Filipendula glaberrima Nakai extract inhibits the bacterial infection by induction of HBD2 and HBD3 expression, and reduction of the inflammatory activity.

Defensins and inflammation are innate immune barriers of the body against infectious pathogens. Searching for a compound that can inhibit infectious diseases by affecting human ß-defensin (HBD) and proinflammatory cytokines is the new trend in research to control bacterial infection. The aim of this study is to provide a natural compound, Filipendula glaberrima Nakai extract (FGE), which is able to induce the expression of an antimicrobial defensin as well as reduce inflammation. FGE induced the expression of HBD2 and HBD3 through activating both p38 and NF-κB signaling pathways. Furthermore, FGE inhibited the expression of TNF-α and IL-6 via p38 and NF-κB pathways in Staphylococcus aureus-stimulated THP1 cells. Injection of FGE alleviated cutaneous erythema and swelling caused by S. aureus injection in mice ears. Taken together, FGE could reduce bacterial infection by inducing the expression of defensin and anti-inflammatory activity.

MSF Enhances Human Antimicrobial Peptide ß-Defensin (HBD2 and HBD3) Expression and Attenuates Inflammation via the NF-κB and p38 Signaling Pathways.

Both defensin and inflammation are part of the human innate immune system that responds rapidly to pathogens. The combination of defensins with pro- or anti-inflammatory effects can be a potential research direction for the treatment of infection by pathogens. This study aimed to identify whether MSF (Miracle Synergy material made using Filipendula glaberrima), a probiotic lysate of Filipendula glaberrima extracts fermented with Lactiplantibacillus plantarum K8, activates the expression of human ß-defensin (HBD2 and HBD3) to protect the host against pathogens and inhibit inflammation caused by S. aureus, in vitro with Western blot analysis, qRT-PCR and in vivo studies with a mouse model were used to evaluate the effects of MSF. The MSF treatment induced HBD2 and HBD3 expression via the p38 and NF-κB pathways. Furthermore, MSF treatment significantly reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1ß, IL-6, and IL-8), also through p38 and NF-κB in S. aureus-induced inflammatory condition. MSF treatment remarkably reduced erythema in mice ears caused by the injection of S. aureus, while K8 lysate treatment did not initiate a strong recovery. Taken together, MSF induced the expression of HBD2 and HDB3 and activated anti-inflammatory activity more than the probiotic lysates of L. plantarum K8. These findings show that MSF is a potential defensin inducer and anti-inflammatory agent.

Alleviation of LPS-Induced Inflammation and Septic Shock by Lactiplantibacillus plantarum K8 Lysates.

We previously showed that Lactiplantibacillus plantarum K8 and its cell wall components have immunoregulatory effects. In this study, we demonstrate that pre-treatment of L. plantarum K8 lysates reduced LPS-induced TNF-α production in THP-1 cells by down-regulating the early signals of mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB). The down-regulation of signals may be caused by the induction of negative regulators involved in toll-like receptor (TLR)-mediated signaling. However, co-treatment with high concentrations of L. plantarum K8 lysates and lipopolysaccharide (LPS) activated the late signaling of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and NF-κB pathways and resulted in the induction of absent in melanoma 2 (AIM2) inflammasome-mediated interleukin (IL)-1ß secretion. Intraperitoneal injection of L. plantarum K8 lysates in LPS-induced endotoxin shock mice alleviated mortality and reduced serum tumor-necrosis factor (TNF)-α, IL-1ß, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. In addition, the mRNA levels of TNF-α, IL-1ß, and IL-6 decreased in livers from mice injected with L. plantarum K8 followed by LPS. Hematoxylin and eosin (H&E) staining of the liver showed that the cell size was enlarged by LPS injection and slightly reduced by L. plantarum K8 lysate pre-injection followed by LPS injection. Macrophage infiltration of the liver also decreased in response to the combination injection compared with mice injected with only LPS. Taken together, our results show that although L. plantarum K8 lysates differentially regulated the production of LPS-induced inflammatory cytokines in THP-1 cells, the lysates inhibited overall inflammation in mice. Thus, this study suggests that L. plantarum K8 lysates could be developed as a substance that modulates immune homeostasis by regulating inflammation.

