Tumor necrosis factor-alpha causes release of cytosolic interleukin-18 from human neutrophils

Cf-02, a novel benzamide-linked small molecule, blunts NF-κB activation and NLRP3 inflammasome assembly and improves acute onset of accelerated and severe lupus nephritis in mice

In the present study, acute onset of severe lupus nephritis was successfully treated in mice using a new, benzamide-linked, small molecule that targets immune modulation and the NLRP3 inflammasome. Specifically, 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (Cf-02) (a) reduced serum levels of IgG anti-dsDNA, IL-1β, IL-6, and TNF-α, (b) inhibited activation of dendritic cells and differentially regulated T cell functions, and (c) suppressed the NF-κB/NLRP3 inflammasome axis, targeting priming and activating signals of the inflammasome. Moreover, treatment with Cf-02 significantly inhibited secretion of IL-1β in lipopolysaccharide-stimulated macrophages, but this effect was abolished by autophagy induction. These results recommend Cf-02 as a promising drug candidate for the serious renal conditions associated with systemic lupus erythematosus. Future investigations should examine whether Cf-02 may also be therapeutic in other types of chronic kidney disease involving NLRP3 inflammasome-driven signaling.

Modulation of γδ T-cell activation by neutrophil elastase

γδ T cells are non-conventional, innate-like T cells, characterized by a restricted T-cell receptor repertoire. They participate in protective immunity responses against extracellular and intracellular pathogens, tumour surveillance, modulation of innate and adaptive immune responses, tissue healing, epithelial cell maintenance and regulation of physiological organ function. In this study, we investigated the role of neutrophils during the activation of human blood γδ T cells through CD3 molecules. We found that the up-regulation of CD69 expression, and the production of interferon-γ and tumour necrosis factor-α induced by anti-CD3 antibodies was potentiated by neutrophils. We found that inhibition of caspase-1 and neutralization of interleukin-18 did not affect neutrophil-mediated modulation. By contrast, the treatment with serine protease inhibitors prevented the potentiation of γδ T-cell activation induced by neutrophils. Moreover, the addition of elastase to γδ T-cell culture increased their stimulation, and the treatment of neutrophils with elastase inhibitor prevented the effect of neutrophils on γδ T-cell activation. Furthermore, we demonstrated that the effect of elastase on γδ T cells was mediated through the protease-activated receptor, PAR1, because the inhibition of this receptor with a specific antagonist, RWJ56110, abrogated the effect of neutrophils on γδ T-cell activation.

Role of IL-18 in atopic asthma is determined by balance of IL-18/IL-18BP/IL-18R

It is recognized that IL‐18 is related to development of asthma, but role of IL‐18 in asthma remains controversial and confusing. This is largely due to lack of information on expression of IL‐18 binding protein (BP) and IL‐18 receptor (R) in asthma. In this study, we found that plasma levels of IL‐18 and IL‐18BP were elevated in asthma. The ratio between plasma concentrations of IL‐18 and IL‐18BP was 1:12.8 in asthma patients. We demonstrated that 13‐fold more monocytes, 17.5‐fold more neutrophils and 4.1‐fold more B cells express IL‐18BP than IL‐18 in asthmatic blood, suggesting that there is excessive amount of IL‐18BP to abolish actions of IL‐18 in asthma. We also discovered that more IL‐18R+ monocytes, neutrophils and B cells are located in asthmatic blood. Once injected, IL‐18 eliminated IL‐18R+ monocytes in blood, but up‐regulated expression of IL‐18R in lung macrophages of OVA‐sensitized mice. Our data clearly indicate that the role of IL‐18 in asthma is very likely to be determined by balance of IL‐18/IL‐18BP/IL‐18R expression in inflammatory cells. Therefore, IL‐18R blocking or IL‐18BP activity enhancing therapies may be useful for treatment of asthma.

