Effect of bacterial endotoxin LPS on expression of INF-gamma and IL-5 in T-lymphocytes from asthmatics

Neonatal immune challenge induces female-specific changes in social behavior and somatostatin cell number

Decreases in social behavior are a hallmark aspect of acute "sickness behavior" in response to infection. However, immune insults that occur during the perinatal period may have long-lasting consequences for adult social behavior by impacting the developmental organization of underlying neural circuits. Microglia, the resident immune cells of the central nervous system, are sensitive to immune stimulation and play a critical role in the developmental sculpting of neural circuits, making them likely mediators of this process. Here, we investigated the impact of a postnatal day (PND) 4 lipopolysaccharide (LPS) challenge on social behavior in adult mice. Somewhat surprisingly, neonatal LPS treatment decreased sociability in adult female, but not male mice. LPS-treated females also displayed reduced social interaction and social memory in a social discrimination task as compared to saline-treated females. Somatostatin (SST) interneurons within the anterior cingulate cortex (ACC) have recently been suggested to modulate a variety of social behaviors. Interestingly, the female-specific changes in social behavior observed here were accompanied by an increase in SST interneuron number in the ACC. Finally, these changes in social behavior and SST cell number do not appear to depend on microglial inflammatory signaling, because microglia-specific genetic knock-down of myeloid differentiation response protein 88 (MyD88; the removal of which prevents LPS from increasing proinflammatory cytokines such as TNFα and IL-1β) did not prevent these LPS-induced changes. This study provides novel evidence for enduring effects of neonatal immune activation on social behavior and SST interneurons in females, largely independent of microglial inflammatory signaling.

The monocyte-dependent immune response to bacteria is suppressed in smoking-induced COPD

COPD patients have an increased susceptibility to bacterial airway infections that can induce exacerbations. In response to infections, circulating monocytes become recruited to the infected tissue and secrete cytokines. We hypothesized that this cytokine response is reduced in COPD. Cultured peripheral blood monocytes of never smokers (NS) and smokers without (S) and with COPD (3 study populations, n = 36-37) were stimulated with extracts of Haemophilus influenzae, Staphylococcus aureus, or Streptococcus pneumoniae or with four different pathogen-associated molecular patterns (PAMPs). Four cytokines and 9 PAMP-related signaling molecules were measured and compared between the groups. Granulocyte-macrophage-colony-stimulating-factor responses to all stimulants were reduced in S and COPD compared to NS. Tumor-necrosis-factor-α responses to all bacterial extracts, peptidoglycan, and lipopolysaccharide were reduced in S and/or COPD. Interleukin-10 responses to S. aureus and lipoteichoic acid were increased in COPD. Correlations to pack-years and lung function were found. The peptidoglycan-receptor NOD2 and the mRNA of the lipopolysaccharide-receptor TLR4 were reduced in S and COPD. Cytokine responses of monocytes to bacteria are suppressed by smoking and in COPD possibly due to NOD2 and TLR4 reduction and/or interleukin-10 increase. This might help to explain the increased susceptibility to bacterial infections. These systemic molecular pathologies might be targets for therapeutic strategies to prevent infection-induced exacerbations. KEY MESSAGES: COPD subjects have an increased susceptibility to bacterial infections. This implies defects in the immune response to bacteria and is critical for disease progression. The cytokine response of monocytes to bacteria is reduced in COPD. This might be due to a reduced NOD2 and TLR4 and an increased IL-10 expression. This can explain the increased susceptibility to infections and help to identify drug targets.

Simvastatin requires activation in accessory cells to modulate T-cell responses in asthma and COPD

