Negative regulation of IL-1beta production at the level of transcription in macrophages stimulated with LPS

Vibrio alginolyticus Triggers Inflammatory Response in Mouse Peritoneal Macrophages via Activation of NLRP3 Inflammasome

Vibrio alginolyticus is a food-borne marine Vibrio that causes gastroenteritis, otitis media, otitis externa, and septicemia in humans. The pathogenic mechanisms of V. alginolyticus have previously been studied in aquaculture animals; however, the underlying mechanisms in mammals remain unknown. In this study, an in vitro model of mouse peritoneal macrophages infected with V. alginolyticus was established. qPCR results revealed that V. alginolyticus induced the transcription levels of various cytokines, including IL-1β, IL-12, IL-18, TNF-α, IL-17, IL-6, IFN-γ, and IL-10, and the secretion level of IL-1β is the most significant. Inhibition assays with Ac-YVAD-CHO (a caspase-1 inhibitor) and Z-VAD-FMK (a pan-caspase inhibitor) were conducted to determine whether caspase-1 or caspase-11 is involved in V. alginolyticus-triggered IL-1β secretion. Results showed that IL-1β secretion was partly inhibited by Ac-YVAD-CHO and absolutely blocked by Z-VAD-FMK. To explore the sensed pattern recognition receptors, several NLR family members and the AIM2 receptor were detected and many receptors were upregulated especially NLRP3. Moreover, the NLRP3 protein displayed a puncta-like surrounding cell nucleus, which signified that the NLRP3 inflammasome was activated in response to V. alginolyticus infection. Inhibition assays with glyburide and CA-074 methyl ester (K⁺ outflow inhibitor and cathepsin B inhibitor) blocked IL-1β secretion, which demonstrated the essential role of the NLRP3 inflammasome in inflammatory response. To better understand how V. alginolyticus affects IL-1β release, the NLRP3 inflammasome was detected with doses ranging from 0.1 to 10 MOIs and time periods ranging from 3 to 12 h. Results showed that V. alginolyticus-mediated NLRP3 inflammasome activation was in a time- and dose-dependent manner and IL-1β release peaked at MOI of 1 for 12 h. Most importantly, blocking the NLRP3 inflammasome with inhibitors and the use of NLRP3^-/- and caspase-1/11^-/- mice could attenuate pro-inflammatory cytokine secretion, such as IL-1β, IL-6, IL-12, and TNF-α. Taken together, our study first found that the NLRP3 inflammasome plays vital roles in V. alginolyticus triggered inflammatory response in mouse peritoneal macrophages. This may provide reference information for the development of potential anti-inflammatory treatments against V. alginolyticus infection.

Negative regulation of interleukin 1β expression in response to DnaK from Pseudomonas aeruginosa via the PI3K/PDK1/FoxO1 pathways

Interleukin (IL)-1β is crucial for a wide range of inflammatory responses. Previously, we reported that IL-1β is produced in response to Pseudomonas aeruginosa-derived DnaK via NF-κB and JNK pathways; however, the signaling pathways that counter the process to maintain IL-1β homeostasis are unknown. Here, we show that DnaK-mediated expression of IL1β is increased markedly in macrophages upon blockade of PI3K/PDK1. This was verified by measuring released IL-1β protein. The negative effect of PI3K on IL-1β production was dependent on suppression of both NF-κB and JNK activation. Intriguingly, PDK1 (an underlying mediator of PI3K) acted as an upstream regulator for the activation of NF-κB, but downregulated JNK activation. Furthermore, production of IL-1β and activation of JNK were triggered by inhibition of phosphorylated FoxO1; phosphorylation of FoxO1 was controlled by PDK1 signaling in response to DnaK. Thus, IL-1β production is modulated by P. aeruginosa-derived DnaK via cross-talk between JNK and PI3K/PDK1/FoxO1 pathways.

