Hyperglycaemia amplifies TLR-mediated inflammatory response of M(IL4) macrophages to dyslipidemic ligands.

Hyperglycaemia is critical for initiation of diabetic vascular complications. We systemically addressed the role of hyperglycaemia in the regulation of TLRs in primary human macrophages. Expression of TLRs (1-9) was examined in monocyte-derived M(NC), M(IFNγ) and M(IL4) differentiated in normoglycemic and hyperglycaemic conditions. Hyperglycaemia increased expression of TLR1 and TLR8 in M(NC), TLR 2 and 6 in M(IFNγ), and TLR4 and TLR5 in M(IL4). The strongest effect of hyperglycaemia in M(IL4) was the upregulation of TLR4 gene and protein expression. Hyperglycaemia amplified TLR4-mediated response of M(IL4) to LPS by significantly enhancing IL1beta and modestly supressing IL10 production. In M(IL4), hyperglycaemia in combination with synthetic triacylated lipopeptide (TLR1/TLR2 ligand), amplified expression of TLR4, and production of IL1beta. In summary, hyperglycaemia enhanced inflammatory potential of homeostatic, inflammatory and healing macrophages by increasing specific profiles of TLRs. In combination with dyslipidemic ligands, hyperglycaemia can stimulate low-grade inflammatory program in healing macrophages supporting vascular diabetic complications.

Titanium induces pro-inflammatory and tissue-destructive responses in primary human macrophages.

Implants and medical devices are efficient and practical therapeutic solutions for a multitude of pathologies. Titanium and titanium alloys are used in orthopedics, dentistry, and cardiology. Despite very good mechanical properties, and corrosion resistance titanium implants can fail due to inflammatory or tissue-degradation related complications. Macrophages are major immune cells that control acceptance of failure of the implant. In this study, for the first time, we have performed a systematic analysis of the response of differentially activated human macrophages (M(Control), M(IFNγ) and M(IL-4)) to the polished and porous titanium surfaces in order to identify the detrimental effect of titanium leading to the tissue destruction and chronic inflammation. Transcriptome analysis revealed that the highest number of differences between titanium and control settings are found in M(IL-4) that model healing type of macrophages. RT-qPCR analysis confirmed that both polished and porous titanium affected expression of cytokines, chitinases/chitinase-like proteins and matrix metalloproteinases. Titanium-induced release and activation of MMP7 by macrophages was enhanced by fibroblasts in both juxtacrine and paracrine cell interaction models. Production of titanium-induced MMPs and cytokines associated with chronic inflammation were independent of the presence of Staphylococcus aureus. MMP7, one of the most pronounced tissue-destroying factor and chitinase-like protein YKL-40 were expressed in CD68+ macrophages in peri-implant tissues of patients with orthopedic implants. In summary, we demonstrated that titanium induces pro-inflammatory and tissue-destructing responses mainly in healing macrophages, and the detrimental effects of titanium surfaces on implant-adjacent macrophages are independent on the bacterial contamination.

Hyperglycemia Induces Inflammatory Response of Human Macrophages to CD163-Mediated Scavenging of Hemoglobin-Haptoglobin Complexes.

Hyperglycemia, a hallmark of diabetes, can induce inflammatory programming of macrophages. The macrophage scavenger receptor CD163 internalizes and degrades hemoglobin-haptoglobin (Hb-Hp) complexes built due to intravascular hemolysis. Clinical studies have demonstrated a correlation between impaired scavenging of Hb-Hp complexes via CD163 and diabetic vascular complications. Our aim was to identify whether hyperglycemia is able to amplify inflammation via Hb-Hp complex interactions with the immune system. M(IFNγ), M(IL-4), and control M0 macrophages were differentiated out of primary human monocytes in normo- (5 mM) and hyperglycemic (25 mM) conditions. CD163 gene expression was decreased 5.53 times in M(IFNγ) with a further decrease of 1.99 times in hyperglycemia. Hyperglycemia suppressed CD163 surface expression in M(IFNγ) (1.43 times). Flow cytometry demonstrated no impairment of Hb-Hp uptake in hyperglycemia. However, hyperglycemia induced an inflammatory response of M(IFNγ) to Hb-Hp1-1 and Hb-Hp2-2 uptake with different dynamics. Hb-Hp1-1 uptake stimulated IL-6 release (3.03 times) after 6 h but suppressed secretion (5.78 times) after 24 h. Contrarily, Hb-Hp2-2 uptake did not affect IL-6 release after 6h but increased secretion after 24 h (3.06 times). Our data show that hyperglycemia induces an inflammatory response of innate immune cells to Hb-Hp1-1 and Hb-Hp2-2 uptake, converting the silent Hb-Hp complex clearance that prevents vascular damage into an inflammatory process, hereby increasing the susceptibility of diabetic patients to vascular complications.

