Regulation of macrophage and dendritic cell function by pathogens and through immunomodulation in the avian mucosa

Macrophages (MPh) and dendritic cells (DC) are members of the mononuclear phagocyte system. In chickens, markers to distinguish MPh from DC are lacking, but whether MPh and DC can be distinguished in humans and mice is under debate, despite the availability of numerous markers. Mucosal MPh and DC are strategically located to ingest foreign antigens, suggesting they can rapidly respond to invading pathogens. This review addresses our current understanding of DC and MPh function, the receptors expressed by MPh and DC involved in pathogen recognition, and the responses of DC and MPh against respiratory and intestinal pathogens in the chicken. Furthermore, potential opportunities are described to modulate MPh and DC responses to enhance disease resistance, highlighting modulation through nutraceuticals and vaccination.

Development and characterization of sulfasalazine loaded fucosylated PPI dendrimer for the treatment of cytokine-induced liver damage

The present investigation was aimed at exploring the targeting potential of sulfasalazine (NF-κB inhibitor drug) loaded fucose tethered poly (propylene imine) (PPI) dendritic nanoarchitecture (SSZ-FUCO-PPID) to Kupffer cells for effective management of cytokine-induced liver damage. The SSZ-FUCO-PPID formulation was characterized for entrapment efficiency, in vitro release, stability, toxicological investigations, macrophage uptake, NF-κB inhibition, and in vivo studies. In cell uptake assay the uptake of SSZ-FUCO-PPID was found to be higher and preferentially by J774 macrophage cell line. Cytokine assay suggested that the SSZ-FUCO-PPID potentially inhibited the IL-12 p40 production in LPS activated macrophages. Western blot analysis clearly suggested that SSZ-FUCO-PPID inhibited the activation of NF-κB as indicated by the absence of p-IκB band. Pharmacokinetic study revealed improved bioavailability, half-life and mean residence time of SSZ upon fucosylation of dendrimers. The biodistribution pattern clearly established the higher amount of SSZ-FUCO-PPID in liver. Hematological data suggest that the fucosylated formulations are less immunogenic as compared to unconjugated formulations. The results suggest that the SSZ-FUCO-PPID formulation holds targeting potential to Kupffer cells for the treatment of cytokine-induced liver damage.

Inhibition of spleen tyrosine kinase as treatment of postoperative ileus

OBJECTIVE

Intestinal inflammation resulting from manipulation-induced mast cell activation is a crucial mechanism in the pathophysiology of postoperative ileus (POI). Recently it has been shown that spleen tyrosine kinase (Syk) is involved in mast cell degranulation. Therefore, we have evaluated the effect of the Syk-inhibitor GSK compound 143 (GSK143) as potential treatment to shorten POI.

DESIGN

In vivo: in a mouse model of POI, the effect of the Syk inhibitor (GSK143) was evaluated on gastrointestinal transit, muscular inflammation and cytokine production. In vitro: the effect of GSK143 and doxantrazole were evaluated on cultured peritoneal mast cells (PMCs) and bone marrow derived macrophages.

RESULTS

In vivo: intestinal manipulation resulted in a delay in gastrointestinal transit at t=24 h (Geometric Center (GC): 4.4 ± 0.3). Doxantrazole and GSK143 significantly increased gastrointestinal transit (GC doxantrazole (10 mg/kg): 7.2 ± 0.7; GSK143 (1 mg/kg): 7.6 ± 0.6), reduced inflammation and prevented recruitment of immune cells in the intestinal muscularis. In vitro: in PMCs, substance P (0-90 μM) and trinitrophenyl (0-4 μg/ml) induced a concentration-dependent release of β-hexosaminidase. Pretreatment with doxantrazole and GSK143 (0.03-10 μM) concentration dependently blocked substance P and trinitrophenyl induced β-hexosaminidase release. In addition, GSK143 was able to reduce cytokine expression in endotoxin-treated bone marrow derived macrophages in a concentration-dependent manner.

CONCLUSIONS

The Syk inhibitor GSK143 reduces macrophage activation and mast cell degranulation in vitro. In addition, it inhibits manipulation-induced intestinal muscular inflammation and restores intestinal transit in mice. These findings suggest that Syk inhibition may be a new tool to shorten POI.

Inflammasome activation by altered proteostasis

The association between altered proteostasis and inflammatory disorders has been increasingly recognized, but the underlying mechanisms are not well understood. In this study, we show that deficiency of either autophagy or sequestosome 1 (p62 or SQSTM) led to inflammasome hyperactivation in response to LPS and ATP in primary macrophages and in mice in vivo. Importantly, induction of protein misfolding by puromycin, thapsigargin, or geldanamycin resulted in inflammasome activation that was more pronounced in autophagy- or p62-deficient macrophages. Accumulation of misfolded proteins caused inflammasome activation by inducing generation of nonmitochondrial reactive oxygen species and lysosomal damage, leading to release of cathepsin B. Our results suggest that altered proteostasis results in inflammasome activation and thus provide mechanisms for the association of altered proteostasis with inflammatory disorders.

The effect of particle agglomeration on the formation of a surface-connected compartment induced by hydroxyapatite nanoparticles in human monocyte-derived macrophages

Agglomeration dramatically affects many aspects of nanoparticle–cell interactions. Here we show that hydroxyapatite nanoparticles formed large agglomerates in biological medium resulting in extensive particle uptake and dose-dependent cytotoxicity in human macrophages. Particle citration and/or the addition of the dispersant Darvan 7 dramatically reduced mean agglomerate sizes, the amount of particle uptake and concomitantly cytotoxicity. More surprisingly, agglomeration governed the mode of particle uptake. Agglomerates were sequestered within an extensive, interconnected membrane labyrinth open to the extracellular space. In spite of not being truly intracellular, imaging studies suggest particle degradation occurred within this surface-connected compartment (SCC). Agglomerate dispersion prevented the SCC from forming, but did not completely inhibit nanoparticle uptake by other mechanisms. The results of this study could be relevant to understanding particle–cell interactions during developmental mineral deposition, in ectopic calcification in disease, and during application of hydroxyapatite nanoparticle vectors in biomedicine.

Regulation of the HIF-system in human macrophages--differential regulation of HIF-α subunits under sustained hypoxia

Macrophages are often associated to pathophysiological processes and were found at hypoxic areas. However, cell adaption greatly depends on hypoxia-inducible factors (HIF). Activation of these transcription factors is induced by heterodimerization of an α-(HIF-1α, -2α, -3α) and HIF-1β subunit. The main regulatory pathway is represented by α-subunit stability. Beside, little is known about the exact mechanisms of fine-tuning in Hif-regulation. The present study characterizes the hypoxia-induced regulation of HIF-1α and -2α in human macrophages. The hypoxic increase of both subunits is initially mediated by protein stabilization. Sustained hypoxia caused a distinct regulation of HIF-1α and -2α. The striking increase of HIF-2α protein expression was contrasted by a dramatic decrease of HIF-1α. The long-term downregulation of HIF-1α is due to downregulation of its mRNA. This decrease was accompanied by increased expression of ahif, a natural cis-antisense transcript of HIF-1α. The ahif-transcript was strongly inducible by hypoxia and rapidly degraded under reoxygenation. Using an adenoviral overexpression and siRNA silencing approach revealed that the targeted regulation of ahif is mediated by the HIF-system itself. Furthermore it could be shown that ahif indeed is able to modulate the hypoxic expression of HIF-1α and influences the expression of the HIF-target gene Enolase-2. Taken together, this study characterizes a new regulation process of the HIF-transcription factor-system in human macrophages under hypoxia. For the first time evidence is provided that ahif is regulated by the HIF-system and influences HIF-1α expression in primary human macrophages.

