Murine lung injury caused by Leptospira interrogans glycolipoprotein, a specific Na/K-ATPase inhibitor

Abstract

BackgroundLeptospiral glycolipoprotein (GLP) is a potent and specific Na/K-ATPase inhibitor. Severe pulmonary form of leptospirosis is characterized by edema, inflammation and intra-alveolar hemorrhage having a dismal prognosis. Resolution of edema and inflammation determines the outcome of lung injury. Na/K-ATPase activity is responsible for edema clearance. This enzyme works as a cell receptor that triggers activation of mitogen-activated protein kinase (MAPK) intracellular signaling pathway. Therefore, injection of GLP into lungs induces injury by triggering inflammation.MethodsWe injected GLP and ouabain, into mice lungs and compared their effects. Bronchoalveolar lavage fluid (BALF) was collected for cell and lipid body counting and measurement of protein and lipid mediators (PGE2 and LTB4). The levels of the IL-6, TNFα, IL-1B and MIP-1α were also quantified. Lung images illustrate the injury and whole-body plethysmography was performed to assay lung function. We used Toll-like receptor 4 (TLR4) knockout mice to evaluate leptospiral GLP-induced lung injury. Na/K-ATPase activity was determined in lung cells by nonradioactive rubidium incorporation. We analyzed MAPK p38 activation in lung and in epithelial and endothelial cells.ResultsLeptospiral GLP and ouabain induced lung edema, cell migration and activation, production of lipid mediators and cytokines and hemorrhage. They induced lung function alterations and inhibited rubidium incorporation. Using TLR4 knockout mice, we showed that the GLP action was not dependent on TLR4 activation. GLP activated of p38 and enhanced cytokine production in cell cultures which was reversed by a selective p38 inhibitor.ConclusionsGLP and ouabain induced lung injury, as evidenced by increased lung inflammation and hemorrhage. To our knowledge, this is the first report showing GLP induces lung injury. GLP and ouabain are Na/K-ATPase targets, triggering intracellular signaling pathways. We showed p38 activation by GLP-induced lung injury, which was may be linked to Na/K-ATPase inhibition. Lung inflammation induced by GLP was not dependent on TLR4 activation.

Na/K Pump and Beyond: Na/K-ATPase as a Modulator of Apoptosis and Autophagy

“…Thus, sodium transport and oedema clearance are associated with better outcomes in patients with sepsis and ARDS [ 76 ]. Ouabain inhibits AFC in isolated, perfused fluid-filled mouse lungs [ 79 ] and in animals in vivo [ 80 , 81 , 82 , 83 , 84 ]. The overexpression of FXYD1 in the lungs of ARDS patients may limit Na/K-ATPase activity and contribute to oedema persistence [ 85 ].…”

Acute Respiratory Distress Syndrome: Role of Oleic Acid‐Triggered Lung Injury and Inflammation

“…Furthermore, we showed that the GLP lipid content handles NKA inhibition indicating that oleic acid has a crucial role in NKA inhibition either alone or as a part of a macromolecular complex. Recently we showed that GLP induces lung injury similar to ouabain and oleic acid [ 50 ]. Thus, oleic acid prevents edema clearance and can trigger protein-rich edema formation by intravenous or intratracheal routes [ 36 , 38 ].…”

Comparison of Bacterial Burden and Cytokine Gene Expression in Golden Hamsters in Early Phase of Infection with Two Different Strains of Leptospira interrogans

“…Several leptospiral factors are known to induce the production of cytokines or the expression of cytokine genes [ 29 – 34 ]. Leptospiral lipopolysaccharide (LPS) activates monocytes through Toll-like receptor 2, releasing inflammatory cytokines [ 29 ].…”

“…Leptospiral lipoprotein LipL32 and hemolysins have been shown to induce inos , tnfalpha , and ccl2 expression in cultured mouse renal proximal tubule cells and IL-6, IL-1β, and TNF-α production in cultured human and murine macrophages [ 31 – 33 ]. Injection of leptospiral glycoprotein GLP into mouse lung has been shown to trigger the production of IL-6, IL-1β, TNF-α, and MIP-1α [ 34 ]. The genome copy number of serovar Manilae was not significantly different from that of serovar Hebdomadis in blood, kidney, and lung.…”