T-cell-dependent airway and systemic inflammation triggers the progression of chronic obstructive pulmonary disease (COPD) and asthma. Retrospective studies suggest that simvastatin has anti-inflammatory effects in both diseases but it is unclear, which cell types are targeted. We hypothesized that simvastatin modulates T-cell activity. Circulating CD4+ and CD8+ T-cells, either pure, co-cultured with monocytes or alveolar macrophages (AM) or in peripheral blood mononuclear cells (PBMCs), were ex vivo activated towards Th1/Tc1 or Th2/Tc2 and incubated with simvastatin. Markers for Th1/Tc1 (IFNγ) and Th2/Tc2 (IL-5, IL-13) were measured by ELISA; with PBMCs this was done comparative between 11 healthy never-smokers, 11 current smokers without airflow limitation, 14 smokers with COPD and 11 never-smokers with atopic asthma. T-cell activation induced IFNγ, IL-5 and IL-13 in the presence and absence of accessory cells. Simvastatin did not modulate cytokine expression in pure T-cell fractions. β-hydroxy-simvastatin acid (activated simvastatin) suppressed IL-5 and IL-13 in pure Th2- and Tc2-cells. Simvastatin suppressed IL-5 and IL-13 in Th2-cells co-cultivated with monocytes or AM, which was partially reversed by the carboxylesterase inhibitor benzil. Simvastatin suppressed IL-5 production of Th2/Tc2-cells in PBMCs without differences between cohorts and IL-13 stronger in never-smokers and asthma compared to COPD. Simvastatin induced IFNγ in Th1/Tc1-cells in PBMCs of all cohorts except asthmatics. Simvastatin requires activation in accessory cells likely by carboxylesterase to suppress IL-5 and IL-13 in Th2/Tc2-cells. The effects on Il-13 are partially reduced in COPD. Asthma pathogenesis prevents simvastatin-induced IFNγ up-regulation. Simvastatin has anti-inflammatory effects that could be of interest for asthma therapy.

A systemic defect in Toll-like receptor 4 signaling increases lipopolysaccharide-induced suppression of IL-2-dependent T-cell proliferation in COPD

The susceptibility to bacterial infections is increased in chronic obstructive pulmonary disease (COPD). This promotes exacerbations. IL-2 triggers CD4(+)/Th1-cell proliferation, which is important for infection defense. Bacterial endotoxin (LPS) activates MyD88/IRAK and TRIF/IKKε/TBK1 pathways via Toll-like receptor-4 (TLR4) in Th1 cells. Systemic defects in TLR pathways in CD4(+)/Th1 cells cause an impairment of IL-2-dependent immune responses to bacterial infections in COPD. Peripheral blood CD4(+) T cells of never smokers, smokers without COPD, and smokers with COPD (each n = 10) were ex vivo activated towards Th1 and stimulated with LPS. IL-2, MyD88, and TRIF expression, and cell proliferation was analyzed by ELISA, quantitative RT-PCR, and bromodeoxyuridine (BrdU) and trypan blue staining comparative among the cohorts. IL-2 release from activated T cells was increased in COPD vs. smokers and never smokers. LPS reduced IL-2 expression and T-cell proliferation. These effects were increased in COPD vs. never smokers and inversely correlated with FEV1 (%predicted). The MyD88/TRIF ratio was decreased in Th1 cells of COPD. The suppression of IL-2 by LPS was abolished by MyD88/IRAK blockade in never smokers but by TRIF/IKKε/TBK1 blockade in COPD. Moxifloxacin restored IL-2 expression and T-cell proliferation in the presence of LPS by blocking p38 MAPK. The increased IL-2 release from Th1 cells in COPD might contribute to airway inflammation in disease exacerbations. A switch from MyD88/IRAK to TRIF/IKKε/TBK1 signaling amplifies the suppression of IL-2-dependent proliferation of CD4(+) T cells by LPS in COPD. This molecular pathology is of systemic origin, might impair adaptive immune responses, and could explain the increased susceptibility to bacterial infections in COPD. Targeting TLR4-downstream signaling, for example, with moxifloxacin, might reduce exacerbation rates.

Risks for infection in patients with asthma (or other atopic conditions): is asthma more than a chronic airway disease?

Most of the research effort regarding asthma has been devoted to its causes, therapy, and prognosis. There is also evidence that the presence of asthma can influence patients' susceptibility to infections, yet research in this aspect of asthma has been limited. There is additional debate in this field, with current literature tending to view the increased risk of infection among atopic patients as caused by opportunistic infections secondary to airway inflammation, especially in patients with severe atopic diseases. However, other evidence suggests that such risk and its underlying immune dysfunction might be a phenotypic or clinical feature of atopic conditions. This review argues (1) that improved understanding of the effects of asthma or other atopic conditions on the risk of microbial infections will bring important and new perspectives to clinical practice, research, and public health concerning atopic conditions and (2) that research efforts into the causes and effects of asthma must be juxtaposed because they are likely to guide each other.