Kocuran, an exopolysaccharide isolated from Kocuria rosea strain BS-1 and evaluation of its in vitro immunosuppression activities

In an ongoing survey for bioactive potential of microorganisms from different biosphere zones of India, a promising Kocuria rosea strain BS-1 was identified which produced an exopolysaccharide (designated as Kocuran) exhibiting in vitro antioxidant and immunosuppression properties. Kocuran was characterized as a heteropolysaccharide with repeating monosaccharide residues of glucose, galactose, mannose and glucuronic acid with an average molecular mass of 51.2 kDa. In RAW 264.7 macrophages, Kocuran significantly downregulated the LPS-stimulated ROS, NO, TNF-α, IL-6 and C3 complement component secretion to 4.71±0.08%, 4.11±0.06%, 11.19±0.06 pg ml⁻¹, 9.12±0.07 pg ml⁻¹ and 20.81±0.06 ng/10⁶ cells ml⁻¹, respectively. Furthermore, it inhibited the PHA-stimulated proliferation of human peripheral blood mononuclear cells with IC₅₀ of 100.13±2.1 μg ml⁻¹. In addition, the classical and alternative pathway mediated hemolysis was also inhibited with CH₅₀ and AH₅₀ of 100.96±1.75 and 98.60±1.93 μg ml⁻¹, respectively. Kocuran did not inhibit the LPS-induced LAL enzyme and the binding of FITC-LPS to macrophages suggesting that Kocuran does not neutralize the LPS activity. These results demonstrate the in vitro suppression of activation and macrophage-derived inflammatory cytokines and complement mediated hemolysis indicating its in vitro immunosuppression activity.

Escherichia coli K1 induces pterin production for enhanced expression of Fcγ receptor I to invade RAW 264.7 macrophages

Macrophages serve as permissive niches for Escherichia coli (E. coli) K1 to attain high grade bacteremia in the pathogenesis of meningitis in neonates. Although pterin levels are a diagnostic marker for immune activation, the role of macrophages in pterin production and in the establishment of meningitis is unknown. Here, we demonstrate that macrophages infected with E. coli K1 produce both neopterin and biopterin through increased expression of GTP-cyclohydrolase 1 (GCH1). Of note, increased production of biopterin enhances the expression of Fc-gamma receptor I (CD64), which in turn, aided the entry of E. coli K1 in macrophages while increased neopterin suppresses reactive oxygen species (ROS), thereby aiding bacterial survival. Inhibition of GCH1 by 2, 4-Diamino-6-hydroxypyrimidine (DAHP) prevented the E. coli K1 induced expression of CD64 in macrophages in vitro and the development of bacteremia in a newborn mouse model of meningitis. These studies suggest that targeting GCH1 could be therapeutic strategy for preventing neonatal meningitis by E. coli K1.

miR-125a-5p regulates differential activation of macrophages and inflammation

Macrophage activation is a central event in immune responses. Macrophages undergoing classical activation (M1 macrophages) are proinflammatory, whereas alternatively activated macrophages (M2 macrophages) are generally anti-inflammatory. miRNAs play important regulatory roles in inflammatory response. However, the manner in which miRNAs regulate macrophage activation in response to different environmental cues has not been well defined. In this study, we found that M-BMM macrophages (M2) express greater levels of miR-125a-5p than do GM-BMM macrophages (M1). Stimulation of macrophages through TLR2 and TLR4 but not through TLR3 enhanced miR-125a-5p expression. Up-regulation of miR-125a-5p after TLR2/4 activation requires the adaptor MYD88 but not TRIF. Overexpression of miR-125a-5p diminished M1 phenotype expression induced by LPS but promoted M2 marker expression induced by IL-4. In contrast, knockdown of miR-125a-5p promoted M1 polarization and diminished IL-4-induced M2 marker expression. We found that miR-125a-5p targets KLF13, a transcriptional factor that has an important role in T lymphocyte activation and inflammation. KLF13 knockdown had similar effects on M1 activation as did miR-125a-5p overexpression. In addition, miR-125a-5p regulates phagocytic and bactericidal activities of macrophages. Our data suggest that miR-125a-5p has an important role in suppressing classical activation of macrophages while promoting alternative activation.

In alcoholic hepatitis the macrophages are M1 and M2

Background

Liver cell injury in alcoholic hepatitis (AH) is in part, due to macrophage generated proinflammatory cytokines i.e., M1, M2a, M2b, and M2c might be involved in ALD. The T cell response to chemokines and cytokines differs not only when M1 and M2 macrophages are compared but even when individual M2 subtypes are profiled.

Purpose

In AH, M1 monocytes in the blood show increased sensitivity in the TNF-α response to LPS. Immunohistochemistry (IHC) studies showed that the liver sinusoids in ALD are abundantly populated by CD163 expressing type 2 macrophages. In this report, we profile many of the molecules associated with M1 and M2 macrophages in livers with AH using IHC.

Methods

Using immunofluorescent antibody-labeling, we profiled the receptors, cytokines and chemokines observed in M1, M2a, M2b, and M2c macrophages in liver biopsies from patients with AH.

Results

The increased CD 163 expression found in previous studies was confirmed as well an additional macrophage phenotypic marker CD206, suggesting that AH pathogenesis at least partially involves M2a and M2c macrophages. TGF-β was found to be robustly over expressed by liver sinusoidal macrophages. Macrophage expression of the phenotypic markers TLR-2, TLR-4 and TLR-8 – found in both M1 and M2 macrophages – as well as the chemokines CCL-1 and CCL-18 was found. However, IRF-4, which is related to IL-4 production and M2a polarization as well as the cytokines CCL-1 and Il-1β and the chemokine CXCL-1 were also observed, suggesting that M2a and M2b also play a role in AH pathogenesis.

Conclusion

Livers with AH show robust macrophage over expression of TGF-β, a growth factor more commonly associated with M2 type macrophages and mostly known for its fibrogenetic properties. However, our immunoprofiling of macrophage over expression also shows that AH is driven by receptors, interferons, and cytokines that are commonly associated not just with M2 macrophages, but with M1 as well. Thus, a complex interplay between different types of macrophages expressing a diverse array of molecules and receptors is involved in AH.

IRF3 helps control acute TMEV infection through IL-6 expression but contributes to acute hippocampus damage following TMEV infection

IRF3 is an innate anti-viral factor whose role in limiting Theiler's murine encephalomyelitis virus (TMEV) infection and preventing TMEV-induced disease is unclear. Acute disease and innate immune responses of macrophages were examined in IRF3 knockout mice compared with C57Bl/6 mice following in vitro or intracranial infection with either TMEV GDVII or DA. IRF3 deficiency augmented viral infection, as well as morbidity and mortality following intracranial infection with neurovirulent TMEV GDVII. In contrast, IRF3 deficiency prevented hippocampal injury following intracranial infection with persistent TMEV DA. The extent of TMEV infection in macrophages from C57Bl/6 mice was significantly less than that in IRF3 deficient macrophages, which was associated with poor IFN-β and IL-6 expression in response to TMEV. Reestablishing IRF3 expression in IRF3 deficient macrophages increased control of TMEV replication and increased expression of IFN-β and IL-6. In addition, IRF3 deficient macrophages failed to exhibit IL-6 antiviral effects, which was associated with inability to sustain IL-6-induced STAT1 activation compared with C57BL/6 macrophages. Altogether, IRF3 contributes to early control of TMEV replication through induction of IL-6 and IFN-β and support of IL-6 antiviral effects, but contributes to TMEV-induced hippocampal injury.

Cucurbitacin D is a new inflammasome activator in macrophages

We previously reported that cucurbitacin D isolated from Trichosanthes kirilowii has anti-tumor roles to leukemia cells. However, the effect of cucurbitacin D on immune cells is not fully understood although there is no toxic activity to normal cells. In this study, immunomodulating activities of cucurbitacin D were investigated in macrophages. Cucurbitacin D could increase LPS-induced interleukin (IL)-1β production in culture supernatant of THP-1 cells, peritoneal exudate cells (PECs), bone marrow derived macrophages (BMDMs), and RAW264 cells. At the transcriptional level, cucurbitacin D enhanced LPS-induced IL-1β mRNA expression through activation of ERK1/2 mitogen-activated protein kinases (MAPKs). At the posttranscriptional level, the activation of caspase-1 induced by cucurbitacin D has also been demonstrated following treatment with a caspase-1 inhibitor and siRNA. Importantly, cucurbitacin D has further been shown to induce inflammasome activation independent of ERK1/2 activation. Western blotting showed interaction of NOD-like receptor family, pyrin domain containing 3 (NALP3) and apoptosis-associated speck-like protein containing a caspase-activating and recruitment domain (ASC), suggesting activation of the inflammasome and a possible reason for activation of caspase-1. Taken together, these results suggest that cucurbitacin D could initiate immunomodulating activity in macrophages to lead to inflammasome activation as well as enhancement of LPS signaling.

