Bacterial Lipoproteins Research Articles

Haplotype structure and positive selection at TLR1

Toll-like receptor 1, when dimerized with Toll-like receptor 2, is a cell surface receptor that, upon recognition of bacterial lipoproteins, activates the innate immune system. Variants in TLR1 associate with the risk of a variety of medical conditions and diseases, including sepsis, leprosy, tuberculosis, and others. The foremost of these is rs5743618 c.2079T>G(p.(Ile602Ser)), the derived allele of which is associated with reduced risk of sepsis, leprosy, and other diseases. Interestingly, 602Ser, which shows signatures of selection, inhibits TLR1 surface trafficking and subsequent activation of NFκB upon recognition of a ligand. This suggests that reduced TLR1 activity may be beneficial for human health. To better understand TLR1 variation and its link to human health, we have typed all 7 high-frequency missense variants (>5% in at least one population) along with 17 other variants in and around TLR1 in 2548 individuals from 56 populations from around the globe. We have also found additional signatures of selection on missense variants not associated with rs5743618, suggesting that there may be multiple functional alleles under positive selection in this gene.

Empty liposomes induce antitumoral effects associated with macrophage responses distinct from those of the TLR1/2 agonist Pam3CSK 4 (BLP).

Liposomes are frequently used in cancer therapy to encapsulate and apply anticancer drugs. Here, we show that a systemic treatment of mice bearing skin tumors with empty phosphatidylcholine liposomes (PCL) resulted in inhibition of tumor growth, which was similar to that observed with the synthetic bacterial lipoprotein and TLR1/2 agonist Pam(3)CSK(4) (BLP). Both compounds led to a substantial decrease of macrophages in spleen and in the tumor-bearing skin. Furthermore, both treatments induced the expression of typical macrophage markers in the tumor-bearing tissue. As expected, BLP induced the expression of the M1 marker genes Cxcl10 and iNOS, whereas PCL, besides inducing iNOS, also increased the M2 marker genes Arg1 and Trem2. In vitro experiments demonstrated that neither PCL nor BLP influenced proliferation or survival of tumor cells, whereas both compounds inhibited proliferation and survival and increased the migratory capacity of bone marrow-derived macrophages (BMDM). However, in contrast to BLP, PCL did not activate cytokine secretion and induced a different BMDM phenotype. Together, the data suggest that similar to BLP, PCL induce an antitumor response by influencing the tumor microenvironment, in particular by functional alterations of macrophages, however, in a distinct manner from those induced by BLP.

Molecular Cloning and Characterization of a Surface-Localized Adhesion Protein in Mycoplasma bovis Hubei-1 Strain

Mycoplasma bovis (M. bovis) is an important pathogen that causes various bovine diseases, such as mastitis in cows and pneumonia in calves. The surface proteins are generally thought to play a central role in the pathogenesis of this organism. We screened the entire genome of M. bovis Hubei-1 and discovered a gene named vpmaX that encodes the 25 kDa variable surface lipoprotein A (VpmaX). Sequence analysis revealed that VpmaX contains several repetitive units and a typical bacterial lipoprotein signal sequence. The vpmaX gene was cloned and expressed in E. coli to obtain recombinant VpmaX (rVpmaX). Western blot analysis using a rabbit antibody against rVpmaX demonstrated that VpmaX is a membrane protein. Immunostaining visualized via confocal laser scanning microscopy showed that rVpmaX was able to adhere to embryonic bovine lung cells (EBL), and this was also confirmed by a sandwich ELISA. In summary, a surface-localized adhesion protein was identified in M. bovis Hubei-1.

Cytoplasmic receptors recognizing nucleic acids and mediating immune functions in neutrophils

Cells belonging to the innate immune system, including neutrophils, rapidly respond to invading microorganisms by recognizing a wide range of microbial-derived products referred to as pathogen-associated molecular patterns (PAMPs). Generally speaking, PAMPs include molecular structures associated with microbial envelopes (such as bacterial lipopolysaccharide, lipoproteins, and flagellin) and microbial nucleic acids. PAMPs bind to and activate various families of germline-encoded receptors carried by cells of the innate immune system, known as pattern-recognition receptors (PRRs). This group of receptors, located in various subcellular compartments, in turn generates a series of intracellular signaling pathways that coordinately modulate the transcription of hundreds of inflammatory genes, the products of which directly control infection and/or contribute to promote the development of the innate and adaptive immune responses. Herein, we summarize current knowledge on neutrophil recognition and response to foreign cytoplasmic nucleic acids.

