Modulation of respiratory syncytial virus-induced prostaglandin E2 production by n-3 long-chain polyunsaturated fatty acids in human respiratory epithelium

Respiratory viral infection and resolution of inflammation: Roles for specialized pro-resolving mediators

Respiratory viral infections with influenza A virus (IAV) or respiratory syncytial virus (RSV) pose a significant threat to public health due to excess morbidity and mortality. Dysregulated and excessive inflammatory responses are major underlying causes of viral pneumonia severity and morbidity, including aberrant host immune responses and increased risk for secondary bacterial infections. Currently available antiviral therapies have not substantially reduced the risk of severe viral pneumonia for these pathogens. Thus, new therapeutic approaches that can promote resolution of the pathogen-initiated inflammation without impairing host defense would represent a significant advance. Recent research has uncovered the potential for specialized pro-resolving mediators (SPMs) to transduce multipronged actions for the resolution of serious respiratory viral infection without increased risk for subsequent host susceptibility to bacterial infection. Here, we review recent advances in our understanding of SPM production and SPM receptor signaling in respiratory virus infections and the intriguing potential of harnessing SPM pathways to control excess morbidity and mortality from IAV and RSV pneumonia.

Pharmaconutrition strategy to resolve SARS-CoV-2-induced inflammatory cytokine storm in non-alcoholic fatty liver disease: Omega-3 long-chain polyunsaturated fatty acids

Inflammation is one of the primary factors associated with the causation and/or progression of several lifestyle disorders, including obesity, type 2 diabetes and non-alcoholic fatty liver disease (NAFLD). NAFLD is a spectrum of disorders, and starts with simple steatosis, progresses to non-alcoholic steatohepatitis, and then advances to fibrosis, cirrhosis and finally, hepatocellular carcinoma, due to perpetual cycles of insults caused by inflammation and other cellular stress. Emerging evidence has documented that patients with NAFLD have severe coronavirus disease 2019 (COVID-19), and patients with COVID-19 have a higher liver injury and mortality. Although the exact cause or mechanism is not known, inflammatory cytokine storm is a characteristic feature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and is known to be associated with higher mortality among COVID-19 patients. Therefore, the COVID-19 pandemic seems to be a major concern in NAFLD patients, who have contracted SARS-CoV-2 infection and develop COVID-19. This is evident in patients at any stage of the NAFLD spectrum, as the inflammatory cytokine storm may cause and/or aggravate the progression or severity of NAFLD. Thus, there is a need for resolution of the inflammatory cytokine storm in these patients. A large body of evidence has demonstrated the efficacy of omega-3 long-chain polyunsaturated fatty acids (ω-3 LCPUFA) in NAFLD conditions, due to their anti-inflammatory, immunomodulatory and anti-viral properties. Therefore, intervention with ω-3 LCPUFA, an effective pharmaconutrient along with the standard treatment for COVID-19 may be useful in the management of the NAFLD spectrum in COVID-19 patients with pre-existing NAFLD conditions by resolving the inflammatory cytokine storm and thereby attenuating its progression. Although there are challenges in implementation, optimistically they can be circumvented and the pharmaconutrition strategy may be potentially helpful in tackling both the pandemics; NAFLD and COVID-19 at least in this subset of patients.

Changes in PTGS1 and ALOX12 Gene Expression in Peripheral Blood Mononuclear Cells Are Associated with Changes in Arachidonic Acid, Oxylipins, and Oxylipin/Fatty Acid Ratios in Response to Omega-3 Fatty Acid Supplementation

Introduction

There is a high degree of inter-individual variability among people in response to intervention with omega-3 fatty acids (FA), which may partly explain conflicting results on the effectiveness of omega-3 FA for the treatment and prevention of chronic inflammatory diseases. In this study we sought to evaluate whether part of this inter-individual variability in response is related to the regulation of key oxylipin metabolic genes in circulating peripheral blood mononuclear cells (PBMCs).

Methods

Plasma FA and oxylipin profiles from 12 healthy individuals were compared to PBMC gene expression profiles following six weeks of supplementation with fish oil, which delivered 1.9 g/d eicosapentaenoic acid (EPA) and 1.5 g/d docosahexaenoic acid (DHA). Fold changes in gene expression were measured by a quantitative polymerase chain reaction (qPCR).