Stabilin-1 mediates beneficial monocyte recruitment and tolerogenic macrophage programming during CVB3-induced viral myocarditis.

Pathological innate and adaptive immune response upon viral infection may lead to cardiac injury and dysfunction. Stabilin-1 is a scavenger receptor that regulates several aspects of the innate immunity. Whether stabilin-1 affects the inflammatory response during viral myocarditis (VM) is entirely unknown. Here, we assess the role of stabilin-1 in the pathogenesis of VM and its suitability as a therapeutic target. Genetic loss of stabilin-1 increased mortality and cardiac necrosis in a mouse model of human Coxsackievirus B3 (CVB3)-induced myocarditis. Absence of stabilin-1 significantly reduced monocyte recruitment and strongly reduced the number of alternatively activated anti-inflammatory macrophages in the heart, enhancing a pro-inflammatory cardiac niche with a detrimental T lymphocyte response during VM. Yeast two-hybrid screening, confirmed by affinity chromatography, identified fibronectin as a stabilin-1 interacting partner. Absence of stabilin-1 specifically decreased monocyte adhesion on extracellular fibronectin in vitro. Loss of Type III repeats Extra Domain A (EDA) of fibronectin during VM also increased the mortality and cardiac necrosis as in stabilin-1 knockout mice, with reduced monocytic cardiac recruitment and increased T lymphocyte response. Collectively, stabilin-1 has an immune-suppressive role of limiting myocardial damage during VM, regulating anti-inflammatory monocyte-recruitment to the site of inflammation.

Titanium Nanoparticles Enhance Production and Suppress Stabilin-1-Mediated Clearance of GDF-15 in Human Primary Macrophages.

Macrophages are key innate immune cells that mediate implant acceptance or rejection. Titanium implants degrade over time inside the body, which results in the release of implant wear-off particles. Titanium nanoparticles (TiNPs) favor pro-inflammatory macrophage polarization (M1) and lower tolerogenic activation (M2). GDF-15 regulates immune tolerance and fibrosis and is endocytosed by stabilin-1. How TiNPs affect the healing activities of macrophages and their release of circulating cytokines is an open question in regenerative medicine. In this study for the first time, we identified the transcriptional program induced and suppressed by TiNPs in human pro-inflammatory and healing macrophages. Microarray analysis revealed that TiNPs altered the expression of 5098 genes in M1 (IFN-γ-stimulated) and 4380 genes in M2 (IL-4-stimulated) macrophages. 1980 genes were differentially regulated in both M1 and M2. Affymetrix analysis, confirmed by RT-PCR, demonstrated that TiNPs upregulate expression of GDF-15 and suppress stabilin-1, scavenger receptor of GDF-15. TiNPs also significantly stimulated GDF-15 protein secretion in inflammatory and healing macrophages. Flow cytometry demonstrated, that scavenging activity of stabilin-1 was significantly suppressed by TiNPs. Confocal microscopy analysis showed that TiNPs impair internalization of stabilin-1 ligand acLDL and its transport to the endocytic pathway. Our data demonstrate that TiNPs have a dual effect on the GDF-15/stabilin-1 interaction in macrophage system, by increasing the production of GDF-15 and suppressing stabilin-1-mediated clearance function. In summary, this process can result in a significant increase of GDF-15 in the extracellular space and in circulation leading to unbalanced pro-fibrotic reactions and implant complications.

SI-CLP inhibits the growth of mouse mammary adenocarcinoma by preventing recruitment of tumor-associated macrophages.

