Mitochondrial perturbations in low-protein-diet-fed mice are associated with altered neutrophil development and effector functions

Severe malnutrition is associated with infections, namely lower respiratory tract infections (LRTIs), diarrhea, and sepsis, and underlies the high risk of morbidity and mortality in children under 5 years of age. Dysregulations in neutrophil responses in the acute phase of infection are speculated to underlie these severe adverse outcomes; however, very little is known about their biology in this context. Here, in a lipopolysaccharide-challenged low-protein diet (LPD) mouse model, as a model of malnutrition, we show that protein deficiency disrupts neutrophil mitochondrial dynamics and ATP generation to obstruct the neutrophil differentiation cascade. This promotes the accumulation of atypical immature neutrophils that are incapable of optimal antimicrobial response and, in turn, exacerbate systemic pathogen spread and the permeability of the alveolocapillary membrane with the resultant lung damage. Thus, this perturbed response may contribute to higher mortality risk in malnutrition. We also offer a nutritional therapeutic strategy, nicotinamide, to boost neutrophil-mediated immunity in LPD-fed mice.

Neutrophil responses to RSV infection show differences between infant and adult neutrophils

INTRODUCTION

Respiratory syncytial virus (RSV) causes a severe respiratory condition, bronchiolitis, in infants but not in adults. Bronchiolitis is characterised by neutrophilic infiltration in the airways, but whether neutrophils enhance recovery from infection or contribute to its pathology remains unknown.

METHODS

We used a novel in-vitro model to compare term umbilical cord blood (infant) (n=17 donors) and adult neutrophils (n=15 donors) during migration across RSV-infected differentiated human nasal airway epithelial cells (AECs) in a basolateral to apical direction.

RESULTS

Greater numbers of infant neutrophils (mean (95% CI)) (336 684 (242 352 to 431 015)) migrated across RSV-infected AECs to the apical compartment (equivalent to the airway lumen) compared with adult neutrophils (56 586 (24 954 to 88 218)) (p<0.0001). Having reached the apical compartment of infected AECs, much greater numbers of infant neutrophils (140 787 (103 117 to 178 456)) became apoptotic compared with adult (5853 (444 to 11 261)) (p=0.002). Infant neutrophils displayed much greater expression of CD11b, CD64, neutrophil elastase (NE) and myeloperoxidase (MPO) than adult neutrophils at baseline and at all points of migration. However, as adult neutrophils migrated, expression of CD11b, CD64, NE and MPO became greater than at baseline.

DISCUSSION

The high proportion of infant neutrophils migrating across RSV-infected AECs correlates with the neutrophilic infiltrate seen in infants with severe RSV bronchiolitis, with large numbers undergoing apoptosis, which may represent a protective mechanism during infection. Compared with adult neutrophils, infant neutrophils already have high expression of surface markers before contact with AECs or migration, with less capacity to increase further in response to RSV infection or migration.

Age-related decline in the resistance of mice to bacterial infection and in LPS/TLR4 pathway-dependent neutrophil responses

Host defense against bacterial and fungal infections diminishes with age. In humans, impaired neutrophil responses are thought to contribute to this decline. However, it remains unclear whether neutrophil responses are also impaired in old mice. Here, we investigated neutrophil function in old mice, focusing on responses primed by lipopolysaccharide (LPS), an endotoxin released by gram-negative bacteria like E. coli, which signals through toll-like receptor (TLR) 4. We show that old mice have a reduced capacity to clear pathogenic E. coli during septic peritonitis. Neutrophil recruitment was elevated during LPS-induced but not aseptic peritonitis. Neutrophils from old mice showed reduced killing of E. coli. Their reactive oxygen species (ROS) production was impaired upon priming with LPS but not with GM-CSF/TNFα. Phagocytosis and degranulation were reduced in a partially LPS-dependent manner, whereas impairment of NET release in response to S. aureus was independent of LPS. Unexpectedly, chemotaxis was normal, as were Rac1 and Rac2 GTPase activities. LPS-primed activation of Erk and p38 Mapk was defective. PIP₃ production was reduced upon priming with LPS but not with GM-CSF/TNFα, whereas PIP₂ levels were constitutively low. The expression of 5% of neutrophil proteins was dysregulated in old age. Granule proteins, particularly cathepsins and serpins, as well as TLR-pathway proteins and membrane receptors were upregulated, whereas chromatin and RNA regulators were downregulated. The upregulation of CD180 and downregulation of MyD88 likely contribute to the impaired LPS signaling. In summary, all major neutrophil responses except chemotaxis decline with age in mice, particularly upon LPS priming. This LPS/TLR4 pathway dependence resolves previous controversy regarding effects of age on murine neutrophils and confirms that mice are an appropriate model for the decline in human neutrophil function.