TLR-Stimulated Neutrophils Instruct NK Cells To Trigger Dendritic Cell Maturation and Promote Adaptive T Cell Responses

Polymorphonuclear neutrophils (PMNs) are innate effector cells with pivotal roles in pathogen recognition, phagocytosis, and eradication. However, their role in the development of subsequent immune responses is incompletely understood. This study aimed to identify mechanisms of relevance to the cross talk between human neutrophils and NK cells and its potential role in promoting adaptive immunity. TLR-stimulated PMNs were found to release soluble mediators to attract and activate NK cells in vitro. PMN-conditioned NK cells displayed enhanced cytotoxicity and cytokine production, and responded vigorously to ensuing stimulation with exogenous and endogenous IL-12. The neutrophil-induced activation of NK cells was prevented by caspase-1 inhibitors and by natural antagonists to IL-1 and IL-18, suggesting a role for the NOD-like receptor family pyrin domain containing-3 inflammasome. In addition, PMN-conditioned NK cells triggered the maturation of monocyte-derived dendritic cells, which promoted T cell proliferation and IFN-γ production. These data imply that neutrophils attract NK cells to sites of infection to convert these cells into an active state, which drives adaptive immune responses via maturation of dendritic cells. Our results add to a growing body of evidence that suggests a sophisticated role for neutrophils in orchestrating the immune response to pathogens.

Inflammasome-dependent and -independent IL-18 production mediates immunity to the ISCOMATRIX adjuvant

Adjuvants are an essential component of modern vaccines and used for their ability to elicit immunity to coadministered Ags. Many adjuvants in clinical development are particulates, but how they drive innate and adaptive immune responses remains poorly understood. Studies have shown that a number of vaccine adjuvants activate inflammasome pathways in isolated APCs. However, the contribution of inflammasome activation to vaccine-mediated immunity in vivo remains controversial. In this study, we evaluated immune cell responses to the ISCOMATRIX adjuvant (IMX) in mice. Like other particulate vaccine adjuvants, IMX potently activated the NALP-3-ASC-Caspase-1 inflammasome in APCs, leading to IL-1β and IL-18 production. The IL-18R pathway, but not IL-1R, was required for early innate and subsequent cellular immune responses to a model IMX vaccine. APCs directly exposed to IMX underwent an endosome-mediated cell-death response, which we propose initiates inflammatory events locally at the injection site. Importantly, both inflammasome-related and -unrelated pathways contributed to IL-18 dependence in vivo following IMX administration. TNF-α provided a physiological priming signal for inflammasome-dependent IL-18 production by APCs, which correlated with reduced vaccine-mediated immune cell responses in TNF-α- or TNFR-deficient mice. Taken together, our findings highlight an important disconnect between the mechanisms of vaccine adjuvant action in vitro versus in vivo.

Characterization of IL-18 expression and release in the pathogenesis of chronic rhinosinusitis

BACKGROUND

Interleukin-18 (IL-18) is a member of the IL-1 cytokine family that affects chronic inflammation. We sought to characterize IL-18 expression and investigate its release during chronic rhinosinusitis (CRS).

METHODS

The expression of IL-18 in nasal polyps (NPs) and uncinate tissues (UTs) from both CRS and non-CRS patients was examined via immunohistochemistry. After culturing dispersed NP cells (DNPCs) with or without various stimulations, IL-18 levels were measured in the culture supernatants. Furthermore, the effect of IL-18 neutralization on staphylococcus enterotoxin B (SEB)-induced cytokine production was also examined.

RESULTS

Similar expression of IL-18 in the epithelial layers was observed between the NPs and UTs. However, there was a significantly higher number of IL-18(+) cells in the lamina propria from NPs compared to UTs without CRS. This increased number was significantly correlated with the radiological severity of sinusitis and local eosinophilia. After the dispersion, IL-18 was spontaneously released by NP cells in a phase-dependent manner. While SEB, fungal antigens, and TLR agonists did not enhance the release, exposure to protease or one cycle of a freeze-and-thaw treatment did induce release of IL-18 from rested DNPCs. In addition, neutralization of IL-18 significantly suppressed SEB-induced IL-5, IL-13, and IFN-γ, but not IL-17A production.