Enhancement of bone regeneration by dual release of a macrophage recruitment agent and platelet-rich plasma from gelatin hydrogels

Macrophages play an important role in regulating inflammatory responses and tissue regeneration. In the present study, their effect on bone remodeling is investigated by the simultaneous application of a macrophage recruiting agent, SEW2871 of a sphingosine-1 phosphate agonist, and platelet-rich plasma (PRP). The non-water soluble SEW2871 was solubilized in water through micelles formation with l-lactic acid grafted gelatin, and the resulting micelles with PRP were incorporated into gelatin hydrogels. Mixed SEW2871-micelles and PRP were released from gelatin hydrogels in a controlled fashion both in vitro and in vivo. In vitro migration assay revealed that the presence of PRP synergistically promoted SEW2871-induced macrophages migration. When applied to a bone defect of rats, the hydrogels incorporating mixed SEW2871-micelles and PRP recruited a higher number of macrophages than those hydrogels incorporating either SEW2871-micelles or PRP. The hydrogels incorporating mixed SEW2871-micelles and PRP enhanced the level of tumor necrosis factor (TNF)-α of pro-inflammatory cytokine, 3 days after application, while pro-inflammatory responses coupled with a significant increase in the expression level of osteoprotegerin (OPG) and interleukin (IL)-10 and transforming growth factor (TGF)-β1 of anti-inflammatory cytokine were observed 10 days postoperatively. The hydrogels incorporating mixed SEW2871-micelles and PRP promoted bone regeneration to a significant great extent compared with those incorporating PBS and either SEW2871-micelles or PRP. It is concluded that macrophages recruitment contributed to PRP-induced bone regeneration.

Drosophila pupal macrophages--a versatile tool for combined ex vivo and in vivo imaging of actin dynamics at high resolution

Molecular understanding of actin dynamics requires a genetically traceable model system that allows live cell imaging together with high-resolution microscopy techniques. Here, we used Drosophila pupal macrophages that combine many advantages of cultured cells with a genetic in vivo model system. Using structured illumination microscopy together with advanced spinning disk confocal microscopy we show that these cells provide a powerful system for single gene analysis. It allows forward genetic screens to characterize the regulatory network controlling cell shape and directed cell migration in a physiological context. We knocked down components regulating lamellipodia formation, including WAVE, single subunits of Arp2/3 complex and CPA, one of the two capping protein subunits and demonstrate the advantages of this model system by imaging mutant macrophages ex vivo as well as in vivo upon laser-induced wounding.

Identification of a receptor for neuropeptide VGF and its role in neuropathic pain

VGF (nonacronymic) is a neuropeptide precursor that plays multiple roles in regulation of energy balance, reproduction, hippocampal synaptic plasticity, and pain. Data from a number of pain models showed significant up-regulation of VGF in sensory neurons. TLQP-21, one of the VGF-derived neuropeptides, has been shown to induce a hyperalgesic response when injected subcutaneously into the hind paw of mice. However, the precise role of VGF-derived neuropeptides in neuropathic pain and the molecular identity of the receptor for VGF-derived peptides are yet to be investigated. Here we identified gC1qR, the globular heads of the C1q receptor, as the receptor for TLQP-21 using chemical cross-linking combined with mass spectrometry analysis. TLQP-21 caused an increase in intracellular Ca²⁺ levels in rat macrophages and microglia. Inoculation of TLQP-21-stimulated macrophages into rat hind paw caused mechanical hypersensitivity. The increase in intracellular Ca²⁺ levels in macrophages was attenuated by either siRNA or neutralizing antibodies against gC1qR. Furthermore, application of the gC1qR-neutralizing antibody to rats with partial sciatic nerve ligation resulted in a delayed onset of nerve injury-associated mechanical hypersensitivity. These results indicate that gC1qR is the receptor for TLQP-21 and plays an important role in chronic pain through activation of macrophages. Because direct association between TLQP-21 and gC1qR is required for activation of macrophages and causes hypersensitivity, disrupting this interaction may be a useful new approach to develop novel analgesics.

All-trans retinoic acid protects against dextran sulfate sodium-induced colitis in mice

AIM: To investigate the effect of all-trans retinoic acid (ATRA) on dextran sulfate sodium (DSS)-induced colitis in mice.

METHODS: Mice were randomly divided into four groups: a normal control group, a DSS group, an ATRA group, and a LE135 group. Except the normal control group, the other groups were fed 3%DSS (w/v) solution from days 1 to 8 to induce colitis. The DSS group and ATRA group were intraperitoneally injected with ATRA 0.5 mg/d and LE135 0.1 mg/d from day 3, respectively. Disease activity index (DAI) was recorded daily. The expression of CD68, NF-κB p65, MPO activity, and TNF level in the colon of mice of each group were measured.

RESULTS: DAI was significantly lower in the ATRA group than in the DSS and LE135 groups (both P < 0.05). The histological score and MPO activity in colonic tissue in the ATRA group were significantly lower than those in the DSS and LE135 groups (histological score: 7.63 ± 1.19 vs 10.13 ± 1.36, 10.38 ± 1.30, both P < 0.05; MPO activity: 7.88 ± 0.68 vs 11.36 ± 0.96, 12.65 ± 0.77, both P < 0.05), but were higher than those in the control group (7.63 ± 1.19 vs 0.25 ± 0.463, P < 0.05; 7.88 ± 0.68 vs 3.52 ± 0.58, P < 0.05). The levels of TNF in colonic tissue were significantly lower in the ATRA group than in the DSS and LE135 groups (178.63 ± 39.37 vs 316.67 ± 43.68, 362.45 ± 62.75, both P < 0.05). The numbers of CD68 positive cells and NF-kB positive cells in lamina propria in the ATRA group were significantly lower than those in the DSS and LE135 groups (all P < 0.05), but higher than those in the control group (all P < 0.05).

CONCLUSION: ATRA protects against DSS-induced colitis in mice possibly by inhibiting immune cell activation in the lamina propria and infiltration of macrophage into colon tissue.

The enhanced immune response of hepatitis B virus DNA vaccine using SiO2@LDH nanoparticles as an adjuvant

Various approaches have been used to improve systemic immune response to infectious disease or virus, and DNA vaccination has been demonstrated to be one of these effective ways to elicit protective immunity against pathogens. Our previous studies showed that layered double hydroxides (LDH) nanoparticles could be efficiently taken up by the MDDCs and had an adjuvant activity for DC maturation. To further enhance the immune adjuvant activity of LDH, core-shell structure SiO2@LDH nanoparticles were synthesized with an average diameter of about 210 nm. And its high transfection efficiency in vitro was demonstrated by using GFP expression plasmid as model DNA. Exposing SiO2@LDH nanoparticles to macrophages caused a higher dose-dependent expression of IFN-γ, IL-6, CD86 and MHC II, compared with SiO2 and LDH respectively. Furthermore, in vivo immunization of BALB/c mice indicated that, DNA vaccine loaded-SiO2@LDH nanoparticles not only induced much higher serum antibody response than naked DNA vaccine and plain nanoparticles, but also obviously promoted T-cell proliferation and skewed T helper to Th1 polarization. Additionally, it was proved that the caveolae-mediated uptake of SiO2@LDH nanoparticles by macrophage lead to macrophages activation via NF-κB signaling pathway. Our results indicate that SiO2@LDH nanoparticles could serve as a potential non-viral gene delivery system.

Restricted 5'-end gap repair of HIV-1 integration due to limited cellular dNTP concentrations in human primary macrophages

HIV-1 proviral DNA integration into host chromosomal DNA is only partially completed by the viral integrase, leaving two single-stranded DNA gaps with 5'-end mismatched viral DNA flaps. It has been inferred that these gaps are repaired by the cellular DNA repair machinery. Here, we investigated the efficiency of gap repair at integration sites in different HIV-1 target cell types. First, we found that the general gap repair machinery in macrophages was attenuated compared with that in dividing CD4(+) T cells. In fact, the repair in macrophages was heavily reliant upon host DNA polymerase β (Pol β). Second, we tested whether the poor dNTP availability found in macrophages is responsible for the delayed HIV-1 proviral DNA integration in this cell type because the Km value of Pol β is much higher than the dNTP concentrations found in macrophages. Indeed, with the use of a modified quantitative AluI PCR assay, we demonstrated that the elevation of cellular dNTP concentrations accelerated DNA gap repair in macrophages at HIV-1 proviral DNA integration sites. Finally, we found that human monocytes, which are resistant to HIV-1 infection, exhibited severely restricted gap repair capacity due not only to the very low levels of dNTPs detected but also to the significantly reduced expression of Pol β. Taken together, these results suggest that the low dNTP concentrations found in macrophages and monocytes can restrict the repair steps necessary for HIV-1 integration.

