IL-10 modulates cytokine gene transcription by protein synthesis-independent and dependent mechanisms in lipopolysaccharide-treated neutrophils

Neutrophil responsiveness to IL-10 impairs clearance of Streptococcus pneumoniae from the lungs

The early immune response to bacterial pneumonia requires a careful balance between pathogen clearance and tissue damage. The anti-inflammatory cytokine interleukin (IL)-10 is critical for restraining otherwise lethal pulmonary inflammation. However, pathogen-induced IL-10 is associated with bacterial persistence in the lungs. In this study, we used mice with myeloid cell specific deletion of IL-10R to investigate the cellular targets of IL-10 immune suppression during infection with Streptococcus pneumoniae, the most common bacterial cause of pneumonia. Our findings suggest that IL-10 restricts the neutrophil response to S. pneumoniae, as neutrophil recruitment to the lungs was elevated in myeloid IL-10 receptor (IL-10R)-deficient mice and neutrophils in the lungs of these mice were more effective at killing S. pneumoniae. Improved killing of S. pneumoniae was associated with increased production of reactive oxygen species and serine protease activity in IL-10R-deficient neutrophils. Similarly, IL-10 suppressed the ability of human neutrophils to kill S. pneumoniae. Burdens of S. pneumoniae were lower in myeloid IL-10R-deficient mice compared with wild-type mice, and adoptive transfer of IL-10R-deficient neutrophils into wild-type mice significantly improved pathogen clearance. Despite the potential for neutrophils to contribute to tissue damage, lung pathology scores were similar between genotypes. This contrasts with total IL-10 deficiency, which is associated with increased immunopathology during S. pneumoniae infection. Together, these findings identify neutrophils as a critical target of S. pneumoniae-induced immune suppression and highlight myeloid IL-10R abrogation as a mechanism to selectively reduce pathogen burdens without exacerbating pulmonary damage.

Urine biomarkers in ESSIC type 2 interstitial cystitis/bladder pain syndrome and overactive bladder with developing a novel diagnostic algorithm

This study aimed to investigate the diagnostic values of urine cytokines in interstitial cystitis/bladder pain syndrome (IC/BPS) and overactive bladder (OAB) patients, and to develop a novel diagnostic algorithm. Urine samples were collected from 40 IC/BPS, 40 OAB patients, and 30 controls. Commercially available multiplex immunoassays were used to analyze 31 targeted cytokines. Urine cytokine profiles were significantly different among study groups and controls. MIP-1β showed the highest sensitivity (92.2%) for identifying diseased study patients from controls. The cytokines with high diagnostic values for distinguishing between IC and OAB included IL-10, RANTES, eotaxin, CXCL10, IL-12p70, NGF, IL-6, IL-17A, MCP-1, and IL-1RA. The diagnostic algorithm was subsequently developed according to the diagnostic values obtained. MIP-1β was selected for the initial screening test to diagnose diseased patients and controls with diagnostic rates of 81.6% and 68.4%, respectively. As confirmation tests for IC/BPS, the diagnostic rates of eotaxin, CXCL10, and RANTES were 73.3%, 72.7%, and 69.7%, respectively. As the confirmation test for OAB, the diagnostic rate of IL-10 was 60%. Urine cytokine profiles of IC/BPS and OAB patients differed from those of controls and might be useful as biomarkers for diagnosis. A novel pilot diagnostic algorithm was developed based on these profiles.

Identification of a miR-146b-Fas ligand axis in the development of neutropenia in T large granular lymphocyte leukemia

Tlarge granular lymphocyte leukemia (T-LGLL) is characterized by the expansion of several large granular lymphocyte clones, among which a subset of large granular lymphocytes showing constitutively activated STAT3, a specific CD8⁺/CD4^- phenotype and the presence of neutropenia has been identified. Although STAT3 is an inducer of transcription of a large number of oncogenes, so far its relationship with miRNAs has not been evaluated in T-LGLL patients. Here, we investigated whether STAT3 could carry out its pathogenetic role in T-LGLL through an altered expression of miRNAs. The expression level of 756 mature miRNA was assessed on purified T large granular lymphocytes (T-LGLs) by using a TaqMan Human microRNA Array. Hierarchical Clustering Analysis of miRNA array data shows that the global miRNome clusters with CD8 T-LGLs. Remarkably, CD8 T-LGLs exhibit a selective and STAT3-dependent repression of miR-146b expression, that significantly correlated with the absolute neutrophil counts and inversely correlated with the expression of Fas ligand (FasL), that is regarded as the most relevant factor in the pathogenesis of neutropenia. Experimental evidence demonstrates that the STAT3-dependent reduction of miR-146b expression in CD8 T-LGLs occurs as a consequence of miR-146b promoter hypermethylation and results in the disruption of the HuR-mediated post-transcriptional machinery controlling FasL mRNA stabilization. Restoring miR-146b expression in CD8 T-LGLs lead to a reduction of HuR protein and, in turn, of FasL mRNA expression, thus providing mechanistic insights for the existence of a STAT3-miR146b-FasL axis and neutropenia in T-LGLL.

