Targeting SIRP‐α protects from type 2‐driven allergic airway inflammation

The interplay between innate and adaptive immune responses is essential for the establishment of allergic diseases. CD47 and its receptor, signal regulatory protein α (SIRP‐α), govern innate cell trafficking. We previously reported that administration of CD47^+/+ but not CD47^−/− SIRP‐α⁺ BM‐derived DC (BMDC) induced airway inflammation and Th2 responses in otherwise resistant CD47‐deficient mice. We show here that early administration of a CD47‐Fc fusion molecule suppressed the accumulation of SIRP‐α⁺ DC in mediastinal LN, the development of systemic and local Th2 responses as well as airway inflammation in sensitized and challenged BALB/c mice. Mechanistic studies highlighted that SIRP‐α ligation by CD47‐Fc on BMDC did not impair Ag uptake, Ag presentation and Ag‐specific DO11.10 Tg Th2 priming and effector function in vitro, whereas in vivo administration of CD47‐Fc or CD47‐Fc‐pretreated BMDC inhibited Tg T‐cell proliferation, pinpointing that altered DC trafficking accounts for defective Th priming. We conclude that the CD47/SIRP‐α axis may be harnessed in vivo to suppress airway SIRP‐α⁺ DC homing to mediastinal LN, Th2 responses and allergic airway inflammation.     

MD-1 is a critical part of the mechanism causing Th1-cytokine-triggered murine fetal loss syndrome

PROBLEM: Fetal loss syndrome (abortion/resorption) occurring on or after gestation day (gd) 9.5 in CBA/J×DBA/2 matings is dependent upon presence of TNF‐α + IFN‐γ, which act by increasing expression of fgl2 prothrombinase at the feto‐maternal interface. The magnitude by which the abortion rate can be boosted by an injection of these cytokines on gd 7.5 depends on endogenous rate of loss, and appears to depend on microbial flora. Is cytokine‐triggered abortion dependent upon a third signaling pathway that senses ‘danger'? METHODS: Female CBA/J were mated to DBA/2 males and, C57Bl/6 and C57Bl/6 TNFαR1^?/?Mak were mated to C57Bl/6 control or TNFαR1^?/?Mak males. LPS from Escherichia coli and Salmonella enteritidis, or the combination of TNF‐α + IFN‐γ, was injected to stimulate abortions. The effect of anti‐MD‐1, which interferes with expression of CD14 and, hence, with signaling by LPS via the CD14‐tlr4 complex, on TNF‐α + IFN‐γ was tested. The presence of MD‐1 in the uterus was evaluated by in situ hybridization, and effect of lipopolysaccharide (LPS) on mice lacking TNF‐αR1 was tested. RESULTS: Anti‐MD‐1 completely abrogated TNF‐α + IFN‐γ ‐induced abortions. MD‐1 was expressed on trophoblast and in deciduas on gd 8.5 but LPS could not abort mice that lacked the type 1 receptor for TNF‐α. Pregnant CBA/J females had classical resorptions (abortions) countable on gd 13.5–14.5 in response to LPS from E. coli or S. enteritidis, but C57Bl/6 strain mice resorbed only in response to the latter, and E. coli LPS appeared to induce ‘occult’ losses. ‘Occult’ loss did not require TNF‐α R1. CONCLUSIONS: TNF‐α + IFN‐γ could not induce murine abortions without co‐presence of a ‘danger’ signal such as LPS acting via CD14 on toll receptors, and LPS could not act without co‐signaling by TNF‐α. Classical resorptions/abortions and ‘occult’ losses have a different mechanism in these models as reflected in type of endotoxin and requirement for TNF‐αR1 signaling.     

