Age-dependent changes in porcine alveolar macrophage function during the postnatal period of alveolarization

The impact of age on vitamin D receptor expression, vitamin D metabolism and cytokine production in ex vivo Rhodococcus equi infection of equine alveolar macrophages

Rhodococcus equi (R. equi), a pneumonia-causing intracellular bacterium, results in significant morbidity and mortality in young foals, while healthy adult horses rarely develop disease. Survival and replication within alveolar macrophages (AMφ) are the hallmarks of R. equi's pathogenicity. The vitamin D receptor (VDR) and its ligand, the active vitamin D metabolite 1,25(OH)2D, are important in immune responses to intracellular bacteria. The vitamin D/VDR pathway regulates the downstream production of cytokines in infected human AMφ. The immunomodulatory role of the vitamin D/VDR pathway in equine leukocytes is unknown. The objective of the current study was to determine the impact of R. equi infection and age on synthesis of 1,25(OH)2D, VDR expression, and cytokine production in an ex vivo model of R. equi infection in equine AMφ. AMφ were collected from ten healthy foals at 2-, 4- and 8-weeks old and from nine healthy adult horses once via bronchoalveolar lavage. AMφ were mock infected (CONTROL) or infected with a virulent laboratory strain of R. equi for 7 days (INFECTED). VDR expression was determined via RT-qPCR from cell lysates. 1,25(OH)2D and cytokines were measured in cell supernatant by immunoassays. VDR expression was impacted by age (P = 0.001) with higher expression in AMφ from 8-week-old foals than from 2-week-old foals and adults. There was no significant effect of infection in foal AMφ, but in adults, relative VDR expression was significantly lower in INFECTED AMφ compared to CONTROL AMφ (P = 0.002). There was no effect of age or infection on 1,25(OH)2D concentration (P > 0.37). Mean TNFα production was significantly higher from INFECTED compared to CONTROL AMφ from 4- and 8-week-old foals and adults (P < 0.005). Mean IFNγ production was significantly higher from AMφ from foals at 8-weeks-old compared to 2-weeks-old (P = 0.013) and higher from INFECTED AMφ than from CONTROL AMφ in foals at 4-weeks-old and in adults (P < 0.027). The proportion of samples producing IL-1β and IL-10 was also significantly higher from INFECTED compared to CONTROL AMφ isolated from 4-week-old foals (P < 0.008). Similarly, in adult samples, IL-17 was produced from a greater proportion of INFECTED compared to CONTROL samples (P = 0.031). These data document age-associated changes in VDR expression and cytokine production in equine AMφ in response to R. equi infection. This preliminary investigation supports the need for further research to fully elucidate if the vitamin D pathway has an immunomodulatory role in the horse.

Age-related changes in vitamin D metabolism and vitamin D receptor expression in equine alveolar macrophages: a preliminary study

The vitamin D receptor (VDR)-vitamin D axis modulates pulmonary immunity in people but its role in equine immunity is unknown. Bacterial pneumonia causes high morbidity/mortality in foals and alveolar macrophages (AMφ) are important for pulmonary defenses. Age-related variations in vitamin D-mediated function of AMφ might contribute to the foal's susceptibility to pneumonia. Our aim was to assess the impact of age on equine vitamin D metabolism and VDR expression in AMφ. AMφ and plasma was collected from healthy foals (2, 4 and 8 weeks old) and adult horses (once). AMφ VDR expression was determined via RT-qPCR and plasma vitamin D metabolites quantified via immunoassays. Data were analyzed with linear mixed models. Inactive-vitamin D metabolite concentrations were lowest in foals at 2 weeks and lower at 2 and 4 weeks compared to adults (P < 0.001). Active-vitamin D metabolite concentrations were higher in foals than adults (P < 0.05). VDR expression was detected in AMφ in all animals and was highest in 2-week-old foals. Vitamin D metabolism and AMφ VDR expression are impacted by age in horses. This may have immunological consequences in foals given the key role that the VDR-vitamin D axis has in pulmonary immunity in other species.

