| 1. |
- Gela, Anele, et al.
(författare)
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Eotaxin-3 (CCL26) exerts innate host defense activities that are modulated by mast cell proteases
- 2015
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Ingår i: Allergy. - : Wiley. - 1398-9995 .- 0105-4538. ; 70:2, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundDuring bacterial infections of the airways, a Th1-profiled inflammation promotes the production of several host defense proteins and peptides with antibacterial activities including -defensins, ELR-negative CXC chemokines, and the cathelicidin LL-37. These are downregulated by Th2 cytokines of the allergic response. Instead, the eosinophil-recruiting chemokines eotaxin-1/CCL11, eotaxin-2/CCL24, and eotaxin-3/CCL26 are expressed. This study set out to investigate whether these chemokines could serve as innate host defense molecules during allergic inflammation. MethodsAntibacterial activities of the eotaxins were investigated using viable count assays, electron microscopy, and methods assessing bacterial permeabilization. Fragments generated by mast cell proteases were characterized, and their potential antibacterial, receptor-activating, and lipopolysaccharide-neutralizing activities were investigated. ResultsCCL11, CCL24, and CCL26 all showed potent bactericidal activity, mediated through membrane disruption, against the airway pathogens Streptococcus pneumoniae, Staphylococcus aureus, Nontypeable Haemophilus influenzae, and Pseudomonas aeruginosa. CCL26 retained bactericidal activity in the presence of salt at physiologic concentrations, and the region holding the highest bactericidal activity was the cationic and amphipathic COOH-terminus. Proteolysis of CCL26 by chymase and tryptase, respectively, released distinct fragments of the COOH- and NH2-terminal regions. The COOH-terminal fragment retained antibacterial activity while the NH2-terminal had potent LPS-neutralizing properties in the order of CCL26 full-length protein. An identical fragment to NH2-terminal fragment generated by tryptase was obtained after incubation with supernatants from activated mast cells. None of the fragments activated the CCR3-receptor. ConclusionsTaken together, the findings show that the eotaxins can contribute to host defense against common airway pathogens and that their activities are modulated by mast cell proteases.
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| 2. |
- Gela, Anele, et al.
(författare)
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Midkine in Host Defense.
- 2014
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Ingår i: British Journal of Pharmacology. - : Wiley. - 1476-5381 .- 0007-1188. ; 171:4, s. 859-869
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Forskningsöversikt (refereegranskat)abstract
- Midkine shares several features in common with antibacterial proteins of the innate immune system. These include growth factor properties, heparin-binding regions, and effects on immune cells (i.e. recruitment and activation of neutrophils and macrophages). Indeed, recent research has demonstrated potent bactericidal and fungicidal activities of midkine. This protein is constitutively expressed at relevant concentrations at barriers of the body, such as in the skin and in the large airways, where the body first encounters potential pathogens. The antibacterial properties of midkine orthologues are preserved during evolution, as exemplified by miple2 of Drosophila. In addition to retinoic acid, gene expression can be promoted by additional factors present at sites of infection, reactive oxygen species, activation of the transcription factor NFκ-B, and hypoxia. In the light of the emerging resistance of pathogenic bacteria to conventional antibiotics, midkine is an interesting molecule that could serve as a template in developing novel pharmaceutical strategies against bacterial and fungal infections, either alone or in combination with conventional antibiotics.
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| 3. |
- Gela, Anele
(författare)
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On airway host defence during allergic inflammation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Asthma is a chronic inflammatory disease of the airways, affecting and disablingapproximately 300 million people worldwide. The inflammatory profile ischaracterized by infiltration of eosinophils, which are a rich source of factors thatare implicated in tissue remodeling. The chronic inflammatory response and theremodeled phenotype create a hospitable environment for secondary bacterialinfections. In recent years, systemic infections caused by Streptococcuspneumoniae in asthmatics have received global attention. The risk of acquiringpneumonia in patients suffering from asthma is 2-10 fold increased as compared tohealthy individuals. The cause is not known and in this thesis we hypothesized thatthe dysregulated allergic response may impair innate host defenses. Themechanisms being investigated may help to explain how the prolonged anddysregulated inflammatory response increases the vulnerability of asthmatics toinvasive pneumococcal disease. Initially, the regulation of chemokines, inparticular eotaxins, by mast cell proteases was investigated. From this study, wewere able to map the region of eotaxin-3/CCL26 that harbors antimicrobial(COOH-terminal) and anti-endotoxin (NH2-terminal) activity followingproteolytic cleavage with mast cell chymase and tryptase, respectively. However,the receptor activating properties (NH2-terminal) were lost. In a separate study, theanti-endotoxin fragment derived from CCL26 conferred therapeutic benefits in amouse model of LPS-induced inflammation. Furthermore, the interaction ofchemokines, particularly Th-2 chemokines, with osteopontin (OPN) wasinvestigated. OPN is an anionic glycoprotein that is upregulated in asthma and itsexpression increases with the severity of asthma. OPN bound to the COOHterminalof chemokines and completely abolished their antimicrobial activitywithout affecting their NH2-terminal localized functions, including LPSneutralizationand receptor activating properties. To ascertain if whether theeffects of OPN are generic or specific for Th-2 chemokines, we investigated itsinteraction with the classical antimicrobial peptides that are constitutivelyexpressed and upregulated during COPD. Interestingly, OPN bound andneutralized their antimicrobial activity but did not interfere with the muraminidaseactivity and protease inhibitory function of lysozyme and secretory leukocyteprotease inhibitor (SLPI), respectively. These studies suggest that chemokines andantimicrobial peptides can serve as host defense peptides but their actions aremodulated by mast cell proteases and OPN. Therefore, there is an urgent need forstudies focusing on modification of antimicrobial peptides to become resistant toproteolytic cleavage, altered pH and various salt conditions. Also, the elucidationof the novel roles of OPN during allergic inflammation could present potentialpharmaceutical targets. Taken together, this thesis explains several mechanismsthat impair innate host defenses during allergic inflammation.