Results

Healthy individuals supplemented with omega-3 FA had differential responses in prostaglandin-endoperoxide synthase 1 (PTGS1), prostaglandin-endoperoxide synthase 2 (PTGS2), arachidonate 12-lipoxygenase (ALOX12), and interleukin 8 (IL-8) gene expression in isolated PBMCs. In those individuals for whom plasma arachidonic acid (ARA) in the phosphatidylethanolamine (PE) lipid class decreased in response to omega-3 intervention, there was a corresponding decrease in gene expression for PTGS1 and ALOX12. Several oxylipin product/FA precursor ratios (e.g. prostaglandin E₂ (PGE₂)/ARA for PTGS1 and 12-hydroxyeicosatetraenoic acid (12-HETE)/ARA for ALOX12) were also associated with fold change in gene expression, suggesting an association between enzyme activity and gene expression. The fold-change in PTGS1 gene expression was highly positively correlated with ALOX12 gene expression but not with PTGS2, whereas IL-8 and PTGS2 were positively correlated.

Conclusions

The regulation of important oxylipin metabolic genes in PBMCs varied with the extent of change in ARA concentrations in the case of PTGS1 and ALOX12 regulation. PBMC gene expression changes in response to omega-3 supplementation varied among healthy individuals, and were associated with changes in plasma FA and oxylipin composition to different degrees in different individuals.

Trial Registration

clinicaltrials.gov NCT01838239

Derivation of Candidate Clinical Decision Rules to Identify Infants at Risk for Central Apnea

BACKGROUND AND OBJECTIVES

Central apnea complicates, and may be the presenting complaint in, bronchiolitis. Our objective was to prospectively derive candidate clinical decision rules (CDRs) to identify infants in the emergency department (ED) who are at risk for central apnea.

METHODS

We conducted a prospective observational study over 8 years. The primary outcome was central apnea subsequent to the initial ED visit. Infants were enrolled if they presented with central apnea or bronchiolitis. We excluded infants with obstructive apnea, neonatal jaundice, trauma, or suspected sepsis. We developed 3 candidate CDRs by using 3 techniques: (1) Poisson regression clustered on the individual, (2) classification and regression tree analysis (CART), and (3) a random forest (RF).

RESULTS

We analyzed 990 ED visits for 892 infants. Central apnea subsequently occurred in the hospital in 41 (5%) patients. Parental report of apnea, previous history of apnea, congenital heart disease, birth weight ≤2.5 kg, lower weight, and age ≤6 weeks all identified a group at high risk for subsequent central apnea. All CDRs and RFs were 100% sensitive (95% confidence interval [CI] 91%-100%) and had a negative predictive value of 100% (95% CI 99%-100%) for the subsequent apnea. Specificity ranged from 61% to 65% (95% CI 58%-68%) for CDRs based on Poisson models; 65% to 77% (95% CI 62%-90%) for CART; and 81% to 91% (95% CI 78%-92%) for RF models.

CONCLUSIONS

All candidate CDRs had a negative predictive value of 100% for subsequent central apnea.

Relationship between caloric intake and length of hospital stay for infants with bronchiolitis

OBJECTIVE

Poor oral intake is a common presenting symptom among infants hospitalized with bronchiolitis. The prevalence, degree, and duration of iminished caloric intake in these infants have not been studied. Our goal was to determine the daily caloric intake among infants admitted with bronchiolitis and to evaluate the relationship between early hospital caloric intake and length of stay (LOS).

METHODS

We conducted a retrospective chart review of infants aged <1 year admitted to Children's Hospital of Wisconsin with bronchiolitis who were placed in the bronchiolitis treatment protocol during the 2004-2005 season. Patient-, disease-, respiratory-, and nutrition-specific data were abstracted.

RESULTS

A total of 273 patients with bronchiolitis were admitted between November 1, 2004, and April 15, 2005; placed on the bronchiolitis protocol; and included in the study. Median caloric intake was diminished on day 1 (53 kcal/kg per day) and day 2 (64 kcal/kg per day). Caloric intake was slower to normalize in infants with progressively longer LOS, and a slower rate of increase from day 1 to day 2 was significantly correlated with longer LOS (r= -0.18; P= .002). Subgroup analysis revealed significant correlations between hospital day 2 caloric intake and LOS in formula-fed infants, breastfed infants, infants aged <183 days, and infants aged > or =183 days.