CD11c+ macrophages and levels of TNF‐α and MMP‐3 are increased in synovial and adipose tissues of osteoarthritic mice with hyperlipidaemia

To understand more clearly the link between osteoarthritis and hyperlipidaemia, we investigated the inflammatory macrophage subsets and macrophage‐regulated matrix metalloprotease‐3 (MMP‐3) and A disintegrin and metalloprotease with thrombospondin motifs‐4 (ADAMTS4) in synovial (ST) and adipose tissues (AT) of osteoarthritic mice with hyperlipidaemia (STR/Ort). CD11c⁺F4/80⁺CD11b⁺ macrophage populations in the ST and AT of 9‐month‐old STR/Ort and C57BL/6J mice were characterized and compared by flow cytometry and real‐time polymerase chain reaction (PCR) analyses. Expression of tumour necrosis factor (TNF)‐α, MMP‐3 and ADAMTS4, and the response of these factors to anionic liposomal clodronate induced‐macrophage depletion were also evaluated by real‐time PCR. Expression of TNF‐α in CD11c⁺ cells, which were isolated by magnetic beads, was compared to CD11c^– cells. In addition, the effect of TNF‐α on cultured synovial fibroblasts and adipocytes was investigated. CD11c⁺F4/80⁺CD11b⁺ macrophages were increased in ST and AT of STR/Ort mice. The CD11c⁺ cell fraction highly expressed TNF‐α. Expression of TNF‐α and MMP3 was increased in ST and AT, and was decreased upon macrophage depletion. TNF‐α treatment of cultured synovial fibroblasts and adipocytes markedly up‐regulated MMP‐3. CD11c⁺F4/80⁺CD11b⁺ macrophages were identified as a common inflammatory subset in the AT and ST of STR/Ort mice with hyperlipidaemia. The induction of inflammation in AT and ST may be part of a common mechanism that regulates MMP3 expression through TNF‐α. Our findings suggest that increased numbers of CD11c⁺ macrophages and elevated levels of TNF‐α and MMP‐3 in AT and ST may explain the relationship between hyperlipidaemia and OA.     

Human metapneumovirus infection activates the TSLP pathway that drives excessive pulmonary inflammation and viral replication in mice

Human metapneumovirus (hMPV) is a leading cause of acute respiratory tract infections in children and the elderly. The mechanism by which this virus triggers an inflammatory response still remains unknown. Here, we evaluated whether the thymic stromal lymphopoietin (TSLP) pathway contributes to lung inflammation upon hMPV infection. We found that hMPV infection promotes TSLP expression both in human airway epithelial cells and in the mouse lung. hMPV infection induced lung infiltration of OX40L⁺CD11b⁺ DCs. Mice lacking the TSLP receptor deficient mice (tslpr^?/?) showed reduced lung inflammation and hMPV replication. These mice displayed a decreased number of neutrophils as well a reduction in levels of thymus and activation‐regulated chemokine/CCL17, IL‐5, IL‐13, and TNF‐α in the airways upon hMPV infection. Furthermore, a higher frequency of CD4⁺ and CD8⁺ T cells was found in tslpr^?/? mice compared to WT mice, which could contribute to controlling viral spread. Depletion of neutrophils in WT and tslpr^?/? mice decreased inflammation and hMPV replication. Remarkably, blockage of TSLP or OX40L with specific Abs reduced lung inflammation and viral replication following hMPV challenge in mice. Altogether, these results suggest that activation of the TSLP pathway is pivotal in the development of pulmonary pathology and pulmonary hMPV replication.     

Selective blockade of endothelial NF‐κB pathway differentially affects systemic inflammation and multiple organ dysfunction and injury in septic mice