Chitinase-like proteins (CLP) are chitin-binding proteins that lack chitin hydrolyzing activity, but possess cytokine-like and growth factor-like properties, and play crucial role in intercellular crosstalk. Both human and mice express two members of CLP family: YKL-40 and stabilin-1 interacting chitinase-like protein (SI-CLP). Despite numerous reports indicating the role of YKL-40 in the support of angiogenesis, tumor cell proliferation, invasion and metastasis, the role of its structurally related protein SI-CLP in cancer was not reported. Using gain-of-function approach, we demonstrate in the current study that the expression of recombinant SI-CLP in mouse TS/A mammary adenocarcinoma cells results in significant and persistent inhibition of in vivo tumor growth. Using quantitative immunohistochemistry, we show that on the cellular level this phenomenon is associated with reduced infiltration of tumor-associated macrophages (TAMs), CD4+ and FoxP3+ cells in SI-CLP expressing tumors. Gene expression analysis in TAM isolated from SI-CLP-expressing and control tumors demonstrated that SI-CLP does not affect macrophage phenotype. However, SI-CLP significantly inhibited migration of murine bone-marrow derived macrophages and human primary monocytes toward monocyte-recruiting chemokine CCL2 produced in the tumor microenvironment (TME). Mechanistically, SI-CLP did not affect CCL2/CCR2 interaction, but suppressed cytoskeletal rearrangements in response to CCL2. Altogether, our data indicate that SI-CLP functions as a tumor growth inhibitor in mouse breast cancer by altering cellular composition of TME and blocking cytokine-induced TAM recruitment. Taking into consideration weak to absent expression of SI-CLP in human breast cancer, it can be considered as a therapeutic protein to block TAM-mediated support of breast tumor growth.

Generation of anti-inflammatory macrophages for implants and regenerative medicine using self-standing release systems with a phenotype-fixing cytokine cocktail formulation.

The immediate tissue microenvironment of implanted biomedical devices and engineered tissues is highly influential on their long term fate and efficacy. The creation of a long-term anti-inflammatory microenvironment around implants and artificial tissues can facilitate their integration. Macrophages are highly plastic cells that define the tissue reactions on the implanted material. Local control of macrophage phenotype by long-term fixation of their healing activities and suppression of inflammatory reactions are required to improve implant acceptance. Herein, we describe the development of a cytokine cocktail (M2Ct) that induces stable M2-like macrophage phenotype with significantly decreased pro-inflammatory cytokine and increased anti-inflammatory cytokine secretion profile. The positive effect of the M2Ct was shown in an in vitro wound healing model; where M2Ct facilitated wound closure by human fibroblasts in co-culture conditions. Using a model for induction of inflammation by LPS we have shown that the M2Ct phenotype is stable for 12days. However, in the absence of M2Ct in the medium macrophages underwent rapid pro-inflammatory re-programming upon IFNg stimulation. Therefore, loading and release of the cytokine cocktail from a self-standing, transferable gelatin/tyraminated hyaluronic acid based release system was developed to stabilize macrophage phenotype for in vivo applications in implantation and tissue engineering. The M2Ct cytokine cocktail retained its anti-inflammatory activity in controlled release conditions. Our data indicate that the direct application of a potent M2 inducing cytokine cocktail in a transferable release system can significantly improve the long term functionality of biomedical devices by decreasing pro-inflammatory cytokine secretion and increasing the rate of wound healing. STATEMENT OF SIGNIFICANCE: Uncontrollable activation of macrophages in the microenvironment of implants and engineered tissues is a significant problem leading to poor integration of implants and artificial tissues. In the current manuscript we demonstrate that self-standing, transferable gelatin/tyraminated hyaluronic acid based thin films are perspective tools for controlled release of anti-inflammatory cytokine combinations and can be used to down-modulate macrophage activation on implant surfaces. We also show that optimized cytokine cocktail consisting of IL4/IL10/TGFß1 (M2Ct) induces long-term anti-inflammatory and pro-healing phenotype in human primary monocyte-derived macrophages. This cocktail formulation could be loaded on gelatin/tyraminated films and promoted favorable M2-like macrophage phenotype with low responsiveness to pro-inflammatory stimuli. Such self-standing release systems can be used for prolonged local control of macrophage phenotype upon implantation.

Hyperglycemia induces mixed M1/M2 cytokine profile in primary human monocyte-derived macrophages.

Hyperglycaemia is a key factor in diabetic pathology. Macrophages are essential regulators of inflammation which can be classified into two major vectors of polarisation: classically activated macrophages (M1) and alternatively activated macrophages (M2). Both types of macrophages play a role in diabetes, where M1 and M2-produced cytokines can have detrimental effects in development of diabetes-associated inflammation and diabetic vascular complications. However, the effect of hyperglycaemia on differentiation and programming of primary human macrophages was not systematically studied. We established a unique model to assess the influence of hyperglycaemia on M1 and M2 differentiation based on primary human monocyte-derived macrophages. The effects of hyperglycaemia on the gene expression and secretion of prototype M1 cytokines TNF-alpha and IL-1beta, and prototype M2 cytokines IL-1Ra and CCL18 were quantified by RT-PCR and ELISA. Hyperglycaemia stimulated production of TNF-alpha, IL-1beta and IL-1Ra during macrophage differentiation. The effect of hyperglycaemia on TNF-alpha was acute, while the stimulating effect on IL-1beta and IL-1Ra was constitutive. Expression of CCL18 was supressed in M2 macrophages by hyperglycaemia. However the secreted levels remained to be biologically significant. Our data indicate that hyperglycaemia itself, without additional metabolic factors induces mixed M1/M2 cytokine profile that can support of diabetes-associated inflammation and development of vascular complications.