Cytokine production by human neutrophils: Revisiting the "dark side of the moon"

Polymorphonuclear neutrophils are the most numerous leucocytes present in human blood, and function as crucial players in innate immune responses. Neutrophils are indispensable for the defence towards microbes, as they effectively counter them by releasing toxic enzymes, by synthetizing reactive oxygen species and by producing inflammatory mediators. Interestingly, recent findings have highlighted an important role of neutrophils also as promoters of the resolution of inflammation process, indicating that their biological functions go well beyond simple pathogen killing. Consistently, data from the last decades have highlighted that neutrophils may even contribute to the development of adaptive immunity by performing previously unanticipated functions, including the capacity to extend their survival, directly interact with other leucocytes or cell types, and produce and release a variety of cytokines. In this article, we will summarize the main features of, as well as emphasize some important concepts on, the production of cytokines by human neutrophils.

Multi-Step Regulation of the TLR4 Pathway by the miR-125a~99b~let-7e Cluster

An appropriate immune response requires a tight balance between pro- and anti-inflammatory mechanisms. IL-10 is induced at late time-points during acute inflammatory conditions triggered by TLR-dependent recognition of infectious agents and is involved in setting this balance, operating as a negative regulator of the TLR-dependent signaling pathway. We identified miR-125a~99b~let-7e as an evolutionary conserved microRNA cluster late-induced in human monocytes exposed to the TLR4 agonist LPS as an effect of this IL-10-dependent regulatory loop. We demonstrated that microRNAs generated by this cluster perform a pervasive regulation of the TLR signaling pathway by direct targeting receptors (TLR4, CD14), signaling molecules (IRAK1), and effector cytokines (TNFα, IL-6, CCL3, CCL7, CXCL8). Modulation of miR-125a~99b~let-7e cluster influenced the production of proinflammatory cytokines in response to LPS and the IL-10-mediated tolerance to LPS, thus identifying this gene as a previously unrecognized major regulatory element of the inflammatory response and endotoxin tolerance.

RelB activation in anti-inflammatory decidual endothelial cells: a master plan to avoid pregnancy failure?

It is known that excessive inflammation at fetal-maternal interface is a key contributor in a compromised pregnancy. Female genital tract is constantly in contact with microorganisms and several strategies must be adopted to avoid pregnancy failure. Decidual endothelial cells (DECs) lining decidual microvascular vessels are the first cells that interact with pro-inflammatory stimuli released into the environment by microorganisms derived from gestational tissues or systemic circulation. Here, we show that DECs are hypo-responsive to LPS stimulation in terms of IL-6, CXCL8 and CCL2 production. Our results demonstrate that DECs express low levels of TLR4 and are characterized by a strong constitutive activation of the non-canonical NF-κB pathway and a low responsiveness of the canonical pathway to LPS. In conclusion, DECs show a unique hypo-responsive phenotype to the pro-inflammatory stimulus LPS in order to control the inflammatory response at feto-maternal interface.

IL-10-induced microRNA-187 negatively regulates TNF-α, IL-6, and IL-12p40 production in TLR4-stimulated monocytes

IL-10 is a potent anti-inflammatory molecule that, in phagocytes, negatively targets cytokine expression at transcriptional and posttranscriptional levels. Posttranscriptional checkpoints also represent the specific target of a recently discovered, evolutionary conserved class of small silencing RNAs known as "microRNAs" (miRNAs), which display the peculiar function of negatively regulating mRNA processing, stability, and translation. In this study, we report that activation of primary human monocytes up-regulates the expression of miR-187 both in vitro and in vivo. Accordingly, we identify miR-187 as an IL-10-dependent miRNA playing a role in IL-10-mediated suppression of TNF-α, IL-6, and the p40 subunit of IL-12 (IL-12p40) produced by primary human monocytes following activation of Toll-like receptor 4 (TLR4). Ectopic expression of miR-187 consistently and selectively reduces TNFα, IL-6, and IL-12p40 produced by LPS-activated monocytes. Conversely, the production of LPS-induced TNF-α, IL-6, and IL-12p40 is increased significantly when miR-187 expression is silenced. Our data demonstrate that miR-187 directly targets TNF-α mRNA stability and translation and indirectly decreases IL-6 and IL-12p40 expression via down-modulation of IκBζ, a master regulator of the transcription of these latter two cytokines. These results uncover an miRNA-mediated pathway controlling cytokine expression and demonstrate a central role of miR-187 in the physiological regulation of IL-10-driven anti-inflammatory responses.