Complement Inactivation Strategy of Staphylococcus aureus Using Decay-Accelerating Factor and the Response of Infected HaCaT Cells.

Staphylococcus aureus is a species of Gram-positive staphylococcus. It can cause sinusitis, respiratory infections, skin infections, and food poisoning. Recently, it was discovered that S. aureus infects epithelial cells, but the interaction between S. aureus and the host is not well known. In this study, we confirmed S. aureus to be internalized by HaCaT cells using the ESAT-6-like protein EsxB and amplified within the host over time by escaping host immunity. S. aureus increases the expression of decay-accelerating factor (CD55) on the surfaces of host cells, which inhibits the activation of the complement system. This mechanism makes it possible for S. aureus to survive in host cells. S. aureus, sufficiently amplified within the host, is released through the initiation of cell death. On the other hand, the infected host cells increase their surface expression of UL16 binding protein 1 to inform immune cells that they are infected and try to be eliminated. These host defense systems seem to involve the alteration of tight junctions and the induction of ligand expression to activate immune cells. Taken together, our study elucidates a novel aspect of the mechanisms of infection and immune system evasion for S. aureus.

Differential role of lipoteichoic acids isolated from Staphylococcus aureus and Lactobacillus plantarum on the aggravation and alleviation of atopic dermatitis.

Lipoteichoic acid (LTA), a cell wall component of gram-positive bacteria, up-regulates inflammatory cytokine production through the toll-like receptor 2 (TLR2) signaling pathway, and also contributes to anti-inflammatory responses against immune cells stimulated by lipopolysaccharides. In the current study, we examined the effects of LTAs isolated from Staphylococcus aureus (aLTA) and Lactobacillus plantarum (pLTA) on the aggravation and alleviation of atopic dermatitis (AD). aLTA strongly induced CCL2 production in THP-1 cells. CCL2 was regulated by the TLR2 pathway including the activation of IRAK2, NF-κB and JNK. CCL2 induced Th2 polarization of CD4+T cells through induction of interleukin (IL)-2, -4, and -5 and inhibition of interferon-gamma (IFN-γ). CCL2 levels and immunoglobulin E (IgE) production were increased in aLTA-injected mice. On the other hand, pLTA moderately affected CCL2 production and it inhibited aLTA-mediated CCL2 production. The serum levels of CCL2 and IgE were inhibited by pLTA pre-injection followed by aLTA reinjection, which resulted in the alleviation of irritant contact dermatitis (ICD) symptoms. Our results suggest that S. aureus infection causes an increase in CCL2 production, and may exacerbate atopic dermatitis (AD)-like symptoms through the excessive IgE production. Alternatively, pLTA alleviated AD-like symptoms by inhibiting aLTA-induced CCL2 and IgE production.

Distinct CD55 Isoform Synthesis and Inhibition of Complement-Dependent Cytolysis by Hepatitis C Virus.

CD55/DAF, one of the regulators of complement activation, is known to limit excess complement activation on the host cell surface by accelerating the decay of C3 convertase. We reported previously that hepatitis C virus (HCV) infection or virus core protein expression upregulates CD55 expression. CD55 associates with HCV particles, potentially protecting HCV from lysis in circulation. An increase in CD55 on the surface of HCV-infected cells may inhibit complement-mediated cell killing. In this study, we show that Abs against cancer cell surface proteins induce complement-dependent cytolysis or Ab-dependent cell-mediated cytotoxicity of immortalized human hepatocytes in the presence of CD55-blocking Ab. CD55 has a secreted isoform (sCD55) that is generated by alternative splicing. We observed that sCD55 is induced in HCV-infected or HCV replicon-harboring cells, as well as in liver biopsy samples from chronically HCV-infected patients. Conditioned medium from HCV-infected hepatoma cells (Huh7.5 cells) or immortalized human hepatocytes inhibited C3 convertase activity and complement-dependent cytolysis of sheep blood erythrocytes. Chronically HCV-infected patient sera inhibited C3 convertase activity, further implicating HCV-specific impairment of complement function in infected humans. CD55-blocking Ab inhibited erythrocyte lysis by conditioned medium, suggesting that CD55/sCD55 impairs convertase activity. Together, our data show that HCV infection induces sCD55 expression in HCV-infected cell culture-conditioned medium and inhibits C3 convertase activity. This may have implications for modulating complement-mediated immune function in the microenvironment and on HCV-harboring cells.