Differential role of Dok1 and Dok2 in TLR2-induced inflammatory signaling in glia

Accumulating evidence continues to underpin the role of the innate immune system in pathologies associated with neuroinflammation. Innate immunity is regulated by pattern recognition receptors that detect pathogens, and in the case of Gram-positive bacteria, binding of bacterial lipopeptides to toll-like receptor (TLR)2 is emerging as an important mechanism controlling glial cell activation. In the present study, we employed the use of the synthetic bacterial lipoprotein and a selective TLR2 agonist, Pam3CSK4, to induce inflammatory signaling in microglia and astrocytes. The adaptor proteins, downstream of kinase (Dok)1 and Dok2, are known to have a role in negatively regulating the Ras-ERK signaling cascade, with downstream consequences on pro-inflammatory cytokine expression. Data presented herein demonstrate that TLR2 enhanced the tyrosine phosphorylation of Dok1 and Dok2 in astrocytes and microglia, and that knockdown of these adaptors using small interfering RNA robustly elevated TLR2-induced ERK activation. Importantly, TLR2-induced NF-κB activation, and IL-6 production was exacerbated in astrocytes transfected with Dok1 and Dok2 siRNA, indicating that both Dok proteins negatively regulate TLR2-induced inflammatory signaling in astrocytes. In contrast, Dok1 knockdown attenuated TLR2-induced NF-κB activation and IL-6 production in microglia, while Dok2 siRNA failed to affect TLR2-induced NF-κB activity and subsequent cytokine expression in this cell type. Overall, this indicates that Dok1 and Dok2 are novel adaptors for TLR2 in glial cells and importantly indicates that Dok1 and Dok2 differentially regulate TLR2-induced pro-inflammatory signaling in astrocytes and microglia.

Fried to a CRISPR

Molecular Biology The CRISPR-Cas system, found in many bacteria and archea, is known as an adaptive defense against the invasion of foreign DNA. The bacteria/archea capture fragments of plasmids and phages and incorporate them into one or more CRIPSR loci. The captured sequences are then transcribed and cleaved into short CRISPR (cr)RNAs, which, when bound by a Cas nuclease complex, are used to target the invading nucleic acid for destruction. Previous work suggested a link between bacterial virulence and the CRISPR system. Sampson et al. now show that in the intracellular parasite Francisella novicida , CRISPR-Cas is required for evasion of the host's innate immune system. The F. novicida CRISPR locus encodes a small CRISPR/Cas-associated RNA (scaRNA) that has complementarity to both a trans-acting crRNA (tracrRNA) and its own lipoprotein gene. The scaRNA, together with the tracrRNA and Cas9 nuclease, acts to repress expression of the F. novicida lipoprotein during host infection. This allows the infecting bacteria to avoid detection by one of the host's pathogen pattern recognition receptors, which binds to bacterial lipoproteins, and activates the host's innate immune response. CRISPR-Cas regulation of endogenous genes may play a broad role in bacterial virulence. Nature 10.1038/nature12048 (2013).

Lipoproteins are an important bacterial component responsible for bone destruction through the induction of osteoclast differentiation and activation

Bacterial infection can cause inflammatory bone diseases accompanied by the bone destruction resulting from excess generation of osteoclasts. Although lipoproteins are one of the major immunostimulating components of bacteria, little is known about their effects on bone metabolism. In this study, we investigated the role of lipoproteins in bacteria-induced bone destruction using Staphylococcus aureus wild type, its lipoprotein-deficient mutant, and synthetic lipopeptides Pam2CSK4 and Pam3CSK4 known to mimic bacterial lipoproteins. Formaldehyde-inactivated S. aureus or the synthetic lipopeptides induced severe bone loss in the femurs of mice after intraperitoneal administration and in a calvarial bone implantation model, whereas the lipoprotein-deficient S. aureus did not show such effects. Mechanism studies further identified three action mechanisms for the lipopeptide-induced osteoclast differentiation and bone resorption via (i) enhancement of osteoclast differentiation through Toll-like receptor 2 and MyD88-dependent signaling pathways; (ii) induction of pro-inflammatory cytokines, TNF-α and IL-6; and (iii) upregulation of RANKL expression with downregulation of osteoprotegerin expression in osteoblasts. Taken together, these results suggest that lipoprotein might be an important bacterial component responsible for bone destruction during bacterial infections through augmentation of osteoclast differentiation and activation.