Genome-wide analysis of STAT3 binding in vivo predicts effectors of the anti-inflammatory response in macrophages

Inflammation is a powerful response of the immune system against invading pathogens, and must be cancelled when unneeded or otherwise death inevitably follows. In macrophages, the anti-inflammatory response (AIR) is driven by STAT3 upon IL-10 signaling. The role of STAT3 is to stimulate the expression of specific genes that in-turn suppress the transcription of proinflammatory genes. Here we describe a systematic approach to identify the elusive STAT3-controlled effectors of the AIR. In vivo STAT3-binding sites were identified by ChIP-seq, coupled to expression analysis by RNA-seq, both in resting and IL-10-treated peritoneal macrophages. We report the genomic targets of STAT3 and show that STAT3's transcriptional program during the AIR is highly specific to IL-10-stimulated macrophages, that STAT3 is a positive transcriptional regulator, and we predict severalputative AIR factors that merit further investigation. This is the first in-depth study of the AIR by next-generation sequencing and provides an unprecedented degree of detail into this fundamental physiologic response.

SH2-domain mutations in STAT3 in hyper-IgE syndrome patients result in impairment of IL-10 function

Autosomal-dominant hyper-IgE syndrome (AD-HIES) is a primary immunodeficiency caused by STAT3 mutations. This inherited condition is characterized by eczema, staphylococcal cold abscesses and recurrent pulmonary infections. Given that STAT3 is involved in IL-10 signaling, we examined the immunoregulatory role of IL-10 in inflammation by studying the effects of IL-10 on monocytes, neutrophils and monocyte-derived DCs from HIES subjects. Analysis of gene expression in PBMCs and neutrophils isolated from HIES patients and stimulated with LPS in the presence of IL-10 showed reduced expression of IL1RN, which encodes IL-1 receptor antagonist (IL-1ra), and SOCS3 mRNA but increased CXCL8 mRNA expression. Moreover, secretion of the anti-inflammatory protein IL-1ra was reduced in AD-HIES patients. DCs from HIES patients secreted higher levels of TNF-α, IL-6 and, to a lesser extent, IL-12 when these cells were cultured in the presence of IL-10. These results suggest that IL-10 activity is affected in myeloid cells (e.g. monocytes, DCs) of HIES patients. Impairment of IL-10 signaling in patients with AD-HIES might result in an altered balance between pro-inflammatory and anti-inflammatory signals and might lead to persistent inflammation and delayed healing after infections.

Understanding the molecular mechanisms of the multifaceted IL-10-mediated anti-inflammatory response: lessons from neutrophils

Analysis of the molecular mechanisms governing the ability of IL-10 to keep inflammation under control has highlighted the existence of a great degree of plasticity and specificity with regard to innate immune cells. In this respect, neutrophils represent a perfect example of innate immune cells conditioned by external signals (for instance, by LPS), as well as by intracellular regulatory pathways, that render them optimally responsive to IL-10 only when required. The focus of this review are the recent experimental findings that have uncovered the sophisticated and complex molecular mechanisms responsible for the modulation of pro- and anti-inflammatory cytokine production by IL-10 in neutrophils and other innate immune cells. Understanding how IL-10 exerts its anti-inflammatory response, particularly in the case of neutrophils, will provide novel clues leading, hopefully, to the therapeutic control of neutrophil-driven inflammatory reactions, such as septic infections, rheumatoid arthritis, osteoarthritis and chronic obstructive pulmonary disease.

Proliferating cell nuclear antigen acts as a cytoplasmic platform controlling human neutrophil survival

Cytosolic proliferating cell nuclear antigen (PCNA) binds to procaspases and protects human neutrophils from apoptosis.

