Defective Macrophage Research Articles

Phagocytosis and Inflammation: Exploring the effects of the components of E-cigarette vapor on macrophages.

E‐cigarettes are perceived as harmless; however, evidence of their safety is lacking. New data suggests E‐cigarettes discharge a range of compounds capable of physiological damage to users. We previously established that cigarette smoke caused defective alveolar macrophage phagocytosis. The present study compared the effect E‐cigarette of components; E‐liquid flavors, nicotine, vegetable glycerine, and propylene glycol on phagocytosis, proinflammatory cytokine secretion, and phagocytic recognition molecule expression using differentiated THP‐1 macrophages. Similar to CSE, phagocytosis of NTHi bacteria was significantly decreased by E‐liquid flavoring (11.65–15.75%) versus control (27.01%). Nicotine also decreased phagocytosis (15.26%). E‐liquid, nicotine, and E‐liquid+ nicotine reduced phagocytic recognition molecules; SR‐A1 and TLR‐2. IL‐8 secretion increased with flavor and nicotine, while TNF α, IL‐1β, IL‐6, MIP‐1α, MIP‐1β, and MCP‐1 decreased after exposure to most flavors and nicotine. PG, VG, or PG:VG mix also induced a decrease in MIP‐1α and MIP‐1β. We conclude that E‐cigarettes can cause macrophage phagocytic dysfunction, expression of phagocytic recognition receptors and cytokine secretion pathways. As such, E‐cigarettes should be treated with caution by users, especially those who are nonsmokers.

Modulation of innate immunity of patients with Alzheimer's disease by omega-3 fatty acids.

The innate immune system of patients with Alzheimer's disease and mild cognitive impairment (MCI) is deregulated with highly increased or decreased transcription of inflammatory genes and consistently depressed phagocytosis of amyloid-β1-42 (Aβ) by monocytes and macrophages. Current immune therapies target single mechanisms in the adaptive immune system but not innate immunity. Here, we summarize recent advances in therapy by ω-3, ω-6, and epoxy fatty acids; specialized proresolving mediators; and vitamin D3 that have proven immune effects and emerging cognitive effects in patients with MCI. The hypothesis of this approach is that macrophages of normal participants, but not those of patients with Alzheimer's disease and MCI, possess effective phagocytosis for Aβ and protect homeostasis of the brain and, furthermore, that defective MCI macrophages recover phagocytic function via ω-3. Recent studies of fish-derived ω-3 supplementation in patients with MCI have shown polarization of Apoε3/ε3 patients' macrophages to an intermediate M1-M2 phenotype that is optimal for Aβ phagocytosis and the stabilization of cognitive decline. Therefore, accumulating preclinical and preliminary clinical evidence indicates that ω-3 supplementation should be tested in a randomized controlled clinical trial and that the analysis should involve the apolipoprotein E genotype and intervening conditions during trial.-Fiala, M., Kooij, G., Wagner, K., Hammock, B., Pellegrini, M. Modulation of innate immunity of patients with Alzheimer's disease by omega-3 fatty acids.

Effects of PI3Kδ-RhoA pathway on phagocytosis defect of alveolar macrophages in a mouse model of chronic obstructive pulmonary disease

