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Taste receptors in innate immunity.
Lee, RJ, Cohen, NA
Cellular and molecular life sciences : CMLS. 2015;(2):217-36
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Abstract
Taste receptors were first identified on the tongue, where they initiate a signaling pathway that communicates information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has shown that taste receptors are also expressed in a myriad of other tissues, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these extraoral taste receptors remain unknown, but emerging evidence suggests that bitter and sweet taste receptors in the airway are important sentinels of innate immunity. This review discusses taste receptor signaling, focusing on the G-protein-coupled receptors that detect bitter, sweet, and savory tastes, followed by an overview of extraoral taste receptors and in-depth discussion of studies demonstrating the roles of taste receptors in airway innate immunity. Future research on extraoral taste receptors has significant potential for identification of novel immune mechanisms and insights into host-pathogen interactions.
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Haemophilus influenzae: recent advances in the understanding of molecular pathogenesis and polymicrobial infections.
Jalalvand, F, Riesbeck, K
Current opinion in infectious diseases. 2014;(3):268-74
Abstract
PURPOSE OF REVIEW Non-typeable Haemophilus influenzae (NTHi) is a human-specific mucosal pathogen and one of the most common causes of bacterial infections in children and patients with chronic obstructive pulmonary disease. It is also frequently found in polymicrobial superinfections. Great strides have recently been made in the understanding of the molecular mechanisms underlying NTHi pathogenesis. RECENT FINDINGS By using new methodology, such as experimental human colonization models and whole-genome approaches, investigators have shed light upon the various strategies of NTHi that are involved in pathogenesis. These include the escape of the mucociliary elevator, evasion of host immunity, survival in environments with scarce nutrients, and finally participation in polymicrobial infections. Lipooligosaccharide branching, proteinous adhesins, metabolic adaption to nutrient availability and many scavenging systems are implicated in these processes. Interestingly, genome-based studies comparing virulent and commensal strains have identified many hypothetical proteins as virulence determinants, suggesting that much regarding the molecular pathogenesis of NTHi remains to be solved. SUMMARY NTHi is an opportunistic pathogen and highly specialized colonizer of the human respiratory tract that has developed intricate mechanisms to establish growth and survival in the human host. Continued research is needed to further elucidate NTHi host-pathogen and pathogen-pathogen interactions.
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Adaptation of Pseudomonas aeruginosa to the cystic fibrosis airway: an evolutionary perspective.
Folkesson, A, Jelsbak, L, Yang, L, Johansen, HK, Ciofu, O, Høiby, N, Molin, S
Nature reviews. Microbiology. 2012;(12):841-51
Abstract
The airways of patients with cystic fibrosis (CF) are nearly always infected with many different microorganisms. This environment offers warm, humid and nutrient-rich conditions, but is also stressful owing to frequent antibiotic therapy and the host immune response. Pseudomonas aeruginosa is commonly isolated from the airways of patients with CF, where it most often establishes chronic infections that usually persist for the rest of the lives of the patients. This bacterium is a major cause of mortality and morbidity and has therefore been studied intensely. Here, we discuss how P. aeruginosa evolves from a state of early, recurrent intermittent colonization of the airways of patients with CF to a chronic infection state, and how this process offers opportunities to study bacterial evolution in natural environments. We believe that such studies are valuable not only for our understanding of bacterial evolution but also for the future development of new therapeutic strategies to treat severe chronic infections.
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Mucins, mucus, and sputum.
Voynow, JA, Rubin, BK
Chest. 2009;(2):505-512
Abstract
Normal airway mucus lines the epithelial surface and provides an important innate immune function by detoxifying noxious molecules and by trapping and removing pathogens and particulates from the airway via mucociliary clearance. The major macromolecular constituents of normal mucus, the mucin glycoproteins, are large, heavily glycosylated proteins with a defining feature of tandemly repeating sequences of amino acids rich in serine and threonine, the linkage sites for large carbohydrate structures. The mucins are composed of two major families: secreted mucins and membrane-associated mucins. Membrane-associated mucins have been reported to function as cell surface receptors for pathogens and to activate intracellular signaling pathways. The biochemical and cellular functions for secreted mucin glycoproteins have not been definitively assigned. In contrast to normal mucus, sputum production is the hallmark of chronic inflammatory airway diseases such as asthma, chronic bronchitis, and cystic fibrosis (CF). Sputum has altered macromolecular composition and biophysical properties which vary with disease, but unifying features are failure of mucociliary clearance, resulting in airway obstruction, and failure of innate immune properties. Mucin glycoprotein overproduction and hypersecretion are common features of chronic inflammatory airway disease, and this has been the underlying rationale to investigate the mechanisms of mucin gene regulation and mucin secretion. However, in some pathologic conditions such as CF, airway sputum contains little intact mucin and has increased content of several macromolecules including DNA, filamentous actin, lipids, and proteoglycans. This review will highlight the most recent insights on mucus biology in health and disease.
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Echinacea purpurea and mucosal immunity.
Hall, H, Fahlman, MM, Engels, HJ
International journal of sports medicine. 2007;(9):792-7
Abstract
This investigation examined the effects of Echinacea purpurea on mucosal immunity and the incidence and duration of upper respiratory tract infection (URTI). 32 subjects completed an exercise protocol known to affect mucosal immunity. Saliva was collected prior to and five minutes after completion of exercise testing. Subjects then took either a placebo (C) or Echinacea supplement (E) for 4 weeks and the testing procedure was repeated. Each time, s-IgA concentrations and saliva flow rate were measured and the secretion rate of s-IgA was calculated. In addition, standard logs indicating symptoms of URTI were completed throughout the study. Both groups demonstrated significant exercise induced reductions in s-IgA (C - 69 %; E - 43 %) and the secretion rate of s-IgA (C - 79 %; E - 53 %) at the beginning of the study (p < 0.05). Following the 4-week intervention, only the control group experienced the post intervention decrease in s-IgA (C - 45 %; E + 7 %) and the secretion rate of s-IgA (C - 45 %; E - 7 %). Further, while there was no significant difference in the number of URTI between groups, the reported duration was significantly different (C 8.6 days vs. E 3.4 days). The results suggest that Echinacea may attenuate the mucosal immune suppression known to occur with intense exercise and reduce the duration of URTI that subjects incur.