Intratracheal delivery of hepatocyte growth factor directly attenuates allergic airway inflammation in mice

Nutrition, Gut Microbiota, and Allergy Development in Infants

The process of gut microbiota development in infants is currently being challenged by numerous factors associated with the contemporary lifestyle, including diet. A thorough understanding of all aspects of microbiota development will be necessary for engineering strategies that can modulate it in a beneficial direction. The long-term consequences for human development and health of alterations in the succession pattern that forms the gut microbiota are just beginning to be explored and require much further investigation. Nevertheless, it is clear that gut microbiota development in infancy bears strong associations with the risk for allergic disease. A useful understanding of microbial succession in the gut of infants needs to reveal not only changes in taxonomic composition but also the development of functional capacities through time and how these are related to diet and various environmental factors. Metagenomic and metatranscriptomic studies have started to produce insights into the trends of functional repertoire and gene expression change within the first year after birth. This understanding is critical as during this period the most substantial development of the gut microbiota takes place and the relations between gut microbes and host immunity are established. However, further research needs to focus on the impact of diet on these changes and on how diet can be used to counteract the challenges posed by modern lifestyles to microbiota development and reduce the risk of allergic disease.

Reviewing the evidence on breast milk composition and immunological outcomes

A large number of biologically active components have been found in human milk (HM), and in both human and animal models, studies have provided some evidence suggesting that HM composition can be altered by maternal exposures, subsequently influencing health outcomes for the breastfed child. Evidence varies from the research studies on whether breastfeeding protects the offspring from noncommunicable diseases, including those associated with immunological dysfunction. It has been hypothesized that the conflicting evidence results from HM composition variations, which contain many immune active molecules, oligosaccharides, lactoferrin, and lysozyme in differing concentrations, along with a diverse microbiome. Determining the components that influence infant health outcomes in terms of both short- and long-term sequelae is complicated by a lack of understanding of the environmental factors that modify HM constituents and thereby offspring outcomes. Variations in HM immune and microbial composition (and the differing infantile responses) may in part explain the controversies that are evidenced in studies that aim to evaluate the prevalence of allergy by prolonged and exclusive breastfeeding. HM is a "mixture" of immune active factors, oligosaccharides, and microbes, which all may influence early immunological outcomes. This comprehensive review provides an in-depth overview of existing evidence on the studied relationships between maternal exposures, HM composition, vaccine responses, and immunological outcomes.

Endotyping of non-allergic, allergic and mixed rhinitis patients using a broad panel of biomarkers in nasal secretions

Background

Endotyping chronic rhinitis has proven hardest for the subgroup of non-allergic rhinitis (NAR) patients. While IgE-related inflammation is typical for allergic rhinitis (AR), no markers have been found that can be seen to positively identify NAR. A further complication is that AR and NAR might co-exist in patients with mixed rhinitis. As previous studies have considered only a limited number of inflammatory mediators, we wanted to explore whether a wider panel of mediators could help us refine the endotyping in chronic rhinitis patients.

Objective

To endotype chronic rhinitis, and non-allergic rhinitis in particular, with help of molecular or cellular markers.

Method

In this study we included 23 NAR patients without allergen sensitizations and with persistent rhinitis symptoms, 22 pollen sensitized rhinitis patients with seasonal symptoms, 21 mixed rhinitis patients with pollen-related symptoms and persistent symptoms outside of the pollen season, and 23 healthy controls without any symptoms. Nasal secretions were collected outside of pollen season and differences between the endotypes were assessed for a broad range of inflammatory mediators and growths factors using a multiplex ELISA.

Results

Although we were able to identify two new nasal secretion makers (IL-12 and HGF) that were low in mixed and AR patients versus NAR and healthy controls, the most intriguing outcome is that despite investigating 29 general inflammatory mediators and growth factors no clear profile of non-allergic or mixed rhinitis could be found.

Conclusion

Classical inflammatory markers are not able to differentiate between non-allergic or mixed rhinitis patients and healthy controls.

Immune Components in Human Milk Are Associated with Early Infant Immunological Health Outcomes: A Prospective Three-Country Analysis

The role of breastfeeding in improving allergy outcomes in early childhood is still unclear. Evidence suggests that immune mediators in human milk (HM) play a critical role in infant immune maturation as well as protection against atopy/allergy development. We investigated relationships between levels of immune mediators in colostrum and mature milk and infant outcomes in the first year of life. In a large prospective study of 398 pregnant/lactating women in the United Kingdom, Russia and Italy, colostrum and mature human milk (HM) samples were analysed for immune active molecules. Statistical analyses used models adjusting for the site of collection, colostrum collection time, parity and maternal atopic status. Preliminary univariate analysis showed detectable interleukin (IL) 2 and IL13 in HM to be associated with less eczema. This finding was further confirmed in multivariate analysis, with detectable HM IL13 showing protective effect OR 0.18 (95% CI 0.04-0.92). In contrast, a higher risk of eczema was associated with higher HM concentrations of transforming growth factor β (TGFβ) 2 OR 1.04 (95% CI 1.01-1.06) per ng/mL. Parental-reported food allergy was reported less often when IL13 was detectable in colostrum OR 0.10 (95% CI 0.01-0.83). HM hepatocyte growth factor (HGF) was protective for common cold incidence at 12 months OR 0.19 (95% CI 0.04-0.92) per ng/mL. Data from this study suggests that differences in the individual immune composition of HM may have an influence on early life infant health outcomes. Increased TGFβ2 levels in HM are associated with a higher incidence of reported eczema, with detectable IL13 in colostrum showing protective effects for food allergy and sensitization. HGF shows some protective effect on common cold incidence at one year of age. Future studies should be focused on maternal genotype, human milk microbiome and diet influence on human milk immune composition and both short- and long-term health outcomes in the infant.