Objective: To investigate effects of Phosphoinositide3-Kinases (PI3Kδ)-Ras homolog gene family member A(RhoA) pathway on phagocytosis deficiency of alveolar macrophages (AMs) in a mouse model of chronic obstructive pulmonary disease (COPD). Methods: Twenty mice were exposed to cigarette smoking to establish the COPD model, with 20 mice as the control group. AMs were isolated from lung tissue by discontinuous density gradient centrifugation and then divided into a healthy control group, a COPD group, a healthy IC87114 group and a COPD IC87114 group. The culture of IC87114 group was mixed with a final concentration of 1 nmol/L IC87114 for 24 hours. Mean fluorescence intensity (MFI) and the positive percent of AMs engulfing flurescein isothiocyanate-labeled Escherichina coli (FITC-E.coli) (AM%) were detected by flow cytometry. Real-Time PCR(RT-PCR)and Western blot were applied to detect mRNA and protein. G-LISA RhoA Kit was used to detect the activity of RhoA, and laser scanning confocal microscopy was used to observe the cytoskeleton structure of AMs. Results: Phagocytosis of AM: MFI and AM %in the COPD group [(4 512±517), (32.2±4.6)%] were decreased than those in the healthy control group [(9 857±1 042), (68.0±4.0)%, all P<0.01]. Compared with the COPD group, MFI and AM% in the COPD IC87114 group [(6 894±472), (50.6±2.1)%] were increased (all P<0.01). The expressions of mRNA and protein of PI3Kδ in the COPD group (3.14±0.54, 0.84±0.08) were increased than those in the healthy control group (1.00±0.00, 0.57±0.07) (all P<0.01). Compared with the COPD group, the expressions of mRNA and protein of PI3Kδ in the COPD IC87114 group (1.52±0.28, 0.66±0.13) were decreased (all P<0.01). The RhoA mRNA, protein and activity in the COPD group (0.70±0.07, 0.41±0.10, 0.70±0.06) were decreased compared to those in the healthy control group (1.00±0.00, 0.56±0.09, 1.19±0.09) (all P<0.01). Compared with the COPD group, the expression of mRNA, protein and activity of RhoA in the COPD IC87114 group(0.91±0.08, 0.48±0.06, 0.86±0.06) were increased (P<0.01, P<0.05). Cytoskeleton of AM: The pseudopods of the healthy control group and the healthy IC87114 group extended well, and the ability of phagocytosing FITC-E.coli was intact, but there were some defects in the COPD group. Compared with the COPD group, the COPD IC87114 group was better, both in phagocytosing and extending of pseudopods. Negative correlations existed between the mRNA, protein of PI3Kδ with mRNA, protein and activity of RhoA. Negative correlations also existed between the mRNA, protein of PI3Kδ with MFI, but positive correlations between RhoA and MFI were observed in all groups. Conclusion: The phagocytosis of AMs in COPD mice was defective, with abnormal rearrangement of the cytoskeleton. PI3Kδ negatively regulated RhoA, while PI3Kδ over activation resulted in decreasing activity of RhoA and then induced abnormal cytoskeleton rearrangement in AMs, which led to phagocytosis deficiency.IC87114 inhibited PI3Kδ activation, improved the activity of RhoA and partly recovered phagocytosis of AMs.

CFTR-dependent defect in alternatively-activated macrophages in cystic fibrosis

BackgroundThe role of the macrophages in cystic fibrosis (CF) lung disease has been poorly studied. We hypothesized that alternatively activated M2 macrophages are abnormal in CF lung disease. MethodsBlood samples were collected from adults (n=13) children (n=27) with CF on admission for acute pulmonary exacerbation and when clinically stable. Monocytes were differentiated into macrophages and polarized into classical (M1) and alternatively-activated (M2) phenotypes, function determined ex-vivo and compared with healthy controls. ResultsIn the absence of functional cystic fibrosis trans-membrane conductance regulator (CFTR), either naturally in patients with CF or induced with CFTR inhibitors, monocyte-derived macrophages do not respond to IL-13/IL-4, fail to polarize into M2s associated with a post-transcriptional failure to produce and express IL-13Rα1 on the macrophage surface Polarization to the M1 phenotype was unaffected. ConclusionsCFTR-dependent imbalance of macrophage phenotypes and functions could contribute to the exaggerated inflammatory response seen in CF lung disease.

Porphyromonas gingivalis gingipains cause defective macrophage migration towards apoptotic cells and inhibit phagocytosis of primary apoptotic neutrophils

Periodontal disease is a prevalent chronic inflammatory condition characterised by an aberrant host response to a pathogenic plaque biofilm resulting in local tissue damage and frustrated healing that can result in tooth loss. Cysteine proteases (gingipains) from the key periodontal pathogen Porphyromonas gingivalis have been implicated in periodontal disease pathogenesis by inhibiting inflammation resolution and are linked with systemic chronic inflammatory conditions such as rheumatoid arthritis. Efficient clearance of apoptotic cells is essential for the resolution of inflammation and tissue restoration. Here we sought to characterise the innate immune clearance of apoptotic cells and its modulation by gingipains. We examined the capacity of gingipain-treated macrophages to migrate towards and phagocytose apoptotic cells. Lysine gingipain treatment of macrophages impaired macrophage migration towards apoptotic neutrophils. Furthermore, lysine gingipain treatment reduced surface expression levels of CD14, a key macrophage receptor for apoptotic cells, which resulted in reduced macrophage interactions with apoptotic cells. Additionally, while apoptotic cells and their derived secretome were shown to inhibit TNF-α-induced expression by P. gingivalis lipopolysaccharide, we demonstrated that gingipain preparations induced a rapid inflammatory response in macrophages that was resistant to the anti-inflammatory effects of apoptotic cells or their secretome. Taken together, these data indicate that P. gingivalis may promote the chronic inflammation seen in periodontal disease patients by multiple mechanisms, including rapid, potent gingipain-mediated inflammation, coupled with receptor cleavage leading to defective clearance of apoptotic cells and reduced anti-inflammatory responses. Thus, gingipains represent a potential therapeutic target for intervention in the management of chronic periodontal disease.