Hepatitis C virus impairs natural killer cell-mediated augmentation of complement synthesis.

UNLABELLED: Natural killer (NK) cells and the complement system play critical roles in the first line of defense against pathogens. The synthesis of complement components C4 and C3 is transcriptionally downregulated by hepatitis C virus (HCV) core and NS5A proteins, and this negative regulation is apparent in chronically HCV-infected patients. In this study, we have examined the potential contribution of an NK cell line as a model in regulating complement synthesis. Coculture of NK cells (NK3.3) with human hepatoma cells (Huh7.5) expressing HCV core or NS5A protein led to a significant increase in C4 and C3 complement synthesis via enhanced specific transcription factors. Reestablishment of complement protein expression was found to be mediated by direct interaction between NKG2D on NK cells and the hepatocyte protein major histocompatibility complex class I-related chains A and B (MICA/B) and not to be associated with specific cytokine signaling events. On the other hand, C4 and C3 synthesis remained impaired in a coculture of NK cells and Huh7.5 cells infected with cell culture-grown HCV. The association between these two cell types through NKG2D and MICA/B was examined further, with MICA/B expression in HCV-infected hepatocytes found to remain inhibited during coculture. Further experiments revealed that the HCV NS2 and NS5B proteins are responsible for the HCV-associated decrease in MICA/B. These results suggest that HCV disables a key receptor ligand in infected hepatoma cells, thereby inhibiting the ability of infected cells to respond to stimuli from NK cells to positively regulate complement synthesis. IMPORTANCE: The complement system contributes to the protection of the host from virus infection. However, the involvement of complement in viral hepatitis has not been well documented. Whether NK cells affect complement component expression in HCV-infected hepatocytes remains unknown. Here, we have shown how HCV subverts the ability of NK cells to positively mediate complement protein expression.

Forkhead box transcription factor regulation and lipid accumulation by hepatitis C virus.

UNLABELLED: We have previously shown that hepatitis C virus (HCV) infection modulates the expression of forkhead box transcription factors, including FoxO1 and FoxA2, which play key roles in gluconeogenesis and ß-oxidation of fatty acid, respectively. The aim of the present study was to determine the role of forkhead box transcription factors in modulating lipid metabolism. HCV infection or core protein expression alone in transfected Huh7.5 cells increased expression of sterol regulatory element binding protein 1c (SREBP-1c) and its downstream target, fatty acid synthase (FASN), which are key proteins involved in lipid synthesis. Knockdown of FoxO1 by small interfering RNA in HCV-infected cells significantly decreased SREBP-1c and FASN expression. Further, HCV infection or core protein expression in Huh7.5 cells significantly decreased the expression of medium-chain acyl coenzyme A dehydrogenase (MCAD) and short-chain acyl coenzyme A dehydrogenase (SCAD), involved in the regulation of ß-oxidation of fatty acids. Ectopic expression of FoxA2 in HCV-infected cells rescued the expression of MCAD and SCAD. Oil red O and neutral lipid staining indicated that HCV infection significantly increases lipid accumulation compared to that in the mock-infected control. This was further verified by the increased expression of perilipin-2 and decreased activity of hormone-sensitive lipase (HSL) in HCV-infected hepatocytes, implying increased accumulation of neutral lipids. Knockdown of FoxO1 and ectopic expression of FoxA2 significantly decreased HCV replication. Taken together, these results suggest that HCV modulates forkhead box transcription factors which together increase lipid accumulation and promote viral replication. IMPORTANCE: Hepatic steatosis is a frequent complication associated with chronic HCV infection. Its presence is a key prognostic indicator associated with the progression to hepatic fibrosis and hepatocellular carcinoma. Several mechanisms have been proposed to account for the development of steatosis and fatty liver during HCV infection. We observed that HCV infection increases expression of both SREBP-1c and FASN. Further investigation suggested that the expression of SREBP-1c and FASN is controlled by the transcription factor FoxO1 during HCV infection. In addition, HCV infection significantly decreased both MCAD and SCAD expression, which is controlled by FoxA2. HCV infection also increased lipid droplet accumulation, increased perilipin-2 expression, and decreased HSL activity. Thus, knockdown of FoxO1 (decreased lipogenesis) and overexpression of FoxA2 (increased ß-oxidation) resulted in a significant disruption of the platform and, hence, a decrease in HCV genome replication. Thus, targeting of FoxO1 and FoxA2 might be useful in developing a therapeutic approach against HCV infection.

