Combined Acid Aspiration and Endotoxin Synergistically Recruit Airway Neutrophils and Disrupt Barrier Function and Lung Mechanics.

Allen, GB; Tetenev, Konstantin; Reyn, JA von; Cloutier, M.; Bates, J.H.T.

doi:10.1164/ajrccm-conference.2009.179.1_meetingabstracts.a3882

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“…To evaluate the time course of inflammatory change and barrier disruption independent of any potential effect from mechanical ventilation, additional mice (n ϭ 6 per group and time point) were again anesthetized with isoflurane for aspiration of 4 l/gm of normal saline or HCl in saline (pH 1.3) and assigned to receive aerosolized LPS or nothing 1 h later. The mice were euthanized at 2, 5, 13, 25, or 49 h following aspiration (1,4,12,24, or 48 h following LPS), at which time BALF was collected in the same manner described above. The spun BALF cell pellets were resuspended and stained, and the total cell counts were determined manually using a hemacytometer.…”

Section: Methodsmentioning

confidence: 99%

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Synergy between acid and endotoxin in an experimental model of aspiration-related lung injury progression

Tetenev

Cloutier

Reyn

et al. 2015

American Journal of Physiology-Lung Cellular and Molecular Phys

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Aspiration is a common cause of lung injury, but it is unclear why some cases are self-limited while others progress to acute respiratory distress syndrome (ARDS). Sporadic exposure to more than one insult could account for this variable progression. We investigated whether synergy between airway acid and endotoxin (LPS) amplifies injury severity in mice and whether LPS levels in human patients could corroborate our experimental findings. C57BL/6 mice aspirated acid (pH 1.3) or normal saline (NS), followed by LPS aerosol or nothing. Bronchoalveolar lavage fluid (BALF) was obtained 2 to 49 h later. Mice were injected with FITC-dextran 25 h after aspiration and connected to a ventilator, and lung elastance (H) measured periodically following deep inflation (DI). Endotracheal and gastric aspirates were also collected from patients in the intensive care unit and assayed for pH and LPS. Lung instability (ΔH following DI) and pressure-volume hysteresis in acid- or LPS-exposed mice was greater than in controls but markedly greater in the combined acid/LPS group. BALF neutrophils, cytokines, protein, and FITC-dextran in the acid/LPS mice were geometrically higher than all other groups. BALF from acid-only mice markedly amplified LPS-induced TNF-α production in cultured macrophages. Human subjects had variable endotracheal LPS levels with the highest burden in those at higher risk of aspiration. Acid aspiration amplifies LPS signaling in mice to disrupt barrier function and lung mechanics in synergy. High variation in airway LPS and greater airway LPS burden in patients at higher risk of aspiration could help explain the sporadic progression of aspiration to ARDS.

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Section: Methodsmentioning

confidence: 99%

“…Our findings support the notion of synergy between acid injury and LPS in the pathogenesis of lung injury in mice and open new potential explanations for the variable clinical course following aspiration in human patients. Some of the results of these studies have been previously reported in the form of an abstract (4,38).…”

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confidence: 94%