IFN-γ inhibits liver progenitor cell proliferation in HBV-infected patients and in 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet-fed mice

BACKGROUND & AIMS

Proliferation of liver progenitor cells (LPCs) is associated with inflammation and fibrosis in chronic liver diseases. However, how inflammation and fibrosis affect LPCs remains obscure.

METHODS

We examined the role of interferon (IFN)-γ, an important pro-inflammatory and anti-fibrotic cytokine, in LPC expansion in HBV-infected patients and in mice challenged with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)- or choline-deficient, ethionine-supplemented (CDE) diet as well as in primary LPCs and LPC cell line.

RESULTS

The CK19 staining scores correlated with inflammation and fibrosis grades in the livers from 110 HBV-infected patients. Nine-month IFN-γ treatment decreased LPC numbers, inflammation, and fibrosis in these HBV-infected patients. Similarly, a two-week IFN-γ treatment also decreased LPC activation in DDC-treated mice. Disruption of IFN-γ or its signaling components (e.g., IFNGR, STAT1, and IRF-1) increased LPC proliferation and liver fibrosis in DDC-fed mice. In contrast, deletion of IFN-γ did not increase, but rather slightly reduced LPC proliferation in CDE-fed mice. In vitro, IFN-γ attenuated proliferation of the LPC cell line BMOL and of primary LPCs from wild type mice, but not STAT1(-/-) or IRF-1(-/-) mice. Furthermore, co-culture assays suggest that IFN-γ can indirectly promote LPC proliferation via the activation of macrophages but attenuate it via the inhibition of hepatic stellate cells.

CONCLUSIONS

IFN-γ inhibits LPC expansion via the direct inhibition of LPC proliferation and indirect attenuation of liver fibrosis in the DDC model, but it may also enhance LPC expansion via the promotion of inflammation in the CDE model; thereby playing dual roles in regulating LPC proliferation in vivo.

Activation profile of dorsal root ganglia Iba-1 (+) macrophages varies with the type of lesion in rats

The interactions between neurons, immune and immune-like glial cells can initiate the abnormal processes that underlie neuropathic pain. In the peripheral nervous system the resident macrophages may play an important role. In this study we investigated in experimental adult Sprague-Dawley rats how Iba-1 (ionized calcium binding adaptor molecule 1) (+) resident macrophages in the dorsal root ganglion (DRG) are activated after a spinal nerve ligation (SNL) or streptozotocin (STZ)-induced diabetes. The activation profile was defined by comparing the responses of resident macrophages against microglia in the spinal cord as they share a common origin. After SNL, the Iba-1 (+) macrophages in L5 DRG reached their activation peak 5 days later, clustered as satellite cells around large A-neurons, expressed the MHC-II marker, but did not show p-p38 and p-ERK1/2 activation and did not secrete IL-18. After STZ-induced diabetes, the Iba-1 (+) macrophages reached their activation peak 1 week later in L4 and L5 DRG, remained scattered between neurons, expressed the MHC-II marker only in L5 DRG, did not show p-p38 and p-ERK1/2 activation and did not secrete any of the investigated cytokines/chemokines. These responses suggest that depending on the type of lesion DRG Iba-1 (+) resident macrophages have different activation mechanisms, which are dissimilar to those in microglia.

Characterization of PAMP/PRR interactions in European eel (Anguilla anguilla) macrophage-like primary cell cultures

The eel (Anguilla anguilla) has been identified as a vulnerable species with stocks dramatically declining over the past decade. In an effort to support the species from overfishing of wild stocks increased interest in eel aquaculture has been notable. In order to expand the scarce knowledge concerning the biology of this species significant research efforts are required in several fields of biology. The development of cell culture systems to study the immune response is a key step towards an increased understanding of the immune response and to develop resources to support further study in this threatened species. Macrophages are one of the most important effector cells of the innate immune system. The capacity to engulf pathogens and orchestrate the immune response relies on the existence of different surface receptors, such as scavenger receptors and toll-like receptors. We have developed and described an eel macrophage-like in vitro model and studied its functional and transcriptomic responses. Macrophage-like cells from both head kidney and purified peripheral blood leukocytes were obtained and phagocytic activity measured for different whole bacteria and yeast. Moreover, based on PAMP-PRR association the innate immune response of both head kidney and PBL derived macrophage-like cells was evaluated against different pathogen-associated molecular patterns (PAMPs). Results highlight that peptidoglycan stimulation strongly induces inflammatory mRNA expression reflected in the up-regulation of pro-inflammatory genes IL1β and IL18 in PBL derived cells whereas IL8 is upregulated in head kidney derived cells. Furthermore TLR2 mRNA abundance is regulated by all stimuli supporting a multifunctional role for this pathogen recognition receptor (PRR) in eel macrophage-like cells.

Expressions of transcription factors in goldfish (Carassius auratus L.) macrophages and their progenitors

The development of macrophages is a highly regulated process requiring coordination amongst transcription factors. The presence/absence, relative levels, antagonism, or synergy of all transcription factors involved is critical to directing lineage cell fate and differentiation. While relative levels of many key myeloid transcription factors have been determined in mammalian macrophage differentiation, a similar set of studies have yet to be conducted in a teleost system. In this study, we report on the mRNA levels of transcription factors (cebpa, cjun, cmyb, egr1, gata1, gata2, gata3, lmo2, mafb, pax5, pu.1 and runx1) in sorted goldfish progenitor cells, monocytes, and macrophages from primary kidney macrophage cultures. The mRNA levels of runx1 and pu.1 were significantly higher, gata3 and pax5 mRNA levels were lower, in monocytes compared to progenitors, and the mRNA levels of cjun, egr1, gata2, gata3, mafb and pax5 were significantly decreased in macrophages compared to progenitor cells. The relative mRNA levels of the interferon regulatory factor family of transcription factors, irf1, irf2, irf5, irf7, irf8 and irf9 in sorted progenitors, monocytes and macrophages were also measured. In contrast to other irf family transcription factors examined, irf8 mRNA levels were increased in monocytes compared to progenitors by greater than three-fold, suggesting that irf8 is important for monopoiesis. Lastly, we show the differential regulation of myeloid transcription factor mRNA levels in sorted progenitor cells from 1, 2, or 3-day old cultures in response to the recombinant goldfish growth factors, rgCSF-1 and rgKITLA.

Sphingosine kinases are not required for inflammatory responses in macrophages

Sphingosine kinases (Sphks), which catalyze the formation of sphingosine 1-phosphate (S1P) from sphingosine, have been implicated as essential intracellular messengers in inflammatory responses. Specifically, intracellular Sphk1-derived S1P was reported to be required for NFκB induction during inflammatory cytokine action. To examine the role of intracellular S1P in the inflammatory response of innate immune cells, we derived murine macrophages that lack both Sphk1 and Sphk2 (MΦ Sphk dKO). Compared with WT counterparts, MΦ Sphk dKO cells showed marked suppression of intracellular S1P levels whereas sphingosine and ceramide levels were strongly up-regulated. Cellular proliferation and apoptosis were similar in MΦ Sphk dKO cells compared with WT counterparts. Treatment of WT and MΦ Sphk dKO with inflammatory mediators TNFα or Escherichia coli LPS resulted in similar NFκB activation and cytokine expression. Furthermore, LPS-induced inflammatory responses, mortality, and thioglycolate-induced macrophage recruitment to the peritoneum were indistinguishable between MΦ Sphk dKO and littermate control mice. Interestingly, autophagic markers were constitutively induced in bone marrow-derived macrophages from Sphk dKO mice. Treatment with exogenous sphingosine further enhanced intracellular sphingolipid levels and autophagosomes. Inhibition of autophagy resulted in caspase-dependent cell death. Together, these data suggest that attenuation of Sphk activity, particularly Sphk2, leads to increased intracellular sphingolipids and autophagy in macrophages.