Endothelium has long been considered both a source and a target of systemic inflammation. However, to what extent endothelial activation contributes to systemic inflammation remains unclear. This study addresses the relative contribution of endothelial activation to systemic inflammation and multiple organ dysfunction and injury (MOD/I) in an E. coli peritonitis model of sepsis. We prevented endothelial activation using transgenic (TG) mice that conditionally overexpress a mutant I‐κBα, a NF‐κB inhibitor, selectively on endothelium. TG mice and their transgene negative littermates (WT) were injected with saline or E. coli (10⁸ CFU per mouse). At 7 h after E. coli infection, markers of systemic inflammation, endothelial activation, and MOD/I were assessed. WT‐E. coli mice showed significantly increased serum levels of TNF‐α, IL‐1β, IFN‐γ, IL‐6, KC, and MCP‐1; tissue levels of TNF‐α, IL‐6, KC, MCP‐1, ICAM‐1, and VCAM‐1; endothelial leakage index in heart, lungs, liver, and kidney; significantly increased serum levels of AST, ALT, BUN, and creatinine; and increased mortality. Blockade of NF‐κB‐mediated endothelial activation in TG mice had no effects on serum levels of TNF‐α, IL‐1β, IFN‐γ, IL‐6, KC, and MCP‐1 (markers of systemic inflammation), and tissue levels of TNF‐α, IL‐6, KC, and MCP‐1, but significantly reduced tissue levels of ICAM‐1 and VCAM‐1 (markers of endothelial inflammation and activation) in those four organs. TG‐E. coli mice displayed reversed endothelial leakage index; reduced serum levels of AST, ALT, BUN, and creatinine; and improved survival. Our data demonstrate that endothelial NF‐κB‐driven inflammatory response contributes minimally to systemic inflammation, but plays a pivotal role in septic MOD/I, suggesting that endothelium is mainly a target rather than a source of systemic inflammation. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Tumor necrosis factor‐α augments lipopolysaccharide‐induced suppressor of cytokine signalling 3 (SOCS‐3) protein expression by preventing the degradation

The regulatory role of tumour necrosis factor‐α (TNF‐α) on the expression of suppressor of cytokine signalling 3 (SOCS‐3) in response to lipopolysaccharide (LPS) was examined using peritoneal macrophages from TNF‐α‐deficient mice. The LPS‐induced SOCS‐3 expression was markedly augmented in macrophages from wild‐type mice whereas such augmentation was not seen in the cells from TNF‐α‐deficient mice. However, there was no significant difference in the level of SOCS‐3 messenger RNA expression between macrophages from wild‐type mice and those from TNF‐α‐deficient mice. The addition of exogenous TNF‐α augmented the LPS‐induced SOCS‐3 expression in macrophages from TNF‐α‐deficient mice. The pulse chase analysis suggested augmented degradation of LPS‐induced SOCS‐3 protein in macrophages from TNF‐α‐deficient mice. Moreover, MG 132, a 26S proteasome inhibitor, sustained the LPS‐induced SOCS‐3 expression in those cells. The tyrosine phosphorylation of SOCS‐3 was definitely induced in LPS‐stimulated macrophages from TNF‐α‐deficient mice but not wild‐type mice. A tyrosine phosphatase inhibitor enhanced the tyrosine phosphorylation of SOCS‐3 in wild‐type mice and accelerated the degradation. Therefore, it was suggested that TNF‐α prevented the degradation of SOCS‐3 protein via inhibition of the tyrosine phosphorylation in LPS‐stimulated macrophages.     

Immunoregulatory potential of exopolysaccharide from Lactobacillus rhamnosus KL37: effects on the production of inflammatory mediators by mouse macrophages

The ability to produce exopolysaccharides (EPS) is widespread among lactobacilli including Lactobacillus rhamnosus, the commonly used probiotic bacteria. Exopolysaccharides are a major component of the bacterial biofilm with a well‐documented impact on adherence of bacteria to host cells. However, their immunoregulatory properties are unknown. The aim of this study was to examine the immunostimulatory potential of EPS derived from L. rhamnosus KL37. We investigated the effect of EPS on the production of inflammatory mediators by mouse peritoneal macrophages and compared it with the effect of Lipopolysaccharide (LPS). Exopolysaccharides, at concentrations higher than those of LPS, stimulated production of both pro‐inflammatory (TNF‐α, IL‐6, IL‐12) and anti‐inflammatory (IL‐10) cytokines. Interestingly, analysis of the balance of TNF‐α/IL‐10 production showed a potential pro‐inflammatory effect of EPS. Furthermore, our data demonstrate that exposure of macrophages to LPS induced a state of hyporesponsiveness, as indicated by reduced production of TNF‐α after restimulation with either LPS or EPS (‘cross‐tolerance’). By contrast, EPS could make cells tolerant only to subsequent stimulation by the same stimulus. We also examined the relationship between TNF‐α production and activation of mitogen‐activated protein kinases (MAPKs) by EPS and LPS. Pretreatment of macrophages with specific inhibitors of p38 and ERK MAPKs reduced TNF‐α production induced by both stimuli to the same extent. In conclusion, these data demonstrate that EPS can effectively stimulate production of inflammatory mediators by macrophages in vitro. However, to predict whether EPS could be clinically useful as an immunomodulatory agent, further in vivo studies with highly purified EPS are necessary.     