Hepatitis C virus suppresses C9 complement synthesis and impairs membrane attack complex function.

Hepatitis C virus (HCV) proteins inhibit complement component expression, which may attenuate immunity against infection. In this study, we examined whether HCV regulates the membrane attack complex (MAC) via complement component C9. MAC is composed of C5b to C9 (C5b-9) and mediates cell lysis of invaded pathogens. Liver biopsy specimens from chronically HCV-infected patients exhibited a lower level of C9 mRNA expression than liver biopsy specimens from unrelated disease or healthy control human liver RNA. Hepatocytes infected with cell culture-grown HCV or expressing HCV core protein also displayed significant repression of C9 mRNA and protein levels. Promoter analysis suggested that the T cell factor-4 (TCF-4E) transcription factor is responsible for HCV core-mediated C9 promoter regulation. Sera from chronically HCV-infected patients displayed a lower level of C5b-9 and a reduced antimicrobial effect on model organisms compared to unrelated patient sera or sera from healthy volunteers. Together, these results for C9 regulation by HCV core protein coupled with functional impairment of the membrane attack complex underscore HCV-mediated attenuation of immune mechanisms.

Hepatitis C virus infection upregulates CD55 expression on the hepatocyte surface and promotes association with virus particles.

CD55 limits excessive complement activation on the host cell surface by accelerating the decay of C3 convertases. In this study, we observed that hepatitis C virus (HCV) infection of hepatocytes or HCV core protein expression in transfected hepatocytes upregulated CD55 expression at the mRNA and protein levels. Further analysis suggested that the HCV core protein or full-length (FL) genome enhanced CD55 promoter activity in a luciferase-based assay, which was further augmented in the presence of interleukin-6. Mutation of the CREB or SP-1 binding site on the CD55 promoter impaired HCV core protein-mediated upregulation of CD55. HCV-infected or core protein-transfected Huh7.5 cells displayed greater viability in the presence of CD81 and CD55 antibodies and complement. Biochemical analysis revealed that CD55 was associated with cell culture-grown HCV after purification by sucrose density gradient ultracentrifugation. Consistent with this, a polyclonal antibody to CD55 captured cell culture-grown HCV. Blocking antibodies against CD55 or virus envelope glycoproteins in the presence of normal human serum as a source of complement inhibited HCV infection. The inhibition was enhanced in the presence of both the antibodies and serum complement. Collectively, these results suggest that HCV induces and associates with a negative regulator of the complement pathway, a likely mechanism for immune evasion.

Differential effects of low and high doses of lipoteichoic acid on lipopolysaccharide-induced interleukin-6 production.