Autocrine and paracrine modulation of microRNA-155 expression by globular adiponectin in RAW 264.7 macrophages: involvement of MAPK/NF-κB pathway

Adiponectin, a hormone produced from adipose tissue, regulates various biological responses, including inflammation and many metabolic processes. MicroRNAs control expression of diverse target genes and various physiological responses. Many of these responses are commonly regulated by adiponectin. However, effects of adiponectin on microRNAs regulation are largely unknown. Herein we demonstrated that globular adiponectin induces increase in miR-155 expression, which plays an important role in inflammatory response, in RAW 264.7 macrophages. We further showed that this effect was modulated by and MAPK/NF-κB dependent mechanisms. These results suggest that miR-155 would be a novel promising target mediating adiponectin-induced various biological responses.

The role of macrophages in obstructive airways disease: chronic obstructive pulmonary disease and asthma

Macrophages are a major cellular component of the innate immune system, and play an important role in the recognition of microbes, particulates, and immunogens and to the regulation of inflammatory responses. In the lung, macrophages react with soluble proteins that bind microbial products in order to remove pathogens and particles and to maintain the sterility of the airway tract. Chronic obstructive pulmonary disease and asthma are both obstructive airway diseases that involve chronic inflammation of the respiratory tract which contributes to disease progression. In the case of COPD, there is increasing evidence that lung macrophages orchestrate inflammation through the release of chemokines that attract neutrophils, monocytes and T cells and the release of several proteases. On the other hand, in asthma, it seems that alveolar macrophages are inappropriately activated and are implicated in the development and progression of the disease. In this review we summarize the current basic and clinical research studies which highlight the role of macrophages in asthma and COPD.

Potentiated macrophage activation by acid sensing under low adiponectin levels

Adiponectin can protect against inflammation; one of the mechanisms involves direct, inhibition of macrophages (MΦ). We postulated that adiponectin anti-sense transgenic (AsTg) mice raised in our laboratory are prone to inflammation because of systemic low adiponectin levels. The writhing response to acetic acid was utilized as an in vivo inflammatory model, and using Ca(2)(+), response to the acid was exploited in vitro to evaluate the function of resident peritoneal MΦ. The in vivo response to the acid was increased and the Ca(2)(+) response of MΦ was enhanced in AsTg mice, compared with those in wild type (WT) mice. In parallel with these enhanced responses, MΦ from AsTg mice augmented TNF-α and IL-6 mRNA expression. We further analyzed the enhancement in activity of MΦ from AsTg mice by acid sensing using specific inhibitors, amiloride for acid-sensing ion channels (ASICs) and KB-R7943 for Na(+)/Ca(2)(+) exchangers (NCXs). Our results indicated that in AsTg mice, the Ca(2)(+) response to the acid was facilitated in MΦ by a low threshold of ASIC1 and NCX1 molecules and the activity of these channel was possibly regulated by adiponectin.

Pulmonary pathology in pediatric cerebral malaria

Respiratory signs are common in African children where malaria is highly endemic, and thus, parsing the role of pulmonary pathology in illness is challenging. We examined the lungs of 100 children from an autopsy series in Blantyre, Malawi, many of whom death was attributed to Plasmodium falciparum malaria. Our aim was to describe the pathologic manifestations of fatal malaria; to understand the role of parasites, pigment, and macrophages; and to catalog comorbidities. From available patients, which included 55 patients with cerebral malaria and 45 controls, we obtained 4 cores of lung tissue for immunohistochemistry and morphological evaluation. We found that, in patients with cerebral malaria, large numbers of malaria parasites were present in pulmonary alveolar capillaries, together with extensive deposits of malaria pigment (hemozoin). The number of pulmonary macrophages in this vascular bed did not differ between patients with cerebral malaria, noncerebral malaria, and nonmalarial diagnoses. Comorbidities found in some cerebral malaria patients included pneumonia, pulmonary edema, hemorrhage, and systemic activation of coagulation. We conclude that the respiratory distress seen in patients with cerebral malaria does not appear to be anatomic in origin but that increasing malaria pigment is strongly associated with cerebral malaria at autopsy.

Uncoupling of osteoblast-osteoclast regulation in a chemical murine model of Gaucher disease

Gaucher disease (GD) is caused by mutations in the GBA gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to accumulation of the glycolipid glucocerebroside in the lysosomes of cells of monocyte/macrophage system. Type I GD is the mildest form and is characterized by the absence of neuronopathic affection. Bone compromise in Gaucher disease patients is the most disabling aspect of the disease. However, pathophysiological aspects of skeletal alterations are still poorly understood. The homeostasis of bone tissue is maintained by the balanced processes of bone resorption by osteoclasts and formation by osteoblasts. We decided to test whether bone resorption and/or bone formation could be altered by the use of a chemical in vitro murine model of Gaucher disease. We used two sources of cells from monocyte/macrophages lineage isolated from normal mice, splenocytes (S) and peritoneal macrophages (PM), and were exposed to CBE, the inhibitor of GCase (S-CBE and PM-CBE, respectively). Addition of both conditioned media (CM) from S-CBE and PM-CBE induced the differentiation of osteoclasts precursors from bone marrow to mature and functional osteoclasts. TNF-α could be one of the factors responsible for this effect. On the other hand, addition of CM to an osteoblast cell culture resulted in a reduction in expression of alkaline phosphatase and mineralization process. In conclusion, these results suggest implication of changes in both bone formation and bone resorption and are consistent with the idea that both sides of the homeostatic balance are affected in GD.

Re-evaluation of the involvement of NK cells and C-type lectin-like NK receptors in modulation of immune responses by multivalent GlcNAc-terminated oligosaccharides

Recognition of glycosylation patterns is one of the basic features of innate immunity. Ability of C-type lectin-like receptors such as NKR-P1 to bind saccharide moieties has become recently a controversial issue. In the present study, binding assay with soluble fluorescently labeled recombinant rat NKR-P1A and mouse NKR-P1C proteins revealed apparently no affinity to the various neoglycoproteins. Lack of functional linkage between NKR-P1 and previously described saccharide binder was supported by the fact, that synthetic N-acetyl-D-glucosamine octabranched dendrimer on polyamidoamine scaffold (GN8P) did not change gene expression of NKR-P1 isoforms in C57BL/6 and BALB/c mice divergent in the NK gene complex (both in vitro and in vivo). Surprisingly, N-acetyl-D-glucosamine-coated tetrabranched polyamido-amine dendrimer specifically binds to NKT cells and macrophages but not to NK cells (consistently with changes in cytokine patterns). Despite the fact that GN8P has been tested as an immunomodulator in anti-cancer treatment animal models for many years, surprisingly no changes in cytokine profiles in serum relevant to anti-cancer responses using B16F10 and CT26 harboring mouse strains C57BL/6 and BALB/c are observed. Our results indicate possible indirect involvement of NK cells in GN8P mediated immune responses.

Homocysteine modifies extracellular ATP availability in macrophages

Increased levels of plasma homocysteine (hyperhomocysteinemia-HHcy) are associated to the development of coronary artery disease (CAD), peripheral vascular disease and thrombosis. In addition, recent studies have shown that inflammation, probably mediated by macrophages, mediates the pathogenesis associated to high levels of homocysteine (Hcy). In the present study, we evaluated the Hcy effects in the ATP hydrolysis and its breakdown products in murine macrophages. The results showed that micromolar concentrations of Hcy increased the ATP, ADP and AMP hydrolysis. Additionally, our results show decreased inosine levels in the extracellular milieu of Hcy-exposed macrophages. The increasing in ATP, ADP and AMP hydrolysis are not explained by increased transcription or protein expression of NTPDases and ecto-5'-nucleotidase (ecto-5'-NT/CD73) enzymes. Moreover, the formation of reactive oxygen species did not interfere in the Hcy effects, which suggest that Hcy or Hcy metabolites act directly on the modulation of NTPDases and ecto-5'-NT/CD73 activities. In conclusion, Hcy induces the rapid breakdown of ATP, ADP and AMP to adenosine (ADO), which is classically known as an anti-inflammatory response in immune cells. However, by the action of these enzymes, the extracellular adenosine generated during Hcy treatment probably is uptaken into the cells, as evidenced by the decreased in inosine formation, and thus collaborating to the inflammatory complications associates to HHcy.

Liposomal clodronate reduces Akt and mitogen-activated protein kinase expression in the intestinal mucosa of rats with severe acute pancreatitis

AIM: To study the effect of liposomal clodronate on the expression of protein kinase B (Akt) and mitogen-activated protein kinase [MAPK (ERK1/2)] in the intestinal mucosa of rats with severe acute pancreatitis (SAP), and to investigate the mechanism behind the therapeutic effect of liposomal clodronate on SAP-associated intestinal mucosal injury.