CONCLUSIONS

Caloric intake was diminished in the early course of hospitalization for infants who had bronchiolitis and slowest to normalize in infants with the longest LOS. Interventions aimed at decreasing LOS among infants admitted with bronchiolitis should consider the potential significance of nutrition for severely affected infants with this condition.

Role of TNF-α in virus-induced airway hyperresponsiveness and neuronal M₂ muscarinic receptor dysfunction

BACKGROUND AND PURPOSE

Infections with respiratory viruses induce exacerbations of asthma, increase acetylcholine release and potentiate vagally mediated bronchoconstriction by blocking inhibitory M₂ muscarinic receptors on parasympathetic neurons. Here we test whether virus-induced M₂ receptor dysfunction and airway hyperresponsiveness are tumour necrosis factor-alpha (TNF-α) dependent.

EXPERIMENTAL APPROACH

Guinea pigs were pretreated with etanercept or phosphate-buffered saline 24 h before intranasal infection with parainfluenza. Four days later, pulmonary inflation pressure, heart rate and blood pressure were measured. M₂ receptor function was assessed by the potentiation by gallamine (an M₂ receptor antagonist) of bronchoconstriction caused by electrical stimulation of the vagus nerves and measured as increased pulmonary inflation pressure. Human airway epithelial cells were infected with influenza and TNF-α concentration in supernatant was measured before supernatant was applied to human neuroblastoma cells. M₂ receptor expression in these neuroblastoma cells was measured by qRT-PCR.

KEY RESULTS

Influenza-infected animals were hyperresponsive to vagal stimulation but not to intravenous ACh. Gallamine did not potentiate vagally induced bronchoconstriction in virus-infected animals, indicating M₂ receptor dysfunction. Etanercept prevented virus-induced airway hyperresponsiveness and M₂ receptor dysfunction, without changing lung viral titres. Etanercept caused a non-significant decrease in total cells, macrophages and neutrophils in bronchoalveolar lavage. Influenza infection significantly increased TNF-α release from isolated epithelial cells, sufficient to decrease M₂ receptors in neuroblastoma cells. This ability of supernatants from infected epithelial cells to inhibit M₂ receptor expression was blocked by etanercept.

CONCLUSIONS AND IMPLICATIONS

TNF-α is a key mediator of virus-induced M₂ muscarinic receptor dysfunction and airway hyperresponsiveness.

Nasopharyngeal prostaglandin E(2) in infant bronchiolitis

The mechanism by which severe bronchiolitis can result in the development of recurrent childhood wheeze is unclear. However, mucosal inflammation and immune activation may play a major role. Prostaglandin (PG) E(2) has been highlighted as a possible therapeutic target for both the treatment of bronchiolitis and the prevention of subsequent airway hyperresponsiveness. The aim of this pilot study was to examine PGE(2) in the airways of infants hospitalised with bronchiolitis. Nasopharyngeal aspirates (NPA) were collected from 18 infants within 12 hours of admission and assayed by enzyme immunoassays for PGE(2), interleukin (IL)-10, and IL-12, as well as cyclooxygenase (COX) 1 and 2 activity. NPA PGE(2) concentration correlated with length of illness preadmission, but was not related to disease severity, causal virus, or IL-10. NPA COX 1 and 2 activity and IL-12 were all below the level of detection. Neither NPA PGE(2) nor disease severity was related to development of recurrent wheeze over 3 years following bronchiolitis. These data suggest that nasopharygeal PGE(2) at hospital admission may be neither directly causal or diagnostic of severity of infant bronchiolitis, or prognostic of development of recurrent wheeze. However, large-cohort temporal examinations are required to adequately define this mediator as a therapeutic target for bronchiolitis.

The host response and molecular pathogenesis associated with respiratory syncytial virus infection

Since the isolation of respiratory syncytial virus (RSV) in 1956, its significance as an important human pathogen in infants, the elderly and the immunocompromised has been established. Many important mechanisms contributing to RSV infection, replication and disease pathogenesis have been uncovered; however, there is still insufficient knowledge in these and related areas, which must be addressed to facilitate the development of safe and effective vaccines and therapeutic treatments. A better understanding of the molecular pathogenesis of RSV infection, particularly the host-cell response and transcription profiles to RSV infection, is required to advance disease intervention strategies. Substantial information is accumulating regarding how RSV proteins modulate molecular signaling and regulation of cytokine and chemokine responses to infection, molecular signals regulating programmed cell death, and innate and adaptive immune responses to infection. This review discusses RSV manipulation of the host response to infection and related disease pathogenesis.