Mint Oils: In Vitro Ability to Perform Anti-Inflammatory, Antioxidant, and Antimicrobial Activities and to Enhance Intestinal Barrier Integrity

The objectives of the study were to test the biological activities of peppermint and spearmint oils via (i) measuring in vitro anti-inflammatory effects with porcine alveolar macrophages (PAMs), (ii) determining the barrier integrity of IPEC-J2 by analyzing transepithelial electrical resistance (TEER), (iii) testing their antioxidant activities, and (iv) investigating the antimicrobial activity against enterotoxigenic Escherichia coli (ETEC) F18+. Briefly, (i) macrophages were seeded at 10⁶ cells/mL and treated (24 h) with mint oils and lipopolysaccharide (LPS). The treatments were 2 (0 or 1 μg/mL of LPS) × 5 (0, 25, 50, 100, 200 µg/mL of mint oils). The supernatants were collected for TNF-α and IL-1β measurement by ELISA; (ii) IPEC-J2 cells were seeded at 5 × 10⁵ cells/mL and treated with mint oils (0, 25, 50, 100, and 200 μg/mL). TEER (Ωcm²) was measured at 0, 24, 48, and 72 h; (iii) the antioxidant activity was assessed (0, 1, 50, 100, 200, 500, and 600 mg/mL) using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reducing power assays; (iv) overnight-grown ETEC F18+ were quantified (CFU/mL) after supplementing with peppermint and spearmint oils (0, 1.44, 2.87, 5.75, 11.50, and 23.00 mg/mL). All data were analyzed using the MIXED procedure. Both mint oils significantly inhibited (p < 0.05) IL-1β and TNF-α secretion from LPS-stimulated PAMs. Mint oil treatments did not affect TEER in IPEC-J2. Spearmint and peppermint oils exhibited (p < 0.05) strong antioxidant activities in DPPH and reducing power assays. Both mint oils also dose-dependently inhibited (p < 0.05) the growth of ETEC F18+ in vitro. The results of the study indicated that both mint oils are great candidate feed additives due to their in vitro anti-inflammatory, antioxidant, and antimicrobial effects. Further research is needed to evaluate their efficacy in vivo.

Age-Dependent Translocation of Gold Nanoparticles across the Air-Blood Barrier

Do immature lungs have air-blood barriers that are more permeable to inhaled nanoparticles than those of fully developed mature lungs? Data supporting this notion and explaining the underlying mechanisms do not exist as far as we know. Using a rat model of postnatal lung development, here the data exactly supporting this notion, that is, significantly more gold nanoparticles (NPs) cross from the air space of the lungs to the rest of the body in neonates than in adults, are presented. Moreover, in neonates the translocation of gold NPs is not size dependent, whereas in adult animals smaller NPs cross the air-blood lung barrier much more efficiently than larger NPs. This difference in air-blood permeability in neonate versus adult animals suggests that NP translocation in the immature lungs may follow different rules than in mature lungs. Supporting this notion, we propose that the paracellular transport route may play a more significant role in NP translocation in immature animals, as suggested by protein expression studies. Findings from this study are critical to design optimal ways of inhalation drug delivery using NP nanocarriers for this age group, as well as for better understanding of the potential adverse health effects of nanoparticle exposures in infants and young children.

The Effect of Inactivated Mycobacterium Paratuberculosis Vaccine on the Response to a Heterologous Bacterial Challenge in Pigs

Background: Vaccines may have non-specific effects, affecting resistance to heterologous pathogens. Veterinary vaccines have seldom been investigated for their non-specific effects. However, recent observational studies suggest that an inactivated paratuberculosis vaccine reduced all-cause mortality in goats and cattle. Aim: We tested if vaccination with a killed mycobacterial vaccine may have heterologous effects in swine (Sus domesticus), specifically on the pathogenic and clinical effects of a heterologous challenge with Actinobacillus pleuropneumoniae in young pigs. Methods: Newborn piglets were randomized to vaccination s.c. with the inactivated paratuberculosis vaccine Gudair (Zoetis Inc.) (n = 17) or no vaccine (n = 16). At 4-5 weeks after vaccination, all piglets were challenged intra-nasally with a high (Gudair: n = 8; control: n = 8) or a low (Gudair: n = 9; control: n = 8) dose of the gram-negative bacterium A. pleuropneumoniae causing acute porcine pleuropneumonia. The effect and severity of pathogen challenge was evaluated by measuring acute phase proteins C-reactive protein, haptoglobin and Porcine α1-acid glycoprotein, and by gross pathology 1 day post challenge. Specific and non-specific in vitro cytokine responses to vaccination were evaluated in whole blood before bacterial challenge. Results: The vaccine was immunogenic in the pigs as evidenced by increased IFN-γ responses to purified protein derivative of Mycobacterium paratuberculosis. However, Gudair vaccine did not affect IL-6 responses. The gross pathology of the lungs as well as the acute phase protein responses after the high A. pleuropneumoniae dose challenge was slightly increased in the vaccinated animals compared with controls, whereas this was not seen in the animals receiving the low-dose bacterial challenge. Conclusion: The inactivated paratuberculosis vaccine exacerbated the pathological and inflammatory effects of an experimental A. pleuropneumoniae infection in young pigs.