Radioresistant cells expressing TLR5 control the respiratory epithelium's innate immune responses to flagellin

Bacterial products (such as endotoxins and flagellin) trigger innate immune responses through TLRs. Flagellin‐induced signalling involves TLR5 and MyD88 and, according to some reports, TLR4. Whereas epithelial and dendritic cells are stimulated by flagellin in vitro, the cell contribution to the in vivo response is still unclear. Here, we studied the respective roles of radioresistant and radiosensitive cells in flagellin‐induced airway inflammation in mice. We found that i.n. delivery of flagellin elicits a transient change in respiratory function and an acute, pro‐inflammatory response in the lungs, characterized by TLR5‐ and MyD88‐dependent chemokine secretion and neutrophil recruitment. In contrast, TLR4, CD14 and TRIF were not essential for flagellin‐mediated responses, indicating that TLR4 does not cooperate with TLR5 in the lungs. Respiratory function, chemokine secretion and airway infiltration by neutrophils were dependent on radioresistant, TLR5‐expressing cells. Furthermore, lung haematopoietic cells also responded to flagellin by activating TNF‐α production. We suggest that the radioresistant lung epithelial cells are essential for initiating early, TLR5‐dependent signalling in response to flagellin and thus triggering the lung's innate immune responses.     

High mortality rate of (NZW x BXSB)F1 mice induced by administration of lipopolysaccharide attributes to high production of tumour necrosis factor-alpha by increased numbers of dendritic cells

(NZW × BXSB)F1 mice (W/BF1 mice) have been reported to be a type of autoimmune‐prone mice, showing symptoms of proteinuria, anti‐DNA antibodies and anti‐platelet antibodies. In this paper, we report that W/BF1 mice show hyperproduction of tumour necrosis factor (TNF)‐α, responding to lipopolysaccharide (LPS) in comparison with normal mice, resulting in induction of death. In normal mice, monocytes/macrophages (Mo/MØ) are the main producer of TNF‐α, while both Mo/MØ and dendritic cells (DCs) produce TNF‐α in W/BF1 mice. Because the number of DCs is higher in W/BF1 mice, the main producers of TNF‐α in W/BF1 mice are thought to be DCs. Moreover, administration of anti‐TNF‐α antibodies rescued the W/BF1 mice from death induced by LPS, suggesting that TNF‐α is crucial for the effect of LPS. Although there is no significant difference in the expression of Toll‐like receptor‐4 (TLR‐4) on DCs between B6 and W/BF1 mice, nuclear factor kappa b activity of DCs from W/BF1 mice is augmented under stimulation of LPS in comparison with that of normal mice. These results suggest that the signal transduction from TLR‐4 is augmented in W/BF1 mice in comparison with normal mice, resulting in the hyperproduction of TNF‐α and reduced survival rate. The results also suggest that not only the quantity of endotoxin, but also the host conditions, the facility to translate signal from TLR, and so on, could reflect the degree of bacterial infections and prognosis.     