Advantages and Limitations of the Neonatal Immune System

During early post-natal life, neonates must adjust to the transition from the sheltered intra-uterine environment to the microbe-laden external world, wherein they encounter a constellation of antigens and the colonization by the microbiome. At this vulnerable stage, neonatal immune responses are considered immature and present significant differences to those of adults. Pertinent to innate immunity, functional and quantitative deficiencies in antigen-presenting cells and phagocytes are often documented. Exposure to environmental antigens and microbial colonization is associated with epigenetic immune cell reprogramming and activation of effector and regulatory mechanisms that ensure age-depended immune system maturation and prevention of tissue damage. Moreover, neonatal innate immune memory has emerged as a critical mechanism providing protection against infectious agents. Still, in neonates, inexperience to antigenic exposure, along with enhancement of tissue-protective immunosuppressive mechanisms are often associated with severe immunopathological conditions, including sepsis and neurodevelopmental disorders. Despite significant advances in the field, adequate vaccination in newborns is still in its infancy due to elemental restrictions associated also with defective immune responses. In this review, we provide an overview of neonatal innate immune cells, highlighting phenotypic and functional disparities with their adult counterparts. We also discuss the effects of epigenetic modifications and microbial colonization on the regulation of neonatal immunity. A recent update on mechanisms underlying dysregulated neonatal innate immunity and linked infectious and neurodevelopmental diseases is provided. Understanding of the mechanisms that augment innate immune responsiveness in neonates may facilitate the development of improved vaccination protocols that can protect against pathogens and organ damage.

Innate immunity ascertained from blood and tracheal aspirates of preterm newborn provides new clues for assessing bronchopulmonary dysplasia

Aim

The study aimed to establish how granulocytes, monocytes and macrophages contribute to the development of bronchopulmonary dysplasia (BPD).

Materials and methods

Study A: samples of blood and tracheal aspirates (TAs) collected from preterm newborn infants during the first 3 days of life were investigated by flow cytometry, and testing for white blood cells (WBCs), neutrophils and neutrophil extracellular traps (NETs). Maternal blood samples were also collected. Study B: data from previously-tested samples of TAs collected from preterm newborn infants were re-analyzed in the light of the findings in the new cohort.

Results

Study A: 39 preterm newborn infants were studied. A moderate correlation emerged between maternal WBCs and neutrophils and those of their newborn in the first 3 days of life. WBCs and neutrophils correlated in the newborn during the first 8 days of life. Decision rules based on birth weight (BW) and gestational age (GA) can be used to predict bronchopulmonary dysplasia (BPD). Neutrophil levels were lower in the TAs from the newborn with the lowest GAs and BWs. Study B: after removing the effect of GA on BPD development, previously-tested newborn were matched by GA. Monocyte phenotype 1 (Mon1) levels were lower in the blood of newborn with BPD, associated with a higher ratio of Monocyte phenotype 3 (Mon3) to Mon1. Newborn infants from mothers with histological chorioamnionitis (HCA) had lower levels of classically-activated macrophages (M1) and higher levels of alternatively-activated macrophages (M2) in their TAs than newborn infants from healthy mothers.

Conclusion

Immune cell behavior in preterm newborn infants was examined in detail. Surprisingly, neutrophil levels were lower in TAs from the newborn with the lowest GA and BW, and no correlation emerged between the neutrophil and NET levels in TAs and the other variables measured. Interestingly, monocyte phenotype seemed to influence the onset of BPD. The rise in the ratio of Mon 3 to Mon 1 could contribute to endothelial dysfunction in BPD.

Semiquantitative Proteomics Enables Mapping of Murine Neutrophil Dynamics following Lethal Influenza Virus Infection

Neutrophils are rapidly deployed innate immune cells, and excessive recruitment is causally associated with influenza-induced pathologic conditions. Despite this, the complete set of influenza lethality-associated neutrophil effector proteins is currently unknown. Whether the expression of these proteins is predetermined during bone marrow (BM) neutrophil maturation or further modulated by tissue compartment transitions has also not been comprehensively characterized at a proteome-wide scale. In this study, we used high-resolution mass spectrometry to map how the proteomes of murine neutrophils change comparatively across BM, blood, and the alveolar airspaces to deploy an influenza lethality-associated response. Following lethal influenza infection, mature neutrophils undergo two infection-dependent and one context-independent compartmental transitions. Translation of type I IFN-stimulated genes is first elevated in the BM, preceding the context-independent downregulation of ribosomal proteins observed in blood neutrophils. Following alveolar airspace infiltration, the bronchoalveolar lavage (BAL) neutrophil proteome is further characterized by a limited increase in type I IFN-stimulated and metal-sequestering proteins as well as a decrease in degranulation-associated proteins. An influenza-selective and dose-dependent increase in antiviral and lipid metabolism-associated proteins was also observed in BAL neutrophils, indicative of a modest capacity for pathogen response tuning. Altogether, our study provides new and comprehensive evidence that the BAL neutrophil proteome is shaped by BM neutrophil maturation as well as subsequent compartmental transitions following lethal influenza infection.