Stabilin-1 is expressed in human breast cancer and supports tumor growth in mammary adenocarcinoma mouse model.

Stabilin-1 is a multifunctional scavenger receptor expressed on alternatively-activated macrophages. Stabilin-1 mediates phagocytosis of "unwanted-self" components, intracellular sorting, and endocytic clearance of extracellular ligands including SPARC that modulates breast cancer growth. The expression of stabilin-1 was found on tumor-associated macrophages (TAM) in mouse and human cancers including melanoma, lymphoma, glioblastoma, and pancreatic insulinoma. Despite its tumor-promoting role in mouse models of melanoma and lymphoma the expression and functional role of stabilin-1 in breast cancer was unknown. Here, we demonstrate that stabilin-1 is expressed on TAM in human breast cancer, and its expression is most pronounced on stage I disease. Using stabilin-1 knockout (ko) mice we show that stabilin-1 facilitates growth of mouse TS/A mammary adenocarcinoma. Endocytosis assay on stabilin-1 ko TAM demonstrated impaired clearance of stabilin-1 ligands including SPARC that was capable of inducing cell death in TS/A cells. Affymetrix microarray analysis on purified TAM and reporter assays in stabilin-1 expressing cell lines demonstrated no influence of stabilin-1 expression on intracellular signalling. Our results suggest stabilin-1 mediated silent clearance of extracellular tumor growth-inhibiting factors (e.g. SPARC) as a mechanism of stabilin-1 induced tumor growth. Silent clearance function of stabilin-1 makes it an attractive candidate for delivery of immunomodulatory anti-cancer therapeutic drugs to TAM.

A novel GGA-binding site is required for intracellular sorting mediated by stabilin-1.

Stabilin-1 is a unique scavenger receptor that combines endocytic and intracellular sorting functions in macrophages. Stabilin-1 mediates the endocytosis of acetylated low-density lipoprotein (acLDL), SPARC, and growth hormone family member placental lactogen (PL). At the same time, stabilin-1 is involved in trans-Golgi network-to-endosome routing of the endogenous chitinase-like protein SI-CLP (stabilin-interacting chitinase-like protein). A DDSLL motif in the cytoplasmic tail of stabilin-1 interacts with GGA adaptors; however, the deletion of DDSLL reduces but does not abrogate this interaction. Here, we identified a novel GGA-binding site, EDDADDD, in the cytoplasmic tail of stabilin-1. The deletion of EDDADDD impaired and the deletion of both the DDSLL and EDDADDD sites abrogated the interaction of stabilin-1 with GGAs. The surface exposure of stabilin-1 and stabilin-1-mediated endocytosis of acLDL, SPARC, and PL were not affected by the deletion either of DDSLL or EDDADDD or both. At the same time, both GGA-binding sites were necessary for the intracellular sorting of SI-CLP performed by stabilin-1. Our data indicate that the novel GGA-binding site EDDADDD is essential for stabilin-1-mediated intracellular sorting but is not required for endocytosis.

Alternatively activated macrophages regulate extracellular levels of the hormone placental lactogen via receptor-mediated uptake and transcytosis.

Alternatively activated (M2) macrophages regulate immune responses and tissue remodelling. In many tissues including placenta, M2 express stabilin-1, a multidomain protein that exerts a dual role as a scavenger receptor for acetylated low density lipoprotein (acLDL) and SPARC (secreted protein acidic and rich in cysteine) and as an intracellular cargo carrier for SI-CLP. Using yeast two-hybrid screening, we identified the developmental hormone placental lactogen (PL) as a novel ligand of stabilin-1. In Chinese hamster ovary-stabilin-1 cells and M2, FACS and confocal microscopy demonstrated that stabilin-1 mediates internalization and endosomal sorting of PL. In M2 macrophages, PL was partially degraded in lysosomes; part of PL escaped degradation and was delivered to novel PL+ storage vesicles lacking endosomal/lysosomal markers. During formation, PL+ vesicles underwent transient interaction with the trans-Golgi network (TGN). Upon placement of PL-loaded M2 into PL-free medium, PL was secreted into the supernatant. Leupeptin, an inhibitor of lysosomal hydrolases, reduced PL degradation, enhanced sorting of PL into the TGN/storage vesicle pathway and increased PL secretion. Thus, processing of PL in M2 macrophages occurs either by the classical lysosomal pathway or by a novel TGN-associated trans-secretory pathway. Macrophages isolated from human placental villi efficiently endocytosed PL-FITC and transported it to the storage vesicles. Our data show that extracellular PL levels are determined by uptake, degradation, storage, and release in M2. During pregnancy PL concentration reaches 10 microg/ml in maternal circulation and stays below 0.5 microg/ml in fetal circulation. We propose that stabilin-1-positive macrophages determine the difference in PL levels between maternal and fetal circulation.