Characterization of the acute temporal changes in excisional murine cutaneous wound inflammation by screening of the wound-edge transcriptome

This work represents a maiden effort to systematically screen the transcriptome of the healing wound-edge tissue temporally using high-density GeneChips. Changes during the acute inflammatory phase of murine excisional wounds were characterized histologically. Sets of genes that significantly changed in expression during healing could be segregated into the following five sets: up-early (6-24 h; cytokine-cytokine receptor interaction pathway), up-intermediary (12-96 h; leukocyte-endothelial interaction pathway), up-late (48-96 h; cell-cycle pathway), down-early (6-12 h; purine metabolism) and down-intermediary (12-96 h; oxidative phosphorylation pathway). Results from microarray and real-time PCR analyses were consistent. Results listing all genes that were significantly changed at any specific time point were further mined for cell-type (neutrophils, macrophages, endothelial, fibroblasts, and pluripotent stem cells) specificity. Candidate genes were also clustered on the basis of their functional annotation, linking them to inflammation, angiogenesis, reactive oxygen species (ROS), or extracellular matrix (ECM) categories. Rapid induction of genes encoding NADPH oxidase subunits and downregulation of catalase in response to wounding is consistent with the fact that low levels of endogenous H2O2 is required for wound healing. Angiogenic genes, previously not connected to cutaneous wound healing, that were induced in the healing wound-edge included adiponectin, epiregulin, angiomotin, Nogo, and VEGF-B. This study provides a digested database that may serve as a valuable reference tool to develop novel hypotheses aiming to elucidate the biology of cutaneous wound healing comprehensively.

Intracellular storage of surfactant and proinflammatory cytokines in co-cultured alveolar epithelium and macrophages in response to increasing CO2 and cyclic cell stretch

Cell stretch stimulates both surfactant and cytokine production. The authors proposed that stretch, through these effects, modifies the pathogenesis of lipopolysaccharide-induced acute lung injury (ALI), and that this is CO(2) dependent. Rat alveolar type II cells and macrophages were co-cultured with lipopolysaccharide in 5%, 10%, or 20% CO(2) +/- stretch (30%, 60 cycles/min) for 6 hours. Intracellular TNF-alpha and IL-6 increased whereas secreted cytokine and surfactant decreased with increasing CO(2). Stretch independently increased intracellular TNF-alpha and decreased IL-6 secretion. Elevated CO(2) may therefore diminish secretion of proinflammatory cytokines by alveolar cells, contributing to an explanation for protective hypercapnia in ALI.

Oral eicosapentaenoic acid supplementation as possible therapy for endometriosis

OBJECTIVE

To investigate the anti-inflammatory effect of n-3 eicosapentaenoic acid (EPA) compared with n-6 linoleic acid (LA) in an endometriosis rat model. We focused on the relationship between lipid metabolism and inflammatory reactions in endometriosis based on the hypothesis that a lipid intake imbalance is one of the factors responsible for the recent increase of endometriosis.

DESIGN

Prospective, randomized experimental study.

SETTING

Animal surgery laboratory in a university hospital.

ANIMAL(S)

Sprague-Dawley rats (female, 6 weeks old).

INTERVENTION(S)

Rats were fed a diet with EPA (n = 9) or with LA (n = 9) for 2 weeks. Two weeks after feeding, the uterus was autotransplanted to the peritoneum to construct an endometriosis model. Feeding was continued for a total of 6 weeks. Two and 4 weeks after autotransplantation, three rats of each group were killed and evaluated.

MAIN OUTCOME MEASURE(S)

Endometriotic lesions were morphologically evaluated and their fatty acid composition was examined. Gene expression in these tissues was evaluated by cDNA microarray analysis and quantative real-time reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULT(S)

In the EPA group, the n-3:n-6 ratio in each tissue significantly increased and the thickening of the interstitium, an active site for inflammation in endometriosis, was significantly suppressed (0.30 +/- 0.09 mm [EPA group] vs. 0.77 +/- 0.23 mm [LA group]). The mRNA of metalloproteinases, interleukin-1beta, interleukin-1r, prostaglandin E synthase (Ptges), and nuclear factor (NF)-kappaB were reduced in the EPA group.

CONCLUSION(S)

EPA supplementation might be a valid strategy for the treatment of endometriosis.

