254 research outputs found
Chemosensory cells in the respiratory tract as crucial regulators of innate immune responses
During recent years chemosensory cells in extraoral tissues have been established as mediators for the detection and regulation of innate immune processes in response to pathogens. Under physiological conditions, chemosensory cells are present throughout the respiratory epithelium of the upper and lower airways as well as in the main olfactory epithelium. Additionally, they emerge in the alveolar region of the lung upon viral infections. Chemosensory cells in the upper and the lower airways detect signalling molecules from gram-positive and gram-negative bacteria as well as aeroallergens and fungi. Upon stimulation they release multiple molecules, such as the transmitter acetylcholine, the cysteinyl leukotriene E4 and the cytokine interleukin-25, which act as autocrine and paracrine signals and thereby orchestrate the innate immune responses in the respiratory system. Activation of chemosensory cells stimulates various immune cells, e.g. type 2 innate lymphoid cells, modulates mucociliary clearance and induces a protective neurogenic inflammation. This review compiles and discusses recent findings regarding chemosensory cell function in the respiratory tract
Nicotinic Acetylcholine Receptors in the Respiratory Tract
Nicotinic acetylcholine receptors (nAChR) are widely distributed in neuronal and nonneuronal tissues, where they play diverse physiological roles. In this review, we highlight the recent
findings regarding the role of nAChR in the respiratory tract with a special focus on the involvement
of nAChR in the regulation of multiple processes in health and disease. We discuss the role of nAChR
in mucociliary clearance, inflammation, and infection and in airway diseases such as asthma, chronic
obstructive pulmonary disease, and cancer. The subtype diversity of nAChR enables differential
regulation, making them a suitable pharmaceutical target in many diseases. The stimulation of the
α3β4 nAChR could be beneficial in diseases accompanied by impaired mucociliary clearance, and
the anti-inflammatory effect due to an α7 nAChR stimulation could alleviate symptoms in diseases
with chronic inflammation such as chronic obstructive pulmonary disease and asthma, while the
inhibition of the α5 nAChR could potentially be applied in non-small cell lung cancer treatment.
However, while clinical studies targeting nAChR in the airways are still lacking, we suggest that
more detailed research into this topic and possible pharmaceutical applications could represent
a valuable tool to alleviate the symptoms of diverse airway diseases
Caveolin-3 differentially orchestrates cholinergic and serotonergic constriction of murine airways
The mechanisms of controlling airway smooth muscle (ASM) tone are of utmost clinical importance as inappropriate constriction is a hallmark in asthma and chronic obstructive pulmonary disease. Receptors for acetylcholine and serotonin, two relevant mediators in this context, appear to be incorporated in specialized, cholesterol-rich domains of the plasma membrane, termed caveolae due to their invaginated shape. The structural protein caveolin-1 partly accounts for anchoring of these receptors. We here determined the role of the other major caveolar protein, caveolin-3 (cav-3), in orchestrating cholinergic and serotonergic ASM responses, utilizing newly generated cav-3 deficient mice. Cav-3 deficiency fully abrogated serotonin-induced constriction of extrapulmonary airways in organ baths while leaving intrapulmonary airways unaffected, as assessed in precision cut lung slices. The selective expression of cav-3 in tracheal, but not intrapulmonary bronchial epithelial cells, revealed by immunohistochemistry, might explain the differential effects of cav-3 deficiency on serotonergic ASM constriction. The cholinergic response of extrapulmonary airways was not altered, whereas a considerable increase was observed in cav-3â -/- intrapulmonary bronchi. Thus, cav-3 differentially organizes serotonergic and cholinergic signaling in ASM through mechanisms that are specific for airways of certain caliber and anatomical position. This may allow for selective and site-specific intervention in hyperreactive states
Nicotine stimulates ion transport via metabotropic β4 subunit containing nicotinic ACh receptors
Background and Purpose
Mucociliary clearance is an innate immune process of the airways, essential for removal of respiratory pathogens. It depends on ciliary beat and ion and fluid homeostasis of the epithelium. We have shown that nicotinic ACh receptors (nAChRs) activate ion transport in mouse tracheal epithelium. Yet the receptor subtypes and signalling pathways involved remained unknown.
Experimental Approach
Transepithelial short circuit currents (ISC) of freshly isolated mouse tracheae were recorded using the Ussing chamber technique. Changes in [Ca2+]i were studied on freshly dissociated mouse tracheal epithelial cells.