CONCLUSIONS

These results suggest that the pro-inflammatory effect of IL-18 released by danger signals may be involved in the pathogenesis of CRS, which includes eosinophilic inflammation and NP formation, via the augmentation of both Th2- and Th1-associated cytokine production.

Toll-like receptor 4 is involved in bacterial endotoxin-induced endothelial cell injury and SOC-mediated calcium regulation

Bacterial endotoxins may lead to vascular endothelial cell injury. Our study explored the role of TLR4 (Toll-like receptor 4) and STIM1 (stromal interaction molecule 1) in bacterial endotoxin-induced calcium overload and inflammatory reactions in HUVECs (human umbilical vein endothelial cells). It showed that under LPS (lipopolysaccharide) stimulation, LBP (LPS-binding protein) mRNA levels peaked at 24 h, TLR4 levels at 12 h and NF-κB (nuclear factor κB) levels at 6 h (all P<0.01). LBP levels increased gradually and peaked at 24 h of LPS treatment. TLR4 protein levels increased significantly at 1 h and peaked at 12 h. NF-κB protein levels markedly increased at 1 h and peaked at 6 h. Knockdown of STIM1 alone, TLR4 alone or both STIM1 and TLR4 together, markedly abolished LPS-induced increase in calcium influx into cells (P<0.05, P<0.01 and P<0.01 respectively). LBP-TLR4 and STIM-NF-κB interactions were detected without LPS treatment, enhanced by LPS stimulation, and markedly reduced by knocking down TLR4 and STIM respectively. Both the NF-κB inhibitor, PDTC (pyrrolidine dithiocarbamate) and TLR4 knockdown could block LPS induction of NF-κB, STIM, TNFα (tumour necrosis factor α) and IL-6 (interleukin 6). The data indicate LPS-LBP may activate TLR4 signalling and downstream transcription factor NF-κB, which further can activate STIM1 and eventually lead to calcium influx and injury of HUVECs. Inhibition of TLR4 effectively reverses LPS induction of inflammatory mediator generation and extracellular calcium influx mediated by STIM1.

Antroquinonol differentially modulates T cell activity and reduces interleukin-18 production, but enhances Nrf2 activation, in murine accelerated severe lupus nephritis

OBJECTIVE

Accelerated severe lupus nephritis (ASLN), with an acute onset of severe clinical manifestations and histopathologic renal lesions, may represent transformation of mild LN to a severe form of glomerulonephritis. Abnormal activation of T and B cells and/or oxidative stress may play a major role in the pathogenesis of ASLN. This study tested the hypothesis that antroquinonol, a purified compound and major effective component of Antrodia camphorata with antiinflammatory and antioxidant activities, might prevent the transformation of mild LN into higher-grade (severe) nephritis in a murine lupus model.

METHODS

Experimental ASLN was induced in (NZB×NZW)F1 mice by twice weekly intraperitoneal injections of Salmonella-type lipopolysaccharide (LPS). Starting 2 days after the first dose of LPS, mice were treated daily with antroquinonol, administered by gavage, for different durations up to 5 weeks.

RESULTS

Antroquinonol administration significantly ameliorated the proteinuria, hematuria, impairment of renal function, and development of severe renal lesions, especially cellular crescent formation, neutrophil infiltration, fibrinoid necrosis, and T cell proliferation in the glomerulus, as well as periglomerular interstitial inflammation. Mechanistic analyses revealed that antroquinonol 1) inhibited T cell activation/proliferation, but enhanced Treg cell suppression and reduced renal production of interleukin-18 (IL-18); 2) inhibited production of reactive oxygen species and nitric oxide, but increased activation of Nrf2 in the kidney; and 3) suppressed renal inflammation via blocking of NF-κB activation.

CONCLUSION

Antroquinonol may have therapeutic potential for the early treatment of ASLN via its differential regulation of T cell function and lowering of IL-18 production, but also via the promotion of Nrf2 activation.