Immunomodulatory constituents of human milk change in response to infant bronchiolitis

Although epidemiological evidence is generally supportive of a causal association between respiratory syncytial virus (RSV) bronchiolitis during infancy and the development of persistent wheeze/asthma, if not allergy, the mechanism by which this occurs and an explanation for why all children do not succumb remains to be elucidated. Breast feeding has been found to confer a protective effect against respiratory infections such as RSV bronchiolitis and allergy; however, again there is little direct evidence and no clear mechanism. In this study, we examined whether human milk immunomodulatory factors (cells, cytokines) change in response to clinically diagnosed, severe bronchiolitis in the recipient breast-fed infant. We examined milk from 36 breast feeding mothers of infants hospitalized with bronchiolitis and compared them with milk from 63 mothers of postpartum age-matched healthy controls. Milks from mothers of infants hospitalized with bronchiolitis had significantly greater numbers of viable cells when compared with the milks obtained from mothers of healthy infants (1.3 +/- 0.4 vs. 0.3 +/- 0.03 x 10(6) cells/ml, mean +/- s.e.m.; p < or = 0.001). Further, the cells obtained from the mothers of infants hospitalized with bronchiolitis were found to produce a skewed cytokine profile ex vivo in response to stimulation by live RSV but not when cultured with a non-specific mitogen (concanavalin A). This study provides preliminary evidence for an immunological link between mothers and their breast-fed infants during severe respiratory infections as well as a possible contributing factor to the development of persistent wheeze in these infants.

Polyunsaturated fatty acids regulate cytokine and prostaglandin E2 production by respiratory cells in response to mast cell mediators

A protective association between breastfeeding and the development of bronchial asthma has been demonstrated. However, a mechanism remains unclear. FA present in human milk but rare in infant formula have been associated with marked immunological modulation as well as some indications of protection from asthma development. We examined the effect of in vitro manipulation of membrane phospholipid on the production of cytokines and prostaglandin (PG)E2 by respiratory epithelial cells (A549) in response to stimulation by mast cell mediators of allergic disease [histamine, tumor necrosis factor (TNF)-alpha, interleukin (IL)-4 and IL-5]. DHA and CLA significantly decreased the production of IL-8 in response to stimulation by TNF-alpha [2907 +/- 970 (DHA) and 6471 +/- 1203 (CLA) vs. 12,287 +/- 2309 (control) pg/mL; P < or = 0.05, mean +/- SEM], whereas both EPA and DHA reduced histamine-stimulated RANTES (regulation on activation, T cell-expressed and -secreted) production [2314 +/- 861 (EPA) and 877 +/- 326 (DHA) vs. 8526 +/- 1118 (control) pg/mL; P < or = 0.03]. PGE2 released in response to histamine was decreased by n-3 [1305 +/- 399 (alpha-linolenic acid), 406 +/- 73 (EPA), and 265 +/- 32 (DHA) vs. 9324 +/- 3672 (control) pg/mL; P < or = 0.05] and increased by n-6 [18,843 +/- 4439 (arachidonic acid) vs. 9324 +/- 3672 (control) pg/mL; P = 0.02], with CLA producing a decrease of the same magnitude as DHA [553 +/- 126 (CLA) vs. 9324 +/- 3672 (control) pg/mL; P = 0.03]. This study demonstrates the potential for immunological manipulation of the respiratory epithelium by FA in situ during allergic responses and suggests that further investigation into FA intervention in infants via human milk or supplemented infant formula, to prevent the development of allergic disease, may be worthwhile.

Infants fed docosahexaenoic acid- and arachidonic acid-supplemented formula have decreased incidence of bronchiolitis/bronchitis the first year of life

To assess the effect of docosahexaenoic acid and arachidonic acid supplementation in infant formula on the incidence of respiratory illnesses, pediatricians assigned infants to receive docosahexaenoic acid/arachidonic acid-supplemented formula or control formula. Anthropometrics, medical history, and illnesses were reported. Among 1342 infants, there was a higher incidence of bronchiolitis in control versus docosahexaenoic acid/arachidonic acid-supplemented groups at 5, 7, and 9 months (P < .01). Weight, length, and head circumference were similar for both groups. Infants fed formula supplemented with 0.32% docosahexaenoic acid and 0.64% arachidonic acid experienced a lower incidence of bronchiolitis compared with infants fed formula supplemented with no docosahexaenoic acid/arachidonic acid or lower levels of docosahexaenoic acid/arachidonic acid in the first year of life.