METHODS: Liposomal clodronate was prepared by means of thin film. Forty-eight SD rats were randomly divided into a model control group (C), a liposome control group (P), and a liposomal clodronate group (T). SAP was induced in rats of groups P and T by injection of sodium taurocholate under the pancreatic capsule, while group C received equal volume of normal saline. Serum levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and AMS were measured 2 and 6 h after SAP induction. Pathological alterations in the intestinal mucosa were observed.

RESULTS: Serum levels of AMS, IL-6 and TNF-α were significantly elevated in group P compared to group C (all P < 0.01). Compared with group P, serum levels of AMS, IL-6 and TNF-α were significantly decreased in group T (all P < 0.01). Pathological alterations (scores) in the intestinal mucosa were significantly attenuated in group T compared to group P. The expression of Akt and MAPK (ERK1/2) was significantly decreased in group T compared to group P.

CONCLUSION: Macrophages play an important role in the pathogenesis of intestinal mucosal injury in SAP. Macrophages can be depleted via phagocytosis of liposome encapsulated clodronate. Liposomal clodronate alleviates intestinal mucosal injury in SAP rats possibly by decreasing the expression of Akt and MAPK (ERK1/2).

Epidermal growth factor (EGF)-enhanced vascular cell adhesion molecule-1 (VCAM-1) expression promotes macrophage and glioblastoma cell interaction and tumor cell invasion

Activated EGF receptor (EGFR) signaling plays an instrumental role in glioblastoma (GBM) progression. However, how EGFR activation regulates the tumor microenvironment to promote GBM cell invasion remains to be clarified. Here, we demonstrate that the levels of EGFR activation in tumor cells correlated with the levels of macrophage infiltration in human GBM specimens. This was supported by our observation that EGFR activation enhanced the interaction between macrophages and GBM cells. In addition, EGF treatment induced up-regulation of vascular cell adhesion molecule-1 (VCAM-1) expression in a PKCε- and NF-κB-dependent manner. Depletion of VCAM-1 interrupted the binding of macrophages to GBM cells and inhibited EGF-induced and macrophage-promoted GBM cell invasion. These results demonstrate an instrumental role for EGF-induced up-regulation of VCAM-1 expression in EGFR activation-promoted macrophage-tumor cell interaction and tumor cell invasion and indicate that VCAM-1 is a potential molecular target for improving cancer therapy.

5-Lipoxygenase contributes to PPARγ activation in macrophages in response to apoptotic cells

Macrophage polarization to an anti-inflammatory phenotype upon contact with apoptotic cells is a contributing hallmark to immune suppression during the late phase of sepsis. Although the peroxisome proliferator-activated receptor γ (PPARγ) supports this macrophage phenotype switch, it remains elusive how apoptotic cells activate PPARγ. Assuming that a molecule causing PPARγ activation in macrophages originates in the cell membrane of apoptotic cells we analyzed lipid rafts from apoptotic, necrotic, and living human Jurkat T cells which showed the presence of 5-lipoxygenase (5-LO) in lipid rafts of apoptotic cells only. Incubating macrophages with lipid rafts of apoptotic, but not necrotic or living cells, induced PPAR responsive element (PPRE)-driven mRuby reporter gene expression in RAW 264.7 macrophages stably transduced with a 4xPPRE containing vector. Experiments with lipid rafts of apoptotic murine EL4 T cells revealed similar results. To verify the involvement of 5-LO in activating PPARγ in macrophages, Jurkat T cells were incubated with the 5-LO inhibitor MK-866 prior to induction of apoptosis, which failed to induce mRuby expression. Similar results were obtained with lipid rafts of apoptotic EL4 T cells preexposed to the 5-LO inhibitors zileuton and CJ-13610. Interestingly, Jurkat T cells overexpressing 5-LO failed to activate PPARγ in macrophages, while their 5-LO overexpressing apoptotic counterparts did. Our results suggest that during apoptosis 5-LO gets associated with lipid rafts and synthesizes ligands that in turn stimulate PPARγ in macrophages.

LOX-1 deletion and macrophage trafficking in atherosclerosis

BACKGROUND

Atherosclerosis is associated with macrophage accumulation. LOX-1 has been shown to induce macrophage attachment, and its deletion (LOX-1 knockout, KO) reduces atherosclerosis in LDLr KO mice fed a high cholesterol diet. We examined differences in macrophage trafficking in age-matched wild type, LOX-1 KO, LDLr KO, and LDLr/LOX-1 double KO mice.

METHODS

Sections of aortas of mice fed high cholesterol diet were collected at weeks 0, 4, 8, 12 and 19 and analyzed by immunohistochemistry and flow cytometry.

RESULTS

In the LDLr KO mice aorta, CD68 positivity (macrophage accumulation) increased over time up to 12 weeks, and then the accumulation fell modestly but significantly. The periaortal fat and adventitia showed more CD68 positivity than the media and intima. This pattern was also evident in the non-atherosclerotic areas. Importantly, LOX-1 KO and LDLr-LOX-1 double KO mice showed diminished CD68 positivity in comparison to wild type and LDLR KO mice, respectively. Further, macrophages from LOX-1 KO mice revealed a marked reduction in migration (vs. macrophages from wild type mice) in in vitro migration assay.

CONCLUSIONS

LOX-1 deletion translates into reduction in macrophage trafficking in the aorta of LDLr KO mice. Most of the macrophage trafficking appears in the subadventitial regions.

Novel role for p21-activated kinase 2 in thrombin-induced monocyte migration

To understand the role of thrombin in inflammation, we tested its effects on migration of THP-1 cells, a human monocytic cell line. Thrombin induced THP-1 cell migration in a dose-dependent manner. Thrombin induced tyrosine phosphorylation of Pyk2, Gab1, and p115 RhoGEF, leading to Rac1- and RhoA-dependent Pak2 activation. Downstream to Pyk2, Gab1 formed a complex with p115 RhoGEF involving their pleckstrin homology domains. Furthermore, inhibition or depletion of Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, or Pak2 levels substantially attenuated thrombin-induced THP-1 cell F-actin cytoskeletal remodeling and migration. Inhibition or depletion of PAR1 also blocked thrombin-induced activation of Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, and Pak2, resulting in diminished THP-1 cell F-actin cytoskeletal remodeling and migration. Similarly, depletion of Gα12 negated thrombin-induced Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, and Pak2 activation, leading to attenuation of THP-1 cell F-actin cytoskeletal remodeling and migration. These novel observations reveal that thrombin induces monocyte/macrophage migration via PAR1-Gα12-dependent Pyk2-mediated Gab1 and p115 RhoGEF interactions, leading to Rac1- and RhoA-targeted Pak2 activation. Thus, these findings provide mechanistic evidence for the role of thrombin and its receptor PAR1 in inflammation.

Macrophages: supportive cells for tissue repair and regeneration

Macrophages, and more broadly inflammation, have been considered for a long time as bad markers of tissue homeostasis. However, if it is indisputable that macrophages are associated with many diseases in a deleterious way, new roles have emerged, showing beneficial properties of macrophages during tissue repair and regeneration. This discrepancy is likely due to the high plasticity of macrophages, which may exhibit a wide range of phenotypes and functions depending on their environment. Therefore, regardless of their role in immunity, macrophages play a myriad of roles in the maintenance and recovery of tissue homeostasis. They take a major part in the resolution of inflammation. They also exert various effects of parenchymal cells, including stem and progenitor cell, of which they regulate the fate. In the present review, few examples from various tissues are presented to illustrate that, beyond their specific properties in a given tissue, common features have been described that sustain a role of macrophages in the recovery and maintenance of tissue homeostasis.

Characterization of the AtsR hybrid sensor kinase phosphorelay pathway and identification of its response regulator in Burkholderia cenocepacia

AtsR is a membrane-bound hybrid sensor kinase of Burkholderia cenocepacia that negatively regulates quorum sensing and virulence factors such as biofilm production, type 6-secretion, and protease secretion. Here we elucidate the mechanism of AtsR phosphorelay by site-directed mutagenesis of predicted histidine and aspartic acid phosphoacceptor residues. We demonstrate by in vitro phosphorylation that histidine 245 and aspartic acid 536 are conserved sites of phosphorylation in AtsR, and we also identify the cytosolic response regulator AtsT (BCAM0381) as a key component of the AtsR phosphorelay pathway. Monitoring the function of AtsR and its derivatives in vivo by measuring extracellular protease activity and swarming motility confirmed the in vitro phosphorylation results. Together we find that the AtsR receiver domain plays a fine-tuning role in determining the levels of phosphotransfer from its sensor kinase domain to the AtsT response regulator.