Asthma and risk of non-respiratory tract infection: a population-based case-control study

OBJECTIVES

Asthmatics have increased risks of airway-related infections. Little is known about whether this is true for non-airway-related serious infections such as Escherichia coli bloodstream infection (BSI). We assessed whether asthma is associated with a risk of developing community-acquired E coli BSI.

DESIGN

The study was designed as a population-based retrospective case-control study.

SETTING

This population-based study was conducted in Olmsted County, Minnesota.

PARTICIPANTS

The study included 259 all eligible community-acquired E coli BSI cases in Olmsted County, MN between 1998 and 2007 and 259 birthday-matched, gender-matched and residency-matched controls.

PRIMARY AND SECONDARY OUTCOME MEASURES

Only community-acquired E coli BSI cases as the primary outcome was included. Asthma status as an exposure was ascertained by predetermined criteria. An adjusted OR and 95% CI for the association between asthma and risk of community-acquired E coli BSI was calculated using conditional logistic regression.

RESULTS

Of 259 eligible cases, 179 (69%) were women and mean age was 61±22 years. Of the 259 cases 37 (14%) and 16 (6%) of 259 controls had a prior history of asthma (adjusted OR 2.74; 95% CI 1.11 to 6.76; p=0.029). The population attributable risk of asthma for community-acquired E coli BSI was 9%. Although not statistically significant, there was a borderline association between having a history of food allergy and increased risk of community-acquired E coli BSI (6% vs 2%; adjusted OR 3.51; 95% CI 0.94 to 13.11; p=0.062).

CONCLUSIONS

Based on the findings of the current population-based, case-control investigation, a history of asthma may be associated with risk of community-acquired E coli BSI. The impact of asthma on risk of microbial infections may go beyond airways.

The role of TLR2 and 4 in Behçet's disease pathogenesis

TLRs are PRRs that play a pivotal role in sensing exogenous pathogens and endogenous danger signals. Their role in the pathogenesis of inflammatory and immune-related diseases is gradually being unravelled. TLR2 and TLR4 are capable of sensing the oral microbial community, which is considered a potential trigger for Behçet's disease (BD). This study aimed to investigate the expression and function of TLR2 and TLR4 in the oral mucosa of BD. A total of 87 patients was included: 55 BD, 24 healthy controls and eight recurrent aphthous stomatitis. Total RNA was purified from non-lesional oral mucosal brush biopsies and analysed for the presence of TLR2 and TLR4 mRNA, along with their splice variants. The response of peripheral blood mononuclear cells to classical TLR2 and TLR4 agonists was also investigated. TLR2b, TLR2d, TLR2e, TLR4.3 and TLR4.4 were significantly elevated in relapsed BD. A significant defect in the response to cognate agonists of TLR1/2 heterodimer and TLR4 was also observed in BD. The expression of unusual splice variants of TLR2 and TLR4 might explain the observed defect in these receptors' function in BD.

Effect of lipoteichoic acid on IL-2 and IL-5 release from T lymphocytes in asthma and COPD

Susceptibility to infections with gram-positive bacteria, which are an important trigger of exacerbations, is increased in COPD and asthma. Unraveling the underlying mechanisms may help developing therapeutic strategies to reduce exacerbation rates. The aim of this study was to evaluate the effects of lipoteichoic acid (LTA), a danger signal from gram-positive bacteria, on T cell cytokines related to bacterial infection defense in COPD and asthma. T cell populations within peripheral blood mononuclear cells (PBMCs) were ex-vivo activated towards T(H)2/T(C)2 subtypes and subsequently stimulated with LTA. IL-2 and IL-5 concentrations in cell culture supernatants were measured by ELISA comparative between non-smokers (NS), current smokers without airflow limitation (S), smokers with moderate to severe COPD and mild to moderate asthmatics (A) (each n=10). IL-2 and IL-5 baseline levels were without differences between the cohorts. After T cell activation, IL-2 and IL-5 releases were increased in all cohorts, however, for IL-2 this increase was significantly higher in S and by trend in COPD compared to the other groups. LTA time-dependently suppressed IL-2 release in NS, S and COPD but not in A. LTA reduced IL-5 release in COPD and A but not in NS and S. Summarized, LTA reduces T(H)2/T(C)2 cytokines indicating immunosuppressive effects, which are dysregulated in COPD and asthma. This implies a misguided response to gram-positive bacterial infections, which might help to explain the increased susceptibility to bacterial infections in COPD and asthma.