Expression of Osteoarthritis Marker YKL-39 is Stimulated by Transforming Growth Factor Beta (TGF-beta) and IL-4 in Differentiating Macrophages.

YKL-39 is a Glyco_18 domain containing chitinase-like protein which is currently recognized as a biomarker for the activation of chondrocytes and the progress of the osteoarthritis in human. YKL-39 was identified as an abundantly secreted protein in primary culture of human articular chondrocytes. Two biological activities of YKL-39 might contribute to the disease progression. One is the induction of autoimmune response and second is the participation in tissue remodeling. Other mammalian chitinase-like proteins including chitotriosidase, SI-CLP, YKL-40 and YM1 are expressed by macrophages in various pathological conditions. In contrast, YKL-39 was never reported to be produced by macrophages. We used in vitro model of human monocyte-derived macrophage differentiation to analyse regulation of YKL-39 expression. Expression of YKL-39 was examined by real-time RT-PCR. CD14+ MACS sorted human monocytes differentiated for 6 days under different stimulations including IFNgamma, IL-4, dexamethasone and TGF-beta. We found that both IL-4 and TGF-beta have weak stimulatory effect on YKL-39 expression in all donors tested (3.2 +/- 1.7 fold, p = 0.006 and 6.3 +/- 3.1 fold, p = 0.014 respectively). However the combination of IL-4 and TGF-beta had strong stimulatory effect on the expression of YKL-39 in all analysed individual macrophage cultures (34 +/- 36 fold, p = 0.05). IFN-gamma did not show statistically significant effect of YKL-39 mRNA expression. Presence of dexamethasone almost completely abolished the stimulatory effects of IL-4 and TGF-beta. In summary, we show here for the first time, that human cells of monocyte origin are able to produce YKL-39. Maturation of monocyte derived macrophages in the presence of Th2 cytokine IL-4 and TGF-beta leads to the strong activation of YKL-39 expression. Thus elevated levels of YKL-39 observed during chronic inflammations can not be attributed solely to the activity of chondrocytes. In perspective, YKL-39 might serve as a useful biomarker to detect macrophage-specific response in pathologies like tumour, atherosclerosis and Alzheimer disease.

Novel stabilin-1 interacting chitinase-like protein (SI-CLP) is up-regulated in alternatively activated macrophages and secreted via lysosomal pathway.

Mammalian Glyco_18-domain-containing proteins include catalytically active chitinases and chitinase-like proteins with cytokine activity involved in host defense and Th2-type inflammatory reactions. Here, we describe a novel human Glyco_18-domain-containing protein, SI-CLP, as an interacting partner of the endocytic/sorting receptor stabilin-1. Similarly to the chitinase-like cytokines YKL-39, YKL-40, and YM1/2, SI-CLP lacks a chitin-binding domain and catalytic amino acids. Using a novel mAb 1C11, we demonstrated that SI-CLP is sorted into late endosomes and secretory lysosomes in human alternatively activated macrophages. The direct interaction of SI-CLP with stabilin-1, their colocalization in the trans-Golgi network, and the reduced sorting of SI-CLP into lysosomes in macrophages treated with stabilin-1 siRNA suggest that stabilin-1 is involved in intracellular sorting of SI-CLP. Expression of SI-CLP in macrophages was strongly up-regulated by the Th2 cytokine IL-4 and by dexamethasone. This effect was suppressed by IFNgamma but not affected by IL-10. In contrast, expression of YKL-40 was induced by IFNgamma and suppressed by dexamethasone. Macrophages treated with IL-4 secreted SI-CLP, while costimulation with dexamethasone blocked secretion and resulted in intracellular accumulation of SI-CLP. The 1C11 mAb detected SI-CLP in human bronchoalveolar lavage and peripheral-blood leukocytes (PBLs), and can be used to analyze the role of SI-CLP in human disorders.