Macrophage-colony stimulating factor and interleukin-34 induce chemokines in human whole blood

Alpha-Fetoprotein as a Factor of Differentiation and Functional Activity of Myeloid-Derived Suppressor Cells

We studied the role of alpha-fetoprotein (AFP) in regulation of differentiation and functional activity of human myeloid-derived suppressor cells (MDSC) in vitro. To obtain MDSC, CD11b+ cells were isolated from the peripheral blood of healthy donors followed by cytokine induction (IL-1β+GM-CSF) into the MDSC phenotype. The cell functions were assessed by the expression of indoleamine 2,3-dioxygenase (IDO) and arginase-1 (Arg1) and cytokine profile of the cell cultures. Native AFP did not affect the total number of MDSC and the percentage of polymorphonuclear MDSC (PMN-MDSC), but increased the number of monocytic MDSC (M-MDSC). AFP did not change the expression of Arg1, but in low concentrations (10 and 50 U/ml) increased the number of IDO-containing cells. AFP modulated the cytokine profile of CD11b+ cells: it reliably decreased the level of IL-19 (50 and100 U/ml) and showed a tendency to decrease the levels of IL-34, MMP-2, sCD163, CHI3L1, OPN and to increase the levels of IL-29, IL-32, APRIL, PTX3, and sTNF-R1. Thus, we have demonstrated a regulatory effect of native AFP at the level of MDSC generated from CD11b+ cells under conditions of cytokine induction in vitro.

Serum Interleukin-34 in Psoriatic arthritis patients and its correlation with disease 1 activity, and subclinical atherosclerosis

Background

Psoriatic arthritis (PsA) is a chronic multi-domains autoimmune inflammatory disorder. Patients with PsA have a significant prevalence of cardiovascular affection. Upregulated Interleukin-34 (IL-34) has been seen in many autoimmune disorders, and also in atherosclerotic plaques. The aim of this observational case–control study was to evaluate the serum levels of il-34 in PsA patients and correlate between its level and disease activity, and subclinical cardiovascular affection.

Results

In this study, there were 70 PsA patients and 70 healthy volunteers, 43 patients were on Methotrexate, 6 on sulfasalazine, while 40 patients were on biological therapy either monotherapy or in combination with DMARDs. There were significant differences between PsA patients and controls in ESR, high sensitivity-CRP, total lipid profile, and IL-34 levels (p < 0.05) while there were no significant differences regarding Echo and ECG results. Also, we found that there was significant elevation in DAPSA score, hs-CRP, IL-34, and cIMT in the active patients when we compared them with inactive patients. IL-34 had significant positive correlations with DAPSA score, hs-CRP, and cIMT (r = 0.654, 0.579, and 0.658 respectively).

Conclusion

Serum interleukin-34 is an important marker in PsA as its levels were elevated in PsA patients and were correlated with disease activity and subclinical cardiovascular affection.

Anoxia Rapidly Induces Changes in Expression of a Large and Diverse Set of Genes in Endothelial Cells

Sinusoidal endothelial cells are the predominant vascular surface of the bone marrow and constitute the functional hematopoietic niche where hematopoietic stem and progenitor cells receive cues for self-renewal, survival, and differentiation. In the bone marrow hematopoietic niche, the oxygen tension is usually very low, and this condition affects stem and progenitor cell proliferation and differentiation and other important functions of this region. Here, we have investigated in vitro the response of endothelial cells to a marked decrease in O2 partial pressure to understand how the basal gene expression of some relevant biological factors (i.e., chemokines and interleukins) that are fundamental for the intercellular communication could change in anoxic conditions. Interestingly, mRNA levels of CXCL3, CXCL5, and IL-34 genes are upregulated after anoxia exposure but become downmodulated by sirtuin 6 (SIRT6) overexpression. Indeed, the expression levels of some other genes (such as Leukemia Inhibitory Factor (LIF)) that were not significantly affected by 8 h anoxia exposure become upregulated in the presence of SIRT6. Therefore, SIRT6 mediates also the endothelial cellular response through the modulation of selected genes in an extreme hypoxic condition.

Endothelial cells-directed angiogenesis in colorectal cancer: Interleukin as the mediator and pharmacological target

Enhanced angiogenesis is a cancer hallmark and critical for colorectal cancer (CRC) invasion and metastasis. Upon exposure to proangiogenic factors, therefore, targeting tumor-associated proangiogenic factors/receptors hold great promise as a therapeutic modality to treat CRC, particularly metastatic CRC. Accumulating evidence from numerous studies suggests that tumor endothelial cells (ECs) are not only the target of proangiogenic factors, but also function as the cellular source of proangiogenic factors. Studies showed that ECs can produce different proangiogenic factors to participate in the regulation of angiogenesis process, in which ECs-derived interleukins (ILs) show a potential stimulatory effect on angiogenesis via either an direct action on their receptors expressed on progenitor of ECs or an indirect way through enhanced production of other proangiogenic factors. Although a great deal of attention is given to the effects of tumor-derived and immune cell-derived ILs, few studies describe the potential effects of vascular ECs-derived ILs on the tumor angiogenesis process. This review provides an updated summary of available information on proangiogenic ILs, such as IL-1, IL-6, IL-8, IL-17, IL-22, IL-33, IL-34, and IL-37, released by microvascular ECs as potential drivers of the tumor angiogenesis process and discusses their potential as a novel candidate for antiangiogenic target for the treatment of CRC patients.

The bidirectional biological interplay between microbiome and viruses in periodontitis and type-2 diabetes mellitus

Periodontitis was an inflammatory disease associated with a dysbiosis of the oral flora characterized by a chronic sustained inflammation inducing the resorption of alveolar bone and leading to tooth loss. Type 2 diabetes mellitus (T2D) was a metabolic disease caused by impaired insulin action. The oral microbiome played a crucial role in modulating both the innate and adaptive immune system during the trigger and exacerbation of periodontitis and T2D. The bidirectional relationship of T2D and periodontitis had been the focus of intensive research, but those were not well explored. In this commentary, an in-depth analysis of the changes of microbiome and bacterial metabolites in periodontitis with or without diabetes was described. The promotion of periodontitis to T2D might involve inflammatory factors/receptors, oxidative stress, microRNA and so on. The effect of diabetes on periodontitis might involve adipose factor pathway, AGE/RAGE and RANK/RANKL pathway etc. Generally, periodontitis and diabetes are closely related to the microecological-epithelial interaction, soft tissue degradation, bone coupling disorder, immune regulation and gene transcription. The viruses, including HBV, HCV, HSV-1, Coronavirus, HCMV, EBV, HIV, phageome and so on, played an important role in the development of T2D and periodontitis. An in-depth understanding of the relationship between microbiome and host was of great significance to clarify the bidirectional mechanisms, suggesting that the periodontitis or T2D remission will have a positive impact on the other.

Unravelling the Proteomics of HLA-B*57:01+ Antigen Presenting Cells during Abacavir Medication

Type B adverse drug reactions (ADRs) are unpredictable based on the drug’s pharmacology and represent a key challenge in pharmacovigilance. For human leukocyte antigen (HLA)-mediated type B ADRs, it is assumed that the protein/small-molecule interaction alters the biophysical and mechanistic properties of the antigen presenting cells. Sophisticated methods enabled the molecular appreciation of HLA-mediated ADRs; in several instances, the drug molecule occupies part of the HLA peptide binding groove and modifies the recruited peptide repertoire thereby causing a strong T-cell-mediated immune response that is resolved upon withdrawal of medication. The severe ADR in HLA-B*57:01⁺ patients treated with the antiretroviral drug abacavir (ABC) in anti-HIV therapy is an example of HLA-drug-T cell cooperation. However, the long-term damages of the HLA-B*57:01-expressing immune cells following ABC treatment remain unexplained. Utilizing full proteome sequencing following ABC treatment of HLA-B*57:01⁺ cells, we demonstrate stringent proteomic alteration of the HLA/drug presenting cells. The proteomic content indisputably reflects the cellular condition; this knowledge directs towards individual pharmacovigilance for the development of personalized and safe medication.

