Activation of calcitonin gene-related peptide receptor during ozone inhalation contributes to airway epithelial injury and repair

Air Pollutant impacts on the brain and neuroendocrine system with implications for peripheral organs: a perspective

Air pollutants are being increasingly linked to extrapulmonary multi-organ effects. Specifically, recent studies associate air pollutants with brain disorders including psychiatric conditions, neuroinflammation and chronic diseases. Current evidence of the linkages between neuropsychiatric conditions and chronic peripheral immune and metabolic diseases provides insights on the potential role of the neuroendocrine system in mediating neural and systemic effects of inhaled pollutants (reactive particulates and gases). Autonomically-driven stress responses, involving sympathetic-adrenal-medullary and hypothalamus-pituitary-adrenal axes regulate cellular physiological processes through adrenal-derived hormones and diverse receptor systems. Recent experimental evidence demonstrates the contribution of the very stress system responding to non-chemical stressors, in mediating systemic and neural effects of reactive air pollutants. The assessment of how respiratory encounter of air pollutants induce lung and peripheral responses through brain and neuroendocrine system, and how the impairment of these stress pathways could be linked to chronic diseases will improve understanding of the causes of individual variations in susceptibility and the contribution of habituation/learning and resiliency. This review highlights effects of air pollution in the respiratory tract that impact the brain and neuroendocrine system, including the role of autonomic sensory nervous system in triggering neural stress response, the likely contribution of translocated nano particles or metal components, and biological mediators released systemically in causing effects remote to the respiratory tract. The perspective on the use of systems approaches that incorporate multiple chemical and non-chemical stressors, including environmental, physiological and psychosocial, with the assessment of interactive neural mechanisms and peripheral networks are emphasized.

Compartment-specific transcriptomics of ozone-exposed murine lungs reveals sex- and cell type-associated perturbations relevant to mucoinflammatory lung diseases

Ozone is known to cause lung injury, and resident cells of the respiratory tract (i.e., epithelial cells and macrophages) respond to inhaled ozone in a variety of ways that affect their survival, morphology, and functioning. However, a complete understanding of the sex-associated and the cell type-specific gene expression changes in response to ozone exposure is still limited. Through transcriptome profiling, we aimed to analyze gene expression alterations and associated enrichment of biological pathways in three distinct cell type-enriched compartments of ozone-exposed murine lungs. We subchronically exposed adult male and female mice to 0.8 ppm ozone or filtered air. RNA-Seq was performed on airway epithelium-enriched airways, parenchyma, and purified airspace macrophages. Differential gene expression and biological pathway analyses were performed and supported by cellular and immunohistochemical analyses. While a majority of differentially expressed genes (DEGs) in ozone-exposed versus air-exposed groups were common between both sexes, sex-specific DEGs were also identified in all of the three tissue compartments. As compared with ozone-exposed males, ozone-exposed females had significant alterations in gene expression in three compartments. Pathways relevant to cell division and DNA repair were enriched in the ozone-exposed airways, indicating ozone-induced airway injury and repair, which was further supported by immunohistochemical analyses. In addition to cell division and DNA repair pathways, inflammatory pathways were also enriched within the parenchyma, supporting contribution by both epithelial and immune cells. Further, immune response and cytokine-cytokine receptor interactions were enriched in macrophages, indicating ozone-induced macrophage activation. Finally, our analyses also revealed the overall upregulation of mucoinflammation- and mucous cell metaplasia-associated pathways following ozone exposure.

The Wnt7b/β-catenin signaling pathway is involved in the protective action of calcitonin gene-related peptide on hyperoxia-induced lung injury in premature rats

Background

Calcitonin gene-related peptide (CGRP) can protect against hyperoxia-induced lung injury, making the upregulation of CGRP a potential therapeutic approach for this type of injury. However, the effects of CGRP on the Wnt7b/β-catenin signaling pathway are unclear. In this study, we investigated the roles of CGRP and the Wnt7b/β-catenin signaling pathway in hyperoxia-induced lung injury.