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| 4. |
- Gela, Anele, et al.
(författare)
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Osteopontin binds and modulate functions of eosinophil-recruiting chemokines.
- 2016
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Ingår i: Allergy. - : Wiley. - 1398-9995 .- 0105-4538. ; 71:1, s. 58-67
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Tidskriftsartikel (refereegranskat)abstract
- Allergic asthma is characterized by eosinophilic inflammation and airway obstruction. There is also an increased risk of pulmonary infection caused by Streptococcus pneumoniae, in particular during severe asthma where high levels of the glycoprotein, osteopontin (OPN) are present in the airways. Eosinophils can be recruited by chemokines activating the receptor CCR3 including eotaxin-1/CCL11, eotaxin-2/CCL24, eotaxin-3/CCL26, RANTES/CCL5, and MEC/CCL28. In addition to inducing chemotaxis, several of these molecules have defensin-like antibacterial properties. This study set out to elucidate the functional consequences of OPN-binding to eosinophil-recruiting chemokines.
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| 5. |
- Gela, Anele, et al.
(författare)
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Osteopontin That Is Elevated in the Airways during COPD Impairs the Antibacterial Activity of Common Innate Antibiotics.
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial infections of the respiratory tract contribute to exacerbations and disease progression in chronic obstructive pulmonary disease (COPD). There is also an increased risk of invasive pneumococcal disease in COPD. The underlying mechanisms are not fully understood but include impaired mucociliary clearance and structural remodeling of the airways. In addition, antimicrobial proteins that are constitutively expressed or induced during inflammatory conditions are an important part of the airway innate host defense. In the present study, we show that osteopontin (OPN), a multifunctional glycoprotein that is highly upregulated in the airways of COPD patients co-localizes with several antimicrobial proteins expressed in the airways. In vitro, OPN bound lactoferrin, secretory leukocyte peptidase inhibitor (SLPI), midkine, human beta defensin-3 (hBD-3), and thymic stromal lymphopoietin (TSLP) but showed low or no affinity for lysozyme and LL-37. Binding of OPN impaired the antibacterial activity against the important bacterial pathogens Streptococcus pneumoniae and Pseudomonas aeruginosa. Interestingly, OPN reduced lysozyme-induced killing of S. pneumoniae, a finding that could be explained by binding of OPN to the bacterial surface, thereby shielding the bacteria. A fragment of OPN generated by elastase of P. aeruginosa retained some inhibitory effect. Some antimicrobial proteins have additional functions. However, the muramidase-activity of lysozyme and the protease inhibitory function of SLPI were not affected by OPN. Taken together, OPN can contribute to the impairment of innate host defense by interfering with the function of antimicrobial proteins, thus increasing the vulnerability to acquire infections during COPD.
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| 6. |
- Nordin, Sara, et al.
(författare)
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High Expression of Midkine in the Airways of Patients with Cystic Fibrosis.
- 2013
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Ingår i: American Journal of Respiratory Cell and Molecular Biology. - 1535-4989. ; 49:6, s. 935-942
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Tidskriftsartikel (refereegranskat)abstract
- Mutations in the CFTR gene result in impaired host defense during cystic fibrosis (CF), where Pseudomonas aeruginosa becomes a key pathogen. We investigated the expression pattern of the antibacterial growth factor midkine in CF and possible interference with its activity by the altered airway microenvironment. High midkine expression was found in CF lung tissue compared with controls, involving epithelium of the large and small airways, alveoli, and cells of the submucosa (i.e. neutrophils and mast cells). In CF sputum, midkine was present at 100-fold higher levels but was also subject to increased degradation, compared with midkine in sputum from healthy controls. Midkine had a bactericidal effect on P. aeruginosa but increasing salt concentrations and low pH impaired the activity. Molecular modeling suggested that the effects of salt and pH were due to electrostatic screening and a charge-neutralization of the membrane, respectively. Both neutrophil elastase and elastase of P. aeruginosa cleaved midkine to smaller fragments, resulting in impaired bactericidal activity. Thus, midkine is highly expressed in CF but its bactericidal properties may be impaired by the altered microenvironment as reflected by the in vitro conditions used in this study.
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