Human Cystic Fibrosis Macrophages Have Defective Calcium-Dependent Protein Kinase C Activation of the NADPH Oxidase, an Effect Augmented by Burkholderia cenocepacia.

Macrophage intracellular pathogen killing is defective in cystic fibrosis (CF), despite abundant production of reactive oxygen species (ROS) in lung tissue. Burkholderia species can cause serious infection in CF and themselves affect key oxidase components in murine non-CF cells. However, it is unknown whether human CF macrophages have an independent defect in the oxidative burst and whether Burkholderia contributes to this defect in terms of assembly of the NADPH oxidase complex and subsequent ROS production. In this article, we analyze CF and non-CF human monocyte-derived macrophages (MDMs) for ROS production, NADPH assembly capacity, protein kinase C expression, and calcium release in response to PMA and CF pathogens. CF MDMs demonstrate a nearly 60% reduction in superoxide production after PMA stimulation compared with non-CF MDMs. Although CF MDMs generally have increased total NADPH component protein expression, they demonstrate decreased expression of the calcium-dependent protein kinase C conventional subclass α/β leading to reduced phosphorylation of NADPH oxidase components p47 phox and p40 phox in comparison with non-CF MDMs. Ingestion of B. cenocepacia independently contributes to and worsens the overall oxidative burst deficits in CF MDMs compared with non-CF MDMs. Together, these results provide evidence for inherent deficits in the CF macrophage oxidative burst caused by decreased phosphorylation of NADPH oxidase cytosolic components that are augmented by Burkholderia These findings implicate a critical role for defective macrophage oxidative responses in persistent bacterial infections in CF and create new opportunities for boosting the macrophage immune response to limit infection.

Vitamin D Deficiency in Human and Murine Sepsis.

Vitamin D deficiency has been implicated as a pathogenic factor in sepsis and ICU mortality but causality of these associations has not been demonstrated. To determine whether sepsis and severe sepsis are associated with vitamin D deficiency and to determine whether vitamin D deficiency influences the severity of sepsis. Sixty-one patients with sepsis and severe sepsis from two large U.K. hospitals and 20 healthy controls were recruited. Murine models of cecal ligation and puncture and intratracheal lipopolysaccharide were undertaken in normal and vitamin D deficient mice to address the issue of causality. Patients with severe sepsis had significantly lower concentrations of 25-hydroxyvitamin D3 than patients with either mild sepsis or age-matched healthy controls (15.7 vs 49.5 vs 66.5 nmol/L; p = 0.0001). 25-hydroxyvitamin D3 concentrations were significantly lower in patients who had positive microbiologic culture than those who were culture negative (p = 0.0023) as well as those who died within 30 days of hospital admission (p = 0.025). Vitamin D deficiency in murine sepsis was associated with increased peritoneal (p = 0.037), systemic (p = 0.019), and bronchoalveolar lavage (p = 0.011) quantitative bacterial culture. This was associated with reduced local expression of the cathelicidin-related antimicrobial peptide as well as evidence of defective macrophage phagocytosis (p = 0.029). In the intratracheal lipopolysaccharide model, 1,500 IU of intraperitoneal cholecalciferol treatment 6 hours postinjury reduced alveolar inflammation, cellular damage, and hypoxia. Vitamin D deficiency is common in severe sepsis. This appears to contribute to the development of the condition in clinically relevant murine models and approaches to correct vitamin D deficiency in patients with sepsis should be developed.