A novel multi-biomarker combination predicting relapse from long-term remission after discontinuation of biological drugs in rheumatoid arthritis

Biological disease modifying anti-rheumatic drugs (bDMARDs) show dramatic treatment efficacy in rheumatoid arthritis (RA). Long-term use of bDMARDs, however, has disadvantages such as high costs and infection risk. Therefore, a methodology is needed to predict any future RA relapse. Herein, we report a novel multi-biomarker combination which predicts relapse after bDMARDs-withdrawal in patients in remission. Forty patients with RA in remission for more than 12 months were enrolled. bDMARDs were withdrawn and they were followed monthly for the next 24 months. Fourteen patients (35%) of 40 in the cohort remained in remission at 24 months, whereas 26 (65%) relapsed at various time-points. Serum samples obtained longitudinally from patients in remission were assessed for the relapse-prediction biomarkers and index from 73 cytokines by the exploratory multivariate ROC analysis. The relapse-prediction index calculated from the 5 cytokines, IL-34, CCL1, IL-1β, IL-2 and IL-19, strongly discriminated between patients who relapsed and those who stayed in remission. These findings could contribute to clinical decision-making as to the timing of when to discontinue bDMARDs in RA treatment.

Colony-stimulating factor-1 receptor blockade attenuates inflammation in inflamed gingival tissue explants

BACKGROUND AND OBJECTIVE

Colony-stimulating factor-1 receptor (CSF-1R) regulates myeloid cell function and mediates osteoclastogenesis. CSF-1R blockade has been suggested as a potential therapeutic target to halt inflammation and bone resorption; however, the expression and function of CSF-1R in human gingiva is yet unknown.

METHODS

Gingival tissue was collected from 22 non-periodontitis controls and 31 periodontitis (PD) patients. CSF-1R expression in gingival tissue was assessed with q-PCR, western blot, and immunohistochemistry (IHC). Cell surface expression of CSF-1R was analyzed by flow cytometry. The effects of CSF-1R inhibition on the production of inflammatory mediators by inflamed gingival tissue explants and peripheral blood mononuclear cells (PBMCs) were assessed with a bead-based multiplex array and ELISA.

RESULTS

CSF-1R protein expression was increased in gingival tissue from PD patients compared with controls as assessed with western blot (1.5-fold increase) and IHC (4.5-fold increase). Similar proportions of HLA-DR⁺ CD64⁺ cells and comparable CSF-1R expression in this cell population were found in gingival tissue from PD patients and controls. In peripheral blood monocytes, CSF-1R was predominantly expressed by non-classical and intermediate monocytes. Targeting CSF-1R in gingival tissue explants attenuated the production of MMP-1, MMP-2, MMP-12, and MMP-13. The blocking in PBMCs attenuated the production of IL-8 and MMP-9.

CONCLUSION

These results indicate that CSF-1R is elevated in PD, and its inhibition attenuates inflammatory mediators in the inflamed gingival tissue and circulating myeloid cells. Together these findings suggest that CSF-1R might be involved in regulating inflammatory processes in PD, and a potential therapeutic target to reduce the harmful inflammation.

Clinical Implications of IL-32, IL-34 and IL-37 in Atherosclerosis: Speculative Role in Cardiovascular Manifestations of COVID-19

Atherosclerosis, which is a primary cause of cardiovascular disease (CVD) deaths around the world, is a chronic inflammatory disease that is characterised by the accumulation of lipid plaques in the arterial wall, triggering inflammation that is regulated by cytokines/chemokines that mediate innate and adaptive immunity. This review focuses on IL-32, -34 and -37 in the stable vs. unstable plaques from atherosclerotic patients. Dysregulation of the novel cytokines IL-32, -34 and -37 has been discovered in atherosclerotic plaques. IL-32 and -34 are pro-atherogenic and associated with an unstable plaque phenotype; whereas IL-37 is anti-atherogenic and maintains plaque stability. It is speculated that these cytokines may contribute to the explanation for the increased occurrence of atherosclerotic plaque rupture seen in patients with COVID-19 infection. Understanding the roles of these cytokines in atherogenesis may provide future therapeutic perspectives, both in the management of unstable plaque and acute coronary syndrome, and may contribute to our understanding of the COVID-19 cytokine storm.

IL-34 affects fibroblast-like synoviocyte proliferation, apoptosis and function by regulating IL-17

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by proliferation and insufficient apoptosis of fibroblast-like synoviocytes (FLSs).The biology and functions of interleukin (IL)-34 are only beginning to be uncovered. We previously demonstrated IL-34 could upregulate the expression of IL-17 in RA patients. In this study, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry of Annexin V and PI staining were performed to assess cell proliferation and apoptosis progression in RA-FLSs after stimulated with increasing concentrations of IL-34, respectively. Inflammatory cytokines and angiogenic factors were measured using quantitative real-time PCR, Western blotting and ELISA. We explored the association between IL-34 and RA-FLS proliferation and apoptosis in the context of RA. Stimulating RA-FLSs with different concentrations of IL-34 significantly promoted the proliferation and inhibited the apoptosis of RA-FLSs in a concentration-dependent manner. Neutralization of IL-17 with the IL-17 inhibitor plumbagin (PB) reduced the effects of IL-34. Proinflammatory cytokine (IL-17A IL-6 and tumor necrosis factor-α, TNF-α) and angiogenic factor (vascular endothelial growth factor, VEGF and hypoxia-inducible factor-1α, HIF-1α) expression was markedly upregulated in RA-FLSs stimulated by IL-34. PB-mediated inhibition of IL-17A also decreased the expression of IL-6, TNF-α, HIF-1α and VEGF in RA-FLSs. Taken together, these findings suggest that targeting IL-34 production in RA-FLSs may be a therapeutic strategy for RA.

Increased serum interleukin-34 levels as a novel diagnostic and prognostic biomarker in patients with acute ischemic stroke

BACKGROUND

Recent data reveal that interleukin-34 (IL-34) can drive inflammatory response, thereby participating in the pathogenesis of inflammatory diseases. However, the potential effect of IL-34 in acute ischemic stroke (AIS) remains unknown. The purpose of this study was to explore whether the levels of serum IL-34 were correlated with clinical severity or prognosis in AIS patients.

METHODS

In this prospective cohort study, serum IL-34 levels were detected in 150 healthy controls and 155 AIS patients. Univariate and multivariate logistic regression analysis were conducted to investigate the effect of IL-34 on the diagnosis and prognosis of AIS. ROC curve was utilized to evaluate predictive values for IL-34.

RESULTS

Serum IL-34 levels at admission were significantly higher in AIS patients than those in the healthy controls. Univariate and multivariate logistics regression analysis showed that IL-34 was an independent predictor of occurrence and functional outcome of AIS. The ROC curve demonstrated that IL-34 had a good predictive effect on the diagnosis and prognosis of AIS.

CONCLUSIONS

IL-34 can be used as a novel and independent diagnostic and predicting prognostic biomarker in AIS.

Circulating IRAPe, Irisin, and IL-34 in Relation to Insulin Resistance in Patients With Type 2 Diabetes

PURPOSE

This study aimed to evaluate the role of the extracellular part of insulin-regulated aminopeptidase (IRAPe), interleukin (IL)-34, irisin, and visfatin in the development of insulin resistance (IR) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This observational parallel-group study was conducted in 60 subjects without T2DM who served as a control group and 60 patients with newly diagnosed T2DM. The 2 groups were matched for age, sex ratio, and body mass index. Anthropometric parameters; fasting blood glucose; fasting plasma insulin; Homeostatic Model Assessment for IR (HOMA-IR) index; glycated hemoglobin (HbA_1c); and circulating levels of IL-34, visfatin, irisin, and IRAPe were assessed.