Effects of Ascaris and Trichuris antigens on cytokine production in porcine blood mononuclear and epithelial cells

Helminth parasites are highly prevalent in swine production, causing chronic infections and considerable morbidity due to growth retardation. Moreover, helminths actively modulate host immune responses to other pathogens and/or vaccines. Here, we investigated the modulatory effects of Ascaris suum adult body fluid (ABF) and Trichuris suis Soluble Products (TsSP) on the cytokine response in porcine peripheral blood mononuclear cells (PBMCs) and the intestinal epithelial cell line IPEC-J2. In PBMCs, TsSP induced the secretion of IL-6, IL-10 and IL-1β, but not TNF-α. Moreover, TsSP significantly enhanced the production of bacterial lipopolysaccharide (LPS)-induced IL-6 and IL-10 but suppressed the production of LPS-induced TNF-α. ABF did not induce cytokine secretion from PBMC, but suppressed LPS-induced secretion of TNF-α and IL-6. ABF did not have any effect on cytokine production in IPEC-J2 cells. In contrast, TsSP selectively induced the secretion of IL-6, and enhanced the IL-6 response induced by LPS. The IL-6 response appeared to be a conserved response to T. suis products, as significant secretion was also observed in alveolar macrophages. Thus, T. suis products have diverse modulatory effects on cytokine secretion in vitro, with IL-6 production a consistent feature of the innate host response.

Vascular Endothelial Growth Factor Enhances Compensatory Lung Growth in Piglets

BACKGROUND

Vascular endothelial growth factor has been found to accelerate compensatory lung growth after left pneumonectomy in mice. The aim of this study was to determine the natural history and the effects of vascular endothelial growth factor on compensatory lung growth in a large animal model.

METHODS

To determine the natural history of compensatory lung growth, female Yorkshire piglets underwent a left pneumonectomy on days of life 10-11. Tissue harvest and volume measurement of the right lung were performed at baseline (n = 5) and on postoperative days 7 (n = 5), 14 (n = 4), and 21 (n = 5). For pharmacokinetic studies, vascular endothelial growth factor was infused via a central venous catheter, with plasma vascular endothelial growth factor levels measured at various time points. To test the effect of vascular endothelial growth factor on compensatory lung growth, 26 female Yorkshire piglets underwent a left pneumonectomy followed by daily infusion of vascular endothelial growth factor at 200 µg/kg or isovolumetric 0.9% NaCl (saline control). Lungs were harvested on postoperative day 7 for volume measurement and morphometric analyses.

RESULTS

Compared with baseline, right lung volume after left pneumonectomy increased by factors of 2.1 ± 0.6, 3.3 ± 0.6, and 3.6 ± 0.4 on postoperative days 7, 14, and 21, respectively. The half-life of VEGF ranged from 89 to 144 minutes. Lesser doses of vascular endothelial growth factor resulted in better tolerance, volume of distribution, and clearance. Compared with the control group, piglets treated with vascular endothelial growth factor had greater lung volume (P < 0.0001), alveolar volume (P = 0.001), septal surface area (P = 0.007) and total alveolar count (P = 0.01).

CONCLUSION

Vascular endothelial growth factor enhanced alveolar growth in neonatal piglets after unilateral pneumonectomy.

Pre- and Postnatal Lung Development: An Updated Species Comparison

The purpose of this review is to give an outline of respiratory tract morphological and functional development with an emphasis on perinatal and postnatal maturational processes. In view of the rising need for qualitative and quantitative data for the development of pediatric pharmaceuticals, a comparison of the human situation to experimental animal models is made, and functional data as well as suitable models for human airway diseases and functional testing are presented. Birth Defects Research 109:1519-1539, 2017. © 2017 Wiley Periodicals, Inc.