Cysteamine re-establishes the clearance of Pseudomonas aeruginosa by macrophages bearing the cystic fibrosis-relevant F508del-CFTR mutation

Cystic fibrosis (CF), the most common lethal monogenic disease in Caucasians, is characterized by recurrent bacterial infections and colonization, mainly by Pseudomonas aeruginosa, resulting in unresolved airway inflammation. CF is caused by mutations in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein, which functions as a chloride channel in epithelial cells, macrophages, and other cell types. Impaired bacterial handling by macrophages is a feature of CF airways, although it is still debated how defective CFTR impairs bacterial killing. Recent evidence indicates that a defective autophagy in CF macrophages leads to alterations of bacterial clearance upon infection. Here we use bone marrow-derived macrophages from transgenic mice to provide the genetic proof that defective CFTR compromises both uptake and clearance of internalized Pseudomonas aeruginosa. We demonstrate that the proteostasis regulator cysteamine, which rescues the function of the most common F508del-CFTR mutant and hence reduces lung inflammation in CF patients, can also repair the defects of CF macrophages, thus restoring both bacterial internalization and clearance through a process that involves upregulation of the pro-autophagic protein Beclin 1 and re-establishment of the autophagic pathway. Altogether these results indicate that cysteamine restores the function of several distinct cell types, including that of macrophages, which might contribute to its beneficial effects on CF.

Defective macrophage phagocytosis and particle clearance in Niemann-Pick disease type C1 mice

Defective macrophage phagocytosis and particle clearance in Niemann-Pick disease type C1 mice

Abstract 13229: Varying ABCG1 Expression is Associated With Macrophage Apoptosis&amp;Phagocytosis

Introduction: ATP-binding cassette transporter G1(ABCG1)is a transmembrane protein mediated efflux of cellular cholesterol to HDL, which plays a vital part in macrophage lipid homeostasis, but the role of ABCG1 in atherosclerosis still remains controversial. Our previous study demonstrated that human ABCG1 -367 G&gt;A polymorphism in promoter region, which leads to lower ABCG1 protein expression, was associated with a reduced risk of CAD. However, the mechanism behind is not fully understood. Hypothesis: Oxysterols, the oxidized derivatives of cholesterol, whose efflux are mediated by ABCG1, exert cytotoxic effect on macrophage and accelerate cell apoptosis. Low ABCG1 expression induces excess oxysterols accumulation in macrophage, which augments the inflammatory response and accelerates apoptosis. Since defective apoptotic macrophage clearance in late lesions promotes atherosclerosis progression, we hypothesize that macrophage with lower ABCG1 expression may remove apoptotic cells more efficiently, thereby generating an antiatherogenic effect. Methods: To investigate the effect of ABCG1 expression on macrophage, we established ABCG1 knockdown cell line by means of lentivirus mediated shRNA. Apoptosis was determined by flow cytometry (FCM). Fluorescence labeled apoptotic model was generated and macrophage phagocytosis was evaluated. The inflammatory factors level and phagocytosis associated gene expression were measured by ELISA and realtime PCR. Results: Compared with control group, macrophage with lower ABCG1 expression had a higher secretion level of Inflammatory factors, such as TNF-α and IL-1β, showing an increased expression of classic inflammatory M1 phenotype markers,such as CD86 and TGF-β, and a down-regulation of CD163,Arg and IL-6 expression, which are markers of anti-inflammatory M2 phenotype macrophage. The apoptosis was significantly accelerated and the phagocytic clearance was enhanced after ABCG1 expression decreased, which means apoptotic cells could be removed more quickly. Both CD36 and Mertk showed a higher mRNA level in ABCG1 knockdown group. Conclusions: Decreased expression of macrophage ABCG1 may exert antiatherogenic function through accelerating apoptosis and enhancing phagocytosis.

Impaired Recognition of Mycobacterium tuberculosis by Alveolar Macrophages From Diabetic Mice.

Diabetes mellitus is associated with increased tuberculosis risk and severity. We previously reported that tuberculosis susceptibility in diabetic mice results from a delay in innate immune response to inhaled Mycobacterium tuberculosis, leading to delayed adaptive immune priming and, consequently, a higher plateau lung bacterial burden and greater immune pathology. We tested the capacity of alveolar macrophages from diabetic mice to phagocytose M. tuberculosis ex vivo and promote T-cell activation in vivo. Alveolar macrophages from diabetic mice had reduced expression of CD14 and macrophage receptor with collagenous structure (MARCO), which recognize the bacterial cell wall component trehalose 6,6'-dimycolate (TDM). Diabetic alveolar macrophages exhibited reduced phagocytosis of M. tuberculosis or TDM-coated latex beads. This alveolar macrophage phenotype was absent in peritoneal and bone marrow-derived macrophages. Transfer of infected alveolar macrophages from diabetic mice into nondiabetic recipients confirmed an intrinsic alveolar macrophage defect that hindered T-cell priming. The diabetic alveolar macrophage phenotype depended in part on expression of the receptor for advanced glycation end products. Reduced MARCO and CD14 expression contributes to defective sentinel function of alveolar macrophages, promoting tuberculosis susceptibility in diabetic hosts at a critical early step in the immune response to aerosol infection.