Neutrophil apoptosis is a highly regulated process essential for inflammation resolution, the molecular mechanisms of which are only partially elucidated. In this study, we describe a survival pathway controlled by proliferating cell nuclear antigen (PCNA), a nuclear factor involved in DNA replication and repairing of proliferating cells. We show that mature neutrophils, despite their inability to proliferate, express high levels of PCNA exclusively in their cytosol and constitutively associated with procaspases, presumably to prevent their activation. Notably, cytosolic PCNA abundance decreased during apoptosis, and increased during in vitro and in vivo exposure to the survival factor granulocyte colony-stimulating factor (G-CSF). Peptides derived from the cyclin-dependent kinase inhibitor p21, which compete with procaspases to bind PCNA, triggered neutrophil apoptosis thus demonstrating that specific modification of PCNA protein interactions affects neutrophil survival. Furthermore, PCNA overexpression rendered neutrophil-differentiated PLB985 myeloid cells significantly more resistant to TNF-related apoptosis-inducing ligand– or gliotoxin-induced apoptosis. Conversely, a decrease in PCNA expression after PCNA small interfering RNA transfection sensitized these cells to apoptosis. Finally, a mutation in the PCNA interdomain-connecting loop, the binding site for many partners, significantly decreased the PCNA-mediated antiapoptotic effect. These results identify PCNA as a regulator of neutrophil lifespan, thereby highlighting a novel target to potentially modulate pathological inflammation.

Beyond conventional DMARDs: extending TNF-regulant therapies to the vast majority/less privileged who do need them

This article is a plea to find (better) ways to extend the benefits of anti-cytokine therapies to ensure they will become available as widely as possible. Pessimistically, this will probably involve substituting more affordable, although somewhat less specific, non-biological agents for present target-specific bio-DMARDs (disease-modifying antirheumatic drugs) to ensure far wider distribution of benefits. Optimistically, new developments in technology and bio-engineering might dramatically reduce costs of present 'biological' therapies. (The antibiotics we now take for granted were once also horrendously expensive.). Pragmatically, one goal for this mission should include seriously pursuing more research and pilot clinical trials of non-protein combination therapies able to control: (i) TNF or other pro-inflammatory cytokines; and also (ii) other mediators sustaining chronic inflammation (-->pain, effusion, fibrosis, porosis, etc.). This can be immediately facilitated by drawing upon the immense resources of non-prescription Asia-Pacific traditional therapies--particularly when these have already been shown to either reduce TNF synthesis or control TNF-induced responses in preclinical studies. Could this be a major goal for the next decade, helping rectify some of the omissions of the current Bone & Joint Decade 2000-2010?

Urine cytokines suggest an inflammatory response in the overactive bladder: a pilot study

PURPOSE

To study the hypothesis of detecting bladder inflammation associated with overactive bladder (OAB) through altered urine levels of cytokines, chemokines, and growth factors.

METHODS

Midstream urine specimens were collected from a prospective study done on eight asymptomatic control subjects and 17 idiopathic OAB patients. The urine was analyzed by a multiplex panel screen for 12 chemokines, cytokines, growth factors, and soluble receptors using Luminex™ xMAP(®) technology. Protein concentration values were normalized to the levels of creatinine.

RESULTS

This analysis revealed a significant elevation of seven key proteins in the urine of OAB patients relative to controls (*P < 0.05). A greater than tenfold elevation was measured in OAB, relative to controls, in the levels of monocyte chemotactic protein-1 (MCP-1), soluble fraction of the CD40 ligand (sCD40L) in urine was obtained from OAB patients relative to controls. At least five fold elevations were detected in the levels of macrophage inflammatory protein (MIP-1β), IL-12p70/p40, IL-5, epidermal growth factor (EGF), and growth-related oncogene GRO-α compared to controls. Significant threefold elevation was also noticed in the urine levels of sIL-2Rα, and IL-10 in the OAB group. The levels of the remaining proteins tested were not statistically significantly different from control values.

CONCLUSIONS

The presence of elevated levels in urine of inflammatory biomarkers involved in inflammation and tissue repair suggests a role for inflammation in OAB, and may help in diagnosis and treatment of this disease.