CD11b(+) Mononuclear Cells Mitigate Hyperoxia-Induced Lung Injury in Neonatal Mice

Bronchopulmonary dysplasia (BPD) is a common consequence of life-saving interventions for infants born with immature lungs. Resident tissue myeloid cells regulate lung pathology, but their role in BPD is poorly understood. To determine the role of lung interstitial myeloid cells in neonatal responses to lung injury, we exposed newborn mice to hyperoxia, a neonatal mouse lung injury model with features of human BPD. In newborn mice raised in normoxia, we identified a CD45(+) F4/80(+) CD11b(+), Ly6G(lo-int) CD71(+) population of cells in lungs of neonatal mice present in significantly greater percentages than in adult mice. In response to hyperoxia, surface marker and gene expression in whole lung macrophages/monocytes was biased to an alternatively activated phenotype. Partial depletion of these CD11b(+) mononuclear cells using CD11b-diphtheria toxin (DT) receptor transgenic mice resulted in 60% mortality by 40 hours of hyperoxia exposure with more severe lung injury, perivascular edema, and alveolar hemorrhage compared with DT-treated CD11b-DT receptor-negative controls, which displayed no mortality. These results identify an antiinflammatory population of CD11b(+) mononuclear cells that are protective in hyperoxia-induced neonatal lung injury in mice, and suggest that enhancing their beneficial functions may be a treatment strategy in infants at risk for BPD.

Effects of age and macrophage lineage on intracellular survival and cytokine induction after infection with Rhodococcus equi

Rhodococcus equi, a facultative intracellular pathogen of macrophages, causes life-threatening pneumonia in foals and in people with underlying immune deficiencies. As a basis for this study, we hypothesized that macrophage lineage and age would affect intracellular survival of R. equi and cytokine induction after infection. Monocyte-derived and bronchoalveolar macrophages from 10 adult horses and from 10 foals (sampled at 1-3 days, 2 weeks, 1 month, 3 months, and 5 months of age) were infected ex vivo with virulent R. equi. Intracellular R. equi were quantified and mRNA expression of IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12 p40, IL-18, IFN-γ, and TNF-α was measured. Intracellular replication of R. equi was significantly (P<0.001) greater in bronchoalveolar than in monocyte-derived macrophages, regardless of age. Regardless of the macrophage lineage, replication of R. equi was significantly (P=0.002) higher in 3-month-old foals than in 3-day old foals, 2-week-old foals, 1-month-old foals, and adult horses. Expression of IL-4 mRNA was significantly higher in monocyte-derived macrophages whereas expression of IL-6, IL-18, and TNF-α was significantly higher in bronchoalveolar macrophages. Induction of IL-1β, IL-10, IL-12 p40, and IL-8 mRNA in bronchoalveolar macrophages of 1-3-day old foals was significantly higher than in older foals or adult horses. Preferential intracellular survival of R. equi in bronchoalveolar macrophages of juvenile horses may play a role in the pulmonary tropism of the pathogen and in the window of age susceptibility to infection.

M2 macrophage polarisation is associated with alveolar formation during postnatal lung development

Background

Macrophages are traditionally associated with inflammation and host defence, however a greater understanding of macrophage heterogeneity is revealing their essential roles in non-immune functions such as development, homeostasis and regeneration. In organs including the brain, kidney, mammary gland and pancreas, macrophages reside in large numbers and provide essential regulatory functions that shape organ development and maturation. However, the role of macrophages in lung development and the potential implications of macrophage modulation in the promotion of lung maturation have not yet been ascertained.

Methods

Embryonic day (E)12.5 mouse lungs were cultured as explants and macrophages associated with branching morphogenesis were visualised by wholemount immunofluorescence microscopy. Postnatal lung development and the correlation with macrophage number and phenotype were examined using Colony-stimulating factor-1 receptor-enhanced green fluorescent protein (Csf1r-EGFP) reporter mice. Structural histological examination was complemented with whole-body plethysmography assessment of postnatal lung functional maturation over time.

Flow cytometry, real-time (q)PCR and immunofluorescence microscopy were performed to characterise macrophage number, phenotype and localisation in the lung during postnatal development. To assess the impact of developmental macrophage modulation, CSF-1 was administered to neonatal mice at postnatal day (P)1, 2 and 3, and lung macrophage number and phenotype were assessed at P5. EGFP transgene expression and in situ hybridisation was performed to assess CSF-1R location in the developing lung.