The Vitamin D Receptor Regulates Tissue Resident Macrophage Response to Injury.

Ligand-dependent actions of the vitamin D receptor (VDR) play a pleiotropic role in the regulation of innate and adaptive immunity. The liganded VDR is required for recruitment of macrophages during the inflammatory phase of cutaneous wound healing. Although the number of macrophages in the granulation tissue 2 days after wounding is markedly reduced in VDR knockout (KO) compared with wild-type mice, VDR ablation does not alter macrophage polarization. Parabiosis studies demonstrate that circulatory chimerism with wild-type mice is unable to rescue the macrophage defect in the wounds of VDR KO mice and reveal that wound macrophages are of local origin, regardless of VDR status. Wound cytokine analyses demonstrated a decrease in macrophage colony-stimulating factor (M-CSF) protein levels in VDR KO mice. Consistent with this, induction of M-CSF gene expression by TGFβ and 1,25-dihydroxyvitamin D was impaired in dermal fibroblasts isolated from VDR KO mice. Because M-CSF is important for macrophage self-renewal, studies were performed to evaluate the response of tissue resident macrophages to this cytokine. A decrease in M-CSF induced proliferation and cyclin D1 expression was observed in peritoneal resident macrophages isolated from VDR KO mice, suggesting an intrinsic macrophage abnormality. Consistent with this, wound-healing assays in mice with macrophage-specific VDR ablation demonstrate that a normal wound microenvironment cannot compensate for the absence of the VDR in macrophages and thus confirm a critical role for the macrophage VDR in the inflammatory response to injury.

Correcting the NLRP3 inflammasome deficiency in macrophages from autoimmune NZB mice with exon skipping antisense oligonucleotides.

Inflammasomes are molecular complexes activated by infection and cellular stress, leading to caspase-1 activation and subsequent interleukin-1β (IL-1β) processing and cell death. The autoimmune NZB mouse strain does not express NLRP3, a key inflammasome initiator mediating responses to a wide variety of stimuli including endogenous danger signals, environmental irritants and a range of bacterial, fungal and viral pathogens. We have previously identified an intronic point mutation in the Nlrp3 gene from NZB mice that generates a splice acceptor site. This leads to inclusion of a pseudoexon that introduces an early termination codon and is proposed to be the cause of NLRP3 inflammasome deficiency in NZB cells. Here we have used exon skipping antisense oligonucleotides (AONs) to prevent aberrant splicing of Nlrp3 in NZB macrophages, and this restored both NLRP3 protein expression and NLRP3 inflammasome activity. Thus, the single point mutation leading to aberrant splicing is the sole cause of NLRP3 inflammasome deficiency in NZB macrophages. The NZB mouse provides a model for addressing a splicing defect in macrophages and could be used to further investigate AON design and delivery of AONs to macrophages in vivo.

Is Alveolar Macrophage Phagocytic Dysfunction in Children With Protracted Bacterial Bronchitis a Forerunner to Bronchiectasis?

Children with recurrent protracted bacterial bronchitis (PBB) and bronchiectasis share common features, and PBB is likely a forerunner to bronchiectasis. Both diseases are associated with neutrophilic inflammation and frequent isolation of potentially pathogenic microorganisms, including nontypeable Haemophilus influenzae (NTHi), from the lower airway. Defective alveolar macrophage phagocytosis of apoptotic bronchial epithelial cells (efferocytosis), as found in other chronic lung diseases, may also contribute to tissue damage and neutrophil persistence. Thus, in children with bronchiectasis or PBB and in control subjects, we quantified the phagocytosis of airway apoptotic cells and NTHi by alveolar macrophages and related the phagocytic capacity to clinical and airway inflammation. Children with bronchiectasis (n = 55) or PBB (n = 13) and control subjects (n = 13) were recruited. Alveolar macrophage phagocytosis, efferocytosis, and expression of phagocytic scavenger receptors were assessed by flow cytometry. Bronchoalveolar lavage fluid interleukin (IL) 1β was measured by enzyme-linked immunosorbent assay. For children with PBB or bronchiectasis, macrophage phagocytic capacity was significantly lower than for control subjects (P = .003 and P < .001 for efferocytosis and P = .041 and P = .004 for phagocytosis of NTHi; PBB and bronchiectasis, respectively); median phagocytosis of NTHi for the groups was as follows: bronchiectasis, 13.7% (interquartile range [IQR], 11%-16%); PBB, 16% (IQR, 11%-16%); control subjects, 19.0% (IQR, 13%-21%); and median efferocytosis for the groups was as follows: bronchiectasis, 14.1% (IQR, 10%-16%); PBB, 16.2% (IQR, 14%-17%); control subjects, 18.1% (IQR, 16%-21%). Mannose receptor expression was significantly reduced in the bronchiectasis group (P = .019), and IL-1β increased in both bronchiectasis and PBB groups vs control subjects. A reduced alveolar macrophage phagocytic host response to apoptotic cells or NTHi may contribute to neutrophilic inflammation and NTHi colonization in both PBB and bronchiectasis. Whether this mechanism also contributes to the progression of PBB to bronchiectasis remains unknown.