The cholesterol-binding antibiotic nystatin induces expression of macrophage inflammatory protein-1 in macrophages

Nystatin, a polyene antifungal antibiotic, is a cholesterol sequestering agent. The antifungal agent alters composition of the plasma membrane of eukaryotic cells, whereas its effects on cells are poorly investigated. In the current study, we investigated the question of whether nystatin was able to induce expression of macrophage inflammatory protein-1 (MIP-1). THP-1 cells rarely express MIP-1α and MIP-1β, however, upon exposure to nystatin, significantly elevated expression of MIP-1α and MIP-1β was observed in a dose-dependent fashion at the messenger and protein levels. Cellular factors activated by nystatin as well as involved in nystatin-induced expression of MIP-1 proteins were identified in order to understand the molecular mechanisms of action of the anti-fungal agent. Treatment with nystatin resulted in enhanced phosphorylation of Akt, ERK, p38 MAPK, and JNK. Abrogation or significant attenuation of nystatin-induced expression of MIP-1α and MIP-1β was observed by treatment with Akt inhibitor IV, LY294002, and SP6001250. Inhibition of ERK or p38MAPK using U0126 and SB202190 did not lead to attenuation of MIP-1 expression. In addition, inhibitors of protein kinase C, such as GF109203X and Ro-318220, also attenuated expression of MIP-1. These results indicate that nystatin is able to activate multiple cellular kinases and, among them, Akt and JNK play primary roles in nystatin-induced expression of MIP-1 proteins.

Development of a reverse genetics system to generate recombinant Marburg virus derived from a bat isolate

Recent investigations have shown the Egyptian fruit bat (Rousettus aegyptiacus) to be a natural reservoir for marburgviruses. To better understand the life cycle of these viruses in the natural host, a new reverse genetics system was developed for the reliable rescue of a Marburg virus (MARV) originally isolated directly from a R. aegyptiacus bat (371Bat). To develop this system, the exact terminal sequences were first determined by 5' and 3' RACE, followed by the cloning of viral proteins NP, VP35, VP30 and L into expression plasmids. Novel conditions were then developed to efficiently replicate virus mini-genomes followed by the construction of full-length genomic clones from which recombinant wild type and GFP-containing MARVs were rescued. Surprisingly, when these recombinant MARVs were propagated in primary human macrophages, a dramatic difference was found in their ability to grow and to elicit anti-viral cytokine responses.

Regulation of TREM-1 expression by 1,25-dihydroxyvitamin D3 in human monocytes/macrophages

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a recently identified cell surface receptor that is expressed mainly on monocytes and neutrophils, and acts as an amplifier of immune responses. In this study, 1,25(OH)2D3 strongly upregulated the expression of TREM-1 in human monocytes and macrophages. 1,25(OH)2D3 stimulated TREM-1 mRNA expression by augmenting transcription, and not by inhibiting mRNA degradation. The upregulated expression of TREM-1 by 1,25(OH)2D3 was dependent on the NF-κB signaling pathway and required new protein synthesis in differentiated U937 macrophages. Our results show that 1,25(OH)2D3 can affect the innate and inflammatory responses by upregulating TREM-1 expression, and suggest that 1,25(OH)2D3 may function as an enhancer of the innate immune response by upregulating TREM-1 expression, in addition to inducing the antimicrobial peptide cathelicidin.

Diagnostic utility of a direct immunofluorescence test to detect feline coronavirus antigen in macrophages in effusive feline infectious peritonitis

The antemortem diagnosis of feline infectious peritonitis (FIP) remains challenging in clinical practice, since current testing methods have suboptimal diagnostic accuracy. Immunohistochemical testing of biopsy specimens and postmortem examination are the standard diagnostic methods, although direct immunofluorescence (DIF) testing to detect feline coronavirus in macrophages in effusion specimens has been reported to have 100% specificity and has been recommended as an antemortem confirmatory test. The aim of this study was to compare the results of DIF testing in antemortem feline effusions with postmortem results using field samples. Effusion specimens were collected antemortem from 17 cats and tested by DIF, followed by postmortem examination. Histopathological examination of specimens collected at postmortem confirmed FIP in 10/17 cases and ruled out FIP out in 7/17 cases. Antemortem DIF testing was positive in all 10 cases confirmed as FIP at postmortem examination. In the seven cats where FIP was ruled out at postmortem examination, DIF was negative in five cases and positive in the remaining two cases. The calculated sensitivity of DIF testing was 100% and the specificity was 71.4%. Duplicate effusion specimens from eight cats that were initially DIF positive were stored refrigerated (4 °C) or at room temperature (22–25 °C) and subjected to serial DIF testing to determine the duration of positive results. DIF-positive specimens stored at both temperatures retained their positive status for at least 2 days.

Pathways of IL-1β secretion by macrophages infected with clinical Mycobacterium tuberculosis strains

The pro-inflammatory cytokine IL-1β is a key mediator of inflammation and plays an important role in the host resistance to Mycobacterium tuberculosis infections. To date, most studies have examined the mechanisms of IL-1β secretion using laboratory strains of M. tuberculosis and the findings may not be widely applicable to contemporary clinical strains. Here, we investigated the primary pathways of IL-1β secretion in macrophages infected with a panel of 17 clinical M. tuberculosis isolates, representing Euro-American, Indo-Oceanic and East-Asian/Beijing lineages. Our aim was to dissect the pathways involved in M. tuberculosis induced IL-1β secretion and to determine whether they are common to all clinical isolates. We found that the isolates were capable of eliciting variable concentrations of IL-1β from infected murine macrophages, but this phenomenon could not be attributed to differential IL-1β mRNA transcription or pro-IL-1β accumulation. We demonstrate that viable bacteria are required to induce IL-1β secretion from macrophages, but IL-1β secretion was only partially abrogated by caspase-1 inhibition. Almost complete IL-1β secretion inhibition was produced with combined caspase-1 and some serine protease inhibitors. Taken together, these findings demonstrate that clinical strains of M. tuberculosis employ a unique caspase-1 independent pathway to stimulate IL-1β secretion from macrophages.

A study of immunomodulatory genes responses to macrophages of Schistosoma japonicum infection during different stages by microarray analysis

Macrophages initiate, modulate, and also serve as final effector cells in immune responses during the course of schistosomal infections. In this study, we investigated the gene expression profile and functional changes of macrophages in immune responses against the Schistosoma japonicum by microarray analysis. Hierarchical clustering analysis demonstrated that a significant switch in gene transformation associated with a type-1 response and linked with a type-2 cytokine phenotype occurs between 4.5 and 8 weeks post-infection. Moreover, the gene profiles at 3 later time-points following egg challenge were similar in complexity and magnitude. The data also showed that there were mostly inhibition of gene expression related TLR, IFN, MHC and TNFrsf at the switch between 4.5 and 8 weeks post-infection, It is suggested that these immunomodulatory genes may be down-regulated in defense against S. japonicum eggs and granuloma pathology. The induction of alternatively activated macrophage (AAMϕ) was important for dampening the inflammation in hepatic granulomas and contributing to a decrease in cytotoxicity. The gene expressions involved in repair/remodeling during liver fibrosis were also observed after egg production. Understanding the immune mechanisms associated with parasitic resistance, pathology of parasite infection, and parasite growth will provide useful insight on host-schistosome interactions and for the control of schistosomiasis.

Inflammation, immunity, vaccines for Helicobacter pylori infection

Over the last decades, it has become evident that chronic infection by Helicobacter pylori is achieved by colonizing an almost exclusive niche and hiding from many of the host's cellular immune defense mechanisms. Although recent years have seen progress in our understanding of the innate and adaptive immune response against H. pylori, it is still uncertain how to promote the development of immunity with the final goal of a successful vaccine. Research published in the last year revealed an intriguing mutual regulation of innate response mechanisms of mucosal epithelial cells by the host and H. pylori, respectively. A further focus was put on the interaction between H. pylori and dendritic cells, with some emphasis on the inflammasome and the resulting T-cell responses. Moreover, the function of microRNAs in macrophages and gastric MALT lymphoma development has been studied in more detail. Several novel antigens and adjuvants have been tested as vaccination strategies, primarily in mice. In this review, we present a concise summary of advances in the area of inflammation, immunity, and vaccines during the last twelve months.