Results

Macrophages in embryonic lungs were abundant and densely located within branch points during branching morphogenesis. During postnatal development, structural and functional maturation of the lung was associated with an increase in lung macrophage number. In particular, the period of alveolarisation from P14-21 was associated with increased number of Csf1r-EGFP+ macrophages and upregulated expression of Arginase 1 (Arg1), Mannose receptor 1 (Mrc1) and Chemokine C-C motif ligand 17 (Ccl17), indicative of an M2 or tissue remodelling macrophage phenotype. Administration of CSF-1 to neonatal mice increased trophic macrophages during development and was associated with increased expression of the M2-associated gene Found in inflammatory zone (Fizz)1 and the growth regulator Insulin-like growth factor (Igf)1. The effects of CSF-1 were identified as macrophage-mediated, as the CSF-1R was found to be exclusively expressed on interstitial myeloid cells.

Conclusions

This study identifies the presence of CSF-1R+ M2-polarised macrophages localising to sites of branching morphogenesis and increasing in number during the alveolarisation stage of normal lung development. Improved understanding of the role of macrophages in lung developmental regulation has clinical relevance for addressing neonatal inflammatory perturbation of development and highlights macrophage modulation as a potential intervention to promote lung development.

Age-related changes in phagocytic activity and production of pro-inflammatory cytokines by lipopolysaccharide stimulated porcine alveolar macrophages

The aim of the present study was to determine the age-related changes of phagocytic capacity and the kinetic production of cytokines in lipopolysaccharide-stimulated porcine alveolar macrophages. For this purpose, AMs were isolated from 5 (newborn), 40 (post-weaned) and 120 (young) day old pigs. Results of phagocytosis assay showed that AMs from newborn piglets had less phagocytic capacity than those of young pigs (P<0.05). For the kinetics study, cells and supernatant were collected at 1, 6, 12, 24, 36 and 48 h after LPS stimulation for quantification of cytokine mRNA and protein by quantitative real-time PCR and ELISA, respectively. The kinetics results showed that AMs from newborn piglets were significantly less capable of producing IL1β, IL6, IL12β, TNFα and IL8 than post-weaned piglets or young pigs. IL18 mRNA did not show significant differences between ages. MIP2 and MCP1 mRNA was higher in young pigs. Hence, higher production of cytokines by AMs may be the surfactant factors in the pulmonary host defense system. These results indicate that AMs from newborn piglets might be functionally immature, which may lead to increased susceptibility to lung infections. Future studies of cytokine kinetics in more animals are clearly needed to confirm these results across a wider age range.

Anti-inflammatory effects of several plant extracts on porcine alveolar macrophages in vitro

Certain plant extracts are bioactive substances of some foods or traditional herbs, known to possess antioxidant, antibacterial, and perhaps immunoregulatory effects. This study investigated the in vitro anti-inflammatory effects of 7 plant extracts (anethol, capsicum oleoresin, carvacrol, cinnamaldehyde, eugenol, garlicon, and turmeric oleoresin) on porcine alveolar macrophages collected from weaned pigs (n = 6 donor pigs) by bronchoalveolar lavage. The experimental design for this assay was a 2 [with or without 1 μg lipopolysaccharide (LPS)/mL] × 5 (5 different amounts of each plant extract) factorial arrangements in a randomized complete block design. The application of plant extracts were 0, 25, 50, 100, and 200 μg/mL, except for cinnamaldehyde and turmeric oleoresin, which were 0, 2.5, 5, 10, and 20 μg/mL. The 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay was used to determine the number of live cells, Griess assay was applied to detect nitric oxide (NO) production, and ELISA was used to measure tumor necrosis factor-α (TNF-α), IL-1β, transforming growth factor-β (TGF-β), and IL-10 in the cell culture supernatants of macrophages. The LPS increased (P < 0.001) the secretion of TNF-α, IL-1β, and TGF-β. Without LPS, anethol and capsicum oleoresin increased (linear, P < 0.001) cell viability of macrophages, whereas other plant extracts reduced (linear, P < 0.001) it. Anethol, capsicum oleoresin, and carvacrol enhanced (linear, P < 0.001) the cell proliferation of LPS-treated macrophages. Without LPS, anethol, capsicum oleoresin, cinnamaldehyde, or turmeric oleoresin stimulated TNF-α secretion, whereas all plant extracts except eugenol enhanced IL-1β concentration in the supernatants of macrophages. However, all plant extracts suppressed (linear, P < 0.001) TNF-α, and all plant extracts except turmeric oleoresin decreased (linear, P < 0.05) IL-1β secretion from LPS-treated macrophages. Anethol and capsicum oleoresin decreased (linear, P < 0.001) TGF-β from macrophages in the absence of LPS, but the other plant extracts increased it. Anethol, capsicum oleoresin, and carvacrol also suppressed (linear, P < 0.001) TGF-β from macrophages with LPS stimulation; the other plant extracts enhanced or did not affect it. The anti-inflammatory cytokine, IL-10, was not detected in any supernatants. Only very low amounts of NO were detected in the supernatants of macrophages. In conclusion, the TNF-α results indicate all plant extracts tested here may have anti-inflammatory effects to varying degrees.