Methods

Premature Sprague Dawley (SD) rats were exposed to 21, 40, 60 and 95% oxygen for 3, 7 and 14 days. The animals’ body weights, survival rates and endogenous CGRP levels were measured. Lung samples were harvested for histological analyses and measurements of malondialdehyde (MDA) concentration and total antioxidant capacity (TAOC). We also assessed the MDA concentration and TAOC in the lung tissues after administration of 200 nmol/kg CGRP_8–37 (a CGRP antagonist). Finally, alveolar epithelial type II (AEC II) cells were isolated from premature rats, exposed to 21 or 95% oxygen for 3, 7 and 14 days, and treated with 10^− 8 mol/l exogenous CGRP. The protein expressions of Wnt7b and β-catenin were assessed using western blotting, and TCF and c-myc mRNA expressions were assessed using qPCR.

Results

Rats exposed to 60 and 95% oxygen had significantly lower body weights and survival rates than the 21 and 40% groups, and the decrease was time dependent. Endogenous CGRP was elevated in the lung tissues of premature rats exposed to 95% oxygen. CGRP_8–37 induced apparent inflammation in the lung tissue and alveolar structural remodeling. In addition, the expression levels of Wnt7b and β-catenin were markedly increased after exposure for 3 days. They peaked at 7 days, then declined at 14 days. The levels of TCF/c-myc in AEC II cells increased significantly after CGRP treatment when compared with cells that had only undergone hyperoxia.

Conclusions

CGRP protected against hyperoxia-induced lung injury in premature rats. This process involves the Wnt7b/β-catenin signaling pathway.

Intratracheal Administration of Mesenchymal Stem Cells Modulates Tachykinin System, Suppresses Airway Remodeling and Reduces Airway Hyperresponsiveness in an Animal Model

BACKGROUND

The need for new options for chronic lung diseases promotes the research on stem cells for lung repair. Bone marrow-derived mesenchymal stem cells (MSCs) can modulate lung inflammation, but the data on cellular processes involved in early airway remodeling and the potential involvement of neuropeptides are scarce.

OBJECTIVES

To elucidate the mechanisms by which local administration of MSCs interferes with pathophysiological features of airway hyperresponsiveness in an animal model.

METHODS

GFP-tagged mouse MSCs were intratracheally delivered in the ovalbumin mouse model with subsequent functional tests, the analysis of cytokine levels, neuropeptide expression and histological evaluation of MSCs fate and airway pathology. Additionally, MSCs were exposed to pro-inflammatory factors in vitro.

RESULTS

Functional improvement was observed after MSC administration. Although MSCs did not adopt lung cell phenotypes, cell therapy positively affected airway remodeling reducing the hyperplastic phase of the gain in bronchial smooth muscle mass, decreasing the proliferation of epithelium in which mucus metaplasia was also lowered. Decrease of interleukin-4, interleukin-5, interleukin-13 and increase of interleukin-10 in bronchoalveolar lavage was also observed. Exposed to pro-inflammatory cytokines, MSCs upregulated indoleamine 2,3-dioxygenase. Moreover, asthma-related in vivo upregulation of pro-inflammatory neurokinin 1 and neurokinin 2 receptors was counteracted by MSCs that also determined a partial restoration of VIP, a neuropeptide with anti-inflammatory properties.

CONCLUSION

Intratracheally administered MSCs positively modulate airway remodeling, reduce inflammation and improve function, demonstrating their ability to promote tissue homeostasis in the course of experimental allergic asthma. Because of a limited tissue retention, the functional impact of MSCs may be attributed to their immunomodulatory response combined with the interference of neuropeptide system activation and tissue remodeling.

