Secretory leukocyte protease inhibitor reduces inflammation and alveolar bone resorption in LPS-induced periodontitis in rats and in MC3T3-E1 preosteoblasts

In periodontitis, alveolar bone resorption is induced by excessive host immune and inflammatory response against bacterial infection. Secretory leukocyte protease inhibitor (SLPI) has anti-bacterial and anti-inflammatory activity in inflammatory responses. SLPI inhibits joint inflammation and bone destruction, but the function of SLPI in periodontitis is unclear. Therefore, this study investigated whether SLPI inhibits the inflammatory response and alveolar bone resorption in LPS-induced periodontitis of rats. Micro-computed tomography and histological analysis showed that SLPI inhibited alveolar bone resorption by LPS-induced periodontitis. Immunohistochemistry revealed that SLPI decreased tumor necrosis factor-α (TNF-α) and interleukine-1β (IL-1β) expression in periodontitis tissue, and decreased mRNA and protein expression of TNF-α and IL-1β in LPS-stimulated MC3T3-E1 cells. The results indicated that SLPI reduced alveolar bone resorption in LPS-induced periodontitis and inhibited inflammatory cytokine, such as TNF-α and IL-1β, expression in LPS-stimulated MC3T3-E1 preosteoblasts. Therefore, SLPI could be a regulatory molecule by inhibiting alveolar bone resorption through the reduction of inflammatory cytokines, and inducing osteoblast activation for bone formation.     

Endogenous regulation of the acute inflammatory response

The acute inflammatory response has been triggered in rat lungs by deposition of IgG immune complexes. The inflammatory reaction triggered is highly tissue damaging and requires activation of NF-kappaB with ensuing generation of chemokines and cytokines. Endogenous generation of IL- 10 and IL- 13 as well as secretory leukocyte protease inhibitor (SLPI), significantly regulates this inflammatory response. IL-10 and IL-13 attenuate NF-kappaB activation by interfering with breakdown of IkappaBalpha, while SLPI likewise suppresses NF-kappaB activation, but by interfering with breakdown of IkappaBbeta. Antibody induced blockade of IL-10, IL-13 or SLPI enhances NF-KB activation in lung and exacerbates the lung inflammatory response and injury. These data indicate that endogenous IL-10, IL-13 and SLPI are important regulators of the inflammatory response by reducing gene activation with resultant generation of peptide mediators/cytokines and chemokines.     

Endogenous regulation of the acute inflammatory response

The acute inflammatory response has been triggered in rat lungs by deposition of IgG immune complexes. The inflammatory reaction triggered is highly tissue damaging and requires activation of NF-B with ensuing generation of chemokines and cytokines. Endogenous generation of IL-10 and IL-13 as well as secretory leukocyte protease inhibitor (SLPI), significantly regulates this inflammatory response. IL-10 and IL-13 attenuate NF-B activation by interfering with breakdown of IB, while SLPI likewise suppresses NF-B activation, but by interfering with breakdown of IB. Antibody induced blockade of IL-10, IL-13 or SLPI enhances NF-B activation in lung and exacerbates the lung inflammatory response and injury. These data indicate that endogenous IL-10, IL-13 and SLPI are important regulators of the inflammatory response by reducing gene activation with resultant generation of peptide mediators/cytokines and chemokines.     

Action of intracellular IL-1Ra (Type 1) is independent of the IL-1 intracellular signalling pathway

The balance between IL-1 and its naturally occurring inhibitor IL-1 receptor antagonist (IL-1ra) is critical in determining the inflammatory response. Four splice variants of the IL-1ra gene have been identified; one secreted (sIL-1ra) and three intracellular (icIL-1ra1-3). The biological roles of the intracellular isoforms remain largely unclear. We wished to determine whether icIL-1ra1 had intracellular functions regulating IL-1 signalling. Signalling was determined using an NF-kappaB reporter assay measuring induction of the IL-8 promoter in transfected cells. Over-expression of icIL-1ra1 in HeLa cells had no effect on IL-1 stimulated IL-8 activity. In contrast over-expression of sIL-ra significantly attenuated IL-1 activity. In addition, transfection of icIL-1ra1 in HeLa cells did not cause inhibition of IL-8 promoter activity following over-expression of the IL-1 signalling components MyD88, IRAK-1, TRAF-6, Ikappakappabeta or RelA. This implies that icIL-1ra1 does not act to alter IL-1 mediated intracellular signalling in this system. We investigated whether ATP and/or over-expression of the P2X7 receptor caused icIL-1ra1 inhibition of IL-1beta mediated IL-8 reporter activation, by permitting its release. In HeLa cells, no effect of icIL-1ra1 was observed in ATP stimulated and/or P2X7 transfected cells, compared to a significant inhibition in sIL-1ra transfected cells. However, in endothelial cells stimulated with ATP, the released fraction was effective in attenuating IL-1beta activation of the IL-8 reporter. These results suggest that icIL-1ra1 does not act at an intracellular level to alter IL-1 mediated signalling, and is effective in inhibiting IL-1 responses only when released in an ATP-dependent and cell type specific manner.     