Anti-inflammatory properties and expression in selected organs of canine interleukin-1β splice variant 1

The IL-1β gene can be also be spliced with the intron 4 retention; the result is a IL-1β splice variant 1 (IL-1βsv1), which was significantly up-regulated in failing myocardium of dogs suffering from chronic degenerative valvular disease (CDVD). Expression of IL-1βsv1 was assessed, at both RNA and protein levels, in organs affected by heart failure, namely, kidneys, liver, and lungs from 35 dogs suffering chronic degenerative valvular disease (CDVD) and in 20 disease free control dogs. IL-1βsv1 RNA was detected in the dogs from both groups. In the CDVD group, the highest RNA and protein IL-1βsv1 levels were observed in lungs, followed, in that order, by the liver and kidneys. IL-1βsv1 protein was found in the cytoplasm of hepatocytes and IL-1βsv1-overexpressing DH82 cells. In lungs, IL-1βsv1 was localized in the cytoplasm and in the nuclei of bronchiolar epithelial and smooth-muscle cells. Cytoplasmic and nuclear IL-1βsv1 expression was observed in macrophages, and a strong nuclear signal was detected in epithelial cells of the alveolar sacs. Following lipopolysaccharide (LPS) stimulation, overexpression of IL-1βsv1 in DH82 cells decreased the pro-inflammatory response. Our results indicate that IL-1βsv1 is constitutively expressed in both normal tissues and in tissues from cases of heart failure. The presence of IL-1βsv1 in tissues exposed to invading agents and its anti-inflammatory activity in DH82 cells may point to its immunomodulatory role in vivo.

Differential effects of irradiation with carbon ions and x-rays on macrophage function

Macrophages are potent elicitors of inflammatory reactions that can play both positive and negative roles in radiotherapy. While several studies have investigated the effects of X-rays or gamma-rays on macrophages, virtually no work has been done on the responses of these cells to irradiation with carbon ions. Investigations into the effects of carbon ion irradiation are of particular interest in light of the fact that this type of radiation is being used increasingly for cancer therapy. In the present investigation we compared the effects of 250 kV X-rays with those of 9.8 MeV/u carbon ions on RAW 264.7 macrophages over a wide range of radiation doses. Macrophage functions including vitality, phagocytic activity, production of the proinflammatory cytokines IL-1beta and TNFalpha and production of nitric oxide (NO) were measured. In comparison to lymphocytes and fibroblasts, macrophages showed only a small decrease in vitality after irradiation with either X-rays or carbon ions. Proinflammatory cytokines and NO were induced in macrophages by LPS but not by irradiation alone. X-rays or carbon ions had little modulating effect on LPS-induced TNFalpha production. However, LPS-induced NO increased in a dose dependent manner up to 6-fold after carbon ion irradiation, while X-ray irradiation did not have this effect. Carbon ion irradiation mediated a concomitant decrease in IL-1beta production. Carbon ions also had a greater effect than X-rays in enhancing the phagocytic activity of macrophages. These results underscore the greater potential of carbon ion irradiation with regard to radiobiological effectiveness.

Exogenous ghrelin modulates release of pro-inflammatory and anti-inflammatory cytokines in LPS-stimulated macrophages through distinct signaling pathways

BACKGROUND

Ghrelin, an orexigenic 28-amino-acid peptide, has been studied primarily in relation to the control of appetite and fat metabolism. In addition to these well-known functions, ghrelin, and its target receptors, growth hormone secretagogue receptors (GHS-Rs), have been localized to neutrophils, lymphocytes, and macrophages, which suggests that ghrelin may be involved in immune modulation.

METHODS

To assess the therapeutic role of ghrelin in production of pro-inflammatory and anti-inflammatory cytokines, the effects of exogenous ghrelin administration on the regulation of cytokine release in lipopolysaccharide (LPS)-activated murine RAW 264.7 macrophages were analyzed.