Drosophila WASH is required for integrin-mediated cell adhesion, cell motility and lysosomal neutralization.

The Wiskott-Aldrich syndrome protein and SCAR homolog (WASH; also known as Washout in flies) is a conserved actin-nucleation-promoting factor controlling Arp2/3 complex activity in endosomal sorting and recycling. Previous studies have identified WASH as an essential regulator in Drosophila development. Here, we show that homozygous wash mutant flies are viable and fertile. We demonstrate that Drosophila WASH has conserved functions in integrin receptor recycling and lysosome neutralization. WASH generates actin patches on endosomes and lysosomes, thereby mediating both aforementioned functions. Consistently, loss of WASH function results in cell spreading and cell migration defects of macrophages, and an increased lysosomal acidification that affects efficient phagocytic and autophagic clearance. WASH physically interacts with the vacuolar (V)-ATPase subunit Vha55 that is crucial to establish and maintain lysosome acidification. As a consequence, starved flies that lack WASH function show a dramatic increase in acidic autolysosomes, causing a reduced lifespan. Thus, our data highlight a conserved role for WASH in the endocytic sorting and recycling of membrane proteins, such as integrins and the V-ATPase, that increase the likelihood of survival under nutrient deprivation.

Potential Link between the Sphingosine-1-Phosphate (S1P) System and Defective Alveolar Macrophage Phagocytic Function in Chronic Obstructive Pulmonary Disease (COPD).

IntroductionWe previously reported that alveolar macrophages from patients with chronic obstructive pulmonary disease (COPD) are defective in their ability to phagocytose apoptotic cells, with a similar defect in response to cigarette smoke. The exact mechanisms for this defect are unknown. Sphingolipids including ceramide, sphingosine and sphingosine-1-phosphate (S1P) are involved in diverse cellular processes and we hypothesised that a comprehensive analysis of this system in alveolar macrophages in COPD may help to delineate the reasons for defective phagocytic function.MethodsWe compared mRNA expression of sphingosine kinases (SPHK1/2), S1P receptors (S1PR1-5) and S1P-degrading enzymes (SGPP1, SGPP2, SGPL1) in bronchoalveolar lavage-derived alveolar macrophages from 10 healthy controls, 7 healthy smokers and 20 COPD patients (10 current- and 10 ex-smokers) using Real-Time PCR. Phagocytosis of apoptotic cells was investigated using flow cytometry. Functional associations were assessed between sphingosine signalling system components and alveolar macrophage phagocytic ability in COPD. To elucidate functional effects of increased S1PR5 on macrophage phagocytic ability, we performed the phagocytosis assay in the presence of varying concentrations of suramin, an antagonist of S1PR3 and S1PR5. The effects of cigarette smoking on the S1P system were investigated using a THP-1 macrophage cell line model.ResultsWe found significant increases in SPHK1/2 (3.4- and 2.1-fold increases respectively), S1PR2 and 5 (4.3- and 14.6-fold increases respectively), and SGPL1 (4.5-fold increase) in COPD vs. controls. S1PR5 and SGPL1 expression was unaffected by smoking status, suggesting a COPD “disease effect” rather than smoke effect per se. Significant associations were noted between S1PR5 and both lung function and phagocytosis. Cigarette smoke extract significantly increased mRNA expression of SPHK1, SPHK2, S1PR2 and S1PR5 by THP-1 macrophages, confirming the results in patient-derived macrophages. Antagonising SIPR5 significantly improved phagocytosis.ConclusionOur results suggest a potential link between the S1P signalling system and defective macrophage phagocytic function in COPD and advise therapeutic targets.