Expression of Toll-like receptors and downstream genes in lipopolysaccharide-induced porcine alveolar macrophages

The aim of the present study was to determine the age-related kinetic changes of Toll-like receptors (TLRs) and downstream genes expression, and secretion of cytokine in lipopolysaccharide (LPS) stimulated porcine alveolar macrophages (AM). For this purpose, AMs were isolated from 5-day-old newborn piglets and 120-day-old young pigs. mRNA expression and cytokine measurement was determined by quantitative real-time PCR and ELISA, respectively. First, AMs were incubated for 24 h in the absence or presence of increasing concentrations of LPS. Results showed the up-regulation of TLRs 2, 4, 5 and 9 mRNA from all concentrations of LPS used, as compared to non-stimulated cells, and TLR4 was the highest expression in both ages (P<0.05). Furthermore, quantitative analysis demonstrated increased expression of mRNAs encoding TLRs 2, 4, 5 and 9, LBP, CD14, MD2, MyD88, IRAK4 and TRAF6 in both ages in a time-dependant manner (P<0.05). Overall, LPS inducible mRNA for TLR4, LBP, CD14 and MyD88 had higher expression in newborn piglets compared with those of young pigs (P<0.05). The level of cytokine protein IL6 and TNFα in supernatant fluid significantly varied with time of incubation and age of animals. Their concentration increased immediately at 1 h after LPS stimulation and remained significantly higher up to 48 h in both ages. Production of pro-inflammatory cytokine protein IL6 and TNFα in supernatant was significantly higher in young pigs than those of piglets. This study suggests that differential age-related changes in the expression of TLRs and downstream genes, and pro-inflammatory cytokine could contribute to a different age-related innate immune response during pulmonary infection. Further investigation is warranted to determine the precise effects of LPS on porcine AMs by means of a functional study across a wider age range.

Impaired neonatal macrophage phagocytosis is not explained by overproduction of prostaglandin E2

BACKGROUND

Neonates and young infants manifest increased susceptibility to bacterial, viral and fungal lung infections. Previous work has identified a role for eicosanoids in mediating host defense functions of macrophages. This study examines the relationship between alveolar macrophage (AM) host defense and production of lipid mediators during the neonatal period compared to adult AMs.

METHODS

AMs were harvested from young (day 7 and day 14) and adult (~10 week) rats. The functionality of these cells was assessed by examining their ability to phagocytose opsonized targets, produce cytokines, eicosanoids and intracellular cAMP measured by enzyme immunoassays, and gene expression of proteins, enzymes and receptors essential for eicosanoid generation and phagocytosis measured by real time RT-PCR.

RESULTS

AMs from young animals (day 7 and 14) were defective in their ability to phagocytose opsonized targets and produce tumor necrosis factor (TNF)- α. In addition, young AMs produce more prostaglandin (PG) E(2), a suppressor of host defense, and less leukotriene (LT) B(4), a promoter of host defense. Young AMs express higher levels of enzymes responsible for the production of PGE(2) and LTB(4); however, there was no change in the expression of E prostanoid (EP) receptors or LT receptors. Despite the similar EP profiles, young AMs are more responsive to PGE(2) as evidenced by their increased production of the important second messenger, cyclic AMP. In addition, young AMs express higher levels of PDE3B and lower levels of PDE4C compared to adult AMs. However, even though the young AMs produced a skewed eicosanoid profile, neither the inhibition of PGE(2) by aspirin nor the addition of exogenous LTB(4) rescued the defective opsonized phagocytosis. Examination of a receptor responsible for mediating opsonized phagocytosis showed a significant decrease in the gene expression levels of the Fcgamma receptor in young (day 7) AMs compared to adult AMs.