Conversion of proepithelin to epithelins: roles of SLPI and elastase in host defense and wound repair

Increased leukocyte elastase activity in mice lacking secretory leukocyte protease inhibitor (SLPI) leads to impaired wound healing due to enhanced activity of TGFbeta and perhaps additional mechanisms. Proepithelin (PEPI), an epithelial growth factor, can be converted to epithelins (EPIs) in vivo by unknown mechanisms with unknown consequences. We found that PEPI and EPIs exert opposing activities. EPIs inhibit the growth of epithelial cells but induce them to secrete the neutrophil attractant IL-8, while PEPI blocks neutrophil activation by tumor necrosis factor, preventing release of oxidants and proteases. SLPI and PEPI form complexes, preventing elastase from converting PEPI to EPIs. Supplying PEPI corrects the wound-healing defect in SLPI null mice. Thus, SLPI/elastase act via PEPI/EPIs to operate a switch at the interface between innate immunity and wound healing.     

Immunomodulatory effects of inactivated parapoxvirus ovis (ORF virus) on human peripheral immune cells: induction of cytokine secretion in monocytes and Th1-like cells

Inactivated parapoxvirus ovis (Orf virus; PPVO) recently displayed strong immunostimulating and modulating capacities in several animal models for acute and chronic virus infections through the induction of gamma interferon (IFN-gamma) as a key mediator of antiviral activity. The data presented in this work demonstrate that inactivated PPVO has strong effects on cytokine secretion by human immune cells, including the upregulation of inflammatory and Th1-related cytokines (IFN-gamma, tumor necrosis factor alpha [TNF-alpha], interleukin 6 [IL-6], IL-8, IL-12, and IL-18) as well as anti-inflammatory and Th2-related cytokines (IL-4, IL-10, and IL-1 receptor antagonist [IL-1ra]). Studies on the mechanism of action revealed virus particles to be the effective components of the preparation. The virus particles activate monocytes or other antigen-presenting cells (APC), e.g., plasmacytoid dendritic cells, through signaling over CD14 and a Toll-like receptor and the intracellular presence of certain PPVO-specific components. The activation of monocytes or APC is followed by the release of early proinflammatory cytokines (TNF-alpha, IL-6, and IL-8) as well as the Th1-related cytokines IL-12 and IL-18. Both IL-18 and IL-12 are involved in PPVO-mediated IFN-gamma release by T cells and/or NK cells. The proinflammatory response is accompanied by the induction of anti-inflammatory and Th2-related cytokines (IL-4, IL-10, and IL-1ra), which exert a limiting efffect on the inflammatory response induced by PPVO. We conclude that the induction of a natural immune response with physiologically significant amounts of different cytokines and with antiviral potential might provide advantages over existing antiviral immunotherapies.     

Potent antimycobacterial activity of mouse secretory leukocyte protease inhibitor

Secretory leukocyte protease inhibitor (SLPI) has multiple functions, including inhibition of protease activity, microbial growth, and inflammatory responses. In this study, we demonstrate that mouse SLPI is critically involved in innate host defense against pulmonary mycobacterial infection. During the early phase of respiratory infection with Mycobacterium bovis bacillus Calmette-Guérin, SLPI was produced by bronchial and alveolar epithelial cells, as well as alveolar macrophages, and secreted into the alveolar space. Recombinant mouse SLPI effectively inhibited in vitro growth of bacillus Calmette-Guérin and Mycobacterium tuberculosis through disruption of the mycobacterial cell wall structure. Each of the two whey acidic protein domains in SLPI was sufficient for inhibiting mycobacterial growth. Cationic residues within the whey acidic protein domains of SLPI were essential for disruption of mycobacterial cell walls. Mice lacking SLPI were highly susceptible to pulmonary infection with M. tuberculosis. Thus, mouse SLPI is an essential component of innate host defense against mycobacteria at the respiratory mucosal surface.     

