Macrophage origin limits functional plasticity in helminth-bacterial co-infection

Rapid reprogramming of the macrophage activation phenotype is considered important in the defense against consecutive infection with diverse infectious agents. However, in the setting of persistent, chronic infection the functional importance of macrophage-intrinsic adaptation to changing environments vs. recruitment of new macrophages remains unclear. Here we show that resident peritoneal macrophages expanded by infection with the nematode Heligmosomoides polygyrus bakeri altered their activation phenotype in response to infection with Salmonella enterica ser. Typhimurium in vitro and in vivo. The nematode-expanded resident F4/80high macrophages efficiently upregulated bacterial induced effector molecules (e.g. MHC-II, NOS2) similarly to newly recruited monocyte-derived macrophages. Nonetheless, recruitment of blood monocyte-derived macrophages to Salmonella infection occurred with equal magnitude in co-infected animals and caused displacement of the nematode-expanded, tissue resident-derived macrophages from the peritoneal cavity. Global gene expression analysis revealed that although nematode-expanded resident F4/80high macrophages made an anti-bacterial response, this was muted as compared to newly recruited F4/80low macrophages. However, the F4/80high macrophages adopted unique functional characteristics that included enhanced neutrophil-stimulating chemokine production. Thus, our data provide important evidence that plastic adaptation of MΦ activation does occur in vivo, but that cellular plasticity is outweighed by functional capabilities specific to the tissue origin of the cell

Particulate Matter-Induced Lung Inflammation Increases Systemic Levels of PAI-1 and Activates Coagulation Through Distinct Mechanisms

Exposure of human populations to ambient particulate matter (PM) air pollution significantly contributes to the mortality attributable to ischemic cardiovascular events. We reported that mice treated with intratracheally instilled PM develop a prothrombotic state that requires the release of IL-6 by alveolar macrophages. We sought to determine whether exposure of mice to PM increases the levels of PAI-1, a major regulator of thrombolysis, via a similar or distinct mechanism. mice but was absent in mice treated with etanercept, a TNF-α inhibitor. Treatment with etanercept did not prevent the PM-induced tendency toward thrombus formation.Mice exposed to inhaled PM exhibited a TNF-α-dependent increase in PAI-1 and an IL-6-dependent activation of coagulation. These results suggest that multiple mechanisms link PM-induced lung inflammation with the development of a prothrombotic state

Protective Effect of Curcumin on Pulmonary and Cardiovascular Effects Induced by Repeated Exposure to Diesel Exhaust Particles in Mice

Particulate air pollution has been associated with increased risk of cardiopulmonary diseases. However, the underlying mechanisms are not fully understood. We have previously demonstrated that single dose exposure to diesel exhaust particle (DEP) causes lung inflammation and peripheral thrombotic events. Here, we exposed mice with repeated doses of DEP (15µg/animal) every 2nd day for 6 days (a total of 4 exposures), and measured several cardiopulmonary endpoints 48 h after the end of the treatments. Moreover, the potential protective effect of curcumin (the yellow pigment isolated from turmeric) on DEP-induced cardiopulmonary toxicity was assessed. DEP exposure increased macrophage and neutrophil numbers, tumor necrosis factor α (TNF α) in the bronchoalveolar lavage (BAL) fluid, and enhanced airway resistance to methacoline measured invasively using Flexivent. DEP also significantly increased plasma C-reactive protein (CRP) and TNF α concentrations, systolic blood pressure (SBP) as well as the pial arteriolar thrombosis. It also significantly enhanced the plasma D-dimer and plasminogen activator inhibitor-1 (PAI-1). Pretreatment with curcumin by oral gavage (45 mg/kg) 1h before exposure to DEP significantly prevented the influx of inflammatory cells and the increase of TNF α in BAL, and the increased airway resistance caused by DEP. Likewise, curcumin prevented the increase of SBP, CRP, TNF α, D-dimer and PAI-1. The thrombosis was partially but significantly mitigated. In conclusion, repeated exposure to DEP induced lung and systemic inflammation characterized by TNFα release, increased SBP, and accelerated coagulation. Our findings indicate that curcumin is a potent anti-inflammatory agent that prevents the release of TNFα and protects against the pulmonary and cardiovascular effects of DEP