RESULTS

The group with T2DM showed significantly higher IL-34 and visfatin levels and significantly lower irisin and IRAPe levels as compared to the healthy control group. IL-34 and visfatin were significantly positively correlated with fasting blood glucose, fasting plasma insulin, HOMA-IR, and HbA_1c. On the other hand, irisin and IRAPe were significantly negatively correlated with fasting blood glucose, fasting plasma insulin, HOMA-IR, and HbA_1c. IL-34 was positively associated with visfatin, while negatively associated with both irisin and IRAPe.

IMPLICATIONS

IL-34, visfatin, irisin, and IRAPe may play a vital role in T2DM and in diabetes-associated IR. Additionally, IRAPe may represent a useful and direct marker for use in the detection of IR in the diabetic population. ClinicalTrials.gov identifier: NCT04107259.

DDIT4 mediates the proliferation-promotive effect of IL-34 in human monocytic leukemia cells

Interleukin 34 (IL-34) is a cytokine that shares the receptor with colony-stimulating factor 1 (CSF-1). IL-34 is involved in a broad range of pathologic processes including cancer. We previously demonstrated that IL-34 promoted the proliferation and colony formation of human acute monocytic leukemia (AMoL) cells. However, the mechanism has not been elucidated. Here, by analyzing the gene profiles of Molm13 and THP1 cells overexpressing IL-34 (Molm13-IL-34 and THP1-IL-34), upregulation of the DNA damage-inducible transcript 4 (DDIT4) was detected in both series. Knockdown of DDIT4 effectively inhibited the proliferation, promoted apoptosis and colony formation in Molm13-IL-34 and THP1-IL-34 cells. Our results suggest that DDIT4 mediates the proliferation-promotive effect of IL-34 whereas does not mediate the promotive effect of IL-34 on colony formation in AMoL cells.

Impact of IL-34, IFN-α and IFN-λ1 on activity of systemic lupus erythematosus in Egyptian patients

Background

Systemic lupus erythematosus (SLE) is an autoimmune, multi-system inflammatory disease. Among cytokines involved in SLE pathogenesis, interferons (particularly IFN-α) and interleukin 34 play a pivotal role. Interestingly, the gene signatures of type III (IFN-λ1) and type I IFNs may overlap. Increased levels of IFN-λ also have been reported in SLE.

Objectives: The aim of this study was to assess serum levels of IL-34, IFN-λ1, IFN-α and the relationship between these cytokines and clinical and laboratory parameters and response to treatment in a cohort of Egyptian SLE patients.

Material and methods

The study included 82 newly diagnosed SLE patients: male 17.1% (n = 14), female 82.9% (n = 68), mean age ±SD: 48.6 ±8.2 and 60 healthy subjects matched by age and gender as a control group. Medical history, physical examination and laboratory tests for confirming SLE diagnosis and assessment of disease activity were collected. The assessment of serum levels of studied cytokines were performed using the ELISA method.

All studied patients after first cytokine evaluation were treated with a combination of antimalarial drugs, glucocorticosteroids and/or immunosuppressive drugs with follow-up after six months of treatment.

Results

In the SLE group the mean serum levels of IL-34, IFN-α and IFN-λ1 were 175.9 ±125.9 pg/ml, 109.3 ±32.5 pg/ml and 227.9 ±144.8 pg/ml respectively. These cytokine levels were significantly higher in the SLE group than in healthy controls. 39% of SLE patients (n = 32) had SLAM > 6 and 26.8% (n = 22) had SLEDAI >6. There were 21 SLE patients (25.6%) with lupus nephritis.

IL-34 and IFN-λ1 were positively correlated with anti-dsDNA antibodies but negatively correlated with C3 complement component (p ≤ 0.05). IL-34, INF-α and IFN-λ1 were significantly higher in lupus nephritis patients, and correlated with poorest response to treatment.

IL-34 and IFN-λ1 were correlated with higher SLAM > 6 and SLEDAI > 6 results; there was no such correlation between IFN-α and disease activity.

Accumulation of three or more clinical features during follow-up was significantly associated with high levels of studied cytokines. Triple high positivity was found in 17 patients (20.7%) and correlated with presence of anti-dsDNA antibodies, low levels of C3 component of complement and lupus nephritis.

Conclusions

SLE patients with high serum levels of IL-34, IFN-α and IFN-λ1 more often had lupus nephritis and poor response to immunosuppressive treatment.

The triple cytokine elevation was strongly associated with higher disease activity. These results may indicate the need to distinguish this group of patients with such aggressive phenotype and consider targeted multi-therapy.

Mudskipper interleukin-34 modulates the functions of monocytes/macrophages via the colony-stimulating factor-1 receptor 1

Interleukin-34 (IL-34) is a novel cytokine that plays an important role in innate immunity and inflammatory processes by binding to the colony-stimulating factor-1 receptor (CSF-1R). However, information on the function of IL-34 in fish remains limited. In the present study, we identified an IL-34 homolog from mudskippers (Boleophthalmus pectinirostris). In silico analysis showed that the mudskipper IL-34 (BpIL-34) was similar to other known IL-34 variants in sequence and structure and was most closely related to an orange-spotted grouper (Epinephelus coioides) homolog. BpIL-34 transcripts were constitutively expressed in various tissues, with the highest level of expression found in the brain. Edwardsiella tarda infection significantly up-regulated the mRNA expression of BpIL-34 in the mudskipper tissues. The recombinant mature BpIL-34 peptide (rBpIL-34) was purified and used to produce anti-rBpIL-34 IgG. Western blot analysis combined with PNGase F digestion revealed that native BpIL-34 in monocytes/macrophages (MOs/MФs) was N-glycosylated. In vitro, rBpIL-34 treatment enhanced the phagocytotic and bactericidal activity of mudskipper MOs/MФs, as well as the mRNA expression of pro-inflammatory cytokines like tumor necrosis factor α (BpTNF-α) and BpIL-1β in these cells. Furthermore, the knockdown of mudskipper CSF-1R1 (BpCSF-1R1), but not mudskipper BpCSF-1R2, significantly inhibited the rBpIL-34-mediated enhanced effect on MO/MФ function. In conclusion, our results indicate that mudskipper BpIL-34 modulates the functions of MOs/MФs via BpCSF-1R1.

Interleukin-34 as a marker for subclinical proliferative lupus nephritis

Background

Lupus nephritis (LN) is an ominous manifestation of systemic lupus erythematosus (SLE). Clinical renal affection is present in about 70% of lupus patients, and more patients have histological evidence of renal involvement without clinical manifestations. This study aimed to investigate the potential role of serum interleukin-34 (IL-34) as an early marker for the detection of silent LN.

Methods

Thirty-three lupus patients with silent LN (group I), 37 patients with clinical LN (group II) and 20 controls were included. The SLE Disease Activity Index (SLEDAI), IL-34, anti-dsDNA antibodies and renal biopsy were assessed in all patients.

Results

Serum IL-34 levels were significantly higher in all lupus patients compared to healthy controls ( p < 0.001) and showed a significant positive correlation with SLEDAI score. SLE patients with positive anti-dsDNA antibodies had more active disease according to SLEDAI and higher levels of IL-34 than those with negative anti-dsDNA antibodies. In both studied groups, serum IL-34 levels were significantly higher in patients with proliferative LN (class III and class IV) than those with non-proliferative lupus (class II and class V) and controls. Yet, in both groups, IL-34 was not useful in differentiating active from chronic renal affection.

Conclusion

In lupus patients with insignificant proteinuria, serum levels of IL-34 distinguished the different histological classes of subclinical LN. Serum IL-34 may be used as a surrogate marker for early renal affection in silent LN, especially the proliferative type.

Interleukin-34 Levels Were Associated with Prognosis in Patients with Acute Myocardial Infarction

Inflammatory factors have specific value in acute myocardial infarction (AMI). Our previous studies have identified the prognostic value of interleukin (IL)-34 during chronic heart failure. However, the potential impact of IL-34 on AMI remains unknown.Serum IL-34 was measured in 287 AMI patients, and they were followed up for the composite endpoint, including cardiovascular death, heart failure hospitalization, recurrent nonfatal myocardial infarction (MI), and nonfatal stroke.IL-34 levels were significantly associated with the presence of heart failure at baseline and its aggravation after a year. During the five-year follow-up, there was a significant increase in the risk of the composite endpoint (hazard ratio [HR] 1.38 [95% confidence intervals (CI) 1.12-1.70], P < 0.01) and cardiovascular death (HR 1.48 [95%CI 1.03-2.27], P = 0.03) after full adjustment as IL-34 levels increased.Higher IL-34 levels in the acute phase were associated with an increased risk of heart failure after MI and poor prognosis.