Biological Roles of Neutrophil-Derived Granule Proteins and Cytokines

Neutrophils, the most abundant white blood cells in human circulation, entertain intense interactions with other leukocyte subsets, platelets, and stromal cells. Molecularly, such interactions are typically communicated through proteins generated during granulopoiesis, stored in granules, or produced on demand. Here, we provide an overview of the mammalian regulation of granule protein production in the bone marrow and the de novo synthesis of cytokines by neutrophils recruited to tissues. In addition, we discuss some of the known biological roles of these protein messengers, and how neutrophil-borne granule proteins and cytokines can synergize to modulate inflammation and tumor development. Decoding the neutrophil interactome is important for therapeutically neutralizing individual proteins to putatively dampen inflammation, or for delivering modified neutrophil-borne proteins to boost host defense.

Integrated transcriptomic and proteomic analysis of pathogenic mycobacteria and their esx-1 mutants reveal secretion-dependent regulation of ESX-1 substrates and WhiB6 as a transcriptional regulator

The mycobacterial type VII secretion system ESX-1 is responsible for the secretion of a number of proteins that play important roles during host infection. The regulation of the expression of secreted proteins is often essential to establish successful infection. Using transcriptome sequencing, we found that the abrogation of ESX-1 function in Mycobacterium marinum leads to a pronounced increase in gene expression levels of the espA operon during the infection of macrophages. In addition, the disruption of ESX-1-mediated protein secretion also leads to a specific down-regulation of the ESX-1 substrates, but not of the structural components of this system, during growth in culture medium. This effect is observed in both M. marinum and M. tuberculosis. We established that down-regulation of ESX-1 substrates is the result of a regulatory process that is influenced by the putative transcriptional regulator whib6, which is located adjacent to the esx-1 locus. In addition, the overexpression of the ESX-1-associated PE35/PPE68 protein pair resulted in a significantly increased secretion of the ESX-1 substrate EsxA, demonstrating a functional link between these proteins. Taken together, these data show that WhiB6 is required for the secretion-dependent regulation of ESX-1 substrates and that ESX-1 substrates are regulated independently from the structural components, both during infection and as a result of active secretion.

Degradation of Extracellular DNA Significantly Ameliorates Necrotizing Enterocolitis Severity in Mice

BACKGROUND

Necrotizing enterocolitis (NEC) is one of the most devastating diseases in neonates and is characterized by high morbidity and mortality. It has been suggested that neutrophils play a crucial role in NEC pathogenesis and contribute to the hyperinflammatory reaction after bacterial colonization, which ultimately induces NEC. The aim of this study was to investigate whether dissolution of neutrophil extracellular traps (NETs) by systemic DNase1 therapy reduces NEC manifestation and morbidity.

METHODS

NEC was induced in neonatal mice by gavage feeding of lipopolysaccharide mixed in Neocate, followed by hypoxia q12 h for 5d. Inactivated DNase1 and DNase1 were administered intraperitoneally twice daily in the control and treatment groups, respectively, starting on day 5 for 72 h. Survival, NEC score, intestinal damage (Chiu score, malondialdehyde [MDA], glutathione peroxidase [GPx]), inflammation (neutrophil elastase [NE], myeloperoxidase [MPO], toll-like receptor 4 [TLR4]), and NETs markers (SYTOX orange, cell-free DNA [cfDNA], DNase, citrullinated Histone 3 [H3cit]) were then assessed.

RESULTS

In total, 44 neonatal mice were used in the experiment. Mice in the treatment group demonstrated significantly reduced NEC rates (44 versus 86%, P = 0.029) and improved survival in comparison to controls (65 versus 35%, P = 0.01). Furthermore, mice treated with DNase1 showed significantly less tissue damage (cfDNA, Chiu score), oxidative stress (MDA, GPx), and inflammation (NE, MPO, H3cit, TLR4), which ultimately lead to a significant reduction in mortality.

CONCLUSIONS

The results of the study indicate that systemic DNase1 treatment leads to a significant reduction in tissue damage, NEC severity, and mortality. Therefore, after validation of our findings in human subjects, DNase1 treatment should be considered as a therapeutic option in neonates diagnosed with NEC.