Human Hemoglobin Shares Bioactivities Ascribed to Human Tumor Necrosis Factor‐α

Hemoglobin mediated cytotoxicity and apoptosis has been evaluated in Tumor necrosis factor‐α (TNF‐α) sensitive cell line, U937 and compared with TNF‐α. Both species of hemoglobin, Hemoglobin A₂ and Hemoglobin A₀ induced apoptosis and cytotoxicity in U937 cell as measured by flow cytometry and 3‐(4,5‐dihydro‐6‐(4‐(3,4‐dimethoxybenzooyl)‐1‐piperazinyl)‐2(1H)‐quinoline (MTT) assay respectively. Different concentration of Hemoglobin A₀ (4 ng/mL to 4000 ng/mL) induced apoptosis ranging from 9% to 16% in U937 cells. 4000 ng/mL hemoglobin A₀ showed maximal apoptotic cells. TNF‐α showed 87% apoptotic U937 cells at concentration of 1 pg/mL. HbA₀ displayed cytotoxicity in U937 cell line at higher concentration in comparison to TNF‐α. 4000 ng/mL of hemoglobin A₀ showed optimal cytotoxic response in U937 cells. A dose response curve was also observed with varying doses of hemoglobin A₀. U937 cells pretreated with serum activated LPS for 1 hr and incubated with different concentration of hemoglobin or human TNF‐α for 24 h reduced the cytotoxic effect on U937. Dexamethasone treatment of U937 cells helped in protecting the HbA₀ and HbA₂ mediated cytotoxicity and anti‐TNF‐α antibody neutralized the hemoglobin mediated apoptosis and cytotoxicity. It is therefore apparent that human hemoglobin shares some of the bioactivities previously ascribed to TNF‐α. Sharing of bioactivities of TNF‐α by hemoglobin is interesting and suggests that cell free hemoglobin can mimic TNF‐α functionally.     

ORIGINAL ARTICLE: Effect of Progesterone on Proinflammatory Cytokine Production by Monocytes Stimulated with Pathogens Associated with Preterm birth

Problem A number of clinical trials have demonstrated that supplemental progesterone (P₄) can prevent preterm birth. Although P₄ can decrease the production of mediators of inflammation by lipopolysaccharide (LPS)‐stimulated macrophages, a majority of infections associated with preterm birth are due to Ureaplasma urealyticum, which does not contain LPS. Therefore, we studied whether P₄ could lower the production of proinflammatory cytokines by monocytes stimulated with U. urealyticum. Method of study Human monocytes (THP‐1 cells) were treated with P₄ and then stimulated with heat‐killed Escherichia coli or U. urealyticum. Cytokine concentrations in the conditioned medium were then measured by ELISA and relative viability of the cells was assessed colorimetrically. The impact of P₄ on interleukin (IL)‐1β, tumor necrosis factor‐α (TNF‐α) and IL‐8 production was assessed by comparing levels across different P₄ dosages and organism concentrations. Results Both organisms increased IL‐1β, TNF‐α and IL‐8 production in a dose‐dependent manner. P₄ enhanced the production of IL‐1β and IL‐8, but inhibited TNF‐α production by monocytes stimulated with either organism. Conclusion P₄ modulates cytokine production by E. coli and U. urealyticum‐stimulated monocytes in a similar manner and is not strictly immunosuppressive. This suggests that P₄ does not prevent preterm birth by simply suppressing bacteria‐stimulated cytokine production.     

Soluble TNF‐α but not transmembrane TNF‐α sensitizes T cells for enhanced activation‐induced cell death

In addition to its proinflammatory effects, TNF‐α exhibits immunosuppression. Here, we compared the capacities of transmembrane TNF‐α (tmTNF) and soluble TNF‐α (sTNF) in regulating expansion of activated T cells by apoptosis. Splenic CD4⁺ T cells from wtTNF, TNF‐α‐deficient (TNF^?/?) and TNF^?/? mice expressing a non‐cleavable mutant tmTNF showed comparable proliferation rates upon TCR‐mediated stimulation. Activation‐induced cell death (AICD), however, was significantly attenuated in tmTNF and TNF^?/?, compared with wtTNF CD4⁺ T cells. Addition of sTNF during initial priming was sufficient to enhance susceptibility to AICD in tmTNF and TNF^?/? CD4⁺ T cells to levels seen in wtTNF CD4⁺ T cells, whereas addition of sTNF only during restimulation failed to enhance AICD. sTNF‐induced, enhanced susceptibility to AICD was dependent on both TNF receptors. The reduced susceptibility of tmTNF CD4⁺ T cells for AICD was also evident in an in vivo model of adoptively transferred CD4⁺ T‐cell‐mediated colonic inflammation. Hence, the presence of sTNF during T‐cell priming may represent an important mechanism to sensitize activated T cells for apoptosis, thereby attenuating the extent and duration of T‐cell reactivities and subsequent T‐cell‐mediated, excessive inflammation.     