Interleukin-34 Ameliorates Survival and Bacterial Clearance in Polymicrobial Sepsis

OBJECTIVES

Sepsis is a devastating condition with a high mortality rate and limited treatments. Sepsis is characterized by a failed host immune response to contain the infection, resulting in organ dysfunction. Interleukin-34 is new cytokine involved in infection and immunity. Whether interleukin-34 is beneficial or deleterious to sepsis and the underlying mechanisms remains unknown.

DESIGN

Prospective randomized animal investigation and in vitro studies.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Wild-type C57BL/6 mice were used for in vivo studies, and septic human patients and healthy human subjects were used to obtain blood for in vitro studies.

INTERVENTIONS

Interleukin-34 concentrations were measured in human sepsis patients and healthy individuals. The effects of interleukin-34 administration on survival, bacterial burden, organ injury, and inflammatory response were assessed in a murine model of cecal ligation and puncture-induced polymicrobial sepsis.

MEASUREMENTS AND MAIN RESULTS

Interleukin-34 levels were significantly elevated in human sepsis and cecal ligation and puncture-induced experimental sepsis. Interleukin-34 administration improved survival and bacterial clearance, although suppressed vascular leakage and organ injury after cecal ligation and puncture-induced polymicrobial sepsis. Neutralization of interleukin-34 increased mortality rate and decreased bacterial clearance in septic mice. An increased neutrophil and macrophage influx were developed in interleukin-34-treated mice at the site of infection, accompanied by elevated production of neutrophil chemokine chemokine (C-X-C motif) ligand 1 and macrophage chemokine C-C motif chemokine ligand 2 in the peritoneal cavity. Depletion of neutrophils or macrophages reversed interleukin-34-mediated protection against polymicrobial sepsis.

CONCLUSIONS

We reported for the first time a potential therapeutic role for interleukin-34 in sepsis and suggested that interleukin-34 is a novel target for the development of therapeutic agents against sepsis.

Interleukin-34 as a promising clinical biomarker and therapeutic target for inflammatory arthritis

Interleukin-34 (IL-34), recently identified as a novel inflammatory cytokine and the second ligand for colony-stimulating factor-1 receptor, is known to play regulatory roles in the development, maintenance, and function of mononuclear phagocyte lineage cells - especially osteoclasts. Regarding its primary effect on osteoclasts, IL-34 has been shown to stimulate formation and activation of osteoclasts, which in turn magnifies osteoclasts-resorbing activity. In addition to its role in osteoclastogenesis, IL-34 has been implicated in inflammation of synovium via augmenting production of inflammatory mediators, in which altered IL-34 expression is regulated by pro-inflammatory cytokines responsible for cartilage degradation. Indeed, IL-34 has been documented to be highly expressed in inflamed synovium of rheumatoid arthritis (RA) and knee osteoarthritis (OA) patients, which are recognized as inflammatory arthritis. Furthermore, a number of clinical studies demonstrated that IL-34 levels were significantly increased in the circulation and synovial fluid of patients with RA and knee OA. Its levels were also found to be positively associated with disease severity - especially radiographic severity of both RA and knee OA patients. Interestingly, emerging evidence has accumulated that functional blockage of IL-34 with specific antibody can alleviate the severity of inflammatory arthritis. It is therefore reasonable to speculate that IL-34 may be developed as a potential biomarker and a new therapeutic candidate for inflammatory arthritis. To date, there are numerous studies showing IL-34 involvement and association with many aspects of inflammatory arthritis. Herein, this review aimed to summarize the recent findings regarding regulatory role of IL-34 in synovial inflammation-mediated cartilage destruction and update the current comprehensive knowledge on usefulness of IL-34-based treatment in inflammatory arthritis - particularly RA and knee OA.

Biological functions and clinical implications of interleukin-34 in inflammatory diseases

Interleukin (IL)-34 is a recently discovered cytokine and ligand of the colony-stimulating factor (CSF)-1 receptor. Although CSF-1 and IL-34 share similar biological properties, their expression patterns and downstream signaling pathways are distinct. IL-34 can influence differentiation and has functions in multiple cell types (e.g., dendritic cells, monocytes, macrophages). In the pathological conditions, IL-34 is induced by pro-inflammatory stimuli (e.g., cytokines, pathogen-associated molecular patterns, and infection). Current evidence shows that IL-34 is a critical player in inflammatory response and is involved in the pathogenesis of inflammatory autoimmune dysfunction. Therefore, IL-34 may be a promising clinical biomarker and therapeutic target for treating inflammatory related disorders. In this article, we review the advances in biological functions of IL-34 and our understanding of its role in the development of inflammatory diseases as well as therapeutic applications.

CSF1R inhibitors exhibit antitumor activity in acute myeloid leukemia by blocking paracrine signals from support cells

To identify new therapeutic targets in acute myeloid leukemia (AML), we performed small-molecule and small-interfering RNA (siRNA) screens of primary AML patient samples. In 23% of samples, we found sensitivity to inhibition of colony-stimulating factor 1 (CSF1) receptor (CSF1R), a receptor tyrosine kinase responsible for survival, proliferation, and differentiation of myeloid-lineage cells. Sensitivity to CSF1R inhibitor GW-2580 was found preferentially in de novo and favorable-risk patients, and resistance to GW-2580 was associated with reduced overall survival. Using flow cytometry, we discovered that CSF1R is not expressed on the majority of leukemic blasts but instead on a subpopulation of supportive cells. Comparison of CSF1R-expressing cells in AML vs healthy donors by mass cytometry revealed expression of unique cell-surface markers. The quantity of CSF1R-expressing cells correlated with GW-2580 sensitivity. Exposure of primary AML patient samples to a panel of recombinant cytokines revealed that CSF1R inhibitor sensitivity correlated with a growth response to CSF1R ligand, CSF1, and other cytokines, including hepatocyte growth factor (HGF). The addition of CSF1 increased the secretion of HGF and other cytokines in conditioned media from AML patient samples, whereas adding GW-2580 reduced their secretion. In untreated cells, HGF levels correlated significantly with GW-2580 sensitivity. Finally, recombinant HGF and HS-5-conditioned media rescued cell viability after GW-2580 treatment in AML patient samples. Our results suggest that CSF1R-expressing cells support the bulk leukemia population through the secretion of HGF and other cytokines. This study identifies CSF1R as a novel therapeutic target of AML and provides a mechanism of paracrine cytokine/growth factor signaling in this disease.

CSF1R Stimulation Promotes Increased Neuroprotection by CD11c+ Microglia in EAE

Microglia are resident immune cells of the central nervous system. Their development and maintenance depend on stimulation of Colony Stimulating Factor-1 receptor (CSF1R). Microglia play an important role in neurodevelopment and a population of microglia that expresses the complement receptor CD11c is critical for primary myelination. This population is virtually absent in the healthy adult brain but increases dramatically upon neuroinflammatory conditions, and these microglia are suggested to play a protective role in central nervous system (CNS) diseases. To date, the molecular trigger for their expansion is unknown. Here we showed that stimulation of CSF1R by either of its ligands, CSF1 and interleukin (IL)-34, can induce expansion of CD11c+ microglia. In addition, such stimulation resulted in amelioration of EAE symptoms and decreased demyelination. Treatment with CSF1R ligands also induced expression of the chemokine CCL2, and we showed that experimental overexpression of CCL2 in the brain led to a dramatic increase of CD11c+ microglia, independent of CCR2. Moreover, this led to elevated CSF1 expression, suggesting a positive feedback loop between CSF1R and CCL2. These data provide new insights to microglia biology and open new perspectives for modulating microglial activity in neuroinflammatory diseases such as multiple sclerosis.