RESULTS

Ghrelin and GHS-Rs are expressed in murine macrophages. In addition, exogenous ghrelin inhibited the production of pro-inflammatory cytokines IL-1beta and TNF-alpha in LPS-stimulated murine macrophages in a dose dependent and time-dependent fashion. Exogenous ghrelin pretreatment resulted in a decrease in LPS-induced NFkappaB activation and was presumably the reason for this ghrelin-mediated effect. In contrast to these findings, exogenous ghrelin significantly augmented the release of the anti-inflammatory cytokine IL-10 in a dose-dependent and time-dependent fashion from LPS-stimulated murine macrophages. Ghrelin administration enhanced activation of p38 MAPK, which is known to control the release of IL-10 in macrophages independent of the NFkappaB pathway. These effects of ghrelin on both pro-inflammatory and anti-inflammatory cytokines were offset when a specific GHS-R receptor antagonist was added to the culture media.

CONCLUSIONS

These data suggest that ghrelin has potent anti-inflammatory properties through modulation of secretion of both pro-inflammatory and anti-inflammatory cytokines from LPS-stimulated macrophages through distinct signaling cascades. Therapeutic utility of ghrelin to control, modulate, or treat pathologic inflammatory conditions like endotoxemic shock and ulcerative colitis requires additional investigation.

Induction of murine interleukin-1 beta expression by water-soluble components from Hericium erinaceum

AIM

To investigate the inductive effect of water extract from Hericium erinaceum (WEHE) on interleukin-1beta (IL-1beta) expression.

METHODS

A murine macrophage cell-line, RAW 264.7 was stimulated with 1 to 10 mg/L WEHE and inductions of IL-1beta protein and its steady state mRNA were examined using a bioassay, Western blotting, and reverse transcription-polymerase chain reaction (RT-PCR) analysis. The inductive effect of WEHE on IL-1beta gene expression was further investigated by a chloramphenicol acetyltransferase (CAT) reporter gene assay using a transient transfection with pIL-1(870 bp)-CAT where the expression of the CAT gene was regulated by a IL-1beta promoter. An electrophoretic mobility shift assay (EMSA) was also performed to examine transcription factors, nuclear factor-kappa B (NF-kappaB), activator protein 1 (AP-1), nuclear factor interleukin-6 (NF-IL6), and cAMP response element (CRE)/activating transcription factor (ATF).

RESULTS

WEHE induced IL-1beta production in both its mRNA and protein expression in a dose-dependent manner. The inductive effect of WEHE on IL-1beta gene expression was due to the augmentation of the IL-1beta transcription. Furthermore, EMSA showed that WEHE markedly increased the binding activities of NF-kappaB, and to a lesser extent, those of AP-1 and NF-IL6 to their cognate DNA recognition sites, whereas CRE/ATF binding remained constant, all of which are known to be involved in the regulation of IL-1beta gene expression.

CONCLUSION

WEHE induces IL-1kappa expression in macrophages at a transcriptional level by enhancing the activation of transcription factors, NF-kappaB, NF-IL6, and AP-1.

Extracellular human thioredoxin-1 inhibits lipopolysaccharide-induced interleukin-1beta expression in human monocyte-derived macrophages

Oxidative stress plays an important role in atherosclerotic vascular disease, and several recent studies were focused on thioredoxin-1 (Trx-1) and its potential protective role against oxidative stress. Since human monocyte-derived macrophages (HMDM) are important cells in several inflammatory diseases including atherosclerosis, we conducted this study to evaluate the impact of extracellular recombinant human Trx-1 (rhTrx-1) on gene expression in lipopolysaccharide-activated HMDM. Our results showed that rhTrx-1 was capable of reducing interleukin (IL)-1beta mRNA and protein synthesis in a dose-dependent manner. This effect was partly mediated through a reduction of NF-kappaB activation as analyzed by transient transfection and gel shift assays. In addition, we showed that the attenuation of NF-kappaB activity was the result of the reduction of both p50 and p65 subunit mRNA and protein synthesis on one hand and of the induction of I-kappaBalpha mRNA and protein expression on the other hand. Moreover, inhibition of endogenous Trx-1 mRNA was also observed, suggesting a contribution to the diminution of NF-kappaB activity since endogenous Trx-1, in contrast to the exogenous Trx-1, activates the NF-kappaB system. Finally, H2O2-oxidized rhTrx-1 reduced IL-1beta mRNA synthesis in lipopolysaccharide-activated HMDM. This result highly suggested that the rhTrx-1 used in this study could be oxidized in the culture medium and, in turn, reduced IL-1beta mRNA and protein synthesis. Taken together, these data indicated a potential new mechanism through which extracellular rhTrx-1 exerts an anti-inflammatory function in HMDM.