BMP4 induces an epithelial–mesenchymal transition-like response in adult airway epithelial cells

Bone morphogenetic proteins (BMPs) are critical morphogens and play key roles in epithelial–mesenchymal transitions (EMTs) during embryogenesis. BMP4 is required for early mesoderm formation and also regulates morphogenesis and epithelial cell differentiation in developing lungs. While, BMP signalling pathways are activated during lung inflammation in adult mice, the role of BMPs in adult lungs remains unclear. We hypothesised that BMPs are involved in remodelling processes in adult lungs and investigated effects of BMP4 on airway epithelial cells. BEAS-2B cell growth decreased in the presence of BMP4. Cells acquired a mesenchymal-like morphology with downregulation of adherens junction proteins and increased cell motility. Changes in extracellular matrix-related gene expression occurred with BMP4 treatment including upregulation of collagens, fibronectin and tenascin C. We conclude that the activity of BMP4 in EMT during development is recapitulated in adult airway epithelial cells and suggest that this activity may contribute to inflammation and fibrosis in vivo.     

Tumor necrosis factor-alpha from macrophages enhances LPS-induced clara cell expression of keratinocyte-derived chemokine

Tumor necrosis factor (TNF)-alpha is a cytokine produced by alveolar macrophages in response to LPS in the lung. Clara cells are bronchiolar epithelial cells that produce a variety of proinflammatory cytokines in response to LPS but not to TNF-alpha. In this study, we examined whether TNF-alpha affects Clara cell cytokine production in the setting of LPS stimulation. Using a transformed murine Clara cell line (C22), we observed that both LPS and TNF-alpha induced production of keratinocyte-derived chemokine (KC) and monocyte chemoattractant protein (MCP)-1. We also found that simultaneous LPS and TNF-alpha stimulation is synergistic for KC production, but additive for MCP-1 production. By using a Transwell coculture system of RAW264.7 macrophages and Clara cells isolated from C57Bl/6 mice, we found that macrophages produce a soluble factor that enhances Clara cell KC production in response to LPS. Cocultures of Clara cells from mice deficient in TNF-alpha receptors with RAW264.7 macrophages demonstrated that the effect of macrophages on Clara cells is mediated primarily via TNF-alpha. To determine whether these findings occur in vivo, we treated wild-type and TNF receptor-deficient mice intratracheally with LPS and examined the expression of KC. LPS-treated, TNF receptor-deficient mice showed much less KC mRNA in airway epithelial cells compared with wild-type mice. In contrast, a similar number of KC-expressing cells was seen in the lung periphery. Thus, upregulation of KC by Clara cells in the setting of LPS stimulation is largely dependent on TNF-alpha originating from alveolar macrophages. These findings shed light on macrophage-Clara cell interactions in regulating the pulmonary inflammatory response to LPS.     

Multifunctional CD4+ T cells correlate with active Mycobacterium tuberculosis infection