The presence of maternal asthma during pregnancy suppresses the placental pro-inflammatory response to an immune challenge in vitro

The mechanisms that contribute to adverse outcomes for the neonate in pregnancies complicated by asthma may be mediated via changes in placental immune function. This study was designed to determine whether the presence of maternal asthma during pregnancy alters the placental pro-inflammatory immune response in vitro. A prospective cohort study of women with asthma (n = 22) and control (n = 11) subjects had placentae collected immediately after delivery. Placental explants were exposed to an immune challenge, lipopolysaccharide, in the presence and absence of cortisol in vitro. Cytokines, glucocorticoid receptor α (GR α) and p38 MAPK protein were measured. Placentae of control pregnancies had an increase in pro-inflammatory cytokine production over a 24 h period. Placentae from pregnancies complicated by maternal asthma had a reduced pro-inflammatory cytokine response to an immune challenge relative to the controls especially in relation to the production of interleukin (IL)-1β and TNFα regardless of fetal sex. Cortisol inhibition of placental cytokine production was dependent on timing of exposure, fetal sex and presence and absence of asthma. GRα and p38 MAPK protein expression did not appear to contribute to differences in response to endotoxin or cortisol. Maternal asthma during pregnancy induces a hyposensitive inflammatory state in the placenta which is regulated by cortisol in a sexually dimorphic manner.

The T-helper cell type 1 immune response to gram-negative bacterial infections is impaired in COPD

RATIONALE

The increased susceptibility to bacterial infections in chronic obstructive pulmonary disease (COPD) is critical for exacerbations. Toll-like receptor-4 (TLR4) detects bacteria via LPS and induces IFN-γ-based immune responses. The direct responsiveness of Th1 lymphocytes to LPS is disputed because they lack surface expression of the TLR4 coreceptor CD14.

OBJECTIVES

We hypothesized that the Th1-mediated adaptive immune response to bacterial infections is impaired in COPD.

METHODS

LPS-induced TLR4 expression and IFN-γ release in and from ex vivo-generated Th1 cells was compared among nonsmokers (n = 14), smokers without COPD (n = 13), and smokers with COPD (n = 25) via quantitative reverse transcription polymerase chain reaction, Western blot, and ELISA. TLR4 transfection experiments were performed to functionally link receptor to IFN-γ dysregulation in COPD.

MEASUREMENTS AND MAIN RESULTS

Short-chain LPS from Salmonella species and nontypeable Haemophilus influenzae and nontypeable Haemophilus influenzae whole-cell extract all induced TLR4 expression via TLR4/MyD88/IRAK/mitogen-activated protein-kinase signaling and IFN-γ release via TLR4/TRIF/IKKε/TBK1 signaling in Th1 cells of nonsmokers. These effects were all impaired in smokers with and without COPD. The LPS responses were partially dependent on soluble CD14 and correlated positively to lung-function parameters but negatively to cigarette smoking (pack-years). Endogenous MyD88/IRAK signaling antagonists were up-regulated in Th1 cells of smokers and COPD, and TLR4 overexpression in Th1 cells of COPD restored LPS-dependent IFN-γ release.

CONCLUSIONS

Th1 cells directly respond to short-chain LPS. Cigarette smoking suppresses Th1-mediated immune responses to gram-negative bacterial infections by interfering with MyD88/IRAK signaling thereby reducing LPS-induced TLR4 expression. This can explain the increased susceptibility to bacterial infections in COPD. Targeting TLR signaling might be useful to reduce exacerbation rates.

Differential effects of propofol and isoflurane on the activation of T-helper cells in lung cancer patients

It is suggested that activation and differentiation of T-helper cells are required for peri-operative anti-tumor and anti-infection immunity. The present study aimed to evaluate whether propofol stimulates the activation and differentiation of these cells in patients undergoing pulmonary lobectomy for non-small-cell lung cancer. Thirty patients were randomly allocated to receive propofol or isoflurane throughout surgery. The CD4(+)CD28(+) percentage (p < 0.0001) and the ratio of interferon-gamma:interleukin-4 (p = 0.001) all increased with propofol but showed no change with isoflurane. In contrast, cortisol increased with isoflurane (p < 0.0001) but not with propofol over time (p = 0.06). We conclude that propofol promotes activation and differentiation of peripheral T-helper cells.