MicroRNA-146a Is Upregulated by and Negatively Regulates TLR2 Signaling

TLR signaling is a crucial component of the innate immune response to infection. MicroRNAs (miRNAs) have been shown to be upregulated during TLR signaling. Specifically, microRNA-146a (miR-146a) plays a key role in endotoxin tolerance by downregulating interleukin-1 receptor-associated kinase 1 (IRAK-1). The aim of this study was to assess the role of miR-146a in the TLR2 signaling and development of bacterial lipoprotein (BLP) self-tolerance and cross-tolerance to bacteria. Expression of miR-146a increased in a dose- and time-dependent manner in BLP-stimulated human THP-1 promonocytic cells. In BLP-tolerised cells miR-146a was even further upregulated in response to BLP re-stimulation (p<0.001). Re-stimulation of BLP-tolerised cells with heat-killed gram-negative Salmonella typhimurium (S. typhimurium), but not gram-positive Staphylococcus aureus (S. aureus), led to significant overexpression of miR-146a (p<0.05). Transfection of naive cells with a miR-146a mimic substantially suppressed TNF-α production (p<0.05). Furthermore, overexpression of miR-146a resulted in strong reduction in IRAK-1 and phosphorylated IκBα expression in naive and S. typhimurium-stimulated THP-1 cells. Collectively, miR-146a is upregulated in response to BLP and bacterial stimulation in both naive and BLP-tolerised cells. Overexpression of miR-146a induces a state analogous to tolerance in BLP-stimulated cells and therefore may represent a future target for exogenous modulation of tolerance during microbial infection and sepsis.

A CRISPR/Cas system mediates bacterial innate immune evasion and virulence

CRISPR/Cas (clustered regularly interspaced palindromic repeats/CRISPR-associated) systems are a bacterial defence against invading foreign nucleic acids derived from bacteriophages or exogenous plasmids. These systems use an array of small CRISPR RNAs (crRNAs) consisting of repetitive sequences flanking unique spacers to recognize their targets, and conserved Cas proteins to mediate target degradation. Recent studies have suggested that these systems may have broader functions in bacterial physiology, and it is unknown if they regulate expression of endogenous genes. Here we demonstrate that the Cas protein Cas9 of Francisella novicida uses a unique, small, CRISPR/Cas-associated RNA (scaRNA) to repress an endogenous transcript encoding a bacterial lipoprotein. As bacterial lipoproteins trigger a proinflammatory innate immune response aimed at combating pathogens, CRISPR/Cas-mediated repression of bacterial lipoprotein expression is critical for F. novicida to dampen this host response and promote virulence. Because Cas9 proteins are highly enriched in pathogenic and commensal bacteria, our work indicates that CRISPR/Cas-mediated gene regulation may broadly contribute to the regulation of endogenous bacterial genes, particularly during the interaction of such bacteria with eukaryotic hosts.

Using biotinylation to determine the orientations of Pal in Escherichia coli

Nontypable Haemophilus influenzae (NTHi) causes otitis media and other respiratory diseases in people of all ages, conferring the need for a vaccine against the bacteria. P6, a lipoprotein vaccine candidate for NTHi, was recently discovered to exhibit two populations: one facing out of the cell and one facing in towards the periplasm. We hypothesized that dual orientation is a novel, widespread phenomenon among bacterial lipoproteins. To corroborate our hypothesis, we performed a biotinylation experiment on Pal, homolog to P6, in Escherichia coli (E. coli). In the experiment, whole cells were incubated with a cell‐impermeable biotinylating reagent (NHS‐LC‐LC‐biotin) in order to label all surface exposed proteins. The labeled, outer proteins were separated from the unlabeled, internal proteins via streptavidin‐agarose beads. Standard protein detection and immunoblotting techniques confirmed that Pal exists in two orientations in E. coli, with the majority of Pal facing in toward the periplasmic space. Only one other protein (Lpp of E. coli) has been shown to exhibit dual orientations. The results of this experiment suggest that lipoprotein dual orientation may be more widespread than originally thought, which could have important implications in the field of bacterial lipoprotein biology. This study was funded by the Rochester Institute of Technology and NIH NIDCD RO1 08671 (to MEP).

