Metabolomics in Lung Inflammation:A High-Resolution¹H NMR Study of Mice Exposedto Silica Dust

Abstract

Here we report the first (1)H NMR metabolomics studies on excised lungs and bronchoalveolar lavage fluid (BALF) from mice exposed to crystalline silica. High-resolution (1)H NMR metabolic profiling on intact excised lungs was performed using slow magic angle sample spinning (slow-MAS) (1)H PASS (phase-altered spinning sidebands) at a sample spinning rate of 80 Hz. Metabolic profiling on BALF was completed using fast magic angle spinning at 2 kHz. Major findings are that the relative concentrations of choline, phosphocholine (PC), and glycerophosphocholine (GPC) were statistically significantly increased in silica-exposed mice compared to sham controls, indicating an altered membrane choline phospholipids metabolism (MCPM). The relative concentrations of glycogen/glucose, lactate, and creatine were also statistically significantly increased in mice exposed to silica dust, suggesting that cellular energy pathways were affected by silica dust. Elevated levels of glycine, lysine, glutamate, proline, and 4-hydroxyproline were also increased in exposed mice, suggesting the activation of a collagen pathway. Furthermore, metabolic profiles in mice exposed to silica dust were found to be spatially heterogeneous, consistent with regional inflammation revealed by in vivo magnetic resonance imaging (MRI).

Lactic Acid Is Elevated in Idiopathic Pulmonary Fibrosis and Induces Myofibroblast Differentiation via pH-Dependent Activation of Transforming Growth Factor-β

“…We previously demonstrated that lactic acid concentrations are elevated in the lung tissue of mice exposed to silica compared with control mice (11), and on the basis of these data, we examined whether lactate concentrations were also elevated in the lung tissue of patients with IPF. H-PASS NMR spectroscopy of lung tissue homogenates demonstrated that the concentrations of lactic acid were significantly increased in tissue from patients with IPF compared with healthy control subjects (Figures 1A and 1B).…”

“…High-resolution 1 H nuclear magnetic resonance (NMR) metabolomics using the technique of slow magic angle spinning (i.e., 1 H-PASS) (29), was used to determine the concentrations of lactic acid in fibroblast cell lysates and in whole lung homogenates from patients with IPF and from healthy control subjects using previously reported procedures (11).…”

“…The role of endogenous more physiological pH changes pertaining to TGF-b activation is not well understood. We recently became interested in the role of lactic acid in lung disease after metabolomic analysis of lung tissue of mice exposed to the fibrogenic agent silica demonstrated elevated concentrations of lactic acid in fibrotic lung tissue compared with healthy control mice (11). The finding of an abnormally elevated metabolic byproduct raised the possibility that there was dysregulation in cellular metabolism.…”

Metabolomics Approach for Hazard Identification in Human Health Assessment of Environmental Chemicals

“…Some of the mammalian in vitro systems involved exposing A549 human lung carcinoma cells to cigarette smoke (Vulimiri et al, 2009), human embryonic stem cells to various teratogens (West et al, 2010), and reaggregating neuronal cultures to methylmercury (van Vliet et al, 2008). From in vivo studies, intact organs from exposed experimental animals have been evaluated to include the analysis of intact lung after intratracheal instillation of silica dust (Hu et al, 2008) as well as liver and lung after exposure to 1-nitronaphthalene (Azmi et al, 2005). Also, metabolomics has been able to demonstrate different metabolic responses between mixtures of environmental chemicals.…”

Proteomics and Metabolomics in Aortic Stenosis: Studying Healthy Valves for a Better Understanding of the Disease

“…This rapid spinning at this precise angle has the effect of reducing dipolar coupling effects and narrowing of the broad lines found in this tissue. HRMAS-NMR has been applied successfully to analyze different intact cells and tissues [80][81][82][83][84][85], so it seems to be a powerful tool for the analyses of aortic valve tissue.…”