Large-Scale Label-Free Quantitative Mapping of the Sputum Proteome

Analysis of induced sputum supernatant is a minimally invasive approach to study the epithelial lining fluid and, thereby, provide insight into normal lung biology and the pathobiology of lung diseases. We present here a novel proteomics approach to sputum analysis developed within the U-BIOPRED (unbiased biomarkers predictive of respiratory disease outcomes) international project. We present practical and analytical techniques to optimize the detection of robust biomarkers in proteomic studies. The normal sputum proteome was derived using data-independent HDMS^E applied to 40 healthy nonsmoking participants, which provides an essential baseline from which to compare modulation of protein expression in respiratory diseases. The "core" sputum proteome (proteins detected in ≥40% of participants) was composed of 284 proteins, and the extended proteome (proteins detected in ≥3 participants) contained 1666 proteins. Quality control procedures were developed to optimize the accuracy and consistency of measurement of sputum proteins and analyze the distribution of sputum proteins in the healthy population. The analysis showed that quantitation of proteins by HDMS^E is influenced by several factors, with some proteins being measured in all participants' samples and with low measurement variance between samples from the same patient. The measurement of some proteins is highly variable between repeat analyses, susceptible to sample processing effects, or difficult to accurately quantify by mass spectrometry. Other proteins show high interindividual variance. We also highlight that the sputum proteome of healthy individuals is related to sputum neutrophil levels, but not gender or allergic sensitization. We illustrate the importance of design and interpretation of disease biomarker studies considering such protein population and technical measurement variance.

High performance mass spectrometry based proteomics reveals enzyme and signaling pathway regulation in neutrophils during the early stage of surgical trauma

PURPOSE

In clinical conditions trauma is associated with high mortality and morbidity. Neutrophils play a key role in the development of multiple organ failure after trauma EXPERIMENTAL DESIGN: To have a detailed understanding of the neutrophil activation at primary stages after trauma, neutrophils are isolated from control and surgical trauma rats in this study. Extracted proteins are analyzed using nano liquid chromatography coupled with tandem mass spectrometry.

RESULTS

A total of 2924 rat neutrophil proteins are identified in our analysis, of which 393 are found differentially regulated between control and trauma groups. By using functional pathways analysis of the 190 proteins up-regulated in surgical trauma, we found proteins related to transcription initiation and protein biosynthesis. On the other hand, among the 203 proteins down-regulated in surgical trauma we found enrichment for proteins of the immune response, proteasome degradation and actin cytoskeleton. Overall, enzyme prediction analysis revealed that regulated enzymes are directly involved in neutrophil apoptosis, directional migration and chemotaxis. Our observations are then confirmed by in silico protein-protein interaction analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Collectively, our results reveal that neutrophils drastically regulate their biochemical pathways after the early stages of surgical trauma, showing lower activity. This implies higher susceptibility of the trauma patients to infection and bystander tissues damage.

Distinct mechanisms of the newborn innate immunity

The ontogeny of immunity during early life is of high importance as it shapes the immune system for the entire course of life. The microbiome and the environment contribute to the development of immunity in newborns. As immune responses in newborns are predominantly less experienced they are increasingly susceptible to infections. Though the immune cells in newborns are in 'naïve' state, they have been shown to mount adult-like responses in several circumstances. The innate immunity plays a vital role in providing protection during the neonatal period. Various stimulants have been shown to enhance the potential and functioning of the innate immune cells in newborns. They are biased against the production of pro-inflammatory cytokines and this makes them susceptible to wide variety of intracellular pathogens. The adaptive immunity requires prior antigenic experience which is very limited in newborns. This review discusses in detail the characteristics of innate immunity in newborns and the underlying developmental and functional mechanisms involved in the immune response. A better understanding of the immunological milieu in newborns could help the medical fraternity to find novel methods for prevention and treatment of infection in newborns.

Peptidylarginine Deiminases as Drug Targets in Neonatal Hypoxic-Ischemic Encephalopathy

Oxygen deprivation and infection are major causes of perinatal brain injury leading to cerebral palsy and other neurological disabilities. The identification of novel key factors mediating white and gray matter damage are crucial to allow better understanding of the specific contribution of different cell types to the injury processes and pathways for clinical intervention. Recent studies in the Rice-Vannucci mouse model of neonatal hypoxic ischemia (HI) have highlighted novel roles for calcium-regulated peptidylarginine deiminases (PADs) and demonstrated neuroprotective effects of pharmacological PAD inhibition following HI and synergistic infection mimicked by lipopolysaccharide stimulation.