Local administration of interleukin-1beta for the treatment of lung abscesses induces neutrophil activation and changes in proinflammation cytokine production

Interleukin-1 (IL-1) is a potent immunostimulatory molecule with broad range biological activity that limits its systemic application in humans. Alternatively, IL-1 can be applied locally, directly to the inflammatory site for stimulation of local defense mechanisms, without activating an acute phase response. IL-1beta preparations have been successfully used for local therapy of patients with purulent bacterial lung abscesses who were resistant to usual antibiotic treatment. IL-1beta was applied directly to the abscess cavity at a concentration of 10 ng/ml, once a day for 7 days. Before IL-1beta administration, local leukocyte functional activity was significantly reduced compared to the same activity in neutrophils isolated from the peripheral blood of the same patient. Local application of IL-1beta led to increases in adhesion, chemotaxis, oxygen radical production and phagocytosis of abscess fluid neutrophils. After local IL-1beta treatment, the concentration of IL-8 and TNF-alpha in the abscess fluids increased, while in nearly all patients levels of endogenous IL-1beta decreased. Immunocytochemical analysis showed that IL-1beta increased the numbers of cytokine-producing cells and induced proinflammatory cytokine production by neutrophilic granulocytes. According to the results obtained, the mechanism of the local immunostimulatory activity by IL-1beta is associated with the significant activation of neutrophilic granulocyte functions and changes in cytokine production at the inflammatory site. IL-1beta can be used as a highly effective immunotherapeutic drug when applied locally at adequate immunostimulatory dose levels.     

The presence of elafin, SLPI, IL1-RA and STNFalpha RI in head and neck squamous cell carcinomas and their relation to the degree of tumour differentiation

Biopsy samples of head and neck carcinomas were investigated with regard to elafin, secretory leukocyte protease inhibitor (SLPI), interleukin 1-receptor antagonist [(IL)1-RA] and soluble tumour necrosis factor alpha receptor antagonist (STNFalpha RI). SLPI and elafin are serine protease inhibitors produced in the serous cells of the upper respiratory airways and in the keratinocytes, respectively. We have now found the presence of elafin and SLPI in squamous cell carcinomas of the upper respiratory tract (tonsillar, hypopharyngeal, tongue, mouth floor, gingival and laryngeal cancer). Significantly higher amounts of SLPI and elafin are present in well-differentiated and moderately differentiated tumours than in poorly differentiated tumours (p < 0.0001 and p < 0.0015). Tumour necrosis factor-alpha and IL-1beta have been shown to stimulate the production of SLPI and elafin. Since these cytokines can both be difficult to detect, we chose to study their inhibitors, STNFalpha RI and IL1-RA, instead. IL1-RA was expressed in highly differentiated tumours as well as in poorly differentiated ones. No significant difference was seen between the groups. STNFalpha RI was only found in very small amounts, sparsely distributed in the tumours, and was not related to the degree of differentiation.     

Genome-Wide Association Study of Genetic Variants in LPS-Stimulated IL-6, IL-8, IL-10, IL-1ra and TNF-α Cytokine Response in a Danish Cohort

Background

Cytokine response plays a vital role in various human lipopolysaccharide (LPS) infectious and inflammatory diseases. This study aimed to find genetic variants that might affect the levels of LPS-induced interleukin (IL)-6, IL-8, IL-10, IL-1ra and tumor necrosis factor (TNF)-α cytokine production.

Methods

We performed an initial genome-wide association study using Affymetrix Human Mapping 500 K GeneChip® to screen 130 healthy individuals of Danish descent. The levels of IL-6, IL-8, IL-10, IL-1ra and TNF-α in 24-hour LPS-stimulated whole blood samples were compared within different genotypes. The 152 most significant SNPs were replicated using Illumina Golden Gate® GeneChip in an independent cohort of 186 Danish individuals. Next, 9 of the most statistical significant SNPs were replicated using PCR-based genotyping in an independent cohort of 400 Danish individuals. All results were analyzed in a combined study among the 716 Danish individuals.