Activation of an immunoregulatory and antiviral gene expression program in poly(I:C)-transfected human neutrophils

Neutrophils, historically known for their involvement in acute inflammation, are also targets for infection by many different DNA and RNA viruses. However, the mechanisms by which they recognize and respond to viral components are poorly understood. Polyinosinic:polycytidylic acid (poly(I:C)) is a synthetic mimetic of viral dsRNA that is known to interact either with endosomal TLR3 (not expressed by human neutrophils) or with cytoplasmic RNA helicases such as melanoma differentiation-associated gene 5 (MDA5) and retinoic acid-inducible gene I (RIG-I). In this study, we report that intracellularly administered poly(I:C) stimulates human neutrophils to specifically express elevated mRNA levels encoding type I IFNs, immunoregulatory cytokines, and chemokines, such as TNF-alpha, IL-12p40, CXCL10, CXCL8, CCL4, and CCL20, as well as classical IFN-responsive genes (IRG), including IFIT1 (IFN-induced protein with tetratricopeptide repeats 1)/IFN-stimulated gene (ISG)56, G1P2/ISG15, PKR (dsRNA-dependent protein kinase), and IFN-regulatory factor (IRF)7. Investigations into the mechanisms whereby transfected poly(I:C) promotes gene expression in neutrophils uncovered a crucial involvement of the MAPK-, PKR-, NF-kappaB-, and TANK (TNF receptor-associated NF-kappaB kinase)-binding kinase (TBK1)/IRF3-signaling transduction pathways, as illustrated by the use of specific pharmacological inhibitors. Consistent with the requirement of the cytoplasmic dsRNA pathway for antiviral signaling, human neutrophils were found to constitutively express significant levels of both MDA5 and RIG-I, but not TLR3. Accordingly, neutrophils isolated from MDA5-deficient mice had a partial impairment in the production of IFN-beta and TNF-alpha upon infection with encephalomyocarditis virus. Taken together, our data demonstrate that neutrophils are able to activate antiviral responses via helicase recognition, thus acting at the frontline of immunity against viruses.

Characterization of the immune response in the synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome

OBJECTIVE

The aetiology of SAPHO (synovitis, acne, palmoplantar pustulosis, hyperostosis, osteitis) syndrome seems to involve genetic, infectious and immunological components. We examined innate and adaptive immune responses in SAPHO syndrome, as compared with PsA and RA. We also studied the effect of etanercept on immunological parameters.

METHODS

We studied 29 patients with SAPHO syndrome, as well as 22 patients with RA, 21 patients with PsA and 15 healthy controls. Adaptive immune responses were investigated by assaying total serum immunoglobulins and several autoantibodies. Innate immunity was studied by quantifying blood PMN functions and plasma cytokine levels. PMN responses to Propionibacterium acnes were tested ex vivo. Eight patients who received etanercept for refractory rheumatic disorders were tested before and after 28 days of treatment.

RESULTS

SAPHO syndrome was associated with elevated IL-8 and IL-18 plasma levels. IL-8 and TNF-alpha production by purified PMN was higher in the three patient groups than in the healthy controls, but the oxidative burst and IL-18 production were normal. No autoantibodies were detected in SAPHO patients. Induction of PMN IL-8 and TNF-alpha production by P. acnes was impaired in the SAPHO group as compared with the RA and PsA groups. After 28 days of etanercept therapy, PMN IL-8 and TNF-alpha production was down-regulated and TNF-alpha plasma levels were increased.

CONCLUSIONS

These results support the view that the SAPHO syndrome may be triggered by an infectious state involving P. acnes, contributing to the strong humoral and cellular pro-inflammatory responses. Etanercept modulation of PMN activation status emphasizes these new immunological findings.

Circulating neutrophils of septic patients constitutively express IL-10R1 and are promptly responsive to IL-10

Previous studies have demonstrated that neutrophils isolated from the blood of healthy donors do not respond to IL-10 in terms of either activation of signal transducer and activator of transcription-3 (STAT3) tyrosine phosphorylation or induction of suppressor of cytokine signalling (SOCS)-3 protein, unlike autologous mononuclear cells. This was explained by the fact that circulating neutrophils of healthy donors express only IL-10R2, but not IL-10R1, the latter IL-10R chain being essential for mediating IL-10 responsiveness. In this study, we report that peripheral blood neutrophils of septic patients constitutively display, besides IL-10R2, also abundant levels of surface IL-10R1. Consequently, septic neutrophils are promptly responsive to IL-10 in vitro, as revealed by a direct IL-10-mediated induction of STAT3 tyrosine phosphorylation and SOCS-3 gene transcription, mRNA and protein expression. Consistent with the presence of a fully functional IL-10R, modulation of LPS-induced CXCL8, CCL4, tumour necrosis factor-alpha and IL-1ra gene expression was also rapidly induced by IL-10 in septic, but not normal, neutrophils. Collectively, these data uncover that neutrophils of septic patients are predisposed to be promptly responsive to IL-10, presumably to help limiting their pro-inflammatory state. They also fully validate our previous observations, herein in the context of a human disease, that responsiveness of human neutrophils to IL-10 is strictly dependent upon the modulation of IL-10R1 expression.