Toll-like receptor expression on peripheral blood mononuclear cells in asthmatics; implications for asthma management

BACKGROUND

Accumulating evidence indicates that cells expressing Toll-like receptors (TLRs) play an important role in allergic diseases. The authors undertook this study to explore the hypothesis that TLR-mediated inflammatory signals are important from the perspective of asthma management.

METHODS

The expressions of TLR1, TLR2, TLR3, TLR4, TLR6, and TLR9 and levels of pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6, IL-8, and IFN-gamma) on the peripheral blood mononuclear cells (PBMCs) of 36 stable asthmatics on treatment (the on-treatment group), 15 asthmatics (the treatment-naïve group) before and after a 7-day course of oral prednisolone (30 mg/day), and on the PBMCs of 15 healthy controls were measured after in vitro stimulation using TLR-specific ligands.

RESULTS

In the on-treatment group, TLR1, TLR2, TLR6, and TLR9 expressions on PBMCs were significantly different between asthmatics and controls. And the expression of TLR4 on PBMCs and TNF-alpha production stimulated by lipopolysaccharide (LPS), were significantly higher in mild to moderate than in severe asthmatics. Interestingly, in the treatment-naïve group, short-term prednisolone significantly increased LPS-induced TNF-alpha and IFN-gamma productions by PBMCs.

CONCLUSION

TLR-mediated inflammatory signals contribute to the development and severity of asthma and are not reduced by glucocorticoid treatment, which suggests that a TLR-specific antagonist and glucocorticoid are required for the effective control of airway inflammation in asthmatics.

Inhibition effects of Vitex rotundifolia on inflammatory gene expression in A549 human epithelial cells

BACKGROUND

Vitex rotundifolia has long been used in traditional medicine to treat asthma and other allergic diseases.

OBJECTIVE

To evaluate the anti-inflammatory mechanisms of V rotundifolia in cultured A549 human alveolar epithelial cells.

METHODS

In the present study, A549 cells were stimulated with tumor necrosis factor alpha, interleukin 4, and interleukin 1beta to induce expression of chemokines and adhesion molecules involved in eosinophil chemotaxis. The anti-inflammatory effects of V rotundifolia on stimulated A549 cells were then evaluated by analyzing eotaxin secretion and eosinophil migration. In addition, the effects of V rotundifolia on gene expression profiles in stimulated A549 cells were evaluated by oligonucleotide microarray and real-time reverse transcription-polymerase chain reaction (RTRP).

RESULTS

The V rotundifolia-treated A549 cells had significantly suppressed eotaxin secretion and eosinophil migration in a dose-dependent manner. In addition, the results of the microarray analysis and RTRP revealed that inflammation-related genes and cell adhesion-related genes were down-regulated in V rotundifolia-treated A549 cells. Furthermore, several genes related to the mitogen-activated protein kinase pathway were down-regulated in V rotundifolia-treated A549 cells.

CONCLUSIONS

The mechanism responsible for the effects of V rotundifolia on A549 cells is closely associated with regulation of the mitogen-activated protein kinase pathway. Thus, V rotundifolia may be useful in the treatment of asthma and other allergic diseases.

Different doses of lipopolysaccharides regulate the lung inflammation of asthmatic mice via TLR4 pathway in alveolar macrophages

Allergic asthma is a complicated genetic disorder caused by interaction of the acquired and innate immune responses. Acquired immune responses to protein antigens could induce type 2 T lymphocyte-driven responses and result in atopic asthma. Recent studies demonstrated that endotoxin, LPS and air pollution-induced innate immunity induce asthma through Toll-like receptors (TLR). However, the definite mechanism of LPS-induced asthma is still not known. Here, we investigated the effects of different doses of LPS in a mouse model of allergic asthma to define the molecular mechanism of LPS-induced asthma. We found that low doses of LPS in OVA induced significant inflammatory infiltration in lung tissue of asthmatic mice. Histologic studies demonstrated that lungs of these asthmatic mice were characterized by the recruitment of both eosinophils and neutrophils, increased airway mucus secretion and the elevated levels of Th2 cytokines. A high dose of LPS in OVA can induce a Th1 associated response, histologically characterized by neutrophil recruitment, the absence of airway mucus secretion and an increase of IFN-gamma production. Regardless of high or low dose of LPS, TLR4 in alveolar macrophages (AM) was up-regulated in lungs of asthmatic mice. Our data demonstrated that the dose of LPS exposure determines the type of inflammatory response and a low dose of LPS together with OVA augments the antigen-induced lung inflammation in asthma. This study demonstrates that the TLR4 signaling pathway plays a vital role in the development of asthma and indicates the tight connection between endotoxin exposure and asthma prevalence in the clinic.