Local Macrophage Proliferation, Rather than Recruitment from the Blood, Is a Signature of T<sub style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-weight: inherit; font-style: inherit; font-size: 0.85em; font-family: inherit; line-height: 0; text-align: inherit; vertical-align: sub;">H2 Inflammation</sub>

A defining feature of inflammation is the accumulation of innate immune cells in the tissue that are thought to be recruited from the blood. We reveal that a distinct process exists in which tissue macrophages undergo rapid in situ proliferation in order to increase population density. This inflammatory mechanism occurred during T helper 2 (T(H)2)-related pathologies under the control of the archetypal T(H)2 cytokine interleukin-4 (IL-4) and was a fundamental component of T(H)2 inflammation because exogenous IL-4 was sufficient to drive accumulation of tissue macrophages through self-renewal. Thus, expansion of innate cells necessary for pathogen control or wound repair can occur without recruitment of potentially tissue-destructive inflammatory cells

Cardiovascular health and particulate vehicular emissions: a critical evaluation of the evidence

A major public health goal is to determine linkages between specific pollution sources and adverse health outcomes. This paper provides an integrative evaluation of the database examining effects of vehicular emissions, such as black carbon (BC), carbonaceous gasses, and ultrafine PM, on cardiovascular (CV) morbidity and mortality. Less than a decade ago, few epidemiological studies had examined effects of traffic emissions specifically on these health endpoints. In 2002, the first of many studies emerged finding significantly higher risks of CV morbidity and mortality for people living in close proximity to major roadways, vs. those living further away. Abundant epidemiological studies now link exposure to vehicular emissions, characterized in many different ways, with CV health endpoints such as cardiopulmonary and ischemic heart disease and circulatory-disease-associated mortality; incidence of coronary artery disease; acute myocardial infarction; survival after heart failure; emergency CV hospital admissions; and markers of atherosclerosis. We identify numerous in vitro, in vivo, and human panel studies elucidating mechanisms which could explain many of these cardiovascular morbidity and mortality associations. These include: oxidative stress, inflammation, lipoperoxidation and atherosclerosis, change in heart rate variability (HRV), arrhythmias, ST-segment depression, and changes in vascular function (such as brachial arterial caliber and blood pressure). Panel studies with accurate exposure information, examining effects of ambient components of vehicular emissions on susceptible human subjects, appear to confirm these mechanisms. Together, this body of evidence supports biological mechanisms which can explain the various CV epidemiological findings. Based upon these studies, the research base suggests that vehicular emissions are a major environmental cause of cardiovascular mortality and morbidity in the United States. As a means to reduce the public health consequences of such emissions, it may be desirable to promulgate a black carbon (BC) PM2.5 standard under the National Ambient Air Quality Standards, which would apply to both on and off-road diesels. Two specific critical research needs are identified. One is to continue research on health effects of vehicular emissions, gaseous as well as particulate. The second is to utilize identical or nearly identical research designs in studies using accurate exposure metrics to determine whether other major PM pollutant sources and types may also underlie the specific health effects found in this evaluation for vehicular emissions

IL-4 directly signals tissue-resident macrophages to proliferate beyond homeostatic levels controlled by CSF-1

Macrophages (M Phi s) colonize tissues during inflammation in two distinct ways: recruitment of monocyte precursors and proliferation of resident cells. We recently revealed a major role for IL-4 in the proliferative expansion of resident M Phi s during a Th2-biased tissue nematode infection. We now show that proliferation of M Phi s during intestinal as well as tissue nematode infection is restricted to sites of IL-4 production and requires M Phi-intrinsic IL-4R signaling. However, both IL-4R alpha-dependent and -independent mechanisms contributed to M Phi proliferation during nematode infections. IL-4R-independent proliferation was controlled by a rise in local CSF-1 levels, but IL-4R alpha expression conferred a competitive advantage with higher and more sustained proliferation and increased accumulation of IL-4R alpha(+) compared with IL-4R alpha(-) cells. Mechanistically, this occurred by conversion of IL-4R alpha(+) M Phi s from a CSF-1-dependent to -independent program of proliferation. Thus, IL-4 increases the relative density of tissue M Phi s by overcoming the constraints mediated by the availability of CSF-1. Finally, although both elevated CSF1R and IL-4R alpha signaling triggered proliferation above homeostatic levels, only CSF-1 led to the recruitment of monocytes and neutrophils. Thus, the IL-4 pathway of proliferation may have developed as an alternative to CSF-1 to increase resident M Phi numbers without coincident monocyte recruitment