Interleukin-34 Levels in Gingival Crevicular Fluid and Plasma in Healthy and Diseased Periodontal Tissue in Presence or Absence of Obesity: A Clinico-biochemical Study

Interleukin (IL)-34 has recently been identified as an alternative ligand for colonystimulating factor-1 receptor and plays an important role in osteoclastogenesis. The aim of this study was to assess and compare IL-34 levels in gingival crevicular fluid (GCF) and plasma in obese individuals in the presence or absence of periodontal disease and to determine whether they showed a correlation with disease severity. Forty patients aged between 25 and 40 yr were enrolled and categorized into 4 groups: 10 non-obese patients with healthy periodontium (Group I); 10 obese patients with healthy periodontium (Group II); 10 non-obese patients with chronic periodontitis (Group III); and 10 obese patients with chronic periodontitis (Group IV). Demographic variables such as age and body mass index score were recorded and assessed, together with clinical periodontal parameters such as the gingival index, probing pocket depth, and clinical attachment level scores in all groups. The GCF and plasma levels of IL-34 were quantified using enzyme-linked immunosorbent assay. The results showed that the mean IL-34 concentrations in GCF or plasma were highest in Group IV, followed by Group III, Group II, and Group I, with the difference among them being statistically significant (p<0.05). These results suggest that obese individuals with periodontitis have higher GCF and plasma IL-34 levels than non-obese individuals with healthy periodontium. This suggests IL-34 as a potential inflammatory marker of periodontal disease and obesity.

IL-34-Dependent Intrarenal and Systemic Mechanisms Promote Lupus Nephritis in MRL-Faslpr Mice

BACKGROUND

In people with SLE and in the MRL-Fas^lpr lupus mouse model, macrophages and autoantibodies are central to lupus nephritis. IL-34 mediates macrophage survival and proliferation, is expressed by tubular epithelial cells (TECs), and binds to the cFMS receptor on macrophages and to a newly identified second receptor, PTPRZ.

METHODS

To investigate whether IL-34-dependent intrarenal and systemic mechanisms promote lupus nephritis, we compared lupus nephritis and systemic illness in MRL-Fas^lpr mice expressing IL-34 and IL-34 knockout (KO) MRL-Fas^lpr mice. We also assessed expression of IL-34 and the cFMS and PTPRZ receptors in patients with lupus nephritis.

RESULTS

Intrarenal IL-34 and its two receptors increase during lupus nephritis in MRL-Fas^lpr mice. In knockout mice lacking IL-34, nephritis and systemic illness are suppressed. IL-34 fosters intrarenal macrophage accumulation via monocyte proliferation in bone marrow (which increases circulating monocytes that are recruited by chemokines into the kidney) and via intrarenal macrophage proliferation. This accumulation leads to macrophage-mediated TEC apoptosis. We also found suppression of circulating autoantibodies and glomerular antibody deposits in the knockout mice. This is consistent with fewer activated and proliferating intrarenal and splenic B cells in mice lacking IL-34, and with our novel discovery that PTPRZ is expressed by macrophages, B and T cells. These findings appear translatable to human patients with lupus nephritis, whose expression of IL-34, cFMS, and PTPRZ is similar to that seen in the MRL-Fas^lpr lupus mouse model. Moreover, expression of IL-34 in TECs correlates with disease activity.

CONCLUSIONS

IL-34 is a promising novel therapeutic target for patients with lupus nephritis.

Oral administration of oat beta-glucan preparations of different molecular weight results in regulation of genes connected with immune response in peripheral blood of rats with LPS-induced enteritis

Purpose

Beta-glucans are biologically active polysaccharides having antioxidant, immunomodulatory, and antiinflammatory properties. This study investigated the transcriptomic profile in peripheral blood of rats with LPS-induced enteritis, which were fed a diet supplemented with high- (G1) and low- (G2) molecular-weight oat beta-glucans.

Methods

Two-color rat gene expression microarrays were applied and the analysis was performed using a common reference design to provide easy means of comparing samples from various experimental conditions against one another. Common reference sample was labeled with cyanine 3 (Cy3) and investigated samples from each experimental group: C-G0 (control group fed semi-synthetic diet), LPS-G0 (LPS-challenged group fed semi-synthetic diet), LPS-G1 (LPS-challenged group fed G1 beta-glucan enriched diet), and LPS-G2 (LPS-challenged group fed G2 beta-glucan enriched diet) were labeled with cyanine 5 (Cy5). Each microarray was performed in quadruplicate. Statistical analysis was performed using one-way ANOVA and Tukey’s HSD post-hoc test (p < 0.05). A multiple testing correction was performed using Benjamini and Hochberg False Discovery Rate < 5%. A quantitative real-time RT-PCR was performed to verify the expression of chosen transcripts.

Results

The microarray analyses revealed differentially expressed transcripts between: the LPS-G0 and the control groups: C-G0 (138 genes), the LPS-G1 and LPS-G0 groups (533 genes), and the LPS-G2 and LPS-G0 groups (97 genes). Several differentially expressed genes in the beta-glucan-supplemented groups encoded proteins belonging to TLR and NLR signaling pathways, as well as prostaglandin synthesis and regulation pathways. Both beta-glucans up-regulated the expression of Atg10, which belongs to the family of autophagy-related genes, suggesting a possible link between autophagy induction and beta-glucan supplementation.

Conclusion

The changes in gene expression observed in the peripheral blood indicate that oat beta-glucans exerted a protective effect in rats with an induced inflammatory state caused by LPS challenge. The greater number of differentially expressed genes was observed in group supplemented with G1 beta-glucan, pointing at the differences in the mode of action of high- and low-molecular-weight beta-glucans in the organism.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1838-3) contains supplementary material, which is available to authorized users.

Interleukin-34, a comprehensive review

IL-34 is a novel cytokine that was identified in 2008 in a comprehensive proteomic analysis as a tissue-specific ligand of CSF-1 receptor (CSF-1R). IL-34 exists in all vertebrates including fish, amphibians, birds, and mammals, showing high conservation among species. Structurally, IL-34 belongs to the short-chain helical hematopoietic cytokine family but shows no apparent consensus structural domains, motifs, or sequence homology with other cytokines. IL-34 is synthesized as a secreted homodimeric glycoprotein that binds to the extracellular domains of CSF-1R and receptor-type protein-tyrosine phosphatase-zeta (PTP-ζ) in addition to the chondroitin sulfate chains of syndecan-1. These interactions result in activating several signaling pathways that regulate major cellular functions, including proliferation, differentiation, survival, metabolism, and cytokine/chemokine expression in addition to cellular adhesion and migration. In the steady state, IL-34 contributes to the development and maintenance of specific myeloid cell subsets in a tissue-specific manner: Langerhans cells in the skin and microglia in the brain. In pathological conditions, changes in IL-34 expression-increased or decreased-are involved in disease pathogenesis and correlate with progression, severity, and chronicity. One decade after its discovery, IL-34 has been introduced as a newcomer to the big family of interleukins with specific physiological functions, critical pathological roles, and promising clinical applications in disease diagnosis and treatment. In this review, we celebrate the 10th anniversary of IL-34 discovery, introducing its biological characteristics, and discussing the importance of IL-34 signaling network in health and disease.

Increased Serum Interleukin-34 Levels Are Related to the Presence and Severity of Cardiac Dysfunction in Patients With Ischemic Cardiomyopathy

Background: Several inflammatory factors have been demonstrated with diagnostic or prognostic value in patients with ischemic cardiomyopathy (ICM). Interleukin 34 (IL-34), an additional ligand of colony stimulating factor-1 receptor (CSF-1R), has been identified as a biomarker of coronary artery disease (CAD) and chronic kidney disease (CKD). However, the potential effect of IL-34 in ICM remains unknown.

Methods: Serum IL-34 levels were detected in 360 subjects with ICM and in 465 subjects without ICM; the latter group included 233 controls without CAD and 232 patients with CAD and normal cardiac function. Uni- and multivariable logistic regression analyses were conducted to analyze the relationship between IL-34 and ICM.

