Acat-1 Inhibition Reduces Inflammatory Response to Bleomycin-mediated Lung Injury

Emily R. Stevenson, Melissa L. Wilkinson, Elena Abramova, Chiangjiang Guo, Andrew J. Gow

Research output: Contribution to journalArticlepeer-review

Abstract

Acute lung injury (ALI) is characterized by epithelial damage, barrier dysfunction, and pulmonary edema. Macrophage (MΦ) activation and failure to resolve play a role in in ALI, thus MΦ phenotype modulation is a rational target for therapeutic intervention. Large, lipid-laden MΦs have been observed in various injury models, including intratracheal bleomycin (ITB), suggesting that lipid storage may play a role in ALI severity. The mitochondrial enzyme Acat-1 is highly expressed in MΦs where it catalyzes the esterification of cholesterol, leading to intracellular lipid accumulation. We hypothesize that inhibition of Acat-1 will reduce MΦ activation and reduce ITB-mediated lung injury. K-604, a selective inhibitor of Acat-1, was used to reduce lipid accumulation in ITB. Male and female C57BL6/J mice (n=16-21/group) were administered PBS, K-604, ITB, or ITB +K-604 on d0, PBS or K-604 on d3, and were sacrificed on d7. ITB caused significant (*p<0.05 v PBS) body weight loss (-13.92±2.05%* v 2.66±0.78%) and an increase in cholesterol accumulation (71.63±11.7 μM* v 15.51±9.1 μM) and size (29.67±10.6 μm* v 11±4.3 μm) of pulmonary MΦs. These changes were mitigated by Acat-1 inhibition, as ITB+K-604 mice had significantly (#p<0.05 v ITB) reduced body weight loss (4.04±1.03%#), cholesterol accumulation (13.79±5.4#), and MΦ diameter (14.0±3.7 μm#), confirming successful inhibition of Acat-1 in the lung. Histological analysis showed that K-604 significantly reduced ITB-induced alveolar wall thickening (2.3±0.05 μm# v 4.35±0.04 μm) and reduced measures of consolidation and cell infiltration. Surface active function was normalized as indicated by a significant decrease in phospholipid:SP-B ratio in ITB+K-604 compared to ITB (7.95±1.22# v 13.28±2.17). K-604 administration rescued ITB-mediated loss of resident alveolar MΦs (CD45+/Siglec F+/F/480+, CD11c+, CD11b-) (72.00±5.67%# v 49.58±8.52%) and was found to decrease the % of pro-inflammatory alveolar MΦs (CD45+/Siglec F+/F/480+, Ly6c+, CD206-) (3.86±0.88%# v 8.22±1.76%). K-604 reduced ITB-mediated increases in NOS2 (64.23±20.07# v 131.89±17.07) and ARG1 expression (42.39±8.14# v 177.41±52.2) in BAL MΦs, suggesting reduced inflammatory signaling and immunometabolic demand. In our ITB model, K-604 also decreased the % of interstitial MΦs (IMs) (tissue-derived CD45+, Siglec F -, F4/80+, CD11b+) expressing markers of maturity and fibrotic potential (CD11c+/CD206+) (5.89±2.15%# v 19.72±1.93%). IMs were also found to have an increased rate of lipid uptake after K-604 regardless of ITB administration as measured by the uptake of fluorescently labeled LDL and visualization by confocal microscopy. These data, along with changes in cholesterol ester accumulation, suggest that Acat-1 inhibition alters lipid storage and uptake within pulmonary macrophages, affecting cell phenotype and function. Thus, Acat-1 may be a target for intervention in ALI.

Original languageEnglish (US)
JournalFASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume36
DOIs
StatePublished - May 1 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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