Results

Only one marker of the 500 K Gene Chip in the discovery study showed a significant association with LPS-induced IL-1ra cytokine levels after Bonferroni correction (P<10⁻⁷). However, this SNP was not associated with the IL-1ra cytokine levels in the replication dataset. No SNPs reached genome-wide significance for the five cytokine levels in the combined analysis of all three stages.

Conclusions

The associations between the genetic variants and the LPS-induced IL-6, IL-8, IL-10, IL-1ra and TNF-α cytokine levels were not significant in the meta-analysis. This present study does not support a strong genetic effect of LPS-stimulated cytokine production; however, the potential for type II errors should be considered.     

Neutrophil gelatinase-associated lipocalin is up-regulated in human epithelial cells by IL-1 beta, but not by TNF-alpha

Synthesis of the antimicrobial protein neutrophil gelatinase-associated lipocalin (NGAL) increases dramatically in bronchial epithelial cells and alveolear type II pneumocytes during lung inflammation. IL-1beta induces a >10-fold up-regulation of NGAL expression in the type II pneumocyte-derived cell line A549 cells, whereas TNF-alpha, IL-6, and LPS had no effect. Similar IL-1beta selectivity was demonstrated in primary bronchial epithelial cells and epidermal keratinocytes and for an NGAL promoter fragment transfected into A549 cells. By deletion and substitution analysis of the NGAL promoter, a 40-bp region containing an NF-kappaB consensus site was found to control the IL-1beta-specific up-regulation. Involvement of the NF-kappaB site was demonstrated by site-directed mutagenesis, by transfection with a dominant-negative inhibitor of the NF-kappaB pathway, and by EMSA. TNF-alpha activation of NF-kappaB, in contrast, did not increase NGAL synthesis, even though induced binding of NF-kappaB to the NGAL promoter was observed in vitro. IL-1beta specificity was not contained within the NF-kappaB site of the NGAL promoter, as determined by exchanging the NGAL promoter's NF-kappaB-binding sequence with that of the IL-8 promoter or with the NF-kappaB consensus sequence and by testing the NF-kappaB-binding sequence of the NGAL promoter against the heterologous SV40 promoter. Selectivity for the IL-1 pathway was substantiated by demonstrating that NGAL promoter activity could be induced by LPS stimulation of A549 cells transiently expressing Toll-like receptor 4, which use the same intracellular signaling pathway as the IL-1R. Together, this demonstrates a selective up-regulation of NGAL by the IL-1 pathway.     

The interleukin-1-related cytokine IL-1F8 is expressed in glial cells, but fails to induce IL-1beta signalling responses

The putative new interleukin (IL)-1 family member IL-1F8 (IL-1eta, IL-1H2) has been shown recently to activate mitogen activated protein kinases (MAPKs), extracellular signal-regulated protein kinase (ERK1/2) and c-Jun N-terminal kinase (JNK), and nuclear factor-kappa B (NFkappa B) via a mechanism that requires IL-1Rrp2 expression in cell lines. The aim of this study was to test the hypothesis that IL-1F8 contributes to brain inflammation and injury, by studying its expression and actions in the different cell types of the mouse brain in culture. Messenger RNA for IL-1F8 was detected in neurons and glia (microglial cells, oligodendrocytes progenitor cells and to a lesser extent astrocytes) by RT-PCR. Bacterial lipopolysaccharide (LPS) had no effect on IL-1F8 mRNA levels in mixed glial cultures. Recombinant mouse IL-1beta induced strong activation of ERK1/2, p38, JNK and NFkappa B, and significant release of IL-6 and PGE2, which was blocked by IL-1ra. In contrast, recombinant mouse IL-1F8 did not influence any of these parameters. These results demonstrate that CNS cells may be a source of IL-1F8, but the failure of LPS to modulate IL-1F8 mRNA expression, and of recombinant IL-1F8 to induce any of the classical IL-1 responses, suggest that this cytokine has restricted activities in the brain, or that it may act via alternative pathway(s).     

