The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

Reputable evidence from multiple studies suggests that excessive and uncontrolled inflammation plays an indispensable role in mediating, amplifying, and protracting acute lung injury (ALI). Traditionally, immunity and energy metabolism are regarded as separate functions regulated by distinct mechanisms, but recently, more and more evidence show that immunity and energy metabolism exhibit a strong interaction which has given rise to an emerging field of immunometabolism. Mammalian lungs are organs with active fatty acid metabolism, however, during ALI, inflammation and oxidative stress lead to a series metabolic reprogramming such as impaired fatty acid oxidation, increased expression of proteins involved in fatty acid uptake and transport, enhanced synthesis of fatty acids, and accumulation of lipid droplets. In addition, obesity represents a significant risk factor for ALI/ARDS. Thus, we have further elucidated the mechanisms of obesity exacerbating ALI from the perspective of fatty acid metabolism. To sum up, this paper presents a systematical review of the relationship between extensive fatty acid metabolic pathways and acute lung injury and summarizes recent advances in understanding the involvement of fatty acid metabolism-related pathways in ALI. We hold an optimistic believe that targeting fatty acid metabolism pathway is a promising lung protection strategy, but the specific regulatory mechanisms are way too complex, necessitating further extensive and in-depth investigations in future studies.

Peroxiredoxin 3 has a crucial role in the macrophage polarization by regulating mitochondrial homeostasis

Acute lung injury (ALI) is one of the life-threatening complications of sepsis, and macrophage polarization plays a crucial role in the sepsis-associated ALI. However, the regulatory mechanisms of macrophage polarization in ALI and in the development of inflammation are largely unknown. In this study, we demonstrated that macrophage polarization occurs in sepsis-associated ALI and is accompanied by mitochondrial dysfunction and inflammation, and a decrease of PRDX3 promotes the initiation of macrophage polarization and mitochondrial dysfunction. Mechanistically, PRDX3 overexpression promotes M1 macrophages to differentiate into M2 macrophages, and enhances mitochondrial functional recovery after injury by reducing the level of glycolysis and increasing TCA cycle activity. In conclusion, we identified PRDX3 as a critical hub integrating oxidative stress, inflammation, and metabolic reprogramming in macrophage polarization. The findings illustrate an adaptive mechanism underlying the link between macrophage polarization and sepsis-associated ALI.

NKX2-8 deletion-induced reprogramming of fatty acid metabolism confers chemoresistance in epithelial ovarian cancer

Background

Aberrant fatty acid (FA) metabolism is a unique vulnerability of cancer cells and may present a promising target for cancer therapy. Our study aims to elucidate the molecular mechanisms by which NKX2–8 deletion reprogrammed FA metabolism-induced chemoresistance in epithelial ovarian cancer (EOC).

Methods

The deletion frequency and expression of NKX2–8 in 144 EOC specimens were assayed using Fluorescence in situ hybridization and immunochemical assays. The effects of NKX2–8 deletion and the fatty acid oxidation (FAO) antagonist Perhexiline on chemoresistance were examined by Annexin V and colony formation in vitro, and via an intraperitoneal tumor model in vivo. The mechanisms of NKX2–8 deletion in reprogrammed FA metabolism was determined using Chip-seq, metabolomic analysis, FAO assays and immunoprecipitation assays.

Findings

NKX2–8 deletion was correlated with the overall and relapse-free survival of EOC patients. NKX2–8 inhibited the FAO pathway by epigenetically suppressing multiple key components of the FAO cascade, including CPT1A and CPT2. Loss of NKX2–8 resulted in reprogramming of FA metabolism of EOC cells in an adipose microenvironment and leading to platinum resistance. Importantly, pharmacological inhibition of FAO pathway using Perhexiline significantly counteracted NKX2–8 deletion-induced chemoresistance and enhanced platinum's therapeutic efficacy in EOC.

Interpretation

Our results demonstrate that NKX2–8 deletion-reprogrammed FA metabolism contributes to chemoresistance and Perhexiline might serve as a potential tailored treatment for patients with NKX2–8-deleted EOC.

