expression relative to plaques from non-treated patients. In conclusion, this proteomic approach has shown that statins are able to modulate the secretome of atherosclerotic plaques, and new therapeutical targets for statins have been characterised.

Montelukast prevents the decrease of interleukin-10 and inhibits NF-kappaB activation in inflammatory airway of asthmatic guinea pigs

Interleukin (IL)-10 is an important immunoregulatory and anti-inflammatory cytokine, whereas nuclear factor-kappaB (NF-kappaB) plays an important role in the pathogenesis of asthma. In the present study, the effects of montelukast on the level of IL-10 and on the activation of NF-kappaB in the inflammatory airway of asthmatic guinea pigs were investigated. Guinea pigs were sensitized by ovalbumin. Pulmonary inflammation was observed by hematoxylin and eosin staining. The eosinophils in broncho-alveolar lavage fluid and blood were separated by density gradient centrifugation and counted under microscope. The level of IL-10 in broncho-alveolar lavage fluid was measured by enzyme-linked immunoadsorbent assay. Activation of NF-kappaB in lung tissues was inspected by immunohistochemistry. Montelukast at medium and high doses prevented the decrease of IL-10 in broncho-alveolar lavage fluid (n = 8, p < 0.01 vs. asthma model group), inhibited the activation of NF-kappaB in lung tissues (n = 8; medium dose, p < 0.05; high dose, p < 0.01; vs. asthma model group). There was a significantly negative correlation between the level of IL-10 and the activation of NF-kappaB in lung tissues (r = -0.488, p < 0.01). Montelukast reduced the severity of airway inflammation and the number of eosinophils in asthmatic guinea pigs. From all these findings we conclude that montelukast can prevent the decrease of IL-10 and inhibit the activation of NF-kappaB in inflammatory airway of asthmatic guinea pigs, which may be the new important mechanisms of montelukast's anti-airway-inflammation effects in asthmatic guinea pigs.

Carrageenan is a potent inhibitor of papillomavirus infection

Certain sexually transmitted human papillomavirus (HPV) types are causally associated with the development of cervical cancer. Our recent development of high-titer HPV pseudoviruses has made it possible to perform high-throughput in vitro screens to identify HPV infection inhibitors. Comparison of a variety of compounds revealed that carrageenan, a type of sulfated polysaccharide extracted from red algae, is an extremely potent infection inhibitor for a broad range of sexually transmitted HPVs. Although carrageenan can inhibit herpes simplex viruses and some strains of HIV in vitro, genital HPVs are about a thousand-fold more susceptible, with 50% inhibitory doses in the low ng/ml range. Carrageenan acts primarily by preventing the binding of HPV virions to cells. This finding is consistent with the fact that carrageenan resembles heparan sulfate, an HPV cell-attachment factor. However, carrageenan is three orders of magnitude more potent than heparin, a form of cell-free heparan sulfate that has been regarded as a highly effective model HPV inhibitor. Carrageenan can also block HPV infection through a second, postattachment heparan sulfate–independent effect. Carrageenan is in widespread commercial use as a thickener in a variety of cosmetic and food products, ranging from sexual lubricants to infant feeding formulas. Some of these products block HPV infectivity in vitro, even when diluted a million-fold. Clinical trials are needed to determine whether carrageenan-based products are effective as topical microbicides against genital HPVs.

Sexually transmitted human papillomavirus (HPV) infections are very common. Although most HPV infections don't cause noticeable symptoms, persistent infection with some genital HPV types can lead to cervical cancer or other anal/genital cancers. Another subset of HPV types can cause genital warts. Recent studies have suggested that condoms are not highly effective in preventing HPV infection. Although HPV vaccines will soon become available, they probably will not protect against all genital HPV types and will be too expensive for use in the developing world. Inexpensive HPV-inhibitory compounds (known as topical microbicides) might be useful for blocking the spread of HPV. Using a newly developed cell culture–based HPV inhibition test, we have discovered that an inexpensive gelling agent called carrageenan is an unexpectedly potent HPV infection inhibitor. Carrageenan is also under investigation as a topical microbicide targeting HIV and herpes viruses, but it is a thousand times more effective against HPV in cell culture tests. Interestingly, carrageenan is used as a thickener in some commercially available sexual lubricants and lubricated condoms. Several of these commercial lubricant products are potent HPV inhibitors in our cell culture–infection system. Clinical trials are needed to determine the effectiveness of carrageenan as a topical microbicide against HPV.