Transcriptome and proteome dynamics in larvae of the barnacle Balanus Amphitrite from the Red Sea

Background

The barnacle Balanus amphitrite is widely distributed in marine shallow and tidal waters, and has significant economic and ecological importance. Nauplii, the first larval stage of most crustaceans, are extremely abundant in the marine zooplankton. However, a lack of genome information has hindered elucidation of the molecular mechanisms of development, settlement and survival strategies in extreme marine environments. We sequenced and constructed the genome dataset for nauplii to obtain comprehensive larval genetic information. We also investigated iTRAQ-based protein expression patterns to reveal the molecular basis of nauplii development, and to gain information on larval survival strategies in the Red Sea marine environment.

Results

A nauplii larval transcript dataset, containing 92,117 predicted open reading frames (ORFs), was constructed and used as a reference for the proteome analysis. Genes related to translation, oxidative phosphorylation and cytoskeletal development were highly abundant. We observed remarkable plasticity in the proteome of Red Sea larvae. The proteins associated with development, stress responses and osmoregulation showed the most significant differences between the two larval populations studied. The synergistic overexpression of heat shock and osmoregulatory proteins may facilitate larval survival in intertidal habitats or in extreme environments.

Conclusions

We presented, for the first time, comprehensive transcriptome and proteome datasets for Red Sea nauplii. The datasets provide a foundation for future investigations focused on the survival mechanisms of other crustaceans in extreme marine environments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2262-1) contains supplementary material, which is available to authorized users.

Proteasome Inhibition Diminishes the Formation of Neutrophil Extracellular Traps and Prevents the Death of Cardiomyocytes in Coculture with Activated Neutrophils during Anoxia-Reoxygenation

OBJECTIVE

Polymorphic mononuclear neutrophils (PMN) are very important cells participating in nonspecific defense of the organism. Among their well-known functions, the formation of neutrophil extracellular traps (NET) is interesting and potentially dangerous for the mechanisms of other cells. Ubiquitin-dependent proteasomal proteolysis is a very important regulator of all cellular activities, but the role of proteasomal proteolysis in NET formation has not been investigated.

METHODS

We performed experiments with PMN activated to form NET with phorbol 12-myristate 13-acetate (PMA) and the application of a proteasome inhibitor. We also added activated neutrophils to primary culture of isolated rat neonatal cardiomyocytes with or without anoxia-reoxygenation modeling.

RESULTS

The data obtained show that proteasomes participate in NET formation and proteasome inhibitors facilitate the blocking of the NET program. The percentage of NET after PMA application was 70.8 ± 7.2 and the proteasome inhibitor decreased this amount to 4.7 ± 0.9%. In coculture with cardiomyocytes during anoxia-reoxygenation, this effect prevented cardiac cell death induced by activated PMN. The stimulation of NET formation by PMA in coculture with isolated cardiomyocytes led to an increase in the number of necrotic cardiomyocytes of up to 33.1 ± 12.9% and a corresponding decrease in living cardiomyocytes to 66.9 ± 12.9%. The number of living cardiomyocytes in coculture after incubation with both PMA and proteasome inhibitor was 76.6 ± 13.3% (p < 0.05), and the number of necrotic cardiomyocytes was 23.4 ± 13.3% (p < 0.05).

CONCLUSION

Proteasome inhibition blocks NET formation and prevents cardiomyocyte necrosis in coculture with activated neutrophils.

Regulators and Effectors of Arf GTPases in Neutrophils

Polymorphonuclear neutrophils (PMNs) are key innate immune cells that represent the first line of defence against infection. They are the first leukocytes to migrate from the blood to injured or infected sites. This process involves molecular mechanisms that coordinate cell polarization, delivery of receptors, and activation of integrins at the leading edge of migrating PMNs. These phagocytes actively engulf microorganisms or form neutrophil extracellular traps (NETs) to trap and kill pathogens with bactericidal compounds. Association of the NADPH oxidase complex at the phagosomal membrane for production of reactive oxygen species (ROS) and delivery of proteolytic enzymes into the phagosome initiate pathogen killing and removal. G protein-dependent signalling pathways tightly control PMN functions. In this review, we will focus on the small monomeric GTPases of the Arf family and their guanine exchange factors (GEFs) and GTPase activating proteins (GAPs) as components of signalling cascades regulating PMN responses. GEFs and GAPs are multidomain proteins that control cellular events in time and space through interaction with other proteins and lipids inside the cells. The number of Arf GAPs identified in PMNs is expanding, and dissecting their functions will provide important insights into the role of these proteins in PMN physiology.