Integrative metabolome and transcriptome profiling reveals discordant energetic stress between mouse strains with differential sensitivity to acrolein‐induced acute lung injury

Abstract

A respiratory irritant, acrolein is generated by overheating cooking oils or by domestic cooking using biomass fuels, and is in tobacco smoke, an occupational health hazard in the restaurant workplace. To better understand the metabolic role of the lung and to generate insights into the pathogenesis of acrolein-induced acute lung injury, SM/J (sensitive) and 129×1/SvJ (resistant) inbred mouse strains were exposed and the lung metabolome was integrated with the transcriptome profile. A total of 280 small molecules were identified and mean values (log 2 >0.58 or <−0.58, .p<0.05) were considered different for between-strain comparisons or within-strain responses to acrolein treatment. At baseline, 24 small molecules increased and 33 small molecules decreased in the SM/J mouse lung as compared to 129×1/SvJ mouse lung. Notable among the increased compounds was malonyl carnitine. Following acrolein exposure, several compounds indicative of glycolysis and branched chain amino acid metabolism increased similarly in both strains, whereas SM/J mice were less effective in generating metabolites related to fatty acid β-oxidation. These findings suggest management of energetic stress varies between these strains, and that the ability to evoke auxiliary energy generating pathways rapidly and effectively may be critical in enhancing survival during acute lung injury in mice.

Functional Genomic Assessment of Phosgene-Induced Acute Lung Injury in Mice

“…In a process that consumes 40% of a cell's energy, Na,K-ATPase maintains the sodium-potassium electrochemical gradient across the plasma membrane by exporting three Na 1 and importing two K 1 for each ATP hydrolyzed (77). In previous metabolomics analyses of acrolein-and chlorine-induced lung injury, we observed that the lung undergoes energetic stress and that resistant mice appear better able to use substrates for energy production (33,34). The Na,K-ATPase-generated electrochemical gradient is essential for edema fluid absorption from the alveolus (1, 3).…”

“…The genetic and transcriptomic findings here may be limited to this compound and thus may not be relevant to other forms of ALI. We previously identified candidate genes associated with acrolein-induced (32,33) and chlorine-induced ALI (34), and these genes differed from those identified with phosgene. Until several types of chemically induced ALI have been evaluated, generalizations to other forms may not be warranted.…”

“…Genome-wide association analysis was performed using efficient mixed-models association corrected for confounding from population structure and genetic relatedness (43,44). Previously, we determined that one statistical association by chance will occur in a genome-wide scan when the threshold is decreased to 1.6 3 10 25 or 2log (P) ¼ 4.8 (25,(32)(33)(34). Therefore, we used a significance threshold of -log (P) .…”

“…Recently, nextgeneration whole genome sequencing information has been obtained on 17 mouse strains (29), which has strengthened the existing single nucleotide polymorphism (SNP) database for over 40 mouse strains (29)(30)(31). Using a genetically diverse panel of >40 inbred mouse strains, we previously conducted functional genomic analyses of acrolein-induced (32,33) and chlorine-induced (34) ALI. In this study, we sought to compare these findings with an additional chemical, phosgene, also known to produce ALI after accidental or intentional terrorist exposures.…”

Integrative Assessment of Chlorine-Induced Acute Lung Injury in Mice

“…Microarrays (n ¼ 5 mice/strain/time) and quantitative RT-PCR (n ¼ 8 mice/strain/time) were used to contrast transcript levels of candidate genes. Metabolomic profiling was performed as described previously (60)(61)(62)(63), using lung tissue (n ¼ 5 mice/strain/time) that was homogenized in deionized water containing recovery standards, extracted (80:20 methanol/water), and analyzed by positive or negative ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry (LC:Surveyor; ThermoFisher, Pittsburgh, PA) (61), or by gas chromatography-mass spectrometry (ThermoFinnegan Mat-95XP; ThermoFisher) (61). In contrast to the accuratemass and elution-time tags used in shotgun proteomics, our library-based approach combines accurate retention times and tandem mass spectrometric fragmentation patterns to unambiguously identify .2,400 biochemicals (63).…”