Human Lipopolysaccharide-binding Protein (LBP) and CD14 Independently Deliver Triacylated Lipoproteins to Toll-like Receptor 1 (TLR1) and TLR2 and Enhance Formation of the Ternary Signaling Complex

Bacterial lipoproteins are the most potent microbial agonists for the Toll-like receptor 2 (TLR2) subfamily, and this pattern recognition event induces cellular activation, leading to host immune responses. Triacylated bacterial lipoproteins coordinately bind TLR1 and TLR2, resulting in a stable ternary complex that drives intracellular signaling. The sensitivity of TLR-expressing cells to lipoproteins is greatly enhanced by two lipid-binding serum proteins known as lipopolysaccharide-binding protein (LBP) and soluble CD14 (sCD14); however, the physical mechanism that underlies this increased sensitivity is not known. To address this, we measured the ability of LBP and sCD14 to drive ternary complex formation between soluble extracellular domains of TLR1 and TLR2 and a synthetic triacylated lipopeptide agonist. Importantly, addition of substoichiometric amounts of either LBP or sCD14 significantly enhanced formation of a TLR1·TLR2 lipopeptide ternary complex as measured by size exclusion chromatography. However, neither LBP nor sCD14 was physically associated with the final ternary complex. Similar results were obtained using outer surface protein A (OspA), a naturally occurring triacylated lipoprotein agonist from Borrelia burgdorferi. Activation studies revealed that either LBP or sCD14 sensitized TLR-expressing cells to nanogram levels of either the synthetic lipopeptide or OspA lipoprotein agonist. Together, our results show that either LBP or sCD14 can drive ternary complex formation and TLR activation by acting as mobile carriers of triacylated lipopeptides or lipoproteins.

Immunopathology of Brucella Infection

In spite of the protean nature of the disease, inflammation is a hallmark of brucellosis and affected tissues usually exhibit inflammatory infiltrates. As Brucella lacks exotoxins, exoproteases or cytolysins, pathological findings in brucellosis probably arise from inflammation-driven processes. The cellular and molecular bases of immunopathological phenomena probably involved in Brucella pathogenesis have been unraveled in the last few years. Brucella-infected osteoblasts, either alone or in synergy with infected macrophages, produce cytokines, chemokines and matrixmetalloproteinases (MMPs), and similar phenomena are mounted by fibroblast-like synoviocytes. The released cytokines promote the secretion of MMPs and induce osteoclastogenesis. Altogether, these phenomena may contribute to the bone loss and cartilage degradation usually observed in brucellar arthritis and osteomyelitis. Proinflammatory cytokines may be also involved in the pathogenesis of neurobrucellosis. B. abortus and its lipoproteins elicit an inflammatory response in the CNS of mice, leading to astrogliosis, a characteristic feature of neurobrucellosis. Heat-killed bacteria (HKBA) and the L-Omp19 lipoprotein elicit astrocyte apoptosis and proliferation (two features of astrogliosis), and apoptosis depends on TNF-α signaling. Brucella also infects and replicates in human endothelial cells, inducing the production of chemokines and IL-6, and an increased expression of adhesion molecules. The sustained inflammatory process derived from the longlasting infection of the endothelium may be important for the development of endocarditis. Therefore, while Brucella induces a low grade inflammation as compared to other pathogens, its prolonged intracellular persistence in infected tissues supports a long-lasting inflammatory response that mediates different pathways of tissue damage. In this context, approaches to avoid the invasion of host cells or limit the intracellular survival of the bacterium may be suitable to prevent the pathological consequences of Brucella infections. The article presents some of the recent patents related to such approaches. Keywords: Astrogliosis, bacterial lipoproteins, cytokines, inflammation, matrix metalloproteinases, osteoclastogenesis, TLR2, Neurobrucellosis, osteomyelitis, lipopolysaccharide

Immune Enhancing Bacterial Endophytic Components in Echinacea and Other Botanicals