Results: IL-34 levels were significantly increased in patients with ICM compared with both groups of subjects without ICM (122.52 ± 115.30 vs. 95.02 ± 101.43 vs. 82.57 ± 84.24 pg/ml, respectively; P < 0.001). Moreover, serum IL-34 level was significantly positively correlated to NT-proBNP level (r = 0.223, P < 0.001), left ventricular end diastolic diameter and New York Heart Association (NYHA) functional class, indicating that a higher IL-34 level reflects more severe heart failure (HF). Multivariable regression analyses revealed that IL-34 was remarkably associated with the presence and severity of ICM after adjusting for age, sex, conventional risk factors as well as medication [odds ratio (OR): 1.501, 95% confidence interval (CI): 1.249–1.803, P < 0.001, per SD increase]. The predictive value of IL-34 value remained significant in patients already diagnosed with CAD.

Conclusion: Increased IL-34 levels are relevant to the presence and severity of ischemic HF in all subjects and in patients with CAD. IL-34 may be used as a novel clinical biomarker of ICM with predictive value.

IL-34 regulates IL-6 and IL-8 production in human lung fibroblasts via MAPK, PI3K-Akt, JAK and NF-κB signaling pathways

IL-34 plays diverse roles in disease due to its inflammatory and immunosuppressive properties. Elevated IL-34 expression has been observed in lung cancers and pulmonary infections although its role is unclear. We found that IL-34 addition to primary lung fibroblasts significantly promoted IL-6 and IL-8 expression in a dose and time dependent manner. These effects were reversed when JAK, NF-κB, Akt and p38 inhibitors were included before IL-34 addition. Protein phosphorylation in these pathways was also observed through western-blotting. Stimulation of human lung fibroblasts with IL-34 in combination with TNF-α, IL-17A and IL-4 enhanced inflammatory cytokine production. Our data confirmed the inflammatory effect of IL-34 on human lung fibroblasts and suggested that the IL-34/CSF-1R axis may be a novel therapeutic target in pulmonary disease.

Elevated Serum Interleukin-34 Level in Patients with Systemic Lupus Erythematosus Is Associated with Disease Activity

We measured the interleukin-34 (IL-34) level in sera from patients with systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) using an enzyme-linked immunosorbent assay (ELISA). Blood tests, including assays to determine C-reactive protein (CRP), complement (C) 3, C4, immunoglobulin (Ig) A, IgG, IgM, anti-double-stranded DNA antibody (Anti-dsDNA Ab) and hemoglobin (Hb) levels and white blood cell (WBC) and platelet (PLT) counts, were performed using standard methods. Lupus nephritis (LN) was diagnosed according to the American College of Rheumatology (ACR) renal criteria. The SLE disease activity was scored using the SLE Disease Activity Index (SLEDAI). Among the 110 SLE cases, IL-34 could be detected in 79 cases (71.8%). IL-34 was barely detected in the control group. The serum level of IL-34 was significantly higher in the SLE group. No change was observed in the serum IL-34 concentration in the SLE patients regardless of LN status. Correlations were observed between the serum IL-34 level and the disease activity parameters. The SLE patients with detectable IL-34 levels had higher SLEDAI and IgG concentrations and lower C3 and Hb levels than patients with undetectable IL-34 levels. Therefore, IL-34 could be a potential disease activity marker for SLE.

Interleukin-34 levels in gingival crevicular fluid and plasma in periodontal health and disease with and without type-2 diabetes mellitus

AIM

The aim of the present study was to evaluate and correlate the levels of interleukin-34 (IL-34) in gingival crevicular fluid (GCF) and plasma in chronic periodontitis (CP) patients with and without type-2 diabetes mellitus (DM).

METHODS

A total of 175 patients were divided into five groups: (a) group I had 35 periodontally-healthy patients; (b) group II had 35 chronic gingivitis patients; (c) group III had 35 CP patients without type-2 DM; (d) group IV had 35 CP patients with type-2 DM; and (e) group V had 35 type-2 DM patients without CP. The GCF and plasma levels of IL-34 were quantified using enzyme-linked immunosorbent assay. Clinical and systemic parameters, such as gingival index, probing pocket depth, clinical attachment loss, and glycated hemoglobin levels, were evaluated.

RESULTS

The mean IL-34 concentration in GCF and plasma was highest for group IV, followed by groups III, V, and II, and lowest in group I. The difference between them was statistically significant (P < .05). There was a positive correlation between IL-34 concentration in GCF and plasma in the study groups, with the exception of group I, for which there was a negative correlation.

CONCLUSION

IL-34 can be considered a possible GCF and plasma inflammatory biomarker of periodontal disease progression and DM.

Interleukin-34 sustains pro-tumorigenic signals in colon cancer tissue

Interleukin-34 (IL-34), a cytokine produced by a wide range of cells, binds to the macrophage colony-stimulating factor receptor (M-CSFR-1) and receptor-type protein-tyrosine phosphatase zeta (PTP-z) and controls myeloid cell differentiation, proliferation and survival. various types of cancers over-express IL-34 but the role of the cytokine in colorectal cancer (CRC) remains unknown. We here investigated the expression and functional role of IL-34 in CRC. A more pronounced expression of IL-34 was seen in CRC samples as compared to matched normal/benign colonic samples and this occurred at both RNA and protein level. Immunohistochemical analysis of CRC tissue samples showed that both cancer cells and lamina propria mononuclear cells over-expressed IL-34. Additionally, CRC cells expressed both M-CSFR-1 and PTP-z, thus suggesting that CRC cells can be responsive to IL-34. Indeed, stimulation of DLD-1 cancer cells with IL-34, but not with MSCF1, enhanced the cell proliferation and cell invasion without affecting cell survival. Analysis of intracellular signals underlying the mitogenic effect of IL-34 revealed that the cytokine enhanced activation of ERK1/2 and pharmacologic inhibition of ERK1/2 abrogated IL-34-driven cell proliferation. Consistently, IL-34 knockdown in HT-29 cells with a specific IL-34 antisense oligonucleotide reduced ERK1/2 activation, cell proliferation and enhanced the susceptibility of cells to Oxaliplatin-induced death. This is the first study showing up-regulation of IL-34 in CRC and suggesting a role for this cytokine in colon tumorigenesis.

Tregs: Where We Are and What Comes Next?

Regulatory T cells are usually recognized as a specialized subset of CD4⁺ T cells functioning in establishment and maintenance of immune tolerance. Meanwhile, there is emerging evidence that regulatory T cells (Tregs) are also present in various non-lymphoid tissues, and that they have unique phenotypes credited with activities distinct from regulatory function. Their development and function have been described in plenty of manuscripts in the past two decades. However, with the deepening of research in recent years, emerging evidence revealed some novel mechanisms about how Tregs exert their activities. First, we discuss the expanding family of regulatory lymphocytes briefly and then, try to interpret how fork-head box P3 (Foxp3), a master regulator of the regulatory pathway in the development and function of regulatory T cells, functions. Subsequently, another part of our focus is varieties of tissue Tregs. Next, we primarily discuss recent research on how Tregs work and their faceted functions in terms of soluble mediators, functional proteins, and inhibitory receptors. In particular, unless otherwise noted, the term “Treg” is used here to refer specially to the “CD4⁺CD25⁺Foxp3^+” regulatory cells.

Immunoregulatory properties of the cytokine IL-34

Interleukin-34 is a cytokine with only partially understood functions, described for the first time in 2008. Although IL-34 shares very little homology with CSF-1 (CSF1, M-CSF), they share a common receptor CSF-1R (CSF-1R) and IL-34 has also two distinct receptors (PTP-ζ) and CD138 (syndecan-1). To make the situation more complex, IL-34 has also been shown as pairing with CSF-1 to form a heterodimer. Until now, studies have demonstrated that this cytokine is released by some tissues that differ to those where CSF-1 is expressed and is involved in the differentiation and survival of macrophages, monocytes, and dendritic cells in response to inflammation. The involvement of IL-34 has been shown in areas as diverse as neuronal protection, autoimmune diseases, infection, cancer, and transplantation. Our recent work has demonstrated a new and possible therapeutic role for IL-34 as a Foxp3+ Treg-secreted cytokine mediator of transplant tolerance. In this review, we recapitulate most recent findings on IL-34 and its controversial effects on immune responses and address its immunoregulatory properties and the potential of targeting this cytokine in human.

