Severe pneumonia is the leading single cause of mortality in children aged less than five years worldwide and the sixth leading cause of death in seniors over age 65 in the US. Streptococcus pneumoniae represents the main etiological agent of the disease. Moreover, mortality after influenza A virus (IAV) infection has been suggested to be mainly due to secondary pneumoccocal infections. Intriguingly, death in pneumococcal-induced pneumonia can occur days after initiation of antibiotic therapy, when tissues are sterile and the pneumonia is clearing. This mortality correlates with the presence of pneumococcal virulence factors, the most important one of which is the pore-forming toxin pneumolysin (PLY). A major complication of severe pneumonia is permeability edema, characterized by a dramatically increased pulmonary endothelial hyperpermeability and an impaired alveolar liquid clearance (ALC). The enzyme PKC-(, which is activated by PLY-mediated Ca2+ influx, has recently been suggested to be implicated in the downregulation of the epithelial sodium channel (ENaC) expression, as well as in endothelial barrier dysfunction. Our preliminary data demonstrate that the lectin-like domain of TNF, mimicked by the TIP peptide, is able to blunt PLY-induced PKC-( activation, endothelial hyperpermeability and ALC dysfunction. Our overall hypothesis is that the lectin-like domain of TNF restores alveolar liquid clearance and improves barrier integrity during G+-infection- associated pneumonia, by means of blunting exotoxin-mediated PKC-( activation. We will test three specific aims to this purpose. First, we will unravel the mechanism by which the TIP peptide restores epithelial sodium channel activity and expression in PLY-treated alveolar epithelial cells. Second, we will determine at which step(s) in the cascade of events leading to PLY-induced endothelial dysfunction, the TIP peptide intervenes and what is the most upstream event affected by the peptide. Third, we will test the hypothesis that the lectin-like domain of TNF restores ALC and preserves pulmonary endothelial barrier integrity in PLY-treated mice, upon blunting PKC-( activation, making use of Triple mTNF knock-in mice, expressing a lectin-deficient mutant of TNF. The results of this research program can thus provide important information about mechanisms leading to permeability edema and dysfunctional ALC during bacterial pneumonia and can thus lead to the identification of novel therapeutic strategies.
One of the major complications of severe bacterial pneumonia is permeability edema, characterized by endothelial hyperpermeability and a dysfunctional alveolar liquid clearance (ALC) capacity. Our recent data from mouse models and in vitro studies using human endothelial and airway epithelial cells indicate that the TNF-derived TIP peptide, mimicking its lectin-like domain, restores ALC and endothelial barrier integrity upon treatment with the G+ bacterial exotoxin pneumolysin (PLY). This project aims to demonstrate that the protective activity of the TIP peptide in bacterial pneumonia relies on its capacity to blunt PLY-induced Protein Kinase C-( activation, which plays a crucial role in both the induction of endothelial hyperpermeability and in the down-regulation of the epithelial sodium channel, as such providing a basis for novel therapeutic strategies to combat severe bacterial pneumonia.
|Gross, Christine M; Rafikov, Ruslan; Kumar, Sanjiv et al. (2015) Endothelial nitric oxide synthase deficient mice are protected from lipopolysaccharide induced acute lung injury. PLoS One 10:e0119918|
|Gonzales, J N; Lucas, R; Verin, A D (2015) The Acute Respiratory Distress Syndrome: Mechanisms and Perspective Therapeutic Approaches. Austin J Vasc Med 2:|
|Loose, Maria; Hudel, Martina; Zimmer, Klaus-Peter et al. (2015) Pneumococcal hydrogen peroxide-induced stress signaling regulates inflammatory genes. J Infect Dis 211:306-16|
|Czikora, István; Alli, Abdel; Bao, Hui-Fang et al. (2014) A novel tumor necrosis factor-mediated mechanism of direct epithelial sodium channel activation. Am J Respir Crit Care Med 190:522-32|
|Chen, Feng; Kumar, Sanjiv; Yu, Yanfang et al. (2014) PKC-dependent phosphorylation of eNOS at T495 regulates eNOS coupling and endothelial barrier function in response to G+ -toxins. PLoS One 9:e99823|
|Schwameis, Richard; Eder, Sandra; Pietschmann, Helmut et al. (2014) A FIM study to assess safety and exposure of inhaled single doses of AP301-A specific ENaC channel activator for the treatment of acute lung injury. J Clin Pharmacol 54:341-50|
|Czikora, Istvan; Sridhar, Supriya; Gorshkov, Boris et al. (2014) Protective effect of Growth Hormone-Releasing Hormone agonist in bacterial toxin-induced pulmonary barrier dysfunction. Front Physiol 5:259|
|Aggarwal, Saurabh; Gross, Christine M; Kumar, Sanjiv et al. (2014) Dimethylarginine dimethylaminohydrolase II overexpression attenuates LPS-mediated lung leak in acute lung injury. Am J Respir Cell Mol Biol 50:614-25|
|Umapathy, Siddaramappa Nagavedi; Siddaramappa Umapathy, Nagavedi; Kaczmarek, Elzbieta et al. (2013) Adenosine A1 receptors promote vasa vasorum endothelial cell barrier integrity via Gi and Akt-dependent actin cytoskeleton remodeling. PLoS One 8:e59733|
|Lucas, Rudolf; Czikora, Istvan; Sridhar, Supriya et al. (2013) Mini-review: novel therapeutic strategies to blunt actions of pneumolysin in the lungs. Toxins (Basel) 5:1244-60|
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