Fund

This work was supported by Natural Science Foundation of China; Guangzhou Science and Technology Plan Projects; Natural Science Foundation of Guangdong Province; The Fundamental Research Funds for the Central Universities.

Lack of myeloid Fatp1 increases atherosclerotic lesion size in Ldlr-/- mice

BACKGROUND AND AIMS

Altered metabolism is an important regulator of macrophage (MΦ) phenotype, which contributes to inflammatory diseases such as atherosclerosis. Broadly, pro-inflammatory, classically-activated MΦs (CAM) are glycolytic while alternatively-activated MΦs (AAM) oxidize fatty acids, although overlap exists. We previously demonstrated that MΦ fatty acid transport protein 1 (FATP1, Slc27a1) was necessary to maintain the oxidative and anti-inflammatory AAM phenotype in vivo in a model of diet-induced obesity. The aim of this study was to examine how MΦ metabolic reprogramming through FATP1 ablation affects the process of atherogenesis. We hypothesized that FATP1 limits MΦ-mediated inflammation during atherogenesis. Thus, mice lacking MΦ Fatp1 would display elevated formation of atherosclerotic lesions in a mouse model lacking the low-density lipoprotein (LDL) receptor (Ldlr^-/-).

METHODS

We transplanted bone marrow collected from Fatp1^+/+ or Fatp1^-/- mice into Ldlr^-/- mice and fed chimeric mice a Western diet for 12 weeks. Body weight, blood glucose, and plasma lipids were measured. Aortic sinus and aorta lesions were quantified. Atherosclerotic plaque composition, oxidative stress, and inflammation were analyzed histologically.

RESULTS

Compared to Fatp1^+/+Ldlr^-/- mice, Fatp1^-/-Ldlr^-/- mice exhibited significantly larger lesion area and elevated oxidative stress and inflammation in the atherosclerotic plaque. Macrophage and smooth muscle cell content did not differ by Fatp1 genotype. There were no significant systemic alterations in LDL, high-density lipoprotein (HDL), total cholesterol, or triacylglyceride, suggesting that the effect was local to the cells of the vessel microenvironment in a Fatp1-dependent manner.

CONCLUSIONS

MΦ Fatp1 limits atherogenesis and may be a viable target to metabolically reprogram MΦs.

Endothelial specific SIRT3 deletion impairs glycolysis and angiogenesis and causes diastolic dysfunction

Endothelial glycolysis plays a critical role in the regulation of angiogenesis. We investigated the role of Sirtuin 3 (SIRT3) on endothelial cell (EC) glycolytic metabolism, angiogenesis, and diastolic function. Our aim was to test the hypothesis that loss of SIRT3 in ECs impairs endothelial glycolytic metabolism and angiogenesis and contributes to myocardial capillary rarefaction and the development of diastolic dysfunction. Using SIRT3 deficient ECs, SIRT3 was found to regulate a metabolic switch between mitochondrial respiration and glycolysis. SIRT3 knockout (KO)-ECs exhibited higher mitochondrial respiration and reactive oxygen species (ROS) formation. SIRT3 knockout (KO)-ECs exhibited a reduction in the expression of glycolytic enzyme, PFKFB3, and a fall in glycolysis and angiogenesis. Blockade of PFKFB3 reduced glycolysis and downregulated expression of VEGF and Angiopoietin-1 (Ang-1) in ECs. Deletion of SIRT3 in ECs also impaired hypoxia-induced expression of HIF-2α, VEGF, and Ang-1, as well as reduced angiogenesis. In vivo, endothelial-specific SIRT3 KO (ECKO) mice exhibited a myocardial capillary rarefaction together with a reduced coronary flow reserve (CFR) and diastolic dysfunction. Histologic study further demonstrated that knockout of SIRT3 in ECs significantly increased perivascular fibrosis in the coronary artery. These results implicate a role of SIRT3 in modulating endothelial function and cardiac function. Ablation of SIRT3 leads to impairment of EC glycolytic metabolism and angiogenic signaling, which may contribute to coronary microvascular rarefaction and diastolic dysfunction in SIRT3 ECKO mice.