Toll-like receptor 4 and Toll-IL-1 receptor domain-containing adapter protein (TIRAP)/myeloid differentiation protein 88 adapter-like (Mal) contribute to maximal IL-6 expression in macrophages

Previous studies have shown that engagement of Toll-like receptors (TLR) 2 and 4 can induce macrophages to express a variety of proinflammatory cytokines. We have recently demonstrated that TLR2 agonists poorly induce a subset of TLR4-inducible proinflammatory genes (e.g., inducible protein (IP)-10, inducible NO synthase (iNOS), monocyte chemoattractant protein-5, IL-12p40), due in part to differential activation of IFN-beta production and phosphorylation of the transcription factor STAT1. TLR4, but not TLR2, agonists can induce IFN-beta expression via a mechanism that requires the adapter protein Toll-IL-1R domain-containing adapter protein (TIRAP)/myeloid differentiation protein 88 (MyD88) adapter-like (Mal), but not the adapter protein MyD88. Thus, the failure of TLR2 agonists to induce STAT1-dependent genes results, in part, from their failure to induce the expression of IFN-beta. In this study, we show that IL-6 expression is also preferentially induced by activation of TLR4. TLR4-dependent induction of IL-6 expression did require Toll-IL-1R domain-containing adapter protein (TIRAP)/MyD88 adapter-like (Mal), but unlike iNOS and IP-10, it did not require the expression of IFN-beta. Although exogenous IFN-beta and IFN-gamma could synergize with TLR2 agonists to restore high levels of iNOS expression and NO production, these IFNs could not synergize with TLR2 agonists to induce high levels of IL-6. Similarly, neutralizing anti-IFN Abs could block iNOS gene expression in LPS-stimulated murine macrophages, whereas these Abs had little effect on IL-6 gene expression in these cells. Together, these studies demonstrate that IL-6, like iNOS and IP-10, is differentially expressed in macrophages stimulated via TLR2 vs TLR4, although these differences appear to arise from distinct signaling mechanisms.

Silica-induced apoptosis in murine macrophage: involvement of tumor necrosis factor-alpha and nuclear factor-kappaB activation

Alveolar macrophages play a critical role in silica-induced lung fibrosis. Silica exposure induces tumor necrosis factor (TNF)-alpha release and nuclear factor (NF)-kappaB activation, and apoptotic mechanisms have been implicated in silica-induced pathogenesis. To characterize potential relationships between these signaling events, we studied their induction in two murine macrophage cell lines. The RAW 264.7 macrophage cell line was more sensitive, and the IC-21 macrophage cell line more tolerant to silica exposure (0.2 or 1 mg/ml for 6 h) as evidenced by significantly higher apoptotic responses in RAW 264.7 (P < 0.05). RAW 264.7 macrophages exhibited enhanced TNF-alpha production and NF-kappaB activation in response to silica, whereas IC-21 macrophages did not produce TNF-alpha in response to silica and did not induce NF-kappaB nuclear binding. Inhibition of NF-kappaB in RAW 264.7 cells with BAY11-7082 significantly increased apoptosis while inhibiting TNF-alpha release. In addition, TNF-alpha and NF-kappaB activation, but not apoptosis, were induced by lipopolysaccharide (LPS) in both cell lines, and NF-kappaB inhibition reduced LPS-induced TNF-alpha release. These data suggest that TNF-alpha induction is dependent on NF-kappaB activation in both cell lines. However, silica can induce apoptosis in murine macrophages, independently of TNF-alpha stimulation, as in IC-21 macrophages. Furthermore, NF-kappaB activation in macrophages may play dual roles, both pro- and antiapoptotic during silica injury.