Differential synthesis of two interleukin-1 receptor antagonist variants and interleukin-8 by peripheral blood neutrophils

With a short lifespan and containing only few ribosomes and endoplasmic reticulum structures, neutrophils are thought to have a limited capacity for protein synthesis. We here show that peripheral blood polymorphonuclear neutrophils (PMN) are able react to stimulants with differential production of two interleukin (IL)-1 receptor antagonist (IL-1ra) isoforms, secreted IL-1ra (sIL-1ra) and the 16kDa intracellular form of IL-1ra (icIL-1ra3), as well as IL-8. Neutrophils of a high purity and with a low degree of preactivation upregulate mRNA and de novo synthesize protein of both IL-1ra variants and IL-8 in response to granulocyte-macrophage colony-stimulating factor and lipopolysaccharide. The cytokines are differentially regulated and distributed in two intracellular compartments. In comparison with peripheral blood mononuclear cells (PBMC), PMN produce distinctly more sIL-1ra but significantly less IL-8. This may indicate an anti-inflammatory role, enabling PMN to antagonize proinflammatory signals. It is therefore possible that PMN play an important role in immune regulation by counteracting a dysregulation of the inflammatory process.     

Interleukin-1 receptor antagonist modulates the early phase of liver regeneration after partial hepatectomy in mice

Background

Cytokine administration is a potential therapy for acute liver failure by reducing inflammatory responses and favour hepatocyte regeneration. The aim of this study was to evaluate the role of interleukin-1 receptor antagonist (IL-1ra) during liver regeneration and to study the effect of a recombinant human IL-1ra on liver regeneration.

Methods

We performed 70%-hepatectomy in wild type (WT) mice, IL-1ra knock-out (KO) mice and in WT mice treated by anakinra. We analyzed liver regeneration at regular intervals by measuring the blood levels of cytokines, the hepatocyte proliferation by bromodeoxyuridin (BrdU) incorporation, proliferating cell nuclear antigen (PCNA) and Cyclin D1 expression. The effect of anakinra on hepatocyte proliferation was also tested in vitro using human hepatocytes.

Results

At 24h and at 48h after hepatectomy, IL-1ra KO mice had significantly higher levels of pro-inflammatory cytokines (IL-6, IL-1β and MCP-1) and a reduced and delayed hepatocyte proliferation measured by BrdU incorporation, PCNA and Cyclin D1 protein levels, when compared to WT mice. IGFBP-1 and C/EBPβ expression was significantly decreased in IL-1ra KO compared to WT mice. WT mice treated with anakinra showed significantly decreased levels of IL-6 and significantly higher hepatocyte proliferation at 24h compared to untreated WT mice. In vitro, primary human hepatocytes treated with anakinra showed significantly higher proliferation at 24h compared to hepatocytes without treatment.

Conclusion

IL1ra modulates the early phase of liver regeneration by decreasing the inflammatory stress and accelerating the entry of hepatocytes in proliferation. IL1ra might be a therapeutic target to improve hepatocyte proliferation.     

IL-6 enhances plasma IL-1ra,IL-10, and cortisol in humans

The purpose of the present study was to test the hypothesis that a transient increase in plasma IL-6 induces an anti-inflammatory environment in humans. Therefore, young healthy volunteers received a low dose of recombinant human (rh)IL-6 or saline for 3 h. Plasma IL-6 levels during rhIL-6 infusion were approximately 140 pg/ml, corresponding to the levels obtained during strenuous exercise. The infusion of rhIL-6 did not induce enhanced levels of the proinflammatory cytokine TNF-alpha but enhanced the plasma levels of the two anti-inflammatory cytokines IL-1 receptor agonist (IL-1ra) and IL-10 compared with saline infusion. In addition, C-reactive protein increased 3 h post-rhIL-6 infusion and was further elevated 16 h later compared with saline infusion. rhIL-6 induced increased levels of plasma cortisol and, consequently, an increase in circulating neutrophils and a decrease in the lymphocyte number without effects on plasma epinephrine, body temperature, mean arterial pressure, or heart rate. In conclusion, this study demonstrates that physiological concentrations of IL-6 induce an anti-inflammatory rather than an inflammatory response in humans and that IL-6, independently of TNF-alpha, enhances the levels not only of IL-1ra but also of IL-10. Furthermore, IL-6 induces an increase in cortisol and, consequently, in neutrocytosis and late lymphopenia to the same magnitude and with the same kinetics as during exercise, suggesting that muscle-derived IL-6 has a central role in exercise-induced leukocyte trafficking.