The effect of hepatocyte growth factor on secretory functions in human eosinophils

Hepatocyte growth factor (HGF), originally identified as a potent mitogen for mature hepatocytes, is now recognized as a humoral mediator in inflammatory and immune responses. Previous studies indicated that HGF negatively regulated allergic airway inflammation. In view of eosinophils playing a role in the pathogenesis of asthma, especially in airway remodeling as a rich source of pro-fibrogenic mediators, the effects of HGF on the different types of eosinophil secretory functions were examined in this study. We found that HGF significantly inhibited IL-5-induced secretion of TGF-β and VEGF from human eosinophils. The inhibitory effect is not associated with TGF-β transcription; rather, it is associated with ultrastructural granule emptying and loss of intracellular TGF-β contents, indicating HGF inhibits the process of piecemeal degranulation. The effect of HGF on extracellular trap cell death (ETosis) that mediates cytolytic degranulation was also investigated; however, immobilized IgG- or phorbol myristate acetate-induced ETosis was only minimally attenuated by HGF. These results reveal the effect of HGF on the distinct pathways of eosinophil secretory functions and also provide novel insights into the role of HGF in the pathogenesis of allergic inflammation.

Regulation of hepatocyte growth factor in mice with pneumonia by peptidases and trans-alveolar flux

Hepatocyte growth factor (HGF) promotes lung epithelial repair after injury. Because prior studies established that human neutrophil proteases inactivate HGF in vitro, we predicted that HGF levels decrease in lungs infiltrated with neutrophils and that injury is less severe in lungs lacking HGF-inactivating proteases. After establishing that mouse neutrophil elastase cleaves mouse HGF in vitro, we tested our predictions in vivo by examining lung pathology and HGF in mice infected with Mycoplasma pulmonis, which causes neutrophilic tracheobronchitis and pneumonia. Unexpectedly, pneumonia severity was similar in wild type and dipeptidylpeptidase I-deficient (Dppi^-/-) mice lacking neutrophil serine protease activity. To assess how this finding related to our prediction that Dppi-activated proteases regulate HGF levels, we measured HGF in serum, bronchoalveolar lavage fluid, and lung tissue from Dppi^+/+ and Dppi^-/- mice. Contrary to prediction, HGF levels were higher in lavage fluid from infected mice. However, serum and tissue concentrations were not different in infected and uninfected mice, and HGF lung transcript levels did not change. Increased HGF correlated with increased albumin in lavage fluid from infected mice, and immunostaining failed to detect increased lung tissue expression of HGF in infected mice. These findings are consistent with trans-alveolar flux rather than local production as the source of increased HGF in lavage fluid. However, levels of intact HGF from infected mice, normalized for albumin concentration, were two-fold higher in Dppi^-/- versus Dppi^+/+ lavage fluid, suggesting regulation by Dppi-activated proteases. Consistent with the presence of active HGF, increased expression of activated receptor c-Met was observed in infected tissues. These data suggest that HGF entering alveoli from the bloodstream during pneumonia compensates for destruction by Dppi-activated inflammatory proteases to allow HGF to contribute to epithelial repair.

Growth factors released from gelatin hydrogel microspheres increase new neurons in the adult mouse brain

Recent studies have shown that new neurons are continuously generated by endogenous neural stem cells in the subventricular zone (SVZ) of the adult mammalian brain. Some of these new neurons migrate to injured brain tissues and differentiate into mature neurons, suggesting that such new neurons may be able to replace neurons lost to degenerative disease or injury and improve or repair neurological deficits. Here, we tested whether delivering growth factors via gelatin hydrogel microspheres would support neurogenesis in the SVZ. Insulin-like growth factor-1 (IGF-1)-containing microspheres increased the number of new neurons in the SVZ. Hepatocyte growth factor (HGF)-containing microspheres increased the number of new neurons migrating from the SVZ towards the injured striatum in a stroke model in mouse. These results suggest that the strategy of using gelatin hydrogel microspheres to achieve the sustained release of growth factors holds promise for the clinical regeneration of damaged brain tissues from endogenous neural stem cells in the adult SVZ.