Adiposity and immune-muscle crosstalk in South Asians &Europeans: A cross-sectional study.

South Asians (SA) are at higher risk of cardiometabolic disorders than Europeans (EU), yet the potential determinants of this risk are poorly understood. We tested the hypotheses that 1) South Asians (SA) have greater muscle inflammation compared to Europeans (EU) at similar fat mass 2) differential regional adiposity in SA compared to EU is associated with enhanced muscle inflammation in SA. This cross-sectional study was conducted at a tertiary academic center in Hamilton, Ontario, Canada. The study included 29 EU and 26 SA. Quantitative real-time PCR and western blot were used to measure muscle inflammation. Statistical analysis was done using a General Linear Model. Despite having similar macrophage content to EU, SA muscle had lower levels of chemokine CCL2 compared to EU at gene expression (β -1.099, SE β 0.521, p-value 0.04) and protein (0.84 ± 0.69 versus 1.10 ± 0.60, p-value 0.052) levels. SA had more pronounced abdominal and hepatic adiposity, with smaller Intramyocellular lipid particles compared to EU (0.26 ± 0.12 μm2 versus 0.15 ± 0.06 μm2, p-value 0.02). In conclusion, CCL2 downregulation in SA may be an attempt to protect muscle against macrophage infiltration, and defects in fatty acid partitioning to muscle may lead to the disproportionate adiposity and adverse cardiometabolic profile in SA.

Quantification of type VI secretion system activity in macrophages infected with Burkholderia cenocepacia.

The Gram-negative bacterial type VI secretion system (T6SS) delivers toxins to kill or inhibit the growth of susceptible bacteria, while other secretion systems target eukaryotic cells. Deletion of atsR, a negative regulator of virulence factors in B. cenocepacia K56-2, increases T6SS activity. Macrophages infected with a K56-2 ΔatsR mutant display dramatic alterations in their actin cytoskeleton architecture that rely on the T6SS, which is responsible for the inactivation of multiple Rho-family GTPases by an unknown mechanism. We employed a strategy to standardize the bacterial infection of macrophages and densitometrically quantify the T6SS-associated cellular phenotype, which allowed us to characterize the phenotype of systematic deletions of each gene within the T6SS cluster and ten vgrG genes in K56-2 ΔatsR. None of the genes from the T6SS core cluster nor the individual vgrG genes were directly responsible for the cytoskeletal changes in infected cells. However, a mutant strain with all vgrG genes deleted was unable to cause macrophage alterations. Despite not being able to identify a specific effector protein responsible for the cytoskeletal defects in macrophages, our strategy resulted in the identification of the critical core components and accessory proteins of the T6SS assembly machinery and provides a screening method to detect T6SS effectors targeting the actin cytoskeleton in macrophages by random mutagenesis.

Forward genetics screens using macrophages to identify Toxoplasma gondii genes important for resistance to IFN-γ-dependent cell autonomous immunity.

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan pathogen. The parasite invades and replicates within virtually any warm blooded vertebrate cell type. During parasite invasion of a host cell, the parasite creates a parasitophorous vacuole (PV) that originates from the host cell membrane independent of phagocytosis within which the parasite replicates. While IFN-dependent-innate and cell mediated immunity is important for eventual control of infection, innate immune cells, including neutrophils, monocytes and dendritic cells, can also serve as vehicles for systemic dissemination of the parasite early in infection. An approach is described that utilizes the host innate immune response, in this case macrophages, in a forward genetic screen to identify parasite mutants with a fitness defect in infected macrophages following activation but normal invasion and replication in naïve macrophages. Thus, the screen isolates parasite mutants that have a specific defect in their ability to resist the effects of macrophage activation. The paper describes two broad phenotypes of mutant parasites following activation of infected macrophages: parasite stasis versus parasite degradation, often in amorphous vacuoles. The parasite mutants are then analyzed to identify the responsible parasite genes specifically important for resistance to induced mediators of cell autonomous immunity. The paper presents a general approach for the forward genetics screen that, in theory, can be modified to target parasite genes important for resistance to specific antimicrobial mediators. It also describes an approach to evaluate the specific macrophage antimicrobial mediators to which the parasite mutant is susceptible. Activation of infected macrophages can also promote parasite differentiation from the tachyzoite to bradyzoite stage that maintains chronic infection. Therefore, methodology is presented to evaluate the importance of the identified parasite gene to establishment of chronic infection.