OBJECTIVE: Interleukin-6 (IL-6), which is increased in patients who are suffering from septic shock, is an important mediator of the inflammatory response. Here, we examined the priming effect of lipoteichoic acid (LTA) and lipopolysaccharide (LPS) on IL-6 production in a monocyte-like cell line. METHODS: THP-1 cells were primed by treatingwith a low or high dose of LTA isolated from Staphylococcus aureus (aLTA) and then re-treated with LPS. IL-6 production, receptor expression, and the variation of signaling molecules were examined by ELISA, reverse transcriptase polymerase chain reaction, and western blotting, respectively. RESULTS: LPS-mediated IL-6 production was dramatically increased in THP-1 cells pretreated with a low dose aLTA, while it was significantly decreased when a high dose of aLTA was given along with LPS. LPS-induced IL-6 production in low dose aLTA priming cells mediated by NF-κB and MAPKs pathways, and Akt functioned as a negative regulator of IL-6 production. Together, the results of this study suggest that different doses of bacterial cell surface components can mediate a diverse range of responses with respect to inflammatory cytokine production.

Lactiplantibacillus plantarum K8 lysates regulate hypoxia-induced gene expression.

Hypoxic responses have been implicated in critical pathologies, including inflammation, immunity, and tumorigenesis. Recently, efforts to identify effective natural remedies and health supplements are increasing. Previous studies have reported that the cell lysates and the cell wall-bound lipoteichoic acids of Lactiplantibacillus plantarum K8 (K8) exert anti-inflammatory and immunomodulative effects. However, the effect of K8 on cellular hypoxic responses remains unknown. In this study, we found that K8 lysates had a potent suppressive effect on gene expression under hypoxia. K8 lysates markedly downregulated hypoxia-induced HIF1α accumulation in the human bone marrow and lung cancer cell lines, SH-SY5Y and H460. Consequently, the transcription of known HIF1α target genes, such as p21, GLUT1, and ALDOC, was notably suppressed in the K8 lysate supplement and purified lipoteichoic acids of K8, upon hypoxic induction. Intriguingly, K8 lysates decreased the expression of PHD2 and VHL proteins, which are responsible for HIF1α destabilization under normoxic conditions, suggesting that K8 may regulate HIF1α stability in a non-canonical pathway. Overall, our results suggest that K8 lysates desensitize the cells to hypoxic stresses and suppress HIF1α-mediated hypoxic gene activation.

Hepatitis C virus proteins inhibit C3 complement production.

The third component of human complement (C3) plays a central role in innate immune function as its activation is required to trigger classical as well as alternative complement pathways. In this study, we have observed that sera from patients chronically infected with hepatitis C virus (HCV) displayed significantly lower C3 levels than sera from healthy individuals. Liver biopsy specimens from the same patients also exhibited lower C3 mRNA expression than liver tissues from healthy donors. C3 mRNA level was reduced in hepatocytes upon infection with cell culture-grown HCV genotype 1a or 2a in vitro. Further analysis suggested that HCV core protein displayed a weak repression of C3 promoter activity by downregulating the transcription factor farnesoid X receptor (FXR). On the other hand, HCV NS5A protein strongly downregulated C3 promoter activity at the basal level or in the presence of interleukin-1ß (IL-1ß) as an inducer. In addition, the expression of the transcription factor CAAT/enhancer binding protein beta (C/EBP-ß), which binds to the IL-1/IL-6 response element in the C3 promoter, was inhibited in liver biopsy specimens. Furthermore, expression of C/EBP-ß was reduced in hepatocytes infected with cell culture-grown HCV, as well as in hepatocytes transfected with the NS5A genomic region of HCV. Together, these results underscore the role of HCV NS5A protein in impairing innate immune function.

Hepatitis C virus-mediated inhibition of cathepsin S increases invariant-chain expression on hepatocyte surface.