CONCLUSION

These results suggest that elevated production of PGE(2) and decreased production of LTB(4) do not contribute to impaired opsonized macrophage phagocytosis and highlight an important difference between young and adult AMs.

Effects of mannan oligosaccharide on cytokine secretions by porcine alveolar macrophages and serum cytokine concentrations in nursery pigs

This study explored the hypothesis that mannan oligosaccharide (MOS) acts to reduce systemic inflammation in pigs by evaluating cytokine production of alveolar macrophages (AM) and serum cytokine concentrations. A total of 160 pigs were fed diets containing 0.2 or 0.4% MOS for 2 or 4 wk postweaning compared with control diets without MOS. Dietary MOS did not affect the serum concentration of tumor necrosis factor (TNF)-α and tended (P = 0.081) to increase that of IL-10. These cytokine concentrations also changed over time (P < 0.001). After 2-wk feeding of the control or MOS diets, AM were collected and stimulated ex vivo with lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (PLIC) as infection models. The LPS-stimulated AM from MOS-fed pigs (n = 12) secreted less TNF-α (P < 0.001) and more IL-10 (P = 0.026) than those from control-fed pigs (n = 6). However, dietary MOS had less effect on ex vivo TNF-α and IL-10 production by PLIC-stimulated AM (P = 0.091 and P > 0.10, respectively. Further, effects of MOS were examined in 4 in vitro experiments. In Exp. 1 (n = 4 pigs), MOS and mannan-rich fraction (MRF), when added to AM cultures, were able to increase TNF-α production. This direct effect of MOS was not due to endotoxin contamination as verified in Exp. 2 (n = 6 pigs) using polymyxin B, an inhibitor of LPS activation of toll-like receptor 4. Polymyxin B inhibited production of TNF-α by AM after treatment with LPS (P < 0.001), but not after treatment with MOS in the absence of LPS (P > 0.70). In Exp. 3 (n = 6 pigs), when MOS was directly applied in vitro, the pattern of cytokine production by LPS-activated AM was similar to that observed ex vivo, as MOS suppressed LPS-induced TNF-α (P < 0.001) and enhanced LPS-induced IL-10 (P = 0.028). In Exp. 4 (n = 6 pigs), when MRF replaced MOS, AM-produced TNF-α induced by LPS or PLIC was suppressed by MRF (P = 0.015 or P < 0.001, respectively). These data establish that MOS and MRF suppress LPS-induced TNF-α secretions by AM. Generally, the study suggests that MOS may be a potent immunomodulator because it directly activates AM to secrete TNF-α and alters the cytokine responses of bacterial endotoxin-induced AM in both ex vivo and in vitro systems. In particular, feeding MOS to pigs for 2 wk reduces TNF-α and increases IL-10 concentrations after ex vivo treatment of AM with LPS. These immunomodulatory properties of MOS may have important implications for both host defense and avoidance of harmful overstimulation of the immune system.

Circulating levels of inflammatory markers in intrauterine growth restriction

We aimed to investigate possible alterations in circulating levels of the perinatal stress markers high sensitivity (hs)-CRP, PAI-1, and S100B—probably reflecting brain and adipose tissue inflammation—in intrauterine growth-restricted-(IUGR) and appropriate-for-gestational-age-(AGA) pregnancies, given that these groups differ in fat mass and metabolic mechanisms involving aseptic inflammation. Serum hs-CRP, PAI-1, and S100B levels were measured in 40 mothers, and their 20 AGA and 20 IUGR full-term fetuses and neonates on postnatal days 1 and 4. hs-CRP, PAI-1, and S100B levels did not differ at all time points between AGA and IUGR groups. We conclude that the lack of difference in hs-CRP, PAI-1 and S100B levels, between IUGR and AGA fetuses/neonates—despite the lower birth weight, reflecting reduced fat mass in the former—might indicate more intense adipose tissue and nervous system inflammation in IUGRs. However, implication of other inflammation-related mechanisms, common in the IUGR state (e.g. preeclampsia), cannot be excluded.