Necrotizing fasciitis associated with systemic lupus erythematosus in a child.

Sir, Necrotizing fasciitis (NF) is a rapidly progressive, potentially fatal necrotizing infection of skin and subcutaneous tissues.[1] It is rarely seen in children and its association with systemic lupus erythematosus (SLE) is even rarer. We report a 11-year-old female child who developed NF of the lower leg and was incidentally diagnosed to have SLE. Patients with SLE are predisposed to develop fatal infections. Early recognition of this condition and its association is important to prevent mortality. A 11-year-old female child was referred from the pediatric intensive care unit for evaluation of painful skin lesions on her left lower limb since two weeks. There was a history of local trauma following which the child developed swelling and pain of her left lower limb associated with fever. She was diagnosed to have cellulitis and treated with intravenous antibiotics ceftriaxone, amikacin, and metrogyl with not much improvement. Past history was noncontributory. Cutaneous examination revealed ill-defined ecchymotic plaque with overlying bullae on the medial aspect of left lower leg [Figure 1]. The entire limb was edematous and tender with local increase in temperature. Over one day, the lesions blackened with areas of necrosis and yellowish slough involving the entire lower limb. In few days, there was necrosis extending into deeper planes of skin. Laboratory investigations showed anemia (hemoglobin: 6.2 mg%), leukopenia (2500 cells/mm3), thrombocytopenia (32,500 cells/mm3), increased liver enzymes, and hyponatremia. Urine routine test showed hematuria and proteinuria. Erythrocyte sedimentation rate (ESR) and C-reactive protein were highly elevated. Chest radiography and ultrasonogram abdomen were normal. Serology for Human immunodeficiency virus (HIV) and blood culture was negative. Culture from the tissue and pus grew group A Streptococcus, Klebsiella, and Escherichia coli. A diagnosis of NF was considered. In view of the above clinical features and investigations, antinuclear antibody and anti-double-stranded DNA tests were done, which were strongly positive. A final diagnosis of systemic lupus erythematosus with NF was made. Surgical debridement of necrotic tissue was done [Figure 2]. As the necrosis had reached the bony tissues, amputation was done. However, the child died due to sepsis.Figure 1: Ecchymotic plaque with overlying bullae and necrotic areas on the medial aspect of left lower legFigure 2: Surgical debridement showing necrotic tissue extending into deeper planesNF is a life-threatening infection with a high mortality rate ranging from 20% to 80% despite the use of appropriate treatment modalities. The etiology of NF is polymicrobial in nature. Most patients with NF have associated comorbidities such as diabetes, HIV infection, renal failure that predispose them to infections.[2] Clinically the patient presents with ecchymosis, bullae, necrosis, and gangrene. The inflammation rapidly progress to involve deep fascial planes thus making the importance of early diagnosis and exploration. Infections are the major cause of mortality in SLE. Even though SLE patients are prone to develop infections, NF is rarely reported. There is an increased risk of infections in SLE due to impaired cell-mediated immunity, immunoglobulin deficiencies, complement factor deficiency, and various defects in other immune effector cells, including neutrophils, macrophages, and natural killer cell.[3] Genetic predisposition and presence of R131variant of FCrRIIA on Fc receptor are believed to contribute to the risk of infection.[4] NF has been associated with other rheumatic disorders that include dermatomyositis, polymyositis, systemic sclerosis, rheumatoid arthritis, and ankylosing spondylitis.[5] Clinically, NF may not be diagnosed early and only when necrosis occurs diagnosis may become evident. In our case, the child had been diagnosed as having soft tissue infection before presenting to us and treated with antibiotics, which were unresponsive. This indicated deeper infection that required aggressive approach and exploration. Even though appropriate interventions and surgical debridement was done, as the child had presented to us late, there was a delay in diagnosis; the child had to undergo amputation and eventually succumbed to sepsis. There is partly increased risk of infections due to use of oral steroids and immunosuppressants in SLE cases but our case was treatment naïve and it was SLE-associated immunosuppression that must have contributed to the infection. Impaired immune response in SLE is a primary risk factor for developing NF which is an emergency condition requiring early detection and quick debridement. Increased awareness of this condition and its association is necessary to prevent mortality.