Serum Interleukin-34 Levels Are Elevated in Patients with Systemic Lupus Erythematosus

Interleukin-34 (IL-34) was initially identified as an alternative ligand for the colony-stimulating factor-1 receptor (CSF-1R) to mediate the biology of mononuclear phagocytic cells. Recently, IL-34 was found to be associated with chronic inflammation, such as in rheumatoid arthritis (RA). Both RA and systemic lupus erythematosus (SLE) are multifactorial autoimmune diseases and are characterized by excessive immune and inflammatory responses. Thus, we investigated whether IL-34 is involved in the pathogenesis of SLE. In all, 78 SLE patients and 53 healthy controls were enrolled in the research. Enzyme-linked immunosorbent assay (ELISA) was employed to measure the concentrations of serological IL-34. Then serum IL-34 levels between the SLE group and healthy controls were analyzed by the Mann-Whitney U test. Meanwhile, the correlations between the serum IL-34 levels and disease activity indexes and other established serum markers were assessed. Furthermore, the serum IL-34 levels of 20 active SLE patients were reevaluated when diseases were in the remission stage from corticosteroids or immunosuppressive drugs. Serum IL-34 levels were significantly higher in SLE patients compared to healthy controls. Their levels were remarkably associated with accumulation of the clinical features of SLE. Additionally, IL-34 titers were positively correlated with the SLE disease activity indexes, anti-double-stranded DNA antibody (anti-dsDNA) titers and C-reactive protein (CRP) levels, and inversely with complement3 (C3) levels. Moreover, serum IL-34 levels were significantly decreased after successful treatment of SLE. Serum IL-34 could be a candidate biomarker for SLE as there are elevated serum levels in treatment-naive SLE patients and we saw a significant decrease after effective treatment.

IL-34 is associated with the presence and severity of renal dysfunction and coronary artery disease in patients with heart failure

Pro-inflammatory mediators are identified in patients with heart failure (HF), some of which may be used as biomarkers with diagnostic or prognostic value. As an additional ligand of Colony Stimulating Factor-1 Receptor (CSF-1R), interleukin-34 (IL-34) has been identified as a pro-inflammatory cytokine participating in chronic heart failure (CHF). However, the potential impact of IL-34 in CHF complications remains unknown. In order to determine the clinical significance of serum IL-34 in CHF patients, especially those with kidney dysfunction and coronary artery disease (CAD) comorbid conditions, serum IL-34 was measured in 510 consecutive patients with CHF in a cross-sectional study. The present study demonstrated that higher serum IL-34 levels were associated with poorer renal function and more severe anemia in patients with CHF. After adjusting for age, gender, conventional risk factors, and other significant covariates, IL-34 positively correlated with the presence and severity of renal dysfunction (as measured by eGFR and cystatin C) on multivariable linear and logistic regression analysis. IL-34 was also demonstrated to be an independent risk factor for CAD among HF patients. In conclusion, elevated serum IL-34 levels were demonstrated to be independently associated with renal insufficiency and CAD in patients with CHF, regardless of the systolic function.

Receptor-Type Protein-Tyrosine Phosphatase ζ and Colony Stimulating Factor-1 Receptor in the Intestine: Cellular Expression and Cytokine- and Chemokine Responses by Interleukin-34 and Colony Stimulating Factor-1

Differential intestinal expression of the macrophage growth factors colony stimulating factor-1 (CSF-1), interleukin (IL)-34, and their shared CSF-1 receptor (CSF-1R) in inflammatory bowel disease (IBD) has been shown. Diverse expression between CSF-1 and IL-34, suggest that IL-34 may signal via an alternate receptor. Receptor-type protein-tyrosine phosphatase ζ (PTPRZ1, RPTP-ζ), an additional IL-34 receptor, was recently identified. Here, we aimed to assess PTPRZ1 expression in IBD and non-IBD intestinal biopsies. Further, we aimed to investigate cellular PTPRZ1 and CSF-1R expression, and cytokine- and chemokine responses by IL-34 and CSF-1. The expression of PTPRZ1 was higher in non-IBD colon compared to ileum. PTPRZ1 expression was not altered with inflammation in IBD, however, correlated to IL34, CSF1, and CSF1R. The expression patterns of PTPRZ1 and CSF-1R differed in peripheral blood mononuclear cells (PBMCs), monocytes, macrophages, and intestinal epithelial cell line. PBMCs and monocytes of the same donors responded differently to IL-34 and CSF-1 with altered expression of tumor-necrosis factor α (TNF-α), IL-1β, interferon γ (IFN-γ), IL-13, IL-8, and monocyte chemotactic protein-1 (MCP-1) levels. This study shows that PTPRZ1 was expressed in bowel tissue. Furthermore, CSF-1R protein was detected in an intestinal epithelial cell line and donor dependently in primary PBMCs, monocytes, and macrophages, and first hints also suggest an expression in these cells for PTPRZ1, which may mediate IL-34 and CSF-1 actions.

Functions of interleukin-34 and its emerging association with rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic, synovial inflammation affecting multiple joints, finally leading to extra-articular lesions for which limited effective treatment options are currently available. Interleukin-34 (IL-34), recently discovered as the second colony-stimulating factor-1 receptor (CSF-1R) ligand, is a newly discovered cytokine. Accumulating evidence has disclosed crucial roles of IL-34 in the proliferation and differentiation of mononuclear phagocyte lineage cells, osteoclastogenesis and inflammation. Recently, IL-34 was detected at high levels in patients with active RA and in experimental models of inflammatory arthritis. Blockade of functional IL-34 with a specific monoclonal antibody can reduce the severity of inflammatory arthritis, suggesting that targeting IL-34 or its receptors may constitute a novel therapeutic strategy for autoimmune diseases such as RA. Here, we have comprehensively discussed the structure and biological functions of IL-34, and reviewed recent advances in our understanding of the emerging role of IL-34 in the development of RA as well as its potential utility as a therapeutic target.

Colony-stimulating factor (CSF) 1 receptor blockade reduces inflammation in human and murine models of rheumatoid arthritis

Background

CSF-1 or IL-34 stimulation of CSF1R promotes macrophage differentiation, activation and osteoclastogenesis, and pharmacological inhibition of CSF1R is beneficial in animal models of arthritis. The objective of this study was to determine the relative contributions of CSF-1 and IL-34 signaling to CSF1R in RA.

Methods

CSF-1 and IL-34 were detected by immunohistochemical and digital image analysis in synovial tissue from 15 biological-naïve rheumatoid arthritis (RA) , 15 psoriatic arthritis (PsA) and 7 osteoarthritis (OA) patients . Gene expression in CSF-1- and IL-34-differentiated human macrophages was assessed by FACS analysis and quantitative PCR. RA synovial explants were incubated with CSF-1, IL-34, control antibody (Ab), or neutralizing/blocking Abs targeting CSF-1, IL-34, or CSF1R. The effect of a CSF1R-blocking Ab was examined in murine collagen-induced arthritis (CIA).

Results

CSF-1 (also known as M-CSF) and IL-34 expression was similar in RA and PsA synovial tissue, but lower in controls (P < 0.05). CSF-1 expression was observed in the synovial sublining, and IL-34 in the sublining and the intimal lining layer. CSF-1 and IL-34 differentially regulated the expression of 17 of 336 inflammation-associated genes in macrophages, including chemokines, extra-cellular matrix components, and matrix metalloproteinases. Exogenous CSF-1 or IL-34, or their independent neutralization, had no effect on RA synovial explant IL-6 production. Anti-CSF1R Ab significantly reduced IL-6 and other inflammatory mediator production in RA synovial explants, and paw swelling and joint destruction in CIA.