Th1 CD4⁺ T cells and their derived cytokines are crucial for protection against Mycobacterium tuberculosis. Using multiparametric flow cytometry, we have evaluated the distribution of seven distinct functional states (IFN‐γ/IL‐2/TNF‐α triple expressors, IFN‐γ/IL‐2, IFN‐γ/TNF‐α or TNF‐α/IL‐2 double expressors or IFN‐γ, IL‐2 or TNF‐α single expressors) of CD4⁺ T cells in individuals with latent M. tuberculosis infection (LTBI) and active tuberculosis (TB). We found that triple expressors, while detectable in 85–90%TB patients, were only present in 10–15% of LTBI subjects. On the contrary, LTBI subjects had significantly higher (12‐ to 15‐fold) proportions of IL‐2/IFN‐γ double and IFN‐γ single expressors as compared with the other CD4⁺ T‐cell subsets. Proportions of the other double or single CD4⁺ T‐cell expressors did not differ between TB and LTBI subjects. These distinct IFN‐γ, IL‐2 and TNF‐α profiles of M. tuberculosis‐specific CD4⁺ T cells seem to be associated with live bacterial loads, as indicated by the decrease in frequency of multifunctional T cells in TB‐infected patients after completion of anti‐mycobacterial therapy. Our results suggest that phenotypic and functional signatures of CD4⁺ T cells may serve as immunological correlates of protection and curative host responses, and be a useful tool to monitor the efficacy of anti‐mycobacterial therapy.     

Anti‐retroviral effects of type I IFN subtypes in vivo

Type I IFN play a very important role in immunity against viral infections. Murine type I IFN belongs to a multigene family including 14 IFN‐α subtypes but the biological functions of IFN‐α subtypes in retroviral infections are unknown. We have used the Friend retrovirus model to determine the anti‐viral effects of IFN‐α subtypes in vitro and in vivo. IFN‐α subtypes α1, α4, α6 or α9 suppressed Friend virus (FV) replication in vitro, but differed greatly in their anti‐viral efficacy in vivo. Treatment of FV‐infected mice with the IFN‐α subtypes α1, α4 or α9, but not α6 led to a significant reduction in viral loads. Decreased splenic viral load after IFN‐α1 treatment correlated with an expansion of activated FV‐specific CD8⁺ T cells and NK cells into the spleen, whereas in IFN‐α4‐ and ‐α9‐treated mice it exclusively correlated with the activation of NK cells. The results demonstrate the distinct anti‐retroviral effects of different IFN‐α subtypes, which may be relevant for new therapeutic approaches.     

Corticosteroid enhances TNF‐α‐mediated leukocyte adhesion to pulmonary microvascular endothelial cells

Background: Some severe asthma patients are characterized by elevated levels of tumor necrosis factor alpha (TNF‐α) and neutrophilic inflammation in the airways. Although such phenotypic changes in asthma might contribute to corticosteroid refractoriness, the role of TNF‐α in the process remains unclear. TNF‐α exerts its biological effects mainly by acting on the vascular endothelium, and thereby upregulates leukocyte recruitment into inflamed tissues. The aim of this study was to investigate the effects of dexamethasone (DEX) on the TNF‐α‐mediated responses of human microvascular endothelial cells from lung blood vessels (HMVEC‐LBl) in vitro. Methods: HMVEC‐LBl were cultured with TNF‐α in the presence and absence of DEX. The effects of DEX on various TNF‐α‐mediated responses, such as the expressions of chemokines and cellular adhesion molecules, leukocyte adhesion were determined. Results: TNF‐α significantly induced growth‐related oncogene alpha (GRO‐α), interleukin 8 (IL‐8), regulated on activation, normal T‐cell expressed and secreted (RANTES) and interferon‐inducible protein 10 (IP‐10) productions and cell surface expressions of intracellular adhesion molecule 1 (ICAM‐1) and vascular cell adhesion molecule 1 (VCAM‐1) on HMVEC‐LBl. TNF‐α‐induced GRO‐α and IL‐8 were slightly attenuated by DEX treatment (reaches to 89% and 79%, respectively), whereas expressions of IP‐10, ICAM‐1 and VCAM‐1 were significantly enhanced by the same treatment (up to 172%, 152% and 139%, respectively). Correspondingly, in vitro adhesion of eosinophils and neutrophils to TNF‐α‐treated HMVEC‐LBl were significantly enhanced by DEX. Conclusions: Some proinflammatory effects of DEX, a corticosteroid, were found in TNF‐α‐mediated in vitro reactions of pulmonary microvascular endothelial cells, i.e. chemokine productions and leukocyte adhesion. These in vitro results may explain, at least in part, the corticosteroid refractoriness accompanied by a marked increase in TNF‐α production that is seen in severe asthmatic patients.     