Light-dark oscillations in the lung transcriptome: implications for lung homeostasis, repair, metabolism, disease, and drug action

Diurnal-nocturnal, or circadian-like, rhythms are 24-h variations in biological processes, evolved for the efficient functioning of living organisms. Such oscillations and their regulation in many peripheral tissues are still unclear. In this study, we used Affymetrix gene chips in a rich time-series experiment involving 54 animals killed at 18 time points within the 24-h cycle to examine light-dark cycle patterns of gene expression in rat lungs. Data mining identified 646 genes (represented by 1,006 probe sets) showing robust oscillations in expression in lung that were parsed into 8 distinct temporal clusters. Surprisingly, more than two-thirds of the probe sets showing cyclic expression peaked during the animal's light/inactive period. Six core clock genes and nine clock-related genes showed rhythmic oscillations in their expression in lung. Many of the genes that peaked during the inactive period included genes related to extracellular matrix, cytoskeleton, and protein processing and trafficking, which appear to be mainly involved in the repair and remodeling of the organ. Genes coding for growth factor ligands and their receptors, which play important roles in maintaining normal lung function, also showed rhythmic expression. In addition, genes involved in the metabolism and transport of endogenous compounds, xenobiotics, and therapeutic drugs, along with genes that are biomarkers or potential therapeutic targets for many lung diseases, also exhibited 24-h cyclic oscillations, suggesting an important role for such rhythms in regulating various aspects of the physiology and pathophysiology of lung.

The role of hepatocyte growth factor/c-Met in chronic rhinosinusitis with nasal polyps

BACKGROUND

Hepatocyte growth factor (HGF) is a growth factor thought to attenuate Th2-driven eosinophilic airway inflammatory responses. Increased expression of HGF and its receptor c-Met in nasal polyps suggests a role in disease pathogenesis. The effect of HGF on human sinonasal epithelial cell (SNEC) responses to Th2 inflammatory cytokines in chronic rhinosinusitis with nasal polyps (CRSwNP) has not been explored.

METHODS

SNECs isolated from patients with CRSwNP and control subjects were grown in cell culture at the air-liquid interface. The Th2 cytokine IL-13 was applied for 24 hours in the presence or absence of HGF. Eotaxin-3 and c-Met expression was assessed using real-time PCR, immunohistochemistry, and flow cytometry.

RESULTS

SNECs obtained from both CRSwNP and control subjects showed markedly increased expression of eotaxin-3 after exposure to IL-13. HGF significantly blocked IL-13-induced expression of eotaxin-3 in control SNECs, but not in SNECs derived from CRSwNP subjects.

CONCLUSION

SNECs are active participants in sinonasal mucosal immunity, expressing inflammatory mediators in response to potential pathogens and endogenous cytokines. Although Th2 cytokines can elicit expression of proeosinophilic mediators by SNECs, HGF appears to have a down-regulating effect on this response. In patients with CRSwNP, SNECs are resistant to this attenuation, showing continued IL-13-induced eotaxin-3 expression despite HGF treatment. Abnormalities in the regulation of epithelial cell responses to endogenous cytokines and growth factors may contribute to the persistent eosinophilic inflammatory state in CRSwNP.

A tandem repeat of a fragment of Listeria monocytogenes internalin B protein induces cell survival and proliferation

Hepatocyte growth factor (HGF) is critical for tissue homeostasis and repair in many organs including the lung, heart, kidney, liver, nervous system, and skin. HGF is a heterodimeric protein containing 20 disulfide bonds distributed among an amino-terminal hairpin, four kringle domains, and a serine protease-like domain. Due to its complex structure, recombinant production of HGF in prokaryotes requires denaturation and refolding, processes that are impractical for large-scale manufacture. Thus, pharmaceutical quantities of HGF are not available despite its potential applications. A fragment of the Listeria monocytogenes internalin B protein from amino acids 36-321 (InlB₃₆₋₃₂₁) was demonstrated to bind to and partially activate the HGF receptor Met. InlB₃₆₋₃₂₁ has a stable β-sheet structure and is easily produced in its native conformation by Escherichia coli. We cloned InlB₃₆₋₃₂₁ (1×InlB₃₆₋₃₂₁) and engineered a head-to-tail repeat of InlB₃₆₋₃₂₁ with a linker peptide (2×InlB₃₆₋₃₂₁); 1×InlB₃₆₋₃₂₁ and 2×InlB₃₆₋₃₂₁ were purified from E. coli. Both 1× and 2×InlB₃₆₋₃₂₁ activated the Met tyrosine kinase. We subsequently compared signal transduction of the two proteins in primary lung endothelial cells. 2×InlB₃₆₋₃₂₁ activated ERK1/2, STAT3, and phosphatidylinositol 3-kinase/Akt pathways, whereas 1×InlB₃₆₋₃₂₁ activated only STAT3 and ERK1/2. The 2×InlB₃₆₋₃₂₁ promoted improved motility compared with 1×InlB₃₆₋₃₂₁ and additionally stimulated proliferation equivalent to full-length HGF. Both the 1× and 2×InlB₃₆₋₃₂₁ prevented apoptosis by the profibrotic peptide angiotensin II in cell culture and ex vivo lung slice cultures. The ease of large-scale production and capacity of 2×InlB₃₆₋₃₂₁ to mimic HGF make it a potential candidate as a pharmaceutical agent for tissue repair.