Induction of the unfolded protein response in familial amyotrophic lateral sclerosis and association of protein-disulfide isomerase with superoxide dismutase 1

Mutations in Cu/Zn superoxide dismutase (SOD1) are linked to motor neuron death in familial amyotrophic lateral sclerosis (ALS) by an unclear mechanism, although misfolded SOD1 aggregates are commonly associated with disease. Proteomic analysis of the transgenic SOD1(G93A) ALS rat model revealed significant up-regulation of endoplasmic reticulum (ER)-resident protein-disulfide isomerase (PDI) family members in lumbar spinal cords. Expression of SOD1 mutants (mSOD1) led to an up-regulation of PDI in motor neuron-like NSC-34 cells but not other cell lines. Inhibition of PDI using bacitracin increased aggregate production, even in wild type SOD1 transfectants that do not readily form inclusions, suggesting PDI may protect SOD1 from aggregation. Moreover, PDI co-localized with intracellular aggregates of mSOD1 and bound to both wild type and mSOD1. SOD1 was also found in the microsomal fraction of cells despite being a predominantly cytosolic enzyme, confirming ER-Golgi-dependent secretion. In SOD1(G93A) mice, a significant up-regulation of unfolded protein response entities was also observed during disease, including caspase-12, -9, and -3 cleavage. Our findings therefore implicate unfolded protein response and ER stress-induced apoptosis in the patho-physiology of familial ALS. The possibility that PDI may be a therapeutic target to prevent SOD1 aggregation is also raised by this study.

Proteomic approach in the search of new cardiovascular biomarkers

With the increasing incidence of cardiovascular diseases worldwide, specifically atherosclerosis and heart failure, the search for novel biomarkers remains a priority. As opposed to complex diagnostic techniques that may not be suitable to be applied to the wider population, biomarkers are useful for population screening. The search for novel biomarkers is based on knowledge of the molecular and cellular processes that take place in the development of a specific disease. Atherosclerosis and heart failure are characterized by a long period of silent disease progression, allowing early diagnosis and the potential of early therapeutic intervention. The use of the so-called proteomic techniques allows not only protein identification but partial characterization, which includes expression and also post-translational modification of these proteins. This allows for the discovery of previously unknown proteins involved in cardiovascular diseases, including some that may be suitable to be used as biomarkers. However, to approach this issue, we have to overcome difficulties such as tissue heterogeneity (vessel wall or myocardium) and the lack of fresh human samples. We discuss the proteomic study of human plaques, secreted proteins by pathologic and normal vessel wall, and left ventricular hypertrophy as potential sources of new biologic markers of cardiovascular disease.

FAD oxidizes the ERO1-PDI electron transfer chain: the role of membrane integrity

The molecular steps of the electron transfer in the endoplasmic reticulum from the secreted proteins during their oxidation are relatively unknown. We present here that flavine adenine dinucleotide (FAD) is a powerful oxidizer of the oxidoreductase system, Ero1 and PDI, besides the proteins of rat liver microsomes and HepG2 hepatoma cells. Inhibition of FAD transport hindered the action of FAD. Microsomal membrane integrity was mandatory for all FAD-related oxidation steps downstream of Ero1. The PDI inhibitor bacitracin could inhibit FAD-mediated oxidation of microsomal proteins and PDI, but did not hinder the FAD-driven oxidation of Ero1. Our data demonstrated that Ero1 can utilize FAD as an electron acceptor and that FAD-driven protein oxidation goes through the Ero1-PDI pathway and requires the integrity of the endoplasmic reticulum membrane. Our findings prompt further studies to elucidate the membrane-dependent steps of PDI oxidation and the role of FAD in redox folding.