Effect of Piperine on the Inhibition of Nitric Oxide (NO) and TNF‐α Production

Abstract

Effect of piperine which is an alkaloid present in plants such as Piper nigrum and Piper longum on the production of nitric oxide (NO) and tumor necrosis factor‐α (TNF‐α) level was analyzed using in vitro as well as in vivo systems. The level of nitrite in the LPS stimulated Balb/C mice (95.3 µM) was reduced in the piperine treated animals (25 µM) significantly. Nitrite level in the Concanavalin‐A (Con‐A) treated control animals (83.1 µM) was also significantly reduced to 18.5 µM in the piperine treated mice. The drastically elevated levels of TNF‐α in the lipopolysaccharide (LPS) stimulated animals (625.8 pg/mL) was lowered in the piperine treated animals (105.8 pg/mL). Piperine also inhibited the Con‐A induced TNF‐α production. Piperine could inhibit the nitrite production by in vitro activated macrophages (116.25 µM) to the normal level (15.67 µM) at concentration of 5 µg/mL. In vitro L929 bioassay also revealed the inhibition of TNF‐α production by the piperine treatment.     

Differential partial activation phenotype and production of tumour necrosis factor‐α by conventional dendritic cells in response to lipopolysaccharide in HIV+ viraemic subjects and HIV+ controllers

HIV⁺ subjects are reported to have increased soluble CD14 (sCD14) in plasma, an indicator of microbial translocation. We evaluated if microbial translocation has a differential impact on the activation and function of conventional dendritic cells (cDC) from viraemic HIV⁺ subjects and HIV⁺ controllers (CTs). The HIV⁺ subjects were classified into two groups according to their plasma viral load (pVL): CT and viraemic. Subjects without HIV were included as controls (HIV^–). The frequencies and phenotypes of cDC from these subjects were evaluated by multi‐parameter flow cytometry. In addition, peripheral blood mononuclear cells (PBMCs) were stimulated with lipopolysaccharide (LPS) or single‐stranded RNA40 (ssRNA40), the phenotype of the cDC and the intracellular production of tumour necrosis factor (TNF)‐α by the cDC were evaluated by flow cytometry. We observed a partial activation phenotype for the cDC in the viraemic subjects and CTs ex vivo and after LPS activation, which showed differences in the expression of CD40 and CD86. Furthermore, in response to LPS the cDC from the viraemic subjects produced more TNF‐α compared to the cDC from CTs. Interestingly, the percentage of TNF‐α⁺ cDC was found to be correlated positively with the pVL. The partial activation of cDC and the over‐production of TNF‐α in response to LPS in viraemic HIV⁺ subjects might be related to the increased chronic activation observed in these subjects. In contrast, cDC from CTs seem to have a regulated response to LPS, indicating that they respond differently to chronic immune activation. These results may have implications in the development of HIV therapies and vaccines using DC.     

Activation of p38 mitogen-activated protein kinase is critical step for acquisition of effector function in cytokine-activated T cells, but acts as a negative regulator in T cells activated through the T-cell receptor

Peripheral blood CD4⁺ CD45RO⁺ T cells activated in vitro are able to induce expression of tumour necrosis factor‐α (TNF‐α) in monocytes via a contact‐dependent mechanism. Activation is achieved either with interleukin‐2 (IL‐2)/IL‐6/TNF‐α over an 8‐day period or cross‐linking CD3 using anti‐CD3 antibody for 48 hr. In this paper, we show that the p38 mitogen‐activated protein kinase (MAPK) signalling pathway played different roles in the generation of effector function in these two types of activated T cells. In anti‐CD3 activated T cells, p38 MAPK is a negative regulator for anti‐CD3 induced cell proliferation and has no significant effect on the acquisition of either the effector function (induction of monocyte‐derived TNF‐α) or production of T‐cell cytokines. In contrast, the p38 MAPK signalling pathway is required for the acquisition of cytokine‐induced effector function and promotes cell proliferation and cytokine production.