Hepatocytes are the main source of hepatitis C virus (HCV) replication and contain the maximum viral load in an infected person. Chronic HCV infection is characterized by weak cellular immune responses to viral proteins. Cathepsin S is a lysosomal cysteine protease and controls HLA-DR-antigen complex presentation through the degradation of the invariant chain. In this study, we examined the effect of HCV proteins on cathepsin S expression and found it to be markedly decreased in dendritic cells (DCs) exposed to HCV or in hepatocytes expressing HCV proteins. The downregulation of cathepsin S was mediated by HCV core and NS5A proteins involving inhibition of the transcription factors interferon regulatory factor 1 (IRF-1) and upstream stimulatory factor 1 (USF-1) in gamma interferon (IFN-γ)-treated hepatocytes. Inhibition of cathepsin S by HCV proteins increased cell surface expression of the invariant chain. In addition, hepatocytes stably transfected with HCV core or NS5A inhibited HLA-DR expression. Together, these results suggested that HCV has an inhibitory role on cathepsin S-mediated major histocompatibility complex (MHC) class II maturation, which may contribute to weak immunogenicity of viral antigens in chronically infected humans.

Nanoparticles of Lactiplantibacillus plantarum K8 Reduce Staphylococcus aureus Respiratory Infection and Tumor Necrosis Factor Alpha- and Interferon Gamma-Induced Lung Inflammation.

Multiple studies have confirmed that Lactiplantibacillus plantarum has beneficial effects in respiratory diseases, including respiratory tract infections, asthma, and chronic obstructive pulmonary disease. However, the role of L. plantarum lysates in respiratory diseases is unclear. Staphylococcus aureus infects the lungs of mice, recruits immune cells, and induces structural changes in alveoli. Lung diseases can be further aggravated by inflammatory cytokines such as CCL2 and interleukin (IL)-6. In in vivo studies, L. plantarum K8 nanoparticles (K8NPs) restored lung function and prevented lung damage caused by S. aureus infection. They inhibited the S. aureus infection and the infiltration of immune cells and prevented the increase in goblet cell numbers in the lungs of S. aureus-infected mice. K8NPs suppressed the expression of CCL2 and IL-6, which were increased by the combination treatment of tumor necrosis factor alpha and interferon gamma (TI), in a dose-dependent manner. In in vitro studies, the anti-inflammatory effect of K8NPs in TI-treated A549 cells and TI-injected mice occurred through the reduction in activated mitogen-activated protein kinases and nuclear factor kappa-B. These findings suggest that the efficacy of K8NPs in controlling respiratory inflammation and infection can be used to develop functional materials that can prevent or alleviate respiratory diseases.

Anti-obesity potential of heat-killed Lactiplantibacillus plantarum K8 in 3T3-L1 cells and high-fat diet mice.

Probiotics exert anti-obesity effects in high-fat diet (HFD) obese mice, but there are few studies on anti-obesity using heat-killed probiotics. Here, we investigated the effect of heat-killed Lactiplantibacillus plantarum K8 (K8HK) on the anti-differentiation of 3T3-L1 preadipocytes and on anti-obesity in HFD mice. K8HK decreased triglyceride (TG) accumulation in 3T3-L1 cells. Specifically, 1 × 109 CFU/mL K8HK showed the greatest anti-obesity effect, while the same concentration of live L. plantarum K8 (K8 Live) showed cytotoxicity. K8HK increased suppressor of cytokine signaling (SOCS)-1, which might affect the JAK2-STAT3 signaling pathway activated during differentiation. As a result, the levels of transcription factors of adipogenesis such as Peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα) decreased in K8HK-treated cells. We also observed a decrease in the lipogenic enzymes and fatty acid binding protein 4 (FABP4). In the mouse study, oral ingestion of K8 Live and K8HK showed weight reduction and decrease in blood TG content at 12 weeks of feeding. In addition, TG synthesis was suppressed in liver and adipose tissues, and genes related to fat metabolism were suppressed. This study suggests that K8HK could be a good material to prevent obesity by inhibiting adipogenesis genes related to fat metabolism.

ISG56 and IFITM1 proteins inhibit hepatitis C virus replication.