We have found that the bacterial components lipopolysaccharides (LPS) and Braun-type lipoproteins are responsible for the majority of the in vitro macrophage activation exhibited by extracts of Echinacea and other immune enhancing botanicals. Furthermore, we show that endophytic bacteria are the principal source of these components. We also show that total bacterial load within Echinacea samples are strongly correlated with the innate immune stimulatory activity (NF-κB activation in THP-1 cells) and content of bacterial LPS within extracts of this plant material. Differences in the levels of these two bacterial components are responsible for the substantial variation observed (˜200-fold) in innate immune cell activation from E. purpurea material obtained from six major growers/commercial suppliers in North America. This substantial variability in bacterial component content/activity could be a factor contributing to the inconsistent outcomes exhibited in Echinacea clinical trials. We also demonstrate that the oral consumption of extracts rich in these bacterial components is therapeutically relevant with respect to enhancing immune parameters and for impacting disease outcomes in both animal models and in humans. Acknowledgements: This research was partially funded by grants from the National Institutes of Health R21AT01207, R01AT002360 and R01AT007042 (NCAAM) to DSP and by the USDA, Agricultural Research Service Specific Cooperative Agreement No. 58 – 6408 – 02 – 1-612.

Degradation of MAC13243 and studies of the interaction of resulting thiourea compounds with the lipoprotein targeting chaperone LolA

The discovery of novel small molecules that function as antibacterial agents or cellular probes of biology is hindered by our limited understanding of bacterial physiology and our ability to assign mechanism of action. We previously employed a chemical genomic strategy to identify a novel small molecule, MAC13243, as a likely inhibitor of the bacterial lipoprotein targeting chaperone, LolA. Here, we report on the degradation of MAC13243 into the active species, S-(4-chlorobenzyl)isothiourea. Analogs of this compound (e.g., A22) have previously been characterized as inhibitors of the bacterial actin-like protein, MreB. Herein, we demonstrate that the antibacterial activity of MAC13243 and the thiourea compounds are similar; these activities are suppressed or sensitized in response to increases or decreases of LolA copy number, respectively. We provide STD NMR data which confirms a physical interaction between LolA and the thiourea degradation product of MAC13243, with a Kd of ∼150μM. Taken together, we conclude that the thiourea series of compounds share a similar cellular mechanism that includes interaction with LolA in addition to the well-characterized target MreB.

The crystal structure of human soluble CD14 reveals a bent solenoid with a hydrophobic amino-terminal pocket.

Human monocyte differentiation Ag CD14 is a pattern recognition receptor that enhances innate immune responses to infection by sensitizing host cells to bacterial LPS (endotoxin), lipoproteins, lipoteichoic acid, and other acylated microbial products. CD14 physically delivers these lipidated microbial products to various TLR signaling complexes that subsequently induce intracellular proinflammatory signaling cascades upon ligand binding. The ensuing cellular responses are usually protective to the host but can also result in host fatality through sepsis. In this work, we have determined the x-ray crystal structure of human CD14. The structure reveals a bent solenoid typical of leucine-rich repeat proteins with an amino-terminal pocket that presumably binds acylated ligands including LPS. Comparison of human and mouse CD14 structures shows great similarity in overall protein fold. However, compared with mouse CD14, human CD14 contains an expanded pocket and alternative rim residues that are likely to be important for LPS binding and cell activation. The x-ray crystal structure of human CD14 presented in this article may foster additional ligand-bound structural studies, virtual docking studies, and drug design efforts to mitigate LPS-induced sepsis and other inflammatory diseases.

Toll-like Receptor 11 (TLR11) Prevents Salmonella Penetration into the Murine Peyer Patches

Toll-like receptors (TLRs) are key molecular sensors used by the mammalian innate immune system to detect microorganisms. Although TLR functions in colonic immune homeostasis and tolerance to commensal bacteria have been intensively researched, the precise roles of different TLRs in response to pathogen infection in the gut remain elusive. Peyer patches are the major entrance of Salmonella infection and antigen transportation in intestine. Here, we report that, in contrast to TLR5 as a "carrier of Salmonella," TLR11 works as a "blocker of Salmonella" to prevent highly invasive Salmonella from penetrating into the murine Peyer patches and spreading systemically. TLR11 plays an important role in mediating TNF-α induction and systemic inflammation in response to Salmonella infection. Remarkably, in mice lacking TLR11, apparent hemorrhages at Peyer patches are induced by highly invasive Salmonella, a phenotype resembling human Salmonella infection. Therefore, our results indicate a potentially important role for TLR11 in preventing murine intestinal infection and modulating antigen transportation in the gut and imply an important role for various TLRs in cooperation with tight control of pathogens penetrating into Peyer patches. The TLR11 knock-out mouse can serve as a good animal model to study Salmonella infection.