Understanding how lipopolysaccharide impacts CD4 T-cell immunity

Lipopolysaccharide (LPS) is a natural adjuvant synthesized by gram-negative bacteria that has profound effects on CD4 T-cell responses. LPS stimulates cells through the Toll-like receptor 4 (TLR4), causing the release of inflammatory cytokines and upregulation of costimulatory molecules on antigen-presenting cells (APCs). The combination of signals from antigens, costimulation, and cytokines allows CD4 T cells to overcome suppressive barriers and accumulate in large numbers. T cells that are primed in an LPS-stimulated environment are programmed for long-term survival following clonal expansion. LPS is well-known for generating Th1 responses. However, under appropriate conditions it can also support differentiation into other T-helper lineages, demonstrating its pleiotropic nature. Although molecular analyses have provided insights into how immune responses are controlled by LPS in vivo, its powerful adjuvant activity is also associated with toxicity. Research on partial TLR4 agonists such as monophosphoryl lipid A have demonstrated that toxicity and immunogenicity are not always linked, making them useful candidates for human vaccines. In this sense, many years of LPS research have ultimately contributed to vaccine design, and the next generation may involve studying how the balance between different CD4 T-cell subsets is controlled.

Innate immunity in asthma

Asthma is a complex disorder and evidence now suggests that it is not solely attributable either to allergy or eosinophilia. Non-eosinophilic asthma accounts for up to one half of all cases and a large proportion have a non-allergic aetiology. The innate immune system responds to a variety of triggers, including viral and bacterial components which are known non-allergic triggers of asthma. The innate immune response may be involved in both the development of and protection against asthma. Factors which are likely to determine the nature of the response include the timing of the exposure (childhood or adulthood), baseline asthma inflammatory subtype (eosinophilic or non-eosinophilic) and the dose of the exposure. Gene-environment interactions are likely to modify the response. Further research is required to elucidate the specific mechanisms involved in the innate immune response in asthma and will be important in the identification of new targets for therapy and management.

Induction of TLR2 expression by inflammatory stimuli is required for endothelial cell responses to lipopeptides

Human endothelial cells (EC) express Toll-like receptor 4 (TLR4), a receptor for lipopolysaccharides (LPS), but little or no TLR2, a lipopeptide receptor. The aim of this study was to investigate to what extent inflammatory stimuli modify the expression by EC of TLR4 and TLR2, of the TLR2 co-receptors TLR1 and TLR6 and of the TLR2-accessory proteins CD14 and CD36. Stimulation of umbilical vein derived EC with TNF-alpha, LPS or IL-1beta for 24h induced a strong increase in TLR2 mRNA but not in TLR1, TLR4 and TLR6 mRNA. Inflammatory activation had little effect on CD14 mRNA, but decreased the expression of CD36 mRNA. TLR2 antigen was readily detected by flow cytometry on activated EC, but not on resting EC. A significant proportion of TLR2 was found to be located intracellularly. By using specific signalling pathway inhibitors we established that the induction of TLR2 by inflammatory stimuli was dependent on NF-kappaB, p38-MAP kinase and c-Jun kinase. IRAK-1 phosphorylation after treatment with 10mug/ml of lipoteichoic acid (LTA), a TLR2 agonist, was only observed in TNF-alpha-stimulated EC and not in resting EC. Furthermore, LTA potentiated the increase of the inflammatory markers E-Selectin or IL-8 in EC pre-treated with TNF-alpha, LPS or IL-1beta, but not in resting EC. These results imply that the up-regulated TLR2 is functionally active. Interestingly, LTA had no effect on TLR2 expression, nor maintained TLR2 expression, in activated EC. This suggests that lipopeptide responses of EC are dependent on the continued presence of inflammatory cytokines, provided by other cell types, or LPS. In conclusion, inflammatory stimuli induce a high TLR2 expression in EC, which in turn enables the cells to strongly respond to lipopeptides. The up-regulation of TLR2 may be of relevance for the vascular effects of Gram-positive bacteria.