Transcriptome profiling of the newborn mouse lung response to acute ozone exposure

Ozone pollution is associated with adverse effects on respiratory health in adults and children but its effects on the neonatal lung remain unknown. This study was carried out to define the effect of acute ozone exposure on the neonatal lung and to profile the transcriptome response. Newborn mice were exposed to ozone or filtered air for 3h. Total RNA was isolated from lung tissues at 6 and 24h after exposure and was subjected to microarray gene expression analysis. Compared to filtered air-exposed littermates, ozone-exposed newborn mice developed a small but significant neutrophilic airway response associated with increased CXCL1 and CXCL5 expression in the lung. Transcriptome analysis indicated that 455 genes were down-regulated and 166 genes were up-regulated by at least 1.5-fold at 6h post-ozone exposure (t-test, p < .05). At 24h, 543 genes were down-regulated and 323 genes were up-regulated in the lungs of ozone-exposed, compared to filtered air-exposed, newborn mice (t-test, p < .05). After controlling for false discovery rate, 50 genes were identified as significantly down-regulated and only a few (RORC, GRP, VREB3, and CYP2B6) were up-regulated at 24h post-ozone exposure (q < .05). Gene ontology enrichment analysis revealed that cell cycle-associated functions including cell division/proliferation were the most impacted pathways, which were negatively regulated by ozone exposure, an adverse effect that was associated with reduced bromo-deoxyuridine incorporation. These results demonstrate that acute ozone exposure alters cell proliferation in the developing neonatal lung through a global suppression of cell cycle function.

Calcitonin gene-related peptide promotes the wound healing of human bronchial epithelial cells via PKC and MAPK pathways

Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide derived from the calcitonin gene. CGRP is widely distributed in the central and peripheral neuronal systems. In the lung, CGRP could modulate dendritic cell function, stimulate proliferation of alveolar epithelial cells and mediate lung injury in mice. In this study, we investigated the effect of CGRP on the wound healing of human bronchial epithelial cells (HBECs) in vitro. The results showed that CGRP accelerated the recovery of wound area of monolayer HBECs in a dose-dependent manner. CGRP inhibited the lipopolysaccharide-induced apoptosis in HBECs. The percentage of S phase and G2/M phase was increased in HBECs after CGRP treatment. CGRP upregulated the expression of Ki67 in a dose-dependent manner. Some pathway inhibitors were used to investigate the signal pathway in which CGRP was involved. We found out that PKC pathway inhibitor (H-7) and MAPK pathway inhibitor (PD98059) could partially attenuate the effect of CGRP, which indicated that CGRP might promote the wound healing of HBECs via PKC and/or MAPK dependent pathway by accelerating migration and proliferation, and inhibiting apoptosis.

Postnatal exposure history and airways: oxidant stress responses in airway explants

Postnatally, the lung continues to grow and differentiate while interacting with the environment. Exposure to ozone (O(3)) and allergens during postnatal lung development alters structural elements of conducting airways, including innervation and neurokinin abundance. These changes have been linked with development of asthma in a rhesus monkey model. We hypothesized that O(3) exposure resets the ability of the airways to respond to oxidant stress and that this is mediated by changes in the neurokinin-1 receptor (NK-1R). Infant rhesus monkeys received episodic exposure to O(3) biweekly with or without house dust mite antigen (HDMA) from 6 to 12 months of age. Age-matched monkeys were exposed to filtered air (FA). Microdissected airway explants from midlevel airways (intrapulmonary generations 5-8) for four to six animals in each of four groups (FA, O(3), HDMA, and HDMA+O(3)) were tested for NK-1R gene responses to acute oxidant stress using exposure to hydrogen peroxide (1.2 mM), a lipid ozonide (10 μM), or sham treatment for 4 hours in vitro. Airway responses were measured using real-time quantitative RT-PCR of NK-1R and IL-8 gene expression. Basal NK-1R gene expression levels were not different between the exposure groups. Treatment with ozonide or hydrogen peroxide did not change NK-1R gene expression in animals exposed to FA, HDMA, or HDMA+O(3). However, treatment in vitro with lipid ozonide significantly increased NK-1R gene expression in explants from O(3)-exposed animals. We conclude that a history of prior O(3) exposure resets the steady state of the airways to increase the NK-1R response to subsequent acute oxidant stresses.