Conclusions

Simultaneous inhibition of CSF1R interactions with both CSF-1 and IL-34 suppresses inflammatory activation of RA synovial tissue and pathology in CIA, suggesting a novel therapeutic strategy for RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0973-6) contains supplementary material, which is available to authorized users.

Induction of Monocyte Chemoattractant Proteins in Macrophages via the Production of Granulocyte/Macrophage Colony-Stimulating Factor by Breast Cancer Cells

Monocyte chemoattractant protein-1 (MCP-1)/CCL2 plays an important role in the initiation and progression of cancer. We previously reported that in 4T1 murine breast cancer, non-tumor stromal cells, including macrophages, were the major source of MCP-1. In the present study, we analyzed the potential mechanisms by which MCP-1 is upregulated in macrophages infiltrating 4T1 tumors. We found that cell-free culture supernatants of 4T1 cells (4T1-sup) markedly upregulated MCP-1 production by peritoneal inflammatory macrophages. 4T1-sup also upregulated other MCPs, such as MCP-3/CCL7 and MCP-5/CCL12, but modestly upregulated neutrophil chemotactic chemokines, such as KC/CXCL1 or MIP-2/CXCL2. Physicochemical analysis indicated that an approximately 20-30 kDa 4T1 cell product was responsible for the capacity of 4T1-sup to upregulate MCP-1 expression by macrophages. A neutralizing antibody against granulocyte/macrophage colony-stimulating factor (GM-CSF), but not macrophage CSF, almost completely abrogated MCP-1-inducing activity of 4T1-sup, and recombinant GM-CSF potently upregulated MCP-1 production by macrophages. The expression levels of GM-CSF in 4T1 tumors in vivo were higher than other tumors, such as Lewis lung carcinoma. Treatment of mice with anti-GM-CSF antibody significantly reduced the growth of 4T1 tumors at the injection sites but did not reduce MCP-1 production or lung metastasis in tumor-bearing mice. These results indicate that 4T1 cells have the capacity to directly upregulate MCP-1 production by macrophages by releasing GM-CSF; however, other mechanisms are also involved in increased MCP-1 levels in the 4T1 tumor microenvironment.

Interleukin-34 Induces Cc-chemokine Ligand 20 in Gut Epithelial Cells

BACKGROUND AND AIM

Production of chemokines by intestinal epithelial cells is a key step in the amplification of the destructive immune-inflammatory response in patients with inflammatory bowel diseases [IBD]. In this study, we examined whether intestinal epithelial cells express macrophage colony-stimulating factor receptor 1 [M-CSFR-1], the functional receptor of interleukin-34 [IL-34], a cytokine that is over-produced in IBD and supposed to sustain inflammatory pathways.

METHODS

M-CSFR-1 expression was evaluated in intestinal samples of IBD patients, controls, and colon epithelial cell lines by real-time polymerase chain reaction [PCR], immunohistochemistry, and western blotting. DLD-1 cells were stimulated with IL-34 in the presence or absence of MAP kinase inhibitors, chemokine induction was assessed by real-time PCR and enzyme-linked immunosorbent assay [ELISA], and mitogen-activated protein (MAP) kinase activation was monitored by western blotting. The effect of a neutralising IL-34 antibody on CC chemokine ligand (CCL) 20 synthesis was tested in ex vivo organ cultures of IBD mucosal explants.

RESULTS

Enhanced expression of M-CSFR-1 RNA transcripts was seen in inflamed mucosa of IBD patients as compared with controls. Immunohistochemical analysis confirmed up-regulation of M-CSFR-1 in IBD and showed that both epithelial and lamina propria mononuclear cells expressed this receptor. Stimulation of DLD-1 with IL-34 increased CCL20 production through an ERK1/2-dependent mechanism. Consistently, treatment of IBD explants with anti-IL-34 reduced CCL20 production.

CONCLUSIONS

These data show that intestinal epithelial cells are a target of IL-34 and suggest that this cytokine contributes to mediating the cross-talk between epithelial cells and immune cells in IBD.

IL-34 is a Treg-specific cytokine and mediates transplant tolerance

Cytokines and metabolic pathway-controlling enzymes regulate immune responses and have potential as powerful tools to mediate immune tolerance. Blockade of the interaction between CD40 and CD40L induces long-term cardiac allograft survival in rats through a CD8+CD45RClo Treg potentiation. Here, we have shown that the cytokine IL-34, the immunoregulatory properties of which have not been previously studied in transplantation or T cell biology, is expressed by rodent CD8+CD45RClo Tregs and human FOXP3+CD45RCloCD8+ and CD4+ Tregs. IL-34 was involved in the suppressive function of both CD8+ and CD4+ Tregs and markedly inhibited alloreactive immune responses. Additionally, in a rat cardiac allograft model, IL-34 potently induced transplant tolerance that was associated with a total inhibition of alloantibody production. Treatment of rats with IL-34 promoted allograft tolerance that was mediated by induction of CD8+ and CD4+ Tregs. Moreover, these Tregs were capable of serial tolerance induction through modulation of macrophages that migrate early to the graft. Finally, we demonstrated that human macrophages cultured in the presence of IL-34 greatly expanded CD8+ and CD4+ FOXP3+ Tregs, with a superior suppressive potential of antidonor immune responses compared with non-IL-34-expanded Tregs. In conclusion, we reveal that IL-34 serves as a suppressive Treg-specific cytokine and as a tolerogenic cytokine that efficiently inhibits alloreactive immune responses and mediates transplant tolerance.

IL-34 is associated with obesity, chronic inflammation, and insulin resistance

OBJECTIVES

IL-34 is a recently identified alternative ligand for colony-stimulating factor-1 (CSF-1) receptor. IL-34 and CSF-1 are regulators of differentiation, proliferation, and survival in mononuclear phagocytes. Here, we investigated the IL-34 serum concentration and expression in human adipose tissues and any associations with insulin resistance.

METHODS

We recruited 19 nondiabetic obese women, 9 type 2 diabetic women, and 27 normal-weight women. Metabolic parameters, abdominal fat distribution, serum IL-34 concentration, and IL-34 mRNA expression were measured in abdominal sc adipose tissue (SAT) and visceral adipose tissue (VAT). In addition, the expression/secretion and putative effects of IL-34 were assessed in human differentiated adipocytes. Serum IL-34 concentration was measured before and 5 to 9 months after laparoscopic Roux-en-Y gastric bypass surgery was performed on the 20 obese patients.

RESULTS

Regardless of diabetes status, obese patients demonstrated significantly higher serum IL-34 concentrations than controls. Serum IL-34 was significantly and positively correlated with insulin resistance-related metabolic parameters. IL-34 mRNA was significantly higher in VAT than SAT. IL-34 was expressed in adipocytes as well as nonadipocytes, and expression was significantly higher during adipogenesis. In differentiated adipocytes, the expression/secretion of IL-34 was enhanced by TNFα and IL-1β. In addition, IL-34 augmented fat accumulation and inhibited the stimulatory effects of insulin on glucose transport. Moreover, serum IL-34 was significantly decreased after Roux-en-Y gastric bypass-induced weight loss.

CONCLUSION

The present study demonstrates, for the first time, that IL-34 is expressed in human adipose tissues and the circulating concentration is significantly elevated in obese patients. This suggests that IL-34 is associated with insulin resistance.

Targeting IL-34 in chronic inflammation

A second ligand for colony-stimulating factor-1 receptor (CSF-1R) with distinct biologic activities had long been implicated but not appreciated until the recent discovery of interleukin (IL)-34. IL-34 and CSF-1 signal through this common receptor to mediate the biology of mononuclear phagocytic cells. Aberrant macrophage activation by CSF-1 and/or IL-34 is associated with numerous diseases, and clinical therapies targeting this pathway are being tested. Although IL-34 and CSF-1 have distinct activities under physiologic conditions, they appear functionally redundant in various disease states. Thus, blocking the activity of both might be necessary for maximal efficacy.