Characterizing Activation, Proliferation, and Ontogeny of Murine Macrophages in Parasitic Helminth Infections

Helminth parasites infect approximately 1/3 of the human population. They induce a characteristic immune response whose main focus seems to be to contain the worm parasites and avoid excessive damage to the host. Macrophages are a central player in this response and research using helminth infection models has highlighted the heterogeneity of macrophage responses including distinct recruitment mechanisms, subset-specific activation profiles, and functional diversity. Thus, helminth infection models offer the excellent opportunity to analyze a unique part of the macrophage activation spectrum as well as dissect the functional contributions of macrophages to a wide variety of biologically relevant conditions like wound healing, fibrosis, and immunoregulation.As an example for the analysis of macrophages associated with helminth infection this chapter describes the isolation and magnetic enrichment of pleural macrophages from mice infected with the natural rodent parasite Litomosoides sigmodontis. In addition, it includes a detailed description of how to determine the ontogeny and proliferation status of macrophage populations in helminth infections. Although the focus of this chapter is on helminth infection-derived macrophages, the described methods can easily be adapted to other disease models.</p

The biology of nematode- and IL4Rα-dependent murine macrophage polarization in vivo as defined by RNA-Seq and targeted lipidomics.

Alternatively activated macrophages (AAMφ) are a major component of the response to helminth infection; however, their functions remain poorly defined. To better understand the helminth-induced AAMφ phenotype, we performed a systems-level analysis of in vivo derived AAMφ using an established mouse model. With next-generation RNA sequencing, we characterized the transcriptomes of peritoneal macrophages from BALB/c and IL4Rα(−/−) mice elicited by the nematode Brugia malayi, or via intraperitoneal thioglycollate injection. We defined expression profiles of AAMφ-associated cytokines, chemokines, and their receptors, providing evidence that AAMφ contribute toward recruitment and maintenance of eosinophilia. Pathway analysis highlighted complement as a potential AAMφ-effector function. Up-regulated mitochondrial genes support in vitro evidence associating mitochondrial metabolism with alternative activation. We mapped macrophage transcription start sites, defining over-represented cis-regulatory motifs within AAMφ-associated promoters. These included the binding site for PPAR transcription factors, which maintain mitochondrial metabolism. Surprisingly PPARγ, implicated in the maintenance of AAMφ, was down-regulated on infection. PPARδ expression, however, was maintained. To explain how PPAR-mediated transcriptional activation could be maintained, we used lipidomics to quantify AAMφ-derived eicosanoids, potential PPAR ligands. We identified the PPARδ ligand PGI(2) as the most abundant AAMφ-derived eicosanoid and propose a PGI(2)-PPARδ axis maintains AAMφ during B malayi implantation

Exposure to polycyclic aromatic hydrocarbons and serum inflammatory markers of cardiovascular disease

Polycyclic aromatic hydrocarbons (PAHs) are environmental and occupational carcinogens produced by the incomplete combustion of organic materials, such as coal and petroleum product combustion, tobacco smoking, and food cooking, that may be significant contributors to the burden of cardiovascular disease in human populations. The purpose of this study was to investigate associations between ten monohydroxy urinary metabolites of four PAHs and three serum biomarkers of cardiovascular disease (fibrinogen, homocysteine, and white blood cell count). Using data on 3,219 participants aged 20 years and older from the National Health and Nutrition Examination Survey (NHANES) 2001–2004 dataset, the associations between PAH metabolites and serum inflammatory markers were analyzed using Spearman correlations and multiple linear regression modeling. The PAH metabolites of naphthalene, fluorene, phenanthrene, and pyrene each showed both positive and negative correlations with homocysteine, fibrinogen, and white blood cell count (correlation coefficient range: −0.077 to 0.143) in nonsmoking participants. Using multiple linear regression models adjusted for age, gender, race/ethnicity, and body mass index, estimates of weighted geometric means of inflammatory marker levels were not significantly different between high and low levels (75(th) vs. 25(th) percentiles) for all PAH metabolites in nonsmoking subjects. The results of this study do not provide evidence for a relationship between PAH exposure (as measured by urinary levels of PAH metabolites) and serum biomarkers of cardiovascular disease after controlling for tobacco use