Hepatitis C virus (HCV) often leads to persistent infection. Interferon (IFN) and IFN-stimulated genes (ISGs) are amplified during HCV infection but fail to eliminate virus from the liver in a large number of infected patients. We have observed previously that HCV infection induces IFN-ß production in immortalized human hepatocytes (IHH) as early as 24 h after infection, although virus replication is not inhibited. To gain insights on possible countermeasures of virus for the suppression of host antiviral response, the cellular transcriptional profiles of ISGs were examined after various treatments of IHH. The majority of ISGs were upregulated in IFN-treated IHH from the level for mock-treated cells. However, the comparison of ISG expression in IFN-treated IHH and IFN-pretreated, HCV genotype 2a-infected IHH indicated that virus infection suppresses the upregulation of a subset of effector molecules, including ISG56 and IFITM1. Similar results were observed for HCV-infected Huh7 cells. Subsequent study suggested that the exogenous expression of ISG56 or IFITM1 inhibits HCV replication in IHH or Huh7 cells, and the knockdown of these genes enhanced HCV replication. Further characterization revealed that the overexpression of these ISGs does not block HCV pseudotype entry into Huh7 cells. Taken together, our results demonstrated that ISG56 and IFITM1 serve as important molecules to restrict HCV infection, and they may have implications in the development of therapeutic modalities.

Manganese superoxide dismutase induced by lipoteichoic acid isolated from Staphylococcus aureus regulates cytokine production in THP-1 cells.

Lipoteichoic acid isolated from Staphylococcus aureus (aLTA) is known to regulate the production of pro-inflammatory cytokines through TLR2-mediated signaling pathways. In our previous study, we found that aLTA significantly increased manganese superoxide dismutase (MnSOD) in the THP-1 human monocyte-like cell line, but the role of MnSOD in the regulation of cytokine production was not elucidated. In the current study, we found that MnSOD was involved in aLTA-mediated cytokine production. The signaling pathways associated with aLTA-mediated MnSOD induction in THP-1 cells included TLR2-MyD88-IRAK2, JNK (c-Jun N-terminal kinases)1/2 and nuclear factor- κB (NF-κB). We also found MnSOD was involved in the regulation of IL-1ß and TNF-α, which were induced by early signaling pathways, including JNK1/2, p38, and NF-κB p65. In addition, MnSOD was also involved in the production of IL-6 and CCL2 in aLTA-stimulated THP-1 cells through activation of late signaling pathways such as JAK2-STAT3. Taken together, our data suggest that aLTA-mediated MnSOD production involved in the regulation of cytokine production and it may be the cause of one of the excessive inflammatory reactions caused by S. aureus.

Lipoteichoic Acid from Staphylococcus aureus Activates the Complement System via C3 Induction and CD55 Inhibition.

Staphylococcus aureus inhibits complement activity by secreting a variety of toxins. However, the underlying mechanism of complement component regulation by lipoteichoic acid (LTA), a cell wall component of S. aureus, has not been elucidated. In this study, we observed that aLTA (LTA of S. aureus) increased C3 expression in THP-1 cells. The mechanism of aLTA-mediated C3 induction includes an aLTA-toll-like receptor (TLR) 2 interaction, interleukin 1 receptor associated kinase (IRAK) 2 recruitment, and nuclear factor kappa B (NF-kB) activation. In HepG2 cells, C3 protein production begins to increase from 3 h and increases steadily until 48 h. On the other hand, CD55 levels increased up to 6 h after aLTA treatment and started to decrease after 24 h and levels were decreased at 48 h by more than 50% compared to untreated cells. The expression of CD55 in HepG2 cells was shown to be regulated by IRAK-M induced by aLTA. Serum C3 levels increased in mice injected with aLTA, which resulted in an increase in the amount and activity of the membrane attack complex (MAC). We also observed that CD55 mRNA was increased in the liver 24 h after aLTA injection, but was decreased 48 h after injection. These results suggest that aLTA increases complement levels via induction of C3 and inhibition of CD55, which may cause associated MAC-mediated liver damage.