Key Results
Apical application of the nAChR agonist nicotine transiently increased ISC. The nicotine effect was abolished by the nAChR antagonist mecamylamine. α‐Bungarotoxin (α7 antagonist) had no effect. The agonists epibatidine (α3β2, α4β2, α4β4 and α3β4) and A‐85380 (α4β2 and α3β4) increased ISC. The antagonists dihydro‐β‐erythroidine (α4β2, α3β2, α4β4 and α3β4), α‐conotoxin MII (α3β2) and α‐conotoxin PnIA (α3β2) reduced the nicotine effect. Nicotine‐ and epibatidine‐induced currents were unaltered in β2−/−mice, but in β4−/− mice no increase was observed. In the presence of thapsigargin (endoplasmatic reticulum Ca2+‐ATPase inhibitor) or the ryanodine receptor antagonists JTV‐519 and dantrolene there was a reduction in the nicotine‐effect, indicating involvement of Ca2+ release from intracellular stores. Additionally, the PKA inhibitor H‐89 and the TMEM16A (Ca2+‐activated chloride channel) inhibitor T16Ainh‐A01 significantly reduced the nicotine‐effect.
Conclusion and Implications
α3β4 nAChRs are responsible for the nicotine‐induced current changes via Ca2+ release from intracellular stores, PKA and ryanodine receptor activation. These nAChRs might be possible targets to stimulate chloride transport via TMEM16A
Human airway tuft cells influence the mucociliary clearance through cholinergic signalling
Background Airway tuft cells, formerly called brush cells have long been described only morphologically in human
airways. More recent RNAseq studies described a chemosensory cell population, which includes tuft cells, by a distinct
gene transcription signature. Yet, until which level in the tracheobronchial tree in native human airway epithelium tuft
cells occur and if they function as regulators of innate immunity, e.g., by regulating mucociliary clearance, remained
largely elusive.
Methods We performed immunohistochemistry, RT-PCR and immunoblotting analyses for various tuft cell markers
to confirm the presence of this cell type in human tracheal samples. Immunohistochemistry was conducted to
study the distribution of tuft cells along the intrapulmonary airways in humans. We assessed the influence of bitter
substances and the taste transduction pathway on mucociliary clearance in mouse and human tracheal samples by
measuring particle transport speed.
Results Tuft cells identified by the expression of their well-established marker POU class 2 homeobox 3 (POU2F3)
were present from the trachea to the bronchioles. We identified choline acetyltransferase in POU2F3 expressing cells
as well as the transient receptor potential melastatin 5 (TRPM5) channel in a small population of tracheal epithelial
cells with morphological appearance of tuft cells. Application of bitter substances, such as denatonium, led to an
increase in mucociliary clearance in human tracheal preparations. This was dependent on activation of the TRPM5
channel and involved cholinergic and nitric oxide signalling, indicating a functional role for human tuft cells in the
regulation of mucociliary clearance. Conclusions We were able to detect tuft cells in the tracheobronchial tree down to the level of the bronchioles.
Moreover, taste transduction and cholinergic signalling occur in the same cells and regulate mucociliary clearance.
Thus, tuft cells are potentially involved in the regulation of innate immunity in human airways
Identification of immunogenic candidate for new serological tests for Brucella melitensis by a proteomic approach.
Background:
The diagnosis of brucellosis by serological tests is based on antigen suspensions derived from smooth lipopolysaccharide extracts, which can give false-positive results linked to cross-reactivity with other Gram-negative microorganisms, especially Yersinia enterocolitica O:9 and Escherichia coli O157:H7.
Objective:
The objective of the present study was the characterization by proteomic analysis of specific immunogenic proteins not associated with smooth lipopolysaccharide to improve the diagnostic tests used in the ovine brucellosis eradication programs.
Methods:
The serum from a sheep positive to Brucella melitensis was treated to eliminate all antibodies against such lipopolysaccharides and highlight the reaction towards the immunoreactive proteins in western blotting.
Results:
The immunoreactive bands were identified by nLC-MS/MS, and through bioinformatics tools, it was possible to select 12 potential candidates as protein antigens specific for Brucella melitensis.
Conclusion:
The detection of new antigens not subjected to cross-reactivity with other Gram-negative microorganisms can offer additional tools for the serological diagnosis of such diseases
Empirical Investigation on Agile Methods Usage: Issues Identified from Early Adopters in Malaysia
Agile Methods are a set of software practices that can help to produce products faster and at the same time deliver what customers want. Despite the benefits that Agile methods can deliver, however, we found few studies from the Southeast Asia region, particularly Malaysia. As a result, less empirical evidence can be obtained in the country making its implementation harder. To use a new method, experience from other practitioners is critical, which describes what is important, what is possible and what is not possible concerning Agile. We conducted a qualitative study to understand the issues faced by early adopters in Malaysia where Agile methods are still relatively new. The initial study involves 13 participants including project managers, CEOs, founders and software developers from seven organisations. Our study has shown that social and human aspects are important when using Agile methods. While technical aspects have always been considered to exist in software development, we found these factors to be less important when using Agile methods. The results obtained can serve as guidelines to practitioners in the country and the neighbouring regions
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