The paired-box homeodomain transcription factor Pax6 binds to the upstream region of the TRAP gene promoter and suppresses receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation

Osteoclast formation is regulated by balancing between the receptor activator of nuclear factor-κB ligand (RANKL) expressed in osteoblasts and extracellular negative regulatory cytokines such as interferon-γ (IFN-γ) and interferon-β (IFN-β), which can suppress excessive bone destruction. However, relatively little is known about intrinsic negative regulatory factors in RANKL-mediated osteoclast differentiation. Here, we show the paired-box homeodomain transcription factor Pax6 acts as a negative regulator of RANKL-mediated osteoclast differentiation. Electrophoretic mobility shift and reporter assays found that Pax6 binds endogenously to the proximal region of the tartrate acid phosphatase (TRAP) gene promoter and suppresses nuclear factor of activated T cells c1 (NFATc1)-induced TRAP gene expression. Introduction of Pax6 retrovirally into bone marrow macrophages attenuates RANKL-induced osteoclast formation. Moreover, we found that the Groucho family member co-repressor Grg6 contributes to Pax6-mediated suppression of the TRAP gene expression induced by NFATc1. These results suggest that Pax6 interferes with RANKL-mediated osteoclast differentiation together with Grg6. Our results demonstrate that the Pax6 pathway constitutes a new aspect of the negative regulatory circuit of RANKL-RANK signaling in osteoclastogenesis and that the augmentation of Pax6 might therefore represent a novel target to block pathological bone resorption.

Engineered protease-resistant antibodies with selectable cell-killing functions

Molecularly engineered antibodies with fit-for-purpose properties will differentiate next generation antibody therapeutics from traditional IgG1 scaffolds. One requirement for engineering the most appropriate properties for a particular therapeutic area is an understanding of the intricacies of the target microenvironment in which the antibody is expected to function. Our group and others have demonstrated that proteases secreted by invasive tumors and pathological microorganisms are capable of cleaving human IgG1, the most commonly adopted isotype among monoclonal antibody therapeutics. Specific cleavage in the lower hinge of IgG1 results in a loss of Fc-mediated cell-killing functions without a concomitant loss of antigen binding capability or circulating antibody half-life. Proteolytic cleavage in the hinge region by tumor-associated or microbial proteases is postulated as a means of evading host immune responses, and antibodies engineered with potent cell-killing functions that are also resistant to hinge proteolysis are of interest. Mutation of the lower hinge region of an IgG1 resulted in protease resistance but also resulted in a profound loss of Fc-mediated cell-killing functions. In the present study, we demonstrate that specific mutations of the CH2 domain in conjunction with lower hinge mutations can restore and sometimes enhance cell-killing functions while still retaining protease resistance. By identifying mutations that can restore either complement- or Fcγ receptor-mediated functions on a protease-resistant scaffold, we were able to generate a novel protease-resistant platform with selective cell-killing functionality.

Extracts of Crinum latifolium inhibit the cell viability of mouse lymphoma cell line EL4 and induce activation of anti-tumour activity of macrophages in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Crinum latifolium L. (CL) leaf extracts have been traditionally used in Vietnam and are now used all over the world for the treatment of prostate cancer. However, the precise cellular mechanisms of the action of CL extracts remain unclear.

AIM OF THE STUDY

To examine the effects of CL samples on the anti-tumour activity of peritoneal murine macrophages.

MATERIALS AND METHODS

The properties of three extracts (aqueous, flavonoid, alkaloid), one fraction (alkaloid), and one pure compound (6-hydroxycrinamidine) obtained from CL, were studied (i) for redox capacities (DPPH and bleaching beta-carotene assays), (ii) on murine peritoneal macrophages (MTT assay) and on lymphoma EL4-luc2 cells (luciferine assay) for cytotoxicity, (iii) on macrophage polarization (production of ROS and gene expression by PCR), and (iv) on the tumoricidal functions of murine peritoneal macrophages (lymphoma cytotoxicity by co-culture with syngeneic macrophages).

RESULTS

The total flavonoid extract with a high antioxidant activity (IC50=107.36 mg/L, DPPH assay) showed an inhibitory action on cancer cells. Alkaloid extracts inhibited the proliferation of lymphoma cells either by directly acting on tumour cells or by activating of the tumoricidal functions of syngeneic macrophages. The aqueous extract induced mRNA expression of tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin 6 (IL-6) indicating differentiation of macrophages into pro-inflammatory M1 polarized macrophages. The total flavonoid, alkaloid extracts and an alkaloid fraction induced the expression of the formyl peptide receptor (FPR) on the surface of the polarized macrophages that could lead to the activation of macrophages towards the M1 phenotype. Aqueous and flavonoid extracts enhanced NADPH quinine oxido-reductase 1 (NQO1) mRNA expression in polarized macrophages which could play an important role in cancer chemoprevention. All the samples studied were non-toxic to normal living cells and the pure alkaloid tested, 6-hydroxycrinamidine, was not active in any of the models investigated.

CONCLUSIONS

Our results indicate that CL extracts and alkaloid fraction (but not pure 6-hydroxycrinamidine) inhibit the proliferation of lymphoma cells in multiple pathways. Our results are in accordance with traditional usage and encourage further studies and in vivo assays.

A fraction of stem bark extract of Entada africana suppresses lipopolysaccharide-induced inflammation in RAW 264.7 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Entada africana is a plant used in African traditional medicine for the treatment of stomachache, fever, liver related diseases, wound healing, cataract and dysentery.

AIMS OF THE STUDY

This study aimed at evaluating the anti-inflammatory activity of fractions of the stem bark extract of the plant using lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophages model.

MATERIALS AND METHODS

The crude extract was prepared using the mixture CH2Cl2/MeOH (1:1, v/v) and fractionated by flash chromatography using solvents of increasing polarity to obtain five different fractions. The effects of the fractions on the cells viability were studied by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and their inhibitory activity against LPS-induced nitric oxide (NO) production screened by Griess test. The most active fraction was further investigated for its effects on reactive oxygen species (ROS) production using flux cytometry, the expression of inducible nitric oxide synthase (iNOS), pro-and anti-inflammatory cytokines (IL1β, TNFα, IL6, IL10 and IL13) by RT-PCR, and the activity of the enzyme p38 MAPK kinase by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The fractions presented no significant effect on the viability of macrophages at 100 μg/ml after 24h incubation. The CH2Cl2/MeOH 5% (Ea5) fraction was found to be the most potent in inhibiting NO production with a half inhibition concentration (IC50)=18.36 μg/ml, and showed the highest inhibition percentage (89.068%) in comparison with Baicalin (63.34%), an external standard at 50 μg/ml. Ea5, as well as Baicalin significantly (P<0.05) inhibited the expression of TNFα, IL6 and IL1β mRNA, attenuated mRNA expression of inducible NO synthase in a concentration-dependent manner, stimulated the expression of anti-inflammatory cytokines (IL10 and IL13), and showed a 30% inhibition of the activity of p38 MAPK kinase.

CONCLUSION

The results of the present study indicate that the fraction Ea5 of Entada africana possesses most potent in vitro anti-inflammatory activity and may contain compounds useful as a therapeutic agent in the treatment of inflammatory related diseases cause by over-activation of macrophages.

The yin and the yang of follicular lymphoma cell niches: role of microenvironment heterogeneity and plasticity

Follicular lymphoma (FL) results from the malignant transformation of germinal center B cells and is characterized by recurrent genetic alterations providing a direct growth advantage or facilitating interaction with tumor microenvironment. In agreement, accumulating evidences suggest a dynamic bidirectional crosstalk between FL B cells and surrounding non-malignant cells within specialized tumor niches in both invaded lymph nodes and bone marrow. Infiltrating stromal cells, macrophages, and T/NK cell subsets either contribute to anti-tumor immune response, or conversely form a tumor supportive network promoting FL B cell survival, growth, and drug resistance. This review depicts the phenotypic heterogeneity and functional plasticity of the most important FL cell partners and describes their complex interplay. We also unravel how malignant B cells recruit and subvert accessory immune and stromal cells to trigger their polarization toward a supportive phenotype. Based on these observations, innovative therapeutic approaches have been recently proposed, in order to benefit from local anti-tumor immunity and/or to selectively target the protective cell niche.