First ever isolation of bacterial prolipoprotein diacylglyceryl transferase in single step from Lactococcus lactis

The unique bacterial enzyme phosphatidylglycerol: prolipoprotein diacylglyceryl transferase (Lgt) is the least studied enzyme of the ubiquitous bacterial lipoprotein synthetic pathway, mostly due to the low abundance of the enzyme. So far, Lgt has been studied to a limited extent in gram-negative bacteria, mainly in Escherichia coli. We, for the first time, report the isolation of an adequate amount of Lgt from the gram-positive lactic acid bacteria, Lactococcus lactis and compare this wild-type bacterial enzyme with the E. coli enzyme. The L. lactis Lgt, when purified by cationic-exchange chromatography, showed a 20-fold increase in the specific activity compared to that of the load, and 75% of the total Lgt activity loaded was recovered. Kinetically, L. lactis Lgt was found to be similar to the E. coli enzyme with matching Km and Vmax, whereas the specific activity of the L. lactis enzyme was about 20 times less than that of the E. coli enzyme. Comparative bioinformatic analysis of L. lactis, E. coli and Staphylococcus aureus Lgt revealed that the conserved and catalytically important His-103 residue in E. coli Lgt, was altered to Tyr in L. lactis. Investigations showed that other bacteria where this alteration is visible, form a diversion within the gram-positive bacteria in evolution. Further analysis revealed Mycobacterium smegmatis to be the species which evolved with the alteration of His to Tyr.

Lipoproteins in bacteria: structures and biosynthetic pathways

Bacterial lipoproteins are characterized by the presence of a conserved N-terminal lipid-modified cysteine residue that allows the hydrophilic protein to anchor onto bacterial cell membranes. These proteins play important roles in a wide variety of bacterial physiological processes, including virulence, and induce innate immune reactions by functioning as ligands of the mammalian Toll-like receptor 2. We review recent advances in our understanding of bacterial lipoprotein structure, biosynthesis and structure-function relationships between bacterial lipoproteins and Toll-like receptor 2. Notably, 40 years after the first report of the triacyl structure of Braun's lipoprotein in Escherichia coli, recent intensive MS-based analyses have led to the discovery of three new lipidated structures of lipoproteins in monoderm bacteria: the lyso, N-acetyl and peptidyl forms. Moreover, the bacterial lipoprotein structure is considered to be constant in each bacterium; however, lipoprotein structures in Staphylococcus aureus vary between the diacyl and triacyl forms depending on the environmental conditions. Thus, the lipidation state of bacterial lipoproteins, particularly in monoderm bacteria, is more complex than previously assumed.

Effects of over-expression of TLR2 in transgenic goats on pathogen clearance and role of up-regulation of lysozyme secretion and infiltration of inflammatory cells

BackgroundToll-like receptor 2 (TLR2) is important to host recognition of invading gram-positive microbes. In goats, these microbes can cause serious mastitis, anthrax, tetanus, and other problems. Transgenic goats constitutively over-expressing TLR2 in many tissues serve as a suitable model for the study of the role of TLR2 over-expression in bacterial clearance.ResultsCapra hircus TLR2 over-expression vector (p3S-LoxP-TLR2) was used to generate transgenic goats by egg microinjection. The integration efficiency was 8.57%. Real-time PCR and immunohistochemical results confirmed that the goats over-expressing the TLR2 gene (Tg) expressed more TLR2 than wild-type goats (WT). Monocyte-macrophages from the bloodstreams of transgenic goats were stimulated with synthetic bacterial lipoprotein (Pam3CSK4) and by the promotion of interleukin-6 (IL-6) and IL-10 expression in vitro. The oxidative damage was significantly reduced, and lysozyme (LZM) secretion was found to be up-regulated. Ear tissue samples from transgenic goats that had been stimulated with Pam3CSK4 via hypodermic injection showed that transgenic individuals can undergo the inflammation response very quickly.ConclusionsOver-expression of TLR2 was found to decrease radical damage to host cells through low-level production of NO and MDA and to promote the clearance of invasive bacteria by up-regulating lysozyme secretion and filtration of inflammatory cells to the infected site.

MiR-20a regulates ASK1 expression and TLR4-dependent cytokine release in rheumatoid fibroblast-like synoviocytes

ObjectiveTo evaluate whether miR-20a belonging to the cluster miR-17–92 is a negative regulator of inflammation in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) by modulating expression of apoptosis signal-regulating kinase (ASK)...